Ash deposition characteristics of external surface of flue gas swept across tube bundles

doi:10.11949/j.issn.0438-1157.20180498

Abstract

Abstract:

The problem of high exhaust temperature universally exists around the industrial boilers, which causes waste of energy. The surface of flue gas heat exchanger is easily to produce ash. To develop an efficient heat transfer element with self-cleaning function and extended heating surface, calcareous dust has the characteristic of high concentration. The characteristics of the physical, chemical and external working process of exhaust dust are studied. The physical and chemical properties of the particle size distribution, appearance and chemical composition of the ash are studied by using scanning electron microscopy, XRD and other instruments. Experimental research on the properties of heat transfer elements is carried out. The results indicated that the surface of lime dust ash have many holes with different sizes, and the particle structure is compact, it is easily to produce physical deposition to form loose ash. The increase of ash concentration will increase the amount of ash accumulation. The higher the ash concentration in the same time, the larger the ash content, and the sleek surface is more likely to be produced. When the flow velocity of flue gas is large, the amount of ash accumulation is quickly stable, and the increase of gas flow velocity will lead to the decrease of ash content in the windward area and the increase of the ash amount of the leeward area. There is the best flue gas flow velocity makes the minimum deposition of fly ash particles on the surface of the pipe. Increasing the lateral pitch and reducing the longitudinal pitch are beneficial to reduce the ash content.

Key words: ash deposition characteristic, ash characteristics, flue gas heat exchanger, hydrodynamics, flow, size distribution

摘要：

针对石灰线生产中烟尘易沉积，烟气换热器表面积灰的问题，为开发具有自清灰功能和扩展受热面的高效传热元件，对粉尘物理、化学和外部工作过程特性进行研究，通过采用扫描电子显微镜及XRD等仪器，研究灰的粒径分布、外观形貌及化学成分等物理化学特性，并对管束外表面积灰特性进行实验研究，结果表明：石灰线粉尘粒径较大，颗粒结构紧密，表面有大小不一的孔，易产生物理沉积形成松散积灰；灰样浓度的增大会导致积灰量增加，相同时间内灰样浓度越高积灰量越大，顺风面更易产生积灰现象；烟气流速较大时，积灰量很快达到稳定，烟气流速的增加会导致迎风面积灰量减少，背风面积灰量增加，存在最佳的烟气流速使飞灰颗粒在管道表面的沉积量最小；增加横向节距、减少纵向节距有利于减少积灰量。

关键词: 积灰特性, 灰分特性, 烟气换热器, 流体动力学, 流动, 粒度分布

CLC Number:

TK01⁺8

PENG Yan, ZHAO Qinxin, WANG Weishu. Ash deposition characteristics of external surface of flue gas swept across tube bundles[J]. CIESC Journal, 2018, 69(12): 5034-5041.

彭岩, 赵钦新, 王为术. 烟气横掠管束外表面的积灰特性[J]. 化工学报, 2018, 69(12): 5034-5041.

