Analysis of the causes of cracks in the pellets produced by the biomass pellet machine

In the production of Biomass Pellet Machine, sometimes there will be particles with abnormal appearance. Experienced pellet machine manufacturers will know the cause of this situation and can quickly eliminate it. For inexperienced or new wood pellet manufacturers For example, sometimes you can't find the crux of the problem, and you can only ask for help from the outside world or the pellet machine manufacturer.

The following is the introduction of the causes and improvement methods of 7 common wood pellets with abnormal appearance. This is a summary of Shandong Jingerui pellet machine manufacturer's years of work experience in pellet machine development and debugging, for comparison in the production of wood pellets refer to.

1. The sawdust pellets are bent and have many cracks on one side

This phenomenon usually occurs when wood pellets leave the ring die. In production, when the position of the cutter is adjusted farther from the surface of the ring die and the edge of the knife is blunt, the particles are easily broken by the cutter instead of being cut off when extruding from the die hole. At this time, some particles bend to one side and the other There are many cracks on one side.

The wood pellets tend to break from these cracks when entering the cooler for cooling or transportation, resulting in too much powder or too short pellets produced. Improvement method:

Increase the compression force of the ring die on the wood pellets, that is, increase the compression ratio of the ring die, thereby increasing the density and hardness of the pellets;

Grind the sawdust raw material wood chips finer to increase the compactness of the wood chips and prevent the wood chips from being soft;

Adjust the distance between the cutting knife and the surface of the ring die, usually the distance between the knife edge and the outer surface of the ring die is not greater than the diameter of the wood pellets produced, or use a sharper cutting blade;

2. Horizontal cracks across the entire wood particle

Somewhat similar to the phenomenon in case 1, the cracks occur in the cross-section of the wood particle, but the particle is not bent. This can happen when pelletizing fluffy wood chips that contain more fibres. This kind of wood pellets is often produced when the wood chips are squeezed into the granulation hole of the ring die, because it contains fibers longer than the hole diameter. , producing a fir bark-like wood pellet appearance.

The improvement method is to increase the compression force of the ring die on the wood chips, that is, to increase the compression ratio of the ring die; to control the crushing fineness of the fibers, and the maximum length cannot exceed one-third of the particle diameter; to reduce the output to reduce the passage of wood chips The speed of the die hole increases the compactness;

3. Biomass pellet machine produces vertical cracks

During the production process, due to the type of dryer selected by some customers, the raw materials cannot be dried evenly, resulting in uneven moisture content of the raw materials. The elasticity and bounce off, resulting in vertical cracks.

The way to improve is to improve the drying effect of the dryer and increase the effective length of the die hole.

4. Sawdust particles produce radiation cracks from one source point

The main reason for this situation is that the sawdust contains relatively large sawdust. Raw materials with similar fiber levels will be extruded and fused with each other when they are granulated. If there are larger fibers, the interaction between fibers will be affected. He is not as easy to soften as other finer raw materials, but when cooling, due to the different degrees of softening, the shrinkage is different, resulting in radial cracks.

The improvement method is to properly control the thickness and uniformity of the powdered feed raw materials, and add a simple sieve to sieve the sawdust with larger particles before pelleting.

5. The surface of the pellets is uneven

This situation is that the powder used for granulation contains large particle raw materials that have not been crushed or semi-crushed. Because the particles are relatively hard and relatively large, they cannot be well combined with other raw materials when passing through the die hole of the granulator. Together, the grains appear bumpy. The way to improve is to properly control the thickness of powdery raw materials.

6. The color of individual particles or particles is inconsistent, commonly known as "flower material"

The main manifestation is that the color of individual particles extruded from the ring die is darker or lighter than other normal particles, or the surface color of individual particles is inconsistent. The reasons for this phenomenon mainly include the following aspects:

There is recycled material for repeated granulation in the silo to be granulated. The granulated pellets can only become finished materials after cooling and screening. The fine powder or small pellets after screening often enter the process for re-granulation, usually into the mixer or the granulation bin. Because this kind of recycled material is re-granulated, when it is unevenly mixed with other raw materials or mixed with recycled small particles, sometimes "flowery material" will be produced.

7. The smoothness of the inner wall of the ring die aperture is inconsistent. Due to the inconsistency of the finish of the die hole, the resistance and extrusion force of the particles during extrusion are not the same, and the color change is not consistent. In addition, some ring dies have burrs on the small hole walls, and the particles will scratch the surface during extrusion, resulting in different surface colors of individual particles.

For the above-listed reasons for the occurrence of "flowers", the improvement method is very clear, control the recycled materials, and for the particles that are prone to "flowers", the recycled materials should be mixed with the raw materials and then crushed again; The ring die with guaranteed quality is used to control the smoothness of the die hole. If necessary, the die hole is sanded before use.

In short, for the particles with abnormal appearance in the production of Wood Pellet Machine, several representative manifestations are discussed above, and some abnormal appearance of particles are not listed here because they are not representative. It can be seen from the above discussion that there are many reasons for these phenomena, and they are not completely isolated from each other. This requires us to do more analysis and grasp the key points of the problem when dealing with such problems in actual work. Only then can the problem be solved. Hope this article can help you all.