| In this study,when Shougang Jingtang Iron and Steel Works tried to stop sinter spraying calcium chloride,the index of sinter’s low temperature reduction disintegration rate was seriously low.From May to July 2016,the average index of sinter RDI+3.15 was only 51.58%,which resulted in high pressure difference at the upper part of the blast furnace and seriously affected the operation and production technical indexes of 5500m3 blast furnace.So the subject was brought forward to solve the problem.Through basic experiments,simulation experiments and sinter pot experiments,the status quo of sintering raw materials was clarified,the mechanism of low temperature reduction was revealed,and the law of influence of sintering conditions on iron ore mineralization was obtained.A technical measure of MgO addition was put forward,which was verified to be feasible by sintering production and blast furnace practice.In July 2019,Shougang Jingtang Iron and Steel Works ended the history of spraying calcium chloride into sinter.Through the above studies,the following innovative understandings and conclusions are obtained:(1)Through the sintering and reduction experiment of changing the content of Al2O3 and MgO in iron ore powder,it is clear that the solid solubility of Al2O3 in hematite is the main reason for the serious disintegrating of sinter at low temperature reduction;At the same time,it is found that the presence of Al2O3 can promote the transformation of hematite to calcium ferrite,so that the presence of Al2O3 and MgO can weaken the negative effect of MgO on the formation of liquid phase in the sintering of iron ore powder,laying the foundation of the technical measures with MgO.(2)The sintering process of various iron ore powders was studied in situ by TG-DSC method,and it was found that liquid phase formation concentrated in two temperature ranges.It was clear that the addition of homemade powder and Yangdi powder was conducive to the formation of these two low temperature liquid phase and high temperature liquid phase,respectively,and it was verified that they had good assimilation to the low melting point mineral calcium ferrite at the early stage of sintering process.At the same time,it was found that the increase of mineral species was helpful to promote the formation of liquid phase.On this basis,an appropriate ore blending scheme was proposed to add MgO to inhibit the low temperature reduction disintegration of sinter:4/12 Yangdi powder-6/12 calorie powder-1/12 King powder-1/12 Ba powder.The results of sinter pot experiment showed that when MgO content was 1.6%,RDI+3.15 index reached 75.8%,which was 7.3%higher than that of field mixed sinter.(3)The production of sinter containing MgO and its application in a 5500m3 blast furnace verify the feasibility of this scheme.The MgO content of sinter increases from 1.03%to 2.0%at the beginning,and the low temperature reduction disintegration rate RDI+3.15 increases from 52%to about 70%.The application of MgO-containing sinter in the blast furnace reduces the upper pressure difference from 0.6-0.65kg/cm2 to 0.45-0.5kg/cm2,which promotes the stable operation and lifting index of the furnace condition,and provides theoretical support and production reference for the stable operation of large blast furnaces. |
PDF Full Text Request