What are the classification of granulators? Let's analyze it together.
Underwater granulator is similar to air granulator and water jet granulator. Its equipment mainly includes: plastic granulator, single-screw plastic extruder, plastic film blowing machine, bag making machine, printing machine, coating machine, belt cutting machine, slitter machine, baler, modified formula, mainly alloy materials, especially PET, PC, ABS, (PP, PA), the application field is constantly expanding. Plastic formula: cling film, degradation film, PET adhesive toughening, etc. The difference is that it has a steady water flow through the die surface, and it is in direct contact with the die surface. The granulation chamber is just large enough to allow the granulator to rotate freely on the die surface without limiting the water temperature, the molten polymer is extruded from the die, the rotary knife cuts the pellet, and the pellet is removed from the granulation chamber by the temperatule-adjusted water and into the centrifugal dryer. In the desiccator, the water is discharged back to the storage tank, cooled and recycled; Dehydration was performed using a centrifugal dryer.
The cost of strip production line is not high, the operation is simple, and the cleaning is convenient. This has its advantages for color blending, since the replacement of two different batches of color must thoroughly clean the equipment. However, the disadvantage of the strip making method is that the cooling section takes up space, and its length is determined according to the temperature requirements of the polymer.
Most polymers must be mixed before being made into products and then pelleted to become marketable raw materials, and the power required by the granulator is proportional to the amount of extrusion and exponentially related to the size of the filter screen. There are many different granulator designs, but all granulators can be divided into two categories: cold pelleting systems and die surface thermal pelleting systems. The main difference between the two is the timing of the pelleting process. Cold granulation system, where pellets are cut from the cured polymer at the end of the processing process; In the die surface thermal granulation system, when the molten polymer emerges from the die, it is pelleted, and the pellet is cooled downstream. Both pelleting systems have advantages and disadvantages.
Cold pelleting system: The cold pelleting system includes a die, a cooling zone (air-cooled or water-cooled), a drying zone (if water-cooled), and a pelleting chamber. There are two kinds of cold pelleting system, namely sheet granulator and strip granulator.
The molten polymer is extruded from the hot die and cut into pellets by a rotary knife rotating on the die surface, this sweet pellet system is characterized by its specially designed water-jet pelleting chamber. The water flows in a spiral fashion until it exits the jelly chamber, and after cutting, they are thrown into the stream for initial quenching, the granular water slurry is discharged into the granular slurry tank for further cooling, and then sent to a centrifugal dryer to remove moisture.
Strip granulators have been used almost as long as granule granulators. "It includes a die, a cooling section (water bath or blower), a drying section (if water-cooled), and a pelletizer." The molten polymer extruded by the extruder or gear pump is passed through a horizontally mounted mold to form a strip (modern molds are precisely machined and evenly heated to produce strips of stable quality). After the strip is discharged from the mold, it is cooled by blower or air/vacuum equipment or water bath. If water cooling is used, the strip needs to pass through the drying section, the moisture is blown away by forced ventilation, and then the strip is sent into the granulation chamber, and the strip is cut precisely to the desired length using the shear action of a pair of fixed and rotary knives.
