Abstract
NKK jointly with Asahi Glass Co., Ltd. have developed a Hot Blast Control Valve (HBCV) which can control the flow rate at each tuyere. 19 HBCVs out of 38 tuyeres were installed in Keihin No. 2 BF in 1986. Through various test operations, innovative technologies for blast furnace operation have been developed. This paper reports the circumferential balance control of stock line levels.
(1)At the proper block with closed HBCVs, the coke consumption amount at the tuyere decreases, however the burden descending rate at the throat becomes faster. Applying these phenomena, it is Possible to control the circumferential balance of SL levels.
(2)The simple stand-alone method, where the HBCVs at the block with higher SL level are closed based on the average SL levels during the past definite period of time, had sometimes put into disorder, and it was impossible to continue a stable control of SL levels.
(3) For further stable control, Successive Alleviative Integration (SAINT) method has been developed, taking account of their interferences of each HBCV opening, dead time and integral action of changes in valve opening.
(4)The test operation in Keihin No. 2 BF showed that it is extremely effective for the improvement of furnace conditions and decrease of Si content in hot metal to control the circumferential balance of SL levels on the SAINT method.
