In the production, sometimes the appearance of abnormal sawdust particles appear, experienced wood pellet mill manufacturers will know what is the reason for this situation and can quickly rule out, for inexperienced or new wood pellet producers , And sometimes can not find the crux of the problem where only the outside world or particle machine manufacturers to help the following seven common abnormal appearance of sawdust particles and the reasons for improvement introduced to you this is the author in the particle machine Development and commissioning of many years of work experience summary for the production of wood pellets for comparison reference.
1, sawdust particles bent and showed many cracks on one side
This phenomenon is usually generated when the sawdust particles leave the ring die.In production, when the cutter position is adjusted away from the surface of the ring mold and the blade is relatively blunt, the particles are easily cut by the cutter when squeezed out of the die hole Or tearing rather than being cut off, at which time some of the wood chips turn to one side and many cracks on the other side. Such wood chips tend to break from these cracks as they enter the cooler for cooling or shipping, resulting in a Wood dust particles too much powder or particles are too short.
Improvements:
a) Increase the compression force of the ring mold on the wood pellets, that is, increase the compression ratio of the ring mold so as to increase the density and hardness value of the pellets;
b) crushed the wood chips of the raw material of sawdust particles more finely so as to increase the solidity of the wood chips and prevent the wood chips from being loose;
c) Adjust the cutter from the surface of the ring mold, the distance between the knife edge and the outer surface of the mold is usually not greater than the diameter of the particle size of the wood particles produced, or replace the use of sharper blade;
2, the horizontal crack across the entire wood particles
This phenomenon is somewhat similar to that of Case 1 in that the cracks occur in the cross-section of the sawdust particles except that the particles are not bent, as is the case when fluffy sawdust containing more fibers is pelleted, Is that when the chips are squeezed into the ring-shaped granulation holes, since the fibers contain fibers longer than the diameter, after the granules are extruded, the granules are caused to cross-crack in the cross-section due to the expansion of the fibers to produce fir bark Shaped sawdust particles appearance.
The improved method is to increase the compression force of the ring mold to the wood pellets, that is, to increase the compression ratio of the ring mold; to control the fineness of the crushing of the fiber, the maximum length of which can not exceed one third of the grain diameter; to reduce the output so as to reduce the passage of the wood pellets Die hole speed, increase the density;
3, sawdust particles produce vertical cracks
Some customers in the production process, due to the type of dryer selection, wood chips can not be evenly dried, resulting in uneven moisture content of raw wood chips, granulated by the ring after the model will be due to the role of water and the material itself The elasticity has bounced off, creating a vertical crack.
The improved approach is: to improve the dryer drying effect, increase the effective length of the die hole.
4, sawdust particles from a source point radiation cracks
The main reason for this is that the sawdust contains relatively large sawdust, and the raw materials with similar degree of fiber will not squeeze each other when they are pelletized. If there are larger fibers, the mutual influence among the fibers He does not soften as easily as other finer materials, and when cooled, causes a difference in shrinkage due to the difference in degree of softening, resulting in radiative cracking.
The improvement lies in properly controlling the thickness and uniformity of the raw materials for the powdered feed, and adding simple sawdust particles with larger size before the granulation.
5, the uneven surface of the pellet
This situation is that the powder used for granulation, containing no crushed or half-crushed large particles of raw materials, because the particles are relatively hard and relatively large, through the die hole when the machine can not be well combined with other raw materials Together, make the particles look rugged.
The improvement is to properly control the thickness of the powdery raw materials.
6, a single particle or individual particle color inconsistencies, commonly known as 'flowers'
This is rare, mainly because the individual particles extruded from the ring die are darker or lighter in color than the other normal particles, or the surface color of the individual particles is inconsistent, thereby affecting the overall appearance quality of the feed. The main reasons are the following aspects:
a) Recycled material with repeated granulation in the granulator to be granulated After the granulated granulated material is cooled and sieved, it can become the finished product, and the sieved fine powder or small granule often goes into the process Re-granulation, usually into the mixer or to be granulated warehouse, as this back is re-granulation, mixing with other raw materials are not uniform or mixed with a return small particles, and sometimes produce 'flowers '.
b) ring die aperture inconsistencies in the inner wall due to inconsistent die hole finish, the particles in the extrusion resistance and extrusion pressure are not the same, the color change is inconsistent.Other ring mold hole wall with burrs, particles Will scratch the surface when extruded, resulting in a different particle surface color.
For the four reasons above listed for producing 'flowers', the improvement is clear and control the return materials. For the granules that are easy to produce 'flowers', the return materials and the raw materials should be mixed and resuspended. The use of quality guaranteed ring die, control die hole finish, if necessary, after the mold hole sanding before use.
In summary, there are several representative forms of particle appearance that occur in the production of sawdust particles, as well as some of the appearance anomalies of particles, which are not representative and are not discussed here. It can be seen that the reasons for these phenomena are manifold and not completely isolated from each other. This requires that when we deal with such problems in practical work, we should analyze more and grasp the key issues in order to solve them The problem is this article can give everyone help.
