The kinetics of dissolved oxygen reaction in aqueous sodium dithionite solutions

The kinetics of the reaction between dissolved oxygen and sodium dithionite in alkaline aqueous solution was investigated in a stirred cell. For dithionite concentrations below 0.08 kmol/m³ and sodium hydroxide concentrations from 0.044 to 0.27 kmol/m³, the results show the reaction to be first order in dithionite and zero order in oxygen. The Arrhenius activation energy was determined to be 76.2 MJ/kmol in the temperature range 15 to 34°C. Addition of other electrolytes (sodium sulphate or potassium chloride) had no effect on the kinetics.     

臭氧在对硝基苯酚溶液中的吸收与模拟过程

研究了鼓泡塔中臭氧在对硝基苯酚溶液中的吸收传质过程。首先探讨了pH值和气速对对硝基苯酚降解速率的影响。在 298K下,臭氧被连续通入对硝基苯酚溶液中,臭氧的传质速率因为溶解臭氧与对硝基苯酚的快速反应而大大加强。然后运用与实验条件相同的操作参数,进行了臭氧在鼓泡塔中吸收过程的模拟研究,采用MATLAB软件求解吸收过程的质量平衡方程,模拟了吸收过程中臭氧和对硝基苯酚浓度的变化,并与实验值进行了比较。结果表明,在短的鼓泡塔中,应用全混流模型来描述气相和液相的流体状态是可行的,在 80%的对硝基苯酚降解之前,模拟值和实验值能很好地一致。     

Kinetics of absorption of oxygen in aqueous solutions of cuprous chloride

The kinetics of absorption of oxygen in aqueous solutions of cuprous chloride (in acidic and neutral solutions) was studied in a glass stirred cell. The reactions were found to be second order with respect to cuprous chloride and first order with respect to oxygen. The reaction rate constants at 30°C were found to 295 (1/g mole)² sec⁻¹ for 5 M HCl solution and 334 (1/g mole)² sec⁻¹ for 3·75 M NaCl solution. The activation energies were to be 8·35 and 5·9 Kcal/mole for the acidic and neutral solutions, respectively. The effect of ionic strength on the rate constant for the acidic solution was also investigated.     

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     

Kinetics of carbon dioxide chemical absorption into cyclic amines solutions

Chemical reaction kinetics between carbon dioxide with two cyclic amines (pyrrolidine and piperidine) have been studied using a stirred tank reactor with a planar interfacial area. The operational variables considered in this work have been the amine concentration in the liquid phase and the reaction temperature. Specific absorption rates have been determined under different experimental conditions. Results indicate that the absorption process occurs in a pseudo first reaction regime exhibited first‐order kinetic with respect carbon dioxide and a second order for both cyclic amines. The reaction‐rate constant was determined under the different experimental conditions, and it was correlated depending on the temperature by means of an Arrhenius type equation. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Absorption kinetics of ozone in aqueous O-cresol solutions

The kinetics of ortho-cresol ozonation in water has been studied using the film theory. At most experimental conditions investigated, the kinetic regime of the absorption has been fast pseudo first order with respect to ozone. At 30°C mass transfer plays an important role in controlling the absorption rate of ozone. The selfdecomposition reaction of ozone does not take place because of the great reactivity of o-cresol with ozone. Reaction rate constants have been determined at pH 7 for different temperatures below 30°C. The following Arrhenius equation was obtained: k_T = 2.2 × 10²³ exp(-11784/T), L/mol ? s At temperatures below 30°C there exists an ozone partial pressure value above which the ozone absorption kinetic regime changes to fast second order regardless of experimental conditions.     

