Study On Effect Of Zinc On Blast Furnace Smelting Process

Under the pressure of ironmaking cost,a lot of blast furnaces are forced to use the low-grade iron ore and the poor metallurgical properties coke which leads to the increase of zinc content in blast furnace burden materials.And that has brought great influence on blast furnace smelting.This paper studied the effects of zinc on metallurgical properties of sinter and coke,and the primary slag formation process of the comprehensive burden.The results showed that the increase of zinc content would lead to the decrease of sinter’s RDI and RI properties,the improvement of coke’s CRI and the reduction of coke’s CRI.The increase of zinc content in the comprehensive burden would cause the increase of the drip-starting temperature,widening of the soften-melting temperature interval,obvious enlargement of permeable resistance index S and frequent fluctuation of pressure drop.This means that the increase of zinc load may bring about a thickening of the cohesive zone,worsening of its permeability and an unstable pressure drop.It can be found that the amount of zinc would increase noticeably in the lower furnace from the chemical composition of the dropped molt iron and primary slag.And this may aggravate the harmful effects of zinc on refractory materials and coke in the lower furnace.The viscosity tests of different zinc contents of the primary slag were done.And it could be found that the viscosity increased and the fluidity got worse as the zinc content of primary slag increased.The start deformation temperature increases as the the increase of ZnO content of the frozen slag.And this would lead to the thickness of frozen slag increase by analyzing the heat transfer model calculation.It means that the increase of zinc load may cause accretion of furnace body and bad effect on smooth operation of blast furnace.