Quenching and tempering is an important part of feed granulation and puffing process. Since the advent of feed granulator and feed puffing machine, feed quenching and tempering technology and equipment have been continuously developed, especially the rapid development of domestic and international aquaculture in the past 20 years. Due to the special demand for water resistance of aquatic feeds, the development of feed quenching and tempering technology and equipment has grown by leaps and bounds. In order to better understand the impact of feed conditioning on the quality of finished products, some discussions have been held on the process and equipment for feed conditioning.
1 The purpose of feed conditioning and quenching and tempering mechanism Feed quenching and tempering is one of the feed ripening process, which converts the raw meal into a powder with a certain degree of maturity. The feed is well tempered and the equipment is beneficial to feed granulation and puffing. .
1.1 The purpose of feed quenching and tempering 1.1.1 Conducive to feed granulation molding makes the feed easy to granulate and reduce the pulverization rate of granulation.
1.1.2 Increasing the digestion and absorption rate of feed can increase the digestion and absorption rate of protein and starch components by 10%~12%.
1.1.3 Increasing the stability of aquatic pellets in water improves the gelatinization degree of starch, so that the stability of pellet feed in water can reach 30min, up to 3~6h, and its stability mainly depends on formula and quenching and tempering. performance. Of course, the granulation process also helps to improve the stability of the water.
1.1.4 Increase the output of the granulator, reduce the power consumption and increase the output of the granulator by 25%~50%.
1.1.5 Reduce the wear of the stamper and press roller The life of the stamper and press roller is extended by 30%~50%.
1.1.6 Destroy and kill harmful factors by 20%~60%.
1.1.7 Two or three liquid components can be added during the quenching and tempering process.
Since the quenching and tempering process is that the feed is treated with heat and mass (moisture) steam for a certain period of time, the high temperature steam will have different degrees of loss to the heat sensitive component of the feed. How to reduce the loss of heat-sensitive components and to make the feed have good quality control effect has not been solved yet, indicating that in the feed conditioning and heat-sensitive components and the addition process, Many topics need to be studied together to improve. The following analysis and discussion on the feed conditioning equipment are for reference.
1.2 The mechanism of quenching and tempering and the process of quenching and tempering Feed quenching and tempering is the process of heat treatment of feed water. The feed conditioning is actually the heat and quality of the gas phase (steam), liquid phase (fine water-dispersed water droplets) to the solid phase (powder material) The process of transferring heat and mass. Steam is both a heat transfer body and a moisture transfer body during the quenching and tempering process of the feed. Moreover, the heat and quality of the feed are constantly changing during the quenching and tempering process, and the quenching and tempering is also a process in which the heat and mass in the steam are transferred to the inside through the outer surface of the powdery particulate material.
The quenching and tempering of the powdery material is a process in which the steam uniformly surrounds the periphery of the powdery material and forms an interface layer near the surface of the particulate material. The heat transfer and mass transfer rate of the quenching and tempering process is determined by factors such as temperature gradient, velocity gradient, humidity gradient, material properties (density, particle size, water content) of the interior and interface layers of the steam and powdery particulate materials.
When the solid phase powdery material with low temperature and low water content enters the conditioner with a certain speed, the steam pressure is reduced from 200~400kpa to normal pressure, and the steam temperature is reduced from 142.9~158°C to 100°C. The tempering and aging of the raw meal. The key to material ripening is the quality of the steam (referring to the steam moisture content and the enthalpy value), because the steam is divided into wet steam, saturated steam (dry steam), superheated steam (see Figure 1). The difference between the three is that the enthalpy (kJ/kg) and temperature are different. The wet steam has a lower enthalpy value, and the wet steam and saturated steam (dry steam) have the same temperature (100 ° C), but the saturated steam enthalpy is higher than the wet steam. The enthalpy and temperature of superheated steam are higher than the former two. Wet steam is a mixture of water (finely dispersed water droplets) and steam. If the heating amount is continued, the enthalpy value increases and the steam temperature does not rise. The heat energy supplies the heat energy (vaporization latent heat) vaporized by the finely dispersed water droplets. The more the heat energy is supplied, the higher the enthalpy value and the lower the water content of the steam. The higher the steam content. The degree of steam content is the saturation (dryness) of the steam. For example, the saturation (dryness) of steam x = 0.8 indicates that 80% is steam and 20% is finely dispersed water droplets. At normal pressure, the steam content reaches 100%, that is, at a saturation temperature of 100 ° C, the steam becomes steam containing no water, which is saturated steam. As the saturated steam continues to be heated, the enthalpy and temperature of the saturated steam continue to increase, which becomes superheated steam, which is the quality of the steam required for granulation. If the vapor pressure increases with the increase of steam pressure, the required temperature of wet steam, saturated steam and superheated steam will also increase accordingly (see Figure 1 for the upward shift).
