An experimental investigation on the rate of CO<Subscript>2</Subscript> absorption into aqueous methyldiethanolamine solutions

In this paper, the CO₂ absorption rates into aqueous solutions of Methydiethanolamine (MDEA) at various concentrations of 1, 2, 3 and 4 M and temperatures varying from 293 to 323 K were measured by using a laboratory stirred reactor. The kinetics experiments were conducted under a pseudo first order regime. The data were analyzed by means of chemical absorption theory and the kinetic parameters associated with the reaction, such as the reaction order and the reaction rate constants, were evaluated. The effect of temperature on the reaction rate constant was assessed and the activation energy was evaluated at about 44.12 kJoule/mol.     

Absorption of carbon dioxide into aqueous methyldiethanolamine

Gas absorption rates in a laminar liquid jet were measured for carbon dioxide in methyl- diethanolamine (MDEA) solutions. It was found that for the short contact times (<0.012s) of these absorption experiments there is only a small effect of any reaction between carbon dioxide and MDEA. Solubilities and molecular diffusivities for carbon dioxide in aqueous MDEA are estimated from measurements with nitrous oxide. The absorption rate data are described well using the solubilities and diffusivities measured in this work. Solubilities were measured over the temperature range 15 to 35°C and for MDEA concentrations up to 40%. Diffusion coefficients and viscosities were measured over the same temperature range and MDEA concentrations up to 20%.     

以MDEA为主体的混合胺溶液吸收CO2研究进展

综述了近年来乙醇胺、二乙醇胺、哌嗪、碳酸酐酶以及离子液体与N-甲基二乙醇胺的混合溶液用于CO2吸收的研究进展;分析了混合溶液的吸收机理和CO2吸收的动力学;讨论了混合溶液组成、体系温度、压力等对吸收性能的影响;并对该法未来的研究方向和发展前景进行了展望.     

Kinetic of CO2 absorption and carbamate formation in aqueous solutions of diethanolamine

The absorption rates of CO₂ into aqueous solutions of Diethanolamine (DEA) with varying concentrations from 0.2 to 4M and temperature range from 293 to 323 K were measured by using a laboratory stirred reactor. The CO₂ partial pressure was varied in a range that the reaction would occur in pseudo first order regime. Experimental data were analyzed and the kinetic parameters associated with the reaction were determined. The activation energy for the deprotonation of the intermediate zwitterion was estimated at about 11.4 kcal/mol. The contribution of carbamate formation to the overall absorbed CO₂ was experimentally evaluated and found to be of the order of 100%.     

A comparative kinetics study of CO2 absorption into aqueous DEEA/MEA and DMEA/MEA blended solutions

The kinetics of CO₂ absorption into aqueous solutions of N,N‐diethylethanolamine (DEEA), and N,N‐dimethylethanolamine (DMEA), and their blends with monoethanolamine (MEA) have been studied in a stopped‐flow apparatus. The kinetics experiments were carried out at the concentrations of DEEA and DMEA varying from 0.075 to 0.175 kmol/m³, respectively, and that of MEA ranging between 0.0075 and 0.0175 kmol/m³, over the temperature range of 293–313 K. Two kinetics models are proposed to interpret the reaction in the blended amine systems and the results show that the model which incorporates the base‐catalyzed hydration mechanism and termolecular mechanism resulted in a better prediction. Furthermore, the kinetics behaviors of CO₂ absorption into two blended systems are comprehensively discussed according to their molecular structures. It can be concluded that the interaction between tertiary amines and primary amines as well as the alkyl chain length of tertiary amines have a significant influence on the kinetics. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1350–1358, 2018     

Comparison of the rate of CO2 absorption into aqueous ammonia and monoethanolamine

