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Study of the plasma based production of tetrafluoroethylene

Nell, Annalien (1999-06)

Thesis (MIng) --Stellenbosch University, 1999.


ENGLISH ABSTRACT: A method was developed at the Atomic Energy Corporation of South Africa (AEC) for the plasma based production of tetrafluoroethylene (TFE). The process involves the feeding of carbon particles into a direct-current CF4 plasma. The resultant plasma gas is quenched rapidly to obtain TFE and other fluorocarbons. The mixing of the particles with the plasma gas is very important in order to achieve a high C:F-ratio in the gas phase, which promotes the desired reactions. The gas enthalpy in the reactor is a governing factor in the TFE yields that are obtained. In this study research was done on particle mixing and the enthalpy distribution in the laboratory scale reactor. An enthalpy probe was used as the main diagnostic tool. Results indicated that particle mixing is quite uniform throughout the reactor. A basic one-dimensional mechanistic model of the reactor was also expanded to assist in· the scale-up of the process. In its present form the model is adequate for predicting trends in the reactor. The model could still be expanded further to include reaction kinetics and internal heat transfer in the particles. Considering the restrictions of the model, satisfactory agreement was obtained between the model and experimental results.

AFRIKAANSE OPSOMMING: 'n Proses vir die plasmagebaseerde produksie van tetrafluoroetileen (TFE) is deur die Atoomenergiekorporasie van Suid-Afrika (AEK) ontwikkel. Koolstofpartikels word in 'n gelykstroomCF4- plasma gevoer en die resulterende plasmagas word vinnig geblus ten einde TFE en ander fluoor-koolstofverbindings as produkte te verkry. Goeie vermenging van die koolstofpartikels met die plasmagas is van uiterste belang ten einde 'n hoe C:F-verhouding, wat die gewenste reaksies bevorder, in die gasfase te verkry. Die entalpie van die plasmagas in die reaktor is 'n bepalende faktor in die opbrengs TFE wat verkry word. Vir die doel van hierdie werkstuk is navorsing op laboratoriumskaal gedoen oor partikelvermenging en die entalpie-verspreiding in die reaktor. Die hoof diagnostiese apparaat wat vir die doel aangewend is, is die entalpiesonde. Resultate toon dat partikelvermenging naastenby uniform deur die reaktor voorkom. Verder is 'n basiese een-dimensionele meganistiese model van die reaktor uitgebrei ten einde van nut te wees in die opskaling van die proses. In sy huidige vorm is die model voldoende om algemene neigings in die reaktor te voorspel. Die model kan nog verder uitgebrei word om reaksie-kinetika en interne hitte-oordrag in die partikels in te sluit. Die beperkings van die model in ag genome, is ooreenstemming tussen die model en eksperimentele resultate egter bevredigend.

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