CONTRIBUTION TO PACKED COLUMNS SCALE-UP IN SEPARATION PROCESSES

Correlations will be presented to describe liquid hold up, loading and flooding capacity, volumetric mass transfer coefficients on liquid and gas or vapour phase and the pressure drop as a basis for computing packed columns, dumped and regular as well, including the influence of end effects on scaling. The relationships are found on a sound physical and mathematical basis and their validity were confirmed by experimental investigations of many packings; some of them were selected to be considered in this work.

Design of Pilot Plant Packed Column for the Dehydration of Water from Ethanol-Water Mixtures

This use of biomass-based adsorbent has been explored for the column study of the adsorptive dehydration of water in ethanol-water mixtures. The column study was carried out using enzyme modified corn starch and the breakthrough curve parameters were used to design the packed bed column. The effect of flow rate on the breakthrough curves revealed that adsorption efficiency decreased with increased inflow rate. The empty bed contact time (τ) of the pilot plant packed column was 35.35 min while the breakthrough time is 40.78 min. 66.7% was the fraction of capacity left unused for the pilot plant from the design.

A NEW MATHEMATICAL MODEL FOR MASS TRANSFER IN A PACKED COLUMN

A new mathematical model,designated as stochastic state pool model,is proposed for simulating the liquid flow andmass transfer behaviour,including the concentration profiles of liquid and gas phascs in a packed column.Application ofthe new model is demonstrated by an example of the desorption of CO2 in a packed column.

Extraction of Caprolactam from Aqueous Ammonium Sulfate Solution in Pulsed Packed Column Using 250Y Mellapak Packings

Liquid-liquid equilibrium (LLE) data of water-caprolactam-benzene-(NH4)2SO4 system at 303 K were measured for extraction of caprolactam from aqueous ammonium sulfate solution. The influence of fluid flow rate, pulsation intensity on flooding velocity and mass transfer was studied for extraction of caprolactam from ammonium sulfate solution in a laboratory pulsed packed column. The flooding velocities and overall apparent height of a transfer unit were given under various operation conditions. An industrial column developed based on above study is operated well. The scale-up effect is discussed.

Removal of high concentration CO_2 from natural gas at elevated pressure via absorption process in packed column

Carbon dioxide （CO2） removal is an essential step in natural gas （NG） processing to provide high quality gas stream products and minimize operational difficulties. This preliminary study alms to investigate the removal of CO2 at high concentration level from the mixture of CO2-NG gas stream at elevated pressure via absorption process. This is to explore the possibility of exploring high CO2 content natural gas reserves by treatment at offshore platform. A mixed amine solvent, Stonvent-II, was used for the absorption of approximately 75 vol% CO2 in CO2-NG stream at a pressure of 10 barg. The initial solvent temperature was varied in order to study the impact of initial temperature on the absorption performance. Preliminary study at temperatures of 35 ℃ and 45 ℃ indicates that Stonvent-II was able to perform almost 100% removal of CO2 under both conditions. However, the CO2 absorption effect took place faster when the initial liquid temperature was lower. This is because when the initial liquid temperature is high, the temperature increase in the packing bed caused by the reaction heat is high which impacts the efficiency of absorption negatively.

Novel predictive tool for accurate estimation of packed column size

Traditionally the majority of fractionation columns in natural gas processing plants were equipped with trays.However an option to trayed columns is to use packing.Packed columns offer a larger surface area per unit volume for mass transfer and the continuous gas to liquid contact throughout the column rather than at specific levels （such as in tray columns）.For process design purposes,it is essential to estimate the pressure drop for enabling the proper operation of packed columns.In this study,a simple generalized pressure drop correlation （GPDC） which is easier than existing approaches requiring more complicated and longer computations is developed for sizing randomly packed fractionation columns for pressure drops up to 150 mm water per meter of packing.This correlation can be used to estimate pressure drop for a given loading and column diameter.Alternatively,for a given pressure drop the diameter can be determined.The predictions from the proposed correlation have been compared with reported data and found good agreement with average absolute deviation hovering around 4.9%.The proposed predictive tool is superior owing to its accuracy and clear numerical background,wherein the relevant coefficients can be retuned quickly if new and more accurate data are available in the future.This proposed simple-to-use approach can be of immense practical value for the engineers and scientists to have a quick check on the pressure drop in packed columns for a given loading and column diameter.In particular,gas engineers would find the proposed approach can be used very friendly involving no complex expressions with transparent and easy-to-handle calculation steps.

