摘要
煤颗粒在流化床燃烧过程中的灰渣形成特性对锅炉的设计，运行具有很大的影响。不同特性的煤颗粒具有不同的灰渣形成特性，而即使同属一煤种的煤颗粒之间的特性也会存在较大的差异。本文开展了煤颗粒特性对灰渣形成的影响的研究。
本文在概述了国内外关于在流化床燃烧过程中煤颗粒特性对灰渣形成特性影响的研究现状的基础上开展相关研究。通过采用ZnCl_2溶液浮选和筛分的方法把义马烟煤煤样按密度和粒径分成具有不同特性各档颗粒，并在所建的小型流化床燃烧实验台上进行了各颗粒档的多工况燃烧实验。通过对燃烧形成的底渣和飞灰的粒度分布、份额及其含碳量等特性的分析，获得不同密度和粒径下的灰渣形成特性，以及燃烧时间的影响特性。
实验结果表明：(1)同一种煤中，各煤颗粒的性质是不同的，随着密度的增大，煤颗粒的挥发分、碳、氢、氮、氧的含量降低、热值降低，灰分含量增加。(2)对于含灰量较低的低密度颗粒经流化床燃烧后几乎不生成底渣，其燃烧过程主要以单收缩核模式进行；而含灰量较高的密度较高的颗粒则生产大量的底渣，其燃烧过程主要以双收缩核模式进行燃烧。(3)在燃烧时间和入炉粒径相同的条件下，随着密度的增大，底渣份额增加，底渣中细颗粒份额明显减少，底渣的燃尽率下降。(4)随着入炉煤密度的增加，入炉颗粒粒度对底渣粒度分布的影响程度逐渐增加。
在实验研究基础上，以所建的考虑爆裂，破碎及磨损等过程的煤颗粒流化床燃烧模型对燃烧时间为5分钟和20分钟的实验工况下的实验数据进行了拟合，然后预测了各颗粒档在燃烧时间为30分钟时的灰渣特性，预测结果与实验结果总体上吻合。
最后，在一台0.5MW大型循环流化床燃烧试验台上进行了义马烟煤的流化床燃烧特性实验研究，重点讨论了该煤种的灰渣形成特性，并给出燃用该煤种的锅炉的设计和运行建议。
Ash formation behaviors of coal partice have great influences on the boiler design and operation for a fluidized bed boiler. The coal particles with differenct properties behave differently on ash formation. Unfortunately, the coal particle properties may be varied form time to time enven for a given coal type. This thesis focuses on the research of effect of particle properties on ash formation.
Firstly, a review on the effect of the coal properties on ash formation during f ludized bed combustion is completed. Yima bituminous coal sample is divided into several ranks with different density and size by the ZnCl2 solution floatation and the size sieving processes. Experiments on a bench-scale fluidized bed combustor for every coal rank are completed in different operation conditions. Based on the measurements results, effects of particle density and size on the ash formation behaviors such as ash size distribution, fly ash mass fraction, carbon content in the bottom ash and fly ash are obtained. In additional, effect of burning residence time are discussed.
The experimental results indicate that: (1) There are different characteristic particles in the same type of coal. With increasing of coal particle density, the content of ash, volatile matter, C, H, N and 0 and the quantity of heat decreas. (2)As far as the low density particles with low ash content are concerned, there is no bottom ash left after a long term combustion in the fluidized bed. The mode of combustion is "single combusting surface" mode. On the contrary, the high density coal with the high ash content produces large amount of bottom ash and the mode is mainly "two combusting surface" mode. (3)At the condition of the same combustion interval and particle size, with the increasing of coal density, the proportion of bottom ash increases. And the carbon content of fly ash decreases. The proportion of the particle left in the original particle size rank increases distinctly, while the fine particle proportion decreases dramatically. And the burn exhaust ratio decreases. (4)With the increasing of par
tcle density, the extent of the impact of the particle size distribution to the distribution of bottom ash size gradually
ABSTRACT
increases.
A simple mathematical model is established based on the single particle coal combustion mode and experimental results. The experimental results of burning for 5min and 20min are matched. The prediction of buring for SOmin is made. The comparison and analysis of model results and experimental results are made.
