高温干燥对褐煤孔隙结构及水分复吸的影响
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摘要
利用卧式固定床实验炉制得不同温度下干燥处理的煤样,采用低温氮吸附法测试煤样的比表面积、孔体积和孔径分布等孔隙特征参数,使用复吸实验装置测定不同干燥程度褐煤煤样的平衡含水量,探索了高温干燥处理后褐煤孔隙结构的演变与其复吸特性之间的关联规律。结果表明:褐煤原煤及不同干燥温度(600～800℃)下半焦的等温吸附曲线均属于第Ⅱ类吸附等温线,褐煤原煤、600℃和700℃干燥半焦的吸附回线均属于L1型,800℃干燥半焦的吸附回线有从L1型转变为L2型的趋势;随着干燥温度的增加,干燥半焦的比表面积先增大后减小,介孔峰值的孔径微分同样先增大后减小,而大孔孔径微分基本保持不变;分形维数D1和D2呈相反的变化趋势,且D2>D1;不同干燥程度半焦的复吸曲线变化趋势相同,且平衡含水量随着干燥温度的升高而减小;半焦复吸特性与孔隙结构有关,平衡含水率与其孔容积之间呈较好的线性关系。
The coal samples dried at different temperatures were prepared by horizontal fixed bed experimental furnace. The specific surface area, pore volume and pore diameter distribution of the coal samples were determined using nitrogen adsorption isotherm(-196℃). The relationship between the pore structure and moisture reabsorption behavior of the lignite samples was investigated using a self-designed reabsorption device. The experimental results show that the N2 adsorption behavior of the semi-coke dried under different temperatures followed the type IIadsorption is otherm, and the adsorption loops of the(raw coal and the semi-coke prepared under 600 and 700℃)belonged to type L1, while the adsorption loop of the semi-coke dried at 800℃ showed a transformation tendencyfrom type L1 to type L2. With the increasing of drying temperature, the specific surface area of the dried semi-cokefirst increased slowly and then decreased and the pore diameter differential corresponded to the mesopore peakshowed the same trend. Meanwhile, the pore diameter differential of the macropores remained unchanged. As the drying temperature increased, the fractal dimensions D1 and D2changed in the opposite trends, and the value of D2 was higher than D1. The moisture reabsorption behaviors of the semi-coke followed the same trend, and theequilibrium moisture content decreased with the increasing drying temperature. The moisture reabsorptioncharacteristics of the semi-coke were closely related to the pore structure, and the equilibrium moisture content hada good linear relationship with the pore volume.
The coal samples dried at different temperatures were prepared by horizontal fixed bed experimental furnace. The specific surface area, pore volume and pore diameter distribution of the coal samples were determined using nitrogen adsorption isotherm(-196℃). The relationship between the pore structure and moisture reabsorption behavior of the lignite samples was investigated using a self-designed reabsorption device. The experimental results show that the N2 adsorption behavior of the semi-coke dried under different temperatures followed the type IIadsorption is otherm, and the adsorption loops of the(raw coal and the semi-coke prepared under 600 and 700℃)belonged to type L1, while the adsorption loop of the semi-coke dried at 800℃ showed a transformation tendencyfrom type L1 to type L2. With the increasing of drying temperature, the specific surface area of the dried semi-cokefirst increased slowly and then decreased and the pore diameter differential corresponded to the mesopore peakshowed the same trend. Meanwhile, the pore diameter differential of the macropores remained unchanged. As the drying temperature increased, the fractal dimensions D1 and D2changed in the opposite trends, and the value of D2 was higher than D1. The moisture reabsorption behaviors of the semi-coke followed the same trend, and theequilibrium moisture content decreased with the increasing drying temperature. The moisture reabsorptioncharacteristics of the semi-coke were closely related to the pore structure, and the equilibrium moisture content hada good linear relationship with the pore volume.