Aqueous ammonia has been proposed as an absorbent for use in CO₂ post combustion capture applications. It has a number of advantages over MEA such as high absorption capacity, low energy requirements for CO₂ regeneration and resistance to oxidative and thermal degradation. However, due to its small molecular weight and large vapour pressure absorption must be carried at low temperature to minimise ammonia loss. In this work the rate of CO₂ absorption into a falling thin film has been measured using a wetted-wall column for aqueous ammonia between 0.6 and 6 mol L^?1, 278–293 K and 0–0.8 liquid CO₂ loading. The results were compared to 5 mol L^?1 MEA at 303 and 313 K. It was found that the overall mass transfer coefficient for aqueous ammonia was at least 1.5–2 times smaller than MEA at the measured temperatures. From determination of the second-order reaction rate constant k₂ (915 L mol^?1 s^?1 at 283 K) and activation energy E_a (61 kJ mol^?1) it was shown that the difference in mass transfer rate is likely due to both the reduced temperature and differences in reactivity between ammonia and MEA with CO₂.     

填料塔中活化MDEA吸收CO2的模拟研究

根据近期国内外关于活化MDEA(N 甲基二乙醇胺)溶液吸收二氧化碳的基础研究,以及有关填料塔的研究结果,针对目前脱碳工业设计与改造的需求,对工业脱碳塔的吸收过程进行了深入研究。以化学工程的基本原理为基础建立了数学模型,对活化MDEA脱碳过程中吸收塔的塔高计算提出了新的模拟方法,建立了相应的模拟软件,通过与工业实际的对比,计算获得了较好的效果。     

Kinetics of absorption of carbon dioxide into aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol

In this work the kinetics of the reaction between CO₂ and a sterically hindered alkanolamine, 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) were determined at temperatures of 303.15, 313.15 and 323.15 K in a wetted wall column contactor. The AHPD concentration in the aqueous solutions was varied in the range 0.5-2.4 kmol m⁻³. The ratio of the diffusivity and Henry's law constant for CO₂ in solutions was estimated by applying the N₂O analogy and the Higbie penetration theory, using the physical absorption data of CO₂ and N₂O in water and of N₂O in amine solutions. Based on the pseudo-first-order for the absorption of CO₂, the overall pseudo-first-order rate constants were determined from the kinetics measurements. By considering the zwitterion mechanism for the reaction of CO₂ with AHPD, the zwitterion deprotonation and second-order rate constants were calculated. The second-order rate constant, k₂, was found to be 285, 524, and 1067 m³ kmol⁻¹ s⁻¹ at 303.15, 313.15, and 323.15 K, respectively.     

低分压CO2在有机胺水溶液中的溶解度

建立了一套用于测定低分压CO2在有机胺水溶液中溶解度的实验装置。在298、308 K下分别测定了低分压CO2在较低浓度的乙醇胺(MEA)、二乙醇胺(DEA)水溶液中的溶解度。结果表明,在较低的溶解度下,CO2在有机胺水溶液中的平衡分压接近于0;当溶解度增大到一定程度后,平衡分压随其增加而急剧增大,同时,温度的升高和有机胺浓度的增大均能增大CO2的平衡分压。通过实验数据拟合得到的理论模型参数与实验值符合较好。     

Unsteady-state absorption of CO2 into w/o emulsion with aqueous alkaline liquid droplets

Unsteady-state absorption of CO₂ into w/o emulsion was studied by experimental measurements and prediction from mathematical modeling. Absorption experiments were performed by using a stirred vessel with a flat gas-liquid interface under 0.101 MPa and 25 °C. Continuous phase was benzene that has larger solubility than water. Dispersed phase was an aqueous solution of NaOH and AMP. The effects of reactant concentration, size of emulsified droplets, volume fraction of continuous phase and stirring speed on the absorption rate of CO₂ were investigated. In the mathematical model, the mechanism of CO₂ absorption into the continuous phase through a gas-liquid interface was described on the basis of the penetration model, while the subsequent absorption/reaction in the dispersed aqueous droplets was modeled by the film model.     

