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Publication > Issue > Articles

Oil price underpins Gulf brimstone output

Summary

The Middle East is set to become the fastest growing source of brimstone through the early years of a new century. Chris Cunningham reviews new and planned projects around the Gulf that will contribute to this brimstone bonanza.

Abstract

When the Oil Producing and Exporting Countries (OPEC) get together in Caracas this March to discuss crude oil production rates following last year’s cutbacks, there will be little expectation of restored production. With crude prices spiking through the US$30 per barrel mark into February, it hardly seems worth OPEC’s while reversing a clearly successful policy to reverse the 1998-99 price slump.

Instead of worrying about survival, the organisation’s members in the Arabian/Persian Gulf region are planning how to spend it.

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Addressing safety issues of liquid SO2

Summary

New technologies and processes have been developed to minimise the hazards associated with the manufacture, handling, transportation and storage of liquid sulphur dioxide. Lisa Connock reports on three new processes from Calabrian, NEAT and Cansolv Technologies which address these issues.

Abstract

Sulphur dioxide (SO2) has long been recognised as a versatile and cost effective chemical for many applications, as outlined later. How­ever, the manufacture, handling and use of liquid sulphur dioxide continues to undergo significant change and close scrutiny because of the regulatory pressure on sulphur dioxide emissions.

With the implementation of the Risk Management Planning (RMP) requirements in the USA last year, manufacturers and consumers have become more sensitive than ever to the on-site storage and handling of hazardous compounds, including sulphur dioxide. Some consumers have chosen to substitute the use of sulphur dioxide with other compounds such as sodium bisulphite at substantial additional cost. But, with today’s bottom line focus of nearly every corporation and with sulphur dioxide economics far superior in the majority of applications compared to the use of other sulphur chemicals, continued use of sulphur dioxide is desirable. Industry’s consideration of sulphur dioxide should be like any other chemical compound. Understanding the characteristics of the product, minimising the risk of exposure and release, and maintaining proper awareness and respect for the product in the workplace should afford the opportunity for continued use of this cost effective sulphur chemical.

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Heat recovery enhances ­profits

Summary

In locations where fresh water is a scarce or costly resource, significant economic and environmental benefits can be achieved by recovering the heat from circulating acid in the sulphuric acid production process for the desalination of sea or brackish water. Andrea Lovato of Alfa Laval Water Technologies, Denmark, reports on this new trend.

Abstract

It is a well-known fact that the ­production of sulphuric acid is a highly exothermic process. Despite that, and considering the high cost of energy, it is surprising just how little heat is recovered from the process. Most often the process is just cooled off by means of seawater or in air coolers.

When recovering heat from the absorption- and drying tower coolers, only minor changes to the process is needed. With plate heat exchangers (PHEs), the heat can be recovered with negligible temperature losses and minimum space requirements. The PHE can take crossing temperature programs and temperature pinches of less than 5°C, while still having k-values of about 2500 kW/°C,m2.

The recovered heat can be used for district heating of cities, boiler feed water preheating or as heating media in connected processes or adjacent plants. A very interesting use of this heat when the sulphuric acid plant is situated close to the coast is for the pro­duction of fresh water by desalination of sea or brackish water. The ther­mal duties in the acid coolers are very well adapted for heat recovery in combination with production of fresh water, by means of multi-effect distillation (MED). The evaporation temperature in a MED system is typically lower than 80°C and the heating energy requirement is in the range of 60-360 kWh/m3 fresh water produced, depending on the number of effects.

The water produced is of high quality. The total dissolved solids (TDS), is typically below 5 ppm.

There are big advantages as regards installation and operation when using falling film PHEs for the total thermal exchange surface in the desalination system. The high k-value of the plate system gives smaller heat transfer areas and compact installations.

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Optimising acid tower design

Summary

Although the concept and practice of using packed towers in sulphuric acid plants has been around for decades, a greater understanding of acid tower design in recent years has led to significant improvements that should be considered when selecting a new tower or replacing an existing tower. Lisa Connock reports.

Abstract

Packed towers are a critical component in the overall operation of sulphuric acid plants. On all double absorption plants there are three acid towers: the drying tower, the intermediate absorption tower and the final absorption tower.

Gas enters at the bottom of the tower and flows upward through the packing which is completely wetted by a downward flow of sulphuric acid. The gas leaving the top of the packing passes through a demisting device before leaving the tower.

A clear understanding of the alternative tower designs available is needed to make the best choice. Different approaches include: alloy versus brick-lined tower shells; dome versus arch and beam packing support; high performance and structured packing versus standard saddle; and alternative acid distributor designs, e.g. pipe with downcomer versus trough with downcomer versus pipe.

Primary criteria in designing acid towers are as follows:

  • Safety
  • Analysis and clear understanding of clients’ requirements
  • Optimum performance: low pressure drop, high absorbency efficiency and low mist generation
  • Cost effective designs
  • Ease of maintenance

 

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