纳米CaCO_3孔径调控及其对碳酸化反应性能的影响

研究了纳米CaCO_3颗粒间孔径调控对CaO与CO_2碳酸化反应性能的影响。通过有机模板法制备得到一系列比表面积相近、孔径分布不同的纳米CaCO_3,并考察其再生和碳酸化反应性能差异。结果表明:增大平均孔径能促进纳米CaCO_3的热分解反应,并降低分解温度约15℃。将平均孔径由15 nm增大至113 nm可显著提高碳酸化反应速率和转化率。研究认为平均孔径和比表面积对碳酸化反应转化率的影响存在交互作用;比表面积小的纳米CaCO_3,表现出碳酸化反应转化率受扩散控制影响较大,而比表面积较大的表现为碳酸化反应转化率以表面反应影响控制为主的规律。     

间歇氯化对电石渣循环捕集CO2性能的影响

提出在碳酸化气氛中间歇加入HCl（间歇氯化）提高电石渣在循环煅烧/碳酸化反应中捕集CO₂性能的新思路。在双固定床反应器上,在不同循环次数加入HCl、碳酸化温度、CO₂/HCl体积比等条件下,研究HCl间歇加入对电石渣循环碳酸化特性的影响。结果表明,在循环煅烧/碳酸化反应中间歇加入HCl使电石渣间歇氯化能提高其循环捕集CO₂性能。在前N次循环碳酸化时加入0.1% HCl,当N=4时能使电石渣获得最优CO₂捕集性能,第10个循环时的CO₂吸收量比无HCl时提高了51%。HCl与CaCO₃发生氯化反应,破坏致密产物层对CO₂扩散的阻碍,提高了电石渣的碳酸化转化率。在碳酸化气氛加入HCl时,最佳碳酸化温度仍为700℃。随CO₂/HCl体积比增大,HCl对电石渣捕集CO₂性能的促进作用减弱。     

Cl含量对钙基吸收剂微观结构以及动力学性能的影响

通过浸渍法向分析纯CaCO₃中添加Cl,在双固定床反应器系统和热重分析仪上研究了其对钙基吸收剂循环捕集CO₂性能的影响,利用离子反应模型对添加Cl后吸收剂化学反应控制阶段进行动力学分析。结果显示：Cl对钙基吸收剂循环捕集CO₂性能具有不利影响。当Cl/Ca摩尔比大于0.25%后,随Cl/Ca摩尔比增加,化学反应控制阶段反应速率和持续时间均减小,导致在该阶段最终碳酸化转化率降低。对添加Cl前后吸收剂孔隙分布特性进行分析发现,添加Cl导致煅烧后吸收剂烧结加剧,比表面积降低,10~120nm范围内孔分布减少,导致CO₂在吸收剂内部扩散阻力增加,同时能与CO₂反应的CaO量减少,这是导致吸收剂化学反应控制阶段碳酸化反应速度较慢、最终碳酸化转化率较低的主要原因。鉴于Cl的不利影响,在选择钙基材料作为CO₂吸收剂或合成高活性复合吸收剂时,应避免吸收剂中Cl含量过高。     

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。     

钙硅酸盐矿物湿法碳酸化封存二氧化碳实验研究

钙硅酸盐矿物湿法碳酸化封存CO₂是具有发展前景的固碳技术。为了比较不同种类的含钙硅酸盐矿物固碳效果的差异，研究了温度、压力、液固比(mL/g)、粒度及矿物添加剂(NaHCO₃和NaCl)对硅灰石和钙长石湿法碳酸化封存CO₂效果的影响。结果表明，硅灰石和钙长石的碳酸化产物分别是方解石和文石，热重实验结果显示，方解石的热稳定性强于文石。各实验条件下硅灰石碳酸化转化率均高于钙长石，两种矿物碳酸化转化率随压力增大、粒度减小、NaHCO₃和NaCl的加入而增大；获得了硅灰石和钙长石的最大碳酸化转化率分别为83.62%、16.20%，二者差异显著。在温度为120～210℃两种矿物溶解吉布斯自由能(ΔG_r)的计算表明，硅灰石溶解过程的吉布斯自由能始终小于钙长石溶解吉布斯自由能，说明硅灰石溶解速率和溶解反应自发进行的程度都大于钙长石，这是影响钙硅酸盐矿物碳酸化反应活性的关键因素。     

