Several users of large coal pulverizers are attempting to crush blends of 10 to 30 percent petroleum coke with various coals. Since the pet coke has much lower grindability than the coal, I maintain that the coal will preferentially be a much higher percentage of the fine product. Our specification is 70 % thru 200 mesh, 99 % thru 50 mesh.
Does anyone have test data showing that the 50 mesh product is primarily coke fines?
My concern is primarily with medium speed vertical spindle mills such as Raymond or MPS mills, where much of the crushing is done between coal particles, rather than between metal/coal lump interfaces.
As a result of this preferential grinding, there will be excessive classifier wear (high recirculation of the hard coke particles). We also observe high unburned carbon in the bottom ash, since the hard, difficult-to-ignite coke particles drop out of the flame pattern.
I would like to suggest dedicating one pulverizer to the coke, and blend the coal/coke inside the furnace. Is anyone successfully doing this? ■
Coal Pulverizers
Several users of large coal pulverizers are attempting to crush blends of 10 to 30 percent petroleum coke with various coals. Since the pet coke has much lower grindability than the coal, I maintain that the coal will preferentially be a much higher percentage of the fine product. Our specification is 70 % thru 200 mesh, 99 % thru 50 mesh.
Does anyone have test data showing that the 50 mesh product is primarily coke fines?
My concern is primarily with medium speed vertical spindle mills such as Raymond or MPS mills, where much of the crushing is done between coal particles, rather than between metal/coal lump interfaces.
As a result of this preferential grinding, there will be excessive classifier wear (high recirculation of the hard coke particles). We also observe high unburned carbon in the bottom ash, since the hard, difficult-to-ignite coke particles drop out of the flame pattern.
I would like to suggest dedicating one pulverizer to the coke, and blend the coal/coke inside the furnace. Is anyone successfully doing this? ■