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.
Attachments:
AIB030 Barmac Improves Grinding Mill Performance (PDF 62kb) 
AIB037 Barmac Increases Cement Plant Capacity (PDF 1807kb)
