Energy and exergy investigation on two improved IGCC power plants with different CO2 capture schemes

Two power generation systems composed of the chemical looping air separation (CLAS) technology and the integrated gasification combined cycle (IGCC) with CO2 capture are conceptually presented, thermodynamically analyzed and compared. Different CO2 capture approaches including the pre-combustion with polyethylene glycol dimethyl ether (PGDE) and the post-combustion with monoethanolamine (MEA) are respectively adopted in the two systems. Blocked energy losses and exergy destructions are calculated to investigate the overall efficiencies of the systems. Sensitivity analyses are carried out to investigate the effects of different operating parameters including the oxygen to coal mass ratio (ROC), the steam to coal mass ratio (RSC) and the temperature of the reduction reactor (TRR) on the energy efficiencies (ηen) and exergy efficiencies (ηex) of the two systems. The maximum energy losses and exergy destructions are found in the CO2 capture units. ROC of 0.75, RSC of 0.06 and TRR of 850 °C are recommended as the optimum operation parameters based on the sensitivity analyses. With the optimized parameters, the energy and exergy efficiencies are predicted to be 37.36% and 34.50% for the system with post-combustion CO2 capture, while 38.67% and 36.19% for the system with pre-combustion CO2 capture.