静电效应对有无埋管气固鼓泡床内气泡特性的影响分析
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摘要
采用基于双流体模型(TFM)耦合静电模型的方法,研究颗粒的静电对有无埋管气固鼓泡床内气固流动特性和气泡特性的影响。首先在无静电场存在的条件下,利用双流体模型对自由鼓泡床和埋管鼓泡床内的流动情况进行模拟并与实验结果进行对比;进一步耦合静电模型,考察静电对自由鼓泡床和埋管鼓泡床内床层的整体性质和气泡特性的影响。研究结果表明,在无静电场条件下采用双流体模型能较好地预测自由鼓泡床和埋管鼓泡床内的气固流动状况以及气泡的平均直径和气泡的上升速度。埋管的存在使鼓泡床内气固流动发生强烈扰动,并使气泡的平均直径和气泡的上升速度均呈振荡分布。静电的存在对自由鼓泡床和埋管鼓泡床内床层的平均固含率影响不大,但对气泡分布规律影响较大,使得自由鼓泡床内气泡数目减少,而埋管鼓泡床下部区域的气泡分布比较集中,上部有大气泡出现。
The present paper studied the effects of electrostatics on gas-solids hydrodynamics and bubble characteristics of gas-solids bubbling bed with and without immersed horizontal tubes by applying the two-fluid model coupling with the electrostatic model. At first, the two-fluid model without electrostatic field was adopted to simulate the hydrodynamics in the gas-solids bubbling bed with and without immersed horizontal tubes. Further coupled with the electrostatic model, the effects of electrostatics on bubble distribution characteristics in the gas-solids bubbling bed with and without the immersed horizontal tubes were investigated. The results demonstrated that in the electrostatic field conditions, the two-fluid model can be used to predict gas-solid flow conditions, the bubble diameter, and bubble riser velocity for gas-solids bubbling bed with and without immersed horizontal tubes. However, the immersed horizontal tubes in gas-solids bubbling bed caused an intense disturbance of gas-solids, making a concussion in the distribution of the bubble diameter and bubble riser velocity. The electrostatics did not have a large effect on the average solids holdup of the bed, but showed a greater impact on the bubble characteristics. The electrostatics decreased the number of bubbles of the gas-solids bubbling bed without the immersed horizontal tubes and made more number of bubbles be concentrated in the lower region of the gas-solids bubbling bed with the immersed horizontal tubes and more number of large bubbles be located in the upper part of the gas-solids bubbling bed with the immersed horizontal tubes.
The present paper studied the effects of electrostatics on gas-solids hydrodynamics and bubble characteristics of gas-solids bubbling bed with and without immersed horizontal tubes by applying the two-fluid model coupling with the electrostatic model. At first, the two-fluid model without electrostatic field was adopted to simulate the hydrodynamics in the gas-solids bubbling bed with and without immersed horizontal tubes. Further coupled with the electrostatic model, the effects of electrostatics on bubble distribution characteristics in the gas-solids bubbling bed with and without the immersed horizontal tubes were investigated. The results demonstrated that in the electrostatic field conditions, the two-fluid model can be used to predict gas-solid flow conditions, the bubble diameter, and bubble riser velocity for gas-solids bubbling bed with and without immersed horizontal tubes. However, the immersed horizontal tubes in gas-solids bubbling bed caused an intense disturbance of gas-solids, making a concussion in the distribution of the bubble diameter and bubble riser velocity. The electrostatics did not have a large effect on the average solids holdup of the bed, but showed a greater impact on the bubble characteristics. The electrostatics decreased the number of bubbles of the gas-solids bubbling bed without the immersed horizontal tubes and made more number of bubbles be concentrated in the lower region of the gas-solids bubbling bed with the immersed horizontal tubes and more number of large bubbles be located in the upper part of the gas-solids bubbling bed with the immersed horizontal tubes.
引文
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[13]JALALINEJAD F,BI X T,GRACE J R.Effect of electrostatic charges on single bubble in gas–solid fluidized beds[J].International Journal of Multiphase Flow,2012,44:15-28.
[14]SUN J,WANG J,YANG Y,et al.Effects of external electric field on bubble and charged particle hydrodynamics in a gas–solid fluidized bed[J].Advanced Powder Technology,2015,26(2):563-575.
[15]PEI C,WU C Y,ENGLAND D,et al.DEM-CFD modeling of particle systems with long-range electrostatic interactions[J].AICh E Journal,2015,61(6):1792-1803.
[16]HASSANI M A,ZARGHAMI R,NOROUZI H R,et al.Numerical investigation of effect of electrostatic forces on the hydrodynamics of gas–solid fluidized beds[J].Powder Technology,2013,246:16-25.
[17]ASEGEHEGN T W,SCHREIBER M,KRAUTZ H J.Investigation of bubble behavior in fluidized beds with and without immersed horizontal tubes using a digital image analysis technique[J].Powder Technology,2011,210(3):248-260.
[18]LI T,BENYAHIA S.Evaluation of wall boundary condition parameters for gas–solids fluidized bed simulations[J].AICh E Journal,2013,59(10):3624-3632.
[19]GIDASPOW D,LU H L.Collisional viscosity of FCC particles in a CFB[J].AICh E Journal,1996,42(9):2503-2510.
