| The steel industry consumes a lot of energy,and the energy consumption of blast furnace ironmaking process accounts for about 70%of the energy consumption of iron and steel industry.Therefore,it can be seen that reducing the energy consumption of the iron making process is the most important factor in reducing the total energy consumption of steel enterprises.Blast furnace slag is an important by-product of iron making process,which plays an important role in blast furnace smelting,and also has an important impact on the heat in the hearth.The specific heat capacity of blast furnace slag will directly affect the smelting process.The specific heat capacity has a great influence on the furnace temperature and energy consumption.With the increase of imported iron ore,the content of Al2O3 in the burden increases,which makes the fluidity of slag worse,which is not conducive to blast furnace smelting.Therefore,it is particularly important to study the melting characteristics and specific heat capacity of high alumina blast furnace slag.In this paper,mineral transform and specific heat capacity change of synthesized blast furnace slag(CaO-SiO2-MgO-Al2O3)with high A12O3 during heating process were discussed based on the results of thermogravimetry(TG)and differential scanning calorimetry(DSC)by using a synchronous thermal analyzer.The effects of different w(MgO)/w(Al2O3),basicity R and w(Al2O3)on slag melting characteristics and specific heat capacity were analyzed.The main conclusions are as follows:(1)During the heating process of the premelted slag,the TG curve of the premelted slag is basically unchanged,and the weight of the obtained slag can be basically unchanged,which shows that there is no reaction of volatilization and absorption of external gas in the heating process.(2)DSC curves and specific heat capacity changes of the blast furnace slag are complex during the heating process,and there are 1 exothermic peaks at low temperature and multiple endothermic peaks at elevated temperature.The exothermic peak at low temperature of 900? is due to the phase transform of amorphous material into a crystal process(amorphous substance (?)? (?)SiO2(Tridymite));1250? endothermic peak is the generation of liquid phase caused by eutectic reverse reaction of CaO·Al2O3-2SiO2 and 2CaO·0.5MgO·0.5Al2O3·1.5SiO2;some components of 1270? endothermic peak happened L+Fo (?)Cen+An;endothermic peak between 1290? and 1310? is also the generation of liquid phase due to eutectic reverse reaction CaO·SiO2 and 2CaO.Al2O3·SiO2;the blunt endothermic peak with a long tail at 1390?-1450? is the melting peak of left slag(residual solid).(3)In this paper,the melting process of slag is analyzed.With the increase of w(MgO)/w(Al2O3),the change of melting start temperature and melting end temperature is very small,and the maximum temperature difference is about 40?;with the increase of basicity,the melting temperature increases,as the alkalinity increases from 1.15 to 1.25,the melting temperature increases by about 70?,and when the alkalinity increases from 1.15 to 1.20,the rate of change of the melting temperature is greater than the alkalinity increases from 1.20 to 1.25.With the increase of w(Al2O3),the melting start temperature decreased and the melting end temperature increased.(4)The heat of melting of the slag is 128J/g-210J/g.With the increase of w(MgO)/w(Al2O3),the heat of melting of slag increases;when w(Al2O3)=15%,the heat of fusion increases with the increase of alkalinity;when w(Al2O3)=18%and 20%,w(MgO)/w(Al2O3)=0.25 and 0.35,the melting heat is the smallest when R=1.20.With the increase of Al2O3 content,the melting heat tends to increase.(5)Before the melting of the blast furnace slag,the specific heat capacity changes are complicated,which does not satisfy the law that the specific heat capacity of the solid material increases with the increase of temperature,which reflects the complexity of the slag structure.(6)In the test range,the change range of specific heat capacity of slag is 0.67J/(g·?)? 1.71 J/(g·?)at 1500?.With the increase of w(MgO)/w(Al2O3)and Al2O3 content,they first increase and then decrease,and reach the maximum at w(MgO)/w(Al2O3)=0.35 and w(Al2O3)=18%,respectively;the Cp of slag increases with the increase of basicity R,and the change rate of Cp when basicity increases from 1.15 to 1.20 is greater than that when basicity increases from 1.20 to 1.25,and the maximum difference of Cp between basicity 1.20 and 1.25 is 0.49 J/(g·?).(7)The relationships between Cp with temperature and between Cp with compositions(R2,ratio of w(MgO)/w(Al2O3),and w(Al2O3))were established with a good fitting.In summary,through experimental research on the melting characteristics and Cp of high alumina blast furnace slag,within this test range,a suitable slag composition is R=1.20,w(MgO)/w(Al2O3)=0.35.The research content of this thesis can provide theoretical guidance for the actual smelting of high-alumina blast furnace slag,and is conducive to improving the level of blast furnace smelting process. |
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