通气料仓下料过程中气泡运动行为
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摘要
利用高速摄像仪拍摄二维充气料仓粉体下料过程中气泡的运动图像,得到不同工况下气泡运动行为特性,获得了气泡体积、形状、位置、聚并、分裂及湮灭的基本规律和特点。研究表明:气泡生成后,其体积先增大后减小,同时上升速率逐渐增大并最终趋于一稳定值;气泡在其生命周期内形状依次为斜长形、倒直角梯形、帽状;先后生成上下2个气泡,上部气泡会吸引下部气泡发生聚并,较大气泡和较扁平气泡由于受力不均匀会发生分裂而生成2个小气泡;实验范围内的所有气泡均会湮灭在料仓中,但会呈现3种不同的湮灭方式。
The entrained-flow pulverized coal gasification process has emerged as a promising and attractive coal utilization technology in China,where it demonstrates a great advantage in energy conversion and environmental protection.Aeration in a hopper used to enhance the flow capability of powder has been widely applied in the coal gasification process and other production processes.Bubbles in entrained-flow bed play an important role in the flow capability,like bubbles in the gas-solid fluidized beds,as they governed the hydrodynamics and efficiency of the operation for which the bed is used,such as gas-solid mixing,heat transfer,mass transfer,and material sorting.This work aims at investigation of the characteristics of the bubble behaviors in the process of powder discharge.All experiments were carried out in a two-dimensional(2 D)aerated hopper for visual studies,and the movements of bubbles in different operation conditions were recorded by a high-speed camera.By analyzing the recorded images,both basic rules and the characteristics of bubble movements in the volume,shape,position,coalescence,splitting and annihilating were gained in hoppers.The experimental results showed that the bubble volume increased initially followed by a decrease,while the velocity of bubble increased until it reached a constant value.During the rise of the bubble,its position,size and shape continually changed.In the first stage,bubbles attached to the gas inlet,and showed oblique long shape.In the middle stage,bubbles showed the right angle trapezoid shape and went up uniformly.In the final stage,bubbles showed cap-shaped or round shape and went up uniformly.Aggregation and splitting occurred during bubble rising,and eventually annihilated in the hopper.Aggregation was actually the process that a small bubble was attracted by the large bubble,and finally formed a bigger bubble.Splitting was the result of the uneven force of the bubble,leading to the flow of particles at the top of the bubble.Splitting was more common in larger,flatter bubbles,as the additional pressure was not sufficient to support the upper particles due to the large radius of curvature in these bubbles.The annihilation was the result of the gas entering the bubble less than the gas that infiltrating the solid phase.
The entrained-flow pulverized coal gasification process has emerged as a promising and attractive coal utilization technology in China,where it demonstrates a great advantage in energy conversion and environmental protection.Aeration in a hopper used to enhance the flow capability of powder has been widely applied in the coal gasification process and other production processes.Bubbles in entrained-flow bed play an important role in the flow capability,like bubbles in the gas-solid fluidized beds,as they governed the hydrodynamics and efficiency of the operation for which the bed is used,such as gas-solid mixing,heat transfer,mass transfer,and material sorting.This work aims at investigation of the characteristics of the bubble behaviors in the process of powder discharge.All experiments were carried out in a two-dimensional(2 D)aerated hopper for visual studies,and the movements of bubbles in different operation conditions were recorded by a high-speed camera.By analyzing the recorded images,both basic rules and the characteristics of bubble movements in the volume,shape,position,coalescence,splitting and annihilating were gained in hoppers.The experimental results showed that the bubble volume increased initially followed by a decrease,while the velocity of bubble increased until it reached a constant value.During the rise of the bubble,its position,size and shape continually changed.In the first stage,bubbles attached to the gas inlet,and showed oblique long shape.In the middle stage,bubbles showed the right angle trapezoid shape and went up uniformly.In the final stage,bubbles showed cap-shaped or round shape and went up uniformly.Aggregation and splitting occurred during bubble rising,and eventually annihilated in the hopper.Aggregation was actually the process that a small bubble was attracted by the large bubble,and finally formed a bigger bubble.Splitting was the result of the uneven force of the bubble,leading to the flow of particles at the top of the bubble.Splitting was more common in larger,flatter bubbles,as the additional pressure was not sufficient to support the upper particles due to the large radius of curvature in these bubbles.The annihilation was the result of the gas entering the bubble less than the gas that infiltrating the solid phase.
