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Fluidized bed dryers are often used to extract water from granular materials. When the drying process is mainly limited by the resistance against water transport inside the particle the drying behaviour is said to be diffusion-limited. In the literature there are several models that predict this drying process with very diverging results. In this study a model is set up to arrive at a better prediction for this drying process. The heat and mass transfer in the granular material and the drying air is described. The resulting equations are solved numerically. The model must be extended to incorporate the heat capacity of the dryer. 相似文献
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ABSTRACT Fluidized bed dryers are often used to extract water from granular materials. When the drying process is mainly limited by the resistance against water transport inside the particle the drying behaviour is said to be diffusion-limited. In the literature there are several models that predict this drying process with very diverging results. In this study a model is set up to arrive at a better prediction for this drying process. The heat and mass transfer in the granular material and the drying air is described. The resulting equations are solved numerically. The model must be extended to incorporate the heat capacity of the dryer. 相似文献
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Ifa Puspasari Meor Zainal Meor Talib Wan Ramli Wan Daud Siti Masrinda Tasirin 《Drying Technology》2013,31(6):619-630
The drying kinetics of oil palm frond particles in a laboratory-scale agitated fluidized bed dryer were investigated under various operating conditions: inlet air temperature (50–80°C), superficial air velocity (0.6–1.0 m/s), bed load (200–300 g), and agitation speed (300–500 rpm). To study the effects of these variables on the drying time and drying rate, an experimental design using Taguchi orthogonal array was employed. Based on analysis of variance (ANOVA), the results indicated that inlet air temperature greatly affected the drying rate, followed by superficial air velocity and bed load. The effect of agitation speed on the drying rate was found to be small. The experimental drying kinetics data were compared with the values obtained from three different models, namely, the Page model, modified quasi-stationary method (MQSM), and a new composite model. It was found that the proposed new model could satisfactorily predict the complete drying rate curve for the drying of oil palm fronds. 相似文献
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Solid particles were dried in the riser of circulating fluidized bed with internals to study the drying kinetics. Experiments were conducted in a circulating fluidized bed, having perforated plates as internals covering wide range in the operating parameters. The effects of various operating parameters, i.e., initial moisture content, temperature, and flow rate, of the heating medium and solid circulation rate on the rate of drying have been critically examined. It has been observed from the present investigation that the presence of internals enhances the solids holdup in the riser of circulating fluidized bed. The drying efficiency of a circulating fluidized bed with internals has been compared with the drying performance of a circulating fluidized bed without internals under the same operating conditions. 相似文献
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Solid particles were dried in the riser of circulating fluidized bed with internals to study the drying kinetics. Experiments were conducted in a circulating fluidized bed, having perforated plates as internals covering wide range in the operating parameters. The effects of various operating parameters, i.e., initial moisture content, temperature, and flow rate, of the heating medium and solid circulation rate on the rate of drying have been critically examined. It has been observed from the present investigation that the presence of internals enhances the solids holdup in the riser of circulating fluidized bed. The drying efficiency of a circulating fluidized bed with internals has been compared with the drying performance of a circulating fluidized bed without internals under the same operating conditions. 相似文献
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This article deals with investigation and modeling of batch drying process of solids in fluidized bed apparatus. There has been used model of fluidized bed drying, which consists two zones: emulsion zone and bubbling zone with taking into consideration the presence of solid particles in the bubbles. The results of theoretical expectations that arise from simulation calculations have been verified with experimental data obtained with the use of fluidized bed dryer 0.225 m in diameter. A drying process of silica gel, sand, and ammonium sulfate has been tested. To verify the model, the concept of a generalized drying curve has also been employed. 相似文献
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Abdolsamad Tadayyon Gordon A. Hill W. Mike Ingledew Shahab Sokhansanj 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1997,68(3):277-282
A fluidized bed dryer and drying system have been designed, constructed and operated to produce a powdered formulation of the fungus Penicillium bilaii. The dryer includes an air-shear atomizer and rotatable air vibrator to produce particles which are evenly coated with P. bilaii. The drying system included a humidifier, oven, vacuum pump and instrumentation to ensure precise control of operating conditions. Instant skim milk powder was found to be the best particle source for fixing the spores due to its solubility in water, its highly porous nature and because its moisture isotherms were similar to those of the spores. The dryer was operated at 35°C to maximize the drying rate while still preventing thermal death of the spores. The fluidizing air was best provided at an RH of 30%, thereby producing skim milk/spore particles with just the right amount of moisture to ensure long term storage viability. Storage under refrigeration conditions showed little long term decline in spore viability after 3 months of tests. Room temperature storage demonstrated a small decline rate in spore viability with little significant change if held at room temperature for a few days. © 1997 SCI. 相似文献
