Experimental determination of gas holdup and volumetric mass transfer coefficient in a jet bubbling reactor

The hydrodynamics and mass transfer characteristics of a lab-scale jet bubbling reactor(JBR) including the gas holdup, volumetric mass transfer coefficient and specific interfacial area were assessed experimentally investigating the influence of temperature, p H and superficial gas velocity. The reactor diameter and height were 11 and 30 cm,respectively. It was equipped with a single sparger, operating at atmospheric pressure, 20 and 40℃, and two p H values of 3 and 6. The height of the liquid was 23 cm, while the superficial gas velocity changed within 0.010–0.040 m·s~(-1) range. Experiments were conducted with pure oxygen as the gas phase and saturated lime solution as the liquid phase. The liquid-side volumetric mass transfer coefficient was determined under unsteady-state oxygen absorption in a saturated lime solution. The gas holdup was calculated based on the liquid height change, while the specific interfacial area was obtained by a physical method based on the bubble size distribution(BSD) in different superficial gas velocities. The results indicated that at the same temperature but different p H, the gas holdup variation was negligible, while the liquid-side volumetric mass transfer coefficient at the p H value of 6 was higher than that at the p H = 3. At a constant p H but different temperatures, the gas holdup and the liquid-side volumetric mass transfer coefficients at 40℃ were higher than that of the same at 20℃. A reasonable and appropriate estimation of the liquid-side volumetric mass transfer coefficient(kla) in a pilot-scale JBR was provided which can be applied to the design and scale-up of JBRs.     

搅拌式有限氧补偿条件下乳状液中多不饱和脂肪酸氧化模型

The oxidation of polyunsaturated fatty acids （PUFA） in emulsion with stirring and limited oxygen compensation was studied. A mathematical model of diffusion-oxidation was developed considering the mass transfer resistance of a gas-liquid boundary, the resistance of the boundary layer from the emulsifier membrane, and the autocatalytic-type autoxidation reaction of PUFA. The dynamic mass transfer coefficient of the emulsifier membrane, k0, was introduced. The model was verified by comparing the predictions of the model with the experi- mental data. The results indicated that the model was in good agreement with the oxygen diffusion and linoleic acid oxidation in the emulsion, and showed good applicability in the prediction of the effect of the emulsifier type on the oxidation of PUFA in the emulsion. It indicated that the oxidation of PUFA in emulsions, with stirring and limited oxygen compensation from the atmosphere, was controlled mostly by mass transfer resistance from the emulsifier membrane.     

几何结构对滤压式电解槽内部传质的影响

Effect of configuration （structure of electrode, interelectrode gap, positions of inlet and outlet, volume of the cell and additional nets） on mass transfer characteristic of a filter-press type electrochemical cell has been studied. The mass transfer coefficients on the electrodes were obtained by using the well-known technique based on the determination of limiting diffusion current. It is found that mass transfer coefficients with mesh electrode are greater than that of with plate electrode. Mass transfer coefficient is decreased with interelectrode gap. While interelectrode gap achieved a certain value （7 ram）, mass transfer coefficient is steady, no more declining. Mass transfer characteristic for different positions of inlet and outlet are different and dimensionless number groups correlated equations are obtained by experiment. Mass transfer characteristic is the best when inlet located on the top and outlet on the bottom of the cell respectively. While magnified the volume of the cell to eight times, mass transfer characteristic changes little. Mass transfer characteristic without nets is lower than that of with additional nets in the exit region, but higher than that of with additional nets in the entry region.     

非理想多组分混合物中质量传递过程基于Maxwell-Stefan扩散理论的建模及数值分析(英文)

The Intalox metal tower packing was used to simulate an industrial relevant extractive distillation column for purifying azeotropic multicomponent mixture.In order to explain the inconsistencies in the modeling of transfer process in nonideal multicomponent distillation column,a method was developed with equilibrium stage models(EQ)and non-equilibrium model(NEQ)incorporated with Maxwell-Stefan diffusion equations in the framework of AspenONE  simulator.Dortmund Modified UNIFAC(UNIFAC-DMD)thermodynamic model was employed to estimate activity coefficients.In addition,to understand the reason for the diffusion against driving force and the different results by EQ and NEQ models,explicit investigations were made on diffusion coefficients, component Murphree efficiency and mass transfer coefficients.The results provide valuable information for basic design and applications associated with extractive distillation.     

