Gas-Liquid Mass Transfer Characteristics in a Gas-Liquid-Solid Bubble Column under Elevated Pressure and Temperature

abstract The volumetric mass transfer coefficient kLa of gases (H2, CO, CO2) and mass transfer coefficient kL on liquid par-affin side were studied using the dynamic absorption method in slurry bubble ...     

合成气制二甲醚三相淤浆床反应器的数学模型研究

A mathematical model for a bubble column slurry reactor is presented for dimethyl ether synthesis from syngas. Methanol synthesis from carbon monoxide and carbon dioxide by hydrogenation and the methanol dehydration are considered as independent reactions, in which methanol, dimethyl ether and carbon dioxide are the key components. In this model, the gas phase is considered to be in plug flow and the liquid phase to be in partly back mixing with axial distribution of solid catalyst. The simulation results show that the axial dispersion of solid catalysts, the operational height of the slurry phase in the bubble column slurry reactor, and the reaction results are influenced by the reaction temperature and pressure, which are the basic data for the scale-up of reactor.     

富镧稀土镍-苯浆液体系中液相苯加氢反应动力学研究

The kinetics of liquid-phase hydrogenation of benzene in misch metal nickel-five (MlNi5) and benzene slurry system was studied by investigating the influences of the reaction temperature, pressure, alloy concentration and stirring speed on the mass transfer-reaction processes inside the slurry. The results show that the whole process is controlled by the reaction at the surface of the catalyst. The mass transfer resistance at gas-liquid interface and that from the bulk liquid phase to the surface of the catalyst particles are negligible. The apparent reaction rate is zero order for benzene concentration and first order for hydrogen concentration in the liquid phase. The kinetic model obtained fits the experimental data very well. The apparent activation energy of the hydrogen absorption reaction of MlNi5-C6H6 slurry system is 42.16 kJ.mol-1.     

Kinetics of Liquid-Phase Hydrogenation of Benzene in a Metai Hydride Slurry System Formed by MlNi_5 and Benzene

The kinetics of liquid-phase hydrogenation of benzene in misch metai nickel-five (MINi5) and benzene slurry system was studied by investigating the influences of the reaction temperature, pressure, alloy concentration and stirring speed on the mass transfer-reaction processes inside the slurry. The results show that the whole process is controlled by the reaction at the surface of the catalyst. The mass transfer resistance at gas-liquid interface and that from the bulk liquid phase to the surface of the catalyst particles are negligible. The apparent reaction rate is zero order for benzene concentration and first order for hydrogen concentration in the liquid phase. The kinetic modei obtained fits the experimental data very well. The apparent activation energy of the hydrogen absorption reaction of MINi5-C6H6 slurry system is 42.16kJ·mol-1.     

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.     

一串上升气泡周围流体的湍动特性(英文)

The turbulence behavior of gas-liquid two-phase flow plays an important role in heat transfer and mass transfer in many chemical processes. In this work, a 2D particle image velocimetry (PIV) was used to investigate the turbulent characteristic of fluid induced by a chain of bubbles rising in Newtonian and non-Newtonian fluids. The instantaneous flow field, turbulent kinetic energy (TKE) and TKE dissipation rate were measured. The results demonstrated that the TKE profiles were almost symmetrical along the column center and showed higher values in the central region of the column. The TKE was enhanced with the increase of gas flow and decrease of liquid viscosity. The maximum TKE dissipation rate appeared on both sides of the bubble chain, and increased with the increase of gas flow rate or liquid viscosity. These results provide an understanding for gas-liquid mass transfer in non-Newtonian fluids.     

