Renewable energy storage system via coal hydrogasification with co-production of electricity and synthetic natural gas

Abstract

In this paper a novel integrated plant, designed for the co-production of electricity and synthetic natural gas (SNG), has been proposed as suitable strategy for renewable energy storage and CO2 emission control.The hydrogen generation by electrolysis and its use for SNG production is the approach chosen for the energy storage (chemical storage), while the CO2 control is performed by using (or recycling) the CO2, concentrated in the anode exhausts of a molten carbonate fuel cell, in the chemical processes of the plant (coal hydrogasification and SNG production processes).The proposed HyCRESt plant, acronym of Hydrogasification of Coal for Renewable Energy Storage, consists of three main sections: i) the hydrogasification island, in which the coal is gasified in hydrogen environment to a methane rich fuel gas stream (syngas); ii) the power island, in which the syngas is used as fuel for the electric power generation by using a molten carbonate fuel cell (MCFC) power unit; iii) the SNG island, in which the syngas is converted into a synthetic natural gas stream.The plant performance, in terms of co-production efficiency, CO2 avoided and fuel saving, has been evaluated by means of thermochemical and electrochemical models able to predict energy and mass balances.Results have pointed out that the co-production of electric and chemical powers allows to achieve system efficiencies greater than 55% with fuel saving values higher than 6% and CO2 avoided ranging from 20% (only electric power generation) to 120% (only SNG generation).