Design and simulation of a recirculating bed reactor for coal hydrogasification. Final report, Part III. Linear programming analysis of hydrogasification strategies

Abstract

This report describes an initial attempt to examine the implications of the process design on the recirculating bed hydrogasifier (RBR) operating conditions and the efficiency of RBR hydrogasification. The results are both informative, and at times, counter-intuitive. The design and simulation of a recirculating bed reactor for coal hydrogasification requires that standards of performance be established for the hydrogasifier's operation. Primarily this means specifying optimal operating conditions - temperature, pressure, and carbon conversion; however, it also means identifying the best mechanisms for control of the reactor heat balance - i.e., heat recovery and/or heat addition. Unfortunately, the criteria for specifying the hydrogasifier's optimal process design encompasses the entire process. Two reasons account for this statement: first, within a product (methane); and, second, the process thermal efficiency ultimately dictates how much carbon is converted to methane. Thus, the design of the hydrogasifier is implicitly controlled by the process design. Alternate routes to methane production include both direct hydrogenation of coal and methanation of carbon monoxide with hydrogen. In turn, the hydrogen used in each of these previous reactions can be produced in a variety of ways. The key to effective process design is to select an optimal arrangement of these reactionsmore » such that a maximum thermal efficiency is achieved.« less