Density,refractive index and liquid–liquid equilibrium data of polyethylene glycol 3000 + potassium formate + water at different pH values

New liquid–liquid equilibrium data for polyethylene glycol(PEG) 3000 + CHO_2K + H_2O systems were measured at 298.15 K and pH values of 7.95, 8.40 and 9.98. It was found that an increase in pH caused the binodal curve to be displaced downward and the two-phase region to expand. Accordingly, the binodal curve was adjusted to the Pirdashti equation and the tie-line compositions were correlated using the Othmer–Tobias, Bancroft and Hand equations. The study measured the refractive index and densities of several homogeneous binary and ternary solutions. The solutions were used for calibration within a range of 0% to 30% of the mass of the PEG and potassium formate. The density and refractive index data show a linear variation with the mass fraction of the polymer and the salt. The effect of pH on the binodal, tie-line lengths(TLL) and slope of the tie-line(STL) in the systems was examined. It was found that an increase in pH increased the TLL and decreased the STL. It was observed that the density of the aqueous two-phase system was influenced by the TLL. The difference in density between phases(Δρ) increased as the TLL and pH increased. It was found that the TLL and Δρ showed a linear relationship. The effective excluded volume(EEV) of the PEG was obtained and it was found that EEV also increased as the pH increased.     

Mass transfer area in a multi-stage high-speed disperser with split packing

In this study, the mean droplet diameter in the cavity zone and the total mass transfer area of a multi-stage highspeed disperser(HSD) reactor with different packing combinations were measured and evaluated. The effects of rotational speed and packing radius, as well as the packing ring radius and numbers, on the mean droplet diameter and the total mass transfer area were evaluated. A model was established to calculate the mass transfer area in the cavity zone in the HSD reactor, and it was found that the packings contribute 61%–82% of the total mass transfer area. A correlation for predicting the mass transfer area in the packing zone was regressed by the dimensionless analysis method. An enhancement factor based on the mass transfer area in the packing zone was proposed to evaluate the effect of packing combination on mass transfer area. Two optimum packing combinations were proposed in consideration of the mean droplet diameter and the enhancement factor.     

Desorption of VOC from polymer adsorbent in multistage fluidized bed

The desorption process of volatile organic compounds(VOC) from a polymer adsorbent in counter-current multistage fluidized bed was studied. And a mathematical model considering the mass transfer dynamics was developed, which was validated from experiment data. The gaseous ethyl acetate mass transfer was discussed, and the limiting step is the intraparticle mass transfer of the desorption process. The value of intraparticle mass transfer coefficient is between 1.85 × 10~(-6) and 1.38 × 10~(-5) m·s~(-1) under temperature of 100–160 °C. Experiments under different operating conditions were carried out. The effects of operating conditions such as gas–solid flow ratio,gas inlet temperature and total stage number of multistage fluidized bed on outlet VOCs concentration and desorption efficiency were discussed. The maximum outlet VOCs concentration and corresponding desorption efficiency of the multistage fluidized bed desorber was calculated under different gas inlet temperatures and total stage numbers.     

用于污水处理的柔性纤维膜反应器氧传递及动力学研究

A flexible fibre biofilm reactor was developed for treatment of organic wastewaters. The hydrodynamic characteristics and mass transfer coefficients of oxygen were studied and compared with those of the conventional activated sludge processes. Tracer experiments were performed to obtain the residence time distributions of the reactors. The results indicated that both reactors could be treated as mixed flow reactors. The effects of flow rates of water and air on the overall mass transfer coefficient of oxygen were investigated, and the correlations between the mass transfer coefficient and the ratio of flow rates were obtained. Compared to the conventional activated sludge reactor, the mass transfer coefficients in the flexible fibre reactor were similar to but slightly lower, and less sensitive to the variation in the ratio of flow rates. It indicated that the fibre packing in the reactor hindered the oxygen transfer to some extent.     

