Particle Migration Behavior of Coal Gasification Fine Slag During Spiral Chute Separation

Coal gasification generates fine slag with high residual carbon, but its porous structure hinders efficient separation. This study investigates carbon–ash separation of gasification fine slag using a spiral chute. Particle size and pore structure jointly determine separation outcomes. Effective separation was achieved for +0.125 mm and 0.125–0.045 mm fractions, which exhibit developed porous carbon skeletons, yielding concentrate ash of 20.22% and 39.50%, respectively. Conversely, the −0.045 mm fraction (41.16% of feed) consists predominantly of mineral microspheres with poorly developed pores, leading to high feed ash (80.73%) and poor separation (concentrate ash 76.35%). Pore structure governs separation by reducing effective density through water absorption: high-porosity particles behave as light products and report to concentrate. Optimal conditions (10% concentration, 1.96 m3/h) achieved 64.67% carbon recovery and 52.92% concentrate ash. A Bagnold-based model reveals that radial particle position is co-determined by effective density and particle size, with fine particle entrainment limiting separation precision.