Causes and improvement methods of abnormal appearance of granular materials

3 Causes of abnormal appearance of pellets and improvement methods In production, pellet feed products sometimes have different degrees of appearance quality defects. The processing defects that often occur in pellet feed are summarized as follows, and the causes of the defects are analyzed, and various improvement measures are proposed.
3.1 The particles are curved and have many cracks on one side
3.1.1 Cause: This phenomenon is usually caused when the particles leave the ring mold. The reasons are as follows: 1 When the knife edge is far from the surface of the ring mold and the pressure roller, or the angle between the cutter plane and the meshing area is unreasonable or the knife edge is blunt, the particles are broken by the cutter when being extruded from the die hole. Or tearing rather than being cut; 2 the decompression hole is too large. These two conditions cause some of the particles to bend and many cracks on one side.
3.1.2 Improvement measures: 1 increase the compression ratio of the ring mold, increase the compression force of the ring mold and the pressure roller on the material; thereby increase the density, hardness and strength of the granular material; 2 increase the fineness of the crushing; 3 if the molasses is added Or grease should control the amount added and improve the uniformity of the distribution of molasses or oil. In order to improve the compactness of the feed, to prevent the feed from becoming soft; 4 to adjust the distance and angle of the cutter from the surface of the ring mold; 5 use a relatively thin cutter (manganese steel sheet with a thickness of 1 to 1.2 mm is better) and in the production process After wear, it should be sharply sharpened in time; 6 if necessary, use binder to improve the bonding force inside the pellet; 7 the difference between the diameter of the decompression hole and the diameter of the effective hole should be controlled at 0.2-0.4mm.
3.2 Horizontal cracks run through the entire particle
3.2.1 Cause: Similar to the appearance of grain bending, the crack occurs on the cross section of the particle, but there is no bending. The main causes are as follows: (1) When fluffy feed granules containing more fibers contain fibers having a longer specific diameter, when the granules are extruded, the granules cause penetrating cracks on the cross-section due to the expansion of the fibers. 2 The quenching and tempering temperature is low or the time is short, the quenching and tempering is insufficient, and the feed maturity is insufficient. 3 The content of the binder raw material is too small. 4 After tempering, the moisture is high.
3.2.2 Improvement measures: 1 increase the compression ratio of the ring mold, increase the compressive force of the ring molding roller on the material; thereby increase the density, hardness and strength of the granular material; 2 increase the fineness of the crushing, so that the length of the fiber is long. Do not exceed one third of the particle size; 3 reduce the yield to reduce the speed of the feed through the die hole and increase the compactness. 4 Improve the quality of quenching and tempering: lengthen the time of quenching and tempering, or use multi-layer conditioner or high-efficiency conditioner. 5 When the moisture content of the powder is too high or contains urea, it may also produce eucalyptus-like cracks, and the added water and urea content should be controlled.
3.3 Particles produce longitudinal cracks
3.3.1 Causes: 1 The formula contains fluffy and slightly elastic raw materials. After quenching and tempering, it will absorb water and swell. After being compressed and granulated by ring mold, it will bounce off due to the action of moisture and the elasticity of the raw materials. Longitudinal crack. The 2-ring mold ratio is too low. 3 The tempering temperature is low or the time is short, the conditioning is not sufficient, and the feed ripening degree is not enough.
3.3.2 Improvements: 1 Adjust the formula if necessary and at the cost of the formula. 2 Use a more saturated dry steam to reduce the moisture after quenching the powder. 3 Reduce the yield or increase the compression ratio, and extend the time of the feed in the ring mold as much as possible; 4 Adding a binder if necessary can also reduce the longitudinal cracking of the particles. 5 Improve the quality of quenching and tempering: lengthen the time of quenching and tempering, or use multi-layer conditioner or high-efficiency conditioner. 6 Increase the post-aging process if necessary.
3.4 Particles produce radiant cracks
3.4.1 Causes This appearance is mainly due to the large particles contained in the particles. When these large particles are tempered, it is difficult to fully absorb the moisture and heat in the water vapor, unlike other finer materials, it is easy to soften. On the other hand, when cooling, the difference in the degree of softening causes a difference in the amount of shrinkage, so that a radiant crack is generated.
3.4.2 Improvement measures: 1 Control the pulverization fineness and particle uniformity of the raw materials. 2 The quenching and tempering is fully uniform, so that the components of the raw materials can be fully and uniformly softened. 3 Reduce the cooling air volume and extend the cooling time. 4 Increase the post-aging process if necessary.
3.5 The surface of the particles is uneven
3.5.1 Causes: The surface of the feed is uneven, which affects the beauty of the feed. When it is fed into the water, the water resistance of each part of the feed is different, and the feed is broken in a short time. The reason is: 1 The granulated powder contains large pulverized raw materials which are not pulverized or semi-crushed, and cannot be sufficiently softened during the quenching and tempering process, and cannot be well combined with other raw materials when passing through the die holes, so that the granules are It looks rugged. 2 The quenched and tempered raw material is mixed with steam bubbles, which cause bubbles to be generated during the process of pressing into the granules. When the granules are extruded into the ring mold, the bubbles are broken due to pressure changes and embossing occurs on the surface of the particles. Uneven phenomenon. This can happen with any fiber-containing feed.
