ORYX GTL: from conception to reality

G A S TO L I Q U I D S
The Oryx GTL plant is the first newgeneration commercial-scale
gas-to-liquids plant using the lowtemperature Fischer-Tropsch process.
Oryx GTL from
conception to reality
Qatar has ambitions to become the GTL capital of the world. Kevin Halstead of Foster Wheeler
provides a case study of Oryx GTL, the first new-generation commercial-scale gas-to-liquids plant
using the low temperature Fischer-Tropsch process. The new technology provides an attractive
alternative to crude-derived transportation fuels. Some of the many technical challenges faced
throughout the project are outlined.
ryx GTL, a joint venture between
state-owned Qatar Petroleum (51%)
and South African-based petrochemical company Sasol Ltd (49%), is the
world’s first new generation, commercialscale, gas-to-liquids (GTL) facility. Oryx GTL
is the first of a series of projects for Qatar,
whose stated ambition is to become the
“GTL capital of the world.”
The plant is located at Ras Laffan Industrial City (RLIC), a significant industrial development of 100 km2, located 75 km
north of Qatar’s capital, Doha. RLIC already
has significant LNG and chemical processing facilities in operation and contains
extensive infrastructure to support additional gas processing facilities including a
well-equipped modern port.
Oryx GTL is a grassroots facility able to
O
Nitrogen+Syngas 292 | March - April 2008
process 9.3 million m3/d of lean natural
gas from Qatar’s North gas field to produce
34,000 bbl/d of liquids (24,000 bbl/d of
GTL diesel, 9,000 bbl/d of naphtha and
1,000 bbl/d of liquefied petroleum gas).
Fischer-Tropsch process
Prior to the startup of Oryx GTL there were
three GTL plants in operation in the world
using the Fischer-Tropsch (F-T) process –
two in South Africa operated by Sasol and
PetroSA (under Sasol licence) and one in
Malaysia, operated by Shell.
The F-T process, discovered in the early
1920s by Franz Fischer and Hans Tropsch,
converts a hydrogen and carbon monoxide
mixture (syngas) into long-chain hydrocarbons and water when passed over an iron-
or cobalt-based catalyst.
The F-T process was taken forward in
the 1930s by German company Ruhrchemie, in conjunction with other partners,
one of which was Lurgi. The F-T process
was used to produce fuel during the Second World War.
In the early 1950s, Sasol bought the
rights from these companies and utilised the
technology to develop its coal-to-liquids (CTL)
process. Sasol’s early plants utilised Lurgi
coal gasifiers and Sasol Synthol reactors for
CTL conversion, producing high-grade fuels
and chemical feedstock.
Since 1989 the Sasol Advanced Synthol (SAS) reactors have been used. All of
these early plants utilise high-temperature
Fischer-Tropsch (HTFT) technology with an
iron-based catalyst.
43
GAS TO LIQU IDS
Fig 1: Oryx GTL project stages versus oil price
70
GTL feasibility
GTL pre-feasibility
60
Oryx
FEED
Oryx
feasibility
Oryx
EPC
50
40
$/bbl
economic
viability of
GTL likely
to proceed
30
20
10
economic
viability of
GTL subject
to review
0
1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
average monthly data from July 1988 through March 2006
New generation technology
© oilnergy.com, 2006
In 1993, Sasol successfully proved its lowtemperature Fischer-Tropsch (LTFT) technology, with an iron-based catalyst, to
convert coal-derived syngas to liquid products. The plant is a relatively small 2,500
bbl/d commercial-scale facility which has
recently been converted to natural gas.
Sasol has continued to develop and
refine its LTFT processes to utilise high-performance cobalt-based catalyst in the Sasol
Slurry Phase Distillate™ (Sasol SPD™)
process used for Oryx GTL.
Feasibility economics
Sasol employed Foster Wheeler to conduct
pre-feasibility studies for the use of Sasol’s
GTL processes in 1995. These studies
were initially based on a generic GTL plant
located in a remote coastal region producing 20,000 bbl/d of GTL product. Designs
were developed and capital costs estimated based on stick-built and fully modularised designs. One of the objectives of the
studies was to reduce the total project
costs from initial estimates of over
$30,000 per bbl/d of the plant’s capacity
(which would have given a 20,000 bbl/d
plant a $600 million price tag) to an economically viable level.
