循环流化床锅炉炉膛横向温度非均匀性模型研究
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摘要
随着循环流化床锅炉不断向大型化高参数发展,炉膛截面在尺度上已远超过化工领域的循环流化床反应装置,炉膛内运行参数的横向非均匀性问题愈发突出,尤其是横向温度偏差问题,严重影响锅炉汽水系统安全和高效运行。针对300 MW亚临界三分离器循环流化床锅炉燃烧系统建立二维整体小室模型,模型以分离器为回路单元将截面划分为3个并联的小室,包括炉内气固流动模型、密相区气固横向扩散模型、稀相区气固横向扩散模型、燃烧模型及传热模型等子模型。模型计算和实炉测试结果显示,炉膛宽度方向的温度分布存在明显的不均匀性,炉膛中间小室温度高于炉膛两侧小室,并且温度偏差沿床高方向一直存在。稀相区扩散系数的取值对温度横向分布有明显影响,根据模型计算和测试数据结果比较分析,稀相区的扩散系数取值应在0. 006～0. 010 m~2/s。密相区颗粒横向混合扩散作用强烈,改变各个给煤点给煤量分配时,局部浓度变化很快被强烈的横向混合扩散作用消除,因此炉膛横向温度分布受给煤量分布变化的影响较小,与测试结果一致。导致炉膛温度偏差的主要原因是两侧小室内水冷壁面积比中间小室多,使两侧小室温度偏低,通过调整炉内屏式受热面的布置位置,可有效改善温度分布不均的问题。
With the large-scale development of CFB boilers,the furnace cross-section has far exceeded the CFB reactor in the chemical industry.The lateral non-uniformity of boiler operating parameters,especially temperature,seriously affects the safety and efficient operation of boilers.Accordingly,a two-dimensional cell model is established for the combustion system of a 300 MW CFB boiler.The model divides the cross-section into three parallel cells.The model includes gas-solid fluidization model,lateral dispersion model,combustion model and heat transfer model.The calculation and test results show that the temperature distribution in the width direction is obvious non-uniform.The temperature of the intermediate circuit is higher than that of the sides.The dispersion coefficient of dilute region has a significant influence on the lateral temperature distribution. According to the model calculation and test data,the dispersion coefficient of dilute region should be in the range of 0.006-0.010 m~2/s.In the dense bed,the lateral dispersion of particles is severe.When the coal flowrate of each coal feeding point is changed,the local concentration of coal is quickly eliminated by lateral mixing and dispersion. Therefore,the lateral temperature distribution of the furnace is less affected by the change of coal feeding distribution.The key point for the temperature deviation is that the water wall area of each cell on sides is larger than that of the middle one.By adjusting the arrangement of the screen heating surface in the furnace,the problem of uneven temperature distribution can be effectively improved.
With the large-scale development of CFB boilers,the furnace cross-section has far exceeded the CFB reactor in the chemical industry.The lateral non-uniformity of boiler operating parameters,especially temperature,seriously affects the safety and efficient operation of boilers.Accordingly,a two-dimensional cell model is established for the combustion system of a 300 MW CFB boiler.The model divides the cross-section into three parallel cells.The model includes gas-solid fluidization model,lateral dispersion model,combustion model and heat transfer model.The calculation and test results show that the temperature distribution in the width direction is obvious non-uniform.The temperature of the intermediate circuit is higher than that of the sides.The dispersion coefficient of dilute region has a significant influence on the lateral temperature distribution. According to the model calculation and test data,the dispersion coefficient of dilute region should be in the range of 0.006-0.010 m~2/s.In the dense bed,the lateral dispersion of particles is severe.When the coal flowrate of each coal feeding point is changed,the local concentration of coal is quickly eliminated by lateral mixing and dispersion. Therefore,the lateral temperature distribution of the furnace is less affected by the change of coal feeding distribution.The key point for the temperature deviation is that the water wall area of each cell on sides is larger than that of the middle one.By adjusting the arrangement of the screen heating surface in the furnace,the problem of uneven temperature distribution can be effectively improved.
引文
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[16]李金晶,胡南,姚宣,等.裤衩腿型循环流化床炉膛的翻床实验[J].中国矿业大学学报,2011,40(1):54-59.LI Jinjing,HU Na,YAO Xuan,et al.Experimental study of the bed Inventory overturn in pant-legs furnace of CFB boiler[J].Journal of China University of Mining&Technology,2011,40(1):54-59.