References 31

[1]	陈衡, 潘佩媛, 赵钦新, 等. 燃煤工业锅炉黏性积灰和露点腐蚀耦合机理[J]. 化工学报, 2017, 68(12):4774-4783. CHEN H, PAN P Y, ZHAO Q X, et al. Coupling mechanism of viscose ash deposition and dewpoint corrosion in industrial coal-fired boiler[J]. CIESC Journal, 2017, 68(12):4774-4783.
[2]	李飞, 孙奉仲, 史月涛. 积灰与酸耦合作用下套管换热器传热特性热态实验[J]. 化工学报, 2014, 65(8):2876-2881. LI F, SUN F Z, SHI Y T, Hot-state experiment on double-pipe heat exchanger under coupled effect of fouling and acid[J]. CIESC Journal, 2014, 65(8):2876-2881.
[3]	翟勇, 张明, 尹洪超, 等.水泥窑余热发电技术的应用及其经济性分析[J]. 节能, 2013, 32(12):48-50+3. ZHAI Y, ZHANG M, YIN H C, et al. The application of waste heat power generation and economy analysis[J]. Energy Conservation, 2013, 32(12):48-50+3.
[4]	王文龙, 施正伦, 骆仲泱, 等. 燃煤电厂锅炉联产水泥的技术现状与前景[J]. 浙江大学学报(工学版), 2003, 37(2):225-230. WANG W L, SHI Z L, LUO Z Y, et al. The status and perspective of cement generation in coal fired power boilers[J]. Journal of Zhejiang University (Engineering Science), 2003, 37(2):225-230.
[5]	韩辉. 气体换热器强化换热及腐蚀积灰特性的数值模拟与实验研究[D]. 西安:西安交通大学, 2014. HAN H. Numerical and experimental studies on heat transfer enhancement and erosion and fouling characteristics in heat exchanger of gas[D]. Xi'an:Xi'an Jiaotong University, 2014.
[6]	张鑫. 锅炉烟气余热利用系统分析与优化研究[D]. 北京:华北电力大学, 2015. ZHANG X. Research on system analysis and optimization of boiler flue gas waste heat utilization[D]. Beijing:North China Electric Power University, 2015.
[7]	ZBOGAR A, FRANDSEN F, JENSEN P A, et al. Shedding of ash deposits[J]. Progress in Energy & Combustion Science, 2009, 35(1):31-56.
[8]	MARNER W J, SUITOR J W. A survey of gas-side fouling in industrial heat-transfer equipment[R]. Jet Propulsion Lab Report, 1983.
[9]	岑可法, 樊建人, 池作和. 锅炉和热交换器的积灰、结渣、磨损和腐蚀的防止原理与计算[M]. 北京:科学出版社, 1994. CEN K F, FAN J R, CHI Z H. Prevention Principle and Calculation of Ash Deposition, Slagging, Abrasion and Corrosion of Boilers and Heat Exchangers[M]. Beijing:Science Press, 1994.
[10]	BAXTER L L. Ash deposition during biomass and coal combustion:a mechanistic approach[J]. Biomass & Bioenergy, 1993, 4(2):85-102.
[11]	WEBER R, MANCINI M, SCHAFFEL-MANCINI N, et al. On predicting the ash behaviour using computational fluid dynamics[J]. Fuel Processing Technology, 2013, 105(1):113-128.
[12]	WACLAWIAK K, KALISZ S. A practical numerical approach for prediction of particulate fouling in PC boilers[J]. Fuel, 2012, 97(7):38-48.
[13]	WANG Y, HU C, HUI S, et al. Deposition of cement kiln ash on the tubes of waste heat recovery boiler[C]//IEEE PES Asia-Pacific Power and Energy Engineering Conference. 2011:1-4.
[14]	ROGERS L N, REED J. The adhesion of particles undergoing an elastic-plastic impact with a surface[J]. Journal of Physics D, 1984, 17(4):677-689.
[15]	CHIRONE R, MICCIO F, SCALA F. Mechanism and prediction of bed agglomeration during fluidized bed combustion of a biomass fuel:effect of the reactor scale[J]. Chemical Engineering Journal, 2006, 123(3):71-80.
[16]	HAN H, HE Y L, TAO W Q, et al. A parameter study of tube bundle heat exchangers for fouling rate reduction[J]. International Journal of Heat & Mass Transfer, 2014, 72(72):210-221.
[17]	NARUSE I, KAMIHASHIRA D, KHAIRIL, et al. Fundamental ash deposition characteristics in pulverized coal reaction under high temperature conditions[J]. Fuel, 2005, 84(4):405-410.
[18]	BAXTER L L. Ash deposition during biomass and coal combustion:a mechanistic approach[J]. Biomass & Bioenergy, 1993, 4(2):85-102.
