Published January 4, 2001 | Version v1
Miscellaneous Open

Study and modelling of rotary kilns for defluorination and reduction of UO2F2

Creators

Description

This work is concerned with the study and modelling of rotary kilns for uranium oxides preparation. The first chapter deals with the study of the movement of solid in rotary kilns equipped with lifters. A method was developed to calculate the average distribution of powder in a transverse section of the kiln. It is based on geometrical considerations and on experiments (unloading law of the lifters and velocity of the falling swarms of powder). Measurements of Residence Time Distribution allowed to determine the mean residence time and the axial dispersion in the industrial kilns, making it possible to choose a model to calculate the bed depth profile. The second chapter is concerned with mechanisms and kinetic laws, established experimentally in the operating conditions of the industrial kilns in terms of temperature and gas composition. On this base, a kinetic model was set up, which allows to calculate the conversion of solid as a function of the powder transverse distribution by using the law of additive reaction times. The third chapter describes thermal aspects of rotary kilns. The thermal balances are established on the solid, the gas and the inner equipments. The thermal conductivities of powders and the emissivities of walls and powders were experimentally measured. The heat transfer coefficients were obtained by means of measurements in a laboratory kiln or from correlations from the literature. The complete model of kilns, described in the fourth chapter, is based on the measurements presented in the previous chapters, and on dynamic, kinetic and thermal models developed concurrently. At the present time, the model represents satisfactorily how industrial kilns work, and allows to suggest ways to improve the process. (author)

Abstract (French)

Ce travail porte sur l'etude et la modelisation des fours tournants de defluoration et reduction du difluorure d'uranyle. Le premier chapitre traite de l'etude dynamique du mouvement de la charge solide dans les fours. Une methode a ete mise au point pour determiner la repartition moyenne de la poudre dans une section transversale de four, basee sur des considerations geometriques et sur des mesures experimentales de loi de dechargement des releveurs et de vitesse de chute des essaims de poudre. Des mesures de Distribution des Temps de Sejour ont permis de determiner le temps de sejour moyen et la dispersion axiale dans les fours industriels, et de choisir un modele pour calculer le profil de chargement. Le deuxieme chapitre concerne le schema reactionnel et la loi cinetique, etablis experimentalement dans les conditions de fonctionnement des fours industriels en termes de temperature et de composition gazeuse. Sur cette base, un modele cinetique a ete mis en place, qui permet de calculer l'avancement des reactions en fonction de la repartition transversale de la poudre en utilisant la loi des temps caracteristiques additifs. Le troisieme chapitre decrit des aspects thermiques des fours tournants. Les bilans thermiques sont etablis sur la charge solide, la phase gazeuse et les equipements internes. Les conductivites thermiques des poudres et les emissivites des parois et des poudres sont determinees experimentalement. Les coefficients d'echange thermique sont obtenus a l'aide de mesures dans un four de laboratoire ou a partir des correlations de la litterature. Le modele global de four, presente au quatrieme chapitre, est base sur l'ensemble des mesures exposees dans les chapitres precedents, et sur les modeles dynamiques, cinetiques et thermiques developpes parallelement. Dans son etat actuel, le modele represente de facon satisfaisante le fonctionnement des fours industriels, et permet de suggerer des pistes pour l'amelioration du procede. (auteur)

Files

52006939.pdf

Files (2.8 MB)

Name Size Download all
md5:fe80fd905dab5cffecfbbdbbf96f596f
2.8 MB Preview Download

Additional details

Additional titles

Original title (French)
Etude et modelisation des fours tournants de defluoration et reduction du difluorure d'uranyle

Publishing Information

Imprint Pagination
301 p.
Report number
FRNC-TH--11366

INIS

Country of Publication
France
Country of Input or Organization
France
INIS RN
52006939
Subject category
S42: ENGINEERING; S37: INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; S11: NUCLEAR FUEL CYCLE AND FUEL MATERIALS;
Resource subtype / Literary indicator
Thesis
Descriptors DEI
CHEMICAL REACTION KINETICS; COMPUTERIZED SIMULATION; DEHALOGENATION; EMISSIVITY; FLOW RATE; HEAT TRANSFER; MASS TRANSFER; POWDERS; REDUCTION; ROTATION; SENSITIVITY ANALYSIS; TEMPERATURE DISTRIBUTION; THERMAL CONDUCTIVITY; TUNNEL FURNACES; URANIUM OXIDES U3O8; URANYL FLUORIDES
Descriptors DEC
ACTINIDE COMPOUNDS; CHALCOGENIDES; CHEMICAL REACTIONS; ENERGY TRANSFER; FLUORIDES; FLUORINE COMPOUNDS; FURNACES; HALIDES; HALOGEN COMPOUNDS; KINETICS; MOTION; OPTICAL PROPERTIES; OXIDES; OXYGEN COMPOUNDS; PHYSICAL PROPERTIES; REACTION KINETICS; SIMULATION; SURFACE PROPERTIES; THERMODYNAMIC PROPERTIES; URANIUM COMPOUNDS; URANIUM OXIDES; URANYL COMPOUNDS; URANYL HALIDES

Optional Information

Notes
90 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses