Flow patterns and the associated residence time distribution are
important factors affecting the performance of a chemical reactor.
This dissertation investigates the flow patterns in a scale-model
of a gas reactor where opposing inlet jets are used to create
mixing. The effects of different vessel geometries and gas flowrates
are investigated.
The residence time distribution (RTD) was measured by means of
radioactive tracer techniques. The extremely short mean re^’dence
time in the vessel necessitated the use of sharp tracer pulses and
a computerised digital recording system. Flow visualisation
experiments were also performed to aio interpretation of the
results.
The results were analysed using the method of frequency analysis,
in which the coefficients of the Fourier Series arc used to
characterise the RTD curves. It was found that the shape of the
RTD curve is unaffected by change in flowrate; i.e. the flow
patterns are independent of flowrate over the range investigated.
The geometry of the vessel however plays a major role. The effect
of reducing the length/diameter ratio of the reactor is an increase
in the mixedness in the vessel. Internal recirculation
patterns are well-defined at a higher length/diameter ratio.
The RTD curves were also used to set up mathematical flow models. Simple multi-parameter models were used, where the vessel was
viewed as consisting of interconnected flow regions such as plug
flow, stirred tank, and axial dispersion. Close fits of the
mathematical models to the experimental RTD curves were obtained.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/18044 |
| Date | 02 July 2015 |
| Creators | Rabbitts, M C |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf, application/pdf, application/pdf |
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