气体搅动的筛板萃取塔性能实验研究

在筛板萃取塔中引入气体搅动,既能明显提高装置的传质效率,又能大幅提高装置处理能力。筛板塔的通量随气速的变化规律与填料塔有显著区别,其性能研究有重要意义。利用煤油(苯甲酸)-水-空气体系,考察了气体搅动和筛孔直径对萃取塔流体力学和传质性能的影响。结果表明,随着表观气速的增加,气含率、分散相含率、液泛速率和传质效率均明显增加。但过高的气速也会导致分散相的过于分散和乳化,传质性能下降,直至液泛。不同直径的筛孔相比,较小的筛孔使分散相停留时间延长,分散相含率和传质效率提高,但液泛速率和处理能力降低。     

填料特性对鼓泡填料萃取塔性能影响

填料的结构与表面性能对鼓泡填料萃取塔性能有直接影响。利用空气 煤油 (苯甲酸 ) 水体系 ,测定了未装填料和分别装填板波填料、丝网填料、压延孔环填料的鼓泡萃取塔水力学性能和传质性能。实验表明 ,对未装填料和装有填料的萃取塔 ,气相搅拌都可以显著提高液液两相的接触与传质性能 ;液泛速度随表观气速的增大而下降 ;流道设计合理的规整填料传质性能明显高于散装填料 ;表面光滑的填料分散相滞存率低 ,因而液泛速度较高 ;填料的作用有利于降低轴向返混 ,明显提高萃取塔传质性能。     

EFFECT OF MASS TRANSFER ON FLOODING AND HOLDUP IN A KARR COLUMN

This work considers flooding and dispersed phase holdup, with and without mass transfer, in a 7.6?cm diameter reciprocating plate extraction column using the liquid system toluene-acetone-water. The present flooding data in respect to the absence of mass transfer were well correlated by the hydrodynamic model based on the dispersion of drops by turbulent energy dissipation. During mass transfer the flooding characteristics were found to be dependent on the direction of mass transfer.

Dispersed phase holdup data were obtained by two different measuring techniques. Local holdup was found to vary with column height, while the overall holdup depended on agitation speed, phase throughputs and mass transfer direction. The holdup data thus obtained are compared with data published for the case without mass transfer, and new correlations are presented.     

空气搅动的填料萃取塔性能实验研究

引　言气体搅动是一种外加能量的萃取方法 .与机械搅拌相比 ,气体搅动的萃取塔内无运动部件 ,操作稳定 ,结构简单 ,能耗低 .过去已有数篇关于气体搅动的混合 -澄清槽[1] 、喷洒塔[2～ 4 ] 、多级连续萃取器[5] 等无填料的萃取过程水力学性能和传质性能的文献报道 .而在填料塔萃取过程中加入气体搅动技术 ,一方面继承了填料可以有效地降低轴向返混的优越性能 ;另一方面 ,通过外加能量进一步强化液 -液两相接触与传质 ,提高传质系数 ,综合了外加能量的萃取技术和填料萃取技术的优点 .关于这方面的内容目前少有报道[6] .1　实验装置与实验方法…     

Holdup and flooding in reciprocating plate extraction columns

Measurements of dispersed phase holdup and flooding conditions have been carried out in a 5 cm diameter reciprocating plate extraction column. A simplified predictive model for holdup and flooding has been developed assuming uniform hydrodynamic conditions throughout the column. The model has been confirmed for several systems but may be limited in application by the following factors: (a) mass transfer, particularly from dispersed to continuous phase (coalescence effect), (b) wettability of plates by dispersed phase, (c) axial non-uniformity of holdup (noticed particularly for high interfacial tension systems), (d) the use of exceptionally high frequencies or low amplitudes of agitation.     

