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Chinese sulphur supply and demand

Summary

Last year was a dramatic one for the sulphur industry in China, and for the elemental sulphur exporters who helped to meet the remarkable surge in Chinese imports of brimstone. The background to this extraordinary episode in world sulphur trade is explained here by Tamikiyo Hasegawa, who is General Manager of the Sulphur and Sulphuric Acid Section in the Fertilizer and Inorganic Chemicals Group of Mitsui & Co Limited, Tokyo, Japan.

Abstract

"SulPhuriC acid is the mother of the chemical industry", it is said in China, and the scale of the country's acid production lends added weight to the saying. In 1996, China produced more than 18 million tonnes of sulphuric acid, and thus ranked second only to the United States in tonnage output. When it is recalled that merely a decade ago, Chinese sulphuric acid production in the mid1980s was running at some 8 million tly, the evidence for the development of the nation's chemical industry is very clear. And it is expected that this progression will continue into the medium term with the steady growth of the Chinese fertilizer and chemical industries. Estimates in the Ninth Five-Year Plan are that China's production of sulphuric acid will reach 22 million tonnes in the year 2000, and climb to 30 million tonnes in 2010.

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Alkylation and sulphuric acid demand: recent developments

Summary

The worldwide drive towards improved air quality has caused significant and ongoing adaptation in the composition of refined petroleum products, especially motor gasoline. One of the aspects of this adaptation has been a quickened interest in alkylates, a class of fuels whose manufacture consumes sulphuric acid. The clean air drive is most advanced in the United States, but is gathering force in the rest of the world: this article by Nathan Edmonson examines its implications for sulphuric acid demand.

Abstract

The worldwide drive towards improved air quality has caused significant and ongoing adaptation in the composition of refined petroleum products, especially motor gasoline. One of the aspects of this adaptation has been a quickened interest in alkylates, a class of fuels whose manufacture consumes sulphuric acid. The clean air drive is most advanced in the United States, but is gathering force in the rest of the world: this article by Nathan Edmonson examines its implications for sulphuric acid demand.

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European refinery planning promotes sulphur capcities

Summary

Tighter curbs on the sulphur content of fuels, consequent revisions to refinery processing streams, and changes in the market for oil products are combining to underline the significance of refinery-based sulphur recovery operations, reports Martin Horseman, in a regional preview of the projects listing in this edition

Abstract

Oil refinery recovered sulphur will be the main focus of future elemental sulphur production capacity growth in Europe. The greater prominence of these sulphur operations owes much to the reconfiguration of refinery processing lines so that refiners are able to meet changing product trends and environmental regulations.

Most crude oils contain sulphur, and the proportion of sulphur present can be as high as 2-3% by weight depending on the origin of the crude. The sulphur in crude oil is usually in the form of organic compounds - eg, sulphides, disulphides thiophenes and mercaptans - each with varying chemical characteristics and behaviours. As a result of their variable natures, these sulphur compounds become differentially distributed between refinery intermediate and finished products during the processing sequence. In general, the lighter the refined fraction the less its sulphur content. Very little sulphur appears in products such as LPGs and gasolines, rather more in middle products such as kerosine and diesel fuels, and most in heavy products such as fuel oils and bitumen. The latter, heavy residues tend to contain a higher proportion of sulphur than the original crude - a 2-3% crude perhaps giving rise to a residue containing 4-5% S.

During the past decade there has been a pronounced concern with the environmental impact of these sulphur presences in fuels. Legislation at both the national and international level is establishing gradually tighter limits on the sulphur content of refinery products, and on the emissions of sulphur dioxide arising from the combustion of fuels containing the reducing amounts of sulphur. The oil industry in Europe has been addressing these curbs by increasing the recovery of sulphur from refinery streams with the result that there has been a considerable investment in new, hydrogen-based sulphur-removal technologies and a consequential uplift in oil derived sulphur production.

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Controlling hydrogen sulphide emissions

Summary

Numerous processes exist for treating H2S-containing gas streams, and the most applicable one for a specific application will depend upon the type of gas stream being treated, the amount of gas and H2S to be treated, the concentration of H2S and the turndown required. Gary Nagl of U.S. Filter/Engineered Systems reviews the various options.

Abstract

Few gases are as potent as hydrogen sulphide (H2S) at assaulting the human olfactory senses. The human nose can detect the obnoxious "rotten egg" odour of H2S at a level of only 0.4 parts per billion (ppb). Few compounds can be drtected at so low a level. Hydrogen sulphide is also quite toxic and can cause permanent physical harm and even death. While the ppb levels of odour detection are not hazardous, prolonged exposure to levels in the hundreds of parts per million range can be harmful. The maximum allowable exposure for prolonged periods is 10 ppm, the maximum concentration for one hour exposure is 300 ppm and exposure to concentrations greater than 600 ppm for 30 minutes is fatal. In addition, hydrogen sulphide desensitizes the human olfactory senses to the point where even high concentrations of H2S are no longer odorous, thus people exposed to high levels of H2S are not aware that they are in danger.