3.5.2 Improvement measures: 1 Properly control the fineness of the powder and improve the quenching and tempering effect so that all the raw materials can be fully softened during quenching and tempering. 2 For raw materials containing more fiber, do not add too much steam to this formulation because it is easy to contain steam bubbles.
3.6 Particles appear as whiskers
3.6.1 Causes If too much steam is added, too much steam is not fully absorbed in the fiber or powder, and when the particles are extruded into the ring mold, the steam bubbles burst due to a sharp change in pressure. The granule raw material protrudes from the surface to form whiskers, especially when producing high starch, high fiber content feed, the steam is used too much, the more serious the situation.
3.6.2 Improvement measures to improve the quality of quenching and tempering. For high starch and high fiber content feeds, low pressure steam (0.1 to 0.2 MPa) should be used. The lower the vapor pressure, the shorter the time to start coagulation, which is beneficial to allow the moisture and heat in the steam to be fully released to the feed. If the steam pressure is too high, the pressurized steam will easily flash when it enters the conditioner. The steam will not condense until the temperature drops to 100 °C. Therefore, some of the steam is accumulated in the tempered feed material, which causes the whisker-like particle effect described above when granulating. In particular, special attention should be paid to the pressure regulation of the steam. Also pay attention to improve the quality of quenching and tempering so that the added steam is fully absorbed by the raw materials.
3.7 Inconsistent color of individual particles or individual particles, commonly known as "flower material"
3.7.1 Causes The uneven color of the feed makes it easy for farmers to doubt the quality of the product. In general, uneven color of the feed is associated with ripening and mixing and conditioning processes. Insufficient particle size of the raw material can easily lead to uneven mixing of the raw materials, thereby affecting the degree of ripening of different parts of the feed pellet. In addition, factors such as excessive temperature and particle size during the curing process may also affect the color of the feed particles. The main performance is that the color of the individual particles extruded from the ring die is darker or lighter than the color of other normal particles, or the surface color of the individual particles is inconsistent, thereby affecting the appearance quality of the whole batch of feed. In general, the main reasons are: 1 the composition of the feed complex is complex, the variety of raw materials; 1 uneven mixing; 3 uneven quenching, the moisture content of the powder before granulation is inconsistent; the amount of recycled material of the 4 replicates Large; 5 ring die hole inner wall roughness, die roll gap, die roll wear amount is inconsistent, the ring mold is uneven, etc., resulting in uneven ring die discharge; 6 crushing fineness does not meet the requirements; 7 powder in the silo There is a grading phenomenon.
3.7.2 Improvement measures: 1 Improve mixing effect; 2 Improve quenching and tempering quality: lengthen quenching and tempering time, use multi-layer conditioner or high-efficiency conditioner, extend quenching and tempering time; 3 control fineness and uniformity of powder; 4 The amount of machine material added back, the added material must be mixed; 5 trim or replace the ring mold, pressure roller; 6 adjust the mold roll gap to the good position, and make all the gaps consistent.
3.8 poor particle water resistance
3.8.1 Causes The water resistance of the feed refers to the ability of the feed to resist corrosion in water, usually expressed by the dissolution rate of the feed in water under specified conditions. The national standard stipulates that the water resistance of shrimp feed should reach 30 min. Poor water resistance of the feed can cause the feed to dissolve in the water before it is eaten, causing waste of feed and contaminating the water. The reasons for the poor water resistance of the particles are as follows: 1 The quenching time is short, the quenching and tempering temperature is low, and the quenching and tempering is insufficient, the temperature is low, the maturation is insufficient, and the moisture is insufficient. 2 The content of cohesive raw materials such as starch is insufficient. The compression ratio of the 3 ring mode is too low. 4 The fat content is too high or the crude fiber content is too high. 5 crushing fineness is not enough.
3.8.2 Improvement measures: 1 Increase the moisture content of the raw materials, adjust the angle of the pulp to prolong the quenching and tempering time, and increase the quenching and tempering steam. 2 Add steam to the conditioner layer and heat it, if necessary, increase the post-aging stabilization equipment. 3 adjust the formula to increase the starch content, reduce the content of fat, crude fiber; add a binder if necessary. 4 Increase the compression ratio of the ring mold and increase the fineness of the crushing.
3.9 Granules containing more powder
3.9.1 Farmers often complain about excessive feed in the feed. There are three reasons for the powder: 1 because the surface of the feed pellet is not smooth, the particles are loose, the slit is not neat, etc. The feed is easy to be powdered during transportation; 2 the graded sieve powder is blocked, and the powder produced by granulation cooling is not Screen out. 3 The material in the finished product warehouse is funnel-type blanking. The fluidity of the granular material will be first, the fluidity of the powder will be accumulated poorly, and will collapse when it is certain. The collapsed granular material contains particularly high powder. If you do not pay attention to check the material when picking up the material, it will cause a few batches of powder in the batch to be particularly heavy.