Determination of External Mass Transfer Model for Hydrolysis of Jatropha Oil Using Immobilized Lipase in Recirculated Packed-Bed Reactor

In this study, a simple and effective technique for establishing an external mass transfer model in a recirculated packed-bed batch reactor (RPBBR) with an immobilized lipase enzyme and Jatropha oil system is presented. The external mass transfer effect can be represented with a model in the form of Colburn factor JD = K Re-(1–n). The value of K and n were derived from experimental data at different mass flow rates.The experiment shows an average increment of 1.51% FFA for calcium alginate and 1.62% FFA for carrageenan after the hydrolysis took place. Based on different biopolymer material used in immobilized beads, JD = 1.674 Re-0.4 for calcium alginate and JD = 1.881 Re-0.3 for k-carrageenan were found to be adequate to predict the experimental data for external mass transfer in the reactor in the Reynolds number range of 0.2 to 1.2. The purposed model can be used for the design of industrial bioreactor and scale up. Besides, the external mass transfer coefficients for the hydrolysis of Jatropha oil reaction and the entrapment efficiency for the two biopolymer materials used were also investigated.

Methanol Distillation System: Process Analysis and Column Design

Base on industrial research and experience, the process of methanol distillation is analyzed,and above all, a new concept of high pressure flowsheet and low pressure flowsheet is defined. The new configuration helps to handle problems encountered in many factories in China. The inter influence between process and column internal pattern is also pointed out. Recommendation of new column internal designs is given. Finally, industrial examples tell the how the new concept works and the possibility of combining process to give more opens to solve engineering problems.

CFD Analysis of Gas Distributor in Packed Column ——Prediction of Gas Flow and Effect of Tower Internals Geometry Structure

Computational fluid dynamics (CFD) simulations were carried out on the gas flow patterns of twin-tangential annular deflector gas distributor in the absence of liquid flow in a packed column (6.4 m in diameter), and the gas flow field in the column was presented close to reality on the whole. Furthermore, after ame-(lioration) of this gas distributor frame, turbulence energy and turbulence energy dissipation rate were both decreased greatly.Simulation results showed that the flow pattern and the distribution of gas flow were strongly affected by the column bottom frame; the proper column bottom frame could decrease the flow pressure drop greatly. Multifold factors, such as the column bottom geometry structure and distributor structure which affects the distribution capacity, must be considered.

武汉地区湖泊沉积物重金属的分布及潜在生态效应评价

对武汉地区6个湖泊沉积物重金属元素Hg、Cd、Cu、Pb、Zn、As、Cr、Ni的空间分布特征及其潜在生态效应进行研究。调查区的湖泊底泥重金属含量表现出市区内湖泊沉积物的重金属含量普遍高于郊区湖泊,其中墨水湖中重金属含量最高;湖泊沉积物柱重金属元素垂向分布表现为城区受到一定程度污染的湖泊某些元素表现出表层沉积物显著高于底部沉积物含量的特征,而郊区湖泊除Cd外其它元素垂向含量变化不大,说明郊区湖泊受到人为影响较小。利用潜在生态危害指数法对湖泊沉积物进行生态危害评价,显示武汉地区湖泊元素生态危害排序为:Cd>Hg>As>Cu>Pb>Zn;墨水湖沉积物重金属潜在生态危害相对最高,其次是金银湖;其它湖泊重金属生态危害都比较轻,总体而言武汉湖泊重金属生态危害还是较小的。但参照国外沉积物基准的生态数据库阈值,市区受到人为污染较严重的湖泊沉积物可能会对生物产生负面影响。

Seismic behavior of large-scale FRP–recycled aggregate concrete–steel columns with shear connectors

The application of fi ber-reinforced polymer (FRP) composites for the development of high-performance composite structural systems has received signifi cant recent research attention. A composite of FRP–recycled aggregate concrete (RAC)–steel column (FRSC), consisting of an outer FRP tube, an inner steel tube and annular RAC fi lled between two tubes, is proposed herein to facilitate green disposal of demolished concrete and to improve the ductility of concrete columns for earthquake resistance. To better understand the seismic behavior of FRSCs, quasi-static tests of large-scale basalt FRSCs with shear connectors were conducted. The infl uence of the recycled coarse aggregate (RCA) replacement percentage, shear connectors and axial loading method on the lateral load and deformation capacity, energy dissipation and cumulative damage were analyzed to evaluate the seismic behavior of FRSCs. The test results show that FRSCs have good seismic behavior, which was evidenced by high lateral loads, excellent ductility and energy dissipation capacity, indicating RAC is applicable in FRSCs. Shear connectors can signifi cantly postpone the steel buckling and increase the lateral loads of FRSCs, but weaken the deformation capacity and energy dissipation performance.

