بررسي پروفيل هاي حرارتي در احياي كربوترمي بسترهاي كامپوزيتي هماتيت - گرافيت و تاثير افزودني هاي آهن و آلومينيوم

چكيده انگليسي :

Study of the thermal profiles in the carbothermic reduction of hematite graphite composite beds and influence of the additives iron and aluminum Masoud Fathian m fathian@ma iut ac ir August 22 2015 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Dr M Panjepour Assoc Prof Email panjepour@cc iut ac irDr M Meratian Assoc Prof Email meratian@cc iut ac irAbstractNumerous studies have been conducted on kinetics and mechanisms of iron oxide carbonsystems most of them introducing the endothermic reaction of carbon gasification Boudouard reaction which is the controlling stage of the reduction process Hence understanding the kinetics of carbothermic reduction of iron oxides and acceleratingfactors are very important In this research the effects of accelerating factors includingmechanical activation additives and catalysts on the rate of heat transfer in composite bedshave been investigated For this purpose a laboratory reactor equipped with a hot surfacewas designed which was enable of creation of temperature gradients or in other word onedirectional heat transfer along the bed Temperature profiles in a fixed bed with hot surfacetemperature of 1200 C were measured for 60 minutes using thermocouples placed indifferent regions of the bed the results of temperature profiles and phase identification byXRD revealed that decrease of heat flux into the bed due to the endothermic carbongasification reaction and low effective heat transfer of the bed leads to a decrease in thedegree of reduction at areas far from the hot surface In continuation to evaluate the effectof mechanical activation as well as the effects of iron as an additive for increasing theconductive heat transfer rate and catalytic effect in Boudouard reaction and aluminum asan energy source by thermite reaction for improving the amount of generated heat on thethermal profiles and temperature gradients in mentioned bed the temperature profiles weremeasured Temperature profiles of milled specimens indicate reduction of temperaturegradient increase in heat transfer rate in reaction bed and drastic drop in reductiontemperature which can be because of particle refinement and consequently increase inparticle contact area In fact above parameters might result in an increase in mixedconductive heat transfer and decrease in reaction heat consumption Presence of ironimproves the conductive heat transfer throughout the bed For specimens milled for longdurations significant decrease in reduction temperature and increase in heat transfer ratewere observed on temperature profiles which might be due to severe microstructuralchanges of reaction mixture in the presence of iron and also its catalytic effect Addition ofaluminum as an energy source results in reduction of temperature difference in differentregions of the bed by providing required heat of carbothermic reactions via occurrence ofendothermic aluminuthermic reactions so in the milled condition higher degree ofreduction is achievable in composite beds and utilizing of larger pellets is possible Therefore it can be concluded that any change in heat transfer rate in the bed mightsignificantly affect the rate of carbothermic reduction reaction Keywords Kinetics Reduction Heat transfer rate Boudouard reaction Pellet Milling Temperature profile Heat conduction Iron Aluminum

فتحيان، مسعود

بررسي پروفيل هاي حرارتي در احياي كربوترمي بسترهاي كامپوزيتي هماتيت - گرافيت و تاثير افزودني هاي آهن و آلومينيوم

سينتيك , انتقال حرارت , واكنش بو دوارد , گندله , آسيا , نمودار دمايي , هدايت حرارتي