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Acid plants address environmental issues

Summary

The sulphuric acid industry can no longer be viewed as a significant contributor to sulphur dioxide pollution. Due to recent developments, for example, in design, simulation packages, catalyst, and mist eliminators, acid plant emissions of sulphur dioxide to the environment are minimal. Other environmental issues such as the conservation of water are also being addressed.

Abstract

Modern sulphuric acid plants are based on the contact process using a vanadium pentoxide catalyst and are designed and built with reliability as a key factor. The use of computer based design, simulation packages and improved materials developed over the past few years have led to more reliable acid plants. The process technology for the manufacture of sulphuric acid differs de­pending upon the source of sulphur dioxide gas. Basically there are two types of acid plants:

  • Those that use dry sulphur dioxide gas e.g. from elemental sulphur. In these plants the air is dried before use in the sulphur burner;
  • Those that use wet gas as in the case of copper, zinc, and lead roasters or from hydrogen sulphide plants. In these plants wet gas is required to be cleaned and cooled in a series of scrubbers and electrostatic precipitators and finally dried before entering the contact plants.

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Of boats and biofuels

Summary

With sulphur in road fuels moving off the agenda, European refiners gathered to discuss how to clean up the heavy end of the barrel in response to EU rules on marine fuels, and how to rely less on imported crude and keep sulphur levels down by stepping up biofuels production. Chris Cunningham reports from the World Refining Association's 6th European Fuels Conference in Paris.

Abstract

It was a close call, but the speaker from the European Commission arrived not quite breathless after a dash across Paris in time to deliver the latest hot news about the politics of sulphur in marine fuels. As it turned out (see our story on page 10 of this issue), the news was to cool quite quickly in the days to follow. However, a report on the European Parliament’s renewed determination to crack down hard on ships’ emissions of sulphur dioxide by cleaning up their fuel helped to emphasise that sulphur is always hovering ominously in the background when refiners gather to share their central concerns.

The speaker, Nicola Robinson of the European Commission’s Direc­torate-General for Environment, had arrived hot-foot from a meeting of the European Parliament’s Environment Committee where MEPs had reaffirmed an earlier statement of intent. The commission’s efforts to cut airborne pollution generated by ships were too soft-hearted and they would see to it that ocean-going trade made a proper job of cleaning up its act.

The commission’s draft directive calls for a reduction in the sulphur content of marine fuel oils to a maximum 1.5 per cent in specified areas of sea, whilst the parliamentarians threw in a new maximum figure of 0.5 per cent. As another speaker was to point out, an apparently modest one point difference in sulphur content represents a very much bigger difference in terms of refining technology and investment.

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Second wave in Jose

Summary

PdVSA's foreign partners are lining up a second generation of heavy oil upgraders which will add to Venezuela's developing role as a major sulphur exporter provided potential legal hurdles to agreement can be overcome.

Abstract

Already a significant producer and exporter of sulphur through its new upgrading industry based on heavy oil produced in the Faja de Orinoco fields, Venezuela is set to take on a role of even more influence in the international supply of brimstone. Oil companies who have previously form­ed joint ventures with state-run Pet­roleos de Venezuela (PdVSA) are looking to raise their stake in the industry with firm proposals for two more projects involving production, transportation and upgrading of extra-heavy crude.

One of these is Sincor II, a jv of France’s Total, Norwegian Statoil and PdVSA. Its scale of production and investment is expected to match the original Sincor project, a producer of 800 t/d of sulphur for export. The second project involves US-based Chev­ronTexaco – whose Petrozuata holding was the first to produce light synthetic crude (syncrude) from heavy Faja crude – along with Spain’s Repsol YPF, also in association with PdVSA. Investment in the project is expected to be in the region of $5-6 billion.

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Zirconium passes the acid test

Summary

Zirconium has proven its outstanding corrosion resistance performance in a wide variety of sulphuric acid steel pickling conditions. Steve Sparkowich, Corrosion Laboratory Manager at ATI Wah Chang, discusses the advantages of zirconium over other metals and reports on the successful use of zirconium heat exchangers in acid recovery systems.

Abstract

Pickling is an economical method of using acid to remove impurities and scale from metals for etching surfaces in preparation for galvanising, painting, etc. (see Fig. 1). Wide variations are possible in the type, strength, and temperature of the acid solutions used. Sulphuric acid in the 5 to 40 % concentration range is a common pickling acid for iron and steel. Sulphuric acid pickling tanks are typically heated to a temperature between 60 °C (140 °F) and 93 °C (200 °F) using steam or hot water circulating through a heat exchanger.

Compared with non-metallic alt­er­natives, metal heat exchangers, some­times referred to as steam coils, are generally preferred for heating sulphuric acid pickling solutions because they are:

  • more compact
  • easier to clean
  • more durable
  • easier to work with
  • compatible with pressurised steam

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Catalyst performance in the presence of aromatics

Summary

The effect of BTX on titania Claus catalyst has been determined in contract research commissioned by Saudi Aramco and carried out by ASRL. The performance of several commercially available titania and titania-alumina hybrid catalysts in the presence of BTX is presented and discussed in the context of Saudi Aramco's continuing efforts to increase sulphur recovery at its facilities.

Abstract

Saudi Aramco has contended with the problem of lean acid gas SRU feed with aromatic contaminants for over 20 years at two of its major gas plants. The difficulty in pro­cessing lean acid gas (<50 % H2S) containing aromatics such as benzene, toluene and xylene (BTX) is that it results in a low reaction furnace temperature, which does not support complete destruction of the benzene, toluene or xylene. As the acid gas becomes leaner, the problem is further compounded because the reaction furnace flame temperature decreases to the point where a bypass is needed to maintain a stable flame. This allows the aromatics to pass unreacted to the first converter where they crack and damage Claus catalyst by depositing coke on active sites within the pore structure (Fig. 1).

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