Publication

Transcription

Publication

6
8
Contents
Regular features
3
Comment
by Thoko Majozi, University of the Witwatersrand
25 SAIChE News
33 Et cetera
36 Sudoku No 97 and solution to No 96 / Et cetera
Cover story
4 GEMÜ products’ role in hot water cascade system for sterilizing liquids
Special report
6 Micro-distillation and the spirit smiths
Like wine or beer, spirits are a natural product that will be imbibed by people, not machines. The subtlety and complexity of flavour is a gift given by one person to another. Only the nose and senses of one person can appreciate how another will experience it.
by Gavin Chait
Water treatment
8 Recent developments in microbiological approaches for securing mine wastes and for recovering metals from mine waters
Advances in biotechnologies are proposed, both those which secure reactive mine tailings and those which remediate mine waters. Empirical management of tailings ponds to promote the growth of micro-algae to reverse the processes that cause acid mine drainage are discussed, as well as targeted biomineralization, which allows metals in mine waters to be recovered and recycled.
by D Barrie Johnson, College of Natural Sciences, Bangor University, Bangor, UK
16 Focus on water treatment
18
26
Separation and filtration technologies
18 Thinking like Sherlock Holmes for process filtration technology selection
Sherlock Holmes and Dr John Watson are fictional characters of Sir Arthur Conan Doyle. Process engineers who live in the real world can learn many things from the two of them for solving process filtration problems. This article will intertwine the detective techniques (mindfulness, astute observation, logical deduction and others) of Holmes and Watson with the problem-
solving skills required to select process filtration systems.
by Barry A Perlmutter, President & Managing Director, BHS-
Sonthofen Inc, Filtration, Mixing & Recycling Divisions, Charlotte, North Carolina, USA
23 Focus on separation and filtration technologies
Materials of construction
26 High temperature shape memory polymer
A high switching temperature shape memory polymer system was developed from metal salts of sulphonated polyether ether ketone (PEEK) ionomer and ionomer/fatty acid salt compounds. This showed moderate shape memory behaviour, but compounds show even more promising shape memory behaviour.
by Ying Shi and R A Weiss, University of Akron, Akron, Ohio, USA
Transparency You Can See
Average circulation
(April – June 2014)
Paid: 17
Free: 3 969
Total: 3 713
Chemical Technology is
endorsed by The South
African
Institution of Chemical
Engineers
31 Focus on materials of construction
and the Southern African
Association of Energy
Efficiency
DISCLAIMER
The views expressed in
this journal are not necessarily those of the editor
or the publisher.
Generic images courtesy
of www.shutterstock.com
Comment
The subtle marriage of
process integration
and process control
by Thoko Majozi
R
Published monthly by:
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Publisher:
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Editor:
Glynnis Koch
BAHons, DipLibSci (Unisa),
DipBal (UCT)
Consulting editor:
Thoko Majozi PrEng
PhD (UMIST), MScEng (Natal),
BScEng (Natal), MASSAf,
FWISA, MSAIChE
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BTech Hons Creative Art
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Postage extra outside RSA
ecently, I had the privilege to give an
address at the 19th World Congress of
the International Federation of Automatic Control (IFAC), which was held in Cape
Town towards the end of August. When I was
initially invited to speak, my first reaction was
an unequivocal no, simply because Automatic
Control is largely at the periphery of what I
would call my forté. As a principle, I tend not to
pronounce on matters that I do not sufficiently
understand. Moreover, there is a widely held,
but certainly misplaced, view, that my area of
expertise militates against process control. After giving the request some thought, I realised
that I was actually wrong. Let me explain why.
I work in integration of batch chemical
processes; multipurpose batch chemical processes, to be more specific. These operations
have become very common in recent times
due to their flexibility and adaptability to variations in demand and quality; a situation mostly
encountered in pharmaceutical and specialty
chemical industries.
Batch chemical processes are broadly
categorised into multiproduct and multipurpose batch plants. In multiproduct batch
plants, each produced batch follows the
same sequence of unit operations from
raw materials to final products. However,
the produced batch need not belong to the
same product and the duration of tasks corresponding to different products can vary.
Consequently, multiproduct batch facilities
are ideally suited to products with identical
and fixed recipes. If the recipes of the products involved vary from one batch to another,
multipurpose batch facilities tend to be the
ideal choice. The variation in recipes for the
different batches does not necessarily mean
the variation in products. In other words, the
same product can have different recipes. As
a result, multipurpose batch facilities are appropriate in the manufacture of products that
are characterized by variations in recipes.
It is evident from the foregoing description
that multipurpose batch chemical plants are
combinatorially more complex than multiproduct batch plants. This complexity is not only
confined to operation of the plant, but also
extends to mathematical formulations that
describe multipurpose batch plants. Invariably,
a mathematical formulation that describes
multipurpose batch plants is also applicable
to multiproduct batch plants. However, the
opposite is not true. It is solely for this reason
that most of the effort in the development
of mathematical models for batch chemical
plants should be aimed at multipurpose rather
than multiproduct batch plants.
Batch chemical process integration is a
specialised branch of the broader field of process integration. As we may all know, process
integration is not necessarily a new field; it was
founded in the late ‘70s for energy optimization
and evolved to what became known as Pinch
Technology, with most contributions emanating from the then University of Manchester
Institute of Science and Technology (UMIST).
The fact that this technology emphasizes
the unity of a process, instead of treating a
process as an assembly of discrete unit operations, suggests inherent complexity of control.
Implicitly, the technology was geared towards
continuous processes at steady-state. It has
been applied with great success ever since,
not only in energy optimisation, but also in
resource conservation.
However, there is always an aspect of this
success that is rarely reported in literature.
Steady-state, which is very close to the heart
of every chemical engineer, does not actually
exist – certainly not by itself. At the very best,
it is only with the aid of advanced control
systems that steady-state can be realised.
Consequently, it is automatic control that is
behind the success of Pinch Technology.
That observation implies that there exists
an inextricable confluence between process
integration and automatic control. As a result,
it was acceptable for someone in my research
area to address a gathering of experts in automatic control.
Chemical Technology • September 2014
3
GEMÜ products’ role
in hot water cascade system
for sterilizing liquids
G
EMÜ is one of the world’s leading manufacturers of
valves, measurement and control systems. Over the
course of 50 years, this globally focused, independent, family-owned enterprise has established itself in important industrial sectors thanks to its innovative products
and customised solutions for process media control. GEMÜ
is the world market leader for sterile valve applications in
the pharmaceutical industry and biotechnology industries.
The sterilization of liquids plays a large role in pharmaceutical and biotechnological production. This is just as
important in research and development and in the production of sterile goods as it is in handling parenteral solutions
in hospital pharmacies.
The hot water cascade system developed by MMM
MünchenerMedizinMechanik GmbH, enables liquids in
closed receptacles made of glass, or other temperatureresistant materials (such as ampoules), to be sterilised
quickly, reliably and gently.
The advantage of the hot water cascade system lies in
its very short cycle times, which are achieved through a high
circulation rate and cascade density in combination with
short heating-up and cooling-down times.
efficient method of transferring heat enables the item to
be heated up quickly and gently. In the subsequent cooling
phase, the sterilisation water flows through the now watercooled heat exchanger and cools the item being sterilised
down to a specific temperature.
Once again, GEMÜ 554 globe valves control the way in
which the heat exchanger is heated by steam and cooled
using water.
Throughout the process, temperature-controlled supporting pressure generated by sterile-filtered compressed
air prevents the tightly closed receptacle from bursting
or deforming. GEMÜ 490 butterfly valves are used in the
circulation line, as these have significantly more compact
installation dimensions, yet very high flow rates, in comparison with pneumatically operated angle seat globe valves of
the same nominal diameter.
Liquids are usually sterilized at 121 °C for 20 minutes;
however, handling time can be adjusted depending on
product requirements or on the customer’s requests. To
meet the stringent requirements of the hot water cascade
system, GEMÜ valves are fitted with highly resistant TFM
plastics TM and FDA-approved silicone as a sealing material.
Operating principle and use of GEMÜ
products
Fifty years of experience in valve design
First, the chamber containing the item to be sterilised is
filled to a pre-defined level (below the item being sterilised)
with deionised sterilization water. Pneumatically actuated
GEMÜ 554 globe valves control the filling of the sterilisation
chamber with water. This water then circulates through a
steam-heated heat exchanger and cascades over the item
being sterilised at a continuously rising temperature. This
4
The company Gebrüder Müller Apparatebau GmbH & Co KG –
GEMÜ for short – based in Ingelfingen, Baden-Württemberg,
is celebrating its 50th anniversary this year. Founded by Fritz
Müller in his parents’ garage, the manufacturer of valves,
measurement and control systems can now look back on
an impressive history.
When the first process valve made of plastic was delivered by GEMÜ in 1964, nobody suspected that this one-
Cover story
man operation would develop into a company with 1 400
employees and 24 subsidiaries all over the world within
the next 50 years. With Gert Müller as Managing Director, the second generation answered the call of the family
company in 2011.
Thanks to its consistent innovation and an emphasis
on quality and customer focus, GEMÜ has developed into
the world market leader in the area of valve designs for all
main and auxiliary processes of the pharmaceutical and
biotechnology industries.
One core area of GEMÜ’s expertise is, for example, its
multi-port valve blocks milled from block material. Originally
made of stainless steel, these allow a plant to be designed
much more compactly and, at the same time, more flexibly.
These requirements are also becoming increasingly important in plastic plant engineering. The company’s decades
of experience in stainless steel block construction and
manufacturing produces synergies, which are now also applied to the manufacturing of plastic multi-port valve blocks.
This expertise makes GEMÜ the technological leader in
the field of complex multi-port valve blocks made of plastic.
With its broad product range, GEMÜ can offer solutions
for a wide range of customer groups. This product variety,
combined with an active customer focus, makes GEMÜ the
right partner for a very wide range of applications in the field
of valves, measurement and control systems.
The company also offers state-of-the-art products for the
increasing levels of electrification and automation now used
in plant engineering. GEMÜ already offers its customers a
relevant range of components and systems, for example,
electric actuators for globe and control valves, butterfly
valves and diaphragm valves. Depending on the version,
these can be equipped with the corresponding positioners or
process controllers as standard or connected to commonly
used communication interfaces.
The company and its employees look forward to developing new innovations and mastering new challenges in the
future together with customers and suppliers.
Today, the GEMÜ Group employs over 800 employees in
Germany and more than 1 400 worldwide. Manufacturing
is carried out at six manufacturing sites in Germany, Switzerland, China, Brazil, France and the USA. GEMÜ plans
to continue to establish itself in future markets with its
international growth strategy. To achieve this, the company
opened a new Production and Logistics Centre in 2013.
A broad based modular system and adapted automation components mean that predefined standard products
and customised solutions can be combined to make over
400 000 product versions.
GEMÜ Africa
In 2008 GEMÜ Africa established a dedicated office in
Northriding, Johannesburg. Currently with ten employees,
GEMÜ Africa offers high quality solutions at competitive
pricing to various market sectors, such as: mining and
minerals, oil and gas, pharmaceutical, water treatment,
power generation, automotive and food and beverage.
GEMÜ Africa's well established warehouse ensures prompt
delivery to their customers.
For more information contact Claudio Darpin at GEMÜ Valves
Africa (Pty) Ltd on tel: +27 (0)11 462 7795 Ext. 13, or cell
+27 79 692 60 95. Email: [email protected], or
go to www.gemue.co.za z
5
Micro-distillation
and the spirit smiths
by Gavin Chait
Like wine or beer, spirits are a natural product
that will be imbibed by people, not machines.
The subtlety and complexity of flavour is a gift
given by one person to another. Only the nose
and senses of one person can appreciate how
another will experience it.
“I
t is a curious fact, and one to which no-one knows quite how
much importance to attach, that something like 85 percent
of all known worlds in the Galaxy, be they primitive or highly
advanced, have invented a drink called jynnan tonyx, or gee-N’NT’N-ix, or jinond-o-nicks, or any one of a thousand variations on this
phonetic theme,” says Douglas Adams in The Restaurant at the End
of the Universe.
The Earth-based version is called Gin and Tonic. Obeying the
guidance of Winston Churchill, who said, “I would like to observe the
vermouth from across the room while I drink my martini,” we’ll pay
attention to the gin.
The production of fine spirits – gin, whiskey, cognac – all begins
with the process of heating a fermented liquor or washing and distilling
that to extract a specific mixture of volatiles. The fermentation process
is left as an exercise to the more adventurous reader.
Persian alchemists developed the alembic, a very simple still
consisting of two clay pots and a lid-tube attachment. Technically, the
hooded tube is the alembic. Filling one pot with liquor and heating
it will transfer steam up into the alembic, and the steam cools and
trickles down into the other pot. The result is a refined liquid containing
a much higher proportion of the volatiles. Redistillation of the liquid
can result in ever greater purity of the final distillate.
The most basic pot stills, with their fluted copper pots, are simply
scaled up alembics. Alcohol boils at 78 °C, and water boils at 100 °C. It
is that differential which allows the separation of the two. Methanol’s
boiling point is 64,7 °C. This means that the first part of the distillate
will contain a high concentration of stuff that will make you blind. It
is discarded.
This single pot distillation is also known as batch distillation.
Extracts have to be redistilled to ensure purity and initial distillate is
broken into component batches. It’s a tiresome and inefficient process.
Fractional distillation is far more efficient. The steam from the pot
is first passed through a fractionating column where the temperate is
measured from bottom to top. Vapour rises in the column and passes
over various distillation plates, with the temperate falling along a
gradient to the top. The column forms a temperature equilibrium and
6
different fractions can be tapped at different levels to draw off the
appropriate distillate.
The process can run continuously and is the basis for most commercial distillation. Crude oil, for example, is heated in a furnace with
diesel coming off at 300 °C, petrol at 150 °C, and propane at 20 °C.