At last, the thesis introduces a combustion experiment carried out on a 0. 5MW circulating f luidized bed combustion test rig. The characteristic of ash formation is discussed through the analysis of experimental results including the ash particle distribution, the propotion of bottom ash and fly ash, ash carbon content and combustion efficency. Some suggestions are provided on the boiler design.
引文
[1] Adanez J., L. F. de. Diego, P. Gayan, L. Armesto and A. Cabanillas, 1995, "Modelling of Coal Combustion in Circulating Fluidized Bed Combustion", Proceeding of the 1995 nInt. Conf. on FBC, pp305-315
[2] Adewumi, M. A, and H. Arastoopoour, 1986, "Two-Dimensional Steady State Hydrodynamic Analysis of Gas-Solids Flow in Vertical Pneumatic Convering Systems", Powder Technol. Vol. 48, pp67-74
[3] Franz Winter and Xin Liu, Ash Formation during CFB Coal Combustion-a Laboratory Study[C].
[4] Stubing J F. The effects of fragmentation on devolatilization of large coal particles[J]. Fuel, 1989, 68: 155-160
[5] Yue Guangxi, Wang Lan, Li Yan et al. Ash size formation characteristics in CFB coal combustion[A]. Proceedings of 4th International Conference on Fluidized Bed Combustion[C]. New York, 1993
[6] Kerstein A R. Fragmentaion during carbon conversion: predictions and measurements[A]. Proceedings of 20th Symposium(International) on Combustion[C]. Pittsburgh, 1984
[7] Douglas R. Hajicek, Michael D. Mann, Thomas A. Moe, The Effect of Coal Properties on CFBC Performance[J], Fluidized Bed Combustion, 1993
[8] Chirone R, Massimilla L, Salatino P. Communition of carbons in fluidized bed combustion[J]. Prog Energy Combust Sci, 1991, 17: 297-326
[9] Arena, U., Malandrino, A. Marzocchella and A. L. Massimilla, 1991, "Flow Structures in the Risers of Laboratory and Pilot CFB Units", in Circulating Fluidized Bed Technology Ⅲ ed. P. Basu, M. Horio and M. Hasatani, Pergamon Press, New York, pp. 137-144.
[10] Peter L. Rozelle, Sarma V. Pisupati, and Alan W. Scaroni, The effect of fuel properties on the bottom ash generation rate by a laboratory fluidized bed combustor.
[11] Babij W N, et al. Verbreanungs daten von. Teilchen unterschiedlicher Kohlesorten ans dem Kohlerevier Kuzniezk(Russ.) [J]. Teploenergetika, 1977(1): 13～15
[12] Duane H. Smith, george J. Haddad and Ulrich Grimm, Composition and chemistry of particulates from a PRBC demonstration plant[J], Fuel, 76(8)