碳材料吸附脱除二氧化硫性能的影响因素

选用了7种不同物理化学特性的碳材料,分别为活性炭-1 (比表面积1779m²/g)、活性炭-2 (比表面积970m²/g)、多孔纳米炭-1 (平均孔径14nm)、多孔纳米炭-2 (平均孔径85nm)、多孔纳米炭-3 (平均孔径4.7nm,掺氮)、多孔纳米炭-4 (平均孔径4.1nm,不掺氮)和纳米碳纤维。在对比这7种不同的碳材料的物理化学特性与其脱硫性能的基础上,研究材料的物理化学特性、脱硫温度、反应空速等因素对碳材料吸附脱除SO₂性能的影响。结果表明,碳材料吸附脱除SO₂的性能受材料的比表面积、孔隙结构、表面官能团、脱硫温度和反应空速的综合影响。不同的碳材料中,材料的孔隙结构和表面官能团对材料的脱硫性能影响很大,以微孔结构为主的碳材料SO₂去除率较高,以介孔结构为主的碳材料脱硫容量较高;随着脱硫温度升高,碳材料的吸附脱硫性能降低;随着反应空速降低,碳材料的吸附脱硫性能升高。本研究中,多孔纳米炭NCP-10的吸附脱除SO₂性能最好,能在室温下保持100%的...     

基于响应曲面法的纳米颗粒增强水泥浆体制备研究

基于响应曲面法,考虑纳米颗粒掺量、减水剂掺量、水胶比三个关键影响因素,以水泥硬化浆体抗压强度为响应,利用中心复合设计法设计试验,建立纳米SiO₂、纳米CaCO₃、纳米Al₂O₃增强水泥浆体的强度模型,并以纳米CaCO₃增强水泥浆体强度模型为例,分析各因素对强度的影响规律,对强度模型进行验证。结果表明,当纳米颗粒与水泥质量比为0.027 0、减水剂与水泥质量比为0.017 5、水胶比为0.25时,三种纳米颗粒增强水泥浆体具有较高强度。纳米SiO₂、CaCO₃、Al₂O₃增强水泥浆体的强度模型具有较高的精度和可靠性。纳米CaCO₃增强水泥浆体的抗压强度响应值随着纳米颗粒掺量、减水剂掺量的增大先增大后减小,随着水胶比的增大逐渐减小。     

电石渣直接湿法碳酸化固定CO2的反应特性

碱性固废湿法碳酸化是一种矿化固定CO₂的有效方式。为探究电石渣废弃物直接湿法碳酸化固定CO₂的反应特性，基于高压反应釜试验装置，在常温环境下研究液固比(5～20)、碳酸化时间(0～4 h)和反应压力(0.1～1.0 MPa)对电石渣碳酸化速率和CO₂固定能力的影响。结果表明，电石渣具备良好的CO₂固定能力，1 h内整体碳酸化反应基本完成，CO₂固定能力会随液固比和反应压力的增加而提升。反应时间4 h,最优工况(1 MPa、液固比20)下电石渣的CO₂固定量达9.26 mmol/g,而在0.1 MPa、液固比5时，电石渣的CO₂固定量仅3.58 mmol/g。电子扫描显微镜和热重分析证明了电石渣碳酸化反应后生成了大量CaCO₃,且碳酸化产物的粒径显著减小。因此，在反应釜中常温加压条件下，电石渣直接液相碳酸化即具备较好的CO₂固定能力和较高的碳酸化效率。本研究结果能为电石渣加速矿化固定CO     

