填料塔内液相轴向返混研究

本文报导了应用非理想脉冲注入-两点检测技术,以0.1N NaCl溶液作示踪剂,用电导法测量示踪剂的停留时间分布曲线。采用优化加权矩量法估计模型参数,应用最小二乘多元线性回归得到计算Pe_d的关联式:彼克列数Pe_d与液相流速关系较大,与气相流速关系甚小。最适用的模型仍是以彼克列数(Pe=(UH)/D)为参数的扩散活塞流模型。     

规整填料塔内液相返混的CFD模拟

通过对规整填料塔内部结构的分析,认为其内部存在三种基本结构单元：同一盘填料内的交叉单元、上下两盘填料旋转90度的衔接单元和填料与塔壁的衔接单元。使用RNG k—ε湍流模型对不同的结构单元进行三维CFD模拟计算,发现不同的结构单元具有不同的流动特性。同时．使用示踪激励响应技术,研究了不同结构单元的轴向返混情况。     

加压下规整填料塔内气液两相流返混的实验研究:气相返混系数

规整填料因具有生产能力大、分离效率高、压降低、操作弹性大、持液量低等诸多优点 ,目前已被广泛应用于精馏、吸收及萃取等多种化工单元操作中 .通常只在常压或减压条件下操作 ,而在高压或大液相负荷下 ,因流体物性的变化及流动状态的改变 ,使塔内产生严重的返混 ,塔效率显著降低 .因此 ,研究加压下规整填料塔内流体的流动状态具有重要意义 .对于加压下填料塔内气相返混的研究 ,中国台湾的ＴａｎＣｈｕｎｇ -Ｓｕｎｇ[1] 在低实验气速 (0 .0 0 2～ 0 .1ｃｍ·ｓ- 1)下做过初步的研究 ,其实验填料为散堆填料 .Ｋｕｒｔｚ[2 ] 在这方面的研究…     

隔壁塔内半圆填料层中壁流与返混特性研究

在填料塔三参数壁流模型的基础上,提出了应用于隔壁塔半圆型填料层的壁流模型。通过实验对模型参数进行了估计。模型计算值与实验值吻合较好。在内径为580 mm、高2800 mm的半圆冷模塔内,常温常压下以空气-水为介质,测取了散堆填料的壁流曲线,分析了气液速率变化对壁流的影响。以氯化钠溶液为示踪剂,通过脉冲注入扰动响应技术获得停留时间分布曲线。发现气液速率变化均对停留时间分布产生不同程度影响。同时比较了同一填料层高度塔壁区和整体区的平均停留时间,在壁流充分发展阶段,塔壁区的平均停留时间明显小于整体区。从另一方面量化了壁流效应的影响。应用线性回归得到单相流和气液逆流时计算Pe_d的关联式。对于新型填料及塔内件的开发、改进隔壁塔的设计方法,从而实现安全有效放大具有参考意义。     

填料塔中液体轴向返混行为对精馏分离效率影响的理论解

合理地作了一些近似假设,得到能反映液相轴向返混行为的等板高度理论计算公式。精度分析表明,等板高度近似理论解误差很小。在推导理论解的过程中,提出返混影响精馏分离效率的准数———返混特征准数,表明液相轴向返混行为对精馏分离效率的影响随液相轴向返混系数的增加而增加,而随汽相总传质单元高度和液相轴向有效流速的增加而减小。文中还给出了等板高度加长因子随返混特征准数和相平衡常数变化的计算公式和曲线图     

