مطالعه آزمايشگاهي و مدلسازي رياضي فرايند جذب سطحي اسيد هيدروفلوئوريك بر روي قرصهاي فلوئوريد سديم

چكيده انگليسي :

Experimental Study and Mathematical Modeling of Hydrogen Fluoride Adsorption on Sodium Fluoride Sahar Afzal E mail afzal860@yahoo com 2008 11 29 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiMohammad Reza Ehsani E mail mr ehsani@ce iut ac irAmir Rahimi E mail rahimi@eng ui ac irAbstract Being one of the most important and widely used gases in uranium conversion industry Fluorine F2 isusually used to produce 18000 21000 tons of uranium hexafluoride per year worldwide which needs 6000 7000 tons of fluorine gas The production of fluorine in nuclear industries is mainly based on the electrolysisof potassium anhydride difluoride which also leads to the production of hydrogen fluoride gas HF as animpurity The amount of impurity of HF in the fluorine gas which is produced by the above mentioned reaction isin the range of 5 10 mole percent In order to use fluorine gas in uranium conversion facilities it is necessaryto purify electrolysis product and decrease the amount of its HF to 0 2 mole percent In uranium conversionindustry the fluorine gas is used as chemical raw material gas to produce UF4 and UF6 while its purity isvery important As a part of a main study the purpose of the present paper is to investigate the process of HFadsorption on NaF pellets and to determine the corresponding adsorption isotherm in different operatingconditions To our knowledge due to the very specific nature and applications of such studies and theirresults very few data have been published in the literature In a second part the obtained results of this studyare used in order to verify a mathematical model which has been developed for predicting the HF adsorptionperformance on NaF pellets in a fixed bed adsorber In this study the adsorption process of hydrogen fluoride as an impurity in the process of fluorineproduction on sodium fluoride pellets is experimentally studied in a lab scale fixed bed adsorber Also theeffects of some operating parameters including inlet concentration and inlet temperature of hydrogen fluorideon the adsorption process are intensively investigated The data of adsorption are analyzed and correlated byLangmuir Freundlich and Temkin isotherms The adsorption capacity is found to be 1 908 and 0 750 grHF gr NaF by the Langmuir isotherm at 22 and 54 C respectively The favorable nature of adsorption whichis expressed in terms of a dimensionless separation factor RL is found to be more than 1 indicating anunfavorable adsorption In addition the data analysis shows that the Langmuir and Temkin isotherms fit theequilibrium isotherms better than that of Freundlich Also a mathematical model for non isothermal operation was established based on the conservationlaws to illustrate the mechanism of gas solid heat and mass transfer The governing equations solvednumerically and the accuracy of the model results were demonstrated by the fact that most of the predictedexit concentration of HF and breakthrough curves agreed well with the experimental data After model validation software was developed in order to predict the performance of adsorption towerwhich can be used to investigate the effect of operating parameters on removal efficiency and adsorbeddesign Key words Adsorption Hydrogen fluoride Sodium fluoride Isotherm

افضل، سحر

مطالعه آزمايشگاهي و مدلسازي رياضي فرايند جذب سطحي اسيد هيدروفلوئوريك بر روي قرصهاي فلوئوريد سديم

ايزوترم , فرآوري اورانيوم