活性炭床吸附VOCs传热传质耦合数值模拟研究

Numerical Simulation Study of Coupled Heat and Mass Transfer for VOCs Adsorption on Activated Carbon Beds

为了进一步研究活性炭固定床内挥发性有机化合物(volatile organic compounds,VOCs)吸附的传热传质规律,基于已有的吸附实验数据,采用计算流体动力学(computational fluid dynamics,CFD)技术对固定床的吸附分离过程进行研究,建立了活性炭吸附VOCs的传热传质气固两相耦合数学模型,同时对比实验验证了模型的准确性。研究了进气浓度、进气温度、进气流速和活性炭颗粒直径对吸附工艺的影响。结果表明:处理高浓度废气时,床层吸附容量随进气浓度增大而减小;处理低浓度废气时,其吸附容量则随进气浓度增大而增大。相比高浓度废气,处理低浓度废气时,进气浓度的影响更加显著;选用较低的进气温度,可提高床层吸附容量,且不会增大床层压降;床层吸附容量随着进气流速增大而增大,进气流速增大,会导致床层利用不充分且增大压降;减小固定床颗粒直径可以提高活性炭床利用率,但会使床层压降增大,从而增大能耗。

To further study the heat and mass transfer law of VOCs adsorption in activated carbon fixed bed,based on the existing adsorption experimental data,the adsorption and separation process of the fixed bed was investigated by using Computational Fluid Dynamics CFD technique,and the heat and mass transfer gas-solid two-phase coupled mathematical model for VOCs adsorption on activated carbon was established,and meanwhile,comparative experiments were carried out to validate the accuracy of the model.The effects of inlet gas concentration,inlet gas temperature,inlet gas flow rate,and activated carbon particle diameter on the adsorption process were investigated.The results showed that:when treating high-concentration waste gases,the adsorption capacity of the bed layer decreases as the inlet gas concentration increases;when treating low-concentration waste gases,its adsorption capacity increases as the inlet gas concentration increases.The effect of the inlet gas concentration was more significant when treating the low-concentration waste gas than that of the high-concentration waste gas;the selection of lower inlet gas temperature could improve the adsorption capacity of the bed and would not increase the pressure drop of the bed;the adsorption capacity of the bed increased with the decrease of the inlet gas flow rate;the increase of the inlet gas flow rate would lead to the under-utilization of the bed and the increase of the pressure drop;reducing the diameter of fixed bed particles can increase the utilization rate of activated carbon beds,but it will increase the bed pressure drop and thus increase the energy consumption.