Effects Of Limestone On The Quality Of Sinter

As an important strategic resource,the rational and efficient use of iron ore is of great significance to the sustainable development of China's steel industry.In order to study the optimal proportion of limestone instead of quicklime,this paper studied the improvement of sinter quality through mixture granulation,sintering cup experiment,sinter phase analysis and industrialization experiments.In order to improve the quality of sinter and reduce the cost of blast furnace Iron cost to provide technical support and theoretical basis.(1)The subject first introduced the basic formation of flux used in the experiment,including activity determination,micro structure determination and so on.Through the activity test,it is clear that the activity of the quicklime flux is lower than the theoretical value calculated by the chemical composition.The experiment also shows that the activity of the limestone for sintering is higher than that of the dolomite.Experiments show that the optimal calcining temperature of dolomite and limestone is about 1300?.When the calcining temperature of flux is lower than 1300?,the activity of dolomite and limestone increases with the increase of temperature,Further increase the calcination temperature of 1400?,the activity of dolomite and limestone decreased significantly.Experiments show that dolomite,limestone and quicklime contain more impurities,and by SEM-EDS shows that the distribution of impurities in the flux is not uniform.In the actual sintering process,impurities in the flux react easily with the active CaO of the flux,so that the effective CaO in the flux is greatly reduced and the content of the calcium ferrite is greatly reduced,which is not conducive to the sintering of the iron ore.(2)Secondly,through the experimental study of sintering cup,the use of quicklime,all limestone and the different proportion of quicklime,limestone mixed sinter on the strength of sinter,to explore low-cost energy-saving programs.Different proportions of activated lime.limestone powder sintering as long as the fuel ratio is reasonable and can be produced by the particle size of qualified sinter,but the limestone powder decomposition left more voids with limestone powder increased the proportion of small particles increased.The experimental results show that as the proportion of limestone in sintering mixture decreases,the burning rate of sintered solid decreases obviously,the utilization coefficient increases obviously,while the growth rate of electric consumption increases first and then increases.The limestone in the amount of 25%when the minimum.Reduce the amount of sintering flux does not affect the strength of the drum,but can improve the sinter drum strength;in ensuring the strength of the finished mine to meet the requirements of the circumstances,with the limestone content of raw materials increased with the increase The amount of fuel is also increased,the utilization factor is reduced,the allocation of active lime is conducive to improving the sintering utilization factor and reduce fuel consumption.The purchasing cost of limestone is obviously lower than that of quicklime.In the actual sintering production,a certain proportion of limestone and lime are usually used to produce high alkalinity sinter.By using this method of production,the usage of quicklime can be greatly reduced and limestone powder can be added Of the use of.(3)Furthermore,the paper studies the influence mechanism of limestone proportion on the phase structure of sinter by means of the phase microscope.High alkalinity sinter has both low FeO,good reducibility,but also has the characteristics of high strength,the fundamental reason is that the main binder phase is calcium ferrite(SFCA).Scanning electron microscopy analysis showed that with the increase of sintering plus limestone content,the proportion of calcium ferrite in sinter phase increased significantly.The basicity value(m(CaO)/m(SiO2))of high-quality high-basicity sinter is generally in the range of 1.8 to 2.2,and the calcium ferrite mainly exists in the form of needles.Sinter metallurgical properties of the best,low energy consumption.The alkalinity is below 1.8,the ferrosilicate liquid phase increases in the sinter,the alkalinity is above 2.2,too much calcium ferrite is generated,and a considerable amount of calcium ferrite,or even calcium ferrite,is present,Are not conducive to the strength and reducing sinter.(4)Finally,based on the previous experiment of sintering cup and the analysis of the structure of the ore phase,the industrialization experiment was carried out.The influence of the ratio of limestone on the technical indexes of sintering technology and the metallurgy performance of sinter was clarified.The best technology condition.With the increase of the proportion of limestone in sinter,the reduction index(RI)of sinter decreases gradually.When the limestone proportion is 25%and 50%,the reduction index(RI)of sinter is 81.85%and 79.57%,respectively.When limestone proportion exceeds 50%,the reduction index(RI)of sinter decreases more.Therefore,from the point of view of reducibility index,the proportion of limestone in sinter should be controlled below 50%.