[13] Bellgardt, F. Hembach, M. Schossler, and J. Werther, 1987, "Modeling of Large Scale Atmospheric Fluidized Bed Cjombustors", Proceed of the 1987 Int. Conf. on FBC. pp713-722
[14] 岑可法，倪明江，骆仲泱，严建华等，《循环流化床锅炉理论设计与运行》，中国电力出版社，1997
[15] 王勤辉，“循环流化床锅炉总体数学模型及性能试验”，浙江大学博士论文，1997
[16] 张迎春，宽筛分流化床稀相区水平单管的传热研究，浙江大学硕士学位论文，1990
[17] 王勤辉，骆仲泱，倪明江，岑可法，循环流化床锅炉炉内颗粒分布平衡模型[J]，中国电机工程学报，2001
[18] 王智微，吴晓玲，冷洪川，循环流化床锅炉物料分布特征分析[J]．热电技术，2002，3：7-9
[19] 张宏焘，“煤在流化床燃烧过程中破碎特性及焦炭表面灰层扩散传质特性的研究”，浙江大学硕士论文，1990
[20] 王勤辉，骆仲泱，方梦祥，倪明江，岑可法，循环流化床锅炉炉内流动和燃烧特性的试验研究[J]，动力工程，1999，19(3)
[21] 肖显斌，杨海瑞，吕俊复，岳光溪，“循环流化床燃烧数学模型”，煤炭转化，2002，25(3)
[22] P．巴苏，S．A．弗雷泽，《循环流化床锅炉的设计与运行》，科学出版社，1994
[23] 吴正舜，张春林等，煤在燃烧过程中的模型的建立[J]，燃料化学学报，2003，31(1)
[24] 马利强，路霁鸽，岳光溪，流化床条件下煤的一次爆裂特性的实验研究[J]，燃料化学学报，2000，28(1)
[25] 李爱民，池涌等，大颗粒炭在流化床中燃烧的热应力破碎理论[J]，煤炭学报，1998，23(2)
[26] 吕俊复，杨海瑞，张剑胜等，流化床燃烧煤的成灰磨耗特性[J]，燃料科学与技术，2003，9(1)
[27] 刘德昌，吴正舜等，煤的颗粒粒径分布对循环流化床锅炉设计和运行的影响[J]，中国粉体技术，1999，5(2)
[28] 于广辉，路霁鸽，郭庆杰，岳光溪，循环流化床锅炉飞灰残碳生成机理研究，煤炭转化，2000，23(3)
[29] 邹峥，何宏舟，翁其颖等，福建无烟煤粒度分布对循环流化床锅炉燃烧影响的工业实验[J]，工业锅炉，2002
[30] 刘宝森，李正义，姜义道，吕俊复，刘青，岳光溪，循环流化床锅炉对煤种适应性及灰平衡与煤种的关系，2000，16(2)
[31] 刘福明，曹勇，准格尔煤灰分与发热量关系的动态解算，露天采煤技术，2001
[32] 煤炭科学研究总院北京煤化学研究所，分类煤样的保存及减灰密度对G_(R·I) 测值的影响
[33] 孙冬，段旭琴，李忠廉等，适合中小选煤厂的精煤快速测灰方法[J]，煤炭加工与综合利用，1997
[34] 马秀国，孙昭星，高灰分碳颗粒燃烧的数学模型求解[J]，工程热物理学报，1991，12(3)
[35] 蒋月美，苏艺，冯莉莉，锅炉结渣机理分析[J]，锅炉技术，2001，6
[36] 沈来宏，“循环流化床燃烧数学模型及试验研究”，煤炭转化，1999，22(4)
[37] 容銮恩等，《电站锅炉原理》，中国电力出版社，1997
[38] 王勤辉，骆仲泱，李绚天等，“循环流化床锅炉炉内流动和燃烧特性的理论模拟”，动力工程，1999，19(4)
[39] 陈晓平，赵长遂等，贾汪15MW增压流化床联合循环中试机组PFB锅炉投入满负荷运行[J]．黑龙江电力，2002，1(24)：5-10
[40] 马丽锦，宽筛分物料调和平均粒径计算方法的探讨[J]，热力发电，1999(6)
[41] X. Querol, Z. Klika, Z. Weiss, R. B. Finkelman, ect., Determination of element affinities
by density fraction of bulk coal samples[J], Fuel, 80(2001) 83-96
[42] C. L. Senior, T. Zeng, J. Che, M. R. Ames, A. F. Sarofim, ect., Distribution of trace elements in selected pulverized coals as a function of particle size and density[J], Fuel, 63(2000) 215-241
[43] R. Hurt, K. Davis, N. Yang, D. Hardesty, The origin and properties of unburned carbonfrom pulverized coal combustion, EPRI Report, TR-105734, 1995
[44] P. Jaud et al, The Provence 250Mwe Unit: The largest CFB boiler ready for operation. 3rd International Symposium on coal combustion, Sept, 1995, Beijing.
