GB534276A - Improvements in or relating to the heat treatment of metals - Google Patents

Abstract

534,276. Heat treating metals. SURFACE COMBUSTION CORPORATION. Aug. 30, 1939. Nos. 24896, 24897 and 24898. Convention dates, Aug. 30, 1938, Dec. 22, 1938, and Dec. 29, 1938. [Class 51 (ii)] A method of heat treating metals in a furnace chamber consists in maintaining a body of carbonaceous material in an externally heated retort at a temperature substantially the same as that of the furnace chamber, the retort having an offtake delivering to the furnace chamber and an opening remote from the offtake for the inflow of carbonaceous material and for the outflow of volatile gases given off by the carbonaceous material on being heated, and delivering to the retort at a point remote from the opening a sufficient volume of a reactive gas, to ensure simultaneous outflow of gas through the opening and offtake so that gas which flows into the furnace chamber is devoid of volatile gases. The reactive gas may be air, dried flue gas, dried ammonia combustion products or producer gas which will react with the carbonaceous material to produce oxides of carbon substantially free from hydrogen. Fig. 1 shows a furnace for carrying out the above method comprising a muffle 10 arranged in a furnace chamber 14 in which is also arranged a retort 20 in which the gaseous atmosphere is produced and delivered from the retort to the muffle through an offtake 25. The carbonaceous material is fed to the retort from a hopper C having a valve controlled vent 18 for volatile gases produced in the zone B of the retort. Reaction gases are supplied to the lower end of the retort through a pipe 22 and the gases produced in the zone A of the retort pass through the offtake 25 into the muffle. In a modification the offtake 25 is arranged at the lower end of the retort and the pipe 22 is carried down through the hopper and upper, part of the retort and discharges at some distance from the offtake. The retort may be maintained at the desired temperature in a separate furnace and the gases for heat treatment may be withdrawn at a point intermediate of its length while the volatiles are conducted away from the top of the retort through a vent pipe in the hopper.