准东煤燃烧中不同形态无机元素向颗粒物的转化行为
|
摘要
准东煤田是我国已探明的最大煤田,但由于准东煤普遍含有较高的Na,Ca,Mg,Fe等碱性元素,其燃烧利用过程中出现了严重的沾污结渣问题。为解决准东煤的沾污结渣问题,有必要对其无机元素在燃烧过程中的转化机理进行深入研究。采用逐级提取的方法对准东煤进行处理,依次制备了水洗煤、乙酸铵洗煤和盐酸洗煤,在沉降炉中开展了各煤样的颗粒物生成特性实验,研究了准东煤中不同形态无机元素向颗粒物的转化行为。燃烧温度1 300℃,模拟空气燃烧气氛,气流量10 L/min,给粉速率0. 1 g/min。使用低压撞击器(LPI)收集燃烧生成的颗粒物,使用精密电子天平称量颗粒物的质量,获得其质量粒径分布规律;采用扫描电子显微镜和能谱(SEM-EDS)分析颗粒物的成分和形貌。研究表明,准东煤中Na主要以水溶态形式存在,Ca和Mg主要以乙酸铵溶态和盐酸溶态形式存在,Fe主要以盐酸不溶态和盐酸溶态形式存在。燃烧后生成的颗粒物主要分布在1～10μm,并且主要来自煤中乙酸铵溶态和盐酸溶态Ca,Mg的转化。它们大部分形成富Ca,Mg的烧结状无规则形貌颗粒,小部分形成球形的硅铝酸盐颗粒。Na很大一部分生成PM1(尤其是PM0. 1),其他则以硅铝酸盐形式分布在PM1～10中。Fe燃烧后主要分布在PM1～10中,其中盐酸溶态Fe有较大贡献。通过本研究可以认识到有机结合态和盐酸溶态元素是引起准东煤沾污结渣的主要元素形态,通过酸洗去除准东煤中的部分无机元素是缓解其沾污结渣的一种可行方法。
Zhundong coal field is the largest coal field in China.However,the content of Na,Ca,Mg and Fe in the coal is usually very high,which has caused severe slagging and fouling problems during Zhundong coal combustion.In order to solve the slagging and fouling problems,the transformation mechanism of inorganic elements during combustion should be well understood.This study aims to investigate the transformation of inorganic elements in different forms into ash particles during Zhundong coal combustion.A set of coal samples were prepared by water washing,ammonium acetate washing and diluted hydrochloric acid washing.All the coals were burned in a drop tube furnace at 1 300 ℃ in air condition.The air flow rate was 10 L/min.Coal was fed at the rate of 0.1 g/min.The combustion generated ash particles were collected by a low pressure impactor( LPI).The mass of particles was measured by a precision balance.The composition and morphology were analyzed by SEM-EDS.The results showed that Na was mainly in water soluble form.Ca and Mg were mainly in the ammonium acetate soluble and hydrochloric acid soluble form.While Fe was mainly in the hydrochloric acid soluble and insoluble form.After combustion,most of the ash particles were distributed in the range of 1-10 μm.These particles mainly came from the ammonium acetate soluble and hydrochloric acid soluble Ca and Mg in the coal.Most of them were irregular in shape with high content of Ca and Mg.The remaining particles were Ca/Mg contained alumino-silicates with spherical shapes.Na mainly contributed to the formation of PM1( especially to PM0.1),and the rest was presented in PM1-10.Fe was mainly distributed in PM1-10,and the contribution of acid soluble Fe was significant.From this study,it can be found that inorganic elements in the form of ammonium acetate soluble and hydrochloric acid soluble were the key that resulted in the ash deposition of Zhundong coal.The use of acid to remove the inorganics in the coal is a way to mitigate the ash deposition problem.
