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October 02, 2019

Good grinding starts with the feeding: Feeding systems for hammer mills

by Tietjen Verfahrenstechnik, Germany

Hammer mills are among the most common mill types for many applications in the grinding of grain or other biomass raw materials; for example, in the production of animal feed or in the food industry.

Good grinding depends, on the one hand, on the technical design of the hammer mill itself (sieve surface, impact surface, motorisation, speed and sieve perforation) and, on the other hand, on the aspiration of the mill (air volume flow, air velocity, filter type, filter surface).
 


In addition, the feeding of the hammer mill also plays an important role. The grinding plant can only be operated efficiently with optimum feeding and the appropriate dosing of the input material.

Tasks of the feeding system
The feeding system for a hammer mill essentially has four important tasks to fulfil:

1. Distribution of the feed material: The distributed feed of the product over the entire width of the hammer mill has a significant influence on the grinding process, because only in this way can the existing impact and screen surface of a hammer mill be fully utilised. In addition, wear is reduced because the screens and beaters are worn more evenly. An even distribution also leads to an energy-efficient use of the mill’s drive power.

2. Adaptation to product properties: Particularly in product mixtures (eg in the post-grinding of animal feed), products that are heavier and easier to grind (eg barley and corn) may be present as individual layers in the premix. The feeding system has the task of adjusting the throughput capacity of the mill to the product present in the mixture, so that the mill is always operated at its optimum operating point. For this purpose, the load of the mill motor is monitored and the conveying capacity of the feeding device is controlled on the basis of the motor current (load-dependent dosing).

3. Separation of impurities: Due to harvesting, handling, storage, etc, the raw material may contain impurities such as metal parts or stones, which can lead to considerable damage if they get into the mill (eg sieve breakage). Contact of foreign matters with the rapidly rotating components of the mill can also lead to sparking and, associated with this, to a risk of fires and explosions. The feeding equipment therefore has the task of reliably separating foreign parts in front of the mill.


Read more HERE.
 

The Global Miller
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which is published by Perendale Publishers Limited.


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