Experimental investigation on continuous reaction crystallizer for CO2 capture by phase-change method

Reducing the energy consumption of the regenerator has been the most intractable problem for CO2 capture processes. An energy-efficient phase change-based carbon dioxide absorption process by potassium carbonate/bicarbonate solution is proposed to reduce the capture energy consumption to less than 1.5 GJ/(t·CO2), and an energy-saving continuous reaction crystallizer integrating reaction and separation is developed here to collect CO2-rich solid products. This capture process is expected to significantly reduce the energy penalty due to high absorbent concentration, high mass transfer rate from the microbubbles, and no repeated solvent heating and vaporization procedure during regeneration. The effects of superficial gas velocity and fluid jet velocity on liquid circulating velocity, gas holdup, and volumetric mass transfer coefficient in the reaction crystallizer are thoroughly investigated. The experimental results demonstrate that the superficial gas velocity is crucial in improving the solid–liquid separating efficiency, particle size classification, and reaction rate. Empirical models which can accurately describe the hydrodynamics are proposed to select proper operating conditions of CO2 absorption in such a kind of multiphase continuous crystallizer. The reaction system shows an effective behavior in absorbing CO2 and producing KHCO3 crystals, and the mean diameters are verified to be controllable by manipulating the superficial gas velocity and fluid jet velocity.