引文
[1] WANG J,VAN DER HOEF M A,KUIPERS J A M.Coarse grid simulation of bed expansion characteristics of industrial-scale gas-solid bubbling fluidized beds[J].Chemical Engineering Science,2010,65(6):2125-2131.
[2] LU H F,GUO X L,GONG X,et al.Experimental study on aerated discharge of pulverized coal[J].Chemical Engineering Science,2012,71(13):438-448.
[3] DONSG,FERRARI G.Improvement of bulk flow properties of powders[J].Powder Technology,1991,65(1-3):469-476.
[4] OUWERKERK C E D,MOLENAAR H J,FRANK M J W.Aerated bunker discharge of fine dilating powders[J].Powder Technology,1992,72(3):241-253.
[5] YUU S,UMEKAGE T.Simulation of granular flows and pile formation in a flat-bottomed hopper and bin,and experimental verification[J].Materials,2011,4(12):1440-1468.
[6] TOOMEY R O,JOHNSTONE H F.Gaseous fluidization of solid particles[J].Chemical Engineering and Processing,1952,48:220-226.
[7]陈甘棠,王樟茂.流态化技术的理论和应用[M].北京:中国石化出版社,1996.
[8] CAICEDO G R,MARQUES J J P,RUIZ M G,et al.A study on the behaviour of bubbles of a 2Dgas-solid fluidized bed using digital image analysis[J].Chemical Engineering&Processing Process Intensification,2003,42(1):9-14.
[9] HERNNDEZ-JIMNEZ F,GMEZ-GARCA A,SANTANA D,et al.Gas interchange between bubble and emulsion phases in a 2Dfluidized bed as revealed by two-fluid model simulations[J].Chemical Engineering Journal,2013,215:479-490.
[10] MOVAHEDIRAD S,GHAFARI M,MOLAEI DEHKORDI A.A novel model for predicting the dense phase behavior of3Dgas-solid fluidized beds[J].Chemical Engineering&Technology,2014,37(1):103-112.
[11] VERMA V,PADDING J T,DEEN N G,et al.Bubble characterstics in a 3-D gas-solid fluidized bed:Predictions from ultra-fast x-ray tomography and two fluid model[C]∥Proceedings of the International Conference on Fluidized Bed Technology.USA:[s.n.],2014.
[12]郭奋,周游.沸腾转化催化剂床内气泡特性研究与工业反应器的模拟和优化[J].硫酸工业,1990(6):3-8.
[13] LARE C E J V,PIEPERS H W,SCHOONDERBEEK J N,et al.Investigation on bubble characteristics in a gas fluidized bed[J].Chemical Engineering Science,1997,52(5):829-841.
[14] RDISLI M,SCHILDHAUER T J,BIOLLAZ S M A,et al.Bubble characterization in a fluidized bed by means of optical probes[J].International Journal of Multiphase Flow,2012,41(2):56-67.
[15] NIEUWLAND J J,VEENENDAAL M L,KUIPERS J A M,et al.Bubble formation at a single orifice in gas-fluidised beds[J].Chemical Engineering Science,1996,51(17):4087-4102.
[16]周云龙,杨宁,彭颖,等.基于数字图像技术的垂直流化床气泡分析[J].工程热物理学报,2015,36(6):1268-1273.
[17] BOKKERS G A,LAVERMAN J A,ANNALAND M V S,et al.Modelling of large-scale dense gas-solid bubbling fluidised beds using a novel discrete bubble mode[J].Chemical Engineering Science,2006,61(17):5590-5602.
