Vertical mill

Application

 

Vertical mill is widely used for pulverized coal preparation system in power plant, cement plant, metallurgy industry, chemical plant, etc. It could be used to grind bituminite, meagre coal, and anthracite & lignite with high moisture under some conditions.

 

Vertical mill adopts low speed, big roller diameter, high loading force design. It has the widest adaptability to coal types and variation in coal properties, big grinding surface & ability, low rolling resistance, low energy consumption, stable output, etc.

 

Working principle

 

Coal is sent into vertical mill through central entrance by coal feeder, and falls down on the grinding table. Under the action of centrifugal force, coal is pushed to the edge of table. Under the force of spring loaded roller, coal is compressed and sheared. During grinding process, pulverized coal is blown upwards by hot air from primary air fan.

 

Hot air stream has three functions here:

 

1. Convey pulverized coal to boiler furnace.
2. Provide momentum for coal classification.
3. Dry pulverized coal to make grinding easier.

 

Fine particles are taken away to boiler furnace, while oversized particles are separated by classifier for grinding again.

 

Vertical mill advantages

 

1. Low energy consumption, 20-30% lower compared with ball mill.
2. Much smaller footprint compared with ball mill.
3. Regulation within 15-100% load.
4. Fast response to boiler load requirement, better ability to match with power grid regulation.
5. It could grind lignite coal with moisture content Mar<40% as received basis.