Gasification continued costs

The high cost of coal handling and preparation and treatment of effluents, compounded by continuing low prices for cmde oil and natural gas, has precluded significant exploitation of coal as a feedstock for methanol. A small amount of methanol is made from coal in South Africa for local strategic reasons. Tennessee Eastman operates a 195,000-t/yr methanol plant in Tennessee based on the Texaco coal gasification process to make the methyl acetate intermediate for acetic anhydride production (15). 

After World War II, direct liquefaction of coal became uneconomical as the use of lower-cost petroleum products became more widespread. However, the German process of indirect coal liquefaction, the Fischer-Tropsch process, continued to hold some interest. The Fischer-Tropsch process first involved production of a carbon monoxide and hydrogen-rich synthesis gas by the controlled gasification of coal followed by a catalytic reaction process to yield a valuable mixture of hydrocarbon products. Simplified Fischer-Tropsch reactions are shown by the following equations ... 

However, we still believe that it will be usefiil to continue testing different bed materials or mixtures of bed materials to further optimise the gasification process and achieve the best result i.e. minimum of deposits, cost and best possible gas quality. On the other hand, deposits can also be handled with a suitable design of the gasifier and the down-stream conqionents. 

Catalysts for fluidized bed gasification of biomass should be efficient for the reforming of hydrocarbons and have high selectivity for syngas and high resistance to attrition and carbon deposition. They should also be relatively low cost, because the formation of ash and char necessitates the continual removal, and replenishment with fresh or regenerated material, of the bed inventory. In dual fluidized bed gasifiers, the inventory is also exposed to... 

Coal gasification has been expected for many years to become the preferred route for syn generation in the United States because of large indigenous coal reserves however, given the continued availability of natural gas and the hi er cost of coal conversion, the boom in coal as a chemical feedstock has yet to come. Significant development work in this area continues nonetheless, and several designs have been successfully commercialized. 

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