Method and device for combusting a solid phase fuel, where the fuel is caused, by the help of a non-pneumatic feeding element (11), to be fed to an inlet opening (11a) in a burner device (10), where the burner device (10) includes a first inlet (13a) for the oxidant through which an oxidant is caused to flow via a first supply conduit (13). The first inlet (13a) for oxidant is arranged in the form of a first opening arranged by the inlet opening, through which the oxidant is caused to flow out, through a burner pipe (16) and out through a burner orifice (17) to a combustion space (18), so that the oxidant by ejector action causes the fuel to be conveyed through the burner pipe and out through the burner orifice (17), and water vapour is added to the oxidant before the oxidant reacts with the fuel.