三维菱形结构微通道内气液传质与强化

研究了具有三维交错菱形结构的微通道对离子液体1-丁基-3-甲基咪唑四氟硼酸盐([Bmim][BF₄])水溶液吸收CO₂过程的传质增强作用。实验主要聚焦于弹状流和破碎弹状流。考察了弹状流型下气液流量、离子液体浓度对体积传质系数k_La、增强因子E、CO₂吸收率X及压力降ΔP的影响。结果表明,较之于直通道,三维菱形通道可以显著提高体积传质系数和CO₂吸收率,其增强因子可达2.1,压力降仅增加 0.9 kPa。提出了一个新的体积传质系数k_La预测式,预测效果良好。采用VOF法模拟了微通道内气液两相流动过程,获得了连续相的速度矢量场。三维菱形通道能诱导涡流,强化传质过程。     

微孔射流毛细管反应器内液-液两相传质和反应选择性

微反应技术在化工过程强化领域已得到广泛应用,尤其适用于快速复杂竞争反应体系。对于液-液两相快速竞争反应,反应过程受传质限制,显著影响反应转化率和收率。本文开发了一种新型的微孔射流毛细管反应器（MJCM）,采用微孔射流强化进口处液-液两相传质性能,分别采用水-苯甲酸-煤油体系和水-氢氧化钠-甲苯-苯甲酸-氯乙酸乙酯体系研究了不同操作参数（流量、流量比、表面活性剂浓度、温度）和结构参数（孔径、管长）下液-液两相传质特性和反应选择性,并获得了舍伍德数Sh的关联式。结果表明：随着两相流量的增加,传质效率E呈下降趋势,总体积传质系数k_La呈增加趋势,反应选择性指数X_s则先减小后增大;孔径的增大则会减弱液液传质和反应选择性;随着毛细管长的增加,E和X_s逐渐增大,k_La则逐渐减小;水相-有机相流量比的变化对E和k_La会产生不同影响,而温度的适当升高则可以提升反应选择性,表面活性剂的加入降低了传质和反应选择性。与其他液液传质设备对比,MJCM在液-液两相传质、反应选择性方面性能良好,可以用于工业生产进行液液传质与反应过程的强化。     

排气管直径与深度对水力喷射空气旋流器传质性能的影响

对水力喷射空气旋流器(WSA)的中心排气管直径D_e和排气管插入深度S进行了设计优化研究,实验考察了不同D_e和S对WSA脱氨传质系数K_La和气相压降的影响,提出了综合评价传质过程效率的概念——单位压降传质效率η_p,讨论了D_e和S的设计取值。研究表明,当D_e增大时,K_La和气相压降均随之降低,较小D_e的WSA具有较高的气液传质性能,但气相压降比较大,而K_La和气相压降均随S增大而增大。综合能效关系表明,随着D_e的增大η_p增大,随着S的增大η_p出现先增大后降低的趋势,WSA设计中D_e与WSA直径D之比D_e/D宜为0.42～0.53,S与WSA筒体长度H之比S/H适宜取值约为0.70。     

[Bmim][BF4]/MEA混合水溶液吸收CO2的吸收性能与液液分相机理

对液液两相CO₂吸收剂1-丁基-3-甲基咪唑四氟硼酸盐（[Bmim][BF₄]）/乙醇胺（MEA）混合水溶液吸收性能进行了实验测定,研究了离子液体[Bmim][BF₄]的引入对吸收性能和液液分相的影响,并通过定量碳谱核磁共振法对分相机理和各相中的物质分布进行分析。研究结果表明,一定配比的[Bmim][BF₄]/MEA混合水溶液吸收CO₂之后会出现互不相溶的液液两相,这种现象伴随着CO₂产物的富集;导致液液分相的原因是氨基甲酸盐浓度的增大;随着[Bmim][BF₄]质量分数的增大,溶液吸收速率呈现出先增大后减小的趋势;分层后H₂O主要分布在富液相,[Bmim][BF₄]主要分布在贫液相,H₂O的质量分数直接影响分层后富液相的传质性能。     