Kinetics of CO2 absorption by aqueous 3‐(methylamino)propylamine solutions: Experimental results and modeling

Experimental data and a model for the initial kinetics of CO₂ into 3‐(methylamino)propylamine (MAPA) solutions are presented in work. MAPA has been tested as an activator for tertiary amines with encouraging results. The measurements were performed in a string of discs contactor and, as no initial kinetics data are available in literature, additional measurements were carried out and in a wetted wall column. The obtained overall mass‐transfer coefficients from both apparatuses are in reasonable agreement. To obtain values for the observed kinetic constant, , the experimental results were interpreted using a two‐film mass‐transfer model and invoking the pseudo‐first order assumption. Needed experimental values for density, viscosity, and Henry's law coefficient for CO₂ were measured and are given. The results indicate that MAPA is almost twice as fast as piperazine, eight times faster than 2‐(2‐aminoethyl‐amino)ethanol (AEEA), and 15 times faster than monoethanolamine, when comparing unloaded 1 M solutions at 25°C. The observed kinetic constant was modeled using the direct mechanism. The final expression for can be applied for any concentration and temperature within the experimental data range, and, together with the presented physical data, comprises a complete model for calculating absorption fluxes. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3792–3803, 2014     

Kinetics of absorption of sulfur dioxide in dimethylaniline solution

Absorption of sulfur dioxide accompanied by reversible reaction in dimethylaniline has been studied using a short falling-film apparatus. Solutions of the amine in kerosene were used for this purpose. The effects of gas and liquid concentrations, contact time and temperature on the rate of absorption were investigated. Reaction equilibrium constant values were obtained at different temperatures from separate measurement of solubility of sulfur dioxide gas in kerosene as well as in dimethylaniline solutions. The heat of reaction was also calculated from these data. The absorption data could be satisfactorily interpreted by using the penetration theory of mass transfer with simultaneous pseudofirst order chemical reaction. The rate equations for the forward and reverse reactions were established.     

双效并流立体旋液式塔板压降的实验研究

采用全新工艺流程,设计了一种新型双效气液并流吸收塔,塔内安装有改进型立体旋液式塔板。分别以空气、空气-水作为研究体系进行实验,考察了不同操作参数与塔板结构参数下双效气液并流吸收塔的干塔压降、湿塔压降以及立体旋液式塔板的干板压降、湿板压降,明确了双效气液并流吸收塔的操作参数范围。实验结果表明:立体旋液式塔板单板干板压降及湿板压降分别控制在70 Pa,180 Pa以内。在一效、二效各逆向安装3块塔板,全塔共完全安装6块塔板时,全塔压降最大,但是干塔压降及湿塔压降可分别控制在2 400 Pa,2 800 Pa以内,双效气液并流吸收塔与立体旋液式式塔板的组合在能耗及操作弹性方面优势明显。     

Kinetics of absorption of carbon dioxide in aqueous piperazine solutions

In the present work the absorption of carbon dioxide into aqueous piperazine (PZ) solutions has been studied in a stirred cell, at low to moderate temperatures, piperazine concentrations ranging from 0.6 to , and carbon dioxide pressures up to 500 mbar, respectively. The obtained experimental results were interpreted using the DeCoursey equation [DeCoursey, W., 1974. Absorption with chemical reaction: development of a new relation for the Danckwerts model. Chemical Engineering Science 29, 1867-1872] to extract the kinetics of the main reaction, 2PZ+CO₂→PZCOO^-+PZH⁺, which was assumed to be first order in both CO₂ and PZ. The second-order kinetic rate constant was found to be at a temperature of , with an activation temperature of . Also, the absorption rate of CO₂ into partially protonated piperazine solutions was experimentally investigated to identify the kinetics of the reaction . The results were interpreted using the Hogendoorn approach [Hogendoorn, J., Vas Bhat, R., Kuipers, J., Van Swaaij, W., Versteeg, G., 1997. Approximation for the enhancement factor applicable to reversible reactions of finite rate in chemically loaded solutions. Chemical Engineering Science 52, 4547-4559], which uses the explicit DeCoursey equation with an infinite enhancement factor which is corrected for reversibility. Also, this reaction was assumed to be first order in both reactants and the second-order rate constant for this reaction was found to be at 298.15 K.     

填料塔中磷酸钠缓冲溶液吸收低体积分数SO2的体积传质系数

为满足磷酸一钠和二钠缓冲溶液脱硫设计开发的需要,采用磷酸钠缓冲盐溶液为吸收剂,测定和计算了在鲍尔环填料塔中磷酸钠溶液吸收模拟烟气中SO2的体积总传质系数KYa.在常温常压下,考察了空塔气速、喷淋密度、入口SO2体积分数、吸收液磷酸根浓度和初始pH等工艺参数对KYa的影响.结果表明,KYa随着空塔气速、喷淋密度、初始pH和磷酸根浓度的增加而增大;随着入口SO2体积分数的增加先增加后减小;该体系的传质过程受气膜和液膜共同控制.     

