In-situ and Ex-situ Conversion of Coal to Methane using Hydrogen

Abstract

This paper explains a process to produce methane using coal, steam, and hydrogen by autothermal reactions. In coal gasification, oxygen is used to burn extra coal for providing the necessary energy to the process. The proposed process uses hydrogen in place of oxygen to provide the necessary energy to produce methane. The process uses fossil coal as a feedstock only and not as a fuel. Both ex-situ and in-situ methods are feasible to produce methane/natural gas from coal and green hydrogen. For one unit mass of hydrogen, nearly 24 times methane production is feasible. The required carbon-neutral hydrogen can be generated adequately and economically from water electrolysis by using green renewable electricity from solar PV and wind power potential. The carbon footprint of methane production using coal and green hydrogen is nearly 83% more than that of fossil natural gas but 23% less compared to fossil coal on an equivalent energy basis. The abundant inferior quality coal deposits in India can be used as carbon feedstock to produce methane gas for the fuel requirements of domestic, commercial, and road transport sectors. The existing natural gas infrastructure like cross country pipelines, PNG infrastructure, CNG filling stations, LNG storage facilities, etc remain in use and are further expanded to use the methane produced from coal deposits. The green carbon dioxide gas available from biomass gasification can be sequestered into underground caverns and depleted natural gas or crude oil deposits to brand the grey methane, produced from fossil coal, as carbon neutral fuel. Thus, India can transform into a carbon-neutral economy with robust energy security/independence from a predominantly fossil fuels importing country to an exporter of green fuels, chemicals, and products by harnessing its vast coal, biomass, and renewable energy resources.