PURPOSE: To produce high-purity quick lime using a sintering machine at a low cost by mixing powdery limestone having specific granule size with powdery coke at a specific ratio, humidifying and granulating the mixture, charging into a pallet of a sintering machine and sintering in the pallet.

CONSTITUTION: Powdery limestone containing ≥90% of fraction having particle diameter of ≤3mm and powdery coke having particle diameter of ≤3mm are supplied to a mixer 2 through hoppers 1a, 1b, 1c, etc., at a ratio (coke/limestone) of 10.5-12.2% and mixed with each other. The water-content of the mixture is adjusted to 3.8-5% and the mixture is granulated with a mixer 3, transferred through a surge hopper 4, a drum feeder 5, a slopping chute 6, etc., and charge into a pallet 8 of a sintering machine 7. The upper surface of the mixture is ignited with an ignition furnace 9 and the calcined product is treated with a crusher 10, a cooler 11 and a screen 12. The obtained quick lime is crushed with a crusher 13 and stored in a hopper 14.