Abstract: For cleaning at least one of the sides of the essentially vertical heat-transmitting walls between two fluids in a heat exchanger, solid particles are introduced into a stream of fluid, which particles are smaller than the distance between opposite walls defining the flow of fluid, said fluid with particles being introduced into part of a collection or distribution space above said walls and said particles being collected below said vertical walls and discharged from the heat exchanger. The particles are so heavy that they move downwards in the fluid even if this has an upward direction of flow between the walls. The particles are introduced above only part of the transverse plane above the vertical walls and switch means allow switching of said introduction to other parts of said transverse plane periodically. Thereby, the normal operation of the heat exchanger can continue with hardly any pressure loss during cleaning.

Abstract: Installations for operating physical and/or chemical processes, for example heat exchangers, comprising a bundle of parallel vertical tubes which, via tube plates, are in open connection with a bottom header and a top header, are known to operate with a granular mass maintained in a steady or quasi-steady fluidized state, at least in the tubes, by means of a medium flowing upwards through the headers and tubes. At start-up and shut-down of such installations problems are encountered because the granular mass tends to settle to form a packed bed, in particular if the upwardly flowing medium may contain solid impurities or has a rather high viscosity. The invention solves such problems by using a storage vessel, to which the granular mass is flushed at shut-down of the installation, a partial stream of the flowing medium being first fed through the tubes at start-up, after which the granular mass is flushed from the storage vessel to the tubes and only thereafter the main stream of medium is fed to the tubes.

Abstract: Apparatus for carrying out physical and/or chemical processes has a lower chamber, an upper chamber, vertical riser tubes for the passage of a first fluid medium from the lower chamber to the upper chamber and an intermediate chamber through which the riser tubes exetend so that a second fluid medium can contact the riser tubes. A granular mass is fluidized in at least the riser tubes by the flow of the first medium. A vertical gravity tube for return passage of the granular mass from the upper to the lower chamber has an outlet below the inlets of the riser tubes. A distribution plate for the first medium is mounted in the lower chamber between the inlets of the riser tubes and the outlet of the gravity tube. To allow the granular mass to fall below the distribution plate for start-up of the apparatus the gravity tube has, at least one opening connecting to the lower chamber above the distribution plate.