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Publication > Issue > Articles

Return of the sulphur glut?

Summary

For several years there have been predictions of a major surplus of sulphur ahead which have not come to pass. However, rapidly rising output from sour gas processing looks set to finally deliver the promised surplus over the coming decade.

Abstract

Sulphur production in all forms was about 80 million tonnes S per year in 2011, and was forecast to reach about 85 million tonnes S in 2012. Of this elemental sulphur production now accounts for about 55 million t/a, or 65%, with the remainder coming from metallurgical sulphuric acid and some from pyrites roasting. Recovery from sour gas processing is set to deliver the largest incremental volumes. Keywords: markets, sour gas, nickel leaching, refinery, recovery

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Sulphur in aviation fuels

Summary

With first land vehicle and now maritime fuels facing increasing pressure to lower their sulphur content, it seems inevitable that aviation fuels will soon face the same kind of restrictions.

Abstract

Although sulphur levels in ground vehicle fuels have been steadily declining over the past couple of decades, down to 10-30 ppm in much of the developed world, and the International Maritime Organisation (IMO) is taking steps over the next decade – albeit controversial ones – to drastically lower sulphur emissions from ships, especially in designated ‘emission control zones’ near heavily populated areas, the sulphur content of aviation fuel still remains comparatively loosely regulated. According to recent studies1, the sulphur content of aviation fuel tends to be from about 500-1,000 ppm and averages around 600 ppm, but levels of 3,000 ppm – of the level normally only seen in bunker fuels – are permitted in JET A and A-1 according to current legislation, and up to 4,000 ppm for JP5 and JP8, while the average level of sulphur in aviation fuels has been noted to be increasing recently due to the use of higher sulphur crudes from the Middle East and Venezuela. Table 1 gives figures from a survey of refiners conducted by CRC and CONCAWE in September – December 2010. Keywords: environment, sulphur dioxide, SO2, refinery, regulation

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New acid plant meets AMV's needs

Summary

Leandro Casas of Acidos y Minerales de Venezuela recounts the major challenges and difficulties that were overcome by the resourceful engineers and skilled workforce at AMV in the construction of a sulphuric acid plant at its Puerto Ordaz production site to meet the requirements of its aluminium sulphate production.

Abstract

Acidos y Minerales de Venezuela, C.A. (AMV) is a Venezuelan company with over 17 years of successful operation in the chemical industry, especially in the production of iron-free aluminum sulphate. Aluminium sulphate is primarily used for water purification but is also used in the oil, and paper industries. AMV is located in the city of Puerto Ordaz, Estado Bolivar, in southeastern Venezuela, south of the Orinoco River. Puerto Ordaz is a modern city on the confluence of the Orinoco and Caroni rivers where Venezuela’s heavy industries, mainly iron, steel and aluminium plants are based. Close by, on the Caroni River, are four hydroelectric dams that supply over 75% of the country’s electrical power, including Guri dam, one of the world’s largest. North of the Orinoco is the Faja Petrolifera del Orinoco, the world’s biggest reserves of oil (and enormous amounts of sulphur). To the south is the beautiful region of the Gran Sabana, with the tepuys (flat topped mountains), and the highest waterfall in the world, Angel Falls.

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Challenges of SWS gas treatment

Summary

Processing ammonia-bearing SWS acid gas in a Claus SRU presents serious challenges in the design and operation of the SRU, especially as refineries are forced to process crude feeds containing increased levels of nitrogen and sulphur at a time when environmental regulations have become more and more stringent with regard to sulphur and NOx emissions. Hydrocarbons can also create a number of operational and performance problems in the SRU and need to be eliminated. This article identifies the main problems and discusses how to protect and maximise the efficiency of the sulphur plant.

Abstract

Sour water stripping (SWS) is one of the first stages in the waste water treatment process in many industrial operations, and especially in refineries. Water streams from throughout a refinery are typically sent to the stripper, which is designed to remove both H2S and ammonia from the water. There are several designs of sour water strippers, all playing upon the same theme of using heat to break the bond between NH4SH in the wastewater. This liberates gaseous ammonia and hydrogen sulphide in a produced acid gas. In some cases the ammonia and H2S are separated and sent to individual destinations, but in the majority of SWS set-ups the effluent acid gas from a sour water stripper overhead is processed in the sulphur plant (SRU). Sour water stripping process The purpose of a sour water stripper is to remove components that are toxic or cause undesired odour; primarily H2S and NH3 (ammonia) as well as dissolved gases, solids and hydrocarbons. Keywords: WorleyParsons BSR-Ammonia; SINI ammonia Claus; John Zink NOxIDIZER; Sulphur Experts

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Sulphuric acid boost without the NOx

Summary

Boosting production capacity and reducing NOx emissions in sulphuric acid manufacture can be achieved by combining oxygen enrichment for process intensification with LoTOx technology for NOx removal. N.J. Suchak and F.R. Fitch of Linde Gases Division discuss how these technologies can be applied to increase revenue and lower unit product costs, while improving acid quality and addressing environmental requirements.

