Thesis (PhD)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: The growing need to improve accounting accuracy, precision and to standardise generally accepted measurement methods in the mining and processing industries has led to the joining of a number of organisations under the AMIRA International umbrella, with the purpose of fulfilling these objectives. As part of this venture, Anglo Platinum undertook a project on the material balancing around its largest smelter, the Waterval Smelter. The primary objective of the project was to perform a statistical material balance around the Waterval Smelter using the Maximum Likelihood method with respect to platinum, rhodium, nickel, sulphur and chrome (III) oxide. Pt, Rh and Ni were selected for their significant contribution to the company’s profit margin, whilst S was included because of its environmental importance. Cr2O3 was included for its importance in as far as the difficulties its presence poses in smelting of PGMs. The objective was achieved by performing a series of statistical computations. These include; quantification of total and analytical uncertainties, detection of outliers, estimation and modelling of daily and monthly measurement uncertainties, parameter estimation and data reconciliation. Comparisons were made between the Maximum Likelihood and Least Squares methods. Total uncertainties associated with the daily grades were determined by use of variographic studies. The estimated Pt standard deviations were within 10% relative to the respective average grades with a few exceptions. The total uncertainties were split into their respective components by determining analytical variances from analytical replicates. The results indicated that the sampling components of the total uncertainty were generally larger as compared to their analytical counterparts. WCM, the platinum rich Waterval smelter product, has an uncertainty that is worth ~R2 103 000 in its daily Pt grade. This estimated figure shows that the quality of measurements do not only affect the accuracy of metal accounting, but can have considerable implications if not quantified and managed. The daily uncertainties were estimated using Kriging and bootstrapped to obtain estimates for the monthly uncertainties. Distributions were fitted using MLE on the distribution fitting tool of the JMP6.0 programme and goodness of fit tests were performed. The data were fitted with normal and beta distributions, and there was a notable decrease in the skewness from the daily to the monthly data. The reconciliation of the data was performed using the Maximum Likelihood and comparing that with the widely used Least Squares. The Maximum Likelihood and Least Squares adjustments were performed on simulated data in order to conduct a test of accuracy and to determine the extent of error reduction after the reconciliation exercise. The test showed that the two methods had comparable accuracies and error reduction capabilities. However, it was shown that modelling of uncertainties with the unbounded normal distribution does lead to the estimation of adjustments so large that negative adjusted values are the result. The benefit of modelling the uncertainties with a bounded distribution, which is the beta distribution in this case, is that the possibility of obtaining negative adjusted values is annihilated. ML-adjusted values (beta) will always be non-negative, therefore feasible. In a further comparison of the ML(bounded model) and the LS methods in the material balancing of the Waterval smelter complex, it was found that for all those streams whose uncertainties were modelled with a beta distribution, i.e. those whose distribution possessed some degree of skewness, the ML adjustments were significantly smaller than the LS counterparts It is therefore concluded that the Maximum Likelihood (bounded models) is a rigorous alternative method of data reconciliation to the LS method with the benefits of; -- Better estimates due to the fact that the nature of the data (distribution) is not assumed, but determined through distribution fitting and parameter estimation -- Adjusted values can never be negative due to the bounded nature of the distribution The novel contributions made in this thesis are as follows; -- The Maximum Likelihood method was for the first time employed in the material balancing of non-normally distributed data and compared with the well-known Least Squares method -- This was an original integration of geostatistical methods with data reconciliation to quantify and predict measurement uncertainties. -- For the first time, measurement uncertainties were modeled with a distribution that was non-normal and bounded in nature, leading to smaller adjustments / AFRIKAANSE OPSOMMING: Die groeiende behoefte aan rekeningkundige akkuraatheid, en om presisie te verbeter, en te standardiseer op algemeen aanvaarde meetmetodes in die mynbou en prosesseringsnywerhede, het gelei