甘露醇喷雾干燥过程中液滴粒度分布变化的群体粒数衡算模拟和实验研究
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摘要
利用群体粒数衡算(population balance,PB)计算机模拟和实验研究了甘露醇水溶液的喷雾干燥过程中液滴的粒度分布的变化规律。液滴干燥过程中的颗粒粒度的萎缩速率,在群体粒数衡算模型中描述为液滴的逆(或负)生长项,通过单个液滴反应动力学方法 (reaction engineering approach,REA)获得。基于单个液滴干燥的反应工程方法模型REA和群体粒数衡算模型PB集成建立了PBREA模型。PBREA模型的求解是通过高分辨率数值方法。本文模拟研究了不同工况下,不同粒径液滴的干燥时间、液滴平均含湿量以及液滴粒度分布随时间的变化。结果显示,液滴粒径越大,干燥时间越长,模型预测的颗粒平均粒径为实验值的1.0～1.5倍,粒度分布跨度是实验值的0.61～0.89倍。模拟误差主要来源于液滴及颗粒粒径分布统计精度、单个静止液滴与群体运动液滴干燥的差异、热导率及扩散系数是经验值3个方面。在使用Buchi 290小型喷雾干燥仪进行的实验中,使用了图像采集和分析方法得到了液滴及颗粒的数密度分布,并和模拟结果做了对比。结果表明该模型可以有效地预测喷雾干燥过程中干燥颗粒的平均粒度及分布跨度。
Computer simulation and experimental study were carried out on the evolution of droplet size distribution during spray drying of mannitol dissolved in water.The shrink rate of the diameter of a droplet during spray drying was treated as a negative growth rate in the population balance(PB)model which was obtained using the reaction engineering approach(REA).The integration of PB and REA yielded the PBREA model,which was solved using a high-resolution numerical method.The drying time of droplets of varied sizes,the change of the mean moisture content of droplets and the droplet size distribution were simulated under different spray drying conditions.The results showed that the drying time increased with the increase of droplet diameter.The ratio of the predicted and measured particle mean diameters was between 1.0 to 1.5,and the span was from 0.61 to 0.89.The errors were analyzed and attributed to three main factors:error due to the statistical analysis of droplet and particle sizes,the difference in drying a single static droplet and a group of droplets in motion,and the empirical thermal conductivity and diffusion coefficient values.Images were collected and analyzed to obtain droplet and particle size distributions with the Buchi 290 spray dryer.The simulated and experimental results showed that the PBREA model could effectively predict the mean diameter and span of particles during spray drying process.
Computer simulation and experimental study were carried out on the evolution of droplet size distribution during spray drying of mannitol dissolved in water.The shrink rate of the diameter of a droplet during spray drying was treated as a negative growth rate in the population balance(PB)model which was obtained using the reaction engineering approach(REA).The integration of PB and REA yielded the PBREA model,which was solved using a high-resolution numerical method.The drying time of droplets of varied sizes,the change of the mean moisture content of droplets and the droplet size distribution were simulated under different spray drying conditions.The results showed that the drying time increased with the increase of droplet diameter.The ratio of the predicted and measured particle mean diameters was between 1.0 to 1.5,and the span was from 0.61 to 0.89.The errors were analyzed and attributed to three main factors:error due to the statistical analysis of droplet and particle sizes,the difference in drying a single static droplet and a group of droplets in motion,and the empirical thermal conductivity and diffusion coefficient values.Images were collected and analyzed to obtain droplet and particle size distributions with the Buchi 290 spray dryer.The simulated and experimental results showed that the PBREA model could effectively predict the mean diameter and span of particles during spray drying process.
引文
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[18] FU N, WOO M W, SELOMULYA C, et al. Drying kinetics of skimmilk with 50%initial solids[J]. Journal of Food Engineering, 2012,109(4):701-711.
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[20] WANG W-N, PURWANTO A, LENGGORO I W, et al.Investigation on the correlations between droplet and particle sizedistribution in ultrasonic spray pyrolysis[J]. Industrial&Engineering Chemistry Research, 2008, 47(5):1650-1659.
[21]陈文武,毕荣山,刘振东,等.气液喷射反应器内液滴粒径分布PLIF研究[J].化工进展, 2012, 31(4):754-757.CHEN Wenwu, BI Rongshan, LIU Zhendong, et al. PILF study ondroplet size distribution in gas-liquid jet reactor[J]. ChemicalIndustry and Engineering Progress, 2012, 31(4):754-757.
[22]郭金海,谭心舜,毕荣山,等.压力旋流喷嘴雾化滴径分布的模型预测和实验[J].化工进展, 2012, 31(3):528-532.GUO Jinhai, TAN Xinshun, BI Rongshan, et al.Model predictionand experiment study on spray droplet size distribution of pressureswirl nozzle[J]. Chemical Industry and Engineering Progress,2012, 31(3):528-532.
[23] KIEVIET F G. Modelling quality in spray drying[D]. Holland:Technische Universiteit Eindhoven, 1995.
[24] WAWRZYNIAK P, ASKULSKI M, ZBICI?SKI I, et al. CFDmodelling of moisture evaporation in an industrial dispersedsystem[J]. Advanced Powder Technology, 2016, 28(1):167-176.
[25] ULLUM T, SLOTH J, BRASK A, et al. Predicting spray dryerdeposits by CFD and an empirical drying model[J]. DryingTechnology, 2010, 28(5):723-729.
