Enrichment of heavy water in flat-plate thermal diffusion columns inclined for improved performance

The optimum angles of inclination for maximum separation, maximum production rate and minimum column length in a flat-plate thermal-diffusion column for enrichment of heavy water have been determined. Essential improvement in performance is obtainable if the column is tilted at the optimum angle, instead of being placed vertically, so that the convection strength can be properly reduced and controlled, resulting in suppressing the undesirable remixing effect while still preserving the desirable cascading effect. Accordingly, considerable saving in fixed and operating charges can be achieved, particularly for lower production rate operations, or for smaller degree of separation.     

THE OPTIMUM PLATE-SPACING FOR THE BEST PERFORMANCE IN A FLAT-PLATE THERMAL DIFFUSION COLUMN WITH TRANSVERSE SAMPLING STREAMS

The equations for estimating optimum plate-spacing for maximum separation and for maximum production rate in a flat-plate thermal diffusion column with transverse sampling stream and with fixed operating expense, have been derived. Considerable improvement in performance is obtainable if the optimum plate-spacing is selected so that the convective strength can be properly reduced and controlled, resulting in suppressing the undesirable remixing effect while still preserving the desirable cascading effect and thereby leading to improved performance.     

Feed concentration and column temperature in production and preparative chromatography

For large scale chromatographic separations, economic operation will require high concentrations of the feed material in the mobile phase entering the column. The different types of ultimate concentration limit encountered in liquid and gas chromatography are described. When separating thermally stable materials with a gas—liquid column, an optimum column temperature exists where the throughput at the ultimate concentration limit goes through a maximum. Equations are derived for calculating the optimum temperature and throughput. For heat-sensitive materials the column should be operated at the optimum temperature or the degradation temperature, whichever is the lower. The effect of temperature on the length of column required for separation is described.The treatment is made possible by taking the width and concentration of the feed band as roughly independent parameters, a satisfactory approximation when wide bands are used.     

The best performance in spiral wired thermal diffusion columns

The Improvement in performance of a concentric tube thermal diffusion column by means of a wire spiral, having a diameter equal to the annular spacing and inserted as a spacer in the annular region, was investigated. Equations of the optimum wire angle of inclination from the vertical for the maximum separation, maximum output and minimum column height have been derived. Considerable improvements in performance are obtainable if the spiral wired columns are employed, instead of using the open column (without wire), so that the convection strength can be reduced and controlled, resulting in suppressing the undesirable remixing effect while still preserving the desirable cascading effect.     

THE BEST PERFORMANCE IN SPIRAL WIRED THERMAL DIFFUSION COLUMNS

The Improvement in performance of a concentric tube thermal diffusion column by means of a wire spiral, having a diameter equal to the annular spacing and inserted as a spacer in the annular region, was investigated. Equations of the optimum wire angle of inclination from the vertical for the maximum separation, maximum output and minimum column height have been derived. Considerable improvements in performance are obtainable if the spiral wired columns are employed, instead of using the open column (without wire), so that the convection strength can be reduced and controlled, resulting in suppressing the undesirable remixing effect while still preserving the desirable cascading effect.     

精密精馏填料塔的稳态特性

本文第一部分探讨精密精馏填料塔的最佳回流比。文中提出一个关联式来估算在一定回流比下的传质单元数,并由此导出最佳回流比图。精密精馏最佳回流比的最大值约为1.4R_m。 本文第二部分探讨最佳的塔径与填料尺寸比。实验是在内径分别为20、28、32、44mm,填料层高从1020到1475mm四个填料塔中用2.5×2.5mm三角螺旋填料以正庚烷-甲基环己烷系统进行。根据实验求得的全塔浓度分布曲线,在除去塔顶及塔底两端的端效应后,得出填料层的真实分离效率（即传质单元高度或每米填料高的传质单元数）。以真实分离效率与塔径及填料尺寸比作图,所有恒气速下的曲线都呈现出最佳点,并且其比值几乎相同。对于这种填料,最佳塔径与填料尺寸比约为13—14,此值与普通填料或工业填料大致相似。     