tot die samwewerking van 'n aantal van organisasies onder die AMIRA International sambreel, met die doel om bogenoemde behoeftes aan te spreek. As deel van hierdie onderneming, het Anglo Platinum onderneem om 'n projek op die materiaal balansering rondom sy grootste smelter, die Waterval smelter. Die primêre doel van die projek was om 'n statistiese materiaal balans rondom die Waterval smelter uit te voer deur gebruik te maak van die sogenaamde maksimum waarskynlikheid metode met betrekking tot platinum, rodium, nikkel, swawel en chroom (iii) oxied. Pt, Rh en Ni was gekies vir hul beduidende bydrae tot die maatskappy se winsmarge, terwyl S ingesluit was weens sy belangrike omgewingsimpak. Cr2O3 was ingesluit weens sy impak op die smelting van Platinum groep minerale. Die doelstelling was bereik deur die uitvoering van 'n reeks van statistiese berekeninge. Hierdie sluit in: die kwantifisering van die totale en analitiese variansies, opsporing van uitskieters, beraming en modellering van daaglikse en maandelikse metingsvariansies, parameter beraming en data rekonsiliasie. Vergelykings was getref tussen die maksimum waarskynlikheid en kleinste kwadrate metodes. Totale onsekerhede of variansies geassosieer met die daaglikse grade was bepaal deur ’n Variografiese studie. Die beraamde Pt standaard afwykings was binne 10% relatief tot die onderskeie gemiddelde grade met sommige uitsonderings. Die totale onsekerhede was onderverdeel in hul onderskeie komponente deur bepaling van die ontledingsvariansies van duplikate. Die uitslae toon dat die monsternemings komponente van die totale onsekerheid oor die algemeen groter was as hul bypassende analitiese variansies. WCM, ‘n platinum-ryke Waterval Smelter produk, het 'n onsekerheid in die orde van ~twee miljoen rand in sy daagliks Pt graad. Hierdie beraamde waarde toon dat die kwaliteit van metings nie alleen die akkuraatheid van metaal rekeningkunde affekteer nie, maar aansienlike finansiële implikasies het indien nie die nie gekwantifiseer en bestuur word nie. Die daagliks onsekerhede was beraam deur gebruik te maak van “Kriging” en “Bootstrap” metodes om die maandelikse onsekerhede te beraam. Verspreidings was gepas deur gebruik te maak van hoogste waarskynlikheid beraming passings en goedheid–van-pas toetse was uitgevoer. Die data was gepas met Normaal en Beta verspreidings, en daar was 'n opmerklike vermindering in die skeefheid van die daaglikse tot die maandeliks data. Die rekonsiliasies van die massabalans data was uitgevoer deur die gebruik die maksimum waarskynlikheid metodes en vergelyk daardie met die algemeen gebruikde kleinste kwadrate metode. Die maksimum waarskynlikheid (ML) en kleinste kwadrate (LS) aanpassings was uitgevoer op gesimuleerde data ten einde die akkuraatheid te toets en om die mate van fout vermindering na die rekonsiliasie te bepaal. Die toets getoon dat die twee metodes het vergelykbare akkuraathede en foutverminderingsvermoëns. Dit was egter getoon dat modellering van die onsekerhede met die onbegrensde Normaal verdeling lei tot die beraming van aanpassings wat so groot is dat negatiewe verstelde waardes kan onstaan na rekosniliasie. Die voordeel om onsekerhede met 'n begrensde distribusie te modelleer, soos die beta distribusie in hierdie geval, is dat die moontlikheid om negatiewe verstelde waardes te verkry uitgelsuit word. ML-verstelde waardes (met die Beta distribusie funksie) sal altyd nie-negatief wees, en om hierdie rede uitvoerbaar. In 'n verdere vergelyking van die ML (begrensd) en die LS metodes in die materiaal balansering van die waterval smelter kompleks, is dit gevind dat vir almal daardie strome waarvan die onserkerhede gesimuleer was met 'n Beta distribusie, dus daardie strome waarvan die onsekerheidsdistribusie ‘n mate van skeefheid toon, die ML verstellings altyd beduidend kleiner was as die ooreenkomstige LS verstellings. Vervolgens word die Maksimum Waarskynlikheid metode (met begrensde modelle) gesien as 'n beter alternatiewe metode van data rekosiliasie in vergelyking met die kleinste kwadrate metode met die voordele van: • Beter beramings te danke aan die feit dat die aard van die onsekerheidsdistribusie nie aangeneem word nie, maar bepaal is deur die distribusie te pas en deur van parameter beraming gebruik te maak. • Die aangepaste waardes kan nooit negatief wees te danke aan die begrensde aard van die verdeling. Die volgende oorspronklike bydraes is gelewer in hierdie verhandeling: • Die Maksimum Waarskynlikheid metode was vir die eerste keer geëvalueer vir massa balans rekonsiliasie van nie-Normaal verspreide data en vergelyk met die bekendde kleinste kwadrate metode. • Dit is die eerste keer geostatistiese metodes geïntegreer is met data rekonsiliasie om onsekerhede te beraam waarbinne verstellings gemaak word. • Vir die eerste keer, is meetonsekerhede gemoddelleer met 'n distribusie wat nie- Normaal en begrensd van aard is, wat lei tot kleiner en meer realistiese verstellings.