Zhundong coal field is the largest coal field in China.However,the content of Na,Ca,Mg and Fe in the coal is usually very high,which has caused severe slagging and fouling problems during Zhundong coal combustion.In order to solve the slagging and fouling problems,the transformation mechanism of inorganic elements during combustion should be well understood.This study aims to investigate the transformation of inorganic elements in different forms into ash particles during Zhundong coal combustion.A set of coal samples were prepared by water washing,ammonium acetate washing and diluted hydrochloric acid washing.All the coals were burned in a drop tube furnace at 1 300 ℃ in air condition.The air flow rate was 10 L/min.Coal was fed at the rate of 0.1 g/min.The combustion generated ash particles were collected by a low pressure impactor( LPI).The mass of particles was measured by a precision balance.The composition and morphology were analyzed by SEM-EDS.The results showed that Na was mainly in water soluble form.Ca and Mg were mainly in the ammonium acetate soluble and hydrochloric acid soluble form.While Fe was mainly in the hydrochloric acid soluble and insoluble form.After combustion,most of the ash particles were distributed in the range of 1-10 μm.These particles mainly came from the ammonium acetate soluble and hydrochloric acid soluble Ca and Mg in the coal.Most of them were irregular in shape with high content of Ca and Mg.The remaining particles were Ca/Mg contained alumino-silicates with spherical shapes.Na mainly contributed to the formation of PM1( especially to PM0.1),and the rest was presented in PM1-10.Fe was mainly distributed in PM1-10,and the contribution of acid soluble Fe was significant.From this study,it can be found that inorganic elements in the form of ammonium acetate soluble and hydrochloric acid soluble were the key that resulted in the ash deposition of Zhundong coal.The use of acid to remove the inorganics in the coal is a way to mitigate the ash deposition problem.
引文
[1]杨忠灿,刘家利,何红光.新疆准东煤特性研究及其锅炉选型[J].热力发电,2010,39(8):38-40.YANG Zhongcan,LIU Jiali,HE Hongguang. Study on properties of Zhundong coal in Xinjiang region and type-selection for biolers burning this coal sort[J].Thermal Power Generation,2010,39(8):38-40.
[2] LI J,ZHUANG X,QUEROL X,et al. Environmental geochemistry of the feed coals and their combustion by-products from two coalfired power plants in Xinjiang Province,Northwest China[J].Fuel,2012,95(1):446-456.
[3] ZENG X,YU D,LIU F,et al. Scavenging of refractory elements(Ca,Mg,Fe)by kaolin during low rank coal combustion[J].Fuel,2018,223(1):198-210.
[4] DAI B Q,LOW F,DE Girolamo A,et al.Characteristics of ash deposits in a pulverized lignite coal-fired boiler and the mass flow of major ash-forming inorganic elements[J]. Energy&Fuels,2013,27(10):6198-6211.
[5] XU J,YU D,FAN B,et al. Characterization of ash particles from co-combustion with a Zhundong coal for understanding ash deposition behavior[J].Energy&Fuels,2013,28(1):678-684.
[6] XU L,LIU J,KANG Y,et al.Safely burning high alkali coal with kaolin additive in a pulverized fuel boiler[J]. Energy&Fuels,2014,28(9):5640-5648.
[7] DAI B Q,WU X,DE Girolamo A,et al.Inhibition of lignite ash slagging and fouling upon the use of a silica-based additive in an industrial pulverised coal-fired boiler.Part 1.Changes on the properties of ash deposits along the furnace[J].Fuel,2015,139(1):720-732.
[8] WANG X B,XU Z X,WEI B,et al.The ash deposition mechanism in boilers burning Zhundong coal with high contents of sodium and calcium:A study from ash evaporating to condensing[J].Applied Thermal Engineering,2015,80(1):150-159.
[9] WEI B,WANG X,TAN H,et al.Effect of silicon-aluminum additives on ash fusion and ash mineral conversion of Xinjiang high-sodium coal[J].Fuel,2016,181(1):1224-1229.
[10] GAO X,RAHIM M U,CHEN X,et al.Significant contribution of organically-bound Mg,Ca,and Fe to inorganic PM10emission during the combustion of pulverized Victorian brown coal[J].Fuel,2014,117(1):825-832.
[11] BENSON S A,HOLM P L. Comparison of inorganic constituents in three low-rank coals[J]. Industrial&Engineering Chemistry Product Research and Development,1985,24(1):145-149.
[12] QUANN R J,SAROFIM A F.A scanning electron microscopy study of the transformations of organically bound metals during lignite combustion[J].Fuel,1986,65(1):40-46.
[13] ZYGARLICKE C,STEADMAN E,BENSON S.Studies of transformations of inorganic constituents in a Texas lignite during combustion[J]. Progress in Energy and Combustion Science,1990,16(4):195-204.
[14] MILLER S F,SCHOBERT H H.Effect of the occurrence and modes of incorporation of alkalis,alkaline earth elements,and sulfur on ash formation in pilot-scale combustion of Beulah pulverized coal and coal-water slurry fuel[J].Energy&Fuels,1994,8(6):1208-1216.
[15] LI G,LI S,HUANG Q,et al. Fine particulate formation and ash deposition during pulverized coal combustion of high-sodium lignite in a down-fired furnace[J].Fuel,2015,143(1):430-437.
