汞吸附过程的试验研究和数学模型

Fixed-bed Experiments and Mathematical Modeling for Adsorption of Mercury Vapors

在固定床试验台上,以汞渗透管和其它主要气体成分模拟烟气条件,采用活性炭和飞灰对汞的吸附过程进行了试验研究。结果表明:随Hg0入口含量的增加,活性炭、飞灰的吸附量增加,初始吸附量与Hg0的含量成正比例增加;吸附反应温度升高,活性炭、飞灰的吸附能力降低,这主要是由物理吸附的机理决定的。颗粒物理特性的差异成为飞灰与活性炭的吸附能力之差距的原因之一。另外,针对固定床吸附过程,建立了由质量平衡、传质过程以及吸附剂表面反应过程等综合决定的吸附动力学模型。模拟值与试验结果较吻合,因此该模型可用于某些待定影响因素的预测计算。

A simulated flue gas is prepared by mixing heated, nitrogen gas streams containing mercury vapors （by an elemental mercury diffusion tube） and other main composition of flue gas. Bench-scale, fixed-bed tests are conducted with activated carbon （AC） and fly ash sorbents. The effects of inlet mercury concentration, and adsorption temperature are investigated to determine the abilities of mercury removal from simulated flue gas streams. Results show that the adsorption of AC and fly ash samples had the similar trend： the adsorption capacity increases outstandingly with higher Hg^0 inlet content, and because of the kinetics of physical adsorption, the performance of the sorbents deteriorates with increasing temperature. It suggested that the different of particles structure properties influence the capture of Hg^0. It is also presented a theoretical model based on the mechanisms of surface equilibrium and mass transfer, and a material balance model for the fixed-bed reactor. The simulation results indicated that the model is capable of describing the tests data, and this model also can be applied to determine the effects of various sorbents properties on mercury removal at different conditions.