Development of Control Techniques for Mixing Small Coke at Bell-less Top Blast Furnace

Increased gas utilization and improved permeability have been desired in order to achieve low RAR (Reducing Agent Rate) operation of blast furnace. Coke mixed charging in the ore layer is one effective measure for realizing these improvements. In this research, burden distribution control technique for mixing small coke at a parallel type bell-less top and at a center feed type bell-less top were developed and investigated in an experiments with scale models of two actual blast furnaces at JFE Steel. The mixed coke ratio was controlled by the discharge pattern of the mixed small coke and the mixing position. With the center feed bell-less top, the optimum patterns was discharge of the small coke from the coke bin after discharge of the ore, and the parallel type bell-less top, the optimum pattern was discharge of the small coke on the ore at the front of an overlapped quarter part. These patterns were applied to two actual blast furnaces, and improvement of permeability was confirmed as a result of increased mixed small coke ratio.