A complex, hot process gas is to be cleaned through intensive cooling below the acid dew point. In this case, the SO2 and SO3 contained in the gas reacts together with the injected lower-concentrated sulfuric acid solution to form sulfuric acid. This sulfuric acid condenses on the cold droplets and collects at the end of the reactor in liquid form. In this condition, it can be processed comparatively easily. The result is a SO3-free, cold exhaust gas. Lechler supports you in planning these complex processes and helps to avoid explosive and expensive experiments.