Holman Wilfley Trial Report

Transcription

WRAP MDD018/23 WEEE separation
techniques
Holman Wilfley wet shaking table
trial report
Abstract
This report describes trials conducted with SGS Mineral Services on a Holman Wilfley Wet
Shaking table for WRAP project MDD018/23. The aim of the project was to trial innovative
techniques to tackle some of the more difficult separations encountered by primary and
secondary WEEE processors. Recovering copper from mixed WEEE is a notoriously difficult
separation and several techniques have been tested during this project to attempt to find a
solution to the problem.
The wet shaking table is a technique which originates from the mineral processing industries
and has been in use for many years. Its use in the recycling industry is a recent
development.
The aim of this specific trial was to test the technique’s ability to recover fine copper from a
copper plastic mixture. Fine copper is often found in the WEEE plastic stream and the
recovery of it from plastic is currently a problem for which there are no suitable solutions.
The copper-rich plastic mixture was pre-treated in two ways in order to size reduce the
sample material. This allowed for an investigation into the effect of particle size on the
success of the separation to be carried out. One sample of the copper-rich plastic was
granulated to a <2.36mm fraction and a 2.36 to 5mm fraction. Another sample was
hammer milled, producing three fractions with size ranges 0-3mm, 3 to 5mm and >5mm.
Some of the copper-rich plastic material was left in its original condition at 8-12mm.
Each of the samples was processed on the wet shaking table, with the following conclusions.
The <2.36mm and 0-3mm fractions performed best and significant amounts of copper were
recovered from both. The other four fractions performed poorly, but it should be noted that
in the cases where the material had been size reduced and screened, most of the copper
from the feed material appeared in the smallest particle size fraction and hence there was
actually very little copper to recover from the larger fractions.
If a wet shaking table is selected as a technique to recover a copper fraction from WEEE,
the copper-rich plastic should be size reduced to below 3mm.
WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report A wet shaking table capable of processing 1 tonne per hour of size reduced copper-rich
plastic from WEEE processing has an installed capital cost of £110,000 and a payback time
of nine months. Therefore this technique has good potential for use in the WEEE recycling
sector.
Table of contents
Abstract.......................................................................................................................... 1
1.0
Information from Trial ........................................................................................... 6
1.1
Photograph of Trial Equipment ........................................................................... 6
1.2
Description of Trial Equipment ............................................................................ 7
1.3
Trial Objectives................................................................................................ 10
1.4
Sample Material ............................................................................................... 10
1.5
Trial Methodology ............................................................................................ 10
2.0
Trial 1 - less than 2.36mm granulated copper rich plastic ...................................... 12
2.1
Feed Material................................................................................................... 12
2.2
Results ............................................................................................................ 13
2.3
Photographs of product samples ....................................................................... 14
2.4
Analysis of product samples.............................................................................. 16
2.5
Discussion of results ........................................................................................ 17
2.6
Conclusions from trial....................................................................................... 18
3.0
Trial 2 - 2.36 to 5mm granulated copper rich plastic.............................................. 19
3.1
Feed Material................................................................................................... 19
3.2
Results ............................................................................................................ 19
3.3
3.4
Analysis of results samples ............................................................................... 22
3.5
3.6
4.0
Trial 3 - Copper-rich plastic without pre-treatment ................................................ 23
4.1
Feed Material................................................................................................... 23
4.2
Results ............................................................................................................ 24
4.3
4.4
4.5
4.6
2 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report 5.0
Trial 4 - +5mm milled copper rich plastic.............................................................. 29
5.1
Feed Material................................................................................................... 29
5.2
Results ............................................................................................................ 29
5.3
5.4
Analysis of results samples ............................................................................... 32
5.5
5.6
6.0
Trial 5 - 3mm to 5mm hammer milled copper rich plastic....................................... 33
6.1
Feed Material................................................................................................... 33
6.2
Results ............................................................................................................ 33
6.3
6.4
6.5
6.6
7.0
Trial 6 - 0mm to 3mm milled copper rich plastic.................................................... 37
7.1
Feed Material................................................................................................... 37
7.2
Results ............................................................................................................ 37
7.3
7.4
7.5
7.6
8.0
Economic calculation ........................................................................................... 43
9.0
Overall final conclusions of the trial ...................................................................... 46
3 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report List of figures
Figure 1: Photograph of the trial equipment...................................................................... 6
Figure 2: Close up of wet shaking table deck .................................................................... 7
Figure 3: Schematic indicating where each of the product fractions is collected in relation to
the table......................................................................................................................... 9
Figure 4: Photograph of the -2.36mm granulated copper-rich plastic feed material ........... 12
