Overview

Coal Vertical Roller Mill (VRM) is an air swept, medium-speed, vertical pulverizer with integral classifier. It pulverizes coal by applying hydraulically-loaded grinding pressure through three grinding roller onto a rotating bed of coal. Grinding pressure can be adjusted to account for variations in coal grindability and desired product fineness. 

Vertical roller mill can replace ball mills or tube mills used for preparing coal. Today VRMs with capacities up to 50 tph are the dominant technology for coal grinding. Grinding media wear in a VRM will only be 5 to 10 g/ton of coal powder, as compared to 100 g/ton of coal powder in a ball mill.   

Application: 

The coal powder grinding system is mainly used for burner of burning system in cement plant, lime plant etc, which can also applied in making coal powder which are used for the boilers in power plant and thermal power plant. 

Production Process Flow Chart

The raw coal is stored in the raw coal bunker and fed into the vertical mill by the belt weigher in bottom of raw coal bunker. After drying, grinding and powder classifying, the coarse coal powder with unqualified size will be fall down onto the millstone again for grinding. Meanwhile the qualified coal powder will be discharged with airflow, and entered into the high concentration bag filter especially for coal mill, the air cleansing by bag fiter will be exhausted into the atmosphere., The coal powder collected by the dust collector will be conveyed into coal powder silo through the conveyor belt. Any sundries inside the raw coal, like coal gangue, metal block, etc, will be discharged out of the mill by vane.

The coal powder prepareation system is designed with safety measures, like anti-explosion value, inert gas fire extinguishing system, etc. 

Project Cases

Pulverized Coal Preparation Station in Shangdong	Coal Powder Vertical Grinding Mill in Ningxia

Features

1. VRM can handle materials with sizes greater than 85mm                                    

2. VRM mill can remove more than 20% moisture                

3. Vertical roller mills plants use less space                                          

4. Grinding plants VR mills have lower specific energy consumption (15-40%)                             

5. VRM are more flexible, the capacity can easily be varied from 40 to 100% of the nominal capacity

6. Lower noise level for VRM grinding plants       

Parameter

Remarks: the basic standard for vertical mill is as following:

(1)Power consumption:slag≤25kWh/t,cement≤18kWh/t,raw meal≤9kWh/t;

(2)Moisture content:slag≤15%,cement≤3%,raw meal≤7%;

(3)Ffinished product fineness: specificsurface area of slag 4200~112500px²/g,specificsurface area of cement  3300~380 cm²/g,raw meal fineness-80μmR 12~15%;

(4)Moisture content of refined powder:slag 0.5~1.0%,cement 0.5~1.0%,rawmeal 0.5~1.0%;

(5)The specific installed capacity and parameterscan be adjusted properly according to actual material nature.

(6)The above parameters are applicable forgranular blast furnace slag, cement and raw meal and the model selection  is determined by material property.