Orientador: Luis Augusto Barbosa Cortez / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola / Made available in DSpace on 2018-08-05T15:58:35Z (GMT). No. of bitstreams: 1 MesaPerez_JuanMiguel_D.pdf: 6859619 bytes, checksum: c3322e7576316c3eb38397a94e624ce4 (MD5) Previous issue date: 2004 / Resumo: Neste trabalho são apresentados e discutidos testes experimentais conduzidos na planta de pirólise rápida de biomassa da Unicamp visando à operação estável do reator de leito fluidizado em regime borbulhante. Esses resultados permitiram identificar os principais problemas relativos à operação do reator, assim como analisar as possíveis causas e as soluções postas em prática. O problema de maior influência sobre o trabalho estável do reator foi o vazamento de gases da pirólise pelo sistema de alimentação, mostrando-se como solução mais eficaz, o aumento da porcentagem de preenchimento da rosca alimentadora com biomassa. Após a estabilização da operação do reator, estudou-se a influência da porcentagem de ar em relação ao estequiométrico e da altura do leito fixo de inerte sobre as características de qualidade e rendimento dos finos de carvão. O estudo permitiu concluir que, para 8% de ar em relação ao estequiométrico e 207 mm de altura do leito fixo de areia, a pirólise acontece de forma mais intensa. Essa análise parte do princípio de que a pirólise é um processo de concentração de carbono nos finos de carvão e liberação de oxigênio da biomassa. Tomando-se como base os resultados anteriores, foram conduzidos novos testes visando à coleta e caracterização de amostras de bio-óleo. Os resultados mostraram que tanto a viscosidade quanto o teor de insolúveis das amostras de bio-óleo apresentaram altos valores, quando comparados com dados da literatura. Com base na experiência acumulada dos estudos anteriores é proposta e parcialmente avaliada uma estratégia para a otimização e a mudança de escala do processo de pirólise em leito fluidizado. A estratégia objetiva o uso das informações obtidas a partir dos modelos matemáticos ajustados no reator modelo para o projeto de reatores comerciais. O procedimento anterior mostra-se eficiente quando os fatores independentes e seus níveis durante a otimização do processo no reator modelo são criteriosamente selecionados. Finalmente, são mostradas, por meio de um exemplo, as dificuldades durante a mudança de escala quando os experimentos realizados no reator modelo não são planejados com o objetivo de reduzir as distorções na escalada / Abstract: This research discusses a strategy to optimize and scale up the pyrolysis process in fluidized bed. The strategy uses adjusted mathematical models applied to the model reactor to the project commercial reactors. Several steps of that procedure were appraised based on the adjusted model for the percentage of elutriated fine charcoal in the model reactor. It was verified that, during the scale-up, the mathematical model was not effective; however it predicts problems associated to the change of scale. Exploratory tests were carried out to guarantee the stable operation of the reactor, which made possible the identification of the main problems related to the procedure during the fast pyrolysis in fluidized bed with atmospheric air. The possible causes of the problems, as well their solutions, are also analyzed. The greater difficulty in the operation was the leak of pyrolitic gases through the feeding system. The increase of the percentage of biomass stuffing of the feeding thread was the most effective solution to avoid gas leaking. When the reactor operation was stabilized, the influence of the percentage of air in relation to the stoichiometric and the height of the inert fixed bed on the quality characteristics and yield of the fine charcoal. That study allowed conclude that, for 8% of air in relation to the stoichiometric and 207 mm of the fixed sand bed height, the pyrolysis happens in a more intense way. The analysis was based on the principle that the pyrolysis process is a process to concentrate carbon in charcoal and release oxygen from the biomass. Finally, bio-oil samples were collected using a centrifugal separator and characterized. The viscosity and the insoluble content presented high values, when compared with the literature data. Based on those results, a system to bio-oil recovery was projected and built. It combines the direct contact followed by centrifugal separation / Doutorado / Construções Rurais e Ambiencia / Doutor em Engenharia Agrícola

