NOVELTY - Production of fuel gases by thermal conversion of a solid charge, in particular by pyrolysis, thus generating solid residues and raw gases. Combustion of the solid residues produces combustion gases and thermal cracking of the raw gases produces fuel gases. All or part of the combustion gases are used to supply thermal energy to the thermal cracking of the raw gases.    USE - For producing fuel gases from a solid charge, such as biomass or industrial or domestic waste    ADVANTAGE - All the pyrolysis gases are converted to fuel gases    DETAILED DESCRIPTION - Part of the combustion gases supply the energy required for thermal conversion of the solid charge before being used in the cracking operation. The combustion gases supply at least one means of heating to the thermal cracking of the raw gases. The combustion gases are mixed with fresh air to obtain the desired temperature for thermal cracking. The temperature and speed of increase of temperature in the means of cracking is controlled by altering the flow and quantity of combustion gases and/or fresh air. The raw gases are heated indirectly or directly during the thermal cracking operation.    An INDEPENDENT CLAIM is included for an installation for carrying out the above process, with means (10) of thermal conversion of the solid charge, means (28) of burning the solid residues and means (12) of thermally cracking the raw gases. The thermal energy from the means of burning is transferred to the means of cracking via a means of transport (38). A link (30) connects the means of thermal conversion to the means of combustion and the means of transport has a bypass (38, 40) to the link which supplies the means (42) of heating the cracker. The means of heating the cracker is also supplied with fresh air through a fresh air feed (48). The means of heating the cracker are indirect or direct, with means (42) of injecting the combustion gases into the cracker.    DESCRIPTION OF DRAWING(S) - The figure shows schematically shows the above process.    Cracker (10)    Means of thermal conversion of solid charge (12)    Means of burning solid residues (28)    Link (30)    Bypass transporting heat to cracker (38)    Bypass (40)    Means of heating cracker (42)    Fresh air feed (48)