引文
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[4]赵洪宇,任善普,贾晋炜,等.褐煤经四氢化萘处理后的结构及热解-气化特性分析[J].化工学报, 2015, 66(10):4193-4201.Zhao H Y, Ren S P, Jia J W, et al. Structure and pyrolysisgasification characteristics of lignite treated with tetralin[J].CIESC Journal, 2015, 66(10):4193-4201.
[5]郭熙,张守玉,董爱霞,等.高温烟气中单颗粒褐煤干燥特性实验研究[J].上海理工大学学报, 2014, 36(6):516-521.Guo X, Zhang S Y, Dong A X, et al. Experimental study on drying characteristics of single particle lignite in high temperature flue gas[J]. Journal of University of Shanghai for Science and Technology, 2014, 36(6):516-521.
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[9] Mraw S C, O'Rourke D F. Water in coal pores:the enthalpy of fusion reflects pore size distribution[J]. Journal of Colloid&Interface Science, 1982, 89(1):268-271.
[10]赵孟浩,张守玉,郑红俊,等.低阶煤中含氧官能团干燥前后的演变规律[J].煤炭学报, 2016, 41(2):483-489.Zhao M H, Zhang S Y, Zheng H J, et al. Evolution of oxygencontaining functional groups before and after drying in low-rank coals[J]. Journal of China Coal Society, 2016, 41(2):483-489.
[11]李尤,张守玉,茆青,等.干燥温度对褐煤干燥后复吸特性的影响[J].煤炭学报, 2016, 41(10):2454-2459.Li Y, Zhang S Y, Mao Q, et al. Effects of drying temperature on resuction properties of lignite after drying[J]. Journal of China Coal Society, 2016, 41(10):2454-2459.
[12]杨云龙.蒙东褐煤的干燥特性及其对水分复吸的影响[D].太原:太原理工大学, 2013:23-27.Yang Y L. Drying characteristics of Mengdong brown coal and its effect on water resorption[D]. Taiyuan:Taiyuan University of Technology, 2013:23-27.
[13]李开志,杨海平,陈应泉,等.棉杆热解过程中焦孔隙结构演变及分形特征[J].中国电机工程学报, 2012, 32(s1):115-120.Li K Z, Yang H P, Chen Y Q, et al. Evolution and fractal characteristics of coke pore structure during the pyrolysis of cotton stalks[J]. Proceedings of the CSEE, 2012, 32(s1):115-120.
[14]刘业凤,王如竹.新型复合吸附干燥剂的吸附动力学特性研究[J].上海理工大学学报, 2006,(2):107-110.Liu Y F, Wang R Z. Study on adsorption kinetics of novel composite adsorption desiccant[J]. Journal of University of Shanghai for Science and Technology, 2006,(2):107-110.
[15]周游,孙莉云,郑国强,等.乳状液超声凝聚破乳[J].化工学报,2009, 60(8):1997-2002.Zhou Y, Sun L Y, Zheng G Q, et al. Ultrasonic coagulation and demulsification of emulsion[J]. CIESC Journal, 2009, 60(8):1997-2002.
[16]胡松,孙路石,向军,等.高速热解条件下谷壳颗粒物理结构的演化[J].化工学报, 2007, 58(11):2889-2894.Hu S, Sun L S, Xiang J, et al. Evolution of physical structure of chaff particles under high-speed pyrolysis conditions[J]. Journal of Chemical Industry and Engineering(China), 2007, 58(11):2889-2894.
[17]陈萍,唐修义.低温氮吸附法与煤中微孔隙特征的研究[J].煤炭学报, 2001, 26(5):552-556.Chen P, Tang X Y. Low-temperature nitrogen adsorption and micro-pore characteristics in coal[J]. Journal of China Coal Society, 2001, 26(5):552-556.
[18]黄少萌.褐煤孔隙特性及水分脱除的迁移研究[D].北京:中国矿业大学, 2016:32-34.Huang S M. Study on pore characteristics and removal of water from lignite[D]. Beijing:China University of Mining and Technology, 2016:32-34.