筛板塔气-液-液系统内相含率和传质特性研究

The gas and dispersed phase holdups and mass transfer coefficients of liquid-iquid were determined for gas-liquid-liquid three phase system in a screen plate column. The flow pattern of gas-liquid-liquid three phase system was studied under different gas velocities. The shape factors showed the geometric properties of screen plates and the corrected drop chaxacteristic velocities were introduced. The phase holdup in two phases was correlated.The research results indicated that mass transfer coefficient for liquid-liquid system in a column with screen plates and gas agitation was found to increase apparently.     

Gas Holdup and Solid‐Liquid Mass Transfer in Newtonian and non‐Newtonian Fluids in Bubble Columns

Gas holdup and surface‐liquid mass transfer rate in a bubble column have been experimentally investigated. De‐mineralized water, 0.5 and 1.0% aqueous solutions of carboxy methyl cellulose (CMC), and 60% aqueous propylene glycol have been used as the test liquids. Effects of column diameter, liquid height to column diameter ratio, superficial gas velocity and liquid phase viscosity on gas holdup and mass transfer rate are studied. Generalized correlations for the average gas holdup and wall to liquid heat and mass transfer coefficients are proposed. These are valid for both Newtonian and pseudoplastic non‐Newtonian fluids.     

φ50折流板脉冲萃取柱水力学性能

以30％TRPO煤油溶液和1 mol·L^-1硝酸溶液为体系,在φ50折流板脉冲萃取柱中考察了折流板脉冲萃取柱的操作参数（脉冲振幅、脉冲频率、流速和流比）和结构参数（开孔率和板间距）对其水力学性能（液泛通量、液泛存留分数和正常操作时分散相存留分数）的影响.结果表明：在乳化操作区,液泛通量随着开孔率增加、脉冲强度和流比的减小而增大,与板间距无关;根据液泛存留分数的结果,给出了最优开孔率为23％;此时正常操作时分散相存留分数与连续相的流速、流比和脉冲振幅呈正比,而与脉冲频率无关,浸润性的影响造成了板间距对以硝酸溶液和30%TRPO煤油溶液为连续相时的分散相存留分数影响规律不同.     

气-液-液萃取的流体力学研究

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。本文研究了气-液-液三相下油滴的流动形态,并对不同填料的流体力学性能进行了测定。实验结果表明,气相速度的增加可导致气含率、液含率的增加,从而提高分散相在填料萃取塔中的停留时间,在一定的速度范围内明显降低萃取的表观传质单元高度,极大地强化传质效果。通过与散装填料对比,发现规整填料更利于强化萃取效果,其液泛速度平均增加25%。     

Interfacial area and mass transfer in gas-liquid cocurrent upflow and countercurrent flow in reciprocating plate column

The volumetric mass transfer coefficient and the interfacial area were measured for carbon dioxide absorption into water using a reciprocating plate column of plate geometry different from a Karr column. The specific interfacial area was governed by a change in bubble size at low agitation rates and by a variation in gas holdup at high agitation rates. The liquid phase mass transfer coefficient was strongly influenced by the agitation rate, the phase velocities and the plate geometry.     

Investigation of hydrodynamic performance and effective mass transfer area for Sulzer DX structured packing

The hydrodynamic performance in terms of pressure drop (?P) and liquid holdup (h_L), and tshe effective mass transfer area (a_e) of Sulzer DX structured packing were investigated at 293.15 K and 101.3 kPa. In addition, the flooding velocity (u_F) was also calculated based on the experimental results of liquid holdup, and the effective voidage correction factor (?) was obtained by combining the Billet model and the experimental effective fraction. The liquid volume method and pressure difference from just below to above the column packing approach are used to describe the hydrodynamic performance in a structured packing column. Experimental results showed that the operational conditions in terms of gas flow rate, liquid flow rate, viscosity, and liquid systems strongly affect the hydrodynamic performance. The experimental comparison between the pressure drop profiles in air‐water (polyethylene oxide [PEO]) and MEA‐H₂O‐CO₂ systems indicated that both the reacting MEA and CO₂ partial pressure can enhance the pressure drop value. In addition, the Bain‐Haugen correlation model was developed to predict the flooding velocity data with an acceptable AARD of 8.1%, and a model was also successfully proposed to predict the values of liquid holdup with an AARD of 11.8%, which is lower than 14.7% in Billet model. Furthermore, the effective mass transfer area was found to be increased by increasing both the liquid and gas flow rate by using NaOH‐H₂O‐CO₂ system. A model was also proposed to calculate the experimental a_e with an acceptable AARD% of 19.52, and this built model (Eq. 39) can reasonably explain the experimental phenomenon. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3625–3637, 2018     

