Sunflower protein precipitation in a tubular precipitator

Isoelectric precipitation of sunflower protein was carried out in a 20 m long, 6 mm internal diameter glass tubular precipitator. Effects of feed flow rate, protein concentration in the feed stream, and mean residence time on particle size distribution (PSD) were studied. The population balance equation (PBE) for the tubular precipitator was solved using the orthogonal collocation multiple shooting method. A simulated annealing method was used to determine the precipitation kinetic parameters for the nucleation rate, growth rate, aggregation rate, and breakage rate from the experimental data. Due to the lack of experimental data on the kinetics of sunflower protein precipitation in the literature, the extracted kinetics from our experiments were used to evaluate the predictive capability of the present model for experiments whose results had not been used to derive the kinetics. The model predictions of the particle size distribution along the tubular precipitator showed better agreement with the experimental data for large particles in comparison to the small particles (< 10 μm).     

Removal of Trace Cd2+ Using Continuous Multistage Ion Foam Fractionation: Part II—The Effects of Operational Parameters

A multistage ion foam fractionation column with bubble-cap trays was employed to study the removal of cadmium ions from simulated wastewater having low Cd concentrations (10–30 mg/L), examining the effects of foam height, air flow rate, feed flow rate, and feed Cd concentration. Sodium dodecyl sulfate (SDS) was used to generate foam in this study. An increase in foam height, which reduces liquid hold-up in the generated foam, resulted in the enhancement of the enrichment ratios of both SDS and Cd while the removal and residual factor of Cd showed insignificant change. An increase in air flow rate increased the foam generation rate, foamate volumetric ratio, and the removal efficiency of Cd but decreased the enrichment ratios of both Cd and SDS. The separation factors of both Cd and SDS decreased with increasing feed flow rate, which is mainly attributable to both the effects of the enhancement of foamate volumetric ratio and the increases in both SDS and Cd input rates. An increase in feed Cd concentration was found to increase Cd effluent concentration and SDS removal but to decrease the enrichment ratios of both Cd and SDS because of the increasing liquid entrainment in the produced foam.     

Study on Evaporating Characteristics of a Coaxial Two Impinging‐Stream Concentrator

Based on the coaxial two impinging‐streams principle, a new device for solution concentration was built and studied theoretically and experimentally. The experimental study focused on the effects of inlet air temperature, inlet air flow rate, and accelerating pipe length on the volumetric evaporative coefficient of the impinging‐stream concentrator (ISC). The results show that the ISC has a relatively high volumetric evaporative coefficient, which increases with higher inlet air flow rates and higher inlet air temperature, and the ISC with a shorter accelerating pipe is more efficient. A theoretical model was suggested based on the consideration of mass, heat, and momentum transfers between liquid droplets and hot air. The concentration process of a sucrose solution in the ISC was simulated using the model and the results were compared with the experimental results, which indicated that the suggested model is reliable with a maximum relative error of less than 6.6 %.     

Application of Counter-Current Solvent Extraction to the Separation of Naphthalene and Nonionic Surfactants

This study conducted counter-current solvent extraction to investigate the influence of solvent/solution volumetric ratio, solvent flow rate, and surfactant concentration on extraction efficiency. Fitting formulas for predicting the partition coefficients of the contaminant and surfactant between the aqueous and solvent phases were developed to optimize the counter-current solvent extraction. It is found that the solvent/solution volumetric ratio and the surfactant concentration had greater impact than the solvent flow rate on the extraction efficiency. The relationship between the partition coefficient K and the solvent/solution volumetric ratio or surfactant concentration was closely related to power function. Besides, the accuracy of the fitting formulas was consistent with the experimental results.     

