BLOW-DOWN OPERATION OF BLAST FURNACE

PROBLEM TO BE SOLVED: To facilitate the ejecting word of remained material in a furnace by reducing the remained material in the furnace at the time of blowing down a blast furnace, by keeping a theoretical combustion temp. in the front of a tuyere in specific temp. range just before blowing down the blast furnace. SOLUTION: Just before blowing down the blast furnace, charging material is gradually reduced, and the operation is executed while changing the operational condition according to the reduced quantity thereof. At this time, the theoretical combustion temp. in the front of the tuyere TFT shown by equation I is kept to in the range of 1,600-1,800 deg.C to execute the blow down operation of the blast furnace. A in equation I is shown by equation II, and B is shown by equation III. In equations II, III, VB is blasting quantity (Nm /min), TB is blasting temp. ( deg.C), MB is moisture content in the blasting (g/Nm ) and VD is enriched oxygen quantity (Nm /min). This theoretical combustion temp. range is mainly kept by adjusting the moisture content in the blasting. By this method, even in the case of operation with high fuel ratio, the producing of a large quantity of SiO2 is restrained and the viscosities of molten iron and slag are kept low.