Abstract

Boosting production capacity in an existing sulphuric acid production plant is always interesting for plant operators as it can lead to higher productivity and greater profitability. For a plant operating at rated capacity, it makes good economic sense to boost production by employing oxygen enrichment or oxy-fuel combustion in the SO2 generation and or oxidation stages. By this means some or all of the inert nitrogen from the air feed can be replaced. Replacing some air by oxygen not only allows increased throughput, but also improves process and thermal efficiencies thereby reducing fuel requirements and producing additional steam, with overall reduction in a unit product cost. Increasing sulphuric acid throughput is, however, often limited by the ability of process equipment to handle additional gas flow without losing performance. Typical sulphuric acid processing equipment has adequate processing capacity to handle 20 to 30% additional SO2 but not an equivalent increase in gas flow. Much of the downstream equipment such as waste heat recovery equipment, fans, etc. operate more effectively when maintained within design or rated process gas flow rates but can handle higher concentrations of SO2. The practice of oxygen enrichment for both combustion (SO2 generation stage) and oxidation of SO2 to SO3 is one of the most attractive options for process intensification. Keywords: oxygen enrichment; SAR; ozone

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High silicon steels stand the test of time

Summary

Since the introduction of special stainless steels for concentrated sulphuric acid in the 1980s, equipment in strong acid applications has achieved new levels in performance, reliability and safety. Advanced materials for sulphuric acid plant operations have resulted in advancement in design flexibility, competitiveness, plant maintainability and operational reliability, environment and safety improvements and extension of service life.

Abstract

The production and processing of sulphuric acid places high demands on the materials used for equipment, especially in the drying and absorptions systems of sulphuric acid plants, where materials need to handle high acid concentrations at high temperatures. Corrosion resistant materials specially developed for this environment can provide maximum operating times and reduce maintenance requirements. The choice of material has a decisive influence on investment and lifecycle costs. It is important to weigh up the investment costs versus influence on the operation and maintenance costs of the sulphuric acid plant. In this article we report on how the speciality materials SX, SARAMET® and ZeCor-Z® have stood the test of time. Outotec® Edmeston SX material Sandvik first started development work on a material designed exclusively for use in concentrated sulphuric acid in the 1970s, resulting in the release of SX material in 1984 by its subsidary Edmeston. Since its introduction, fine adjustments have been made to the composition of the base material, and the weld filler material has been improved1. Keywords: SX; SARAMET; Ze-COR-Z; acid distributors; acid coolers; acid piping; corrosion

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Stripping phenolic water

Summary

Sour water strippers (SWS) have always been designed using equilibrium stages. However, tray efficiencies remain obscure, leaving designers with less than complete confidence in the reliability of their final design, and often forcing costly overdesign. In this article, R.H. Weiland, N.A. Hatcher and C.E. Jones of Optimized Gas Treating, Inc. show how a new mass transfer rate model is used to demonstrate (a) the effect of heat stable salts on stripping ammonia, H2S, and especially HCN, (b) where to inject caustic soda for remediation, and (c) what effect excess caustic injection has on stripper performance as measured by residual ammonia, H2S, and HCN levels in the stripped water.

Abstract

Most refinery sour water systems contain very little CO2, but H2S ­levels can become quite high. This high capacity for H2S is a direct result of the weak acid-weak base reactivity between H2S and ammonia, and it can make sour water extremely foul. H2S removal from sour water to low values is mandatory to avoid unacceptable pollution levels. In a similar vein, HCN being a weak acid, also reacts with ammonia and so is held in solution not just as a result of its physical solubility but also because of the alkaline environment. Sour water is generally classified as phenolic and non-phenolic. Non-phenolic water contains almost exclusively NH3, H2S, and possibly a trace of CO2. It is generated by refinery hydro-treating (hydrodesulphurisation or HDS) units. When stripped of contaminants, non-phenolic water can typically be recycled for reuse in the HDS unit as wash water, or it can be used as makeup water to the crude desalting process. Phenolic (or more broadly, non-HDS) water typically contains heat stable salts (HSSs), HCN, phenols, and caustic. Coal derived gas can be quite high in both ammonia and hydrogen cyanide, and coke oven gas is especially high in these components. Keywords: heat stable salts; HCN removal; caustic injection

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