Knowledge Management System Of Institute of process engineering,CAS
挥发性有机物（Volatile Organic Compounds, VOCs）是石油、化工及其相关行业排放的最常见的空气污染物，参与雾霾形成过程，严重破坏生态环境、影响人类身体健康。流化床吸附装置具有气固接触效率高、床内传热速率高、操作气速高等优点，是处理工业大风量、低浓度废气的发展方向。对流化床用吸附剂的研究基本上处于空白，缺少专用的吸附剂限制了流化床吸附净化装置的推广使用。本研究工作针对流化床用吸附剂短缺的问题开发研制了低成本、高耐磨强度、具有较大的吸附容量和较高的吸附速率并且具有良好的吸脱附循环性能的流化床用吸附树脂和球形活性炭，并以制得的吸附树脂为吸附剂设计了流化床吸附器。以聚苯乙烯为原料，通过氯甲基化反应和后交联反应，合成了超高交联树脂，并通过在溶剂中添加介孔模板剂的方法对其孔径进行了调变。介孔模板剂正己烷可有效调控超高交联树脂的孔径，树脂平均孔径随着介孔模板剂用量的增加而增大，介孔比表面积随着介孔模板剂用量的增加而出现了先增后减的趋势。超高交联树脂具有较高硬度和极强的耐磨性能，磨损指数r168<0.1%，可耐受流化床中高强度摩擦，同时具有较高的比表面积和孔体积，强的疏水性和亲有机物性，对VOCs有着极高的吸附量。通过固定床吸附实验测定了该树脂的穿透曲线，利用穿透曲线计算了总传质系数和内、外扩散系数。超高交联树脂的内扩散系数是商用吸附树脂的4.68倍，传质阻力较小，吸附速率快，具有更加优异的传质特性。以超高交联树脂为原料，通过水蒸气活化、氯化锌活化和水蒸气-氯化锌协同活化的方法制备了不同孔结构的树脂基球形活性炭。通过对孔结构的分析，水蒸气活化有利于产生微孔结构，氯化锌活化有利于产生介孔结构。三种活性炭磨损指数均小于0.1%，压碎强度大于18 N/particle，耐磨性能优异，可满足流化床使用条件。树脂基活性炭对VOCs有着较高的吸附容量，其二甲苯、乙酸乙酯、丙酮吸附量均高于进口流化床用活性炭。活性炭的总传质系数和内、外扩散系数同样通过穿透曲线计算得到。水蒸气活化的球形活性炭的内扩散系数是商用流化床活性炭的1.66倍，在传质方面具有较大的优势。以HCP-5为吸附剂，计算了流化床吸附器的设计参数，在处理任务为流量30000 m3/h，浓度0.5 g/m3，以乙酸乙酯为代表污染物的废气时，需要的流化床吸附器直径为5.46 m，床层数为2层，吸附剂下料率为108.43 kg/h。;Volatile organic compounds (VOCs) are the most common air pollutants emitted by petroleum, chemical industry and related industries. They participate in the formation of haze, seriously destroy the ecological environment and affect human health. The fluid bed adsorption device with the advantages of high gas-solid contact efficiency, high heat transfer rate, high operating gas velocity, is a promising development direction of the treatment of high-volume, low-concentration industrial exhaust gas. The study of adsorbent for fluid bed is basically in blank. The lack of dedicated adsorbents limits the popularization of the fluid bed adsorption purification device.In this thesis, adsorbents, specifically adsorption resins and spherical activated carbons, with low-cost, high abrasion strength, high adsorption capacity and rate, as well as good performance of adsorption and desorption cycle, have been developed to solve the problem of shortage of adsorbents used in fluid bed. Additionally, the design parameter of the fluid bed was calculated with the adsorption resins as adsorbents.Polystyrene was used as raw material to synthesize hypercrosslinked polymers (HCPs) through chloromethylation reaction and post-crosslinking reaction. The pore size of HCPs was controlled effectively by adding n-hexane in the reaction process which served as mesoporous template agent. The average pore size of the resin rises with the increase of the amount of mesoporous template agent; the mesoporous specific surface area increased first and then decreased with the increase of the amount of n-hexane. HCPs with high rigidity and strong wear resistance (abrasion index r168<0.1%), satisfy the requirement of fluid bed. HCPs also have a high specific surface area and pore volume, strong hydrophobicity, and high adsorption capacity of VOCs. Breakthrough curves of were measured by fixed bed adsorption experiments in order to obtain the total mass transfer coefficient, internal and external diffusion coefficients. As calculation result shown, the internal diffusion coefficient of HCPs is 4.68 times of the commercial adsorption resins, indicating HCP-5 have smaller mass transfer resistance and faster adsorption rate.Using HCPs as raw material, polymer-based activated carbon beads (PCBs) with different pore structure was prepared by water vapor activation, ZnCl2 activation and synergistic activation of water vapor-ZnCl2. Vapor activation was favorable for the production of microporous structure, while ZnCl2 activation is conducive to the production of mesoporous structure. PCBs presented excellent wear resistance and hardness with abrasion index less than 0.1% and crushing strength greater than 18 N/particle, able to meet the requirement of fluid bed. PCBs also have high adsorption capacity of VOCs, and their xylene, ethyl acetate and acetone adsorption capacity are all higher than imported commercialized activated carbon used as adsorbents in fluid bed. The total mass transfer coefficient, internal and external diffusion coefficients of PCBs were calculated from breakthrough curves. The internal diffusion coefficient of the PCBs activated by water vapor is 1.66 times of the commercialized fluid bed activated carbon, with a great advantage in mass transfer.In the design of fluid bed using HCPs as adsorbents, to complete the design task of exhausted gas with ethyl acetate concentration of 0.5 g/m3 and flow rate of 30000 m3/h, the required diameter of fluid bed was 5.46 m with 2 layers, and the solid flow rate was 108.43 kg/h.
|常远. 用于流化床吸附工艺的VOCs吸附剂的研制[D]. 中国科学院大学,2018.|
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