Feasibility of Power and Methanol Production by an Entrained-Flow Coal Gasification System

Sustainability metrics, a cradle-to-gate life cycle assessment, and a technoeconomic evaluation are presented for an optimized entrained-flow coal oxy-combustion plant with carbon capture to produce power and methanol. The aim of the study is to assess the feasibility of coproducing methanol in a coal-based power plant with an entrained-flow coal gasification system. Coal-based methanol, as an attractive liquid transportation fuel as well as an essential intermediate chemical feedstock, can fill a possible gap between declining fossil fuel supplies and movement toward the hydrogen economy. Within the plant, first the coal is fed to a pyrolysis reactor, and then the volatile matter is fed into an oxy-combustion reactor while the char is gasified in an entrained-flow gasifier. The remaining char is gasified. The heat is used to produce electricity, while the syngas is converted to methanol. The integral plant, consisting of an air separation unit, oxy-combustion of coal, gasification of char, electric power production, carbon capture, and conversion to methanol, was designed and optimized using the Aspen Plus package. The optimization includes the design specification of process heat integration using an energy analyzer toward a more efficient clean-coal technology with methanol production. The plant uses 500 metric tons (MT) of Powder River Basin coal and 2231.03 MT of air per day and produces 32.76 MWh of electric power and 207.99 MT of methanol per day. The total amount of captured CO₂ is 589.75 MT/day, and nitrogen is also produced at 1309.33 MT/day. A multicriteria decision matrix consisting of economic indicators as well as the sustainability metrics is developed to assess the feasibility of the extended plant. Methanol production in addition to power production may improve the overall feasibility of coal-powered plants.