Enrichment of residual carbon in entrained-flow gasification coal fine slag by ultrasonic flotation

Abstract

Entrained-flow gasification coal fine slag is a low value and difficult-to-separate solid waste. In this work, ultrasonic flotation experiments are adopted to enrich the residual carbon and are compared to conventional flotation. The concentrate yield and concentrate ash content decrease by 9.94% and 16.54%, respectively, with the flotation perfect index 12.60% higher. Scanning electron microscopy/energy-dispersive X-ray spectroscopy and thermogravimetric analysis show that the ultrasonic flotation has a positive effect on the residual carbon enrichment. Furthermore, the wet screening results prove that the ultrasonic flotation has a more significant crushing effect on the entrained-flow gasification coal fine slag particles than conventional flotation, mainly benefitting the flotation of small particles (i.e. 0.15–0 mm size fractions). Moreover, after ultrasonic emulsification, the collector can be dispersed more evenly and the surface tension of the collector-deionized water system is decreased, which is beneficial to improving the selectivity of the collector. In addition, with ultrasonic pretreatment at 180 W for 4 min in pulp and emulsification at 180 W for 20 s in the collector-deionized water system, the bubbles in the froth layer are the smallest and most stable, and the merging of the bubbles becomes less obvious.