添加CaO对煤热解过程中砷和硫迁移转化的影响

秦跃强; 陈雪莉; 陈汉鼎; 刘海峰

添加CaO对煤热解过程中砷和硫迁移转化的影响

华东理工大学煤气化及能源化工教育部重点实验室, 上海市煤气化工程技术研究中心, 上海 200237

基金项目:

国家重点研发计划项目 2016YFB0600400-02

详细信息

通讯作者:
陈雪莉,E-mail:cxl@ecust.edu.cn

中图分类号: TQ530.2
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- 被引次数: 0
出版历程
- 收稿日期: 2016-08-23
- 修回日期: 2016-10-09
- 网络出版日期: 2021-01-23
- 刊出日期: 2017-02-10

Effects of adding CaO on the release and transformation of arsenic and sulfur during coal pyrolysis

Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education, Shanghai Engineering Research Center of Coal Gasification, East China University of Science and Technology, Shanghai 200237, China

Funds:

National Key Research and Development Project 2016YFB0600400-02

More Information

Corresponding author: E-mail:cxl@ecust.edu.cn

摘要

摘要: 利用高频炉反应器在800-1 200℃对添加质量分数10% CaO的云南镇雄煤（YNZX）进行了快速热解实验，采用连续化学提取、X射线衍射（XRD）、扫描电子显微镜-能谱（SEM-EDX）和X射线光电子能谱（XPS）等分析手段，考察了CaO添加对煤快速热解过程中砷和硫迁移转化的影响。结果表明，CaO能显著抑制砷与硫的释放。CaO对砷释放的抑制率在800℃时最高达41.19%，对硫释放的抑制率在1 000℃时最高，为39.89%；两者的抑制率呈负相关。As-Ca复合物和CaS的形成是砷与硫释放率降低的主要原因；添加CaO后，As-Ca复合物的生成使残渣态砷含量增加，CaS的形成使硫化物结合态砷含量减少。热解后硫元素在CaO表面富集，占据更多的吸附活性位，对砷的固定产生抑制作用；添加CaO后焦中硫仍主要以硫化物的形式存在，亚硫酸盐的含量有所增加。
- 热解 /
- 砷 /
- 硫 /
- 氧化钙 /
- 迁移转化
Abstract: The pyrolysis experiments of YNZX coal with 10% CaO at 800-1 200℃ were conducted in a high frequency furnace.The effects of adding CaO on the release and transformation of arsenic and sulfur during pyrolysis have been investigated with the aid of sequential chemical extraction, XRD, SEM-EDX, and XPS.The results show that CaO can inhibit the release of arsenic and sulfur significantly.The retention rate to arsenic amounts to 41.19% at 800℃, and that to sulfur reaches 39.89% at 1 000℃, there is a negative correlation between the two retention rates.The formation of As-Ca compounds and CaS accounts for the decrease of release rates of arsenic and sulfur.The sulfur is enriched on the surface of CaO, which occupies more active adsorption sites after pyrolysis and inhibits the retention of arsenic, most sulfur is presented as sulfides in char and the amount of sulfites increases after adding CaO.
- pyrolysis /
- arsenic /
- sulfur /
- CaO /
- release and transformation

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图 1 高频炉实验装置示意图

Figure 1 Schematic diagram of high frequency furnace

1: power controller; 2: cool water; 3: high frequency current generator; 4: temperature controller; 5: flowmeter; 6: value; 7: argon cylinder; 8: molybdenum crucible; 9: quartz tube; 10: thermocouple; 11: gas-washing bottle

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图 2 连续化学提取实验流程示意图

Figure 2 Flow diagram of sequential chemical extraction

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图 3 原煤热解过程砷与硫的释放率随恒温热解时间的变化

Figure 3 Release rates of As and S versus isothermal pyrolysis time during raw coal pyrolysis

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图 4 添加CaO前后砷与硫的释放率随热解温度的变化

Figure 4 Release rates of As and S versus pyrolysis temperature before and after adding CaO