High temperature superheated steam, high enthalpy value, high heat, no water, superheated steam enters the conditioner and the pressure drops from 200~400kpa to normal pressure. After the temperature drops from 142.9~158°C to 100°C, it is converted into saturated steam or wet. steam. At the same time, the steam releases heat, and the saturation of the saturated steam gradually decreases. The water content in the saturated steam gradually increases and continues to release heat, but the steam temperature remains at 100 °C. At this time, the hot steam and the cold solid phase powdery material meet because there is a temperature gradient (temperature difference) and a humidity gradient (humidity difference) between the hot steam and the powdery material. Therefore, between the hot steam and the cold solid phase powdery material, both heat transfer and mass (moisture) transfer, the difference between the hot steam and the solid phase powdery material, is the heat and mass transfer. driving force. The quenching and tempering process is a process in which the heat and mass of the steam are simultaneously transferred to the inside through the outer surface of the powdery material. Moreover, the amount of heat and mass between the hot steam and the powdered material is balanced during the transfer (the temperature of the air inside the conditioner is raised and the heat emitted by the conditioner cylinder). During the heat transfer and mass transfer process, the heat of the steam is released, so that the temperature of the powdery material rises to the temperature required for quenching and tempering (granulation 80-85 ° C, puffing over 95 ° C), the saturation of saturated steam continues to decrease, saturated steam The gradually increasing water content. When the quenching temperature of the powdery material commonly used in the conditioner is 80-85 ° C and the saturation of the steam (dryness) X = 0.6-0.9, under this condition, it is generally considered that the powdery material is raised by 11 ° C, Its moisture increased by 1%. After the powdery material is absorbed or added with water, the water content required for granulation and puffing (17%~18% granulation, 28%~30% puffing). In order to ensure that the granulation requires low moisture, it is reasonable to use superheated steam. For example, it is easy to precipitate excessive moisture by using wet steam, which affects granulation. It is advisable to use saturated steam or lower superheated steam with a higher saturation (dryness) for steam supply, so that the powdery granular material can obtain more water and obtain higher temperature, which is in line with the material. The requirements for puffing. The granulator in the structure should be insulated and insulated, and the puffing and tempering device can be treated without heat insulation.
The goal and requirements of quenching and tempering: The feed powder is softened by the action of water and heat during the quenching and tempering process. The softening and softening requirement is that the softening of the center of the granular material is optimal, which is the goal and requirement of quenching and tempering.
During the quenching and tempering process, the partial pressure of water vapor in the steam is higher than the partial pressure of water vapor on the surface of the powdered granular material. For this reason, the surface of the powdery granular material continuously absorbs the moisture in the water vapor (see Figure 2, from 1 to 4 for the material). The process of absorbing water). At this time, the surface moisture of the powdery material is higher than the internal moisture of the material (ie, the humidity gradient). For this reason, there is a moisture pressure difference between the surface moisture and the internal moisture of the material, and follows the law that the region where the water pressure is high flows to the region where the water pressure is low. Therefore, the powdery particulate material not only adsorbs moisture on the surface but also transfers to the inside.