Kinetics of carbon dioxide absorption in aqueous solutions of diisopropanolamine

A bubble column absorber was used to investigate kinetics of the reaction between carbon dioxide and aqueous solutions of diisopropanolamine (DIPA), by means of gas absorption experiments. These were conducted in the temperature range of 20 to 40°C, with DIPA concentrations from 5 to 500 mol/m³, and CO₂ partial pressures between 5 and 101 kPa. A model based on the Danckwerts' surface reneval theory was used to analyze the experimental results and to determine the rate constant. The obtained data support the assumption of a second-order overall reaction, with the rate constants being well correlated by the Arrhenius equation:      

Absorption of oxygen by aqueous sodium sulphite solutions

New data have been reported on the absorption of oxygen by aqueous sodium sulphite solutions with cobalt sulphate as catalyst at 30°C. It is observed that the absorption rate increases up to a critical sulphite concentration beyond which the absorption rate becomes constant and this critical concentration varies with the catalyst concentration. The order of reaction with respect to sulphite and oxygen in the constant absorption rate regime was found to be zero and two respectively. The absorption rate is affected by the total ionic strength (sulphite and sulphate) in addition to the effect of pH and catalyst concentraion. The reported data were also analysed to ascertain the effect of temperature and a relationship has been proposed for prediction of the second order reaction rate constant.     

NO与乙二胺合钴离子气液反应动力学研究

用乙二胺合钴水溶液实现NO的液相催化氧化,乙二胺合钴离子作氧化催化剂,废气中残存的氧气作氧化剂,使NO的氧化和吸收同时进行。采用搅拌反应器分别在有氧和无氧时,对NO与乙二胺合钴离子气液反应动力学进行研究,结果表明当乙二胺合钴浓度大于0.02mol/L时,过程为气膜控制。氧的存在有利于NO的吸收,其分压越大,越有利于NO的氧化和脱除。气体中有氧存在时,最佳NO脱除温度为50℃,并推得吸收反应动力学方程。     

Kinetics of the dissolution of silica in aqueous sodium hydroxide solutions at high pressure and temperature

The kinetic of the reaction of sand with aqueous NaOH corresponding to the ratio SiO₂/Na₂O = 2 was studied in a pressure vessel at 220°C and 2.7 MPa. Since the kinetic curves could not be obtained directly from the experimental data, a new method is proposed to plot the entire kinetic graph from experimental data. An analytical expression of the type α = A [1 -exp(-Bt)] describes the system perfectly. The constants A and B were calculated for a silica sample having a narrow granulometric distribution (range i.e. 300–315 μm). The value of A is found to be almost constant, between 0.95 to 0.99 and B ranges from 0.03 to 0.14 when [OH-] increases from 0.5 to 12.5 mol/L. The kinetic order with respect to OH^? is equal to 0.470 + 0.013 and the kinetic constant at 220°C is 3.933 × 10^?6 g/m².s.     

Flow regimes and mass transfer in counter-current bubble columns

Counter current bubble columns have the feature that specific gas-liquid interfacial area and gas holdup are larger than those for standard and cocurrent bubble columns. In this study, three different flow regimes, churn-turbulent flow, bubble flow and bubble down-flow, have been observed in a counter-current bubble column and correlations of gas holdup and volumetric liquid-phase mass transfer coefficient have been proposed as functions of operating variables such as the superficial velocities of gas and liquid, the gas-liquid slip velocity and the liquid properties.     

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.     

旋流吸收器气液吸收传质过程研究

根据旋流吸收器中分散液相不同的运动形态建立了伴有化学反应的气液吸收传质模型,且该模型的表达形式与Danckwerts的表面更新理论一致。从模型上看,液侧传质系数kL正比于扩散系数DA和表面更新率S的平方根,这一正比关系还得到了实验结果的部分验证。根据实验结果可以看出,与其他吸收器相比,作为一种结构简单的静态设备,旋流吸收器同样可以提供一个强化传热、传质的流体力学环境。