钙基吸收剂循环吸收CO2技术的研究进展

阐述了对钙基吸收剂循环吸收CO₂技术的研究现状,包括各个可能因素对CaO碳酸化反应的影响,如吸收剂成分、颗粒特性、反应温度、反应时间、CO₂浓度等,并总结了各种CaO吸收CO₂反应动力学模型。同时对钙基吸收剂循环吸收CO₂技术未来的研究方向作了简述。     

复合钙基CO2吸收剂的反应性能及显微结构

采用溶胶-凝胶法制备了掺杂La3+、Mg2+的复合钙基CO2吸收剂,并在固定床反应器上进行了多循环的煅烧/碳化实验,对其CO2吸收活性及循环反应稳定性进行了研究.实验结果表明,掺杂La3、Mg2+的复合钙基吸收剂可以显著提高吸收剂在多循环煅烧/碳化过程中的反应活性和循环稳定性.在XRD分析的基础上,计算和比较了不同钙基...     

基于钙基吸收剂循环煅烧/碳酸化反应捕集CO2的试验

利用钙基吸收剂循环煅烧/碳酸化反应(CCCR)吸收CO2是一种新型、廉价、有效的CO2捕集方法.采用热重分析仪研究了吸收剂的矿物组成、颗粒粒径、煅烧温度和碳酸化温度对CCCR快速反应阶段吸收剂循环碳酸化率(XN)的影响.结果表明:吸收剂的碳酸化反应由快速化学反应控制阶段、过渡阶段和缓慢产物层扩散控制阶段组成;白云石具有良好的抗烧结能力,白云石的XN高于石灰石;随着颗粒粒径的增大,吸收剂的XN逐渐降低;当煅烧温度超过950℃时,随着循环反应次数的增加,吸收剂的XN严重降低;吸收剂在725℃碳酸化温度时的XN最高.     

烟气中水蒸气对钙基吸收剂碳酸化的影响特性

在循环煅烧/碳酸化反应系统上考察煅烧气氛和碳酸化气氛中水蒸气含量以及CO₂分压对钙基吸收剂成型颗粒碳酸化的影响,通过对钙基吸收剂微观结构分析(扫描电镜、氮吸附分析)以理解水蒸气影响碳酸化特性的机理。结果表明,煅烧气氛和碳酸化气氛中的水蒸气均可提高钙基吸收剂的碳酸化转化率,水蒸气含量分别为10%和5%时,吸收剂的碳酸化性能较好;水蒸气在碳酸化气氛中对高铝水泥改性吸收剂的改善作用较石灰石显著。煅烧气氛中的CO₂分压越高,烧结现象越严重,降低钙基吸收剂的捕集效率;碳酸化气氛CO₂分压提高,有利于提高钙基吸收剂的碳酸化转化率。烟气中水蒸气丰富了吸收剂的微观孔隙,使得吸收剂捕集CO₂性能得到改善。     

钙基CO2吸收剂的循环特性

对钙基CO₂吸收剂的循环特性进行了实验研究,考察了煅烧温度和碳酸化（吸收）温度对吸收剂最大转化率的影响,比较了常压煅烧-碳酸化（CC）过程和煅烧-水合-碳酸化（CHC）过程中吸收剂的最大吸收能力,并就添加剂对吸收剂循环性能的影响进行了实验研究.结果表明,随着循环次数的增加,吸收剂的吸收能力明显下降,未经处理的吸收剂,循环10次后,其吸收能力基本都下降到20％左右;温和的煅烧温度和较高的吸收温度下,吸收剂的最大转化率比较高;CC过程中吸收剂的最大转化率明显低于CHC过程;添加了氯化钠和碳酸钠的吸收剂的吸收能力急剧下降,但循环性能稳定;多次循环后对吸收剂进行再活化,可使其活性恢复到初始的95％.     

