Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Hydrocyclones are separation devices that are widely used throughout the chemical engineering and mineral processing industries. Although simple in design, the intricate flow structure of the device complicates control. As an alternative to conventional empirical and theoretical modelling, process state monitoring methods have recently been employed as a means to control hydrocyclones. The purpose of process state monitoring methods is to distinguish between the desired operating state with favourable separation, the transition state, and the troublesome operating state of dense flow separation. In comparison to previously employed monitoring techniques, image analysis of the underflow is regarded as a promising approach. Preliminary studies have indicated that the technique complies with hydrocyclone monitoring requirements: sensitivity, non-invasiveness, sampling times less than one second, robustness and low cost. The primary objective of this study was therefore defined as investigating the feasibility of image analysis of hydrocyclone underflow as a monitoring technique. Data collection entailed the recording of hydrocyclone underflow for different operating states. Six case studies were performed in total: Gold, Ilmenite, Platreef, Merensky 1, Merensky 2 and Merensky 3 (with the case study names indicating the different ore types used). An image analysis technique, consisting of feature extraction through motion detection, as well as various noise reduction methods, was consequently developed and applied to the video data. Classification of the various operating states was attempted by performing modelling by one-class support vector machines (SVM). Results indicated that the developed image analysis technique effectively addresses background noise, random noise and system vibration through image enhancement and a motion threshold. Extremely low contrast differences and foreground noise did, however, prove problematic in Ilmenite and Merensky 1 case studies respectively. For the remaining case studies, it was found that the various operating states were identified with high accuracy through one-class SVM classification. This is particularly true for the identification of the troublesome dense flow separation for which extremely low missing alarm rates were obtained (0 % in most cases). In terms of practicality, the technique proved to be sensitive, non-intrusive and economical. The sampling time of 30 frames per second and estimated processing to video time ratio of 1:1, is furthermore satisfactory. Ultimately, the results indicate that the image analysis of hydrocyclone underflow is a viable monitoring technique. The robustness of the technique might further be improved by use of backlighting and an air-knife. It is also recommended that future work should focus on testing the monitoring technique on an industrial hydrocyclone setup. / AFRIKAANSE OPSOMMING: Hidrosiklone is skeidingsapparate wat algemeen gebruik word in chemiese ingenieurswese en mineraalprosesserings industrieë. Alhoewel die apparaat ‘n eenvoudige ontwerp het, bemoeilik die komplekse interne vloeistruktuur die beheer daarvan. Prosestoestandmoniteringsmetodes is vir hidrosikloonbeheer toegepas as alternatief vir konvensionele empiriese en teoretiese modellering. Die doel van prosestoestandmoniteringsmetodes is om te onderskei tussen die gewenste bedryfstoestand met gunstige skeiding, die oorgangstoestand, en die moeilike bedryfstoestand van digtevloeiskeiding. In vergelyking met vorige toegepaste moniteringstegnieke, word beeldverwerking van die ondervloei beskou as ‘n belowende tegniek. Voorlopige studies het aangedui dat die tegniek voldoen aan die hidrosikloonmoniteringvereistes: sensitiwiteit, nie-indringendheid, monsternemingstydperke laer as een sekonde, robuustheid en lae koste. Die primêre doelwit van hierdie studie is daarom gedefineer as die ondersoek van die doenlikheid van beeldverwerking van hidrosikloon ondervloei as ‘n moniteringstegniek. Die data versameling het die afneem van hidrosikloon ondervloei vir verskillende bedryfstoestande behels. Ses gevallestudies is in totaal uitgevoer: Goud, Ilmeniet, Platreef, Merensky 1, Merensky 2 en Merensky 3 (die gevallestudie