The New Anglo Platinum Converting Project

P Viviers1 and K Hines2

ABSTRACT was used for the final verification of feeding and control
arrangements. The Anglo Platinum Converting Process (ACP)
Anglo Platinum is the world’s largest producer of platinum group metals,
and also produces large quantities of nickel, copper and cobalt at its project included raw materials management, feed material
Refining complex in Rustenburg, South Africa. preparation and conveying equipment, a lance fed, water-cooled
In 1995 Anglo Platinum embarked on a smelter modernisation project, converter and a combined catalytic/Petersen Fattinger tower
primarily to reduce site emissions to below the guideline limit of plant for acid production. The Capital Budget Estimate (CBE)
20 tonnes per day SO2, but also to increase the converting capacity in line approved was for R1.5 billion in March 2002 money and a
with future projected production profiles. second converter for standby service was included in this
To achieve these requirements the existing Pierce Smith converters estimate.
were replaced with a single large Ausmelt converter and a new acid plant. Construction was completed in early 2002 within a credible
This was the first time that an Ausmelt furnace had been used for 18 months. Hot commissioning finished in April 2003 when the
converting, but it had the advantages of being a very robust furnace and acid plant was online. The commissioning and optimisation
was fully enclosed, giving good gas capture. It was thus considered the phases led to several fundamental changes to the process and
most appropriate technology from both a process and an environmental
perspective. It also enabled the smelting and converting furnaces to be
energy balance.
decoupled. After two years, the project has exceeded throughput
The plant was commissioned from late 2001 and the first tap was in requirements. Furthermore, the site emission has been reduced
June 2002. Despite being a new technology, ramp-up has been similar to from 200 tonnes per day of sulfur dioxide (tpd SO2) to achieve
other large scale pyrometallurgical operations. Numerous process the emission limit of 20 tpd SO2 at a higher throughput. Basic
improvements have been made since start-up, most notably a change from re-engineering activities around the converter have also been
two-stage batch to fully continuous, resulting in the plant now operating successful in imparting both operational flexibility and
above design in terms of throughput. Optimisation of freeboard accretion robustness.
control was also a major component of the ramp-up activity.
The current site focus is on reducing operating costs,
This paper discusses the commissioning and ramp-up issues of the new
improving first pass recoveries on base metals and maintaining
Ausmelt converting furnace, concentrating on the design and process
changes, and summarises current operating performance against the
the current high product quality levels.
original design objectives.
PROCESS FLOW SHEET
INTRODUCTION
Pre-ACP flow sheet
Anglo Platinum’s Waterval Smelter is located in Rustenburg,
North West Province, South Africa. The complex was established Wet concentrate (12 - 18 per cent moisture) is received from
in 1969 and has developed since to become established as the various Anglo Platinum concentrators in the group. Concentrate
world’s largest platinum smelter. The 20th century complex is dried (<0.5 per cent moisture) in one of four coal-fired flash
consisted of two electric furnaces for primary smelting with driers and stored in a 2500 tonne silo. Dry concentrate is
Peirce Smith converters producing the product matte for refining. pneumatically conveyed and then batch fed to two 34 MW
The smelting activity can best be likened to Nickel pyrometallurgy six-in-line furnaces from which a slag and a matte are
with a circa 45 per cent Ni in final product output. periodically tapped. Furnace slag is granulated, milled and
The early 1990s saw increasing regional focus on sulfur floated for final value recovery and then discarded. The furnace
emission abatement along with significant expansion planning. off-gas is de-dusted via ceramic filters and vented to atmosphere
As a result of these imperatives, an investigation of various via a stack together with Peirce-Smith converter gas in excess of
pyrometallurgical technologies was undertaken to identify the acid plant capacity.
best fit solution for the Waterval Smelter complex. The mandate The molten matte from the six-in-line furnaces is transferred
was to identify an economically efficient converting process that across the aisle to one of six Peirce-Smith converters. The matte
would enable the following design criteria to be achieved: is blown to final product quality and cast into ingots for slow
cooling. After a predetermined slow cooling period, the slow
• less than 20 tpd SO2 emissions for the complex,
cooled matte is dispatched to the Base Metal Refinery for further
• 30 000 tpa Nickel (an increase of nearly 50 per cent), processing.
• maintain stringent product quality levels, and The process gas from the Peirce-Smith converters was
de-dusted and routed to an acid plant for SO2 conversion to
• enable off-site furnace matte to be treated. sulfuric acid.
The technology selected was supplied by Ausmelt and
consisted of the submerged lance configuration with several Post-ACP flow sheet
basic engineering changes around vessel cooling and off-take
geometry facilitated through industry specialists. Several The pre and post flow sheets are identical until the tapping of the
process piloting exercises were undertaken in both Australia and molten matte from the electric furnaces. The highlighted portion
South Africa. A pilot plant at Anglo Platinum’s Research Centre in Figure 1 shows the changes to the flow sheet with the ACP in
operation.
Molten Waterval furnace matte is now granulated, dewatered
1. Lead Process Engineer, Anglo Platinum, PO Box 62179, and conveyed some 200 m to liquid petroleum gas-fired
Marshalltown 2107, South Africa. Email: pviviers@angloplat.com pneumodryers, which discharge into a 3000 ton silo ahead of the
2. Technical Manager – Smelters, Anglo Platinum, PO Box 62179, ACP converter. Matte from the other two remote Anglo Platinum
Marshalltown 2107, South Africa. Email: khines@angloplat.com furnace complexes, namely Union Smelter and Polokwane

