高硅煤中Si-Al-Fe-Ca四元体系碳热反应研究

雍其润; 龚本根; 赵永椿; 张军营

高硅煤中Si-Al-Fe-Ca四元体系碳热反应研究

华中科技大学煤燃烧国家重点实验室, 湖北武汉 430074

基金项目:

国家自然科学基金 41672148

国家自然科学基金 U1510201

详细信息

中图分类号: TQ53
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- 被引次数: 0
出版历程
- 收稿日期: 2017-05-31
- 修回日期: 2017-07-18
- 网络出版日期: 2021-01-23
- 刊出日期: 2017-11-10

Carbothermal reduction of Si-Al-Fe-Ca quaternary system in a high-silica coal

State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China

Funds:

the National Natural Science Foundation of China 41672148

the National Natural Science Foundation of China U1510201

More Information

Corresponding author: ZHANG Jun-ying, Tel:18971412881, E-mail:jyzhang@hust.edu.cn

摘要

摘要: 研究了不同温度条件下高硅煤中矿物组成比例下的Si-Al-Fe-Ca多元体系的碳热反应以及其影响因素。通过XRD和FESEM-EDS技术对各还原产物进行分析。结果表明，Fe₂O₃对含硅矿物的碳热反应起促进作用，Fe可以有效提高Si反应活性。CaO在较低温度时与灰中的Al₂O₃和SiO₂反应形成致密的Ca-Al-Si相共熔体CaAl₂Si₂O₈，阻碍含硅矿物碳热反应的进行。随着温度的升高，继续反应生成SiC、CaAl₄O₇和CaSiO₃。热力学模拟计算与实验结果基本吻合。
- 高硅煤 /
- Si-Al-Fe-Ca四元体系 /
- 含硅矿物 /
- 碳热反应
Abstract: During coal pyrolysis and gasification, the minerals in coal undergo various transformations, which affects coal conversion and characteristics of coal ash obviously. Carbothermal reduction of Si-Al-Fe-Ca quaternary system in high-silica coal under different temperature was investigated. Composition of products obtained was analyzed by X-ray diffraction (XRD) and field emission scanning electron microscope-energy dispersive spectrometer (FESEM-EDS) technology. The results show that Fe₂O₃ plays a positive role in carbothermal reaction of silicon-bearing minerals, which could effectively improve activity of Si. On the contrary, CaO reacts with Al₂O₃ and SiO₂ to form dense Ca-Al-Si eutectic, mainly CaAl₂Si₂O₈, at lower temperature, covering surface of the reactant, which hinders the carbothermal reaction of silicon-containing minerals. With increasing temperature, CaAl₂Si₂O₈ reacts with graphite to generate SiC, CaAl₄O₇ and CaSiO₃. The related thermodynamic calculations are in accordance with the experiment results.
- high-silica coal /
- Si-Al-Fe-Ca quaternary system /
- silicon-containing mineral /
- carbothermal reduction

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图 1 实验系统示意图

Figure 1 Scheme of experiment system

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图 2 SiO₂不同温度下还原产物XRD谱图

Figure 2 XRD patterns of products of quartz at different temperatures

Q: Quartz; Cr: Cristobalite; G: Graphite; C: Corundum; SC: Silicon Carbide

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图 3 不同比例Si-Al-Fe-Ca四元体系还原产物XRD谱图

Figure 3 XRD patterns of the products of different synthetic ashes

Q: Quartz; Cr: Cristobalite; G: Graphite; C: Corundum; A: Anorthite; H: Hematite; SC: Silicon Carbide; W: Wollastonite; P: Pseudowollastonite; Wu: Wustite; S: Silimanite; FS: Fe₃Si; FS2: Fe_1.34Si_0.66; FS3: Fe₅Si₃; CA1: CaAl₄O₇; CA2: CaAl₁₂O₁₉; CS: Ca₂SiO₄; CF: CaFe₃O₅; He: CaFeSi₂O₆; AC: Al₄Ca; FC: Fe₃C; FA: FeAl₃; FAS: Fe₃Al₂Si₃; FSO: Fe_2.56Si_0.44O₄

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图 4 不同添加物的产物SEM照片

Figure 4 SEM of the product of different additives

(a): the unreacted graphite; (b): the product of SiO₂ at 1 600 ℃; (c): magnification of the product of SiO₂ at 1 600 ℃; (d): the product of sample mixed with CaO at 1 600 ℃; (e): the product of sample mixed with Fe₂O₃ at 1 600 ℃; (f): magnification of the product of sample mixed with Fe₂O₃ at 1 600 ℃

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图 5 各点(1#-3#)的能谱图

Figure 5 EDS of the points(1#-3#) in Figure 4

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图 6 Si-Al-Fe-Ca系主要化学反应ΔG⁰-T图

Figure 6 Diagram of ΔG⁰-T for the main reactions in Si-Al-Fe-Ca system

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表 1 Si-Al-Ca-Fe多元系比例表

Table 1 Compositions of synthetic ashes

	SiO₂	Al₂O₃	Fe₂O₃	CaO
1	50	30	15	5
2	50	30	5	15
3	55	30	10	5
4	60	25	10	5
5	55	30	5	10
6	60	30	5	5
7	65	30	0	5
8	65	30	5	0
9	50	35	10	5
10	100	0	0	0

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表 2 图 4各点元素成分组成

Table 2 Composition of elements of the points(1#-3#) in Figure 4

1#			2#			3#
Element	w/%	w_A/%	Element	w/%	w_A/%	Element	w/%	w_A/%
Si	52.14	31.84	Si	34.01	28.3	Si	13.89	16.12
C	47.86	68.19	Al	34.06	29.49	Fe	70.16	40.71
			Ca	5.05	2.94	C	15.94	43.17
			O	26.88	39.26

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表 3 Si-Al-Fe-Ca系主要反应及相应的吉布斯-亥姆霍兹方程^[21-23]

Table 3 Gibbs-Helmholtz equations of the main reactions in Si-Al-Fe-Ca system

	Reaction formular	ΔG⁰/(kJ·mol^-1)
(1)	SiO₂+3C=SiC+2CO(g)	616.56-0.353 0T
(2)	Fe₂O₃+3C=2Fe+3CO(g)	466.35-0.505 8 T
(3)	3Fe+SiO₂+2C=Fe₃Si+2CO(g)	570.32-0.349 9 T
(4)	3Fe+C=Fe₃C	22.594-0.013 7 T
(5)	CaO+2SiO₂+Al₂O₃=CaAl₂Si₂O₈	-91.211+0.028 9 T
(6)	CaAl₂Si₂O₈+Al₂O₃+6C=CaAl₄O₇+2SiC+4CO(g)	1 315.117-0.713 3 T
(7)	CaAl₂Si₂O₈+3C=CaSiO₃+Al₂O₃+SiC+2CO(g)	618.647-0.324 9 T
(8)	CaO+3C=CaC₂+CO(g)	464.34-0.210 9 T
(9)	CaO+C=Ca+CO(g)	525.75-0.194 3 T
(10)	Ca+2C=CaC₂	-59.413-0.017 4 T
(11)	Ca+SiO₂+2C=CaSi+2CO(g)	539.151-0.345 9 T
(12)	Ca+2SiO₂+4C=CaSi₂+4CO(g)	1 228.926-0.694 9 T
(13)	2Al₂O₃+9C=Al₄C₃+6CO(g)	2 414.4-1.066 1 T

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