Abstract: In a thermochemical method, a syngas comprising oxygen is combusted in a furnace, thereby producing a hot exhaust gas. The exhaust gas is subsequently discharged into the surroundings while the inner energy of the exhaust gas is at least partly used to carry out a reformation reaction. For this purpose, steam together with a hydrocarbon-containing fuel and an oxygen-containing gas are supplied to a reformer and converted into syngas in an endothermic reaction using inner energy of the exhaust gas. The heat of the exhaust gas is used in particular to evaporate water and supply same to the reformer in a superheated state. The syngas is then supplied to the furnace as fuel. The invention prevents undesired constituents of the furnace atmosphere, in particular sulfur compounds, from being supplied to the reformer.