Classification of pellet mill and working principle

Pellet mill, also knows as pellet press and pellet making machine. Wide applying type of pellet mill are mostly flat die pellet mill and ring die pellet mill. In addition, there are multifunctional pellet mill, soft pellet mill and pellet-fodder expander. 

 

1. Flat die pellet mill and working principle

The main component of flat die pellet mill includes a flat round iron die and a group of (2-4) free rolling rollers with grooves. Feedstock falls into the roller clearance from above to bottom which enters into the holes of die through rotating force, then extruding into long cylinder from the bottom of die hole, cutting by the cutter into pellets. There are mainly three driving models, driving roller, driving flat die and dual drive. Flat die pellet mill has the features of simple structure, easy to manufacture, low cost and fit for coarse fiber materials. But the internal diameter and external diameter of flat die has different surface speed (peripheral speed) and feedstock on the flat die bear different centrifugal force, which make the feedstock bear different compressing force. So the diameter of flat die is not too large, or the quality of finished product will be affected. 

2. Ring die pellet mill and its working principle

Compress roller of ring die pellet mill is a cylinder wall with many hole, it depends on driving motion to rotate. There are 2-4 free rotating rollers and driven roller with grooves. After coming into the iron model, feedstock enter into the making pellet chamber along with the rotating of roller, embedding into the die hole, compressing through the outer surface of ring die, and cuting into cylinder shape pellet. Main character of ring die pellet is the same surface speed of ring die and compress rollers. There is no extra friction force and all the compress force is being use to make pellet. So the operating is efficient. 

3. Multifunctional pellet mill

This machine mainly depends on mechanical milling, coextrusion and friction force to generate heat, to make the starch dextrinization. At the same time, its own moisture content of the fodder has the plasticity which is easy to form, drying and cut, to finish this process one time. 

4. Soft pellet mill

Soft pellet mill is use to process material which contains 20-30% moisture content. The beating green fodder should mix with powder material to make pellet. Generally, as the process of making pellet, they are use for forage. It is necessary to drying the pellets before storage. Soft pellet mill includes screw type, impeller type and ball roller. Screw type is being use more often. It consists of cylinder body, screw, die holes and so on.  

5. Pellet-fodder expander

Pellet-fodder expander consists of rotating feeder, wet mixing, chamber of making pellet, cutter, and power transmission and so on. It contains pupa rod and sleeve simply. Working principle of pellet-fodder expander is that screw are rotating with high speed in the sleeve, after compressing and friction force, temperature in the sleeve is increasing( up to 150℃, pressure is up to 30-100 kg/ m³)。 When the feedstock is compress out from the chamber, the temperature and pressure are lowering quickly. Under the effect of temperature contrast and pressure contrast, moisture content in the feed is evaporating quickly, the volume is expander quickly. So the fodder becomes porous and the moisture content is lowering at 6-9%.   

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Wood pellet mill is becoming pioneer of energy-saving and emission-reduction

 

New energy machinery like wood pellet mill and straw pellet mill are important equipments during this energy-saving and emission-reduction project. Because the new biomass fuel which produced by this machine can replace of the traditional fuel and meet the effect of energy-saving and emission-reduction.