The powdery granular material significantly increases the velocity gradient of the steam flow on the surface of the material particles and the surface at different positions of the particles under the striking and turning of the conditioner. Due to the different velocity gradients at different parts of the surface of the material particles, the temperature gradient and humidity gradient on the surface of the material particles are increased. Therefore, the heat transfer and mass transfer process between the steam and the material and between the material surface and the material interior is accelerated. At the same time, the plate has a certain amount of extrusion on the material particles, which increases the transfer of moisture to the inside of the particles. In addition to the partial pressure of water vapor, the rate of moisture transfer is also related to the size of the particles, the particle density, the particle state and the speed of the conditioner. If the tempering speed is high, the powder particles are fiercely turned, the speed gradient is increased more, and the steam and material contact uniformity is good. The impact force is large, the steam and the powder particles are in full contact, the water is transferred to the inside of the particles quickly, and the amount of water added can also be increased. The transfer of moisture is referred to as the internal diffusion of moisture, which causes the powdery particulate material to increase moisture. The increased moisture is physicochemical combined with water and mechanically bound water (free water is also called free water). When the material is tempered at 18%, the physicochemical combined water (permeate combined with water) is powdery particles that increase moisture. main body. In addition, there is a part of the steam water droplets adsorbed on the surface of the powdery particles to form mechanically bound water (free water, free water). The original chemically bound water (crystal water) of the powdery particles combined with the physical and chemical combination of water and physico-chemically combined water, becomes the equilibrium moisture of the powdery granular material at this temperature and relative humidity (see Figure 3). The equilibrium moisture changes with temperature and relative humidity. The equilibrium moisture of the powdery material decreases with increasing temperature and increases with increasing relative humidity. Since the physical and chemical combination of the material and the mechanically bound water of the appropriate amount of surface (free water, ie 2% to 3% of free water) is very advantageous for granulation, a good granulation effect can be obtained. The powdery granular material is combined with the high temperature and moisture in the conditioner, and after a proper time of quenching and tempering, starch gelatinization, protein denaturation, harmful factors are destroyed and inactivated, and the powdery granular material is softened to reach A preferred granulation effect. It can be said that feed quenching and tempering is a very critical process in the process of feed granulation and puffing. Without excellent quenching and tempering processes and equipment, it is difficult to obtain high-yield, high-quality, low-energy granulation and puffing effects.
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Due to the different moisture content of the materials required in the granulation and puffing process, the granulation is generally between 17% and 18%, and the puffing requirement is between 28% and 30%. The quenching and tempering temperature is generally 80~90 °C. Under normal circumstances, the steam saturation in the conditioner is 65%~95%. At this point, the material should also have a corresponding equilibrium moisture (the time required to reach the equilibrium water under the tempering condition, otherwise it can not reach the amount of equilibrium water), the physico-chemical bonding water after tempering and puffing must be 16% and 22%~25%, and mechanically bound water (free water, free water) is 2% to 3% and 3% to 5%. For this reason, the requirements for the moisture content of the materials are different. Obviously, the steam requirements are different. The process parameters of the two are different, so as to ensure that the materials after quenching and tempering have different water increase. The steam required for granulation is superheated steam, but the amount of steam is small. The amount of steam required for puffing is more than the amount of steam used for granulation, in order to ensure the high temperature and high moisture after quenching and tempering of the puffed material (due to the short steam conditioning time, the steam is not enough to increase the moisture after quenching and tempering, it is difficult to achieve the balance under this condition. Moisture, the need to add moisture in the mixing section). In the above analysis, the utilization rate of steam has not been considered, and the steam consumption in the granulation process is about 3.5% to 4% of the flow rate of the tempered material (including other heating and loss of 5%).
2 The process of quenching and tempering process and equipment The understanding of water and heat in the feed quenching process and equipment is gradually deepened. Therefore, the quenching and tempering process and equipment have been developing, and there are many forms. Although the importance of water and heat treatment for granulation and puffing has been widely recognized, the feed water and heat treatment processes have been strengthened. The quenching and tempering effect is obviously improved. But so far, there have been very few reports on feed quenching and tempering, mostly from a macroscopic and conceptual point of view. This analysis of the quality and effect of quenching and tempering is difficult to determine.
The quenching and tempering process and equipment were mostly the combination of feeding and quenching and tempering before the 1950s and 1960s. The feeding and quenching and tempering were separated from the late 1960s to the 1970s. The second and third grades were successively produced in the 1980s and 1990s. Different diameters and horizontal double cylinder quenching and tempering, double cylinder differential quenching and tempering, kettle type quenching and tempering, high pressure quenching and other various quenching and tempering processes and equipment have achieved different quenching and tempering effects. From the surface, various quenching and tempering processes and equipment can basically meet the requirements of granulation or puffing. In fact, different quenching and tempering processes and equipment have different process parameters (tempering speed, quenching and tempering time, etc.). For this reason, there are also big differences in the effects of tempering and aging, and different tempering and ripening effects to adapt to the requirements of different materials. It is now discussed as follows.
