甲基二乙醇胺水溶液在改进的湿壁塔上吸收二氧化碳的动力学模型

To get more accurate kinetic data of the absorption of CO2 into aqueous solution of N-methyldiethanolamine, a wetted wall column was modified to more uniformly distribute the liquid on the column surface and gas in the absorbing chamber and change the length of the column. The average liquid film thickness and the liquid-phase mass transfer coefficient were measured, and a correlation for the Sherwood number, Reynolds number and Schmidt number was obtained for the modified wetted wall column. The equilibrium concentrations in chemical reactions were calculated with a minor absolute error for calculating the rate constant more accurately. A mathematical model for the CO2 absorption was established based on the diffusional mass transfer accompanied with parallel reversible reactions, and the partial differential equation was solved by Laplace transform. An analytical expression for the concentration of carbon dioxide as a function of time and penetration depth in liquid film and the average interphase mass transfer rate was obtained. This model was also used to calculate the rate constant for a second-order reaction, which was in good agreement with reported data.     

应用降膜结晶法将十二烷二酸从同系物中分离及精制

Separation and purification of dodecanedioic acid (DDDA) from its homologous compounds were studied experimentally by falling film crystallization (FFC). The influences of various operation parameters, including crystallizing time, flow rate of melt and temperature of glycerine bath, on purity of DDDA and crystallizing rate were investigated. Over 99% (by mole) DDDA was obtained for a feed composition of 96% (by mole). The main factors affecting the separation efficiency are flow rate of melt and temperature of glycerine bath. The crystallizing layer of DDDA was further purified by sweating and blasting. A set of optimized operation data are provided for better understanding the mechanism of heat and mass transfer in FFC, and for further industrial application of DDDA purification process.     

应用降膜结晶法将十二烷二酸从同系物中分离及精制

Separation and purification of dodecanedioic acid (DDDA) from its homologous compounds were studied experimentally by falling film crystallization (FFC). The influences of various operation parameters, including crystallizing time, flow rate of melt and temperature of glycerine bath, on purity of DDDA and crystallizing rate were investigated. Over 99% (by mole) DDDA was obtained for a feed composition of 96% (by mole). The main factors affecting the separation efficiency are flow rate of melt and temperature of glycerine bath. The crystallizing layer of DDDA was further purified by sweating and blasting. A set of optimized operation data are provided for better understanding the mechanism of heat and mass transfer in FFC, and for further industrial application of DDDA purification process.     

溶液自发结晶过程动力学参数研究

The batch cooling crystallization initiated from spontaneous nucleation for aqueous solution of potas- sium nitrate was studied.The concentration and transmittance data were acquired on line throughout the operation. Based on solute mass transfer in both liquid and solid phases,a kinetic model was deduced by assuming that the late period of primary nucleation resembles the initial period of the secondary nucleation.Nucleation and crystal growth stages were identified.Kinetic parameters were estimated piecewise from online experimental data and compared with those in literature.The estimated kinetic parameters for stages without apparent primary nucleation agreed well with those in literature.Further,a simulated concentration curve was also drawn from the estimated kinetic parameters and it matched well with that in experiment.     

基于多场协同理论的渗透蒸发传质模型

Toprovide a theoretical basis for optimizing the pervaporation procedure, a mass transfer model for pervaporation for binary mixtures was developed basedon the multi-fields synergy theory. This model used the mechanism of sorption-diffusion-desorption and introduced a diffusion coefficient, which was dependent on the feed concentration and temperature. Regarding the strong coupling effect in the mass transfer, the concentration distribution in membrane was predicted using the Flory-Huggins thermodynamic theory. The batch experiments and other experiments with constant composition-were conducted-using a modified chitosan pervaporatioffmembrane to separate tert-butyl alcohol （TBA）-water mixtures. The parameters of the mass transfer model were obtained from the flux of the experiments with a constant composition and the activity coefficients available through phase equilibrium equation, using the Willson equation in the feed side and the Flory-Huggins thermodynamic theory within the membrane The simulation results of the experiments .are in good agreement with the results, of the experiments.     

间歇结晶器中维生素C的结晶热力学与动力学研究

The bench-scale cooling crystallization for ternary solution of L-ascorbic acid (Vitamin C) was studied.The solid-liquid phase diagram of Vitamin C-water-ethanol system was obtained on the basis of differential scanning calorimeter (DSC) curves. The heat of crystallization of Vitamin C was calculated with the aid of quantitative analysis. According to the population balance equation under unsteady state, the rates of nucleation and growth were determined. The parameters of crystallization kinetics equations were estimated by regression of experimental data. Crystal morphology and size were determined with x-ray diffraction and TA Ⅱ Coulter Counter.     

