THEORY AND OPERATING DATA OF CYCLONE IMPROVEMENT IN A CFB BOILER

摘要

The public utility company, Stadtwerke Flensburg GmbH, operates three circulating fluidized bed (CFB) boilers (boilers 9, 10 and 11), which are almost identical in construction.Over the years numerous modifications have been made to the steam generators.Consequently, a fuel mixture is combusted today totally different from the one for which the installations were originally designed.Ruhr coal has been completely supplanted by import coal.Furthermore, up to 12％ refuse derived fuel (RDF) is now utilized.Due to economic pressures, as much RDF as possible must be burned.Therefore, several CFB boilers often operate concurrently, to some extent also under adverse load conditions.Technical difficulties arose as a result of the fuel changeover and consequently numerous modifications were performed, such as cladding the combustion chambers membrane walls in all three CFB boilers with silicon carbide plates and the installation of a smaller superheater in boiler 9.Due to those changes the functioning of all three CFB boilers was impaired, in particular, however, that of boiler 9.The steam generator could no longer be operated under full load.In order to ensure trouble-free operation, the separation efficiency of the cyclone separator has been improved by installing an eccentrically narrowed vortex finder with swirl vane inserts and a barrier in the inlet duct.