空气与水逆流直接接触热质交换过程模型计算及分析

Based on reasonable model hypotheses and the energy analysis of heat and mass transfer of air and water in a direct contact counter flow, a set of general equations that can describe the internal relationship between the state parameters of air and water and dimensionless parameters of transfer process are given. A method utilizing MATLAB to solve these general equations is also proposed. Calculations and analysis with the model of a cooling- dehumidifying process give a consistent result with that of previous experiment. A new method for designing equipment such as evaporating cooler and cooling tower, and for analyzing experiment data of heat and mass transfer of air and water in a direct contact counter flow can be derived from this study.     

MASS TRANSFER IN DRIPPING PLATE COLUMN FOR NON-NEWTONIAN FLUIDS

In this paper, the mass transfer for non-Newtonian liquid has been studied in a dripping plate column fitted with perforated trays. The rate of evaporation of polymer solution in the column was measured and correlated. It was found that temperature, presure, mass flow rate and the non-Newtonian behavior of the solution are the significant factors having effects on mass transfer.     

散装填料塔设计及核算软件开发

在查阅了大量国内外文献资料的基础上,研究了填料塔的流体力学计算模型以及其他一些参数的计算模型。并利用Microsoft Visual Basic6．0开发了一套可适用于拉西环、鲍尔环、阶梯环、弧鞍、矩鞍、金属环矩鞍等散装填料塔设计及核算软件。本文主要通过金属阶梯环介绍了散装填料塔设计及核算软件的具体开发过程,并以具体实例作为软件的考核评估。     

一种新型单体填料的气液接触性能

本文试验研究了新近研制的组合环 (UR)单体填料的流体力学和传质性能 ,并对其泛点和压降进行了关联。结果表明 ,这种填料具有通量大、阻力小和传质效率高的优点 ,可望代替鲍尔环、环矩鞍等常用填料。     

QH-2型扁环填料的流体力学和传质性能研究

在内径60 0填料塔中 ,用空气 富氧水系统对3 8和5 0QH 2型扁环填料的流体力学和传质性能进行了研究 ,得出计算其压降、液泛气速和传质单元高度的关联式。并与3 8鲍尔环、5 0鲍尔环和3 8环矩鞍填料进行了比较 ,结果表明 ,QH 2型扁环具有优良的流体力学和传质特性。     

Effective interfacial area and liquid and gas side mass transfer coefficients in a packed column

The theory of gas absorption accompanied by fast pseudo-mth order reaction was used to obtain values of effective interfacial area in a packed column, irrigated with aqueous solutions and provided with 1 in. ceramic Raschig rings, 1 in. P.V.C. Raschig rings, 1 in. ceramic Intalox saddles, 1 in. polypropylene Intalox saddles, 1 in. stainless steel Pall rings and 1 in. polypropylene Pall rings. The values of liquid side mass transfer coefficient were obtained by physical absorption of carbon dioxide in water. In addition, the values of gas side mass transfer coefficient for a range of gas and liquid flow rates were obtained.     

Comparative performance of packings for gas-liquid contacting columns

The performances of Raschig rings, Pall rings, Intalox saddles, and Berl saddles were compared in respect to pressure drop and mass transfer efficiency, in a 6-in. I. D. tower having a packed height of 4-ft., over a matrix of gas and liquid flowrates representing the irrigating and loading flow regimes. The mass transfer experiments were conducted employing a gas absorption system in which both phase films control the overall rate of mass transfer, an improvement in terms of industrial applicability over many previous studies. The Berl saddles were observed to yield the lowest pressure drops of the four. The Intalox saddles yielded the highest overall mass transfer coefficients, followed closely by the Berl saddles and Raschig rings.     

