Effect of Nut Coke-sinter Mixture on the Blast Furnace Performance

Abstract

Among different ways to reduce the coke consumption in the blast furnace, not so much attention was paid for decreasing the coke losses through finding suitable application of small size coke called “nut coke”. In meantime modern blast furnaces use nut coke with different amount (10–140 kg/t hot metal) and different grain size (10–40 mm) in the sinter layer to reduce the coke losses. The objective of this paper is to clarify the influence of nut coke on the shaft permeability and sinter reducibility under blast furnace simulating conditions. The effect of various factors such as nut coke rate, gas flow rate, and layer thickness on the shaft permeability was estimated using cold model rig. The influence of nut coke on the isothermal and non-isothermal reduction of sinter was estimated under different gas compositions and temperatures using muffle reduction furnaces. The isothermal reduction of sinter with 30%CO–70%N₂ exhibited reduction retardation at elevated temperatures (>1373 K). The reduction retardation increased by the presence of CO₂ gas in the reducing atmosphere while decreased by participation of H₂ gas. Mixing nut coke in the sinter bed improves the sinter reducibility and inhibits the reduction retardation phenomenon.