辛醇与氨胺化反应催化剂Co/SiO2的制备与性能

采用溶胶-凝胶法制备SiO₂负载的钴催化剂Co/SiO₂-t,并对催化剂进行SEM、XRD、XPS、H₂-TPR、BET等表征，以1-辛醇与氨的胺化为模型反应，研究焙烧温度对催化剂结构、性能的影响。结果表明，随着焙烧温度的升高，催化剂Co/SiO₂-t的比表面积呈现先增加后降低的趋势，平均孔径逐渐增大，Co结晶度逐渐升高，粒径尺寸逐渐增大，Co分散度与还原度逐渐降低。焙烧温度为550℃的催化剂比表面积最大、催化性能最佳。催化剂Co/SiO₂-550的Co平均粒径为13.22 nm,比表面积为288 m²/g,平均孔径为7.83 nm,还原度为83.75%,分散度为7.42%。催化剂Co/SiO₂-550的转化率为93.12%,对1-辛胺的选择性为71.34%。     

B2O3改性Na2CO3催化剂用于甲醇脱氢制无水甲醛

以B₂O₃为助催化剂,采用研磨混合法改性Na₂CO₃催化剂,在固定床反应器中催化甲醇脱氢制备无水甲醛,考察催化剂的组成和反应条件等对催化反应的影响,采用XRD、TG-DTG、N₂吸附-脱附、SEM和CO₂-TPD等对催化剂进行表征。结果表明,以B₂O₃为助催化剂采用机械研磨混合法改性的Na₂CO₃催化剂,增加了催化剂的比表面积,在(10～30) nm增加了大量的孔道,平均孔径达18.44 nm,比表面积为1.65 m²·g^-1,且B₂O₃分布均匀,改性后的催化剂碱性降低,在催化甲醇脱氢制备无水甲醛的反应中,催化活性明显高于Na₂CO₃催化剂,表明B₂O₃改性Na₂CO₃催化剂能提高甲醇转化率和甲醛选择性。在B₂O₃/Na₂CO₃催化剂中B₂O₃质量分数为30%、甲醇进料质量分数为26%、反应温度为650 ℃和甲醇重时空速为2.94 h^-1条件下,甲醇转化率达59.97%,甲醛选择性达83.28%。     

Preparation and Application of the Sol-Gel Combustion Synthesis-Made CaO/CaZrO3 Sorbent for Cyclic CO2 Capture Through the Severe Calcination Condition

abstract Calcium looping method has been considered as one of the efficient options to capture CO2 in the combustion flue gas. CaO-based sorbent is the basis for application of calcium looping and shou...     

Enhancement of CO2 capture and microstructure evolution of the spent calcium-based sorbent by the self-reactivation process

The effect of self-reactivation on the CO_2 capture capacity of the spent calcium based sorbent was investigated in a dual-fixed bed reactor.The sampled sorbents from the dual-fixed bed reactor were sent for XRD,SEM and N_2 adsorption analysis to explain the self-reactivation mechanism.The results show that the CaO in the spent sorbent discharged from the calciner absorbs the vapor in the air to form Ca(OH)_2 and further Ca(OH)_2·2 H_2 O under environmental conditions,during which process the CO_2 capture capacity of the spent sorbent can be self-reactivated.The microstructure of the spent sorbent is improved by the self-reactivation process,resulting in more porous microstructure,higher BET surface area and pore volume.Compared with the calcined spent sorbent that has experienced 20 cycles,the pore volume and BET surface area are increased by 6.69 times and 56.3% after self-reactivation when φ=170%.The improved microstructure makes it easier for the CO_2 diffusion and carbonation reaction in the sorbent.Therefore,the CO_2 capture capacity of the spent sorbent is enhanced by self-reactivation process.A self-reactivation process coupled with calcium looping process was proposed to reuse the discharged spent calcium based sorbent from the calciner.Higher average carbonation conversion and CO_2 capture efficiency can be achieved when self-reactivated spent sorbent is used as supplementary sorbent in the calciner rather than fresh CaCO_3 under the same conditions.     

