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CFD facilitates the design process

Summary

BOC Gases has developed a computational fluid dynamics (CFD) model which can be used to optimise and assess oxygen-enriched equipment for Claus reaction furnaces and burners. J. S. Norman* and R. W. Watson** describe how the technique has enabled the integration of burner and furnace to be optimised over an entire range of operating conditions.

Abstract

Recently, changes in the nature of crude oil, together with increased pollutant legislation have placed additional demand on the sulphur recovery unit (SRU). To meet this increase, either revamping of existing or addition of new plant is required.

Oxygen enrichment of the SRU is a proven technique that enables capacity increase through minimal capital investment. Indeed, through a combination of technologies, oxygen usage can allow up to 150% increase in plant throughput (based on an existing air based plant).

However, the design strategy used for air based SRU plant is not directly transferable to oxygen enriched systems. The higher flame temperatures and combustion intensity associated with oxygen enrichment require additional design techniques to be adopted to ensure optimum burner design and overall unit reliability and performance. This article describes a predictive technique that BOC Gases has developed that enables the performance of oxygen enriched equipment to be assessed without having to extrapolate the theoretically based assumptions traditionally used to design air based SRUs.

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New SO2 scrubbing technologies abound

Summary

As environmental regulations on gaseous sulphur dioxide emissions continue to tighten, and with the sulphur content of crude oil and natural gas rising, there has been a spate of new technologies proposed to meet these increased demands. Refiners and gas processors are now faced with a wide array of processes to choose from. Lisa Connock provides an update on emerging SO2 scrubbing technologies for Claus tail gas treatment.

Abstract

Today’s refiners and gas processors are faced with tougher environmental demands and increasing sulphur content of crude oil and natural gas. Several new pro­cesses based on SO2 scrubbing have evolved in recent years as a solution to these problems. Established SO2 recovery systems for Claus incinerator tail gas, such as the Wellman Lord process and the Clintox process have the advantage of being able to achieve extremely low emissions of sulphur dioxide. Not surprisingly, over the past couple of years there has been strong interest in the development of new processes of this type. Emerging technologies in this category include: the Cansolv process, the ClausMaster process, the Labsorb process (based on the Elsorb process), the Clausorb process and the Turbotak SO2 removal process. The basic principles behind these processes is the incineration or catalytic oxidation of Claus tail gas streams to convert all sulphur species to sulphur dioxide, followed by SO2 scrubbing and recycle of the SO2 stream to the front end of the Claus sulphur recovery unit. The main difference between the pro­cesses lies in the different scrubbing mediums employed to remove and recycle the sulphur dioxide. Key benefits of these systems compared to some of the more conventional Claus tail gas processes are listed below:

  • Lower SO2 emissions
  • Competitive or lower capital cost
  • Fewer catalytic Claus stages required
  • Enhanced sulphur recovery (99.9-99.95% total sulphur recovery)
  • Increased total capacity of the Claus unit
  • Recovered SO2 can alternatively be converted to marketable sulphur products eg. liquid SO2, sulphuric acid, elemental S etc.
  • Safer to handle SO2

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Maintaining the flow

Summary

Experience at a shipping terminal taught sulphur distributor Martin Gas Sales that a bolt-on thermal maintenance system can have important life cycle advantages over gut tracing or welded jacketed pipe. Henry P. Gaines, PE, VP of Controls Southeast, Inc. tells the story.

Abstract

Major sulphur distributor Martin Gas Sales markets and transports liquefied petroleum gas and sulphur, and processes sulphur for dry and liquid fertilizer. Martin Gas is the largest independent distributor of sulphur in the USA with over one million tons handled every year. It now operates three US Gulf liquid sulphur terminals with docks connected to massive holding tanks. The Neches River terminal near Beaumont, Texas, went into operation in August 1992. The Tampa, Florida, terminal became operational in January 1996, and the new Stanolind Cut terminal, also near Beaumont, Texas, opened in 1999.

At all three locations, long pipe­lines transfer liquid sulphur from ships and barges to and from the holding tanks. More piping carries sulphur from trucks to the tanks. Between all the heated storage and transport vessels, thermal maintenance in the pipes and valves is essential to keep the sulphur flowing and the entire operation moving.

Sulphur stays molten only within a temperature range of 246-320ºF (119ºC to 160ºC). Outside that tight temperature band, its viscosity increases rapidly and soon becomes totally immovable. To keep the product flowing, a thermal maintenance system is required to make up the heat lost to the environment. “We try to maintain everything from 260 to 280ºF,” explains Martin Gas project engineer Keith West.

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Sour imports fill the Gulf

Summary

Oil refiners on the US Gulf Coast are preparing for a major refit that will enable them to process heavier, sourer and cheaper supplies of imported crude. Chris Cunningham reviews the impact of this capital programme on the region's production of sulphur.

Abstract

As recently as 1997, the US oil production industry was preparing for an offshore bonanza in the Gulf of Mexico whilst the price of oil worldwide rose steadily. Then prices hit the floor. An initially promising but eventually short-lived rebound in the second quarter of this year seemed to confirm that they will stay that way for some time.

The promised rush for deep water oil failed to emerge as production simply became economic. Refiners along the coast instead have turned increasingly to imports of crude. And as long as US prices stay ahead of the rest on the contract market (see Table 1), the record for imported crude set by refiners last year, more than 55% of the total they processed, looks set to be broken consistently.

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Diesel drives Indian expansion

Summary

New Indian oil refining capacity and phosphate production are about to earn the title 'world's largest'. Chris Cunningham assesses their impact on a key market for sulphur exporters.

Abstract

The Indian government’s planning of the country’s future economy leans on the principle of swedeshi, or self-reliance. However, many within Indian industry would say that the country’s recent succession of governments is all too reliant on its own opinion and that policy decisions demonstrate a marked lack of input from industrialists.

In particular, there have been strong complaints of late from a sector of industry – oil refining – that is close to making a big impact on international trade in sulphur and that has been on the receiving end of unilateral government decision-making.

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Under the volcano

Summary

And under the cosh. Europe's refining industry held its major annual get-together, Primark WEFA's European Oil Refining Conference, in the shadow of Mount Etna, Sicily in mid-June. Chris Cunningham highlights a sombre session for an industry beset by low margins and growing environmental pressures.

Abstract

One of the world’s most active volcanoes was in aggressive mood as refiners gathered for the WEFA conference. At Giardini-Naxos, on the coast below Mount Etna, there was more heat and steam building as refiners gathered to hear the prospects for a way out of tight operating economics and demands for lower levels of sulphur in the product pool – vehicle fuels in particular.

Amid the conference’s traditional tips to refiners for better housekeeping, cannier trading and higher levels of safety, other matters were sure to make the headlines. And they were certain to revolve around sulphur. The politicians were there to remind the refining industry of the implications of last year’s unwelcome news, Auto-Oil II. Even the downstream oil industry’s old allies in the automotive sector could only deliver fire and brimstone with a reminder that when the politicians are on your back it’s every industry for itself.

The car makers had emerged from a run-in with the European Commis­sion last year knowing that, to meet European directives on green­house gas emissions from the vehicles they manufacture, current technology demands low levels of sulphur in gasoline and Diesel. Auto-Oil was all very well, was their message, but no sulphur at all would be much better from their point of view.

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