柱切换直接进样高效液相色谱法测定蜂蜜中3种抗生素的残留量

建立了柱切换反相高效液相色谱法直接进样分离、测定蜂蜜中3种四环素族抗生素(土霉素OTC、四环素TC、金霉素CTC)残留量的分析方法.方法包括:用缓冲溶液溶解样品、直接进样、二次蒸馏水作流动相在C18预柱上在线富集和净化,然后用柱切换阀将预柱与一个C18分析柱接通,草酸溶液-乙腈-甲醇作流动相、紫外检测器在350 nm处检测.各组分回收率均大于85%;相对标准偏差小于10%;标准曲线的相关系数在0.9983～0.9991之间;最低检出浓度(≤0.02 mg/kg),满足欧盟和日本等国要求(0.05mg/kg).

Achievements of Truss Models for Reinforced Concrete Structures

Achievements are presented for truss models of RC structures developed in previous years: 1. Two constitutive models, biaxial and triaxial, are based on regular trusses, with bars obeying nonlinear uniaxial σ-ε laws of material under simulation;both models have been compared with test results and show a dependence of Poisson ratio on curvature of σ-ε law. 2. A truss finite element has been used in the nonlinear static and dynamic analysis of plane RC frames;it has been compared with test results and describes, in a simple way, the formation of plastic hinges. 3. Thanks to the very simple geometry of a truss, the equilibrium equations can be easily written and the stiffness matrix can be easily updated, both with respect to the deformed truss, within each step of a static incremental loading or within each time step of a dynamic analysis, so that to take into account geometric nonlinearities. So the confinement of a RC column is interpreted as a structural stability effect of concrete. And a significant role of the transverse reinforcement is revealed, that of preventing, by its close spacing and sufficient amount, the buckling of inner longitudinal concrete struts, which would lead to a global instability of the RC column. 4. The proposed truss model is statically indeterminate, so it exhibits some features, which are not met by the “strut-and-tie” model.

Hydrodynamics of air-kerosene bubble column under elevated pressure in homogeneous flow regime

A multiphase computational fluid dynamics(CFD)model coupled with the population balance equation(PBE)was developed in a homogeneous air-kerosene bubble column under elevated pressure(P).The specific pressure drop(ΔP/L),gas holdup(α_(G)),and Sauter mean diameter(d_(32))were experimentally measured in the bubble column with 1.8 m height and 0.1 m inner diameter,which was operated at a superficial gas velocity of 12.3 mm·s^(-1),and P=1-35 bar(1 bar=10^(5) Pa).A modified drag coefficient model was proposed to consider the effect of bubble swarm and pressure on hydrodynamics of the bubble column.The Luo breakage model was modified to account for liquid density,viscosity,surface tension and gas density.TheΔP/L,α_(G),and d_(32) obtained from the CFD model were compared with experimental data,and the gas density-dependent parameters of the CFD model were identified.With increasing P from 1 to 35 bar,theα_(G) varied from 5.4%to 7.2% and the d32 decreased from 2.3 to 1.5 mm.The CFD-PBE model is applicable to predict hydrodynamics of pressurized bubble columns for gas-organic liquid in the homogeneous regime.

Modeling bubble column reactor with the volume of fluid approach:Comparison of surface tension models

This work aims at comparing surface tension models in VOF(Volume of Fluid) modeling and investigating the effects of gas distributor and gas velocity. Hydrodynamics of a continuous chain of bubbles inside a bubble column reactor was simulated. The grid independence study was first conducted and a grid size of 1.0 mm was adopted in order to minimize the computing time without compromising the accuracy of the results. The predictions were validated by comparing the experimental studies reported in the literature. It was found that all surface tension models can describe the bubble rise and bubble plume in a column with slight deviations.

Seismic Behavior of Diaphragm-Through Connections of Concrete-Filled Square Steel Tubular Columns and H-Shaped Steel Beams

Based on the introductions of a type of diaphragm-through connection between concrete-filled square steel tubular columns (CFSSTCs) and H-shaped steel beams,a finite element model of the connection is developed and used to investigate the seismic behavior of the connection.The results of the finite element model are validated by a set of cyclic loading tests.The cyclic loading tests and the finite element analyses indicate that the failure mode of the suggested connections is plastic hinge at the beam with inelastic rotation angle exceeding 0.04 rad.The suggested connections have sufficient strength,plastic deformation and energy dissipation capacity to be used in composite moment frames as beam-to-column rigid connections.