Kinetics of the absorption of carbon dioxide into aqueous ammonia solutions

Experiments were performed in a customized double stirred tank reactor to study the kinetics of CO₂ absorption into NH₃ solutions at concentrations ranging from 0.42 to 7.67 kmol·m^?3 and temperatures between 273.15 and 293.15 K. The results show that the reactive absorption was first order with respect to CO₂ but fractional order (1.6–1.8) with respect to ammonia. Experimental data can be satisfactorily interpreted by a termolecular mechanism using and . © 2016 American Institute of Chemical Engineers AIChE J, 62: 3673–3684, 2016     

有机醇胺溶液脱除硫化氢气体的研究进展

本论文介绍了目前常用的脱除硫化氢的方法,重点回顾了有机醇胺溶液脱除硫化氢的发展历程,阐述了其脱除硫化氢的机理和工艺过程。针对新的条件下不同组分的气体的净化要求,结合有机醇胺溶液脱除硫化氢气体的特点提出了其在选择性脱除硫化氢气体方面的研究进展,并针对以上情况提出了有机醇胺溶液在脱除硫化氢气体方面存在的问题其未来发展趋势。     

Kinetics of the absorption of carbon dioxide into mixed aqueous solutions of 2-amino-2-methyl-l-propanol and piperazine

The reaction kinetics of the absorption of CO₂ into aqueous solutions of piperazine (PZ) and into mixed aqueous solutions of 2-amino-2-methyl-l-propanol (AMP) and PZ were investigated by wetted wall column at 30-40 °C. The physical properties such as density, viscosity, solubility, and diffusivity of the aqueous alkanolamine solutions were also measured. The N₂O analogy was applied to estimate the solubilities and diffusivities of CO₂ in aqueous amine systems. Based on the pseudo-first-order for the CO₂ absorption, the overall pseudo first-order reaction rate constants were determined from the kinetic measurements. For CO₂ absorption into aqueous PZ solutions, the obtained second-order reaction rate constants for the reaction of CO₂ with PZ are in a good agreement with the results of Bishnoi and Rochelle (Chem. Eng. Sci. 55 (2000) 5531). For CO₂ absorption into mixed aqueous solutions of AMP and PZ, it was found that the addition of small amounts of PZ to aqueous AMP solutions has significant effect on the enhancement of the CO₂ absorption rate. For the CO₂ absorption reaction rate model, a hybrid reaction rate model, a second-order reaction for the reaction of CO₂ with PZ and a zwitterion mechanism for the reaction of CO₂ with AMP was used to model the kinetic data. The overall absolute percentage deviation for the calculation of the apparent rate constant k_app is 7.7% for the kinetics data measured. The model is satisfactory to represent the CO₂ absorption into mixed aqueous solutions of AMP and PZ.     

On the modelling and simulation of sour gas absorption by aqueous amine solutions

A rigorous rate-based model for reactive sour gas absorption by aqueous amine solutions is presented which governs both the coupling of mass transfer and reaction and specific features of electrolyte species. The acceleration of mass transfer due to reactions in the liquid phase is taken into account rigorously, without application of enhancement factors. The model is implemented into the simulation environment Aspen Custom Modeler and validated by comparison of published pilot plant data with the simulation results. It is shown, that the model possesses a good predictivity for pilot plant scale as well as for industrial scale applications. In addition, the influence of reaction kinetics on the absorber performance is studied.     

Kinetics and modeling of carbon dioxide absorption into aqueous solutions of piperazine

In this work, the kinetics of the reaction between CO₂ and aqueous piperazine (PZ) have been estimated over the temperature range of 298-313 K from the absorption data obtained in a wetted wall contactor. The absorption data are obtained for the PZ concentrations of 0.2- and for CO₂ partial pressures up to 5 kPa. A coupled mass transfer-kinetics-equilibrium mathematical model based on Higbie's penetration theory has been developed with the assumption that all reactions are reversible. The model is used to estimate the rate constants from the experimental data for absorption of CO₂ in aqueous PZ. The estimated rate constants of this study are in good agreement with those reported in the literature.     