多层合采油藏最大有效井径数学模型及精确解

The maximum effective hole-diameter mathematical model describing the flow of slightly compressible fluid through a commingled reservoir was solved rigorously with consideration of wellbore storage and different skin factors. The exact solutions for wellbore pressure and the production rate obtained from layer j for a well production at a constant rate from a radial drainage area with infinite and constant pressure and no flow outer boundary condition were expressed in terms of ordinary Bessel functions. These solutions were computed numerically by the Crump‘‘s numerical inversion method and the behavior of systems was studied as a function of various reservoir parameters. The model was compared with the real wellbore radii model. The new model is numerically stable when the skin factor is positive and negative, but the real wellbore radii model is numerically stable only when the skin factor is positive.     

Maximum Effective Hole Mathematical Modei and Exact Solution for Commingled Reservoir

The maximum effective hole-diameter mathematical modei describing the flow of slightly compressible fluid through a commingled reservoir was solved rigorously with consideration of wellbore storage and different skin factors. The exact solutions for wellbore pressure and the production rate obtained from layer j for a well production at a constant rate from a radial drainage area with infinite and constant pressure and no flow outer boundary condition were expressed in terms of ordinary Bessel functions. These solutions were computed numerically by the Crump's numerical inversion method and the behavior of systems was studied as a function of various reservoir parameters. The modei was compared with the real wellbore radii modei. The new modei is numerically stable when the skin factor is positive and negative, but the real wellbore radii modei is numerically stable only when the skin factor is positive.     

Crystallization and pressure filtration of anhydrous milk fat: Mixing effects

Melt crystallization of anhydrous milk fat and subsequent filtration of the slurry is a common process for obtaining milk fat fractions with different physical and chemical properties. The crystallization mechanism is very complex and little is known about how the crystallizer conditions and the crystal size distribution (CSD) affect the filtration process. The objective of this study was to characterize the fractionation process and determine which geometric parameters of the crystallizer affect the filtration step. Two scales of fractionation were studied, 0.6 L and 3.6 L, with crystallization at 28°C. The slurry was pressure-filtered after 24 h at 500 kPa in a 1-L chamber. Impeller diameters and speeds were varied for both scales. Photomicroscopy and spectrophotometry were used to characterize the crystallization process, and filtration rates were measured by weighing the amount of filtrate passing through the filter. Filtration resistance values, calculated using the constant pressure filtration equation, as well as photomicroscopy results indicated that the agglomerates and crystals that formed had different morphological characteristics for the different mixing and flow regimes in the crystallizer. Crystallization conditions that provide an optimal filtration time, a solid fraction with minimal liquid entrainment, and a CSD with an intermediate range of sizes (80–500 μm) having good packing properties for filtration were found.     

液膜性质的小尺度研究

Structured packing is a good candidate for CO₂ capture process because of its higher mass transfer efficiency and lower pressure drop.Now,the challenging problem of CO₂ capture and storage demands more and more efficiency equipment.The aim of the present study is to investigate the liquid film characteristics under counter current gas phase and throw some insight into the enhancing mechanism of mass transfer performance in structured packing.A high speed digital camera,non-intrusive measurement technique,was used.Water and air were working fluids.Experiments were carried out for different gas/liquid flow rates and different inclination angles.The time-average and instantaneous film widths for each set of flow parameters were calculated.It is shown that the effects of gas phase could be neglected for lower flow rate,and then,become more pronounced at higher flow rate.According to instantaneous film width,three different stages can be distinguished.One is the constant width of liquid film.The second is the slight decrease of film width and the smooth surface.This kind of character will lead to less interfacial area and deteriorate the packing mass transfer performance.For the third stage,the variation of film width shows clearly chaotic behavior.The prediction model was also developed in present work.The predicted and experimental results are in good agreement.     

