正十二烷-水乳液吸收丙烷的传质增强作用(英文)

A one-dimensional unsteady heterogeneous parallel mass transfer (ODUHPMT) model was developed for the absorption enhancement of volatile organic compounds (VOC) by the dispersed droplets. An analytical solution for enhancement factor was obtained based on surface renewal theory and the Laplace domain transformation. The absorption rate of propane into water at dif-ferent stirring speeds with the added micro dodecane droplets was investigated experimentally in a thermostatic stirred tank. The mass transfer flux across the gas-liquid interface and the enhancement factor were measured. The results showed that the dodecane has an obvious enhancement effect on propane absorption into water, the maximum enhancement factor reached 11. The enhance-ment factor increased with increasing dodecane volume fraction and decreased with increasing stirring speed. The experiment data agreed well with the model predictions and showed high prediction accuracy of ODUHPMT model.     

臭氧吸收及反应过程的传质系数与增强因子

从双膜理论、溶质渗透理论、膜－渗透理论和表面更新理论出发，研究分析了臭氧气体在液相中的物理吸收过程传质系数，臭氧与液相中的污染物化学反应过程的吸收系数。基于双膜模型理论，推导出在不同pH值区间内伴随着臭氧与污染物化学反应过程的增强因子表达式。     

微通道内单乙醇胺水溶液吸收CO2/N2混合气的传质特性

采用高速摄像仪对400 μm×400 μm T形微通道内单乙醇胺（MEA）水溶液吸收混合气中CO₂过程的气液两相流及传质特性进行了实验研究,微通道内的压力降采用压力传感器进行测量。考察了弹状流型下气液两相流量及MEA浓度对压力降、比表面积和传质性能的影响。结果表明,当MEA浓度不变,气液两相流量增大时,压力降、比表面积、传质系数、体积传质系数和增强因子均增大,并逐渐趋于恒定。当气液流量不变,MEA浓度增大时,压力降、传质系数、体积传质系数和增强因子增大,但比表面积减小。实验条件下,压力降范围为2.00~5.23 kPa,化学吸收过程的传质系数范围为7.74×10^-4~2.97×10^-3 m·s^-1。对于伴有快速化学反应的传质过程,以Sherwood数、Reynolds数、Schmidt数及增强因子为变量建立了体积传质系数的预测关联式,平均偏差为5.09%,具有良好的预测性能。     

臭氧相关水处理工艺及其传质特征研究进展

通过对臭氧的性质和不同的反应机理介绍,回顾了臭氧在水处理中的应用发展概况,并介绍了臭氧在实际处理应用中的设备的3个关键部分,包括臭氧发生器、臭氧接触反应系统和臭氧破坏装置。在工艺设计、活化及催化方法开发的基础上,臭氧在水中传质过程的优化也是技术创新的重要环节,所以本文阐述了臭氧的传质速率影响因素,而臭氧接触器是改善传质的具体工程手段。基于人们对臭氧传质过程的理解,逐渐对臭氧接触器进行了设计和改进,本文对几种典型类型的接触器的发展历程和研究现状进行了介绍,并且对其各自的传质特征研究进行对比与总结,结果得出大流量工况下静态混合器的体积传质系数K_La高达2s^-1,而小流量工况下射流式接触器和微气泡反应器的K_La可分别达到216.15s^-1和4000s^-1,并且发现臭氧反应中仍有某些问题需要进一步研究,如气泡直径等参数可以多加注意和臭氧体系中的界面反应的进一步研究。     

水力喷射-空气旋流器中气液传质特性及其机理

对一种新型高效的气液传质设备--水力喷射-空气旋流器(WSA)的传质机理进行了研究。分别采用化学吸收法(CO₂-空气-NaOH体系)和物理吸收法(CO₂-空气-H₂O体系)测定了不同进口气速、不同液体喷射速度下的有效相界面积a和液膜传质系数k_L,并由此得到体积传质系数k_La。结果表明,由于WSA中气液间的强交互作用,a、k_L以及k_La均随进口气速和液体喷射速度增大而增大。采用量纲分析法对实验数据进行了归纳,拟合出了a、k_L和k_La随气相Reynolds数Re_g、液相Weber数We_L之间的经验公式:a=0.0024Re_g^1.25We_L^0.079,Sh_L=35.31Re_g^0.2303We_L^0.13,k_La=6.52×10^-8Re_g^1.48We_L^0.21,这些关联式能较好地预测WSA的传质性能。研究还表明,在WSA中的气液射-旋流传质体系中,传质过程符合双膜理论、表面更新理论和溶质渗透理论,但以表面更新机理为主。     

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。     

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.     