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图 5 不同赋存形态砷含量随热解温度的变化

Figure 5 Content of different occurrence forms of As versus pyrolysis temperature

(a): YNZX; (b): YNZX+10% CaO : ion exchangeable;: bound to sulfides;: bound to organic;: residual

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图 6 CaO捕集砷与硫的机理示意图^{[16-20, 36-38]}

Figure 6 Mechanism of capture of As and S by CaO

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图 7 原料及热解焦的矿物组成

Figure 7 Mineral composition of raw materials and chars

(a): raw coal and chars at 800-1 200 ℃; (b): coal with 10% CaO and chars at 800-1 200 ℃Q-quartz(SiO₂); M-mullite(xAl₂O₃·ySiO₂); T-troilite(FeS); O-oldhamite(CaS); L-lime(CaO); K-kaolinite(Al₂(Si₂O₅)(OH)₄); P-pyrite(FeS₂); C-calcite(CaCO₃)

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图 8 热解后CaO表面SEM-EDX照片

Figure 8 SEM-EDX analysis of the surface of CaO after pyrolysis

(a): raw CaO; (b): CaO at 800 ℃ after pyrolysis;(c): CaO at 1 000 ℃ after pyrolysis; (d): CaO at 1 200 ℃ after pyrolysis

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图 9 原煤及热解焦中硫的XPS形态分析

Figure 9 XPS analysis of S in raw coal and chars

(a): raw coal; (b): char at 1 000 ℃ of raw coal; (c): char at 1 000 ℃ of coal with 10% CaO

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图 10 砷与硫抑制率的关系

Figure 10 Relationship between retention rates of As and S

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表 1 煤样的工业分析和元素分析

Table 1 Proximate and ultimate analysis of coal sample

Sample	Proximate analysis w_d/%			Ultimate analysis w/%
Sample	A	V	FC	C_d	H_d	O^a	N_d	S_d
YNZX	25.07	9.39	65.54	60.88	2.18	8.35	0.86	2.66
^a: oxygen is calcuated by difference

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表 2 煤样的无机矿物组成

Table 2 Ash composition of coal sample

Ash sample	Ash chemical composition w/%
Ash sample	SiO₂	Al₂O₃	Fe₂O₃	CaO	SO₃	TiO₂	MgO	Na₂O	K₂O	P₂O₅	others
YNZX	49.48	26.74	12.03	4.38	3.09	1.80	0.92	0.64	0.62	0.11	0.19

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表 3 原煤中不同赋存形态砷的含量

Table 3 Content of different occurrence forms of As in raw coal

Sample	Exchangeable /%	As-sulfide /%	As-organic /%	Residual /%	As /(μg·g^-1)
YNZX	0.05	43.40	2.06	54.48	11.49

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表 4 不同热解温度下CaO对砷与硫的抑制率

Table 4 Retention rates of As and S by CaO at different pyrolysis temperatures

Element	X₂/%
Element	800 ℃	900 ℃	1 000 ℃	1 100 ℃	1 200 ℃
As	41.19	30.11	25.99	30.19	33.29
S	28.86	35.71	39.89	34.40	35.24

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表 5 热解后CaO表面元素分布

Table 5 Element distribution on the surface of CaO after pyrolysis

Element	Atomic /%
Element	a area 1	b area 1	c area 1	d area 1	d area 2	d spot 1
O	35.30	37.80	47.82	52.70	42.20	69.09
Ca	64.20	44.00	36.16	28.62	41.98	17.73
S	0.50	18.20	16.02	18.68	15.82	13.18

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表 6 硫的赋存形态及摩尔含量

Table 6 Chemical forms and mol content of S

Valence state	Binding energy E/eV	Compound	a/%	b/%	c/%
-2	163.8 ± 0.2	sulfide,pyrite	24	74	77
+4	168.0 ± 0.5	sulfoxide,sulfite	48	11	20
+6	170.4 ± 0.3	sulphone,sulfate	28	15	3

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