First Extractive Metallurgy Operators’ Conference Brisbane, QLD, 7 - 8 November 2005 1

P VIVIERS and K HINES

ALL FUGITIVES

Final flow sheet COMBINED AND

VENTED UP STACK

Furnace Gas
CONCENTRATE Cleaning

FURNACE
OFF -GAS
FLASH DRIER
CONVERTER
PFM and GAS CLEANING
UFM AND COOLING ACID PLANT

WFM
MATTE CONVERTER
GRANULATION MATTE FEED
6 IN-LINE FURNACE
OFF -GAS
SLAG DE -WATERING
& DRYING

SLAG
GRANULATION
SCF Raw Material
AUSMELT Handling
CONVERTER
DE -WATERING SLAG WCM
SLAG
GRANULATION

FLOTATION
CONCENTRATE
DE -WATERING SLOW COOL
SLAG MILL AND & DRYING MOULD
DISCARD FLOTATION
SLAG TAILS

FIG 1 - Waterval Smelter flow sheet.

Smelter, is transported to the ACP plant in trucks and and resulfurdisation of base metal oxides. The tuyeres were fed
pneumatically discharged into dedicated storage bins. The matte with atmospheric air blowing directly into the matte. Skimmed
is pneumatically fed into the converter via the lance. slag was originally returned to the electric furnaces to assist with
The product matte from the ACP is slow cooled and sent to the slag resistivity as well as allowing for further recovery of
Base Metal Refinery for further processing. The ACP slag is entrained matte and oxidised base metals.
granulated, dried and fed to the newly installed Slag Cleaning
Furnace for further metal recovery. The ACP converter off-gas is Anglo Platinum converting process
de-dusted and processed to produce 98.5 per cent sulfuric acid.
A two-stage batch process was proposed in the design stage and
Due to the environmental limits on SO2 emissions, the electric
these are described below.
furnace gas had to be captured and processed. The electric
furnace off-gas is de-dusted further, producing a low strength First stage – smelting. The first stage is the feed stage, where
acid (76 per cent sulfuric acid). The 76 per cent acid is used in 100 t of cold granular furnace matte is fed via a lance into the
the process to form the 98 per cent H2SO4 that is sold. starting bath. Target iron in matte of 13 per cent by mass was
All prominent complex fugitive gasses are captured and intended to reduce oxidised base metal losses in the two first
stacked as part of the ACP project. stage slag taps and silica flux was added to provide the fayalite
slag.
ACP CONVERTER DESIGN ISSUES During the matte feed stage lasting ~2 hours, slag would be
tapped twice so as not to increase the overall bath height above
Following on from the basic process selection, there were several the Ausmelt specified height of 1.2 m. However, the mixing of
critical areas identified for detailed design. Notable amongst the matte in the converter was poor, leading to stratification of
these were the process recovery of base metals with final product the matte. The slag would be granulated and sent to the slag
quality and the perennial pyrometallurgical issues of vessel cleaning furnace for entrained matte loss recovery and some
integrity and accretion management. minor base metal reduction. The matte level in the converter
would be at maximum level after the feed stage and due to the
Process recovery and product quality configuration of feeding whilst tapping slag, an allowance of up
to four per cent nickel in slag (primarily as a sulfide through
The slow-cooled converter matte is processed through a magnetic matte entrainment) was provided.
concentration plant where the Platinum Group Metals are
recovered with a magnetic base metal alloy. This process is Second stage – converting. The convert stage followed the feed