Studies on nonisothermal crystallization of ultra–high molecular weight polyethylene in liquid paraffin

The nonisothermal crystallization kinetics for ultra–high molecular weight polyethylene (UHMWPE) in liquid paraffin (LP) systems was investigated through differential scanning calorimetry (DSC) measurement. The influence of UHMWPE concentration and cooling rate on crystallization mechanism and spherulitc structure as implied by the modified Avrami equation and Mo's analysis was determined, whereas the Ozawa's approach fails to describe the crystallization behaviors of these UHMWPE‐diluent systems. As a result, in the modified Avrami analysis, it was found that the Avrami exponent is constant around five at various concentrations of UHMWPE and cooling rates. Further, the value of F(T) in the Mo's approach increases with the increasing of relative crystallinity and UHMWPE content in the blends. The nonisothermal crystallization kinetics presented here are the first for UHMWPE‐diluent systems. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Nonisothermal crystallization kinetics of poly(vinylidene fluoride) in a poly(vinylidene fluoride)/dibutyl phthalate/di(2‐ethylhexyl)phthalate system via thermally induced phase separation

The nonisothermal crystallization kinetics of poly(vinylidene fluoride) (PVDF) in PVDF/dibutyl phthalate (DBP)/di(2‐ethylhexyl)phthalate (DEHP) blends via thermally induced phase separation were investigated through differential scanning calorimetry measurements. The Ozawa approach failed to describe the crystallization behavior of PVDF in PVDF/DBP/DEHP blends, whereas the modified Avrami equation successfully described the nonisothermal crystallization process of PVDF. Two stages of crystallization were observed in this analysis, including primary crystallization and secondary crystallization. The influence of the cooling rate and DBP ratio in the diluent mixture on the crystallization mechanism and crystal structure was determined by this method. The Mo approach well explained the kinetics of primary crystallization. An analysis of these two methods indicated that the increase in the DBP ratio in the diluent mixture caused a decrease in the crystallization rate at the primary crystallization stage. The activation energy was determined according to the Kissinger method and also decreased with the DBP ratio in the diluent mixture increasing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of polyethylene glycol on the performance of ultrahigh‐molecular‐weight polyethylene membranes

Porous, flat membranes of ultrahigh‐molecular‐weight polyethylene (UHMWPE) were prepared by thermally induced phase separation, with mineral oil as a diluent and poly(ethylene glycol) with a weight‐average molecular weight of 20,000 (PEG20000) as an additive. Through the control of the rheological behavior, crystallite size, and pore structure, the influential factors, including the diluent, poly(ethylene glycol) (PEG) content, and cooling rate, were investigated. The results suggested that PEG could decrease the viscosity of UHMWPE/diluent apparently. The crystal density decreased when mineral oil was added, which made the melting point and crystallinity of UHMWPE lower. The crystallization rate and crystallinity also increased with the addition of PEG. However, the addition of excess PEG restrained crystal growth. PEG20000 in membranes could be extracted absolutely through the soaking of the membranes with fresh water for 7 days. With increasing PEG content, both porosity and pure water flux first increased and then decreased, reaching a maximum at a PEG mass fraction of 10%. The cooling rate had a direct effect the crystal structure. A slow cooling rate was good for crystal growth and diluent integration. Therefore, the pure water flux increased along with the temperature of the cooling medium, whereas porosity first increased and then decreased, reaching a maximum at 40°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The influence of paraffin wax addition on the isothermal crystallization of LLDPE

The influence of paraffin wax addition on the isothermal crystallization kinetics of linear low density polyethylene (LLDPE) was studied in a temperature range where the wax was always in the molten state and could be considered a solvent for LLDPE. The LLDPE/wax blends were prepared by melt mixing in the following compositions: 100/0, 95/5, 90/10, 80/20, 70/30, and 60/40. The results obtained show that the rate of isothermal crystallization is depressed by wax addition at constant crystallization temperatures. LLDPE needs a higher amount of supercooling to start crystallizing as the content of wax increases in the blends. The Flory–Huggins theory (FH) for polymer/diluent mixtures was applied employing equilibrium melting temperature values obtained by extrapolation with the Hoffman–Weeks method. The results of the FH analysis indicate that the interactions between wax and LLDPE are nonlinear and strongly depend on composition. This nonlinear composition dependence of wax/LLDPE interactions is reflected in the complex way in which the overall crystallization kinetics rate depends on both supercooling and composition. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44398.     

Membrane formation of poly(vinylidene fluoride)/poly(methyl methacrylate)/diluents via thermally induced phase separation

The role of the single diluents and mixed diluents on the poly (vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend membranes via thermally induced phase separation (TIPS) process was investigated. The crystallization behaviors of PVDF in the diluted samples were examined by differential scanning calorimetry. The melting and crystallization temperatures of those diluted PVDF blend were decreased with the enhanced interactions between polymer chains and diluent molecules. The crystallinity of PVDF in the diluent was always higher than that obtained in PVDF blend sample. This can be explained by the dilution effects, which increased the average spatial separation distances between crystallizable chains. Thus, the PVDF crystallization was favored. Additionally, solid‐liquid (S‐L) phase separation occurred in the quenched samples. Illustrated by scanning electron microscopy, inter‐ and intraspherulitic voids were formed in the ultimate membranes, which related to the polymer/diluent interactions, the kinetics of crystallization and diluent rejection from the growing crystal. The porosity of the PVDF blend membranes obtained from the mixed diluents was higher than those obtained from the single diluent samples. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of diluents on membrane formation via thermally induced phase separation