Development of airlift bubble column dispersed with micro‐bubbles

Micro‐bubbles were dispersed in the bubble column with draft tube, and the length and diameter of draft tube were changed. The flow characteristics in air–water system were measured. Ozone gas and methylene‐blue aqueous solution were used, and the decomposition performance was examined. With increasing draft tube length, both the gas holdup and liquid velocity in the annular section increased. When the diameter ratio of draft tube to column was about 0.5, both the gas holdup and liquid circulation flow rate had maxima. For the decomposition by using ozone, the installation of draft tube enhanced the mass transfer and decomposition performance.     

Liquid Holdup in a Pilot‐Scale Turbulent Contact Absorber – An Experimental and Comparative Study

Liquid holdup in a turbulent contact absorber was determined experimentally. Experiments were performed in a 44.7 cm diameter Perspex column. Hollow spherical high‐density polyethylene balls were used as packing. The effect of liquid and gas velocities, static bed height, diameter and density of packing on liquid holdup was investigated for the range of gas velocities greater than minimum fluidization velocities. Also, the effect of gas and liquid distributors on liquid holdup was studied. Correlations for liquid holdup were developed and compared with those in the literature. It was observed that liquid holdup increased with the increase in liquid velocity, packing density, and the decrease in static bed height. Liquid holdup also increased with gas velocity when the gas distributor section was included, while no effect was observed for the bed. Lack of information on the contribution of liquid and gas distributors seems to be the logical explanation for the wide variation in data reported in the literature.     

QH-1型扁环填料用于高液气比操作时的性能研究

在内径186mm有机玻璃塔中 ,对16和2 5QH 1型扁环填料的流体力学和传质性能进行了研究 ,得出了计算其压降、液泛气速、泛点填料因子、湿填料因子和液相总传质单元高度的关联式。并与16鲍尔环填料进行比较 ,结果表明 ,QH 1具有优良的流体力学和传质特性。     

Modeling the axial distribution of mass transfer coefficient in an agitated-pulsed extraction column

The dispersed phase holdup and drop size in solvent extraction columns vary along the column height and this affects the mass transfer coefficient and interfacial area. In this article, mass transfer study was performed experimentally using a 25 mm diameter agitated pulsed column. The axial distribution of mass transfer coefficient was determined by coupling population balance equation and axial dispersion model by taking the longitudinal variation in hydrodynamic performance into consideration. Feasibility of different mass transfer models in predicting concentration profiles was evaluated and a novel correlation based on effective diffusivity was developed. The results showed that both overall and volumetric mass transfer coefficients have significant change along the column height and greatly depends on the agitation speed and pulsation intensity. Increasing dispersed phase velocity also augments the overall mass transfer coefficient. The maximum number of transfer unit was measured to be 10 m⁻¹ at agitation speed of 1000 rpm.     

Dispersed phase holdup and slip velocity of phases in a pulsed packed column in conditions with and without mass transfer

Dispersed phase holdup and slip velocity of phases were measured in a pilot plant pulsed packed column with a diameter of 76.2 mm for two different chemical systems in conditions with and without mass transfer. The effects of pulsation intensity, dispersed and continuous phases flow rates, interfacial tension and solute concentration on dispersed phase holdup and slip velocity of phases were investigated. A new empirical correlation in terms of the above‐mentioned parameters developed from the measurements is given for the prediction of slip velocity. The dispersed phase holdup was calculated by means of this correlation and very good agreement between calculated and experimental values was obtained.     

