Utilization of a Latent Heat Storage for Waste Heat Recovery from an Aluminum Die Casting Plant and the Supply of Preheating and Heat Treatment Furnaces with Stored Heat

Aluminum die casting is an important industrial process and due to melting very energy intensive. Currently, there is a lot of unused waste heat from moulding and cooling in the casting cell. This represents the source of waste heat utilization in this paper. A preheating furnace act as a proper and large enough heat sink. Hence waste heat supply and demand not always coincide a latent thermal energy storage is used to close this gap, utilizing the melting and crystallization enthalpy of the storage medium, the phase change material (PCM). For waste heat recovery and continuous preheating, we designed a system consisting of PCM storage and preheating furnace. At the laboratory at the Austrian Institute of Technology (AIT) there is a PCM storage unit, where experiments can be carried out. As a first step a simulation model was developed using Modelica/Dymola, where thermal oil is used to utilize the waste heat from die casting to preheat aluminum ingots. Simulation results showed that with this system energy savings of 10 to 15% can be achieved and even be surpassed by further optimization. With higher waste heat temperatures (up to 300 ℃) and therefor higher preheating temperatures, and an optimally interconnected system of larger PCM storages, energy savings up to 30% seem possible.