Abstract:

The harmless disposal and resource utilization of coal gasification slag are currently focal issues faced by the coal chemical industry. This study analyzed the combustion performance and ash characteristics of coal gasification slag. It utilized a step grate pre-burner and high-temperature tertiary air in cement kilns for the pre-combustion treatment of coal gasification slag and explored the potential for large-scale disposal of coal gasification slag as a novel alternative fuel in cement kilns. The results showed that the combustion performance of the slag samples decreased with an increase of heating rate, indicating that the combustion reaction required sufficient time. At a combustion temperature of 800℃, the residual carbon in the samples was completely burned off, and calcium carbonate also decomposed. The ash after combustion was primarily composed of silicate minerals and the stability of heavy metals was increased. The step grate pre-burner, by providing extra pre-combustion space and excess tertiary air, significantly improved the combustion performance of the gasification slag and reduced the impact of moisture on the thermal field of the decomposing furnace. The cement kiln's capacity and operational conditions were favorable, with an addition rate of 5t/h of gasification slag achieving a coal heat replacement rate of 8.5%, and temperature fluctuations at the kiln head and tail controlled within 2%. Furthermore, the co-processing of gasification slag in cement kilns played a positive role in controlling emissions of gaseous pollutants, with reductions of 23.2% in NO _x and 5.5% in SO₂ emissions. Additionally, an additional rate of 5t/h of gasification slag could also replace 3t/h of raw material addition, reducing the minimum clinkering temperature by 11℃ without affecting the mechanical properties of the cement clinker. This study provided an economically feasible large-scale treatment technology for the full utilization of coal gasification slag through pilot experiments.

Key words: coal gasification slag, alternative fuel, step grate furnace, tertiary air, cement kiln

摘要：

煤气化渣的无害化处置和资源化应用是目前煤化工行业面临的焦点问题。本文通过分析煤气化渣燃烧性能及灰分特性，采用阶梯预燃炉和水泥窑的高温三次风进行煤气化渣的预燃处理，并探究了将煤气化渣作为水泥窑新型替代燃料的规模化处置潜力。结果表明，煤气化渣样品的燃烧性能随升温速率增加而降低，燃烧反应需要充分的时间。在800℃的燃烧温度下，样品中的残炭得以完全燃尽，碳酸钙也能分解。燃烧后的灰分主要由硅酸盐矿物组成，且重金属的稳定性有所增加。阶梯预燃炉通过提供额外的预燃空间和过量三次风，显著改善了煤气化渣的燃烧性能，并降低了水分对分解炉热场的影响。水泥窑的产能和运行工况良好，5t/h的煤气化渣投加量对水泥窑尾煤热量替代率达到8.5%，窑头和窑尾的温度波动控制在2%以内。同时，水泥窑协同处置煤气化渣对气相污染物排放的控制表现出积极的作用，NO _x 和SO₂的排放量分别降低了23.2%和5.5%。此外，5t/h的煤气化渣投加量同样可替代3t/h的生料投加量，并将熟料的最低烧成温度降低了11℃，且不影响水泥熟料的力学性能。通过煤气化渣替代水泥窑燃料的中试试验研究为煤气化渣的全利用提供了一种经济可行的规模化处理技术。

关键词: 煤气化渣, 替代燃料, 阶梯预燃炉, 三次风, 水泥窑