Novel approach to diagnosis of blast furnace conditions: Thermal distribution analysis based on [eta] H[sub 2]

It has been confirmed from the results of measurement of furnace temperature by a vertical probe that even when the blast furnace is operated with high rate of pulverized coal injection, a 500 C to 800 C low temperature thermal reserve zone (LTTR zone) occurs in the shaft. On the other hand, even when the reduction degradation index (RDI) of sinter is the same, the rate of reduction degradation of sinter varies according to temperature. Fine sinter produced by reduction degradation accumulates in the shaft, causing the gas flow distribution to become uneven and the LTTR zone to become firmer. Therefore, in blast furnace operation, it is important to set control indexes for early detecting the occurrence of a LTTR zone and take appropriate counteraction without delay. According to furnace operation data or results of analysis by a Blast Furnace Inner Reaction Simulator (BIS), the hydrogen utilization rate ([eta]H[sub 2] [equals] H[sub 2]O / (H[sub 2] + H[sub 2]O)) declines when a LTTR zone occurs. Thus, it has been found that [eta]H[sub 2] can be used as an index of the uniformity of gas flow and the temperature level of the lumpy zone in the shaft. This paper describes themore » relationship between [eta]H[sub 2] and furnace operation, the results of BIS analysis of mechanisms by which the LTTR zone occurs, a method of locating the LTTR zone occurs, a method of locating the LTTR zone, and countermeasures to be taken when the LTTR zone occurs.« less