Furnace for the treatment of expandable of volcanic rock, in particular perlite

摘要

1,152,164. Furnaces for heat treating granular solids. BRITISH & OVERSEAS MINERALS Ltd. 27 Nov., 1967 [22 May, 1967], No. 23573/67. Heading F4B. A furnace for heat treating expandable perlite comprises an open steel tube 16 having narrowed end portions into the lower of which an oil or gas burner 10 fires. The tube 16 is surrounded by further casings 22, 24 and 28, the tube 16 and casing 22 being provided with longitudinally extending slots whereby butane or preheated air may be introduced into the tube to vary the atmosphere or the temperature along its length as required. Insulating material 30 is located between the casings 24 and 28. The burner 10 may be raised or lowered to vary the combustion rate within tube 16. Crushed perlite to be expanded is fed from hopper 14 through spiral preheating tube 26 into tube 16, the heat expanded perlite being carried with the combustion gases out through pipe 38, any unexpanded perlite dropping out of the bottom of tube 16. Cool air from inlet 40 may be introduced into pipe 38 to cool the combustion gases which are separated from the expanded perlite in a succeeding water cooled separating unit (Fig. 1B, not shown) formed of two cyclone separators, the separated gases then passing to a stack through a plant pressure regulating valve and a suction fan.