*Article* **Modeling and Experimental Studies on Carbon Dioxide Absorption with Sodium Hydroxide Solution in a Rotating Zigzag Bed**

**Zhibang Liu 1, Arash Esmaeili 1, Hanxiao Zhang 1, Dan Wang 2,3, Yuan Lu <sup>4</sup> and Lei Shao 1,\***


**Abstract:** The enhancement of mass transfer is very important in CO2 absorption, and a rotating zigzag bed (RZB) is a promising device to intensify the gas–liquid mass transfer efficiency. In this study, the mass transfer characteristics in an RZB in relation to the overall gas-phase volumetric mass-transfer coefficient (*K*G*a*) were investigated with a CO2–NaOH system. A mathematical model was established to illustrate the mechanism of the gas–liquid mass transfer with irreversible pseudofirst-order reaction in the RZB. The effects of various operating conditions on *K*G*a* were examined. Experimental results show that a rise in the liquid flow rate, inlet gas flow rate, rotational speed, absorbent temperature, and absorbent concentration was conducive to the mass transfer between gas and liquid in the RZB. It was found that the rotational speed had the largest impact on *K*G*a* in the RZB. The *K*G*a* predicted by the model agreed well with that by the experiments, with deviations generally within 10%. Therefore, this model can be employed to depict the mass transfer process between gas and liquid in an RZB and provide guidance for the application of RZBs in CO2 absorption.

**Keywords:** rotating zigzag bed; modeling; gas–liquid mass transfer; carbon dioxide; absorption