甲基二乙醇胺水溶液吸收CO2的研究

溶剂吸收法捕集CO2是目前应用最为广泛的方法。以甲基二乙醇胺(MDEA)为吸收液,对其吸收混合气中CO2的性能进行了研究。实验结果表明,在MDEA中添加活化剂可以有效提高其吸收能力,在MDEA浓度为3 mol/L,活化剂浓度为0.3 mol/L时,哌嗪(PZ)的活化效果最好,对CO2的吸收容量最大。以PZ为活化剂的MDEA水溶液吸收CO2的适宜操作条件:MDEA浓度为3 mol/L,PZ浓度为0.6 mol/L,吸收温度为60℃。MDEA水溶液吸收CO2的性能随着PZ浓度的增加而增加。吸收液具有良好的再生性能,适宜的再生时间为3 h,再生温度为106℃。     

单乙醇胺水溶液化学吸收CO2的研究

有机胺水溶液化学吸收CO2在工业上广泛应用,对其传质过程的微观机理进行研究十分必要。文中以对流扩散方程为基础,考虑了界面阻力对传质的影响,建立了带有化学反应的气液吸收过程液相侧非稳态传质模型,得到了传质系数表达式。利用激光全息干涉仪对不同液相主体流速下单乙醇胺(MEA)水溶液化学吸收CO2过程进行了实验研究,测定了传质达到稳态时的液相侧近界面浓度、浓度边界层厚度和传质系数。结果表明:随着液相主体流速的增加,近界面浓度和浓度边界层厚度减小,而传质系数增大;MEA在水溶液中的质量分数由0.1%增大到0.2%时,CO2吸收过程达到稳态时的近界面浓度、浓度边界层厚度及传质系数均增大。传质系数模型计算值与实验值吻合良好。     

The absorption rate of CO2/SO2/NO2 into a blended aqueous AMP/ammonia solution

The Inter-governmental Panel on Climate Change (IPCC) reported that human activities result in the production of greenhouse gases (CO₂, CH₄, N₂O and CFCs), which significantly contribute to global warming, one of the most serious environmental problems. Under these circumstances, most nations have shown a willingness to suffer economic burdens by signing the Kyoto Protocol, which took effect from February 2005. Therefore, an innovative technology for the simultaneously removal carbon dioxide (CO₂) and nitrogen dioxide (NO₂), which are discharged in great quantities from fossil fuel-fired power plants and incineration facilities, must be developed to reduce these economical burdens. In this study, a blend of AMP and NH₃ was used to achieve high absorption rates for CO₂, as suggested in several publications. The absorption rates of CO₂, SO₂ and NO₂ into aqueous AMP and blended AMP+NH₃ solutions were measured using a stirred-cell reactor at 293, 303 and 313 K. The reaction rate constants were determined from the measured absorption rates. The effect of adding NH₃ to enhance the absorption characteristics of AMP was also studied. The performance of the reactions was evaluated under various operating conditions. From the results, the reactions with SO₂ and NO₂ into aqueous AMP and AMP+NH₃ solutions were classified as instantaneous reactions. The absorption rates increased with increasing reaction temperature and NH₃ concentration. The reaction rates of 1, 3 and 5 wt% NH₃ blended with 30 wt% AMP solution with respect to CO₂/SO₂/NO₂ at 313 K were 6.05～8.49×10^?6, 7.16–10.41×10^?6 and 8.02～12.0×10^?6 kmol m^?2s^?1, respectively. These values were approximately 32.3–38.7% higher than with aqueous AMP solution alone. The rate of the simultaneous absorption of CO₂/SO₂/NO₂ into aqueous AMP+NH₃ solution was 3.83–4.87×10^?6 kmol m^?2s^?1 at 15 kPa, which was an increase of 15.0–16.9% compared to 30 wt% AMP solution alone. This may have been caused by the NH₃ solution acting as an alternative for CO₂/SO₂/NO₂ controls from flue gas due to its high absorption capacity and fast absorption rate.