搅拌塔式反应器传热特性研究

分析了搅拌塔式反应器（ＳＣＲ）中多级冷却盘管隔板的传热特性,用稳态和非稳态的传热方法进行了实验研究。提出了同时考察拌雷诺数和轴向液流雷诺数影响的ＳＣＲ中多级冷却盘管隔板表面传热膜系数的关联式。研究结果表明,对于ＳＣＲ中冷却盘管隔板表面的传热膜系数,轴向液轩诺系数的影响与搅拌雷诺数的影响相比具有同等的重要性。     

Ionic Liquids as Modifying Agents for Protein Separation in Centrifugal Partition Chromatography

Aqueous two‐phase systems (ATPSs) can be applied in centrifugal partition chromatography (CPC) to separate biomolecules. Two ionic liquids (ILs) served as modifying agents to tune partition coefficients in the separation of two model proteins, myoglobin and lysozyme. Myoglobin was not affected by the ILs, while the partition coefficient of lysozyme was lowered with addition of IL. High stationary phase retention was achieved with ATPSs in a CPC column with cell size and geometry specially designed for unstable biphasic systems. When ILs were used as modifying agents, no notable decrease in stationary phase retention was observed. The injection volume was increased to 20 % of the total column volume and process simulations indicate that a further increase in the injection volume is possible.     

Effects of temperature,repeated exposure,and aging on polybutylene permeation by organic chemicals

The permeation parameters, partition coefficient and diffusion coefficient, were obtained for polybutylene (PB) with toluene using a gravimetric method. A PB sample was repeatedly exposed and desorbed, and the partition coefficient and diffusion coefficient were measured. Permeation parameters were also measured at different temperatures. The results were compared with those obtained from a 12-year-old PB pipe sample, which had experienced structural failure. Tests at an elevated temperature of 45°C failed to simulate the effect of polymer aging, whereas repeated sorption/desorption tests produced permeation parameters compatible with those of a 12-year-old PB pipe in service.     

The separation of glycerides by liquid-liquid column partition chromatography

A liquid-liquid partition chromatography method was developed to separate triglycerides. The solvent was a two phase mixture of acetone, heptane, and water supported on silane treated celite. A study was made of the best means for equilibrating the solvents and support, packing the column, and introducing the sample. The effect of various operating variables such as flow rate, sample size, column length, and solvent compositions was studied using trilaurin and trimyristin as model glycerides. Under the best conditions achieved, it was calculated that glycerides differing by two carbon atoms or one double bond would not separate completely, but glycerides differing by two double bonds or four carbon atoms would be separated. Cocoa butter, a relatively simple triglyceride, was fractionated, and the fatty acid composition of each fraction was determined by gas chromatography. The glyceride composition was calculated and compared with theoretical compositions. The results indicate that useful glyceride separation can be obtained with this system. Probably even more useful separations could be obtained if a more sensitive device were used to detect the triglycerides in the effluent. This would allow the use of solvent compositions which give larger retention volumes and more plate efficiency. Journal Paper No. J-4517 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa, Project No. 1517. Presented at the AOCS meeting in Toronto, Canada, 1962. Based on a thesis presented by B. C. Black in partial fulfillment of the requirements for a master’s degree.     

Heat transfer in a liquid-liquid spray column

A theoretical and experimental study of direct contact heat transfer in a kerosene-water spray column has been carried out. A mathematical model for the process with a drop size distribution is proposed, and the associated computer program for the numerical solution developed. Correlations for the overall area heat transfer and axial dispersion coefficients for the column were obtained. Applying the mathematical model with experimentally obtained parameters, temperature profiles of both phases could be predicted. Comparisons with previous work in the literature support the present study. From the results, operation with uniform drop size in a short column is recommended.     

Pyrolysis of scrap tire rubbers: Relationships of process variables with pyrolysis time

The functional relationships of industrially interesting variables such as pyrolysis temperature, heating rate, and sample size with pyrolysis time were explored to provide basic information on designing energy efficient processes. Pyrolysis kinetics of scrap tire rubbers tested in this study were investigated to formulate the functional relationships of pyrolysis temperature and heating rate. The pyrolysis time decreases exponentially with increasing pyrolysis temperature and heating rate, indicating high activation energies of pyrolysis reaction of the scrap tire rubbers tested in this study. The effect of heat transfer on the pyrolysis kinetics was evaluated by seeking the functional relationship between the sample size and pyrolysis time.The pyrolysis time increases linearly with increasing sample diameter. The slope of the straight line is proportional to the specific heat of the sample.     

