A slag door arrangement (10) for a metallurgical furnace (1) includes a furnace vessel (2) with a slag tunnel (8) having a rectangular opening cross section extending laterally through the furnace vessel (2). A pivoting movement of the slag door about a horizontal pivoting axis and a lifting movement of the slag door in a direction perpendicular to the horizontal pivoting axis are independent of each other. A method for cleaning a slag opening of such a metallurgical furnace (1) includes pivoting the slag door to perform a cleaning movement from a position of the slag door in the slag tunnel near the interior of the furnace towards the outside of the furnace out of the slag tunnel at controllably different distances (clearances) from the bottom of the slag opening or of the slag tunnel.

The invention relates to a furnace for the treatment of material, in particular for the oxidative treatment of fiber material, in particular for producing carbon fibers, comprising a housing (12) having a housing inner space (14), which is gas-tight with the exception of passage areas (18, 20) for the fibers (22). In the housing inner space (14) of the housing (12), a process chamber (28) is located. A hot working atmosphere (40) can be generated by means of an atmosphere device (42). The atmosphere device (42) comprises a flow system (46) having flow channels (48), which are arranged in the housing inner space (14) each defining one flow chamber (50), and are provided with flow passages such that the respective flow chambers (50) are fluidically connected to the process chamber (28) in such a way that hot working atmosphere (40) can be delivered to the process chamber (28) in at least one main flow direction (44) and can be discharged from the process chamber (28). A revision system (72) is provided, through which flow chambers (50) of flow channels (48) are accessible through the housing (12).

A slag discharge door device for an electric furnace is provided. The device prevents slag from flowing out via a slag discharge port by making a discharge control door body move up and down to and from the upper surface of a supporting body where slag is discharged by flowing to the upper surface, and the discharge of slag is controlled, such that during steel-making work in the electric furnace, the outflow of slag is prevented and heat losses are reduced, the efficiency of arc heat due to the formation of foamed slag is increased, and valuable metals are recovered from the molten slag thereby increasing the percentage of molten steel recovered.