sensitive to the iron levels in the matte for proper collection and stage. During this period silica would be added to the molten
minimised magnetic concentrate mass pull. bath to control the Fe:Si ratio at ~1.7. Hence the total bath level
increases while the matte level would decrease as the Fe and
sulfur in the matte is oxidised. Target for final matte composition
Peirce Smith is three per cent +0.5 Fe and 22 per cent +0.2 sulfur. Finally
The Peirce Smith operation was characterised by batch addition converted matte is tapped from the converter into slow cool
of electric furnace matte that was gradually oxidised from levels moulds. Downstream recovery of base metal oxides in the ACP
of 40 per cent iron down to three per cent iron. The addition of second-stage slag will be poor as the float plant is based on
each additional ladle of furnace matte allowed for the reduction recovering sulfide material, not oxides.

2 Brisbane, QLD, 7 - 8 November 2005 First Extractive Metallurgy Operators’ Conference

 THE NEW ANGLO PLATINUM CONVERTING PROJECT

The converter bath height variation through the cycle is In the case of the ACP, the furnace refractory wear was
represented in Figure 2. modelled and an equilibrium position calculated. Short campaign
Splitting the matte feed and convert stages was required to lives of up to three months were initially envisaged for the side
reduce the base metal oxide losses to slag, especially cobalt walls in the reaction zone. Undercutting of the freeboard bricks
losses. A slag cleaning furnace was designed and built to treat due to the consumption of the sidewall bricks below them could
ACP slag and smelter reverts. A further advantage of the slag result in the freeboard bricks dislodging and falling into the
cleaning furnace is the fact that the slag chemistry can be altered reaction bath and potentially causing a runaway situation.
to improve base metal oxide losses. In considering the engineering of the vessel, it was decided
The continuous dropping of iron content in the matte through that the refractory wear issues would be eliminated by replacing
the cycle required matte grade monitoring. A bath sampling the crucible walls with high-intensity Hatch water-cooled copper.
system was piloted at the test facility and this led to the inclusion A specialised wall design, employing Hatch copper cooler
of an automatic sampling lance and robot laboratory in the technology and a water-cooled freeboard, was used. The problem
project. A twenty minute sample interval was specified to ensure and design intent is represented in Figure 3.
the iron removal could be tracked through the cycle. Two rows of two-metre-high copper coolers were used to
form the crucible of the converter with a high-pressure hot
Vessel integrity water freeboard above the copper coolers. Allowance was made
for an expansion gap between the copper coolers and freeboard
The transition from six Peirce Smith converters to a single to allow for thermal expansion. A sacrificial brick of 230 mm
processing unit placed a significantly higher focus on was used on the inner face of the copper coolers while the
fundamental converting equipment availability issues. The freeboard was coated with gunnite. Equilibrium brick
relatively high temperature fayalite slag had already proved to be thicknesses were calculated. A safety factor of four was used
aggressive on the Peirce Smith refractory performance with for the copper coolers when calculating the heat flux from the
campaigns of less than 40 cycles per lining repair. molten bath.