离子液体支撑液膜的CO2/CH4分离性能

由于离子液体对CO₂具有较好的溶解选择性,离子液体支撑液膜分离CO₂越来越受到关注。比较了含3种不同阴离子的常规离子液体([bmim][BF₄]、[bmim][PF₆]、[bmim][Tf₂N])作为支撑液膜的液膜相分离CO₂/CH₄的性能,考察了咪唑环上烷基链长对离子液体支撑液膜性能的影响。考虑向离子液体中引入胺基和羧基等亲CO₂基团,制备了1-丁基-3-甲基咪唑丙氨酸离子液体([bmim][β-Ala]),考察了 [bmim][β-Ala]支撑液膜分离CO₂/CH₄的性能,并对在CO₂渗透测试前后的支撑液膜进行了FT-IR分析,发现氨基酸离子液体中的-NH₂和CO₂的较强作用以及该离子液体的高黏性影响了CO₂的透过性,使[Bmim][β-Ala]支撑液膜的CO₂透过率低。     

超强碱离子液体-有机胺-水复配溶剂高效CO2捕集

CO₂捕集是实现碳减排的重要技术之一。其中，化学吸收法是一种有效的、适用于低CO₂分压的CO₂捕集技术。开发出一种高效、低能耗、环保的吸收剂是该领域的研究难点和热点。离子液体(ILs)作为一类绿色溶剂，在CO₂捕集中具有结构可调节、反应速率快、吸收量高等优势，但存在黏度大、价格昂贵等问题，本工作提出将超强碱离子液体1,8-二氮杂二环[5,4,0]十一碳-7-烯咪唑([HDBU][Im])与单乙醇胺(MEA)复配得到离子液体复配溶剂，来提高吸收剂的CO₂吸收量并降低吸收CO₂后溶剂的黏度。研究了离子液体浓度、吸收温度、CO₂分压等对离子液体复配溶剂捕集CO₂性能的影响，测定了离子液体复配溶剂在不同CO₂负荷下的密度和黏度等物性。结果表明，30wt%MEA+10wt%[HDBU][Im]具有较好的吸收能力，在40℃下，CO₂吸收量达到0.1453 g CO₂     

离子液体-水复配吸收剂捕获CO2性能

基于绿色合成方法制备出亲水性离子液体(ILs)[NH₂-C₃mim][Br],从有效降低CO₂吸收-解吸操作成本出发,采用ILs-H₂O复配吸收剂,开展了常温加压CO₂吸收及吸收剂常温减压解吸再生实验。结果表明,比CO₂吸收量(基于复配吸收剂或离子液体组分)随复配吸收剂中ILs组分浓度而变;吸收初期,CO₂吸收速率随吸收剂配比变化显著;以CO₂高吸收率和吸收剂低成本为目标,优选出新型水基复配吸收剂(离子液体与水质量比为1.38:1)。分别以水基离子溶液、改良热钾碱液和活化复配醇胺液为吸收剂,在自行搭建的超重力场强化吸收-连续逆流接触(加热或减压)解吸再生台架实验装置上进行了CO₂捕获与吸收剂再生连续化实验。结果表明,在超重力场作用下,改良热钾碱液和活化复配醇胺液对CO₂有较好的捕获,吸收率分别在98%、96%和90%以上,3种吸收剂经加热或减压解吸再生后均可循环回用,水基离子溶液吸收剂在常温减压下解吸更具有实际可操作性。     

1-氨丙基-3-甲基咪唑溴功能型离子液体对CO2的吸收性能

1-氨丙基-3-甲基咪唑溴盐([APMIm])对CO₂等酸性气体具有较强的选择性吸收性能,在能源及环保领域有较好应用前景。运用等容饱和吸收法在高压不锈钢反应釜中测得CO₂在3种不同含水量的1-氨丙基-3-甲基咪唑溴盐水溶液中的溶解度数据,实验的温度范围为278.15~348.15 K,实验压力由低于大气压到最高6.5 MPa。实验结果表明,当水的质量分数达到60.84%以上,离子液体水溶液吸收CO₂的能力和速率才会得到显著提升。尤其值得注意的是,在278.15 K、120 kPa达到吸收平衡时,CO₂在含水质量分数为60.84%的1-氨丙基-3-甲基咪唑溴盐水溶液中的溶解度达到0.459 mol CO₂ ·(mol IL)^-1,接近理论最大吸收值0.5 mol CO₂·(mol IL)^-1。在较高压力下(3.9 MPa)最大CO₂吸收量为1.894 mol CO₂·(mol IL)^-1。     

