Performance of CO2 absorption in a diameter-varying spray tower

The application of spray towers for CO₂ capture is a development trend in recent years. However, most of the previous jobs were conducted in a cylindrical tower by using a single spray nozzle, whose configuration and performance is not good enough for industrial application. To solve this problem, the present work proposed a diameter-varying spray tower and a new spray mode of dual-nozzle opposed impinging spray to enhance the heat and mass transfer of CO₂ absorption process. Experiments were performed to investigate the mass transfer performance (in terms of the CO₂ removal rate (η) and the overall mass transfer coefficient (K_Ga_e2 are major factors, which affect the absorption performance and the maximums of η and K_Ga_e that are 94.0% and 0.574 kmol·m^-3·h^-1·kPa^-1, respectively, under the experimental conditions. Furthermore, new correlations to predict the mass transfer coefficient of the proposed spray tower are developed in various CO₂ concentrations with a Pearson Correlation Coefficient over 90%.     

NaOH-CO2体系下并流立体旋流筛板塔传质性能

二氧化碳捕集是应对全球气候变暖问题的重要技术之一。本文使用NaOH溶液和CO₂作为实验体系,在并流塔中对立体旋流筛板（TRST）的传质性能进行实验研究,测定并计算出全塔及塔板段的气相总体积传质系数[K_Ga_e,(K_Ga_e)_t],重点考察塔板安装数量和方式、空塔气相动能因子和喷淋密度、CO₂和NaOH浓度等参数的影响规律。研究结果表明,塔板段是传质过程的主要区间,增加塔板数量以及采用塔板逆向安装方式是提升传质性能的有效技术手段;塔板段的气相总体积传质系数随空塔气相动能因子和NaOH浓度的增加呈先增大后减小的趋势,随喷淋密度和CO₂浓度的增加而减小,最高可达12.18kmol/(m³·h·kPa);建立塔板段的气相总体积传质系数的经验模型,模型计算值与实验数据的吻合性较好,相对误差小于20%。     

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.     

The CO2 absorption and desorption performance of the triethylenetetramine + N,N-diethylethanolamine + H2O system

Post-combustion CO₂ capture (PCC) process faces significant challenge of high regeneration energy consumption. Biphasic absorbent is a promising alternative candidate which could significantly reduce the regeneration energy consumption because only the CO₂-concentrated phase should be regenerated. In this work, aqueous solutions of triethylenetetramine (TETA) and N,N-diethylethanolamine (DEEA) are found to be efficient biphasic absorbents of CO₂. The effects of the solvent composition, total amine concentration, and temperature on the absorption behavior, as well as the effect of temperature on the desorption behavior of TETA-DEEA-H₂O system were investigated. An aqueous solution of 1 mol·L^-1 TETA and 4 mol·L^-1 DEEA spontaneously separates into two liquid phases after a certain amount of CO₂ is absorbed and it shows high CO₂ absorption/desorption performance. About 99.4% of the absorbed CO₂ is found in the lower phase, which corresponds to a CO₂ absorption capacity of 3.44 mol·kg^-1. The appropriate absorption and desorption temperatures are found to be 30℃ and 90℃, respectively. The thermal analysis indicates that the heat of absorption of the 1 mol·L^-1 TETA and 4 mol·L^-1 DEEA solution is -84.38 kJ·(mol CO₂)^-1 which is 6.92 kJ·(mol CO₂)^-1 less than that of aqueous MEA. The reaction heat, sensible heat, and the vaporization heat of the TETA-DEEA-H₂O system are lower than that of the aqueous MEA, while its CO₂ capacity is higher. Thus the TETA-DEEA-H₂O system is potentially a better absorbent for the post-combustion CO₂ capture process.     

