METSO Barmac B-Series VSI Crushers Industrial minerals

Barmac VSI – The best kept secret in the industry

Keeping ahead of the competition means keeping secrets. The secret behind many successful industrial mineral installations is a Barmac VSI. A Barmac VSI is essential for fast, cost effective production of the materials you need.

With features such as controlled product grading, preferential crushing, low production costs and the ability to produce finely graded products, the addition of a Barmac VSI can optimise the performance of mineral processing installations.

Industrial minerals are broadly defined as all those minerals man takes out of the earth’s crust except for fuels, metallic ores, water and gemstones.

Industrial minerals are a diverse group of natural and man-made materials, with varying physical and chemical properties. Even though they do not have the high profile of the quarrying and the mining industries, industrial minerals represent one of the most important areas of material processing.

Materials the Barmac VSI is asked to crush come in a variety of grades and chemical compositions. Around the world the Barmac VSI has been crushing these materials since the machine’s conception in the 1970’s.

Uses for industrial minerals are varied, depending from the chemical composition and the market for each mineral.

However they can be divided up into several common use categories:
Manufacture of glass.
Mild to harsh abrasive in industrial and commercial applications.
As a slag conditioner.
Additive in ceramics.
As refractory minerals.
As fillers.

Abrasives

The two most important cost factors associated with crushing practice are wear cost of components and power required to run equipment.

In crushing abrasive to extremely abrasive materials these considerations should be taken very seriously when looking at purchasing equipment, particularly for processing industrial minerals.

Barmac VSIs are currently employed in the fine crushing of such materials as bauxite, fused alumina, quartzite, cement clinker, abrasive limestone and many more difficult and abrasive materials as required in the quarrying and mineral processing industries.

Benefits of Barmac VSI product

After adding a Barmac VSI to a crushing circuit in an industrial minerals application, the resulting product will be superior to that coming from any other crusher.

The unique rock-on-rock crushing action provides a mechanism for obtaining the best final product results. Variables such as feed gradation, cascade percentage, crushing chamber configuration and rotor tip speed can be altered to maximise the production of required size fractions. This leads to improved returns for the operator.

Barmac VSI product allows for improved wear rates and improved screening efficiencies. This results in lower operating costs and greatly improved final product.

Contamination

The reduced wear costs of operating a Barmac VSI, lessens the metallic wear per tonne of product produced.

This is extremely important in the industrial minerals market where metallic contaminants must be kept to a minimum.

In most industrial mineral applications, high metallic content from wear on crusher parts results in a sub-standard final product. This requires further, costly, processing to have metallic constituents removed. If they aren’t removed a lower sale value of the processed mineral will result.

When dealing with fine profit margins, operators are constantly looking for ways of reducing this aspect of their costs.

Fine crushing

Barmac VSIs are currently employed in the fine crushing of such materials as bauxite, fused alumina, quartzite, cement clinker, abrasive limestone and many more difficult and abrasive materials as required in the mineral processing and quarrying industries.

In a Barmac VSI, the high energies required for crushing fine particles are not required to the extent of conventional compression crushing equipment.

Cement

The Barmac VSI crusher can be used as an alternative pregrinding machine in cement industries and mineral processing. Its strength is in the optimisation of existing grinding plants, where capacity is required to be increased and energy requirements decreased.

It should be noted that grinding is the single largest user of energy within the raw material and cement clinker process circuit.

In the cement manufacturing industry, limestone or dolomite raw materials require grinding twice before the final cement product can be packaged and sold.

Initially, the process is a typical crushing and screening application. Rock is blasted from the quarry face, crushed and screened down to a 40mm to 20mm product before being placed through a mill. The milled raw material is then heated in a kiln to produce cement clinker which in turn requires grinding to produce a saleable cement product.

As the communition process decreases the particle size, subsequent costs and energy requirements of producing fine material go up. With a Barmac VSI installed the cost of producing high amounts of fine material can be done at a minimal cost.

The rock-on-rock crushing action of both the rotor and the crushing chamber promotes the generation of substantial fine material and lower wear costs per hour than conventional compression crushers for a similar throughput and lower power consumption per tonne of product.

The Barmac VSIs rock-on-rock crushing action uses attrition and abrasion crushing mechanisms as well as cleavage and shatter to crush material. The attrition and the abrasion crushing mechanisms of the crushing action produce micro fines and fines in the crusher product. The ability of the Barmac VSI to produce a product with a high proportion of fine material improves milling circuit performance by reducing energy requirement.

This is achieved with the mill doing less work by adding additional fines in the feed and a smaller feed top size. This leads to an increase plant capacity. Furthermore, the improved shape of the mill feed can produce increased grinding media and wear plate life.

