Mass and heat transfer study in osmotic membrane distillation-crystallization for CO2 valorization as sodium carbonate

Crystallization of Na2CO3·10H2O using a membrane contactor is proposed in this work as the last stage of a whole integrated membrane system for the capture of CO2. The performance of an osmotic membrane distillation-crystallization setup was evaluated, considering the effect caused by the flow rates and the concentration of both the feed and the osmotic solution, as well as the feed temperature, on the mass and heat transfer coefficients. Variation of flow rates and feed concentration did not produce a significant effect on the mass transfer coefficient (except for feed flow rates under 50 mL min−1). On the other hand, decreasing the concentration of the osmotic solution or increasing the temperature led to a decrease in the mass transfer coefficient. Understanding this negative effect of the osmotic solution and temperature on the performance of membrane distillation-crystallization is critical for the further application of this technology in real systems. A deep interpretation is done in this work based on polarization effects and possible membrane wetting. In addition, the resistance-in-series model was applied, which showed the membrane as the main resistance to mass transfer, and the permeate stream to heat transfer.