Optimization of Oxygen Purity for Coal Conversion Energy Reduction

Abstract

The conversion of coal into gaseous and liquid fuels and chemical feedstock will require large quantities of oxygen. This oxygen will be produced in large multi-train air separation plants which will consume about 350 kilowatt hours of energy for each ton of coal processed. Thus, the oxygen plants in a commercial coal conversion facility may require 150 megawatts. Design of the oxygen plants will require close attention to energy consumption. Many coal conversion processes can accept oxygen at less than the historical 99.5% purity with significant savings in energy and cost. The air separation process is reviewed with emphasis on optimum oxygen purity. An energy reduction of 8.4% can be achieved when oxygen purity is reduced from 99.5% to 95%.

Oxygen is a major tonnage chemical which is also highly energy intensive. The current United States capacity of about 80 thousand tons per day places it in the top five of basic chemicals, and its energy requirement of 350 to 450 kilowatt hours per ton makes it a major energy consumer.

The growing synfuels industry -- conversion of coal into hydrocarbon fuels and chemical feed-stocks -- will greatly increase the production of oxygen and presents major opportunities for energy conservation.