The effect of diluents on isotactic polypropylene (iPP) membrane formation via thermally induced phase separation was investigated. The diluents were methyl salicylate (MS), diphenyl ether (DPE), and diphenylmethane (DPM). The cloud-point curve was shifted to a lower temperature in the order iPP–MS, iPP–DPE, and iPP–DPM, whereas the crystallization temperature was not influenced so much by diluent type. Droplet-growth processes were investigated under two conditions: quenching the polymer solution at the desired temperature and cooling at a constant rate. Although droplet sizes were in the order iPP–MS, iPP–DPE, and iPP–DPM in both cases, the difference was more pronounced with the constant cooling rate condition. Scanning electron microscopy indicated that interconnected structures were obtained when the polymer solution was quenched in ice water. The effect of the diluents on these structures was observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 169–177, 2001     

苯基磷酸锌对聚乳酸结晶行为影响的研究

采用DSC,POM研究了成核剂苯基磷酸锌（PPZn）对聚乳酸结晶行为的影响。结果表明：PPZn可以作为聚乳酸的高效成核剂,PPZn的加入显著提高了聚乳酸的结晶速率和结晶度。当PPZn的质量分数为5％0时TCs（起始结晶温度）降低了约24℃,TCe（终止结晶温度）降低了约29℃。PPZn的加入使聚乳酸的半结晶时间大大缩短。当PPZn的质量分数为2％时,结晶速率常数增大约5个数量级。     

头孢拉定连续结晶工艺研究

采用三级混合悬浮混合产品出料结晶器(MSMPR),搭建了头孢拉定连续结晶实验装置。通过单因素实验研究了养晶pH值、晶种添加量、原料液浓度、停留时间、结晶系统温度及搅拌速率等结晶工艺条件对头孢拉定连续结晶产品收率及粒度分布的影响,优化了头孢拉定连续结晶工艺参数。通过实验获得优化结晶工艺参数：结晶温度293.15 K,搅拌速率180 r·min^-1,养晶pH=2.85,晶种添加量为3%(质量分数),头孢拉定原料液浓度11%(质量分数),停留时间33.3 min,此条件下可以获得平均粒径为85.3μm,收率为76.53%的头孢拉定连续结晶产品。     

乳化液膜法提取废水中的阿司匹林

针对阿司匹林（ASA）结晶母液经处理后产生的废液,采用搅拌和超声结合的方法制备了乳化液膜体系来回收ASA。以环己烷为膜溶剂,Span80做表面活性剂,石蜡做膜稳定剂,氢氧化钠（NaOH）为内水相,研究了表面活性剂浓度、内水相NaOH浓度、内水相类型、外相pH、油内比、乳水比、搅拌速度、膜溶剂类型、盐浓度、ASA初始浓度等试验条件对ASA萃取效果的影响,并进行了破乳研究。结果表明：在最佳实验条件下[环己烷90%（质量分数）、Span80 6%（质量分数）、C（NaOH）=0.1mol/L、油内比1：1、水乳比1：4、搅拌速度200r/min、ASA初始浓度500mg/L],不对外相进行pH调节时,15min后ASA的萃取率可高达97.4%。对实验后的乳液进行离心破乳,20min后破乳率可达72.9%,破乳后的油相重复利用5次后,对ASA的提取率仍在76%左右。     

蒸氨废水化学沉淀除氟结晶动力学模型

以质量扩散-表面反应两步结晶理论为基础,推导出氟化钙沉淀结晶动力学模型,以蒸氨废水为研究对象,氯化钙为沉淀剂,采用间歇结晶和在线粒度监测技术测定了氟化钙结晶动力学数据,采用非线性优化技术获得了氟化钙结晶动力学模型参数,并对该模型进行了实验验证,结果表明模型及模型参数效果良好,模型值与实验值平均相对误差为3.37%。氟化钙沉淀结晶过程属于表面反应控制过程,氟化钙存在明显的聚结现象。模型模拟结果表明:钙离子浓度一定时,氟离子初始浓度越高则初始阶段氟离子浓度下降越快,初始氟离子浓度过高或过低,最终均不利获得较低的氟离子浓度;适当提高操作温度可以促进氟离子的净化,但温度过高则不利。