Method and roller mill for grinding material

Abstract

The invention relates to a method for grinding mill material and to a roller mill and is suited in particular to a finest grinding of relatively hard and dry materials, for example cement clinker and granulated blast furnace slag and also for relatively large roller mills. In order to avoid mill vibrations due to over-grinding of the mill material and to reduce the specific work requirement as well as increasing the throughput a fine material nozzle is arranged after each grinding roller, from which fine material nozzle an air jet with defined impulse is directed from above onto a fine material concentration zone. The fine material concentration zone is formed directly after the grinding zone of each grinding roller and is virtually free of supplied material to be ground and accumulated on a retention rim region. The fine material blown outwards and upwards is fed to a rising conveying air flow and subsequent classifying process.

Description

technical field [0001] The invention relates to a method and a roller mill for grinding materials. [0002] The invention is especially intended for fine grinding of relatively hard and dry materials such as cement clinker, granulated blast furnace slag, as well as cement raw meal and ores, the invention is also used in relatively large roller mills . Background technique [0003] Known vertical roller mills of the LOESCHE type, also known as roller disc mills, for grinding cement clinker and granulated blast furnace slag are capable of achieving a production rate of more than 300 t / h with two or three Impulse grinding rolls and associated leveling rolls for degassing the grinding bed. Grinding rollers and smoothing rollers roll on grinding tracks of rotating grinding discs or grinding beds formed thereon, wherein the grinding discs can have a diameter of from more than 4 m to nearly 7 m. A smoothing or pre-pressing roll (also called a service roll) is arranged before eac...

AI Technical Summary

Problems solved by technology

If there is no retention edge around the perimeter of the rotating grinding disc, the abrasive material will leave the grinding disc unhindered and a sufficiently thick grinding bed will not form between the grinding roller and the grinding disc or grinding track

However, the accumulation of material to be ground, which is necessary for the production of the grinding machine, simultaneously prevents the ground material from leaving the grinding disc

Thus, the fully ground material again reaches under the grinding roll, so overgrinding occurs which leads to a higher specific energy requirement of the grinding roll

There is a process of overgrinding due to the required stagnation edge in a horizontal flat grinding disc or grinding track through its height and shape resulting in a higher grinding bed and a longer residence time of the grinding material on the grinding disc

A taller grinding bed leads to a spring effect through its higher elasticity, which has a negative effect on the grinding efficiency and further increases the tendency in larger grinders due to the generally finer ground material on the grinding discs to tendency to vibrate

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