Abstract: A heat exchanger has been developed with a helical insert (9) permanently mounted in a housing (2). Between the windings in the insert (9) there is formed a helical channel (20) for one heat exchange medium. The insert (9) is designed with a channel (10) for the second heat exchange medium. The heat exchanger is designed with a central tube (13) which is axially movable and rotatable. The central tube (13) is designed with scraper elements for removal of deposits in the channel (20). In one embodiment the scraper element is formed by a helical insert (15) of the same design as the insert (9). The insert (15) is designed with a channel (16) for the second heat exchange medium. In a further embodiment the central tube (13) is designed with one or more scraper arms (23) which may be liquid-cooled. Deposits are often formed on the heat transfer surfaces.

Abstract: A method of operating a combustion plant including a reactor, e.g. a fluidized-bed reactor which transfers heat form a fuel to a granular medium, such as sand, and wherein a part of the heated medium during operation is discharged from the combustion chamber (2) of the reactor (1) and supplied to a heat-producing heat exchanger (11). The plant further includes a storing means (9) which is connected to the combustion chamber (2) of the reactor (1), and a part of the discharged hot medium is transferred to the storing means (9) which stores the medium in order to accumulate the heat therein. In case of increased energy demand, hot medium is supplied from the storing means (9) to one or more additional heat exchangers (28, 29, 30) for supplementing the heat production of the first-mentioned heat exchanger (11).