[Bmim][BF4]/MEA混合水溶液的CO2汽液平衡和解吸能耗分析

搭建汽液平衡实验台,对液液分相CO₂吸收剂1-丁基-3-甲基咪唑四氟硼酸盐（[Bmim][BF₄]）/乙醇胺（MEA）混合水溶液与CO₂的汽液平衡进行了实验测量与分析,并对该吸收剂解吸能耗进行计算。结果表明,随着温度的升高,相同担载量溶液对应的CO₂分压升高,[Bmim][BF₄]质量分数的改变对汽液平衡的影响不明显。与传统有机胺溶液30%（质量）MEA相比,该吸收剂在能耗方面主要优势在于解吸过程中显热和潜热的减小。其反应热在担载量大于0.45之后明显减小,潜热的减小主要由于解吸塔内H₂O气相分压和摩尔分数的减小,当[Bmim][BF₄]质量分数大于30%时,显热可以减少30%以上,减少的原因主要为比热容的降低和富液胺浓度的提升。     

富氧燃烧烟气冷凝塔钠碱法脱硫过程SO2和CO2共吸收建模与实验研究

建立SO₂与CO₂共吸收到钠基溶液中的吸收速率模型,假设该模型中SO₂的水解反应为瞬间反应;关于CO₂水解反应存在两种假设：有限动力学假设和瞬间反应假设。由这两种方法计算分别获得SO₂的吸收速率并与完全预混气液反应器中的的动态实验进行对比。采用瞬间反应假设可以预测反应速率的趋势,绝对反应速率误差仍然较大。而采用有限动力学假设的模拟值与实验值在pH>3吻合良好。CO₂对SO₂吸收速率的影响主要通过影响气相传质系数和相同pH下溶液总硫浓度产生。根据CO₂存在与否对SO₂吸收速率的影响,获得五个不同的相互作用pH的区间。pH>11.42时,SO₂/N₂吸收速率大于SO₂/CO₂,主要由于气相传质系数影响;7.8 < pH < 11.42时,SO₂/N₂的吸收速率和SO₂/CO₂吸收速率相似,主要由于气相传质系数和溶液总硫影响抵消;5.41 < pH < 7.8时,SO₂/CO₂的吸收速率相对较高,主要由于溶液总硫影响更大;2.8 < pH < 5.41时,SO₂/CO₂的吸收速率相对较低,主要由于气相传质系数影响;pH < 2.8时,SO₂/N₂和SO₂/CO₂吸收速率相似,主要受液相传质的控制。模拟同时获得不同pH下溶液中碳和硫相关离子的转化规律和SO₂吸收速率的控制步骤,为富氧燃烧冷却塔同时脱硫设备的设计和运行提供参考。     

Gas-Liquid Mass Transfer Characteristics in a Gas-Liquid-Solid Bubble Column under Elevated Pressure and Temperature

abstract The volumetric mass transfer coefficient kLa of gases (H2, CO, CO2) and mass transfer coefficient kL on liquid par-affin side were studied using the dynamic absorption method in slurry bubble ...     

阵列凸起微通道内气液两相传质特性研究

研究了阵列凸起微通道内N-甲基二乙醇胺（MDEA）吸收CO₂过程的气液两相传质特性。在弹状流型下,考察了气液两相流量、MDEA浓度对体积传质系数、CO₂吸收效率、压力降以及能量损耗的影响。弹状气泡受到阵列凸起的挤压作用发生形变,促进了气液两相间的传质。与平滑通道相比,阵列凸起微通道在实验条件下具有更好CO₂吸收效率。在相同的能量损耗时,阵列凸起微通道具有更大的体积传质系数。     

Absorption of carbon dioxide into aqueous colloidal silica solution with diisopropanolamine

Carbon dioxide was absorbed into the aqueous nanometer-sized colloidal silica solution of 0–31 wt% and diisopropanolamine of 0–2 kmol/m³ in a flat-stirred vessel with the impeller of various sizes and speeds at 25 °C and 0.101 MPa to measure the absorption rate of CO₂. The volumetric liquid-side mass transfer coefficient (k_La) of CO₂ was used to obtain the empirical correlation formula containing the rheological behavior of the aqueous colloidal silica solution. Reduction of the measured k_La was explained by the viscoelastic properties of the aqueous colloidal silica solution. The theoretical value of the absorption rate of CO₂ was estimated from the model based on the film theory accompanied by chemical reaction and compared with the measured value.     

Using expansion units to improve CO_2 absorption for natural gas purification——A study on the hydrodynamics and mass transfer

The usage of capillary tubes for CO₂ absorption suffers from small residence time, which leads to reduced performance for large throughput. This work presents a method of connecting expansion units to capillary tubes to serve as a residence time delayer. The effect of the expansion unit on gas-liquid hydrodynamics, pressure drop and mass transfer coefficient (k_La) are investigated under various operating pressures up to 4.0 MPa, for both physical and chemical absorption. A novel periodic jetting flow is found in the expansion unit, which can intensify the CO₂ absorption. Experimental results show that the strategy can significantly decrease the pressure drop while maintaining the absorption performance to a large extent. The overall k_La for physical and chemical absorption are correlated to pressure drop, respectively. Besides, CO₂ loading in rich absorbents increases dramatically compared to literature studies with only micromixers or capillary tubes, which is beneficial to regenerate solvent. The study verifies the concept that pre-treatment with water can largely reduce the usage of amines, and can also provide a guide for process design in natural gas purification such as biogas recovery.     