[2]郭义,胡建华,杨梓剑,等.核黄素结晶母液的处理及回收利用[J].化工进展, 2016, 35(11):324-327.GUO Yi, HU Jianhua, YANG Zijian, et al. Treatment andrecycling of riboflavin crystallization mother liquor[J]. ChemicalIndustry and Engineering Progress, 2016, 35(11):324-327.
[3]张丽丽.冲击式气流喷雾雾化机理及干燥过程数值模拟的研究[D].济南:山东大学, 2008.ZHANG L L. Study on atomization mechanism and numericalsimulation of drying process of air-blast spray[D]. Jinan:Shandong University, 2008.
[4] WAWRZYNIAK P, JASKULSKI M, ZBICI?SKI I, et al. CFDmodelling of moisture evaporation in an industrial dispersedsystem[J].Advanced Powder Technology, 2017, 28(1):167-176.
[5] NANDIYANTO A B D, OKUYAMA K. Progress in developingspray-drying methods for the production of controlled morphologyparticles:from the nanometer to submicrometer size ranges[J].Advanced Powder Technology, 2011, 22(1):1-19.
[6] KEMP I C, WADLEY R, HARTWIG T, et al. Experimental studyof spray drying and atomization with a two-fluid nozzle to produceinhalable particles[J]. Drying Technology, 2013, 31(8):930-941.
[7] ELVERSSON J, MILLQVIST FUREBY A, ALDERBORN G, etal. Droplet and particle size relationship and shell thickness ofinhalable lactose particles during spray drying[J]. Journal ofPharmaceutical Sciences, 2003, 92(4):900-910.
[8] ALI M, MAHMUD T, HEGGS P J, et al. A one-dimensional plug-flow model of a counter-current spray drying tower[J].ChemicalEngineering Research and Design, 2014, 92(5):826-841.
[9] LIU J J, MA C Y, HU Y D, et al. Modelling proteincrystallisation using morphological population balance models[J].Chemical Engineering Research and Design, 2010, 88(4):437-446.
[10] FALOLA A, BORISSOVA A, WANG X Z.Extended method ofmoment for general population balance models including sizedependent growth rate, aggregation and breakage kernels[J].Computers&Chemical Engineering, 2013, 56(56):1-11.
[11] LANGRISH TAG, KOCKEL T K. The assessment of acharacteristic drying curve for milk powder for use incomputational fluid dynamics modelling[J]. Chemical EngineeringJournal, 2001, 84(1):69-74.
[12] LIN S, CHEN X D. A model for drying of an aqueous lactosedroplet using the reaction engineering approach[J]. DryingTechnology, 2006, 24(11):1329-1134.
[13] WOO M W, DAUD W R W, MUJUMDAR A S, et al.Comparative study of droplet drying models for CFD modelling[J].Chemical Engineering Research and Design, 2008, 86(9):1038-1048.
[14] LIN S, CHEN X D. Changes in milk droplet diameter duringdrying under constant drying conditions investigated using theglass-filament method[J].Food&Bioproducts Processing, 2004,82(3):213-218.
[15] HAR C L, FU N, CHAN E S, et al.Unraveling the droplet dryingcharacteristics of crystallization prone mannitol–experimentsand modeling[J].AIChE Journal, 2017, 63(6):1839-1852.
[16] WIJLHUIZEN A E, KERKHOF P J A M, BRUIN S.Theoreticalstudy of the inactivation of phosphatase during spray drying of skim-milk[J].Chemical Engineering Science, 1979, 34(5):651-660.
[17] TOMINAGA T, MATSUMOTO S. Diffusion of polar and nonpolarmolecules in water and ethanol[J]. Bulletin of the ChemicalSociety of Janpan, 2006, 63(2):533-537.
[18] FU N, WOO M W, SELOMULYA C, et al. Drying kinetics of skimmilk with 50%initial solids[J]. Journal of Food Engineering, 2012,109(4):701-711.
[19] LEVEQUE R J, MIHALAS D, DORFI E A, et al.Computationalmethods for astrophysical fluid flow[M]. Berlin:Springer, 1998:71-90.
[20] WANG W-N, PURWANTO A, LENGGORO I W, et al.Investigation on the correlations between droplet and particle sizedistribution in ultrasonic spray pyrolysis[J]. Industrial&Engineering Chemistry Research, 2008, 47(5):1650-1659.
[21]陈文武,毕荣山,刘振东,等.气液喷射反应器内液滴粒径分布PLIF研究[J].化工进展, 2012, 31(4):754-757.CHEN Wenwu, BI Rongshan, LIU Zhendong, et al. PILF study ondroplet size distribution in gas-liquid jet reactor[J]. ChemicalIndustry and Engineering Progress, 2012, 31(4):754-757.
[22]郭金海,谭心舜,毕荣山,等.压力旋流喷嘴雾化滴径分布的模型预测和实验[J].化工进展, 2012, 31(3):528-532.GUO Jinhai, TAN Xinshun, BI Rongshan, et al.Model predictionand experiment study on spray droplet size distribution of pressureswirl nozzle[J]. Chemical Industry and Engineering Progress,2012, 31(3):528-532.
[23] KIEVIET F G. Modelling quality in spray drying[D]. Holland:Technische Universiteit Eindhoven, 1995.
[24] WAWRZYNIAK P, ASKULSKI M, ZBICI?SKI I, et al. CFDmodelling of moisture evaporation in an industrial dispersedsystem[J]. Advanced Powder Technology, 2016, 28(1):167-176.
[25] ULLUM T, SLOTH J, BRASK A, et al. Predicting spray dryerdeposits by CFD and an empirical drying model[J]. DryingTechnology, 2010, 28(5):723-729.
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