[18] MOVAHEDIRAD S,GHAFARI M,DEHKORDI A M.Discrete bubble model for prediction of bubble behavior in 3D fluidized beds[J].Chemical Engineering&Technology,2012,35(5):929-936.
[19] PANNALA S,DAW C S,HALOW J.Simulations of reacting fluidized beds using an agent-based bubble model[J].International Journal of Chemical Reactor Engineering,2003,DOI:10.2202/1542-6580.1089.
[20] PANNALA S,DAW C S,HALOW J S.Dynamic interacting bubble simulation(DIBS):An agent-based bubble model for reacting fluidized beds[J].Chaos,2004,14(2):487-498.
[21]陶秀祥,丁玉,骆振福.高密度浓相流化床内气泡行为的研究[J].中国矿业大学学报,2003,32(6):601-607.
[22] CLIFT R,GRACE J R.Continuous Bubbling and Slugging in Fluidization[M].[s.l.]:Academic Press,1985.
[23]付琳,陆海峰,郭晓镭,等.煤粉通气料仓的优化设计[J].华东理工大学学报(自然科学版),2017,43(3):297-303.
[24]陶顺龙,陆海峰,郭晓镭,等.煤粉料仓通气下料流动行为[J].化工学报,2014,65(4):1186-1193.
[25] DAVIDSON J F,HARRISON D,CARVALHO J R F G D.On the liquidlike behavior of fluidized beds[J].Annual Review of Fluid Mechanics,1977,9(9):55-86.
[26]张廷龙.大颗粒二维流态化床流体动力学特性的试验研究[D].西安:西安建筑科技大学,2003.
[27] JONG J F D,ANNALAND M V S,KUIPERS J A M.Experimental study on the hydrodynamic effects of gas permeation through horizontal membrane tubes in fluidized beds[J].Chemical Engineering Science,2011,66(11):2398-2408.
[28] SNIDER D M.Three fundamental granular flow experiments and CPFD predictions[J].Powder Technology,2007,176(1):36-46.
[29] HORIO M,IWADATE Y,SUGAYA T.Particle normal stress distribution around a rising bubble in a fluidized bed[J].Powder Technology,1998,96(2):148-157.
[30]胡英.物理化学[M].第5版.北京:高等教育出版社,2007.
[2] LU H F,GUO X L,GONG X,et al.Experimental study on aerated discharge of pulverized coal[J].Chemical Engineering Science,2012,71(13):438-448.
[3] DONSG,FERRARI G.Improvement of bulk flow properties of powders[J].Powder Technology,1991,65(1-3):469-476.
[4] OUWERKERK C E D,MOLENAAR H J,FRANK M J W.Aerated bunker discharge of fine dilating powders[J].Powder Technology,1992,72(3):241-253.
[5] YUU S,UMEKAGE T.Simulation of granular flows and pile formation in a flat-bottomed hopper and bin,and experimental verification[J].Materials,2011,4(12):1440-1468.
[6] TOOMEY R O,JOHNSTONE H F.Gaseous fluidization of solid particles[J].Chemical Engineering and Processing,1952,48:220-226.
[7]陈甘棠,王樟茂.流态化技术的理论和应用[M].北京:中国石化出版社,1996.
[8] CAICEDO G R,MARQUES J J P,RUIZ M G,et al.A study on the behaviour of bubbles of a 2Dgas-solid fluidized bed using digital image analysis[J].Chemical Engineering&Processing Process Intensification,2003,42(1):9-14.
[9] HERNNDEZ-JIMNEZ F,GMEZ-GARCA A,SANTANA D,et al.Gas interchange between bubble and emulsion phases in a 2Dfluidized bed as revealed by two-fluid model simulations[J].Chemical Engineering Journal,2013,215:479-490.
