Simulating the medium temperature chalcopyrite oxidation system in batch and continuous autoclaves

Steyl, Johann Du T. (2012-12)

Thesis (PhD)--Stellenbosch University, 2012.

Thesis

ENGLISH ABSTRACT: A detailed mathematical description of the pressure oxidation of chalcopyrite concentrates in acidic sulfate solutions is presented in this dissertation, including descriptions of the most important accompanying reactions under typical medium operating temperatures (140-155ºC) in batch and steady-state continuous stirred tank reactors. The mathematical framework consists of various modules, each addressing particular thermodynamic and kinetic aspects of the primary processes occurring in a pressure oxidation reactor. Comprehensive literature investigations are presented which constituted the departure point of this study, supplemented by phenomenological data obtained from controlled batch and continuous experimentation. The different modules are each covered in a chapter of this dissertation, and include the following: i) the solution thermodynamic framework, ii) the interfacial oxygen mass transfer rate, iii) the iron(II) oxidation rate, iv) the iron(III) precipitation rate, (v) the intrinsic oxidation kinetics of the sulfide minerals, and vi) the particulate batch and continuous reactor frameworks. These modules are imbedded within a continuous mass and energy balance platform of a primary leaching – solvent extraction circuit, while the batch reactor analogy describes the conservation of mass, and its movement between phases, in a stand-alone configuration. Literature information proved particularly important in deriving the generic functional forms of the most important reaction rate expressions, while the phenomenological expressions were refined, and the associated constants obtained, from low pulp density batch experimentation. Higher pulp density batch reactor and continuous (pilot plant) data were then used to confirm the successful integration of these expressions in the overall simulation. This is the first truly comprehensive study of chalcopyrite concentrate pressure oxidation, the kinetics of the accompanying reactions and each of the underlying thermodynamic aspects. Consistent theoretical arguments and insights are presented, while conceptual proposals are tabled in cases where the fundamental information is lacking. This dissertation presents an internally consistent simulation, with each of the modules contributing to an overall mathematical description of the pressure oxidation of chalcopyrite concentrates. It provides a powerful research and process engineering tool, and may be used to simulate the performance of a primary leaching circuit on a full-scale plant. As an example, the simulation was used to study the impact of selected intrinsic properties and control parameters on the autoclave and primary leach circuit performance. Various recommendations on improving the simulation are highlighted, as well as the aspects to explore in follow-up studies.

AFRIKAANSE OPSOMMING: Hiedie verhandeling stel 'n gedetailleerde wiskundige beskrywing van die drukoksidasie van chalkopiriet-konsentrate in suuragtige sulfaatoplossings bekend, sowel as die evaluering van die belangrikste meegaande reaksies by tipiese gemiddelde bedryftemperature (140-155ºC) in enkellading en gestagdigde-vloei mengvatreaktore. Die wiskundige raamwerk bestaan uit verskeie modules, wat elk beide die termodinamiese- en kinetiese-aspekte aanspreek van die primêre prosesse wat binne in 'n drukoksidasie reaktor plaasvind. Gedetailleerde literatuurondersoeke word aangebied wat the vertrekpunt van hierdie studie gevorm het, aangevul deur fenomenologiese data wat uit gekontroleerde enkellading en gestagdigde-vloei eksperimentering verkry is. Die verskillende modules, wat elk 'n hoofstuk van hierdie verhandeling beslaan, sluit die volgende in i) die oplossings termodinamika raamwerk, ii) gas/vloeistof massaoordrag van suurstof, iii) die kinetika van yster(II) oksidasie, iv) die kinetika van yster(III) presipitasie, v) die intrinsieke oksidasiekinetika van die sulfiedminerale, en vi) die partikelraamwerke van die enkellading en gestadigde-vloei reaktore. Hierdie modules is ingebed in 'n gestadigde massa- en energiebalansplatform van 'n primêre loog – oplosmiddel ekstraksievloeidiagram, terwyl die enkellading reaktoranalogie beskryf word deur die behoud van massa, en die beweging daarvan tussen fases, in 'n losstaande konfigurasie. Literatuur inligting was veral belangrik in die afleiding van die generiese funksionele vorme van die belangrikste reaksietempovergelykings, terwyl die fenomenologiese uitdrukkings verfyn, en die gepaardgaande konstantes, uit lae pulpdigtheid enkellading eksperimentering verkry is. Hoër pulpdigtheid enkellading reaktor en gestadigde-vloei (loods aanleg) data is toe gebruik om die suksesvolle integrasie van hierdie vergelykings in die algehele simulasie te bevestig. Hierdie is die eerste volledige studie van die drukoksidasie van chalkopiriet-konsentrate, die kinetika van elk van die gepaardgaande reaksies en die onderliggende termodinamiese aspekte. Konsekwente teoretiese argumente en insigte word aangebied, terwyl konseptuele voorstelle ter tafel gelê word in gevalle waar die fundamentele inligting ontbreek. Hierdie verhandeling bied 'n interne konsekwente simulasie aan, met elk van die modules wat bydra tot 'n algehele wiskundige beskrywing van die drukoksidasie van chalkopiriet-konsentrate. Dit bied 'n kragtige navorsings en proses-ingenieurswese instrument aan, wat gebruik kan word om die gedrag van 'n primêre loogvloeidiagram op 'n volskaalse aanleg te simuleer. As 'n voorbeeld, is die simulasie gebruik om die impak van geselekteerde intrinsieke eienskappe en beheerparameters op die gedrag van die autoklaaf en primêre loogvloeidiagram te bestudeer.Verskeie aanbevelings oor die verbetering van die simulasie word uitgelig, asook die aspekte om in opvolgstudies te verken.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/71978
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