Absorption of carbon dioxide into aqueous PAA solution containing diethanolamine

Carbon dioxide was absorbed into aqueous polyacrylamide (PAA) solution containing diethanolamine (DEA) of 0–2 kmol/m³ in a flat-stirred vessel with the impeller of 0.034 m and agitation speed of 50 rpm at 25 °C and 0.101 MPa to measure the absorption rate of CO₂. The volumetric liquid-side mass transfer coefficient (k_La) was obtained from the dimensionless empirical correlation formula presenting the rheological behavior of aqueous PAA solution. PAA with elastic property of non-Newtonian liquid made the rate of chemical absorption of CO₂ accelerate compared with Newtonian liquid based on the same viscosity of the solution. The estimated value of the absorption rate of CO₂ was obtained from the model based on the film theory accompanied by chemical reaction and compared with the measured value.     

Gas–liquid mass transfer coefficient in stirred tanks interpreted through models of idealized eddy structure of turbulence in the bubble vicinity

Experimental data on the average mass transfer liquid film coefficient (k_L) in an aerated tank stirred by two Rushton turbines on common shaft are presented. Liquid media used were distilled water and 0.5 M sodium sulphate solution. Volumetric mass transfer coefficient (k_La) was measured by the dynamic pressure method with pure oxygen absorption. Specific interfacial area a was taken from Alves et al. [Chem. Eng. Proc., in press] who measured data on local gas hold-up and local average bubble diameter in the same apparatus and batches. Values of k_L are quantitatively interpreted in terms of correlations based on idealized eddy structures of turbulence in the bubble vicinity, namely by “eddy” model by Lamont and Scott [AIChE J. 16 (1970) 513] in the form of k_L=0.523(eν/ρ)^0.25(D/ν)^1/2, which fits the data with the mean deviation of 4.7%. It is shown that the decisive quantity to correlate k_L in the stirred tank is power dissipated in the liquid phase rather than the bubble diameter and the slip velocity as assumed by Alves et al.     

Kinetics and slurry-type reactor modelling during catalytic hydrogenation of o-cresol on Ni/SiO2

The effect of kinetic parameters (reactant concentrations, temperature) was investigated on the initial reaction rate for the catalytic hydrogenation of o-cresol on Ni/SiO₂, carried out in a batch or semi-batch agitated slurry-type reactor.

The data were interpreted by a kinetic model based on the Langmuir-Hinshelwood mechanism with non-dissociative and non-competitive adsorption of o-cresol and hydrogen on different sites, where the limiting step is due to the reaction of adsorbed reactants. The activation energy (E_a = 82 kJ/mol) is in good agreement with previous literature values reported for the catalytic hydrogenation of phenol.

Taking into account thermodynamic (solubilities) and mass transfer kinetics (k_La) data measured in situ, the integral reactor conversion rate of this three-phase catalytic reaction was simulated accurately in the physical regime by taking into account external and internal mass transfer resistances.     

Experimental studies of air-blast atomization on the CO2 capture with aqueous alkali solutions

In this work, an air-blast atomizing column was used to study the CO₂ capture performance with aqueous MEA (mono-ethanol-amine) and NaOH solutions. The effects of gas flow rate, the liquid to gas ratio (L/G), the CO₂ concentration on the CO₂ removal efficiency (η) and the volumetric overall mass transfer coefficient (K_Ga_v) were investigated. The air-blast atomizing column was also compared with the pressure spray tower on the studies of the CO₂ capture performance. For the aqueous MEA and NaOH solutions, the experimental results show that the η decreases with increasing gas flow rate and CO₂ concentration while it increases with increasing L/G. The effects on K_Ga_v are more complicated than those for η. When the CO₂ concentration is low (3 vol%), K_Ga_v increases with increasing gas flow rate while decreases with increasing L/G. However, when the CO₂ concentration is high (9.5 vol%), as the gas flow rate and L/G increases, K_Ga_v increases first and then decreases. The aqueous MEA solution achieves higher η and K_Ga_v than the aqueous NaOH solution. The air-blast atomizing column shows a good performance on CO₂ capture.