[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。     

相变吸收捕集烟气中CO2技术的发展现状

化学吸收法作为目前最有效的CO₂捕集技术,吸收剂常用有机胺,但过高的再生能耗和成本限制了其在工业中的应用。基于传统有机胺溶剂开发出来的相变吸收剂被认为可以大幅减少解吸能耗,成为近几年研究的热点。本文详细介绍了相变吸收剂的常见类型、分相机理,并根据其具体组成进行了种类划分,对比分析了常用相变吸收剂和传统乙醇胺（MEA）吸收液的再生能耗,并指出温度、CO₂负荷以及相分离等因素对相变吸收剂的工艺流程长期运行稳定性的影响。在制备相变吸收剂的过程中,可加入活化剂来降低CO₂富液黏度,加入助溶剂来提高传质特性。本文阐述了现有相变吸收剂的挥发、降解和腐蚀等特性的研究现状。最后,结合研究现状和烟气捕集需求对相变吸收剂今后的研究方向给出了建议。     

环丁砜对乙醇胺溶液吸收和解吸CO2的影响

利用物理溶剂环丁砜替代部分水,采用气液搅拌实验装置和真实热流量热法测定了环丁砜对乙醇胺（MEA）溶液吸收和解吸二氧化碳（CO₂）过程的影响,考察了CO₂循环负载、吸收速率、吸收热和解吸热等性质变化。研究表明：环丁砜对MEA溶液负载CO₂的吸收热影响较小,但对吸收速率、循环吸收容量和解吸过程影响较大。环丁砜可降低MEA溶液对CO₂的表观吸收速率,且随CO₂负载量的增大,降幅也逐渐变大。环丁砜有利于富液解吸过程,加快解吸速率,增大CO₂解吸程度,同时单位热流负荷、单位冷流负荷和单位能耗均有不同程度的降低。在燃煤电厂烟气条件下,20% MEA+20% sulfolane体系相对20% MEA体系,其表观吸收速率平均降低约10%,CO₂循环吸收容量增加24%,单位CO₂解吸能耗降低18%。     

沼气提纯过程中醇胺溶液吸收CO2传质性能

醇胺溶液吸收CO₂是沼气提纯领域重要的研究课题。在实验填料吸收塔中,以乙醇胺(MEA)、二乙醇胺(DEA)为吸收剂,研究了吸收剂浓度、进气流量、CO₂浓度、进液温度对吸收过程转化率η、吸收速率N以及气相总体积传质系数K_Ga_e的影响。结果表明,吸收剂浓度增加可有效提高η、N及K_Ga_e;进气流率增加,η逐渐降低,N先增加后降低,K_Ga_e先增加后降低最终趋于稳定;随着CO₂浓度增加,η和K_Ga_e不断降低,N逐渐增加;随着进液温度升高,η和K_Ga_e均先升高后降低;MEA、DEA的最佳进液温度在40～60℃之间,并随CO₂负载量增大而逐渐降低。研究结果对于醇胺溶液吸收法沼气提纯技术的研究开发和实际应用有参考作用。     

[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。     

中空纤维膜接触器中N,N-二甲基乙醇胺吸收CO2的特性

N,N-二甲基乙醇胺（DMEA）是一种很有前途的吸收剂,具有较快的反应速率和较高的CO₂捕集能力。在本研究中,DMEA作为一种新型吸收剂被应用于中空纤维膜接触器,用于从CO₂/CH₄气体混合物中分离CO₂。通过建立二维稳态数学模型,模拟了MEA、DEA、MDEA和DMEA四种吸收剂在不同操作条件下对CO₂吸收性能的影响。结果表明,脱碳性能大小为MEA>DMEA>DEA>MDEA;气相参数对脱碳率的影响比液相参数更显著;提高气体流速和CO₂浓度,脱碳率均会下降;提高液速和吸收剂浓度,脱碳率均增大,适当提高吸收剂流速和吸收剂浓度可以提高CO₂去除效率。此外,CO₂吸收通量将随着气体速度的增加而增加,随着液相中CO₂负荷的增加而减少。最后,通过两种影响因素共同作用确定了膜接触器分离酸性气体的最佳操作条件。因此,膜吸收法在天然气脱碳方面有良好的潜力。     