name dui die verskillende erts tipes wat gebruik is aan). ‘n Beeldverwerkingstegniek, wat bestaan uit kenmerkekstraksie deur bewegingsopsporing, asook verskeie geruisverlagingsmetodes, is gevolglik ontwikkel en toegepas op die video data. Klassifikasie van die verskeie bedryfstoestande is beproef deur modellering met enkelklassteunvektormasjiene. Resultate het aangedui dat die ontwikkelde beeldverwerkingstegniek agtergrond geruis, onreëlmatige geruis en sisteem vibrasie suksesvol aanspreek deur beeldversterking en ‘n bewegingslimiet. Beduidende lae kontrasverskille en voorgrond geruis blyk wel problematies in die Ilmeniet en Merensky 1 gevallestudies onderskeidelik. Vir die orige gevallestudies is gevind dat die verskillinde bedryfstoestande met hoë akkuraatheid geïdentifiseer is deur enkelklassteunvektormasjiene klassifisering. Dit is veral waar vir die identifisering van die moeilike digtevloeiskeiding waarvoor beduidende lae vermiste-alarmmaatstawwe behaal is (0 % in die meeste gevalle). Aangaande die praktiese aspekte, blyk die tegniek sensitief, nie-indringend en ekonomies. Die monsternemingstydperk van 30 raampies per sekonde en die beraamde prosesserings- tot videotyd verhouding van 1:1, is ook voldoende. Ten slotte dui die resultate daarop dat die beeldverwerking van hidrosikloon ondervloei ‘n uitvoerbare moniteringstegniek is. Die robuustheid van die tegniek sou verder verbeter kon word deur gebruik te maak van agtergrondverligting en ‘n lugspuit. Dit word ook aanbeveel dat toekomstige werk op die toetsing van die moniteringstegniek op ‘n industriële hidrosikloon toestel moet fokus.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2011. / Please refer to full text to view abstract.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: See item for full text / AFRIKAANSE OPSOMMING: Sien item vir volteks

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Recombinant glycoproteins are important biopharmaceuticals, providing solutions for numerous previously untreatable illnesses, in everything from cancer to infertility. Most recombinant biopharmaceuticals are produced in mammalian cells due to their ability to provide the correct post-translational processing for use in humans. The post-translation processing influences many of the protein’s properties including pharmacokinetics, bioactivity, secretion, half-life, solubility, recognition and antigenicity. The aim of this thesis is to further study the upstream production of a glycosylated recombinant protein produced by Chinese hamster ovary (CHO) cells on production scale within the confines of an existing process. The process in question uses adherent CHO cells to produce a glycosylated recombinant hormone. As with most recombinant protein production processes, this process has two sections to the upstream production: a seed train to grow enough cells to inoculate production, and a production section, which focuses on the production of a recombinant protein. The seed train is predominantly conducted in roller bottles, while the production section takes place in perfusion bioreactors, where the cells are attached to microcarriers, with spin-filters for cell retention. The whole process uses medium with serum. There are two process challenges regarding an existing recombinant-protein production process: 1. The gradual increase, over the past several campaigns, of the final population doubling level of the cells (which must remain within certain specified limits) at the end of the seed train. 2. The low glycosylation levels of the product seen in certain campaigns, which meant that a certain number of final product batches were below the specified acceptable glycosylation limits. Following a literature survey several controlled process variables were chosen for investigation and hypotheses made on their effect on the seed train or glycosylation. To investigate their effect on the PDL and cell growth in the seed train: - Medium volume: decreasing the medium volume will yield a lower PDL due to slower cell growth caused by lower glucose availability. - Seeding density: if cells obtain confluence by the time they are harvested, decreasing the seeding density will yield a higher PDL. - Cultivation temperature: decreasing the temperature ought to