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Sulphur recovery from gasification

Summary

The resurgence of gasification technology in recent years has led to sulphur recovery from gasification becoming a more significant area of focus for the sulphur industry. Although gasification facilities typically produce a lean acid gas feedstock containing impurities that presents challenges when designing the sulphur recovery unit, other features, such as oxygen availability and physical solvent AGRU integration opportunities, can reduce capital cost investment and provide much greater operation flexibility, stability and reliability.

Abstract

Gasification is a partial oxidation process which converts carbon-rich materials, under a high-pressure, high-temperature, reducing environment, into a synthesis gas (or syngas), which can then be used to produce electric power and valuable products such as chemicals, fertilizers, substitute natural gas, hydrogen, and transportation fuels (see Fig. 1). The gasification process was first developed in the 1700s and commercialised in the early 1900s. Gasification has been used worldwide on a commercial scale by the chemical, refining and fertilizer industries for more than 75 years and by the electric power industry for more than 35 years. Employment of the technology declined in the mid-1900s when natural gas became readily available; however, in the past decade, the technology has experienced resurgence due to an abundance of gasification raw feedstock materials (e.g. coal, petroleum coke, residue oil, biomass, etc.) and concomitant need to minimise carbon emissions. It is currently playing an important role in meeting energy needs in the US and around the world. In new settings it is being adopted in smaller-scale applications to solve the problem of waste disposal via extraction of valuable energy from waste. Although regulations for CO2 emissions have not yet been put in place globally, most gasification plants need to be designed as ready for CO2 capture and utilisation. Keywords: IGCC, gasification feedstock, carbon capture,physical solvent, Rectisol®, oxygen enrichment, SUPERCLAUS/EUROCLAUS, OxyClaus®, emission free, SO2 recovery

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New approach to acid mist elimination

Summary

Proper selection of internals for mist elimination in sulphuric acid drying and absorption towers is still a challenge as regards performance and materials of construction. In sulphuric acid drying towers, knitted wire mesh pads are the principal type of equipment used. Poorly designed, corroded or fouled drying tower mist eliminators are common sources of excessive entrainment. In drying towers the operating life of mist eliminators is affected by two primary factors: corrosion and fouling. A new PTFE filament used in the Sulzer KnitMesh XCOAT mist eliminator provides an innovative approach to these problems.

Abstract

Proper selection of equipment for mist elimination in sulphuric acid drying and absorption towers is still a challenge from the performance and material points of view. Operating evidence shows that the gas-liquid interface represents one of the highest risks of corrosion and since mist eliminators operate in this region, they are one of the most challenging corrosion environments in the plant. In sulphuric acid drying towers, knitted wire mesh pads are the principal type of equipment used. One of the common sources of excessive entrainment are corroded and fouled mist eliminators used in drying towers which causes acid condensation during shut-downs and thus degradation of the catalyst. Several factors have therefore to be considered in the selection of the mist eliminator type and the material of construction where the longevity depends on the operating conditions, acid concentration and used material. Keywords: corrosion resistant materials, fluoroplastics, nickel based alloys, silica containing stainless steels.

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New AGE strategies with HIGHSULF

Summary

A new member of HIGHSULF™ technologies, called HIGHSULF PLUS™, for improved acid gas enrichment and tail gas treatment performance, is presented by T.K. Khanmamedov of TKK Company and R.H. Weiland of Optimized Gas Treating, Inc. Prospective applications include shale gas treatment and acid gas enrichment (AGE) in hot climates where it can be difficult to achieve low enough lean amine temperatures using ambient air.

Abstract

The basic concept of HIGHSULF technology for acid gas enrichment (AGE) and tail gas treating (TGTU) has been discussed in previous issues of Sulphur (No.s 318, 330 and 342). In this article the latest process strategy, HIGHSULF PLUS, is discussed. The most common processing scheme for AGE is the conventional flowsheet shown in Fig. 1. Low quality acid gas (H2S, CO2 plus other trace components) is contacted with selective solvent in the low pressure AGE absorber. This is intended to recover most of the H2S and reject as much CO2 as possible. The shortcoming of this scheme is that the acid gas feed itself is fixed by upstream processing; whereas, if it could be made to contain more H2S, the gas to the SRU would automatically be of higher quality. Keywords: HIGHSULF PLUS, MDEA based AGE, acid gas streams

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Growth of a sulphur powerhouse

Summary

Abu Dhabi is set to become the world's largest exporter of sulphur by 2015. Sulphur looks at progress so far with the country's ambitious sour gas projects, and the implications for the future.

Abstract

Rising demand for natural gas for power generation and constraints on associated gas production from oil fields have driven Abu Dhabi to begin to tap its large reserves of sour gas in the deep desert. Discovered as far back as the 1960s, many of these fields were originally deemed to be too remote and the gas too sour (23% H2S at the Shah wellheads) to make economic recovery technically feasible. However, as the cities of the Emirates like Abu Dhabi and Dubai grow rapidly, so does their need for power and associated utilities. Abu Dhabi’s population has grown tenfold since 1975, from 210,000 to 2.1 million in 2010, with annual growth rates of 7.7% in the past five years, some of the highest anywhere in the world. By 2030 this is projected to have reached 3.1 million. Keywords: SHAH, BAB, HABSHAN, GASCO, ADNOC, ADCO, TAKREER, RUWAIS, TRANSPORTATION

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Nickel leaching update

Summary

The near-simultaneous start-up of several large nickel leaching plants around the world has the potential to consume large volumes of sulphur and sulphuric acid, but technical and environmental difficulties have dogged many of the projects.

Abstract

High demand for stainless steel, particularly in China, has driven a boom in the nickel market over the past decade. Available and accessible concentrations of nickel sulphide ores are becoming scarcer, and so attention has begun to focus on lower grade laterite ores. However, the concentration of nickel in laterites is often quite low – as little as 1% – and the nickel is more difficult to extract. Extraction from laterites tends to involve sulphuric acid leaching, but heap leaching methods tend to take a long time for the acid to dissolve the rock, and so a technique using acid at high pressures and temperatures has evolved; high pressure acid leaching or HPAL. In HPAL the ores are treated with sulphuric acid at 240-270C in an autoclave at pressures of 5-7 atmospheres. This extracts the nickel more rapidly, but using hot sulphuric acid at high pressures leads to severe difficulties with corrosion, and large investment costs associated with titanium autoclaves and the like. As a consequence, many of the HPAL projects have been dogged by technical issues which have merely multiplied up the already considerable investment costs. Several so-called ‘second generation’ projects, developed in Australia in the 1990s, were forced to close down. Keywords: AMBATOVY, RAVENSTHORPE, GORO, RAMU, TAGANITO, ACOJE, HPAL

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