The Optimum Column Number for the Best Performance of Thermal Diffusion in the Frazier Scheme with the Total Sum of Column Height Fixed

The effect of column number N, as well as the column height h of thermal diffusion columns, on the degree of separation in the Frazier scheme with the total sum of the column height L (=Nh) fixed, has been investigated. The equations, which may be employed to predict the optimum column number N* for the maximum separation Δ _N,max, have been derived. Considerable performance in separation is obtainable if the column number, as well as the column height, in a Frazier scheme with the total sum of the column height fixed is properly assigned for a certain flow-rate operation.     

PART Ⅱ OPTIMUM REFLUX RATIO AND PACKING SIZE

It has been well-known that the optimum reflux ratio and the optimum packing size are importantcharacteristics of a packed column,especially for close-boiling fractionation.A correlation is proposed toestimate the NTU at finite reflux and from which a relationship to find the optimum reflux ratio is de-rived based on minimum cost.It is found that the maximum value of optimum reflux ratio is about 1.4R_M.For the study of optimum packing size,experimental work is undertaken with n-heptane-methylcyclohex-ane system in four laboratory columns ranging from 20 to 44 mm in diameter and being packed with 2.5×2.5mm angular helices.The optimum ratio of column diameter to packing size is found to be 13-14which is in rough agreement with that for ordinary or industrial size of packing.     

The Optimum Plate Aspect Ratio for the Best Performance in a Flat-Plate Thermal Diffusion Column with Transverse Sampling Streams

ABSTRACT

The effects of plate aspect ratio on the degree of separation, production rate, and plate surface area in a flat-plate thermal diffusion column with transverse sampling streams have been investigated. Theoretical considerations show that when a thermal diffusion column is constructed with the best plate aspect ratio, either maximum separation or maximum production rate or minimum plate surface area can be obtained. The optimum plate aspect ratio for maximum separation is obtained with a given production rate and plate surface area, while that for the maximum production rate is determined with the degree of separation and plate surface area fixed, and that for the minimum plate surface area is estimated with a known degree of separation and the production rate. It is interesting that the optimum plate aspect ratio for maximum separation is exactly the same as that for minimum plate surface area. The maximum separation and maximum production rate are achieved without changing the total expenditure, while the design with minimum plate surface area results in minimizing the total expenditure.     

The best performance of spiral wired thermal diffusion columns of the frazier scheme

Equations have been derived for the optimum wire angles of inclination for maximum separation, maximum production rate and minimum column height in the Frazier scheme of concentric‐tube thermal diffusion columns with a tight fitting wire spiral, having a diameter equal to the annular spacing, and wrapped on the entire inner tube. Considerable improvement in performance is obtained when a Frazier scheme is operated at the optimum corresponding wire angle of inclination, especially for the scheme of high column number.     

The optimum plate aspect ratio for the best performance in a flat-plate thermal diffusion column of the frazier scheme

The effects of plate aspect ratio on the degree of separation, production rate and plate surface area in a flat-plate thermal diffusion column of the Frazier scheme, have been investigated. Theoretical considerations show that when the thermal diffusion columns of the Frazier scheme are constructed with the best plate aspect ratio, maximum separation, maximum production rate or minimum plate surface area can be obtained. The optimum plate aspect ratio for maximum separation is obtained with given production rate and plate surface area, while that for maximum production rate is determined with the degree of separation and plate surface area fixed, and that for minimum plate surface area is estimated with known degree of separation and production rate. It is interesting that the optimum plate aspect ratio for maximum separation is exactly the same as that for minimum plate surface area. The maximum separation and maximum production rate are achieved without changing any total expenditure, while the design with minimum plate surface area results in minimizing the total expense.     