连续泡沫分离蛋白质

本文以空气-明胶水溶液体系为研究对象，较为详细地考察了通气量、进料流量、进料浓度、进料位置、泡沫高度、溶液pH值等因素对连续泡沫分离明胶过程中明胶富集度变化的影响．     

填料塔中哌嗪二胺吸收低浓度SO_2的传质性能

为满足有机胺法脱硫设计开发的需要,采用动态吸收法测定了填料塔中哌嗪二胺(PA-A)水溶液吸收低浓度SO2的体积总传质系数KGa,考察了吸收工艺参数如吸收液中的PA-A浓度和初始pH值、液相流率、吸收温度、进气SO2浓度及流速等对KGa的影响。结果表明:KGa随着吸收液中的PA-A浓度和初始pH值、液相喷淋密度的增加而增大;随着吸收温度、气相流率及进气SO2浓度的增加而减小。通过实验结果分析得到体积总传质系数KGa与气液相流率比(qG/qL)之间符合指数关系式,该经验关系可用于工程设计计算。     

气隙式膜蒸馏在溴化锂吸收式制冷系统中的应用

以1H, 1H, 2H, 2H-全氟癸基三乙氧基硅烷（PFDTES）为改性剂,采用表面接枝方法制备疏水性PFDTES-Al₂O₃管式复合膜,并将其应用于溴化锂吸收式制冷系统。通过LiBr/H₂O溶液的气隙式膜蒸馏实验,测试管式复合膜对溶液的分离性能。结果表明：通过PFDTES成功制备出疏水性PFDTES-Al₂O₃管式复合膜;膜蒸馏渗透通量随着操作压力、进料温度及进料流量的增大而增大,随着进料浓度的增大而减小;对于LiBr的截留率始终保持在99.99%以上。在膜蒸馏实验结果的基础上,进一步利用Aspen Plus软件模拟了基于PFDTES-Al₂O₃复合膜的新型溴化锂吸收式制冷系统的换热过程,研究该复合膜应用于溴化锂吸收式制冷系统的可行性。结果表明：性能系数（COP）随着LiBr/H₂O稀溶液浓度及流量的增大而减小,随着LiBr/H₂O稀溶液温度的升高而增大;并且LiBr/H₂O稀溶液温度及流量是主要的影响因素。在操作压力0.08MPa、LiBr/H₂O稀溶液流量86L/h、质量分数50%、温度＞70℃、冷侧流量120L/h和温度20℃的条件下,COP＞0.7,说明将PFDTES-Al₂O₃复合膜用于溴化锂吸收式制冷系统,不仅可以减小设备的体积,还能降低运行成本,具有较高的可行性。     

The effects of amine additives and flow rate on the performance of mixed-bed ion exchange at ultralow concentrations

Experimental data were obtained to evaluate the effects of amine additives for pH control of solution and the volumetric flow rate of feed solution on the performance of mixed-bed ion exchange for the removal of ionic impurities in solution. The experiments were performed under various temperatures and cation resin ratios by using a continuous column system with NaCl solution. The breakthrough curves of ions, plotted as the ratio of the effluent to influent concentration versus run time or treated solution volume, give detailed results about the effects of the existence of the pH controller, such as ammonia and morpholine, and the variable flow rate on the fate of each ion in the units. The experimental results show that the morpholine breakthrough occurs earlier than the ammonia breakthrough and that the effect of ammonia on both sodium and chloride exchange rates is more significant than that of morpholine. The addition of ammonia in solution results in the decrease of cation resin capacity for the sodium removal much more than the addition of morpholine. The step changes in the flow rate affect significantly the shapes of sodium and chloride breakthrough curves. The effluent concentrations of sodium and chloride change according to the flow rate. However, the effect increases with decreasing operation capacity of cation resin, while it becomes serious around the breakthrough time of chloride and negligible after the time.     

液隙式热泵膜蒸馏海水淡化系统的热力性能分析

热泵膜蒸馏是一种新型的膜分离技术,在处理高浓度盐水方面具有很大的优势,而目前的热泵膜蒸馏系统存在渗透量较低、冷却水消耗量大等问题。为提高渗透量、减少冷却水的消耗,设计了一种新型液隙式热泵膜蒸馏的海水淡化系统,通过在Aspen Plus中自定义膜模块建立经过实验验证的系统仿真模型,研究了进料液温度、渗透侧温度及进料流量对系统膜通量及能效比等热力参数的影响。结果表明,渗透侧温度降低可引起渗透量增加和能效比减小,且在低渗透侧温度情况下渗透侧温度的改变对能效比影响更大。随着渗透侧温度变化,存在一个渗透侧温度使造水比最大且吨水能耗最小,研究工况下最大造水比可达3.42,最小吨水能耗为463 MJ/t,且该最佳渗透侧温度随进料液温度增加而增加。进料液流量增加可引起渗透量和能效比增加,引起吨水能耗升高和造水比降低,当进料液流量小于3 L/min时,进料液流量增加对吨水能耗和造水比的负面影响较显著,进料液温度为50℃时,料液流量从1.5 L/min增至3 L/min,造水比的降低幅度可达33.5%;料液流量从4.5 L/min增至6 L/min时,造水比的降低幅度降至10.6%。     

