超重力精馏过程传热传质机理研究

以波纹丝网为填料,以立式逆流超重力装置为主要设备,应用热量传递与质量传递理论,建立了超重力精馏装置内气、液温度分布的数学模型;以转子内半径29 mm、外半径63 mm、轴向高度32mm、内置直径1.6 mm、空隙率0.85、比表面积1 750 m2/m3的波纹丝网为填料的超重力装置为精馏设备,以乙醇-水为物系,在常压、室温进料、原料流量20 L/h、原料乙醇质量分数20%、转速800 r/min-1、回流比为1的操作条件下,对模型进行了检验。精馏段气相温度的实测值与模型计算值的偏差为1.41%,提馏段外半径的实测值与模型计算值的偏差为3.87%。     

气-液-液萃取传质效率的研究

在液-液萃取过程中,提高分散相的表面更新速率可有效提高萃取的传质效率.研究发现,在萃取过程中使用气体搅拌可以增加液液之间的接触面积,促进液相内的湍动和循环.据此,本文在气-液-液萃取条件下对不同填料的传质性能进行了测定.实验表明,通入气相后分散相液滴呈现稳定的“油包气”空心状态,这种结构大大降低了分散相液滴的传质层厚度,减小了传质距离,极大地强化传质效率.在适宜气速下,气-液-液萃取效率较传统萃取效率提高20％～40％.通过与散装填料对比,发现规整填料更利于强化萃取效果,传质效率提高约50％.     

膜法供氧的传质过程研究

膜法供氧是一新兴好氧生物处理水体污染的高效供氧技术。为了更好地解释气相操作压力对供氧过程中体积传质系数的影响,对前人建立的膜法供氧的传质理论模型进行了改进,考虑了微气泡、操作压力等因素的影响;同时,建立了膜供氧装置,考察了不同气相操作压力时的供氧效果,尤其是气液二相操作压力对模型中体积传质系数的影响。结果表明,膜供氧过程的传质机理随气相操作压力的变化而不同,总体积传质系数随气相操作压力的提高呈先缓慢增高而后急剧上升最后急剧下降的三阶段变化趋势。     

液液界面传质过程的激光干涉法研究

为了研究液液传质过程的界面现象及传质特征,采用实时激光全息干涉技术,根据不同初始浓度时乙醇通过油水界面传质过程的全息干涉图,得到了传质过程水相侧的浓度分布,据此求出了近界面浓度和基于浓度的传质系数,并关联了近界面浓度与主体相溶质浓度的关系。建立了界面能随溶质浓度改变的函数关系,计算结果与实验值吻合良好。研究结果表明,液液静止界面传质过程基本符合双膜理论,溶质的加入能改变界面性能,传质过程界面处于非平衡状态。     

生产工艺参数对聚醋酸乙烯酯乳液黏度的影响研究

考查了聚醋酸乙烯酯乳液生产工艺参数如醋酸乙烯酯单体活性度、保护胶体聚乙烯醇、引发剂以及乳化剂用量、搅拌速度、pH值调节剂和反应温度对乳液黏度的影响.实验结果表明,要制备目标使用黏度(25℃)为4 000 mPa·s左右的聚醋酸乙烯酯乳液,其优化的配方和工艺条件为:单体活性度600 s;聚乙烯醇缩醛化改性;引发剂用量为单体的0.2%(其中前期种子聚合的加入量为总量的20%);乳化剂用量为单体的1.6%;聚合反应初期和后期都需加入pH值调节剂;搅拌线速度为0.6 m/s;种子聚合温度65℃,反应温度75℃.     

钕系顺丁橡胶-甲苯溶液的表观黏度及流动参数

以中国石油独山子石化公司研究院中试装置生产的钕系顺丁橡胶( NdBR)为胶样,以甲苯为溶剂,制备了NdBR -甲苯溶液,研究了胶液的质量分数(C)、温度(T)和剪切速率(γ)3个因素对胶液表观黏度(η)的影响,并采用外推法考察了胶液的流体常数(a)和零剪切黏度(η0).结果表明,3个因素对η的影响顺序为:C(≥)y≈T...     

Heat and mass transfer in monolithic honeycomb catalysts—I.

The body of information presented in this paper is directed to engineers and scientists concerned with control of automobile emissions and exhaust gases from some industrial processes. The differential equations describing heat and mass transfer in a monolithic honeycomb catalyst are developed. Following transport mechanism is considered: convective heat and mass transfer in the holes of the structure, longitudinal thermal conductivity of the honeycomb support and gas-to-solid heat and mass transfer. The magnitudes of governing parameters for monolithic modules in use are discussed. Two methods for the numerical solution of a system of coupled, nonlinear ordinary differential equations with split boundary conditions are proposed. The first method-shooting procedure can be used only for problems with low values of Peclet number. For high values of Peclet number finite-difference approach along with the Newton-Raphson algorithm is suggested. It is shown that two stable steady states exist in certain regions of operation of a particular monolithic structure. The all-metal monolithic supports are more prone to multiplicity of steady states than the ceramic ones. For ceramic supports the two-phase piston-flow model is sufficiently accurate.     