The feasibility studies at the time
assumed an available feed gas price of
44
$0.5/MMBtu, a low price versus the normally expected price for feed gas, but considered reasonable for remote, stranded or
waste gas. This translated to an estimated
oil equivalent price of around $4.5/bbl of
product produced. Estimated operating
costs of $4.5/bbl were roughly equal to
estimated feedstock costs. The estimated
capital cost was roughly twice feedstock
costs at $9/bbl. In conclusion, for the
generic GTL plant to be economically
attractive, an oil price at least in the upper
teens was required.
By factoring in location-specific criteria
to the generic plant estimate, an estimate
at which Oryx GTL would be economically
attractive, versus the oil price, was established as a basis for project economics.
Having established that the viability of
a gas to liquids plant is sensitive to oil
price, Fig. 1 charts the various project
stages as a timeline superimposed over
the fluctuating oil price.
As would be expected in such situations
during early feasibility and again during
early front-end engineering design (FEED)
the project and its team were on a rollercoaster ride as concerns on project viability came under scrutiny with the fluctuating
price of oil.
The feasibility study for Oryx GTL
started in 2001. With an attractive oil price
prevailing this quickly progressed into a
full-scale FEED.
Front-end engineering design
During the FEED, Foster Wheeler’s main
areas of responsibility were the prequalification and selection of suitable bidders,
development of the engineering, procurement and construction (EPC) contract terms
and integration of the three main technologies. This included production of design
specifications for all unlicensed units, infrastructure and interfaces and development
of project-specific plant layout, standards
and specifications, such that the invitation
to bid (ITB) package produced was suitable
for soliciting high-quality lump sum turnkey
EPC bids. The final ITB was completed and
issued in July 2002.
The project team, jointly led by Sasol
and Foster Wheeler (including licensors
and package suppliers), had to address a
number of integration challenges during the
feasibility and FEED stages. Many of the
challenges undertaken resulted in overall
reductions in capital cost without significantly affecting operating costs, making
the overall project more resistant to fluctuating oil prices. The following highlights
some of the main process challenges:
●
Syngas production (approx 30% of the
total capital cost of the GTL facility) primarily consists of two air separation units
(ASUs) to produce oxygen, and natural
gas reforming processes which include
Nitrogen+Syngas 292 | March - April 2008
GAS TO LIQU IDS
failure, start-up and restart durations
and ensuring that the plant would remain
online when individual units trip. To support this strategy, reliability and maintainability analyses and dynamic simulations of the full plant model ensured
maximum cost-effective availability.
● The security of supply of hydrogen was
essential in achieving plant availability
requirements to protect the sulphur
sensitive catalysts and create the
required operating conditions in the key
processes. Hydrogen management was
crucial in the overall plant design
considerations.
Foundations of the crane rig used at the Oryx GTL plant.
partial combustion to make synthesis
gas in an autothermal reformer (ATR).
Oxygen is produced in the ASUs
through cryogenic separation of air. This
is a hugely expensive physical process
and consumes large amounts of energy.
The Oryx GTL ASUs were the world’s
largest oxygen units in terms of capacity. The availability of the turbine drivers
and compressors had to be rigorously
modelled, and challenges, due to the
sheer size of the equipment, driver type
and cooling arrangements, had to be
mitigated to ensure that overall plant
availability requirements were met.
The ATR required significant pre-heat
energy to produce the quantities of syngas necessary for the process. Optimal
recovery of energy from the resultant
hot syngas exiting the ATR and allocation of users was essential to improve
overall energy efficiency.
● The F-T conversion process represents
approximately 15% of the overall capital
cost of the facility. The slurry bed reactor
is highly exothermic and heat recovery
via cooling to provide steam generation
is critical in controlling the temperature
in such a large vessel. As with the ATR,
recovery and use of this energy was necessary to optimise plant efficiency.