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This article presents experimental and modeled drying kinetics of potato slices of the Desiree variety (9 × 9 × 3 mm3) in a pulsed fluid bed as a function of the air velocity, air temperature, and rotating disk velocity of the pulse generator. A statistical multifactor experimental design (23) was applied to analyze the drying process with two levels each of drying temperature, air velocity, and rotating disk velocity. The results showed that the significant factors were air temperature, air velocity, rotating disk velocity, and the binary interactions of air velocity with both the temperature and the rotating disk velocity. The simplified variable diffusivity model (SVDM) gave the least deviation for the experimental data. The effective diffusivity values determined in this work are similar to those reported in the literature. 相似文献
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This article presents experimental and modeled drying kinetics of potato slices of the Desiree variety (9 × 9 × 3 mm3) in a pulsed fluid bed as a function of the air velocity, air temperature, and rotating disk velocity of the pulse generator. A statistical multifactor experimental design (23) was applied to analyze the drying process with two levels each of drying temperature, air velocity, and rotating disk velocity. The results showed that the significant factors were air temperature, air velocity, rotating disk velocity, and the binary interactions of air velocity with both the temperature and the rotating disk velocity. The simplified variable diffusivity model (SVDM) gave the least deviation for the experimental data. The effective diffusivity values determined in this work are similar to those reported in the literature. 相似文献
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《Drying Technology》2008,26(1):122-131
The drying of carbohydrate suspensions on polypropylene particles in a pulsed fluidized bed was studied by means of a 25 experimental design, to determine the effect of the air flow and temperature, suspension flow rate, and free section and rotating speed of the rotary plate on the Nusselt number, the moisture content of the product, and the percentage of solids retained inside the bed (which were minimized to 4.9 and 14.4%, respectively) with an air flow of 600 m3/h at 90°C and 720 mmHg, a suspension flow rate of 6 L/h, and a plate with 6% free section, rotating at 50 rpm.
Additionally, the effects of temperature, air flow, and suspension flow rate on the residence time distribution (RTD) were determined, using the stimulus-response methodology. The RTD was represented by 1.1 to 2 tanks in series, according to this model. The mean residence time of the dried carbohydrate particles was between 5.4 and 8.2 min.
Finally, an egg suspension could be dried at 4 L/h, with air at 90°C, with a mean residence time about 50% longer that that found for drying carbohydrate suspensions. 相似文献
Additionally, the effects of temperature, air flow, and suspension flow rate on the residence time distribution (RTD) were determined, using the stimulus-response methodology. The RTD was represented by 1.1 to 2 tanks in series, according to this model. The mean residence time of the dried carbohydrate particles was between 5.4 and 8.2 min.
Finally, an egg suspension could be dried at 4 L/h, with air at 90°C, with a mean residence time about 50% longer that that found for drying carbohydrate suspensions. 相似文献
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The drying of carbohydrate suspensions on polypropylene particles in a pulsed fluidized bed was studied by means of a 25 experimental design, to determine the effect of the air flow and temperature, suspension flow rate, and free section and rotating speed of the rotary plate on the Nusselt number, the moisture content of the product, and the percentage of solids retained inside the bed (which were minimized to 4.9 and 14.4%, respectively) with an air flow of 600 m3/h at 90°C and 720 mmHg, a suspension flow rate of 6 L/h, and a plate with 6% free section, rotating at 50 rpm. Additionally, the effects of temperature, air flow, and suspension flow rate on the residence time distribution (RTD) were determined, using the stimulus-response methodology. The RTD was represented by 1.1 to 2 tanks in series, according to this model. The mean residence time of the dried carbohydrate particles was between 5.4 and 8.2 min. Finally, an egg suspension could be dried at 4 L/h, with air at 90°C, with a mean residence time about 50% longer that that found for drying carbohydrate suspensions. 相似文献
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磷肥工业中副产的氟硅酸钠大多采用气流干燥。介绍采用振动流化床干燥的工艺流程,风量、风压的配置以及操作要点,并指出存在8问题和处理方法。 相似文献
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《Drying Technology》2013,31(8):1869-1895
Abstract The use of a fluidized bed dryer with a lateral air flow and mechanical agitation to the drying of sludge from a wastewater treatment plant was investigated. Experimental curves of moisture content vs. drying time, as well as heat transfer coefficients and the size characteristics of the products, were determined at temperatures between 80°C and 110°C, a stirring rate of 55 rpm and air velocity of 0.9 m/s for 3 kg sludge batches with initial moisture contents of 0.55 and 0.65 (d.b.). Experimental drying kinetics were compared with values derived from three models based on Fick's second law, namely: the constant diffusivity model, the simplified variable diffusivity model, and the modified quasi-stationary model. 相似文献
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介绍沸腾床干燥器的用途、工艺特点及沸腾床干燥器恒速干燥阶段底面积的计算,减速干燥阶段物料和气体的状态,物料在沸腾床中的停留时间等设计计算。卧式多室沸腾床干燥器结构特点易于操作,稳定性好,常用来干燥粒径为0.02-4mm的物料。 相似文献
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