Scale-Up Study on the Performance of Annular Pulsed Disc-and-Doughnut Columns

Based on the previous work of the hydraulic, axial mixing, and mass-transfer performance of an annular pulsed disc-and-doughnut column (APDDC), the effects of scaling-up on its performance were studied in APDDCs with different annular space widths. The effect of scaling-up on holdup was discussed, and a more universal correlation was established. The effect of scaling-up on the Sauter drop diameter could be expressed by the previous obtained correlation. The effects of scaling-up on both the flooding holdup and throughput were mainly reflected in the correlation of the Sauter drop diameter. The equations of operating regimes were also independent of the scaling-up effect as demonstrated by experimental data. The scaling-up effects on the axial-dispersion coefficient of the continuous phase, the mass-transfer coefficient, and the height of a transfer unit were also discussed.     

Performance of an Industrial Pulsed Disc-and-Doughnut Extraction Column

Axial-dispersion and plug-flow models have been used to describe the solvent extraction performance of a 18 m high and 4 m diameter industrial pulsed disc-and-doughnut column. Uranium extraction phase-equilibrium data were fitted with the Langmuir model. Using the industrial column dimensions, operational parameters, physical properties, and the Langmuir parameters, the axial-dispersion model was shown to predict the organic-phase outlet concentration and the aqueous-phase outlet concentration, respectively, while the plug-flow model exhibited a poorer predictive ability.,     

Hydraulic Performance of an Annular Pulsed Disc-and-Doughnut Column

The annular pulsed disc-and-doughnut column (APDDC) is an important type of solvent-extraction equipment used in the PUREX process. Though it has been used in several commercial reprocessing plants in the world, there are few research results reported in the literature. In the present work, experiments were carried out in a stainless steel annular pulsed disc-and-doughnut column with aqueous phase and organic phase as the continuous fluid separately. The air-purge method was used to measure parameters including the two-phase densities, column weight, and two-phase interface location, which were fed back to a computer for column control. The holdup and Sauter drop diameter, the latter of which was calculated based on the gravitational settling model, are correlated as functions of the operating conditions (such as pulsation intensity, total flux, and flow ratio). Flooding holdup and throughput were determined experimentally and found in good agreement with those predicted by the model of the Sauter drop diameter. Based on the experimental data, operating regimes are divided referring to existing models. In addition, the effects of internal wettability on the hydraulic characteristics are also discussed.     

Extraction of Uranium Nitrate with 30% (v/v) Tributyl Phosphate in Kerosene in a Pilot Annular Pulsed Disc-and-Doughnut Column—Part II: Axial Mixing and Mass Transfer Performance

Mass transfer experiments were carried out in an annular pulsed disc-and-doughnut column (APDDC) using 30% (v/v) TBP-kerosene + uranium nitrate + nitric acid + water system (uranium nitrate system) for both extraction and stripping processes. Parameters in the axial dispersion model (ADM) and plug-flow model (PFM), namely, the axial dispersion coefficient of the continuous phase and the number of mass transfer units, were regressed by correlating the respective model with the experimental concentration profile. The mass transfer coef?cient is calculated, and new correlations are developed to predict the axial mixing coefficient of the continuous phase and the volumetric mass transfer coefficient. The height of a transfer unit is also calculated. The influence of axial mixing on mass transfer performance for the uranium nitrate system is discussed.     

聚并-分散脉冲筛板萃取塔的传质与轴向混合特性

A new configuration of coalescence-dispersed pulsed-sieve-plate extraction column (CDPSEC) was developed, and the mass transfer and axial mixing characteristics were evaluated with the two-point dynamic method.The influence of operation conditions was discussed with experimental results, showing that the mass transfer performance of CDPSEC mainly depends on the energy input and the holdup of dispersed phase. Higher energy input results in higher holdhp of the dispersed phase, the axial mixing of the continuous phase is suppressed, and the true height of mass transfer unit decreases markedly. On the other hand, higher energy input leads to more serious forward mixing of the dispersed phase, so the energy input should be limited. Accordingly the operation conditions were divided into two regions, and empirical correlations for predicting the mass transfer and axial mixing characteristics in different regions with a satisfactory accuracy were suggested.     

