Design of a water wash column in the CO2 capture process using a polyamine-based water-lean solvent

Abstract

Amine-based water-lean solvents (WLSs) have been studied as energy-saving alternatives to existing aqueous amine solvents for the capture of CO2. However, despite the low energy requirements of WLS-based processes, WLSs are susceptible to amine vaporization loss due to the high amine concentration. In addition, the water content of WLSs is apt to increase, which is caused by the low vaporization pressure of water from the solvent due to the low water content of the solvent. When this happens, it is expensive to return the water content of the solvent to its original state. To address these problems, in this study, we investigated the design of a water wash section for a CO2 capture process based on a WLS consisting of 60 mass% of 3,3′-iminobis (N,N-dimethylpropylamine) (IBDMPA), 10 mass% of water, and a non-amine chemical as the final content. The heat and mass balance around the water wash section was analyzed, including the IBDMPA/water transfer from gas phase to liquid (water) phase within the water wash bed. To achieve this, the mass transfer coefficients of the IBDMPA and water were measured in a modified wetted wall column system, and the binary and ternary vapor–liquid equilibria for the WLS were also measured and modeled. The computation using the ASPEN Plus® simulator showed that IBDMPA emissions of less than 1 ppm and water balance in the WLS could be successfully achieved through the appropriate design of the water wash section.