Relationship between pore structure and hydration activity of CaO from carbide slag

CaO needs to show high activity to be used as Ca-sorbent and slagging agent. Hydration activity is an important characteristic to evaluate the activity of CaO. In this study, carbide slag from polyvinyl chloride (PVC) industry was utilized as precursor for preparing high activity CaO. The roles of crystallite grain, average pore diameter (APD) and volume fraction of pore < 200 nm in diameter (VF200) in hydration activity of CaO from carbide slag (CS-CaO) were respectively investigated. The hydrolysis kinetics model of CaO shows a three-dimensional spherically symmetric diffusion model (D4), which suggests that hydration activity was mainly associated with APD and VF200 of CS-CaO with limited correlation to the crystal size. Specifically, the hydration activity of CS-CaO is increased with increasing VF200, while decreased with increasing APD. Under the invariable calcination temperature, the core-shell structure formed by the addition of graphite or CaCO₃ to CS effectively inhibits the sintering of CS-CaO and improves VF200. Consequently, the hydration activity of CS-CaO increased from 22.79℃·min^-1 to 27.19℃·min^-1 and to 29.27℃·min^-1, with addition of 5% graphite or 5% CaCO₃ into carbide slag, respectively.     

高温下改性钙基吸附剂固定床反应器从烟气中捕捉二氧化碳(英文)

Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors: calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption capacity of those sorbents was investigated in a fixed-bed reactor in the temperature range of 350-650℃. It was found that all of those sorbents showed higher capacity for CO2 absorption when the operating temperature higher than 450℃. The CaAc2-CaO sorbent showed the highest CO2 absorption capacity of 299mg·g-1. The morphology of those sorbents was examined by scanning electron microscope (SEM), and the changes of composition before and after carbonation were also determined by X-ray diffraction (XRD). Results indicated that those sorbents have the similar chemical compositions and crystalline phases before carbonation reaction [mainly Ca(OH)2], and CaCO3 is the main component after carbonation reaction. The SEM morphology shows clearly that the sorbent pores were filled with reaction products after carbonation reaction, and became much denser than before. The N2 adsorption-desorption isotherms indicated that the CaAc2-CaO and CaCO3-CaO sorbents have higher specific surface area, larger pore volume and appropriate pore size distribution than that of CaO-CaO and Ca(OH)2-CaO.     

CHARACTERISTICS OF THE REVERSIBLE REACTION BETWEEN CO2(g) AND CALCINED DOLOMITE

The noncatalytic gas-solid reaction between calcined dolomite and CO₂(g) has been studied in an electrobalance reactor as a function of temperature, pressure, and reactive gas composition. Multicycle tests consisting of as many as ten complete calcination-carbonation cycles were carried out to obtain information on sorbent durability. Surface area, pore volume, and pore size distribution measurements were made to supplement the reaction studies. This reaction is of interest both as a model for studying (he importance of structural property changes in gas-solid reactions, and as the basis for a possible process for the high temperature separation of CO₂ from gas streams.

Calcined dolomite is a superior sorbent to calcined CaCO₃ in that larger fractional conversions of CaO and improved multicycle durability are possible. With CaO obtained from CaCO₃, the first-cycle fractional recarbonation was limited to about 0.80, a value which decreased by 15 to 20% in each subsequent cycle. In contrast, the first-cycle fractional recarbonation of CaO in calcined dolomite was typically 0.90 to 0.95, and this value decreased by only 1 to 2% in each subsequent cycle. These advantages are atlributed to the “excess” pore volume created by the original decomposition of MgCO₃ in dolomite, and by a reduction in the rate of CaCO₃ sintering in the presence of MgO.     

H2O和SO2对CFB内石灰石同时煅烧/硫化反应中煅烧动力学的协同作用

采用自制恒温热重分析仪,研究了CFB工况下石灰石同时煅烧/硫化反应中H₂O和SO₂对石灰石煅烧动力学和孔结构的协同作用。煅烧环境中的H₂O能够促进石灰石的分解,但SO₂会减慢石灰石分解速度,且测试发现SO₂使煅烧后颗粒的孔容积下降,分解反应的效率因子减小。基于此提出SO₂减缓煅烧反应的机理：高温下,石灰石颗粒外层首先分解并生成多孔CaO层,其中的孔隙作为内部CaCO₃分解产生CO₂的外扩散通道,当煅烧气氛中含有SO₂时,颗粒的CaO层与SO₂反应生成CaSO₄,堵塞了CaO中的孔隙,增加了CO₂扩散的阻力,从而减缓了其分解速度。当石灰石在含有15% H₂O和0.3% SO₂的环境中分解时,其分解速度比不含二者的环境下快,而比含15% H₂O但不含SO₂的环境下慢,说明H₂O和SO₂对改变石灰石分解的速度有协同效应,但15% H₂O的作用比0.3% SO₂的作用更大。对效率因子的计算表明,该现象可能由于石灰石煅烧反应的速度控制步骤中本征反应速度的影响比扩散阻力的作用更大,而H₂O能够直接加速煅烧反应的本征速度。温度、粒径等均能够影响石灰石同时煅烧/硫化反应的中的煅烧速度。H₂O还能够促进CaO的烧结,并且H₂O和SO₂在降低石灰石煅烧产物的孔面积和孔容积上具有叠加效应。     

