The MEROS plant is used for the off gas treatment for sintering plants, in whose off gas high concentrations of sulfur dioxide are present. As alternative flue gas purification additive sodiumhydrogencarbonate was tested for four weeks in a industrial test series and placed in comparison to the lab tests at the FH Wels and the first pilot test series. It is to be examined, how far the operation with sodiumhydrogencarbonate as flue gas purification additive for industrial sintering plants is suitable. With the data of the field tests an operating cost comparison calculation is compiled to compare the performance of sodiumhydrogencarbonate to hydrated lime, which was used so far.