Process integration analysis and improved options for an MEA CO2 capture system based on the pinch analysis

Abstract

Pinch analysis for a CO2 capture system of 34.72 kg/s production is carried out to reduce the energy penalty in this paper. Based on the pinch analysis results, the optimal heat exchanger networks are proposed. In order to recover the waste heat further and provide the process integration schemes comprehensively, the process integration of different heat pumps and refrigerators is analyzed based on the pinch analysis. Furthermore, the improved process integration methods are proposed considering the operation characteristics of the carbon capture system. Results show that the process integration of the vapour-compression heat pump, the absorption heat pump, the absorption heat transformer and the vapour-compression refrigerator into the CO2 capture system is valid only when they are set across the pinch temperature. For an absorption refrigerator, placement across the pinch is effective and is the best choice, although it is difficult or even impossible to be implemented in the carbon capture system. If the below-ambient cooling is required in the carbon capture system, placement of an absorption refrigerator below the pinch temperature is also feasible to be implemented, less effective than the best choice. In the CO2 capture system, an absorption refrigerator can be driven by the CO2 + H2O stream from the top of the stripper to liquify the CO2 gas. And the released heat of the CO2 + H2O stream is “free”, thus a direct saving is achieved in the cold utility which must be supplied to cool the CO2 product.