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Disunity in a united city

Summary

In just a year, the targets set for refiners to cut sulphur levels in transportation fuels have receded into the distance. Chris Cunningham reports from the 2000 European Oil Refining Conference in Berlin.

Abstract

A year ago in sun-drenched Sicily refiners, car builders and policy makers sat happily on the same platform to ponder the brave new world of low-sulphur fuels. The requirements for Auto Oil I were in place and the talk was of progress toward even higher fuel specifications, Auto Oil II, all in the cause of the Kyoto agreement on greenhouse gas production.

For this year’s European Oil Refining Conference, leaden skies over Berlin in late June seemed equally to match the mood of discussion. The intervening 12 months has seen the arrival of demands for ultra-low sulphur automotive fuels; delivery – or the promise of delivery – of these materials from some refiners; and tax incentives in Germany to support production of gasoline containing10 parts per million sulphur.

In short, events have moved faster than the pace of negotiations on fuel quality. Oil refiners find themselves spending thin resources of development capital on their transportation fuel streams, only to find that they will have to spend more – much more – giving the light end of their increasingly complex product ranges an even deeper clean. And there is little consolation in doing all of this for a little more sulphur.

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Latest developments in leaching technology for metal ores

Summary

The non-ferrous metals industry has been a growing source of sulphuric acid – produced from smelter gases – for many years. By contrast hydrometallurgical processes for treating metal ores consume sulphuric acid, which remains the major leach medium for most processes. Usage seems set to grow as more leaching projects get under way, some of which will be very large acid consumers.

Abstract

The standard method for producing non-ferrous metals from their ores involves the high temperature smelting of sulphide minerals. The so-called pyrometallurgical route is “tried and tested” but has a number of drawbacks. The smelting process produces stack gases containing SO2, which is an air pollution hazard unless it is recovered as sulphuric acid – the so-called “fatal acid” of the non-ferrous metals industry.

Governed by the mineral occurrences, many smelter operations are sited in remote locations, which in the past has been generally helpful to those unable or unwilling to invest in capture of the SO2, but is otherwise a hindrance to the profitable sale of the fatal acid.

Another factor is the fact smelter-based metal refineries are very capital intensive, with the need for large capacities – generally 200,000 t/a of metal to get economy of scale.

By contrast, hydrometallurgy – low temperature processing of ores by leaching methods – offers a number of advantages, at least on paper. Operations generally have a lower limit for economy of scale; say 50,000 t/a metal in the case of copper, less in the case of more valuable metals. When properly managed, environmental impact is much less, and they can often use some of the fatal acid produced by an adjacent smelter. The technology is not much more than 100 years old, but is now developing rapidly.

Up to now, however, leaching processes have mainly been used on mine wastes and low-grade or secondary ores rather than primary minerals. Recent developments suggest this is all about to change, and that before too long leaching processes will be taking the lead in new base metal production capacity, including that based on primary ores too.

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Smelter acid takes on sulphur burning

Summary

A leading sulphur burning site in the north of England has made the switch to merchant acid supplies as part of a major investment in cost saving and environmental compliance. Chris Cunningham reports on a key development in the emerging market for 'premium' grade sulphuric acid.

Abstract

Huntsman Tioxide plans to spend £30 million ($45 million) on an overhaul of its Grimsby pigment plant and on the supply of raw materials to the plant.

The driving forces behind this major project at Tioxide Grimsby are operating cost and environmental compliance. Many options were available to Huntsman in its selection of the best route to meet a range of targets. The special interest in this case lies in a full scale switch from sulphuric acid production at one of the UK’s major sulphur-burning sites to total reliance on imports of merchant acid.

Whilst on the face of it this is poor news for the European sulphur trade, Huntsman’s scheme does mean the preservation of at least one leading site for the sulphate route to titanium dioxide production, at a time when the alternative, chloride route has been picking up most of the crumbs of new demand for white pigment (see Sulphur 268 p15).

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Silicon carbide supports new improvements in ­sulphur recovery

Summary

The use of a new type of support material, silicon carbide, allows the production of active, selective and stable catalysts for the oxidation of hydrogen sulfide into elemental sulphur over a very large temperature range. Catalysts have been developed that are suitable for Claus plant tail-gas treatment processes ranging from ambient temperature sub-dewpoint (trickle-bed reactor) conditions to the higher temperature above-dewpoint (fixed-bed reactor) systems.

Abstract

More stringent SO2 emission rates from sulphur recovery operations allied to oil refineries and natural gas treatment plants are required by authorities worldwide. However, these are very variable from country to country and may even differ from region to region within the same country. Some countries take into account plant size, and regulations also vary as a function of the gas plant sulphur inlet rate.

In Europe, beside specific national legislation (for example, the German TA-Luft requires sulphur recoveries of 99.5% for plants with a high capacity, and 99.8 % for plants with lower sulphur inlet rates), regulations required by the EU authorities aim to have a sulphur recovery of at least 98.5%. The American standard for sulphur recovery plants is an efficiency of 99.9% for plants with capacities greater than 20 t/d, whereas the Canadian guidelines increase from a sulphur recovery of 98.5 % for plants with a capacity of 50 t/d up to 99% for plants with a capacity of 2,000 t/d.

To satisfy new regulations, the sulphur dioxide (SO2) emissions asso­ciated with sulphur recovery must be drastically reduced.1, 2 To achieve this in the best way, it is necessary to look for efficiency improvement in the so-called modified Claus process itself and the subsequent tail-gas treatment processes, of which there are very many.

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