小型流化床干燥器气固流动和干燥的CPFD数值模拟
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摘要
为掌握炼焦煤工业流化床的颗粒干燥和分级过程,基于计算颗粒流体力学(CPFD)理论方法,以0.3mm为分级粒径对实验室规模的炼焦煤流化床干燥分级过程进行模拟研究.颗粒干燥模型由颗粒汽液平衡推导得出.曳力模型采用不考虑颗粒球形度的Wen-Yu/Ergun模型和考虑颗粒球形度的Ganser模型结合.研究结果发现:两种曳力模型结合得到的模型可更准确地预判流化床中不同粒径段颗粒的分布位置;此外,颗粒干燥模型结果与实验结果吻合,流化风风速越大或风温越高,颗粒干燥时间越短.同时在气固流动方面揭示了流化床干燥器中颗粒的流动特性:粗颗粒集中在流化床底部,而细颗粒分布在流化床上部;颗粒直径越大,颗粒速度越小.研究验证了CPFD手段预测流化床干燥器中气固流动和干燥过程的潜力和可行性,为后续的工业化放大和结构优化打下了基础.
To improve classification and drying process in an industrial fluidized bed,particles with classification size of 0.3 mm was taken to study the multiphase flow and drying process by experiment and simulation with 5 kg/h lab scale fluidized bed dryer.The particle drying model was derived from the particle vapor-liquid equilibrium.The simulation applied a computational particle fluid dynamics(CPFD)modelling approach,which combined the Wen-Yu/Ergun drag model not considering the particle sphericity and the Ganser drag model considering the particle sphericity as its new drag model.The results show that the model combining two drag models is more appropriate to predict the distribution of particles with different particle sizes in the fluidized bed.The results of particle drying model well match the findings of experiments.The particle drying time decreases with the increase of the velocity or temperature of the fluid gas.In terms of gas-solid flow,the results also demonstrate the flow characteristics of particles in the fluidized bed dryer in detail.Larger particles distribute at the bottom of the fluidized bed,while smaller particles distribute at the top.The particle velocity decreases with the increase of their own diameters.This research presents a potential feasibility of applying the CPFD simulation to predict the multiphase flow and drying process in the fluidized bed dryer,which lays a foundation for subsequent industrialization enlargement and structural optimization.
To improve classification and drying process in an industrial fluidized bed,particles with classification size of 0.3 mm was taken to study the multiphase flow and drying process by experiment and simulation with 5 kg/h lab scale fluidized bed dryer.The particle drying model was derived from the particle vapor-liquid equilibrium.The simulation applied a computational particle fluid dynamics(CPFD)modelling approach,which combined the Wen-Yu/Ergun drag model not considering the particle sphericity and the Ganser drag model considering the particle sphericity as its new drag model.The results show that the model combining two drag models is more appropriate to predict the distribution of particles with different particle sizes in the fluidized bed.The results of particle drying model well match the findings of experiments.The particle drying time decreases with the increase of the velocity or temperature of the fluid gas.In terms of gas-solid flow,the results also demonstrate the flow characteristics of particles in the fluidized bed dryer in detail.Larger particles distribute at the bottom of the fluidized bed,while smaller particles distribute at the top.The particle velocity decreases with the increase of their own diameters.This research presents a potential feasibility of applying the CPFD simulation to predict the multiphase flow and drying process in the fluidized bed dryer,which lays a foundation for subsequent industrialization enlargement and structural optimization.
引文
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[15]肖海涛,祁海鹰,由长福,等.循环流化床气固曳力模型[J].计算物理,2003(1):25-30.XIAO Haitao,QI Haiying,YOU Changfu,et al.Theoretical model of drag between gas and solid phase in circulating fluidized bed[J].Chinese Journal of Computational Physics,2003(1):25-30.
[16]CHHABRA R P,AGARWAL L,SINHA N K.Drag on non-spherical particles:An evaluation of available methods[J].Powder Technology,1999,101(3):288-295.
[17]GANSER G H.A rational approach to drag prediction of spherical and nonspherical particles[J].Powder Technology,1993,77(2):143-152.
[18]HAIDER A,LEVENSPIEL O.Drag coefficient and terminal velocity of spherical and nonspherical particles[J].Powder Technology,1989,58(1):63-70.
[19]HARTMAN M,TRNKA O,SVOBODA K.Free settling of nonspherical particles[J].Industrial&Engineering Chemistry Research,1994,33:1979-1983.
[20]CHIEN S F.Settling velocity of irregularly shaped particles[J].SPE Drilling&Completion,1994,9(4):281-290.
[21]SWAMEE P K,OJHA C P.Drag coefficient and fall velocity of nonspherical particles[J].Journal of Hydraulic Engineering,1991,117(5):660-667.
[22]YAWS C L,Chemical properties handbook[M].Beijing:McGraw-Hill,1999:109-110.
[23]WELTY J R,WICKS C E,RORRER G,et al.Fundamentals of momentum,heat,and mass transfer[M].London:John Wiley&Sons Inc,2001:569-580.
[24]刘德昌,陈汉平,张世红,等.循环流化床锅炉运行及事故处理[M].北京:中国电力出版社,2006:32-33.LIU Dechang,CHEN Hanping,ZHANG Shihong,et al.Operation and incident hanging of circulating fluidized bed boiler[M].Beijing:China Electric Power Press,2006:32-33.
