pellet mill maintenance

Pellet mill is the ideal equipment to produce renewable energy fuels for both industrial use and home scale purpose. It has great significance in environmental protection and energy source reusing. Therefore, it is quite important to learn about the correct using method and rational maintenance knowledge of the pellet mill.

Now there are mainly two types of biomass pellet mills in the market: one is flat die pellet mill, the other is ring die pellet mill. the flat die pellet mill is suitable for home or farm scale pellet making usage; it discharge pellets on a 180° plane; it is easy to move, use, maintain and need low investment. While ring die pellet mil extrude pellets on a 360° circle, which is the ideal equipment for middle or large scale biomass pellet mill plants; it has high productivity, long service life, high automaticity, but relatively higher investment.

Pellet mill maintenance tips

1. Grind the pellet mill before use.

The die (plate) of the pellet mill is usually heat treated; after a series procedures of planing, drilling, milling, hardening, etc. the inner holes or the surface of pellet die will have many burrs, and these burrs may probably affect pelletizing result and productivity. As a result, before we put the pellet mill into normal production or when we just change a new pellet mill die, we must fully grind the pellet die.

Usually, for the new small pellet mill, the responsible manufacturers often grind the pellet die for customers before they ship it. If when you receive the pellet mill, its die is not grinded, you can use 5kg of raw material powder (like sawdust), 5kg of waste engine oil, 25kg of fine sand and mix them together, then feed such kind of materials into the running pellet mill. But REMEMBER to adjust the clearance between roller and die to 0.1~0.3mm, so that the rotation of roller and die can extrude pellets. After grinding for 15-40mins, the pellet mill can be put into normal production.

While for ring die industrial pellet mill, the grinding material shall be more, and the clearance between roller and die shall be adjusted to 0.1~0.4mm, then grind for 30-50mins till normal production.

2. Adjust raw material moisture content.

To makes sure the quality of biomass pellets and also prolong the lifespan of pellet mill, it is quite important to adjust raw material moisture content. Generally for small pellet mill, the raw material moisture shall be 13-20%; while for industrial pellet mill, it is 14-25%. This figure also varies in accordance with raw material species and features. Higher moisture content will cause the blockage inside pelletizing chamber, and also corrode pellet mill die and roller; while lower moisture content will cause loose pellet density or even worse, pellets are unable to form.

3. The necessary step before stop the pellet mill.

When one day’s work goes to the end, the pellet mill shall be filled with the grinding material (that is the mixture of raw material, waste engine oil, and sand. Details see Tip1) and press for 1-2mins until all pellet die holes are filled with such oily material. This step is to make sure the operator can start the machine for normal production next day. Besides, such a step can also protect the pellet mill from corrosion.

4. The maintenance of roller and transmission part.

The hard impurities or metal scraps in pellet making raw material shall be cleared away. User can set up a de-ironing separator before the pellet mill, in order to prevent the impurities from affecting the service life of pellet mill roller, die, and main shaft. Also, as the temperature during pellet extruding process can reach 40-80℃, and the roller will bear great pressure during operation, but no effective dust protection device is installed; therefore, for every 2-5 working days, the bearings shall be cleaned and filled with high temperature grease. For every 8 working hours, the main shaft shall be lubricated; the gear box shall be cleaned for every half year

5. Power and daily pellet mill maintenance.

The pellet mill must be equipped with matched power: too low, the productivity is low and result is not good; if too high, the extra power is wasted, and the machine will wear fast. The maintenance shall be conducted under power off condition. The pellet mill shall be put in proper working area and prevent from water, electric leakage, fire and check frequently.

In a word, only under correct utilization and effective maintenance, the pellet mill functions can be fully exerted.