[17]PHILIPP S,JOACHIM W.Solids mixing in the bottom zone of a circulating fluidized bed[J].Powder Technology,2001,120(1):21-33.
[18]刘道银,陈晓平,唐智,等.侧面进料在循环流化床密相区混合特性的试验研究[J].工程热物理学报,2009,30(3):529-532.LIU Daoyin,CHEN Xiaoping,TANG Zhi,et al.Experimental study on the mixing of particles feeding into the Bottom zone of a CFB[J].Journal of Engineering Thermophysics,2009,30(3):529-532.
[19]胡南,郭兆君,杨海瑞,等.CFB锅炉炉膛内颗粒横向扩散系数研究[J].动力工程学报,2016,36(3):168-171.HU Nan,GUO Zhaojun,YANG Hairui,et al.Experimental study on lateral dispersion coefficient of solid particles in a CFB boiler[J].Journal of Chinese Society of Power Engineering,2016,36(3):168-171.
[20]NAMKUNG W,KIM S.Radial gas mixing in a circulating fluidized bed[J].Powder Technology,2000,113(1):23-29.
[21]杨建华.循环流化床内气体扩散及二次风射流规律研究[D].北京:清华大学,2008.
[22]LUECKE K,HARTGE EU,WERTHER J.A 3D model of combustion in large-scale circulating fluidized bed boilers.[J].International Journal of Chemical Reactor Engineering,2004,2:1-49.
[23]刘鸿,周克毅,徐啸虎,等.循环流化床炉内传热特性分析[J].中国电机工程学报,2004,25(6):215-217.LIU Hong,ZHOU Keyi,XU Xiaohu,et al.The heat transfer characteristics of circulating fluidized bed boiler[J].Proceedings of the CSEE,2004,25(6):215-217.
[24]吕俊复,张建胜,岳光溪,等.循环流化床锅炉燃烧室受热面传热系数计算方法[J].清华大学学报(自然科学版),2000,40(2):94-97,101.LYU Junfu,ZHANG Jiansheng,YUE Guangxi,et al.Heat transfer coefficient calculational method for a heater in a circulating fluidized bed furnace[J].Journal of Tsinghua University(Science&Technology),2000,40(2):94-97,101.
[2]张建春,黄逸群,张缦,等.煤矸石燃烧过程模型及其在CFB锅炉设计中的应用[J].洁净煤技术,2018,24(1):115-120.ZHANG Jianchun,HUANG Yiqun,ZHANG Man,et al.Combustion process model of gangue and its application in the design of a circulating fluidized bed boiler[J].Clean Coal Technology,2018,24(1):115-120.
[3]宋畅,吕俊复,杨海瑞,等.超临界及超超临界循环流化床锅炉技术研究与应用[J].中国电机工程学报,2018,38(2):338-347.SONG Chang,LYU Junfu,YANG Hairui,et al.Research and application of supercritical and ultra-supercritical circulating fluidized bed boiler Technology[J].Proceedings of the CSEE,2018,38(2):338-347.
[4]柯希玮,蔡润夏,杨海瑞,等.循环流化床燃烧的NOx生成与超低排放[J].中国电机工程学报,2018,38(2):390-396.KE Xiwei,CAI Runxia,YANG Hairui,et al.Formation and ultralow emission of NOxfor circulating fluidized bed combustion[J].Proceedings of the CSEE,2018,38(2):390-396.
[5]LIU Xuemin,ZHANG Man,LYU Junfu,et al.Effect of furnace pressure drop on heat transfer in a 135 MW CFB boiler[J].Powder Technology,2015,284:19-24.
[6]胡南,循环流化床锅炉燃烧系统非均匀性问题的模型研究[D].北京:清华大学,2013.
[7]胡南,李金晶,刘雪敏,等.大型CFB锅炉床压横向波动的机制研究[J].中国电机工程学报,2013,33(20):1-7.HU Nan,LI Jinjing,LIU Xuemin,et al.Mechanism study of lateral bed pressure wave of large scale CFB boilers[J].Proceedings of the CSEE,2013,33(20):1-7.
[8]宗琛.600 MW超临界循环流化床锅炉给煤均匀性研究[D].重庆:重庆大学,2016.
