Analysis of structure and pyrolysis and gasification characteristics of lignite after tetrahydronaphthalene treatment

doi:10.11949/j.issn.0438-1157.20150262

Abstract

Abstract:

Dewatering and upgrading of Inner Mongolia Xilingol lignite in non-polar solvent (tetrahydronaphthalene, THN) were carried out in a miniature autoclave. The changes of organic functional groups in coal samples at different dewatering temperature were analyzed based on Fourier-transform infrared (FT-IR) analyzer. The fitting calculation for FT-IR spectra has been carried out. Besides, a semi-quantitative analysis for characteristics of chemical structure change was presented. The pyrolysis and gasification reactivity and distributive rules of gas phase product during pyrolysis and gasification of coal with various dewatering temperature were carried out by means of thermogravimetric analysis (TG) and a bench-scale fixed-bed pyrolysis reactor. The kinetic parameters of coal samples were calculated within the range of the maximum weight loss rate. The results showed that the non-polar solvent THN treatment was effective in dewatering and upgrading of Xilingol lignite. The C O bonds started decomposing between 150 and 200℃, while the aromatic C C bonds in the aromatic ring remained relatively stable. With increasing dewatering temperature, the content of aromatic hydrogen decreased first and then increased, while the content of aliphatic hydrogen increased first and then decreased. The aromaticity and aromatic carbon increased gradually with increasing dewatering temperature. When dewatering temperature was higher, the cumulative yields of gas phase products of H₂, CH₄ and CO were increased and CO₂ was dropped during pyrolysis. The reaction activation energy of the dewatered coal increased with increasing dewatering temperature, decreasing the pyrolysis reactivity of the coal samples.

Key words: lignite, tetrahydronaphthalene, dewatering, chemical structure, pyrolysis and gasification

摘要：

在小型反应釜上采用非极性有机溶剂四氢化萘(tetrahydronaphthalene, THN)对内蒙古锡林郭勒褐煤进行脱水,获取了不同温度下的脱水试样,运用傅里叶红外光谱(Fourier transform infrared spectroscopy,FT-IR)分析技术对比研究了在不同脱水温度下煤样中有机官能团的变化,通过FT-IR谱图的分峰拟合计算,对脱水煤样的化学结构变化特征进行半定量分析,并结合热重(thermal gravity analysis/differential thermal gravity,TG/DTG)和实验室固定床反应器(fixed bed reactor)考察了不同脱水温度下煤样的热解气化特性和热解气相产物分布规律,并对脱水煤样在最大失重速率区间的动力学参数进行了计算。试验结果显示:四氢化萘溶剂对褐煤的脱水提质是有效的,150~200℃时C O开始分解,而此时芳香环上的C C仍然相对稳定。随着脱水温度的升高,芳香类氢含量先减小后增大,脂肪类氢含量先增大后减小,芳香度和芳香碳在脱水温度范围内逐渐增大。煤样的脱水温度升高,热解气相产物H₂、CH₄、CO累积产率增大,CO₂累积产率减小;脱水煤样热解活化能随着脱水温度的升高而升高,进而导致脱水温度较高煤样热解失重率降低。

关键词: 褐煤, 四氢化萘, 脱水, 化学结构, 热解气化

CLC Number:

TQ536

ZHAO Hongyu, REN Shanpu, JIA Jinwei, FU Xingmin, LI Zijun, LU Mingyuan, ZENG Ming, SHU Xinqian. Analysis of structure and pyrolysis and gasification characteristics of lignite after tetrahydronaphthalene treatment[J]. CIESC Journal, 2015, 66(10): 4193-4201.

赵洪宇, 任善普, 贾晋炜, 付兴民, 李子君, 鲁明元, 曾鸣, 舒新前. 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.

