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Publication > Issue > Articles

Sulphuric acid: A change in focus

Summary

David Hayes reports from Japan, where Sumitomo's main acid trading company Acids says that it is switching its sulphuric acid export focus to the Philippines.

Abstract

Acids Co. Ltd is a sulphuric acid and sodium sales company founded in 2003 and jointly owned by Sumitomo Metal Mining Co, which owns three smelters in Japan, and Dowa Mining Holdings Co, with another two smelters. The company says that it is planning to increase sulphuric acids sales over the next 18 months to the Philippines, where demand is growing due to planned expansions of nickel leaching and copper smelting activities at various locations across the country. Acids’ owners, Sumitomo Metal Mining Co and Dowa Mining Holdings Co, are two of Japan’s largest sulphuric acid producers and together supply about 90% of Acids’ sulphuric acid sales volume. The remaining sales volume is purchased from other sulphuric acid producers. “Sumitomo produces 1.3 million t/a, it’s almost always the same level,” explained Toshio Gunji, Sales Department General Manager at Acids Co Ltd. “We have a one month turnaround every two years. The last time was October/November 2013, so the production that year was 1.2 million t/a.” Keywords: TAGANITO, SUMITOMO, NICKEL, LEACHING, SMELTER

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Sour gas update

Summary

Where and how much sulphur will be produced from sour gas, and how will it find a market in a time of sulphur surplus?

Abstract

Virtually all natural gas contains some hydrogen sulphide, as well as carbon dioxide – the presence of the two gases tend to define what is an ‘acid’ gas. Sour gas is natural gas containing a ‘significant’ proportion of hydrogen sulphide, although definitions of what significant actually means can vary considerably. Pipeline sales gas specifications are generally based around customer odour and health and safety requirements, and so any gas with a higher proportion of H2S than 3-4ppm is regarded as ‘sour’. Other specifications are based around corrosion limits, and here US federal specifications define gas >16ppm H2S as sour, while the state of Texas pushes that definition up to 100ppm (the point at which human olfactory nerves are overwhelmed and are no longer able to detect the presence of H2S). The ‘sour service’ equipment definition is based on sulphide stress cracking and is related to the partial pressure of H2S, but tends to equate to about 50-100ppm. However, natural gas producers have a much higher definition, based on how the gas will be processed to sweeten it. Here sour gas is usually taken to be greater than 1% H2S (ie 10,000 ppm). Keywords: ABU DHABI, SHAH, BAB, QATAR, IRAN, TURKMENISTAN, KASHAGAN, UZBEKISTAN, SAUDI ARABIA, WASIT, RUSSIA, TENGIZ, CHINA, PUGUANG, CHUANDONGBEI, SICHUAN

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The global market for sulphur

Summary

A survey of the latest developments which will affect the supply and demand for sulphur worldwide.

Abstract

The total amount of elemental sulphur recovered in 2014 was about 56 million tonnes, according to CRU figures, of which 31 million tonnes were traded internationally. Over the next few years the total volume produced is expected to rise by 15 million t/a to 71 million t/a in 2019, with trade rising to 35 million t/a by that time. Much of the new supply is projected to come from sour gas projects, and the long-anticipated global market surplus that has been on the cards for several years now is expected to be finally upon us. This means that some sulphur producers are going to have to stockpile sulphur, and the questions then become; who and where? New supply Almost all elemental sulphur produced in the world comes from two main sources; refinery processing of crudes and other hydrocarbon feeds (oil sands, condensates) and processing of sour gas. These between them account for 99% of all elemental sulphur production. Keywords: REFINERY, SOUR, OILSANDS, MINING, PHOSPHATE, LEACHING, PYRITE

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Boosting sulphur recovery with sub-dewpoint processes

Summary

Over the years, improvements to sub-dewpoint processes have allowed sulphur recoveries as high as 99.9% to be reached. More recently, the development of internally cooled catalytic reactors has also opened the door for sub-dewpoint operation in the Claus unit itself.

Abstract

The overall sulphur recovery achieved in conventional Claus units is primarily dictated by the thermodynamic equilibrium of the Claus reaction at the outlet of the final catalytic converter. This thermodynamic equilibrium allows increased sulphur conversions when the temperature is lowered. Conventional Claus reactors are operated at temperatures above the dewpoint of liquid sulphur which limits the achievable conversion to 95-98% (depending on the number of catalytic stages) for typical refinery acid gases. Where the goal is a sulphur recovery efficiency (SRE) of at least 98%, a level exceeding what can be obtained with the conventional modified-Claus process, this limitation can be overcome by operating a Claus catalytic reactor at sulphur sub-dewpoint temperatures and allowing liquid sulphur to accumulate on the catalyst. This has been the basis of the so called dry bed sub-dewpoint processes like Sulfreen™, CBA and MCRC for many years. These sub-dewpoint processes are all variations of the same basic concept, but differ in the method used for regeneration of the sub-dewpoint reactor. Sub-dewpoint processes are generally classified as tail gas treatment (TGT) processes given that the process follows a conventional modified-Claus thermal stage consisting of a thermal reactor, waste heat exchanger, sulphur condenser, reactor preheat step, and catalytic reactor. Keywords: sub-dewpoint processes, CBA, Sulfreen, SmartSulf, tail gas treating

