Characteristics of ash deposit and dew point corrosion in biofuel boiler

doi:10.11949/j.issn.0438-1157.20160733

Abstract

Abstract:

The coupling characteristics between ash deposit and dew point corrosion of deep-cooling flue gas on ND steel and 316 L stainless steel(control) was investigated in a 65 t·h^-1 circulating fluidized bed biofuel boiler. The ash deposit and corrosion layer were studied by X-ray fluorescence spectroscopy(XRF), X-ray diffraction(XRD), scanning electron microscope(SEM) and energy dispersive spectrometer(EDS). Results indicated that the deposits on tube surface could be classified as layers of corrosion, coupling and ash deposit(NH₄Cl、SiO₂ and(NH₄)₂SO₄). The coupling layer contained ash deposit and metal corrosion by-product, which was prone to spall off because of strong adhesion to the ash deposit layer. The corrosion layer, mainly composed of metal compounds of chlorides and oxides, reduced dramatically in thickness with the decrease of inlet water temperature. The degree of corrosion of ND steel increased sharply when wall temperature was below water dew point of flue gas. ND steel showed corrosion resistance inferior to 316 L stainless steel at experimental conditions.

Key words: corrosion, deposition, flue gas, biofuel

摘要：

以ND钢为研究对象，选取316 L不锈钢为对比材料，主要研究了65 t·h^-1生物质循环流化床锅炉烟气深度冷却条件下的积灰与露点腐蚀耦合特性。对积灰和腐蚀层进行了XRF、XRD、SEM和EDS分析。实验结果表明：实验管件表面沉积物可分为腐蚀层、耦合层和灰沉积层（NH₄Cl、SiO₂和（NH₄）₂SO₄）。耦合层包含了灰沉积物和金属腐蚀产物，且与灰沉积层黏结紧密易剥落；腐蚀层多为金属的氯化物和氧化物，其厚度随实验进口水温降低而降低，当管壁温低于烟气水露点时，ND钢被腐蚀的程度急剧加重。在实验条件下，ND钢的抗露点腐蚀能力弱于316L不锈钢。

关键词: 腐蚀, 沉积物, 烟道气, 生物燃料

CLC Number:

TK16

MA Haidong, WANG Yungang, ZHAO Qinxin, CHEN Heng, LIANG Zhiyuan, JIN Xin. Characteristics of ash deposit and dew point corrosion in biofuel boiler[J]. CIESC Journal, 2016, 67(12): 5237-5243.

马海东, 王云刚, 赵钦新, 陈衡, 梁志远, 金鑫. 生物质锅炉积灰特性与露点腐蚀[J]. 化工学报, 2016, 67(12): 5237-5243.

