Process assessment and sensitivity analysis of CO2 capture by aqueous methyldiethanolamine + piperazine blended solutions using membrane contactor: Model development of kinetics and mass transfer rate

A comprehensive steady-state, rate-based mathematical model for CO2 capture in a hollow fiber membrane contactor (HFMC) for non-wetted mode has been developed by taking into accounts the mass transfer resistances and chemical reactions. Aqueous MDEA + PZ blended solution as the CO2 absorbent was flowed in the tube side and the gas mixture was circulated counter-currently in the shell side of HFMC. The model predictions are verified with the experimental results of CO2 absorption in a HFMC reported in literature. In addition, the effects of operating conditions on the membrane performance such as gas and liquid flow rates, liquid temperature, initial CO2 partial pressure, solvent concentration and fiber numbers in the module are investigated and discussed. To investigate the influence of solvent on the separation process, some common industrial chemical absorbents including MDE, MEA, TEA, MDEA and PZ are compared with MDEA + PZ blended solution. Adding small amount of PZ as a promoter to MDEA solution has significant effect on the CO2 absorption. The results show that the CO2 absorption reaction with MDEA + PZ blended solution is faster than that with TEA and MDEA and also comparable with DEA, but it is slower than those with MEA and PZ. The results indicated that CO2 removal performance enhances with increasing the fiber numbers, liquid temperature and liquid flow rate in the tube side, but increasing gas flow rate in the shell side has a negative effect on the absorption performance.