Techno-economic and carbon footprint feasibility assessment for polygeneration process of carbon-capture coal-to-methanol/power and molten carbonate fuel cell

Abstract

Coal-based chemical production processes bring severe greenhouse gas emissions. As a significant clean and energy-efficient technology, the polygeneration process has attracted increasing attentions due to its higher energy efficiency, lower production cost and fewer emissions. Towards this end, this work aims to develop a novel coal-based polygeneration process of carbon-capture coal-to-methanol/power and molten carbonate fuel cell (CTMP-MCFC). In the proposed process, coal is first converted to crude syngas. Afterwards, one part of the crude gas is shifted to H2-rich gas, where a part of H2-rich gas goes into the anode of MCFC, and another part of the H2-rich gas mixed with the rest of unshifted syngas goes into the methanol synthesis (MS) unit. The unreacted syngas out of the MS is then sent into the gas turbine (GT) for power generation. The exhausted gas out of the GT goes into the cathode of MCFC for CO2 and O2 supply and CO2 is enriched to the anode for carbon capture simultaneously. Ultimately, waste heat recovery steam cycle at three levels is proposed for global waste heat recovery. An extended pinch-based Duran-Grossmann (D-G) model is introduced to optimize the waste heat utilization. Sensitivity analysis is conducted to investigate the interactive effects of key parameters in MCFC. A comprehensive techno-economic and carbon footprint performance assessment is performed to verify the feasibility of the proposed polygeneration process. Compared with the base plant, carbon footprint shows the great ability to reduce carbon emissions of the proposed system. The product cost of CTMP-MCFC is 12.47 $/GJ and reduced by 1.68%. The exergy efficiency of CTMP-MCFC is improved by 8.53% and the units with the maximum exergy losses are also identified for further energy conservation. The derived significant contributions of this work highlight strong potentials for the overall performance enhancement via an MCFC-integrated polygeneration process.