Method for operating cement plant

A method for operating a cement plant which includes a preheater that preheats a raw material, a calciner that calcines at least part of the raw material picked out of the preheater, a cement kiln that burns the raw material passed through the preheater and the calciner into cement clinker, and a cooler that cools the cement clinker discharged from the cement kiln, the method comprising:

• feeding first fuel in an amount required for calcining the introduced raw material to the calciner;
• feeding to the cement kiln, along with combustion primary air, second fuel in an amount required for maintaining an inside of the cement kiln at a burning temperature, and introducing air in a certain amount for cooling the cement clinker to the cooler;
• and
• feeding a part of the air as secondary air for assisting combustion of the second fuel to the cement kiln, feeding another part of the air as tertiary air for combustion of the first fuel to the calciner, and discharging the rest of the air from the cooler, wherein
• relation between a first oxygen concentration at an exhaust gas outlet of the calciner and a heat consumption rate determined by the first fuel and the second fuel, and relation between a second oxygen concentration at an exhaust gas outlet of the preheater and the heat consumption rate are beforehand calculated and obtained, the first oxygen concentration at the exhaust gas outlet of the calciner being measured before the second oxygen concentration at the exhaust gas outlet of the preheater, and
• flow rates of the tertiary air and exhaust from the cooler are adjusted such that both the first oxygen concentration and the second oxygen concentration fall within a range including values of the oxygen concentrations at which the heat consumption rate becomes at its minimum, whereby both the combustion at the calciner and the heat consumption rate are simultaneously optimized.