鸟粪石添加剂对准东煤燃烧过程中钠、钙矿物转化和释放的影响

doi:10.16085/j.issn.1000-6613.2020-0969

摘要/Abstract

摘要：

准东煤作为优质动力煤，高含量的Na和Ca导致沾污结渣成为制约其大范围工业应用的因素。选取准东五彩湾煤作为研究对象，使用富磷鸟粪石作为添加剂，分别对500℃下处理后的原煤灰和混合煤灰（掺入质量分数为5%的鸟粪石）进行同步热分析；在管式炉中以空气气氛对原煤和混合煤在不同温度下进行燃烧实验；通过 X射线荧光光谱分析仪（XRF）、X射线衍射分析仪（XRD）、电感耦合等离子体发射光谱仪（ICP-OES）对收集灰分进行分析；并通过热力学软件FactSage对实验结果加以验证。结果表明：鸟粪石添加剂对Na和Ca的释放规律影响较大，大量的Na和Ca在燃烧过程中以磷酸复盐的形式聚集在混合煤灰中，Ca的低温共熔物未能生成；在1000℃之前鸟粪石添加剂对Na和Ca的捕集效果较好，温度上升后有所下降。

关键词: 准东煤, 鸟粪石, 钠/钙捕获, 灰分, 矿物转化

Abstract:

Zhundong coal is a kind of high-quality power coals. However, the high content of Na and Ca in Zhundong coal causes contamination and slag which restrict the large-scale industrial application. In this paper, Zhundong Wucaiwan coal was selected, and the phosphorus-rich mineral struvite was used as an additive. The simultaneous thermal analysis (STA) was performed on raw coal ash and coal ash (doped with 5% struvite) treated at 500℃. Combustion experiments of raw coal and treated coal were performed at different temperatures in a tube furnace under air atmosphere. The ash samples were analyzed by XRF, XRD, and ICP-OES. Supporting evidence for the chemical transformations occurring was obtained from FactSage. The results showed that struvite additives had an obvious effect on the release of Na and Ca. A large amount of Na and Ca were accumulated in the form of phosphate complex salt in the treated coal ash during combustion. The struvite additive had a better trapping effect on Na and Ca before 1000℃, but the capture effect weakened after the temperature continues to rise.

Key words: Zhundong coal, struvite, sodium and calcium capture, ash, mineral transformation

中图分类号:

TQ536.4

于志浩, 金晶, 刘敦禹, 侯封校, 杭伊煊, 张瑞璞, 翟中媛. 鸟粪石添加剂对准东煤燃烧过程中钠、钙矿物转化和释放的影响[J]. 化工进展, 2021, 40(4): 2120-2129.

YU Zhihao, JIN Jing, LIU Dunyu, HOU Fengxiao, HANG Yixuan, ZHANG Ruipu, ZHAI Zhongyuan. Understanding effect of struvite additive on mineral transformations and release of Na and Ca during Zhundong coal combustion[J]. Chemical Industry and Engineering Progress, 2021, 40(4): 2120-2129.

图/表 16

表1 五彩湾原煤基础分析结果（质量分数）

工业分析/%					元素分析/%					Q_net/kJ·kg^-1
M	A	V	FC			C	H	N	S	Q_net/kJ·kg^-1
6.90	3.77	29.35	59.98		70.82	3.85	0.30	0.64	13.72	25960

表2 五彩湾原煤灰成分数据

组分	质量分数/%
Na₂O	5.46
K₂O	1.59
CaO	29.50
MgO	9.33
Fe₂O₃	3.08
SiO₂	10.45
Al₂O₃	6.37
SO₃	28.52
P₂O₅	0.05

表3 灰熔融温度

样品	DT/℃	ST/℃	HT/℃	FT/℃
WC	1247	1294	1301	1318
WC+5% MAP	>1500	>1500	>1500	>1500

表4 100kg原煤成分计算表

元素	质量/g
C	70820
H	4179.22
N	585.42
S	1070.57
O	17202.15
Na	152.70
K	49.76
Ca	794.85
Mg	212.09
Fe	81.21
Si	184.13
Al	127.09
P	0.16
Ti	5.20
Cl	172.67

图1 不同温度下原煤灰中氧化物变化趋势

图2 不同温度下混合煤灰中氧化物变化趋势

图3 500℃ WC原煤灰样的热重曲线图

图4 500℃下制成的混合煤灰样的热重曲线图

图5 原煤在不同温度下燃烧得到的灰样XRD分析图

1—CaSO4；2—Na2SO4；3—MgO；4—Ca2Al2SiO7；5—Mg2SiO4；6—Mg2(SiO3)2；7—CaFe3OHOSi2O7；8—Ca2MgSi2O7；9—Ca5(SiO4)2SO4；10—Ca2Fe2O5；11—Ca2SiO4

图6 不同温度燃烧得到的混合煤灰灰样XRD分析图

1—CaSO4；2—Mg2P2O7；3—Na2SO4；4—CaSiO3；5—MgO；6—NaAlSi3O8；7—Na2CaMg7(PO4)6；8—CaMg(SiO3)2；9—Ca18Mg2(PO4)12P2O7；10—NaCa2(Mg,Fe)4Al3Si6O22(OH)2；11—Al2SiO5；12—Mg2(SiO3)2；13—SiO2；14—Na2CaMg(PO4)2；15—Ca(Mg0.85Al0.15)(Si1.7Al0.3)O6；16—Ca2.86Mg0.14(PO4)2

表5 原煤灰和混合煤灰中的主要矿物对比

温度段/℃	原煤灰	混合煤灰
700~800	CaSO₄、Na₂SO₄、MgO	CaSO₄、NaAlSi₃O₈
900~1000	CaSO₄、Ca₂Al₂SiO₇、MgO	CaSO₄,Na₂CaMg₇(PO₄)₆、Ca₁₈Mg₂(PO₄)₁₂P₂O₇、Al₂SiO₅、SiO₂、MgO
1100~1200	CaSO₄、Ca₂MgSi₂O₇、Ca₂SiO₄	Ca₁₈Mg₂(PO₄)₁₂P₂O₇、Na₂CaMg(PO₄)₂、MgO

图7 原煤灰和混合煤灰在不同温度下对Na和Ca的捕获率对比图

图8 WC原煤燃烧的热力学计算结果中含Na矿物的转化路径图

图9 WC原煤燃烧的热力学计算结果中含Ca矿物的转化路径图

图10 混合煤燃烧的热力学计算结果中含Na矿物的转化路径图

图11 混合煤燃烧的热力学计算结果中含Ca矿物的转化路径图

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