气相色谱法测工业三乙醇胺

以聚甲基硅橡胶毛细管柱为色谱柱 ,乙醇为溶剂 ,氢火焰离子检测器检测 ,分别对工业三乙醇胺中一乙醇胺、二乙醇胺、三乙醇胺进行分离 ,进而测出其含量。并对色谱柱、载气流速、柱温溶剂、进样量等色谱条件的选择 ,以及试样与溶剂的体积比的选择进行了实验。利用保留时间定性 ,对归一化法、内标法、外标法进行了对比实验 ,结果归一化法快速可行。在选定的最佳色谱条件下 ,三乙醇胺样品回收率的测定结果在 98.72 %～ 1 0 3.2 %之间。精密度为 CV=0 .40 3%。对实际样品测试结果 ,色谱法相对标准偏差 CV=0 .1 35% ,化学法相对标准偏差 CV=1 .81 % ,而色谱法不用对分析样品处理 ,操作简单、快速 ,便于工业实际生产监测。     

Wall-to-bed heat transfer in liquid—solid and gas—liquid—solid fluidized beds part I: Liquid—solid fluidized beds

Experimental work was conducted to investigate the effect of particle size and particle density upon the wall-to-bed heat transfer characteristics in liquid—solid fluidized beds with a 95.6 mm column diameter over a wide range of operating conditions. The radial temperature profile was found to be parabolic, indicating the presence of a considerable bed resistance. The effective radial thermal conductivity and the apparent wall film coefficient were obtained on the basis of a series thermal resistance model. The modified Peclet number of the radial thermal conductivity decreases upon the onset of fluidization, has a minimum at a bed porosity of 0.6 to 0.7 and increases with further increase of bed porosity. The modified Peclet number decreases considerably with decreasing particle size or increasing particle density. The apparent wall heat transfer coefficient can be represented well by a Colburn j-factor correlation over a wide range of data as follows: j′_H = 0.137 Re′^?0.271 A close analogy is found to exist between the modified j-factor for wall heat transfer coefficient and that for wall mass transfer coefficient, in liquid—solid fluidized beds.     

Application of Response Surface Methodology for Optimization of Bromelain Extraction in Aqueous Two-Phase System

Extraction of bromelain from pineapple fruit in an aqueous two phase system (ATPS) composed of polyethylene glycol (PEG) 1500 and potassium phosphate has been studied using response surface methodology. The various process variables such as PEG, potassium phosphate and NaCl concentration, and pH were optimized using a central composite rotatable design (CCRD) of response surface methodology (RSM) based on the partition coefficient, % yield, and purification factor of an enzyme. An optimized ATPS composed of 14% (w/w) PEG 1500, 17.66% (w/w) potassium phosphate and 1 mM sodium chloride at pH 7.5 was used to purify bromelain from a pineapple fruit. With this system, a maximum enzyme partition coefficient of 12.62 and %yield of 90.33 in the top PEG-rich phase with a purification factor of 2.4 was predicted. The enzyme partition coefficient, % yield, and purification factor obtained from experimentation are 12.22, 89.65, and 2.8, respectively, in the top PEG phase. The response model is validated by the closeness between the predicted and experimental results.     

Nonlinear Distribution Coefficients in Gas Chromatography

Abstract

Nonlinear partition coefficients of polar solutes on coated and uncoated diatomaceous-earth supports lend themselves to mathematical treatment when proper precautions are taken to reproducibly condition the chromatographic column. A previously derived equation was used to calculate the adsorption and distribution isotherms from adsorption-desorption chromatograms whose diffuse elution curves approached the base line asymptotically. In the concentration ranges studied, the adsorption of acetone on uncoated support obeyed the Temkin isotherm equation. A plot of the amount adsorbed vs. the log of the concentration of the solute in the carrier gas gave a straight line. The adsorption of acetone on coated columns under the same conditions followed a Freundlich isotherm equation, and log-log plots of amount adsorbed vs. concentration of the solute gave straight lines. The equations for the lines obtained from the isotherm plots of the coated and uncoated columns were used to calculate the retention volumes as a function of concentration, by means of the equation V_Ng = dQ/dC. The validity of the retention volume and adsorption equations were checked by the agreement of theoretical and experimental measurements.

Within limits retention volumes may be correlated with sample size, providing the contribution of the bulk liquid phase is known. It is expected that the retention volume-sample size relationship would be more useful in low-loaded columns, where the bulk liquid-phase contribution is either small or negligible. The temperature-effect studies showed that, as expected, stronger adsorption bonds are formed at lower temperatures. The sample size-temperature studies on the inactive (RIC) support coated with tri-o-tolyl phosphate showed that the liquid phase contributed to the non-linearity of the distribution coefficient in a minor but unknown extent.     

