布风板孔径对流化特性影响的数值模拟及试验
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摘要
采用双欧拉流体模型与颗粒流动理论相结合的方法,对3种不同孔径布风板下颗粒流化效果进行数值模拟,获得颗粒的流态化特性。同时通过流化床反应器冷态实验,验证了孔径对流态化特性曲线的影响。结果显示,在1、2、3 mm孔径的布风板中,孔径越小,最终压力降越大,同时临界流化气速越低;1 mm孔径下床层的膨胀较为显著,流化床中气泡所含固体体积分数较低,且漏料最少,同时减小孔径有利于颗粒做规律性的循环运动,从而促进物料混合;流化稳定后,在静床层高度以上的位置上,颗粒体积分数随着高度的增加而迅速下降,且1 mm孔径的下降趋势最平缓,颗粒分布较均匀;颗粒在流化床内的径向分布为典型的环-核结构,且孔径越小,核区的颗粒速度越低,而环区速度越高。
An Eulerian- Eulerian model incorporating the kinetic theory of the granular flow is applied to numerically test the fluidization characteristics of particles in gas distributors. Three different hole diameters are considered in the simulation. Meanwhile,a fluidized-bed reactor equipment and the appropriate distributors are designed. The fluidization is tested in the cold state based on the equipment. The effect of the hole diameter on the fluidization characteristics is verified. It is shown that the ultimate pressure drop increases with the decrease of the hole diameter(1 mm, 2 mm and 3 mm). On the other hand, the critical fluidizing gas velocity increases with the hole diameter. The expansion of the bed is more significant in the case of fluidizing with 1 mm hole diameter. Also,the larger the hole diameter, the more leakage of the material, as is consistent with the observation. The particles circulate in the fluidized- bed more regularly when using the gas distributor of a smaller hole diameter. It is very important since the regular movement of the particles might improve the mixing of the material. In the steady fluidization, the solid concentration is plummeted with the increase of the height of the bed. And this trend is gentler in the case of 1mm hole diameter, which indicates that a smaller hole diameter leads to a more uniform distribution. The result also shows that the radial distribution of the solid is in a typical coreannulus structure. The velocity of the particles at the core and annulus areas decreases and increases with the increase of the hole diameter, respectively.
An Eulerian- Eulerian model incorporating the kinetic theory of the granular flow is applied to numerically test the fluidization characteristics of particles in gas distributors. Three different hole diameters are considered in the simulation. Meanwhile,a fluidized-bed reactor equipment and the appropriate distributors are designed. The fluidization is tested in the cold state based on the equipment. The effect of the hole diameter on the fluidization characteristics is verified. It is shown that the ultimate pressure drop increases with the decrease of the hole diameter(1 mm, 2 mm and 3 mm). On the other hand, the critical fluidizing gas velocity increases with the hole diameter. The expansion of the bed is more significant in the case of fluidizing with 1 mm hole diameter. Also,the larger the hole diameter, the more leakage of the material, as is consistent with the observation. The particles circulate in the fluidized- bed more regularly when using the gas distributor of a smaller hole diameter. It is very important since the regular movement of the particles might improve the mixing of the material. In the steady fluidization, the solid concentration is plummeted with the increase of the height of the bed. And this trend is gentler in the case of 1mm hole diameter, which indicates that a smaller hole diameter leads to a more uniform distribution. The result also shows that the radial distribution of the solid is in a typical coreannulus structure. The velocity of the particles at the core and annulus areas decreases and increases with the increase of the hole diameter, respectively.
引文
[1]王琦,刘倩,贺博,等.流化床生物质快速热解制取生物油试验研究[J].工程热物理学报,2008,29(5):885-888.Wang Qi,Liu Qian,He Bo,et al.Experimrntal research on biomassflash pyrolysis for bio-oil in a fluidized bed reactor[J].Journal ofEngineering Thermophysics,2008,29(5):885-888.
[2]曾涛,漆小波,黄卫星,等.方形气固密相床中局部颗粒浓度分布的实验研究[J].高校化学工程学报,2010,24(5):783-788.Zeng Tao,Qi Xiaobo,Huang Weixing,et al.Experimental study oflocal solid concentration distribution in a square gas-solid fluidized bed[J].Journal of Chemical Engineering of Chinese Universities,2010,24(5):783-788.
