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Improved gas-gas exchanger reliability

Summary

Chemetics' new, patent-pending OPx™ exchanger (Optimum Performance Exchanger), will improve the reliability of cold exchangers, cold reheat exchangers and SO3 coolers in sulphuric acid plants, even with the use of carbon steel materials. Its disengagement chamber will capture the larger particles of entrained acid mist, which are known to be responsible for tube breaches. And its counter- and co-current flow design ensures that the minimum tube wall temperature will always be above the acid vapour dewpoint. O. Perez of Chemetics® discusses the main issues with conventional exchangers and how they can be overcome by technological innovation.

Abstract

Gas-gas exchangers are used extensively in a sulphuric acid plant contact section. Figure 1 shows a typical heat exchange scheme for a double-contact, double-absorption acid plant, where gas-gas exchangers are used to interchange heat between hot SO3-rich gas and cold SO2-rich gas to optimise the oxidation of SO2 in the converter beds. SO3 coolers are used mainly in metallurgical plants to augment cooling in the cold and cold reheat exchangers in times of high SO2 feed gas concentration. In spent acid regeneration plants, economisers are used instead of SO3 coolers to preheat boiler feed water for the waste heat boiler. In sulphur-burning plants, a drying tower, blower, sulphur burner, and waste heat boiler precede catalyst bed no. 1 and a steam superheater exchanges heat between catalyst beds no. 1 and no. 2.

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The impact of changing energy markets on sulphur production

Summary

As most sulphur is now recovered from oil and gas, the changing mix of sweet and sour crudes and natural gases that are used has a major bearing on sulphur supply. Sulphur looks at how new developments such as the US shale gas boom might affect supply in the future.

Abstract

Over the past few decades, elemental sulphur production has come to be dominated by sulphur recovery from oil and gas, in order to meet steadily tightening environmental emissions standards. Elemental sulphur production is now almost completely from such involuntary production; about 95% of sulphur is recovered in this way, with mined sulphur accounting for only a tiny fraction. In terms of sulphur in all forms, recovered sulphur represents about 2/3 of production, as involuntary production of sulphuric acid from metal smelting (and some from mined pyrites) also feed into sulphur’s main market – sulphuric acid.
This concentration on involuntary production has led to supply of sulphur running ahead of demand, and considerable stockpiles of solid sulphur have built up in places where it has been most logistically difficult to bring it to market, such as northern Canada and the Caspian Sea. However, changing patterns of oil and gas production have the potential to change the proportion of sulphur that is recovered. On the debit side, the increased concentration on production of shale gas and other unconventional natural gas sources has the potential to considerably reduce the amount of sulphur produced by the natural gas industry. On the other, increasing production of sour gas, oil sands and use of sourer crudes have the potential to increase sulphur production.

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TGT advances lower operating and capital costs

Summary

Maintaining profitable operation while meeting increasingly strict environmental regulations presents a challenge for plant owners and operators throughout the world. Fluor has developed several patent-pending processes to reduce capital and operating costs while meeting the necessary environmental standards. Two of these, the STREP process and a new DCC process, are highlighted in this article by V.W. Wong, T.M. Flood, J.Y. Mak and T.K. Chow of Fluor Corporation.

Abstract

Recent industry trends focusing on producing cleaner air and fuels around the globe have generated significant demand for improved sulphur recovery efficiency in new and existing gas plants and refineries. Stringent environmental regulations have necessitated the addition or improvement of various systems and/or equipment to reduce the emissions from plants currently in operation. Grassroots facilities frequently must demonstrate the inclusion of best available control technology (BACT) in order to receive the required environmental permits. Hydrogenation/amine is the most widely used tail gas treating technology in the industry for modern facilities.
Since the capital and/or operating expenses associated with hydrogenation/amine tail gas treating can be substantial, it is important to offset costs where possible. Luckily, optimisation of some of the processes within the tail gas treating unit (TGTU) can result in significant cost savings. Fluor has developed several patent-pending processes to reduce utility consumption (and thus operating cost) while still achieving the required sulphur recovery efficiency. In addition to improved performance and reduced operating and capital cost, these processes can also improve operational flexibility and robustness.

