Substitution of Charcoal for Coke Breeze in Iron Ore Sintering

Abstract

The substitution of charcoal as an alternative fuel to coke breeze in a simulated Japanese Steel Mills (JSM) sinter blend was investigated. Compared with coke breeze, higher mix moisture contents were required for the sinter mixture containing charcoal to achieve optimum granulation. The green granules formed from the sinter mixture containing charcoal were clearly less dense and formed a less compacted green bed as evidenced by the packing density. To achieve return fines balance, fuel addition had to be increased from 3.62 to 4.17% (on a dry mixture basis) as the substitution of charcoal increased from 0 to 50%. However, at 100% subsitution, the sinter mixture failed to achieve balance even at a very high fuel addition level of 4.7%. Compared with the sinter fired with coke breeze, the sinter from the mixtures containing up to 50% charcoal was marginally weaker in terms of sinter yield, tumble strength (TI) and reduction disintegration (RDI). The reasons for weaker sinter are discussed. Fuel rate increased considerably with charcoal substitution due to increased fuel addition and decreased sinter yield. However, increasing fuel rate did not lead to a reduction of sintering productivity. In contrast, the sintering speed and productivity were maintained as the charcoal substitution rate increased from 0 to 25% and then increased considerably with further increase in charcoal substitution rate. The emission mechanisms of the CO, CO₂, SO₂ and NO_X and H₂O gases during sintering are clearly quite different. CO, CO₂ and NO_x emission was observed over the entire sintering process and varied slightly as the sintering process progressed. However, the SO₂ and H₂O emissions were observed only towards the completion of the sintering process. Both the CO and CO₂ concentrations in the waste gas increased with the increasing substitution of charcoal for coke breeze; however the concentrations of SO₂ and NO_X in the waste gas decreased.