In the production of spirits, unless the distillery produces different
products, they usually only need one specific fraction, and so the
column is tapped in only one place. Obviously this can get a lot more
complex, with reboilers, reflux drums and various condensers that
ensure a consistent product.
If this is Scotch whiskey production, then the final distillate exits
into a spirit safe. This is a locked, glass-walled container which permits the distiller to analyse the product without being able to touch it.
Once the local representative of Customs and Excise has calculated
the volume of spirit present, and charged the appropriate duty, the
safe can be unlocked.
The Irish felt that continuous distillation methods resulted in tasteless whiskey (they’re wrong) and shunned Aeneas Coffey, an Irishman
who invented a two-column continuous still which quickly became a
global phenomenon back in 1830. Which is why the Irish – using pot
stills – need to triple-distil their broth.
More probably, these are very organic products. In the absence
of serious process control and accurate measurement, the physical
structure of the distillation systems imbues a specific flavour on each
spirit. Swapping out an old pot still for a new column would result in an
entirely different flavour. Not worth the risk for most mature producers.
And so we get to the basics. Gin requires a base of any ethyl alcohol of agricultural origin in which are seeped a mix of botanicals and
then redistilled. Whiskey is really just distilled beer, just as brandy is
distilled wine. Vodka is from potatoes and rum is from sugar. People
have been distilling for a very long time from whatever sugar-bearing
materials happened to be around.
More recently – and in tandem with other ‘third-wave’ artisanal
producers in coffee and beer – the industry is being invigorated by
the influx of new micro-distillers. In 2005 there were 50 craft distillers
in the US. In 2013 there were 600, a growth rate of 30% according to
Petrochemicals
Special Report
the American Distilling Institute. Most are started on more enthusiasm
than experience and end badly.
Stephen Thompson is 70, and a 25-year veteran of working in the
distillation industry. “When I tell people it will likely take at least two
years to even begin processing a first full batch and make something
that is commercially viable, and anywhere from $350 000 to a million
dollars to get off the ground, you see some disbelief,” says Thompson
in Forbes Magazine. “I don’t want to discourage people from their
dreams, but they need to be prepared.”
It is a far more expensive undertaking, with horribly complex legislative hoops, in comparison to craft brewing. At the smallest scale are Ian
Hart and Hilary Whitney who started with a 6-litre still in their home in
Highgate, London, in 2009. Ian has a somewhat unique approach to
distilling. Each of the botanicals is distilled individually, and he uses a
glass still at reduced pressure so that distillation takes place at a much
lower temperature. Amongst the botanicals he blends into his Sacred
Gin are cardamom, nutmeg and frankincense. He also makes vodka.
Sipsmith is the first copper-pot distillery to open inside London in
200 years. Launched by Sam Galsworthy and Fairfax Hall, with Jared
Brown as their master distiller, the distillery produces both gin and
vodka. Prudence, their large 300 litre copper, is a continuous distillation process and they alternate with a distillation column when they
produce vodka.
“We distilled our first batch in 2009,” says Galsworthy in Economia
magazine. “There was such a buzz about craft spirits in the States,
such a powerful romance attached to producing something with
pedigree using old-school distillation that we couldn’t wait. The fact
that we were in the eye of a financial storm was no deterrent. In an
odd way the recession may have helped because what happens, supposedly, is that people cut back on quantity but upgrade on quality.”
The tremendous thing about craft distillers is that, since they serve
smaller and more dedicated groups of clients, they can specialise and
take greater risks in what they produce.
Immortal Spirits in Medford, Oregon, produces absinthe, the aniseflavoured spirit derived from wormwood, green anise and fennel. Laird
& Company in New Jersey, produce applejack, a cider-based spirit.
Tuthilltown produces cassis, a blackberry-based liqueur, as well as
bitters made from rye, sarsaparilla and a mix of herbs and spices
and maple syrup.
Our local distillery regulations don’t make things easy for South
African’s looking to start, but that hasn’t stopped the fledgling industry. Roger Jorgensen created the Jorgensen’s Distillery in 1994 on
Versailles Farm in Wellington. He produces vodka, gin, absinthe and
limoncello for those of you looking to try a different take on the massproduced spirits produced locally. A small number of others, including
Drayman’s in Pretoria, produce single-malt whiskey. If you’re feeling
adventurous, there is even the opportunity to receive training from
Distillique in Pretoria.
The US, though, continues to be the heart of the new wave of
craft distillers despite the painful regulatory environment. Portland,
in Oregon, has more than 20 craft distillers.
Steve McCarthy founded Clear Creek Distillery in 1985 to produce
eau de vie and grappa from his family Williams Pear farm. Eau de vie is
a clear fruit brandy produced from fermentation and double-distillation
in McCarthy’s pot still. Grappa – familiar in South Africa – is a clear
brandy made from distilling the skins, pulp, seeds and stems left over
after grapes have been pressed for wine-making.
As Eric Felten puts it in the Wall Street Journal, “Notoriously difficult
to make, and without barrel-ageing to oak over any flaws, eau-de-vie
is a nakedly exposed test of a distiller’s skill.”
McCarthy started with the belief that he could take a strictly scientific approach to quantifying the exact moment to cut the ‘head’ and
‘tail’ of his distillation. These are the unpleasant volatiles containing
acetone, esters, methanol and other flavour compounds that spoil the
beverage. He bought himself a gas chromatograph and attempted to
build data profiles. It didn’t work. “The only way to do it is by smell,”
he says.
This is unsurprising. Like wine or beer, spirits are a natural product
that will be imbibed by people, not machines. The subtlety and complexity of flavour is a gift given by one person to another. Only the nose
and senses of one person can appreciate how another will experience
it. We’re a long way from being able to program that into a computer. z
7
Recent developments in microbiological approaches
for securing mine wastes and
for recovering metals from mine waters
by D Barrie Johnson, College of Natural Sciences, Bangor University, Bangor, UK
Advances in biotechnologies are proposed,
both those which secure reactive mine tailings
and those which remediate mine waters.
Empirical management of tailings ponds
to promote the growth of micro-algae to
reverse the processes that cause acid mine
drainage are discussed, as well as targeted
biomineralization, which allows metals in mine
waters to be recovered and recycled.
Photo © D B Johnson
Mine water genesis
The mining of metals and of coals generates waste materials that are potentially hazardous to the environment
[1–3]. Protecting aquatic and terrestrial ecosystems from
pollutants generated from mine wastes is a major concern
of environmental protection bodies and the mining industry
itself. Given the increasing demand by an expanding global
population for metals in general and for some, such as the
rare earth elements, for which new markets have arisen
in recent years, it will be necessary to continue to exploit
previously untapped ore bodies, though recovery of metals
from other sources, such as reprocessing mine wastes and
processing electronic scrap (e-wastes) could also provide
significant quantities of metals for manufacturing industries.
Future developments in the metal mining industry are likely
to focus on more environmentally-benign technologies that
are less demanding of energy and have far smaller carbon
footprints than opencast and deep-mining operations, and
using pyrometallurgy to extract metals. For example, in situ
biomining could allow target metals to be extracted from
deeply-buried ore bodies without the need to hoist rocks to
the surface, or to crush and mill the ore [4].
Solid waste generated by metal mining can be divided
into two main categories: waste rock and mine tailings.
8
Dumps of waste rock are composed of sand-sized particles
to large boulders and have less potential to generate polluting drainage waters than tailings. The latter are fine grain
wastes generated during the separation of target metal
minerals from others in milled ores by froth flotation [1].
Many commercially-valuable base metals, such as copper
and zinc, occur as sulfide minerals, and these are often
associated in ore bodies with other, relatively non-valuable
minerals, such as pyrite (FeS2), as well as other gangue
minerals. The occurrence of pyrite and other sulfide minerals in tailings wastes, as well as their fine grain size, makes
them potentially highly reactive. The mechanisms involved
in the oxidative dissolution of sulfide minerals have been
described in many review articles and other publications
(eg, [5]). Pyrite can be oxidised by both molecular oxygen
and ferric iron, the relative importance of which depends
on the solubility of ferric iron, which is pH-dependent [6].
Lime is often added to suppress the flotation of pyrite, and
therefore fresh mine tailings may be alkaline [1]. As pH
declines, ferric iron becomes increasingly important as the
main oxidant of sulfide minerals, for example in which pyrite
is oxidised via the ‘thiosulfate’ pathway [5]:
6Fe3+ + FeS2 + 4H2O → 7Fe2+ + S2O32− + 6H+
(1)
Petrochemicals
Water treatment
For the process to continue, ferrous iron has either to
be re-oxidised in situ, or ferric iron delivered from a more
remote location. Unlike ferric iron-catalysed pyrite oxidation, the re-oxidation of the ferrous generated does require
molecular oxygen and, in low pH liquors, a microbiological
catalyst in the form of an acidophilic iron-oxidizing bacterium
or archaeon. The thiosulfate formed in equation [1] is oxidised via various sulfur intermediates, to sulfuric acid, which
again involves (sulfur-oxidizing) acidophilic prokaryotes, eg,
S2O32− + 2O2 + H2O → 2SO42− + 2H+
(2)
The sulfuric acid produced in this reaction not only increases
the rate of sulfide mineral dissolution (by increasing the
solubility of ferric iron) but also allows other cationic metals
(including aluminium, and many transition metals) to be
retained in solution.
Source control of mine pollution
Acid mine waters can be generated from abandoned mine
workings (deep mines and opencast operations) and from
mine spoils (waste rock dumps and mine tailings). Decommissioned biomining operations (dumps and bio-heaps)
can also continue to produce metal-rich acidic waters when
irrigation ceases, though this is not a cause of concern in
some parts of the world, eg, in the vicinity of the Atacama
Desert in northern Chile, where there are extensive copper
bioleaching operations [7].
When active mining ends, pumping of groundwater is
terminated and water tables rebound. The rate at which
this occurs depends on climatic and other factors. In some
situations, it can be a rapid process and water levels may
approach to the land surface within months of dewatering
being terminated, as was the case at the Wheal Jane tin
mine in Cornwall, UK, which resulted in catastrophic pollution of impacted water courses, including a marine site
[8]. In contrast, water level rises in pit lakes in abandoned
opencast metal mines in the more arid Iberian Pyrite Belt
are relatively slow (eg, [9]). In both cases, flooding produces
water bodies that are stratified in terms of redox potentials,
dissolved oxygen and other factors. Much of the water in
deep mine workings and in pit lakes is anoxic [9,10] which
limits the extent to which residual acid-generating minerals
are oxidised.
Solid wastes generated by mining and deposited at the
land surface often pose more of a threat to the environment, both in the short and long term, than abandoned
mine workings (eg, [11]). Since, as noted previously, both
9
Figure 2: Mesocosms of pyritic mine tailings inoculated with mineraloxidizing acidophilic bacteria (A), mineral-oxidizing and heterotrophic
acidophilic bacteria and acidophilic algae (B) and non-inoculated
controls (C), and incubated at 22°C for one year [21].
Figure 1: Schematic representation of the ‘bioshrouding’ technique for securing mine
tailings [17]. Pyrite particles (depicted in gold) colonized by iron/sulfur-oxidizing bacteria
(in red), generating acid mine drainage (AMD) are shown on the left, and the same
particles encased with EPS (black lines) produced by heterotrophic acidophiles (in blue)
suppressing colonization by iron/sulfur-oxidizing bacteria on the right (not to scale).
oxygen and water are required to promote the biological
oxidative dissolution of pyrite and other sulfide minerals, the
engineering approaches used to control the production of
acid mine drainage (AMD) from solid wastes aim to preclude
access of one these essential factors [12]. In the case of
waste rocks, dry covers can be used to limit water ingress
[13]. Mine tailings, which are far more reactive because of
their smaller grain size and generally far higher content of
reactive minerals, are usually stored under water to limit
contact with oxygen. Even so, ferric iron, generated in the
aerobic upper water layers, can diffuse into the tailings and
oxidise sulfide minerals in the absence of oxygen, as noted
above. One method of limiting oxidation of mine tailings is
to amend them with organic materials that are degraded by
oxygen-consuming heterotrophic bacteria. Various materials
have been tested, and some found to be far more effective
than others. Lindsay et al [14] for example, found that peat
was an ineffective carbon source for this purpose, whereas
municipal biosolids and (especially) spent brewing grain,
retarded AMD production from mine tailings in a field trial
site at a metal mine in Alaska.
Bacteria and archaea that catalyse the oxidative dissolution of pyritic minerals can do this without having physical
contact with the mineral (non-contact leaching), but in most
cases they attach to the sulfides, forming biofilms below
which corrosion of the minerals progresses (contact leaching; [15]). Other bacteria that live in acidic mine waters also
attach to minerals and form biofilms, including species of
heterotrophic acidophiles that reduce ferric iron, rather than
oxidize ferrous iron [16]. These, in theory, have a protective
influence on sulfide mineral oxidation as they can control the
availability of the main chemical oxidant involved at low pH
(Fe3+). Johnson et al [17] showed that, by colonising pyrite
grains by heterotrophic iron-reducing bacteria (Acidiphilium
and Acidocella spp.) before exposing them to autotrophic
iron- and sulfur-oxidising acidithiobacilli, it was possible to
reduce pyrite dissolution by ~80%, even under conditions
deemed highly aggressive (pH < 2 and oxygen-saturated
shake flask cultures). Interestingly, numbers of planktonic-
10
phase (free-swimming) pyrite-oxidizing bacteria were far
greater in cultures where the pyrite had been initially colonized with the heterotrophs, compared to fresh pyrite, the
implication being that biofilm formation by the heterotrophs
limited the ability of the acidithiobacilli to attach to the
minerals. The technique, referred to as ‘bioshrouding’, is
illustrated in Figure 1.
