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Canada after Prism

Summary

Canadian sulphur export consortium the Prism Sulphur Corporation exited its sulphur marketing commitments at the end of last year and is expected to be wound up over the course of this year. Where does this leave Canada's sulphur industry?

Abstract

The Prism Sulphur Corporation, which once controlled more than one third of global sulphur trade, has sold its last cargo of sulphur. Rounding up the company’s operations was completed by the end of 2012, and the legal unwinding of the company is expected to take most of 2013, according to CEO Terry Draycott. All of the operational side of the business has been sold to the Oxbow Sulphur Corporation, part of the Florida-based Oxbow Group owned by billionaire Bill Koch, one time winner of the Americas Cup yachting race and brother to the Koch Industries owners Charles and David Koch. Oxbow got into sulphur in January 2011 via its purchase of ICEC, and now has extended that reach with its buyout of Prism, taking on all of Prism’s outstanding marketing contracts. In many ways the end of Prism marks the end of an era in the Canadian sulphur industry, which only a decade or so ago dominated global sulphur trade. Keywords: Sultran, Cansulex, oil sands, sour gas

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India's hunger for phosphates

Summary

India is the world's second largest consumer of phosphates, with knock-on effects for the sulphuric acid and sulphur industries around the world. However, although the country has significant reserves of phosphate rock, these remain relatively undeveloped, and imports of rock, acid and processed phosphates make up the remainder.

Abstract

India is the world’s second largest consumer of phosphates after China, and hence a mainstay of the world’s phosphate fertilizer industry. Agriculture continues to be very important to the Indian economy, and as India’s population grows, so do its requirements for phosphates. India has a population of 1.2 billion – about 17% of the world’s population, and although it has only 2% of the world’s land area, a relatively high proportion of this is cultivated, giving India, at 195 million hectares, actually a slightly higher cultivated area than China. About 45% of this are is irrigated, and net cropped area is 141 million hectares. Agricultural productivity is higher in China, and much of this is down to relative fertilizer consumption, but India’s agricultural statistics are nonetheless impressive. Total cereal production was 254 million tonnes in 2011, making the country third in the world after China and the USA, and in fact India ranks highest in production of pulses (14.5 million t/a), representing 22% of global output. In oilseed production the country ranks second in groundnut oil production (15% of world output) and third in rapeseed oil production (11%). Fruit and vegetable production was 211 million t/a, the second largest total in the world, and India also ranks second in the world in terms of output of commercial crops such as sugar cane, tea and cotton, with a market share of 17%, 20% and 20% respectively. Keywords: superphosphate, SSP, DAP, MAP, Diammonium, subsidy, Paradeep, Jordan

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ASRL Review: Let the blocking begin – the chemistry of sulphur storage

Summary

A twice yearly review contributed by Alberta Sulphur Research Ltd

Abstract

When I presented an update on sulphur supply/demand at Sulphur 20121, I was not entirely convinced that block storage of sulphur would happen in the imminent future. However, now it seems more certain that we will experience oversupply some time in 2014, forcing some producers to return to storage. Having made that statement, I would be the first to admit that I could be wrong, but a combination of factors which include a continuing soft economic outlook and some major new supply coming on stream in the 2013- 2015 time-frame point to market balance at best. Of course, at this time, I must make my usual comment that this situation is good as plentiful sulphur ensures an adequate phosphate supply for food production, so relieving some pressure on feeding the still growing world population. The purpose of this article is to review some of the chemical aspects of pouring liquid sulphur to block and prolonged storage of the solid. As has been demonstrated since 1970, sulphur can be stored in blocks maintaining both its high purity and with no impact on the surrounding environment, if it is done with due care and attention. But, of course, that due care and attention is required and some knowledge of the chemistry is useful to assess and control the factors which lead to troublesome blocks. The aim of the article is to re-assess the important chemical factors. Keywords: SO2, Thiobacilli, storage

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Eliminating the burner and thermal reactor to improve the SRU

Summary

Conventional "modified Claus" technology with a free-flame thermal section is well known to have a number of operating challenges associated with the reactions that occur in the flame and the thermal reactor. The free-flame section is known to be responsible for most Claus plant problems. An alternative, proven approach is presented here by M. Thundyil, and D. Seeger of GTC Technology US LLC, where the free-flame thermal section is replaced with a catalytic combustor that utilises a durable catalyst that enables sulphur partial oxidation catalysis, resulting in significant process and economic advantages. Overall, GT-CataFlame™ allows upgrades of ageing Claus burners and thermal reactors, and enables a 20-30% reduction in capital costs associated with Claus plants.

Abstract

Over the past decade, researchers at Phillips 66 developed a catalytic combustor that can be used to replace the burner and thermal reactor in modified Claus units to improve the operation and reliability of the SRU1-10. GTC Technology US, LLC, has acquired the exclusive licensing rights to the catalytic combustion technology and markets it under the name GT-CataFlame™. GTC markets the complete SRU process of GT-CataFlame integrated with the downstream Claus converters under the name GT-SPOC™ (Sulphur Partial Oxidation Catalysis). The ultimate design of GT-SPOC is a single vertical vessel that contains all the components of the GT-­CataFlame, followed by the Claus converters and sulphur condensers. GT-SPOC process description GT-SPOC technology uses a patented, durable catalyst in a “short-contact-time” reactor, GT-CataFlame, to achieve near equilibrium H2S conversion and sulphur selectivity in one-tenth of the volume used by a conventional Claus burner and thermal reactor10, 11. The GT-CataFlame catalyst also contains components that eliminate classic Claus catalyst deactivation mechanisms of sulphur poisoning and coke deposition of the catalyst in the first Claus converter during normal sulphur recovery operation and start-up/shut-down activities using fuel gas. Keywords: GT-SPOC; air demand, start-up, shutdown; sulphanes

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Process monitoring of sulphuric acid

Summary

Continuous process monitoring of concentration, density or even mass flow is a basic requirement for sulphuric acid production plants and chemical plants which use sulphuric acid as an important part of the production process. Approved analysers must therefore be reliable and robust even when measuring aggressive fluids at high temperatures and high pressures in large pipes. Dr J. Wylamrzy and F. Gerstmann of FLEXIM GmbH discuss the use of different technologies including non-intrusive, ultrasonic clamp-on measuring technology.