[20]O’BRIEN T J,SYAMLAL M.Particle cluster effects in the numerical simulation of a circulating fluidized bed[C]//AVIDAN A.Proceedings of the Fourth International Conference on Circulating Fluidized Beds.Somerset,PA:1993.
[21]JACKSON J D,FOX R F.Classical electrodynamics[J].American Journal of Physics,1999,67(9):841-842.
[22]SOWINSKI A,MILLER L,MEHRANI P.Investigation of electrostatic charge distribution in gas–solid fluidized beds[J].Chemical Engineering Science,2010,65(9):2771-2781.
[23]朱子川.外加电场下气固流化床的数值模拟[D].杭州:浙江大学,2013.ZHU Z C.Numerical simulation of gas-solid fluidized bed with applied electric field[D].Hangzhou:Zhejiang University,2013.
[2]朱子川,孙婧元,黄正梁,等.外加电场下气固流化床的数值模拟[J].化工学报,2013,64(2):490-497.ZHU Z C,SUN J Y,HUANG Z L,et al.Numerical simulation of gas-solids fluidized bed with applied electric field[J].CIESC Journal,2013,64(2):490-497.
[3]HENDRICKSON G.Electrostatics and gas phase fluidized bed polymerization reactor wall sheeting[J].Chemical Engineering Science,2006,61(4):1041-1064.
[4]王芳,徐怡,于恒修,等.气固流化床中静电压分布及料位检测[J].化工学报,2008,59(3):574-581.WANG F,XU Y,YU H X,et al.Electrostatic potential distribution in gas-solid fluidized beds and measurement of bed level[J].Journal of Chemical Industry and Engineering(China),2008,59(3):574-581.
[5]CANO-PLEITE E,HEMANDEZ-JIMENEZ F,DE V M,et al.Experimental study on the motion of isolated bubbles in a vertically vibrated fluidized bed[J].Chemical Engineering Journal,2014,255:114-125.
[6]SITNAI O,WHITEHEAD A B.Immersed tubes and other internals[M]//Fluidization.London:Academic Press,1985:473-493.
[7]HULL A S,CHEN Z,FRITZ J W,et al.Influence of horizontal tube banks on the behavior of bubbling fluidized beds(1):Bubble hydrodynamics[J].Powder Technology,1999,103(3):230-242
[8]HULL A S,CHEN Z,AGARWAL P K.Influence of horizontal tube banks on the behavior of bubbling fluidized beds(2):Mixing of solids[J].Powder Technology,2000,111(3):192-199.
[9]BOLAND D,GELDART D.Electrostatic charging in gas fluidised beds[J].Powder Technology,1972,5(5):289-297.
[10]CHEN A H,BI H T,GRACE J R.Measurement of particle charge-to-mass ratios in a gas–solids fluidized bed by a collision probe[J].Powder Technology,2003,135:181-191.
[11]DONG K,ZHANG Q,HUANG Z,et al.Experimental investigation of electrostatic effect on bubble behaviors in gas-solid fluidized bed[J].AICh E Journal,2015,61(4):1160-1171.
[12]ROKKAM R G,SOWINSKI A,FOX R O,et al.Computational and experimental study of electrostatics in gas–solid polymerization fluidized beds[J].Chemical Engineering Science,2013,92:146-156.
[13]JALALINEJAD F,BI X T,GRACE J R.Effect of electrostatic charges on single bubble in gas–solid fluidized beds[J].International Journal of Multiphase Flow,2012,44:15-28.
[14]SUN J,WANG J,YANG Y,et al.Effects of external electric field on bubble and charged particle hydrodynamics in a gas–solid fluidized bed[J].Advanced Powder Technology,2015,26(2):563-575.
[15]PEI C,WU C Y,ENGLAND D,et al.DEM-CFD modeling of particle systems with long-range electrostatic interactions[J].AICh E Journal,2015,61(6):1792-1803.
[16]HASSANI M A,ZARGHAMI R,NOROUZI H R,et al.Numerical investigation of effect of electrostatic forces on the hydrodynamics of gas–solid fluidized beds[J].Powder Technology,2013,246:16-25.
[17]ASEGEHEGN T W,SCHREIBER M,KRAUTZ H J.Investigation of bubble behavior in fluidized beds with and without immersed horizontal tubes using a digital image analysis technique[J].Powder Technology,2011,210(3):248-260.
[18]LI T,BENYAHIA S.Evaluation of wall boundary condition parameters for gas–solids fluidized bed simulations[J].AICh E Journal,2013,59(10):3624-3632.
[19]GIDASPOW D,LU H L.Collisional viscosity of FCC particles in a CFB[J].AICh E Journal,1996,42(9):2503-2510.
[20]O’BRIEN T J,SYAMLAL M.Particle cluster effects in the numerical simulation of a circulating fluidized bed[C]//AVIDAN A.Proceedings of the Fourth International Conference on Circulating Fluidized Beds.Somerset,PA:1993.
[21]JACKSON J D,FOX R F.Classical electrodynamics[J].American Journal of Physics,1999,67(9):841-842.
[22]SOWINSKI A,MILLER L,MEHRANI P.Investigation of electrostatic charge distribution in gas–solid fluidized beds[J].Chemical Engineering Science,2010,65(9):2771-2781.
[23]朱子川.外加电场下气固流化床的数值模拟[D].杭州:浙江大学,2013.ZHU Z C.Numerical simulation of gas-solid fluidized bed with applied electric field[D].Hangzhou:Zhejiang University,2013.