近年来,中国西部准噶尔盆地发现的大量低阶准东煤田引起广泛关注。准东煤田是中国目前发现的最大整装煤田,已探明储量3900多亿t,足够供应中国近100a的煤炭消耗。准东煤具有低灰、低硫、反应活性好、储量大、易开采等特点,是未来煤化工、火力发电的优质燃料。然而准东煤中含有大量碱金属钠,钠在燃烧过程中极易挥发,致使锅炉受热面极易发生沾污、结渣等问题,特别是氯化钠和硫酸钠的迁移会引起一系列灰相关的问题,严重制约了准东煤的大规模、高效清洁利用。综述了准东煤的分布及煤质特征,以及钠的赋存形态及测量方法,详细探讨了钠的内部、外部转化机理,以及煤中无机元素如硅铝酸盐、氯、钙、钾等对钠转化的影响,总结了反应条件如温度、压力、反应气氛、颗粒尺度、添加剂对钠迁移特性的影响。尽管已进行了试验、热平衡计算、模拟等多项研究,但准东煤碱金属释放及迁移引起的灰相关问题仍未从根本上得到解决,对其原因的了解还不够全面,重点回顾研究进展,揭示其形成原因。

In recent years, the discovery of a large number of low-ranking Zhundong Coalfield in the Junggar Basin in western China hasattracted extensive attention from scholars. The Zhundong Coalfield is the largest whole coal field discovered in China, with proven reservesof more than 390 billion tons, enough to supply China′s coal consumption for nearly 100 years. Zhundong coals, characterized by low ash,low sulfur, high reactivity, large reserves and easy exploitation, is a high-quality fuel for future coal chemical industry and coal powerprojects. However, the content of alkali metal sodium in Zhundong coals is relatively high, and sodium is easy to volatilize during combustion, resulting in a series of problems such as boiler fouling and slagging, especially sodium chloride and sodium sulfate migrationwill cause a series of ash-related problems, a serious constraint on the large-scale, efficient and clean utilization of Zhundong coal. Thus,the distribution and coal quality characteristics of Zhundong coals, as well as the occurrence and measurement methods of sodium contentwere reviewed in detail. The internal and external migration mechanism of sodium and the effects of inorganic elements such as aluminosilicate, chlorine, calcium and potassium in coal on sodium migration were highlighted. The effects of reaction conditions such as temperature, pressure, atmosphere, particle size and additives on sodium migration were comprehensively reviewed. Although a number of studiesincluding experiments, heat balance calculation and simulation have been carried out, the ash-related problems caused by alkali metal release have not been solved, and the understanding of the causes is not comprehensive enough. Therefore, the focus of this study is to review the research progress and reveal the mechanism of sodium migration.

0 引言

1 准东煤中钠的含量及赋存形式

   1.1 准东煤的分布及煤质特性

   1.2 准东煤中钠的赋存形式

   1.3 准东煤中钠含量的测定

2 准东煤中钠的迁移机理

   2.1 钠的内部迁移机理

   2.2 钠的外部迁移机理

   2.3 煤中无机元素对钠迁移的影响

3 热转化条件对钠迁移的影响

   3.1 温度的影响

   3.2 压力的影响

   3.3 反应气氛的影响

   3.4 煤颗粒粒径的影响

   3.5 添加剂的影响

4 结语

5 展望