[3]田昊一,康明雄,吴元欣,等.布风板对磷矿混合颗粒流化特性与还原反应的影响[J].化学工程,2012,40(12):48-52.Tian Haoyi,Kang Mingxiong,Wu Yuanxin,et al.Effect of gasdistributor on fluidization characteristics and reduction reaction ofmixed phosphate ore particles[J].Chemical Engineering,2012,40(12):48-52.
[4]聂向锋,卢春喜,蓝兴英.高密度液固循环流化床流动特性研究及数值模拟[J].化工学报,2008,59(6):1366-1376.Nie Xiangfeng,Lu Chunxi,Lan Xingying.Experimental andcomputational investigation on hydrodynamics in high-density liquid-solid circulating fluidized bed[J].Journal of Chemical Industry andEngineering,2008,59(6):1366-1376.
[5]Chen X Z,Shi D P,Xi G,et al.A fundamental CFD study of the gas-solid flow field in fluidized bed polymerization reactors[J].PowderTechnology,2011,205(1-3):276-288.
[6]魏新利,马新辉.应用Fluent软件研究流化床中布风板结构[J].能源工程,2006(2):15-19.Wei Xinli,Ma Xinhui,The structral choice and optimum of distributorin fluidized bed by Fluent software[J].Energy Engineering,2006(2):15-19.
[7]王文仲.循环流化床锅炉风帽及布风板的实验与数值模拟研究[D].北京:中国科学院研究生院,2009.Wang Wenzhong.Experimental and numerical study of air distributorsand air caps in CFB boilers[D].Beijing:Graduate School of theChinese Academy of Sciences,2009.
[8]杨士春,刘荣厚.流化床流态化质量影响因素[J].农业工程学报,2009,25(3):205-208.Yang Shichun,Liu Ronghou.Effect of influencing factors onfluidization quality of fluidized bed[J].Transactions of the CSAE,2009,25(3):205-208.
[9]董淑芹,司崇殿,曹长青,等.分布板开孔率对气固流化床流动特性的影响[J].化学反应工程与工艺,2008,24(5):433-439.Dong Shuqin,Si Chongdian,Cao Changqing,et al.Effect of perforatedratio of distributor on the fluidization characteristics in a gas-solidfluidized bed[J].Chemieal Reaction Engineering and Technology,2008,24(5):433-439.
[10]Samruamphianskun T,Piumsomboon P,Chalermsinsuwan B.Effect ofring baffle configurations in a circulating fluidized bed riser usingCFD simulation and experimental design analysis[J].ChemicalEngineering Journal,2012,210:237-251.
[11]王霄,司慧,程琦.环形流化床生物质热裂解反应器的传热分析[J].科技导报,2013,31(14):30-35.Wang Xiao,Si Hui,Cheng Qi.Heat transfer analysis of annularfluidized bed biomass pyrolysis reactor[J].Science&TechnologyReview,2013,31(14):30-35.
[12]Gao X,Wu C,Cheng Y W,et al.Experimental and numerical investigationof solid behavior in a gas-solid turbulent fluidized bed[J].PowderTechnology,2012,228:1-13.
[13]金涌,祝京旭,汪展文,等.流态化工程原理[M].北京:清华大学出版社,2001:17-21.Jin Yong,Zhu Jingxu,Wang Zhanwen et al.Fluidization engineeringprinciples[M].Beijing:Tsinghua University Press,2001:17-21.
[14]王储,周肇秋,阴秀丽,等.木屑在循环流化床中的流动特性研究[J].太阳能学报,2010,31(4):501-506.Wang Chu,Zhou Zhaoqiu,Yin Xiuli,et al.Study of hydrodynamiccharacteristics of sawdust in a circulating fluidized bed[J].ActaEnergiae Solaris Sinica,2010,31(4):501-506.
