【作者】 杨磊；

【导师】 于宏兵；

【作者基本信息】 南开大学 ， 环境工程， 2012， 博士

【摘要】 化石燃料的燃烧向环境中释放了大量温室气体，以CO₂为主的大量温室气体的释放，导致了严重的温室效应及全球气候异常现象，已成为世界各国需要共同关注的全球性问题。在各主要温室气体中，CO₂对温室效应的贡献率达到了55%。我国是以煤炭为主的能源结构，煤炭生产单位热量引起的CO₂排放量比石油和天然气分别高出约36%和61%。因此，我国在温室气体减排方面面临着巨大压力。燃煤电厂生产过程中排放大量CO₂，是最大固定排放源之一。燃烧后捕捉技术，被认为是短期内能够为化石燃料电厂提供有效CO₂分离捕捉的技术。根据燃煤电厂及其烟气系统特点，利用粉煤灰和烟气含有的能量分离捕捉烟气中的CO₂，充分体现了清洁生产和循环经济的思想。针对以上问题，本论文以分离捕捉燃煤电厂烟气中的CO₂为研究对象，利用垂直式固定床反应装置，研究了高温吸收剂循环分离CO₂的碳酸化过程。普通钙基材料存在吸收容量低、循环稳定性差及易烧结等问题，通过改性、掺杂等手段制备了一系列高温钙基吸收剂，用于分离捕捉模拟烟气中的CO₂。论文主要包括以下五部分：1.利用醋酸钙、氢氧化钙、碳酸钙和氧化钙等钙基材料，通过简单制备过程得到四种高温钙基吸收剂，并研究了其碳酸化反应特性。确定反应气流速、吸收剂颗粒粒径及碳酸化反应温度等因素对钙基吸收剂CO₂吸收性能的影响。通过XRD、SEM及氮吸附等表征手段分析吸收剂反应前后的成分，结构及形貌的变化。用失活模型拟合钙基吸收剂吸收CO₂的实验穿透曲线。最后对钙基吸收剂吸收CO₂的机理进行分析；2.在上述钙基吸收剂中掺入粉煤灰，得到钙基粉煤灰吸收剂。以CaO-CaO/FA为例进行前期实验条件确定，如最佳反应气流速为0.1L/min、吸收剂粒径为0.8mm、粉煤灰掺杂量为25%及最佳反应温度为650℃等。XRD分析结果表明CaO-CaO/FA吸收剂通过制备过程形成了大量矿物。失活模型能够很好的拟合CaO-CaO/FA吸收剂吸收CO₂的实验数据。对不同钙基材料制备的钙基粉煤灰吸收剂的碳酸化特性进行了研究。3.高温吸收剂的循环稳定吸收性能十分重要。煅烧温度和煅烧气氛对吸收剂CO₂吸收性能的影响研究表明，850℃为吸收剂最佳煅烧温度，降低煅烧气氛中的CO₂分压能够减缓吸收剂活性的衰减。通过对钙基和钙基粉煤灰吸收剂的多循环研究发现，CaAc₂-CaO和CaAc₂-CaO/FA具有最优越的CO₂吸收性能和循环稳定性。第15次循环后，CaAc₂-CaO/FA比CaAc₂-CaO表现出了更好的循环稳定性。Dolomite-CaO和Dolomite-CaO/FA吸收剂的碳酸化反应特性研究表明，其CO₂吸收性能和循环吸收稳定性能较差。4.研究了La和Ce改性钙基吸收剂的碳酸化特性。10%La/CaO和5%Ce/CaO吸收剂表现出了最优异的CO₂吸收性能。10%La/CaO吸收剂中的La₂O₃不仅是作为一种类“骨架”存在，还是一种活性成分，能够协同捕捉CO₂分子；5%Ce/CaO吸收剂含有部分铈的氧化物，碳酸化反应后生成了Ce₄O₂C₂和CeO2C2物质。多循环研究结果表明，10%La/CaO和5%Ce/CaO在循环吸收CO₂的过程具有良好的循环稳定性。SEM表明，经历20次循环后5%Ce/CaO出现严重的烧结塌陷现象，部分区域颗粒完全粘连到了一起。5.初步研究CaAc₂-CaO和CaAc₂-CaO-FA吸收剂在流化床反应器中的碳酸化特性。多循环流化床实验中，这两种吸收剂仍表现出较好的CO₂吸收性能，但随着循环次数的增加，穿透时间明显变短，穿透曲线出了重合。循环后产物的XRD分析发现，含有部分未反应的CaO，说明吸收剂在流化床反应器中流化状态不佳。最后，我们提出了一种燃煤电厂同步固硫固碳工艺。更多还原