Mass Transfer and Axial Mixing Characteristics in a Coalescence-Dispersion Pulsed-Sieve-Plate Extraction Column

A new configuration of coalescence-dispersed pulsed-sieve-plate extraction column (CDPSEC) was developed, and the mass transfer and axial mixing characteristics were evaluated with the two-point dynamic method. The influence of operation conditions was discussed with experimental results, showing that the mass transfer performance of CDPSEC mainly depends on the energy input and the holdup of dispersed phase. Higher energy input results in higher holdup of the dispersed phase, the axial mixing of the continuous phase is suppressed, and the true height of mass transfer unit decreases markedly. On the other hand, higher energy input leads to more serious forward mixing of the dispersed phase, so the energy input should be limited. Accordingly the operation conditions were divided into two regions, and empirical correlations for predicting the mass transfer and axial mixing characteristics in different regions with a satisfactory accuracy were suggested.     

色谱法测定葡萄糖果糖在制备柱上的传质和扩散系数

色谱模型对研究色谱分离过程中的传质动力学具有重要的意义。根据物料守恒原理,结合传质扩散模型推导色谱分离连续方程。假设吸附过程相平衡是线性,连续性方程推导出理论板数与流速和色谱模型参数有关。在多组不同流速条件下测定色谱柱参数,计算得到两组分的传质系数和扩散系数。分别用测定模型参数模拟脉冲实验,结果表明拟合较好。     

鼓泡床反应器内流动与传质行为的研究进展

总结了有关浆态鼓泡床反应器内流动、混合用气液传质特性的研究成果,详细地介绍了鼓泡床反应器内气含率、液速、液体轴向扩散系数、传质系数的测量方法,阐述了鼓泡床反应器性能的主要影响因素,如系统压力、温度、气体表观气速、液体性质及固含率等对流动、液相混合和传质特性的影响,并对鼓泡床反应器的应用前景进行了详述.     

Modeling and simulation of a horizontal pulsed sieve-plate extraction column using axial dispersion model

In this research, the impact of pulsation intensity and phase flow rates on the volumetric overall mass transfer coefficients based on the continuous phase (K_oca) and the axial dispersion coefficients of phases in a horizontal pulsed sieve-plate column has been investigated using axial dispersion model. The toluene-acetone-water and butyl acetate-acetone-water systems with acetone transfer in both directions were used. In this study, the flow regime transition from pseudo-dispersion regime to emulsion regime has been characterized. Two new correlations have been proposed for prediction of K_oca and E_c.     

Prediction of Concentration Profiles in an L‐Shaped Pulsed Extraction Column

The L‐shaped extraction pulsed plate column is believed to be able to perform under operating conditions between those of the vertical and the horizontal pulsed plate columns. It has an extraction efficiency similar to the vertical pulsed plate column. Here, the mass transfer performance of this novel column type was investigated and the application of three different models, i.e., the plug flow, the axial dispersion, and the back flow models, was evaluated to predict the solute concentration profile along the column length. The water‐acetone‐n‐butyl acetate and the water‐acetone‐toluene systems were used. The influence of the operational parameters on the height of the mass transfer unit and the back flow coefficients was evaluated using the back flow model. New correlations were proposed to predict the height of the mass transfer unit along with the back flow coefficients in each phase, which were in satisfactory agreement with the experimental data.     

填料型饱和热水塔气相传质系数与传热系数的计算与应用

导出了计算填料型饱和热水塔气相传质系数和传热系数的方法,分析了应用气相传质系数和传热系数计算填料层高度的方法,给出了计算实例,计算结果与生产实际相符。     

超声场与添加剂对鼓泡塔中传质性能的影响?

利用超声场鼓泡塔和双电导探针气泡特征参数测量仪实时测定了加入不同种类和不同浓度添加剂前后鼓泡塔内氨气气含率与传质系数变化规律。实验结果表明：无添加剂时,超声频率为20-50-100 kHz组合,功率100 W时,鼓泡塔内气含率比无超声作用时增加了37%~74%,传质系数增大了39%~61%;气含率和传质系数随加入正辛醇浓度的增大呈现逐渐增长的趋势,当正辛醇浓度超过1.0%(V)时,气含率和传质系数趋于稳定;超声频率为20-50-100 kHz组合,超声功率100 W,正辛醇浓度为1.0%时鼓泡塔内气含率比无添加剂加入时增加了20%,传质系数增大了16%,可见超声场与添加剂协同作用有利强化气液相间分布、提高传质效果。     

转盘萃取塔传质单元高度的测定与影响因素的研究

在转盘萃取塔中用清水萃取煤油中的苯甲酸。通过改变转盘的转速、原料的进样流量、油层的厚度,分别测取分散相中苯甲酸的含量,求得传质单元数和传质单元高度。结果表明:转盘转速、油层厚度与传质单元高度成反比;原料的进样口流量与传质单元高度成正比。     

Measurement of Mass Transfer Coefficients and Their Modelling of Continuous Counter-Current Aqueous Two-Phase System in a Packed Extraction Column

Overall dispersed side volumetric mare transfer coeffcieats for protein and amino acids were measured in continuous countercurreat PEG4000/KHP aqueous two-phase systems in a 57 mm I.D. packed extraction column. A model for overall dispersed side volumetric mass transfer coefficients was derived by describing the motion of the drops based upon Navier-Stokes equation combined with the relationship between mass transfer coefficients and the drop velocity. The model provides good predictions and can be successfully used in aqueous two-phase extraction. The awrage relative deviation between calculated values and experimental date ranges from 8% to 14%.     