隔板高度对螺旋隔板套管换热器的影响

采用计算流体力学方法对螺旋隔板套管式换热器壳侧的传热和阻力特性进行模拟,建立了螺旋升角为40o、螺旋隔板高度分别为b, 3b/4, b/2, b/4和b/8 (b为螺距)的换热器模型,分析了螺旋隔板高度对壳程流体传热的影响. 结果表明,相同壳程工质体积流量下,换热器的壳程总换热量、换热系数和阻力系数随隔板高度增加而增加,单位长度压降随隔板高度增加而减小. 隔板高度为b, 3b/4和b/2时比隔板高度为b/8时的换热系数分别提高7.83, 3.68和3倍,壳程进出口压降分别减少98%, 97%和95%,但阻力系数却分别提高34, 15.3和5.3倍. 为提高螺旋隔板强化单管换热器的壳侧综合换热性能,其隔板高度应为1/2b~3/4b.     

低质量流率蒸汽真空水平管内凝结传热特性的实验研究

对换热长度为3.4 m、内径为38 mm的真空水平管内的蒸汽凝结流动换热特性进行了实验研究。分析了蒸汽质量流率小于9 kg/(m²·s),蒸汽饱和温度为50、60和70℃,换热温差为3~7℃时对凝结过程的影响。通过对分层流动冷凝换热机理分析,建立了热分区角计算模型。实验结果表明,热分区角随着质量流率的增加而增加,随着传热温差的增大而增大;饱和温度对管内凝结的局部传热系数和热分区角影响较小。通过以热分区角为分区界限,建立了局部传热系数经验关联式,在预测实验工况下,对于管顶部膜状冷凝区,预测精度在±25%以内;对于管底部冷凝液对流换热区,预测精度在+25%~-35%。     

Direct-Contact Heat Transfer during n-Pentane Vaporization in a Two-Dimensional Water Column

Direct-contact vaporization heat transfer is investigated by analyzing the heat transfer coefficient with the area of liquid-liquid direct-contact interface. The interface areas of liquid-liquid heat transfer are determined by stroboscopic images. At higher temperature, the heat transfer area per unit volume decreases. The water temperature has no significant influence on the heat transfer coefficient. The effects on droplet size distributions of operating variables including inlet water temperature, n-pentane flow rate, and test position with packing and without packing are compared.     

Wall to liquid mass transport and diffusion controlled corrosion in fixed bed reactors

The diffusion controlled corrosion at the inner wall of a fixed bed reactor was studied in terms of the wall to liquid mass transfer coefficient. Variables studied are solution flow rate, physical properties, and packing size and geometry. The effect of drag reducing polymers on the rate of mass transfer and on the rate of corrosion was studied. The presence of the drag reducing polymer decreased the rate of both mass transfer and corrosion by a factor ranging from 8.92% to 39.47%. All variables were correlated by dimensionless equations. Possible applications of these data in heat transfer were highlighted.     

HEAT TRANSFER CHARACTERISTICS OF THREE PHASE FLUIDIZED BEDS

Heat transfer characteristics of two (liquid-gas, liquid-solid) and three (liquid-gas-solid) phase fluidized beds have been studied in a 15.2 cm-ID column fitted with an axially mounted cylindrical healer. Effects of gas velocity (0-12 cm/s). liquid velocity (0-16cm/s), particle size (1.7-8.0 mm) and liquid viscosity (0.001-0.039 Pa s) on heat transfer coefficient were determined. The heat transfer coefficient increased with fluid velocities and particle size and it decreased with liquid viscosity in two and three phase fluidized beds. The bed porosity at which the maximum heat transfer occurred decreased with particle size but increased with liquid viscosity. The coefficient were correlated in terms of experimental variables. Modified Nusselt number from the present and previous studies has been correlated with modified Prandtl and Reynolds numbers.     

Effects of Spray-Drying Conditions on the Physicochemical Properties of Blackberry Powder

The purpose of this work was to study the effects of spray-drying conditions on the physicochemical characteristics of blackberry powder using a central composite rotatable design. Inlet air temperature (140–180°C) and maltodextrin concentration (5–25%) were employed as independent variables. Moisture content, hygroscopicity, anthocyanin retention, color, powder morphology, and particle size were analyzed. A higher inlet air temperature significantly increased the hygroscopicity of the powder, decreased its moisture content, and led to the formation of larger particles with smooth surfaces. Powders produced with higher maltodextrin concentrations were less hygroscopic, slightly lighter and less red, and had a lower moisture content. Anthocyanin retention was mainly affected by drying temperature due to the heat sensitivity of the pigment. The optimal processing conditions were an inlet air temperature of 140–150°C and maltodextrin concentration of 5–7%. Overall, these results indicate that good quality powders can be obtained by spray drying, with potential applications for the food industry.     

