Grinding balls are only one type of grinding media. Grinding media are the means used to crush or grind material (cement, mineral, …) in a mill. Grinding media sorting is performed when the ball load wears out. New grinding balls are then added or full reload is carried out to keep optimum filling degree and hence mill performance.
According to the material to be crushed or ground, grinding media can have
· Different forms: grinding balls, boulpebs (cylinders with rounded tops), rods or even beads.
· Different sizes: balls (diameters from 10 to 150mm), rods (different length and diameters),…
· Different composition (alloy): high or low chromium content for steel and iron balls for example.
· Different manufacturing process: balls for instance, can be cast or forged for instance.
Mines : valuable mineral recovery
In extractive metallurgy, mineral processing consists in separating commercially valuable minerals from their ores. This process is called valuable mineral recovery. Mineral processing involves four types of operation: comminution (particle size reduction), sizing (particle sizes separation), concentration (by taking advantage of physical and surface chemical properties) and dewatering (solid/liquid separation).
Coal pulverizing in power stations
Pulverizing coal consists in grinding coal as fine as possible prior to combustion in the steam-generating furnaces of fossil fuel power plants. Coal pulverization is essential to the overall system process of a coal-fired power station, not just in terms of furnace performance and heat rate but in terms of the mechanical reliability and integrity of the furnace. Pulverizer performance plays a key role in back-end emissions in terms of particulate loading.
Pulverizing coal is viewed as a high wear process and generally considered the “key” to combustion performance; thus the primary consideration of many when it comes to optimizing system performance. Vertical Mills (VM) are the predominant design for coal pulverization and are designed to achieve a specific performance (discharge fineness and capacity) based on known coal parameters. The grinding zone of a vertical mill contains the grinding elements namely the table/ring/bowl (depending on mill design) and the roller/tire.
It is critical that the grinding elements maintain an efficient profile for as long as possible. As the grinding elements wear, the grinding efficiency of the mill declines.