CO2捕集的研究现状及钙基吸收剂的应用

温室气体CO2是当今世界环境恶化的主要原因之一,近年来针对CO2的捕集技术也相继被研究.磷石膏是湿法冶炼磷酸的副产物,具有产量大、微辐射性等特点,严重危害自然环境和人类健康.本文阐述二氧化碳捕集与封存(CCS)以及燃烧后捕集的三大方法的具体技术原理与特点,着重分析利用钙基吸收剂捕集CO2的技术特点和优势,提出CO2捕集技术的探索方向并指出利用磷石膏分解渣作钙基吸收剂矿化捕集CO2的思路.当前对CO2捕集的研究多停留在吸收剂捕集方面,单纯吸收剂虽吸收效果较好,但其成本较高.磷石膏分解渣作钙基吸收剂不仅有着良好的捕集效果,且解决了成本问题,实现了"以废制废"的思路.     

钙基吸收剂吸收CO_2的动力学分析

利用热天平在非等温条件下研究了在N2/CO2气氛下,升温速率、样品粒径及CO2浓度等因素对钙基吸收剂与CO2反应特性的影响,并利用活化能和频率因子进行表征。结果表明:在5种不同前体制备的吸收剂中,草酸钙和乙酸钙制备的钙基吸收剂的活化能最低,更容易与CO2发生反应;在其他条件相同的情况下,分析纯CaCO3制备的钙基吸收剂的活化能,随循环次数增加而逐渐变大,并且在第5次循环到第10次循环之间,活化能增加幅度较大;随着分析纯CaCO3颗粒粒径的增大,其活化能也随之增大;随着升温速率的增大和反应气氛中CO2质量分数的增大,分析纯CaCO3制备的钙基吸收剂的活化能逐渐减小,而频率因子逐渐增大;掺杂有MgO的碳酸钙制备的钙基吸收剂的活化能小于分析纯CaCO3,且MgO掺杂比例为0.05的钙基吸收剂的活化能小于MgO掺杂比例为0.1的钙基吸收剂。     

SO_2对钙基吸收剂吸收NO的作用机理

针对低温条件下SO2对Ca(OH)2吸收NO的影响进行了实验研究,分析了烟气中O2和H2O对SO2促进Ca(OH)2吸收NO的影响。实验结果表明,当烟气不含SO2时,Ca(OH)2对NO基本无吸收作用;烟气中SO2的存在对NO吸收具有促进作用。H2O和O2对SO2促进NO吸收有显著影响;当烟气不含O2时,即使大量的SO2被吸收,NO吸收效率仍较低;只有SO2与O2和H2O共存才能促进NO吸收。脱硫产物CaSO3对NO无氧化作用;NO、H2O和SO2未在吸收剂表面产生可分解释放NO2的大分子中间配合物。分析认为在脱硫过程中产生了可以促进NO与O2反应的非稳定中间活性组分。     

氧化钙基吸收剂低温循环吸收二氧化碳的研究进展

钙循环法被认为是捕集二氧化碳的有效途径，其通过利用氧化钙基吸收剂和二氧化碳之间的可逆反应来实现吸收剂循环使用。近年来，氧化钙基吸收剂因其成本低、二氧化碳吸收率高、原料来源广等优点备受关注，并广泛应用于制氢、水泥行业中的二氧化碳捕集。但是，该吸收剂存在再生温度高、氧化钙活性组分易烧结、吸收二氧化碳性能迅速下降等问题阻碍了其工业化应用。基于此，综述了近年来高性能氧化钙基吸收剂的制备方法，分析了该类型吸收剂在各领域应用中存在的问题，并提出了实现氧化钙基吸收剂低温循环利用的技术路线，为实现大规模工业碳捕集提供参考。     

钾基CO2吸收剂的碳酸化反应特性

对钾基CO2吸收剂的碳酸化反应机理进行研究.利用热重分析、XRD、扫描电镜和氮吸附仪进行试验.结果表明:分析纯碳酸钾的组分为K2CO3·1.5H2O,碳酸化反应速率缓慢;先将分析纯碳酸钾样品脱除结晶水后再进行碳酸化反应时,K2CO3与气氛中的水蒸气迅速生成K2CO3·1.5H2O,不利于碳酸化反应的进行;由KHCO3分解产生的K2CO3却表现出优越的碳酸化反应性能,20 min内转化率高达85%以上,经过多次循环试验后吸收剂仍保持很高的活性.从微观角度分析了两种改性钾基CO2吸收剂碳酸化反应机理差异的原因,通过拟合计算得到了这3种钾基吸收剂的碳酸化反应速率常数,为干法K2CO3/KHCO3循环脱除CO2的研究提供了一定的基础数据.     