Ammonia‐functionalized particulate poly(glycidyl methacrylate‐co‐ethylene dimethacrylate)‐based polymers as stationary phase for protein retention

A poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) polymeric matrix was synthesized, amino‐functionalized and packed to be tested for protein retention and separation. Functionalization was carried out by reacting the epoxy groups with 30% ammonia solution to provide amino groups for anion exchange with proteins. Physical characterization of the particulate material showed that the functionalized polymer is macroporous and exhibits a unimodal pore size distribution. The resin presents good thermal stability. Chromatographic characterization using bovine serum albumin (BSA) and α‐lactalbumin as model proteins showed good retention properties for the amino‐functionalized matrix. The values obtained for the equilibrium constant (K) were around 3 for BSA, both in batch reactor and column‐packed operation mode. The K values for α‐lactalbumin were even higher, 8.01 and 4.65 for the batch and column‐packed experiments, respectively. Finally, axial dispersion coefficients were obtained, with a constant value of 0.0141 cm²s^?1 for BSA. Higher values were obtained for α‐lactalbumin, but in this case the axial dispersion coefficient was not constant and its values were dependent on the flows used. © 2001 Society of Chemical Industry     

Heat transfer in three-phase (G/L/S) circulating fluidized beds with low surface tension media

Characteristics of heat transfer were investigated in a three-phase circulating fluidized bed whose diameter and height were 0.102 m (ID) and 2.5 m, respectively. Effects of gas and liquid velocities, particle size (0.5–3.0 mm), solid circulation rate (2.0–6.5 kg/m² s), and surface tension (47.53–72.75×10⁻³ N/m) of liquid phase on the heat transfer coefficient were examined. It was found that the heat transfer coefficient (h) between the immersed vertical heater and the riser proper of the three-phase circulating fluidized bed increased with increase in gas and liquid velocities, but did not change considerably with a further increase in liquid velocity, even in the higher range. The value of heat transfer coefficient increased gradually with increase in the size of fluidized solid particles without exhibiting the local minimum, which represented that there was no bed contraction in three-phase circulating fluidized beds due to the higher liquid velocity. The heat transfer system could attain a stabilized condition more easily with increase in particle size. The value of heat transfer coefficient increased with increase in solid circulation rate in all the cases studied due to the increase of solid holdup in the riser. The value of heat transfer coefficient decreased with increase in surface tension of liquid phase, due to the decrease of bubbling phenomena and bubble holdup. The decrease in liquid surface tension could lead to an increase in elapsed time from which the temperature difference between the heater surface and the riser became an almost constant value. The experimentally obtained values of heat transfer coefficient were well correlated in terms of dimensionless groups as well as operating variables.     

Emission characteristics of volatile organic compounds from regenerated PET fibers based on the headspace gas chromatograph

The emission behaviors of volatile organic compounds (VOCs) can be characterized by the key parameters: the initial concentration (m₀), partition coefficient (K) and the diffusion coefficient (D). The MHE-GC method was validated to determine the emission characteristics of VOCs (Benzene, Toluene, Ethylbenzene, P-xylene, M-xylene, Styrene, and O-xylene) in regenerated PET fibers. This work has studied the effects of fiber size, sample weight incubation time and incubation temperature on the detection of these VOCs. It showed finer fiber sample with less sample facilitated the emission of VOCs in fibers above detectable limit. The optimized headspace incubation time, fiber sample weight, and headspace incubation temperature were selected as 60 min, about 0.8 g and 110 °C, respectively. In addition, incubation temperature has a negative effect on the gas/fiber partition coefficient. The fibers with greater fineness showed higher activation energy, which revealed a positive release of VOCs from fibers. The relative standard deviation (RSD/%) of detection was 3%–10%. The present method is reliable and suitable for use in testing of the VOCs content in fiber-related materials.     

同轴式内部热耦合精馏塔的传热性能

提出了一种以实验物系的物性数据为基础的计算同轴式内部热耦合精馏塔（HIDiC）总传热系数的方法。本文以乙醇-水为实验物系,以自行搭建的中试规模同轴式HIDiC为研究对象,通过在不同压缩比下（1.4~2.6,步长为0.1）的连续操作实验研究,得到塔内的温度分布,通过计算两塔段的相变给热系数来计算该塔的总传热系数和精馏塔段与提馏塔段间的换热量。在同轴式HIDiC中乙醇-水实验物系总传热系数的计算值在300~800W/(m²·K),并且随着压缩比的增大而逐渐降低。在操作条件和产品纯度与实验值保持一致的情况下,将精馏塔段与提馏塔段间换热量的计算值带入软件中模拟,得到的全塔温度分布与实验中的温度分布在误差范围内吻合良好,证明本文计算同轴式HIDiC总传热系数的方法切实有效。