NOVELTY - Pyrolysis furnace, for treating waste, has a vessel, and a container for a means of heating the vessel. Heating gas is injected through heating line. A by-pass line evacuates the gases, from an envelope with at least one compartment (34) fed with the heating gases by an injector. The heating and outlet lines contain a means of regulating the gas flow.    USE - For incinerating urban and/or industrial waste    ADVANTAGE - The novel system enables control of the temperature in the furnace.    DETAILED DESCRIPTION - Pyrolysis furnace (12), for a solid charge, in particular urban and/or industrial waste, has a vessel (24) to receive the waste for pyrolysis and generation of pyrolysis gases, and a container (32) for a means of heating the vessel. Heating gas is injected through at least one heating line (50) connected to a pipe (48) carrying the gases at high temperature. A by-pass line (62) is between the pipe carrying the gases at high temperature and a pipe (38) for evacuating the gases from the envelope. The envelope has at least one compartment (34) fed with the heating gases by the injector and with a outlet pipe (36) for the heating gases. The heating line contains a means (52) of regulating the gas flow, and the outlet line contains means (72) of regulating the gas flow. The line carrying the gases at high temperature from a heat generator (14).    An INDEPENDENT CLAIM is included for a waste treatment installation for urban and/or industrial waste, containing a furnace and a heat generator as described above. The heat generator includes an inlet for hot gases from the heating of the furnace. The installation also includes a dryer for the solid charge and heat generator includes an inlet for hot gases from the dryer.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the above pyrolysis installation.    Furnace (12)    Heat generator (14)    Vessel (24)    Pyrolysis gases (30)    Envelope (32)    Compartment (34)    Outlet pipe for heating gases (36)    Evacuation pipe (38)    Burner (40)    Combustion gases (42)    Unused fraction of high temperature gases, sent to a heat recovery unit (46)    Pipe carrying gases at high temperature (48)    Connection lines (50)    Flow regulator (52)    Bypass line (62)    Flow regulator (72)