Study Of The Reduction Of Iron Oxide/Carbon Composites By Thermal Analysis-mass Spectrometry And Analysis Of Thermal Analysis Kinetics

The iron ore-coal pellet or block is applied successfully in the blast-furnace and in the non-blast-furnace iron making.Stduy of Mechanism and Kinemics of iron oxides/carbon composites have theoretical value and applicable value.In reduction process of iron oxide/ carbon composites,the reduction process is coupiedly completed by the reduction of iron oxide/carbon and carbon gasification two gas-solid reactions。As to find out the mechanism of reations of iron oxide/carbon composites,Thermal analysis-mass spectrometry experimental technique is used to stdudy it.The experimental of carbon gasification and the reduction of iron oxide/carbon composites is carried out.The main achievements and conclusions are given as follows:(1)The carbon gasification reaction is composited of the slow gasification stage and the quick gasification stage,there is little heat in the slow gasification stage,there is much heat in the quick gasification stage.(2)The reduction of iron oxide and carbon is composited of three stages in iron oxide and carbon composites,the first stage is the reduction process of hematite to magnetite,and the evolved gas is carbon dioxide;the second stage is the reduction process of magnetite to wustite,and the evolved gas are carbon dioxide and carbon monoxide that gradually come into being and its density gradually increases:the last stage is the reduction process of wustite to iron.and the evolved gas are carbon dioxide and carbon monoxide;Based on the expression of Arrhenius differential activation energy,the mathematical expression of non-isothermal differential activation energy is inferred:E_a=E_r+E_f(a)=-(dln(da/dT)R)/(d(T^-1))+(dlnf(a)R)/(d(T^-1)The apparent activation energy is composed of reaction rate activation energy and reaction pattern activation energy.The analyzable results of carbon gasification and the reduction of iron oxide/carbon composites by non-isothermal differential activation energy:(1)Apparent activation energy range from 35 kJ/mol to 282kJ/mol in the quick quick gasification stage of carbon gasification reaction,apparent activation energy is tendential to a constant with the increase of heating rate(2)In iron oxide /carbon composites,apparent activation energy of the reduction of iron oxide range from 3 kJ/mol to 344kJ/mol(R＜20%),apparent activation energy range from 130 kJ/mol to 280kJ/mol(20%＜R＜55%),apparent activation energy range from 2 kJ/mol to 190kJ/mol(R＞55%)。(3)In iron oxide /carbon composites,apparent activation energy of the carbon gasification range below 60 kJ/mol.(R＜20%),apparent activation energy range from 60kJ/mol to300kJ/mol(20%＜R＜55%).apparent activation energy range from 38 kJ/mol to 250kJ/mol(R＞55%)。(4)reaction pattern activation energy is incline to gradually increase with the increase of the process of reaction,reaction pattern activation energyn be contrary.