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1.
A single expression for the prediction of drop size in the mixer-settler, transition and emulsion regimes of operation in pulsed perforated-plate liquid/liquid extraction columns is presented. Analysis of 326 published drop size measurements both with and without mass transfer for 16 liquid/liquid systems from 12 different data sources show that the Sauter mean drop diameter, d 32, in the dispersion is given in terms of column geometry, operating conditions and physical properties of the phases by: in which ρ* and σ * are the density and surface tension of water at 20°C and α and 1 are the fractional plate free area and compartment height respectively. This equation predicts the drop diameter with an average deviation of 11·3% which is much better than the average errors obtained using other available correlations. 相似文献
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The effect of solute impregnation on water loss and oil uptake during potato strip frying was studied. Blanched potato strips were impregnated at 25°C by soaking in a solution of sucrose-NaCl-water, 20-5-75% by weight. After rinsing and air drying, strips were deep fried in sunflower oil at 160, 170 and 180°C. A control treatment, consisting of potato strips blanched but not soaked and later air dried was also conducted. Solute impregnation provided a decrease of the oil uptake. Two models, based on Fick's law were used to describe water loss during frying. The first one is the classic model with an effective moisture diffusion coefficient assumed a constant value. The second model considers that diffusion coefficient varies during the frying process. For a given frying temperature, constant diffusion coefficient for control potatoes resulted in lower values than the impregnated ones. The variable diffusivity model showed a two-stage behavior: during the first stage of frying, diffusion coefficient increased with frying temperatures, but from a given time on an inverse behavior began. This last fact was found to be related to an increase of the measured peak force needed to penetrate the potato crust. 相似文献
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《Drying Technology》2013,31(7):1303-1318
ABSTRACT The effect of solute impregnation on water loss and oil uptake during potato strip frying was studied. Blanched potato strips were impregnated at 25°C by soaking in a solution of sucrose–NaCl–water, 20–5–75% by weight. After rinsing and air drying, strips were deep fried in sunflower oil at 160, 170 and 180°C. A control treatment, consisting of potato strips blanched but not soaked and later air dried was also conducted. Solute impregnation provided a decrease of the oil uptake. Two models, based on Fick's law were used to describe water loss during frying. The first one is the classic model with an effective moisture diffusion coefficient assumed a constant value. The second model considers that diffusion coefficient varies during the frying process. For a given frying temperature, constant diffusion coefficient for control potatoes resulted in lower values than the impregnated ones. The variable diffusivity model showed a two-stage behavior: during the first stage of frying, diffusion coefficient increased with frying temperatures, but from a given time on an inverse behavior began. This last fact was found to be related to an increase of the measured peak force needed to penetrate the potato crust. 相似文献
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Published droplet size data for the system 30X TBP/OK - 2M aqueous nitric acid have been re-evaluated and compared with new measurements for the system 2 OX TBP/OK - 3M aqueous nitric acid. Correlations are presented for the Sauter mean and the dispersed phase holdup. At frequencies in excess of 1.5 Hz, pulsed plate columns tend to operate in the continuous dispersion regime and dvs increases linearly with holduo provided that the column internals ara not wetted by the dispersed phase, so that dvs = dovs + mx In this expression, m is a constant for a given system and is a measure of the rate of increase of droplet size with holdup. The term do vs+ mx is the characteristic droplet size, i.e. the limiting value of dvsat substantially zero holdup and is a function of the system properties and the pulse frequency and amplitude. In the case of the 20% TBP/OK system, it was found that equation (2) only described the variation of droplet size with holdup provided that the additional requirement (2fA) >4 × 10?2ms?1was met.This is thought to reflect the tendency for the sieve plates to promote droplet coalescence when (2fA) < 4 × 10?2ms?1. At pulse frequencies less than 1.5 Hz, mixer- settler type operation is apparent and is accompanied by considerable droplet coalescence during each pulse cycle. In this situation, the mean droplet size becomes larger and independent of holdup so that dvs becomes synonymous with do vsand, for a given system, depends only upon the pulse frequency and amplitude. These results are discussed in the context of the wetting characteristics of the column internals.There is evidence that the latter plays a major part in droplet recombination processes, and gross coalescence induced by wetting can be more significant than simple interdroplet coalescence. Until the wetting characteristics of column internals can be taken into account quantitatively, the present results should be considered specific to the equipment and extraction systems employed. 相似文献
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THEORETICAL PREDICTION OF GAS HOLDUP IN BUBBLE COLUMNS WITH NEWTONIAN AND NON-NEWTONIAN LIQUIDS 总被引:1,自引:0,他引:1
A simple model based on an energy balance which takes into account the friction losses at the gas-liquid interface and the slip velocity of single bubble is used to simulate the gas holdup in bubble columns containing Newtonian and non-Newtonian liquids which circulate in both laminar and turbulent flows. Experimental data available from the literature for bubble columns up to 7 m height and 1 m diameter with water and glycerol as Newtonian liquids and different solutions of CMC in a wide range of concentrations as non-Newtonian liquids are simulated with good agreement despite the simplifications made to describe the gas liquid flow regimes. Most of the differences between experimental and calculated gas holdup are justified on the basis of the simplifying assumptions. 相似文献
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液膜法提取浓缩氨基酸 总被引:4,自引:0,他引:4
本文研究了用液膜法提取浓缩谷氨酸。用TOMAC为载体,ECA4360J为表面活性剂,在适当的酸度下,以氯离子的浓度差作推动力,提取率可达60%,浓缩倍数可达5倍。谷氨酸可以克服11-12倍的浓度梯度进行能动的膜输送而进入内相,这比文献报导的数值高出近一倍。 相似文献