Heat recovery from dairy wastewater
Based in the far north of Germany, in the town of Aurich with its 40,000 inhabitants, the local dairy is specialised on the production of cheese, butter and milk powder. The up to 1.200 m³ wastewater generated each day during the production process has a temperature of 25° to 35° C, which is significantly higher than the temperature of municipal wastewater.
Through cooling by approximately 10 kelvin an energy yield of about 600 kW can be achieved. Combined with a heat pump this thermal output is sufficient to heat about 15,000 m2 living space. To utilize this energy from the wastewater which contains grease and whey residues, a heat exchanger is required that is able to handle sediments and solids without any negative impact on heat transfer and without loss of efficiency.
The HUBER RoWin Wastewater Heat Exchanger is an innovative system that is able to meet these requirements. This HUBER system with automated cleaning of pipe surfaces and sediment discharge is able to cope with the impacts of polluted wastewater and guarantees the maximum heat transfer over the long term. As the warm wastewater flows through the secondary circuit of the heat exchanger it meets with the town’s cold district heating network. Due to the difference in temperature the cooling medium extracts energy from the dairy wastewater and heats up.
There is an approximately 2 km long ring main running through Aurich from which users, with their heat pumps, can tap from the dairy’s wastewater heat up to 80% of the total heating energy they need.
The first big consumer that was connected to this eco-friendly and low-cost energy source was the Aurich multi-function arena. To convince the customer of the efficiency of our technology, we installed a plant for a test period of three months. All relevant parameters were continuously measured and analysed by a data logger. The consumption of about 60 kW is only a fraction of the available total amount of energy but this was constantly and over the long term transferred by the HUBER RoWin heat exchanger.
On the basis of the experience gathered during the pilot tests the requirements of a real size plant will now be determined to ensure the planned all-weather waterpark can be put into operation in 2012 as main user of this economically and ecologically reasonable energy source.
The test series has clearly shown that the HUBER RoWin Wastewater Heat Exchanger is unsusceptible to dairy wastewater. Also varying inflows from the dairy did not have any influence on the heat input into Aurich's district heating network. Certainly, other users will follow the multifunction hall and waterpark in the future to profit from this eco-friendly alternative to expensive heating plants.