[10] MOVAHEDIRAD S,GHAFARI M,MOLAEI DEHKORDI A.A novel model for predicting the dense phase behavior of3Dgas-solid fluidized beds[J].Chemical Engineering&Technology,2014,37(1):103-112.
[11] VERMA V,PADDING J T,DEEN N G,et al.Bubble characterstics in a 3-D gas-solid fluidized bed:Predictions from ultra-fast x-ray tomography and two fluid model[C]∥Proceedings of the International Conference on Fluidized Bed Technology.USA:[s.n.],2014.
[12]郭奋,周游.沸腾转化催化剂床内气泡特性研究与工业反应器的模拟和优化[J].硫酸工业,1990(6):3-8.
[13] LARE C E J V,PIEPERS H W,SCHOONDERBEEK J N,et al.Investigation on bubble characteristics in a gas fluidized bed[J].Chemical Engineering Science,1997,52(5):829-841.
[14] RDISLI M,SCHILDHAUER T J,BIOLLAZ S M A,et al.Bubble characterization in a fluidized bed by means of optical probes[J].International Journal of Multiphase Flow,2012,41(2):56-67.
[15] NIEUWLAND J J,VEENENDAAL M L,KUIPERS J A M,et al.Bubble formation at a single orifice in gas-fluidised beds[J].Chemical Engineering Science,1996,51(17):4087-4102.
[16]周云龙,杨宁,彭颖,等.基于数字图像技术的垂直流化床气泡分析[J].工程热物理学报,2015,36(6):1268-1273.
[17] BOKKERS G A,LAVERMAN J A,ANNALAND M V S,et al.Modelling of large-scale dense gas-solid bubbling fluidised beds using a novel discrete bubble mode[J].Chemical Engineering Science,2006,61(17):5590-5602.
[18] MOVAHEDIRAD S,GHAFARI M,DEHKORDI A M.Discrete bubble model for prediction of bubble behavior in 3D fluidized beds[J].Chemical Engineering&Technology,2012,35(5):929-936.
[19] PANNALA S,DAW C S,HALOW J.Simulations of reacting fluidized beds using an agent-based bubble model[J].International Journal of Chemical Reactor Engineering,2003,DOI:10.2202/1542-6580.1089.
[20] PANNALA S,DAW C S,HALOW J S.Dynamic interacting bubble simulation(DIBS):An agent-based bubble model for reacting fluidized beds[J].Chaos,2004,14(2):487-498.
[21]陶秀祥,丁玉,骆振福.高密度浓相流化床内气泡行为的研究[J].中国矿业大学学报,2003,32(6):601-607.
[22] CLIFT R,GRACE J R.Continuous Bubbling and Slugging in Fluidization[M].[s.l.]:Academic Press,1985.
[23]付琳,陆海峰,郭晓镭,等.煤粉通气料仓的优化设计[J].华东理工大学学报(自然科学版),2017,43(3):297-303.
[24]陶顺龙,陆海峰,郭晓镭,等.煤粉料仓通气下料流动行为[J].化工学报,2014,65(4):1186-1193.
[25] DAVIDSON J F,HARRISON D,CARVALHO J R F G D.On the liquidlike behavior of fluidized beds[J].Annual Review of Fluid Mechanics,1977,9(9):55-86.
[26]张廷龙.大颗粒二维流态化床流体动力学特性的试验研究[D].西安:西安建筑科技大学,2003.
[27] JONG J F D,ANNALAND M V S,KUIPERS J A M.Experimental study on the hydrodynamic effects of gas permeation through horizontal membrane tubes in fluidized beds[J].Chemical Engineering Science,2011,66(11):2398-2408.
[28] SNIDER D M.Three fundamental granular flow experiments and CPFD predictions[J].Powder Technology,2007,176(1):36-46.
[29] HORIO M,IWADATE Y,SUGAYA T.Particle normal stress distribution around a rising bubble in a fluidized bed[J].Powder Technology,1998,96(2):148-157.
[30]胡英.物理化学[M].第5版.北京:高等教育出版社,2007.