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Janina Rodakiewicz-Nowak Masaaki Ito 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(7):809-816
The effect of various water‐miscible organic solvents (ethanol, methanol, acetone, acetonitrile, N,N‐dimethylformamide (DMF) and dimethylsulfoxide (DMSO)) on the kinetics of 4‐tert‐butylcatechol (tBC) oxidation in the presence of different samples of organic solvent‐resistant tyrosinase (OSRT) has been studied. In contrast to mushroom tyrosinase the enzyme shows a high relative stability in solutions of organic solvents and increased activity toward the bulky and hydrophobic substrate, tBC, in respect to catechol. Rates of the studied OSRT‐catalyzed reactions are however reduced by the presence of organic solvents and for all studied samples of OSRT decrease exponentially with the content of an organic solvent. The effect has been satisfactorily described by the effect of organic solvents on the thermodynamic activity of tBC. The correlation of the inhibition parameters with the hydrophobicity of a particular solvent (log P), its intrinsic molar volume, Vi, and the Dimroth–Reichardt parameter, ET(30), are shown. The results allow also the prediction of OSRT activity in aqueous solutions of water‐miscible organic solvents. Copyright © 2003 Society of Chemical Industry 相似文献
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Abdul Quiyoom Vivek V. Buwa S. K. Ajmani 《American Institute of Chemical Engineers》2017,63(8):3582-3598
The present work is carried out to understand the effect of free surface on liquid velocity distribution, dynamics and liquid phase mixing in a shallow basic oxygen furnace (BOF). Three‐dimensional/transient Euler–Lagrange (EL) without/with volume‐of‐fluid (VOF) simulations of dispersed gas–liquid flow in a scaled‐down model of the BOF were performed. For lower H/D ratios, EL simulations performed with no‐slip and free‐slip boundary conditions led to oscillatory plume behavior and higher liquid velocity regions which in turn led to lower mixing time. In contrast, EL + VOF simulations led to reduced meandering motion of bubble plumes and lower liquid velocities resulting in higher mixing times. Interestingly, the mixing time predicted using EL + VOF approach was found to be in a good agreement with the measurements. The results presented in this work show that free surface has a significant effect on dynamics of gas–liquid flow and liquid phase mixing for shallow vessels with H/D ≤ 0.5. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3582–3598, 2017 相似文献
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Gas holdup has been measured in an 83‐mm diameter, 2.2‐m high column at high gas superficial velocities — 0.22 to 2.7 m/s — and at liquid (water) superficial velocities of 0 to 0.47 m/s, by means of a differential pressure transducer. The equation of Hills (1976) based on the slip velocity gives good predictions of the gas holdup for 0.1 ≤ Eg ≤ 0.4. However, the holdups predicted by this approach are considerably higher than the experimental values at gas velocities high enough that Eg > 0.4. Other equations from the literature are also shown to be inadequate. The new data and earlier data at high gas velocities are therefore correlated with a new dimensional equation for Ul ≤ 0.23 m/s. 相似文献
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研究建立了同时测定三磷酸胞苷二钠中乙醇、丙酮、氯甲醚、甲苯、苯乙烯5种有机溶剂残留量的毛细管气相色谱法。样品以乙腈为溶剂,经DB-FFAP(30 m×0.32 mm×0.25μm)毛细管柱分离,氢火焰离子化检测器检测,这5种有机溶剂呈良好的线性响应,平均回收率在98.3%~99.5%,精密度RSD在0.21%~1.92%,最低检出限可达5.0~7.5 mg/kg。本方法简单、灵敏、准确,完全能满足药品中所述有机溶剂残留量的测定要求。 相似文献
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Thanapalan Murugesan G. S. Venkat Rathnam S. Panduranga Rao P. Gangadhar Rao 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):290-294
In the present study of gas–liquid contactors, mean residence/contact time was calculated from knowledge of superficial velocity and the gas phase hold-up, for various gas rates and impeller geometry and speeds, and compared with values obtained from RTD measurements. A new correlation, involving Flow Number, Froude Number, system geometry and the physical properties, is proposed. This uses the authors data and those available in literature. 相似文献
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Mohammad Reza Mehrnia Jafar Towfighi Babak Bonakdarpour Mohammad Mehdi Akbarnegad 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(3):260-267
The mixing and mass transfer characteristics of draft‐tube airlift bioreactors (DTAB) for a water‐in‐kerosene microemulsion, as a cold model of petroleum biodesulfurization, were studied. Incomplete gas disengagement at the top‐section of the DTAB and hence high gas recirculation were obtained with the microemulsion system for all the top‐section configurations employed in the present study especially at the high airflow rates. The ratio (S) of the volumes of the riser and the downcomer to the top‐section together with the gas disengagement abilities of the gas separator were both found to affect the mixing performance of the DTAB employed for the microemulsion system. Increase in the draft‐tube height resulted in significant increase in the mixing time (tm) and a slight increase in the overall volumetric oxygen transfer coefficient (kLa). Increase in the diameter of the top‐section and the height of the liquid above the draft‐tube led to a decrease in kLa, the latter effect being less prominent. New correlations were developed that predicted the mixing time and oxygen transfer coefficients obtained in the present work with reasonable accuracy. Copyright © 2004 Society of Chemical Industry 相似文献
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Gas–liquid interfacial area in the oxygen absorption to oil‐in‐water emulsions in an airlift reactor
The present work includes an exhaustive study about gas–liquid interfacial area between gas phase and liquid heterogeneous medium generated in an airlift bioreactor. The system studied is composed by water, methyl ricinoleate (MR), and Tween‐80, since it is the base of the medium used for the production of γ‐decalactone, a peach‐like aroma compound of industrial interest that can be produced biotechnologically through the biotransformation of ricinoleic acid, by the yeast Yarrowia lipolytica. Experimental results allow describing the hydrodynamic behaviour of the gas phase into the biphasic medium. 相似文献