FIG 2 - Two-stage process cycle.

FIG 3 - Refractory crucible wear mechanism and design solution.

First Extractive Metallurgy Operators’ Conference Brisbane, QLD, 7 - 8 November 2005 3

P VIVIERS and K HINES

Accretion TABLE 1
The plugging or accretion build-up of the uptake is common in Operating dynamics of Peirce Smith versus ACP.
most converters and designs were implemented to reduce the
build-up of accretion in the converter uptake. The diagram below Technology Peirce Smith ACP
shows the areas were the build-up was predicted to have the No of units 3 Running 1 Running
highest build-up potential. 1 Hot standby 1 Cold standby
2 Rebuilding
The lance tip is clearly a point of vigorous bath activity both as
a function of exit velocities and localised reaction. Dust levels in Capacity 22 000 tpa Ni 30 000 tpa Ni
the freeboard and uptake coupled with the lance splash from the Cycle time 10 - 14 hours (variable) 3 hours
bath provide the mechanism for accretion formation.
Feed material Molten furnace matte Fine granulated/crushed
The sloped offtake in the traditional geometry provides an Coarse crushed matte furnace matte
anchor for accretion to build off. Further to this, the change of for cold dope
gas direction from the top of the offtake is another area where
accretion can form.
As a result, the designed roof was raised above standard Training was undertaken at the pilot facility located at Anglo
Ausmelt vessel heights to reduce the potential for build-up on the Platinum’s Research Centre as an integration with the testwork.
roof and the uptake portion. By raising the furnace roof height, In addition, two weeks of exposure training of identified control
the chance of splash reaching the roof would be reduced. room operators and critical maintenance staff was undertaken at
An expansion of the freeboard to uptake area aimed to reduce the an industrial facility.
gas velocity and carry-over of splash and dust into the uptake as
shown in Figure 4. ACP OPERATION
DESIGN
-Taller furnace
As described above, the ACP project had several components of
- Vertical uptake technology innovation including:
• the application of the Ausmelt lance for converting;
• submerged bath Ausmelt lance feeding of converter input;
and
• combination of a Hatch waffle-cooled crucible with a Foster
Wheeler high-pressure water membrane freeboard and uptake.
Due to these innovative components, the project
implementation allowed for the design and construction of the
standby converter to be deferred until operating experience on
the running unit could be assimilated and incorporated into any
redesign deemed prudent. For this period, the Peirce Smith
converters initially ran in parallel with the new converting
section and since May 2004 have served as a cold standby. The
change-over to and commissioning of the standby converter is
due to begin in early 2006.
FIG 4 - Furnace geometry in terms of accretion formation. Commissioning and optimisation processes have long been
completed on the first converter. These activities, as usual, led to
many improvements but it is the fundamental design
Build-up at the direction change in the uptake was identified as performance and changes that form the basis for further
a potential problem area. The objective was to cool the gas
discussion.
sufficiently below the ‘sticky’ point at this stage, therefore
reducing the chance of build-up. A high-pressure hot water
uptake operating at 70 bar was designed to ensure the gas could Process control: two-stage to continuous
be cooled below this point prior to reaching the direction change operation
at the top of the uptake. The presence of high sulfur dioxide
content in the gas set an operating temperature range of 250 to Hot commissioning started in May 2002 and the plant systems
280ºC to ensure the off-gasses remained above the acid were integrated by August. Soon after start-up it was clear that
dewpoint. In addition, rapping hammers formed part of the although it piloted effectively, the two-stage process was unstable
design of the uptake, aiding in the removal of any accretion at the commercial scale. Some of the difficulties experienced
formed. were:
Finally, pilot testwork was used to verify that feeding the • Poor or incomplete mixing led to stratification within the
furnace matte through the lance would minimise carry over of furnace during converting. This resulted in non-equilibrium
input material. conditions and explosive foaming bath perturbations
occurred, particularly toward the end of the convert stage
Operational readiness when the differences in equilibrium were large.
The replacement of the six air-blown Peirce Smith converters • The basis of the two-stage process required tracking through
with a single, oxygen enriched stationary converter required an the converting stage to reach the targeted iron in matte end
operational mindset change with significantly higher emphasis point. Poor access to matte samples prevented this. The
on process vigilance. Table 1 highlights the critical differences in water-cooled sampling lance, which worked well at the small
the operating philosophies. scale, was unable to access the bath whilst operating. Further
to this, the stratification in the bath resulted in non-
Recruitment of operators was undertaken through a national
campaign with secondary education as a prerequisite. The senior representative matte samples.
operational staff were in place some six months prior to hot • Slight variations in the inputs as well as the starting bath
commissioning. made the starting point uncertain so that the convert stage

