不同钙基吸附剂捕集CO2后的硫酸化反应特性研究

钙基吸附剂进行多次CO₂捕集后,碳酸化效率会大幅衰减,此时的吸附剂能否高效脱硫利用是值得重点关注的问题。鉴于此,筛选了高性能合成钙基吸附剂和天然石灰石吸附剂,通过热重分析仪分析对比其在多循环CO₂捕集后的碳酸化和硫酸化反应性能,采用微粒模型研究其硫酸化反应动力学特征。结果发现,高性能合成钙基吸附剂的碳酸化反应速率和CO₂吸附能力明显高于石灰石吸附剂。在长达500循环的CO₂捕集试验后,高性能合成钙基吸附剂的CO₂吸附能力比石灰石高10倍以上,其SO₂吸附能力相较于石灰石提升约40%。经历多次CO₂捕集反应循环后,2种吸附剂的硫酸化能力均有提升:其中,石灰石吸附剂的提升幅度更大,硫酸化转化率从26%提升到35%,而高性能合成钙基吸附剂的硫酸化转化率则从38%提升到43%。通过微粒模型计算发现,2种吸附剂的硫酸化反应均是与SO₂浓度相关的一级反应,多循环捕集CO₂反应后,石灰石吸附剂的硫酸化反应活化能下降接近30%,而高性能合成钙基吸附剂的硫酸化反应活化能只下降了5%。研究结果说明2种不同钙基吸附剂在进行循环CO₂捕集后,脱硫能力得到了不同程度的提高,且均可以较好地应用于SO₂的脱除。     

Sulfation rates of cycled CaO particles in the carbonator of a Ca‐looping cycle for postcombustion CO2 capture

Calcium looping is an energy‐efficient CO₂ capture technology that uses CaO as a regenerable sorbent. One of the advantages of Ca‐looping compared with other postcombustion technologies is the possibility of operating with flue gases that have a high SO₂ content. However, experimental information on sulfation reaction rates of cycled particles in the conditions typical of a carbonator reactor is scarce. This work aims to define a semiempirical sulfation reaction model at particle level suitable for such reaction conditions. The pore blocking mechanism typically observed during the sulfation reaction of fresh calcined limestones is not observed in the case of highly cycled sorbents (N > 20) and the low values of sulfation conversion characteristic of the sorbent in the Ca‐looping system. The random pore model is able to predict reasonably well, the CaO conversion to CaSO₄ taking into account the evolution of the pore structure during the calcination/carbonation cycles. The intrinsic reaction parameters derived for chemical and diffusion controlled regimes are in agreement with those found in the literature for sulfation in other systems. © 2011 American Institute of Chemical EngineersAIChE J, 2012     

A kinetic model of nano‐CaO reactions with CO2 in a sorption complex catalyst

This article describes the reactive kinetics of nano‐CaO with CO₂ in a sorption complex catalyst. Based on an observation of nano‐CaO reaction with CO₂ has a fast surface reaction regime and followed by a slow diffusion‐controlled regime, a criterion has been proposed to divide the fast surface reaction regime and the slow diffusion‐controlled reaction regime. The kinetics of the fast surface reaction was studied, and a new ion reaction mechanism was proposed. A surface reaction‐controlled kinetic model with a Boltzmann equation, X = X_u?X_u/[1+exp((t?t₀)k/X_u)], was developed. Experiments using nano‐CaO to react with CO₂ in a fast surface reaction regime within a sorption complex catalyst were performed using thermogravimetric analysis at 773–873 K under a N₂ atmosphere with 0.010–0.020 MPa CO₂. The activation energy of the kinetic model for carbonation is 30.2 kJ/mol, and the average relative deviation of the sorption ratio is less than 9.8%. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

改性钙基材料吸附CO2性能研究

温室气体CO2的大量排放是全球气候变暖的主要影响因素,对于CO2的捕集再利用研究已引起了学界和工业界的广泛关注.石灰石循环煅烧/碳酸化法捕集工业CO2气体已经被大量报道,但石灰石在循环捕集过程当中其表面容易被烧结而降低了其捕集性能,基于此,我们提出了利用耐高温氧化物(如MgO、Fe2O3、SiO2)微粒对石灰石颗粒表面进行修饰改性以便提高石灰石颗粒的抗烧结能力及其CO2捕集特性并利用TGA和SEM对改性实验进行了捕集性能测试和颗粒形貌表征.试验结果表明,金属氧化物微粒对石灰石改性有效果,其中添加1 wt％ MgO微粒时可以使石灰石捕集CO2的性能提高7％～8％,且吸收剂颗粒孔隙结构得以改善.     