Ecological engineering approaches for limiting the
production of and treating AMD have gained considerable
interest. Sites where mine waters display greater or lesser
degrees of mitigation with no apparent anthropogenic input
(‘natural attenuation’), can serve as models for the design
of ecologically engineered systems. One example was an
acidic (pH 2,2–2,7) metal-rich stream draining an adit at a
small copper mine in the Iberian pyrite belt (IPB) which had
developed thick, stratified microbial growths [18]. These
appeared as green algal streamers overlying light brown
and (at the lowest depth) black-coloured bacterial mats.
Analysis of the mine water at the stream surface and within
the microbial growths showed that a significant fraction of
soluble copper generated in the aerobic mine adit was being
precipitated as a solid sulfide (CuS or Cu2S) within the black
microbial mat, which contained novel acidophilic strains of
sulfate-reducing bacteria (SRB). No ferrous sulfides were
formed in the black mats, due to the fact that interstitial
water in the mats remained extremely acidic (pH 2,9; the
solubility product of CuS is many orders of magnitude lower
than that of FeS). Tuttle et al [19] were the first to report that
SRB could be stimulated in AMD by adding organic carbon,
and that their activities could promote both immobilisation
of some (chalcophilic) metals and mitigation of water acidity.
The IPB mine stream was, however, a site which was being
(partially) attenuated naturally, since the stream received
no extraneous supply of organic carbon.
The assumption that the heterotrophic bacteria (including the SRB) in the microbial mats in the IPB mine drainage
stream were being sustained by carbon derived from the
acidophilic algae was later confirmed in laboratory experiments [20] and used as the basis of a novel ecological engineering approach for securing mine wastes [21]. The latter
involved setting up 60 mesocosms containing pyrite-rich
mine tailings inoculated with different species of mineraldegrading and heterotrophic bacteria (including species
shown to ‘bioshroud’ pyrite), and acidophilic micro-algae,
and incubated for up to one year (Figure 2). Differences in
acid genesis and metal mobilization were apparent between
Water treatment
all inoculation regimes, with the oxidation of the mineral
tailings being significantly less in mesocosms that had been
inoculated with micro-algae and heterotrophic bacteria, as
well as mineral-degrading acidophiles, than in others. The
authors suggested an empirical method for safeguarding
reactive mine tailings stored under water, in which freshlydeposited tailings are inoculated with acidophilic microalgae and iron- and sulfate-reducing bacteria, together with
small amounts of nitrogen and phosphorus to promote their
growth. This approach would allow the establishment of
consortia of microorganisms that retard the oxidative dissolution of sulfide minerals, and therefore AMD production.
Organic carbon (including soluble exudates) produced by the
micro-algae would sustain the growth of the heterotrophic
bacteria, thereby avoiding the need for continuous inputs
of extraneous organic materials (Figure 3).
Migration control of mine pollution
Even where source control practices are in place, it is often
necessary to collect and treat AMD downstream of the mine
or mine spoil from which it arises. Various options are available for remediating mine waters (reviewed in [12]), which
can be broadly divided into ‘active’ and ‘passive’ approaches. Active remediation of mine waters usually involves addition of a basic chemical reagent, such as lime (CaO) coupled
with active aeration to promote oxidation of ferrous iron.
Metals are precipitated chiefly as carbonates and hydroxides
(and calcium as gypsum; CaSO4∙2H2O), though the water pH
may have to exceed pH 8–9 to effectively remove metals
such as manganese. Flocculating agents may be added to
facilitate the production of ‘high density’ sludges [22]. The
technology is proven and effective though expensive, and
does not allow potentially valuable metals present in mine
waters to be recovered and cycled. The latter is also the case
for passive mine water treatment technologies (constructed
wetlands, anaerobic ‘bioreactors’ and permeable reactive
barriers [12]) where biological processes are harnessed to
generate alkalinity and to precipitate metals (sometimes in
combination with limestone which is incorporated into the
bulky organic substrate [23]). However, more recent innovative developments in mine water remediation technologies
include some that facilitate the sequential and/or selective
removal of soluble metals and other pollutants from AMD,
thereby allowing the more valuable components to be recycled and the more toxic pollutants to be immobilized in
more concentrated forms, as described below.
Iron
Iron is often the most abundant metal present in waters
draining metal and coal mines, chiefly because of its occur-
Figure 3: Schematic representation of an ecological engineering strategy for securing reactive mine tailings [21]. Freshlydeposited tailings are inoculated with acidophilic algae and
heterotrophic bacteria. The algae grow as a surface layer on the
tailings in the pond, fixing carbon and providing organic carbon
(CH2O) which sustains the growth of iron- and sulfate-reducing
bacteria within the submerged tailings, thereby essentially
reversing the reactions that generate AMD. Additional protection of the minerals may be mediated by ‘bioshrouding’ by the
heterotrophic acidophiles [17]
rence in many sulfide minerals (eg, chalcopyrite (CuFeS2),
arsenopyrite (FeAsS), pyrrhotite (Fe(1-x)S, where x = 0 to 0,2)
as well as the most abundant of all sulfides, pyrite (FeS2))
though it can also derive from acid-catalysed dissolution
of other minerals, such as chlorite (Mg,Fe)3(Si,Al)4O10).
Because of its intense colour, ferric iron is also responsible
for the typical orange-brown pigmentation of mine waterimpacted streams and sediments, making AMD one of
the most obvious and readily recognised forms of water
pollution.
Iron occurs as both Fe2+ and (complexed) Fe3+ in AMD. At
its point of discharge from an adit draining an abandoned
mine, AMD is often anoxic and iron is present almost exclusively in its more reduced ionic form, which is reflected
in EH values of <+500 mV. Chemical oxidation of ferrous to
ferric proceeds slowly below pH 3,5, though iron-oxidizing
prokaryotes can catalyse this reaction in mine waters that
have pH values of <1,0 to >4. Ferric iron is far less soluble
than ferrous, for example as a (oxy) hydroxide (Table 1 on
page 13) and therefore is more readily precipitated as such
from mine waters. Prerequisites for this are: (i) the oxidation of ferrous iron which, as noted, is not a spontaneous
chemical reaction in acidic liquors; and (ii) sufficient availability of hydroxyl (OH—) ions, which may require addition of
alkali to increase mine water pH to >3 to increase the rate
of ferric iron hydrolysis. Jarosites, basic ferric iron sulfates
(eg, KFe3(SO4)2(OH)6) which form in extremely acidic (pH <
2) oxidized mine waters, do so at rates that are too slow for
effective mine water remediation.
There have been a number of reports describing the
use of bacteria to accelerate the oxidation for ferrous iron
as part a remediation strategy for AMD (eg, [24–26]). The
majority of studies have used the most well-known of all
acidophilic iron-oxidizers, Acidithiobacillus ferrooxidans,
often in packed-bed bioreactors. However, a study that
compared different species of iron-oxidizing acidophiles
concluded that an iron-oxidizing Acidithiobacillus (referred
to at the time as a strain of At. ferrooxidans, though this
particular isolate was subsequently reclassified as the type
stain of At. ferrivorans), was actually the least effective of
those tested, again in packed-bed bioreactors [27].
Few trials using bacteria to oxidise iron and thereby facilitate the removal of soluble iron from mine waters have
gone beyond the laboratory scale. One notable exception
11
Metal
Hydroxide
Sulfide
Al3+
−33.5
-
Cu2+
−19.8
−35.9
Fe2+
−16.3
−18.8
Fe3+
−38.6
-
Mn2+
−12.7
−13.3
Zn2+
−16.1
−24.5
is a pilot-scale operation set up and maintained by the
German company GEOS, at an opencast lignite mine site
at Nochten, eastern Germany [28,29]. Groundwater at
the site contains ~630 mg soluble iron per litre (>99 % as
Fe2+) which is oxidised in a continuous through-flow aerated
bioreactor tank containing bacteria which are immobilized
on plastic sheets. The bioreactor was initially inoculated
with the more well-known iron-oxidising acidophiles At.
ferrooxidans and Leptospirillum ferrooxidans. However,
very soon after the pilot plant was commissioned these
bacteria were present either in very low numbers or were not
detected, and bacteria related to ‘Ferrovum myxofaciens’
(a more recently described iron-oxidizing acidophile [30])
and the neutrophilic iron-oxidizer Gallionella ferruginea
[31] were the dominant bacteria present ([28,29]). The pH
of the ground water was pH 4,9, but following treatment
in the bioreactor this declined to pH 3,0 as a result of iron
oxidation and precipitation. This relatively low pH resulted
in a significant amount of the ferric iron generated (~55%)
remaining in solution (aided by the fact that biological
ferrous iron oxidation can be more rapid that ferric iron
hydrolysis at pH 3), while the rest was precipitated as the
mineral schwertmannite (idealised formula Fe8O8(SO4)(OH)6;
[32]). Production of schwertmannite also caused the sulfate
concentration of the groundwater to be lowered from 2 700
to 2 400 mg/L.
A strain of ‘Fv. Myxofaciens’ (PSTR) had earlier been
reported to be the most effective iron-oxidizing bacterium
in packed-bed bioreactor tests [27]. On the basis of this
observation and the data from the Nochten plant, a laboratory-scale continuous flow reactor system for generating
schwertmannite from synthetic metal mine waters was set
up in which the type strain of ‘Fv. Myxofaciens’ (P3G) was
used as the sole iron-oxidizing acidophile [33]. In contrast
to the Nochten plant, which treats groundwater containing
only one metal (iron) in significant concentrations, tests were
carried out with waters also containing aluminium, copper,
manganese and zinc in order to investigate whether a ‘clean’
schwertmannite product (ie, without other co-precipitated
metals) could be generated. The modular system (Figure 4)
comprised three units: a ferrous iron-oxidising bioreactor, a
schwertmannite precipitation module (in which alkali and a
flocculating agent were added to the oxidised mine waters)
and a packed-bed polishing unit. Over 90 % of iron present
in a synthetic mine water containing 280 mg Fe2+/L were
oxidised in the bioreactor when operated at a dilution rate
of 0,41/h, and the fully-processed water contained <1 mg
soluble iron/L. The schwertmannite produced was virtually free of all other metals present in the synthetic mine
waters tested.
Water treatment
Table 1. Solubility products (logKsp values at 25 °C) of hydroxides and sulfides phases of metals typically found in acid mine
drainage (AMD).
Figure 4: Schematic representation of a modular system
described for precipitating iron present in waters draining metal
mines as schwertmannite [33].
Selective precipitation of other transition
metals
Iron is a relatively low value commodity, though schwertmannite does have potential commercial value as a pigment
and as a low cost adsorbent of anions, such as arsenate
and chromate ([32,34]). In contrast, other transition metals
that may be present in mine drainage waters, such as copper, nickel and zinc, have higher value, and recovery and
recycling of these could help off-set the costs of an active
bioremediation system. Many divalent transition metals
form poorly soluble hydroxide phases, though these are have
larger solubility products than those of trivalent aluminium
and ferric iron (Table 1). However, an alternative approach
is to precipitate chalcophilic transition metals selectively
as sulfide minerals. Speciation of sulfide (H2S, HS− and
S2−) is dictated by pH, and since the species that reacts
with divalent transition metals (S2−) occurs in increasingly
small amounts as the acidity of liquors increases, pH control
can be used as a mechanism for selectively precipitating
metal sulfides. Sulfate-reducing bacteria, as noted previously, use sulfate (the dominant anion in AMD) as terminal
electron acceptor, generating hydrogen sulfide that can
be used to precipitate chalcophilic metals and metalloids.
At least two commercial systems use biosulfidogenesis to
capture metals from mine waters: the Thiopaques® [35] and
Biosulphide® [36] processes. However, the vast majority of
SRB (and sulfur-reducing bacteria, as used in the Biosulphide process) are highly sensitive to acidity and need to
be shielded from direct contact with acidic mine waters,
usually by housing them in separate reactor vessels. Some
stains of acidophilic SRB have been isolated, though most
currently have not yet been formally described or validated
as novel species. In the first demonstration of its kind, a
consortium of acidophilic SRB and other acidophiles was
used to selectively precipitate copper and zinc from mine
waters that also contained other dissolved metals, including aluminium and iron, using on-line bioreactors receiving
direct inflow of mine water [37]. Glycerol was used as the
energy source (electron donor) for the bacteria, and the
generalised reaction (for p recipitating zinc sulfide) is:
4C3H8O3 + 7Zn2+ + 7SO42− → 12CO2 + 7ZnS + 16H2O
(3)
One of the perceived advantages of using acidophilic SRB species in an on-line reactor is that the engineering complexity of a
13
Reduced inorganic sulfur compounds and
sulfate
A variety of reduced inorganic sulfur compounds (RISCs),
such as thiosulfate (S2O32−) and tetrathionate (S4O62−), are
produced by several mechanisms during the (bio)processing
of sulfide ores, including reactions that occur during comminution and flotation, and also as intermediates during
the microbial oxidation of pyrite [5,39]. When discharged
into aerated waters, RISCs are susceptible to microbial
oxidation, generating sulfuric acid (eg, Equation (2).The
combined effect of acidification and oxygen depletion
means that RISC-containing waters pose a severe threat
to impacted water bodies. While RISCs can be destroyed
by chemical treatment, a more environmentally-benign approach is to accelerate their oxidation biologically and to
neutralise the acidity generated, prior to water discharge.
This has been demonstrated at 37 °C using a mixed culture
of mesophilic and moderately thermophilic sulfur-oxidising
bacteria (described [40]) and at 4–10 °C using the coldadapted bacterium At. ferrivorans [39].
