Study on the property and airflow grading of Ningxia coal gasification fine slag

Coal gasification fine slag (FS) is a solid waste of difficult-to-separate nature. In order to improve the reuse rate of coal gasification fine slag resources, so as to improve the value-added utilization and clean transformation for coal chemical industry, which is necessary to deeply study the composition characteristics and effective separation of FS. In this study, the dry pulverized coal gasification fine slag (DPFS) was divided into different particle sizes by wet screening, and the composition and structure characteristics of components with different particle sizes were investigated. Then a combined treatment method of airflow crushing and classification was used to separate DPFS. The results showed that the fixed carbon content, the ash composition, the micro morphology and the pore structure of FS were related to the particle size distribution. The fixed carbon content of particles with particle sizes ranging between 74–98 μm was the highest (about 39.98%), the particles with a size grade of 13–74 μm and larger than 98 μm was between 11.85 and 30.85%, The minimum fixed carbon content of 0–13 μm particle size is 8.69%. The microstructure of DPFS was composed of several relatively independent particle units with special morphology, including porous irregular particles, spherical particles, floccule, and the element contents of these particle units were very different. The residual carbon and ash components in the DPFS could be effectively separated and enriched in different products by airflow crushing and classification. When the grinding gas pressure was set to 0.5 MPa, the low carbon product with fixed carbon content of 4.99% and yield of 19.86% could be obtained. The mechanism of airflow crushing of FS showed that airflow crushing based on impact force and shear force could effectively separate the residual carbon and ash components, and greatly improve the separation and recovery rate of residual carbon. Therefore, the airflow crushing and classification has a good application prospect in the separation and enrichment of residual carbon of gasification fine slag.