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Keeping emissions under control

Summary

Plant design features, plant operating practices and plant maintenance are all key factors to minimise start-up emissions from sulphuric acid plants. Robert W. Grendel of MECS Inc. discusses the measures required to keep emissions within acceptable limits during start-up conditions.

Abstract

Sulphuric acid production plants are subject to SO2 and acid mist emission criteria in the USA and throughout most of the rest of the world today. Typical criteria have been 4 lbs of SO2 per ton of 100% H2SO4 produced (2 kg/tonne) and 0.15 lbs of acid mist per ton of H2SO4 produced (0.075 kg/tonne), but in many locations the criteria are now more stringent. The test for acid mist includes acid mist droplets, SO3 gas, and H2SO4 vapour, and all are combined and reported as 100% H2SO4. In plants of modern design, these criteria are met during normal operations with enough margin to allow for minor variations in control parameters without putting the plants into violation episodes.

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Making hay in Montreal

Summary

British Sulphur's annual Sulphur conference and exhibition moved to Montreal this year. While the industry was buoyed by record prices for sulphur, the spectre of overcapacity loomed large for the future.

Abstract

That a record 450 delegates congregated in Montreal was surely a testament of some kind to the record run of prices which the sulphur industry has enjoyed over the past year. In his opening remarks, John French, conference director, touched on this as he welcomed delegates who must, he said, be asking themselves, “what on earth is happening to sulphur markets?” Recently quoted prices by Adnoc f.o.b. Ruwais were $220/t, compared to a price at the same time last year of $53/t. Prices of up to $300/t c. & f. for spot sulphuric acid have been seen in Chile. The question, John said, was – is this just a ‘blip’ (albeit quite a long one, it seems), or a sea-change in the industry? While he said he did not pretend to know the answers, he hoped that some of the experts gathered together would be able to.

He also took the opportunity to once again thank the various sponsors for their generous support; Interacid for the VIP reception; ICEC, who co-sponsored the opening cocktail reception along with British Sulphur; Solvadis, who sponsored the morning’s champagne breakfast; BP, CN Rail, Enersul, ICEC, Marsulex, PentaSul, Prism, Shell, Sultran and Suncor, who between them sponsored the Canadian evening dinner; Tasweeq for Monday lunch; Astrakhangazprom for the Tuesday evening reception; and last but by no means least Lewis Pumps for the conference bags.

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Gas membranes for highly sour service

Summary

New technology now permits membranes to be used for bulk removal of H2S from natural gas even at very high H2S concentrations and at high operating pressures. Tom Cnop, David Dortmundt and Mark Schott of UOP LLC summarise the principles involved in CO2 and bulk H2S removal by membranes, design considerations, experiences in large natural gas processing plants, and recent UOP innovations in natural gas sweetening.

Abstract

The traditional gas processing approach for sour gas is to utilise solvent systems for natural gas cleanup and Claus technology for H2S conversion to elemental sulphur. While this technology is well known and proven, it can be difficult to operate and uneconomic for highly sour gasses as the operating costs are directly related to the amount of sulphur in the feed gas. Moreover, the production of sulphur is a nuisance as there are insufficient market resources to absorb the large volumes of elemental sulphur now on the market from natural gas treating applications. Today major sour gas production areas are building ever-larger sulphur mountains. New technologies that envisage a more sustainable future are needed.

Membranes have become an established technology for carbon dioxide removal since their first use in this application in 1981. This technology is widely practiced for the treating of pipeline gas, enhanced oil recovery (EOR), bulk removal of CO2 on offshore platforms, and for upgrading of biogas for commercial sale. Membranes are used for the co-removal of CO2 and H2S, but only when the sulphur levels are relatively low. The multiple bene­fits of membrane technology promised by early innovators have since been proven in a wide variety of installations in many locations around the world, and vendors of traditional CO2 removal technologies have been quick to acquire or develop membrane-based processes to supplement their older processing routes. In some cases, the most economical approach is to combine membranes with existing technologies. Membranes are also used to debottleneck existing solvent- based plants.

UOP has developed polymeric membranes that can be used for bulk removal of H2S from natural gas even at very high H2S concentrations and at high operating pressures. This approach allows for more sustainable development of new sour gas fields or for retrofitting into existing applications. The membrane system can be used to make a large bulk cut of the acid gases, typically in the 70-90% reduction range, then final pipeline specifications can be met in a traditional amine process. The permeate gas from the membrane system can ideally be re-injected, as opposed to being converted to elemental sulphur and stored onsite. Significant reductions in ­capital and operating costs, as well as sulphur production costs, can be achieved through this new approach.

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Nickel's symbiosis with sulphur

Summary

Acid leach processing of laterite ores continues to be the fastest developing market for sulphur and for sulphuric acid. Major projects are taking shape in Australia, the Pacific Basin and Eastern Europe, among other laterite-rich zones. Mark Evans reviews the status of this industry's development.

Abstract

The non-ferrous metals industries have for long been indirect contributors to the world sulphur industry via the production of by-product sulphuric acid. Production of non-ferrous metals averages around 80 million t/a. Of these metals, approximately one third are found in nature as sulphide materials and their recovery requires separation from – and also in most cases recovery of – the sulphur content. (Dynamics of Metals Industry on Sulphur Demand, Caline Sahyoun and Geoff Mason, Saint Barbara LLP. Paper presented at The Sulphur Institute Sulphur World Symposium, Amsterdam [March 2007].)

Non-ferrous metals smelters produce approximately 15 million t/a of sulphur, mainly in the form of sulphuric acid, with copper and zinc accounting for around 90% of this total. The balance is accounted mostly by the lead and nickel industries. Out of a total world sulphuric acid production of 192 million tonnes in 2005, metallurgical acid comprised an estimated 50 million tonnes.

