Processing of coal fines using air fluidization in an air table

• 9% (absolute) reduction in ash was achieved in a single stage operation of the air table.
• Complex interaction of variables in defining separation performance was revealed.
• Response models developed and operating regimes identified for target product ash.
• Computed velocities in the xy plane adequately described the separation features.

Dry beneficiation of fine coal was investigated using air fluidization in a vibrating air table. A systematic study based on a response surface method of experimentation revealed the features of separation. The ash content of the − 1.0 mm coal feed was reduced from 25.8% to 16.2% with 40.9% mass yield of the clean coal. Optimization was carried out for a target clean coal ash and process conditions were identified for maximum mass yield. A detailed statistical analysis revealed the complex nature of influence of the operating variables on the separation performance. Mathematical models for the mass yield and ash content of the clean coal were developed based on the statistical analysis. The operating regimes for any target product were identified. It was established that complex interaction of the process variables described the separation performance. The longitudinal and transverse velocities of the particles were estimated by considering the components of force due to side tilt, end tilt, vibration frequency and bulk flow. The experimental results were explained in the light of the findings from force balance analysis. A phenomenological description of the separation features of air table has also been given.