4 Brisbane, QLD, 7 - 8 November 2005 First Extractive Metallurgy Operators’ Conference

 THE NEW ANGLO PLATINUM CONVERTING PROJECT

could not be controlled on a mass balance basis. This also led • The higher oxidation level of the slag has led to significantly
to slag eruptions due to over oxidised baths and fluxing higher base metal oxide losses that require reduction for
control difficulties. recovery.
• Variable off-gas volumes associated with the two different The continuous operation has been optimised further and
stages affected gas volume and SO2 mass flow to the acid matte feed is not stopped during tapping of either matte or slag.
plant. This was problematic for both draft control and acid The matte feed rate is controlled to 45 tph as this produces the
plant stability. optimum gas to the acid plant. The nickel in slag is used to
• High platinum group metals (PGM) losses to the slag determine the oxidation state of the matte and is controlled by
through matte entrainment as the slag is tapped first. varying the air or oxygen flow rates. As the converter bath is
operated under steady state conditions, the matte is constantly
A single-stage or continuous feed process was considered maintained at the endpoint of three per cent Fe.
during the initial design phase, thus feeding and oxidising the
matte to final product quality simultaneously, and had been
piloted.
Vessel integrity: robust system
Having attempted to optimise the two-stage process, including Despite minor high-pressure system leaks, the crucible, freeboard
allowing stoppages for bath settling, the single-stage process was and uptake cooling systems have proved to be extremely robust.
introduced in January 2003 and has been used as the operational During a mandatory boiler inspection in January 2004, the
method since. This method of operation requires sufficient waffle coolers were found to be in exceptional condition. Sharp
oxygen to be added to the matte to convert the matte fed into the edges were still evident on the copper coolers and refractory
ACP converter to the final product. protection between the slag and matte hole elevations was still in
Figure 5 shows the situation at a matte feed rate of 60 tph. The place. However, the equilibrium brick profile above the slag hole
mass of matte fed would determine when matte has to be tapped. was not achieved. Shortly after start-up, the sidewall bricks in
The matte taphole would be closed on slag on every second cycle front of the waffles had worn out. A freeze layer of slag formed
to ensure there is no gradual build-up of matte inventory that on the copper coolers in place of the brick and thus protected the
may report to the slag granulation system. The total furnace level copper coolers as designed. The thickness of the slag was much
would dictate when slag is tapped, but generally directly after the less than the anticipated brick thickness and thus the heat flux to
matte. Some of the major impacts of running at end point the copper coolers was significantly higher. The conservative
continuously are: design safety factor allowed for these situations and the copper
coolers easily withstood these conditions.
• Lance tracking of total bath level to ensure constant Similarly, the boiler tubes showed little wear. This vindication
penetration is simpler. of the design efforts is especially significant, since the converter
• Matte is tapped before the slag, reducing the chance of a was initially planned to have a two year campaign life.
matte explosion during slag granulation as the matte level is The hearth showed no sign of wear. There was some matte
very low. penetration, but this was not deemed significant. However, due to
• Feed tonnages can be varied easily without impacting on signs of hydrated refractory around the slag taphole, it was
quality. decided to replace the hearth as a precaution. Following the
restart of the furnace, hearth temperatures quickly returned to the
• Simplified process control leading to better quality control. stable conditions of the original hearth and have remained there
The process does not have to be assayed as frequently and since.
through checking base metal content in slag, a good
indication of matte grade is achieved. Accretion
• Constant gas flow and SO2 content to the acid plant. The geometry of the furnace was effective in eliminating
• Reduced cycle time through feeding continuously to end accretion from the uptake and spray cooler throat. However, the
point. cooling systems were so effective that the roof and upper

