旋转填充床有效比相界面积的研究

旋转填充床(Rotating Packed Bed简称RPB)是一种新型的传质设备，为研究其传质性能，笔者在旋转填充床上用不同的填料以氢氧化钠水溶液吸收二氧化碳进行快速拟一级化学反应来测定有效比相界面积，研究了旋转填充床选用不同填料时的有效比相界面积与旋转填充床的各种操作条件之间的关系，实验表明随着RPB转速的增大，有效比相界面积增大；随着操作液量增大，有效比相界面积增大。而且由于其独特的操作特性以笔者自制的打孔碟片填料的有效比相界面积为最大。     

搅拌槽内的气液分散和传质特性

本文分两部分。分别探讨鼓泡搅拌槽内的气液分散和传质特性。在本文(Ⅰ)中。应用光纤和微机技术建立了光衰减法测定相界面积的实验装置,测定了鼓泡搅拌槽内的相界面积、气含率和传质系数。以静止、无限液体中单个气泡上升运动为基础,结合各相同性湍流理论,推导了湍流液体中单个气泡上升速度公式,通过恰当假设,应用于气泡群,得到了槽内气含率、相界面积和操作变数之间的关系,和实验结果比较,两者基本一致。在本文(Ⅱ)中,根据表面更新和湍流扩散的概念,推导了更新颇率、湍流扩散参数和操作变数之间的关系,和气含率、相界面积的公式相结合,计算了传质系数kL,和测定的实验结果比较,符合良好。     

气升式环流反应器

本文系统研究了气液环流内循环反应器的气含率εg、液体循环次数、液体循环倍率、体积传质系数k_L a、比相界面积a、液相传质系数k_L和液体停留时间分布等问题,并用多釜串联模型参数N描述了该反应器在不同条件下液体的流动状况。     

气-液和液-液传质设备中相界面积的测定和计算(二)

<正> 二、化学吸收法测定气-液相界面积化学吸收法就是利用液体吸收剂与气体溶质之间的拟n 级快速不可逆反应,测定气体溶质的吸收速率以及溶质和吸收剂的浓度,并根据相应的吸收速率表达式求得液相体积传质系数K_La 值或气相体积传质系数K_Ga 值,然后通过一定的数学处理,将K_La或K_Ga 分离得到真实传质系数K_L 或K_G 和比相界面积a 的值。在化学吸收法测定气-液相界面积中常用的化学吸收系统及其反应     

化学吸收法测定多级离心雾化旋转填料床有效相界面积及体积传质系数

对多级离心雾化旋转填料床的有效相界表面积及体积传质系数,用化学吸收法做了实验测量。实验结果表明：多级离心雾化旋转填料床不仅具有超低气阻,而且可产生良好的喷雾扩展相界面积的作用,体积传质系数比传统填料塔提高一个数量级,接近气液逆流型旋转填料床。多级离心雾化旋转填料床开拓了新的气液传热传质途径。     

化学吸收法测定多级离心雾化旋转填料床有效相界面积及体 …

对多级离心雾化旋转填料床的有效相界表面积及体积传质系数，用化学吸附法收了实验测量，实验结果表明：多级离心雾化填料床不仅具有超低气阻，而且可产生良好的喷雾扩展相界面积的作用，体积传质九比传统填料塔提高一个数量级，接近气流逆充型转填料床。     

气液固微型流化床的气液传质系数

气液固微型流化床兼具微流控系统和宏观流化床的优点,具有潜在的工业应用价值,但是,其应用基础研究十分缺乏。采用床径为1.6、2.0、2.4 mm的微型流化床,平均粒径为160、190、220 μm的玻璃珠,以NaOH水溶液吸收CO₂气体为气液传质研究物系,在三相流动研究的基础上,考察了表观气速、表观液速、床径、粒径等对三相微型流化床气液体积传质系数的影响。结果表明：给定其他条件,增加表观气速和表观液速,均使气液体积传质系数增大;表观气速主要改变气含率和气液相界面积,而表观液速主要改变液相传质系数;床径减小,气液相界面积和气液体积传质系数都有所增加;在气液两相微型鼓泡塔中加入固体颗粒,形成三相分散鼓泡流型,当其固含率在0.15~0.30范围内,可显著增强气液传质,其气液体积传质系数是气液微鼓泡塔的1.1~1.5倍;与宏观流化床相比,相同条件下微型床的相界面积为它的5~10倍,是微型流化床具有更大体积传质系数的主要影响因素。     

