HEAT EXCHANGER
A heat exchanger in the form of a vessel for heat exchange of a pulverulent solid material and a gas, e.g. for preheating raw materials prior to a burning process by use of the hot exit gases fed to the vessel consists of a hollow cylindrical central part (1) with a tangential gas inlet (3), a conical base (2) with a material outlet (5), and a downwardly orientated gas outlet (4), a concave upper part (7, 7') facing the central part and with at least one material inlet (8); the downwardly orientated gas outlet (4) is mounted initially axially as a central pipe inside the vessel and is provided with a skirt (6); the height of the upper part, the distance of the material inlet from the vertical axis of the heat exchanger and the inclination of the inlet to the horizontal plane, the height of the central pipe gas inlet (4) above the lower end level of the central part (1) of the vessel and the inclination of the skirt (6) are all dimensioned so as to provide optimum conditions, partly for heat exchange in radial countercurrent between material and gas, partly for separation of material from gas inside the vessel due to the downwardly orientated axial and tangential gas velocities.