PURPOSE: To make a recovered gas into a high-calorie gas in a range capable of preventing explosion, by using a CO2-containing gas having high concentration as a cooling gas for red-hot coke in dry quenching of coke.

CONSTITUTION: A coke cooling gas containing ≥20% CO2 evolved from a blast furnace is cooled by the heat exchanger 6, sent to the cooling column 3 by the blower 7, and the red-hot coke 1 pushed from a chamber oven put in it is cooled with the cooling gas. The blast furnace gas 5' subjected to heat exchange and provided with high temperature and high calorific value is sent through the flue 8 to the boiler 9 to generate the steam 10, and the gas itself is cooled, sent to the heat exchanger to cool the blast furnace gas 5, and it is recovered as a gas with high calorific value.