Microwave thermal regeneration characteristics of spent activated carbon based on a coupled electromagnetic, heat and mass transfer multiphase porous media model

Microwave thermal regeneration is an emerging technique for activated carbon regeneration, which has been extensively investigated experimentally. However, relevant simulation receives limited attention, with the mechanism of microwave thermal regeneration not very well understood. In this study, a multiphase, porous media model coupling electromagnetic, heat and mass transfer is established to study microwave thermal regeneration characteristics of spent activated carbon. The results show that inhomogeneous electromagnetic distribution in the cavity is the main factor contributing to the inhomogeneity of the sample temperature. The desorption of adsorbate in the hot spot region (dry basis) mainly relies on microwave radiation heating. The desorption of adsorbate in the cold spot region (wet basis) depends on heat conduction and convection in the hot spot region, as well as capillary diffusion caused by the concentration gradient. In addition, the uniformity of sample temperature distribution is optimized by rotating microwave thermal regeneration, and energy consumption is reduced by about 58 %. Therefore, this model can provide technical guidance for optimizing the microwave thermal regeneration process of spent activated carbon while explaining the mechanism of microwave regeneration.