35% energy recovery from air blowers
Since the installation in 1995, the Ryaverket energy plant in Gothenburg has successfully used Lackeby’s heat exchangers air/water after the air blowers to save energy and money.
The heat exchangers recover as much as 35% of the energy needed to run the blowers, by efficiently recovering the heat from the compressed air. The heat is transferred to the hot water system, before the water returns to the boilers. The calculated savings over 10 years’ time is a stunning 640.000 Euro.
But this is not all. While the heat exchangers lower the air temperature, this also contributes to saving on the lifetime of the rubber membranes in the biological tanks. A maximum air temperature of 70°C has highly contributed to an extended lifetime of the membranes, allowing to replace the rubber membranes only after 12-14 years, and by that time, it was recognised, they could have been used even longer. The reason is that for every 10°c exceeding over the 70°C limit, the expected lifetime of EPDM rubber is halved.
For this installation, Läckeby heat exchanger model HAW 500-36 is used, with a design air flow of 13.900 Nm3/h, an air temperature after blower of 80-120°C, a water flow of approx. 4 l/s and a water temperature of approx. 42°C. The water depth in the tanks is 10m.