Carbon Dioxide Desorption In Membrane Flash Process And Compounded Absorbents Research

In the carbon capture, utilization and storage technologies, CO2desorption process is one of the most important operations that makes the absorbents recycling and keeps the CO2enrichment process continuous. However, the traditional CO2thermal desorption process has low mass transfer efficiency and huge energy consumption in the desorption process, which accounts for more than80%of the energy consumption of the whole operation process. Thus, carbon dioxide desorption is becoming the limiting step in entire carbon capture and separation process. Therefore, it is gradually becoming one of the most promising area that developing new methods of efficient and low energy consumption CO2desorption technologies in CO2capture and storage technologies (CO2Capture and Storage, CCS).The membrane flash process (MFP) is the process that combines the membrane dispersion and CO2vacuum desorption process together. Utilizing microporous membrane as the phase dispersion medium, the carrier solution are homogeneous dispersed in gas phase with the assistance of the pressure difference between two sides of the membrane and then releases CO2. On one hand, the interphase mass transfer area is greatly increased because of the smaller size of the scattering liquid droplets, and on the other hand, the driving force and the CO2desorption mass transfer performance is improved due to stable vacuum degree in the permeate side. Moreover, the extremely short residence time of the absorbent in the membrane module makes the handling capacity partly promoting.In our previous studies on CO2desorption process in hollow fiber membrane, we showed that the hollow fiber membrane contactor can improve the mass transfer efficiency of the desorption process due to its large mass transfer area in per volume can effectively. However, CO2absorption and desorption from alcamines aqueous solution is a typical thermodynamic process and is largely affected by chemical reaction restriction. In order to overcome such slow-desorption problem, we have already proposed adding physical absorbent in the commonly used industrial alkanolamine absorbents, and proportioning optimization of the compounded absorbents are selected through solvent screening experiments. We study experimrntally on the effect of absorbent composition, membrane structure and a variety of operating conditions, on this basis, we explore CO2mass transfer mechanism in membrane flash process and determine the optimum operating conditions. As a result, we can provide a valuable experimental data for further industrial application of membrane flash process in CO2capture technology.As is shown in our studies, under the optimal conditions of membrane flash process, which the mass ratio of composite absorbents is MDEA:NHD:H2O=2:4:4, the pore size of flat membrane module is2um the liquid flow rate is5mL·min-1, the degree of vacuum is70kPa and the desorption temperature is70℃, CO2desorption efficiency is as high as95.1%, CO2mass transfer flux is0.171mol·m-2·s-1, CO2desorption energy consumption is only1665kJ/kgCO2, which is far lower than the regeneration energy consumption of3.2～4.0×103]J/kgCO2in traditional chemical absorption process.