With this system, the exhaust air produced during roasting undergoes catalytic afterburning once it has been thermally precleaned. This involves heating the exhaust air from the roasting process to a temperature of around 450 °C using an additional blower burner. Then it is passed through a catalyser. The increase in temperature and the catalytic reaction result in considerably lower emissions. Using thermal precleaning and a catalytic afterburner reduces the total carbon content of the exhaust air produced during roasting to below the limit stipulated in Germany’s air pollution control regulations.
This exhaust air cleaning system also utilises thermal precleaning followed by catalytic afterburning of the exhaust air produced during roasting. However, the use of a low-temperature catalyser here means that it only needs to be heated to 320 °C. The exhaust air nevertheless complies with the total carbon content limit stipulated in Germany’s air pollution control regulations. Thanks to the use of a lower precleaning temperature, it is possible to reduce both energy consumption and NOx emissions (depending on the degree of roast).