بررسي اثر كار مكانيكي و افزودني آلومينيوم بر احياي كربوترمي موليبدنيت در حضور آهك

چكيده انگليسي :

Investigation of Mechanical Activation and Aluminum Additive on the CarbothermicReduction of Molybdenite in the Presence of Lime Mahsa Parsi m parsi@ma iut ac ir Date of Submission September 22 2013 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Dr Mehdi Ahmadian Assistant Professor ahmadian@cc iut ac ir Dr Masood Panjepour Assistant Professor panjepour@cc iut ac irAbstractThe conventional technology for production of molybdenum from molybdeniteconcentrates consists of various steps which include roasting of the concentrates andfinally reduction with hydrogen in two or more steps In this study the effect of mechanicalactivation and aluminum on the carbothermic reduction of molybdenite in the presence oflime was investigated 5 wt of aluminum was added to the powder mixture ofmolybdenite Carbon and lime 1 2 2 Mechanical activation was performed on themixtures in argon atmosphere for different time periods 0 10hr using a planetary ballmill Different samples were thoroughly investigated by simultaneous thermal analysis STA The samples were heated in argon atmosphere with the linear heating rate of10 C min The XRD result for samples before and after milling demonstrated that bymilling up to 5hr and more before heating treatment causing production of molybdenumand aluminum sulfide in the mixture and after heating treatment causing production ofaluminum carbide in the mixture Change in molybdenite crystallite size and structuralmicro strain studied based on integral breadth analysis of obtained XRD patterns Bymechanical activation the grain size and structural strain of molybdenite decreased andincreased respectively The reaction fraction curves versus temperature revealed thatstarting temperature of the reaction for both samples without aluminum and with 5 wtaluminum and without mechanical activation were 1040 C but final reductiontemperature of the reaction of sample with 5 wt aluminum compared to withoutaluminum was decreased about 260 C Also both start and final reduction temperature ofthe reaction of sample milling for 10hr decreased 90 C compared to sample with 5 wtaluminum and without ball milling It means the presence of aluminum increased the rateof reaction Kinetics of molybdenite carbothermic reduction in non isothermal conditionwere studied by model fitting Coats Redfern and model free Ozawa Kissinger andStarink methods It is also obtained that the Boudouard reaction was the controlling stepin the carbothermic reduction of molybdenite in the presence of lime and 5 wt aluminumwith 10hr milling In the presence of aluminum the solid state reactions occur in a verysmall amounts also the Boudouard reaction be actives at lower temperatures The reactioncontrol model was F1 The activation energy and pre exponential factor calculated44 5kcal mol 2 26 1012 s 1 respectively for milling 10hr Keywords Molybdenite Aluminum Mechanical activation Kinetic Carbothermic reduct

پارسي، مهسا

بررسي اثر كار مكانيكي و افزودني آلومينيوم بر احياي كربوترمي موليبدنيت در حضور آهك

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