气液固微型流化床的气液传质系数

气液固微型流化床兼具微流控系统和宏观流化床的优点,具有潜在的工业应用价值,但是,其应用基础研究十分缺乏。采用床径为1.6、2.0、2.4 mm的微型流化床,平均粒径为160、190、220 μm的玻璃珠,以NaOH水溶液吸收CO₂气体为气液传质研究物系,在三相流动研究的基础上,考察了表观气速、表观液速、床径、粒径等对三相微型流化床气液体积传质系数的影响。结果表明：给定其他条件,增加表观气速和表观液速,均使气液体积传质系数增大;表观气速主要改变气含率和气液相界面积,而表观液速主要改变液相传质系数;床径减小,气液相界面积和气液体积传质系数都有所增加;在气液两相微型鼓泡塔中加入固体颗粒,形成三相分散鼓泡流型,当其固含率在0.15~0.30范围内,可显著增强气液传质,其气液体积传质系数是气液微鼓泡塔的1.1~1.5倍;与宏观流化床相比,相同条件下微型床的相界面积为它的5~10倍,是微型流化床具有更大体积传质系数的主要影响因素。     

填料塔高度、端点及溶质浓度对传质系数影响

在填料塔中,一种中间采样技术已经用来研究水吸收氨的传质。这项技术不仅能精确的研究整个塔的一般传质,而且还能研究溶质、端点、高度影响。所得到的一般传质关系式可用于预测相同溶液和相同几何形状填料系统的性能。改变表面张力虽然没发现溶质影响,但会使传质减弱,因为影响传质的有效相界面积改变了。在填料塔下部的底板区域进行的气体吸收会引起一定的端点影响。改变距塔顶部0～(10～12)z/d 处的液相分布会产生高度影响。当液体从塔顶向下喷流时由于液体分布不良,相界面积变化,引起传质速率降低,直至高度为 z/d=10～12左右处,液体分布变为常量,此时传质速率也趋于一个恒值。就填料塔所有这些特性而言,影响传质的主要变量是液体分布,通过液体分布影响填料的相界面积。     

化学法测定转鼓反应器气液相界面积

采用化学法对转鼓反应器内气液相界面积进行测定,考察了转鼓表面超重力因子、气体通量、液体通量对转鼓反应器内气液相界面积的影响。结果表明:反应器气液相界面积分别随超重力因子和液体通量的增大,先增大后趋于平缓;随着气体通量的增加,转鼓反应器内气液相界面积先增大然后减小;在液体通量为5 m3/(m2.h)、转鼓表面超重力因子为77、气体通量为398 m3/(m2.h)时,可获得最大的气液相界面积为0.058 m2,比相界面积为137 m2/m3,约为鼓泡反应器比相界面积的6.8倍。研究结果为转鼓反应器的优化设计和操作条件的选择提供了依据。     

滴流床小颗粒催化剂滴流区和脉动流区传质的研究

本文研究了滴流床小颗粒催化剂在滴流区和脉动流区的气相容积传质系数k_Gα,气液接触有效界面积“α”和脉动流形成时分散气泡的平均直径d_b。实验表明:不同流区的传质与流型和流动介质的能量损失有关。强化传质会增加流动介质的能量消耗及减小催化剂粒度。     

Gas-liquid flow mass transfer in a T-shape microreactor stimulated with 1.7 MHz ultrasound waves

This paper describes the application of ultrasound waves on hydrodynamics and mass transfer characteristics in the gas-liquid flow in a T-shape microreactor with a diameter of 800 μm.A 1.7 MHz piezoelectric transducer (PZT) was employed to induce the vibration in this microreactor.Liquid side volumetric mass transfer coefficients were measured by physical and chemical methods of CO2 absorption into water and NaOH solution.The approach of absorption of CO2 into a 1 mol· L-1 NaOH solution was used for analysis of interfacial areas.With the help of a photography system,the fluid flow patterns inside the microreactor were analyzed.The effects of superficial liquid velocity,initial concentration of NaOH,superficial CO2 gas velocity and length of microreactor on the mass transfer rate were investigated.The comparison between sonicated and plain microreactors (microreactor with and without ultrasound) shows that the ultrasound wave irradiation has a significant effect on kLa and interfacial area at various operational conditions.For the microreactor length of 12 cm,ultrasound waves improved kLa and interfacial area about 21％ and 22％,respectively.From this study,it can be concluded that ultrasound wave irradiation in microreactor has a great effect on the mass transfer rate.This study suggests a new enhancement technique to establish high interfacial area and kLa in microreactors.     