超重力强化AMP-PZ复合溶液脱碳技术及表观动力学

为提高工业上火电厂乙醇胺（MEA）吸收塔脱碳工艺中脱碳率和反应速率,提出了超重力技术耦合2-氨基-2-甲基-1-丙醇-对二氮己环（AMP-PZ）混合胺脱碳方法。正交实验表明：不同操作参数对脱碳率的影响显著性大小依次为：超重力因子、气液比、吸收剂质量浓度、主吸收剂含量、温度;最佳操作条件为：超重力因子为60,气液比为15,吸收剂质量分数为25%,主吸收剂质量分数为60%,温度为25℃,CO₂脱除率可达97.16%。相对传统的乙醇胺（MEA）吸收塔法,CO₂脱除率提高了7.16%。相同操作条件下,旋转填料床的脱碳反应速率常数比曝气反应装置高一倍。建立了超重力场中AMP-PZ脱碳表观动力学模型,不同操作参数对反应速率常数的显著性影响大小依次为：超重力因子>气液比>吸收剂质量浓度。     

微通道内醇胺/离子液体复配水溶液吸收CO2的传质特性

研究了微通道内醇胺[单乙醇胺(MEA)和甲基二乙醇胺(MDEA)]与离子液体[1-丁基-3-甲基咪唑四氟硼酸([Bmim][BF₄])和1-羟乙基-3-甲基咪唑甘氨酸([C₂OHmim][GLY])]复配水溶液吸收CO₂的传质特性。考察了醇胺/离子液体浓度比(c_AA∶c_IL)对液相体积传质系数(k_La)的影响,发现k_La随反应速率的增大而增大。为进一步阐释复配水溶液吸收CO₂的传质机理,分析了比表面积、扩散速率、增强因子和液弹循环对传质速率的影响。结果表明,四种复配溶液中,反应速率和循环频率(f_cir)分别在低流率和高流率下对传质速率起主导作用。k_La可表示为f_cir的函数,低气相流率下k_La与f_cir呈线性关系,斜率与反应速率成正相关,高气相流率下,液弹循环因膜弹传递困难而对整体传质速率的影响减弱,k_La与f_cir呈指数关系,幂律指数小于1。     

Catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al2O3 in a rotating packed bed

This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al₂O₃ (Cat) in a rotating packed bed (RPB) for the first time. The results showed that the value of the overall decomposition rate constant of ozone (K_c) and overall volumetric mass transfer coefficient (K_La) are 4.28×10^-3 s^-1 and 11.60×10^-3 s^-1 respectively at an initial pH of 6, β of 40, of 60 mg·L^-1 and Q_L of 85 L·h^-1 in deionized water, respectively. Meanwhile, the K_c and K_La values of Fenhe water are 0.88×10^-3 s^-1 and 2.51×10^-3 s^-1 lower than deionized water, respectively. In addition, the K_c and K_La values in deionized water for the Cat/O₃-RPB system are 44.86% and 47.41% higher than that for the Cat/O₃-BR (bubbling reactor) system, respectively, indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.     

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.     

CORROSIVITY IN 2-AMINO-2-METHYL-l-PROPANOL(AMP)-CO2 SYSTEM

Weight loss tests were performed to investigate the corrosivity of a new absorbent, 2-amino-2-methyl-l-propanol (AMP) saturated with pure CO₂ and Mixture of CO₂ and air on carbon steel under boiling conditions. The corrosion data were compared with those of a conventional amine, monoethanolamine (MEA), tested under the same conditions. The results indicated that corrosion rates in the AMP system were generally lower than those in the M EA system, probably due to differences in characteristics of the corrosion products in each of the absorbents. Corrosivity in the AMP system tended to stabilize when the amine concentration reached 5 kmol/m³ while corrosion rates in the MEA system were directly proportional to amine concentrations. Furthermore, it was observed that a small amount of O₂ seemed to expedite severe corrosion     

