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Publication > Issue > Articles

A bug's life counts for miners

Summary

Copper miners and researchers are moving quickly to increase their understanding of biological process technology and to bring virtually acid-free metallurgy into commercial production. Chris Cunningham reports.

Abstract

Recent large scale expansion in smelter output in Chile and northern Europe would appear to counter any suggestions that the concentrate-roast approach to copper production is in any danger of disappearing.

In North America, the story is different. Smelter closures in the US and Canada, slow-downs, strikes and other factors contribute to a tight supply of merchant acid, which in turn helps to maintain a strong market elsewhere for long range export of the product. It also supports an absence of over-supply when capacity suggests that there should be an excess over demand.

Japanese exports of, chiefly, smelter acid to Chile’s hydrometallurgical operations stood at 187,000 tonnes in 2001, and had already reached 156,000 tonnes at the halfway point of 2002. Whilst the signs here are for a healthy future in acid trade, the longer term picture is not so positive. In Chile, as elsewhere in the world, supplies of copper oxide ore are dwindling and the mining industry is looking to other resources of copper to meet global demand.

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The future for sulphur forming

Summary

Jim Hyne of Hyjay R&D, Calgary ponders future developments needed in sulphur forming to assure its value to the buyer and to improve further the resistance of premium product to the rigours of handling and long haul transportation.

Abstract

Ahundred years ago sulphur was already a key, basic chemical commodity for industry. As it is today – a starting point for making essential industrial sulphuric acid – so it was in yesteryears. But there is much that we have learned from that century of experience, especially with respect to how to store, handle and transport the commodity.Those who fail to learn the lessons of history are condemned to relive it.

In that century the sulphur industry has moved from transporting solid (mined) product in wooden barrels (with no corrosive interaction!) to sophisticated modern technologies for bulk handling both solid and liquid elemental sulphur, most of it recovered from petroleum and gas processing. The liquid story is an important one, but it is the more common (in terms of world tonnage) formed, solid sulphur story that we address here. Of some 20,000,000 t/y of elemental sulphur traded on world markets over 12,000,000 tonnes is solid, mostly formed, and subject to long haul transportation. The emphasis here is on “long haul”, for it is the procedures involved in this step that place the greatest demands on the physical quality of the formed solid sulphur product.

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Troubleshooting sulphur condenser leaks in Claus SRUs

Summary

Pierre P. Crevier, Gas Processing Specialist at Saudi Aramco describes a technique that enables on-site sulphur plant engineers to quickly and easily monitor sulphur condenser leaks. The leak detection technique uses basic equipment available in any gas plant or refinery. The extent of the leak is determined using a unique, water-soluble, non-volatile tracer that is injected into the BFW flowing to the exchanger.

Abstract

This paper describes a simple, easy technique for diagnosing and monitoring tube and tube sheet leaks in sulphur recovery unit (SRU) condensers designed for steam generation.

A leak in a water-cooled condenser will result in boiler feed water (BFW) flashing into the process side of the exchanger. This can lead to a variety of operational and maintenance problems. Depending on the size of the leak, it may take some time for the water to vaporize completely into the process gas. Claus trains built of carbon steel are not designed for free water on the process side of equipment. Corrosion is a very serious concern if the leak is large.

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Meeting refiners' needs

Summary

In response to forthcoming environmental regulations, researchers at RTI in North Carolina, USA, are developing a process to remove sulphur from gasoline and diesel. Key aims of the project are to reduce capital and operating costs compared to existing processes and to give a higher yield of desulphurised fuel.

Abstract

In September 2000, RTI International received a $1.3 million grant from the US Department of Energy to develop a new process for producing low-sulphur gasoline.The objective of the research was to extend RTI’s earlier success in syngas desulphurisation to the removal of sulphur from gasoline and diesel to produce clean transportation fuels.

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A low cost ULSD solution

Summary

Following successful pilot plant testing, Phillips Petroleum Company is to build its first S Zorb-Diesel SRT unit at its Sweeny, Texas, refinery by the fourth quarter of 2003. Key features of the ultra low sulphur diesel technology include product sulphur levels of 10 ppm or lower with moderate operating conditions, excellent product stability, and far less chemical hydrogen consumption than conventional hydrotreating.

Abstract

The US Environmental Protection Agency (EPA) has mandated that the sulphur content of onroad diesel be lowered from the current 500-ppm cap to 15 ppm at the refinery gate by June 2006. Refiners expect that they will be required to produce diesel containing less than 10-ppm sulphur in order to meet the specification.

Since meeting the new clean fuels specifications will not pay a return on investment, the guiding principle in technology selection is minimising total cost. In hydrodesulphurisation, cost is related to space velocity or catalyst volume, operating pressure, and hydrogen consumption. Oil company Phillips Petroleum Company explored these variables in a benchmark study designed to gauge the parameters necessary to produce ultra low sulphur diesel (ULSD) via hydrodesulphurisation.

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A logical approach for SRU operating challenges

Summary

The design and operation of sulphur plants processing lean acid gas present unique challenges to designers and operators of Claus sulphur plants. In this article J.K. Chen, Thomas K. Chow and John Gebur of Fluor present a logical approach for achieving smooth and cost effective sulphur plant operation. The pros, cons and limitations of various options to handle lean acid gas in a Claus plant are discussed.

Abstract

With the desire to restore and maintain a clean environment for the world we live in, environmental regulatory agencies of many countries continue to promulgate more stringent standards for sulphur emissions from oil, gas and chemical processing facilities. It is therefore necessary to select and implement reliable and cost effective technologies for sulphur plants to ensure reliable and smooth operation.

The modified Claus process is the most commonly used technology for recovering elemental sulphur from acid gas streams containing hydrogen sulphide. The acid gas streams encountered in oil and gas production facilities are often “lean”, containing less than 50% hydrogen sulphide by volume. The design and operation of these sulphur plants processing lean acid gas present unique challenges for the reaction furnace, especially when the lean acid gas streams contain undesirable trace contaminants, such as benzene, toluene and xylene.

The key to successful, smooth and reliable operation of a sulphur plant which processes lean acid gas is achieving sufficiently high flame temperature in the reaction furnace. Sufficient temperature is required for destruction of hydrocarbons in the acid gas feed. As will be detailed later, the required temperature depends on the feed content. The designers and operators of lean acid gas sulphur plants employ various means of increasing the reaction furnace temperature. These techniques will be described and the pros and cons of each will be compared. A good burner is also essential for smooth operation. There are a number of excellent sulphur plant burner designs on the market, but burner design will not be discussed in this paper.

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Preventing excessive refractory temperatures

Summary

With the introduction of oxygen enrichment to Claus sulphur recovery units in the 1980s, increases in refractory, checker-wall and tube ferrule failures highlighted the importance of accurately monitoring reaction furnace temperatures. The current range of temperature measurement devices has overcome many earlier problems. Recent studies have focused on predicting gas and refractory temperatures and identifying the best infrared wavelengths to use for oxygenenriched applications. Lisa Connock reports.

Abstract

Measurement of the temperature of a Claus thermal reactor has always been challenging. It is generally agreed that this temperature measurement is the most severe and demanding one known in the process industry.

Problems of high temperature, corrosion, shifting refractory, quenching, process upsets and changes in the gas composition are challenging obstacles to obtaining reliable and accurate temperature measurement.

There are two technologies available to make this temperature measurement - thermocouple and infrared (IR). A comparison of traditional thermocouple and infrared devices is given in Table 1.

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