Exergy Analysis of Cryogenic Air Separation Unit Integrated with Biomass Gasifier

Cryogenic air separation is the main method to separate air into its constituents like oxygen, nitrogen and argon. Medium purity cryogenic air separation units are mostly required for gasification. As air gasification produces poor quality syngas, oxygen is used as gasifying agent for biomass gasification. Biomass gasification with oxygen as gasifying agent has great potential in applications like integrated gasification combined cycle (IGCC), chemical production and Fischer-Tropsch (F-T) processes. Cryogenic air separation is the process of high energy consumption. In this work, the simulation of medium purity cryogenic air separation integrated with biomass gasifier is performed by using Aspen plus. Exergy analysis of cryogenic air separation and gasification process is performed to check the thermodynamic perfection of the process. It is found that cryogenic ASU produces oxygen with purity 96.2 %mole basis with specific power consumption 0.2435 kW/scmh of O-2. The parameters like syngas composition and heating value also predicted in simulation of biomass gasifier. The exergy loss and exergetic efficiencies of unit operations are also calculated on the basis of simulation results. It is observed that major exergy loss is taking place in main heat exchanger, compressor and distillation units.