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Advanced HCR™ targets zero sulphur emissions

Summary

The new generation HCR technology, having incorporated low temperature catalyst in the reduction section, improved its design to enhance plant operability, and reduced energy demand to limit carbon emissions, now marks a further step towards zero sulphur emissions, by means of weighted selection of the solvent used in the H2S extraction section. L. Micucci of Siirtec Nigi describes the latest advances and reports on a recent case study.

Abstract

In the past decade Siirtec Nigi has invested much effort in the development of a new generation of High Claus Ratio (HCR) technology with the aim of improving the operability of the Claus tail gas treating unit, reducing energy demand and reducing the carbon dioxide footprint.
This work has led to the implementation of low temperature catalysts in the reduction end of the tail gas treatment unit, better integration with the other units of the SRU and a reduction in the steam demand of the amine regeneration section.

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Japan: after the earthquake

Summary

David Hayes talks to Japanese sulphuric acid producers and traders about the after-effects of the devastating earthquake and tsunami earlier in the year on the country's sulphuric acid industry.

Abstract

Japan’s sulphuric acid industry has faced unprecedented operational circumstances this year, following the March 11 earthquake and tsunami disaster which badly affected the Tohoku region and part of the neighbouring Kanto region, including Tokyo. Earthquake damage occurred in an area stretching about 500km north to south from Iwate to Tokyo along the eastern Japanese coastline. The scale of damage and destruction made this the worst earthquake disaster in Japan in recent times. According to the National Police Agency 15,782 people died and 4,086 people are still missing (as of September 11, 2011) following the earthquake and tsunami, which damaged or destroyed over 270,000 buildings and caused flooding up to 10km inland in some areas just north of Tokyo.

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Customised TGTU design at Petroplus Refinery

Summary

Petroplus is adding a new tail gas treating unit (TGTU) designed by Black & Veatch at the Coryton Refinery in the UK to meet a new minimum 99.5% sulphur recovery requirement.

Abstract

Petroplus is adding a new tail gas treating unit (TGTU) designed by Black & Veatch at the Coryton Refinery in the UK to meet a new minimum 99.5% sulphur recovery  requirement. The refinery currently operates two existing three-bed Claus sulphur recovery units each originally rated for 100 t/d of sulphur production. After the tail gas unit installation, each SRU will process 80 t/d, sufficient for maximum expected refinery needs. The new tail gas unit, currently under construction, is scheduled to start-up in early 2012.
The project faced two key design challenges. Refinery plot space available for tail gas treating is limited and was not anticipated during construction of the original SRUs. Likewise, the original SRUs were not designed hydraulically for a future tail gas treating unit. To overcome these challenges, while maintaining maximum operational reliability and minimum project cost, Black & Veatch developed an innovative approach. The third Claus converter in each SRU train was converted to tail gas hydrogenation service, using low-temperature catalyst, allowing reuse of the existing steam-heated reheater for tail gas preheat service. A new quench tower and TGTU absorber for each SRU train was installed downstream of the third converter, now in tail gas hydrogenation service, maintaining separate gas paths for increased reliability and maintainability. A common quench water circulation system, amine circulation system and common amine regeneration system serves both tail gas unit trains, minimising capital cost and overall footprint.

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Sulphur from pyrites

Summary

Although no longer one of the world's major sources of sulphur, pyrites roasting continues to occupy a niche in the Chinese market.

