高硫煤泥燃烧过程中的汞排放特性

doi:10.16085/j.issn.1000-6613.2021-0888

摘要/Abstract

摘要：

通过固定床程序升温汞脱附试验系统对所选高硫煤泥中汞排放特性进行在线监测，并利用热重分析仪对煤泥热解和燃烧特性进行研究，结合试验所得热解和燃烧特性参数，采用分布活化能模型，进行动力学分析。结果表明：煤泥的热解和燃烧过程可分为3个阶段，非等温条件下，随着升温速率增加，热解过程在高温区发生，最大失重率提升，对应峰值温度偏移，产生热滞后，利于挥发分析出；在煤泥热解过程中少量氧气的参与，抑制挥发分的析出，在7% O₂条件下综合热解特性参数值D最大。热解性能随CO₂浓度升高而得到改善；煤泥燃烧性能随升温速率的增加而得到加强，其活化能随转化率变化呈现“U”型趋势分布；煤泥中无机汞化合物主要为HgCl₂、α-HgS、HgSO₄以及硅铝酸盐类结合汞，总汞释放主要范围对应200~600℃；煤泥中汞释放量随O₂浓度增大，CO₂气氛条件下，随着CO₂浓度增加，总汞释放量逐渐增大。

关键词: 煤泥, 固定床, 燃烧, 反应动力学, 脱附, 汞排放

Abstract:

On-line monitoring of mercury emission characteristics from coal slime was carried out by a fixed bed temperature programmed mercury desorption test system, and pyrolysis and combustion characteristics of high sulfur coal slime were studied by thermogravimetric analyzer. Combined with the pyrolysis and combustion characteristic parameters obtained from the experiment, the kinetic analysis was carried out by using the distributed activation energy model. The results show that the pyrolysis and combustion process of coal slime can be divided into three stages. Under non-isothermal conditions, with the increase of heating rate, the pyrolysis process occurs in the high temperature region, and the maximum weight loss rate increases. The corresponding peak temperature shifts, resulting in thermal hysteresis, which is conducive to the precipitation of volatiles; The participation of a small amount of oxygen in the pyrolysis process of coal slime inhibits the precipitation of volatiles, and the comprehensive pyrolysis characteristic parameter D is the largest under the condition of 7% O₂. Pyrolysis performance improved with increasing CO₂ concentration; The combustion performance of coal slime is strengthened with the increase of heating rate, and the activation energy shows a 'U' trend distribution with the change of conversion rate; Inorganic mercury compounds in coal slime are mainly HgCl₂, α-HgS, HgSO₄ and silicoaluminate bound mercury, and the total mercury release ranges from 200°C to 600°C; The release of mercury in coal slime increased with the increase of O₂ concentration. Under CO₂ atmosphere, the total mercury release gradually increased with the increase of CO₂concentration.

Key words: coal slime, fixed-bed, combustion, reaction kinetics, desorption, mercury emissions

中图分类号:

X705

郭晋荣, 程鹏, 贾里, 郭婧楠, 王彦霖, 张永强, 乔晓磊, 樊保国. 高硫煤泥燃烧过程中的汞排放特性[J]. 化工进展, 2021, 40(S2): 411-420.

GUO Jinrong, CHENG Peng, JIA Li, GUO Jingnan, WANG Yanlin, ZHANG Yongqiang, QIAO Xiaolei, FAN Baoguo. Combustion characteristics and mercury emission characteristics of high sulfur coal slime[J]. Chemical Industry and Engineering Progress, 2021, 40(S2): 411-420.

图/表 15

表1 煤泥燃烧试验条件

样品编号	制备种类	制备温度/℃	制备气氛	升温速率 /℃ · min^-1
CS-A	干燥后煤泥	—	—	—
CS-A-Ⅱ	干燥后煤泥	1000	N₂	10
CS-A-Ⅱ-1	干燥后煤泥	1000	3% O₂+97% N₂	10
CS-A-Ⅱ-2	干燥后煤泥	1000	5% O₂+95% N₂	10
CS-A-Ⅱ-3	干燥后煤泥	1000	7% O₂+93% N₂	10
CS-A-Ⅱ-4	干燥后煤泥	1000	10% CO₂+90% N₂	10
CS-A-Ⅱ-5	干燥后煤泥	1000	15% CO₂+85% N₂	10
CS-A-Ⅱ-6	干燥后煤泥	1000	20% CO₂+80% N₂	10
CS-B-Ⅰ	干燥后煤泥	1000	空气	5
CS-B-Ⅱ	干燥后煤泥	1000	空气	10
CS-B-Ⅲ	干燥后煤泥	1000	空气	15
CS-C-400-β	干燥后煤泥	400	空气	—
CS-C-600-β	干燥后煤泥	600	空气	—
CS-C-800-β	干燥后煤泥	800	空气	—
CS-C-1000-β	干燥后煤泥	1000	空气	—