Taylor流下微细颗粒增强CO2:吸收研究（英文）

The physical absorption of CO2 in water containing different types of particles was studied in a microchannel operated under Taylor flow.The maximum enhancement factors of 1.43 2.15 were measured for activated carbon (AcC) particles.The analysis shows that the enhancement effect can be attributed to the shuttle mechanism.Considering the separate contributions of mass transfer from bubble cap and liquid film,a heterogeneous enhancement model is developed.According to this model,the enhancement factors E Cap,E Film and E Ov are mainly determined by mass transfer coefficient KL (KL,Cap and KL,Film),adsorptive capacity of particles m,and coverage fraction of particles at gas-liquid interface ζ.With both effects of particle-to-interface adhesion and apparent viscosity included,the model predicts the enhancement effect of AcC particles reasonably well.     

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.     

第三组分对气液传质影响的研究

The influence of the third component on gas-liquid mass transfer was studied by use of laser holographic interferometry. Four surfactants were added respectively and experimental results show that the mlcroamount of surfactants can change obviously the concentration near the interface on bubble mass transfer process, which indicated that the third component has a significant effect on the bubble mass transfer process.     

基于单气泡非稳膜机理的相际传质模型

A gas-liquid mass transfer model based on an unsteady state film mechanism applied to a single bubble is presented. The mathematical model was solved using Laplace transform to obtain an analytical solution of concentration profile in terms of the radial position r and time t. The dynamic mass transfer flux was deduced and the influence of the bubble size was also determined. A mathematical method for deducing the average mass transfer flux directly from the Laplace transformed concentration is presented. Its accuracy is verified by comparing the numerical results with those from the indirect method. The influences of the model parameters, namely, the bubble size R, liquid film thickness δ, and the surface renewal constant s on the average mass transfer flux were investigated. The proposed model is useful for a better understanding of the mass transfer mechanism and an optimum design of gas-liquid contact equipment.     

高温高压下浆态鼓泡床气液传质系数的测定

采用气体动态吸收法,对高温高压下浆态鼓泡床中气液传质系数进行了测定,考察了系统压力、温度、表观气速及固含量等操作条件对传质系数的影响. 结果表明,在温度298~473 K、气体压力1.0~3.0 MPa、表观气速0.03~0.10 m/s、固含量0%~20%(w)的实验条件下,体积传质系数随着压力、温度及表观气速的增加而增大,随固含量的增加而减小. 同时对不同塔径的传质系数进行了比较,表明在相同的操作条件下,大塔的传质系数略高于小塔.     

高固含率三相鼓泡淤浆反应器气液传质研究及其采用两种气体分布器的比较

以空气-水-黄沙以及空气-液体石蜡-黄沙两种系统为对象，在常压下用溶氧仪研究了采用小孔式及金属烧结板两种分布器的高固含率三相淤浆反应器的气液传质特性，以及固含率和表观气速等因素对容积气液传质系数kLa的影响，最后得到采用上述两种气体分布器的高固含率三相淤浆床关于容积气-液传质系数的经验关联式。实验证明，金属烧结板具有更好的气液传质特性。     

浆态鼓泡床反应器气液传质特性的研究进展

本文总结了有关浆态鼓泡床反应器气液传质特性的研究成果。详细地阐述了主要影响因素如系统压力、温度、气体表观气速、液体性质,固体浓度及其物性等对传质特性的影响,并对浆态鼓泡床传质模型进行了归纳介绍,最后对反应器未来的研究方向进行了预测。     

三相循环流化床中的气液相界面积和传质系数

采用溶氧法测量了三相循环流化床中液相溶氧浓度的轴向分布,并按轴向扩散模型处理实验数据,优化得到气液体积传质系数kLa,同时用光纤探头测量了体系中的气含率和气泡大小分布,计算得到了气液相界面积a和气液传质系数kL,并研究了主要操作条件(表观气速、表观液速和固含率)对气液传质系数的影响规律.     

