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The method of recovering and reusing the residual heat from the extrusion blow molding machine

Effective Waste Heat Recovery Methods for Extrusion Blow Molding Machines

Extrusion blow molding machines are widely used in manufacturing hollow plastic products. However, these machines consume significant energy during operation, with a substantial portion of this energy being released as waste heat. Implementing waste heat recovery systems can reduce energy consumption, lower production costs, and enhance environmental sustainability. Here are several practical waste heat recovery methods tailored for extrusion blow molding machines.

Utilizing Heat Pump Systems for Cooling and Heating Integration

Heat Pump Cooling and Heating Cycle

A heat pump system can be integrated into the extrusion blow molding process to recover waste heat from the cooling system. The system works by absorbing heat from the cooling water used to regulate the temperature of the extruder barrel and mold. This heat is then transferred to a secondary circuit, where it is used to preheat the plastic pellets before they enter the extruder.

Cooling Water Temperature Control: The heat pump's evaporator is connected to the extruder's cooling water circuit. As the cooling water absorbs heat from the extruder, it flows through the evaporator, where the heat is absorbed by the refrigerant. This process lowers the cooling water temperature to the desired range, typically between 25-30°C, ensuring optimal cooling efficiency.
Heat Recovery for Plastic Preheating: The heated refrigerant is then compressed, raising its temperature further. The high-temperature refrigerant flows through the condenser, where it releases heat to a secondary water circuit. This heated water, with temperatures ranging from 50-70°C, is directed to the plastic pellet hopper, preheating the pellets and reducing the energy required for melting in the extruder.

Benefits of Heat Pump Integration

Energy Efficiency: By recovering waste heat from the cooling system, the heat pump reduces the need for additional heating energy, leading to overall energy savings of 15-25%.
Improved Production Efficiency: Preheating the plastic pellets shortens their melting time in the extruder, reducing the production cycle by 5-10% and increasing overall throughput.
Extended Equipment Lifespan: Maintaining optimal cooling water temperatures reduces thermal stress on the extruder components, leading to fewer breakdowns and longer equipment lifespan.

Implementing Air Compressor Waste Heat Recovery

Air Compressor Heat Recovery Mechanism

Air compressors are commonly used in extrusion blow molding facilities to provide compressed air for various operations, such as mold opening and closing and product ejection. During compression, a significant amount of heat is generated, which is typically dissipated into the atmosphere through cooling systems. This waste heat can be recovered and utilized for other purposes within the facility.

Heat Recovery from Compressor Oil: The heat generated during compression is absorbed by the compressor oil. This hot oil can be directed through a heat exchanger, where it transfers its heat to a water circuit. The heated water can then be used for space heating, domestic hot water supply, or preheating process water.
Heat Recovery from Compressed Air: In some cases, the heat from the compressed air itself can be recovered using aftercoolers or regenerative dryers equipped with heat recovery systems. These systems capture the heat from the compressed air before it is cooled and dried, transferring it to a water or air circuit for further use.

Practical Applications of Air Compressor Heat Recovery

Employee Facilities Heating: The recovered heat can be used to provide warm air or hot water for employee facilities, such as locker rooms, showers, and cafeterias, improving worker comfort and reducing the need for additional heating systems.
Process Water Preheating: In extrusion blow molding, process water is often used for cooling molds or cleaning equipment. Preheating this water using recovered heat reduces the energy required to bring it to the desired temperature, leading to energy savings.

Adopting Industrial Heat Exchangers for Waste Heat Recovery

Types of Heat Exchangers for Extrusion Blow Molding

Heat exchangers are versatile devices that can be used to recover waste heat from various sources within an extrusion blow molding facility. The choice of heat exchanger depends on the specific application and the nature of the waste heat stream.

Shell and Tube Heat Exchangers: These are commonly used for recovering waste heat from high-temperature fluids, such as hot exhaust gases from drying ovens or heat treatment furnaces. The hot fluid flows through the tubes, while the cooling medium (usually water or air) flows around the tubes in the shell, absorbing the heat.
Plate Heat Exchangers: Plate heat exchangers are ideal for applications where space is limited, and efficient heat transfer is required. They consist of a series of corrugated metal plates stacked together, with the hot and cold fluids flowing through alternate channels. The large surface area and turbulent flow patterns ensure high heat transfer rates.
Air-to-Air Heat Exchangers: In some cases, waste heat can be recovered directly from the air streams, such as the hot air exhausted from drying processes or the warm air from compressed air systems. Air-to-air heat exchangers use a heat recovery wheel or a plate-type heat exchanger to transfer heat from the exhaust air to the incoming fresh air, preheating it before it enters the facility.