[2]曾涛,漆小波,黄卫星,等.方形气固密相床中局部颗粒浓度分布的实验研究[J].高校化学工程学报,2010,24(5):783-788.Zeng Tao,Qi Xiaobo,Huang Weixing,et al.Experimental study oflocal solid concentration distribution in a square gas-solid fluidized bed[J].Journal of Chemical Engineering of Chinese Universities,2010,24(5):783-788.
[3]田昊一,康明雄,吴元欣,等.布风板对磷矿混合颗粒流化特性与还原反应的影响[J].化学工程,2012,40(12):48-52.Tian Haoyi,Kang Mingxiong,Wu Yuanxin,et al.Effect of gasdistributor on fluidization characteristics and reduction reaction ofmixed phosphate ore particles[J].Chemical Engineering,2012,40(12):48-52.
[4]聂向锋,卢春喜,蓝兴英.高密度液固循环流化床流动特性研究及数值模拟[J].化工学报,2008,59(6):1366-1376.Nie Xiangfeng,Lu Chunxi,Lan Xingying.Experimental andcomputational investigation on hydrodynamics in high-density liquid-solid circulating fluidized bed[J].Journal of Chemical Industry andEngineering,2008,59(6):1366-1376.
[5]Chen X Z,Shi D P,Xi G,et al.A fundamental CFD study of the gas-solid flow field in fluidized bed polymerization reactors[J].PowderTechnology,2011,205(1-3):276-288.
[6]魏新利,马新辉.应用Fluent软件研究流化床中布风板结构[J].能源工程,2006(2):15-19.Wei Xinli,Ma Xinhui,The structral choice and optimum of distributorin fluidized bed by Fluent software[J].Energy Engineering,2006(2):15-19.
[7]王文仲.循环流化床锅炉风帽及布风板的实验与数值模拟研究[D].北京:中国科学院研究生院,2009.Wang Wenzhong.Experimental and numerical study of air distributorsand air caps in CFB boilers[D].Beijing:Graduate School of theChinese Academy of Sciences,2009.
[8]杨士春,刘荣厚.流化床流态化质量影响因素[J].农业工程学报,2009,25(3):205-208.Yang Shichun,Liu Ronghou.Effect of influencing factors onfluidization quality of fluidized bed[J].Transactions of the CSAE,2009,25(3):205-208.
[9]董淑芹,司崇殿,曹长青,等.分布板开孔率对气固流化床流动特性的影响[J].化学反应工程与工艺,2008,24(5):433-439.Dong Shuqin,Si Chongdian,Cao Changqing,et al.Effect of perforatedratio of distributor on the fluidization characteristics in a gas-solidfluidized bed[J].Chemieal Reaction Engineering and Technology,2008,24(5):433-439.
[10]Samruamphianskun T,Piumsomboon P,Chalermsinsuwan B.Effect ofring baffle configurations in a circulating fluidized bed riser usingCFD simulation and experimental design analysis[J].ChemicalEngineering Journal,2012,210:237-251.
[11]王霄,司慧,程琦.环形流化床生物质热裂解反应器的传热分析[J].科技导报,2013,31(14):30-35.Wang Xiao,Si Hui,Cheng Qi.Heat transfer analysis of annularfluidized bed biomass pyrolysis reactor[J].Science&TechnologyReview,2013,31(14):30-35.
[12]Gao X,Wu C,Cheng Y W,et al.Experimental and numerical investigationof solid behavior in a gas-solid turbulent fluidized bed[J].PowderTechnology,2012,228:1-13.
[13]金涌,祝京旭,汪展文,等.流态化工程原理[M].北京:清华大学出版社,2001:17-21.Jin Yong,Zhu Jingxu,Wang Zhanwen et al.Fluidization engineeringprinciples[M].Beijing:Tsinghua University Press,2001:17-21.
[14]王储,周肇秋,阴秀丽,等.木屑在循环流化床中的流动特性研究[J].太阳能学报,2010,31(4):501-506.Wang Chu,Zhou Zhaoqiu,Yin Xiuli,et al.Study of hydrodynamiccharacteristics of sawdust in a circulating fluidized bed[J].ActaEnergiae Solaris Sinica,2010,31(4):501-506.