浅论表面润湿与塔填料传质效率的关系

ADISCUSSIOONTHEWETTABILITY-EFFICIENCYRELATIONINPACKEDCOLUMNS1前言70年代以来,填料塔作为重要的传质分离设备在石油炼制、天然气加工、石油化工、精细化工、化肥、医药、及环保等部门得到越来越广泛的应用。现代化工的发展,出现了许多新的特点：生产规模大型化,要求搭设备具有高通量和低能耗;精细化工和材料工业的发展,需要对化工产品深度加工,往往涉及难分离或热敏性物系,要求塔设备具有高效率和低压降;日益严格的环境保护,对处理排放物料的搭设备也提出了苛刻的要求。’。从而推动了塔填料的工业应…     

气液向下并流填料塔的持液量

用φ15mm的陶瓷拉西环和塑料鲍尔环填料,在内径153mm的有机玻璃塔内,采用空气-水体系,测量了气液向下并流流动时的持液量数据。以Bemer等人提出的颈缩管模型为基础,推导了向下并流填料塔内的持液量计算式,较好地关联了本实验和Dodds等人的结果。并检验Larkins,Charpentier,佐藤等人提出的持液量关联式。     

适用于分批精馏和多用途填料塔的液体分布器

介绍两种适用于分批精馏及多用途填料塔的液体分布器——槽式和双排管式高弹性液体分布器。目前通用型液体分布器的操作弹性一般为4:1,而这种液体分布器,其操作弹性可达10:1左右。本文提出的小孔排量计算方法同样也适用于大型填料塔的液体分布器。     

THE EFFECT OF PARTICLE DILUTION ON WETTING EFFICIENCY AND LIQUID FILM THICKNESS IN SMALL TRICKLE BEDS

Partial wetting in small scale trickle bed reactors results in incorrect determination of intra-particle apparent kinetic parameters as well as in erroneous reactor scale-up. Although a dilution of catalyst particles with inert fines improves the catalyst wetting efficiency, it does not guarantee full external catalyst wetting at all superficial liquid mass velocities. In this work, a method is presented to relate the wetting efficiency obtained at different operating conditions and at different laboratories for diluted and non-diluted beds. Liquid film thickness in diluted and non-diluted beds is estimated. The effect of the operating conditions on partial wetting and liquid film thickness is discussed.     

煤与粘结剂的相互作用和型煤抗压强度的关系

煤的润湿性与型煤抗压强度相关。用于表征煤的润湿性方法有煤与淀粉粘结剂的接触角、粘合功、煤的润湿临界表面张力等。研究证明,随着煤化程度的升高,煤与淀粉粘结剂接触角变小,粘合功增加,粉煤的润湿性改善,型煤抗压强度得以提高。另外,煤的润湿临界表面张力越大,煤的润湿性越好,型煤抗压强度也就越高。     

HOLDUP STRUCTURE IN HIGHLY VISCOUS NEWTONIAN AND NON-NEWTONIAN LIQUIDS IN BUBBLE COLUMNS

Gas holdup structures in highly viscous glycerine and CMC solutions are studied in a 0.305 m diameter batch bubble column. The fractional gas holdups are determined using the dynamic gas disengagement method. Empirical correlations for the gas holdup based on data covering wide ranges of viscosities in Newtonian and pseudoplastic non-Newtonian solutions are presented. For highly viscous pseudoplastic solutions in small diameter columns, the gas holdup has a square root dependence on the diameter of the column. The absence of small bubbles is suggested to be a reason for the very low volumetric mass transfer coefficients in highly viscous solutions, reported in the literature.     

HOLDUP STRUCTURE IN HIGHLY VISCOUS NEWTONIAN AND NON-NEWTONIAN LIQUIDS IN BUBBLE COLUMNS

Gas holdup structures in highly viscous glycerine and CMC solutions are studied in a 0.305 m diameter batch bubble column. The fractional gas holdups are determined using the dynamic gas disengagement method. Empirical correlations for the gas holdup based on data covering wide ranges of viscosities in Newtonian and pseudoplastic non-Newtonian solutions are presented. For highly viscous pseudoplastic solutions in small diameter columns, the gas holdup has a square root dependence on the diameter of the column. The absence of small bubbles is suggested to be a reason for the very low volumetric mass transfer coefficients in highly viscous solutions, reported in the literature.     

