Improvements in kilns for revivifying bone charcoal and substitute or similar material

601,197. Furnaces. STORDY ENGINEERING, Ltd., and STORDY, J. J. Nov. 15, 1945, No. 30539. [Class 51(i)] In a kiln for revivifying bone charcoal and the like comprising vertical tubes 12, which may be provided with internal or external fins or both, between which the heating gases are circulated and through which the charcoal gravitates from a hopper 10 to cooling-tubes 16, uniformity of heating is attained by recirculation of the combustion products. The combustion chamber 22 is fired by a gas-burner, a fan 25 extracting the gases from the opening 24 and passing them to a chamber 27 communicating by passages 28 with the chamber 29 containing the tubes 12. The bulk of the gases return to the combustion chamber 22 through passages 30, but sufficient bleeding is effected through the pipe 31 to allow gas and air for combustion to enter the chamber 22. Pipes 32, connected to discharge pipes 33, collect steam and vapour from the charcoal in the tubes. The cooling tubes 16 are provided internally and externally with pipes 17, 19 open at their lower ends for the admission of cooling-air and connected at their upper ends to headers 20 connected to exhausting- means.