CO2 Desorption Performance from Imidazolium Ionic Liquids by Membrane Vacuum Regeneration Technology

In this work, the membrane vacuum regeneration (MVR) process was considered as a promising technology for solvent regeneration in post-combustion CO2 capture and utilization (CCU) since high purity CO2 is needed for a technical valorization approach. First, a desorption test by MVR using polypropylene hollow fiber membrane contactor (PP-HFMC) was carried out in order to evaluate the behavior of physical and physico-chemical absorbents in terms of CO2 solubility and regeneration efficiency. The ionic liquid 1-ethyl-3-methylimidazolium acetate, [emim][Ac], was presented as a suitable alternative to conventional amine-based absorbents. Then, a rigorous two-dimensional mathematical model of the MVR process in a HFMC was developed based on a pseudo-steady-state to understand the influence of the solvent regeneration process in the absorption–desorption process. CO2 absorption–desorption experiments in PP-HFMC at different operating conditions for desorption, varying vacuum pressure and temperature, were used for model validation. Results showed that MVR efficiency increased from 3% at room temperature and 500 mbar to 95% at 310K and 40 mbar vacuum. Moreover, model deviation studies were carried out using sensitivity analysis of Henry’s constant and pre-exponential factor of chemical interaction, thus as to contribute to the knowledge in further works.

CO2 desorption from activated DEA using membrane contactor with vacuum regeneration technology

Carbondioxide (CO2) content in natural gas must be removed because it inhibits liquefication process of natural gas. CO2 gas separation technology using membrane contactor has been developed, however solvent regeneration using membrane contactors are still rare because it requires a larger energy. The regeneration process by using membrane vacuum technology was put forward to reduce the regeneration energy consumption. In this work, arginine, piperazine (PZ), and potassium carbonate (K2CO3) as activators were added into diethanolamine (DEA) solution to form aqueous solutions of activated DEA. The experiment of CO2 desorption from activated DEA was carried out in hollow fibre membrane contactor (HFMC). The solvent with rich CO2 at 30-70°C was flowed in the lumen of the hydrophobic polypropylene HFMC, and the shell side was maintained at a reduced pressure by a vacuum pump at 20 kPa. The effect of solvent temperature and activators were investigated to get CO2 desorption flux and regeneration efficiency. Experimental result shows that increasing of solvent temperature could enhance CO2 desorption flux and regeneration efficiency. Instead of that, the activated DEA also give better result compared with non-activated DEA. Among three activators, K2CO3 give the best result for desorption flux and regeneration efficiency.

Regeneration of the Absorbent by the PTFE Hollow Fiber Membranes Using Vacuum Membrane Regeneration Technology

The polytetrafluoroethylene (PTFE) hollow fiber membranes were prepared through a cold pressing method including paste extruding, stretching and sintering in this study. Membrane vacuum regeneration technology (MVR) was developed as a novel regeneration technology for regeneration of the absorbent. The membrane structures of the PTFE hollow fiber membranes were investigated. The mixture of N-methyldiethanolamine and piperazine was selected as the absorbent. The PTFE hollow fiber membranes were used for regeneration through vacuum membrane regeneration technology. The CO2 regeneration flux and regeneration ratio increased with the increase of the regeneration temperature and the CO2 loading. The regeneration pressure was negative to the regeneration flux and regeneration ratio. When the flow rate of the rich solution increased, the regeneration ratio decreased and CO2 regeneration flux increased significantly.