2.1 Quenching and tempering process and equipment for the combination of feeding and quenching and tempering The feeding of the granulator in the 1950s and 1960s is continuous spiral, and the quenching and tempering is paddle type, because the feeding amount is based on the granulated particles. The size and the feeding amount must be changed, and the speed must be adjusted. However, in order to ensure the quenching and tempering effect, the speed of the conditioner must be constant. For this reason, the two cannot be balanced. Therefore, the quenching and tempering process of the feeding and quenching and tempering coaxial combination has a poor quality control effect. To this end, the quenching and tempering process of the combination of feedstock and quenching and tempering in the late 1960s and early 1970s was replaced by process equipment with independent feeding and quenching and tempering.
2.2 Process and equipment for separate feeding and quenching and tempering Since people recognize the disadvantages of the coaxial combination of feeding and quenching and tempering, the feeding and quenching and tempering are started separately. At this time, the length of the conditioner is generally short, slightly exceeding the sum of the lengths of the press chamber and the main drive, generally within 2 000 mm. The diameter of the conditioner is generally within 300~400mm, the rotation speed is about 200r/min, and the material staying in the conditioner is within 15~30s. Since the feeding and quenching and tempering functions have been clearly defined, the conditioner is a blade. For this reason, the material quenching effect is improved, and the gelatinization degree of the starch after granulation can reach 25%. Therefore, the starch after the tempering paste The degree of chemical conversion can also be within 15% to 20%, and a variety of liquids can be added. Since the gelatinization degree of starch is not high, the water resistance of the pellet is poor, so the quenching and tempering process can only be used for the production of livestock feed, and cannot be used for the aquatic feed with high water resistance.
2.3 Equal-diameter horizontal double-tube quenching and tempering process and equipment are actually two single-tube quenching and tempering combinations, only the middle without barrel wall, the structure allows materials to flip each other, and some blades rotate in opposite directions to prolong the residence time of materials in the machine. The tempering strength is enhanced, the residence time in the machine is up to 1 min, the gelatinization degree of the starch is up to 20%, the speed of the conditioner is 100~200r/min, and the conditioner is a blade. A variety of liquids can be added. This machine can be used for poultry feed production, and can also be used for fish feed production with low water resistance requirements.
2.4 Second and third grade quenching and tempering process and equipment Due to the special requirements of water resistance of aquatic feed, in order to enhance the quenching and tempering effect of the conditioner, the second and third grade quenching process and equipment are adopted, and the length of the conditioner is up to 3 000~ 4 000mm. The diameter of the conditioner is still about 300~400mm, the conditioner is a blade, and the blades are arranged in various forms. 1 The front half blade is at an angle of 45° to the shaft, and the rear half blade is parallel to the shaft. 2 The angle between the adjacent two blades and the shaft is 75° left-handed and right-handed. The low speed is 100~200r/min and the high speed is 300r/min. Due to the increased length of the conditioner, the high speed blade enhances the quenching and tempering strength. Some conditioners are also used to keep the long cylinders insulated to reduce the intangible loss of heat. The residence time of the materials in the machine is greatly increased by 1~2min, which improves the quenching and tempering effect. The gelatinization degree of starch after quenching and tempering can reach 25 About %, a variety of liquids can be added, which basically meets the requirements of aquatic feeds with high water resistance requirements.
