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Maximising the efficiency of Claus TGTUs

Summary

What can be done to further improve the efficiency of Claus tail gas treating in sulphur plants? Sulphur reports on some of the latest process developments and sulphur plant designs based on many years of industrial experience and research and development including: efficiency improvements to amine tail gas treating systems, the benefits of low temperature hydrogenation catalyst, new developments to the Clauspol process and the application of the liquid redox process for tail gas treatment.

Abstract

The SCOT type tail gas treating process and its derivatives are well established sulphur recovery methods, when near complete recovery is required. They all have in common the catalytic reduction of sulphur species in the tail gas to H2S followed by selective absorption in an amine system. H2S rich acid gas from the regenerated amine is recycled to the front of the sulphur recovery unit (SRU). Typical recoveries range between 99.8 and 99.95% of inlet sulphur to the SRU.
Figure 1 shows a typical process sketch for a conventional SCOT type TGTU. Natural gas and air are burned sub-stoichiometrically in a reducing gas generator (RGG). The sub-stoichiometric combustion results in a net production of hydrogen. This was needed by older generation catalyst in order to assist the equilibrium and kinetics of reducing all sulphur species to H2S. The process design must be based on the reactor EOR conditions which can reach 320°C. The reactor is followed by a waste heat boiler (WHB) to produce low pressure steam (~ 5 barg). The value of LP steam produced is site specific and depends on the local steam balance. The downstream quench column cools the tail gas before going to the amine absorber. A side cooler on the column removes the sensible heat of the tail gas between the WHB outlet and amine absorber inlet, as well as the latent heat of water which is a substantial component of the tail gas, particularly in refineries.

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Sulphur 2010

Summary

This year's Sulphur Conference and Exhibition was held at the Hilton Prague, from November 1st-4th 2010.

Abstract

The industry once again had a buoyant feel, perhaps due to the run of high prices, and the conference was well attended. Monday was given over to a technical symposium organised by Amine Experts, and a fuller report will appear on this in our next issue, January/February 2011.

Sulphur markets

The conference proper began with the usual opening markets session, chaired by Dick Van Meurs of ICEC. Pierre Sigonney, Chief Economist of Total, began by looking at oil and gas markets, although he reminded delegates that Total is also a sulphur producer, with 1.0 million t/a of production this year, and 2.0 million t/a expected by 2020, from Kashagan, Qatar and the Canadian oil sands.

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Sulphuric acid from smelting

Summary

Smelter acid represents almost one third of sulphuric acid production. As involuntary production it is closely tied to the economics of metal production rather than sulphur markets, and production is particularly dominated by the copper industry.

Abstract

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Zero Claus plant SOx emissions

Summary

Fluor has recently developed an integrated acid gas removal/sulphur recovery process for gasification facilities. This new syngas purification technology eliminates SOx emissions from the Claus sulphur recovery unit while capturing over 90% of the CO2 produced from gasification. The technology can be used in gasification based coal to ammonia, coal to urea, and coal to hydrogen based power plants. John Y. Mak, Richard B. Nielsen and Thomas K. Chow of Fluor Energy & Chemicals introduce Fluor's new gas processing and sulphur recovery technology for gasification projects.

Abstract

A new syngas purification technology has recently been developed by Fluor for gasification projects. The process uses tail gas recycle to eliminate SOx emissions from the sulphur plant while capturing over 90% of the CO2 produced from gasification1. The acid gas removal unit (AGRU) uses a physical solvent that selectively absorbs H2S and COS from the high pressure syngas, producing an H2S rich acid gas for the Claus sulphur recovery unit2,3. The integration of the AGRU and Claus SRU and eliminates the conventional Claus plant tail gas treating and incineration units. This integrated design has a lower overall equipment count, which significantly reduces the total project cost. The technology can be used in gasification based coal to ammonia, coal to urea, and in coal to hydrogen based power plants. A typical 2,000 t/d coal to ammonia gasification plant using this technology is depicted in Fig. 14.

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Industrial phosphates where now?

Summary

The issue of eutrophication in water courses has led to the gradual phasing out of phosphates in detergents in the industrialised world, taking with it a major slice of demand for industrial phosphates.

Abstract

While phosphate fertilizers and other agricultural applications (such as in animal feed) account for the major source of phosphate demand worldwide, and hence demand for phosphoric and sulphuric acid, a smaller but still significant share of phosphate demand – around 10% – is accounted for by so-called ‘technical’ or industrial uses, including the food industry. However, environmental pressure to reverse phosphorus pollution of water courses has affected demand for the largest sector – that of detergents.

Technical uses
Alkaline phosphates – phosphorus salts with alkali metals such as sodium or potassium – are used for many food and technical applications. They are salts of purified phosphoric acid, and are more or less polymerised. The presence of a single phosphorus atom makes them an orthophosphate. Two P atoms produce a diphosphate or pyrophosphate, three atoms a tripolyphosphate, and more than three a polyphosphate.

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Technical trends:

Summary

A Sulphur report on emerging technologies, newly patented processes and new equipment for the sulphur and sulphuric acid industries.

Abstract

SulphCo’s ODS: an alternative to HDS
SulphCo, Inc. is currently developing its patented and proprietary Sonocracking™ technology as an alternative to hydrodesulphurisation (HDS) for removing sulphur from petroleum product streams. SulphCo’s desulphurisation process consists of two steps:
l ultrasound assisted conversion of the sulphur compounds to their oxidised analogs;
l and subsequent removal of these oxidised compounds by a separation technique such as adsorption.

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After the surge in China imports what next?

Summary

Sulphur imports have risen from 100,000 tonnes in 1994, surging to a new record last year of 12.4 million tonnes which is an astounding 41% of 2009 global sulphur trade! Ming Xian Fan, PhD and Don Messick, CPSS, CPAg of The Sulphur Institute (TSI) assess the prospects for continuing market growth.

Abstract

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The Sulphur Doctor

Summary

Problem No. 4 Poorly designed or operated sulphur condensers of the SRU. This is the fourth in a series of short articles on the subject of "common problems" with Claus sulphur recovery units (SRUs). In this issue, B. Gene Goar discusses sulphur condensers, based on his wide and varied experience in the design, operation, troubleshooting and remedial problem solving of Claus SRUs.

Abstract

The Claus SRU process consists of three repeating steps: (1) heating, (2) reaction, and (3) cooling/condensing. The sulphur formed in the upstream reaction step is in a vapour state. Sulphur condensers serve the primary function of cooling and condensing the sulphur formed in the reaction steps. Without their use, no sulphur would be produced, and the Claus reaction would be severely limited by its ultimate approach to absolute equilibrium. So, the proper operation of sulphur condensers is extremely critical to the operation and the overall sulphur recovery efficiency of the SRU. Sulphur condensers must be operated at the correct flow rate and outlet temperature and with proper separation and drainage of the liquid sulphur produced in their outlet channel. All of these factors must be considered and provided for in the process and mechanical design of sulphur condensers.

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