基于铁基载氧体的煤化学链气化还原过程中氮元素迁移行为

doi:10.16085/j.issn.1000-6613.2018-2198

摘要/Abstract

摘要：

采用热重-质谱-红外联用技术（TG-MS-FTIR），Ar气氛下对煤进行化学链气化实验，实时分析还原过程热解阶段和水蒸气气化反应阶段的过程中固体质量变化和生成气体成分。使用X射线光电子能谱对固相产物进行表面元素分析，探究化学链气化还原过程不同阶段固相产物中氮赋存形态的变化。研究结果表明：载氧体对化学链气化还原过程不同阶段含氮气体释放均有影响。热解阶段载氧体促进自由基的生成，加速了一次热解阶段含氮气体的释放，高温下，载氧体促使NH₃转化为HCN；气化阶段载氧体的加入使半焦的石墨化程度降低，含氮气体释放速率增加。对固相产物中氮的赋存形态而言，载氧体会抑制热解阶段吡咯型氮的分解与转化，高温下，半焦的石墨化和有序化程度降低的同时，镶嵌在煤大分子里面的质子化吡啶裸露出来，质子化吡啶含量降低，吡啶型氮和吡咯型氮的含量大大提升。

关键词: 化学链气化, 铁基载氧体, 含氮气体, 氮赋存形态

Abstract:

The combined thermo gravimetric-infrared-mass spectrometry (TG-FTIR-MS) analysis was used to conduct chemical-looping gasification experiments of coal under Ar atmosphere, and the mass change and gas composition during pyrolysis stage and steam gasification reaction stage of reduction process were monitored in real time. The surface element analysis of the solid phase was carried out by X-ray photoelectron spectroscopy, when the change of nitrogen functional groups in the solid phase at different stages of chemical-looping gasification reduction process was investigated. The results showed that the oxygen carrier had an effect on the release of nitrogen-containing gas in different stages of the chemical-looping gasification reduction process. During the pyrolysis stage, the oxygen carrier promoted the generation of free radicals, which accelerated the release of nitrogen-containing gas in a pyrolysis stage. At high temperature, the oxygen carrier favored the conversion of NH₃ to HCN, and the addition of the oxygen carrier during the gasification stage reduced the degree of graphitization of the semi-coke and increased the release rate of the nitrogen-containing gas. For the nitrogen functional groups in the solid phase, the oxygen carrier promoted the decomposition and conversion of pyrrole nitrogen in the pyrolysis stage. At high temperature, as the graphitization and ordination degree of semi-coke decreased, the protonated pyridine embedded in coal macromolecules was exposed, the content of protonated pyridine decreased, and the content of pyridine nitrogen and pyrrole nitrogen increased greatly.

Key words: chemical-looping gasification, iron-based oxygen carrier, nitrogen-containing gas, nitrogen functional groups

中图分类号:

TH 3

李彦坤,马晶晶,常国璋,胡修德,郭庆杰. 基于铁基载氧体的煤化学链气化还原过程中氮元素迁移行为[J]. 化工进展, 2019, 38(08): 3631-3639.

Yankun LI,Jingjing MA,Guozhang CHANG,Xiude HU,Qingjie GUO. Migration behavior of nitrogen in chemical-looping gasification reduction process of coal with an iron-based oxygen carrier[J]. Chemical Industry and Engineering Progress, 2019, 38(08): 3631-3639.

图/表 10

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燃料	工业分析/%				元素分析/%					LHV/MJ·kg^-1
燃料	M_ad	A_ad	V_ad	FC_ad	N	C	H	S	O^①	LHV/MJ·kg^-1
金凤煤	7.46	7.26	30.51	62.24	1.49	78.32	4.51	0.49	7.92	25.25

燃料	工业分析/%				元素分析/%					LHV/MJ·kg^-1
燃料	M_ad	A_ad	V_ad	FC_ad	N	C	H	S	O^①	LHV/MJ·kg^-1
金凤煤	7.46	7.26	30.51	62.24	1.49	78.32	4.51	0.49	7.92	25.25

样品	吡啶型氮	吡咯型氮	质子化吡啶	氮氧化物
原煤	31.13	43.23	13.26	12.39
650℃热解	47.31	18.69	26.54	7.46
950℃热解	27.83	14.10	39.04	19.03
950℃气化	26.07	5.69	68.23	0
650℃催化热解	37.13	24.51	30.29	8.07
950℃催化热解	48.31	18.14	26.84	6.71
950℃化学链气化	29.93	32.66	37.41	0

样品	吡啶型氮	吡咯型氮	质子化吡啶	氮氧化物
原煤	31.13	43.23	13.26	12.39
650℃热解	47.31	18.69	26.54	7.46
950℃热解	27.83	14.10	39.04	19.03
950℃气化	26.07	5.69	68.23	0
650℃催化热解	37.13	24.51	30.29	8.07
950℃催化热解	48.31	18.14	26.84	6.71
950℃化学链气化	29.93	32.66	37.41	0

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