动态保压注射成型技术对PA6/EPDM-g-MA共混物相形态与力学性能的影响

采用动态保压注塑成型技术来控制分散相相形态和橡胶粒子在基体中的取向排列。纯尼龙,动态样与静态样具有相同的冲击强度。在加入橡胶后,动态样与静态样的冲击强度变化趋势基本一致,在橡胶含量为2 0 %t时,体系完成脆韧转变冲击强度达到最大,在橡胶含量为30 %和4 0 %时冲击强度又下降。但与静态样相比,当橡胶含量为1 0 %t时,动态样与静态样的冲击强度一致,而当橡胶含量超过1 0 %时,动态样的冲击强度较静态样高。结合平行于熔体流动方向的SEM照片,在橡胶含量为1 0 %时,动态样中的橡胶粒子与静态样一样并未被拉长与取向,而在橡胶含量超过1 0 %时,动态样剪切层中的橡胶粒子被拉长且沿熔体流动方向取向。实验表明,在改善共混物界面相容性的基础上,适当的低剪切应力场能进一步提高橡胶分散相对冲击强度的贡献。

毛细管气相色谱法同时测定盐酸氨溴索中乙醇、醋酸和甲苯残留量

目的:建立盐酸氨溴索原料药中乙醇、醋酸和甲苯3种有机溶剂残留量的测定方法。方法:采用直接进样法,二甲基甲酰胺为溶剂。气相色谱条件:采用 DM-624(化学组成:6%氰丙苯基-94%二甲基聚氧硅烷)毛细管气相色谱柱,30m×0.53mm×3.00μm。程序升温:60℃保持3min,以每分钟5℃升至108℃,再以每分钟30℃升至180℃,保持5min。氮气(纯度:99.9999%)为载气,柱前压为42kPa。分流进样,分流比1∶20。进样口温度250℃,FID 检测器,检测器温度270℃。结果:3种溶剂残留均达到良好分离。乙醇、醋酸和甲苯线性范围分别为15.85-396.3μg·mL^(-1)(r=0.9995),38.33-574.9μg·mL^(-1)(r=0.9999),0.8360-20.90μg·mL^(-1)(r=0.9996,);回收率分别为95.2%-101.9%(RSD≤4.3%,n=3),95.0%-102.3%(RSD≤3.9%,n=3),94.8%-102.0%(RSD≤4.8%,n=3);检出限分别小于20μg·g^(-1),20μg·g^(-1),5μg·g^(-1)。结论:本方法简单、快捷且灵敏度高,可以用于盐酸氨溴索中乙醇、醋酸、甲苯3种有机溶剂残留量的控制。

Desalination of Seawater by Liquid Columns and Decompression Boiling (Recovery of Condensation Latent Heat)

In this study, the concept of a new seawater desalination method and equipment using liquid columns of seawater and desalinated fresh water, decompression boiling and evaporation, condensation, and recovery of condensation latent heat are proposed. The equipment consists of seawater and freshwater columns approximately 10 m high with top spaces. The pressure of the top space, the evaporation and condensation area, of the seawater column, for example, is reduced approximately 30 mmHg (abs.) using the seawater column, after which it is heated from the general seawater temperature of 25°C to 30°C to boil and evaporate the seawater. The vapor is cooled by the seawater at approximately 25°C in a heat exchanger, and then, it is condensed and sent to the fresh water column. At this time, the condensation latent heat is recovered to preheat the newly flowing seawater. The evaporation or condensation rate, namely, the production rate of freshwater, by the new desalination equipment is also estimated by the results of the existing quadruplex effect vacuum evaporator used in the salt production industry. This new desalination method and its associated equipment also can be used to purify polluted water and waste water.

辛基型毛细管液相色谱整体柱的制备、表征及评价

本研究采用以甲基丙烯酸辛酯为单体,乙二醇二甲基丙烯酸酯为交联剂,偶氮二异丁腈为引发剂,正丙醇、1, 4丁二醇和水三元混合物为共溶剂,制备了内径为0. 53mm的毛细管整体柱材料。详细考察了单体/交联剂比例、单体混合物与致孔剂之间的比例,对所制得材料的通透性、孔径分布、粒度大小等性能的影响;应用包括扫描电镜和压汞法对其进行表征;在毛细管液相色谱(c HPLC)操作模式进行了初步色谱评价,结果表明:所制得的整体柱具有优良的通透性能,可在高达100μL/min的流速下进行快速分离,同时在离子对模式下对3种金属离子进行了分离,取得了较理想的效果。