Steady state hydrodynamics and mass transfer characteristics of a karr extraction column

The steady state hydrodynamics of the holdup in a 15 cm column agree quite well with mechanistic predictions at conditions approaching flooding. In the presence of mass transfer (acetic acid from the dispersed kerosene phase to the continuous water phase), the holdup data below flooding are not well predicted by the model due to enhanced droplet coalescence. The prediction of holdup at flooding is a function of the ratio of the flow rates but is independent of the physicochemical properties of the extraction system, and therefore can be used to estimate the flooding holdup regardless of the occurrence of mass transfer. In the second part of the paper, steady state mass transfer characteristics of the column were also simulated using a mechanistic model. Despite the difficulty of estimating parameters such as the mass transfer coefficient, the model curves could be arbitrarily adjusted to fit observed exit concentrations. These steady state results provide useful insights on the non-linearity of the system from a control viewpoint.     

A Simple Approach to Measuring the Gas Phase Heat and Mass Transfer Coefficients in a Bubble Column

A simple experimental approach was developed to measure the gas phase volumetric heat and mass transfer coefficients in a bubble column and a slurry bubble column employing a single gas nozzle. The experimental technique was based on a transfer model that simulates humidification and direct contact evaporation models in the case of a gas bubble rising in a liquid of uniform temperature. The temperature and relative humidity of the inlet and outlet gas in the column are the only measurements required in this technique. Experiments were carried out in a 0.15 m inner diameter column using water as the liquid phase, air as the gas phase, and cation resins of 0.1 mm diameter and a specific gravity of 1.2, as the solid phase. The results showed that, when using solid concentrations in the range of 7–10 wt %, both the volumetric gas‐phase heat and mass transfer coefficients increased with an increase in the gas superficial velocity and were further enhanced by increasing the solid load after a certain minimum superficial velocity had been reached in the column (0.044 m/s in the system used). Increasing the solid load beyond 10 wt %, did not contribute to a further increase in these coefficients. Furthermore, the gas holdup in the column increased with the superficial gas velocity and was further enhanced when the solid‐phase load was in the range of 7–10 wt %. These observations agree well with previously reported findings by other investigators.     

Improved gas holdup in novel bubble column

This investigation reports the experimental and theoretical results carried out to evaluate the gas holdup for air–water system in a novel hybrid rotating and reciprocating perforated plate bubble column under countercurrent condition. The response of this hybrid column is found to be similar to that of reciprocating plate column (RPC) showing mixer‐settler, transition, and emulsion regions. The effect of agitation level, superficial gas velocity, superficial liquid velocity, perforation diameter, and plate spacing on gas holdup is studied and found to be significant. The gas holdup is found to be least in the range of agitation level of 1.3–1.5 cm/s. For all the superficial gas and liquid velocities considered in this present investigation, the critical agitation level at minimum gas holdup remains nearly same. The gas holdup in this hybrid column is 1.2–1.7 times higher in mixer‐settler region and 2.1–2.7 times higher in emulsion region than that of RPC. Correlations have been developed and found to concur with the experimental values. It can be used with 95% accuracy. © 2011 Canadian Society for Chemical Engineering     

Investigation of hydrodynamic and mass transfer of mercaptan extraction in pulsed and non-pulsed packed columns

We investigated the hydrodynamic behavior and mass transfer characteristics of a pilot-scale conventional packed bed extraction column of mercaptan removal from liquid propane. The extraction column was filled with pall rings structured packing where mercaptan was extracted from the continuous phase to the dispersed phase, accompanied by a chemical reaction in propane-mercaptan-caustic system. The pulsing was introduced into the column to enhance the mass transfer rate. Hydrodynamic parameters such as hold up, flooding velocity and mean drop size were studied together with the effect of chemical reaction on increasing mass transfer performance. Finally, the mass transfer and axial mixing coefficients were obtained from the optimization of data by ADM. It was found that at the pulsation intensity from 0.003 to 0.007 m/s, the maximum mass transfer and minimum axial mixing occurred and it can be concluded that pulsation improves the efficiency of mass transfer just at low intensities.