At the high productivity operation of Keihin No. 2 BF (4052 m3, blown in 1979), taking into account the limit of five limited factors (fluidization of burden materials at throat, flooding of dropping liquid below cohesive zone, heat flux ratio, traveling time of burden in furnace and flame temperature at tuyere nose), the appropriate operational diagram with oxygen enrichment and humidity addition has been introduced and estimated. According to this diagram, the steps to increase the productivity have been planned and carried out with the increase of oxygen enrichment and humidity addition simultaneously.
In order to increase the productivity, the increase of blast volume was considered to be more effective than the decrease of coke rate. Therefore, following five countermeasures against the improvement of permeability in furnace have been carried out.
1. Increase in strength and size of coke
2. Decrease in fine ratio of burden materials
3. Improvement of burden distribution controllability by repairing the throat profile
4. Burden distribution control aimed at U-type pattern (sharp central flow with strong peripheral flow)
5. Changes in tapping procedures corresponding to the high productivity operation.
As a result, the high productivity operation over 2.4 t/m3/d has been continued in Keihin No. 2 BF since June of 1989. Especially, the maximum productivity 2.69 t/m3/d (10900 t/d) was recorded in August of 1989.