【Abstract】 The combustion of fossil fuels releases plentiful CO₂to the environment, whichhas led to serious green-house effect and global climate anomaly phenomenon. It hasbecome the common concern global problems all over the world. In all kinds ofgreenhouse gas, the contribution rates of CO₂reach to55%for green-house effect.The China energy structure is dominated by coal, CO₂release of production unit heatfrom coal higher than oil and gas about36%and61%, respectively. Therefore, Chinahas faced great pressure in the greenhouse gas emission reduction. The CO₂emissionfrom coal-fired power plants is one of the major stationary sources. Post-combustionhas been recognized as the more effective CO₂separation and capture technology forcoal-fired power plants in the short term. According to the characteristics ofcoal-fired power plants, using original high-temperature flue gas and fly ash from theproduction process separate and capture CO₂from flue gas, which conform to thecurrent idea of Cleaner Production and Recycling Economy.The separation and capture CO₂from flue gas of coal-fired power plants werestudied in this dissertation. The carbonation reaction processes of high temperaturesorbent were investigated at vertical fixed-bed reactor. Considered ordinary calciumbase materials low CO₂adsorption capacity, poor cycle stability and sinter problem,modification and doping means were used to improve and prepare a series of sorbentsfor CO₂separation and capture from simulate flue gas. This dissertation mainlycontents five sections:1. Use of acetic acid calcium, calcium hydroxide, calcium carbonate and calciumoxide, obtained four kinds of Ca-based sorbents by the simple preparation process,and the carbonation characteristics of those sorbents were studied. Reactionconditions for Ca-based sorbents were determined, such as eaction gas velocity,sorbents particle size and carbonation temperature and so on. The constituents,surface morphology information and physical properties of Ca-based sorbents andreaction products were analyzed by XRD, SEM and N2adsorption-desorption. Thedeactivation mode was used to fit experimental breakthrough curves. The CO₂ absorption mechanism of Ca-based sorbents was discussed.2. Doping fly ash to Ca-based sorbents, obtained the Ca-based fly ash sorbents.Taking CaO-CaO/FA sorbent for example, determined the gas velocity0.1L/min,sorbent particle size of0.8mm,25%fly ash doping content and the optimum reactiontemperature and so on. The XRD results shown that a large number of mineralsformed by the preparation process for Ca-based fly ash sorbents. The CO₂experimental breakthrough curves of Ca-based fly ash sorbents can well be fitted withthe deactivation model. Other Ca-based fly ash sorbents, such as CaAc₂-CaO/FA,CaCO3-CaO/FA, Ca（OH）2-CaO/FA and dolomite sorbents, their characteristics ofcarbonation were investigated in detail.3. The cycles performance of sorbents is of critical importance. Results indicatedthat, the optimum calcination temperature of regeneration is850℃, and reducing theCO₂partial pressure of calcining atmosphere can slow down the sorbents activity. Itwas found from multicycles reaction of Ca-based and Ca-based fly ash sorbents that,CaAc₂-CaO and CaAc₂-CaO/FA had the best CO₂absorption performance and cyclestability. And after15thcycles, CaAc₂-CaO/FA shows the better cycle stability thanCaAc₂-CaO sorbent. The characteristics of carbonation of Dolomite-CaO andDolomite-CaO/FA sorbent showed that, they have low CO₂absorption capacity andpoor cycle stability.4. The carbonation performances of rare earth modified Ca-based sorbents wereinvestigated in fix-bed reactor.10%La/CaO and5%Ce/CaO sorbents showedexcellent CO₂absorption performances. The optimum calcination temperature ofLa-/Ce-doping Ca-based sorbents is850℃for the preparation process. La₂O₃in thesorbents is not only as a kind of “skeleton structure” exists, but also an activeingredient can capture CO₂.5%Ce/CaO sorbent contains a series of cerium oxide,could become Ce₄O₂C₂and CeO2C2after carbonation reaction. Multilcycles reactionresults indicated that,10%La/CaO and5%Ce/CaO sorbents have showed bettercycle stability. The SEM morphology showed clearly that5%Ce/CaO sorbent appearserious sintering and collapse phenomenon after20thcycles, and partially sorbentparticles adhesion together.5. The characteristics of carbonation of CaAc₂-CaO and CaAc₂-CaO-FA sorbents were conducted at the fluidized bed reactor. During multicycles fluidizedbed experiments, it was found that CaAc₂-CaO and CaAc₂-CaO-FA sorbents showgood CO₂absorption performance. With the increase of cycles times, thebreakthrough time obviously become short and curves cross and overlap. The XRD ofproducts after cycles found that contains some unreacted CaO. It is mainly becausethe fluidized state of sorbent not good in the reactor. Finally, we have developed akind of fix sulfur in combustion and capture carbon from flue gas technology forcoal-fired power plants in this dissertation.更多还原