Figure 5: Photograph of the -2.36mm material on the wet shaking table .......................... 13
Figure 6: Photograph of trial 1 concentrate 1 .................................................................. 14
Figure 9: Photograph of trial 1 middlings ........................................................................ 15
Figure 10: Photograph of trial 1 tailings .......................................................................... 16
Figure 11: Photograph of concentrate 1 from scavenge trial ............................................ 18
Figure 12: Photograph of the +2.36 mm granulated copper rich plastic material ............... 19
Figure 13: Photograph of trial 2 concentrate 1 ................................................................ 20
Figure 16: Photograph of trial 2 middlings ...................................................................... 22
Figure 18: Photograph of the copper-rich plastic material ‘as it is’ .................................... 24
Figure 19: Wet shaking table in operation on the copper-rich plastic without size reduction
.................................................................................................................................... 25
Figure 23: Photograph of trial 3 middlings ...................................................................... 27
Figure 25: +5mm milled copper-rich plastic feed material................................................ 29
Figure 26: Trial 4 concentrate 1 ..................................................................................... 30
Figure 29: Trial 4 middlings ........................................................................................... 31
Figure 30: Trial 4 tailings ............................................................................................... 32
Figure 31: 3-5mm milled copper rich plastic feed material ............................................... 33
Figure 37: 0-3mm hammer milled copper rich plastic material.......................................... 37
Figure 38: Wet shaking table in operation on the 0-3mm hammer milled material............. 38
4 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 41: Trial 6 concentrate 3 ..................................................................................... 39
List of tables
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
1: Throughput information for trial 1 ..................................................................... 13
2: Mass balance results for trial 1.......................................................................... 16
3: Analysis of feed, middling and tails fractions from trial 1 .................................... 16
4: Analysis of concentrate 1, 2 and 3 from trial 1 ................................................... 17
5: Results of copper anaylsis including product sepaartion efficiency, Q................... 17
7 : Mass balance results for trial 2......................................................................... 23
9: Mass balance results for trial 3.......................................................................... 28
10: Throughput information for trial 4 ................................................................... 30
11: Mass balance results for trial 4........................................................................ 32
17: Results of analysis on feed, middling and tails from trial 6 ................................ 41
18: Analysis of concentrates 1, 2 and 3 ................................................................. 41
19: Results of copper analysis for trial 6 including product separation efficiency, Q .. 41
20: Payback calculation for a wet shaking table ..................................................... 44
Information from trial
Trial host: SGS Mineral Services, the trial was conducted at a facility in Cornwall, UK.
Trial equipment: Holman Wilfley wet shaking table
Trial date: 10th February 2009
1.1
Photograph of trial equipment
Figure 1 is an annotated photograph of the wet shaking table used in the trial.
Feed trough Deck with riffles Feed hopper Water supply to table Additional water can be added to the feed here
Product collection trough Head motion
Tailings product outlet in buckets Figure 1: Photograph of the trial equipment
6 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Water flows over Copper collects the table in this off this edge of direction the table Top edge
Bottom edge Figure 2: Close up of wet shaking table deck
The table moves backwards and forwards in the direction of the arrow in Figure 2. The
‘riffles’ – shallow longitudinal ridges - can clearly be seen in the photograph. The riffles
decrease in height from the bottom edge to the top edge of the table. Water flows over the
table from the top edge to the bottom edge.
1.2
Description of trial equipment
The wet shaking table at SGS mineral services in Cornwall is a half sized Holman Wilfley
table. This means it has a quarter of the area of a full sized unit but operates in the same
way as a full table.
Figure 1 shows the feed point in the corner of the table where the feed material is added.
Water flows out of holes in a pipe which runs along the top of the table. There is also a
separate supply of water into the feed trough.
In operation, the table moves forward and backward, this motion is called the ‘stroke’. The
table is made with shallow longitudinal ridges running from one side to the other called
‘riffles’. The movement of the stroke is in the direction of the riffles. The table is pushed
forward with a slow stroke, tensioning a spring as it does so. When the table reaches the
specified stroke length the spring then releases its tension and pulls the table back quickly,
hitting the retaining stops. As the table moves forwards the particles rise and are
momentarily suspended. As the table moves backwards the dense particles settle back
down and the motion gradually causes the particles to move along the riffles in the direction
of the table’s forward stroke. The light material stays in the upper layer and flows down
7 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report over the riffles with the flow of water. An analogy for the movement would be to compare it
to a magician pulling a table cloth from under the table contents.
In the context of WEEE separation, copper (coarse, dense material) will settle against the
riffles and travel upwards to the far side of the table. Plastic will settle in the upper layer
and will travel down over the riffles with the water to the bottom edge of the table.
The height of the riffles decreases along the length of the table from the feed to the product
end. The riffles are higher near the feed and tailings edge of the table, approximately 78mm high. The riffles decrease in height to only a few millimetres near the concentration
end and top edge of the table. The riffles are approximately 5cm apart. The plastic
particles jump over the high riffles whilst the copper travels up the riffles. The height of the
riffle is connected to the material being processed on the table and different riffle patterns
can be used depending on the material being processed. For coarser particles, common
within the recycling industry, the height of the riffles can be as much as 20-25mm.