Interfacial Area and Liquid‐Side Volumetric Mass Transfer Coefficient in a Downflow Bubble Column

An experimental investigation was made to measure interfacial area, a, and liquid‐side volumetric mass transfer coefficient, k_La, in a downflow bubble column by chemical methods viz., absorbing CO₂ in aqueous sodium hydroxide and sodium carbonate/bicarbonate buffer solution respectively. The effect of gas and liquid flowrate and nozzle sizes on a and k_La were investigated. The experimental data obtained in the present system were analyzed and correlations were developed to predict a and k_La in terms of superficial gas velocity. The variation of a and k_La with specific power input were shown in graphical plot and compared with other gas‐liquid systems.     

利用计算流体力学及计算传质的方法研究精馏塔传质效率

It has long been found that the flow pattern of the liquid phase on distillation tray is of great importance on distillation process performance. But until now, there was very few published work on quantitative investigation of this subject. By combining the computational fluid dynamics (CFD) with the mass transfer equation, a theoretical model is proposed for predicting the details of velocity and concentration distributions as well as the tray efficiency of distillation tray column. Using the proposed model, four different cases corresponding to different assumptions of liquid and vapor flowing condition for a distillation tray column were investigated. In Case I, the distributions of velocity and concentration of the incoming liquid from the downcomer and the uprising vapor from the underneath tray spacing are uniform. In Case Ⅱ, the distribution of the incoming liquid is non-uniform but the uprising vapor is uniform. In Case Ⅲ, the distribution of the incoming liquid is uniform but the uprising vapor is non-uniform.In Case IV, the distributions of both the incoming liquid and the uprising vapor are non-uniform. The details of velocity and concentration distributions on a multiple sieve tray distillation column in four different cases were simulated using the proposed model. It is found that the shape of the simulated concentration profiles of vapor and the liquid is quite different from case to case. The computed results also show that the tray efficiency is highly reduced by the maldistribution of velocity and concentration of the incoming liquid and uprising vapor. The tray efficiency for Case Ⅰ is higher than Case Ⅱ or Case Ⅲ, and that for Case Ⅳis the lowest. It also reveals that the accumulated effect of maldistribution becomes more pronounced when the number of column trays increased. The present study demonstrates that the use of computational method to predict the mass transfer efficiency for the tray column, especially for the large one, is feasible.     

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.     

Dispersion and Mass Transfer Effects on the Performance of an Immobilized Lipase Packed Bed Reactor During the Hydrolysis of Rice Bran Oil

The performance of an immobilized packed bed reactor for the hydrolysis of rice bran oil has been investigated and can be well described by a dispersion model with an average standard deviation of 0.0388. Global mass transfer coefficients estimated using the model and experimental data ranged from 0.095‐0.482 min^?1, depending on substrate flow rates. A dimensionless mass transfer correlation between the Sherwood number and the Reynolds number was obtained as NSh = 3.96 ×NRe^2.07.     

往复振动筛板萃取塔放的大设计模型

对往复振动筛板萃取塔（RPEC）塔内的传质过程进行了理论分析，并在此基础上，从单液滴传质模型出发，应用数学统计方法建立了RPEC放大设计模型，即进行放大设计时应遵循通量、塔板间距、振幅和频率不变的原则计算表观传质单元高度H_OXP.采用林可霉素-正丁醇-酸水物系对塔径100 mm的RPEC实验塔研究表明：真实传质单元高度H_OX与体系物性、表观速度、输入能量（振幅A×频率f）有关，而与塔径无关，且不受轴向混合的影响，模型较好地预测了H_OX随输入能量的增加而减小，而通量的变化则对其影响较小;分散传质单元高度H_OXD是塔径D、输入能量、通量U_s和体系物性的函数，实验结果表明模型较好地描述了输入能量和通量增加强化传质起主导作用，有效降低分散传质单元高度H_OXD的传质过程部分，而不能描述轴向混合起主导作用部分.应用放大设计模型对直径325 mm的RPEC放大设计结果验证模型的预测误差在20％以内.