Abstract: For the purpose of increasing the efficiency during drying of brown coals having a high water content and for the purpose of facilitating the purification of process waste water resulting in a drying process according to Fleissner it is proposed to spray hot water onto the raw coal and to separate the proportion in fine grain having a maximum grain size of 5 mm, preferably of 1 mm. In the following, the proportion in fine grain is subjected to an adsorption stage (5), noting that after a reaction time of at least 1 min, preferably of 2 to 5 min, a major portion of the soluble substances burdening the waste water becomes adsorbed on this fine grain. Subsequently, the waste water is further purified after a flocculating step in a flocculating reactor (6) and after a separating step (8) for separating solid matter, for which purpose can be used sand filters (10), adsorbing resins and activated carbon.