金属离子促进乙醇胺捕集二氧化碳研究

为了解决醇胺法燃烧后捕集二氧化碳再生能耗过高的问题,研究了一种向胺溶液中添加金属离子以降低其CO₂解吸能耗的方法,称之为金属离子络合物热缓冲自热利用技术。以广泛商业化应用的单乙醇胺（MEA）溶液为研究载体,并在MEA溶液中分别添加金属离子铜或镍, 通过建立含有金属离子的MEA捕集CO₂体系的化学反应模型,解释金属离子热缓冲剂效应的内在机理。机理显示在MEA-金属离子-CO₂-H₂O体系中,金属-MEA络合物作为一种有效的反应热缓冲剂,将有机胺吸收CO₂过程中释放的反应热（放热反应）存储于金属络合物的解离键能中（吸热反应）,在CO₂高温解吸中通过其络合放热反应将储存的能量释放出来用于CO₂解吸,形成自热再生低能耗CO₂捕集技术,从而降低了MEA再生的能耗。本文进行了综合的实验测定来评价金属离子对MEA溶液捕集CO₂过程的性能提升影响,包括CO₂反应热、解吸速率、吸收-解吸循环负载、汽液平衡溶解度等。实验结果表明铜离子或镍离子作为添加剂,能增加MEA的CO₂平衡循环负载14%~20%或7%~10%,同时能够降低MEA的CO₂反应热值6.6%~24%或6.0%~20%。     

乙醇胺捕集燃煤烟气二氧化碳工艺模拟

有机胺法是最有效的燃煤烟气二氧化碳（CO₂）捕集技术之一。使用Aspen plus模拟乙醇胺（MEA）捕获烟气CO₂的过程,先进行单独的吸收塔与再生塔模拟,在单独系统模型收敛的基础上,再进行吸收-解吸的综合模拟。在入塔烟气流量为8.22 m³/min、CO₂物质的量分数为0.18、MEA流量为2 311.3 kg/h、MEA物质的量分数为0.12条件下,MEA捕集燃煤烟气中CO₂的模拟结果: CO₂脱除率为69.3%,净化气中CO₂物质的量分数为5.33×10^-2,再生塔顶再生气中CO₂物质的量分数为0.956,基本达到了设计要求。此为更深入地开展胺法吸收CO₂的研究提供了依据。     

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。     

膜吸收CO2工艺中不同吸收液对膜润湿的影响

以单乙醇胺（MEA）、二乙醇胺（DEA）和N-甲基二乙醇胺（MDEA）作为吸收液,利用聚丙烯（PP）中空纤维膜组件进行分离模拟烟气中CO₂的实验研究,考察不同吸收液的脱除效率以及长时间连续运行下的膜润湿现象。建立膜相传质阻力随时间变化模型,与实验数据拟合较好。同时将膜丝在不同吸收剂中浸泡,结合接触角、场发射扫描电镜（FE-SEM）、衰减全反射红外光谱（ATR-IR）以及热重（TG）表征分析膜性能的改变。结果表明,相同浓度下,单一吸收剂的CO₂脱除效率大小为MEA > DEA > MDEA;当吸收液为1mol/L MEA时,16天后CO₂脱除效率从93.3%下降到72.1%;而吸收液为1mol/L DEA时,脱除效率从88.3%到第16天的78%,下降约12%;理论计算得吸收液为1mol/L MEA和1mol/L DEA时,膜相传质阻力分别为10564.06s/m和4881.08s/m;浸渍时间增加,膜接触角减小,疏水性减弱,同时膜孔径变大,出现润湿现象;红外光谱和热重分析表明在MEA溶液作用下膜丝出现溶胀。     

负载[APMIm][Br]离子液体吸收CO2的性能

1-氨丙基-3-甲基咪唑溴盐（[APMIm][Br]）离子液体通过化学反应捕集CO₂。采用浸渍-蒸发将[APMIm][Br]离子液体负载在硅胶表面,通过比表面孔隙吸附测定仪、热重分析仪（TGA）对吸收剂的结构与性能进行研究,负载量为10%～50%,温度为303.15～323.15 K,CO₂浓度分别为10%、30%、50%。结果表明：硅胶表面的离子液体薄膜厚度达到86 nm（负载40%）时,具有最快的吸收速率,且受CO₂浓度和温度变化的影响较小,平衡吸收量在50% CO₂体系中达到理论吸收量的80%,随着温度的升高而降低,当负载量为50%时,膜厚增加到230 nm,导致吸收速率和平衡吸收量大幅度下降。值得注意的是：负载离子液体吸收剂在循环使用3次之后,结构与性能均保持不变,表现出一定的工业运用前景。