[19]	TOMECZEK J, WACLAWIAK K. Two-dimensional modelling of deposits formation on platen superheaters in pulverized coal boilers[J]. Fuel, 2009, 88(8):1466-1471.
[20]	TANG S Z, WANG F L, REN Q, et al. Fouling characteristics analysis and morphology prediction of heat exchangers with a particulate fouling model considering deposition and removal mechanisms[J]. Fuel, 2017, 203(ICAE):725-738.
[21]	樊建人, 周大冬, 岑可法. 煤灰粒子冲击管束的碰撞和磨损研究[J]. 工程热物理学报, 1989, 10(4):452-455. FAN J R, ZHOU D D, CEN K F. An investigation of tube banks erosion by coal ash impaction[J]. Journal of Engineering Thermophysics, 1989, 10(4):452-455.
[22]	王迎慧, 盛林弘毅, 归柯庭, 等. 烟气横掠螺旋槽管束灰粒沉积特性的数值模拟[J]. 江苏大学学报(自然科学版), 2018, 39(1):32-37. WANG Y H, SHENG L H Y, GUI K T, et al. Numerical simulation on particle deposition in flue gas flowing spirally corrugated tubes in aligned arrangement[J]. Journal of Southeast University (Natural Science Edition), 2018, 39(1):32-37.
[23]	王迎慧, 孙宁, 归柯庭. 烟气横掠螺旋槽管束磨损特性的数值模拟[J]. 东南大学学报(自然科学版), 2014, 44(03):585-590. WANG Y H, SUN N, GUI K T. Numerical simulation on erosion characteristics of flue gas flowing across spirally corrugated tubes in aligned arrangement[J]. Journal of Southeast University (Natural Science Edition), 2014, 44(3):585-590.
[24]	叶侠丰, 丁红蕾, 潘卫国, 等.带拓展面椭圆管束的换热、积灰及磨损特性研究[J]. 中国电力, 2018, 51(6):26-32. YE X F, DING H L, PAN W G, et al. Numerical study on the heat transfer, fouling and erosion characteristics of the elliptical tube bundle with different extended heating surfaces[J]. Electric Power, 2018, 51(6):26-32.
[25]	陈衡, 王云刚, 赵钦新, 等. 燃煤锅炉低温受热面积灰特性实验研究[J]. 中国电机工程学报, 2015, 35(S1):118-124. CHEN H, WAGN Y G, ZHAO Q X, et al. Experimental investigation of ash deposition on low temperature heating surfaces in a coal-fired boiler[J]. Proceedings of the CSEE, 2015, 35(S1):118-124.
[26]	徐晓光. 生物质燃烧过程积灰形成机理的实验研究[D]. 北京:清华大学, 2009. XU X G. Experimental investigation on the formation mechanisms of ash deposition during biomass combustion[D]. Beijing:Tsinghua University, 2009.
[27]	何雅玲, 汤松臻, 王飞龙, 等. 中低温烟气换热器气侧积灰、磨损及腐蚀的研究[J]. 科学通报, 2016, 61(17):1858-1876. HE Y L, TANG S Z, WAGN F L, et al. Gas-side fouling, erosion and corrosion of heat exchanger for middle and low temperature flue gas waste heat recovery[J]. Chinese Science Bulletin, 2016, 61(17):1858-1876.
[28]	裴勇, 何雅玲. H型翅片管换热器烟气低温腐蚀影响因素实验研究[J]. 西安交通大学学报, 2017, 51(3):54-61. FEI Y, HE Y L. Experimental study on the influencing factors of low temperature corrosion of H-type finned rube heat exchangers[J]. Journal of Xi'an Jiaotong University, 2017, 51(3):54-61.
[29]	王飞龙, 何雅玲, 汤松臻, 等. 典型烟气余热换热器气侧积灰特性[J]. 科学通报, 2017, 62(12):1292-1301. WANG F L, HE Y L, TAGN S Z, et al. Numerical study of fouling characteristics on two kinds of typical heat exchangers used in the waste heat recovery systems[J]. Chinese Science Bulletin, 2017, 62(12):1292-1301.
[30]	刘博, 李辉, 李娜, 等. 余热锅炉对流受热面积灰特性的实验研究[J]. 工程热物理学报, 2013, 34(2):290-293. LIU B, LI H, LI N, et al. Experimental study on ash deposition characteristic of convection heating surface in waste heat boiler[J]. Journal of Engineering Thermophysics, 2013, 34(2):290-293.
[31]	汤松臻, 王飞龙, 童自翔, 等. 烟气余热回收换热器积灰抑制技术研究及参数优化[J]. 西安交通大学学报, 2017, 51(9):19-25. TANG S Z, WAGN F L, TONG Z X, et al. Numerical study and parameter optimization for suppressing ash deposition in flue gas heat exchanger[J]. Journal of Xi'an Jiaotong University, 2017, 51(9):19-25.