利用凹凸棒改性石灰石增强CO2循环捕集效率

石灰石作为天然的CO2吸收剂,可有效的捕集烟气中的CO2,但随着循环反应次数的增加,石灰石颗粒表面会发生严重的烧结,使其酸化率迅速发生衰减.本文中利用自然界储量丰富的凹凸棒石对石灰石颗粒进行改性来减缓这一现象的发生,从而提高其CO2的循环捕集效率.凹凸棒石具有的天然纳米纤维状结构可有效的减少石灰石颗粒之间的相互接触,延缓石灰石的烧结团聚现象,从而提高其碳酸化率.实验结果表明:凹凸棒石原矿和提纯后的凹凸棒石均可作为添加剂提高石灰石对CO2的捕集效率,其中经过提纯处理后的凹凸棒石的改性效果最好;通过比较凹凸棒石改性前后的钙基吸收剂经过多次CO2捕集循环后的颗粒微观形貌的变化,可以发现经过凹凸棒石改性后的石灰石颗粒表面仍留有较多的孔道,使其抗烧结能力得到大幅的提高.     

Thermal transport model of a sorbent particle undergoing calcination–carbonation cycling

A numerical model coupling transient radiative, convective, and conductive heat transfer, mass transfer, and chemical kinetics of heterogeneous solid–gas reactions has been developed for a semitransparent, nonuniform, and nonisothermal particle undergoing cyclic thermochemical transformations. The calcination–carbonation reaction pair for calcium oxide looping is selected as the model cycle because of its suitability for solar‐driven carbon dioxide capture. The analyzed system is a single, porous particle undergoing thermochemical cycling in an idealized, reactor‐like environment. The model is used to investigate two cases distinguished by the length of the calcination and carbonation periods. The calcination–carbonation process for a single particle is shown to become periodic after three cycles. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2647–2656, 2015     

用于燃烧后CO2捕集系统的胺基固态吸附材料研究进展

随着工业化的发展和大量化石燃料的消耗,大量的CO₂气体排放到大气中并引发了一系列严重的环境问题,而采用燃烧后CO₂捕集技术可以有效地应对这一问题。寻找一种高效吸附、稳定、价格低廉的固态吸附材料对于开展燃烧后CO₂捕集系统的研究具有重要的实际意义。近年来,胺基固态吸附材料因其高CO₂吸附能力和高吸附选择性成为研究的热点。本文综述了近年来国内外学者对不同胺基固态吸附材料在合成方法、载体材料选择以及性能测试等方面进行的研究,重点讨论了以沸石分子筛、介孔硅分子筛、多孔碳和金属有机骨架为载体的胺基固态吸附材料对CO₂的吸附行为,并指出多孔载体材料的结构改进及有机胺和促进剂的合理选择将会成为未来胺基固态吸附材料的重点研究方向。     

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     

溶液燃烧合成法制备自活化钙铜复合CO2吸收剂的性能

首次采用溶液燃烧合成法制备了钙铜复合吸收剂用于实现低成本CO₂捕捉。在热重分析仪上研究制备参数（燃烧背景温度、煅烧时间）对吸收剂循环载氧和CO₂捕捉性能的影响,并借助SEM和氮吸附分析其微观结构。结果表明,在燃烧背景温度800℃、煅烧时间为0.5h时制得的钙铜比例为1∶1的复合CO₂吸收剂15次循环之后,钙基吸收剂转化率为51.2%,比纯的CaO提高了44.9%;采用该方法制备的吸收剂具备自活化特性,15次循环内碳酸化性能随循环次数的增加不降反升,且载氧性能非常稳定,氧化率始终高于90%。微观结构表征表明,随着循环次数的增加,复合吸收剂未发生严重烧结并且BET比表面积没有下降。实验结果为溶液燃烧合成法制备高性能钙铜复合CO₂吸收剂的进一步研究提供了基础数据。     

弱酸性介质中钙离子与CO2反应制备碳酸钙

研究了弱酸性介质中钙离子与CO2反应生成沉淀碳酸钙的工艺过程,探讨了乙酸钙浓度、反应温度、CO2压力、反应时间及陈化时间等因素对制备碳酸钙的影响。结果表明,在乙酸钙质量分数17%,CO2分压2.5 MPa,反应温度95℃时,反应30 min,陈化5 h的条件下,碳酸钙的收率为20.6%,制备出分散性良好的平均粒径为1.4μm的沉淀碳酸钙。     

铬酸钠碳化反应动力学研究

研究了铬酸钠碳化反应动力学,在1个2 L反应釜内,通过监测反应过程中CO2压力的变化,计算反应速率,避免了因逆反应过快造成的溶液取样分析的困难。实验发现反应速率有一个下降-升高-下降的变化过程。通过反应机理分析,导出了动力学方程,并根据动力学方程较好地解释了实验现象。     