[45] Luc Lafanschere et al. Study of circulating fluidized bed furnace behavior in order to scale up to 600Mw. 3rd International Symposium on coal combustion, Sept, 1995, Beijing
[46] P. Lucat et al. Status of the provence/Gardanne 250Mwe CFB boiler, 5th International conference on circulating fluidized beds. May, 1996
[47] J. Cl. Semedard et al, GEC Alshrom Stein Industre Appoach to the development of very large CFB boilers, 5th International conference on circulating fluidized beds, May, 1996
[48] Skowyra R. S., T. S. Czarnecki, C. Y. Sun, M. P. alkes. Design of a supercritical pressure circulating fluidized bed boiler with vertical water walls. Proceedings of the 13th Int. Conference on FBC, ed. Heinschel. ASME, Orlando, 1995, 17
[49] Zhou Jim, Babcock & Wilcox USA. Supercritical pulverized coal firing for power generation in China. Proceedings of the 17th International Pittsburgh Coal Conference, 2000, 1
[50] Bursi J. M., L. Lafanechere, L. Jestin. Basic design studies for a 600MWe CFB boiler(270b, 2×600℃). Circulating Fluidized Technology Ⅵ, ed. J. Werther, Würzhning Germany, August 22-27, 1999, 913
[51] Rajaram S. Next generation CFBC. Chemical Engineering Science, V. 54, 1999, 5565
[52] Jaud P., L. Jacquet, O. Piedfer, L. Jestin. The Provence 250MWe unit: The largest CFBboiler ready for operation. Proceedings of the 13th Int. Conference on FBC, ed. Heinschel. ASME, Orlando, 1995, 721
[53] Wang Qinhui, Luo Zhongyang, Ni Mingjiang, Cen Kefa, Particle Population Banlance Model for A Circulating Fluidized Bed Boiler, Chemical Engineering Journal, Vol(93), 2003
[54] Di Maggio T, Bursi J M, Lafanechere L, et al. Circulating Fluidized Bed Boiler Numerical, Circulating Bed Technology, Beijing: Science Press, 1996
[55] CLicksman L R. Heat Transfer in Fluidizd Bed Combustion. Fluidized Bed Boiler: Pergamon Press, 1995
[56] Senior R C, Brereton, C Modelling of circulating fluidized bed solids flow and distribution, Chem. Eng. Sci., 1992, 47: 281～296
[57] 金保昇，范新宽，阮征等，“燃煤飞灰循环流化床燃烧数学模型”，工程热物理学报，1990，11(2)
[58] 刘静，“大型燃煤循环流化床锅炉的数学模拟与设计”，浙江大学硕士论文，1994
[59] 李政，“循环流化床锅炉通用整体数学模型、仿真与性能预测”，清华大学博士论文，1994
[60] 过明道，章城，流态燃烧期间煤粒的破碎及其对燃烧速率的影响[J]，工程热物理学报，1987，8(3)：277-280
[61] 傅维标，张燕屏，韩洪樵，等，煤粒热解通用模型[J]，中国科学，1988，A辑(12)：1283—1290
[62] 郑治余，刘信刚，金燕等，循环流化床锅炉燃烧室内焦炭离子燃烧特性的研究，工程热物理学报，1995，16(1)：106-110
[63] 毛健雄，毛健全，等，煤的洁净燃烧[M]，科学出版社，1998
[64] 郑明东，何孝军，动力煤的燃烧性能，化工学报，2003，54(3)
[65] 陈以理，火力发电锅炉直接点燃煤粉的概况[J]，动力工程，1988(3)
[66] 刘德昌，阎维平等，流化床燃烧技术，北京，中国电力出版社，1995
[67] 王树荣，方梦祥，骆仲泱等，“循环流化床锅炉大型化关键设计问题研究”，热力发电，2000(4)
[68] 白泉，李政，倪维斗，“循环流化床锅炉整体自动建模系统的数字模型”，计算机仿真，2003，20(1)
郑楚光，《洁净煤技术》，华中理工大学出版社，1996
[69] 赵若林，“对发展大型循环流化床锅炉的建议”，电站系统工程，1999，15(3)
[70] 郑建学，陈听宽，罗毓珊等，“超临界压力下600Mwe直流锅炉水冷壁内螺纹管摩擦阻力特性研究”，热力发电，2000(2)
[71] 姚西增，吉宪磊，“循环流化床技术的发展现状“，西北电力技术，2002，3
[72] 金国淼，《除尘设备设计》，上海科学技术出版社，1983
[73] 姜初炎，“从石狮热电厂2×75t/h CFB锅炉的成功经验探讨CFB锅炉大型化可行性”，引进与咨询，2002，6
[74] 曹坤龙，王志伟，魏高升，周振堂，刘柏谦，“从法国Gardanne 250MWe CFB锅炉看循环流化床燃烧技术的发展”，东北电力学院学报，2001，21(3)
[75] Rajan R R, Wen C Y, A Comprehensive Model for Fluidized Bed Coal Combustion, A IchE J, 1980, 26(4)
[76] Wei β V,, Scholer J, Fett F N, Mathematical Modeling of Coal Combustion in a Circulating Fluidized Bed Reactor. In: Basu P, Large J F, eds, Circulating Fluidized Bed Technology, Oxford: Pergamon, 1988, 289-298