EFFECT OF OPERATING CONDITIONS ON GAS HOLDUP IN SLURRY BUBBLE COLUMNS WITH A FOAMING LIQUID

This work presents experimental data on gas holdup in slurry bubble columns with a foaming liquid. The effects of solids concentration, solid particle size, superficial phase velocities and column dimensions on the gas holdup are analyzed. At low superficial gas velocities (less than 4cm/s), for which the liquid does not foam, the presence of solids with small particle size does not affect the gas holdup whereas solids with large particle size induce foam formation and thus their presence increases the gas holdup. In the foaming regime, an increase of solids concentration decreases the gas holdup. The operating mode has a strong effect on the gas holdup: the semi-batch operating mode (stagnant liquid-solid suspension) increases the ability of the liquid to foam with respect to the continuous mode. Regarding the effect of column dimensions, the results presented show that the height of the bubble column does not affect at an appreciable extent the gas holdup in the range 6 < LID < 12. At high gas velocities (greater than 6 cm/s) the gas holdups obtained in a 30 cm-internal diameter column are the same as those measured in a 10 cm-internal diameter column.     

PRESSURE DROPS IN PACKED BUBBLE COLUMNS

Pressure drops were measured for air-water system in a cocurrent, upflow bubble column containing each of four types of packing: Raschig rings, Intalox saddle, open-end screen cylinder and solid cylinder. The ranges of variables studied vary from 0 to0.09m/s for gas flow rate, 0 to 0.094 m/s for liquid flow rate and 0.475 to 0.976 for bed porosity. The experimental data well support a single-parameter model developed on the basis of the separated flow concept of Murdock (1962) and Lin (1982).     

填料塔常用的液体分布装置

本文对填料塔常用的液体分布器进行归纳和分类,介绍了它们的特点和适用场合;提供了判断一个分布器分布质量好坏的判据,并对今后液体分布器的发展趋势加以了预测。     

DISPERSED PHASE HOLDUP IN PULSED PERFORATED PLATE COLUMNS

Data on dispersed phase holdup are presented for a range of aqueous-organic systems, and are used to assess the accurancy of existing methods for its prediction. The Griffith model (2) for the mixer-settler region and the Thornton correlation (3) for the dispersion region were found to be the most accurate for high interfaclal tension systems; however their application requires a knowledge of the transition pulse velocity. No technique was found to predict satisfactorily the measured holdup for the low interfaclal tension systems investigated. The refitted Bell and Babb correlation (14)was found to provide an accurate method of interpolating data for a particular system, and can also be used to predict the transition from mixer-settler to emulsion operation.     

ON THE LIQUID FLOW REVERSAL IN BUBBLE COLUMNS

The maximum range of the radial position within which liquid flow reversal can be expected to occur in zero net liquid flow bubble columns is predicted. It is shown that existing models, that employ this position as an input parameter for predicting the liquid velocity profile, are intrinsically valid only when the flow reversal dimensiontess radius is confined to ihe narrow range of 0.644-0.707. It is demonstrated that radial positions outside this range are unacceptable on physical grounds. Guidelines for evaluating the appropriate location of the flow reversal point for typical bubble column operating conditions are proposed.     

滴流床中固相润湿分数的实验研究

用表面镇镇的填料颗粒催化过氧化氢分解的化学反应法，测定了内径75mm的滴流床中固体填料的外润湿分数实验结果表明，润湿分数随表现气速和液速的增加而增加，降低液体的表面张力、增大粘度也有利于提高润湿分数.当表现液速达到5kg／（m2·s）时，固体填料基本上完全润湿，这与文献报道和作者数值模拟结论一致．     

BUBBLE SIZES AND HOLDUP STRUCTURE IN BUBBLE COLUMNS DETERMINED BY DYNAMIC GAS DISENGAGEMENT

A new model for determining bubble size distributions in bubble columns by the dynamic gasdisengagement(DGD)technique is developed.It is based on an idea of non-uniform steady statedirstribution of bubble dispersion.Interpreting the axial non-uniformity,this model gives axial gasholdup distributions.If assuming an axially homogeneous dispersion,a radial gas holdup distributioncan be obtained.The Sauter mean diameters or specific interfacial areas for several systems areestimated by the technique.The results for an air-water system agree with those measured by afive-point conductivity probe technique.The obtained axial gas holdup distributions agree well withreported measurements and the radial gas holdup distributions are also reasonable.     