负载型钾基CO2吸收剂的结构表征和碳酸化反应特性

CO2减排已成为21世纪人类面临的焦点问题.而在我国燃煤电厂作为CO2排放量最大、排放最集中的化石燃料燃烧场所,对其进行CO2减排技术的研究和开发势在必行.     

Effect of CaO content on hydration rates of Ca-based sorbents at high temperature

The CaO hydration behavior of four Ca-based sorbents (Deyang, Yangguan, Dawa, and Kuzuu) with different CaO contents was examined. A high-pressure thermogravimetric apparatus was used to measure the hydration rates at high temperatures (773–923 K) and high steam pressures (1.3–2.3 MPa). CaO hydration occurred at high temperatures up to 923 K at high steam pressure. The hydration rates and the final CaO conversion values varied substantially among the different sorbents. Hydration rate and CaO conversion decreased with increasing CaO content. The order of CaO hydration rate with respect to the difference between the reactant steam pressure and the equilibrium steam pressure (P_H2O − P^?_H2O) varied with CaO content. The apparent activation energy for rate constant k also varied with CaO content.     

负载型K2CO3/Al2O3二氧化碳吸收剂的碳酸化反应特性

引言 全球变暖已经成为一个备受关注的环境问题.据预测,如不采取积极的温室气体减排措施,从现在起到2100年,全球近地面平均气温将继续升高1.4～5.8℃[1].CO2是主要的温室气体,而我国燃煤电厂是CO2排放量最大、最集中的化石燃料燃烧场所.因此研究和开发适用于燃煤电厂的CO2减排技术至关重要.     

钙基碳载体造粒的捕集CO特性及力学性能

采用挤出滚圆法对钙基碳载体Ca（OH）₂进行造粒。在双固定床反应器上研究了黏结剂、支撑体和造孔剂对造粒后钙基碳载体循环捕集CO₂性能的影响,并提出采用多孔Al₂O₃球粉作为新型支撑体。结果表明,选择聚乙烯吡咯烷酮为颗粒黏结剂时最佳添加量为2%。高铝水泥和多孔Al₂O₃球粉均可作为支撑体造粒。多孔Al₂O₃球粉作为支撑体造粒后碳载体的循环捕集CO₂性能更高,其10次循环后CO₂吸收量为0.23g/g,是添加高铝水泥造粒碳载体的1.35倍。微晶纤维素作为造孔剂显著提高了造粒碳载体的循环捕集CO₂性能。多孔Al₂O₃球粉作为支撑体造粒后碳载体的抗压强度略高于高铝水泥作为支撑体。多孔Al₂O₃球粉造粒钙基碳载体拥有大量30~100nm孔隙,其比孔容高于高铝水泥造粒碳载体,这有利于CO₂捕集。     

蒸汽活化水泥支撑钙基吸收剂活性及强度特性

拟通过蒸汽活化实现多次循环后机械成型、水泥支撑钙基吸收剂的活性再生，在鼓泡床上研究了活化前后活性，在颗粒碰撞装置上研究活化前后强度及过热处理的影响，并分析了微观结构。结果表明，失活水泥支撑颗粒活化后活性提升幅度大，950℃煅烧下活化后钙转化率由0.113升至0.419，石灰石仅由0.089增至0.278。碰撞实验显示活化后成型颗粒强度下降明显。石灰石活化后出现大量裂缝，可增加活性和削弱强度；而成型颗粒活化后未出现裂缝，但其孔隙提升更佳且表面松散，活性提升显著，强度下降也明显。对活化后颗粒进行过热处理明显改善了强度，由于其可消除晶格内空穴及缺陷。对失活水泥支撑颗粒蒸汽活化并过热处理可同时提升活性并改善强度。     

