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Rising profile

Summary

Since the mid-1990s, the Former Soviet Union (FSU), and Russia in particular, has emerged as a leading force in the world's market for sulphur. With major hydrocarbon ­projects developing rapidly in the region, that role is certain to expand.

Abstract

Commercial production of sulphur in Russia is dominated by the sour gas treatment plants run by subsidiaries of Gazprom in Astrakhan and Orenburg. The Astra­khan­gazprom (AGP) plant at Aksaraysk serves local, world-scale gas and condensate operations by means of – eventually – four processing trains featuring sulphur recovery.

Each of the sulphur recovery trains has a nameplate capacity of 562,500 t/y. The first plant was commissioned in 1987 and two trains of Phase 2 have been in production since 1997. The third train of this second phase was expected on stream as Sulphur went to press, and the fourth unit will begin operations at the end of 2001, according to Astrakhan­gazprom (AGP).

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Upgrade options for ­single absorption plants

Summary

Retrofitting single absorption sulphuric acid plants for environmental compliance has become a requirement in many locations world-wide. Traditionally, single absorption plants have been upgraded to double absorption. However, as regulatory pressures increase, this alone may no longer be sufficient. A range of new technologies have been developed to address the problem. Lisa Connock reports on the options now available.

Abstract

The sulphuric acid manufacturing process has evolved from the lead chamber process, to the single absorption process, to the currently preferred double absorption process. The driving force for the adoption of the single absorption contact process was economics, while the reason for the current predominance of the double absorption version is reduced emissions. The basic objectives in the design of a modern sulphuric acid plant are to achieve a high overall sulphur efficiency with minimal emissions of obnoxious gases and a high recovery of energy. The sulphur emissions from single absorption plants is typically in the range 1.5-2% input sulphur, while modern sulphuric acid plants typically achieve an overall sulphur efficiency of about 99.8%, i.e. O.2% of input sulphur leaves the plant as emissions of SO2 and SO3. Regulatory pressure to reduce emissions further to below the currently achieved 300 pmv SO2 in the acid plant tail gas continues, focussing attention on technologies to improve environmental performance further.

Tail gas scrubbing with chemical reagents such as caustic, hydrogen peroxide or aqueous ammonia is able to reduce emissions to less than 50 ppmv. However, these methods suffer from the high cost of chemicals consumed and/or bothersome by-product disposal, particularly if the SO2 concentration to be abated is high, such as in the case of single absorption plants emitting 1500+ ppmv. In grass roots plants, double absorption combined with tail gas scrubbing, if necessary, often has the better life cycle cost.

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Emerging sulphur recovery technologies

Summary

New sulphur recovery processes typically promise lower costs, higher overall sulphur recoveries or ideally both. Several new technologies for sulphur recovery have recently been commercialised or are in the process of being commercialised. Lisa Connock reports.

Abstract

Historically, high pressure gas with medium amounts of sulphur has been difficult to treat. Tradi­tional amine/Claus/TGT processes are very capital intensive for this level of sulphur recovery. Direct treatment with aqueous-iron liquid redox pro­cess was once proposed as a more economical processing option; but high-pressure operation of these systems proved infeasible due to severe, inherent operating problems. Two new pro­cesses are now available that overcomes these problems, the CrystaSulf process and the Sulfint HP process.

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