Considerable work has been carried out (and is on-going) in the use of Barmac VSIs as pregrinding machines for the production of raw mill feed and also in the pregrinding of cement clinker. Utilising the Barmac VSI principle, it is possible to increase the output of tube mills while at the same time reducing the specific power requirement when related to kWh/t of production.

The increase in production and savings in energy are directly related to the specific surface area of the cement produced. As might be expected, the coarser or lower the specific surface area the higher the savings.

In actual production, trial increases of output in the order of 25%, with specific power savings of around 20%, have been achieved when cements in the 2800/3000 cm/g (Blaine) have been ground.

As the specific surface area increases, these gains decrease when only the performance of the tube mill alone is considered.

It is important to note that adjustments to the existing grinding circuit, such as resizing of grinding media and changing of mill liners, must be made to gain maximum benefits.

Refractories

The Barmac VSI crusher has the answers when crushing aggregates used for refractory products. Rock-on-rock crushing provides the lowest wear cost per tonne and very low product contamination.

Materials which have the required properties are processed to make bricks for the refractory industry. This involves the reduction of material to a suitable size so high resistant bricks can be made for an industry where extremely high heats are achieved or for abrasive environments.

Bricks are required to be as dense as possible to ensure longevity while in service. The product used to make these bricks must have excellent particle shape so high densities can be achieved. Abrasiveness of materials used in refractory products will cause excessive wear on metallic wear parts.

Traditional crushing systems, such as compression crushers and rock-on-metal impactors, have high wear costs and produce considerable product contamination from metallic wear.

Diamonds

Composed of pure carbon, the diamond has an isometric crystal structure, the most common form being octahedral. The diamond representing the top of Moh’s hardness scale is the hardest known natural substance.

VSI Advantages and Benefits

The Barmac VSI is utilised as a preferential crusher, where it is used to free diamonds from the matrix of placer deposits. The crushing action of the Barmac VSI doesn’t reduce the diamond in any way, therefore maintaining stone integrity.

Processing

Geographically, diamonds are very limited in their distribution. They are only found in kimberlites and lamprolites or as placer deposits. Not all kimberlites produce diamonds, and of the ones that do the minimum economically workable grade is roughly 0.2 to 0.25 carats per ton. At the surface kimberlite deposits are readily weathered due to their unstable mineral assemblages. Weathered materials are eroded and in this way deposits of alluvial diamond accumulate on river banks, in the mouth of rivers and along coastal areas. These sediments are dredged and recovery is by gravity separation.

Uses

The use of diamonds is dependant on their quality. Top quality diamonds are used as gem stones where they fetch the highest price. Lesser quality diamonds are used in industrial applications (referred to as bort) for drilling, cutting, reaming, lapping and wire drawing, where the superior hardness and longevity outweighs cost considerations.

Characteristics

Even though diamonds are very abrasive, they are brittle and will quite readily fracture along octahedral cleavage planes.

Kaolin clay

Clay means different things to different industries.

The use and application of clay denotes the meaning. To the soil scientist and the geologist the word clay generally means a particle less than 0.002mm and/or a group minerals known as clay minerals.

VSI Advantages and benefits

The Barmac VSI excels in processing this type of mineral in partly weathered granites. As the granites weather, kaolin clays are formed.

When utilising the Barmac VSI as a preferential crusher the clay, feldspar and quartz components of weathered granite can be separated. This is due to the different rates of weathering of each of the components. Quartz, being a durable mineral, takes longer to weather than feldspar and the quick weathering minerals that form kaolin.

The Barmac VSI can be placed as a pregrinder of the calcined clay before entering the ball mill. This reduces the mill feed and the subsequent energy consumption of the mill.

Processing

Where clay is formed from the weathering of silica rich rocks such as granite and gneiss, it occurs with feldspar and quartz. The clay is separated from the other constituents by washing with water cannons and the slurry is then centrifuged to remove 75% of the minus 0.002mm fraction. Clay is also processed to remove any contaminating materials such as iron, aluminium quartz and feldspar. It is dried and fired to produce molochite and then fed into a ball mill. Various product gradations can be produced.

Uses

The uses of clay are varied, depending on the type and markets available. The paper industry relies on clay as both as a coating and as a filler. The traditional home of clay is in ceramics where china clay has become synonymous with high quality pottery. The use today has expanded to include ceramics ranging from sanitary ware to bone china, floor and wall tiles to electrical porcelain.

To a lesser extent, clay is used as a refractories, in fiberglass and in portland cement Once the clay is heated to over 500 C it becomes calcinated, forming calcined kaolin. This product has a distinctive crystal structure providing enhanced brightness and opacity.