Vertical roller mill

Currently, the domestic large vertical mill manufacturers are not producing medium and small-sized vertical mills while small vertical mill manufacturers are not capable of making design and producing equipment for whole production line.

 Features

　　Product Application

　　GGBS production line, coal powder production line and other processing industry related to metal and non-metal mine.

　　Processing Material

　　The vertical mill is mainly used for grinding raw meal, clinker, Ground Granulated Blast Furnace Slag, iron ore, limestone, coal powder, coke powder, coal gangue, fly ash, volcanic ash, gypsum, calcite, pyrophyllite, quartz, clay, sandstone, bauxite and other processing industry related to metal and non-metal mine.

　　Product Introduction

　　Currently, the domestic large vertical mill manufacturers are not producing medium and small-sized vertical mills while small vertical mill manufacturers are not capable of making design and producing equipment for whole production line. In order to enable the small and medium investment owners to select the supplier without any difficulties and according to market demand, Great Wall Corp is able to make design and provide technical proposal and equipment for the whole slag powder production line with the annual capacity of 300,000 t, 600,000t,1000,000t, and 1500,000t. The main technical and economical index can reach the domestic advanced level and the mill has the features of reasonable structure, advanced technology, high stability and reliability when operating.

　　The vertical mill has also been widely used and promoted in the electric power, metallurgy, chemical industry, non-metal industry because the overall efficiency attributed to energy-saving and low consumption is becoming more and more evident in the cement industry.

　　GRM series vertical roller mill is developed with the features of high efficiency, energy-saving and environmental protection which is achieved after exchanging ideas with senior experts from home and abroad and making improvements based on same sector experience in the past years.

　　 Great Wall technical center can help our client to finish feasibility study, environment impact assessment and safety assessment and also provides turnkey service with high efficiency.

　　Great Wall has its own various processing equipment and takes strict control measures on product quality, which results in fast delivery within a short time. Besides, Great Wall can guarantee completion and operation as scheduled with its strong service team for installation and after–sales service.

　　Flowsheet of slag production line

　　01.Material feed hopper(wet material);02.Material feed hopper(clinker,dry material);

      03.Weigh feeder;04.Belt conveyor; 05.Magnetic iron remover ;06.Metal detector ;

      07.Material separating valve;08. Hopper for metal material;09.Rotary discharge valve;

　　10.GRM vertical mill ;11.Rotary discharge valve;12. Sealed air pipe (with fan);

      13. High fineness and dry material feed hopper ;14.Dust collector;

      15.Rotary discharge valve;16.Gas flow measuring system;17.Fan;

　　18.Stack (with regulating valve);19.Circulating pipe (with regulating valve) ;

      20.Cool gas valve;21.Blast furnace;22.Material return system ;23.Bucket elevator;

      24. Material separating valve;25. Magnetic drum separator;

　　Great Wall Machinery can provide vertical slag mill production line with simple process flow, high grinding efficiency, high drying capacity and high classifying efficiency. It is very suitable for small and medium investor because of its remarkable features of adjustable fineness, minimal sound emission, lower energy consumption, high automation and low operating cost. Specific surface area: 4200～4500 cm²/g, system energy consumption: ≤43 kWh/t, dust emission ≤30mg/Nm3

　　Characteristic Features

　　1) High grinding efficiency and lower energy consumption

　　2) Lower metal consumption per unit of product

　　3) Grinding on the material layer bed, minimal sound emission

　　4) Operation under negative pressure and minimal dust pollution

　　5) Simple process flow with the combination of grinding, drying and classifying in a single unit

　　6) Less land occupation, tight layout, light weight, lower civil works cost

　　Structure of vertical mill　

　1) The combined classifier improves the powder selection efficiency.

　　2) It is not necessary to distribute material on the grinding plate before start-up. The roller can be lifted up and down automatically and start without load.

　　3) It is well sealed by welded arc plate and structure is simple and reliable

　　4) With the help of roller turning device, it is easily to turn the roller out for maintenance.

　　5) Both sides of roller sleeve can be used so that the service life of refractory material is extended.

　　6) Grinding roller limit device can ensure a certain space between roller and grinding table, which avoids the direct friction and collision between roller and grinding table and enhances safety

　　7) The grinding roller is driven by spinning grinding table. Pressure filling and adjustment and roller lifting can be remotely controlled without operator on-site.

　　8) The roller bearing is circularly lubricated by thin oil to enable it to work under low temperature and clean grease so that the service life is extended

GRM Vertical Roller Mill Can Process Nepheline Used in Ceramic Industry

The nepheline mainly contain the silicate with aluminum and sodium. Its color is colourness or white, sometimes gray, green or red. It has the vitreous luster, the fracture has the greasy fracture. It is mainly used in the aluminum metallurgy, glass manufacturing and ceramic pottery etc. The vertical roller mill can used in the nepheline grinding, control the fineness of production and can be used in the relative areas.

