Quenching and tempering is a processing procedure for hydrothermal treatment of powdered materials before granulation of pellets. Domestic and foreign studies have shown that quenching and tempering is one of the important factors affecting the quality of pelleted feed. Its role in the overall quality of pelleted feed is About 20%. With the improvement of the quality requirements of pellet feed in the market, various feed processing enterprises are paying more and more attention to the quenching and tempering process in feed processing. Improving the upgrading and quenching and tempering equipment is an important means for them to improve the quality of pellet feed products and improve market competitiveness. one.
First, the role of the conditioner in the processing of pellet feed 1. The powdered material is matured. Most animals have low ability to digest starch, but can digest ripe starch to a large extent. The conditioner adjusts the gelatinization degree of the starch under the action of hydrothermal, and also promotes the thermal denaturation of the protein in the material. Denatured proteins are easily digested, thereby increasing the digestion efficiency of the pellet feed.
2. Sterilize the powdered material. Most of the pathogenic bacteria are harmful bacteria such as Escherichia coli and Salmonella, which are not heat-resistant. The use of a conditioner to temper the material at a certain temperature can kill these germs and ensure the feed hygiene level. The method of sterilizing materials has the advantages of low cost, no pollution, no drug residues and side effects compared with drug prevention.
3. The quenching and tempering equipment can significantly improve the water resistance of the pellet feed. In the process of quenching and tempering, by the hydrothermal action of steam, the viscous component of the material can be gelatinized starch and denatured protein can fully exert the role of the binder, which can effectively Bonding the other components in the periphery, under the action of the compression of the stamper, the particles and particles are more closely combined with each other, so that the pellet feed becomes more dense, the appearance is smooth, and it is not easily eroded by water during the feeding process. Increased stability in water.
4. The quenching and tempering equipment can improve the granulating property of the material, increase the output, save the energy consumption of the granulation, and improve the life of the granulator die and the pressure roller. Through quenching and tempering, the material is softened and more malleable. During the extrusion process with the die wall, the inner wall of the die and the outer surface of the press roll, the frictional force is reduced, and a large amount of mechanical energy is converted into heat energy during the granulation process. At the same time, the wear of the stamper and the press roll is slowed down.
Second, the type and working principle of the conditioner 1. Single-axis paddle conditioner This type of conditioner is the earliest and most widely used conditioner in feed processing at home and abroad. Its structure is relatively simple, its cylindrical type A stirring shaft is arranged in the middle of the casing, and a plurality of blades that can be adjusted and replaced are installed on the stirring shaft. When the conditioner is working, the powder particles move in two directions under the agitation of the blade, one is to rotate around the axis, and the other is to move along the axial direction, and the motion trajectory is similar to the spiral. The speed of the general conditioner is 150-450r/min. The propulsion speed of the material is related to the shaft speed and the picking angle of the blade. Under the condition of constant speed, the material can be controlled by adjusting the picking angle of the blade. If the angle of the blade is reduced to the middle position, that is, the angle between the blade and the blade axis is 750-850, so that the pushing effect of each blade on the material can be weakened, thereby prolonging the retention of the material in the conditioning chamber. time. Generally, the single-axis paddle conditioner is 2-3 meters long. The powder can stay in the quenching chamber for 20-30 seconds, and the ripening degree is about 20%, which can basically meet the quenching and tempering requirements of some ordinary pellet feeds.
2. Steam jacketed conditioner The general structure of this type of conditioner is similar to that of the single-shaft paddle conditioner. The difference is that the shell adopts double-layer jacket, and the steam inside the jacket is used for heat preservation. This steam jacket conditioner has limited heating effect on the powder during work, because the heat is only transmitted to the powder through the surface of the conditioner, and the ratio of surface area to capacity is usually low, and the general quenching and tempering The thermal conductivity of the powder is so poor that there is not much heat that can be transferred to the powder, but the steam jacket prevents the heat exchange between the conditioning chamber and the outdoor ambient temperature, effectively reducing heat loss and keeping the inside of the conditioner Higher temperatures, so the use of this conditioner in colder winters and lower temperatures is more significant.
