活性炭和沸石分子筛处理非稳定排放VOCs气体的性能比较

Competitive adsorption and desorption of unsteady emission VOCs on activated carbon and zeolites

通过对活性炭和沸石分子筛的表征和动态吸附/脱附实验,探索2类吸附材料固定床工艺用于非连续、非稳定类型的大风量、低浓度挥发性有机物(VOCs)排放控制的应用前景。结果表明:沸石分子筛孔径分布较为集中,约在0.8 nm,比表面积为393.76 m^2·g^(-1);活性炭孔径分布具有广谱性,微孔集中在1~2 nm之间,比表面积为1 026.71 m^2·g^(-1)。活性炭对二甲苯的平衡吸附量总体高于沸石分子筛,其平衡吸附容量随气相平衡浓度和温度的波动要大于沸石分子筛。动态吸附穿透实验结果显示沸石分子筛单位传质区长度的平均传质速率是活性炭的约1.42~1.66倍。相同吸附和脱附温度条件下,活性炭的工作容量要大于沸石分子筛。沸石分子筛在210℃时基本脱附彻底,且可得到48倍以上的浓缩脱附气体。50次的吸附、脱附重复实验对沸石分子筛的性能影响不大。沸石分子筛作为吸附材料脱附单位质量的二甲苯所需能耗是活性炭的2.9~4.2倍。活性炭和沸石分子筛可采用不同的工艺方式应用于低浓度、大风量、非稳定排放的VOCs气体的净化。

The application of two kinds of adsorbents in a fixed bed was studied by comparing the performances of activated carbon and zeolite in discontinuous and unsteady volatile organic compounds （VOCs） emissions with large flow and low concentration conditions through characterization and dynamic adsorption/desorption experi- ments. The results indicate that the pore size distribution of zeolite was more concentrated, at about 0. 8 nm,while the specific surface area was 393.76 m2· g-1 The pore size distribution of activated carbon was broad,its micro hole was concentrated in 1 to 2 nm,and its specific surface area was 1 026.71 m2 · g-1. The equilibrium adsorp- tion capacity of xylene on activated carbon was generally higher than on zeolite,and the influence of its equilibri- um concentration and temperature on the equilibrium adsorption capacity of activated carbon was more powerful than that of zeolite. Dynamic adsorption breakthrough curves indicate that the average transfer rate per mass transfer zone of zeolite was from 1.42 to 1.66 times more than that of activated carbon. The working capacity of activated carbon was larger than that of zeolite under the same adsorption and desorption temperature conditions. Desorption of xylene from zeolite could be accomplished at 210 ℃ to obtain more than 48 times of the concentrat- ed gas from desorption. The 50 times adsorption-desorption experiments had little effect on the performance of ze- olite. The energy consumption of desorption per kg xylene from zeolite was from 4.2 to 2.9 times of that of acti- vated carbon. Activated carbon and zeolite could be applied for removal of VOCs from low-concentration,large air volume and unsteady emissions by different combined processes.