This master thesis work examines whether it is possible to separate lead from an electrolytic sludge rich in manganese using pyrometallurgical treatment, and also attempts to determine the optimum process parameters for such a treatment. It also includes a theoretical study of the possible applications for lead and manganese, as well as thermodynamic calculations predicting the behaviour of the material at increasing temperatures. The experimental work completed includes characterisation and agglomeration of the raw material, as well as tests in a chamber furnace and a rotary furnace. The anode sludge was characterised using chemical analysis, XRD, SEM and PSD. The anode sludge was agglomerated into pellets using either both bentonite and water, or only water as binder. The smaller scale tests in the chamber furnace examined the impact of several variables on lead removal. These variables included type and amount of reduction agent used, temperature, and whether the anode sludge was added as untreated material or pellets. The most promising of these results were further tested in the rotary furnace at a slightly larger scale. The variables used for the rotary furnace tests were amount of reduction agent added, whether the anode sludge was added as untreated material or pellets, and whether the reduction agent was added at the start of or during the experiment. All samples were sent for chemical analysis, and selected samples were further analysed using XRD and SEM. The conclusions drawn from the results of the thermodynamic calculations and experimental work are as follows: In the untreated anode sludge the primary phases are MnO2, CaSO4, and (Pb,Sr)SO4. The anode sludge can be agglomerated into pellets, with or without added binder. After treatment the primary phases present are MnO and (Ca,Sr)2SiO4. Lead is present as small separate grains. The most effective treatment method should adhere to the following parameters:Use of a rotating furnace. Anode sludge added in the form of pellets, to simplify materials handling. Temperature of 1400-1500 °C. Reduction agent added in batches after initial smoke formation has stopped. Total addition of reduction agent should be 10 wt% of anode sludge. Significant weight loss occurs during treatment. The amount of reduction agent added to the anode sludge has the greatest effect on the removal of lead and zinc. Charcoal is a potential candidate for a renewable reduction agent, but leads to increased weight loss. It is possible to separate lead from the manganese anode sludge using pyrometallurgical treatment, down to 100 ppm. Zinc can also be separated, down to 600 ppm. / Detta examensarbete undersöker huruvida det är möjligt att separera bly från ett anodslam rikt i mangan med hjälp av pyrometallurgiska behandlingsmetoder, och försöker även avgöra de optimala processparametrarna för en sådan behandling. Arbetet inkluderar även en teoristudie av möjliga användningsområden för bly och mangan, samt termodynamiska beräkningar som förutser materialets beteende vid ökande temperaturer. Det experimentella arbetet som utförts inkluderar karakterisering och agglomerering av råmaterialet, samt försök i en kammarugn och en rullugn. Anodslammet karakteriserades med hjälp av kemisk analys, XRD, SEM, och partikelstorleksfördelning. Anodslammet agglomererades till pellets med antingen bentonit och vatten eller bara vatten som bindemedel. Försöken i mindre skala i kammarugnen undersökte hur flera variabler påverkade blyavdrivningen. Dessa variabler inkluderade typ och mängd av reduktionsmedel som tillsattes, temperatur, och huruvida anodslammet som användes var obehandlat material eller pellets. De mest lovande av dessa resultat användes för vidare försök i rullugnen i något större skala. Variablerna som undersöktes vid rullugnsförsöken var mängd reduktionsmedel som tillsattes, huruvida anodslammet som användes var obehandlat material eller pellets, samt huruvida reduktionsmedlet tillsattes vid start eller under försökets gång. Alla prover skickades för kemisk analys, och utvalda prover analyserades ytterligare med XRD och SEM. Slutsatserna som dragits utifrån resultaten av de termodynamiska beräkningarna och det experimentella arbetet är som följande: I det obehandlade anodslammet är de primära faserna MnO2, CaSO4, och (Pb,Sr)SO4. Anodslammet kan agglomereras till pellets. Efter behandling är de primära faserna i materialet MnO och (Ca,Sr)2SiO4. Kvarvarande bly är närvarande som små separata korn. Den mest effektiva behandlingsmetoden bör använda följande parametrar: Användning av en roterande ugn. Anodslam bör tillsättas i form av pellets för att underlätta materialhantering. Temperatur mellan 1400-1500 °C. Reduktionsmedel tillsatt i omgångar efter att initial rökbildningen avstannat. Total tillsats av reduktionsmedel bör vara 10 vikt% av anodslammets vikt. Signifikanta viktförluster under behandling. Mängden tillsatt reduktionsmedel är den faktor som har störst effekt på avlägsnandet av bly och zink. Träkol är en potentiell kandidat för ett förnyelsebart reduktionsmedel, men orsakar ökade viktförluster. Det är möjligt att separera bly från mangan med hjälp av pyrometallurgiska metoder, ned till 100 ppm bly. Zink kan också separeras, ned till 600 ppm.