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2.5 Horizontal double cylinder differential quenching and tempering process and equipment conditioner is a double cylinder differential conditioner. The rotation speed of the small cylinder blade is 1~2 times higher than that of the large cylinder blade, which is about 200~300r/min. All reverse propulsion, pushing the material to the inlet, the diameter of the cylinder is 420~480mm. The speed of the large barrel is about 100r/min, and there are 3~4 groups at the inlet of the blade to push the material to the exit direction. The middle blade is parallel to the axis, only for the turning action, no propulsion function, the blade at the exit has 2~3 The group pushes the material to the inlet direction, but the direction of the blade pushing direction can be adjusted according to the nature of the material. The material advancement is mainly determined by the inlet blade propulsion force being greater than the outlet blade, and the angle of the blade is adjusted to adjust the propulsion speed, that is, the material adjustment. Quality time. The large cylinder has a diameter of 520~560mm. The large and small blades intersect in the diameter direction, and the intersecting amount is close to the length of the small blade, and the blade end and the blade portion have the same shape. Therefore, the quenching and tempering time of the model can reach 2~3min, up to 20min, and the quenching and tempering effect is better. The starch gelatinization degree after quenching and tempering is generally 30%, and the highest gelatinization degree can reach 40%~50%. Above, and can add a variety of liquids, the double-tube differential tempering process and equipment can adapt to the quenching and tempering of various aquatic feeds, but the cost is high, and the quenching and tempering is mainly used for puffing and tempering. Used for tempering of granulation.
2.6 High-speed quenching and tempering, low-speed heat-insulating homogeneous upper and lower double-tube tempering device In 2003~2004, the upper and lower double-tube tempering device with similar structure of horizontal double-cylinder differential tempering device has been introduced, and its performance principle is high-speed tempering. Separated from the heat preservation homogenization, the function division is clear. For this reason, the quenching and tempering effect will be superior to the horizontal double cylinder differential conditioner.
The upper cylinder is high-speed quenching and tempering. Because the quenching and tempering effect depends to some extent on the speed of heat transfer and mass transfer during the quenching and tempering process, the heat transfer and mass transfer rate are determined by the temperature inside the vapor and powdery particulate material and the interface layer. Gradient, velocity gradient, humidity gradient, material properties (density, particle size, water content) and other factors. The high-speed quenching and tempering increases the temperature gradient, velocity gradient and humidity gradient on the surface of the powdery material and the steam and powdery materials and the material, thereby improving the quenching and tempering effect. Its diameter is 400~480mm and the speed is 450~500r/min.
The lower cylinder is heat-insulated and homogeneous. Due to the requirement of quenching and tempering, it takes a certain period of time to make the material quenching and tempering more uniform and ensure the excellent quenching and tempering performance. Therefore, the high-speed and high-temperature quenching and tempering, the quenching and tempering effect of the homogenized heat preservation double-cylinder conditioner will be better than the horizontal double-tube differential vibrator. Its diameter is between 500 and 560mm and the speed is between 50 and 100r/min. The conditioner can be added in an amount of more than 10%.
2.7 There are many types of kettle-type quenching and tempering processes and equipments. Among them, better kettle-type quenching and tempering is about 20 minutes of material quenching and tempering time. It can add a variety of liquids, and the liquid addition amount can reach 10%~25%. The number of tanks can be adjusted to meet different production requirements. The discharge of the conditioner is made up of a planetary screw conveyor, that is, a clear screw conveyor, and the diameter of the kettle type regulator is 1 600~2 700 mm.
2.8 High-pressure quenching process and equipment The above-mentioned conditioners are all operated under normal pressure to achieve the same effect. Compared with high-pressure quenching and tempering time, especially for difficult-to-temperate granular materials, high-pressure quenching should be used. The quenching and tempering temperature can reach above 100 °C, and the quenching and tempering time can be longer, but the tempering device is a pressurized container with a pressure of 20~80 kPa. The tempering device makes the water and heat in the steam easier to enter the inside of the material, and The quenching and tempering effect is more uniform. In the past, high-pressure quenching and tempering was especially suitable for the quenching and tempering treatment of large particles, such as quenching and tempering of tableting materials. In the future, if the high-pressure conditioner is used for the quenching and tempering treatment of the powdered feed, the quenching and tempering effect can be better than the normal pressure and quenching.
3 The main factors affecting the quenching and tempering effect of the conditioner are quenching and tempering, which is an indispensable process for granulation or puffing. Without a good quenching and tempering system, there is no good granulation or puffing effect, and the factors affecting the quenching and tempering effect of the temper are better. More, mainly depends on the following three factors.
3.1 Material properties 3.1.1 Properties of the materials Due to the variety of components of the feed, the properties of the materials are different, and the effects of quenching and tempering are also different. According to the composition of the main body, the material properties are divided into protein type, starch type, fiber type, fat type, heat type, etc., and the operating parameters should be different when quenching and tempering.