Abstract

Iron pyrites (FeS2) are the most common sulphide mineral in the Earth’s crust. There are extensive deposits around the world, and prior to the development of Frasch mining, they were the dominant source of sulphur for sulphuric acid production, throughout the 19th and early 20th centuries. However, they have been overtaken as a source of sulphur, first by Frasch mining which began in 1895, and then by Claus sulphur recovered from oil and gas processing.
Global sulphuric acid production from pyrites reached a peak of over 10 million t/a (sulphur basis) in the 1970s, at which time it represented 22% of sulphur in all forms. It has been in long-term decline since then, down to less than 7% of sulphur production at present. Production largely ceased in the United States in 1988, Brazil and Bulgaria in the 1990s, Albania and Spain in 2001, and Russia in 2008. While some small production continues in countries such as India, Venezuela and in southern Africa (eg, Zimbabwe), the only countries where pyrites remain a significant source of sulphur are China and Finland, and more than 85% of all pyrite production is now in China, where most production is concentrated in the eastern provinces of Guangdong, Anhui, Jiangxi and Liaoning (more than 75% of all Chinese production).

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Customised solutions with RAR technology

Summary

Michele Colozzi of Tecnimont KT SpA reports on how RAR technology can be utilised to customise process flow schemes according to client's needs by utilising different plant configurations and process solutions, and selecting the best absorption liquor in order to minimise capex and opex, in full compliance of the most stringent environmental regulations around the world.

Abstract

Environmental regulations all around the world are imposing very stringent SO2 emissions requirements and it is not uncommon nowadays to receive requests for quotation of technology supply for sulphur recovery facilities with SO2 emissions  in the range of 50-150 ppm dry basis with 3 vol-% excess oxygen in the flue gas.
With such stringent SO2 emissions it is also evident that H2S flaring is no longer tolerated and industrial complexes such as petroleum refineries, oil and gas fields and petrochemical complexes have to adopt and select the Best Available Technology to satisfy these new requirements.

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Caustic scrubbing vs sulphuric acid production

Summary

Sulphur recovery efficiencies of nearly 100% are required from sulphur recovery units in some locations throughout the world. In this article, Mahin Rameshni of Rameshni & Associates Technology & Engineering (RATE) discusses and compares two technology options, caustic scrubbing and sulphuric acid production, both of which can be applied to achieve these most stringent requirements.

Abstract

Environmental regulatory agencies around the world are demanding more stringent standards for sulphur emissions from oil, gas, and chemical processing facilities. Most countries require sulphur recovery efficiencies in the range of 98.5% to 99.9+% from Claus plants including tail gas treating units. In more stringent locations e.g. California, USA, sulphur recovery efficiencies of nearly 100% are required for new or modified sulphur plants and the World Bank requires SO2 emissions of less than 150 mg/Nm3 (~50 ppmv) for loan approval.
The standard allowable emission for SO2 has been 250 ppmv for many years, but improved methods are available that can reduce SO2 emissions from 250 ppmv to 30-50 ppmv. However, any improvement will increase the capital and operating cost of the facility.

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Sulphuric acid in the uranium industry

Summary

While copper and nickel are the major consumers of sulphuric acid for metal leaching, uranium leaching is also a rapidly growing area of demand, as various countries expand their civil nuclear power programmes.

Abstract

After fertilizer production, metals processing is the largest single sector of demand for sulphuric acid. Most consumption is in copper leaching and subsequent solvent extraction/electrowinning (SX/EW) processing, particularly in Chile, while high pressure acid leaching (HPAL) of nickel is projected to equal or even outstrip this use over the next decade. However, there are other metal industries which use sulphuric acid, and one that has seen demand increasing rapidly in recent years has been the processing of uranium ore.

Demand

Uranium demand is almost exclusively for the nuclear power industry. A smaller proportion used to be consumed by military and naval use (e.g. in nuclear-powered military vessels), but this latter use has fallen considerably from its peak in the 1980s. Demand for nuclear power, conversely, has been steadily rising over the past 50 years. Nuclear power represents about 14% of all energy production, with over 440 reactors operating in 31 countries.

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