To let heating gas flow with the same conditions in each inner tube, and to reduce amount of heat dissipation, in an indirect heating type and multiple tube type rotary kiln.
In an outer tube 12 which is arranged horizontally to be rotatably driven and which has a single pipe structure, a plurality of inner tubes 13 having a double pipe structure of an inner pipe 13a and an outer pipe 13b are stored and fixed. One end of each inner pipe 13a of the inner tube 13 is gathered to be located at the entrance 2 of the outer tube 12, and the other end of each inner pipe 13a is gathered to be located at the exit 3 of the outer tube 12. The opening between the inner pipe 13a and the outer pipe 13b of the inner tube 13 is made to be a heating channel 18. A heat insulating layer is formed by enclosing air in a space part 19 between the outer tube 12 and the inner tube 13.
MOGI MIKIO
HAGITANI MUNETAKA