　　The widely usage of nepheline mainly because of its low melt temperature and wide sinter scope. These characters have advantages in the low temperature quickly sintering of large size polishing brick. When making the new type super white polished tile, by adding a certain amount of nepheline powder can reduce the addition amount of zirconium silicate. In this way, the amount of possible radioactive nuclide can be controlled and help the enterprises get rid of the worry about the radioactive limited.

　　The nepheline not only can reduce the worry about radioactive, but also can reduce the sintering temperature and improving the glaze quality of tile. With the suitable add amount in polished tile, it can improve the polished tile strength, reduce the fragility. By this way, it can reduce the damages by mechanical force during sintering, polishing and transportation.

　　Now there is a kind of high purity nepheline powder materials. After usage, people found that nepheline powder has can whitening the ceramic tile and without the radioactive over problem. It is a step during ceramic industry developing. So Great Wall Machinery put out the dedicated vertical roller mill used in nepheline manufacturing and make own contribution for the developing of ceramic industry.

Traditional Ball Mill’s Three Imperfections Compared with Vertical Roller Mill

Ball mill’s broad prospect in China brings the Chinese ball mill companies unprecedented opportunities. There is no doubt that the main ball mill enterprises will guarantee their industry position and market share in three to five years. The new type environmental ball mills emerge, so the traditional ball mills will be replaced.

　　Imperfections of traditional ball mills are as follows:

　　Firstly, abrasion of steel ball and liners is huge, especially wet way grinding operation - chemical corrosion effect increases the abrasion.

　　Secondly, as the ball material crushing effect lacks selectivity, the so grinding particle size is not uniform, and easy to be crushed. As a result, the traditional ball mills rarely work with open circuit, but in closed circuit operation with classifier, to ensure the product particle size requirements.

　　Thirdly, steel balls movement in the barrel is perpendicular to the earth's gravitational field, so grinding medium must overcome gravity to do crushing, so the energy consumption is higher.

　　Vertical roller mill has more advantages no matter from technical point or operation point:

　　1. The production investment cost is greatly reduced.

　　Vertical roller mill has simple design, compact layout, small construction area, (about 70% of the ball mill system and outdoor displacement), which directly reduces the investment cost. Vertical roller mill has a separator, no need for any additional classifier or lifting equipment. Vertical mill dust gas can be collected by the bag type dust collector or electric dust collector.

　　2. High efficiency, energy conservation and environmental protection

　　Vertical mill grinding principle of grinding material layer, low energy consumption (power consumption is lower than ball mill grinding system by 20% ~ 30%), and along with increase of raw material moisture, the electricity saving effect is more obvious. Vertical mill system energy can save 30% ~ 40% compared with that of ball mill system. There is no steel balls and liners colliding with each other in the vertical mill operation, so the noise is low, (20 ~ 25 db lower than the ball mill operation). In addition, the vertical mill adopts complete sealed system, operation under negative pressure, without dust and clean environment.

　　3. High drying capability

　　Materials are conveyed by hot air in the vertical mill, the air temperature will be controlled when the material has high moisture content, to guarantee the products meet the requirements of the final moisture. In the vertical mill can dry materials - grinding materials mositure is as high as 15% ~ 20%.

　　4. Easy operation, convenient maintenance

　　Equipped with automatic control system with remote control, easy operation; Maintain oil cylinder by rotating arm, and convenient and quick replacement of roller cover, liner, reduce enterprise stop losses.

　　5. Product quality stable and easy to detect

　　The chemical composition of product is stable, particle size distribution are even, is good for the calcination. The time for material to stay in the vertical mill is only 2~3 min, but in the ball mill, it is 15~20 min. So the vertical mill product’s chemical composition and fineness can be measured quickly and correction.

　　6. Small abrasion, high utilization rate.

　　Because in the vertical mill roller mill operation, thee is no direct contact between the grinding table and grinding roller, so there is small metal abrasion, the unit metal consumption is 5 ~ 10 g/t.

Better Choice for Energy-saving and Environment-protection - Great Wall Vertical Roller Mill

Recently, Revised Draft of Air Pollution Prevention and Control Law accepted by State Council executive meeting has drawn a heated discussion.

　　The Revised Draft stresses the source management and public participation. It also increases special provisions of collaborative governance and regional joint prevention and control of pollutants on key areas, industry, motor vehicles, dust, etc. It makes clear the punishment measures for undocumented, standard- exceeding discharge and fraud monitoring data behavior.

　　Air pollution caused by coal burning, industry, dust, etc is more and more severe, the Revised Draft requires key discharge units should install emission automatic monitoring equipment in accordance with the national standard, and other enterprises monitor its emissions of industrial waste gas discharge, also requires the implementation of equal or reduction replacement of coal consumption.

　　Serious haze weather in major cities makes people more and more worried in recent years, and requirements of air pollution management are more and more urgent. The air pollution problem is not only related to government's policies and laws, it is but also to improve the living environment.

　　Cement industry as an important factory in China, supplies the cement products for various fields, also provides an important research about the dust pollution and energy-saving problem.

