Molten Carbonate Fuel Cells retrofits for CO2 capture and enhanced energy production in the steel industry

Abstract

This study explores the use of state-of-the-art, high temperature Molten Carbonate Fuel Cells (MCFC) fed with natural gas as retrofit post-combustion CO2 capture technology for an existing integrated steel mill. Quantitative estimates of performances and costs are generated for a reference steelwork producing 4 Mton y−1 of hot rolled coil, where the fuel cell abates three major sources of CO2 emissions: i) power plant; ii) coke oven; iii) hot stoves. The MCFC-based system that removes CO2 and generates power includes a gas processing unit which produces nearly-pure CO2 for permanent storage (or-utilization) and hydrogen that can be conveniently used in the steel mill. The fuel cell operating conditions are adapted to the specific industrial application and its performances are predicted by an in-house process simulation tool. The techno-economic analysis finds conditions complying with the operating constraints of the fuel cell stacks while reducing direct CO2 emissions of the steel mill by more than 70% and achieving apparently interesting economic returns. In addition, the CO2 capture system generates large amounts of carbon-free electricity (up to 545 MWel) and hydrogen (up to 346 MWLHV) yielding a first law efficiency of approximately 60%. The synergistic production of decarbonized steel, hydrogen and electricity is key to the attractiveness the MCFC-CCS configuration proposed here: after assuming reasonable values for the “by-product” hydrogen and electricity and accounting for the CO2 avoidance they bring about, the estimated overall cost of CO2 avoided (CCA) ranges between 25 and-65 $ tonCO2−1.