References 24

[1]	XIONG S J, BURYALL J, ORBERG H, et al. Slagging characteristics during combustion of corn stovers with and without kaolin and calcite[J]. Energy & Fuels, 2008, 22(5):3465-3470.
[2]	KHAN A A, JONG W D, JANSENS P J, et al. Biomass combustion in fluidized bed boilers:potential problems and remedies[J]. Fuel Processing Technology, 2009, 90(1):21-50.
[3]	王爽, 姜秀民, 王谦, 等. 海藻生物质颗粒流化床燃烧试验研究[J]. 化工学报, 2013, 64(5):1592-1600. WANG S, JIANG X M, WANG Q, et al. Fluidized bed combustion of seaweed biomass particles[J]. CIESC Journal, 2013, 64(5):1592-1600.
[4]	国家发展和改革委员会. 可再生能源资源[R]. 2007:1-5. National Development and Reform Commission. Renewable Energy Resource[R]. 2007:1-5.
[5]	NIU Y Q, ZHU Y M, TAN H Z, et al. Biomass boiler exhaust gas temperature factors analysis and improvement measures[J]. Journal of Harbin University of Science & Technology, 2014, 9(3):453-456.
[6]	马海东, 王云刚, 赵钦新, 等. 燃煤电厂烟气冷却器壁上沉积物分析和形成机理[J]. 化工学报, 2015, 66(5):1892-1896. MA H D, WANG Y G, ZHAO Q X, et al. Analysis and formation mechanism of condensates on surface of flue gas cooler of coal-fired power plant[J]. CIESC Journal, 2015, 66(5):1892-1896.
[7]	HANSEN L A, NIELSEN H P, FRANDSEN F J, et al. Influence of deposit formation on corrosion at a straw-fired boiler[J]. Fuel Processing Technology, 2000, 64(1/2/3):189-209.
[8]	JENSEN P A, FRANDSEN F J, DAM-JOHANSEN K, et al. Experimental investigation of the transformation and release to gas phase of potassium and chlorine during straw pyrolysis[J]. Energy & Fuels, 2000, 14(6):1280-1285.
[9]	WESTBERG H M, BYSTROM M, LECKNER B. Distribution of potassium, chlorine, and sulfur between solid and vapor phases during combustion of wood chips and coal[J]. Fuel Processing Technology, 2003, 17(1):18-28.
[10]	DEMIRBAS A. Potential applications of renewable energy sources, biomass combustion problems in boiler power systems and combustion related environmental issues[J]. Progress in Energy and Combustion Science, 2005, 31(2):171-192.
[11]	SONG J H, GU T, LI J, et al. Study on air preheater corrosion problem of CFB biomass directed-fired boiler in Zhanjiang biomass power plant[J]. Applied Mechanics and Materials, 2013, 291:294-299.
[12]	WHITTINGHAM G. The corrosive nature of combustion gases[J]. Anti-Corrosion Methods and Materials, 1954, 1(6):182-193.
[13]	MOSKOVITS P D. Low-temperature boiler corrosion and deposits-a literature review[J]. Industrial and Engineering Chemistry, 1959, 51(10):1305-1312.
[14]	HUIJBREGTS W M, LEFERINK R G. Latest advances in the understanding of acid low-temperature corrosion:corrosion and stress corrosion racking in combustion gas condensates[J]. Anti-Corrosion Methods and Materials, 2004, 51(3):173-188.
[15]	HAN H, HE Y L, TAO W Q. A numerical study of the deposition characteristics of sulfuric acid vapor on heat exchanger surfaces[J]. Chemical Engineering Science, 2013, 101:620-630.
[16]	LI Z M, SUN F Z, SHI Y T, et al. Experimental study and mechanism analysis on low temperature corrosion of coal fired boiler heating surface[J]. Applied Thermal Engineering, 2015, 80:355-361.
[17]	ZHAO Q X, ZHANG Z C, CHENG D N, et al. High temperature corrosion of water wall materials T23 and T24 in simulated furnace atmospheres[J]. Chinese Journal of Chemical Engineering, 2012, 20(4):814-822.
[18]	WANG Y G, ZHAO Q X, ZHANG Z X, et al. Mechanism research on coupling effect between dew point corrosion and ash deposition[J]. Applied Thermal Engineering, 2013, 54(1):102-110.
[19]	LIANG Z Y, ZHAO Q X, WANG Y G, et al. Coupling mechanism of dew point corrosion and viscous ash deposits[J]. Materials and Corrosion, 2014, 65(8):797-802.
[20]	NIU Y Q, TAN H Z, WANG X B, et al. Study on deposits on the surface, upstream, and downstream of bag filters in a 12 MW biomass-fired boiler[J]. Energy & Fuels, 2010, 24:2127-2132.
[21]	NIU Y Q, LIU Y Y, TAN H Z, et al. Origination and formation of NH4Cl in biomass-fired furnace[J]. Fuel Processing Technology, 2013, 106:262-266.
[22]	BJORKMAN E, STEOMBERG B. Release of chlorine from biomass at pyrolysis and gasification conditions[J]. Energy & Fuels, 1997, 11(5):1026-1032.
[23]	VAN-LITH S C, ALONSO-RAMIREZ V, JENSEN P A, et al. Release to the gas phase of inorganic elements during wood combustion(Ⅰ):Development and evaluation of quantification methods[J]. Energy & Fuels, 2006, 20(3):964-978.
[24]	锅炉机组热力计算标准方法[M]. 北京锅炉厂设计科, 译. 北京:机械工业出版社, 1976:62-65. Thermodynamic Calculation Standard for Boiler Unit[M]. Compile Group of Thermodynamic Calculation Standard for Boiler Unit, trans. Beijing:China Machine Press, 1976:62-65.