Mass transfer in packed liquid—liquid extraction columns

The mass transfer characteristics of 3·5, 7·3, 10·16 and 15·6 cm i.d. packed liquid—liquid extraction columns were studied with a variety of packings such as, $\text{3}\text{8}$, $\text{1}\text{2}$ and 1 in. ceramic Raschig rings, $\text{5}\text{8}$ in. stainless steel Raschig rings, $\text{1}\text{2}$ and 1 in. ceramic Intalox saddles, $\text{5}\text{8}$ and 1 in. stainless steel Pall rings, and 1 in. polypropylene Intalox saddles and Pall rings. Some data were also obtained for the co-current mode of operation (up-flow) for packed columns, and without packings. In addition the mass transfer charactersitics of a packed extraction column with film flow were studied.The theory of extraction accompanied by a fast pseudo-first order reaction was employed to measure the values of effective interfacial area. The values of overall (continuous and/or dispersed phase) mass transfer coefficient were measured by the Colburn—Welsh technique. A fairly wide range of physical properties of the two phases was covered.The values of overall (continuous phase) mass transfer coefficient and effective interfacial area for new packings such as Pall rings and Intalox saddles, under otherwise similar conditions, are only about 10 and 35 per cent higher, respectively, than those provided by the conventional packings of the same nominal size. However, the flooding velocities for the newer packings are as much as 80 per cent higher than those for the conventional packings of the same nominal size.     

新型的板网矩鞍填料的流体力学特性研究

作者创制的φ25mm新型板网矩鞍填料,其流体力学特性研究表明,该填料具有压强低、泛点气速高和处理量大等优点,优于同尺寸金属鲍尔环和阶梯环.     

Vapour- and liquid-side volumetric mass transfer coefficients measured in distillation column. Comparison with data calculated from absorption correlations

Volumetric mass transfer coefficients in liquid and vapour phases in distillation column were measured by the method consisting of a fitting of the concentration profile of liquid phase along the column obtained by the integration of a differential model to the experimental one. The mathematical model of distillation process includes mass and energy balances and the heat and mass transfer equations. The film model flux expressions with the convective transport contributions have been considered in the transfer equations. Vapour and liquid phases are supposed to be at their saturated temperatures along the column. Effect of changes of phase flows and physical properties of phases on the mass transfer coefficients along the column and non-ideal thermodynamic behaviour of the liquid phase have been taken into account. The concentration profiles of liquid phase are measured in the binary distillation of the ethanol-water and methanol-ethanol systems at total reflux on metal Pall Rings and Intalox saddles 25 mm in the column with diameter of 150 mm. The distillation mass transfer coefficients obtained by the fitting procedure are compared with those calculated from absorption data using Onda's, Billet's and Linek's correlations. The distillation heat transfer coefficients calculated from the model assuming saturated temperatures in both phases are compared with those calculated from the Chilton-Colburn and penetration model analogy between mass and heat transfer. The results have confirmed an agreement neither between distillation and from absorption correlations calculated mass transfer coefficients nor between analogy and from enthalpy balance calculated heat transfer coefficients. Also the concentration profiles obtained by the integration of the differential model of the distillation column using the coefficients from absorption correlation have differed from the experimental profiles considerably.     

Raschig Super‐Ring Operating Characteristics in Unpulsed Liquid‐Liquid Extraction Columns

Raschig Super‐Rings are well‐established in the field of rectification and absorption. Instead, the efficiency of these packings in liquid‐liquid extraction was not investigated till now. The application of Raschig Super‐Ring No. 0.3 and Raschig Super‐Ring No. 1 packings in unpulsed liquid‐liquid extraction columns of diameters DN 80 and DN 150 is investigated with respect to flooding point and efficiency. As a comparative study, 15‐mm and 25‐mm Pall‐Ring packings are used. The hydrodynamic studies indicate that the Raschig Super‐Ring offers a 9–10 % higher load capacity compared to the Pall‐Rings. In addition, the mass transport investigations performed using the test system toluene/acetone/water reveal that the height of transfer units (HTU) for the Raschig Super‐Ring No. 0.3 is higher than for the comparable 15‐mm Pall‐Ring. On average, the achieved difference of the HTU unit is 0.26 m.     

填料塔内直接接触冷凝实验研究

本文提出了在乱堆填料塔内、描述汽液直接接触冷凝过程的双液膜模型。在内径为250mm的钢塔内,测算了公称尺寸为25mm的聚丙烯矩鞍与阶梯环及16,25mm瓷矩鞍四种填料,在压力1.42～1.90bar范围内、R-11蒸汽与水逆流直接接触凝结平均体积传热系数。根据塔内轴向温度场变化,测定了100cm填充高度中的有效凝结段长度。实验数据依双液膜模型。关联成半理论——半经验准则方程形式。拟合偏差±15％。