● Product work-up, representing approximately 10% of the total capital cost,
uses proprietary hydroprocessing tech-
46
nology to convert the wax produced in
the F-T conversion to primarily GTL
diesel and naphtha by carefully controlling overcracking to obtain the desired
product slate.
● The remaining 45% of total capital costs
was accounted for in the supporting
process units (10%), offsites (20%) and
utilities (15%). This balance of the work,
to integrate the three main licensed
technologies, formed Foster Wheeler’s
main area of involvement. It required
effective interface management, expertise across a number of industries such
as gas processing, chemicals, petrochemicals, refining and power generation, and co-ordination and specification
of all required supporting facilities and
overall plant philosophies such as plant
control and the complex steam balance.
● Overall, the GTL plant is exothermic and
an energy producer, releasing large
amounts of useable energy as waste
heat from high- and low-grade producers. This energy is used to power the
process with the high-grade producers
matched to high energy users as
explained above. The main challenge is
that high-grade energy demand exceeds
availability, so low-grade heat must be
used cost-effectively to obtain an economic design.
● Plant availability challenges were overcome by minimising common modes of
The FEED included enquiry, evaluation and
development of contract terms to allow
the selection of the ASU technology provider. Foster Wheeler could thereby
develop the plant layout beyond what
would normally be expected for a FEED,
and there was a firm price for a significant
portion of the plant. Bidders had to negotiate and integrate the selected ASU into
their bid price.
Additionally, as part of the FEED, Foster
Wheeler developed a comprehensive cost
estimate and a detailed project schedule
from several build scenarios to arrive at the
optimum plant configuration, price and
schedule. The company identified project
critical paths and included methods of
addressing these in the issued ITB. For
example, availability of vendor data was
one critical path and was addressed to
some degree by ensuring that bidders provided fully conditioned bids for identified
key and long lead equipment.
Vendors were selected before the EPC
contract was awarded and all these
orders were placed in the first month of
the EPC contract, securing early vendor
data and equipment deliveries to suppor t
construction.
The major technology suppliers for Oryx
GTL were Haldor Topsøe (synthesis gas production), Sasol (Fischer-Tropsch technology), and Chevron (product work-up).
Foster Wheeler was responsible for the
overall management and co-ordination of
the bid review process. Bid evaluation, clarifications and negotiations were concluded
by the end of December 2002. On conclusion of the financial requirements, the EPC
contract was awarded in March 2003.
At the time of award, the oil price had
risen to a level of around $25/bbl and market forecasts predicted this oil price level
was likely to remain. In the event, the price
Nitrogen+Syngas 292 | March - April 2008
G A S TO L I Q U I D S
of oil has soared to exceptional levels.
The FEED had examined the various
construction build scenarios with associated detailed scheduling and guided the
bidders to address these in their bids. The
following outlines some of the critical activities that needed to be addressed:
Completion of critical engineering discussed above was essential to release
construction work fronts and facilitate
fast-track civil design to support the
required early start on site.
● The FEED determined concrete as the
selected material for piperacks and
structures. Therefore, pre-casting of
piperacks and structures was required
to allow erection of extensive banks of
air coolers and thereby open up the
area to allow pipe erection, a critical
activity. There are not many piperacks
in the world using the double width
design as used on Oryx GTL. The piperacks consisted of two bays of 8-m
width, giving a total width of 16 m.
● A significant number of heavy lifts were
required, fifteen of greater than 200
tonnes. Some of these directly influenced construction sequencing. Heavy
lift strategies were required for assessment during the EPC bid review and the
key principles were essentially established before EPC award. The plot layout implications and construction build
sequencing were addressed early in the
EPC phase at model and constructability reviews.
● Utilities and support units needed to be
in operation early, to support commissioning of the process units. Power,
water air, steam were critical path items
to allow firstly hydrotesting, line flushing and blowing and then to generate
motive power for oxygen and hydrogen
production. These items were identified
during the FEED and requirements
defined in the issued EPC ITB documentation. All were moved forward during bid evaluation with early review and
consolidation after award.
●
Key plant components
The Oryx GTL plant uses the Sasol SPD™
process comprising synthesis gas production, low-temperature Fischer-Tropsch conversion and product work-up. These core
processes are supported by:
● ASU for oxygen, nitrogen and instrument air;
Nitrogen+Syngas 292 | March - April 2008
The world’s largest cold boxes used at the plant weighed approximately 550 t each.
