Chemical looping coal gasification for IGCC process feed

Abstract

One of the fossil fuels which is a vital source of energy for modern society today is coal. Coal is abundant and cheap, but its use results in high carbon dioxide emissions with nearly 2 gigatons of carbon released into the atmosphere annually. Coal gasification has emerged as a clean and effective way to convert solid coal into gas fuel which can be used to generate energy or heat. Hydrogen gas composition from gasification process can be increased by a chemical looping method using calcium oxide (CaO). Calcium oxide is circulated between the two reactors, CaO in the first reactor will capture CO2 by forming CaCO3 and CaCO3 which are formed then flow to another reactor to regenerate CaO. Pure CO2 obtained in this second reactor can be further processed. This process is promising to use with the Integrated Gasification Combined Cycle (IGCC) technology, but the optimum conditions are needed so that the reaction can take place optimally, economically, and safely for the environment. The process is modeled using Aspen Plus software. The results showed IGCC with carbon capture has low carbon emissions with around 0.3-0.5 kg CO2/kWh produced. Increasing the gasification temperature up to 720°C can reduce CO2 emissions and at the same time increase CO and H2 production. The increase in gasification pressure reduces the production of H2 and CO due to the methanation reaction. Increasing the steam/coal ratio to 1.3 increases CO and H2 production, specific power, and specific CO2 emissions. Increasing the CaCO3/coal ratio up to 1.7 can reduce CO2 emissions and at the same time increase H2 production and reduce CO. Parameters that affect the IGCC performance are analyzed in the sensitivity analysis, such as gasifier temperature, steam/coal ratio, gasifier pressure, and CaCO3/coal ratio.