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How to Improve the Efficiency of a Plastic Granulator

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2017-12-04

Plastic pelletizing machines are energy-intensive devices, with the majority of their energy consumption concentrated in the hydraulic and heating systems. Typically, energy usage breaks down as follows: 82% for the oil pump, 13% for heating, and 5% for other components. Increasing efficiency and reducing energy consumption are key objectives in the design and operation of these machines. To achieve this goal, several factors can be considered: 1. Pump selection: As is well known, during operation oil is continuously drawn from the reservoir, pressurized, and then routed through a relief valve, resulting in significant energy losses. Therefore, the pump’s output should be matched to actual demand; variable‑displacement pumps are a suitable choice. 2. Reducing energy consumption in the mold‑clamping system—fundamental principles…

Plastic pelletizing machines are energy-intensive equipment, with the majority of energy consumption concentrated in the hydraulic and heating systems. Typically, energy usage breaks down as follows: 82% for the oil pump, 13% for heating, and 5% for other components. Increasing efficiency and reducing energy consumption are key objectives in the design and operation of plastic pelletizing machines. To achieve these goals, several factors can be considered.

1. Pump selection. As we all know, during operation, oil is constantly drawn from the reservoir, pressurized, and then routed through the relief valve, resulting in unnecessary energy loss. Therefore, the pump’s output should be matched to actual demand; a variable‑displacement pump is a suitable choice.

2. The fundamental principle underlying the reduction of energy consumption in mold‑closing systems is the concept of “spring efficiency,” which arises when deviations occur during the mold‑closing process. As the clamping force continuously increases, the associated energy also accumulates. Once the molded part has cooled and the mold‑closing mechanism opens, the energy stored in the “mold‑closing spring” is released. In hydraulic mold‑closing systems, this energy is invariably dissipated as heat in the hydraulic fluid and carried away by heat exchange. The higher the mold‑closing “spring efficiency”—that is, the greater the spring’s ability to absorb and subsequently release energy—the less energy is consumed during the mold‑closing cycle.

3. Strive to ensure that the melt receives as much heat as possible from the heating zone of the barrel. The rationale is straightforward: in addition to direct conductive heat absorbed within the barrel, the polymer also generates shear heat under the screw’s shearing action, thereby accelerating the plasticization process. A more efficient processing regime delivers greater heat to the polymer. However, electric motors and hydraulic pumps typically exhibit low efficiency, with losses occurring during fluid flow. Similarly, the efficiency of the screw‑driving motor is also limited. Taken together, these factors—along with other mechanical losses—account for roughly 50% to 60% of the energy consumed by the melt. On the other hand, by employing a heat‑free protective heater, up to 90% of the total input energy can be transferred to the melt. Of course, achieving this requires enhancing the screw’s mixing action to produce a uniform melt.