加压下规整填料塔内气液两相轴向返混实验研究

An experimental study of the extent of axial backmixing in both gas and liquid phases was conducted in a 150 mm ID column packed with Mellapak 250Y corrugated structured packing. The column was operated at pressures ranging from 0.3 MPa to 2.0MPa with nitrogen and water flowing countercurrently through the packing. The amount of axial backmixing was experimentally evaluated by the pulse response techniques using hydrogen in gas phase and an aqueous solution of NaCl in liquid phase as inert tracers. The response of the tracer was monitored by means of thermal conductivity in the gas phase and electrical conductance in the liquid phase. The experimentally determined residence time distribution (RTD) curves were interpreted in terms of the diffusion-type modei. The results indicated that the axial backmixing in the gas increased notably with gas flowrate and slightly with operating pressure and liquid flowrate. The liquid-phase axial backmixing was an increasing function of both gas and liquid flowrates an     

填料塔内轴向混合的研究

在充填阶梯环填料的有机玻璃塔内，采用非理想脉冲示踪技术及两点检测法，测定空气和不同粘度水溶液系统的液相停留时间分布。用加权矩量法处理实验数据，得到了泛点以上Ｐｅ准数与粘度校正因子及气液相流速间的关系。     

扩散模型法研究流体返混对传热的影响

将“停留时间分布（ＲＴＤ）”概念引入换热过程研究。以扩散模型法定量地分析了仅仅由于返混而引起的对传热的影响,为确定合理的换热器换热面积理论设计裕度提供了理论依据。     

填料塔中液体铀向返混行为对精馏分离效率影响的理解解

合理地作了一些近似假设,得到能反映液相轴向返混行为的等板高度理论计算公式。精度分析表明,等板高度近似理论解误差很小。在推导理论解过程中,提出返混影响精馏分离效率的准数－返混特征准数,表明液相轴向返混行为对精馏分离效率的影响随液相轴向返混系数的增加而增加,而随汽相总传质单元高度和液相轴向有效流速的增加减小。文中还给出了等板高度加长因子随返混特征准数和相平衡常数变化的计算公式和曲线图。     

粘度对填料塔内轴向混合的影响

在充填塑料阶梯环填料的有机玻璃塔内，采用非理想脉冲示踪技术及两点检测法，测定空气和不同粘度水溶液系统的液相停留时间分布，用加权矩量法处理实验数据，得到了泛点以下Ｐｅ准数与粘度校正及气液相流速间的关系。     

多级鼓泡塔中液相返混系数与交换速度的研究

采用示踪方法对高2 000 mm,内径282 mm多级筛板鼓泡塔内液相返混系数进行测量研究,并通过扩散-返混模型以及RTD曲线给出鼓泡塔内筛板上下二侧液体交换速度,同时考查了表观气速、开孔率等因素对轴向扩散系数与液体交换速度的影响.根据实验得出鼓泡塔内轴向返混系数以及液体交换速度与表观气速、开孔率有很大关系,均随表观气...     

A simplified method of obtaining the backmixing coefficient of a solvent extraction column from tracer pulse data

A method based on transfer function matching is used to obtain the backmixing coefficient of a solvent extraction column. The method demonstrates the exploitation of the symbolic manipulation capability of the current generation of scientific computing software. It starts with the dynamic model of Dongaonkar et al. and makes use of a set of tracer pulse data of Dongaonkar for a Kühni column. Compared to the existing methods of evaluating backmixing coefficient, this new method is more direct and simple to implement on computers. It has the potential of being applicable to more elaborate dynamic models of plate columns.     