THE COMBINED EFFECT OF INCLINED ANGLE AND PLATE SPACING ON THE PERFORMANCES OF FLAT-PLATE THERMAL-DIFFUSION COLUMNS

When the separation is performed in a parallel-plate thermal diffusion column with the operating expense fixed, either increasing the plate spacing and operating at the corresponding optimum inclined angle, or increasing inclined angle and operating at the corresponding plate spacing, will increase the maximum separation and maximum production rate. Il was found that the cosine of optimum inclined angles increase with the plate spacing in the exponents of -9/2 and —4, respectively, for maximum separation and maximum production rate, while the optimum plate spacings increase with the cosine of inclined angle in the exponents of -2/9 and — 1/4, respectively. The plate spacing is generally so small that changing it, as well as changing the inclined angle, may not cause additional fixed change. However, increasing the plate spacing will lead to increasing the difference of plate temperatures in order to keep the operating expense, as well as the energy consumption due to heat conduction between the hot and cold plates, unchanged. Therefore, additional cost is needed to maintain a high value of temperature difference. There do not exist simultaneously the optimum inclined angle and the optimum plate spacing for the best performances.     

Superior mixing performance for airlift reactor with a net draft tube

A modified networks-of-zones model is developed to investigate the mixing performance of three tower-type bioreactors, namely airlift, bubble column and net column (a short notation for airlift reactor with a net draft tube) reactors. A key parameter β, that characterizes the interaction intensity between the neighboring uprising and down-coming streams, is identified to play a decisive role in determining the mixing characteristics of the three tower-type reactors. The concentration dynamics and mixing behaviors of the three types of reactor are studied with a maximum non-zero eigenvalue analysis (the slowest mode analysis). The model predictions are validated with experiments of heat mixing. The superior mixing performance of the net column reactor over the airlift and bubble column reactors is clearly revealed with the present model and is experimentally verified, and can be linked to an optimum mass transfer between the neighboring uprising and down-coming streams, provided by the net draft tube. This optimum mass transfer is a direct result of a balanced flow distribution in the axial and radial directions.     

THEORETICAL EFFICIENCY. OF PULSED POLTURETHANE FOAM COLUMN SEPARATIONS

Abstract

Two experimental arrangements of the pulsed column separation nave been described and their maximum theoretical separation efficiency under optimum conditions has been investigated. It has been found that the theoretical maximum attainable separation efficiency in the closed arrangement equals the value obtained in the static (batch) one-stage separation, and in the open arrangement equals the value of the separation efficiency obtained in the dynamic (flow) column operation with a static column bed. These conclusions were confirmed in the separation of ra-dioiodine from water on the polyurethane foam column with immobilized tri-n-alkylamlne:iodine reagent. A fairly satisfactory agreement has been found between calculated and experimentally determined values of the separation efficiency under the same conditions.     

Optimal erreichbare Werte der Entbenzinierung in der Endstufe einer Miscella-Destillation

Optimum Values Attainable in Solvent Removal at the Final Stage of Miscella Distillation Starting from the theoretical basis and conventional form of construction of a stripping column for miscella distillation, formulas for stripping steam consumption as function of absolute pressure in column and rest solvent content at a maximum distillation temperature t_max. = 80°C are derived for 4 different modes of distillation. The results are represented graphically in two-dimensional diagrams and compared. Based on the costs of extracting solvent, cooling water and steam, the optimum figures for the consumption of stripping steam are obtained. Also in plant designing with the help of the values given, a yield calculation related to investment costs can be made. For undesirable solvent costs, whereby the stripping steam input is maximum, the diameter of the stripping column and the surface of the condenser involved have to be predetermined.     

