Integration optimisation of elevated pressure air separation unit with gas turbine in an IGCC power plant

The integration optimisation between an elevated pressure air separation unit (EP-ASU) and gas turbine is beneficial to promote net efficiency of an integrated gasification combined cycle (IGCC) power plant. This study sets up the thermodynamic model for a 400 MW plant specially coupled with an EP-ASU, aiming to examine system performances under different integrations and acquire the optimum solution. Influences of air extraction rate at conditions of without, partial and full N2 injection, as well as the effects of N2 injection rate when adopting separate ASU, partial and full integrated ASU were both analysed. Special attention has been paid to performance differences between utilising an EP-ASU and a low pressure unit. Results indicated that integration solution with a separate EP-ASU or without N2 injection would not be reasonable. Among various recommended solutions for different integration conditions, N2 injection rate increased with the growth of air extraction rate. The integration with an air extraction rate of 80% and full N2 injection was suggested as the optimum solution. It is concluded that the optimum integration solution when adopting an EP-ASU is different from that using a low pressure one.