[9]ZHANG Pan,LYU Junfu,YANG Hairui,et al.Heat transfer coefficient distribution in the furnace of a 300MWe CFB boiler[C]//Proceeding of the 20th International Conference on Fluidized Bed Combustion.Berlin:Springer Berlin Heidelberg,2009.
[10]李金晶,龚鹏,吕俊复,等.给煤对大型CFB锅炉床温均匀性的影响[J].热能动力工程,2012,27(1):76-80.LI Jinjing,GONG Peng,LYU Junfu,et al.Influence of the coal feed on the bed temperature uniformity of a large-sized CFB boiler[J].Journal of Engineering for Thermal Energy and Power,2012,27(1):76-80.
[11]WEISS V,FETT F N,HELMRICH H,et al.Mathematical modeling of circulating fluidized bed reactors by reference to solids decomposition reaction and coal combustion[J].Chemical Engineering and Processing,1987,22(2):79-90.
[12]杨海瑞.循环流化床锅炉物料平衡研究[D].北京:清华大学,2003.
[13]李少华.循环流化床锅炉分离器后燃问题研究[D].北京:清华大学,2009.
[14]胡南,王巍,姚宣,等.38 m/54 m高循环流化床床内流体动力特性研究[J].中国电机工程学报,2009,29(29):7-12.HU Nan,WANG Wei,YAO Xuan,et al.Study on gas-solids flow properties in the 38 m/54 m riser of circulating fluidized bed[J].Proceedings of the CSEE,2009,29(29):7-12.
[15]YANG H,YUE G,XIAO X,et al.1D modeling on the material balance in CFB boiler[J].Chemical Engineering Science,2005,60(20):5603-5611.
[16]李金晶,胡南,姚宣,等.裤衩腿型循环流化床炉膛的翻床实验[J].中国矿业大学学报,2011,40(1):54-59.LI Jinjing,HU Na,YAO Xuan,et al.Experimental study of the bed Inventory overturn in pant-legs furnace of CFB boiler[J].Journal of China University of Mining&Technology,2011,40(1):54-59.
[17]PHILIPP S,JOACHIM W.Solids mixing in the bottom zone of a circulating fluidized bed[J].Powder Technology,2001,120(1):21-33.
[18]刘道银,陈晓平,唐智,等.侧面进料在循环流化床密相区混合特性的试验研究[J].工程热物理学报,2009,30(3):529-532.LIU Daoyin,CHEN Xiaoping,TANG Zhi,et al.Experimental study on the mixing of particles feeding into the Bottom zone of a CFB[J].Journal of Engineering Thermophysics,2009,30(3):529-532.
[19]胡南,郭兆君,杨海瑞,等.CFB锅炉炉膛内颗粒横向扩散系数研究[J].动力工程学报,2016,36(3):168-171.HU Nan,GUO Zhaojun,YANG Hairui,et al.Experimental study on lateral dispersion coefficient of solid particles in a CFB boiler[J].Journal of Chinese Society of Power Engineering,2016,36(3):168-171.
[20]NAMKUNG W,KIM S.Radial gas mixing in a circulating fluidized bed[J].Powder Technology,2000,113(1):23-29.
[21]杨建华.循环流化床内气体扩散及二次风射流规律研究[D].北京:清华大学,2008.
[22]LUECKE K,HARTGE EU,WERTHER J.A 3D model of combustion in large-scale circulating fluidized bed boilers.[J].International Journal of Chemical Reactor Engineering,2004,2:1-49.
[23]刘鸿,周克毅,徐啸虎,等.循环流化床炉内传热特性分析[J].中国电机工程学报,2004,25(6):215-217.LIU Hong,ZHOU Keyi,XU Xiaohu,et al.The heat transfer characteristics of circulating fluidized bed boiler[J].Proceedings of the CSEE,2004,25(6):215-217.
[24]吕俊复,张建胜,岳光溪,等.循环流化床锅炉燃烧室受热面传热系数计算方法[J].清华大学学报(自然科学版),2000,40(2):94-97,101.LYU Junfu,ZHANG Jiansheng,YUE Guangxi,et al.Heat transfer coefficient calculational method for a heater in a circulating fluidized bed furnace[J].Journal of Tsinghua University(Science&Technology),2000,40(2):94-97,101.