Vertical roller mill is a type of grinder used to grind materials into extremely fine powder for use in mineral dressing processes,

paint Paint is a material or mixture that, when applied to a solid material and allowed to dry, adds a film-like layer. As art, this is used to create an image or images known as a painting. Paint can be made in many colors and types. Most paints are ...

pyrotechnics Pyrotechnics is the science and craft of creating fireworks, but also includes safety matches, oxygen candles, Pyrotechnic fastener, explosive bolts (and other fasteners), parts of automotive airbags, as well as gas-pressure blasting in mining, q ...

cement A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mi ...

s and ceramics. It is an energy efficient alternative for a

ball mill A ball mill is a type of grinder filled with grinding balls, used to grind or blend materials for use in mineral dressing processes, paints, pyrotechnics, ceramics, and selective laser sintering. It works on the principle of impact and attri ...

Overview

The vertical roller mill is a kind of

grinding machine A grinding machine, often shortened to grinder, is any of various power tools or machine tools used for grinding. It is a type of material removal using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts ...

for cement, raw material,

cement clinker 200px, Typical clinker nodules 200px, Hot clinker Cement clinker is a solid material produced in the manufacture of portland cement as an intermediary product. Clinker occurs as lumps or nodules, usually to in diameter. It is produced by sinter ...

slag The general term slag may be a by-product or co-product of smelting (pyrometallurgical) ores and recycled metals depending on the type of material being produced. Slag is mainly a mixture of metal oxides and silicon dioxide. Broadly, it can be c ...

and coal slag. It has the benefits of simple structure and low cost of manufacture and use. Vertical roller mills have many different forms, but they work basically the same. All of these forms come with a roller (or the equivalent of roller grinding parts), and roller along the track of the disc at the level of circular movement imposed by external grinding roller in the vertical pressure on the disc on the material being the joint action of compression and shear, and to crush.

Operation

Material grinding process motor through reducer rotating drive disc, the material falls from the mill under the central entrance and exit, under the action of centrifugal force to the disc edge by the roller to move and the crushing, grinding out lap after the material was speed up the flow to and vertical mill with one of the separator, after the meal by the separator back to the mill, the re-grinding; powder while grinding out with air, dust collection equipment in the system to collect down, that is, products. Established through the mill in the pneumatic conveying of materials, a larger air flow rate, which can use

waste heat Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility ...

of gas, at the same time dry grinding operations.

Principle

Principle of Grinding for these mills are done by Attrition and Compression method. The grinding force are applied through the sets of rollers on to the material bed spread over the rotating grinding table. This causes attrition initially followed by compression from external grinding forces. Used in cement grinding production grinding parts of its various forms, there is a cylinder, cone type, ball type, etc., and roller surface is also flat, curved, convex round noodles. Applied to the grinding roller to roller grinding along the track bed in close contact with the material strength of a spring pressure, hydraulic, etc.

Method of operation

It has two pairs of grinding rollers, each pair of roller composed of two narrow rollers, mounted on the same axis and can rotate at different speeds. There are two circular disc slot, and roller to the tire shape, work pressure in the tank. Disc roller and the relative sliding velocity between small and roller can swing, even if the roller sleeve and the disc after the liner wear can guarantee a good abrasive, will not affect the grinding effect. Roller symmetrical structure, one side can be upside down after use and wear. Material grinding process: hydraulic pneumatic roller device through the pressure applied to the material on the crushing of materials, the materials have been moved to crush the edge of disc, from the disc around the nozzle from the exhaust air to improve these materials to Separator.Meal to separate returns after a concentrated mill, fine powder was collected in the precipitator unloading. In the gas flow is small, the meal can not be increased to enhance air flow, they would fall through the nozzle discharged outside the mill,

bucket elevator A bucket elevator, also called a grain leg, is a mechanism for hauling flowable bulk materials (most often grain or fertilizer) vertically. It consists of: # Buckets to contain the material; # A belt to carry the buckets and transmit the pull; ...

to be transported to the feeder of vertical

roller mill Roller mills are mills that use cylindrical rollers, either in opposing pairs or against flat plates, to crush or grind various materials, such as grain, ore, gravel, plastic, and others. Roller grain mills are an alternative to traditional ...

, and was re-grinding mill feed people. This cycle features of the way there: # ring by adjusting the air valve, can change the product fineness can Shide mill bed load material uniformity and stability, improving the grinding efficiency; # coarse particles in the external circulation, helps reduce Fan power consumption and overall system power.

Benefits over ball mill

# Smaller footprints # Can be erected on site which avoid logistical issues. # Low wear rate #Low operation cost and long service life # More grinding capacity (approx. 20–25% more) than ball mill # lower power consumption (KWh/Ton) than ball mill + pregrinding

Limitations

# Complex system # Maintenance requirement are higher, In cement grinding, Practically need 2 times annually to re-weld roll and table due to excessive wear # Higher overall cost

References

{{Reflist Mining equipment Grinding mills