[16]曾宪鹏,于敦喜,樊斌,等.不同温度下准东煤燃烧颗粒物的生成特性[J].煤炭学报,2015,40(11):2690-2695.ZENG Xianpeng,YU Dunxi,FAN Bin,et al. Particulate matter formation during Zhundong coal combustion at different temperatures[J].Journal of China Coal Society,2015,40(11):2690-2695.
[17] XU L,KANG Y,ZHANG G,et al.Study of alkali emission and control with firing a high Alkali coal[J]. Combustion Science and Technology,2015,187(12):1959-1973.
[18] ZHANG X,ZHANG H,NA Y.Transformation of sodium during the ashing of Zhundong coal[J].Procedia Engineering,2015,102(1):305-314.
[19] LI G,WANG C A,YAN Y,et al.Release and transformation of sodium during combustion of Zhundong coals[J].Journal of the Energy Institute,2016,89(1):48-56.
[20]徐义书,刘小伟,张鹏辉,等.高氯准东煤中典型矿物元素对颗粒物生成的影响[J].化工学报,2017,68(4):1558-1565.XU Yishu,LIU Xiaowei,ZHANG Penghui,et al. Impacts of typical mineral matter in Zhundong coal on formation of particulate matter[J].CIESC Journal,2017,68(4):1558-1565.
[21] QUANN R J,SAROFIM A F.Vaporization of refractory oxides during pulverized coal combustion[C]. Proceedings of the Symposium(International)on Combustion[A],1982,19(1):1429-1440.
[22] YU D,XU M,YAO H,et al.Use of elemental size distributions in identifying particle formation modes[J]. Proceedings of the Combustion Institute,2007,31(2):1921-1928.
[23] GALLAGHER N B,PETERSON T W,WENDT J O L.Sodium partitioning in a pulverzed coal combustion environment[A].Proceedings of the Symposium(International)on Combustion[C],1996,26(2):3197-3204.
[24] WIBBERLEY L J,WALL T F.Alkali-ash reactions and deposit formation in pulverized-coal-fired boilers:The thermodynamic aspects involving silica,sodium,sulphur and chlorine[J]. Fuel,1982,61(1):87-92.
[25] QUANN R J,NEVILLE M,JANGHORBANI M,et al.Mineral matter and trace-element vaporization in a laboratory-pulverized coal combustion system[J]. Environmental Science&Technology,1982,16(11):776-781.
[26] DURIE R.The science of victorian brown coal:Structure,properties and consequences for utilization[M]. Oxyford:Butterworth-Heinemann,2013.
[27]樊斌,于敦喜,曾宪鹏,等.准东煤燃烧中矿物质转化行为的CCSEM研究[J].化工学报,2015,67(5):2117-2123.FAN Bin,YU Dunxi,ZENG Xianpeng,et al. Mineral transformation during Zhundong coal combustion by CCSEM[J].CIESC Journal,2015,67(5):2117-2123.
[28] BRYERS R W. Fireside slagging,fouling,and high-temperature corrosion of heat-transfer surface due to impurities in steam-raising fuels[J]. Progress in Energy and Combustion Science,1996,22(1):29-120.
[2] LI J,ZHUANG X,QUEROL X,et al. Environmental geochemistry of the feed coals and their combustion by-products from two coalfired power plants in Xinjiang Province,Northwest China[J].Fuel,2012,95(1):446-456.
[3] ZENG X,YU D,LIU F,et al. Scavenging of refractory elements(Ca,Mg,Fe)by kaolin during low rank coal combustion[J].Fuel,2018,223(1):198-210.
[4] DAI B Q,LOW F,DE Girolamo A,et al.Characteristics of ash deposits in a pulverized lignite coal-fired boiler and the mass flow of major ash-forming inorganic elements[J]. Energy&Fuels,2013,27(10):6198-6211.
[5] XU J,YU D,FAN B,et al. Characterization of ash particles from co-combustion with a Zhundong coal for understanding ash deposition behavior[J].Energy&Fuels,2013,28(1):678-684.
[6] XU L,LIU J,KANG Y,et al.Safely burning high alkali coal with kaolin additive in a pulverized fuel boiler[J]. Energy&Fuels,2014,28(9):5640-5648.
[7] DAI B Q,WU X,DE Girolamo A,et al.Inhibition of lignite ash slagging and fouling upon the use of a silica-based additive in an industrial pulverised coal-fired boiler.Part 1.Changes on the properties of ash deposits along the furnace[J].Fuel,2015,139(1):720-732.
[8] WANG X B,XU Z X,WEI B,et al.The ash deposition mechanism in boilers burning Zhundong coal with high contents of sodium and calcium:A study from ash evaporating to condensing[J].Applied Thermal Engineering,2015,80(1):150-159.
