If pulverized brown coal is fired in a Schoppe burner and the waste gases Including the fly ash are rapidly cooled down at 55 to 60 degrees C, the SO2 will be found by the ash completely. The result is waste gas with SO2 = O. The burner utilizes a peculiar flow effect, which is produced in a burner-muffle. This is most Likely the cause of the desulphurization effect.