M. Tech., (Faculty of Applied and Computer Science), Vaal University of Technology / There is huge concern in the mining and industries to manage wastewater prior to discharge into the environment. It is generally cheaper and cost reducing for industries to treat its own wastewater before discharging to the local authority sewer. Dense Media Separation (DMS) Powders Company produces milled and atoms ferro-silicon by pyro-metallurgical process. DMS Powders uses municipal water for all processes taking place in the plants. The water used during the processes of milled and atom ferrosilicon powder is discharged into the environment without being treated. By treating this process wastewater before discharging will result in reducing the water consumption by recycling and the penalty costs for polluting the environment. The primary objective of this study is to find suitable method for treatment of DMS Powders’ process water using selected membrane processes. Membrane processes are better choice compared to traditional physical/chemical treatment processes, due to their advantages of approving water quality, no phase change, no chemical addition and simple operation. Two commercial membranes namely; NF-, and SW30HR are used in the treatment of DMS Powders process water. These membranes were purchased from (Dow/Filmtec) Manufacturing Company (Pty) situated in South Africa. Membranes were characterised by Scanning Electron Microscopy (SEM), Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Fourie Transform Infrared (FTIR) instruments. For synthetic water three membranes (NF- , NF90, and SW30HR) are investigated for the study. The fluxibility indicated that NF- membrane has higher flux compared to NF90 and SW30HR membranes. All the three membranes were very good in terms of rejection on single salts. Fouling was studied on DMS Powders process water. Concentration polarization was formed on NF- and SW30HR membranes investigations on selected membranes conclude that NF- membrane will be the suitable membrane for treatment of DMS Powders process water because of its high fluxibility and rejection. Discharged effluent of DMS Powders could comply with the legislature and environmental pollution could be minimised. The study revealed that fouling does occur during treatment of process water. SW30HR showed that M9 Plant had more fouling for M9 samples than other Plants (M8A and M8B). It was because of higher concentrations in suspended solids.or M8A, M8B and M9 process water.

Copper is an essential metal in today’s economy, due to its superior electrical and thermal conductivities, alloying properties, and chemical uses. Most copper is produced viamining and refining, and most copper is found in the earth’s crust as chalcopyrite, CuFeS2. Typically, chalcopyrite is concentrated and fed to a high temperature pyrometallurgical process which produces >99.99% purity copper cathodes. Recently, Freeport-McMoRan Inc. has implemented a hydrometallurgical autoclave-leaching process that takes chalcopyrite concentrate and produces copper cathodes. It is imperative that these pyrometallurgical and hydrometallurgical processes be modeled and compared so that the extraction industry can best decide which technology to apply in the future. This work presents transient, reduced-order models for the comparison of the two processes using exergy balances. Exergy is typically thought of as the maximum work extractable from a system as it spontaneously reacts to the state of the surrounding environment; for extractive processes, it is also helpful to think of exergy as the minimum work required to effect a concentration, e.g. of copper. Exergy balances are thus similar to first law balances, but they comment on the location and magnitude of usefulenergy flows, instead of energy flows in general. For the baseline case, this work found that the pyrometallurgical process up to 99.5% copper anode stored 54% of the fed exergy in product, lost 20% of the fed exergy, and destroyed the remaining 26%. In contrast, the hydrometallurgical process up to 30 grams-per-liter copper pregnant-leach-solution stored 5% of the fed exergy in product, lost 9% of the fed exergy, and destroyed the remaining 86%. The effects of process variations are also looked at. It is recommended that this work be incorporated in whole-plant exergy balances to more precisely examine the tradeoffs between the pyrometallurgical and hydrometallurgical routes of copper extraction from chalcopyrite concentrates.