旋流气液两相强化吸收CO2的传质性能

为强化二氧化碳的吸收过程,采用一类旋流逆向气液多级接触的方式,以NaOH溶液为吸收剂,研究其与大跨度浓度CO₂(2.5%～15%)接触反应的传质性能。分别探讨了吸收剂浓度、吸收剂流量、烟气CO₂浓度、烟气流量及反应温度对气相总体积传质系数(K_ga)的定量影响。结果表明,在实验条件下,其K_ga可达(4.53×10^-5)～(9.22×10^-5)kmol·m^-3·s^-1·kPa^-1。与双级直流喷雾和单级旋流喷雾相比,旋流逆向气液多级接触能够有效强化大跨度浓度CO₂的吸收过程。K_ga随吸收剂浓度、流量和反应温度的增加而增加,随CO₂浓度增加呈现先增加后减小(CO₂浓度大于5%)的非线性关系,随气体流量增加先增加后趋于稳定。     

Mass transfer from discrete gas bubbles in a reciprocating plate column

Measurements have been made of the uptake of oxygen in water from a series of discrete bubbles released into a 5 cm diameter reciprocating plate column. The rate of increase of dissolved oxygen in the water has provided data on the average mass transfer coefficients under the following conditions; (a) free rise in the absence of plates, (b) bubbles rising through a static plate assembly and (c) bubbles rising through moderately agitated plates (frequency up to 1.28 Hz). It was found that the mass transfer coefficients were higher under condition (b) than (a), and were further increased under condition (c). The results were compared with earlier data on mass transfer to agitated bubble dispersions.     

第三分散相液滴增强气体吸收的一维非稳态非均相传质模型

A model for one-dimensional unsteady heterogeneous mass transfer was developed based on Danckwerts’ surface renewal theory in order to describe the mass transfer enhancement of absorption process for a slightly soluble gas in a gas-liquid-liquid system. The model accounts for the mass transfer resistance within the dispersed phase and the effect of emulsion viscosity on mass transfer. An analytical solution for enhancement factor was obtained by Laplace domain transformation. The absorption rates of carbon dioxide in the dodecane-in-water and castor oil-in-water systems were measured in a thermostatic reactor, and the enhancement factors were calculated at different volume fractions of dispersed phase and stirrer speeds. The model predictions agree well with the experi-mental data.     

浆料反应增强气液传质

针对液膜区存在复杂反应的浆料吸收体系,通过气体吸收对分散相颗粒溶解增强作用的研究,建立了反应浆料增强气体吸收的三区域模型.采用搅拌槽间歇吸收实验测定了不同搅拌强度和Mg(OH)₂浆料固含率时SO₂吸收速率增强.研究发现,颗粒粒径、浆料浓度、“惰性区”厚度以及待吸收气体分压等参数是影响吸收增强作用的主要参数.考虑气液近界面“惰性区”和浆料表观黏度影响后的三区域模型结果与实验结果具有良好的一致性.     

Performance of a hydro-filter — Mass transfer coefficient and gas-liquid interfacial area

An experimental study of the effect of operating conditions on the performance of a hydro-filter (marble-bed scrubber) has been conducted. The overall volumetric mass transfer coefficient, K_Ga, remains constant while the gas flow rate changes in the stable operating regions but increases sharply in the region above the loading point, corresponding to a sharp increase in the total pressure drop of the hydro-filter. Since the gas flow is turbulent and the liquid flow is laminar under the present experimental conditions, the value of K_Ga is strongly dependent on the flow conditions of the liquid and its properties, while those of the gas have less effect. The performance of a hydro-filter as a mass transfer device is shown to be superior to other types of scrubbers although its main drawback is large pressure drop.     

Mass transfer in external-loop airlift bioreactors using static mixers

The influence of static mixers on the overall gas-liquid volumetric mass transfer coefficient (K_La_L) was examined in an external-loop type airlift bioreactor (approximately 15 L volume, 1.8 m static liquid height, A_r/A_d = 0.444). The study was conducted with aqueous salt solution (0.15 kmol ? m^?3 NaCl) and with pseudoplastic solutions of carboxymethyl cellulose (0.2 ? 0.6 wt./vol. % (g/100 mL) CMC). Over a broad range of power law parameters K (10^?3 ? 10 Pa ? sⁿ) and n (0.5 ? 1.0), the presence of static mixers in the riser was found to enhance the K_La_L relative to mixer-free mode of operation. The extent of increase in K_La_L depended on the fluid “thickness”, K: the higher the K, the greater the K_La_L intensification due to static mixers. For otherwise identical conditions, the presence of static mixers improved K_La_L by 30-500%, depending on the fluid. The boost in K_La_L was associated with increased gas holdup and gas-liquid interfacial area, which arose due to bubble breakup accomplished by the static mixing elements. Potential advantages of static mixers in upgrading the performance of oxygen-limited fermentations were pointed out.     

