Study on the mechanism of hydrothermal pretreatment enhancing the flotation of coal gasification fine slag

Coal gasification fine slag is a solid waste generated during the coal gasification process, and its resource utilization is a constraint on the development of the coal chemical industry. This paper takes the fine slag from the Shenning furnace dry powder coal gasification process of Ningxia Coal Industry Group Co., Ltd. as the research object. Hydrothermal pretreatment was used to modify the hydrophobicity of the fine slag, and the flotation mechanism was analyzed through contact angle and XPS measurements. Experimental results demonstrate that hydrothermal pretreatment at 250 degrees C for 1 h significantly enhances fine slag flotation performance. Compared to the untreated sample, the ash content of the concentrate decreased by 4.33 %, and the combustible recovery rate increased by 4.07 %. XPS and contact angle analysis indicate that under the 250 degrees C for 1 h condition, the content of hydrophobic functional groups (C-C/C-H/C=C) on the surface of the fine slag increased by 17.41 %, and the contact angle increased by 14 degrees, effectively enhancing the hydrophobicity of the fine slag surface and promoting its flotation. Based on the physicochemical characteristics of the coal gasification fine slag, the Materials Studio software was used to establish models of the residual carbon and ash components after hydrothermal pretreatment. The microscopic adsorption mechanism of n-dodecane on the surfaces of residual carbon, ash, and fine slag models in a water environment was analyzed from the perspectives of MSD and binding energy. Molecular dynamics simulations also demonstrated that hydrothermal pretreatment significantly reduced the van der Waals interaction energy of the reagent on the mineral surface, facilitating spontaneous adsorption and improving flotation efficiency. This study enriches the theoretical analysis of fine slag flotation and provides guidance for subsequent research.