1,172,597. Continuous kilns. KELLER OFENBAU G.m.b.H. 23 March, 1967 [6 April, 1966], No. 13613/67. Heading F4B. A tunnel kiln for firing ceramic material of the type having an oxidizing firing zone 11 followed by a reducing firing zone 13, has roof burners 12 in zone 11 and roof burners 14 in zone 13 firing into the spaces 4 left between stacked material on kiln trucks 6, and roof blast pipes 15 and 24 supplying cooling air from fans 18 and 27 on either side of a zone in which ports 19 in the kiln side walls discharge gases into branch pipes 21 supplying a pair of roof ducts 23 connected at each end to fans 29. Offtakes 10 are provided for waste gases near the kiln entrance and the ducts 23 have valves 32 at intervals along their length. Heated air drawn off by fans 29 may be supplied to a two-stage drying process for the charge material and may be supplied through blast pipes 15 with the addition of water or an inert gas. Interchangeable and adjustable nozzles may be provided on pipes 15 and 24.
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