图1 固定床程序升温汞脱附试验系统

表2 煤泥元素分析和工业分析

样品	工业分析/%				元素分析/%
样品	M_ad	A_ad	V_ad	FC_ad	C	H	O	N	S
CS-A	0.4	51.2	13.1	35.7	37.7	2.2	2.3	1.1	5.6

图2 不同热解气氛下煤泥TG曲线

图3 不同热解气氛下煤泥DTG曲线

表3 干燥后煤泥的热解特性参数

样品	t₁/℃	t₂/℃	t₃/℃	t₄/℃	?TG/%	（dw/dt）_max/% · min^-1	V/%	（dw/dt）_mean/% · min^-1	?t_（1/2）/℃	D
CS-A-Ⅱ	132	552	650	741	44.32	-2.28	12.09	-1.32	159	3.1406×10^-6
CS-A-Ⅱ-1	128	543	626	748	42.60	-1.98	11.84	-1.37	142	3.0542×10^-6
CS-A-Ⅱ-2	139	547	673	750	46.35	-2.32	12.42	-1.38	154	3.3960×10^-6
CS-A-Ⅱ-3	144	556	684	762	44.72	-2.52	12.54	-1.45	161	3.5547×10^-6
CS-A-Ⅱ-4	121	538	663	—	45.75	-2.33	12.36	-1.36	157	3.9196×10^-6
CS-A-Ⅱ-5	110	526	671	—	47.16	-2.38	12.74	-1.41	158	4.6766×10^-6
CS-A-Ⅱ-6	98	519	677	—	48.39	-2.47	12.83	-1.49	163	5.6955×10^-6

图4 不同升温速率下煤泥燃烧TG曲线

图5 不同升温速率下煤泥燃烧DTG曲线

表4 干燥后煤泥的燃烧特性参数

样品	T_i/℃	T_max/℃	T_b/℃	$d w / d t m a x$ /% · min^-1	$d w / d t m e a n$ /% · min^-1	K_r×10^-5/min^-1 · ℃^-2	S×10⁸/min^-2 · ℃^-3
CS-B-Ⅰ	481	547	629	3.21	2.23	1.39	4.92
CS-B-Ⅱ	497	578	710	4.69	3.27	1.89	8.74
CS-B-Ⅲ	512	609	832	6.68	4.31	2.55	13.20

表4 干燥后煤泥的燃烧特性参数

样品	T_i/℃	T_max/℃	T_b/℃	$d w / d t m a x$ /% · min^-1	$d w / d t m e a n$ /% · min^-1	K_r×10^-5/min^-1 · ℃^-2	S×10⁸/min^-2 · ℃^-3
CS-B-Ⅰ	481	547	629	3.21	2.23	1.39	4.92
CS-B-Ⅱ	497	578	710	4.69	3.27	1.89	8.74
CS-B-Ⅲ	512	609	832	6.68	4.31	2.55	13.20

图6 煤泥热解和燃烧过程中的动力学拟合曲线

图7 气氛条件对表观活化能的影响

图8 煤泥中汞脱附TPD曲线

表5 各纯汞化合物汞释放峰值点及温度范围

含汞化合物	析出量最高点温度/℃	析出温度范围/℃
HgCl₂	120±10	70~220
Hg₂Cl₂	130±10	60~220
HgBr₂	110±5	60~220
β-HgS	245±5	170~290
α-HgS	310±10	240~350
HgSO₄	540±20	500~600
Hg₂SO₄	280±10	120~480
HgO	505±10	430~560

图9 煤泥燃烧过程中不同升温速率条件下汞脱附TPD曲线

图10 煤泥燃烧过程中不同气氛条件下汞脱附TPD曲线

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