A substantially vertical apparatus for cooling process gases originating from a gasification process, along with simultaneous separation of solid matter contained in the process gases. The apparatus is a cylindrical container including several cylindrical container parts. A gas inlet is provided in the lower region of the container shell or mantle and substantially tangential thereto. The gas inlet opens into a cyclone. Cooling surfaces are provided above the cyclone, with those directly above the cyclone being embodied as platen heat transfer surfaces, and those further above being embodied as cylindrical heat transfer surfaces. The cylindrical heat transfer surfaces are suspended in the container via support elements in the manner of an immersion heater. The support elements, in conjunction with a tube and a regulating device arranged at the process gas outlet, regulate the volume or quantity of the process gases flowing or circulating around the upper cylindrical heat transfer surface. Aside from the platen heat transfer surface and the cylindrical heat transfer surfaces, container wall cooling surfaces are provided as vertical heat transfer surfaces having a tube-crosspiece-tube construction, the container wall cooling surfaces being centered with respect to the outer wall of the container via a packing mass. Beating or striking devices for cleaning the heat transfer surfaces are associated with each heat transfer surface system, each of the latter being respectively associated with a cylindrical container part.