Abstract

Cryogenic air separation plants are used for production of oxygen, nitrogen and argon with required purity and recovery.The first grade oxygen (purity over 99.99%) is required for welding, cutting, and medical applications. These plants operate at low thermodynamic efficiency with specific power consumption in a range between 0.5-0.6 kw/scmh of O₂. As air gasification produces poor quality syngas, oxygen is used as gasifying agent for biomass gasification. Medium purity cryogenic air separation units (ASU) are chiefly required for 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) products. In this work simulation of medium purity oxygen cryogenic air separation plant integrated with biomass gasifier is carried out by using Aspen plus. Such cryogenic air separation plants which produce oxygen in a range between 85-98% can be used economically for gasification. The cryogenic oxygen plant produces oxygen with purity 96.2 % mole basis with specific power consumption as 0.2435 kw/scmh of O₂. The performance parameters like recovery, purity, temperature and pressure and power consumption of cryogenic air separation unit are obtained. The parameters like syngas composition and heating value also predicted in simulation of biomass gasifier. The effect of parameters (parametric analysis), like vapour fraction of the feed on pure liquid (PL) flow and condenser duty, effect of number of stages on PL and rich liquid (RL) flow and its purity and effect of oxygen flow and gasifier temperature on syngas composition is discussed.

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