Effect of nut coke on the performance of the ironmaking blast furnace

Abstract

The blast furnace consumes a large amount of high quality metallurgy coke (size 35-80 mm) in addition to ore in the form of pellets and sinter. This coke is the coarse fraction, derived from the coke plant. The fine fraction (8 -35 mm), arise after sieving, named nut coke, can’t be directly used in blast furnace. The fraction of smaller than 8 mm is used in the sinter plant. Therefore, a large fraction of coke around 20 % from coking plant/process is not used for iron ore reduction. Recent research indicates that usage of nut coke will be economic if properly used. Nut coke cannot be directly mixed with normal coke because it will decrease the permeability of the coke layer in the blast furnace. However, mixing nut coke into the ferrous burden layer could be an effective way to use the coke resource economically. This mixed charging could improve softening and melting behaviour, reduction kinetics and permeability and also make full use of the coke resource. It may, however, also worsen the layer permeability and even deteriorate the whole blast furnace process. The mechanism of the effect of mixing nut coke into the ferrous burden on the performance of the blast furnace is still not clear, and thus the usage of nut coke is still limited. To investigate the effect and mechanism of using nut coke in the ferrous burden on the performance of the blast furnace, cold flow model experiments and high temperature experiments have been conducted. An advanced Reduction, Softening and Melting experimental facility (RSM) was designed for high temperature experiments at TU Delft.