An efficient, reliable performer
Vertical roller mills are widely accepted as the most efficient means of preparing most moist raw materials for the production of cement clinker. The flexible ATOX™ raw mill can prepare virtually any kiln feed material to your required fineness in an energy-efficient process – regardless of variations in grindability, drying requirements and abrasion. In fact, the ATOX can be adapted to a wide variety of specific requirements.
Our continuous development of the mill over the years has resulted in today’s ATOX raw mill – a compact mill featuring a unique design that delivers superior reliability and performance.
Working principle of ATOX raw mill
The ATOX raw mill uses pressure and shear generated between the rollers and the rotating table to crush and grind raw materials.
Feed material is directed onto the grinding table by the feed chute. The rotation of the grinding table accelerates the material towards the grinding track and passes it under the rollers. Partially ground material passes over the dam ring encircling the grinding table and into the hot gas stream coming from the nozzle ring.
The moisture in the materials evaporates almost immediately, while the finer portion of material is carried by the gas stream to the separator and the coarser portion deflected directly back to the table. The separator allows material that has reached the required fineness to leave the mill, while it rejects oversized material and sends it back to the table for further grinding.
The coarsest fraction of the material that spills over the dam ring may fall through the nozzle ring and be conveyed back to the feed material inlet by a mechanical recirculation system.
Many applications, many adaptations
The ATOX raw mill has demonstrated its suitability for grinding virtually all types of raw materials:
– From very easy-to-grind to very hard-to-grind material
– roughly from less than 3 kWh/t to more than 11 kWh/t – From less than 1% moisture to more than 20% moisture in feed material
– From non-abrasive to very abrasive materials
– From non-sticky to very sticky feed material
Raw materials that are easy to grind – for example, high capacity for the specific mill size, or with high moisture content – may require an increased gas flow through the mill. The ATOX mill is easily adapted to this situation, as it comes with an oversize nozzle ring and an oversize separator.
Basic design concept
The grinding table of the ATOX raw mill has a flat, horizontal grinding track encircled by an adjustable dam ring and an adjustable nozzle ring equipped with an air guide cone. The dam ring is made up of stacked, bolted-on, segmented rings and is easily adjusted by adding or removing one or more segmented rings.
The height of the dam ring determines the thickness of the grinding bed on the table. The roller assembly is kept centred on the grinding table and prevented from rotating by three torque rods attached
to the mill housing. The grinding pressure is exerted hydraulically through three pull rods attached to the outer ends of each roller shaft. This unique ATOX roller suspension ensures the grinding forces are transmitted vertically by the pull rods directly into the hydraulic cylinder and foundation, and horizontally by the torque rods into the mill housing.
The latest generation separator is located above the grinding rollers. The high efficiency of the separator is due to the rotor equipped with an outer ring of louvre plates. The fineness is controlled by adjusting the rotor speed.