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A cleaner alternative

Summary

A new hydrometallurgical route for the processing of copper sulphide concentrates has been developed and demonstrated by Cominco. The new technology is expected to bring cost reductions as well as major environmental advantages compared to the traditional copper smelting route.

Abstract

For decades, Cominco and other experts in the field have been striving to develop a more environmentally friendly way to separate high grade copper from its ore. The conventional pyrometallurgical method achieves high extraction rates for copper but has a number of environmental drawbacks, e.g. sulphur dioxide emissions and the disposal of unwanted sulphuric acid. Hydrometallurgical methods using liquid processes have been developed to overcome the environmental problems but have been unable to achieve the high levels of copper extraction associated with the traditional smelting process.

Cominco Engineering Services Ltd (Vancouver, B.C.) has now successfully piloted and is currently demonstrating a new copper refining technology which uses a hydrometallurgical route to extract high levels of copper in a process which eliminates the gaseous emissions prevalent in conventional copper smelting. The new CESL process leaves only non-hazardous residues. The process is based on a unique combination of previously proven process steps, using existing technology for the equipment.

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Simple ideas are often the best

Summary

Goar Allison & Associates (GAA) has developed and commercialized a new sulphur ­degasification process. The key to the process is the use of elevated pressure and special fixed vessel internals which together result in a low cost, zero emission process that can achieve below 10 ppmw H2S/H2SX in the degassed liquid sulphur.

Abstract

Sulphur degasification is a pro­cess that removes dissolved hydrogen sulphide (H2S) and polysulphides (H2SX) vapour from liquid sulphur. Undegassed sulphur presents odour and potential toxic hazardous conditions in the storage, loading and transport of liquid sulphur. When present in solid sulphur, H2S/H2SX causes odour problems and increases dust problems during handling.

The existing major sulphur degassing technologies use a combination of mechanical, catalytic and/or oxidation techniques to remove H2S/ H2SX in liquid sulphur to the generally accepted residual H2S standard of 10 ppmw.

Goar Allison & Associates, Inc. (Tyler, TX) has recently introduced a new sulphur degasification process which has been designed to overcome the limitations associated with some of the existing processes.1 The new process, named the D’GAASS pro­cess, reduces combined H2S/ H2SX to 10 ppmw in the sulphur product using a simple, low-capital and low-operating cost method. The process operates at elevated pressure, thus allowing the use of a small, low-residence time vessel that is easily retrofitted external to sulphur pits or incorporated in a grass root design. The elevated operating pressure allows for recycling of the overhead vapour stream back to the main bur­ner of the sulphur recovery unit (SRU) thus eliminating the degass­ing process as a source of SO2 emissions.

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The right way

Summary

The old practice of pouring sulphur to poorly prepared or unprepared ground, can have serious and costly future ramifications reports Clive Rutland, Enersul (formerly Procor Sulphur Services), especially if the method used harms its immediate environment.

Abstract

The environmental implications of sulphur block storage were not really considered in the early days. Gravity was often used as a means of moving liquid sulphur through pipelines to a low lying pouring site. The soil in low lying areas around sulphur producing plants in remote locations is quite often boggy or muskeg. The unevenness of the soils, and the characteristics of the underlying soil (for example muskeg) compound sulphur block clean up problems in these areas.

Some sulphur producers have already faced expensive clean ups, at the insistence of regulatory bodies, due to this condition.

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New investment horizons

Summary

South Africa is characterised by its lack of commercial deposits of native sulphur, forcing it to import huge amounts, mostly from Canada, to satisfy sulphuric acid requirements in the fertilizer industry, and to a lesser extent the needs of the mining industry in various metallurgical processes. Jason Stevens examines the interlinking strands of South Africa's sulphur and sulphuric acid industries.

Abstract

Since 1993, South Africa has produced 845,000 tonnes of sulphur, with the years 1995 and 1996 recording the highest levels thus far – almost identical at 233,000 tonnes and 232,000 tonnes respectively (See Table 1).

Most of the sulphur produced locally originates as a by-product in pyrites’ production and is also extracted from four refineries, three of which are located on the coastal regions of South Africa (see accompanying boxes for full refinery reports – Ed).