真空膜蒸馏法分离乙醇溶液的研究

采用聚偏氟乙烯复合中空纤维膜制作膜组件,制备小型实验装置用来分离从低浓度到高浓度的乙醇溶液,研究探讨了进料温度、料液流速、料液浓度、真空度对膜通量和分离因子的影响.进料温度升高时,膜通量及分离因子均增大.冷侧真空度的增加,通量呈线性增长,但分离因子减小.料液流速对膜通量和分离因子的影响温和.结果表明,真空膜蒸馏适用于浓...     

Recovery of Copper Ions from Wastewater by Hollow Fiber Supported Emulsion Liquid Membrane

Recovery of copper ions from wastewater using a hollow fiber supported emulsion liquid membrane (HFSELM) was studied with LIX984N as carrier, kerosene as diluents, and sulfuric acid solution as strippi...     

Preparation of polystyrene/poly(methyl methacrylate) blends by compressed fluid antisolvent technique

Submicron polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends were generated by the precipitation with a compressed antisolvent (PCA) technique. The generation of PS/PMMA blends was carried out by spraying a solution containing PS and PMMA into a precipitator. The blends without coalescence were observed to only be generated when both vapor and liquid CO₂ existed in the precipitator combined with appropriate total polymer concentration in solution, molecular weights (Mws) of PS and PMMA, mass ratio of PS to PMMA, flow rates of CO₂ and polymer solution, and liquid CO₂ level in the precipitator. Two Mws of PS, 144,000 and 44,000, and two Mws of PMMA, 85,000 and 36,000, were used in this study. It was found that the blends could be easier to generate using a higher PS Mw, a lower PMMA Mw, and a higher mass ratio of PS to PMMA. Toluene with a solubility parameter smaller than that of tetrahydrofuran (THF) was found to be the more appropriate solvent for generating spherical PS/PMMA submicron blends. The SEM and TEM images show that the spherical PS/PMMA core/shell blends could be generated at a temperature of 298 K, a pressure of 6.41 MPa, a liquid CO₂ level of 1/2 of the precipitator, a CO₂ flow rate of 2000 mL/min, a solution flow rate of 5 or 10 mL/min, and a total polymer concentration of 0.72 wt% for a PS Mw of 144,000, a PMMA Mw of 36,000, and a PS/PMMA mass ratio of 9/1. Individual and spherical PS and PMMA particles or spherical PS particles partially covered by a PMMA films, however, were generated when the liquid CO₂ level was of 1/8 or lower in the precipitator. A possible mechanism for the formation of core-shell blend was proposed.     

Treatment of sea water using electrodialysis: Current efficiency evaluation

In this paper, desalination of seawater using a laboratory scale electrodialysis (ED) cell was investigated. At steady state operation of ED, the outlet concentration of dilute stream was measured at different voltages (2−6 V), flow rates (0.1−5.0 mL/s) and feed concentrations (5000−30,000 ppm). The electrical resistance of sea water solution in the dilute compartment was initially calculated using basic electrochemistry rules and average concentration of feed and dilute streams. Then, current intensity in each run was evaluated using Ohm's law. Finally, current efficiency (CE) which is an important parameter in determining the optimum range of applicability of an ED cell was calculated. It was found out that, at flow rates larger than 1.5 mL/s, higher feed concentrations lead to larger values of CE. However, exactly opposite behavior was observed at lower flow rates. Increasing the feed flow rate increases CE to a maximum value then decreases it down to zero for all cell voltages and feed concentrations. In the case of higher feed concentrations, maximum values of CE are obtained at higher flow rates. As expected, in almost all experiments, CE increases by intensifying cell voltage. CE values of up to 48 indicate effective ion transfer across the ion exchange membranes in spite of low separation performance of the ED cell.     

