【作者】 邰晓燕；

【导师】 刁永发；

【作者基本信息】 东华大学 ， 环境工程， 2011， 硕士

【摘要】 化学吸收法脱除CO2实质是利用碱性吸收剂与烟气中的CO2接触并发生化学反应,形成不稳定的盐类,而盐类在一定的条件下会逆向分解释放出CO2而再生,从而达到将CO2从烟气中分离脱除的目的。目前具有反应能耗低、循环利用效率高、对设备无腐蚀、无二次污染等优点的干法吸收技术已成为研究热点。本文着重研究了底泥负载K+基二氧化碳干式吸收剂及其模拟待再生剂的制备,并研究模拟待再生剂的再生反应特性及其动力学特性。本文通过对比分析,选用苏州河河道底泥作为制备二氧化碳干式吸收剂的载体,并对河道底泥进行热重分析。实验表明,未经处理的河道底泥热分解主要有三个不同阶段,分别为脱水干燥阶段、有机物碳化热解阶段和煅烧分解阶段。通过SEM分析与氮吸附实验分析,从表面形貌、孔结构与比表面、孔容、孔径方面对比单斜晶系K2CO3与KHCO3热分解生成的六方晶系K2C03,最终选用KHCO3与六方晶系K2CO3分别作为制备模拟待再生剂与干式吸收剂的活性组分。本文粘结剂选用Na2SiO4,添加剂选用广西白泥。对底泥做一定处理后,按照适当比例加入粘结剂与添加剂,并与活性组分充分混合,经颗粒成型制备得到CO2干式吸收剂模拟待再生剂。待再生剂受热分解后便得到CO2干式吸收剂。采用扫描电子显微镜(SEM)与比表面积测定仪对吸收剂进行了表征,分析其表面形貌、微观结构及比表面积等。本研究对化学纯KHCO3在标准条件下与不同分解终温条件下进行了热重分解实验,结果表明,KHCO3热分解一步即可完成,分解反应主要发生在100℃～200℃之间；最佳再生反应终温为200℃左右。对河道底泥负载的K+基吸收剂模拟待再生剂在不同活性组分负载量、不同升温速率及活性组分中添加不同比例K2CO3的条件下进行热重实验,分析其再生反应特性与动力学特性,结果表明,在活性组分负载量为40%-50%时模拟待再生剂的最大转化率达到96.67%,随着KHCO3负载量的增加,反应有向高温方向移动的趋势。升温速率的变化对待再生剂的再生反应影响不大,当升温速率达到5℃/min以上时,其最大转化率均超过90%。在KHCO3和K2CO3共存的状态下,再生过程出现两个失重峰,分别位于60～130℃和130～220℃两个温度区间。由于K2CO3易吸水转化为K2CO3·1.5H2O,因此,再生反应过程中,60～130℃温度区间内为受热脱除结晶水的反应,130～220℃为KHCO3再生反应阶段,再生反应热失重曲线向高温方向移动,最大转化率明显降低,反应难度增大。底泥负载K+基吸收剂模拟待再生剂再生反应的表观活化能为90～110kJ/mol。KHCO3负载量为40%时,待再生剂再生反应所需活化能最低；表观活化能随着升温速率的升高而增大；活性组分中添加K2CO3后,反应表观活化能略有提高。更多还原

【Abstract】 The essences of removing CO2 by chemisorption is to use alkaline absorbent mixed with CO2 in the flue gas, and react to form volatile salts, the salts will revers decomposition under certain conditions to regenerate for releasing CO2, which to achieve the separation of CO2 and flue gas. So far, the dry absorption with the advantage of low energy consumption, high recycling efficiency, no corrosion to equipment and no secondary pollution has become a research hotspot. This paper studies the preparation of the dry sorbent and the analogue regenerant of the sorbent, to simulate the regenerable characteristic and the dynamics characteristic of analogue regenerant.Through comparative analysis, Suzhou Creek river sediment is chosen as the support of dry absorbent for CO2 capture, and the river sediment is researched by thermal gravimetric analyzer. Results of experiments show that there are three main stages of untreated river sediment thermal decomposition, it is respectively the dehydration stage, the organic carbon pyrolysis stage and the calcination stage. Analysis by SEM and nitrogen adsorption analyzer, compared with the surface morphology, pore structure and surface area, pore volume and pore size to devision monoclinic system K2CO3 and hexagonal K2CO3 that was generated by thermal decomposition of KHCO3. In the final selection, KHCO3 and hexagonal K2CO3 were determined to be the active component of dry absorbent for CO2 capture and the analogue regenerant of potassium-based sorbents. Na2SiO4 was used to be binder, and Guangxi plastered as additives in this paper. After some treatment of the sediment, adding into the binder and additives in accordance with the appropriate proportion and fully mixed with the active component, the analogue regenerant of dry sorbents were prepared after forming ballstye particle. And the dry sorbents for CO2 caputure would be obtained after thermal decomposition. The surface morphology, microstructure and specific surface area was analyzed By scanning electron microscopy (SEM) and surface area analyzer in this paper. TGA experiments of chemically pure KHCO3 was studied at standard conditions and different final temperature of decomposition conditions, results show that, decomposition of KHCO3 would be completed with one step, and it mainly occurred between 100℃～200℃. The best final temperature is about 200℃.The regenerant was studied by thermogravimetric analysis on the loading of potassium bicarbonate, the heating rate and the addition of potassium carbonate, to investigate the regenerable characteristic and dynamics characteristic. Experimental and analytical results show that the the maximum conversion rate was 96.67% when the potassium bicarbonate loading was 40%-50%, the reaction shifted to high temperature when potassium bicarbonate loading was increased. Changes of heating rate was an invisible effect to regenerable reaction,and the regenerable conversion exceeding 90% when heating rate was more than 5℃/min. There were two peaks for DTG curves when KHCO3 and K2CO3 in a state of coexistence, and the two steps were located at 60～130℃and 130～220℃. The temperature range of 60～130℃was the step that removing crystal water, because K2CO3 would become K2CO3·1.5H2O easily for hygroscope. The temperature range of 130～220℃was regeneration reaction stage, the DTG curves moved to high temperature direction, the maximum conversion rate become lower significantly, and the difficulty of regenerable reaction increased. The value of the apparent activation energy of regenerable about potassium-based/river channel sediment supported sorbent for CO2 capture was between 90～110 kJ/mol Sediment load simulations of K+-based absorbent agent to be recycled for the regeneration of the apparent activation energy 90～110 kJ/mol. The value of the apparent activation energy was the lowest when KHCO3 loading was 40%, the value would increase with the heating rate higher, and it increased slightly when K2CO3 was added into the active component.更多还原