Experimental study on decarburization process and emission of multi-air-staged and self-sustainable preheating combustion of coal gasification fine slag: From lab-scale study to full-scale demonstration

• Published in: Fuel (Guildford) 2025-02, Vol.381, p.133510, Article 133510
• Main Authors: Shi, Zhaochen, Li, Rui, Dai, Gaofeng, Zhang, Jiaye, Chen, Yongqiang, Yu, Wei, Zhang, Yili, Wang, Xuebin
• Format: Article
• Language: English
• Subjects: Coal gasification fine slag; Decarburization; NOx emission; Preheating combustion
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2024.133510

•A large-scale disposal technology for coal gasification fine slag (CGFS) is proposed.•CGFS preheating combustion technology shows significant decarburization effects.•Staged air distribution effectively controls NOx emissions.•Demonstration project disposes of high moisture content CGFS on a large scale. Coal gasification fine slag (CGFS) is a solid waste produced during the coal gasification process that can potentially harm the environment. It features a high moisture content (55.24 %) and a low volatile content (4.47 %), making its combustion disposal challenging. Preheating combustion is an effective method to achieve stable ignition and efficient burnout of CGFS, facilitating its large-scale and efficient disposal. This study constructed a two-stage preheating combustion experimental system to evaluate the effects of preheating temperature, combustion zone temperature, air distribution method, and excess air coefficient on burnout and pollutant emissions. By increasing the residence time of CGFS in the main combustion zone, the residual carbon content in the ash is reduced to 2.13 % at a combustion zone temperature of 900 °C and nearly 0 % at 1000 °C. Furthermore, adjusting the air distribution method creates a reductive atmosphere in the main combustion zone, reducing NOx emission from 107 ppm to 67 ppm. A 300,000 ton·year−1 full-scale demonstration project is conducted on-site, and optimization suggestions for site operations are provided. The CGFS self-sustainable preheating combustion demonstration project successfully achieves the large-scale disposal of CGFS with an as-received moisture content of 55 %, without the need for auxiliary fuel. The residual carbon content in the ash is further reduced to 1.38 %, and NOx emission is decreased to 57.8 ppm. This study provides an effective method for the large-scale disposal of CGFS.