Depending on the type of material, the size of table used in this trial would be expected to
process 400-450kg/hr. A full size table, dimensions 5.8m long x 1.75m wide x 1.2m high
with a nominal deck area of 8.0m2, can handle around 2-2.5 tonnes per hour. If the
material is coarse and has a close size distribution then the throughput can be as high as
3.5-4.0 tonnes per hour. Finer material or material with a wide size distribution will have a
lower throughput.
There are four process variables for a wet shaking table:

Stroke length (maximum stroke length of 19mm);

Deck angle;

Wash water flow rate; and

Position of splitter plate.
The first three variables have an effect on whether a separation is achieved. The last one
has an effect on the products collected both in terms of quantity and quality.
The stroke length is the distance the table moves forwards and backwards. For all the trials
it remained constant at 15mm. The stroke can be increased to a maximum of 19mm for
coarse material or decreased to 5mm for very fine material. If the particle size is large and
the feed material has a low density then a longer stroke is required to separate the particles.
The deck angle can be adjusted from 0° to a maximum of 9°. During the trials the deck
angle was set at 7°. Typically for fine material a flatter deck angle is used but the actual
settings need to be fined tuned during start up and are relative to the density of the
material.
The feed rate should be kept constant and the solids feed density should be around 25%.
This is to ensure that a steady state on the deck is maintained, as fluctuations in the flow of
8 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report material will affect the separation. The wash water flow rate range is 18 to 38 litres per
minute.
The table produces five product fractions, illustrated in Figure 3. There are three
concentrate fractions produced at the end of the table which consist of the dense material.
Concentrate 1 is from the top corner, concentrate 2 is from the upper middle part of the
table and concentrate 3 is from the lower middle part of the table. Beneath these three
fractions, at the bottom corner of the table, is a fraction known as the middlings. This
fraction will often contain a mixture of the concentrate material and the tailings material and
may need reprocessing. At the centre bottom edge of the table is the tailings fraction which
is the light material. The table can also be tuned for a three way split, one product in the
concentrate, one product in the middlings and one product in the tailings. The copper
material will be found in concentrates 1, 2 and 3. Glass may be found in concentrate 3
whilst the middling and tailings are mainly plastic.
Concentrate 1 Direction of table movement Concentrate 2 Concentrate 3 Riffles Middlings Tailings Figure 3: Schematic indicating where each of the product fractions is collected in relation to
the table
A moveable splitter plate determines what material is collected as concentrate 3 and what
material is rejected in the middlings. During operation the bed of material on the table is
observed in order to determine if the splitter plate position needs to be adjusted. It should
be positioned just at the point where the two materials being separated form a distinct line.
Once correctly set, the table will operate in steady state with constant flows of materials, so
the plate should not require further adjustment. If the splitter plate is positioned incorrectly,
valuable product (i.e. copper) could be rejected to the middlings fraction, which would then
need reworking in order to recover the copper. Conversely, the splitter plate could be
positioned so that the concentrate contains less valuable materials (i.e. plastic/glass), which
is also undesirable. If concentrate 3 contained very little copper and more plastic/glass then
it should be directed into the middlings fraction.
Trial objectives
The overall objective of the trial was to separate valuable metals from glass, stone and
plastic. The specific aim was to produce a high purity copper stream which has a saleable
potential. The key to achieving an effective separation is likely to be the particle size and
shape.
Market research indicates that the combustible component of the copper fraction must be
reduced to below 5% by weight to make it attractive to the majority of copper smelters in
Europe. A higher content of stone and glass can be tolerated as they are inert in the
smelter. However separating copper from stone and glass increases the value of both
fractions. The stone and glass has no value when mixed and sold with copper but may be
saleable as a useful aggregate substitute if it can be separated with a low copper content.
1.4
Sample material
The samples used for these trials were copper-rich plastic fraction sourced from Axion’s
WEEE processing plant in Salford, UK.
The copper-rich plastic was size reduced in two different ways: granulation and hammer
milling. This produced five different fractions, along with the original material itself for
testing. The different samples were chosen to allow the effects of particle size on the
separation to be investigated.
The six samples were:
1.
2.
3.
4.
5.
6.
<2.36mm granulated copper-rich plastic;
2.36-5mm granulated copper-rich plastic;
Copper-rich plastic ‘as it is’;
0-3mm hammer milled copper-rich plastic;
3-5mm hammer milled copper-rich plastic; and
+5mm hammer milled copper-rich plastic.
1.5
Trial methodology
The objective for each sample of material was the same, so the trial methodology used for
each sample was also the same.
Prior to processing the material the feed rate was measured by timing a fixed amount of
material though the feed system. The results for each of the throughputs are shown in the
relevant trial sections.