Sulfate can occur in AMD and mine process waters in
concentrations of up to hundreds of grams per litre, but
since the acidity and metal/metalloid content of these
waters are rightly perceived as posing greater threats to
the environment, lowering sulfate concentrations has
generally not been perceived as a priority issue. However,
increasingly stringent regulations, such as the European
Water Framework Directive, require concentrations of sulfate also to be below an upper limit to allow discharge of
mine waters. As noted previously, some sulfate is removed
(as gypsum) during active chemical treatment of AMD,
and also (as schwertmannite) as part of biological iron
oxidation/precipitation treatment. However, this may not
be sufficient to meet regulatory demands, and techniques
specifically targeting sulfate removal may be required. The
Thiopaques process, described above, can also be used to
convert soluble sulfate to soluble element sulfur [35]. This
is a two-stage process that involves firstly SRB coupling
the reduction of sulfate to the oxidation of an organic (eg,
ethanol) or inorganic (eg, hydrogen) electron donor:
4H2 + SO42− → HS− + 3H2O +OH−
(4)
followed by a bacterial oxidation of hydrogen sulfide to
elemental sulfur under controlled redox:
HS− +O2 + H+ → S0 + H2O(5)
This application of the Thiopaques process, like that for
precipitating metals, also uses neutrophilic SRB. Acidophilic
SRB may also be used to remove sulfate from mine waters
(using glycerol as electron donor) in on-line bioreactors
maintained at pH 2,8 to 4,5 [41].
Other metals and metalloids
Some other metals and metalloids that occur in AMD and
mine process waters may require different approaches to
those described above, and again microbiological options
are often available to remove them. Aluminium and manganese are usually found in relatively elevated concentrations
in AMD, due to their abundance in the lithosphere and
solubility in acidic liquors. Aluminium can be precipitated
as, for example, basaluminite (Al4(SO4)(OH)10∙5(H2O)) at pH
5–6. The alkalinity required to increase AMD pH to that
required for aluminium hydrolysis can be chemical (eg, from
addition of lime) of biological (eg, via sulfate reduction or
oxygenic photosynthesis) in origin. Manganese is present
in AMD predominantly as Mn2+, and although, like ferrous
iron, it can be oxidised biologically to insoluble Mn4+, this
reaction is thermodynamically unfavourable below pH ~4
and proceeds slowly (unless catalysed) below pH 10. Bacteria and fungi have been shown to promote manganese
oxidation and precipitation at moderately acidic pH values
(>5; [42,43]), which is far lower than the pH required (> pH
8–9) to secure effective manganese removal using active
(lime-based) remediation.
Arsenic is a common constituent of mine waters. At the
abandoned Carnoulès metal mine in the south of France,
concentrations of soluble As of up to 350 mg/L have been
reported [44], while mine waters associated with gold ore
processing can contain >10 g As/L [45]. Arsenic can occur
both as As(III) (uncharged H3AsO3 at acidic pH values) and
As(V) (H2AsO4−) in AMD. Anionic As(V) can co-precipitate
with ferric iron (as scorodite; FeAsO4) or be absorbed onto
positively-charged particles, such as (at low pH) schwertmannite [34]. This requires As(III) to be oxidised, which may
be biologically-mediated (eg, by Thiomonas spp, which are
abundant in Carnoulès and other moderately acidic AMD) or
chemically-mediated (eg, by ferric iron). Alternatively, As(III)
may be removed by precipitation as a sulfide. BattagliaBrunet et al [45] demonstrated this using a fixed bed bioreactor colonized by SR fed continuously with an acidic (pH
2,7–5,0) solution containing 100 mg As(V)/L. Arsenic (V)
was reduced to As(III) either directly or indirectly (via H2S) by
the SRB, and orpiment (As2S3) generated within the bioreactor. However, a switch from glycerol to hydrogen as electron
donor resulted in a significant remobilization of arsenic due
to the formation of soluble thioarsenic complexes.
Other metalloids, such as selenium and antimony, that
occur in mine water, though more infrequently, as oxyanions, can also be removed effectively by adsorption onto
iron oxy-hydroxides, such as schwertmannite [46,47]. The
fact that this ferric iron mineral can be readily produced
from ferruginous mine waters in a relatively pure form (as
described above) presents the opportunity in many situations of generating an effective agent for AMD remediation
from the mine water itself [48].
Water treatment
bioremediation system can be much reduced and operating
costs minimised, which is one of the constraining factors in
using active biological technologies to mitigate AMD [38].
Conclusions
Recent developments from research carried out with solid
and liquid mine wastes have led to new opportunities to
use biotechnology to secure reactive mine tailings and to
selectively remove metals and other contaminants from
mine drainage waters. New possibilities for the ecological
engineering of mine wastes, based on mimicking environments that display natural attenuation, and that can limit
15
VEGA has a ‘specialist’ sensor for all
level measurement of water and sewage
Water treatment
acid production and metal-mobilization in reactive mineral
tailings, have been proposed and demonstrated at the
laboratory scale. Active biological remediation systems allow metals to be recovered and recycled, rather than to be
disposed of in mixed-metal sludges (from active chemical
treatment), or in spent composts (from mine water passive
treatment). Using empirical engineering, microbiological
systems can be used to selectively capture (by bio-mineralization) individual metals from mine process waters and
acid mine drainage. Capturing and recycling metals from
mine waters also avoids the necessity of storing metal-rich
sludges and composts produced in current remediation
approaches, which have the inherent risk of remobilisation
of metals and further contamination of the environment.
Conflicts of interest
The author declares no conflict of interest.
References
A list of references for this article is available from the editor, Glynnis Koch, at [email protected]
© 2014 by the author including all illustrative material. This
article is an open access article and is published here with
kind permission of the author and publishers/licensee MDPI,
Basel, Switzerland (www.mdpi.com/journal/minerals) (ISSN
2075-163X).The article first, appeared in, Minerals, 2014, 4,
279-292; (doi:10.3390/min4020279). z
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17
Thinking like Sherlock Holmes
for process filtration technology
selection
by Barry A Perlmutter, President & Managing Director, BHS-Sonthofen Inc, Filtration, Mixing &
Recycling Divisions, Charlotte, North Carolina, USA
Sherlock Holmes and Dr John Watson are
fictional characters of Sir Arthur Conan Doyle.
Process engineers who live in the real world
can learn many things from the two of them
for solving process filtration problems. This
article will intertwine the detective techniques
(mindfulness, astute observation, logical
deduction and others) of Holmes and Watson
with the problem-solving skills required to
select process filtration systems.
O
ne example that Holmes proves time and again
is that there is no benefit to jumping to conclusions. The article begins with a discussion of
the bench-top laboratory tests that are conducted for
problem analysis, technology selection and scale-up.
The tests include pressure/vacuum/centrifugation,
filter media, cake thickness, temperature and viscosity concerns, filter aids and similar process parameters.
Another technique used by Holmes and Watson is ‘recreating events’. Holmes deliberates on his theories aloud to
Watson; only then do gaps and inconsistencies that were not
apparent before, rise to the surface. The article continues
with four case history examples discussing slurry testing
and process analysis, followed by process filtration selection for pressure filtration, vacuum filtration, centrifugation
and clarification.
Finally, the article concludes with a general review of the
problem-solving skills of Holmes and Watson such as the
‘occasional silence’, ‘employing distancing’ and ‘learning to
tell the crucial from the incidental’. These skills can be used
by process engineers as a framework for ‘idea-generation’
when analysing an operating bottleneck issue or new
process development problem. In all cases, by combining
Holmes and Watson with accurate lab and pilot testing, the
optimum filter selection can be realised.
Laboratory testing and why there’s no
benefit to jumping to conclusions
According to Holmes and Watson, it is important to train
yourself to be a better decision maker. For example, using
18
checklists, formulas and structured procedures are your
best bet.
Overview of bench-top testing for pressure
and vacuum filtration
The BHS bench top testing is conducted using the BHS
Pocket Leaf Filter, as shown in Figure 1 on page 20. The
test device is a BHS pocket leaf filter with a filter area of
20 cm² and a vacuum and pressure connection. The testing will analyse cake depths, operating pressures, filter
media, washing and drying efficiencies and qualitative cake
discharge. The data collection sheets are shown in Figure 2
on page 20. The steps in filtration testing are as follows:
First, it is necessary to clearly state the process description. This includes the slurry characteristics (particle
size distribution, particle shape, density, etc), washing of
the cake (ie, number of washes and wash ratios), drying/
pre-drying of the cake (vacuum, pressure blowing, and
mechanical pressing), as well as the upstream and downstream equipment. With this definition, the type of samples
that need to be collected and analysed can be determined.
Secondly, it is necessary to know what the requirements
are for the operation, such as, for example, solids/hour and
cake quality (percent moisture, percent contaminants, etc).
Thirdly, with the above in mind, the testing pretty much
determines the following objectives:
• Choice of a suitable filter cloth
• Vacuum or pressure filtration
• Wash ratios for the washing of the filter cake
• Drying techniques.
Separation/filtration
Petrochemicals
technologies
Overview of bench top testing for
centrifugation
Centrifugation lab testing includes a static settling test, a
filtration rate test and a spin settling rate test. The settling
test will be able to determine the densities of the solid and
liquid phases and if there are different densities, then centrifugal forces may be applicable for separation.
The filtration rate tests are conducted with the BHS
pocket leaf filter using vacuum. Depending upon the vacuum
filtration rates, the type of centrifuge can be determined.
Finally, the spin rate test will determine the effect of
G forces and the time to separate the slurry into distinct
phases. A bench-top test tube spinner is used for these
tests. The baseline testing is at a time of 90 seconds.
In summary, if none of the three lab tests produce a
satisfactory separation, then another type of solid-liquid
separation technology is required.
Process filtration selection for
pressure filtration, vacuum filtration,
centrifugation and clarification
According to Holmes and Watson, it is easy to succumb to
certainty, but every time you find yourself making a judgement upon observation, train yourself to stop and repeat.
Then go back and restate from the beginning and in a different fashion and, most importantly, out loud instead of
silently, as this will save you from many errors in perception.
Process engineers can benefit from discussing options with
technology suppliers who can provide different filtration
solutions.
Case History: Pressure filtration
Process testing was conducted at the site’s laboratory and in
the plant. For the bench-top lab testing, the BHS pressurized
pocket-leaf filter (PLF) with 20 cm2 of filter area was used. For
the continuous pressure pilot testing, a pilot RPF with 0,18 m2
of filter area is installed, as shown in Figure 3 on page 21.
The objectives of the PLF testing are as follows:
•Filtration time vs. filter media
•Filtration time vs. slurry feed mass
•Filtration time vs. differential pressure
•Filtrate quality vs. filter media
•Cake solids wash time and quality
•Cake solids discharge characteristics
•Production scale-up and process guarantee.
The lab testing proved to be uniquely challenging both to
feed the PLF as well as to maintain a pressure to keep the
gas as a liquefied solvent. The plant engineers and BHS
developed a confidential method to meet these challenges.
The PLF tests demonstrated that acceptable filtration
and solids wash rates could be obtained for this product
and acceptable solids levels were observed for the mother
liquor filtrate. Washing results and drying quality parameters
were also achieved.
Additional pilot plant tests with the BHS continuous
pilot unit, RPF 0,18, are recommended to confirm the
PLF lab tests. In these tests, BHS would be able to
identify the necessary slurry solids percentage, cake
solids thickness, solids wash time, solids drying time
as well as cake discharge. Finally, the pilot testing will
be the basis for the mechanical design of the RPF to
19
Customer:
Customer:
Test Number:
Run #
Date :
Wash Material
Filter Media
Wash 3
Suspension
Filling
Time for Filtration
Pressure/Vacuum
Temperature
% Solids in Feed
Drying
Flow Rate
Pressure/Vacuum
Time for Drying
Volume of Filtrate
Pressing Pressure
Time for Filtration
Weight
Thickness
Wash Material
Cake
% Residual Moisture
Pressure/Vacuum
Dry Cake Weight
Volume of Filtrate
Cake Discharge OK?
Time for Filtration
Wash Material
Wash 2
Volume of Filtrate
Density of Slurry
% Solids in Filtrate
Wash 1
Pressure/Vacuum
Volume of Slurry
Temperature
Filtration
Test Number:
Figure 2: Data collection sheet
for BHS Pocket leaf filter
Pressure/Vacuum
Volume of Filtrate
Time for Filtration
Figure 1: BHS Pocket leaf filter To fully evaluate the RPF performance, the site also
compiled the following:
• Slurry solids concentration
• Filtrate quantity (mother liquor, wash, blow down, etc)
• Filtrate yield
• Cake moisture
• Total cake quantity.
ensure that the RPF can be designed for the process with
a liquefied gas slurry.
While the actual data is confidential, the plant engineers
and BHS process engineers gathered the following parameters from the pilot RPF 0,18 m2 testwork.
Process parameters:
• Slurry feed pressure:
• Slurry feed flow:
• Wash pressure:
• Wash flow:
• Dry pressure:
• Drying air flow:
RPF parameters:
• Drum speed:
• Separating elements:
• Cake blow back:
• Cloth blow back:
• Backpressure:
• Cake thickness:
• Filter cloth:
20
Scale-up from RPF 0,18 M2 pilot data
• Calculate specific filter performance from pilot testing
• = kg of dry solids/m2/hour
• Calculate production area required from filter performance and client • Required production rate
• Using the drum speed, time for filtration, washing and
drying and several other RPF factors, the specific filter area is calculated.
Pressure filtration and typical scale-up
calculation – example only
The scale-up is based on 224 g slurry with 1:1 composition
= 112 g dry solids:
Drum revolutions:
s
3600
h . 270° . 0,85 = 85 revolutions
n=
4
8
+
+
h
(
) s 360°
270°:
0,85:
active angle
factor for separating elements
Specific filter performance:
Q = 500
1
1
kg dry solids
⋅ 85 ⋅ 112g = 4760
2
m
h
m2 . h
Separation/filtration
technologies
Figure 3: BHS rotary pressure filter, RPF 0,18 M2,
pilot filter
Figure 4: Pilot vacuum belt filter layout
Required filter area:
kg dry solids
20000
h
A=
= 4,2 m2
kg dry solids
4760
m2h
Selected filter: BHSRotary Pressure Filter, type B16 with
5,4 m² is sufficient to operate 20 000 kg dry solids per hour.
