Nitrogen transformation during coal decoulping combustion I: release behavior of coal-nitrogen during pyrolysis stage
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摘要: 在固定床装置上进行了三种煤的热解实验,考察了热解温度、热解时间等因素对煤氮迁移转化的影响。热解实验表明,A煤1 073 K热解产生HCN,在热解前3 min释放完毕,早于NH3释放,且当NH3开始逸出后HCN生成量急剧减少;三种煤热解HCN、NH3的累积释放量在不同时刻达到各自最大值后急剧下降;半焦氮随热解温度的升高而增加。在973~1 123 K三种煤热解有50%~60%煤氮转化为焦氮,40%~50%煤氮随挥发分一起释放,挥发分氮有20%~50%的氮物种以NH3和HCN的形式存在,其中,HCN占气相氮的50%~60%、NH3占40%~50%。Abstract: Effect of temperature and residence time on coal-nitrogen transformation during pyrolysis of 3 coals from west China was studied in a fixed bed reactor. The results show that the duration time of HCN releasing is about 3 min at 1 073 K for pyrolysis of coal A. The start release time of HCN is earlier than that of NH3, and the released amount of HCN quickly drops to zero as NH3 starts to release. The accumulated release amounts of HCN and NH3 first reach the maximum value at different pyrolysis time and then decrease sharply. The yield of char-nitrogen increases with increasing temperature. At 973~1 123 K, about 50~60 mass percentage of the coal-nitrogen exits in char as char-nitrogen and the rest is released as volatiles, in which about 20~50 mass percentage of the volatile-nitrogen is NH3 and HCN. The mass percentage of NH3 accounts for 40%~50% and that of HCN about 50%~60% in the volatile-nitrogen.
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Key words:
- coal /
- decoupling combustion /
- pyrolysis /
- NH3 /
- HCN
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GLARBORG P, JENSEN A D, JOHNSSON J E. Fuel nitrogen conversion in solid fuel fired systems[J]. Prog Energy Combust Sci, 2003, 29(2): 89-113. LEPPALAHTI J, KOLJONEN T. Nitrogen evolution from coal, peat and wood during gasification: Literature review[J]. Fuel Process Technol, 1995, 43(1): 1-45. KEDENA K, HIROSE Y, AIBARA T, MURATA S, NOMURA M. Analysis of nitrogen-containing species during pyrolysis of coal at two different heating rates[J]. Energy Fuels, 2000, 14(1): 184-189. 赵炜, 常丽萍, 冯志华, 谢克昌. 煤热解过程中生成氮化物的研究[J]. 燃料化学学报, 2002, 30(5): 408-412. (ZHAO Wei, CHANG Li-ping, FENG Zhi-hua, XIE Ke-chang. Formation of nitrogenous species during coal pyrolysis[J]. Journal of Fuel Chemistry and Technology, 2002, 30(5): 408-412.) 常丽萍, XIE Z, 谢克昌, LI Chun-zhu. Loy Yang褐煤热解过程中HCN和NH3形成的主要影响因素[J]. 化工学报, 2003, 54(6): 863-867. (CHANG Li-ping, XIE Zongli, XIE Ke-chang, LI C-Z. Some factors influencing formation of HCN and NH3 during pyrolysis of brown coal[J]. Journal of Chemical Industry and Engineering (China), 2003, 54(6): 863-867.) 赵炜, 常丽萍, 谢克昌, 李春柱. 煤燃烧过程生成氮氧化物前驱体的研究[J]. 燃料化学学报, 2004, 32(4): 385-389. (ZHAO Wei, CHANG Li-ping, XIE Ke-chang, LI Chun-zhu. Release of NOx precursors during coal combustion[J]. Journal of Fuel Chemistry and Technology, 2004, 32(4): 385-389.) XIE J, YANG X, ZHANG L, DING T, SONG W, LIN W. Emissions of SO2, NO and N2O in a circulating fluidized bed combustor during co-firing coal and biomass[J]. J Environ Sci, 2007, 19(1): 109-116. 李静海, 郭慕孙, 白蕴茹, 宋文立, 朱庆山, 姚建中, 杨励丹, 万兴中. 解耦循环流化床燃烧系统及其脱硫与脱硝方法: 中国,1203117A. 1997-06-25. (LI Jing-hai, GUO Mu-sun, BAI Yun-ru, SONG Wen-li, ZHU Qing-shan, YAO Jian-zhong, WANG Xing-zhong. Decoupling combustion system in a circulating fluidized bed and strategies for desulfurization and de-NOx: CN, 1203117A. 1997-06-25.) 谢建军, 杨学民, 吕雪松, 丁同利, 姚建中, 林伟刚. 煤热解过程中硫氮分配及迁移规律研究进展[J]. 