Chemical absorption in a bubble column loading concentrated slurry

Carbon dioxide was absorbed into aqueous slurries of magnesium hydroxide or calcium hydroxide particles in a bubble column at 308 K and 0.1013 MPa. The volumetric mass transfer coefficient and the effective gas-liquid interfacial area were obtained separately by these absorption experiments. It was found that the liquid-side physical mass transfer coefficient as well as the effective gas-liquid interfacial area decrease with increasing the slurry concentration and that there is an optimal point of fine reactant particle concentration where the chemical absorption rate has its maximum value. The process of gas absorption into slurry in a bubble column was formulated by a film-theory model incorporating a finite dissolution rate of solid particles. The observed absorption rates of carbon dioxide into calcium hydroxide slurries in the bubble column were successfully predicted by the proposed model.     

Mass Transfer Characteristics of Syngas Components in Slurry System at Industrial Conditions

The gas‐liquid mass transfer behavior of syngas components, H₂ and CO, has been studied in a three‐phase bubble column reactor at industrial conditions. The influences of the main operating conditions, such as temperature, pressure, superficial gas velocity and solid concentration, have been studied systematically. The volumetric liquid‐side mass transfer coefficient k_La is obtained by measuring the dissolution rate of H₂ and CO. The gas holdup and the bubble size distribution in the reactor are measured by an optical fiber technique, the specific gas‐liquid interfacial area aand the liquid‐side mass transfer coefficient k_L are calculated based on the experimental measurements. Empirical correlations are proposed to predict k_L and a values for H₂ and CO in liquid paraffin/solid particles slurry bubble column reactors.     

HYDRODYNAMIC CHARACTERISTICS AND GAS-LIQUID MASS TRANSFER IN A DRAFT TUBE SLURRY REACTOR

Fundamental characteristics of hydrodynamics and mass transfer have been measured in an air lift slurry reactor with a draft tube. The solid suspension capacity, i.e., the critical solid holdup, the gas holdup and the volumetric gas-liquid mass transfer coefficient were measured in the two draft tube columns of 0.1485 and 0.10?m in diameter. Four activated carbon beads ranging in size from 0.25 to 2.19?mm in average diameter were utilized as suspended solids in the experiments.

The critical solid holdup in the draft tube slurry column is found to be much greater than that in the conventional bubble column. An empirical correlation is developed to account for the critical solid holdup behavior in the draft tube column. The gas holdup in the draft tube column agrees well with that in the bubble column. The overall gas-liquid mass transfer coefficient, k₁awas measured by the oxygen probe method. The effect of solid holdup on k₁a is found to be negligible in the present system. The empirical equation is developed to correlate k₁a in the draft tube slurry reactor.     

Bubble size fractal dimension,gas holdup,and mass transfer in a bubble column with dual internals

As the scale of residual oil treatment increases and cleaner production improves in China, slurry bubble column reactors face many challenges and opportunities for residual oil hydrogenation technology. The internals development is critical to adapt the long-term stable operation. In this paper, the volumetric mass transfer coefficient, gas holdup and bubble size in a gas-liquid up-flow column are studied with two kinds of internals. The gas holdup and volumetric mass transfer coefficient increase by 120% and 42% when the fractal dimension of bubbles increases from 0.56 to 2.56, respectively. The enhanced mass transfer processing may improve the coke suppression ability in the slurry reactor for residual oil treatment. The results can be useful for the exploration of reacting conditions, scale-up strategies, and oil adaptability. This work is valuable for the design of reactor systems and technological processes.     

Mathematical modeling of gas-liquid mass transfer rate in bubble columns operated in the heterogeneous regime

In this paper, a multi-scale approach is followed to study gas-liquid mass transfer in bubble columns. First, a single bubble of equivalent diameter d is considered. Its morphology and its gas to liquid relative velocity are related to the bubble diameter through the use of known correlations. Then, the gas-liquid mass transfer between the bubble and the surrounding liquid is studied theoretically. An equation describing the transport of the transferred species in the viscous boundary layer around the bubble is solved. In a second step, a bubble column of 6-10 m height is studied experimentally. The gas phase in the column is characterized experimentally by means of a gammametric technique. Finally, the two studies are linked, yielding a 1D mathematical model able to predict the gas-liquid mass transfer rate in a bubble column operated in the heterogeneous regime.