Efficient MgO-doped CaO sorbent pellets for high temperature CO2 capture

Novel MgO-doped CaO sorbent pellets were prepared by gel-casting and wet impregnation. The effect of Na⁺ and MgO on the structure and CO₂ adsorption performance of CaO sorbent pellets was elucidated. MgO-doped CaO sorbent pellets with the diameter range of 0.5-1.5 mm exhibited an excellent capacity for CO₂ adsorption and adsorption rate due to the homogeneous dispersion of MgO in the sorbent pellets and its effects on the physical structure of sorbents. The results show that MgO can effectively inhibit the sintering of CaO and retain the adsorption capacity of sorbents during multiple adsorption-desorption cycles. The presence of mesopores and macropores resulted in appreciable change of volume from CaO (16.7 cm³∙mol⁻¹) to CaCO₃ (36.9 cm³∙mol⁻¹) over repeated operation cycles. Ca2Mg1 sorbent pellets exhibited favorable CO₂ capture capacity (9.49 mmol∙g⁻¹), average adsorption rate (0.32 mmol∙g⁻¹∙min⁻¹) and conversion rate of CaO (74.83%) after 30 cycles.     

Experimental investigation of a circulating fluidized‐bed reactor to capture CO2 with CaO

Calcium looping processes for capturing CO₂ from large emissions sources are based on the use of CaO particles as sorbent in circulating fluidized‐bed (CFB) reactors. A continuous flow of CaO from an oxyfired calciner is fed into the carbonator and a certain inventory of active CaO is expected to capture the CO₂ in the flue gas. The circulation rate and the inventory of CaO determine the CO₂ capture efficiency. Other parameters such as the average carrying capacity of the CaO circulating particles, the temperature, and the gas velocity must be taken into account. To investigate the effect of these variables on CO₂ capture efficiency, we used a 6.5 m height CFB carbonator connected to a twin CFB calciner. Many stationary operating states were achieved using different operating conditions. The trends of CO₂ capture efficiency measured are compared with those from a simple reactor model. This information may contribute to the future scaling up of the technology. © 2010 American Institute of Chemical Engineers AIChE J, 57: 000–000, 2011     

Enhancement of reactivity in surfactant-modified sorbent for CO2 capture in pressurized carbonation

The calcination/carbonation loop of calcium-based (Ca-based) sorbents is considered as a viable technique for CO₂ capture from combustion gases. Recent attempts to improve the CO₂ uptake of Ca-based sorbents by adding calcium lignosulfonate (CLS) with hydration have succeeded in enhancing its effectiveness. The optimum mass ratio of CLS/CaO is 0.5 wt.%. The reduction in particle size and grain size of CaO appeared to be parts of the reasons for increase in CO₂ capture. The primary cause of increase in reactivity of the modified sorbents was the ability of the CLS to retard the sintering rate and thus to remain surface area and pore volume for reaction. The CO₂ uptake of the modified sorbents was also enhanced by elevating the carbonation pressure. Experimental results indicate that the optimal reaction condition of the modified sorbents is at 0.5 MPa and 700 °C and a high conversion of 0.7 is achieved after 10 cycles, by 30% higher than that of original limestone, at the same condition.     

负载型钾基CO2吸收剂的结构表征和碳酸化反应特性

The structure identification and carbonation characteristics of several potassium-based supported sorbents for CO₂ capture were investigated with TGA,XRD,XRF,SEM and N₂ adsorption method.Potassium-based sorbents were prepared by impregnation with potassium carbonate on supports,such as cocoanut activated charcoal（AC1）,coal active carbon（AC2）,silica gel（SG）and diatomite（DT）using the iso-volume impregnation method.The results showed that the K₂CO₃ loading amounts of AC1,AC2,SG and DT were 24.1%,22.5%,21.7% and 19.1% respectively.The surface area and pore volume of K₂CO₃/AC1 and K₂CO₃/AC2 were larger than others.In contrast,those of K₂CO₃/DT were small.For K₂CO₃/SG,pore volume was large but surface area was small.K₂CO₃/AC1 and K₂CO₃/AC2 showed excellent carbonation capacity.However,the carbonation capacities of K₂CO₃/SG and K₂CO₃/DT were low.The difference in carbonation capacity of those sorbents were attributed to the difference in pore structure,leading to different supported sorbents.