[19] Ge L, Zhang Y, Wang Z, et al. Effects of microwave irradiation treatment on physicochemical characteristics of Chinese low-rank coals[J]. Energy Conversion&Management, 2013, 71(71):84-91.
[20]张艳丽.提质褐煤复吸水分主要影响因素的解析及其动力学分析[D].太原:太原理工大学, 2015:17-19.Zhang Y L. Analysis of the main influencing factors of reabsorption of upgraded lignite and its dynamics analysis[D].Taiyuan:Taiyuan University of Technology, 2015:17-19.
[21] Haul R. Adsorption, surface area and porosity[J]. Zeitschrift Für Physikalische Chemie, 1969, 63(1/2/3/4):220-221.
[22] Zhang Z, Yang Z. Theoretical and practical discussion of measurement accuracy for physisorption with micro-and mesoporous materials[J]. Chinese Journal of Catalysis, 2013, 34(10):1797-1810.
[23] Pfeifer P, Wu Y J, Cole M W, et al. Multilayer adsorption on a fractally rough surface[J]. Physical Review Letters, 1989, 62(17):1997.
[24] Zhang S, Tang S, Tang D, et al. Determining fractal dimensions of coal pores by FHH model:problems and effects[J]. Journal of Natural Gas Science&Engineering, 2014, 21:929-939.
[25] Xu S, Zhou Z, Yu G, et al. Effects of pyrolysis on the pore structure of four Chinese coals[J]. Energy&Fuels, 2010, 24(2):1114-1123.
[26] Song X X, Tang Y G, Li W, et al. Fractal characteristics of adsorption pores of tectonic coal from Zhongliangshan southern coalmine[J]. Journal of China Coal Society, 2013, 38(1):134-139.
[27] Yao Y, Liu D, Tang D, et al. Fractal characterization of adsorption-pores of coals from North China:an investigation on CH4adsorption capacity of coals[J]. International Journal of Coal Geology, 2008, 73(1):27-42.
[28] Hu S, Li M, Xiang J, et al. Fractal characteristic of three Chinese coals[J]. Fuel, 2004, 83(10):1307-1313.
[29] Liu J Z, Zhu J F, Cheng J, et al. Pore structure and fractal analysis of Ximeng lignite under microwave irradiation[J]. Fuel, 2015, 146:41-50.
[30] Takanohashi T, Yoshida T, Iino M, et al. Mixed solvent extraction yield and structural changes of heat-treated coals and their relation to coal fluidity[J]. Tetsu-to-Hagane, 1996, 82(5):366-371.
[31]孙晓林,郭晓镭,陆海峰,等.呼伦贝尔褐煤等温干燥过程[J].化工学报, 2015, 66(7):2628-2635.Sun X L, Guo X L, Lu H F, et al. Isothermal drying process of Hulunbeier lignite[J]. CIESC Journal, 2015, 66(7):2628-2635.
[32]平传娟,周俊虎,程军,等.混煤热解过程中的表面形态[J].化工学报, 2007, 58(7):1798-1804.Ping C J, Zhou J H, Cheng J, et al. Surface morphology during coal pyrolysis process[J]. Journal of Chemical Industry and Engineering(China), 2007, 58(7):1798-1804.
[2]李恩利,高建国,崔红梅,等.我国褐煤提质项目风险分析[J].煤炭经济研究, 2009,(12):25-26.Li E L, Gao J G, Cui H M, et al. Risk analysis of lignite upgrading project in China[J]. Journal of Coal Economic Research, 2009,(12):25-26.
[3]李昊,张守玉,李尤,等.低阶煤干燥过程水分析出动力学行为分析[J].煤炭学报, 2017, 42(11):3014-3020.Li H, Zhang S Y, Li Y, et al. Analysis of kinetic behavior of water analysis in low rank coal drying process[J]. Journal of China Coal Society, 2017, 42(11):3014-3020.
