Do you know the reason that cause mildew in the feed processing? Keep reading.
1. The pellets are bent and there are many cracks on one side
This phenomenon usually occurs when the pellets leave the ring die. In production, when the position of the cutter is adjusted far away from the surface of the ring die and the blade 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. Many cracks appear to one side and the other. During the process of entering the cooler for cooling or transportation, the pellets tend to break from these cracks, resulting in too much pellet powder produced.
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) Grind the feed material finer. If molasses or fat is added, the uniformity of the molasses or fat should be improved and the amount added should be controlled to improve the compactness of the pellets and prevent the feed from being loose;
c) Adjust the distance between the cutter 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 produced feed pellets, or use a sharper cutter blade, which can also be used for pellets with small diameters. Thin blade and make the thin blade close to the surface of the ring die for production;
d) The use of adhesive granulation aids helps to improve the bonding force inside the granules.
2. Horizontal cracks traverse the entire pellet
Similar to the phenomenon in Case 1, the cracks occurred in the cross-section of the particles, except that the particles were not bent. This can happen when fluffy feeds that contain more fiber are pelleted. This kind of pellets is often when the feed is extruded into the granulation hole of the ring die, because it contains fibers longer than the hole diameter, after the pellets are extruded, the expansion of the fibers causes transverse cracks in the cross section , which produces a fir-bark-like forage appearance.
The way to improve is
Increase the compression force of the ring die on the feed, that is, increase the compression ratio of the ring die;
Control the pulverization fineness of the fiber, and its maximum length cannot exceed one-third of the particle size;
Reduce production to reduce the speed of feed through the die hole and increase the density;
To prolong the conditioning time, use a multi-layer conditioner or a kettle conditioner;
When the moisture content of the powder is too high or contains urea, the appearance of fir bark-like feed may also occur, and the added moisture and urea content should be controlled.
3. The granular material produces vertical cracks
Some feed formulas contain fluffy and slightly elastic raw materials, which will absorb water and expand when they are tempered by a conditioner. Elastic and bouncing, resulting in vertical cracks.
The way to improve is to:
Change the formula, but this may increase the cost of raw materials; control the quality of the steam used in conditioning, try to use more saturated dry steam to minimize the added water; reduce the output or increase the efficiency of the die hole The length of the feed is increased as much as possible in the die hole; the addition of binder also helps to reduce the occurrence of vertical cracks.
4. The granular material produces radial cracks from a source point
This appearance shows that the granular material contains large granular raw materials. When such large granular raw materials are tempered, it is difficult to fully absorb the moisture and heat in the water vapor, and it is not as easy to soften as other finer When the degree of softening is different, the difference in shrinkage is caused, resulting in radiation cracks and an increase in the pulverization rate.
The way to improve is
Properly control the thickness and uniformity of powdered feed raw materials, so that all raw materials can be fully and evenly softened during conditioning.
5. The surface of the granular material is uneven
In this case, the powder used for granulation contains large raw materials that have not been crushed or semi-crushed. Due to insufficient softening during the conditioning process, the particles are relatively hard and relatively large. When the pores are not well combined with other raw materials, the particles appear uneven. Another situation may be that the quenched and tempered raw materials are mixed with steam bubbles. The steam bubbles make the feed produce air bubbles during the process of pressing into pellets. When the pellets are extruded from the ring die, the bubbles burst due to the change of pressure. And uneven phenomenon occurs on the particle surface. This can happen with any feed containing fiber.
The way to improve is
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, steam bubbles are easily mixed, so do not add too much steam to this formula.
6. Whiskers-like granules
When producing pellets, if the amount of steam added is too much, the excess steam will accumulate in the fibers or powders, and when the pellets are extruded from the ring die, the pellets burst due to the sharp change of pressure, and the fibers or pellets will be crushed. The raw material protrudes from the surface, forming a thorn in the whiskers, especially when producing feed with high starch and high fiber content, the more steam is used, the more serious the situation will be.
The way to improve is
Good conditioning. When we pellet the feed with high starch and high fiber content, low pressure steam (0.1-0.2Mpa) should be used so that the water and heat in the steam can be fully released to the feed for absorption. If the steam pressure is too high, or the downstream pipeline behind the pressure reducing valve is too short from the conditioner, generally greater than 4.5m, the steam will not release the water and heat well, so some steam will accumulate. In the conditioned feed material, the whisker-like particle effect described above is caused when pelleting. In a word, special attention should be paid to whether the pressure adjustment of the steam and the installation position of the pressure reducing valve are correct.
7. The color of individual particles or particles is inconsistent, commonly known as "flower material"
This situation is more common in the production of aquatic feed, mainly manifested in that the color of individual pellets extruded from the ring die is darker or lighter than that of other normal pellets, or the surface color of a single pellet is inconsistent, thus affecting the appearance quality of the whole batch of feed. .
The main reasons for this phenomenon are as follows:
a) Due to the complex ingredients of aquatic feed formulations, the variety of raw materials, and the addition of some ingredients is relatively small, when mixing raw materials, if the mixing effect of the mixer is not ideal, it is difficult to ensure that the mixed raw materials entering the granulator are uniform. Therefore, in the process of conditioning and granulation, under the combined action of water, temperature and pressure, the raw materials undergo physical and chemical changes, resulting in inconsistent color changes of raw materials of different components, resulting in "flowers". It is more prominent when the feed formula contains raw materials that are sensitive to changes in temperature and moisture.
b) The moisture content of raw materials used for granulation is inconsistent. In the production process of aquatic feed, in order to make up for the loss of raw material moisture after ultra-fine grinding, a certain amount of water should be added to the mixer, and then mixed into the conditioner for conditioning. Some feed manufacturers have a simpler process, directly pouring a certain amount of water into the mixer instead of using a special nozzle to spray it evenly, so that it is difficult to make the feed evenly distributed after mixing. When this mixed raw material enters the conditioner for conditioning, since the conditioner cannot further distribute the water evenly in a short period of time, under the action of steam, the curing effect of each part of the feed is inconsistent after conditioning, and pelleting The color changes are also inconsistent.
c) There is a return material with repeated granulation in the silo to be granulated. The granulated granules are cooled and sieved before they can become finished materials. The sieved fine powder or small granules often enter the process flow for re-granulation, usually into a mixer or a granulation silo. Since this kind of feed is re-conditioned and granulated, if it is mixed with other raw materials unevenly or mixed with small pellets after conditioning, some feed formulas will sometimes produce "flowers".
d) The inner wall finish of the ring die aperture is inconsistent. Due to the inconsistent finish of the die holes, the resistance and extrusion force of the particles during extrusion are different, and the color changes are inconsistent. In addition, some ring die holes have burrs on the wall, and the particles will scratch the surface during extrusion, resulting in different surface colors of individual particles.
For the above-listed four causes of "flower material", the improvement method has been very clear, mainly to control the mixing uniformity of each component in the formula and the mixing uniformity of the added water; improve the conditioning performance, If necessary, control the tempering temperature, and use a lower tempering temperature to reduce the color change; control the return material. For the formula that is easy to produce "flower material", try not to directly granulate the return material, and the return material and After mixing the raw materials, it is crushed again; a ring die with guaranteed quality is used, the smoothness of the die hole is controlled, and the die hole is sanded before use if necessary.