化工进展, 2004, 23(11): 1214-1218. (XIE Jian-jun, YANG Xue-min, LV Xue-song, DING Tong-li, YAO Jian-zhong, LIN Wei-gang. Progress on transformation behavior of sulfur and nitrogen during coal pyrolysis[J]. Chemical Industry and Engineering Progress, 2004, 23(11): 1214-1218.) BASSILAKIS R, ZHAO Y, SOLOMON P R, SERIO M A. Sulfur and nitrogen evolution in the argonne coals-experiment and modeling[J]. Energy Fuels, 1993, 7(6): 710-720. LEPPALAHTI J. Formation of NH3 and HCN in slow-heating-rate inert pyrolysis of peat, coal and bark[J]. Fuel, 1995, 74(9): 1363-1368. TIAN F, YU J, MCKENZIE L J, HAYASHI J, LI C-Z. Formation of NOx precursors during the pyrolysis of coal and biomass:. Part IX Effects of coal ash and externally loaded-Na on fuel-N conversion during the reforming of coal and biomass in steam[J]. Fuel, 2006, 85(10/11): 1411-1417. LEDESMA E B, LI C-Z, NELSON P F, MACKIE J C. Release of HCN, NH3, and HNCO from the thermal gas-phase cracking of coal pyrolysis tars[J]. Energy Fuels, 1998, 12(3): 536-541. XU W-C, KUMAGAI M. Nitrogen evolution during rapid hydropyrolysis of coal[J]. Fuel, 2002, 81(18): 2325-2334. JOHNSSON J E. Formation and reduction of nitrogen oxides in fluidized-bed combustion[J]. Fuel, 1994, 73(9): 1398-1415. KAMBARA S, TAKARADA T, YAMAMOTO Y, KATO K. Relation between functional forms of coal nitrogen and formation of NOx precursors during rapid pyrolysis[J]. Energy Fuels, 1993, 7(6): 1013-1020. HANSSON K M, SAMUELSSON J, AMAND L E, TULLIN C. The temperature's influence on the selectivity between HNCO and HCN from pyrolysis of 2,5-diketopiperazine and 2-pyridone[J]. Fuel, 2003, 82(18): 2163-2172. TAN L L, LI C-Z. Formation of NOx and SOx precursors during the pyrolysis of coal and biomass: Part II Effects of experimental conditions on the yields of NOx and SOx precursors from the pyrolysis of a Victorian brown coal[J]. Fuel, 2000, 79(15): 1891-1897. XIE Z, FENG J, ZHAO W, XIE K-C, PRATT K C, LI C-Z. Formation of NOx and SOx precursors during the pyrolysis of coal and biomass: Part IV Pyrolysis of a set of Australian and Chinese coals[J]. Fuel, 2001, 80(15): 2131-2138. LI C-Z, NELSON P F. Fate of aromatic ring systems during thermal cracking of tars in a fluidized-bed reactor[J]. Energy Fuels, 1996, 10(5): 1083-1090. NELSON P F, LI C-Z, LEDESMA E. Formation of HNCO from the rapid pyrolysis of coals[J]. Energy Fuels, 1996, 10(1): 264-265. OHTSUKA Y, WATANABE T, ASAMI K, MORI H. Char-nitrogen functionality and interactions between the nitrogen and iron in the iron-catalyzed conversion process of coal nitrogen to N2[J]. Energy Fuels, 1998, 12(6): 1356-1362. TSUBOUCHI N, ABE M, XU C, OHTSUKA Y. Nitrogen release from low rank coals during rapid pyrolysis with a drop tube reactor[J]. Energy Fuels, 2003, 17(4): 940-945. TSUBOUCHI N, OHTSUKA Y. Nitrogen release during high temperature pyrolysis of coals and catalytic role of calcium in N2 formation[J]. Fuel, 2002, 81(18): 2335-2342. TSUBOUCHI N, OHTSUKA Y. Formation of N2 during pyrolysis of Ca-loaded coals[J]. Fuel, 2002, 81(11/12): 1423-1431. WU Z, OHTSUKA Y. Key factors for formation of N2 from low-rank coals during fixed fed pyrolysis: Pyrolysis conditions and inherent minerals[J]. Energy Fuels, 1997, 11(4): 902-908. WU Z, OHTSUKA Y. Nitrogen distribution in a fixed bed pyrolysis of coals with different ranks: Formation and source of N2[J]. Energy Fuels, 1997, 11(2): 477-482. KELEMEN S R, GORBATY M L, KEIATEK P J, FLETCHER T H, WATT M, SOLUM M S, PUGMIRE R J. Nitrogen transformations in coal during pyrolysis[J]. Energy Fuels, 1998, 12(1): 159-173. WOJTOWICZ M A, PELS J R, MOULIJN J A. The fate of nitrogen functionalities in coal during pyrolysis and combustion[J]. Fuel, 1995, 74(4): 507-516. FRIEBEL J, KOPSEL R F W. The fate of nitrogen during pyrolysis of German low rank coals——A parameter study[J]. Fuel, 1999, 78(8): 923-932. BAXTER L L, MITCHELL R E, FLETCHER T H, HURT R H. Nitrogen release during coal combustion[J]. Energy Fuels, 1996, 10(1): 188-196. SOLOMON P R, COLKET M B. Evolution of fuel nitrogen in coal devolatilization[J]. Fuel, 1978, 57(12): 749-755.
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