The basic technology employed in smelting sulphide ores is well established, but it has come under considerable scrutiny for both economic and environmental reasons. In particular, there has been a trend away from traditional pyrometallurgical proces­ses in favour of the increased adoption of hy­drometallurgical processes, such as pressure leaching. The latter is widely seen as a way of reducing the environmental concerns that arise with any new smelting project.

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Sulphur in southern Africa

Summary

High commodity prices are driving a rejuvenation of southern Africa's metal mining industries, and with it will come a huge hike in demand for sulphur and sulphuric acid.

Abstract

China’s economic boom has driven a run on demand in many sectors of the economy, and metals have been no exception. China has recognised this requirement for raw materials and has begun to become politically and economically active in Africa in recent years, with India, the United States, Russia and Australia, among others, not far behind.

Southern Africa, although (with the exception of South Africa itself) relatively economically underdeveloped, has a significant portion of the world’s reserves of various important metals (see map). The southern part of the Democratic Republic of the Congo contains 10% of the world’s copper and 30% of its cobalt. The copper belt extends south into Zambia, where a further 15% of the world’s copper lies. Some 14% of the world’s uranium is in Namibia, while Botswana has fully half of all the world’s diamonds. South Africa itself has 50% of the world’s gold reserves and an astonishing 75% of its platinum. Across the straits of Madagascar, 35% of the world’s nickel can be found on that island.

During the 1990s, low prices for various commodities led to a decline in metal production in the region, and many mines were abandoned, some being left to flood. Prices reached their lowest ebb around 1999-2000, and, coupled with difficulties with dealing in some countries due to nationalisation of industries, interest in developing mining in the region waned. ­However, in recent years high commodity prices for metals (see Figures 1, 2) has led to an upsurge in interest in metal extraction from these regions, in spite of the various difficulties unique to the region, and with metal extraction and smelting has come sulphuric acid production and consumption, and an increasing appetite for sulphur to feed these sulphuric acid plants.

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Latest developments in sulphuric acid catalysts

Summary

Modern sulphuric acid catalysts are designed to increase production campaigns, reduce SO2 emissions to the environment, increase acid production and contribute to improved sulphuric acid plant operations in an economical fashion. Sulphur reports on latest catalyst developments by MECS and Haldor Topse

Abstract

A current focus within the sulphuric acid industry is to reduce sulphur dioxide emissions to the atmosphere while maintaining or increasing acid production. This trend is supported by an industry-wide consolidation of production capabilities and increased emphasis on improving air quality. The use of conventional potassium-promoted sulphuric acid catalyst (K-V) has nearly reached the practical limit regarding minimisation of emissions while increasing acid production rates. The development of an exceptional low temperature catalyst promoted by caesium (Cs) compounds has expanded the useful operating range of sulphuric acid plants, allowing for increased acid production rates (with higher gas strengths and greater volumetric gas flow) while maintaining or reducing SO2 emissions.

In the contact sulphuric acid process, there is often an interest in reducing the inlet temperatures to certain adiabatic catalyst beds in order to provide more favourable equilibrium conditions. The addition of caesium (Cs) salts to the conventional alkali-vanadium sulphuric acid catalyst formulations has long been known to enhance the low temperature properties of the catalyst1. The caesium promoter stabilises the vanadium +5 oxidation state (V5+) at temperatures below 420°C and keeps the active vanadium species solubilised in the molten salt. In the conventional K-V sulphuric acid catalyst, the various vanadium compounds begin precipitating from the molten salt at low bed temperatures, leading to catalyst deactivation2,3. At relatively high operating temperatures (>430°C), the reaction rate is ap­proximately the same for both the conventional material and the caesium-promoted catalyst. However, if the temperature is below 415°C, the conventional catalyst begins to deactivate due to the precipitation while the stabilised caesium catalyst continues to perform well. Therefore, the useable temperature range for effective conversion is greatly expan­ded, providing versatility to the overall operation4.

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Sulphur production to increase by half

Summary

State-run Chinese Petroleum Corporation's (CPC) plans to build a new refinery and Taiwan's No 8 naphtha cracker in Yunlin county on the west coast will increase domestic production of sulphur by about 300,000 t/a once the project is completed in 2016. David Hayes reports.

Abstract

Due to be built at a cost of $11.6bn, the refinery and petrochemical complex’s sulphur output will raise total sulphur production in Taiwan by almost 50% to about 900,000 t/a. With domestic sulphur production already in excess of local demand, most of the new capacity will be exported, with China being the most likely destination.

Plans to build the new refinery and No 8 naphtha cracker are now at the environmental impact study stage. If approved, the project will be undertaken by a consortium of CPC and five private partners. CPC will hold a 43% interest in the project while the partners consisting of four Taiwanese chemical manufacturers and an investment company will take a combined 57% shareholding. The Yunlin energy and naphtha cracker complex will include a 300,000 bbl/day oil refinery, a naphtha cracker and 27 mid-stream plants producing intermediate chemicals for plastics and textiles.

The new refinery will replace CPCs existing refinery in Kaohsiung which the company has agreed to shut by 2015 in response to lengthy complaints from nearby residents about pollution emission. The new refinery will incorporate modern, more efficient technology and help CPC compete with Formosa Petrochemical Corporation, Taiwans only other refiner. The new complex will increase CPCs sulphur output by 150% lifting current production of about 200,000 t/a to 500,000 tonnes annually.

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Sulphur production and trade statistics 2006

Summary

Abstract

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