decrease the growth rate. - Medium feed temperature: there will be no significant difference to the cell culture when pre-heated or cold medium is used. Aeration: using vent caps will increase the oxygen content of the medium in the roller bottles and the cell growth, yielding a higher PDL. To investigate their effect on glycosylation during production: - pH: better glycosylation will be seen at pH 6.9, than at pH 6.7. - Perfusion rate: a higher perfusion rate will lead to better glycosylation due to increased glucose and glutamine concentrations. In the seed train, the only factor that significantly influenced the final PDL was the seeding density. Cell growth was inhibited once cells reached confluence, so lowering the seeding density lead to a higher PDL. It is recommended to use a high seeding density to ensure a lower PDL. Historic data indicated that the seeding density was not the cause of the apparent increase of the final PDL, as all previous campaigns had been seeded with a high seeding density. What then became apparent was that the final PDL remained relatively constant during a campaign and that the increase in final PDL occurred between campaigns. It appears that the apparent increase in the final PDL is due to differences in cell counting between operators as each new campaign was managed by different operators. It is recommended that a mechanical cell counter be used to verify cells counts and to maintain a standard between campaigns. In the bioreactors, varying the pH proved to have no significant effect on the glycosylation levels. However, both the initial perfusion rate and the specific perfusion rate proved to be important from both historical data and the data generated during these experiments. Lower levels of the initial perfusion rate lead to better glycosylation and it is recommended that an initial perfusion rate of 1.0 volumes/day be used. The relationship between the specific perfusion rate and the glycosylation appears to be non-linear and requires further study, for now it is recommended that the specific perfusion rate be kept below 0.3 volumes/day/109 cells. Probable reasons for the unsatisfactory glycosylation seen in certain runs could also be proposed from these two factors: • RP33-133 : Very high specific perfusion rate • RP32-135 : High initial perfusion rate and very high specific perfusion rate • RP32-138 : High initial perfusion rate • RP33-139 : High initial perfusion rate Further research is recommended into the effect of the specific perfusion rate as well as the specific glucose consumption rate and the specific glutamine concentration on the glycosylation. / AFRIKAANSE OPSOMMING: Rekombinante glikoproteïene is baie belangrike biofarmaseutiese produkte wat oplossings bied vir talle voorheen ongeneeslike siektes in alles van kanker tot onvrugbaarheid. Meeste rekombinante farmaseutiese produkte word gemaak deur diere-selle as gevolg van hulle bevoegtheid om die korrekte na-translasie stappe te volg sodat die produkte in mense gebruik kan word. Die na-translasie stappe beïnvloed baie van die proteïene se karaktertreke insluitende die farmakokinetika, bioaktiwiteit, uitskeiding, half-leeftyd, oplosbaarheid, herkenbaarheid and antigeniciteit. Die doel van hierdie tesis is om die stroomop produksie van ‘n rekombinante glikoproteïene vervaardig deur Chinese hamster ovariale (CHO) selle verder te bestudeer binne die grense van ‘n bestaande proses op grootskaalse vlak. Die huidige proses gebruik CHO selle om ‘n rekombinante glikohormoon te produseer. Soos meeste prosesse wat rekombinante proteïene produseer bestaan die stroomop gedeelte van die proses uit twee dele: ‘n saad trein wat genoeg selle maak vir produksie en ‘n produksie gedeelte wat fokus op die vervaardiging van die glikoproteïen. Die saad trein bestaan hoofsaaklik uit roller bottels terwyl produksie plaasvind in perfusie bioreaktors waar die selle op “microcarriers” groei, met spin-filters om die selle binne die bioreaktors te hou; die hele proses gebruik medium met serum. Daar is twee probleme in die stroomop gedeelte van die bestaande proses: 1. Die geleidelike toename oor die afgelope paar jaar van die finale verdubbelingsvlak van die selle aan die einde van die saad trein 2. Die lae glukosilering van