Green Pipe – development of a new cooling concept for the extrusion of plastics pipes

Initial situation

In the extrusion process electrical energy input is transferred into the plastics and transformed into thermal energy for melting the material. After its shaping into profile, pipe or sheet products, it is cooled back to room temperature. During this cooling process, the product is being pulled through cooling tanks constantly reducing the temperature by applying cooling water at approx 15°C at any point of the cooling. Such cooling systems are working in such a way that the cooling process itself needs additional energy input for cooling and circulating the cooling water. At the current state of technology, the cooling process is very energy intensive, running at very low temperature gaps and high volumes. Waste heat utilisation is not possible at current process conditions (cooling temperature input 15°, outlet at 20°) Challenge

Challenge

The aim of this project is to develop a process that reduces the energy input for cooling of the product and at the same time allows waste heat utilisation due to the increased outlet temperature of 60°C. The key is the achievement of an increased temperature gap between in- and outlet by utilising the different product temperatures in the different stages of the cooling process. The cooling water is being applied in consequently utilising the counter flow concept and connecting all cooling tanks in parallel flow. The cooling water starts at the last cooling tank flowing in the counter direction as the cooled product. The energy flow is being managed and controlled in such a way, that the temperature between the cooling water and the product is kept as low as necessary for optimised cooling and as high as possible to achieve a maximum cooling water temperature maintaining sufficient cooling. The higher the achieved outlet temperature the lower is the needed cooling energy input of the cooling system, the lower the volume and hence pumping energy. Finally the waste heat utilisation can be allowed and maximised.

Results

For the extruding company this new cooling concept allows high reduction possibilities in terms of energy consumption and offers cost efficiency improvements. For the main applicant as a worldwide active producer of machinery, this new cooling process improves the competitive situation in this growingly important field of providing the most energy efficient machinery. The next steps will be the design and building of demo lines as well as the integration of the cooling process in commercial use.

Photos: Ecodesign Team