Exergoeconomic estimates for a novel zero-emission process generating hydrogen and electric power

Abstract

This paper presents the exergoeconomic analysis of a novel process generating electric energy and hydrogen. Coal and high-temperature heat are used as input energy to the process. The process is a true “zero-emission process” because (a) no NOX is formed during coal combustion with sulfuric acid, and (b) the combustion products CO2 and SO2 are removed separately as compressed liquids from the overall process. The process cycle is based on two chemical reactions. The first reaction takes place in an electrolytic cell and delivers the hydrogen product. In the second step, coal reacts with sulfuric acid in a high-pressure combustion reactor. The combustion gas is expanded in a gas turbine to produce electric power. The combustion products are compressed and separated so that almost pure CO2 can be removed from the cycle. The overall process is characterized by very high energetic and exergetic efficiencies. However, the overall process is very capital intensive. The electrolytic cell dominates the costs associated with the overall process. Detailed results of the thermodynamic simulation, the economic and the exergoeconomic analyses of the process including estimates of the product costs are presented.