Case History: Vacuum filtration
Bench-top laboratory tests are valuable in selecting a solid/
liquid separation device. The initial lab tests suggested a
vacuum belt or rotary filter would achieve cake quality equal
to or better than the current centrifuge with a major reduction in processing time. The footprint would be comparable
to the current centrifuge and the unit would be suitable for
conversion to a continuous process. After further discussions, the decision was to select a vacuum belt filter for
pilot testing ( Figure 4).
There are five objectives in running a pilot test filter:
1.To verify the time for formation of the cake and the initial
saturation prior to dewatering of the cake;
2.To evaluate the effect of cake thickness on the dewatering time;
3.To investigate alternate ways to improve cake dryness
(ie, compression, gas blowing) that may eliminate the
drying step;
4.To evaluate the quality of the cake (dryness) and its effect
on release from the filter media. (Some initial tests would
be required to make an initial selection of the cloth, but
2-3 cloths may need to be tested in the pilot unit to verify
release characteristics.)
5.To evaluate wash ratio needed to remove solubles and
colour bodies.
The initial laboratory test data suggested a full-scale filter
with from 0,5 to 1,5 m2 of filter area would fit into the current process operations and reduce cycle time in half or
better. A BHS 0,1 m2 vacuum belt filter is available for the
test, which would allow for a feed rate of 0,5 gpm.
Suggested testing order and condition changes:
1.Using a pocket filter and various samples of cloth, pull a
vacuum of 20 in.hg. until no liquid is flowing. Invert the filter and observe the cake release. Describe it qualitatively
(soupy, chunks, fine powder). Scrape out any remaining
material and weight it separately from the material that
was released. Select 2-3 cloths for the pilot testing from
these tests (optional). During the experiment measure
Figure 5: Dry cake after discharge
how much time it takes for the cake surface to become
dry and the dewatering time.
2.The estimated filtrate throughput for a 7 mm cake during cake formation and at the end of cake formation for
vacuum filtration. Since there are 10 zones, in the BHS
filter, samples from the second or third zone would be
taken to evaluate the moisture after cake formation (dry
surface). It may be necessary to stop the unit for this
evaluation so it should only be done occasionally. Cake
thickness can be checked at this time. The other zones
can be sampled to determine the rate of dewatering after
cake formation and wash ratio.
3.A wash ratio comparable to the centrifuge operation
should be used for the previous tests. In the next series,
the wash ratio could be varied to evaluate removal of
solubles as well as the effect on cake stickiness.
4.While maintaining the same cloth rate, the feed rate can
be increased and decreased to vary the cake thickness.
5.Throughout these tests the visual quality of the cake,
especially at the discharge would be evaluated.
The test unit has an optional compression zone that could
be employed. It is also possible to evaluate gas blowing with
and without compression.
The results of the testing is that the BHS continuous-indexing vacuum belt filter will be able to produce a cake with better
washing and drying compared with the existing centrifuge.
Case History: Centrifuge selection
The choice of centrifuges (filtering or sedimentation) is
dependent upon particle sizes, density of the solids and
liquids and the process and application. Filtering centrifuges have a rotating perforated basket or bowl with filter
media while sedimentation centrifuges have a rotating
non-perforated bowl.
The initial testing is as follows:
• Preliminary data to determine centrifuge type and the
initial parameters for pilot tests
• Bench centrifuge tests
• Filter bucket (specialised filtration bucket)
• Vacuum filtration (Buchner or pocket filter)
• Cake moisture versus G-force and time
• Effect of cake thickness on time to reach moisture goal
• Effectiveness of wash
• Optimising conditions (extensive pilot tests)
• Evaluate ways to avoid cake cracking
• Sliding and conveying properties of cake (shear).
21
Separation/filtration technologies
In terms of filtering centrifuges, the choices are between
batch and continuous feed. Continuous feed and liquid flow
can be either continuous moving cake or intermittent moving cake. As for batch feed (fixed cake, batch liquid flow), the
choices are the type of feed (vertical, inclined, horizontal
axis) and the type of discharge.
Major differences between the filtering centrifuges are:
Batch
• Clear liquid
• Cake heel
• Wider size and feed concentration range (100 ppm to
50 %)
• Can be inerted
• Can be used at high temperature.
Continuous
• Liquid clarity poor
• Total discharge
• Feed > 15 %
• Best above 10 micron
• Not suited for volatile liquids and hazardous or abrasive solids
• Operates at ambient temperatures.
Why select a filtering centrifuge:
• Drier cakes than other centrifuges (generally)
• Compact relative to their throughput
• Fully automatic operation
• Particles from 1 micron to 2 mm (coarse – best)
• Fragile solids may have attrition issues
• Wide range of feed concentrations (non-abrasive solids)
• OK for moderately hazardous solids and volatile liquids
• When low moisture required
• Minimal washing required
• High in first cost; gives moderate clarity to the liquid.
Why not select a filtering centrifuge:
• If the solids are only required in slurry form
• If coarse solids will screen or free drain to the necessary
moisture content
• If fine compressible solids are to be filtered, washed
and dried
• If coarse to medium sized solids have exacting washing
requirements but require only moderate dewatering
• If feed solids content is low and the particles are very fine
• If the use of filter aid is contemplated.
As for sedimenting centrifuges:
• Uses difference in density to separate solids
• Also used to separate liquids
• Has limited washing capability
• Wide range of feed concentrations
• Requires uniform feed
• Potential for particle breakage
• May have more wear than filtration devices
• Often wetter cake produced.
In summary, the centrifuge selection depends upon the
process characteristics and the laboratory testing to select
the type and design.
Case History clarification: Replacing
a manual plate filter and bag filter
combination
This specialty chemicals manufacturer produces various
resins that require filtration. Current production includes
22
a neutralisation step which yields metal salts. These salts
are filtered out with a manual plate filter followed by a bag
filter for polishing. Two solvent washes follow the filtration
step to recover as much resin as possible. After washing,
the filters are steamed and opened. The solids are disposed
manually for each batch and the filter paper is replaced.
The goals are to eliminate exposure to heptane, to reduce
the maintenance and operation on the two filters and to
recover a dry catalyst. Current production is 3 000 gallons
in 4 – 5 hours.
The results and conclusions showed that the filtration
flux rate from the BHS laboratory tests ranged between
10-30 L/m²/min at approximately 20 psi feed pressure.
The sock filter cloth is polyester with an air permeability
of 1,0 cfm/ft².
The tests showed that one BHS candle filter, Figure 5,
with 10 m² of filter area can complete the cycle in 4,3 hours
and replace the manual plate filter and bag filter.
The cycle time is as follows:
Cycle Times
Filling
5
min
Filtration
10
min
Wash
4
min
Drain
10
min
Dry
5
min
min
Vent
2
Discharge
5
min
Reserve
9
min
TOTAL
50
min
Concluding remarks and takeaways
Holmes and Watson provide a unique view of problem solving. The world of a process engineer is a distracting place
and Holmes and Watson know that without the occasional
silence, as in The Hound of the Baskervilles, there can be
little hope for success. Engineers can benefit from conducting lab testing at the technology supplier’s site to have time
to think about the process issues at hand.
Finally, Holmes and Watson excel at ‘deduction from
facts and deduction difficulties’. All that matters is what the
premises are (process definition, requirements and testing
objectives) and how the testing unwinds the crucial from
the incidental (what is the critical process parameter) and
finally ending up in the logical conclusion (optimum process
filtration solution).
In summary, it is important to put the project together
from many different perspectives. These include knowing
the process, observing the testing, deducing the solution
only from what is observed (and nothing more), and learning
from your colleagues and the technology supplier’s successes and failures. It is always difficult to apply Holmes’
logic, but as Holmes’ states: “You know my methods, now
apply them.” Engineers must practise these habits such that
even under stress to solve a process problem, these stressors will bring out the very best thought patterns needed.
References
For list of references contact the editor at
[email protected] z
FOCUS ON SEPARATION/
FILTRATION
R300 million investment in ASU adds value to Eastern Cape gas market
Eastern Cape ASU
A substantial R300-million investment in
a new state-of-the-art air separation unit
(ASU) in Port Elizabeth by Sub-Saharan
African gas market leader Afrox, is set to ensure a more reliable supply of atmospheric
gases to the Eastern Cape market, while
stimulating growth for existing customers
and suppliers in the region.
The project was approved by Afrox and
its parent company Linde in 2012. An official sod-turning ceremony was held on 11
February 2014,and the project is now more
than 75 % complete, states Afrox managing
director, Brett Kimber. “The ASU will improve
security in the supply of oxygen, nitrogen
and argon – all critical process components.
It will stimulate regional growth, by reducing
local distribution and delivery turnaround
times.”
According to Kimber, the majority of the
plant’s civil work is nearing completion, and
the ASU is expected to be fully operational
during the first quarter of 2015, as planned.
“One of the major milestones was the arrival of the cold box and storage vessels
in August 2014, which were then installed
within one month.”
The cold box is recognised as the
heart of an ASU, and is the central point
where proprietary technology is utilised
to cryogenically separate ambient air into
nitrogen, oxygen and argon. The Afrox ASU
cold box was designed and manufactured
in Germany by the Linde Group. It weighs
over 100 tons, and is 40 m in height, 5 m
in width and 4 m in breadth.
Due to the sheer size of the cold box,
Kimber admits that a number of logistical challenges have been encountered
in Germany and South Africa. “The major
Efficient fuel processing on board with GEA’s CatFineMaster
GEA Westfalia Separator Africa, part of the
GEA Westfalia Separator Group and industry
leaders in separation technology, recently
launched the new CatFineMaster with intelligent control.
This process is reported to be the first
solution available on the market that ensures maximum reduction of dangerous
catalyst fines (cat fines). The new system is
set to change the off-shore drilling industry
by adding new levels of efficiency to fuel
composition, by a simple touch of a button.
Comprised of silicon and aluminium
compounds, cat fines are utilised in the production of petrol and other fuels from crude
oil. The highly-abrasive nature of these fines,
however, can cause engine damage and
in extreme situations, can result in total
component failure in the refining process.
GEA Westfalia Separator Group has addressed this with the new CatFineMaster
– the first process of its kind that is able to
reduce cat fines while performing efficient
and reliable fuel processing on board.
It consists of a separator as the core element, as well as an adjustable feed pump,
and targets a cat fine concentration of less
than 5 parts-per-million and separation of
all particles larger than 3 micro-metres.
The adjustable feed pump provides
optimum control of the flow quantity of the
heavy fuel oil according to process requirements.
The CatFineMaster is equipped with IO
control units – a new generation of intelligent control technology.
This IO is designed for maximum ease of
operation in which centrifuge regulation is
easily monitored and controlled according
to the specific process requirements of the
application at hand.
challenges include shipping routes and
schedules, abnormal road transport to
and from port in both countries, as well
as rigging and availability of cranes,” he
continues.
Looking to the future, Kimber believes
that the investment in the ASU is set to
become the catalyst for industrial growth in
the Eastern Cape. “Although the ASU will not
have a direct impact on the local community,
its existence will support the development of
opportunities and industrial growth, which
will have a profound impact on the local
economy,” he concludes.
For more information contact Simon Miller,
Corporate Communications Manager, on
tel: 11 490 0466, cell 082 8915149,
email: [email protected], or go
to www.afrox.com z
For more information contact
Taryn Browne, on tel: +27 11 805-6910,
email [email protected] or go to
www.westfalia-sa.co.za z
The new GEA 3882 CatFineMaster with
intelligent control is the first solution on the
market that reduces dangerous cat fines
while performing efficient fuel processing
on board.
23
FOCUS ON
SEPARATION/FILTRATION
Sun Silicates expands facilities for manufacture
of perlite filter media
The perlite plant
Perlite grains
Sun Silicates is a privately owned, local manufacturer of perlite-based filter
media. The company is located in Wadeville, Germiston. Its owners have
been in business for more than ten years, and have recently expanded
its manufacturing facilities to include an exfoliation plant. The company is
managed by its owners who are engineers with many years of experience
in related metallurgical industries.
In this perlite plant, at elevated temperatures, the perlite grains partially
melt. At the same time the entrained moisture expands, creating microceramic bubbles. After this process the bubbles are rapidly cooled and solidified.
Sun Silicates manufactures a full range of perlite filter media. These
products are used in various applications such as the filtration of beer,
wine, fruit juices and a variety of oils. In addition to this, Sun Silicates also
supplies the insulating grades. These grades are used in the refractory as
well as hydroponic industries. Perlite excels in these applications due to its
high melting point, low density and chemically inert nature.
Raw materials are imported and exfoliated in the brand new, ‘state-of-theart’ plant that is fired by natural gas. This ensures food safety compliance
and low cost of manufacture. The company is in the process of registering
as an ISO 9001/2008 and 22000 compliant, processing facilities.
Sun Silicates manufacture a wide range of other products, such as potassium silicates that are used in the manufacture of welding electrodes as well
as in the agricultural field. Extensive laboratory facilities enable Sun Silicates
to ensure process and product compliance. It also enables the technicians to
develop new or modified products for the company’s clients’ specific needs.
It is the company’s vision to supply technology driven products at competitive prices, while supplying hands-on customer-focused technical service.
For more information contact Gerbrand Haasbroek, Managing Director, on
tel: +27 11 824 4600, cell +27 83 7003970,
email [email protected], or go to www.sunsilicates.co.za z
SAIChE general news
SAIChE Journal of Chemical Engineering
SAJChE 2014: Vol 19 is out now and is available
on the SAIChE website.
The titles of the papers that are available
online are listed below:
•Modified coconut fibre used as adsorbent
for the removal of 2-chlorophenol and
2,4,6-trichlorophenol from aqueous solution.
(P. Ojha, S. Rathilal and K Singh)
•Reduction of sulphur in crude tyre oil by gasliquid phase oxidative adsorption. (T.Pilusa,
E. Muzenda and M Shuklai)
•Heterogeneous photocatalytic degradation
of naphthalene using periwinkle shell ash:
effect of operating variables, kinetic and
isotherm study. (F. Aisien, A. Amenaghawon
and M. Assogba)
•Saccharification of bamboo by dilute acid
pretreatment and enzymatic hydrolysis for
cellulosic ethanol production. (H. Cheng, J.