After each of the samples was tested on the table the samples were dried by SGS Services
and returned to Axion’s facility at Salford. A scavenge of the tailings for trial 1 was
conducted. This involved passing the tailings material over the table again to see if there
was any copper which had not been recovered by the first pass.
Two techniques were used to determine the composition of the fractions in order to analyse
the sample material.
10 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report In order to identify any losses of copper in the middlings and tailings fractions a sodium
polytungstate solution was used as a sink-float medium. This method was chosen as any
residual copper would be very small and difficult to hand sort. The same procedure was
applied to the feed material to allow the analysed feed composition and the back calculated
feed composition to be compared.
The same method was used for samples of feed, middlings and tailings. A small sample
spear was used to take a representative sample from each bag. The sample was then
weighed and added to a container of sodium tungstate solution with a density of 1.7g/cm3.
Ideally the copper would sink and everything else would float. The two fractions were
removed from the container and dried.
Where the material was large enough the fractions were hand sorted. An estimation of the
copper content was made for those fractions where a hand sort was not possible due to
very small particle size.
Once the physical analysis of the samples was completed, product and reject separation
efficiencies, Q and R, were calculated.
For this trial the product separation efficiency, Q, is the probability of correctly recovering
copper to the desired product stream.
The reject separation efficiency, R, is the probability that everything else is correctly sorted
to the secondary product stream.
In this case the secondary product stream is of no use and only the copper is a useful
product. The three concentrate fractions from the table are classed as the product stream
and the middling and tailing fractions is the secondary product.
11 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report 2.0 Trial 1 - less than 2.36mm granulated copper rich plastic
2.1 Feed material
The feed material for trial 1 was the <2.36mm granulated copper-rich plastic.
At this particle size there are no ‘plate’ like particles, which are present in the copper-rich
plastic that is normally produced by Axion at Salford. The particles after granulation are
cuboid in shape. The reason for this is that most injection moulded plastic used in WEEE is
3 to 5 mm thick, so when granulated to less than 5mm the cuboid shape arises. It is
thought that evenly shaped particles like the cuboids perform better on a wet shaking table
than the flat plate like particles, so it was expected that the size reduced material with a
cuboid shape would perform well during the trial.
Figure 4: Photograph of the -2.36mm granulated copper-rich plastic feed material
Results
Figure 5: Photograph of the -2.36mm material on the wet shaking table
Figure 5 shows the wet shaking table in operation. The clear boundary between the copper
and plastic is shown by the line.
The feeding system blocked during the trial and required manual intervention to ensure the
table received a consistent flow of material. The throughput was determined by measuring
the time taken for a known quantity of feed material to pass though the feed system. The
results are shown in Table 1. The throughput was quite low but was limited by the capacity
of the feeding system, which may need to be changed for this type of material.
Trial
1
Material Quantity
g
876
Times
Feed rate
s
21.0
kg/hr
150.2
Table 1: Throughput information for trial 1
A sample of the tailings from the trial was reprocessed to see if there was any copper
present. This showed that there was no copper so the first pass of the material had
achieved as good a separation as was possible and reworking of the tailings was not
required.
Photographs of product samples
Figure 6: Photograph of trial 1 concentrate 1
14 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 8: Photograph of trial 1 concentrate 3
Figure 9: Photograph of trial 1 middlings
15 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 10: Photograph of trial 1 tailings
2.4
Analysis of product samples
Table 2 shows the mass balance for trial 1. It should be noted that the feed amount was
not weighed It has been back-calculated from the product fractions so the loss/gain is zero.
For all other trials the feed amount was correctly weighed and the loss determined.
Trial
1
Feed Con 1
Con 2
Con 3
Middlings
Tailings
Amount
g
g
%
g
%
g
%
g
%
g
%
4214.7 193.7 5% 322.9 8% 387.3 9% 867.8 21% 2443 58%
Total Output
g
4215
Loss/Gain
g
0.0
Table 2: Mass balance results for trial 1
The results of the sink float analysis are shown in Table 3.
Trial
1
Sample
Feed
Middlings
Tails
Weight Dry % of of dry copper copper
sample
weight
15.39
2.6
17%
10.56
0.24
2%
5.92
0
0%
Table 3: Analysis of feed, middling and tails fractions from trial 1
16 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report The hand sorting results are shown in Table 4.
Copper
Glass
Plastic
Fraction
weight
Trial 1
g
%
g
% g %
Concentrate 1 186 96% 5 3% 2 1%
Concentrate 2 291 90% 32 10% 0 0%
Concentrate 3 198 51% 189 49% 0 0%
194
323
387
Table 4: Analysis of concentrate 1, 2 and 3 from trial 1
Fraction
Feed
Concentration 1
Concentration 2
Concentration 3
Middlings
Tails
Product totals
Fraction
weight
4215
193.7
322.9
387.3
867.8
2443
Copper
weight
717
186
291
198
17.4
0
% Copper purity
17%
96%
90%
51%
2%
0%
% Copper recovered 4215
692
16%
97%
Q
94%
26%
41%
28%
2%
0%
Table 5: Results of copper anaylsis including product sepaartion efficiency, Q
2.5
Discussion of results
Table 3 and 4 show the results of the analysis for each of the product fractions from the trial
1.
