Thermodynamic assessment of an integrated biomass and coal co-gasification, cryogenic air separation unit with power generation cycles based on LNG vaporization

A novel self-heat system which consists of a coal and biomass co-gasification process, low-temperature air separation based on the LNG vaporization, steam cycle, supercritical CO2 power generation unit and cryogenic carbon dioxide capture section is introduced and analyzed. Some new aspects of this study can be categorized as follows. There is no need to implement external heat sources and refrigeration units. Suitable process integration significantly decreases energy consumption and the heaters and coolers can be eliminated. Co-gasifier produces high yield synthesis gas to supply power and heat energy. The required pure oxygen (99.99%) for gasification is supplied from ASU. The specific energy required for high purity oxygen production is about 0.11 kW h/kg. The results show that the cold gas efficiency of gasifier is 81%. Also due to sufficient integration between LNG vaporization and other subsystems, 40459.53 kW energy is saved in the system. In cryogenic CO2 capture unit, 0.10 kW h/kg-CO2 is required to separate 99% carbon dioxide. Moreover, exergy and sensitivity analyses are carried out on the integrated process. Exergy efficiency and exergy destruction have been calculated for the main equipment of the system. The overall exergy destruction rate of the process is around 1.007 x 105 kW and heat exchangers have the highest portion of irreversibility. Finally, the effect of some significant parameters on the performance of the units is studied.