Reasonable Characterization Method Of Sinter Reducibility And Application

As the main raw materials in the blast furnace process,the metallurgical properties of the sinter have a significant influence on the production efficiency and energy consumption of blast furnace?BF?.The requirements of high-grade iron ore have become more and more with the development of steel industry.However,more and more steel enterprises tend to use low-grade and low-cost iron ore because of the decreasing high-grade iron ore resources and tough situation.These low-grade iron ore resources have many varieties and different characteristics so that the metallurgical properties of sinter become instable.Therefore,to study the metallurgical properties of different sinters is of great significance.It can provide abundant theoretical basis for the optimization of sinter burdening.Reducibility is an important quality index in metallurgical properties of the sinter.However,the national standard method to determine the reducibility of iron ores has some limitations because it neglects the actual situation of iron ores in BF process.As a consequence,this article used reasonable representation of sinter reducibility as breakthrough point,the sinters A-D from different steel enterprieses as research objects,combined the data in BF dissection,BF mathematical simulation and actual BF process to determine the suitable experiment parameters by similarity principle and studied the reducibility of different sinters from different steel enterprises and their dynamic mechanism in reduction process.At the beginning,in order to take the reduction process of sinter in lump zone of BF into consideration,this article determined the similarity criterion in reasonable characterization method of sinter reducibility as Fr according to similarity principle and the gas flow rate as 2-6 mL/min in improved experiments.And then,other experiment parameters were determined according to BF dissection and CO consumption of unit mass ore in actual production.From the analysis of chemical composition,the orede of basicity of sinters was B>A>C>D and the order of FeO content was C>A>D>B.From the analysis of the minerals phases,hematite and magnetite grains in sinter A were bigger than the rest sinters and calcium ferrite mostly formed arborization.The calcium ferrite in sinter B was acicular but strip in sinter C.Besides calcium ferrite,there were more calcium silicate in sinter D,but the porosity was higher than other sinters.In the aspect of reducibility,the reduction degree of sinters A-D were 63.99%,76.35%,74.90%?65.87%respectively in national standard method.So the order of sinter reducibility was B>C>D>A.In the first improved experimental method,the reduction degree of sinters A-D were 24.15%,29.57%,23.12%and 22.29%respectively.The order of sinter reducibility was B>A>C>D.And in the second improved experimental method,the reduction degree of sinters were 28.44%,35.65%,27.80%and 27.17%.The result of sinter reducibility order was consistent with the result in the first improved experimental method.In the aspect of dynamic mechanism,the reduction process of sinter A-D were controlled by one dimensional diffusion mechanism expressed as G???=?².In the first improved experimental method,the reduction process of all sinters were controlled by two dimensional random nucleation and nucleus growth mechanism,which can be represented as G???=[-ln?1-??]^1/2.Nevertheless,the reduction process of all sinters were controlled by three dimensional random nucleation and nucleus growth mechanism in the second improved experimental method and its functional expression was G???=[-ln?1-??]^1/3.