Pellet press classification
In order to make the new and vast subject of the presses more comprehensible, we classified them according to their principles in:
A. Roller presses.
B. Briquetting presses.
C. Gear presses.
D. Ejection presses with fixed flat die.
E. Ejection presses with annular fixed die.
F. Ejection presses with flat rotating die.
G. Ejection presses with annular rotating die. vertically; horizontally.
H. Expander Extruder Conditioner.
Our industry mainly uses the G and F systems for high density pellets. System B has a certain favor for the production of mineral blocks, nitrogen and fodder. Recently the H system has made its appearance in Europe and its importance will be discussed in another article.
In this article we will talk about the first three types of presses.
A. Roller Presses
Principle: two heavy honeycomb rollers compress by turning the flour.
Use: only for large pellets. Relatively weak compression. Great flow.
These machines are no longer built for our industry but there are still a lage number of them in service.
Advantages: high capacity, great solidity and regularity of service, weak driving force per tonne produced, minimal maintenance costs, easy operation, long life.
Disadvantages: weight and large dimensions, it is almost impossible to quickly change the pellet format, it is not possible to produce small pellets. The pellet is less compact and more fragile than with other systems and requires a "tunnel" type horizontal table cooler especially if molasses with more than 5% are added. Outflow to a vertical cooler is practically impossible. The main problem seems to be the precise regulation of the power supply: if there is too much there is a block; if is not enough, the pellet is badly formed.
B. Briquetting presses
Principle: in briquetting machines, there is the action of a piston or a screw on the food contained in a matrix of a mold.
Manufacturers: only used for large briquettes compressed. Relatively weak compression requiring a binder. High flow rate.
The transformation into blocks or briquettes of minerals or mixtures of minerals and proteins began around 1945 in the U.S. Subsequently, this process took on importance in America and Europe, giving birth to an extensive range of forage pallets enriched with minerals, proteins, urea, etc. ...
They are cylindrical or cubic, the weight varies from 10 to 20 kg. One of the delicate points of this manufacture is mixing and maintenance, as the association with high percentages of molasses, minerals, proteins, urea and sometimes forage material requires a very energetic mixing with periodic emptying, directly reducing the capacity of the press. Transportation is not recommended. These mixtures are abrasive, hygroscopic, and non-adhesive. There are two types of compression: through hydraulic system and by compression system.
C. Gear presses
Principle: flour is introduced between two gears that compress it between the tooth and the tooth cavity. The pellet evacuates through the holes in the cavities of the teeth forming the die. It comes out inwards and is cut by two fixed knives.
Manufacturers: several manufacturers have tried and then renounced this system.