填料在充填浮选柱中的应用及研究

介绍了化工填料在浮选柱的应用及研究情况,探讨了填料在浮选柱中所起的作用,说明了今后的研究方法及方向。     

Parametric and nonparametric model based control of a packed distillation column

Parametric and nonparametric model based control systems were applied to control the overhead temperature of a packed distillation column separating methanol–water mixture. Experimental and theoretical studies have been done to observe the efficiency and performance of both control systems. Generalized predictive control (GPC) system based on a parametric model has been tried to keep the overhead temperature at the desired set point. First, a parametric model which is controlled auto regressive integrated moving average (CARIMA) was developed and then the parameters of this model were identified by applying pseudo random binary sequence (PRBS) and using Bierman algorithm. After that this model was used to design the GPC system. Tuning parameters of the GPC system have been calculated using the simulation program of the packed distillation column. Using the predicted parameters, experimental and theoretical GPC systems were found very effective in controlling the overhead temperature. Dynamic matrix control (DMC) system based on a nonparametric model has been used to track the overhead temperature of the packed distillation column. For this purpose, a nonparametric model known as the dynamic matrix was determined using the reaction curve method. A step change in heat input to the reboiler was applied to the manipulated variable and the temperature of the overhead product was observed. After that, the dynamic matrix was used to design the DMC system. Several calculations have been done to define the DMC control parameters. The best values of the tuning parameter were used to realize the DMC system for controlling the overhead temperature experimentally and theoretically. In the presence of some disturbances, the DMC system gives oscillation and offset in experimental studies.     

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.     

Mass transfer coefficients in a pulsed packed extraction column

The volumetric overall mass transfer coefficients have been measured in a pulsed packed extraction column using diffusion model for the toluene/acetone/water system. The experiments were carried out for both mass transfer directions. The effects of operational variables such as pulsation intensity and dispersed and continuous phases flow rates on volumetric overall mass transfer coefficients have been investigated. The experimental findings indicate that pulsation intensity and mass transfer direction have great influence on volumetric overall mass transfer coefficient. Significant, but weaker, are the effects of continuous and dispersed phase flow rates. The experimental results obtained in the present work are compared with some other types of extraction columns. Finally, two empirical correlations for prediction of the continuous phase overall mass transfer coefficient is derived in terms of Sherwood and Reynolds numbers. Good agreement between prediction and experiments was found for all operating conditions that were investigated.     

New predictive correlation for mass transfer coefficient in structured packed extraction columns

Developments in the area of packed columns, particularly structured packed columns, are ongoing, specifically in the area of liquid–liquid extractions in different industries. In the present study, mass transfer coefficients have been obtained experimentally in a structured packed extraction column to develop a new correlation for prediction of continuous phase Sherwood number. The experiments were carried out for toluene/acetic acid/water and n-butyl acetate/acetic acid/water systems with counter current flow in different heights of column. A new dimensionless parameter, d₃₂/h, is introduced in proposed equation. This number considers the effect of column height (h) and mean drop diameter (d₃₂) jointly. The main advantage of this approach is that the principal effect of column height is considered in correlation without which the experimental data could not be fitted with a acceptable accuracy.     

Enzyme mass transfer coefficient in aqueous two phase system using a packed extraction column

Fractional dispersed phase hold-up and dispersed side mass transfer coefficients for amyloglucosidase were measured in a 56 mm i.d. packed extraction column using a sodium sulphate-polyethylene glycol 4000 system. Raschig rings (3 to 13.3 mm), Berl saddles (12 mm), Pall rings (12.6 mm), glass spheres (5.2 mm) and structured wire gauze were used as packings. The effect of packing size was investigated in the case of ceramic Raschig rings. The effect of phase composition of the aqueous phase system also was studied. Correlations have been developed for fractional dispersed phase hold-up and volumetric mass transfer coefficient with packing voidage, dry surface area of packings, superficial dispersed phase velocity and the liquid phase physical properties.     

填料塔气液传质参数研究（Ⅱ）──气膜传质系数

用拟一级快速化学反应吸收法测定了拉西环填料塔的气膜传质系数，并得出其无因次表达式。     

Experimental and CFD analysis of two-phase cross/countercurrent flow in the packed column with a novel internal

The pressure drop and liquid hold-up for the G-L cross/counter-current flow in a packed column with a novel internal was simulated using a Eulerian/Eulerian two-fluid model solved by a commercial CFD software CFX4.4. Simulation results are in good agreement with the experimental data of pressure drop. The internal significantly increases the gas radial velocity and lower the gas axial velocity, which lowers the pressure drop and improves operational flexibility. To minimize bypass flow caused by the internal, optimum baffle thickness and width of the internal's passage are proposed.