3. Two-way and three-way conditioners In order to extend and control the residence time of the powder in the conditioner, 2-3 standard single-axis paddle conditioners are superimposed on the top of the granulator. Said two-way, three-way multi-layer conditioner. The tempering device is characterized by being connected in series with each other and having multiple steam injection ports. During operation, the powder passes through the respective tempering devices in sequence, which prolongs the quenching and tempering time of the powder, and the material and the steam can be more fully contacted and mixed, and the powder can be mixed. The degree of ripening has increased to about 40%.
4. Two-axis differential differential paddle conditioner The two-axis differential differential paddle conditioner is also called DDC pre-conditioner. It is developed on the basis of single-axis paddle conditioner. The casing is welded by two large semicircles with different radii. The casing is provided with two blade agitating shafts with different rotational speeds. The middle part of the casing is provided with a plurality of steam injection ports and liquid adding ports which can individually adjust the amount of steam. During operation, due to the unequal rotation speed of the two shafts, the opposite direction of rotation, and the differential movement of the blades, the powder and the additive liquid are thrown up from the middle of the two agitation shafts and form convection together with the steam, and fully sheared and interlaced. Under the action of the blade, the local motion trajectory is “8†shape, and it is propelled around the axis to advance, and the movement path is greatly increased, so the axial movement speed of the powder has a larger adjustable range. Generally, the conditioner is about 2 meters long. The quenching and tempering time can be controlled from tens of seconds to 240 seconds. It can meet the requirements of high aging rate and high sterilization rate of special pellets. The degree of ripening is usually 50-60%. The higher relative motion of the blades can "wash" each other, which makes this type of conditioner have a higher self-cleaning ability, and the residual phenomenon of the powder in the conditioning chamber is also improved.
5, expander expander also known as EXPANDER, also known as the ring gap extruder in China, its working principle is the same as the extruder, both use mechanical energy to increase the heat added to the powder before granulation. The powder is forced to pass through the narrow gap between the screw and the die under pressure, resulting in compaction and shearing, intense friction with the screw and the cylinder, and a large amount of heat to achieve ripening, sterilization and Improve the purpose of granulation. The difference lies in the adjustable die gap of the expander. During the work, the die gap can be adjusted to control the extrusion, friction and shear strength of the powder in the tempering chamber, thereby controlling the heat diffused into the powder. Generally, the expander can generate a pressure of 40 Pa for the material and a temperature of 120 ° C - 130 ° C. The material stays under these conditions for 3 to 5 seconds, and physical changes occur very quickly, so that the starch gelatinization degree of the material and the protein are soluble. The degree is significantly improved, however, the heat-sensitive nutrients in the material are also greatly lost in this high temperature process.
6. General particle curing machine Universal particle curing machine, UniversalPelletCooker, referred to as UPC, is a new type of quenching and granulating equipment first proposed by the Wenger manufacturing plant in the United States. This system is basically composed of an efficient conditioner and a short residence time. A combination of improved extruders. During operation, the conditioner provides retention and contact time to optimize the quality of the feed, while the improved extruder forces the powder through a die of appropriate size to form a pellet feed. The starch gelatinization level of this equipment is quite high, generally more than 70%. The quality of the feed pellets is excellent and the water resistance is durable. Even if more than 10% fat is added to the powder, the quality of the pelletized pellets produced is still acceptable. Another feature of this system is that it is very simple and convenient to replace the stamper. At present, this kind of quenching and granulating equipment has broad application prospects in aquatic feed, young animal feed and pet feed.
In addition to the above-mentioned conditioner, there is a pressure regulator. The basic concept is to increase the working pressure of the quenching chamber, so that the temperature also rises. The high pressure can force the moisture and heat to enter the powder particles more quickly and thoroughly. Thereby improving the conditioning effect.
There are also quenching tanks, etc., which will not be described in detail here.
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Third, the choice of commonly used conditioners General ordinary livestock and poultry feed mills can choose a single-axis blade-type conditioner, to ensure 30 seconds of quenching and tempering time, can make starch gelatinization degree of about 20%, basically meet the common animals The processing requirements for poultry feed; the aquatic feed mill should use secondary or tertiary regulators or dual-shaft differential differential paddle conditioners to ensure that the maturity of the tempering feed reaches 50% or more.