Görgens, P. Macintosh, M. Garcia-Aparicio
and E. du Toit )
SAIChE
CPD approved courses
Detailed brochures available at http://www.
saiche.co.za/ (under ‘Diary Events’)
•The Institution of Chemical Engineers
(IChemE) “Fundamentals of Process Safety
Management” course is being held at the
Birchwood Hotel, Boksburg from the 3 to
7 November 2014. For more information
go to http://www.icheme.org/fpsm (CPD:
4 credits)
•Cape Peninsula University of Technology in
association with the Fossil Fuel Foundation
and SAIChE present “An Introduction to the
Petroleum Industry”. This will be held on the
6 October 2014 at the Townhouse Hotel, 60
Corporation Street, Cape Town. For bookings,
email: [email protected], before 30 September 2014. (CPD: 5 Credits)
•Courses by RESOLVE (CPD: 3 credits each)
1.Risk Management Practice Training Workshop presented at:
• Durban: 03 to 05 December 2014 - Register before 31 October 2014
2.Hazard and Operability (HAZOP) Training SAICHE NEWS
SAIChE contact details
PO Box 2125, NORTH RIDING, 2162
tel: +27 11 704 5915;
fax: (0) 86 672 9430;
email: [email protected];
website: www.saiche.co.za
Courses presented at:
•Durban: 29 to 31 October 2014 - Register
before 30 September 2014
•Cape Town: 19 to 21 November 2014 Register before 30 September 2014
All these courses will be registered with the Engineering Council of South Africa as Continued
Professional Development Activities. There is
a maximum number of attendees for each of
the courses and early registration is advised to
prevent any disappointment.
Enquiries about any of these courses or other
training needs should be forwarded to Lettie
Hauptfleisch at [email protected] or
fax: 0865 477 846 or visit
http://www.resolvekzn.co.za (under ‘Scheduled Events’).
ECSA mentors required
When members register with ECSA as candidate engineers, most require a mentor who is
already registered as a professional engineer
(Pr.Eng). Contact the SAIChE office if you are
willing to assist and to discuss further. z
25
High temperature shape
memory polymer
by Ying Shi and R A Weiss, University of Akron, Akron, Ohio, USA
A high switching temperature shape memory
polymer system was developed from metal
salts of sulphonated polyether ether ketone
(PEEK) ionomer and ionomer/fatty acid salt
compounds. This showed moderate shape
memory behaviour, but compounds show even
more promising shape memory behaviour.
http://www.diamondmattress.com/
T
hermally-actuated shape memory polymers (SMP)
change shape in a predefined manner when exposed
to heat. The shape memory effect depends on a
combination of the polymer structure, morphology, and the
applied processing and programming technology [1]. Thermally sensitive SMPs have either a covalently cross-linked
or physical cross-linked structure as a permanent network
and a lower temperature reversible physical transition, eg,
vitrification, melting or microphase separation, as a temporary network. The thermodynamic origin of shape memory
is the shape change that accompanies a conformational
entropy change at the transition temperature (Tc)². The
flexible components can be stretched with a loss of entropy above the transition temperature and they become
oriented. Elastic strain energy is stored by the temporary
crosslinked structure during shape fixing. The material
returns to its most disordered conformation and gains
back the entropy lost when the stored energy is released.
As a result, the material is able to recover to its original
shape. Shape memory polymers are lightweight, can be
deformed to high strains, and it is relatively easy compared
with shape alloys to tailor the transition temperature [3-5].
The development of thermally sensitive shape memory
polymers has focused primarily to relatively low transition
temperature (Tc < 100°C) and elastomeric polymers, such
as thermoplastic polyurethane elastomers (TPU), crosslinked polyethylene, poly(ε-caprolactone), sulphonated
EPDM and polynorbornene [6-10]. These materials are appropriate for applications such as biomedical and surgical
26
materials, smart fabrics and heat shrinkable tubing [11].
Materials used as aerospace components often require
higher switching temperatures for shape change and actuation. There has been research on high temperature SMPs
based on thermoset polymers systems. For example, Mather
and Liu described a castable, transparent crosslinked SMP
with a switching temperature between 20 and 110°C [12].
Tong developed a maleimide based crosslinked thermoset
SMP with switching temperature form 150 to 270°C [13].
Gao et al [14] reported an epoxy polymer modified with
poly(ether ether ketone) that exhibited shape memory
behaviour at 150°C, but that material relied on a thermoset polymer. To the best of our knowledge, there have
been no reports of thermoplastic SMPs with controllable
switching temperatures above 100°C. This current paper
describes the development of thermoplastic, high switching
temperature SMPs based on sulphonated poly(ether ether
ketone) with Tc’s as high as 270°C that may be suitable for
aerospace applications.
Materials
PEEK powder with a Mw = 96 000 g/mol was purchased
from Victrex (Grade 450PF). Sulphonated PEEK (SPEEK)
was synthesized by dissolving 10 g PEEK power into 250 mL
concentrated sulphuric acid (95-98 %) with vigorous stirring
at 40°C for 5 hours [15-16]. The SPEEK was precipitated
by drop-wise addition of the solution into rapidly stirred deionized water at 0°C. The product was filtered and washed
repeatedly with de-ionized water until the pH was about 7.
Petrochemicals
The final product was dried in a vacuum oven at 180°C for
24 hours. The sulphonation level was determined by the
titration of the sulphonic acid groups [17]. The degree of
sulphonation, defined as the average number of sulphonate
groups per repeat unit, was calculated as 18 %.
The sulphonic acid derivative of SPEEK was converted
to either Na-SPEEK or Zn-SPEEK by neutralisation with a
2-fold excess of sodium acetate or zinc acetate. The 18 %
sulphonated PEEK was swollen by water, but did not dissolve in water. A slurry of SPEEK in distilled water containing
either sodium acetate or zinc acetate was stirred for 24 h
at 100°C, then washed with water and methanol to remove
the excess metal acetate. The Na-SPEEK and Zn-SPEEK
ionomers were then filtered and dried under vacuum at
120°C for 24 h. The temperature was then increased to
180°C for 2 hours to remove most of the remaining solvent.
Film samples of M-SPEEK and shape memory compounds of 70 parts M-SPEEK and 30 parts sodium oleate
(NaOl, assay >99 %), obtained from Aldrich Chemical Company, were prepared by dissolving the M-SPEEK and NaOl in
refluxing N-methyl-2-pyrrolidone (NMP). The sample notion
used in this paper is MSPEEK/NaOl (30 %), where M stands
for different cation and 30 % denotes the weight percentage of NaOl in the compound. The solution was cast onto a
clean glass plate and then dried at 80°C for 48 h to remove
most of solvent. The film samples were dried at 150°C
under vacuum for 24 h prior to characterization. PEEK film
was also prepared for comparison by compression molding.
The glass transition temperatures (Tg) and melting
temperatures (Tm) were measured with a TA instruments
differential scanning calorimeter (DSC) Q200 using a nitrogen atmosphere, and heating and cooling rates of 10°C/
min. The thermal stability of the materials was measured
using a TA Instruments Q50 thermogravimetric analyzer
(TGA) from room temperature to 800°C with a heating rate
of 20°C/min in nitrogen atmosphere. The tensile stressstain behaviour was measured with an Instron model 1101
universal testing machine using a 100 N load cell. Film
samples were cut into dog-bone specimens with gauge
length dimensions of 7,3 × 3,3 × 0,3 mm. The tests were
conducted at room temperature with a crosshead speed of
2 mm/min. The viscoelastic properties of films were measured with a TA Instruments dynamic mechanical analyzer
(DMA) Q800. The film sample was deformed in the tensile
mode with an oscillatory strain (0,1 %), a frequency of 1 Hz,
and a temperature ramp from room temperature to 300
°C of 3 °C /min. Shape memory cycles to assess fixation
and recovery ratio were measured using the controlled
force mode of the DMA.
Result and discussion
Thermal properties of M-SPEEK and
M-SPEEK/NaOl compounds
The parent PEEK was a semicrystalline thermoplastic polymer with a Tg of 148 °C and a Tm of 338°C. The thermal
transitions of the starting materials, the SPEEK ionomers
and the SPEEK/NaOl compounds are listed in Table 1.
Sulphonation increased Tg, lowered Tm and reduced the
27
Table 1. Thermal characterization of materials
Materials
NaOl
Tg of the M-SPEEK
b T of the NaOl
m
c Crystallinity of
neat PEEK, which
is calculated
from ΔHexperiment/
ΔHliterature
a
PEEK
q/a
--
Tg (°C)a
--
Tm
(°C)
Relative
crystallinity (%)
259
--
148
181
--
--
0,91
229
--
--
H-SPEEK
Na-SPEEK
Table 2 Tensile Properties of M-SPEEK and MSPEEK/NaOl Compounds
338
30,4c
Zn-SPEEK
2,86
253
--
--
NaSPEEK/NaOl(30%)
0,91
176
256b
36.3
ZnSPEEK/NaOl(30%)
2,86
208
250b
47
b
Materials
E (MPa)
σu
PEEK
2368±45a
87±6
(MPa)
c
εu
(%)
6.8±0.06
Na-SPEEK
1556±56
43.3±8
9.3±0.09
Zn-SPEEK
2159±27
60.7±6
15±0.02
Na-SPEEK/
NaOl(30%)
921±87
44.2±11
24±0.08
Zn-SPEEK/
NaOl(30%)
1314±54
39.3±2
45±0.05
standard deviation
(5 specimens were
tested for each
sample)
a
b
property at yield
c
property at break
Figure 2 Engineering tensile stress versus strain for neat PEEK,
M-SPEEK and M-SPEEK/NaOl (30 %) compounds
Figure 1 Thermogravimetric analysis of pure PEEK, H-SPEEK, M-SPEEK and
M-SPEEK/NaOl (30 %).
crystallinity. For 18 % sulphonation, SPEEK was completely
amorphous and the Tg was 181°C. The Tg increase is a
consequence of the restriction of segmental motion by
intermolecular hydrogen bonding for the acid derivative and
dipole-dipole interactions for the salts.
The Tg of the two M-SPEEKs increased with increasing
Coulomb energy of the ion-pair, which is related to the ratio
of q/a, where q is the cation charge and a is the ionic radius
(see Table 1). This is a consequence of stronger interactions of the ionic dipoles as the electrostatic interactions
increase. Thus, Tg of the M-SPEEK ionomers, which can be
used as an activation temperature for a SMP, can be varied
over a wide range – in this case from 181°C to 253°C –
simply by changing the cation used. Further control of Tg can
be achieved by varying the sulphonation level.
The addition of NaOl to the M-SPEEK reduced the Tg of
the composite films by close to 20 %, which indicates some
miscibility of the fatty acid salt and the ionomer. That was
not unexpected, since other studies of compounds of fatty
acids or fatty acid salts and ionomers reported some miscibility [18-20]. The partial miscibility of the two components
is also suggested by the lower relative crystallinity of the
NaOl in the compounds as seen in Table 1. The relative
crystallinity of NaOl in the compounds was estimated from
the ratio of ΔH/ΔHNaOl, where ΔH was the measured value
28
for NaOl in the compound and ΔHNaOl was the corresponding
experimental value for the neat NaOl. Based on previous
work on compounds of fatty acid salts and ionomers, these
observations are interpreted as a consequence of strong
dipolar interactions between the dispersed fatty acid crystals and the ionomer. Previous studies [18,19] have shown
that such strong interactions can be exploited to provide a
robust physical and thermally reversible network for an SMP.
PEEK is thermally stable up to ~500°C, see TGA data in
Figure 1. Degradation occurs in a single step above 520°C,
which is due to random chain scission of the ether and ketone bonds leading to volatile fuel formation. The pyrolysis
left about 50% char at 700°C, which is consistent with the
results of Patel et al. [21] Sulphonation of PEEK reduced
its thermal stability due to desulphonation below 300°C.
In general, the metal salt ionomers were thermally stable
to ~290°C, while the sulphonic acid derivative exhibited
mass loss at ~260°C. NaOl is thermally stable to ~400°C,
so the stability of the sulphonate group is the limiting component in the compounds. The reduction in the stability of
the compound by the introduction of the sulphonate group
is a concern with respect to developing a high temperature
SMP and indicates that these compounds will have limited
utility above 300°C.
Mechanical properties of M-SPEEK and
M-SPEEK/NaOl (30 %) compounds
The Na-SPEEK and Zn-SPEEK films were brittle, but the
composite films were flexible at room temperature. Example
engineering tensile stress versus strain curves for the neat
ionomers and the compounds are shown in Figure 2, and the
Shape memory behaviour
PEEK has been developed as a shape memory device in
biomedical research [22], but the shape memory effect
was triggered by mechanical force. We aim to develop a
high switching temperature shape memory polymer system
that is suitable for the application in aerospace. The shape
memory behaviour of PEEK by thermal activation was
studied as shown in Figure 3. PEEK crystals provided the
permanent network and the switching phase is glass transition. The shape fixation and recovery ratio were calculated
using Lendlein’s equation [1].
Rr =
Rf =
εm − εp (N)
εm − εp (N − 1)
εu (N)
(1)
(2)
εm
Where, εm: is the maximum strain that the material was stretched,
εp(N): is the permanent strain in the Nth cycle,
ε u: is the stain in the stress-free state after the retraction of the stress in the Nth cycle.
PEEK can only recover 35 % strain and only 28 % deformation was fixed by the temporary network. The poor shape
memory behaviour arises from its high crystallinity (~30 %).
The creep of permanent network occurs during test programming. sulphonation and neutralisation of PEEK can
dramatically reduce its crystallinity. Our 18 % sulphonated
M-SPEEK polymer is amorphous and its films show better
shape memory behaviour. Neutralization of the sulphonic
acid groups in SPEEK to a metal salt, such as –SO3-...Zn2+
(Zn- SPEEK), provides a physically cross-linked network due
to dipolar associations of the sulphonate groups which
produce ionic nanodomains that act as multifunctional
crosslinks. The nanodomain structure provides a more
robust ‘permanent’ network than do PEEK crystallites.