FIG 5 - Continuous process bath profile.

First Extractive Metallurgy Operators’ Conference Brisbane, QLD, 7 - 8 November 2005 5

P VIVIERS and K HINES

portions of the furnace had significant build-up problems. A gate TABLE 2

slot cover had been installed at this transition point to allow the
ACP ramp-up significant events and milestones.
freeboard and uptake to be separated if required. This gate slot
was opened to allow the bath splash and accretion to be Timeline Description
observed. Under initially severe accretion, the gate slot was used
Jan 03 - Apr 04 Dual ACP and Peirce Smith converter operations.
to give access for mechanical equipment to break the accretion Two acid plants operating.
and allow the operation to continue.
Jan 03 - Mar 03 Settling 1 stage process, continued PLC/
The off-gas from the converter is ~1150ºC, which is some instrumentation interfacing problems, acid plant
200ºC below the design temperature. Following analysis of the commissioning.
accretion and several design reviews, it was decided that more
heat was required in the roof area to ensure splash remained Apr 03 Acid plant online, converter only operates when acid
plant operating.
molten long enough to return to the bath. After several attempts
to modify the lance’s afterburning area were moderately Jan 04 High-pressure system inspection and hearth
successful, it was decided to inject fuel coal through redundant replacement.
ports in the roof. Apr 04 Switched off Peirce Smith – total throughput via ACP.
This arrangement is illustrated in Figure 6. Jan 06 Planned commissioning of standby converter.
The fine fuel coal injection was effective in eliminating roof
build-up and in significantly slowing the build-up of the
accretion on the sloping freeboard. Cleaning times have reduced Once a week, the ACP converter is shut down for an eight to
from some 12 hours per day to once or twice a fortnight during twelve hour maintenance period. Depending on the maintenance
planned maintenance. required and whether the converter could be kept at temperature,
re-heating of the converter could take from two to six hours.
ACP ramp-up Thus a maintenance day could often result in a no or low
production day. The figure shows that the number of zero
The first controlled matte tap from the ACP converter was in production days has dramatically reduced. It must be noted that
August 2002. As discussed previously, the first few months the many of the zero production days from around October 2003
process was run as a two-stage operation and then switched to onwards are due to a lack of feed material as the ACP can reduce
the single-stage continuous mode from January 2003. The stock levels rapidly. Lance management is another aspect critical
ramp-up curve below shows the progress made since the process
to converter availability and is currently a focus for the
was switched to a single-stage continuous operation. This
process improvements and accretion management contributed operational staff.
significantly to more consistent throughputs. Figure 7 shows the The nameplate capacity for the ACP converter is 620 tpd,
daily tonnage treated via the ACP converter with a thirty day although daily throughput in excess of 1000 tonnes has been
moving average. Since April 2004, all Anglo Platinum furnace achieved. The single-stage continuous process has resulted in an
matte has been treated via the ACP converter. increase in capacity of the converter allowing for rapid catch-up
The milestone events in this ramp-up graph are summarised in without any downstream problems. The 30 day moving average
Table 2. shows the increase in daily throughput.

