| A certain amount of metallurgical dust would inevitably be generated in the production process of iron and steel enterprises,and sintering was an important way to recycle metallurgical dust.However,due to the fine particle size of metallurgical dust and the high content of K,Na,Zn and other elements,so that sintering would be affected,and the quality of the ore and the stable forward run of the subsequent blast furnace.Therefore,the influence mechanism of K,Na and Zn in metallurgical dust on the sintering mineralization process was studied by micro-sintering and first-principles calculation.Then based on the raw materials and process conditions of a certain enterprise,the metallurgical dust and iron ore powder were analyzed.The physical and chemical properties of the sintered ore were studied through micro sintering,sintering cup experiments and industrial data analysis to study the influence of metallurgical dust on the quality of sintered ore.Finally,according to the research results,a process optimization plan for the sintering process was proposed to improve the quality of sintered ore after adding metallurgical dust,as follows:1)Combined with micro-sintering experiment and first-principles theoretical calculation,the influence mechanism of alkali metal and zinc on sintering mineralization process was analyzed.The results showed that the minimum assimilation temperature and liquid phases fluidity index of iron ore powder increased with the content of alkali in the form of chloride or aluminate metalincreasing.With the increase of alkali content in the sinter,the sinter iron acid calcium content decreased,magnetite and silicate content increased,and the microhardness of silicate phase severe degradation,this was mainly due to the silicate of alkali metal ions adsorption capacity was higher than acid calcium,iron in alkali metal silicate phase,and the enrichment of its crystal structure strength degradation.With the content of Zn O increasing,the minimum assimilation temperature of iron ore powder did not change significantly,the liquid fluidity index decreased,the magnetite content in sinter decreased,and the content of calcium ferrite increased first and then decreased.With the increase of Zn Fe2O4 content,the minimum assimilation temperature and fluidity index of iron ore powder increased,and the magnetite content in sinter increased,while the amount of calcium ferrite decreased.With the increase of zinc content,the microhardness of magnetite in sinter decreased,which was mainly because the adsorption energy of zinc element on hematite and magnetite crystals in sinter was higher than that of calcium ferrite complex,leading to the solid solution of zinc element in magnetite crystals and the decrease of their crystal strength.2)Based on the raw material conditions of a certain enterprise,the physical and chemical properties of metallurgical dust mixed ash,sintering ash,high furnace ash and their influence on high temperature sintering characteristics of mixed iron ore powder were studied.The results showed that the content of harmful elements K,Na and Zn in metallurgical dust was higher than that in other iron ores,and there was also20.2%carbon in blast furnace ash.The particle size of metallurgical dust was finer than that of iron ore powder,among which sintered ash has the smallest particle size and absorbs water relatively slowly,while the maximum water holding rate and water absorption rate of mixed ash and blast ash were higher than that of iron ore powder.This was because the internal pore volume of mixed ash and blast ash was 0.019 cm3/g and 0.032 cm3/g respectively,which was higher than that of other iron ore powder.With the increase of metallurgical dust content,the minimum assimilation temperature of mixed iron ore powder decreased and the fluidity index increased,and the mixed ash had the greatest influence on the decrease degree of the minimum assimilation temperature of mixed iron ore,followed by sintered ash and blast furnace ash.The influence of mixed ash and sintered ash on fluidity index of mixed iron ore powder was similar.3)The influence of metallurgical dust on the mineral phase structure and pore distribution of sinter was studied through micro-sintering experiment,and combined with the results of sinter cup experiment and MLP neural network model analysis of industrial production data,the influence of metallurgical dust addition amount on the quality of sinter was studied.The results showed that when the micro sintering temperature was 1280-1300℃,the addition of mixed ash,sintered ash and high furnace ash could promote the assimilation of large particle iron ore powder and the formation of calcium ferrite,and reduced the sample porosity.When the micro sintering temperature was 1320-1340℃,the increase of the addition of mixed ash,sintered ash and blast ash was conducive to the increase of connectivity between pores,and the sintering temperature was too high to promote the increase of regenerated hematite and silicate phase,which is adverse to the strength of sinter.The influence of particle mass percentage of 3-8 mm and permeability index of material layer decreased with the increase of fine particle content of mixed ash,sintered ash and berry essence.The sinter drum index decreased with the increase of sinter ash content,while the sinter drum index did not deteriorate significantly when the mixed ash content was less than 4%and the blast furnace ash content was less than 1.4%.When the addition amount of blast furnace ash increased from 0 to 1.70%,while the addition amount of coke powder decreased from 4.11%to 3.84%,the sinter could maintain good strength.4)Based on the above research,the following optimization scheme was proposed for sintering process of a domestic enterprise:To avoid because of metallurgical dust and fine-grained mine too much caused the loss of granulating effect,permeability variation caused by sintering material layer,the sinter strength degradation problems,Suggestions of metallurgical dust and fine grained ores in the plum essence always with addition should not be more than 26%,mixed ash content should not be more than4.0%,sintered ash content should not be more than 1.4%,high ash content should not be more than 1.4%.Because the high furnace ash contains a certain proportion of carbon,it could provide heat for the sintering process.When the addition amount of high furnace ash in the sintering raw material increases by 1%,the addition amount of coke powder in the raw material could be reduced by 0.16%,so as to ensure the appropriate sintering temperature and guarantee the performance index of sinter.When the amount of fine mineral powder and metallurgical dust was too much,it was necessary to strengthen the granulation to ensure the permeability of the material layer.Based on the above optimization scheme,the process of the third sintering workshop of an enterprise was optimized to keep the sinter drum strength above 80%under the condition of adding metallurgical dust. |
