Development of an integrated system for electricity and hydrogen production from coal and water utilizing a novel chemical hydrogen storage technology

Abstract

A coal gasification-based integrated system is proposed to produce electrical power and hydrogen. The hydrogen produced is stored in a chemical storage medium, which is ammonia. The integrated system contains a water gas shift membrane reactor, a hybrid thermochemical water decomposition cycle based on the chemical couple copper and chlorine and a multistage ammonia production system. A hydrogen fueled supporting combined cycle is used to meet the electrical requirement of the integrated system. Coal is gasified, and the resulting syngas is water shifted in a membrane reactor, which produces hydrogen. The remaining syngas is combusted to generate power through a gas turbine, and the turbine hot exhaust is used to provide the required thermal energy of the water decomposition cycle. The hydrogen outputs from the coal gasification and the water decomposition cycle are fed to the ammonia production system and the supporting combined cycle. The ammonia production system contains multiple stages to achieve a high conversion percentage of hydrogen. The nitrogen fed to the ammonia reactor is provided by the cryogenic air separation unit, which also provides oxygen to the gasifier. The proposed system is simulated with the process simulation software Aspen Plus. The system performance is evaluated through energy and exergy efficiencies. The integrated system is found to have an energy efficiency of 48.7% and an exergy efficiency of 48.4%. The system is capable of producing 0.18kg/s of hydrogen and 1.2MW of power per 1.5kg/s of coal.