碳酸锂碳化三相反应动力学研究

利用5 L的气液固三相机械搅拌反应器,研究了Li2CO3碳化三相反应动力学。对影响碳化过程的诸因素进行了深入的研究和探讨。结果表明,Li2CO3的碳化率随CO2压力、气流大小、搅拌速度的增大而增大;随反应温度、固体浓度、颗粒粒径、物料填充度的增大而减小。通过对实验数据的拟合得出实验范围内该过程的动力学方程;得出该过程受控于化学反应,并计算出了该过程的表观活化能-17.37 kJ/mol。该研究为Li2CO3碳化工艺条件的优化和反应器的设计等问题提供了基本理论依据。     

The maximum capture efficiency of CO2 using a carbonation/calcination cycle of CaO/CaCO3

The use of natural calcium carbonates as regenerable CO₂ sorbents in industrial processes is limited by the rapid decay of the carbonation conversion with the number of cycles carbonation/calcination. However, new processes are emerging to capture CO₂ using these cycles, that can take advantage of the intrinsic benefits of high temperature separations in energy systems. This work presents an analysis of a general carbonation/calcination cycle to capture CO₂, incorporating a fresh feed of sorbent to compensate for the decay in activity during sorbent re-cycling. A general design equation for the maximum CO₂ capture efficiency is obtained by incorporating to the cycle mass balances a simple but realistic equation to estimate the decay in sorbent activity with the number of cycles.     

负载型K2CO3/Al2O3吸收剂吸收CO2反应机理

利用热重分析仪、扫描电镜和氮吸附仪对不同粒径的K₂CO₃颗粒和负载型K₂CO₃/Al₂O₃二氧化碳吸收剂的碳酸化特性进行研究。负载后的吸收剂比表面积和孔隙结构得到较大改善,使得碳酸化反应速率和转化率均提高,吸收剂碳酸化特性得到改善。纯K₂CO₃颗粒吸收剂的反应速率和转化率随着粒径的增加而减小,负载型吸收剂的反应速率和转化率随着粒径的增加略增大。研究了不同粒径和反应时间对K₂CO₃/Al₂O₃颗粒微观结构的影响,结果表明K₂CO₃/Al₂O₃颗粒具有较稳定的微观结构。采用负载型粒子模型对K₂CO₃/Al₂O₃吸收剂吸收CO₂碳酸化过程进行研究,所建立的粒子模型计算结果与试验值吻合较好。利用建立的模型对不同CO₂浓度下K₂CO₃/Al₂O₃吸收剂碳酸化反应特性进行模拟计算,模拟结果具备一定的合理性和准确性,为开展进一步研究提供了基础。     

碳酸锂常压鼓泡碳化宏观反应动力学研究

基于Li2CO3与CO2在水溶液中的反应,在浆态鼓泡床反应器内对粗Li2CO3常压鼓泡碳化反应的动力学进行了实验研究,且对影响碳化过程的诸因素进行了深入的研究和探讨.结果表明,Li2CO3的转化率随表观气速的增大而增大,随反应温度、固体质量浓度、颗粒粒径、反应器中浆料填充度的增大而减小.动力学研究表明:在反应的前期过程受控于化学反应,随反应的进行该过程逐渐转变为内扩散控制.通过对实验数据的拟合得出了实验范围内过程的宏观动力学方程.该研究为Li2CO3碳化工艺条件的优化和反应器的放大设计等提供了基础效据.     

镁负载CaO基吸附剂捕集CO2性能及抗烧结机理

复合钙基吸附剂制备成本过高是限制其工业化应用的主要瓶颈问题。本文以不可溶的CaCO₃和Ca(OH)₂作为钙源,通过燃烧合成法制备钙镁复合吸附剂,在双固定床反应器上研究了其循环捕集CO₂性能。结果显示：制备得到的钙镁复合吸附剂具有更发达的孔隙结构,吸附剂表面Ca和Mg分散均匀,MgO均匀分布于CaO晶粒之间,有效提高了钙镁复合吸附剂的抗烧结特性,因此钙镁复合吸附剂循环反应过程中具有高捕集CO₂活性。以Ca(OH)₂作为钙源时,燃烧合成过程中Ca和Mg均匀同时析出,分散更加均匀,有效避免了CaCO₃作为钙源时Mg的团聚问题,因此得到的钙镁复合吸附剂循环捕集CO₂性能最优。最佳的Ca/Mg摩尔比为(8∶2)~(7.5∶2.5)。本研究以不可溶钙源制备得到高活性钙镁复合吸附剂,有效控制了吸附剂成本,具有更好的工程应用前景。     

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...