Abstract

Continuous process monitoring of concentration, density and flow rates is a basic requirement for the operation of sulphuric acid production plants as well as for chemical plants using sulphuric acid in their production pro­cesses. Sulphuric acid is produced, used, treated and recycled over a wide range of concentrations. The installed process instrumentation has to withstand aggressive fluids and is often exposed to other demanding conditions such as high pressure, high temperatures and huge quantities flowing in rather large pipes. Such demanding conditions can lead to excessive wear and tear, unsatisfactory service life times of the installed instruments and increased maintenance efforts. Berlin-based company FLEXIM develops, manufactures and sells advanced process measuring devices for industrial applications and is one of the leading suppliers of clamp-on ultrasonic flowmeters and process analytical solutions using ultrasonic sound and refractive index. Keywords: Keywords: refractive index; sonic velocity; ultrasonic flow; PIOX R; PIOX S

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How sulphur really forms on the catalyst surface

Summary

The catalytic oxidation of hydrogen sulphide to sulphur plays a major role in the sulphur recovery process. The catalytic stages of a Claus unit produce about 30% of the total sulphur. The catalytic reaction is unique in being practically 100% selective, and it has been intensively investigated for many years in an effort to understand the nature of the active centres. Other research has been carried out to understand the kinetics of the reactions, as well as to elucidate the catalytic oxidation of H2S to sulphur by oxygen. Nevertheless, many aspects of these catalytic reactions remain unexplored. Here, T.K. Khanmamedov of TKK Company and R.H. Weiland of Optimized Gas Treating, Inc., provide a new understanding of the reactions by appealing to the unique nature of sulphur itself.

Abstract

The catalytic Claus process is central to gas processing plants and refineries that include amine desulphurisation and sulphur recovery units (SRUs). The SRU includes the thermal oxidation of H2S in the gas phase with air (or air enriched oxygen) at high temperature with the formation of elemental sulphur, SO2, water and some side products, such as COS, and CS2. H2S + 3/2 O2 → SO2 + H2O (1) exothermic 2H2S + SO2 3/n Sn + 2H2O (2) endothermic 3H2S + 3/2O2 → 3/n Sn + 3H2O (3) overall reaction, n = 1,2 Figure 1 is a simplified diagram of the SRU. The thermal stage is followed by a waste heat boiler (WHB) producing high pressure steam, and a sulphur condenser where liquid sulphur is separated from the gas with the simultaneous generation of medium pressure steam. The gas from the condenser is heated (RH) and sent to catalytic reactors (CatBed) where the remaining H2S and SO2 react with each other to form sulphur. Also, some of the side products such as the COS and CS2 produced in the thermal reactor are converted to H2S in the first catalytic stage. A typical SRU consists of two or three catalytic reactors each served by its own sulphur condenser. The following reversible reaction occurs over activated alumina in a catalytic reactor: Keywords: thermodynamics; kinetic model

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Preventing corrosion in sulphur storage tanks

Summary

Corrosion is believed to be the leading root cause of safety, performance, and longevity issues associated with sulphur storage tanks. The most likely corrosion mechanism results from the combination of solid sulphur and liquid water at metal surfaces. This mechanism can be eliminated by employing a distributed external heating system such as ControTrace to maintain the temperature of all tank internal surfaces above 120°C. Other technologies for heating sulphur tanks can be effective in maintaining the sulphur in molten state, but they do not adequately heat all tank internal surfaces. In order to successfully design an external thermal maintenance system, the designer must have the capability of modelling the tank heat transfer paths and predicting the tank temperatures for the entire range of operating conditions. The success of the system is sensitive to the spacing of steam elements. The tank thermal maintenance model presented in this article by P.D. Clark of Alberta Sulphur Research Ltd, and D. R. Hornbaker and T. C. Willingham of Controls Southeast, Inc. has been validated with field data from multiple tanks

Abstract

Storage tanks for liquid sulphur are utilised in many refineries and sour gas processing facilities for temporary storage of liquid sulphur produced in the sulphur recovery plant. They are usually constructed from carbon steel and insulated and heated to maintain the liquid at a temperature >125°C. Depending on the facility, the tank may receive liquid sulphur which has been treated to remove H2S dissolved in the sulphur or it may be filled with undegassed product. These two cases present significantly different conditions in the tank as undegassed sulphur will slowly release H2S causing that gas, along with sulphur vapour, to build up in the headspace of the tank. Usually, the tank will be drafted with air at a rate so as to limit the concentration of H2S in the headspace. This sweep air, contaminated with small amounts of sulphur and H2S, is then vented from the tank. A typical sulphur storage tank does not store sulphur for long periods. In a refinery, such a tank is used to store liquid sulphur only as a holding point before shipping, forming or blocking. Thus, the tank is rarely full or empty. It is normally receiving sulphur and may be pumped down from several times a day to once every two or three days. Tanks in a sulphuric acid plant are more likely to hold liquid for a longer period, but that is still usually a matter of days. Of course, all tanks are susceptible to unusual conditions that can cause them to remain in most any condition for extended periods, and they must be heated to withstand these conditions. Keywords: thermal maintenance; heating systems; sulphur storage tank

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