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Publication > Issue > Articles

A fresh look at the fourth essential nutrient

Summary

Don Messick of The Sulphur Institute discusses TSI's work to achieve recognition of sulphur's vital role in agriculture.

Abstract

For some time, The Sulphur Institute (TSI) and others have expounded on the need for sulphur as an essential plant nutrient. In some markets, sulphur is even included as one of the top three nutrients for optimal plant growth and economic return. Let’s consider the facts, as well as the developments in the fertilizer and sulphur industries.

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Long-term storage of sulphur

Summary

With more and more sulphur emerging from refineries and sour gas projects, the challenge for the coming decades will be how to store it for long periods. Sulphur examines some of the options.

Abstract

The projections for sulphur production over the next few years, as reiterated once again by Mike Kitto at this year’s Sulphur Conference, look to be quite stark. Within just 2-3 years, the combination of sour gas processing projects in China, the Middle East and Central Asia look, plus numerous refinery expansions and increasingly tighter restrictions on sulphur in fuel, look set to push up to 8-10 million t/a of sulphur onto the world market; way beyond demand projections. In spite of some plans for acid gas reinjection, this remains a technically demanding application, and it seems fairly safe to say that much of this sulphur will end up simply having to be stored.

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The market for sulphuric acid

Summary

Changes to the metal smelting and leaching industries have the potential to change the global sulphuric acid balance going forward.

Abstract

The overall market for sulphuric acid has always been dominated by voluntary production (from burning sulphur) and demand from agriculture, in particular the phosphate industry. However, the phosphate industry tends to operate on acid produced from burning sulphur or pyrites, and so demand in the merchant market is dominated by metal leaching.

Over the past decade the sulphuric acid market has begun to change considerably, with metal production beginning to influence both supply and demand sides of the equation. Involuntary acid production from metal smelting is continuing to grow as a share of overall production, while acid demand for metal leaching is also increasing rapidly, especially for the nickel industry. However, most of this new leaching capacity, and possibly some existing leaching capacity, seems set to be met by voluntary production from sulphur burning, and this is likely to change the shape of the sulphuric acid market in the future.

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Sulphur 2009 Conference & Exhibition

Summary

The Sulphur Conference was held at the Sheraton Vancouver from November 7th-11th 2009.

Abstract

Delegates were welcomed for the first time this year by Nick Morgan, CEO of CRU, parent company of British Sulphur Events, before the conference moved on to the first session, chaired by Bob Hanssen of Weir Minerals Lewis Pumps.

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Oxygen enrichment in SRUs

Summary

A discussion of the pros and cons of different levels of oxygen enrichment in sulphur recovery units from a range of perspectives: the process, the burner and the refractory.

Abstract

The drive towards clean air and clean fuels and the increased demands for diesel products creates great demand for additional hydrodesulphurisation and sulphur recovery capacities in refineries and gas plants worldwide. In addition, seasonal fluctuations in the demand for fuels increases the pressure on refineries to make extra capacity with existing SRUs.

Many operators could find implementation of oxygen enrichment technology to be the most economical route for incremental increases in SRU/TGTU processing capacities.

To understand oxygen enrichment chemistry, the plant designer should keep in mind three fundamental differences for oxygen-enriched sulphur recovery facilities:

  • The concentration or partial pressure of all non-nitrogen compounds is higher. All process equipment operates at higher operating temperature and releases more heat in the SRU.
  • As a result of the higher partial pressure and higher heat release, most of the chemical reactions will shift at equilibrium condition.
  • All major process equipment should be evaluated in the section for the modification or replacement.

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Combating NOx in acid plants

Summary

Nitrogen oxides can be formed via several mechanisms in the upstream operations of sulphuric acid plants. NOx levels may need to be controlled to ensure acid quality and good operation. Several methods of NOx removal are available to meet these needs.

Abstract

Nitrogen oxides (NOx) typically refer to different compounds that are formed out of nitrogen and oxygen, e.g. NO, N2O, NO2, N2O3. A typical specification for NOx in commercial grade sulphuric acid is 5 ppmw oxides of nitrogen as nitrates (equivalent to 10 ppm HNOSO4). Depending on the plant design, this would limit the concentration of NOx in the feed gas to between 5 to 15 ppmv in order to produce a product acid that would require no additional treatment.

The NOx that occurs in an acid plant can be formed through a number of mechanisms in the upstream operations1,2.

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Reconfiguring refinery complexes

Summary

The use of commercial quality industrial gases such as oxygen, nitrogen and hydrogen in the SRU complex has proven very valuable in attaining and maintaining the performance and reliability necessary in today's refineries. In this article, Elmo Nasato and Uday N. Parekh of Goar, Allison & Associates, Inc. provide details on the use of industrial gases in the SRU, the economic and process considerations related to the various modes of industrial gas supply, and the design requirements for safe and reliable industrial gas delivery.

Abstract

Current trends in the characteristics of crude oil supply, petroleum product demand, and tightening environmental regulations require continuous change in the worldwide refining and gas producing industry. Refiners and gas producers are confronted with more stringent environmental, safety and regulatory re­quirements that must be met while maintaining very high on-line factors in a safe and highly efficient operation

More hydrotreating and increased processing severity are required for removing sulphur and nitrogen compounds from fuels to meet current and future environmental regulations. The increase in production of hydrogen sulphide (H2S) and ammonia (NH3) in combination with more stringent sulphur recovery levels, on-line factors, and safety requirements has placed new demands on the processing capability of refinery sulphur recovery units (SRUs). These developments have led to reconfiguring refinery processes with greater use of industrial gases in the sulphur recovery complex. In all cases there are several options in terms of the quantity and quality of the industrial gas supply. The discussion in this article on the economic and process considerations for the supply of the industrial gases, and the design requirements for safe and reliable gas delivery applies to nitrogen, oxygen and hydrogen. The typical tie-in points for these gases in an SRU are shown in Fig. 1.

By their nature some of the industrial gas streams are used intermittently during start-ups and shutdowns and to address intermittent process requirements. The potential intermittent use of industrial gas supply increases the risk for injury to personnel, damage to equipment, and environmental violation.

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