煤气化是实现煤炭清洁高效利用的核心技术,我国煤气化渣产量大、利用率低,通常采用堆存与填埋方式处置,造成严重的土地资源浪费与环境污染。气化渣的资源化利用已成为煤化工行业的研究重点,尤其是占气化渣总排放量70%~80%的气化粗渣。介绍了3种主要煤气化工艺及气化粗渣的形成过程,总结了气化粗渣的理化特性与环境风险,归纳了气化粗渣在建材化利用、土壤改良及高值化利用方面的研究进展。受煤种、煤气化工艺等主要控制因素影响,不同来源气化粗渣的理化特性与环境风险不尽相同,但具有一定共同性。从理化特性看,粗渣粒径远高于细渣,约50%以上粗渣粒径超过0.5mm,且小于0.5mm各粒度级粗渣含量随粒径减小而降低,粗渣还具有较小的比表面积和较大的平均孔径。粗渣中残炭含量低于细渣,粗渣残炭质量分数在3%~20%且在各粒度级内分配不均,0.25mm左右中等粒度级粗渣残炭含量较高。粗渣中无机组分均以SiO2、Al2O3、CaO、Fe2O3为主,其中酸性氧化物占45%~75%,碱性氧化物占20%~45%。从环境风险看,气化粗渣中存在一定重金属富集现象,富集较多的重金属包括Ba、Co、Cs、Th等亲石元素与Cr、Ni等难挥发或半挥发性元素。此外,粗渣中Ni、Cd、As、Cu与Zn等重金属的酸可提取态含量较高,具有较大环境风险,需特别关注。粗渣的理化特性及其环境风险对适用的资源化利用方式影响较大:粗渣由于残炭含量较低、硅铝等无机组分含量较高,可广泛应用于矿井回填、筑路、水泥与混凝土、陶粒与墙体材料等建材化利用领域;残炭含量较高的气化粗渣具有更疏松多孔的结构特征,可用于土壤改良;粗渣的特殊结构和丰富的硅铝组分使粗渣在制备多孔吸附材料及制备陶瓷方面潜力很大;粗渣还可用于制备催化剂或提取回收氧化铝等其他高值化利用。气化粗渣中含有一定种类重金属,具有一定环境风险,制约了粗渣的综合利用。因此,粗渣资源化利用前,要全面分析粗渣中各种重金属的富集情况与赋存状态,严格把控粗渣环境风险评价,避免粗渣资源化利用带来的二次污染。

slag is large while the utilization rate is low. Coal gasification slag is usually disposed by storage and landfill, resulting in serious waste ofland resources and environmental pollution. The resource utilization of coal gasification slag has become the research emphasis ofcoal chemical industry, especially the coal gasification coarse slag, which accounts for 70%-80% of the total coal gasification slag. In thispaper, three coal gasification processes and the formation of coal gasification coarse slag were introduced, and the physicochemical characteristics and environmental risks of coal gasification coarse slag were summarized, and the research progress of coal gasification coarse slagin the utilization of building materials, soil improvement and high value utilization were sum up. Affected by the main control factors suchas coal type and coal gasification process, the physical and chemical characteristics and environmental risks of the gasification coarse slagfrom different sources are not the same, but they do have some commonalities. The particle size of coarse slag is much higher than that offine slag, about 50% of coarse slag has a particle size of more than 0.5 mm, and the content of coarse slag of different particle sizes lessthan 0.5 mm decreases with the decrease of particle size, and the coarse slag also has a smaller specific surface area and a larger averagepore size. The carbon residue content of coarse slag is lower than that of fine slag, and the carbon residue content of coarse slag is generally in the range of 3%-20%, which is unevenly distributed in different particle size grade. Generally, the medium particle size coarse slagof about 0.25 mm has a higher carbon residue content. The inorganic components in the slag are mainly SiO, AlO, CaO and FeO, ofwhich the acid oxides account for 45%-75%, while the basic oxides account for about 20%-45%. There is a certain enrichment of heavy metalsin the coarse slag, including some lithophilic elements such as Ba, Co, Cs, Th, and some non-volatile or semi-volatile elements such asCr and Ni. In addition, the acid extractable content of heavy metals such As Ni, Cd, As, Cu and Zn in coarse slag is high, whichhas great environmental risks and needs special attention. The physical and chemical characteristics of coarse slag and its environmentalrisks have a great impact on the applicable resource utilization. Coarse slag can be widely used in building materials such as mine backfill,road construction, cement and concrete, ceramide and wall materials due to its low carbon residue content and high inorganic component content such as silicon and aluminum. Coarse slag with higher carbon residue content has more loose and porous structure characteristics, which can be used for soil improvement. The special structure of coarse slag and its abundant silicon and aluminum components makethe coarse slag have great potential in preparing porous adsorption materials and ceramics. The coarse slag can also be used to prepare catalyst or extract and recycle alumina and other high value utilization. The coarse slag contains certain kinds of heavy metals, which has certain environmental risks and restricts the comprehensive utilization of the gasification slag. Therefore, before the resource utilizationof coarse slag, it is necessary to comprehensively analyze the enrichment and occurrence state of various heavy metals, and strictly controlthe environmental risk assessment, thus avoiding the secondary pollution caused by the resource utilization of coarse slag.

0 引言

1 主要煤气化工艺及粗渣形成过程

   1.1 固定床煤气化技术

   1.2 流化床煤气化技术

   1.3 气流床煤气化技术

2 煤气化粗渣的理化特性

   2.1 煤气化粗渣的物理特性

   2.3 煤气化粗渣的环境风险

3 煤气化粗渣的资源化利用

   3.1 粗渣用于建材化利用

   3.2 粗渣用于土壤改良

   3.3 粗渣的高值化利用

4 结语及展望