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新疆准东和哈密煤中钠的赋存特征及富集机理差异性研究

Differences in the occurrence and enrichment causes of sodium in coal from Zhundong and Hami of Xinjiang

  • 摘要: 新疆煤炭资源丰富,大多为优质的动力煤和煤化工原料煤,但也富含金属钠,富钠煤燃烧过程中产生的沾污结渣严重影响了新疆煤炭资源的洁净开发利用。研究以准东煤田西黑山露天矿煤和吐哈盆地大南湖矿区F1南井田二矿煤为研究对象,基于改良版逐级化学提取实验、ICP-AES、SEM-EDS和离子色谱仪等测试手段,分析了两矿区煤中钠的分布赋存特征及差异性,明确了煤中钠的富集机理及主控因素。结果表明:在含量分布特征上,两矿区煤样均为典型低阶高钠煤,不同的煤层顶板岩性导致了大南湖煤中钠含量随煤层深度逐渐降低,西黑山煤呈相反趋势。在赋存特征上,煤中钠和水分与有机质均有较强的亲和性。逐级化学提取结果也证明了这点,西黑山煤中钠主要以水溶钠(54.32%)为主,氯化铵溶钠(30.35%)次之,而大南湖煤中钠主要以氯化铵溶钠(41.10%)为主,水溶钠(33.15%)次之。两矿区煤中水溶钠分别主要以NaHCO3和NaCl存在,且惰质体为其亲和性显微组分。煤岩煤质特征、煤化程度及物源沉积体系的差异性均会导致煤中钠的赋存特征不同。新疆煤中钠的富集是多因素相互叠加的结果,主要受地表水淋滤(垂向补给)和地下水驱动效应(侧向补给)双重控制,其中大南湖煤中钠的富集主要受盐碱化土壤的淋滤作用,而西黑山煤主要受含水层岩石和煤层顶板中含钠矿物影响。脱钠预处理方式也应针对钠的赋存状态进行改良,对于富含有机酸钠的高钠煤,低浓度铵盐溶液以及有机酸可作为脱钠溶剂,对于高含水高惰质体的高钠煤可考虑用浮选+乙酸铵进行预处理,同时达到钠的脱除和惰质体的分离,提高精煤中活性组分–镜质体的含量。

     

    Abstract: Xinjiang has abundant coal resources, primarily consisting of high-quality power coal and feed coal for the coal chemical industry. Additionally, it is also rich in sodium elements. However, the issues of staining and slagging during the combustion process of sodium-rich coals have significantly hindered the clean development and utilization of Xinjiang coal resources. The coals from the Xiheishan Open Pit Coal Mine in the Zhundong Coalfield and the Second Mine of the F1 Nanjing Field in the Dananhu Mining Area in the Tuha Basin were used as research objects. An improved stepwise chemical extraction experiment was used, along with testing methods such as ICP-AES, SEM-EDS and ion chromatography, to analyze the distribution and characteristics of sodium in the coals from the two mining areas and the differences between them, and to clarify the enrichment mechanism and main control factors of sodium in the coals. The results show that in terms of content distribution characteristics, the coal samples from the two mining areas are both typical low-rank high-sodium coals. The lithology of the roof slate of different coal seams has resulted in the Na content of the Dananhu coal gradually decreasing with the depth of the coal seam, while the Xiheishan coal shows the opposite trend. In terms of occurrence characteristics, the sodium and moisture in the coal have a strong affinity with the organic matter. This is also evidenced by the results of stepwise chemical extraction. The sodium in Xiheishan coal is mainly water-soluble sodium (54.32%), followed by ammonium chloride-soluble sodium (30.35%). The sodium in Dananhu coal is mainly ammonium chloride-soluble sodium (41.10%), followed by water-soluble sodium (33.15%). The water-soluble sodium in the coals from the two mining areas is mainly NaHCO3 and NaCl, respectively, and the inert group is its affinity microscopic component. The differences in the characteristics of coal rock, coalification degree and the depositional system of the source will lead to differences in the characteristics of the occurrence of Na in coal. The enrichment of sodium in Xinjiang coal is the result of the superposition of multiple factors, mainly controlled by the double effects of surface water leaching (vertical recharge) and groundwater driving effect (lateral recharge). Among them, the enrichment of sodium in Dananhu coal is mainly affected by the leaching of saline-alkali soil, while Xiheishan coal is mainly affected by the sodium-containing minerals in the aquifer rocks and the roof of the coal seam. The pretreatment method for sodium removal should also be improved according to the state of occurrence of sodium. For high-sodium coal rich in sodium organic acids, a low-concentration ammonium salt solution and organic acid can be used as a solvent for sodium removal. For high-sodium coal with high water content and high inert group, flotation and ammonium acetate can be considered for pretreatment, which can achieve the removal of sodium and separation of the inert group, and increase the content of the active component, the mirabilite group, in the clean coal.

     

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