Understanding effect of struvite additive on mineral transformations and release of Na and Ca during Zhundong coal combustion

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

Abstract

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

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

CLC Number:

TQ536.4

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.

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.

Figures/Tables 16

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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

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

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

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

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