Tunnel furnace with preheat zone - has reversible fan to recirculate hot gases in the preheat zone for uniform temps.

摘要

Temps. in the preheat section of a tunnel furnace are evened out using a reverse flow process. At least one reversible fan is used with suction branches in the lower part of the combustion passage. It is connected to reinjection points in the roof of the passage. The hot gases are then cyclically extracted from the lower zone of the furnace and are reinjected via the inlets in the roof. The suction points of the fan are connected both with the lower section of the combustion zone and with the space below the firing trolleys. Partition walls with adjustable slides are provided between the zones below the trolleys. A reverse flow fan can be located at both furnace inlet and outlet and both operated simultaneously in sucking and blowing modes. Used in tunnel furnaces and reduces the temp. differing between the top and bottom of the furnace passage caused by the high thermal inertia of the trolleys.