温度对精炼渣碳酸化效果影响分析

为了有效改善精炼渣的安定性及致密性问题,采用正交试验探讨精炼渣碳酸化过程,以温度为单一影响因素,考察碳酸化粒度分布,结合XRD,SEM,FT-IR,TG-DTA等手段对精炼渣碳酸化效果进行探讨。结果表明,精炼渣碳酸化各因素主次关系为:粒径>CO₂通气量>反应温度>转速>液固比;碳酸化后精炼渣中f-CaO、Ca₂SiO₄、Ca₃SiO₅、12CaO·7Al₂O₃消失,CaCO₃晶型增加明显,且以方解石为主;不同温度(20 ℃、40 ℃、60 ℃、80 ℃)碳酸化后精炼渣总的热分解失重百分率分别为:35.26%、35.24%、34.36%和27.29%。     

循环捕集CO2后煅烧石灰石的硫化特性

ZEC(zero emission coal)系统中,粗煤气进入碳酸化/重整炉前需先脱除H₂S,提出利用经过多次碳酸化/煅烧捕集CO₂循环的煅烧石灰石(CaO)脱除H₂S,并研究循环碳酸化/煅烧次数、硫化温度、H₂S浓度和微观结构对循环CaO硫化特性的影响。结果表明,多次循环碳酸化/煅烧捕集CO₂后CaO仍具有较高H₂S吸收性能。前20次循环,CaO硫化转化率随循环次数增加迅速降低;20次循环后,CaO硫化转化率缓慢下降。硫化120 min后,未循环CaO的硫化转化率接近100%,而经历1、20和100次循环后CaO的硫化转化率分别为94%、81%和74%。H₂S浓度对循环CaO硫化性能影响较大。硫化温度(800～1000℃)对循环CaO的硫化性能影响较小,最佳硫化温度为900℃。随循环次数增加,CaO颗粒发生高温烧结,导致比表面积降低和20～150 nm内孔隙减少,而这是与H₂S吸收密切相关的孔隙,导致CaO硫化转化率降低。     

乙醇-水体系3D纳/微米球形磷酸铁的制备与表征

提出了一种在温和条件下制备高振实密度球形磷酸铁的简单方法。制备过程中无需引入碱性物质调节pH和添加其他模板剂,仅以九水合硝酸铁[Fe（NO₃）·9H₂O]和磷酸（H₃PO₄）为原料,在乙醇-水体系中即可制备3D纳/微米球形磷酸铁（记为FPE）。采用扫描电镜（SEM）、激光粒度仪、X射线衍射仪（XRD）、热重-差式扫描量热仪（TG-DSC）、比表面积测试仪（BET）等对制备的磷酸铁进行表征分析。结果显示,制备的磷酸铁具有3D纳/微米球形结构,平均一次粒径为27.2 nm,二次粒径D₅₀为3.75 μm。FPE的组成为二水合磷酸铁（FePO₄·2H₂O）,纯度较高,具有介孔结构,平均孔径为2.75 nm,比表面积为22.41 cm ²/g,同时具有较高的振实密度（1.34 g/cm ³）。3D纳/微米球形磷酸铁制备方法简单,性能优异,以其为前驱体制备的磷酸铁锂（LiFePO₄/C）具有较高的振实密度（1.46 g/cm ³）,在0.2C倍率下的放电比容量为157.9 mA·h/g。