1 Principle of granulator
In the feed granulation process, the granulator is the most important equipment. According to the working principle of the granulation mechanism, it can be generally divided into two types: forming machine and extruder. The molding machine presses the feed material in a closed body; the extruder uses a resistance generated by the friction of the die wall of the granule to suppress the formation of feed pellets. Pressing the structure characteristics of the granular parts, the pelletizer can be divided into a plunger type, a screw type, a ring mode, and a flat mode granulator.
2 The structure of the granulator
The general granulator is mainly composed of a stepless speed regulation feeding system, a stirring and quenching system, a granulation system, a transmission system, and a security system.
2.1 stepless speed regulation feeding system
The stepless speed feed system consists of two parts: the transmission and the feed auger. The transmission is usually composed of a JZTY type electromagnetic speed control motor and a speed reducer. The speed regulating motor is composed of a three-phase asynchronous AC motor, a eddy current clutch and a tachogenerator, and is used together with the JZTY controller. Through the JZTY electromagnetic speed regulating motor controller, the output speed can be changed, and after the deceleration of the reduction gear ratio of 1:10, the screw feeding auger shaft is rotated to achieve the stepless variable feeding and control different feeding amount. the goal of. The feeding auger is composed of a simplified structure of auger, a twisted shaft, a bearing with a seat, etc., and its function is to convey the powdery material in the storage hopper to the agitator through the rotation of the auger shaft. The simplified structure of the auger, the auger shaft and its blades are made of stainless steel, and the auger shaft blades are full-faced. The auger shaft can be extracted from the auger with the bearing housing to facilitate the cleaning of the inner and the auger shaft.
2.2 Stirring and tempering system
The stirring and quenching and tempering system is mainly composed of a simplified body, a stirring shaft, a bearing with a seat, a reducer, a motor, a steaming port, a molasses adding port, a security magnet, a lifting device and the like. Its function is to make the steam and feed of 0.1~0.4MPa pass intensively to soften the material; at the same time, it can also add the appropriate amount of molasses through the molasses addition port, and raise the temperature to 80~100°C, which is pressurized by the oil pump into a mist. Poison and molasses. The agitator and the agitator and the blade are made of stainless steel, and the agitator shaft and the bearing housing can be pulled out of the machine for maintenance. The agitator shaft is driven by the motor and driven to rotate by a reducer with a reduction ratio of 1:4 to achieve the purpose of mixing and conveying materials.
2.3 granulation system
The granulating system is mainly composed of a blanking chute, a pressing chamber, a cutter and the like, and is the core of the whole granulator, and is also a determining factor of the granulation process and the granulation effect.
The material chute is composed of a chute, a handle, an observation window door and a complete body. The purpose of the chute is to feed the quenched and tempered material in the mixing and tempering device into the pressing chamber for pressing, which plays the role of supporting the upper and lower. Open the observation window door to observe at any time, master the quality of the material, and also serve as an artificial supply port. When the outer handle of the chute machine is pulled, the machine can be discharged outside the machine for trial and troubleshooting.
The pressing chamber is the heart of the granulator and consists of a stamper cover, a feed scraper, a dispenser, an annular die, a cylindrical press roll, a cutter and a door cover. Its function is to distribute the material to be granulated fed by the blank chute to the rotating annular stamper through the distributor. The working surface between the stamper and the columnar pressing roller is filled with the material into the compression zone by the rotating stamper, and then the roller is rotated by the friction with the material to make the material enter the pressing zone and be formed into the die hole. Under strong extrusion, the material overcomes the resistance of the hole wall and is continuously extruded from the die hole. When extruded, it is placed outside the ring die and cut into a suitable pellet feed by a cutter with adjustable position. The feed squeegee distributes the flow evenly to the nip of each press roll and die to reduce vibration and uneven force. The annular die is a ring die having thousands of uniformly distributed orifices. In the process of pressing the granules, the material is forcedly formed through the small holes under the strong pressing action of the stamper and the press roll, so the stamper should have high strength and wear resistance. High quality alloy steel, chrome steel (12%~14% chromium) and carburized stainless steel are generally used. The structural characteristic parameters are usually represented by the die hole diameter, the die thickness, the effective working length, the decompression hole depth, the feed orifice diameter, the feed orifice angle, the die opening ratio, the compression ratio, and the aspect ratio. . The pressure roller is generally inert or driven, and its transmission force is the friction between the die and the pressure roller. Therefore, it is necessary to ensure that the pressure roller has sufficient traction to prevent the pressure roller from "slipping". The main parts of the press roll include the roller shaft, the bearing, the seal and the roll shell. The diameter ratio of the press roll to the die is about 0.4:1, and the line speeds of the two are substantially equal, so the wear rate of the press roll is about 250% higher than that of the press. Therefore, the inner sleeve of the press roll is machined to have an adjustable eccentric mounting surface for assembly and refurbishment. There is also a lubrication oil hole on the roller shaft to lubricate the bearing in time while the granulator is running.
The cutter is a tool for cutting the material extruded from the die hole into pellets of uniform length and shape. Each press roller is equipped with a cutter, and the cutter holder is generally fixed on the door cover, and The spacing of the outer surface of the stamper can be suitably adjusted according to the requirements of the length of the pellet. The material is generally selected from nickel-containing hard alloy steel.
