Migration and enrichment of arsenic during coal washing
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摘要: 在煤炭资源的加工利用过程中，部分重金属元素会在环境中富集，对环境和人体均有一定危害。选用内蒙古低灰高硫煤样和高灰低硫煤样进行浮沉和浮选试验，通过电感耦合等离子质谱仪(ICP-MS)、X射线衍射分析、X射线荧光分析、扫描电镜能谱分析、红外光谱分析等测试方法，研究重金属砷元素在煤中的赋存形式及洗选过程中的迁移富集规律。试验结果表明，在两种煤的矿物组成中，硅铝酸盐结合态存在的砷占比为最高，均达到50 % 以上，但是硅铝酸盐矿物种类并不相同，砷的赋存具有明显的差异性；浮沉结果显示低灰高硫煤中的砷主要与矿物质伴生集中在密度较大的部分，而高灰低硫煤主要富集在密度较低、有机质含量较高的部分；浮选中砷迁移规律也存在差异，低灰高硫煤中的砷在浮选过程中向尾煤中迁移，高灰低硫煤中的砷则相反，浮选过程中向精煤中迁移。以上规律表明，低灰高硫煤通过浮沉和浮选脱除砷是可行的，但是对于高灰低硫煤效果不好。Abstract: During the processing and utilization of coal resources, some heavy metal elements will be enriched in the environment, which is harmful to the environment and the human body.In this study, low-ash, high-sulfur coal samples and high-ash, low-sulfur coal samples from Inner Mongolia were selected for float-and-sink test and flotation, and were analyzed by inductively coupled plasma mass spectrometer (ICP-MS), X-ray diffraction analysis, X-ray fluorescence analysis, and scanning electron microscopy energy spectrum analysis.Infrared spectroscopy and other test methods were used to study the occurrence form of heavy metal arsenic in coal and its migration and enrichment law during the processing.The experimental results show that the two coal samples demonstrates the highest proportion of arsenic present in the aluminosilicate bound state, reaching more than 50 %, but the types of aluminosilicate minerals are not the same, and the occurrence of arsenic has obvious differences.Flotation results show that arsenic in low-ash and high-sulfur coal sample is mainly associated with minerals and concentrated in the denser part, while high-ash and low-sulfur coal is mainly concentrated in the part with lower density and higher organic content; there are also differences in the migration law of arsenic in flotation.During the flotation, the arsenic in low-ash and high-sulfur coal migrates to the tailings, while the arsenic in the high-ash and low-sulfur coal migrates to the clean coal.The above findings show that it is feasible to remove arsenic from low-ash and high-sulfur coal sample by flotation but the effect is not so good for high-ash and low-sulfur coal sample, indicating that the removal of arsenic must consider the impact of coal type.
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Key words:
- Inner Mongolia coal /
- heavy metal elements /
- float-and-sink test /
- flotation /
- migration and enrichment
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图 1 低灰高硫煤和高灰低硫煤的XRD谱
Q—石英类矿物特征峰；G—石膏特征峰；K—高岭石特征峰；
P—黄铁矿特征峰；C—方解石特征峰；H—雌黄铁矿特征峰；
A—硅铝酸盐类特征峰Figure 1. X-ray diffraction (XRD) patterns of LAHS and HALS coal samples
图 10 大浮沉试验中硫与砷含量关系
Figure 10. The relationship between sulfur and arsenic content in large float and sink tests
图 11 小浮沉试验煤中硫与砷含量关系
Figure 11. The relationship between sulfur and arsenic content in small float and sink tests
图 12 低灰高硫煤和高灰低硫煤浮选精煤产率
Figure 12. Clean coal yield of LAHS and HALS coal samples flotation
图 13 低灰高硫煤和高灰低硫煤浮选精煤灰分
Figure 13. Ash content of LAHS and HALS clean coal by flotation
图 14 煤中砷与捕收剂用量的关系
Figure 14. The relationship between the collector dosage and arsenic content
图 15 低灰高硫煤浮选产物中硫含量与砷含量的关系
Figure 15. The relationship between sulfur content and arsenic content in flotation products of low-ash and high-sulfur coal
图 16 高灰低硫煤浮选产物中硫含量与砷含量的关系
Figure 16. The relationship between the sulfur content and the arsenic content in the flotation products of high ash and low sulfur coal
图 17 低灰高硫煤浮选产物中灰分与砷含量的关系
Figure 17. The relationship between ash content and arsenic content in the flotation products of low ash and high sulfur coal
图 18 高灰低硫煤浮选产物中灰分与砷含量的关系
Figure 18. The relationship between ash content and arsenic content in the flotation products of high ash and low sulfur coal
表 1 低灰高硫煤与高灰低硫煤的工业分析与元素分析
Table 1. Proximate analysis and ultimate analysis of LAHS and HALS samples
% 煤样 工业分析 元素分析 Mad Ad Vdaf FCdaf Cdaf Hdaf Odaf Ndaf St，daf 低灰高硫煤 1.44 17.69 44.96 55.04 80.06 5.25 9.47 1.50 3.71 高灰低硫煤 1.46 37.11 43.92 56.08 74.03 5.32 19.16 1.08 0.41 
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表 2 逐级化学提取方法
Table 2. Sequential chemical extraction procedure
提取溶液 提取时间/h 温度/℃ 提取的形态 5 mol/L HCl 6 60 碳酸盐、单硫化物、硫酸盐、磷酸盐及氧化物结合态 40%HF 6 60 硅铝酸盐结合态 5 mol/L HNO3 6 45 二硫化物结合态 H2O2 (pH值为2) 6 85 有机质结合态
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表 3 煤样煤灰成分
Table 3. Ash composition of coal samples
% 样品 各组分质量分数 SiO2 Al2O3 CaO SO3 Fe2O3 TiO2 MgO K2O Na2O 其他 低灰高硫煤 44.05 39.67 6.22 3.36 3.12 1.31 1.18 0.276 0.273 0.541 高灰低硫煤 63.50 26.83 1.31 0.89 2.05 0.74 0.73 3.01 0.53 0.40
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表 4 密度-灰分分布区间
Table 4. Summary of density and ash content
密度/
(g·cm-3)大浮沉灰分
范围/%小浮沉灰分
范围/%总灰分
范围/%< 1.3 3.49~4.73 3.04~3.90 3.04~4.73 1.3~1.4 7.62~9.06 5.81~6.05 5.81~9.06 1.4~1.5 13.85~18.99 11.38~12.45 11.38~18.99 1.5~1.6 23.47~30.45 14.88~19.91 14.88~30.45 1.6~1.8 36.53~47.82 29.31~30.46 29.31~47.82 >1.8 70.38~76.73 58.72~68.06 58.72~76.73
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