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Liquid‐bridge flow in the channel of helical string and its application to gas–liquid contacting process 下载免费PDF全文
Haifeng Cong Zhenyu Zhao Xingang Li Hong Li Xin Gao 《American Institute of Chemical Engineers》2018,64(9):3360-3368
To solve the problems of the traditional packings, such as high pressure drop, mal‐distribution and short liquid residence time, a helical flow structured packings was proposed. Two different flow patterns, liquid‐bridge flow and liquid‐drop flow were identified when the width of the channel of the helical string was adjusted. Moreover, the characteristics of the helical liquid‐bridge flow including maximum liquid loading, mean thickness of liquid film, mean residence time and effective specific surface area, were examined. And the separation efficiency was studied by the lab‐scale distillation column. In comparison, the effective specific surface area of the helical flow type packings is almost as large as the traditional B1‐350Y structured packings, but with thinner liquid film, longer liquid residence time and finally higher separation efficiency. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3360–3368, 2018 相似文献
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Gas hold-up was measured in a 2.54 cm diameter reciprocating plate column for countercurrent flow of air and tap water. The gas hold-up data obtained could not be correlated by the relationship based on slip velocity, modified for circulation effects, as proposed by Rama Rao and coworkers. An analysis using other gas hold-up data available in the literature, obtained in reciprocating plate columns of different sizes and geometries, confirmed that this relationship could not be used for the general prediction of gas hold-up in this type of gas-liquid contactor. 相似文献
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Yefeng Zhou Congjing Ren Jingdai Wang Yongrong Yang 《American Institute of Chemical Engineers》2013,59(4):1056-1065
In many industrial processes involving gas–solid fluidized bed rectors, the addition of a liquid phase significantly alters the hydrodynamics. To fully characterize the hydrodynamics in the fluidized bed, pressure and acoustic measuring techniques were applied to study the behavior of gas bubbles and particles. A camera was used to take pictures to verify the pressure and acoustic results. During the liquid‐addition process, the pressure technique captured the bubble size variation and bubble motion while the acoustic technique reflected particle motion and particle size growth. Hurst and V‐statistics analyses of acoustic emission were used for the first time to detect periodic behavior during the injection process. The new break formation and change trend of Vmax were used as the criteria to judge occurrence of abnormal fluidization states, such as agglomeration and gas channeling formation. These measurement techniques are beneficial in the elimination of adverse effects caused by the addition of liquid. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1056–1065, 2013 相似文献
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Gas–liquid chromatography is used to study the thermodynamic interactions between polystyrene and n‐alkanes (C6–C10). Polystyrene is used as a stationary phase with n‐alkanes as the probe molecules. Retention times and specific retention volumes are measured over the temperature interval of 60 to 170°C. Partial molar free energy of mixing, polymer–solvent interaction parameter, glass‐transition temperature, and solubility parameter of polystyrene at infinite dilution are calculated. Experimental results are discussed in terms of the theoretical calculations and size of the probe molecules. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1291–1298, 2001 相似文献
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建立了美西林中3种残留有机溶剂(甲醇、乙腈、丙酮)的分离测定方法。采用HP-1(60m×0.53μm×5.00μm)毛细管柱,以氮气为载气,FID检测器,程序升温,柱温为30℃,保持6min,以8℃/min的速度升温至60℃,进样口温度200℃,检测器温度250℃,分流直接进样,外标法计算残留溶剂的含量。结果显示,甲醇、乙腈、丙酮的峰面积对浓度均具有良好的线性关系,精密度相对标准偏差(RSD)均≤2.0%,平均回收率在98.8%~99.4%。本法简单、准确、灵敏度高,适用于美西林中3种残留的有机溶剂同时测定。 相似文献
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Thanapalan Murugesan 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1998,72(3):221-226
In the present study, in mechanically agitated gas–liquid contactors (MAC), a generalized correlation for the direct estimation of dispersed gas phase hold-up is proposed. This present proposed new correlation in terms of fundamental operating variables, involving gas velocity, impeller speed in terms of Froude number, vessel geometry and the physical properties, is more accurate than those previously reported and also simpler to use. © 1998 SCI 相似文献
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K. Wang Y. C. Lu J. H. Xu J. Tan G. S. Luo 《American Institute of Chemical Engineers》2011,57(2):299-306
This work focuses on the dispersion of micromonodispersed droplets and bubbles in the capillary embedded T‐junction microfluidic devices. The effects of the microchannel structure, operating conditions, and physical properties on the dispersion rules were carefully investigated. It was found that the extended capillary could greatly affect the dispersion rules, which was favorable for reducing the dispersed size. The dispersed size was mainly dominated by the Ca number, and the effects of dispersed phase flow rate and viscosity ratio of the two phases were also very important. The dispersion mechanism and size rules in the capillary embedded microfluidic devices were discussed seriously by comparing the similarities and differences of the liquid/liquid and gas/liquid dispersion processes. © 2010 American Institute of Chemical Engineers AIChE J, 2011 相似文献
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New experimental data for air–water flow in a horizontal square cross‐section channel (H = 24.25 mm) is presented, including data on liquid hold‐up, gas and liquid velocities, and wave velocities and frequencies. For the majority of gas and liquid flow rates studied, the regime observed was pseudo‐slug. Using visualization studies it was possible to identify wavy‐stratified and pseudo‐slug flows. For the pseudo‐slug regime new correlations were obtained for liquid hold‐up, for gas and liquid velocities as a function of the ratio between gas and liquid mass flow rates, and for the frequency of roll‐waves as a function of gas and liquid mass flow rates. 相似文献