Numerical simulation and experimental investigation on thermal regeneration of spent activated carbon: Thermal desorption of mixed organic adsorbates in porous media

In the thermal regeneration of spent activated carbon, the thermal desorption of the adsorbate is the key process. In the actual desorption process, traditional models lead to inaccurate simulation results due to the presence of residual adsorbent. In this paper, a multi-phase porous media heat and mass transfer model is developed, which can calculate the thermal desorption characteristics of mixed adsorbates in spent activated carbon and reflect the presence of residual adsorbates, with a significant improvement in accuracy compared to the traditional model. The feasibility of the application of the model is verified by comparing the computational simulation results with the experimental results. Based on the simulations and theoretical analysis, it was concluded that the temperature rise and liquid phase content of the spent activated carbon samples under constant heating conditions were characterized by "fast-slow-fast" and "slow-fast-slow", respectively; the fluid flow inside the thermally regenerated samples was dominated by vapor flow The fluid flow within the thermally regenerated samples is dominated by vapor flow, with 90% of the vapor flow being viscous and the liquid flow being driven mainly by Darcy friction. In addition, the design and comparison of column and barrel shaped regeneration samples resulted in savings of up to 24.4% in thermal regeneration time for spent activated carbon at the same external temperature.