Figure 4 shows a typical shape memory cycle for the neat
Zn-SPEEK. The film was heated to 270 °C, stretched to 11 %
strain and cooled under load at constant strain to 30 °C. After
equilibrating at constant strain and temperature, the force
used to maintain the strain during cooling was removed.
tensile properties are summarized in Table 2. The properties of PEEK film were also measured for comparsion. Since
PEEK is not soluble in any convenient solvent for casting
film, the PEEK film was prepared by compression moulding. Sulphonation of PEEK lowered the tensile modulus
and the ultimate stress and strain, which was mostly a
consequence of the elimination of the crystallinity in the
ionomer. Zn-SPEEK was stiffer than Na-SPEEK, which may
be a consequence of the divalent cation, which provides a
salt bridge between two sulphonate groups, as opposed to a
dipole-dipole interaction of sulphonate groups in Na-SPEEK.
The addition of NaOl to the ionomers significantly lowered
the modulus and ultimate strength, to about 40 – 50 % of
the modulus and 45 – 50 % of the yield strength of neat
PEEK film, but it also greatly improved the ductility of the
film. Those results are consistent with some NaOl miscibility
with the ionomers, which acts as a plasticiser with regard
to the mechanical properties.
Figure 3 PEEK shape memory cycle. The sample is stretched
above Tg (path 1). The deformed sample is then cooled under
stress along path 2 and the stress is removed along path 3 to
set the temporary deformed shape. The sample is heated up
to recover its permanent shape (path 4). S and E denoted start
and end of the cycle
The shape recovery was achieved by reheating the film to
270 °C. The shape activation temperature was the Tg of the
ionomer and the permanent network was developed from
strong intermolecular association of the metal-sulphonate
groups in Zn-SPEEK. The relaxation times for the network
are long enough that the nanodomain crosslinks behaved
as a permanent network in the time frame used for the experiments reported here. Zn-SPEEK exhibited better shape
memory behaviour than did Na-SPEEK, which is consistent
with the stronger Coulomb energy of the Zn-sulphonate.
M-SPEEK films exhibited excellent shape recovery, but
the shape fixing was <90%. This problem was ameliorated
by introducing a second physical network into the system,
such that two networks made up the temporary network.
The second network was achieved by adding fatty acid salt
crystals, NaOl, that were expected to interact strongly with
the ionomer. Tm of the NaOl was used as the switching
temperature. After the film was deformed and cooled below
the switching temperature, NaOl crystallizes and forms one
temporary network and vitrification forms a second network.
When heated again above the Tm of the NaOl crystals, the
film reverts to its permanent shape. For Na-SPEEK/NaOl
film, shape fixing and recovery are significantly improved
(Table 3).
As we introduced a new network into M-SPEEK, the MSPEEK/NaOl systems have two switching phases: one is the
melting of NaOl crystals and the other one is M-SPEEK glass
transition. These two separate shape-fixing mechanisms
made M-SPEEK/NaOl systems able to exhibit tripe shape
memory behaviour. Figure 5 shows three continuous tripe
shape memory cycle for Zn- SPEEK/NaOl. According to our
DSC data, Tg of Zn- SPEEK in the compounds is 208°C and
NaOl crystal melts at 250°C. There is about 40°C temperature window to programming the thermomechanical cycle.
Regarding the first cycle concerned, the film was first heated
to 270°C, which is above both transition temperatures, and
the film was deformed to 57% strain at this temperature.
The sample was then cooled to 240°C while keeping the
external force constant, during which the NaOl crystallised
29
Table 3 Shape memory properties of M-SPEEK and M-SPEEK/
NaOl(30%) compound films
Materials
Rf(%)
Rr(%)
PEEK
28
35
Na-SPEEK
74
44
Zn-SPEEK
88
98
Na-SPEEK/
NaOl(30%)
97
96
Zn-SPEEK/
NaOl(30%)
96
100
Figure 4 Shape memory cycle for Zn-SPEEK
Figure 5 Consecutive tripe shape memory cycles for ZnSPEEK/NaOl, transition temperature is 240°C for temporary
shape B and 270°C for temporary shape C
Table 4 Calculated shape fixing and recovery for Zn- SPEEK/NaOl (30%) and
Na-SPEEK/NaOl (30%) triple shape memory behaviour
Material
Cycle
Rf,B (%)
Rf,C (%)
Rr,C→B (%)
Rr,B→A
(%)
Zn- SPEEK/
NaOl(30%)
1
91
95
84
60
2
90
90
88
99
3
89
88
93
99
1
92
93
77
61
2
91
83
83
97
3
93
73
73
100
Zn- SPEEK/
NaOl(30%)
© Society of
Plastics Engineers
(SPE), USA. This
article is based on a
presentation given
at the Society of
Plastics Engineers
(SPE) ANTEC 2013
and is republished
here with kind
permission.
30
and Zn SPEEK was in its devitrified state. The external force
was then removed. This step finished the fixing of the first
temporary shape B corresponding to εB in Figure 5. There
is about 6 % strain contraction after the force removed,
which is also observed in other tripe shape memory systems
[23]. The devitrified Zn-SPEEK attempted to recover to its
equilibrium state but it was prevented by NaOl crystals.
The sample was further deformed by applying a second
force, which is much larger in our case, and a strain of 79%
was achieved. The temperature was then reduced to room
temperature while holding the external force constant. At
this step verification of Zn- SPEEK occurred and removal of
the second force after cooling led to fixing the temporary
shape C (εC). Sequential shape recovery was achieved by
heating the sample with temporary shape C to 240 °C to
recover temporary B, and further heating to 270 °C to revert
its permanent shape A. Shape fixing (Rf) and recovery (Rr)
can be calculated according to the following equations [23]:
(3)
εy − εx
Rf x →y =
ε y, load − ε x
(
Rr
(
)
y
)
→x =
ε y − ε x, rec
(4)
εy − εx
Where x and y: denote two different shapes,
εyload: is the maximum strain after applying force,
εy and εx:
are fixed strains after unloading, and
εxrec:
is the strain after recovery.
Table 4 shows calculated shape fixing and recovery ratio
of each cycle for M-SPEEK/NaOl (30 %) systems. Similar as
one way shape memory behaviour when discussed above,
the tripe shape memory cycles have a similar pattern that
causes a certain amount of permanent strain to occur
during the first cycle. It is noticed that shape recovery from
temporary shape C to B is not as efficient as that from B to
A. At first step recovery, Tg, M-SPEEK<T<Tm, NaOl, the movement of
the polymer chain was restricted by NaOl crystals. Whereas,
shape recovery from B to A is almost perfect, during which
all the crystals melt and polymer chains are free to move.
Na- SPEEK/NaOl (30 %) system displays tripe shape memory behaviour in the same manner as Zn-SPEEK/NaOl(30 %)
system. Na-SPEEK/NaOl (30 %) film has a lower Tg (176 °C),
indicating this material has a larger temperature window
to tune the switching temperate. Since the objective of this
paper is to investigate high temperature shape memory
polymer, the switching temperature for temporary shape C
was set as 230°C for Na- SPEEK/NaOl (30%) system. The
shape fixation from temporary shape B to C, where NaOl
crystallised and acted as physical crosslinkers, was not as
promising as an Zn-SPEEK/NaOl system, because there are
fewer crystals holding the permanent shape.
Conclusions
Metal salts of sulphonated PEEK show moderate shape
memory behaviour, but compounds of the ionomers with
NaOl appear to be more promising candidates for SMPs,
because they are more flexible materials and the plasticisation of Tg to lower temperatures by the fatty acid salt. In
the compounds, the temporary network is provided by a
combination of the glass transition and the dipolar interactions between metal salts and a dispersed crystalline phase
of NaOl. The permanent network provided by microphase
separation of the ionic nanophase that arises from dipolar
interaction of the metal sulphonate groups. The Tm of the
NaOl also provides a potential Tc in addition to the Tg, and
three-way shape memory behaviour is possible.
References
References for this article are available from the editor at
[email protected] z
Nature is well-known for its ability to repel
liquids with lotus leaves, rice leaves, butterfly wings, mosquito compound eyes, cicada
wings, red rose petals, gecko feet, desert
beetles, and spider silk all having the ability
to remain dry.
However, the pitcher plant or Nepenthes,
which is found in countries including Australia, Malaysia and Madagascar, has a special
adaptation which creates a near frictionless
surface with unique self-healing properties.
The ability to repel liquids and contaminants has important applications to industry
and everyday life. Coatings are needed to
help stop the formation of life-threatening
bacteria on medical instruments, ice buildup on air planes, fouling on ship hulls, anticorrosion and the efficient transportation of
products like crude oil by pipeline.
The pitcher plant is different to some
other nature-inspired adaptations by
‘locking-in’ a lubricant layer onto the surface
of its skin which cannot be penetrated by
another liquid and is more damage tolerant. The result is also fatal to the plant’s
prey – insects and small frogs – which are
unable to climb out of its smooth, deep,
tubular-shaped body.
A team at Harvard University has now
been able to mimic the pitcher plant’s inner
skin design to produce a transparent coating capable of being economically applied
to almost any object – large or small.
The multi-stage coating process involves
attaching a thin, but rough layer of porous
silica particles which are used to lock-in a
lubricating layer onto the surface to be protected. Its diverse applications could include
acting as an anti-graffiti coating on walls or
on medical implants to aid blood flow.
This latest development in coating
technology reached the finals of this year’s
Institution of Chemical Engineers (IChemE)
Awards in the UK, which recognises excellence and innovation in the chemical and
process industries worldwide.
FOCUS ON MATERIALS OF
CONSTRUCTION
Carnivorous plant inspires protective coatings
For further information contact: Tony Osborne,
communications officer, IChemE on tel: +44
(0)1788 534454 / +44 (0)7802 834459
or email: [email protected] z
Tokyo Tech scientists synthesise multicyclic type of polymers
Polymers come with a range of properties
dictated by their chemical composition and
geometrical arrangement. Yasuyuki Tezuka
and his team at Tokyo Institute of Technology
have now applied an approach to synthesise
a new type of multicyclic polymer geometry.
“This additional step will give a library of
architectures to allow systematic studies of
what properties derive from what structures,”
explains Tezuka, adding, “Mathematicians
who study these complex geometries are
also interested to know they can be made
at the nanoscale.”
Rings have very different properties to linear polymers, in particular when considering
dynamic rather than static characteristics,
such as diffusion. Tezuka adds that these
differences are amplified when moving from
single ring or linear chains to self-assembled
structures such as micelles — pompom-balllike structures of aggregated linear chains.
However the Tokyo Tech researchers
were motivated more by the geometry itself
than the possible applications. While mathematicians are interested because these
structures have not been realized before,
the geometry studies also provide insights
for chemists. “You may have two complex
structures that are so-called isomers, that
is, they are from identical starting materials
like brothers,” explains Tezuka. “The geometry tells us that the two constructions are
isomers.”
In fact the geometry of the polymer,
known as K3,3, has been a popular field of
study for mathematicians in graph theory.
©
From cited paper, 2014 (Top) The researchers developed a method combining electrostatic selfassembly and covalent fixation to construct two geometries of triply fused tetracyclic polymer
labelled (5).The products were made from molecules with several branches and two negatively
charged groups.(bottom) a scheme showing random combination of the end groups during covalent
conversion to form the two types of triply fused tetracyclic polymer.
The geometry comprises four rings (tetracyclic) fused three ways (triply fused) with an
inherently non-planar structure.
The team’s approach combines fixation
by covalent bonding with electrostatic selfassembly, which involves negatively and
positively charged molecular units coming
together, as in a salt. Salts should be insoluble in organic solvents, “But in polymer
synthesis the situation is different,” explains
Tezuka. “The polymer is a long chain, and
very hydrophobic and organically soluble.
So if you add a little salt it is still soluble.”
While a number of multicyclic polymers
have been achieved using this approach
since it was developed by Tezuka and his
colleagues ten years ago, it is not so easy
when several charged units are involved.
The team succeeded by developing special
highly branched and symmetric molecular
chemicals and adding ionic groups and
polymer chain ends.
For more information contact Professor Yasuyuki Tezuka, Department of Organic and
Polymeric Materials on tel: +81-3-57342498 FAX +81-3-5734-2876; or
email [email protected], or go to
http://www.titech.ac.jp/english/ z
31
FOCUS ON MATERIALS OF
CONSTRUCTION
Polyscope expands portfolio with XERAN®
compatibilisers
Polyscope has broadened its portfolio of XIRAN® neat resins, compounds, powders and liquids with
a range of XERAN® compatibilisers.
The maleic anhydride functionality
in these XERAN copolymers and
terpolymers makes them extremely
suitable as a compatibiliser and
coupling agent in many applications. The XERAN portfolio opens
a window to new polymer systems
that need compatibilisation, as
XERAN improves the adhesion
between two polymers which are
normally immiscible.
Additionally it optimises the
interfacial tension and offers stabilisation of the morphology against
high stresses during conversion.
The compatibilisation results in a
significant improvement of the mechanical properties, predominantly
impact performance. The styrene
based XERAN polymers are highly
suitable for compatibilising styrene
based engineering plastics.
Different immiscible polymeric
systems need different compatibilisers. The new XERAN portfolio
consists of polymers with varying
molar mass and varying maleic
anhydride functionality. Polyscope
has developed XERAN grades that
compatibilise compounds of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) or acrylonitrile
styrene acrylate (ASA), compounds
of polyamide (PA) and ABS and
compounds of polybutylene terephthalate (PBT) and ABS or ASA. The
technical and commercial benefits
are clear in these systems and it is
expected that XERAN will demonstrate its capabilities in many more
polymeric engineering compounds
in the near future. Polyscope even
offers a XERAN coupling agent to
enhance performance of styrene
acrylonitrile (SAN) with glass fibres.