复合萃取剂提取林可霉素机理及填料萃取塔中试研究

以中试填料萃取塔为设备研究了复合萃取剂（正辛醇和煤油）萃取林可霉素的宏观特性及传质强化。使用斜率法确定萃合物的结构和反应平衡常数以指导改进设备和强化传质;为了提高林可霉素萃取效果,考察了溶液pH值、相比（W/O）、填料类型、分布盘的使用等因素对提取林可霉素效果的影响。结果表明：以正辛醇为萃取剂萃取林可霉素的过程中,反应平衡常数K为0.072;复合萃取剂中正辛醇最佳含量为0.8（体积分数）;萃取林可霉素的最佳pH值为10～11,最佳相比（W/O）为3;规整填料和散装填料萃取效果有限,分布盘可以大大加强传质,同时加装分布盘的填料萃取塔的单位体积处理量是混合澄清槽的12.8倍,萃取剂循环量大大减少。研究结果对复合萃取剂的萃取机理和填料萃取塔提取林可霉素的实际应用具有一定指导意义。     

Numerical study of n-heptane/benzene separation by thermal diffusion column

In this article,numerical simulations are performed to investigate the performance of the thermal diffusion column for the separation of n-heptane/benzene mixture.The present work tried to optimize column by analyzing significant parameters such as feed flow rate,temperature and cut.In order to obtain the hydrodynamic and temperature and mass distribution inside thermal diffusion column,computational fluid dynamic(CFD) method is applied to solve the Navier-Stocks equations.Numerical simulations are conducted to study the main parameters in both stationary and time-dependent conditions.By using the separation work unit as a function of cut,the optimal cut for maximum SWU occurs within a limited range of 0.47-0.5 for feed rate between 0.5 and 4 g min-1.Our findings reveal that the optimum feed rate in the range of optimum cut is about 1 g min~(-1).In transient study,results show that the best cut for reaching to steady-state condition is θ=0.5.     

通过Michael反应制备脂肪磺酸基强酸型阳离子交换树脂

以乙二胺化交联聚苯乙烯树脂(PS-Acyl-EDA)和2-丙烯酰胺基-2-甲基丙烷磺酸(AMPS)为原料,通过Michael反应合成脂肪磺酸基强酸型阳离子交换树脂。该磺酸基强酸型阳离子交换树脂与传统的磺酸树脂相比,具有较长的手臂链,易于和其他物质反应或进行离子交换,且避免了芳香族磺酸树脂的磺化逆反应。讨论了反应时间、反应温度、催化剂用量、试剂用量及投料比等因素对反应结果的影响。通过对反应条件的优化,可获得担载量为0~1.15mmol•g^-1的磺酸基强酸型阳离子交换树脂,并对产物进行了表征。该方法可用于色谱预装柱填料的制备。     

Adsorption separation efficiency in the cyclic steady state: A continuous countercurrent analogy and an experimental investigation

For adsorption processes involving concave equilibrium isotherms and finite desorption periods, the choice of cycle time has a decisive influence on separation efficiency. Using forward-flow desorption, efficiency goes through a maximum at an optimum cycle time; with reverse-flow desorption efficien increases with decreasing cycle time. Below, this behavior is explained in terms of a simple graphical solution for the case of a moving-bed countercur column, and by comparison with a continuous-flow permeation process. An experimental study has been made with the system n-heptane/hydrogen/zeolite at 300°C in a computer-controlled benchscale column. Reverse-flow desorption is shown to permit a considerable reduction in the desorption gas volume required to meet efficiency demands.     

HPLC optimization of the separation of explosives and propellant components with an octadecyl phase by computer simulation

High performance liquid chromatography (HPLC) is used in a large extent for environmental analysis. In this field many components have to be determined at the same time, but it is difficult to find the optimum separation conditions. Therefore, retention times of explosives and propellant components were determined at different solvent compositions of methanol/water and different temperatures on a column with an octadecyl phase. From the data constants were calculated for solvent and temperature dependence. With the determined data different column conditions were simulated by computer and the separation was optimized. The optimal separation was verified experimentally and compared with the calculated values. The deviation from calculated and experimental retention times lies as a rule below 2% and has a maximum of approximately 3.3%. Thus, separation of substance mixtures can be optimized by determination of column constants for temperature and solvent dependence.