Carbon Dioxide Separation Using Bipolar Membrane Electrodialysis

We have developed a new CO₂ recovery process for post-combustion CO₂ separation. The process is composed of an absorption step with an alkaline solution such and the sodium hydroxide aqueous solution and a CO₂ recovery step with bipolar membrane electrodialysis. In the absorption step, CO₂ in exhaust gas is captured by the alkaline solution in the form of carbonate ions. Then in the recovery step, captured CO₂ is recovered from the alkaline carbonate solution via bipolar membrane electrodialysis, and the alkaline solution is regenerated at the same time. Effects of the alkaline concentration in the solution, the current density, the flow rate, and the CO₂ concentration in exhaust gas were examined by experimental studies. Based on the experimental results, an optimization of the operation conditions was conducted on the basis of minimization of energy requirement or cost for CO₂ capture.