泡沫分离法回收酶法生产生物柴油中的液体脂肪酶

采用泡沫分离法对酶法生产生物柴油过程中的水相脂肪酶进行回收并富集. 通过正交实验考察了液体脂肪酶溶液中pH值、通气速度、初始酶浓度对富集比、酶蛋白回收率和酶活回收率的影响. 结果表明,气速10 L/(L×h)、进料酶浓度0.2 g/L及pH 7.0时蛋白回收率和酶活回收率接近100%,相应的富集比为3.67;初始酶浓度对富集比和蛋白回收率有显著影响,回收过程中脂肪酶活性无损失. 甲醇的存在能显著提高回收速率,甘油的存在降低了富集比,而生物柴油的存在影响了泡沫的稳定性,要形成稳定的泡沫,生物柴油含量需小于0.01%.     

Permeate-Flux Declination for Ultrafiltration along Membrane Tubes

The correlation equations for predicting local permeate fluxes in tubular-membrane ultrafilters were derived from mass and momentum balances by the modified resistance-in-series model with the considerations of the increment of concentration polarization and the declines of transmembrane pressure and flow rate, along the membrane tube. Ultrafiltration of dextran T500 aqueous solution in a tubular microporous ceramic module has been carried out under various feed concentrations, transmembrane pressures, and feed flow rates, and many experimental data of ten-point local permeate fluxes along the tube were obtained to confirm the correlation predictions. The increment of concentration polarization, as well as the decline of permeate flux, along the tube was also discussed.     

Parametric studies on the performance of anion exchange for nitrate removal

Ion exchange performance to remove nitrate in surface and underground water was studied experimentally in batch and continuous operation systems under various conditions. Data were collected by using commercially available strong-base anion-exchange resins of C1 and OH types. Equilibrium curves, obtained through the batch system and plotted as the concentration ratio versus run time, were used to evaluate the effects of temperature, resin type, and initial feed concentration on the equilibrium characteristics of nitrate. The selectivity coefficients of the resins were correlated as a function of temperature by using the Kraus-Raridon equation. Breakthrough curves, obtained through the continuous column system and plotted as the ratio of effluent to influent concentration versus solution volume passed through the experimental column, gave detailed results about the effects of the system parameters, such as temperature, resin type, feed concentration, volumetric flow rate, column diameter and height on the performance of the anion exchange to remove nitrate. The results of this study could be scaled up and used as a design tool for a water-purification system of real ground water and surface water treatment processes.     

操作条件对γ-Al2O3膜分离性能的影响

通过正交实验探讨了酸性条件下,温度、压力、PH值、流速、浓度对γ-Al2O3管式多孔膜渗透通量和Mg2+的截留率的影响。实验采用溶胶–凝胶法自制管式纳米孔膜和错流循环过滤方式。结果表明,操作压力和温度对膜通量的影响显著,同时压力及pH对截留率影响显著,而酸性环境下有利于γ-Al2O3多孔膜对阳离子的脱除。     

电渗析与萃取耦合技术分离Ni(Ⅱ)与Co(Ⅱ)

为实现混合溶液中Ni(Ⅱ)与Co(Ⅱ)的分离,设计了电渗析与萃取耦合的集成分离技术,借助自行设计的设备,在选P507为萃取剂后,考察了电流密度、酸用量、体积流量、萃取剂皂化率、原料与萃取剂摩尔比、萃取方式等对分离效果的影响。结果表明:在实验范围内,电流密度3.8 mA/cm2,酸用量为理论用量的1.3倍,体积流量60 L/h、皂化率60%,原料与萃取剂摩尔比1∶1.7为优取的操作条件;料液循环重复萃取,能显著提高分离效果。由此表明,电渗析与萃取耦合的分离技术,可分离混合体系中的Ni(Ⅱ)、Co(Ⅱ),且无需溶剂参与。     

Factorial design applied to concentrate bioactive component of Cymbopogon citratus essential oil using short path distillation

Cymbopogon citratus (DC.) Stapf (Gramineae) is the scientific name of a plant known as lemongrass. It is characterized by the high concentrations of citral. This work aimed to analyze the influence of short path distillation process variables (evaporator temperature (EVT), volumetric feed flow rate (Q) and interactions between them), on the concentration of citral in the distillate stream of the process.