[9] WEI B,WANG X,TAN H,et al.Effect of silicon-aluminum additives on ash fusion and ash mineral conversion of Xinjiang high-sodium coal[J].Fuel,2016,181(1):1224-1229.
[10] GAO X,RAHIM M U,CHEN X,et al.Significant contribution of organically-bound Mg,Ca,and Fe to inorganic PM10emission during the combustion of pulverized Victorian brown coal[J].Fuel,2014,117(1):825-832.
[11] BENSON S A,HOLM P L. Comparison of inorganic constituents in three low-rank coals[J]. Industrial&Engineering Chemistry Product Research and Development,1985,24(1):145-149.
[12] QUANN R J,SAROFIM A F.A scanning electron microscopy study of the transformations of organically bound metals during lignite combustion[J].Fuel,1986,65(1):40-46.
[13] ZYGARLICKE C,STEADMAN E,BENSON S.Studies of transformations of inorganic constituents in a Texas lignite during combustion[J]. Progress in Energy and Combustion Science,1990,16(4):195-204.
[14] MILLER S F,SCHOBERT H H.Effect of the occurrence and modes of incorporation of alkalis,alkaline earth elements,and sulfur on ash formation in pilot-scale combustion of Beulah pulverized coal and coal-water slurry fuel[J].Energy&Fuels,1994,8(6):1208-1216.
[15] LI G,LI S,HUANG Q,et al. Fine particulate formation and ash deposition during pulverized coal combustion of high-sodium lignite in a down-fired furnace[J].Fuel,2015,143(1):430-437.
[16]曾宪鹏,于敦喜,樊斌,等.不同温度下准东煤燃烧颗粒物的生成特性[J].煤炭学报,2015,40(11):2690-2695.ZENG Xianpeng,YU Dunxi,FAN Bin,et al. Particulate matter formation during Zhundong coal combustion at different temperatures[J].Journal of China Coal Society,2015,40(11):2690-2695.
[17] XU L,KANG Y,ZHANG G,et al.Study of alkali emission and control with firing a high Alkali coal[J]. Combustion Science and Technology,2015,187(12):1959-1973.
[18] ZHANG X,ZHANG H,NA Y.Transformation of sodium during the ashing of Zhundong coal[J].Procedia Engineering,2015,102(1):305-314.
[19] LI G,WANG C A,YAN Y,et al.Release and transformation of sodium during combustion of Zhundong coals[J].Journal of the Energy Institute,2016,89(1):48-56.
[20]徐义书,刘小伟,张鹏辉,等.高氯准东煤中典型矿物元素对颗粒物生成的影响[J].化工学报,2017,68(4):1558-1565.XU Yishu,LIU Xiaowei,ZHANG Penghui,et al. Impacts of typical mineral matter in Zhundong coal on formation of particulate matter[J].CIESC Journal,2017,68(4):1558-1565.
[21] QUANN R J,SAROFIM A F.Vaporization of refractory oxides during pulverized coal combustion[C]. Proceedings of the Symposium(International)on Combustion[A],1982,19(1):1429-1440.
[22] YU D,XU M,YAO H,et al.Use of elemental size distributions in identifying particle formation modes[J]. Proceedings of the Combustion Institute,2007,31(2):1921-1928.
[23] GALLAGHER N B,PETERSON T W,WENDT J O L.Sodium partitioning in a pulverzed coal combustion environment[A].Proceedings of the Symposium(International)on Combustion[C],1996,26(2):3197-3204.
[24] WIBBERLEY L J,WALL T F.Alkali-ash reactions and deposit formation in pulverized-coal-fired boilers:The thermodynamic aspects involving silica,sodium,sulphur and chlorine[J]. Fuel,1982,61(1):87-92.
[25] QUANN R J,NEVILLE M,JANGHORBANI M,et al.Mineral matter and trace-element vaporization in a laboratory-pulverized coal combustion system[J]. Environmental Science&Technology,1982,16(11):776-781.
[26] DURIE R.The science of victorian brown coal:Structure,properties and consequences for utilization[M]. Oxyford:Butterworth-Heinemann,2013.
[27]樊斌,于敦喜,曾宪鹏,等.准东煤燃烧中矿物质转化行为的CCSEM研究[J].化工学报,2015,67(5):2117-2123.FAN Bin,YU Dunxi,ZENG Xianpeng,et al. Mineral transformation during Zhundong coal combustion by CCSEM[J].CIESC Journal,2015,67(5):2117-2123.
[28] BRYERS R W. Fireside slagging,fouling,and high-temperature corrosion of heat-transfer surface due to impurities in steam-raising fuels[J]. Progress in Energy and Combustion Science,1996,22(1):29-120.