[2]李帅俊,李晓光.煤调湿技术在国内外发展与应用[J].干燥技术与设备,2010,8(6):249-255.LI Shuaijun,LI Xiaoguang.Development and application of coal moisture control technology at home and abroad[J].Drying Technology&Equipment,2010,8(6):249-255.
[3]李训明.焦炉烟道废气的余热利用[J].山东冶金,2014,36(4):50-52.LI Xunming.Utilization of residual heat from flue gas of coke oven[J].Shandong Metallurgy,2014,36(4):50-52.
[4]赵爱华.煤调湿技术在炼焦生产中的应用[J].洁净煤技术,2013,19(2):66-68.ZHAO Aihua.Application of coal moisture control technique in coking production[J].Clean Coal Technology,2013,19(2):66-68.
[5]DA SILVA F R G B,DE SOUZA M,DA COSTA AM D,et al.Experimental and numerical analysis of soybean meal drying in fluidized bed[J].Powder Technology,2012,229:61-70.
[6]EL-BEHERY S M,EL-ASKARY W A,HAMED MH,et al.Numerical simulation of heat and mass transfer in pneumatic conveying dryer[J].Computers&Fluids,2012,68:159-167.
[7]焦杨,章新喜,李海生.潮湿细煤气流分级机内气固两相流的CFD模拟[J].洁净煤技术,2013,19(5):1-5.JIAO Yang,ZHANG Xinxi,LI Haisheng.CFD simulation of gas-solid two-phase flow in air classifier for moist fine coal[J].Clean Coal Technology,2013,19(5):1-5.
[8]WANG Q G,YANG H R,WANG P N,et al.Application of CPFD method in the simulation of a circulating fluidized bed with a loop seal,Part I:Determination of modeling parameters[J].Powder Technology,2014,253:814-821.
[9]WANG Q G,YANG H R,WANG P N,et al.Application of CPFD method in the simulation of a circulating fluidized bed with a loop seal Part II-Investigation of solids circulation[J].Powder Technology,2014,253:822-828.
[10]SNIDER D M.Three fundamental granular flow experiments and CPFD predictions[J].Powder Technology,2007,176(1):36-46.
[11]张瑞卿,杨海瑞,吕俊复.应用于循环流化床锅炉气固流动和燃烧的CPFD数值模拟[J].中国电机工程学报,2013,33(23):75-83.ZHANG Ruiqing,YANG Hairui,LJunfu.Application of CPFD approach on gas-solid flow and combustion in industrial CFB boilers[J].Proceedings of the CSEE,2013,33(23):75-83.
[12]ANDREWS M J,O'ROURKE P J.The multiphase particle-in-cell(MP-PIC)method for dense particulate flows[J].International Journal of Multiphase Flow,1996,22(2):379-402.
[13]谢俊,金保昇,钟文琪.基于MP-PIC模型的流化床煤气化过程三维数值模拟[J].工程热物理学报,2012,33(6):981-984.XIE Jun,JIN Baosheng,ZHONG Wenqi.Three-dimensional numerical of fluidized bed coal gasification based on MP-PIC model[J].Journal of Engineering Thermophysics,2012,33(6):981-984.
[14]吴锋,钟真武.基于CPFD的流化床数值模拟[J].当代化工,2014,43(10):2166-2168.WU Feng,ZHONG Zhenwu.Simulation of fluidized bed reactor based on CPFD model[J].Contemporary Chemical Industry,2014,43(10):2166-2168.
[15]肖海涛,祁海鹰,由长福,等.循环流化床气固曳力模型[J].计算物理,2003(1):25-30.XIAO Haitao,QI Haiying,YOU Changfu,et al.Theoretical model of drag between gas and solid phase in circulating fluidized bed[J].Chinese Journal of Computational Physics,2003(1):25-30.
[16]CHHABRA R P,AGARWAL L,SINHA N K.Drag on non-spherical particles:An evaluation of available methods[J].Powder Technology,1999,101(3):288-295.
[17]GANSER G H.A rational approach to drag prediction of spherical and nonspherical particles[J].Powder Technology,1993,77(2):143-152.
[18]HAIDER A,LEVENSPIEL O.Drag coefficient and terminal velocity of spherical and nonspherical particles[J].Powder Technology,1989,58(1):63-70.
[19]HARTMAN M,TRNKA O,SVOBODA K.Free settling of nonspherical particles[J].Industrial&Engineering Chemistry Research,1994,33:1979-1983.
[20]CHIEN S F.Settling velocity of irregularly shaped particles[J].SPE Drilling&Completion,1994,9(4):281-290.
[21]SWAMEE P K,OJHA C P.Drag coefficient and fall velocity of nonspherical particles[J].Journal of Hydraulic Engineering,1991,117(5):660-667.
[22]YAWS C L,Chemical properties handbook[M].Beijing:McGraw-Hill,1999:109-110.
[23]WELTY J R,WICKS C E,RORRER G,et al.Fundamentals of momentum,heat,and mass transfer[M].London:John Wiley&Sons Inc,2001:569-580.
[24]刘德昌,陈汉平,张世红,等.循环流化床锅炉运行及事故处理[M].北京:中国电力出版社,2006:32-33.LIU Dechang,CHEN Hanping,ZHANG Shihong,et al.Operation and incident hanging of circulating fluidized bed boiler[M].Beijing:China Electric Power Press,2006:32-33.