Fraction
Feed
Concentration 1
Concentration 2
Concentration 3
Middlings
Tails
Product totals
Fraction
weight
4215
193.7
322.9
387.3
867.8
2443
Copper
weight
717
186
291
198
17.4
0
% Copper purity
17%
96%
90%
51%
2%
0%
% Copper recovered 4215
692
16%
97%
Q
94%
26%
41%
28%
2%
0%
Table 5 shows just the copper analysis as this is the main area of focus. It can be seen that
the copper concentration in concentrate 1 is 96% and in concentrate 2 is 90%. Both of
these are high purities for copper fractions recovered from WEEE and should meet the
copper smelter’s requirements. 67% of the copper in the feed was recovered in
17 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report concentrates 1 and 2. Over a quarter of the copper was recovered to concentrate 3 but
only at a 50% purity level.
The back calculated copper content of the feed, 16%, is very close to the actual analysed
copper content of the feed, 17%, which shows that the analysis is consistent.
The product separation efficiency, Q value (which is the probability that the copper is
correctly sorted into one of the three product fractions) is 94% for concentrates 1, 2 and 3.
This is a high separation efficiency and means that the majority of the copper is recovered.
The results of a scavenge on the trial 1 tailings is illustrated in Figure 11 below, concluding
that no copper had been lost in the tailings fraction in the first trial.
Figure 11: Photograph of concentrate 1 from scavenge trial
2.6
Conclusions from trial
The technique is very good for the separation of copper from plastic with this feed material.
A copper fraction with 26% recovery at 96% purity was produced. Taking into account all
three concentrate fractions the copper recovery is 95%, at a purity of 75%. The probability
that the copper is correctly sorted into one of the concentrate fractions is 94%. Therefore
the trial objective of recovering the copper into a saleable fraction has been achieved. With
further system adjustments and fine tuning even better results may be obtained.
18 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report 3.0 Trial 2 - 2.36 to 5mm granulated copper rich plastic
3.1
Feed material
The feed material for trial 2 was the 2.36 to 5mm fraction of the granulated copper-rich
plastic material.
Figure 12: Photograph of the +2.36 mm granulated copper rich plastic material
3.2 Results
There was much less copper in the feed material for trial 2, compared to trial 1, which
indicates that most of the copper went into the less than 2.36mm fraction when the material
was granulated and sieved.
There was a clear layer of glass which occurred at the transition zone between the copper
and plastic. It may be possible to fine tune the machine to produce only glass in the
middling fraction.
The throughput results are shown in Table 6.
19 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Material Trial
Quantity
g
2
540
Times
Feed rate
s
20.5
kg/hr
94.8
3.3 Photographs of product samples
21 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 16: Photograph of trial 2 middlings
Figure 17: Photograph of trial 2 tailings
3.4 Analysis of results samples
Table 7 shows the mass balance for trial 2.
22 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Feed Total Con 1
Con 2
Con 3 Middlings Tailings
Trial
Loss/Gain
Amount
Output
g
g %
g % g %
g
%
g
%
g
g
2
10559 44 0.4% 272 3% 51 0.5% 1440 14% 8257 78% 10064
‐495
Table 7 : Mass balance results for trial 2
The losses in the mass balance are due to the collection technique used for the material.
Buckets were used to collect the product fractions. Losses occurred when these were
swapped over and also when the buckets were emptied.
Because it was clear during the trial that there was very little copper present in the sample
the decision was made not to analyse each product fraction quantitatively.
3.5 Discussion of results
Visual inspection of the samples showed there was very little copper in the concentrate 1
fraction; however there were other metals present. There was more copper in concentrate
2 whilst concentrate 3 contained glass, plate-like plastic particles and copper. Most of the
copper in concentrate 3 was in the form of polyvinylchloride (PVC) coated wires: if the
material was granulated to a smaller size it would liberate the copper from the PVC and the
level of copper recovery would improve.
3.6 Conclusions from trial
The technique did not work very well with this feed material, but this is not thought to be
due to the particle size, but more due to the fact that the copper content of the material
was very low. This is a characteristic of the feed material, with the copper tending to
appear in the smallest particle size fraction during the granulation process.
4.0 Trial 3 - Copper-rich plastic without pre-treatment
4.1
Feed material
The feed material for trial 3 was the copper-rich plastic with no size reduction.
23 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 18: Photograph of the copper-rich plastic material ‘as it is’
4.2 Results
During the trial it was observed that the material tended to flow over the table and the
riffles did not catch the copper. Figure 19 shows the material on the table and it can be
seen that it has lumped together on the table and not spread out correctly. This is probably
due to the shape of the plastic particles; the plate-like shape means they flow with the
water over the riffles.