　　Great Wall Machinery as professional cement equipment manufacturer of cement equipment including vertical roller mill, ball mill, rotary kiln, etc, has done many R & D tests on energy saving, environmental protection, abrasion resistance and automation. Great Wall Vertical Roller Mill is best in environmental protection, energy-saving, the highest degree of automation, enjoys character of large-scale production requirements of cement equipment. You are warmly welcome to visit our company!

vertical roller mills used in coal grinding

Coal pulverisation with vertical roller mills

requirements of pulverisation

Within the power industry, vertical roller mill (VRM) is the predominant equipment used for coal pulverisation. The essential requirements of pulverisation are grinding, heating, classification and transport of the pulverised coal from the pulveriser.

The grinding elements coupled with proper alignment and compression are critical to coal pulverisation in the lower mill body (grinding zone) while the classification of the pulverised coal, discharge and recirculation, is critical in the upper mill body (classification zone).

The proper metering, distribution and control of air flow through the mill, called primary air, is critical throughout the pulveriser and is the bridge between the lower grinding zone and the upper classification zone.

The coal pulveriser is the critical component of the fuel delivery system and is a major influence of combustion efficiency in the burner zone as well as the performance and efficiency of the furnace itself. As such the coal pulveriser is truly the 'heart' of the combustion process for a coal-fired power station.

Coal pulveriser design

In general, coal pulverisers are designed to achieve the maximum rated capacity grinding a design coal with a grindability of 55 HGI and 8-12 per cent moisture and achieving a discharge fineness of 70 per cent passing a 200 mesh screen (74 micron) and 99.5 per cent passing a 50 mesh screen. Variation of the coal hardness and/or moisture content will effect, up or down, the discharge capacity or the discharge fineness.

To achieve these design considerations it is essential that the grinding elements are in good condition and they maintain a consistent profile. The loss of the grinding profile results in a loss of grinding efficiency, meaning the pulveriser must work harder to achieve an equal result.

Ultimately a point will be reached in which either a loss of capacity or a loss of fineness will result under uniform conditions. Longer lasting, more consistent grinding elements are crucial to pulveriser operation yielding longer operating campaigns, reduced maintenance and a lower overall invested cost.


Wear mechanisms in a coal pulveriser

Compression, abrasion and impact are the three wear mechanisms that act upon the grinding elements and the pulveriser internals.

Compression is a wear component that results from the crushing of the material upon itself (attrition) between the grinding elements, ie between the tyres/rolls and the table. Compression is a force that acts normal (perpendicular) to the surface of the grinding elements.

Abrasion (also called erosion) is a velocity driven wear component that results when the crushed material that is suctioned off the bowl and entrained in the primary air rushes past the grinding elements. Abrasion is a shearing force that acts upon the grinding elements at an acute angle. The severity of abrasion is a function of the shear angle, the primary air velocity and the abrasiveness of the entrained material.

Impact is a momentum driven wear component that is a function of the density and the force by which the component being crushed or impacted makes contact with the crushing surface.

The primary source of impact wear in VRMs is generally from undesirable dense rock or tramp metal that enters the pulveriser with the coal.

Compression and abrasion are the primary wear mechanisms that affect the grinding elements in a coal pulveriser.

Several factors will influence the type and the severity of wear. The largest influences will be the quality of the coal being processed, the required capacity factor on the pulveriser, the PA mass flow rate, distribution, and resulting velocity profile around the bowl and pulveriser body and the orientation of the grinding elements relative to the velocity vectors.

Quartz (SiO2), found in ash, is the most abrasive component of coal and has a hardness of 1700-1800 Vickers. Quartz, being dense, will tend to concentrate itself on the table/bowl. The build-up of quartz on the bowl will increase the wear due to compression and the quartz that becomes entrained in the air stream will aggressively attack by abrasion the exposed grinding elements as well as the other exposed mill internals. A small increase in PA velocity can yield a large increase in abrasive wear when significant amounts of quartz are present.



Pulveriser grinding elements

Pulveriser grinding elements that are composed of materials that can withstand these mechanisms of wear will aid by minimising the wear velocity on the tyres and the table thus maintaining a more consistent grinding profile for a longer period thereby achieving optimised grinding efficiency for a much longer duration.

great wall vertical roller mill

Great Wall Machineryis  first-class supplier of complete grinding system,cement mill ,vertical roller mill,raw mill,ball mill,rotary kiln,cement plant..etc in China .


At present, the Chinese cement market has become saturated, we are looking to the global market. In Central Asia, South Asia, Southeast Asia, the Middle East and other regions, demand for cement is growing rapidly. As we all know, the products from China has great quality and affordable price, Great Wall Machinery’s ball mill, vertical roller mill, rotary kiln has these features. We hope our products enter these areas, who can provide support for infrastructure of these countries.

With this objective, we provide chance for cooperation and some jobs. If your company intend to be our agent, please send an email to vip@great-wall.co, attach introduction and website address of your company. If you possess skills and knowledge in machinery or cement industry, our sales job will be right for you. You can send an english resume to vip@great-wall.co, we will contact you asap.

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