Heavy ends recovery (HER) for C5+ and
fuel gas recovery;
● Water treatment unit to separate hydrocarbons and oxygenates from water;
● Hydrogen production (HPU) for hydrogen
and steam;
● Utilities and offsites to provide power,
water, steam, plant air, effluent treatment, tankage and export capability.
During the FEED it was established that
a single-train configuration would in some
cases result in unit/equipment capacities
outside current proven experience.
Therefore, the ASU, synthesis gas production and F-T synthesis units were built
with two parallel operating trains. Product
work-up, being a long-established refinerybased process, comfortably accommodated the required capacities.
Gas conversion to synthesis starts in
the synthesis gas production unit, licensed
by Haldor Topsøe. The gas is first desul●
phurised, then preheated and adiabatically
pre-reformed with steam before entering
the autothermal reformer (ATR). In the ATR
the feed is mixed with oxygen and steam
in Haldor Topsøe’s open flame CTS burner,
where partial combustion takes place
before further steam-methane reforming in
the catalyst bed to produced high-temperature synthesis gas. This high-temperature
gas (approx. 1,000°C) is cooled to produce
HP steam, primarily used to drive the ASU
compressors.
The main reactions in the reforming
process gas are:
CH4 + H2O
CH4 + 3/2O2
CO + H2O
CO + 3H2
CO + 2H2
CO2 + H2
The cooled synthesis gas feeds the LTFT
reactor, licensed by Sasol, entering at the
bottom of the slurry bed of liquid hydrocar-
47
GAS TO LIQU IDS
Fig 2: Outline block diagram for Oryx GTL
fuel gas
air
external recycle
heavy ends
recovery
hydrogen
production
to syngas production
oxygen
air separation
natural gas
LPG
natural gas
syngas
syngas
production
F-T
synthesis
liquid
products
hydrogen
MP steam
HP steam
product
work-up
naphtha
GTL fuel
reaction
water
BFW
plant condensates
treated water
effluent
treatment
utilities
oxygenates
steam, BFW, power to users
plant effluents
bons and F-T catalyst. It is converted into
paraffinic hydrocarbon chains via the
exothermic F-T synthesis reaction:
CO + 2H2 → - CH2- + H2O
The exothermic reaction inside the LTFT
reactor is cooled by steam and the MP
steam generated is primarily used to drive
the steam turbine generators required to
power the plant.
The heavier fractions are removed from
the slurry and fed into the product work-up
unit, licensed by Chevron. Proprietary hydrocracking and fractionation techniques,
known and proven in the refining industry,
are used to break down these long-chain
hydrocarbons into the required product
slate of GTL diesel (70-80% and naphtha
(20-30%).
The HER unit, designed by Foster
Wheeler, and water treatment unit, designed by Sasol, supplement the core
processes. The HER recovers C5+ material
from the F-T synthesis off-gas. The liquid
products are fed to the product work-up
process and gases are recycled to the ATR
and for use as fuel, the latter sent to effluent treatment.
The ASU and HPU support the core
48
processes. The ASU primarily separates
oxygen from air to supply synthesis gas
production and also supplies plant air,
instrument air and nitrogen. The HPU uses
steam-methane reforming to produce the
required plant hydrogen via pressure swing
absorption.
Hydrogen is essential to the overall
process so availability is assured by backup synthesis gas feed from synthesis gas
production.
The relationship and principal material
flows between these units are shown on
the overall block flow diagram in Figure 2.
Project execution
Once the EPC contract was awarded, a
multi-company project management team
(PMT) was appointed to manage the EPC
contractor. Personnel were selected from
Sasol, Qatar Petroleum and Foster Wheeler,
so the team had an interesting mix of corporate and ethnic cultures, which were successfully blended into an effective resultsdriven team.
Engineering progressed to schedule
and the PMT was relocated to site some
15 months after EPC award. Construction
started in October 2003 and the heir
apparent His Highness Sheikh Tamim bin
Hamad Al Thani laid the foundation stone
in December 2003.
