Coal Power Plants with Enhanced Profitability and No Carbon Dioxide Emissions

Coal Power Plants with Enhanced Profitability and No Carbon Dioxide Emissions

A zero carbon dioxide emission process is developed, in which electrical power and formic acid are coproduced from coal. The overall reaction for the proposed process uses coal, oxygen, and water as reactants to generate formic acid as the only product. A thermodynamic analysis is carried out, so that feasible operating limits for the proposed process are identified. Since the process cannot be realized within one single step, a reaction cluster is proposed which consists of feasible chemical reactions. These are: gasification of coal to syngas; CO₂ hydrogenation to formic acid; hydrogen combustion; and CO combustion. The principal technologies employed in this process network include combustion, gasification of coal to syngas, gas compression, supercritical fluid pumping, hydrogen separation using pressure swing adsorption, and formic acid production from CO₂ and H₂. The software UniSim [TM, Honeywell Inc] is employed to simulate the flowsheet. Two Gibbs reactors act as the gasification reactor and a combustor, while a conversion reactor carries out the formic acid reaction. Coal, water, and part of oxygen are fed into the gasification reactor; off-gas from the hydrogen PSA and oxygen are fed into the combustor; pure hydrogen from hydrogen PSA and CO₂ which is compressed to supercritical phase are fed into the formic acid reactor. By adjusting the oxygen delivery ratio, the coal gasification is designed to be energetically self-sufficient, so that the whole process produces the largest amount of power. Heat exchangers, phase separators, compressors, pumps, etc. are also employed to realize the process. Temperature and heat load information for each process stream is obtained from the software simulation and used in carrying out a heat and power integration study. Through the use of heat engine and heat pump subnetworks, a feasible operating envelope for the considered process is identified. A preliminary technicoeconomic analysis is carried out, which establishes the superiority of the proposed process to current coal power plant technology.