Abstract: Fuel gas produced e.g. in a fluid bed gasifier and which comprises deposit-forming materials such as heavy hydrocarbons (e.g. tars) and non-combustible fines is passed via conduits and solid-removing cyclones to a burner for admixture with air and subsequent combustion. Deposits formed in the conduits cyclones and burner are removed by closing off the burner outlet and air inlet, and passing a deposit-removing reactant (e.g. air) into the conduit to oxidize and thereby remove deposits, particularly from the cyclones. Preferably, there are at least two burners for the fuel gas, and they are closed off alternately to remove deposits from their respective conduits and cyclones.

Abstract: Substantially sulfur-free combustible fuel gas under superatmospheric pressure is produced by partial combustion or gasification under superatmospheric pressure of a sulfur-containing solid, liquid or gaseous fuel. The gasification is effected within a fluidized bed of particles containing alkaline earth metal compounds (e.g. the oxides) which are capable of reacting with, and of fixing, the fuel sulfur as sulfides under reducing conditions. Sulfide-containing particles are exposed to an oxidizing atmosphere and the sulfides are thereby converted to oxides with the liberation of SO.sub.2 in useful concentrations, and with the liberation of heat. Particles containing regenerated oxides are re-used for fixing more sulfur during fuel gasification. Expedients are described by which it is ensured that the sulfur-fixing activity of the particles is substantially maintained and that the temperatures of the particles during sulfur-fixing and regeneration are maintained within predetermined ranges.