EXPERIMENTAL STUDY ON GAS-HOLDUP AND GAS-LIQUID INTERFACIAL AREA IN TPCFBs

A new fiber optic probe system has been developed for measuring the gas-holdup ε_g and bubble size distribution P_s(d_b) in multiphase reactors. Experiments have been carried out in a gas-liquid-solid three-phase circulating fluidized bed (TPCFB) with 140mm inner diameter and 3 m height, in which air, tap water and 0.4 mm glass beads are used as the gas, liquid and solid phase, respectively. Based on the measured data, the gas-liquid interracial area a, one or the most important parameters concerning the mass transfer, has been derived. The radial profile of the gas holdup and the gas-liquid interracial area, and the influence or main operating conditions have been studied experimentally in TPCFBs.     

HYDRODYNAMICS AND MASS TRANSFER IN BUBBLE COLUMNS: EFFECT OF SOLIDS

The hydrodynamics and mass transfer in a large diameter bubble column (D_c 0.305 m), specifically, the effects of gas velocity and the presence of solids on the gas holdup structure, gas-liquid interfacial area, and volumetric mass transfer coefficients in viscous as well as low viscosity solutions are studied. The sulfite oxidation technique was employed to measure the gas-liquid interfacial area. Volumetric mass transfer coefficients were measured using a chemical method (sulfite oxidation) as well as physical absorption of oxygen from air, and the overall gas holdups were measured using the hydrostatic head technique. The effect of solids on the gas holdup structure was examined using the dynamic gas disengagement method. With the addition of polystyrene particles, the gas-liquid interfacial area decreased for low viscosity systems, whereas it increased for viscous systems. This was shown to be due to the effect of solids on bubble coalescence. The wettability characteristics of solid surfaces in the presence of different liquids have been suggested as the reason for the effect of solids on coalescence. Oil shale slurries presented a special case because of the mineral dissolution effect.     

EXPERIMENTAL STUDY ON GAS-HOLDUP AND GAS-LIQUID INTERFACIAL AREA IN TPCFBs∗

A new fiber optic probe system has been developed for measuring the gas-holdup ?_g and bubble size distribution P_s(d_b) in multiphase reactors. Experiments have been carried out in a gas-liquid-solid three-phase circulating fluidized bed (TPCFB) with 140mm inner diameter and 3 m height, in which air, tap water and 0.4 mm glass beads are used as the gas, liquid and solid phase, respectively. Based on the measured data, the gas-liquid interracial area a, one or the most important parameters concerning the mass transfer, has been derived. The radial profile of the gas holdup and the gas-liquid interracial area, and the influence or main operating conditions have been studied experimentally in TPCFBs.     

MASS TRANSFER CHARACTERISTICS IN A SLURRY REACTOR

The gas-liquid and solids-liquid mass transfer characteristics of a slurry reactor with vibratory agitation have been studied in gas-liquid-solids three phase systems. It has been found that the rates of mass transfer between both the gas-liquid and the solids-liquid phases are influenced by the solids concentration and the gas flow rate if the solids concentration and the gas flow rate exceed 5 to 10% by volume and about 0.2 cm/s, respectively.     

Microinterface intensification in hydrogenation and air oxidation processes

Hydrogenations and air oxidations usually have low apparent reaction rate,generally controlled by mass transfer rate,and widely exist in the modern chemical manufacturing process.The key to increase the mass transfer rate is the reduction of the liquid film resistance 1/k_La.In this work,the original concept of microinterface intensification for mass transfer and then for these reactions has been proposed.We derived the regulation model and set up the mathematical calculation method of...     

Hydrodynamics and volumetric gas-liquid mass transfer coefficient of a stirred vessel equipped with a gas-inducing impeller

Hydrodynamic and mass transfer characteristics of a gas-liquid stirred tank provided with a radial gas-inducing turbine were studied. The effect of the rotation speed and the liquid submergence on global hydrodynamic and mass transfer parameters such as the critical impeller speed, the induced gas flow rate, the gas holdup, the power consumption and the volumetric gas-liquid mass transfer coefficient were investigated. The experiments are mainly conducted with air-water system. In the case of critical impeller speed determination, two liquid viscosities have been used. The volumetric gas-liquid mass transfer coefficient k_La has been obtained by two different techniques. The gas holdup, the induced gas rate and the volumetric gas-liquid mass transfer coefficient are increasing functions with the rotation speed and decreasing ones with the liquid submergence. The effects of these operating parameters on the measured global parameters have been taken into account by introducing the dimensionless modified Froude number and correlations have been proposed for this type of impeller.