Abstract: The invention relates to an apparatus for the heating of flowing material containing finely divided solids, such as concentrate slurry containing precious metals and/or precious minerals, up to a desired temperature range, for instance the temperature range applied in a treatment process of said material, said apparatus comprising means for feeding and removing the medium used for heating as well as means for feeding and removing the material to be heated in and out of the apparatus. According to the invention, both the flowing space of the material to be heated and the flow channels (3) of the heating medium are installed in an essentially vertical position, so that the material to be heated can be fed to the bottom part of the flowing space, and the heating medium can be fed to the top part of the flow channels (3), and that in the feed chamber (5) of the material to be heated, there are installed means (9) for cleaning the feed chamber (5).