FIG 6 - Areas of accretion and accretion management.

6 Brisbane, QLD, 7 - 8 November 2005 First Extractive Metallurgy Operators’ Conference

 THE NEW ANGLO PLATINUM CONVERTING PROJECT

1000

900

800

Daily Treatment Rate (tpd) 700

600

500

400

300

200

100

0
Jan-03 Apr-03 Jun-03 Sep-03 Dec-03 Mar-04 Jun-04 Sep-04 Dec-04 Mar-05 Jun-05

FIG 7 - Daily throughput – 30 day moving average.

TABLE 3
160.00
Downtime summary.
140.00
SO2 Emissions (ave tpd)

Down time Initial six Jan 2004 April 2005

120.00
months hours/day hours/day
hours/day 100.00

Process upsets 2-3 <0.5 <0.25 80.00

60.00
Sampling 4-6 <0.5 <0.25
40.00
Uptake accretion and 4-6 2.5 - 3.5 <0.5
feed port blockages 20.00

Feed systems 4-6 0.5 - 1.0 <0.5 0.00

03

04

05
04

5
03

04
Tapping and WACS 3-4 2.0 - 3.5 <1.5

-0
-0

-0

l-0
v-

v-

n-
n-
p-

p-

ar
ar

ay

Ju
No

No

Ja
Ja
Se

Se
handling
M

M
M

Lance changes and 3-4 2.5 - 3.5 1.0 - 2.0

trolley problems FIG 8 - SO2 emissions from Waterval Complex.
Production scheduling 1-2 <0.5 -
Networks, 6-8 1.0 - 2.5 <0.5 Further emission reduction initiatives are due to be
instrumentation and implemented over the next two years and the authority guideline
software level of less than 20 tpd SO2 output will be sustainable at higher
Planned shutdown 1-2 1.0 - 2.0 1.0 - 2.0 production levels.
Breakdowns 4-6 1.0 - 2.0 1.0 - 2.0
No feed - 1.5 - 2.5 5 - 10 CONCLUSIONS
Operating factor 5 - 10% 30 - 40% 70% The ACP project was the first time Ausmelt technology was used
for converting in the platinum industry.
Project objectives have been achieved, specifically:

Downtime • nameplate capacity has been exceeded and all the Anglo
Platinum furnace matte is treated via the ACP converter; and
The initial start-up and utilisation of the ACP converter was • the SO2 emitted from the Waterval Smelter has dropped from
difficult, but in line with normal industry standards and over 200 tpd down to the 20 tpd levels and the emissions are
significant improvements have been made as can be seen in ever decreasing.
Table 3.
The selection of the Ausmelt technology and correct sizing as
a high-intensity robust converting process has been validated.
SO2 emissions Especially noteworthy has been the operational flexibility
The main objective of the ACP project was to reduce the total imparted by the water-cooled crucible in terms of process
Waterval Smelter SO2 emissions. Figure 8 shows the overall temperatures.
smelter emissions and the tonnage produced per month. From the The ACP project start-up and ramp-up was not without the
figure it is clear that the SO2 emissions have dropped as the ACP usual start-up problems associated with a plant of this
has been ramped up. complexity. Continuous optimisation since commissioning has

First Extractive Metallurgy Operators’ Conference Brisbane, QLD, 7 - 8 November 2005 7

P VIVIERS and K HINES

resulted in a number of changes that have significantly improved ACKNOWLEDGEMENTS

performance. These include:
The authors would like to thank Anglo Platinum for permission
• change from batch to continuous process, and to publish this data.
• roof addition of coal to control accretion.
In summary, the Anglo Platinum Converting Process has been
successfully implemented and positions the organisation strongly
for a sustainable future.

8 Brisbane, QLD, 7 - 8 November 2005 First Extractive Metallurgy Operators’ Conference