3.1.1.1 protein type feed protein has hydrophilicity, moisture should not increase too much when quenching and tempering, otherwise it is easy to block the film hole. For this reason, it is better to use superheated steam, because protein type feed is more important than heat. .
3.1.1.2 Starch-type feed starch requires high-temperature, high-humidity quenching and tempering conditions. Therefore, it is advisable to use low-pressure superheated steam or add some water in the mixer.
3.1.1.3 Fiber-type feed fiber has poor water holding capacity and cohesiveness. For this reason, the moisture should not be too high, generally 13%~14%, and the material temperature is controlled at 55~60°C. If the material temperature is too high, the pressed particles are prone to cracks, using a lower superheated steam or adding a small amount of water to the mixer to reduce the temperature of the material during pressing.
3.1.1.4 Fat type feed The fat type feed should not be too high. For this reason, the use of higher superheated steam is beneficial to fat type granulation.
3.1.1.5 Thermosensitive feed The heat-sensitive feed strives to have a low quenching temperature. The material temperature is controlled below 60 °C and the moisture is not high. Therefore, lower superheated steam or a small amount of water in the mixer can be used to reduce the material. Temperature is effective.
3.1.2 The particle size and uniformity of the material Due to the variety of components of the feed, the particle size and uniformity of the same type of powdered material are also different, which brings certain difficulties to the operation of the conditioner and raises a higher Claim. Because the quenching and tempering requirements soften the center of each particle, if the small particles have been tempered, the large particle conditioning has not yet met the requirements. If the difference in particle size is larger, the difference in quenching and tempering effect will be greater. The latest research conclusions in foreign countries: The influence of the particle size of powder particles on the quenching and tempering effect is proposed. The particle size of the material is as close as possible to facilitate uniform quenching and tempering. For this reason, for large-scale feed mills with high quenching and tempering requirements, the granules can be graded first, and then quenched and tempered to achieve the best quality control effect, while saving energy.
3.1.3 The moisture and moisture of the material is an important factor affecting the quenching and tempering effect. Under the same conditions of quenching and tempering temperature and quenching and tempering time, the moisture content of the material is high, and the quenching and tempering effect is better than the material with low moisture content. Due to the poor resistance of microorganisms to damp heat, microorganisms can absorb high temperature water in the surrounding medium under the action of steam, thus promoting the solidification of microbial cell proteins and accelerating the death of microorganisms (the time of microbial death of damp heat materials is lower) 1/3 of the moisture material). Therefore, under the condition of high moisture content of the material, the damage and inactivation of the mold and pathogenic bacteria such as Salmonella and the hemagglutinin and protease inhibitor of the plant are high, and the degree of starch gelatinization is also high.
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3.2 Performance of the conditioner 3.2.1 Structure and process parameters of the conditioner 3.2.1.1 Structure of the conditioner 1 The conditioner is a single-layer conditioner or a three-layer conditioner; the conditioner is long (3~4m) ), or short type (2m or less) conditioner; is a double cylinder conditioner, or a single cylinder conditioner; is a constant diameter conditioner, or a differential conditioner; is a large diameter conditioner, or is it Small-diameter tempering device; it is a constant pressure tempering device or a high-pressure tempering device, and its different structure has a great influence on the quenching and tempering effect. For example, the quenching and tempering time, the amount of the liquid component to be tempered, and the ripeness of the tempering are not the same. Therefore, for the shrimp feed with high water resistance requirement, the proportion of the liquid component added is high, and it is preferable to use a conditioner with a long quenching and tempering time and a high quenching and tempering speed, such as a differential cylinder conditioner. Three-layer conditioner, double-tube conditioner and differential conditioner can be used for fish feed with less water resistance requirements. As long as the angle of the conditioner blade is adjusted to control the quenching and tempering time, the quenching and tempering can be satisfied. Requirements, but to compare the economics of investment. Generally, the single-tube large-diameter conditioner and the double-tube conditioner can meet the requirements for use. Differential cylinder conditioner, three-layer conditioner, long-type conditioner, high-speed conditioner, double-tube conditioner have good quenching and tempering performance, among which the differential conditioner and the double-tube conditioner are adjusted. The uniformity of quality is the best, because the differential conditioner solves or improves the problem of uniform longitudinal warpage. Some other conditioners have a certain degree of longitudinal tempering unevenness problem still exists. 2 The different quenching and tempering performances of the blade structure are still different. The blade of the early conditioner is actually a blade, and gradually transforms from a larger area of ​​the blade to a small area of ​​the blade. The blade of the recent conditioner has become Square rod shape (the number of blades is also an important factor affecting the quenching and tempering effect, and the current change is not large). The quenching and tempering effect largely determines the turning performance of the material. The blade is large and the area is large, which is beneficial to material transportation, but there are many relatively static materials, and the turning performance is relatively poor. Therefore, the effect of quenching and tempering is also poor. To this end, the blade of the conditioner is gradually developed into a square rod with a certain area, the number of blades is increased, the material conveying capacity is weakened, the quenching and tempering time is prolonged, and the turning performance is improved, thereby improving the quenching and tempering effect.