The separate throughput timings are shown in Table 8.
Trial
3 Test 1
3 Test 2
Material Quantity
g
666
780
Times
Feed rate
s
20.0
20.5
Average
kg/hr
120
137
128
24 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 19: Wet shaking table in operation on the copper-rich plastic without size reduction
26 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 23: Photograph of trial 3 middlings
Figure 24: Photograph of trial 3 tailings
4.4
27 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Analysis of product samples
Table 9 shows the mass balance details for trial 3.
Trial
3
Feed Total Con 1
Con 2
Con 3
Middlings
Tailings
Amount
Output
g
g
%
g
%
g
%
g
%
g
%
g
10676 53.6 1% 390.8 4% 952.7 9% 4670.0 44% 3666.6 34% 9733.7
Loss/Gain
g
‐942.3
Again there was clearly very little copper in this material, in comparison to trial 1, so
quantitative analysis was not conducted on each of the product fractions.
The separation of this material was not very good as the particles were too big. The plastic
particles tend to be in the range 8-12mm but the copper can vary from very small pieces,
only 2-3mm long and 0.5mm in diameter, up to larger pieces of 10-15mm in length. Higher
riffles and an increased flow of water may possibly improve the separation but this would
require further work to be undertaken in order to confirm this.
There was very little copper material in concentrate 1, only 1% of the feed, and was 4% of
the feed in concentrate 2. Both fractions consisted of a mixture of copper and plastic.
Concentrate 3 contained 9% of the feed but again this was both copper and plastic. The
largest amount of material was in the middlings fraction.
During the trial the plastic often formed a mass on the table which did not allow the copper
to separate out correctly. At the boundary between the copper and plastic, as seen in
Figure 19, the plastic particles did not spread out evenly and formed lumps of material
which prevented the separation from occurring.
Processing the material ‘as it is’ does not yield satisfactory results and the trial objective was
not achieved. This means that in order to recover the copper using a wet shaking table, the
feed material must be size reduced before processing.
28 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report 5.0 Trial 4 - +5mm milled copper rich plastic
5.1 Feed material
The feed material for trial 4 was the +5mm fraction of the hammer milled copper-rich
plastic.
Figure 25: +5mm milled copper-rich plastic feed material
5.2 Results
At the start of this trial it appeared that there was no separation occurring but it became
apparent that there was very little copper in the sample.
The table tilt was increased to 9° to see if this helped achieve a separation, but it had no
effect.
The water pressure dropped during this trial, which had an effect on the wetting of the
material, which was very dry. Even taking this into account the separation would still have
been poor due to the small amount of copper in the feed.
Table 10 shows the throughput information for trial 4, which is in the same range as the
other trials.
Trial
4
Material Quantity
g
585
Times
Feed rate
s
20.4
kg/hr
103.2
29 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Table 10: Throughput information for trial 4
Figure 26: Trial 4 concentrate 1
30 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 28: Trial 4 concentrate 3
Figure 29: Trial 4 middlings
31 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 30: Trial 4 tailings
5.4 Analysis of results samples
Trial
4
Feed Total Con 1
Con 2
Con 3
Middlings Tailings
Loss/Gain
Amount
Output
g
g %
g
%
g
%
g
%
g
%
g
g
10214 260 3% 2343 23% 2746 27% 3074 30% 1439 14% 9863
‐351
Trial
4
Feed Total Con 1
Con 2
Con 3
Middlings Tailings
Loss/Gain
Amount
Output
g
g %
g
%
g
%
g
%
g
%
g
g
10214 260 3% 2343 23% 2746 27% 3074 30% 1439 14% 9863
‐351
As no separation was observed, further analysis was not conducted on any of the product
fractions.
There was very little copper in this sample. The copper was concentrated in the smaller size
fractions produced by hammer milling. The material also appeared to be too dry. Wetting
the feed prior to feeding onto the table may have improved the separation slightly.
There was very little copper present in this fraction so no significant separation occurred.
32 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report 6.0 Trial 5 - 3mm to 5mm hammer milled copper rich plastic
6.1 Feed material
The feed material for trial 5 was the 3 to 5mm fraction of hammer milled copper-rich plastic.
Figure 31: 3-5mm milled copper rich plastic feed material
6.2 Results
Again there was very little copper in this sample of material so no significant separation
occurred. There was a small amount of copper and plastic present in the middling and
tailings fractions and some balled up copper was observed in concentrate 1 and 2.
Table 12 shows the throughput information for trial 5.
Trial
5
Material Quantity
g
542
Times
Feed rate
s
20.0
kg/hr
97.6
33 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report 6.3 Photographs of product samples
Figure 35: Trial 5 middlings
35 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 36: Trial 5 tailings
6.4 Analysis of product samples
Trial
5
Feed Con 1
Con 2
Amount
g
g
%
g %
8549 34.4 0.4% 271 3%
Con 3
g
292
%
3%
Total Loss/Gain
Output
%
g
%
g
g
16% 6280 73% 8224
‐326
Middlings
g
1346
Tailings
As the observed levels of copper in the feed material were low, no further analysis was
conducted on any of the product fractions.