[77] Muir J R, Brereton C, Grace J R, et al. Dynamic Modeling for Simulation and Contral of a Circulating Fluidized Bed Comhnstor. A IchE J, 1997, 43(5)
[78] Hyppanen T, Lee Y Y, Rainio A, A Three-dimensional Model for Circulating Fluidized Bed Boilers, In: Anthony E J, ed. Proceedings of the 11th International Conference on Fluidized Bed Combustion. New York: ASME, 1991, 439-448
[79] Knoebig T, Luecke K, Werther J, Mixing and Reaction in the Circulating Fluldized Bed—A Three-dimensional Combustion Model, Chemical Engineering Science, 1999, 54: 2151-2160
[80] Arastoopour H, Pakdel P, Adewumi M, Hydrodynamics Analysis of Dilute Gas-solid Flow in a Vertical
Pipe, Power Techonology, 1990, 62
[81] Sinclair J L, Hydrodynamics Modeling, In: Grace J R, Avidan A A, Know Iton T M, eds, Circulating Fluidized Beds, London: Chapman & Hall, 1997
[82] Ge W, Li J, Pseudo-particle Approach to Hydrodynamics of Gas-solid Two-phase Flow, In: Kwauk M, Li J, eds, Circulating Fluidized Bed Technoloty Ⅴ, Beijing: Science Press, 1996
[83] Tsuji Y, Kawaguchi T, Tanaka T, Discrete Particle Simulation of Two-dimensional Fluidized Bed, Powder Technology, 1993, 77(1)
[84] Nieuwland J J, Van Annaland M, Kuipers J A M, et al. Hydrodynamic Modeling of Gas/Particle Flows in Riser Reactors, A IChE J, 1996, 42(6)
[85] Samuelsberg A, Hjertager B H, Computational Modeling of Gas/Particle Flow in a Riser Reactors, A IChE J, 1996, 42(6)
[86] Tsuo York Y. P., Yam Y. Lee, Aku Raino and Timo. Hyppanen, 1995, "Three-Dimensional modeling of N_2O and NOx Emissions From CFB Boilers" The Proced. of 1995 Int. Conf. on FBC. P1059-1069.
[87] SKOWYARRS, CZARNECKITS, SUNCY, et al. Desing of a supercritical sliding pressure circulating bed boiler with vertical water walls. 13th International Conference on Fluidized Bed Combustion. USA: Orlando FL, 1995, 17-26
[88] Rajaram S. Next generation CFBC. Chemical Engineering Science, V. 54, 1999, 5565
[89] Jaud P., L. Jacquet, O. Piedfer, L. Jestin. The Provence 250 MWe unit: The largest CFB boiler ready for operation. Proceedings of the 13th Int. Conference on FBC, ed. Heinschel. ASME, Orlando, 1995, 721
[90] U. Arena, A. Cammarota, L. Massimilla, L. Siciliano, P. Basu, Carbon attrition during the combustion of a char in a circulating fluidized bed, Combust. Sci. Technol, 1990(73)
[91] T. J. Pis, A. B. Fuertes, V. Artos, A. Suarez, F. Rubiera, Attrition of coal ash particles in a fluidized bed, Powder Technol, 1991(66)
[92] Arena Umberto and Antonio Cammarota, Hydrodynamics of a Circulating Fluidized Bed With Secondary air Injection, Proceedings of the 1993 Int. Conf. On FBC, 1993
[93] Skowyra R. S., T. S. Czarnecki, C. Y. Sun, M. P. alkes. Design of a supercritical pressure circulating fluidized bed boiler with vertical water walls。ProceedingS of the 13th Int. Conference on FBC, ed. Heinschel. ASME, Orlando, 1995, 17
[94] Zhou Jim, Babcock & Wilcox USA. Supercritical pulverized coal firing for power generation in China. Proceedings of the 17th International Pittsburgh Coal Conference, 2000, 1
[95] Bursi J. M., L. Lafanechere, L. Jestin. Basic design studies for a 600MWe CFB boiler(270b, 2×600℃). Circulating Fluidized Technology Ⅵ, ed. J. Werther, Würzhning Germany, August 22-27, 1999, 913