die eindproduk wat veroorsaak dat sekere lotnommers buite spesifikasie is Na ‘n literatuur studie, was seker beheerde proses parameters gekies om verder te bestudeer en hipotesisse gemaak oor hulle effek op die saad trein of die vlak van glukosilering. Die volgende faktore is bestudeer vir hulle effek op die finale verdubbelingsvlak van die selle in die saad trein: - Medium volume: ‘n laer medium volume sal lei tot a laer verdubbelingsvlak van die selle as gevolg van stadige groei - Konsentrasie van selle vir inokulasie: as die selle konfluent is teen die tyd wat hulle versamel word sal ‘n laer konsentrasie selle lei tot ’n hoër verdubellingsvlak. - Temperatuur: laer temperatuur behoort te lei tot ‘n stadiger groei koers van die selle - Medium voer-temperatuur: die voer-temperatuur van die medium sal geen beduidende verskil maak - Belugting: die gebruik van “vent-caps” sal die suurstof inhoud van die roller bottels verhoog Die volgende faktore is bestudeer vir hulle effek op die glukosilering tydens produksie: - pH: beter glukosilering word verwag by by pH 6.9 dan by pH 6.7 - Perfusie koers: ‘n hoër perfusie koers sal lei tot beter glukosilering as gevolg van hoër glukose en glutamien konsentrasies Die konsentrasie van die selle wat gebruik word vir inokulasie blyk die enigste faktor te wees wat die finale verdubbelingsvlak van die selle en die groei van die selle in die saad trein beïnvloed het. Die groei van die selle was beprek wanneer die selle konfluent geraak het en dus het ‘n laër sel konsentrasie by inokulasie gelei tot ‘n hoër sel verdubbelingsvlak. Dit word aanbeveel dat ‘n hoë sel konsentrasie by inokulasie gebruik word. Die geleidelike toename van die finale verdubbelingsvlak van die selle in die saad trein is waarskynlik as gevolg van die variasie in sel tellings tussen verskillende operateurs eerder as as gevolg van die beheerde proses parameters. Dit word aanbeveel dat ‘n meganiese sel-teller gebruik word om die verskil in sel tellings tussen operateurs te kontroleer en om ‘n standaard te handhaaf tussen produksie lotte. In die bioreaktors, het die pH geen beduidende invloed gehad op die glukosilering maar uit historiese data en die huidige data van hierdie eksperimente blyk albei die begin perfusie koers en die spesifieke perfusie koers ‘n belangrike invloed te hê op die glukosilering. Laër vlakke van die begin perfusie koers lei tot beter glikosilsie en dit word aanbeveel dat elke produksielot ‘n begin perfusie koers het van 1.0 volume/dag. Die verhouding tussen die glukosilering en die spesifieke perfusie koers blyk om nie-liniêr te wees nie. Nog navorsing hieroor word aanbeveel, maar vir nou word dit aanbeveel dat die spesifieke perfusie koers onder 0.3 volumes/dag/109 selle gehou word. Hierde twee faktore blyk die oorsaak te wees vir die lae glukosilering wat in sekere produksielopies gevind was: • RP33-133 : baie hoë spesifieke perfusie koers • RP32-135 : hoë begin perfusie koers en baie hoe spesifieke perfusie koers • RP32-138 : hoë begin perfusie koers • RP33-139 : hoë begin perfusie koers Dit word aanbeveel dat verdere navorsing gedoen word op die effek van die spesifieke perfusie koers asook die spesifieke koers van glukose verbruik en die spesifieke glutamien konsentrasie op die glukosilering van die produk.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A 2 stage heap leach process to extract base and precious metals from the Platreef ore is currently being investigated industrially. A first stage bioleach is used to extract the base metals. In the 2nd stage, cyanide is used as the lixiviant at high pH to extract the platinum group metals and gold. By analogy with current gold recovery practices, the present study investigates the preferential and quantitative adsorption of precious metals (Pt, Pd, Rh and Au) over base metals (Cu, Ni and Fe) from an alkaline cyanide medium, by means of granular activated carbon. Experiments were designed statistically to optimise the process parameters using synthetic alkaline cyanide solutions close in composition to those expected from plant leach solutions. The statistical approach allowed the development of a reliable quantitative approach to express adsorption as a response variable on the basis of a number of experiments. A 