3.9.2 Improvement measures:
1 For the reasons that the surface of the feed pellet is not smooth, the particles are loose, the slit is not neat, etc., the following powder may be taken as follows: according to the characteristics of the raw material and the particle requirement, the appropriate ring die opening area, compression ratio and feed amount are selected; When designing the formula, consider the influence of particle pulverization to reduce the content of fat and fiber, increase the starch content, improve the quality of quenching and tempering by increasing the time of quenching and tempering, increasing the moisture and temperature of the tempering, and improve the degree of ripening of the feed; Adjust or sharpen the cutter to make the grain cuts neat.
2 Clean or overhaul the grading screen.
3 In the process of receiving the material, pay attention to check the powder content of the feed; re-screen the material with the powder rate and exceeding the standard; for the fish material and other powdery materials with strict requirements, if necessary, under the finished product warehouse, the material is called Add a vibrating screen to the second screening of the feed.
3.10 Particles vary in length
3.10.1 Feed pellets of varying lengths affect the overall appearance of the feed and may also result in insufficient feed utilization by the animal and waste. The reasons for the uneven length of the particles are:
1 The material distribution in the granulation chamber is uneven at the same time;
2 The feeding amount of the granulator is not uniform, and the quenching and tempering effect fluctuates greatly;
3 die roll gap is inconsistent;
4 pressure roller wear is inconsistent;
5 The wear amount of the ring guide port is inconsistent along the axial direction or there are more holes blocked on the ring die;
6 along the axial direction of the ring mold, the discharge speed at both ends is less than the intermediate speed.
7 When designing the ring die, the pressure reduction hole is too large compared with the effective hole, and some particles are broken in the pressure reduction hole; the ring die of small particle size is particularly prone to unevenness of the particle length due to the length of the pressure reduction hole.
8 The position or angle of the cutter is not reasonable.
3.10.2 Improvement measures:
1 Adjust the length, width or angle of the fabric scraper.
2 When the production is just started and the production is finished, the feeding amount is small and uneven, which leads to the short length of the particles, and if it is required to be high, it must be taken out. In the production process, the feed volume and steam quenching should be kept stable. The number of cutters to be input should be matched with the output. If necessary, the yield should be sacrificed to obtain a suitable pellet length.
3 Adjust the pressure roller adjustment screw to make the gap of each die roll consistent.
4 The new ring mold should be equipped with a new pressure roller. The wear amount of each pressure roller in use should be consistent; if the axial wear of the pressure roller and the ring mold is inconsistent, the high place should be polished if necessary.
5 Repair the guide port of the ring die; clean it in time, and block the hole on the ring die.
6 When designing the ring die, along the axial direction of the ring die, the compression ratio of the three rows of holes at both ends can be 1 to 2 mm smaller than the middle (according to the formulation and particle size).
7 In the design of the ring mold, the product with strict requirements on the length of the particles, for example, the difference between the effective hole diameter of the fish material and the diameter of the reduced pressure hole should be controlled within the range of 0.2 to 0.4 mm.
8 The thickness of the cutter is controlled within 1.5mm, the cutting edge is sharp, the cutting edge is located on the meshing line of the pressing roller and the ring die, and the cutting plane is tilted by 3 to 5 degrees on the tangent line of the engaging surface of the pressing roller ring die.
9 Regularly check the coaxiality between the ring mold and the granulator. When the standard exceeds the standard, the ring mold should be repaired, the main bearing clearance should be adjusted, or the main shaft and the hollow shaft bearing should be replaced.
3.11 The finished product is too moist
3.11.1 Cause: The moisture content of the feed pellets is too high, which is not conducive to the storage of the feed and is prone to mildew fermentation. The reasons for the excessive moisture of the pellets are:
1 The raw material moisture is too high.
2 The steam saturation is not enough, and the moisture is too high after quenching and tempering.
3 quenching and tempering temperature is too low.
4 drying or cooling time is not enough.
5 Drying or cooling equipment has insufficient capacity or malfunction.
6 low ambient temperature and high relative humidity.
3.11.2 Improvement measures: 1 control raw material moisture in summer 12% ~ 14%, winter 10% ~ 12%. 2 After quenching and tempering, the moisture is controlled at 15% to 17%, and the winter is taken off the line; the temperature of the quenching and tempering is controlled, especially the temperature of the winter quenching and tempering is controlled above 80 °C. 3 increase the saturation of the steam. 4 Extend the drying or cooling time. 5 Control the granulator output to match the dryer or cooler capacity. 6 Check if there is a short circuit or blockage in the cooling air network; check whether the fabric and the material of the cooler are even. 7 In the winter, the cooler is insulated or a steam coil is added to heat the cooling air.

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