Expander is also known as super conditioner. Expanding soybean and corn with expander can improve the palatability and digestibility of feed, and change the antigenic substance and anti-nutritional factor in feed. It can also be used with expander and granulator. Secondary granulation is carried out to form a short-term high temperature by the strong extrusion and shearing of the screw through the expander through the screw and the die, which promotes the gelatinization of the starch and improves the quality of the granules; some feed enterprises directly use the expander to produce the suckling pigs. Sheet and feed such as broiler feed, comprehensive nutrition, good palatability, and a large market space.
Fourth, the correct use of the blade-type conditioner The current most commonly used grain conditioner is the uniaxial blade-type conditioner and the dual-axis differential-speed blade-type conditioner. The following are discussed in several aspects. Talk about the problems that these conditioners should pay attention to when using them.
1. Steam pressure and added amount control steam is the source of moisture and heat during quenching and tempering. Therefore, the quality of the slurry directly affects the effect of quenching and tempering. The blade-type conditioner must be designed with reasonable design of the steam line. The use of stable and reliable steam pressure reducing valve and steam trap ensures that the pressure regulator is dry saturated steam entering the conditioner; the steam should enter the conditioner from the tangential line and be sprayed in the axial direction to make it more strongly mixed with the powder; steam direction It is not possible to face the tempering shaft vertically, which not only does not achieve a good mixing effect, but instead causes the steam to "cavigate" the modulator shaft and cut the tempering shaft. When quenching and tempering, select the appropriate steam pressure and addition amount according to the change of raw materials, formula and climate. When the humidity is high and the moisture content of the raw material is high, the steam pressure should be appropriately increased to reduce the steam addition amount; when the drying season and the moisture content of the raw material are low, Reduce steam pressure and increase steam addition; higher room temperature in summer can reduce steam pressure, because low pressure steam releases heat and moisture more quickly; low temperature in winter can increase steam pressure, enhance quenching and tempering temperature, and reduce condensate in steam pipeline. Helps the ripening of the powder.
2. Control of quenching and tempering time (1) Control of quenching and tempering time of single-axis blade-type conditioners Generally, the single-stage paddle-type conditioner has short tempering time, which can reduce the agitation shaft speed and change the blade angle. The way to increase the conditioning time. The drive motor of the agitation shaft is controlled by a frequency converter or an electromagnetic governor. The adjustment of the blade is recommended at the feed port (ie, the modulator blade axis is from the start end to the rear 1/4 or 1/3). The leaves are kept at the factory setting, which ensures that the powder is quickly driven forward into the conditioning chamber; the adjustment of the blade angle should begin 1/3 of the length of the modulator, for a single-axis paddle conditioner It is not slower, the more the blade angle is perpendicular to the agitation axis, so that although the quenching and tempering time is increased, the too slow rotation speed and the blade which is almost perpendicular to the agitation axis are not enough to throw the powder, so that the powder will be deposited. At the bottom of the tempering chamber, it is gently pushed through the tempering chamber. When the steam is tempered, the upper part flows freely without strong mixing with the powder. The effect is poor, and because the moving speed of the powder is too low, it is easier to adjust. The retaining wall is formed around the chamber of the chamber, so the speed of the general single-axis blade-type conditioner should not be lower than 150r/min, and the minimum is not lower than 100r/min. The production process of controlling the speed with the inverter or electromagnetic governor Medium, the conditioner is also not suitable for working at an ultra-low speed for a long time. under.
(2) Control of quenching and tempering time of biaxial different-path differential paddle conditioner This kind of tempering device can adjust the tempering time in tens of seconds to 240 seconds by adjusting the blade angle alone, so In general work, it is not necessary to change the rotation speed of the blade shaft. The adjustment of the blade angle can be started from the blade of the upper third of the length of the conditioner at the inlet. If the quenching and tempering time is increased, the large diameter and low speed can be increased. The angle between the positive blade and the blade axis. Although the double-axis different-diameter blade-type conditioner has improved the sticking-staying phenomenon, some materials retain the wall retention phenomenon. In this case, the clip of the small-diameter high-speed counter-pulp blade and the stirring shaft can be appropriately reduced. The angle, in order to increase the reverse turbulence of the anti-slurry blades against the powder, reducing the amount of residue.
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