157,318. Polysius, G. [Firm of]. Feb. 1, 1918, [Convention date]. Cooling discharged materials.-In a low temperature carbonization process an externally heated retort is also internally heated by a stream of gas taken from the retort and preheated by being passed through the hot coke ejected from the retort, the coke being cooled thereby. Coal is fed from a container 1 into a rotating externally heated retort 4 and the coke is delivered therefiom through a delivery adjuster 12 into a shaft 5. A fan 7 draws off distillation products through a pipe 6 and condenser 8 and delivers the gas through an annular pipe 9 to the coke shaft, whereby the coke is cooled and the gas heated before entering the retort and completing the cycle.