Abstract: A waste liquor recovery furnace includes a lower combustion chamber and an upper final combustion chamber, separated by a restricted gas passage. The furnace has a basically cylindrical configuration, being defined by a tube membrane shell, and the lower combustion chamber is formed by tubes from said shell being bent, doubly inwards, defining a discharge opening for the liquid combustion residue. A screen of tubes in the final combustion chamber is arranged to direct the gases towards the shell, being substantially solid in the center of the chamber, directly above the discharge opening.

Abstract: Air admittance ports in the wall of a refuse burning furnace are provided with reciprocable sleeve members which in the first hand govern the air flow, but also may be used to scrape the ports free of deposits. These sleeves are interconnected in groups so they can be manipulated simultaneously for cleaning purposes, but nevertheless may be adjusted individually as well as group-wise for flow governing purposes.