For further information contact:Peter
Tackx Polyscope Polymers on tel:
+31 (0)683 638 041, or
email [email protected] z
University of Johannesburg Solar Team
unveils Ilanga II
Ilanga II, the prototype solar energy vehicle of the University
of Johannesburg’s (UJ) Solar Team was unveiled in August
at the UJ Kingsway Campus in Auckland Park, Johannesburg. UJ Solar Team spokesperson and project manager,
Warren Hurter, who has been part of the UJ Solar Team
since they started as undergraduates in 2011, said the
new Ilanga II is one of the most advanced solar powered
vehicles produced by University of Johannesburg students
and industry partners to date. “We are more than ready to
take on our international and local competitors with this
vehicle which echoes values of aerodynamic success and
high performance. In short, Ilanga II is light and it is fast.” z
Whether it’s drinking water, process water
or wastewater, in urban or rural areas:
water has become a scarce and valuable
commodity. The aims of sustainable water management have been clearly set:
supplying sufficient quantities, with areawide distribution, allocation and optimum
cleaning. The result is an increase in the
demands placed on the facility operators.
And not least in terms of proving the quality of the plant, for example in accordance
with self-check and self-monitoring ordinances, and growing safety requirements
in accordance with the Operational Safety
Ordinance. Integration and intelligent data
management are becoming increasingly
important on account of the growing degree
of automation in water and wastewater
treatment plants. However, what is crucial
is the precise measurement of waterflows.
To do this, plant operators require robust,
high-quality flowmeters.
The Promag 400 meets the basic requirements without any 'ifs' or 'buts' and
provides new, cutting edge technology. This
device series represents industry-optimised
design and impresses with its simplicity
and reliable operation. Where accurate
measurement of water quantities is essential, the Promag 400 is the key to optimal
quantity balancing, process regulation
and billing for measuring points. Compliance with guidelines for custody transfer
(MI-001, OIML R49)and the provision of
industry-relevant drinking water approval
goes without saying.
The device configuration and checking
is ingeniously simple - and the latest web
server technology enables time-saving operation without additional software. Upload
and download of parameters can be easily
performed for data storage and fast commissioning of multiple identical measuring
points. Data storage (HistoROM) with trend
analysis and process monitoring is carried out automatically. This ensures rapid
recovery of device data in the event of servicing and enables simple replacement of
electronics without readjustment. Extensive
self-diagnosis functions increase the plant
reliability and provide maximum transparency. The verifiability of the measurement
results is based on traceable verification
concepts, permanent fault monitoring and
clear fault categorisation for specific maintenance measures.
Analog output signals, HART ®, PROFIBUS® DP,MODBUS RS485, through to
Ethernet/IP enable seamless integration
into existing process control systems, including documentation. Since the firmware/
device drivers are available throughout the
etc
Measuring water flow is child’s play...with Promag 400’s industry-optimised design
The Promag 400 family- the perfect measuring device for any application: Tried-and-tested
Promag sensors from Endress+Hauser and the new Promag 400 transmitter (second device from
the right).
entire lifecycle, compatibility between the
field device and the process control system
is guaranteed at all times. The tried-andtested W@M information system provides
efficient life cycle management for design,
maintenance and service.
The power supply is also new: the same
device can be used for alternating voltages of between 18 and 260 V and for DC
voltages of between 18 and 30 V. By using
just one wide-range power unit, the risk of
damage due to incorrect wiring in the field
is ruled out.
Measuring devices are often installed
outdoors and are exposed to heat, dust and
fluctuating climatic conditions. Even more of
a challenge is permanent use underwater
or underground. Promag W 400 is specially
designed for these harsh conditions and
guarantees consistently reliable operation
without any additional protective measures
or costs:
•C ertified corrosion protection (ENISO
12944) for device installation underwater (satisfies Im1 & Im2 in accordance
with EN ISO12944), underground (Im3
in accordance with EN ISO 12944), in
regions with a saline environment(C5 M
in accordance with EN ISO12944), with
strong moisture or temperature fluctuations (deserts, tropics).
•R eliable long-term operation due to
robust, fully-welded sensors and IP 68
protection.
•Anti-corrosion connection housing made
from Lexan polycarbonate with a multisealing concept.
•Whatever the application, the right Promag
device is available.
•Promag L, the versatile standard instrument, with its unique loose flange concept
(DN ≥ 300), Promag L offers maximum
flexibility for installation, regardless of
the orientation of the tube flange pitch
diameter. The weight-saving design with
short installation lengths is available in
the nominal diameters DN 50 to 2400.
•Promag W, the specialist for every occasion, with certified corrosion resistance
and IP 68 protection. Approval for custody
transfer in accordance with MI-001 and
OIMLR49 is available for nominal diameters DN 25 to 2000.
•Promag D, the compact intermediateflange device with a space-saving design
for use in the smallest spaces. The innovative housing design, available in DN
25 to100, enables perfect-fitting and
quick centring. This saves time and offers reliability each time it is brought into
commission.
Electromagnetic flowmeters from
Endress+Hauser have been used successfully for over 35 years in more than
1,5 million applications. Compliance with
high quality standards ensures guaranteed
measurement results for all users in longterm operation, as every device is traceably
tested on an accredited calibration rig (ISO/
IEC 17025).
For more information contact Frans van den
Berg, Product Manager: Flow on tel: +27 11
262 8000 or email [email protected] z
33
etc
AZ-Armaturen re-designs control valve range to increase productivity
AZ control valve with
electro-pneumatic positioner
The entire control valve range of AZ-Armaturen has undergone a complete re-design
resulting in a modular system designed to
increase productivity in the process, food,
chemical and petrochemical industry.
The construction of the control valves is
based on the standard cavity-free plug valve
with PTFE-sleeve or chemical-resistant PFA/
FEP-lining. Furthermore, a wide range of
different materials is available for various
applications. Heat jacketed control valves
are also in stock, as well as different types
of actuations such as pneumatic, electric
and hydraulic systems.
In case of a high flow velocity, a high
pressure drop or solid-containing mediums,
a protection insert can be added to increase
the service life of the control valve.
Zwick triple eccentric valve with superior characteristics
Cut-away control
plug valve with
protection insert
With its triple eccentric design and metalto-metal sealing, the TRI-CON Series guarantees a very sophisticated valve design,
including:
•True cone in cone sealing
•Frictionless operating
•Low torques
•Constant closing angle on the total circumference.
The operating characteristics and the tightness of the valve are not influenced by high
differences in temperatures and pressure
fluctuations because of the triple eccentric
geometry and the valve’s special features.
Maximum service life is achieved by eliminating any ‘rubbing’ between the laminated
seal around the total circumference during
seating which enables a frictionless opening
and closing. This guarantees full tightness
and low operating torques. z
Richter expands its butterfly valve range
Shut off and control butterfly valves are
economical valves. They are easy to install
and dismantle, competitively priced and
compact and they are therefore used in
large numbers in industrial plants.
Richter, a leading manufacturer of fully
lined valves and process pumps, has significantly expanded its butterfly valve range for
isolation, on/off and control. Together with
its partner, Valve & Automation, Richter can
supply valves with a PTFE disc/stem unit up
to DN 750 (30”) or with a metallic disc/stem
unit up to DN 1000 (40”). The body liners
are made of PTFE. Richter butterfly valves
have proven themselves in a wide variety of
process plants. They isolate and control corrosive, hazardous and pure liquids, gases
and vapours, eg, large media flows in the
distribution and treatment of H2SO4, HCl,
NaOH, NaOCl, etc.
The valves are soft-seated and gas-tight,
both with lined and metallic disc/stem units.
34
Leak-tightness against the atmosphere is
in compliance with the German Clean Air
Code (TA Luft).They can be used for operating pressures of 0,1 mbar vacuum up to 10
bar and at operating temperatures of -40°C
to +200°C.
The wetted materials are FDA-compliant
and therefore also suitable for use in food
processing, pharmaceuticals and other
sectors. The version with a metallic disc/
stem unit, is also suitable for free-flowing
bulk materials.
The double-action stem sealing is
maintenance-free and self-adjusting. One
of the special features of the valve with PFA
disc/stem units DN 50-400 is the optionally
available safety stuffing box. With this option
the valves can also be used for environmentally hazardous media.
The valves can be operated with a hand
lever (lockable), a worm gear with hand
wheel or a pneumatic/electric actuator.
To control the pressure, flow or temperature as precisely as possible, ten different
plug forms are available per valve size,
consisting of 5 linear and 5 equal percentage control characteristics. In case of very
large flow rates, the full bore valve may
well be recommended, and if there is a
specific flow rate needed, the plug can be
designed and manufactured according to
the requirements.
The AZ-Armaturen South Africa team
will gladly assist you in choosing the right
system to increase control accuracy and
productivity of the process and service life
of the valve.
For more information tel: +27 (0) 11 397
3665; or email [email protected] z
Safe transport of hazardous
corrosives
The amount of dangerous corrosive liquids
being transported steadily increases. PFAlined valves and pumps fixed to road and rail
tankers, wagons and containers are helping
to ensure the safety of roads, railways and
waterways. Flanged and wafer design PFAlined Richter ball valves are widely used for
this purpose. Fully lined ball valves fig KN/F
and KK/F are ideally suited for the use on
road tankers, tank wagons and transport
containers and comply with the German
Clean Air Act. PFA/PTFE-lined butterfly
valves are used on acid tank ships. Further
examples are PFA-lined diaphragm valves as
filling and drain valves on special bromine
containers and PFA-lined magnetic drive
pumps on road tankers for faster unloading.
The integral PFA fluoroplastic lining has
many advantages in that it is much more
resistant to corrosion than alternative materials. It is an anti-adhesive vacuum-resistant
lining which is easy for CIP (Clean In Place)
and can be also used for high-purity and for
solids-laden fluids with large temperature
ranges from up to -60°C up to 200 °C. z
Valve & Automation (Pty) Ltd are the exclusive agents for Richter in Southern Africa.
For more information on these products
contact Fred Venter, on tel +27 (0)11 397
2833, email [email protected], or
go to www.valve.co.za z
etc
‘Fundamentals of Process Safety Management’ IChemE course 2014
The Institution of Chemical Engineers
(IChemE) “ Fundamentals of Process Safety
Management” (PSM) course is being held
at the Birchwood Hotel and OR Tambo
conference Centre, Boksburg, from the 3-7
November 2014. The proceedings will cover
the entire five-day UK IChemE course.
Course leaders are Rod Prior, a chemical engineer with over 30 years of experience in process industries, including
production, commissioning and health and
safety management; and Nigel Coni, who
has over 40 years’ experience in the chemical industry, in design, project, production
and consulting positions.
The course is aimed at process plant
management, supervisors, engineers, designers and safety experts. The course will
cover, inter alia, a model for PSM and basic
hazard science, performance measurement
and learning from accidents, design safety,
legal framework and much more. By using
case studies and team work, knowledge is
transferred on how to prevent and minimize
fires, explosions and the release of toxic
gases.
The course has been approved by
IChemE and is both ECSA and SAIChE accredited.
Please contact Rod Prior for details. Cell:
082 554 0010. Email: [email protected] z
etc
South African journalist wins prestigious award for excellence in reporting
Mbali Chiya from South Africa is fifth from left in the photograph above
Seven journalists were named earlier in the month as winners of
the “2014 WASH Media Awards” competition for their excellence in
reporting on water, sanitation and hygiene-related (WASH) issues.
The journalists, their winning entries, and the award categories
are:
•Mbali Chiya (South Africa): “Human Rights to Water and Sanitation” (Category: The Human Right to Water and Sanitation)
•Marcelo Leite (Brazil): “The Battle of Belo Monte” (Category:
Water and Energy)
•Natasha Khan (Canada) and Ketaki Gokhale (USA) “No Menstrual
Hygiene For Indian Women Holds Economy Back” (Category:
Equity and Inclusion in Water, Sanitation and Hygiene)
•Seun Aikoye (Nigeria): “Lagosians shun public toilets as open
defecation continues” (Category: Ending Open Defecation)
•Umaru Sanda Amadu (Ghana): “Water Wahala” (Category: WASH
in the Future: The Post-2015 Development Agenda)
•Dilrukshi Handunnetti (Sri Lanka): “Sri Lankan Girls Miss out on
Sanitation Gains” (Category: Monitoring WASH Commitments)
The winners received their awards during a ceremony at the
closing plenary session of the annual World Water Week in Stock-
SUDOKU NO. 97
Have you visited our website today?
36
Complete the grid
so that every row
across, every column
down and every 3x3
box is filled with the
numbers 1 to 9.
That’s all there is to
it! No mathematics
are involved. The grid
has numbers, but
nothing has to add up
to anything else. You
solve the puzzle with
reasoning and logic.
For an introduction to
Sudoku see http://
en.wikipedia.org/
wiki/Sudoku
holm. The week concluded with a 2014 Stockholm Statement on
Water, a collection of films and papers calling for a Sustainable
Development Goal (SDG) on Water.
Journalists are key partners for sanitation, hygiene and water
sector professionals in their awareness-raising, advocacy and behaviour change work. They also play a central role in the highlighting of water and gender related issues and positioning of women
as environmental leaders. Additionally, they greatly contribute to
bringing into the spotlight the too often neglected issues of the
necessity of toilets and hand washing for a dignified, safe and
healthy life for billions of people.
The biannual WASH Media Awards competition is sponsored by
the Water Supply and Sanitation Collaborative Council (WSSCC,
www.wsscc.org) and the Stockholm International Water Institute
(SIWI, www.siwi.org). More than 100 entries from 30 countries were
evaluated by Mark Tran, a notable international correspondent for
The Guardian, UK.
The winning entries can be viewed at:
http://www.wsscc.org/media/wash-media-awards/2012-2014 z
►►►►► ►►►►►
www.crown.co.za
Solution
for SUDOKU
96

Publication

Transcription

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