Enhancement of Low-Density Coal Recovery Through Controlled Comminution Strategies

Coal resources, such as those from the South African Waterberg coal field and the Mozambique coalfields, often contain highly interlayered structures of coal macerals and mineral matter. The mineral matter, which is incombustible, reduces the coal’s calorific value and poses challenges during coal processing due to its adverse impact on plant yields. Effective liberation of coal from mineral matter is crucial to maximize economic recovery and reduce undesirable ash content. This study investigates the effect of various breakage modes on the liberation of coal to attain a high yield of low-ash coal. Coal samples from the Moatize Coalfield in Mozambique were subjected to impact breakage, compressive breakage, and attrition breakage in different combinations to determine the optimal conditions for maximizing coal yield while minimizing fines formation. The results showed that impact breakage to a top size of 6.7 mm followed by attrition breakage significantly enhanced the coal yield, particularly for material with relative density (RD) < 1.4. The study also identified an optimal particle size of 4.75 mm, where the cumulative yield of liberated coal with RD < 1.4 was maximized. The most effective combination for improving coal yield was impact breakage to 6.7 mm, followed by a short attritioning time of 1 minute. This combination achieved a yield of 61%, a significant increase compared to the raw coal yield of 26%. The findings highlight the importance of breakage mode selection and particle size for optimizing coal liberation and yield in processing plants.