表面张力对传质过程的影响

表面张力对传质过程的影响主要是影响传质界面积,当物系为正物系时,对板式塔有较小较稳定的汽泡,对填料塔和湿壁塔,有较稳定的液膜,结果使二者均有较大的传质界面积,传质效果较好;负物系的情况相反。当液体混合物的平均表面张力较小时,也有利于形成较小较稳定的汽泡,从而有利于传质。表面张力对传质过程的影响机理相当复杂,这方面的研究工作有待深入开展。     

鼓泡塔内热质同时传递过程研究

在鼓泡塔内的热模实验表明,塔内存在一个适宜的液汽比。比较鼓泡塔和填料塔得出,完成相近的传热和传质负荷,鼓泡塔传热传质效率不及填料塔、鼓泡塔的蒸汽利用程度比填料塔高;鼓泡塔的操作弹性、设备堵塞等问题优于填料塔。故鼓泡塔亦是较理想的热水塔塔型,可用于水煤浆气化系统。     

Heat and mass transfer on the wavy film absorption process

Recently the absorption heat pumps and chillers have received considerable attention due to their low electricity consumption rate. Therefore, it is important to understand the transport mechanism of an absorption process. In this paper, a numerical study of the heat and mass transfer taking place on a wavy falling liquid film of an absorption process is presented. With previously solved periodic wavy film flow solutions, the finite difference method is employed to solve the heat and mass transport equations. The numerical solution indicates that the waves significantly increase the transport rates. A comparison of the transfer rates of the wavy film to that of the smooth film is presented to show that the mass transfer rate can be doubled.     

Correlation between mass transfer and operating parameters in zinc electrowinning

The effects of antimony additions, acid concentration, and current density on mass transfer and deposition morphology were examined. The mass transfer coefficients of zinc were calculated using a codeposition method with cadmium as a tracer. The experiments were carried out for vertical electrodes in a Hull cell. The results indicate that the mass transfer coefficients increase with increasing antimony additions, acid concentration, and current density. Zinc dissolution is more severe at low current density and higher antimony levels than at higher current densities and lower antimony levels. A mass transfer correlation for pure zinc electrolyte data is $$Sh = 12.47\left( {ReSc} \right)^{0.45} $$ whereSh, Re, andSc are the Sherwood, Reynolds, and Schmidt numbers, respectively. The correlation fits very well with the experimental data. A correlation for electrolytes containing antimony was also obtained and has an exponent of 0.42. The correlations cover a wide range of operating parameters and provide a fast quantitative estimation of the change in mass transfer in zinc electrowinning.     

液体黏度对CO_2吸收塔规整填料传质性能的影响

为了有效提高CO2捕集过程中的传质效率,需要测量规整填料在不同溶液体系下的传质性能。在氢氧化钠水溶液-空气-CO2体系的基础上,通过向液相加入甘油的方法,使液相黏度由0.001 Pa·s最高增加至0.002 5 Pa·s。这一改变使实验体系更加接近真实的CO2吸收体系,如乙醇胺、二乙醇胺水溶液等。利用此改进后的体系,在直径为200 mm、填料高度为800 mm的填料塔中,测量了波纹倾角为45°、齿顶角为90°、波纹峰高为9 mm的金属板波纹规整填料在不同操作条件下的有效传质面积。实验结果显示:黏度的改变直接影响到填料在同等条件下的有效传质面积。在实验的基础上,将黏度参数关联到新的关联式中,可以有效预测在不同黏度体系下的有效传质面积,计算值与实验值吻合较好。     

密封式错流旋转填料床气膜控制传质过程研究

在密封式错流旋转填料床中,利用浓度为0.926 mol/L的NaOH溶液吸收空气中体积分数为0.5%—1%的CO2气体,对气膜控制过程传质性能进行了研究。实验表明:密封式错流旋转填料床CO2的吸收率随气体流量的增大而减小,在低转速下随旋转填料床的转速增大气体吸收率上升较快,高转速时影响变小;转速大于1 000 r/min情况下,CO2的吸收率随液量的增大而上升,转速小于1 000 r/min情况下,CO2的吸收率随液量增大而变小。建立了密封式错流旋转填料床气膜控制过程的气体吸收模型,经验证实验结果与模型计算结果吻合较好。     

Effects of mass transfer on simulated moving bed process

The objective of this work is to present the optimization of SMB operating conditions under the fixed performance of high purity (over 99%), which takes mass transfer effect into account. The parameters for the numerical calculation were used by our previous work [1,2] of binary separation of aqueous mixture of glucose and fructose. The equilibrium isotherm was linear and the mass transfer was described by LDF approximation. The single parameter of Stanton number was used for the mass transfer effect. The result of our work was compared with that of the triangle theory [3]. For the sake of this procedure, an analytical solution for a TMB mode was suggested and compared with the simulated result of SMB mode. The advantage of the TMB model with the mass transfer effect was the rapid determination of the flow conditions of each zone for the required purity of extract and raffinate.     