The trend towards a more circular economy presents a unique challenge for the pyrometallurgical engineer. Secondary feeds bring complexity to the smelter in the form of non-traditional chemistries and minor elements. Models of furnaces will play an important role in this paradigm. Models should be able to predict operations in dynamic systems that do not always operate at equilibrium.The development of a top submerged lance (TSL) model was the subject of this study because the TSL has proven to be capable of treating secondary materials.The furnace consists of a vertical cylindrical vessel, containing molten slag and bullion at the bottom. A lance enters through the roof and the tip is submerged in the slag, into which gas and fuel are blown. Secondary or primary feeds, fluxes and reductants can be fed to the furnace. The reactions and interplay between the liquid phases, gas and added reductants set the temperatures and partial oxygen pressures in the furnace. The Connected Local Equilibria (CLE) method was followed to model the furnace. This approach offers the benefit that speciation can be modelled simultaneously for many elements from thermochemical databases. The methodology is to divide the furnace into several equilibrium volumes, based on expected material flows. With each time step, equilibrium in each volume is calculated by Gibbs free energy minimization. Material is then exchanged between volumes according to expected flows. To validate the method, small scale crucible experiments were carried out. Molten lead-containing ferric calcium silicate slags (PbO-FCS slag, also containing GeO2, TeO2 and SnO2 in concentrations ˂ 1 wt%) were reduced under controlled CO/CO2 atmospheres to produce lead bullion. The kinetics of the process were measured. Similar experiments were carried out with a copper-containing ferric calcium silicate system. The CLE method was applied to simulate the data, using HSC Sim software. The crucible was divided into four equilibrium volumes: slag-gas contact; slag; slag-hearth contact; hearth. The gas flowrate to the slag-gas contact was determined by following a rate-law in the form of chemical reaction control (e.g. Rg-s = kapp.pCO (mol O.cm-2.s-1)). By using a single fitting factor (kapp), the dynamic behaviour of lead and the minor elements (tin, tellurium, germanium) could be predicted. The same method was successfully used for the CuO-FCS system. The use of this method enhanced understanding of the experiments, by showing the component speciation during reduction. Full-scale TSL models were then developed using HSC Chemistry software and SimuSage software. In both cases the CLE method was applied. The flow patterns in the furnace were gleaned from published computational fluid dynamics (CFD) work. The interface areas were not known, and assumptions thus needed to be made to model an industrial process for lead-oxide FCS slag reduction. It was shown that the model can provide useful insight into real-world problems. Two branches of modelling might develop from this work. In one, CFD work can quantify interface areas in the furnace, so that CLE models similar to the current work are possible. In the second, only bulk fluid movement might be used. In either case, this work validates the approach of using a thermochemical approach to model kinetics.:1 INTRODUCTION 1.1 THE METALLURGICAL CHALLENGE TO ACHIEVE A CIRCULAR ECONOMY 1.2 APPLICATION OF UNIT MODELS IN TECHNO-ECONOMIC, EXERGY AND ENVIRONMENTAL FOOTPRINT