Optimisation of carbon capture from flue gas from a Waste-to-Energy plant using surrogate modelling and global optimisation

The optimisation of Post Carbon Capture (PCC) from a Waste-to-Energy plant has been studied using Kriging surrogate models trained from a set of rigorous process simulations. The surrogate models allow fast and efficient calculation of model responses required for the optimisation of operating parameters. Optimisation is performed using Differential Evolution (DE) requiring a vast amount of function calculations (>1000) which would be extremely time consuming if done with a rigorous process simulation model. It is found that for meeting a CO2 removal efficiency of 85% for a flue gas containing 12.6 mole % CO2 and a reboiler temperature limited to max. 120 °C, a L/G ratio of approx. 2.2 (kg/kg) is optimal. This is accompanied by a stripper/regenerator pressure of 1.85 bara, a temperature of the flue gas at the lower bound, a temperature approach of the lean amine entering the absorber of 6.5 °C (to the flue gas temperature), and a temperature approach in the L/R heat exchanger of 5 °C. The optimal lean and rich amine loading is approx. 0.21 and 0.52 (mole CO2/mole MEA).