Study On Thermodynamics And Dynamics Research Of Fluoride Generation During The Sintering Process Of Iron Ore

The baiyanobo iron concentrate which produced in Inner Mongolia has been used byBaotou Iron and Steel Co．. as the main raw materials of iron ore to produce sinter andpellets, its mineral composition is complex, disseminated extent small, high fluorinecontent and containing alkali metal sodium and potassium. The fluorine in the ironconcentrate is mainly existing in the state of fluorite (CaF2). Theory and practice ofsintering production have be showed that CaF2can decrease the sintering liquid viscosityand surface tension in the process of sintering, So that it could make the sinter present aloose porous thin wall structure. A combination of fluorine and alkali can make the sinterpresent low strength and poor reducibility, With the traits of fusible, easy solidified,difficult remelt, blast furnace soft melting zone thicker, and the characteristics of thepermeability is poor; The interaction of F, K, Na in the iron ore concentrate makes thereducing inflation of the pellets high, resulting in the sharply fell of pellets’ strength, andlead the pulverization of pellets. The presence of fluorine and alkali metal in the Ironconcentrate limits the strengthening of blast furnace smelting, The utilization coefficient ofblast furnace is lower than ordinary sinter smelting. Fluorine in the iron ore concentrate ismainly in the form of gaseous fluoride and fluoride dust discharged into the atmosphere, asthe mainly fluorine pollution of Baotou Iron and Steel Co．. Therefore, this paper is studyon the thermodynamics and dynamics research of fluoride generation during sinteringprocess of baiyun obo iron ore. Providing theoretical basis for improving the technology ofbaiyun obo iron concentrate sintering and reducing the fluorine pollution in the sinteringprocess. and for supplementing and perfecting the theory of special ore roasting at thesame time. Providing theoretical guidance to comprehensive utilize of baiyun obo oreresources more efficient, higher quality, and higher yield. This thesis includes two parts:The first part combining the Factsage6.2thermodynamic software to analysis thethermodynamic of the fluoride gas generated during the process of iron concentratesintering, come to the conclusion that the lowest reaction temperature of the gaseous fluorides generated by CaF2in the iron ore concentrate reactions with gangue of eachcomponent during the process of sintering. And by comparing the temperature of the gaswhen it began to escape in the different fluoride partial pressure, It is concluded that howhard the gas is generated, According to the from of easy to difficult order: KF＞NaF＞SiF4＞MgF2＞AlF3.The other part is based on the calculation of thermodynamic, and by pure chemicalreagents, Choose K2O and Na2O to do the kinetics experiments on the fluoride generationreaction. Because of the pure chemical reagents of Na2O, K2O are difficult to obtain, Thisexperiment selected Na2CO3, K2CO3instead. Through the dynamic experimental analysisincluded that the reaction of NaF and KF are the secondary reaction, The reactionactivation energy values are86.833KJ/mol and77.657KJ/mol. In general, most of thereactions’ activation energy are in the range of40~400KJ mol-1.During the process ofthe samples sintering, the greater the value of Eais, the more intense affected to the rateconstant K by temperature. It’s not easy to reaction at a low temperature. So interfacechemical reaction is the restrictive link for this two reactions.