Between 2004 and 2006 the old waste incineration plant in Lausanne, built in 1958 by von Roll (which became HZI), was replaced with a new two-line EfW plant. The new installation was expected to meet ambitious targets: very low emissions, maximised energy output, cost-efficient operation and high availability. HZI planned and built the new plant’s combustion, boiler and flue gas treatment systems to fully meet these stringent requirements. The highly efficient plant was subsequently made even more efficient by installing a further heat exchanger between the flue gas treatment unit and the stack.
In 2016 the client commissioned HZI to look into options for further increasing the installation’s performance. The study findings were persuasive, and in 2017 the client requested a binding quote to install new heat exchangers. The budget was approved by the board of directors in 2018 and the project could go ahead, with the heat exchangers fitted in June 2019. The new equipment reduces the temperature of the clean gas by an additional 45 to 50 Kelvin. The energy extracted is fed into the City of Lausanne’s growing district heat network.
HZI installed one 1.20-metre-high Flucorrex counterflow heat exchanger for each line. This complementary heat exchanger is fitted in the existing flue gas duct between the ID fan and the silencer. On the water side the exchanger is connected to the internal hot water network that heats the district heat network.
The new heat exchanger lowers the flue gas temperature from 170°C to 126/120°C. It consists of 1,188 PFA tubes which at their peak extract more than 1 MW of thermal power from the flue gas.