The construction was conventional
‘stick built’ and proceeded to schedule
with phased equipment and material deliveries making work areas available. There
were some challenges with local concrete
supply, equipment delivery delays and
steel shortages and the team had to
address these challenges to keep the contract progressing.
The utilities and support units needed to
be in operation early to support commissioning of the plant and form several of the
critical activities on the project schedule.
Power, water, air and steam were essential
items to allow completion of construction.
If you were to look at an overview of the
GTL Oryx facility, the notable characteristics
would be the extensive banks of air coolers
and A-frame coolers that provide approximately 85% of total cooling capacity.
The sheer size of some equipment
posed challenges. The ASU contains the
world’s largest cold box and single-shaft air
compressors, and the world’s heaviest lift
by a land crane was undertaken when the
Nitrogen+Syngas 292 | March - April 2008
GAS TO LIQU IDS
Complex piperack arrangements at the plant.
F-T reactors, 2,100 t each, were lifted into
position.
There were six fired heaters, each one
a large complex structure requiring a long
on-site build duration and a significant work
area. The ATR required complex refractory
and exotic pipework material fabrication
and there is an extensive quantity of steam
tracing required on the wax circuits.
Commissioning
The fully-integrated facility required careful
and detailed planning of the plant commissioning and start-up, a subject that was
discussed in detail during the EPC bid evaluation to ensure full understanding of the
complexity of this phase, as described in
the FEED documentation.
The plant was designed to be almost
standalone, importing only start-up power,
cooling water and raw water and discharging effluent within strict environmental limits. The utilities and support units therefore
must be in operation to support phased
start-up of the plant. The very different
phases of construction, commissioning and
operation, by necessity have to take place
simultaneously and in close proximity. This
multi-phase period had to be performed
under strict safety procedures to allow construction trades to work safely and in segregation from commissioning and operation
of demarcated ‘live’ facilities.
50
To facilitate the commissioning sequence, the design philosophy to permit
power distribution, integrated control system availability and essential start-up equipment such as boilers to be available was
fully developed during the FEED phase.
Additionally, services such as fire and
gas systems for safety protection; air for
blowing and instrument operation; firewater; cooling water and raw water for flushing
and steam generation for blowing and
motive power all needed to be available for
commissioning.
With utilities in operation, the water and
effluent treatment, flare, nitrogen, oxygen
and hydrogen production units could be
started up, and feed gas introduced and
processed, followed by sequential commissioning and start-up of syngas production, F-T conversion and product work-up.
The plant was officially inaugurated in June
2006 by His Highness, Sheikh Hamad Bin
Khalifa Al Thani, Emir of the State of Qatar.
Plant improvement
With the building, start-up and operation of
Oryx GTL, lessons have been learned
which will further enhance the next generation of GTL plants.
Already some enhancements learned
from the operation and shutdown of
Sasol’s existing GTL facilities have taken
place in areas such as the Haldor Topsøe
open flame CTS burners, wax treatment
and catalysts.
Future GTL prospects
As Oryx GTL approached start-up there was
much interest throughout the oil and gas
industry, particularly from countries such
as Australia, Indonesia, Russia and Algeria, looking to diversify the way in which
they can monetise their gas reserves.
A Qatar Petroleum and Sasol Chevron
joint venture has since examined possibilities for increasing the capacity of Oryx GTL
by 67,000 bbl/d. Additionally, integrated
GTL facilities for extracting and processing
gas to obtain 140,000 bbl/day have been
investigated.
Outside Qatar, Chevron Nigeria, together with NNPC, is building a 34,000
bbl/d GTL plant in Escravos, Nigeria.
Escravos GTL is of similar capacity and
technology to Oryx GTL and was also engineered by Foster Wheeler.
Foster Wheeler has published several
papers addressing larger, integrated GTL
facilities that combine GTL processes with
offshore gas extraction and onshore gas■
receiving and processing facilities.
Acknowledgement
This article is based on articles first published in
the July 2006 editions of The Chemical Engineer
and Hydrocarbon Engineering.
Nitrogen+Syngas 292 | March - April 2008