Hydrodynamic behaviour and oxygen transfer rate in a pilot plant fermenter. I. Influence of viscosity

The effects of varying impeller speed, aeration rate and viscosity on mixing time, power consumption and oxygen transfer rate were studied in the pilot plant fermenter. The rheological behaviour of erythromycin fermentation broth was simulated by colloidal starch solutions at apparent viscosities of 0.02–0.20 Pa/s. The volumetric oxygen transfer rate coefficient was determined by the sulphite and static method. The experimental results showed that at low viscosities, up to of 0.02 Pa/s, the suitable range of impeller speed is 250–300 min^?1 at aeration rate 0.6–0.8 VVM from the point of view of power input (2.6–2.8 kW/m³) and sufficient coefficient K_La (160–200 h^?1). At viscosities higher than 0.02 Pa/s (with pseudoplastical character) the suitable range of impeller speed is 300–350 min^?1 at the same aeration rate. Then the power input for mixing is 3.0–3.5 kW/m³ and the coefficient K_La ～ 50 h^?1.     

膜吸收法回收烟气CO_2传质过程研究

在0.1~2 m~3/h模拟烟气膜吸收处理装置上,进行了膜吸收法捕集CO_2传质过程研究。在其他条件不变的情况下,考察了气体流量、吸收液流量和吸收液浓度对传质过程的影响;结合吸收溶剂的化学反应增强因子及中空膜本身的参数,建立了膜吸收过程的传质计算模型。试验结果表明:在有化学吸收推动的膜吸收传质过程中,膜吸收的传质阻力集中在气相和膜的界面,而反应发生在液膜界面,所建立的计算模型也很好地反映了这一现象。通过建立传质模型,可以推算出膜表面吸收传质过程,从而为膜吸收过程的工业放大提供支撑。     

Influence from process parameters on void formation in resin transfer molding

The influence of different process variables on the void content in resin transfer modling (RTM) has been investigated experimentally. The moldings were made in a flat mold filled by a parallel flow from one edge of the laminate to the other. The viods were found concentrated in a narrow region close to the ventilation side of the laminate. The void volume fraction in this region was almost constant and dropped over a short distance to basically no voids in the rest of the laminate. Micrographs from cross sections in different directions revealed that the voids were of two different types, long cylinderical bubbles inside the fiber bundles. An efficient way of reducing the void content was to use vacuum assistance during mold filling. This technique was benefical both for the magnitude of the void content and for the extent of the void region. The void content with the highest level of vacuum assistance (≈︁ 1 kPa absolute pressure), was practically negligible. Strong indications for void generation by mechanical entrapment at the flow front was found. The lowering of the void content with vacuum assistance can be interpreted as aresult of compression of voids when the vacuum is released and a higher mobility of voids created at a lower pressure.     

Estimation of mass transfer velocity based on measured turbulence parameters

The aim of this study is to quantify the mass transfer velocity using turbulence parameters from simultaneous measurements of oxygen concentration fields and velocity fields. The surface divergence model was considered in more detail, using data obtained for the lower range of β (surface divergence). It is shown that the existing models that use the divergence concept furnish good predictions for the transfer velocity also for low values of β, in the range of this study. Additionally, traditional conceptual models, such as the film model, the penetration‐renewal model, and the large eddy model, were tested using the simultaneous information of concentration and velocity fields. It is shown that the film and the surface divergence models predicted the mass transfer velocity for all the range of the equipment Reynolds number used here. The velocity measurements showed viscosity effects close to the surface, which indicates that the surface was contaminated with some surfactant. Considering the results, this contamination can be considered slight for the mass transfer predictions. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Study on the transient interfacial tension in a microfluidic droplet formation coupling interphase mass transfer process

In two‐phase dispersion coupling interphase mass transfer process, the variation of interfacial tension is an important factor affecting the dispersion. In this study, we described a microfluidic method for the determination of the transient interfacial tension (TIFT). The method has the advantage of determining TIFT during the whole droplet formation process, rather than only at the rupture moment as reported in previous studies. The TIFTs of several systems were determined. In certain systems, it has been found that the droplet size decreased with the increase of the dispersed phase flow rate, which is obviously different from the constant interfacial tension system. It has also been found that TIFT was mainly affected by two‐phase flow rates, solute type and concentration, and droplet size. A semiempirical equation was finally established to predict TIFT. It has the potential to be used in a variety of industrial equipment with dispersion–mass transfer coupling process. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2542–2549, 2016     

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。