Abstract: A melting furnace for thermal treatment of heavy metal-containing and/or dioxin-containing special wastes, including a clog preventing system including a principal furnace vessel, which exhibits a melting tank for holding a melt; at least one feeder for feeding the material to be treated; a discharge chamber, which is at a spatial distance from the feeder, the feeder being connected gas-tight via a siphon to the melting tank; the principal furnace vessel and the discharge chamber having third heating elements in the form of bath electrodes, by means of which an electric current can be run through the melt and the siphon for additional heating of the melt.

Abstract: A melting furnace for melting residues from refuse incineration plants, in particular filter dust melting furnaces, contains a furnace substructure and a furnace superstructure lined with different refractive material compositions. The lining in the substructure, the melting region, is a refractory material which, in addition to other metal oxides, contains 10-70% wt. % Cr.sub.2 O.sub.3. The lining in the superstructure, the gas atmosphere region, is a refractory material which contains 80 wt. % or more of MgO and is low in Cr.sub.2 O.sub.3 or is virtually Cr.sub.2 O.sub.3 -free. A furnace constructed in this manner exhibits long endurance and does not form toxic chromium compounds in the chromium-free gas region.

Abstract: In a filter dust melting furnace, the waste gases occurring in the interior (9) of the furnace are conducted outward through a waste-gas line (5) in the furnace top. Provided in the course of the waste-gas line is a quench (20) for the abrupt cooling of the waste gas by cold quenching air acting on it. To prevent deposits in the waste-gas line, the quench (6) is arranged in the section of the waste-gas line (5) which directly adjoins the furnace vessel (1) and extends essentially vertically, and means are provided for cooling the quench and the section of the waste-gas line (5) located downstream after the quench.