Thesis (MScEng) -- Stellenbosch University , 2002. / ENGLISH ABSTRACT: The distillation process is the most widely used separating process in the
chemical process industry. The optimal design of the distillation units can
lead to reduced capital costs and improved energy utilisation. This is
particularly the case for structured packed distillation column where design
methods tend to over-predict the column efficiency. This work seeks to
contribute to the development of a reliable mass transfer model for structured
packing.
A gas phase mass transfer correlation was developed based on the
evaporation of pure components into an air stream. The mass transfer rates
were measured in a short triangular wetted wall channel with a corrugated
surface wall. The influence that the geometric configuration as well as
surface structure has on the mass transfer rates was investigated. The
channel geometry and surface wall structure resembled that of the structured
packing (Flexipac 350Y). The influence of the channel geometry on the gas
mass transfer rates was not significant except at low flow conditions. The
liquid phase resistance was investigated for binary mixtures in the triangular
wetted wall channel. It was found that the overall mass transfer rate
decreased with increasing composition of the volatile component. The
enhancement of the gas phase mass transfer rate masked the presence of
the liquid resistance.
ii
The gas phase mass transfer correlations were used in the mass transfer
model to predict the separation efficiency of a structured packed distillation
column. The structured packing used to validate the mass transfer model was
high-capacity Flexipac 350Y and normal Flexipac 350Y. The binary
distillation experiments were done at total reflux conditions for the pressure
range O.33-1atm. The accuracy of the separation efficiencies of the mass
transfer model improved with increasing pressure for both materials. The
mass transfer model was able to predict the variation of separation
efficiencies with column loadings. / AFRIKAANSE OPSOMMING: Distillasie is die skeidingsmetode wat die meeste in die chemiese industrie
gebruik word. Die optimale ontwerp van distillasie eenhede kan lei tot
verlagings in kapitaalkostes en 'n verbeterde gebruik van energie. Dit is veral
waar in die geval van kolomme met gestruktureerde pakking waar huidige
ontwerpsmetodes, die kolomeffektiwiteit nie akkuraat beskryf nie. Hierdie
studie het ten doelom 'n bydrae te lewer tot die ontwikkeling van 'n
betroubare massa-oordragsmodel vir gestruktureerde pakking.
'n Gasfase massa-oordragskorrelasie is ontwikkel gebaseer op metings van
die verdampingstempo van suiwer komponente in 'n lugstroom. Die massaoordragstempos
is gemeet in 'n kort driehoekige benatle wand kanaal waarin
die wand 'n bepaalde oppervlakprofiel het. Die invloed van beide die
kanaalgeometrie en die oppervlakprofiel is ondersoek. Die geometrie en
oppervlakprofiel is soorgelyk aan die van Flexipac 350Y gestruktureerde
pakking. Die invloed van die kanaalgeometrie op die gasfase massaoordragstempos
is slegs beduidend by lae vloeitempos. Die vloeistoffase
weerstand vir binêre mengsels is ondersoek in die driehoekige kanaal. Dit is
gevind dat die algehele massa-oordragstempo verlaag met 'n verhoging in die
konsentrasie van die vlugtige komponent. Die verhoging in die gasfase
massa-oordragstempo verberg die invloed van die vloeistoffase weerstand.
Die gasfase massa-oordragskorrelasies is in 'n massa-oordragsmodel gebruik
om die skeidingseffektiwiteit van gestruktureerde pakking in "n kolom te
voorspel. Metings op hoë-kapasiteit Flexipac 350Y en normale Flexipac 350Y
is gebruik om die modelvoorspellings te evalueer. Die binêre distillasies is by
totale terugvloei gedoen in die drukbereik 0.33 - 1.0 atm. Daar is gevind dat
die model meer akkuraat is by hoër drukke. Die massa-oordragsmodel is in
staat om die variasie in skeidingseffektiwiteit met veranderende kolomlading
te voorspel.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52647 |
| Date | 12 1900 |
| Creators | Kawesha, David Mukuma |
| Contributors | Nieuwoudt, Izak, Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 171 p. : ill. |
| Rights | Stellenbosch University |
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