References 22

[1]	Yang Renjun (杨仁俊). Overview and analysis of coal to oil technology [J]. Journal of Chifeng University: Natural Science Edition (赤峰学院学报:自然科学版), 2012, 28 (5): 54-56.
[2]	Miura K, Shimada M, Mae K, Sock H Y. Extraction of coal below 350℃ in flowing non-polar solvent [J]. Fuel, 2001, 80: 1573-1582.
[3]	Li Kejian (李克健), Wu Xiuzhang (吴秀章), Shu Geping (舒歌平). Development of direct coal liquefaction technologies in China [J]. Clean Coal Technology (洁净煤技术), 2014, 20 (2):39-43.
[4]	Zhao Bianbian (赵变变), Bai Zongqing (白宗庆), Kou Jiawei (寇佳伟), Li Wen (李文), Bai Jin (白进). Effect of moisture on rheo-logical properties of brown coal [J]. Journal of Fuel Chemistry and Technology (燃料化学学报), 2014, 42 (11): 1281-1285.
[5]	Hui Helong (惠贺龙), Fu Xingmin (付兴民), Wang Xiaohua (王小华), Wei Yunzhao (韦云钊), Jia Jinwei (贾晋炜), Shu Xinqian (舒新前). Effect of washing process on the structure and pyrolysis characteristics of coal [J].Proceedings of the CSEE (中国电机工程学报), 2013, 33 (23): 68-74.
[6]	Sato Y, Kushiyama S, Tatsumoto K, Yamaguchi H. Upgrading of low rank coal with solvent [J]. Fuel Processing Technology, 2004, 85 (14): 1551-1564.
[7]	Katalambula H, Gupta R. Low-grade coals: a review of some prospective upgrading technologies [J]. Energy & Fuels, 2009, 23 (7): 3392-3405.
[8]	Li Xian (李显), Zhu Xianqing (朱贤青), Xiao Li (肖黎), Ashida Yuichi (芦田隆一), Miura Kouichi (三浦孝一), Luo Guangqian (罗光前), Yao Hong (姚洪). Degradative solvent extraction of demineralized and ion-exchanged low-rank coals [J]. Journal of Fuel Chemistry and Technology (燃料化学学报), 2014, 42 (8): 897-904.
[9]	Fujitsuka H, Ashida R, Miura K. Upgrading and dewatering of low rank coals through solvent treatment at around 350℃ and low temperature oxygen reactivity of the treated coals [J]. Fuel, 2013, 114:16-20.
[10]	Wang Junhong, Du Juan, Chang Liping, Xie Kechang. Study on the structure and pyrolysis characteristics of Chinese western coals [J]. Fuel Processing Technology, 2010, 91 (4): 430-433.
[11]	Yan Jingchong, Bai Zongqing, Bai Jin, Guo Zhenxing, Li Wen. Effects of organic solvent treatment on the chemical structure and pyrolysis reactivity of brown coal [J]. Fuel, 2014, 128: 39-45.
[12]	Li Qingzhao (李庆钊), Lin Baiquan (林柏泉), Zhao Changsui (赵长遂), Wu Weifang (武卫芳). Chemical structure analysis of coal char surface based on Fourier-transform infrared spectrumeter [J]. Proceedings of the CSEE (中国电机工程学报), 2011, 31 (32): 46-52.
[13]	Ibarra J V, Moliner R, Bonet A. FT-IR investigation on char formation during the early stages of coal pyrolysis [J]. Fuel, 1994, 73 (6): 918-924.
[14]	Sakaguchi M, Laursen K, Nakagawa H, Miura K. Hydrothermal upgrading of Loy Yang Brown coal—effect of upgrading conditions on the characteristics of the products [J]. Fuel Processing Technology, 2008, 89: 391-396.
[15]	Yoshiki S, Satoshi K, Katsunobu T, Hiroshi Y. Upgrading of low rank coal with solvent [J]. Fuel Processing Technology, 2004, 85: 1551-1564.
[16]	Zheng Hongjun, Zhang Shouyu, Guo Xi, Lü Junfu, Dong Aixia, Deng Wenxiang, Tang Wenjiao, Zhao Menghao, Jin Tao. An experimental study on the drying kinetics of lignite in high temperature nitrogen atmosphere [J]. Fuel Processing Technology, 2014, 126: 259-265.
[17]	Solomon P R, Fletcher T H, Pugmire R J. Progress in coal pyrolysis [J]. Fuel, 1993, 72 (5):587.
[18]	Wang Zhiqing, Bai Zongqing, Li Wen, Chen Haokan, Li Baoqing. Quantitative study on cross-linking reactions of oxygen groups during liquefaction of lignite by a new model system [J]. Fuel Processing Technolony, 2010, 91: 410-413.
[19]	Xu Shenqi, Zhou Zhijie, Xiong Jie, Yu Guangsuo, Wang Fuchen. Effects of alkaline metal on coal gasification at pyrolysis and gasification phases [J]. Fuel, 2011, 90: 1723-1730.
[20]	Senneca O, Russo P, Salatino P, Masi S.The relevance of thermal annealing to the evolution of coal char gasification reactivity [J]. Carbon, 1997, 1: 141-151.
[21]	Fu Xingmin (付兴民), Zhang Yuxiu (张玉秀), Guo Zhanying (郭战英), Liu Haibing (刘海兵), Liu Shucheng (柳树成), Jia Jinwei (贾晋炜), Shu Xinqian (舒新前). Characteristics and kinetics of the pyrolysis of coking coal tailings [J].Journal of China Coal Society (煤炭学报), 2013, 38 (2): 320-325.
[22]	Yangali P, Celaya A M, Goldfarb J L. Co-pyrolysis reaction rates and activation energies of West Virginia coal and cherry pit blends [J]. Journal of Analytical and Applied Pyrolysis, 2014, 108: 203-211.