These four refineries along with Sasol’s Synthetic Fuels plant at Secunda account for roughly 277,000 t/y of sulphur, and are regular suppliers of liquid and solid sulphur to downstream fertilizer producers, such as: Indian Ocean Fertilizers (IOF) based in Richard’s Bay; the Kynoch/AECI Fertilizer plants in Potchefstroom/ Umbogin-twini; Omnia Fertilizers in Rusten-burg and Sasolburg; and finally Phalaborwa-based, Fedmis.

Sulphur is purchased on a pool basis by the above, who have a standing agreement with a Greek shipping line who offer low freight rates on Panamax vessels from Vancouver to Richard’s Bay.

In an interesting attempt to stimulate and facilitate downstream chemical business in South Africa, Sasol Chemical Industries (SCI) has contracted its Natref refinery to supply a small portion of its sulphur production to a new sulphur milling plant in Sasolburg. The sulphur could ultimately find its way into rubber manufacturing as a vulcanizing agent. Several other processed-sulphur products are currently being developed and will be added to the product range once commercialized. (See Natref refinery report – Ed).

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Understanding Claus plant upsets using your tail gas analyzer

Summary

Randy N. Hauer (Western Research), John A. Sames (Sulphur Experts) and Colin Hunt (Shell UK) inform readers how to use the data produced by an on-line H2S/SO2 tail gas analyzer for a Claus Sulphur Recovery Unit to full advantage in troubleshooting Claus plants. The intended audience is process operators/engineers who are involved in the day to day operation of the Claus SRU and the purpose is to train these key personnel in interpreting the data so that it can be used to take appropriate action during process upsets.

Abstract

The paper is presented in the form of case studies that describe a specific process upset condition and the resulting analyzer response. These case studies use actual process data where it is available, others are historical and are described using empirical results based on experience in over 600 sulphur plant performance tests as well as input from operating companies.

It is assumed that the personnel involved in the operation and process optimization of the Claus SRU already have a sound foundation in the basics of the modified-Claus process and control of that process. There are two technical papers on these subjects, that form part of the five day Sulphur Recovery Seminar on optimizing the Claus SRU presented by Sulphur Experts Inc and Western Research. Please refer to these for additional details.

The objective of this paper is to cover the following topics:

  • where the tail gas analyzer fits in the process
  • what the analyzer is saying about the process when it is “off-ratio”
  • limitations of the tail gas analyzer
  • secondary sources of information that can be used to confirm the analyzer data
  • training of non-QMI (analyzer) personnel in primary analyzer trouble shooting.

 

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Sulphur research and production in ­western Canada

Summary

The following article by Peter Clark, Director of Research and Chief Operating Officer, Alberta Sulphur Research Ltd, summarizes the research activities of Alberta Sulphur Research Ltd and describes how this effort is related to gas and sulphur recovery in Canada and elsewhere in the world.

Abstract

Canada, and, in particular, Western Canada, has been a major producer of brimstone since the late 1950s as a result of sulphur recovery from the sour natural gas found in the foothills of the Rocky Mountains.

Sulphur recovery from natural gas began in earnest in Alberta in the late 1950s. Today, approximately 8 million tonnes/annum of sulphur are made in Alberta and in NE British Col­umbia by the modified Claus pro­cess, a means of partial oxidation of hydrogen sulphide to sulphur and water. Most of the hydrogen sulphide originates from sour natural gas reserves, but more and more is now produced in the bitumen upgrading facilities of Northern Alberta. More about this source of hydrogen sulphide and sulphur later.

ASRL was formed in 1964 to support the activities of the then emerging sour natural gas industry. It is operated as a not-for-profit research organization within the Chemistry De­par­t­ment of The University of Cal­gary. ASRL is a registered company under Alberta law and is overseen by a Board of Directors and a Technical Advisory Committee selected from the employees of its member companies. The mandate of ASRL is to carry out basic and applied research to enhance the commercial activities of its supporting member companies. Al­though these supporting companies were originally only firms active in Alberta, ASRL now conducts research on behalf of Canadian, American, British, Dutch, German, French, Italian and Nor­wegian-based companies. Its staff have over 150 collective years of sulphur chemistry and technology experience.

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