Hydrogen sulphide is produced naturally by the anaerobic decomposition of any type of organic matter which contains sulphur, such as rotting eggs, wallboard decomposition in landfills, the formation of natural gas from decomposing plant life, sulphate decomposition in sewers, etc. Hydrogen sulphide is also produced synthetically in hydrogenation and hydrodesulphurization processes and in anaerobic thermal treating processes such as coke ovens. Regardless whether present in nature, produced by nature, or produced by human activity, hydrogen sulphide presents severe health and corrosion hazards as well as being an odour nuisance. This article describes the major processes available for removing HzS from various types of gas streams.

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Refinery sulphur plant optimization

Summary

In this paper M. Chiari, M. G. Grottoli and S. Villa of KTI SpA and S. Pierucci of Politecnico di Milano Italy present the results of the implementation of an on-line reconciliation and optimization package at the sulphur recovery unit of the Sannazzaro de' Burgondi AgipPetroli refinery. The results demonstrate the package capability to manage various plant capacities, thus providing operators with a useful support tool. The effective monitoring of the plant performance while meeting air quality requirements on discharged flue gas is the main benefit connected to the on-line implementation of the optimizer. The economical impact of optimized operation is currently under evaluation.

Abstract

Kinetics Technology International S.p.A. (KTI) is an engineering company active in the refining industry as a licensor and constructor of hydrogen and sulphur plants. It has also been engaged in the activity of process modelling and services for plant control and optimization for more than a decade. Several successful installations of on-line optimizers both for petrochemical (olefins) and for refinery (hydrogen) plants have been finalized in the past years. KTI is technically supported by scientists which balance industrial needs with the scientific experience and skills of academics. This cooperation has resulted in successful experiments and applications in several KTI projects.

A project with the major Italian refining company AgipPetroli was initiated in mid-1995 for the on-line optimization of the hydrogen plant at the Sannazzaro de' Burgondi refinery (northern Italy). Application of the On-line Reconciliation and Optimization (ORO) package, named OROHz, has been successfully running online since the autumn of 1995.

A new project was started in mid 1996 with the aim of applying and installing an on-line reconciliation and optimization package at the sulphur plant of the same refinery. The main targets of the project are: effective monitoring of the plant performance to improve the operators' knowledge of the plant, and the optimization of operations to minimize sulphur oxide (SOx) emissions in accordance with environmental protection laws.

In this paper the results of the application of the on-line reconci!iation and optimization package to the sulphur recovery unit (named OROSRU) are presented. For confidentiality reasons it has been necessary to represent some of these results in a qualitative way (e.g. scatter diagrams of measured vs. reconciled values). However, this limitation does not preclude the understanding of the results obtained or the project's success. All the difficulties faced in the different phases of this application and the main package features have also been reported.

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Clauspol achieves 99.9% sulphur recovery

Summary

At Sulphur '96, C. Streicher of IFP* presented the Clauspol 99.9+ process, which is the latest development of the well-known Clauspol process. With the addition of a solvent desaturation loop it is now possible to reach a 99.9% sulphur conversion rate, provided that sufficient hydrolysis of COS and CS2 is obtained in the Claus catalytic stages.

Abstract

Tighter regulations on sulphur emissions require that increasing amounts of the sulphur compounds present in natural gas or in crude oils be converted into nontoxic elemental sulphur. In refineries, natural gas production facilities or chemical plants, the conversion and removal of sulphur compounds generally yield gases with high levels of hydrogen sulphide (H2S), which may then be converted into sulphur using the well-known Claus process. However, the Claus process converts only 94-98% of the hydrogen sulphide into elemental sulphur. Therefore, Claus plants are often combined with a tail gas treatment unit (TGTU) which typically enables the overall sulphur conversion to be increased to more than 99%. Among the many processes available to tail gas treatingl , only a few are able to reach the highest conversion levels (99.9%) now being required by the most severe emission standards (e.g. US emission guidelines for new source performance standards). In such processes these high conversion levels are reached at the expense of fairly high process complexity and accordingly costs.

Institut Francais du Petrole (IFP) developed the Clauspol concept over 25 years ago. Because of its simplicity, ease of operation and low cost this tail gas treating process has now been licensed throughout the world more than 40 times since 1971, making it one of the three most widespread tail gas treating processes.2 The initial version of the process, Clauspol 1500, obtained overall conversions in the range 98.5-99.5%. A fairly recent improved version, Clauspol 300 or Clauspol II, has subsequently permitted conversions reaching 99.7 or even 99.8%, with very few process modifications. The main technological improvements which allowed this progress were: indirect water cooling in the solvent loop and improved control of the H2S/S02 ratio with reliable accurate on-line analyzers. The latest developments at IFP have now led to Clauspol 99.9+, which, in combination with the use of high performance catalysts like the Procatalyse CRS 31 Ti02 catalyst, reaches the 99.9% conversion level, while keeping the simplicity and economy of the initial Clauspol concept.

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