Which two types of pulverizers are most commonly used in coal processing?

The correct answer identifies the ball-race mill and the ring-roll mill as the most commonly used pulverizers in coal processing due to their efficiency and effectiveness in reducing coal to a fine powder suitable for combustion.

Ball-race mills operate by using steel balls to crush the coal particles between them, ensuring a uniform size reduction. This type of pulverizer is highly efficient at achieving the desired particle size and provides a controlled, consistent output, making it excellent for large-scale power generation processes.

Ring-roll mills utilize a combination of rolling and crushing motions, where the coal is crushed against a rotating ring. This method also allows for finely ground material and can accommodate variations in coal types and moisture levels, further enhancing its utility in different operational contexts.

The combination of these two types of pulverizers helps to optimize the pulverization process, yielding a fine and homogeneous coal powder that leads to more efficient combustion and higher thermal efficiency in power plant operations.