3.2.1.2 The speed of the conditioner with the same diameter of the conditioner has a great influence on the quenching and tempering effect. The high speed makes the turning performance of the quenched material stronger, and the velocity gradient of the steam on the surface of the material is increased, thus accelerating the quenching and tempering speed. And effects. At the same time, the blade has a high rotational speed and a large striking force, which accelerates the diffusion of moisture into the material. Therefore, the high-speed conditioner has better quenching and tempering effect, and the liquid component can be adjusted to a ratio of 10%, and still has a good quenching effect.
3.2.1.3 Quenching and tempering time Any heat transfer and quality (moisture) transfer take time to get the best quality control. Moreover, the granularity of pulverization of different finished materials is different, the degree of ripening is different, and the structure of the tempering regulator is different, and the tempering time requirements should also be different. The time for quenching and tempering of general livestock feed is about 30s, and the conditioning time of fish and shrimp feed is 2~20min. In short, quenching and tempering time has a great impact on the quality of quenching and tempering The material can be better tempered by adjusting the angle of the tempering plate, changing the length of the tempering device and adding a heat preservation homogenizing system to increase the quenching and tempering time. At present, the addition of a heat preservation homogenizer to the granulator can improve the quenching and tempering effect to varying degrees.
3.3 Quenching and tempering steam quality Due to the different quality of steam, its temperature and water content are different, the quality of superheated steam is good, the temperature is high and the water content is low, while granulation and quenching and tempering have different materials temperature and material moisture content. It is required that the granulation process generally requires that the temperature of the material entering the granulation chamber be 75 to 85 ° C, the water content of the material is 17% to 18%, and the temperature of the material after granulation is 80 to 85 ° C. The puffing process generally requires that the material temperature of the puffing chamber be above 95 °C, the moisture content of the material is 28%~30%, and the material temperature in the puffing chamber is above 130~140 °C. Since the material after steam quenching and tempering is difficult to reach 28%~30% of water, the puffing process adds water to the mixer or the conditioner when necessary, so that the moisture of the material can reach the requirement of 28%~30%. Adding water to the conditioner is due to the short action time of the water on the material, which results in a physical and chemical combination of less than 25% of water. A large part is mechanically bound water (free water, free water). For granulation, if it is to be humidified, adding water in the mixer is better than adding water in the conditioner, so that the water added by the material is easily combined with water. In general, granulation and puffing should be added to the conditioner, because water easily evaporates from the particles, and the stability is poor, and the particles are easily lost during cooling or drying. The added water is very beneficial for heat sensitive materials. In short, quenching and tempering is an important part of granulation and puffing. Due to different material composition, different feed products, different conditioners, various parameters of quenching and tempering should also be different.
4 The development trend of the conditioner is due to the high quenching speed of the rotor of the conditioner and the amount of liquid added during the quenching and tempering are better than the rotor speed. Therefore, the development trend of the conditioner is to the high speed and strong vibrator. Direction development. After quenching and tempering, there is a good heat preservation homogenization time, which makes the quenching and tempering effect and level get a big improvement.
With the application of high-speed and powerful conditioners, the digestion and absorption rate of feeds should be improved, and the formula of feed should be adjusted to achieve the best breeding effect and the most economic benefits. Otherwise, it may waste raw materials or cause some adverse reactions such as fatty liver.
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