It appears that during the size reduction process the copper has concentrated into the
smallest particle size fraction and hence there was very little copper present in this fraction.
The results from trial 5 are inconclusive because of the small amount of copper in the feed.
36 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report 7.0 Trial 6 - 0mm to 3mm milled copper rich plastic
7.1 Feed material
The feed material for trial 6 was the 0-3mm fraction of the hammer milled copper-rich
plastic.
Figure 37: 0-3mm hammer milled copper rich plastic material
7.2 Results
It was noted during the trial that the feed material contained a significant proportion of
plastic particles greater than 3mm. This means that the material was not screened
correctly, perhaps due to a hole in the screen.
The throughput measurement for this trial is shown in Table 14.
Trial
6
Material Quantity
g
664
Times
Feed rate
s
30.0
kg/hr
79.7
37 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 38: Wet shaking table in operation on the 0-3mm hammer milled material
Figure 38 shows a photograph of the wet shaking table in operation during the trial. At the
top edge of the table a clear copper stream can be seen flowing up and along the riffles. In
the lower section of the photograph there is a darker material, mainly plastic and dust which
is flowing down over the riffles.
39 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Figure 42: Trial 6 middlings
Figure 43: Trial 6 tailings
7.4
40 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Analysis of product samples
Table 15 shows the mass balance for trial 6. Table 16 and 18 are the results of the analysis
on each of the product fractions. Table 18 shows the results for the copper component
only.
Trial
6
Feed Total Con 1
Con 2
Con 3
Middlings Tailings
Loss/Gain
Amount
Output
g
g
%
g
%
g
%
g
%
g
%
g
g
9976 25.7 0.3% 389.3 4% 324.7 3% 361.3 4% 8400 84% 9501.0
‐475.0
Trial
Sample
6
Feed
Middlings
Tails
Weight
of dry sample
45
24
12
Dry copper weight
6
7
0.1
% of copper
12%
31%
1%
Table 16: Results of analysis on feed, middling and tails from trial 6
Copper
Trial 6
Concentrate 1
Concentrate 2
Concentrate 3
Sample weight
% g %
g
0% 15 58%
26
0% 42 11% 389
2% 7 2%
325
Glass Plastic
g
% g
11 41% 0
346 89% 0
313 96% 5
Table 17: Analysis of concentrates 1, 2 and 3
Fraction
Feed material
Concentration 1
Concentration 2
Concentration 3
Middlings
Tails
Total feed material back‐calculated from product weights and compositions
Mass balance error
Product separation efficiency
Fraction
weight
9976
26
389
325
361
8400
Copper
weight
1197
11
346
312
112
84
% Copper purity
12%
41%
89%
96%
31%
1%
9501
865
9%
‐475
‐332
‐3%
Q
56%
% Copper recovered
1%
29%
26%
9%
7%
Table 18: Results of copper analysis for trial 6 including product separation efficiency, Q
41 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report 7.5 Discussion of results
The concentrate fractions contained a significant number of large pieces of plastic (>3mm),
which should not have been present in a 0-3mm sieved fraction. This was probably due to a
fault with the screen used to prepare the trial samples. This did have some effect on the
separation. If the material had been sieved correctly then a better separation would
probably have been achieved because the oversize plastic particles tended to follow the
copper into the concentrate fraction.
The content of copper measured in the feed material was 12%. However back calculating
the feed composition from the measured product compositions gave an estimate of 9%
copper in the feed. This discrepancy is significant and may be due to loss of materials
through spillages during the trial.
The product separation efficiency, Q, was rather low at 56%. This is the probability that
copper was correctly sorted into the concentrate fractions.
10% of the copper was lost to the middling and tailings fractions. This reduces the Q value.
Therefore the machine settings should possibly be adjusted, recover more copper into the
concentrate fraction, for example by repositioning of the splitter plate between concentrate
3 and the middlings fractions.
A small amount of copper was collected in the tailings fraction. It was likely that this was
due to poor wetting of the material which caused some of the copper to be swept over the
riffles with the plastic.
The product photographs show that concentrate 1 contained a small amount of copper and
some large plastic chips, concentrate 2 contained more copper along with some large plastic
chips and concentrate 3 contained both copper and plastic.
If the feed material had been screened correctly and the larger pieces of plastic removed
then the results would have been better as less oversize plastic would have been carried
into the concentrate fractions.
This trial showed that copper in the 0-3mm fraction from the hammer milled product could
be recovered by the wet shaking table. The separation efficiency was rather low at 56% but
the overall copper content of the three concentrate fractions was high at 90%. The
concentrate fractions contained a total of 8.7% combustible plastic. If oversize plastic
material had not leaked through the screen then the concentrates would have contained less
than 5% plastic. This would make the material acceptable for processing by conventional
copper smelters.