GAS HOLDUP AND HEAT TRANSFER FROM IMMERSED SURFACES IN TWO- AND THREE-PHASE SYSTEMS IN BUBBLE COLUMNS

Two experimental slurry bubble column facilities comprising of 10.8 and 30.5 cm diameter columns and appropriate for conducting hydrodynamic and heat transfer studies are described. The average and local gas holdup data are reported for the air-water system as a function of air velocity. The holdups for the three phases are also reported for the air-water-glass beads system over a range of air velocity values. The air holdup data are compared with the predictions of some of the commonly used correlations. The heat transfer coefficient for a 19 mm diameter cylindrical probe and the two- and three-phase dispersions are measured as a function of air velocity. Most of these hydrodynamic and heat transfer data correspond to the churn turbulent regime and the values obtained on the two columns differ appreciably from each other under similar operating conditions. This fact indicates that the scaleup of slurry bubble columns could be quite difficult on the basis of data obtained on the bench and pilot-plant scale units. The continuing data from these facilities on different systems will shed more light in the future on this important aspect which is crucial to the commercialization of indirect coal liquefaction technology.     

气液喷射式环流反应器气含率及传质比表面积的研究

研究了气速、液速对喷射式环流反应器气-液传质比表面积以及全塔、导流管和环隙部分的平均气含率的影响。提出将喷射式环流反应器中传递性能参数随操作条件的变化规律进行分区研究可简化放大过程。根据实验数据和文献数据,获得了计算敏感区域全塔平均气含率(?)和气液传质比表面积a_R的关联式: (?)=7.18×10~(-4)U_g~(0.55)Re_1~(1.24)D~(-0.64) a_R=644U_(g)~(0.44)(ρ_L/V_R)~(0.46)     

气液向上或向下并流固定床动持液量测定

引　言固定床也可用作气 -液 -固三相反应器 ,其中气体和液体可并流向下或并流向上通过催化剂颗粒床层而发生化学反应 .它广泛应用于各种化工过程[1].床层中的动持液量是一个估算液体平均停留时间和液膜厚度必不可少的参数 ,也是反应器内液 -固接触效率的一个量度 ,它直接影响催化剂的润湿程度和反应器的性能 ,因此持液量常是关联固定床 (或滴流床 )反应器内传质系数和传热系数的变量之一 .随着化工工业的发展 ,往往要进行原料脱杂质处理过程 (一般是加氢过程 ) ,需要足够的催化剂床层持液量 .工业上采取催化剂颗粒小型化、异形化和脉动操作…     

旋风筒的分级分离效率与其入口风速的关系

探讨了旋风筒的分级分离效率、切割粒径与其入口风速的关系,并对试验数据进行拟合处理,得到了分级分离效率与入口风速的关系式,提出了一种工切割粒径的计算方法。     

DROPLET COALESCENCE AND BREAKAGE RATES IN LIQUID EXTRACTION COLUMNS

Abstract

A review is given of recent work on the measurement of droplet coalescence and breakage rates in a packed and a pulsed plate extraction column using a newly developed colorimetric technique. The results, which were interpreted in terms of second order coalescence and first order breakage rate constants, showed that the droplet interaction rates are considerably lower in the pulsed column. The rate constants can also be used to predict accurately the steady state droplet size distribution, and to study theoretically the effect of droplet coalescence and breakage on mass transfer rate. Deficiencies in the available mass transfer coefficient data for droplets, both individual and in “swarms”, are pointed out.     

THEORETICAL PREDICTION OF GAS HOLDUP IN BUBBLE COLUMNS WITH NEWTONIAN AND NON-NEWTONIAN LIQUIDS

A simple model based on an energy balance which takes into account the friction losses at the gas-liquid interface and the slip velocity of single bubble is used to simulate the gas holdup in bubble columns containing Newtonian and non-Newtonian liquids which circulate in both laminar and turbulent flows. Experimental data available from the literature for bubble columns up to 7 m height and 1 m diameter with water and glycerol as Newtonian liquids and different solutions of CMC in a wide range of concentrations as non-Newtonian liquids are simulated with good agreement despite the simplifications made to describe the gas liquid flow regimes. Most of the differences between experimental and calculated gas holdup are justified on the basis of the simplifying assumptions.