Coal mills for coal powder grinding line
What is a coal mill
Coal mill also called coal pulverzier or coal powder mill is that grinding mill used in coal mining industry and thermal power plant, such as vertical coal mill. And in general, vertical mill includes mineral series and coal series. The first series grinder can be widely used in cement making, power, metallurgy, chemical, ore industries. And the vertical coal mill also called coal grinder is the most used machine for coal grinding according to our mining experience. In some cases, coal mill is not just one grinder mill, it will include some optional equipment such as vibrating feeder, vibrating screen, belt conveyors and so on to finish the coal milling process. So, coal mill is also used widely in many industries besides coal mining.
The above are the most common coal mills. With increasingly worsening environment, coal power plants should utilize coal more efficiently. This matters not only the profits of the power plant, but also the social development and environmental protection.
Coal mill pulverizer working principle
Raw coal is fed through a central coal inlet at the top of the pulverizer and falls by gravity to the rotating grinding table, mixing with classifier rejects returned for re-grinding. Centrifugal action forces the coal outward to the grinding ring where it is pulverized between the ring and three grinding rollers. Grinding load, transmitted from the tension rods through the loading frame to the roller assemblies, holds the rollers in contact with the grinding ring. The rollers adjust vertically as the depth of the coal load increases or decreases.
A nozzle ring on the outside perimeter of the grinding ring feeds primary air to the pulverizer. Pyrites and tramp metal fall through the nozzle ring openings to be scraped into a rejects hopper.
A stream of low-velocity air carries the particles of pulverized coal upward where they enter the classifier inlet vanes. Fine particles travel to the burners in the primary air stream, but the larger, heavier particles are returned to the grinding zone for further pulverization.
How to operate coal mill safely
What is the proper method to operate coal mill to avoid the disaster?
- change the piling method of the coal to make the coal accumulate little; thus avoid the spontaneous combustion of the coal.
- change the gap of the great bar from 25mm to 22mm; thus decrease the wind speed and increase the drying speed.
- add a settling chamber between the coal mill and the pipe; thus prevent the hot coal powder enter the coal mill.
- add a explosion-proof valve at the opening.
- increase the fineness of the coal from 10% to 15%.
- make up strict safety rules.
If the coal mill stops for 3 days, empty the coal hopper or put a layer of raw meat powder on the surface to isolate the coal from the oxygen before stopping the coal mill, close the hot wind valve and open the close wind valve and then stop the feeding. remember to empty the coal in the coal mill before stopping the machine and not to stop the collector immediately.
Check the following things when operating the coal mill: the airing is ok; there is no overfeeding or underfeeding; the temperature is not too high; the order of starting and stopping the coal mill is right; the temperature of the air from the coal mill is higher the dew point.
Make an emergency plan; when an explosion happens, close the hot wind valve and the pneumatic valve, prevent the hot coal powder enter the collector and if the temperature is over 80 degree centigrade, start the carbon dioxide extinguisher.
we should pay attention to avoid safety problem in operating the coal mill. as long as we obey the safety rules, the safety problems surely can be avoided.
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Coal mill machine