42 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report 8.0 Economic calculation
A simple payback calculation was completed in order to determine the economic potential of
the wet shaking table for recovery of copper from WEEE plastic mixtures.
43 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report Trial Host
Equipment
Trial
Equipment
Holman Wilfley
Wet Shaking Table
Capacity
te/hr
Cost of unit including feed system and installation
£
Basis of operation
hr/yr
Overall Equipment Effectiveness OEE %
Plant Input
te/yr
1
180000
3000
70%
2100
Operating Costs
Water
Quantity
Cost (assuming £2/te)
kg/hr
£/hr
100
0.20
Power
Quantity
Cost (assuming 10p/kW hr)
kW
£/hr
50
5
Water and Power costs
Water and Power costs
£/te of feed
£/yr
5.20
10920
Wear costs for granulator
£/te feed
£/yr
6
12600
Labour costs (assuming £15/hr)
45000
Annual process licence costs 0
Total Operating Costs
Revenue
68520
Product extracted
te/yr
Assume 10% of feed is separated as product
210
Value of product
£/te
1000
Margin
£/yr
£/yr
210000
141480
Payback time
months
15
Table 19: Payback calculation for a wet shaking table
44 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report The calculation assumes a capacity of 1 tonne per hour for a full size Holman Wilfley
separation table and an installed cost for the unit, including feed granulator, of £180,000.
The plant is assumed to operate 12 hours per day, 5 days a week, 50 weeks a year, giving
3,000 hours of operation per year.
The payback calculation assumes a overall equipment effectiveness (OEE) of 70%, where
the OEE is defined as follows:
OEE  capacity rate x quality rate x availability
actual throughput
capacity rate 
rated throughput
quality rate  % of on specification product
availability 
actual run hours
available run hours
Therefore the overall plant throughput will be 2,100 tonnes per year,
Operational costs:
The feed material is currently sent to landfill and once the copper has been recovered the
residue material will still be sent to landfill so there is no net cost or benefit from disposal of
the residue fraction.
It is assumed that 10% fresh water is lost per tonne of material sent to landfill with a water
cost of £2/te.
A total power consumption of 50 kW is assumed for operation of the granulator, separation
table and associated pumps and sieves. The power cost is assumed to be 10p/kW hr.
Wear costs for the granulator are estimated to be £6 per tonne of feed.
The calculation assumes that the system will require one operator at a total job cost of
£45,000 per year.
The revenue estimate assumes that 10% copper is extracted the feed. This means that the
plant will recover about 210 tonnes of copper concentrate. The value of this material will
fluctuate but is assumed to be approximately £1,000 per tonne.
Therefore the margin is £141,480 and so the payback time is nine months.
The economic assessment shows that a unit processing 1 tonne per hour of size reduced
copper-rich plastic from WEEE processing should generate an operating margin of about
£140,000/year. This should pay back the £180,000 installed cost for the system in around
15 months.
45 WRAP MDD018 WEEE Separation Techniques Holman Wilfley Wet Shaking Table Trial Report 9.0 Overall final conclusions of the trial
Fine copper can be successfully recovered from the following feed materials using a wet
shaking table:


-2.4mm granulated copper-rich plastic from secondary WEEE processing; and
0-3mm hammer milled copper-rich plastic.
For the -2.36mm granulated material 95% of the copper was recovered, at a concentration
of 75% copper. For the 0-3mm hammer milled material 56% of the copper was recovered
at 90% purity.
The wet shaking table was partially successful when trying to recover copper from the
+2.4mm size fraction of the granulated copper rich plastic material.
The wet shaking table, could not recover copper efficiently from copper-rich plastic mixtures
which had not been size reduced.
The copper content of the 3-5mm and +5mm fractions from hammer-milled copper-rich
plastic was very low so there was no benefit in trying to separate these fractions.
The trial showed that when copper-rich plastic is size reduced, the majority copper tends to
end up in the smallest fraction; copper-rich plastic should therefore be milled or granulated
to less than 5mm, ideally less than 3mm, prior to using a wet shaking table for copper
recovery.
The feed material should be fully wetted before processing in order to assist with
separation.
The wet shaking table can potentially be tuned to produce a glass fraction in the middlings.
However the presence of glass in the copper fraction is not a problem for copper smelters
because it ends up in the furnace slag fraction and does not interfere with furnace
operation.
The throughput of the quarter size table used for the trial varied from 80 kg/hr to 150 kg/hr
depending on the material being processed. This means that the throughput of a full size
table should be in the range 320 to 600 kg/hr. Axion believes that a modified feed
mechanism should allow a single full size table to achieve 1te/hr with a -3mm feed material.
46

Holman Wilfley Trial Report

Transcription

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