[4]赵洪宇,任善普,贾晋炜,等.褐煤经四氢化萘处理后的结构及热解-气化特性分析[J].化工学报, 2015, 66(10):4193-4201.Zhao H Y, Ren S P, Jia J W, et al. Structure and pyrolysisgasification characteristics of lignite treated with tetralin[J].CIESC Journal, 2015, 66(10):4193-4201.
[5]郭熙,张守玉,董爱霞,等.高温烟气中单颗粒褐煤干燥特性实验研究[J].上海理工大学学报, 2014, 36(6):516-521.Guo X, Zhang S Y, Dong A X, et al. Experimental study on drying characteristics of single particle lignite in high temperature flue gas[J]. Journal of University of Shanghai for Science and Technology, 2014, 36(6):516-521.
[6] Evans D G. The brown-coal/water system(Part 4):Shrinkage on drying[J]. Fuel, 1973, 52(3):186-190.
[7] Deevi S C, Suuberg E M. Physical changes accompanying drying of western US lignites[J]. Fuel, 1987, 66(4):454-460.
[8]景晓霞,杨云龙,李志强,等.褐煤物化结构对水分复吸的影响[J].洁净煤技术, 2014, 20(1):29-33.Jing X X, Yang Y L, Li Z Q, et al. Influence of lignite physical and chemical structure on moisture re-absorption[J]. Clean Coal Technology, 2014, 20(1):29-33.
[9] Mraw S C, O'Rourke D F. Water in coal pores:the enthalpy of fusion reflects pore size distribution[J]. Journal of Colloid&Interface Science, 1982, 89(1):268-271.
[10]赵孟浩,张守玉,郑红俊,等.低阶煤中含氧官能团干燥前后的演变规律[J].煤炭学报, 2016, 41(2):483-489.Zhao M H, Zhang S Y, Zheng H J, et al. Evolution of oxygencontaining functional groups before and after drying in low-rank coals[J]. Journal of China Coal Society, 2016, 41(2):483-489.
[11]李尤,张守玉,茆青,等.干燥温度对褐煤干燥后复吸特性的影响[J].煤炭学报, 2016, 41(10):2454-2459.Li Y, Zhang S Y, Mao Q, et al. Effects of drying temperature on resuction properties of lignite after drying[J]. Journal of China Coal Society, 2016, 41(10):2454-2459.
[12]杨云龙.蒙东褐煤的干燥特性及其对水分复吸的影响[D].太原:太原理工大学, 2013:23-27.Yang Y L. Drying characteristics of Mengdong brown coal and its effect on water resorption[D]. Taiyuan:Taiyuan University of Technology, 2013:23-27.
[13]李开志,杨海平,陈应泉,等.棉杆热解过程中焦孔隙结构演变及分形特征[J].中国电机工程学报, 2012, 32(s1):115-120.Li K Z, Yang H P, Chen Y Q, et al. Evolution and fractal characteristics of coke pore structure during the pyrolysis of cotton stalks[J]. Proceedings of the CSEE, 2012, 32(s1):115-120.
[14]刘业凤,王如竹.新型复合吸附干燥剂的吸附动力学特性研究[J].上海理工大学学报, 2006,(2):107-110.Liu Y F, Wang R Z. Study on adsorption kinetics of novel composite adsorption desiccant[J]. Journal of University of Shanghai for Science and Technology, 2006,(2):107-110.
[15]周游,孙莉云,郑国强,等.乳状液超声凝聚破乳[J].化工学报,2009, 60(8):1997-2002.Zhou Y, Sun L Y, Zheng G Q, et al. Ultrasonic coagulation and demulsification of emulsion[J]. CIESC Journal, 2009, 60(8):1997-2002.
[16]胡松,孙路石,向军,等.高速热解条件下谷壳颗粒物理结构的演化[J].化工学报, 2007, 58(11):2889-2894.Hu S, Sun L S, Xiang J, et al. Evolution of physical structure of chaff particles under high-speed pyrolysis conditions[J]. Journal of Chemical Industry and Engineering(China), 2007, 58(11):2889-2894.
