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Tirax mills Tirax mills are fully airswept mills in which the air flow is employed for drying as well as for transport of the material from the mill to the separator. The mill is designed with only one grinding compartment, and without grates in the out- let end. This results in a reasonably low pressure drop through the mill, even when operated at a relatively high rate of air flow, i.e. at maximum drying capacity. The grinding compartment is fitted with a classifying lining which ensures suit- able distribution of the various sizes of grinding media used in the grinding compartment. The mill is suitable for raw material with high moisture content  Tirax-Unidan mills The Tirax-Unidan mill is a semi-airswept mill designed also with only one grinding compartment and is fitted with a classifying lining. The fan power consumption is lower than for the Tirax mill. The mill can only grind raw material with a lower moisture content.  Flash drier In order to increase the drying capacity in connection with the grinding, flash driers can be installed prior to the inlet of semi-airswept mills. With a reasonable amount of fines in the feed material about half the moisture can be dried off in the flash  Atox mills The Atox raw mill is an airswept vertical roller mill, particularly suited for grinding cement raw materials with high moisture content. The mill handles feed up to 100-150 mm in lump size, thereby reducing the need for pre-crushing. The main advantage of roller mills as compared to ball mills is more efficient grinding by compression compared with grinding by impact and attrition. When grinding to the same sieve residue the specific energy consumption of the roller mill proper is only about half that of a ball mill. The total energy consumption when grinding in a roller mill will usually be 10-20% lower than when grinding in a ball mill. The difference will be greater the higher the moisture content in the mill feed.  Duodan mills The Duodan mill has two grinding compartments and one drying chamber. In Duodan mills the drying gas and material are extracted via the peripherical apertures in the mill body after having passed the drying chamber and first coarse grinding compartment. In this way the optimum grinding efficiency of the two compartment mill is combined with the high drying capacity of a single compartment mill. Drier crusher In cases where the raw materials have a high moisture content and are rather soft and not too abrasive, a drier crusher can be used. The drier is a hammer mill without grates. Feed materials and drying gas are introduced in one side of the hammer mill. The crushed and partly dried material is drawn by the gas up the other side into a cyclone The hammer mill has no bottom discharge. All the material has to be crushed to a maximum size of about 6 mm before it can pass with the drying gas into the cyclone- Crushers of this type are used for chalk with about 15% moisture and for clay with up to 30% moisture. This type of drier crusher is also suitable for filter cake and is being used in connection with conversion from the wet to the semi-dry process.  Roller press Crushing of hard, crystalline, and brittle raw material in a roller press before being fed to a ball mill will improve the grinding economy. The roller presses are from the German supplier Maschinenfabrik Köppern. 
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