ANALYSES 1.3 FOCUS OF THE CURRENT WORK 2 RESEARCH OBJECTIVES 3 LITERATURE REVIEW 3.1 LEAD METALLURGY (INCLUDING WEEE) 3.2 COPPER METALLURGY 3.3 EQUILIBRIUM BEHAVIOUR OF MINOR ELEMENTS IN LEAD AND COPPER METALLURGY 3.4 SLAG REDUCTION KINETICS 3.5 TSL FURNACE 3.6 MODELLING OF BATH-TYPE SMELTERS 3.6.3 CFD Modelling 4 EXPERIMENTAL METHODOLOGY 4.1 MASTER SLAG PREPARATION 4.2 EXPERIMENTAL SETUP 4.3 REDUCTION EXPERIMENT PROCEDURE 4.4 LIST OF EXPERIMENTS 4.5 ANALYTICAL METHOD 4.6 REACTION OF SLAGS WITH CRUCIBLE WALLS 5 EXPERIMENTAL ERROR EVALUATION 5.1 ERROR IN MASTER SLAG COMPOSITION MEASUREMENTS 5.2 REPEAT TESTS 5.3 EXPERIMENTAL ERROR 6 MODELLING OF KINETICS WITH HSC SIM 6.1 HSC CHEMISTRY DYNAMIC MODULE AND CONNECTED LOCAL EQUILIBRIA MODELLING 6.2 RESULTS FOR MODELLING LEAD EXPERIMENTAL RESULTS WITH HSC CHEMISTRY 6.3 RESULTS FOR MODELLING COPPER EXPERIMENTAL RESULTS WITH HSC CHEMISTRY 7 TSL MODEL IN HSC CHEMISTRY 7.1 FLUID FLOW IN TSL FOR CONNECTED LOCAL EQUILIBRIA MODELLING 7.2 TANKS AND OPERATIONS IN HSC SIM MODEL 7.3 EXAMPLE OF HSC SIM CLE MODEL APPLICATION 8 TSL MODEL ON SIMUSAGE PLATFORM 8.1 METHOD FOR SIMUSAGE MODEL 8.2 SPECIES SELECTION IN SIMUSAGE MODEL 8.3 EXAMPLE OF SIMUSAGE CLE MODEL APPLICATION 9 COMPARISON OF HSC SIM AND SIMUSAGE RESULTS 10 CRITICAL ANALYSIS OF MODEL METHODOLOGY 10.1 MEASUREMENT OF BULK VOLUME COMPOSITIONS 10.2 HEAT TRANSFER IN HSC SIM AND SIMUSAGE MODELS 10.3 USING BULK FLUID FLOWS VS INTERFACE APPROACH 11 CONCLUSIONS 11.1 MOTIVATION 11.2 LABORATORY KINETIC MEASUREMENTS AND MODELLING WITH CLE METHOD 11.3 TSL MODELLING WITH HSC SIM AND SIMUSAGE 12 REFERENCES

Coals, from mines in the Highveld coalfield, as well as gasification ash samples were characterised, in order to understand the mineralogical and chemical properties of the individual components in the gasification feedstocks. X-ray diffraction of low temperature oxygen-plasma ash indicates that the coals contain significant proportions of kaolinite, quartz and a fluxing elements-bearing mineral (dolomite), plus minor concentrations of illite and other fluxing elements-bearing minerals namely calcite, pyrite and siderite. Of the feed coal, the -75+53 mm size fraction has a high pyrite, and to a lesser extent a high calcite and dolomite content. However, the small proportion of iron-bearing phases (from the reaction between kaolinite and pyrite) in samples taken from the gasifier implies that pyrite contributes minimally to sintering or slagging in this case. Calcite is mainly present in the >1.8 g/cm3 density fraction of the feed coal, whereas dolomite is mainly present in the 1.5-1.8 g/cm3 density fraction, as inclusions or fine cleats in the coal matrix. Electron microprobe analyses of coals from the six different South African mines confirmed that some Ca, Mg, Al, Si, Na, K, Ti and Fe are present in the organic matrix in the coal samples tested in this study, but the amounts of these are small compared with the fluxing elements in minerals. XRD and microprobe analyses indicate that the ash clinker samples taken from the gasifiers contain a number of crystalline high temperature phases, including anorthite, mullite, cristobalite, quartz and diopside. FactSage confirmed that anorthite and mullite are equilibrium phases at elevated temperatures in the ash clinkers and heated rock fragments. Limited reaction takes place between the included coal minerals and the extraneous rock fragments. / Thesis (PhD)--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / unrestricted