[17]陈萍,唐修义.低温氮吸附法与煤中微孔隙特征的研究[J].煤炭学报, 2001, 26(5):552-556.Chen P, Tang X Y. Low-temperature nitrogen adsorption and micro-pore characteristics in coal[J]. Journal of China Coal Society, 2001, 26(5):552-556.
[18]黄少萌.褐煤孔隙特性及水分脱除的迁移研究[D].北京:中国矿业大学, 2016:32-34.Huang S M. Study on pore characteristics and removal of water from lignite[D]. Beijing:China University of Mining and Technology, 2016:32-34.
[19] Ge L, Zhang Y, Wang Z, et al. Effects of microwave irradiation treatment on physicochemical characteristics of Chinese low-rank coals[J]. Energy Conversion&Management, 2013, 71(71):84-91.
[20]张艳丽.提质褐煤复吸水分主要影响因素的解析及其动力学分析[D].太原:太原理工大学, 2015:17-19.Zhang Y L. Analysis of the main influencing factors of reabsorption of upgraded lignite and its dynamics analysis[D].Taiyuan:Taiyuan University of Technology, 2015:17-19.
[21] Haul R. Adsorption, surface area and porosity[J]. Zeitschrift Für Physikalische Chemie, 1969, 63(1/2/3/4):220-221.
[22] Zhang Z, Yang Z. Theoretical and practical discussion of measurement accuracy for physisorption with micro-and mesoporous materials[J]. Chinese Journal of Catalysis, 2013, 34(10):1797-1810.
[23] Pfeifer P, Wu Y J, Cole M W, et al. Multilayer adsorption on a fractally rough surface[J]. Physical Review Letters, 1989, 62(17):1997.
[24] Zhang S, Tang S, Tang D, et al. Determining fractal dimensions of coal pores by FHH model:problems and effects[J]. Journal of Natural Gas Science&Engineering, 2014, 21:929-939.
[25] Xu S, Zhou Z, Yu G, et al. Effects of pyrolysis on the pore structure of four Chinese coals[J]. Energy&Fuels, 2010, 24(2):1114-1123.
[26] Song X X, Tang Y G, Li W, et al. Fractal characteristics of adsorption pores of tectonic coal from Zhongliangshan southern coalmine[J]. Journal of China Coal Society, 2013, 38(1):134-139.
[27] Yao Y, Liu D, Tang D, et al. Fractal characterization of adsorption-pores of coals from North China:an investigation on CH4adsorption capacity of coals[J]. International Journal of Coal Geology, 2008, 73(1):27-42.
[28] Hu S, Li M, Xiang J, et al. Fractal characteristic of three Chinese coals[J]. Fuel, 2004, 83(10):1307-1313.
[29] Liu J Z, Zhu J F, Cheng J, et al. Pore structure and fractal analysis of Ximeng lignite under microwave irradiation[J]. Fuel, 2015, 146:41-50.
[30] Takanohashi T, Yoshida T, Iino M, et al. Mixed solvent extraction yield and structural changes of heat-treated coals and their relation to coal fluidity[J]. Tetsu-to-Hagane, 1996, 82(5):366-371.
[31]孙晓林,郭晓镭,陆海峰,等.呼伦贝尔褐煤等温干燥过程[J].化工学报, 2015, 66(7):2628-2635.Sun X L, Guo X L, Lu H F, et al. Isothermal drying process of Hulunbeier lignite[J]. CIESC Journal, 2015, 66(7):2628-2635.
[32]平传娟,周俊虎,程军,等.混煤热解过程中的表面形态[J].化工学报, 2007, 58(7):1798-1804.Ping C J, Zhou J H, Cheng J, et al. Surface morphology during coal pyrolysis process[J]. Journal of Chemical Industry and Engineering(China), 2007, 58(7):1798-1804.