微通道内气-液传质研究

以CO₂-H₂O为模型体系，实验考察了当量直径为667 μm的单通道和16个并行通道内的气-液传质行为.实验发现，液体表观速度增加，单通道内液侧体积传质系数明显提高;同一液体表观速度下，液侧体积传质系数随气体表观速度增加而增加;在实验数据基础上关联了液侧体积传质系数与气-液两相流参数间的关系.微通道内的液侧体积传质系数较常规尺度气-液接触设备至少高1～2个数量级.并讨论了并行微通道内气-液两相流分配特性对整体传质性能的影响，表明合理设计气、液流动分布结构，可保证微通道内优异的传质特性.     

高压脉冲放电降解水溶液中4-氯酚过程的数学模型(Ⅱ)鼓泡过程中臭氧传质增强因子E与4-氯酚浓度的关系

臭氧从气相传质到废水溶液中并与其中的有机污染物发生氧化还原反应是一个含有化学反应增强的臭氧吸收过程.在酸性废水中主要发生臭氧与4-氯酚分子和4-氯酚盐离子的反应,而臭氧在水溶液中分解形成的羟基自由基的氧化作用可以忽略.提出了由于发生化学反应而形成的臭氧传质增强因子E与废水中有机物浓度［PCP］的定量关系的表达式.     

物理场强化气液传质的研究进展

分别简述了磁场、电场、电磁场、超声场和超重力场5种物理场的作用机理,综述了这些物理场在强化蒸发、精馏和气体吸收等气液传质过程中的研究进展,同时概述了物理场强化气液传质的热力学研究进展。分析表明,物理场强化气液传质在化工、环保和节能减排等领域具有广泛的应用前景,但目前的研究大多还处于实验阶段,其机理和各种因素对强化效果影响的研究还不够深入和完善。指出今后研究热点主要包括：继续探索物理场强化传质的作用机理,拓展其应用领域,并对过程中的瓶颈问题进行技术攻关;通过实验和热力学研究两种方法对不同种类物理场强化传质效果进行比较,以确定各种物理场的适用体系。     

细颗粒增强气液传质机理及模型研究

分散细颗粒(包括分散固体颗粒和分散液滴)可以明显增强气液传质。简要叙述了目前提出的三种颗粒增强传质机理：传输作用,边界层混合作用和阻止气泡聚并作用,讨论了每种机理可能适用的体系。评述了近年来发展的有代表性的经验模型和基于不同机理的理论模型,并指出今后模型的建立应以湍流理论为桥梁,综合考虑多种传质机理。     

吸收过程的界面传质机理

Based on the method of molecular thermodynamics ,the mass transfer mechanism at gas-liquid interface is studied theoretically,and a nowe mathematical model is proposed,Using laser holographic interference technique,the hydrodynamics and mass transfer characteristics of CO2 absorption are measured,It is shown that the calculated results are in good agreement with the experimental data.     

在搅拌器中油水乳状液的气液传质

选取CO2为气相,苯/辛烷-水乳状液为液相,通过难溶气体的吸收实验,研究了在带有气体分布器的三相混合吸收装置中分散液相对气液传质的增强作用。实验结果表明,传质增强因子随能量输入的增大而增大,且分散相形成的液滴较小时,在膜内停留时间里小液滴对气液传质有增强作用。分析了"传输机理",总结出增强气液传质的本质在于分散液相通过吸收作用改变气液界面液侧组分浓度梯度,并在此基础上提出了新的描述分散液相增强气液传质的解释。     

升温型吸收式热泵吸收器强化传热传质研究进展

文章综合介绍了国内外关于升温型吸收式热泵吸收器强化传热传质的研究进展。主要从添加表面活性剂,采用高效换热管和改进吸收循环结构三个方面进行了简要的阐述,介绍了三种方式强化传质传热的原理及国内外研究的情况。最后对热管式吸收器应用的可能性做了初步的探讨。