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Direct reduction of SO2 to elemental sulphur

Summary

Le Gaz Intégral (LGI) has developed a process to recover elemental sulphur from the SO2 present in the flue gas of nickel and copper ore production facilities. Frank Cross of LGI reports on the process, which involves reduction of sulphur dioxide by methane. This had been attempted in the past without much success, primarily due to the formation of soot. LGI performed extensive laboratory and pilot plant tests to identify in which conditions SO2 and CH4 would react without soot formation. The tests were successful and allowed the identification of soot free operating conditions, but also revealed a number of new issues, related to the introduction of fluids into the reaction furnace, as well as side reactions over the catalyst. LGI has performed extensive research and tests to come up with a solution to these issues.

Abstract

The ore reserves at mines in the Taimyr Peninsula in the Russian Arctic region near the city of Norilsk are very rich in sulphur. Processing the ores in the smelter works creates, as by-product, large amounts of atmospheric emissions of sulphur dioxide (SO2). Emissions of SO2 lead to acid rain, affecting vegetation, soils, rivers, flora and fauna. SO2 is harmful to human life and can lead to respiratory illness. Norilsk Nickel decided to cut these emissions by recovering elemental sulphur from the flue gases. Elemental sulphur will be recovered as a solid and either stored locally or shipped (see Fig. 1). The existing plant flash smelters flue gas treatment comprises waste-heat boilers for gas cooling followed by dust separation. The gases are then sent to stack. A SO2 concentration unit followed by a sulphur recovery unit will be added. Sulphur will be recovered in a two stage process: high temperature reaction of SO2 and CH4, followed by hydrolysis of COS and CS2 and reaction of SO2 and H2S (Claus reaction) to form sulphur over a catalyst. The first stage of the sulphur recovery unit has been attempted numerous times in history. Keywords: smelter flue gas, Norilsk Nickel, LGI, sulphur recovery, soot formation, methane, SO2 reduction

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Desulphurisation of coke oven gas

Summary

New desulphurisation technologies have been developed and implemented to meet the demands of new environmental regulations in steel and power plants. RATE has been involved in the licensing of several grass root sulphur recovery projects including the design of a special acid gas removal process named Coke S-MAX. M. Rameshni and S. Santo of RATE discuss the Coke S-MAX technology and how it has been implemented in steel and power plants for the processing of coke oven gas to achieve zero emissions.

Abstract

Coke oven gas treatment The significance of coke oven gas and its constituents has changed substantially over the past decade. Today, the primary task of a modern coke oven gas treatment facility is to convert crude gas into an environmentally compatible fuel as economically as possible. Crude gas is cooled, compressed and freed from constituents that might be hazardous to the environment or plant. Apart from the cleaned coke oven gas, the only by-products produced in modern plants are crude tar, crude benzol, and sulphur. The necessary process steps and equipment are chosen to eliminate gaseous emissions and to minimise the level of contaminants in the waste water. Coke oven furnaces and heaters have improved over the years. Furnaces are available from different companies e.g. ThyssenKrupp Industrial Solutions. In addition, coke oven gas has been treated by different technologies such as Diomax, physical solvents, and many other absorbents but none of them meet the new environmental regulations in a cost effective manner. Keywords: coke oven gas, desulphurisation, Coke S-MAX, RATE, power plants, zero emissions

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ASRL Review

Summary

Taking advantage of existing equipment in a Claus sulphur recovery system P.D. Clark, S.S. Bhella and N.I. Dowling, Alberta Sulphur Research Ltd.

Abstract

Suggesting and developing new sulphur recovery technology is one thing, but having it implemented in practice is another matter. From a practical viewpoint, we already have working systems that can attain >99 % conversion to sulphur, and this infrastructure has cost billions to put in place around the world. People are not about to abandon such investments just because a better gadget or two might become available. But, even more importantly, we know how to run a modified Claus sulphur recovery system reliably, so people do not want to risk unproven technologies. Nevertheless, lower costs with higher energy efficiency are the goals of modern, large scale industry, so improvements to existing systems are potentially useful. Recently, as part of the ASRL research program, we have examined one adaptation of a Claus plant which could improve it economically and utilise all of the ‘pots and pans’ already in place. Actually – some of the pots and pans can be discarded! Keywords: CLAUS, CATALYST, CATALYTIC, CONDENSER, DEGASSING, H2S, SO2

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