In the production of pellets for pellet mills, sometimes there will be pellets with abnormal appearance. Experienced manufacturers will know what is the cause of this situation. Northeast feed machinery can quickly eliminate them. For lack of experience or new For manufacturers, sometimes they can’t find the crux of the problem, and only ask the outside world or the granulator manufacturer for help. In the following, we will introduce the causes and improvement methods of seven common granular materials with abnormal appearance. This is a summary of the author's years of experience in the development and debugging of granulators for comparison and reference in production.

　　 1. The granular material is bent and there are many cracks on one side

　　 This phenomenon usually occurs when the pellets leave the ring die. In production, when the cutter position is adjusted far away from the surface of the ring die and the knife edge is blunt, the pellets are broken or torn by the cutter instead of being cut when they are extruded from the die hole. At this time, some pellets are bent. There are many cracks on one side and the other. When this kind of granular material enters the cooler for cooling or transportation, it will often break from these cracks, resulting in too much granular powder produced.

　　 Improvement method:

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

　　B) Crush the raw materials to be finer. If molasses or fat is added, the uniformity of the molasses or fat should be improved and the added amount should be controlled to increase the compactness of the pellets and prevent the feed from being soft;

c) Adjust the distance between the cutting knife and the surface of the ring die. Generally, the distance between the knife edge and the outer surface of the ring die is not greater than the diameter of the particles produced, or replace with a sharper cutting blade. For small diameter particles, thinner Blade, and make the thin blade close to the surface of the ring die;

　　D) The use of adhesive granulation aids helps to improve the binding force inside the granules.

　　2, the horizontal crack crosses the entire pellet

　　 is somewhat similar to the phenomenon in case 1, the crack occurs in the cross section of the particle, but the particle is not bent. This can happen when the fluffy pellets containing more fiber are granulated. This kind of pellets is often used to squeeze the feed into the pelletizing holes of the ring die. Because it contains fibers longer than the aperture, when the pellets are extruded, the pellets will have transverse cracks on the cross section due to the expansion of the fibers. , Resulting in a fir-bark-like appearance.

The improvement method is to increase the compression force of the ring die on the raw material, that is, to increase the compression ratio of the ring die; to control the fineness of the fiber pulverization, the maximum length cannot exceed one third of the particle size; to reduce the output to reduce the raw material passing through the die hole Increase the compactness at the speed of time; lengthen the conditioning time, use a multi-layer conditioner or a kettle-type conditioner; when the powder has too high moisture or contains urea, it may also produce a fir-bark-like raw material appearance , The added water and urea content should be controlled.

3. Vertical cracks in the granular material

Some feed formulations contain fluffy and slightly elastic raw materials. This raw material will absorb water and expand when it is tempered by a conditioner. After being compressed and pelletized by a ring die, it will be affected by the effect of water and the raw material itself. It bounced off elastically, producing vertical cracks.

The improvement methods are: change the formula, but doing so may increase the cost of raw materials; control the quality of steam used in tempering, try to use more saturated dry steam, so as to minimize the added water content; reduce the output or Increase the effective length of the die hole to increase the time the feed stays in the die hole as much as possible; adding a binder can also help reduce the occurrence of vertical cracks.

　　4, the granular material produces radiation cracks from a source point

This appearance shows that the granular material contains large granular raw materials. When these large granular raw materials are tempered, it is difficult to fully absorb the water and heat in the steam, and they are not as easy to soften as other finer raw materials. When the degree of softening is different, the shrinkage is different, so that radiation cracks are generated, which increases the powdering rate.

　　The improvement method is to properly control the thickness and uniformity of the powdered feed ingredients, so that all the raw materials can be fully and uniformly softened during conditioning.

　　5, the surface of the granular material is uneven

This situation lies in the fact that the powder used for granulation contains large-grain raw materials that have not been crushed or semi-crushed. Due to the insufficient softening during the quenching and tempering process, the particles are relatively hard and relatively large. When holes are formed, they cannot be well combined with other materials, making the particles appear uneven. Another situation may be that steam bubbles are mixed in the quenched and tempered raw materials. The steam bubbles cause air bubbles in the process of pressing the feed into pellets. When the pellets are extruded out of the ring die, the bubbles burst due to pressure changes. However, unevenness occurs on the surface of the particles. This can happen to any feed that contains fiber.

The improvement method is to properly control the thickness of the powdered feed, so that all raw materials can be fully softened during conditioning; for raw materials with more fiber, they are easy to be mixed with steam bubbles, so do not add too much to this formula Steam.

　　 6, whisker-like granular material

When producing pellets, if the amount of steam added is too much, too much steam will be stored in the fiber or powder. When the pellets are extruded from the ring die, the pellets burst due to the rapid change in pressure and the fibers or pellets The raw material protrudes out of the surface to form pierced whiskers. Especially when producing high starch and high fiber content feed, the more steam is used, the more serious the situation.

　　The way to improve lies in good tempering. When we pellet feeds with high starch and high fiber content, we should use (0.1-0.2Mpa) low-pressure steam so that the water and heat in the steam can be fully released for the feed to absorb. If the steam pressure is too high, or the downstream pipeline behind the pressure reducing valve is too short to the conditioner, generally greater than 4.5m, the steam will inevitably not release its moisture and heat well, so some steam will accumulate In the conditioned feed ingredients, the whisker-like particle effect mentioned above is caused when pelleting. In short, special attention should be paid to the steam pressure regulation and the installation position of the pressure reducing valve.

　　7, the color of individual particles or particles is inconsistent, commonly known as "flower material"

This kind of situation is more common in the production of aquatic feed. It is mainly manifested as the color of individual pellets extruded from the ring die is darker or lighter than other normal pellets, or the surface color of individual pellets is inconsistent, which affects the appearance quality of the entire batch of feed . The main reasons for this phenomenon are as follows:

a) Due to the complex composition of the aquatic feed formula, the variety of raw materials, and the small addition of some ingredients, it is difficult to ensure that the mixed raw materials entering the granulator are uniform when the mixing effect of the mixer is not ideal when the raw materials are mixed. Therefore, in the process of conditioning and granulation, under the combined action of moisture, temperature and pressure, the raw materials undergo physical and chemical changes, resulting in inconsistent color changes of the raw materials of different components, resulting in "flower material". It is more prominent when the feed formula contains raw materials that are more sensitive to changes in temperature and moisture.

　　B) The water content of the raw materials used for granulation is inconsistent. In the aquatic feed production process, in order to make up for the loss of raw material moisture after ultrafine pulverization, a certain amount of water must be added to the mixer, and then enter the conditioner for conditioning after mixing. Some feed manufacturers have simpler processes, and directly pour a certain amount of water into the mixer instead of spraying it evenly with a special nozzle. This makes it difficult to distribute the water evenly after the feed is mixed. When this mixed raw material enters the conditioner for conditioning, it is impossible for the conditioner to further distribute the water evenly in a short time. Under the action of steam, the maturation effect of each part of the feed is inconsistent after conditioning, and pelleting The color change is also inconsistent.