Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / Thesis submitted in partial fulfilment of the requirements for the Degree
of
MASTER OF SCIENCE IN ENGINEERING
(MINERAL PROCESSING)
in the Department of Process Engineering
at the University of Stellenbosch / ENGLISH ABSTRACT: The use of dimensional analysis to scale-up mechanically agitated flotation processes
and to identify deficiencies in froth flotation plants was explored. The full range of
operating variables was considered, such as particle size distribution, reagent suite,
conditioning time, retention time, machine geometry, aeration, solids suspension, power
requirements and turbulence. Dimensional analysis offers a methodology to combine
variables into dimensionless groups to guide the scale-up process based on the notion of
similarity. Ten dimensionless groups were developed and combined with metallurgical
variables, such as liberation, reagents dosage and flow diagrams to produce a scale-up
and evaluation tool, applicable to any mechanically agitated flotation process. In many
hydrodynamic studies, the researchers considered hydrodynamic variables based on
rotor diameter. In this case the hydrodynamic variables based on rotor diameter
represent mechanism “ability”, while parameters based on cell diameter are considered
“requirement”.
Dimensionless groups have also been applied to the definition of basic parameters of the
kinetic constant, such as floatability, bubble surface area flux and froth recovery factor.
It also showed that the bubble surface area flux has a maximum with increased aeration,
where similar models do not show this dependence.
Analysis by computational fluid dynamics and Perspex modelling revealed valuable
insight into the inner working of the Wemco flotation machine, such as air dispersion,
turbulence levels, separation zones and solids concentration. Design changes to the
rotor, disperser, hood and geometrical lay-out produced a marked improvement in
flotation conditions. It also supported certain dimensionless numbers measured in full
scale plants.
Case studies confirmed that almost all flotation plants, irrespective of the minerals
floated, suffer from the same deficiencies. Dimensional similitude offers a unique tool to
identify these deficiencies and to predict the effect of recommended improvements. In
almost every case where the fundamental requirement of similarity was applied, an
improvement in performance was observed. Finally a new algorithm is proposed for the
scale-up of flotation plants and the application is demonstrated in the design and testing
of a pilot plant. / AFRIKAANSE OPSOMMING: Die gebruik van dimensionele analise in die opskaal van flottasieprosesse en die
identifisering van flottasieaanlegprobleme is ondersoek. Die volle bereik van
bedryfsveranderlikes is ondersoek, soos partikelgrootte, kondisioneringstyd, retensietyd,
geometrie, lugvloei, suspensie van vastestowe, turbulensie en drywingsvereistes.
Dimensielose analise is die proses waardeur veranderlikes deur wiskundige manipulasie
gekombineer word in dimensielose groepe. Tien dimensielose groepe is ontwikkel en is
tesame met metallurgiese veranderlikes soos vrystelling, reagensdosering en vloeidiagramme
gekombineer om gebruik te word om gelykvormigheid te bewerkstellig.
Hierdie proses is van toepassing op enige flottasieproses gebaseer op meganies
geagiteerde toerusting.
Dimensielose groepe is ook gebruik in die definisie en kwantifisering van turbulensie,
agitasie, geometrie, suspensie van vastestowe, verspreiding van lug en drywingsvereistes.
Daarbenewens is die groepe gebruik in die definisie van die basiese
veranderlikes van die kinetiese konstante soos lugborreloppervlakvloed, suspensie, en
herwinning in die skuimfase. Die groepe is ook gebruik in die bewys dat die
lugborreloppervlakvloed ´n maksimum het met toename in lugvloei. In baie gevalle word
hidrodinamiese veranderlikes uitgedruk in terme van die rotordiameter en in hierdie
studie word dit beskou as meganisme “vermoë”. Die hidrodinamiese veranderlikes
gebaseer op sel-diameter word beskou as “behoefte”.
Berekeningsvloeidinamika en Perspex modellering het waardevolle insig verskaf in die
binne-werking van die Wemco flottasiemasjien soos lugverspreiding, turbulensie en
partikelkonsentrasie en is ook gebruik om sekere dimensielose getalle wat in volskaalse
aanlegte gemeet is, te verifieer. Gevallestudies het bevestig dat feitlik alle
flottasieaanlegte, ongeag die soort mineraal, gebuk gaan onder dieselfde afwykings.
Dimensionele analise bied ‘n eenvoudige benadering om hierdie afwykings te identifiseer
en om die effek van veranderings te voorspel. In alle gevalle waar die beginsels van
gelykvormigheid slaafs gevolg is, het n merkbare verbetering in prestasie voorgekom.
Ten slotte is ´n nuwe opskaleringsalgoritme ontwikkel en is die toepassing daarvan
gedemonstreer deur die ontwerp en toets van ´n loodsaanleg, gebaseer op die Wemco
geometrie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/5327 |
| Date | 12 1900 |
| Creators | Truter, Marius |
| Contributors | Aldrich, C., University of Stellenbosch. Faculty of Engineering. Dept. of Process Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 178 p. : ill. |
| Rights | University of Stellenbosch |
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