2.4 Transmission System
The power of the transmission system is output by the main motor. After the internal gear-shaped elastic coupling, the gear shaft runs coaxially with the motor, and after a pair of gears are decelerated (or directly decelerated by the pulley), the air shaft is coupled with the transmission shaft. The stamper rotates together. The die and the drive wheel are connected by a screw and a key (or by a hoop). The eccentric roller shaft is mounted in the pressure roller bushing of the spindle and is pressed and fixed by the pressure plate. The pressure roller shaft is provided with a pressing shaft. When the pressing mold rotates, the inner pressing roller rotates due to the friction of the material, and the material brought in by the centrifugal force squeezes the fine particles from the die hole through the squeeze therebetween. The distance between the stamper and the press roller can be changed by adjusting the trimming wheel, and the maximum adjustment distance is generally 10 mm, which is obtained by rotating the eccentric press roller shaft around the main shaft and the coaxial hole on the pressure plate.
2.5 Security System
The security system includes overload protection, security magnets, press room door cover protection switch and off-machine discharge.
2.5.1 Overload Protection
Overload protection means that when a foreign object suddenly enters between the die and the roller, the pressing force will suddenly increase, exceeding the normal pressure, and the pressure roller stops rotating or rotates with the spindle rotating around the spindle axis and driving the original stationary spindle. Break the safety pin (or rotate the inner friction disc). At this time, the travel switch works, cut off the power supply, and the motor stops rotating to ensure that other parts of the machine are not damaged and play the role of overload protection.
2.5.2 Security Magnet
The security magnet means that when metal magnetic impurities are mixed into the material, it can be removed by a security magnet mounted on the agitator (or the chute). The security magnet is fully enclosed in stainless steel, with high life and reliability, and can be quick-released through the handle.
2.5.3 Pressing room door cover protection
When the pressing door cover protection switch is in normal operation, in order to avoid opening the press door cover, and on the side of the door cover, the travel switch disconnects all the control lines of the granulator, so that the granulator stops rotating or cannot start. To ensure the safety of personnel.
2.5.4 Off-machine discharge
When the machine discharges outside the machine, as long as the outer discharge handle is pulled, the chute can be rotated. At this time, the materials of the conditioner are all flowed into the machine without entering the pressing chamber. It is mainly used for the test machine before the normal operation of the granulator and the emergency discharge in the event of failure. After normal operation or troubleshooting, push the discharge handle to reset the chute and cut off normally.
3 granulation process
The granulation process is to remove the iron from the powdery compound feed through the magnetic separation device, and then send it to the stirring and tempering system through the continuously variable screw feeder, and stir with the steam added at the same time (sometimes with molasses, fat). Mixing, the protein and starch in the feed are diluted by water under the action of heat, and become a plastic body with strong plasticity, and the crude fiber is softened by heating. At this time, the feed moisture reached 15% to 17%, and the temperature was 65 to 85 °C. The quenched and tempered material is sent between the running ring die and the work surface of the press roll. The rotating die rotates the press roller by friction with the material, and the material overcomes the resistance of the hole wall under strong extrusion, and is continuously extruded from the die hole. The cutter that is placed outside the die is cut into particles of suitable length when extruded, and the position of the cutter can be adjusted to control the length of the pellet.
4 Using the secondary granulation process to improve the quality of
After years of development in China, the ring mold granulator has been relatively complete. The main difference between the secondary granulation process of the ring die granulating unit and the conventional single-stage tempering granulation process is that two granule machines are provided in the process, and the prepared divided raw materials are subjected to the first coarse granulation before the second granulation. The sub-refined granules, in essence, also enhance the tempering of the granulation to improve the quality of the final granules. The principle is that the material is transferred from the raw material warehouse through the modulator into the pellet machine for the first granulation, usually the pore size is 50% larger than the second-stage granulation, or the old ring mold using the second-stage wear is re-corrected and then used, and then enters the granule. The machine performs the second granulation. The process after granulation is basically the same as the conventional granulation process. The secondary granulation process provides a means of strengthening the tempering, which satisfies the main conditions of pressure, temperature and time necessary to add liquid to the raw material. Moisture has been substantially absorbed prior to secondary granulation to produce high quality pelleted feed. In the specific process configuration, there are direct series and strip-type maturation tanks, which have better direct tandem use and lower investment costs. The addition type aging tank is to add a modulator before the second stage granulation, and the cooler is changed to 4 layers of cooling, and all the liquid additives other than steam are added to the first stage modulator, and the quality of the preliminary granules is very low; In the cooker, the hot dry air input by the cooler through the heat exchanger keeps the material at a temperature to ensure that the material is sufficiently tempered, and steam is added to the second pole modulator to further heat the material while keeping the surface of the material moist. It acts as a lubricant when the feed passes the second pass. The horizontal 4-layer cooler provides both hot and humid air to the cooker and enhances cooling. This method can add molasses and oil in large quantities, especially suitable for the processing of cattle feed and herbivore feed. Although the investment cost and operating cost of secondary granulation are relatively high, the process is easy to control and the quality of the pellet is significantly improved.
5 Summary
The granulator is the key equipment for the quality assurance of pellet feed. By mastering the working principle of granulator to improve the granulation effect and improve the palatability and nutritional balance of pellet feed, it is the basis for improving feed quality.
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