2IV(7-2) fractional factorial design approach was carried out in a batch adsorption study to identify significant experimental variables along with their combined effects for the simultaneous adsorption of Pt(II), Pd(II), Rh(III) and Au(I). The adsorbent was characterized using SEM-EDX, and XRF. Precious metals adsorption efficiency was studied in terms of process recovery as a function of different adsorption parameters such as solution pH, copper, nickel, free cyanide ion, thiocyanate, initial precious metal (Pt, Pd, Rh and Au) ion and activated carbon concentrations. It was shown that adsorption rates within the first 60 minutes were very high (giving more than 90% extraction of precious metals) and thereafter the adsorption proceeds at a slower rate until pseudo-equilibrium was reached. Among the different adsorption parameters, at 95% confidence interval, nickel concentration had the most influential effect on the adsorption process followed by the adsorbent concentration. Adsorption of Ni was found to proceed at approximately the same rate and with the same recovery as the precious metals, showing a recovery of approximately 90% in two hours. The kinetics of Cu adsorption were slower, with less than 30% being recovered at the 120 minute period. This suggests that the co-adsorption of Cu can be minimised by shortening the residence time. Adsorption of Fe was found to be less than 5%, while the recovery of Rh was negligibly small. The effect of thiocyanate ion concentration was not as important as the effect of free cyanide ion concentration but still had some influence. The correlation among different adsorption parameters was studied using multivariate analysis. The optimum experimental conditions resulted in a solution with pH of 9.5, [Cu(I)] of 10 ppm, [Ni(II)] of 10 ppm, [CN ] of 132.44 ppm, [SCN ] of 98.95 ppm, [PMs] of 2.03 ppm and [AC] of 10 g/L. Under these conditions, predicted adsorption percentages of Pt, Pd and Au were approximately 98, 92 and 100%, at the level of 95% probability within two hours as an effective loading time. The negative values of ΔG° for all ions under optimum conditions indicate the feasibility and spontaneous nature of the adsorption process. Chemisorption was found to be the predominant mechanism in the adsorption process of Pt(II), Pd(II) and Au(I). Based on their distribution coefficients, the affinity of activated carbon for metal ions follows the selectivity sequence expressed below. Au(CN) > Pt(CN) > Pd(CN) > Ni(CN) > Cu(CN) Finally, it is important that additional research and development activities in the future should prove the economic viability of the process. Future work is also needed to investigate the adsorption of precious metals (PMs) by comparing the efficiencies and kinetics of adsorption when using sodium hydroxide (in this study) or lime, respectively, in order to control the pH. / AFRIKAANSE OPSOMMING: ʼn Tweefasige hooploogproses vir die ontginning van basis- en edelmetale van die Platrif-erts word tans industrieel ondersoek. ʼn Eerstefase-bioloog word gebruik om die basismetale te ontgin. In die 2de fase word sianied gebruik as die uitloog by hoë pH om die platinum-groepmetale en goud te ontgin. Na analogie van hedendaagse goudherwinningspraktyke het die huidige studie die voorkeur- en kwantitatiewe adsorpsie van edelmetale (Pt, Pd, Rh en Au) bo basismetale (Cu, Ni en Fe) vanuit ʼn alkaliese sianiedmedium met behulp van korrelrige geaktiveerde koolstof ondersoek. Eksperimente is op statistiese wyse ontwerp om die parameters van die proses te optimaliseer deur van sintetiese alkaliese sianiedoplossings wat in hulle samestelling nou ooreenstem met dié wat van oplossings van plant-loog verwag word, gebruik te maak. Die statistiese benadering het die ontwikkeling van ʼn betroubare kwantitatiewe benadering om adsorpsie as ʼn responsveranderlike op grond van ʼn aantal eksperimente uit te druk, moontlik gemaak. ʼn 2IV(7-2) -Fraksionele faktoriale ontwerp-benadering is tydens ʼn lot-adsorpsiestudie gevolg om beduidende eksperimentele veranderlikes tesame met hulle gekombineerde uitwerkings vir die gelyktydige adsorpsie van Pt(II), Pd(II), Rh(III) en Au(I) te identifiseer. Die adsorbeermiddel is met behulp van SEM-EDX en XRF gekenmerk. Adsorpsiedoeltreffendheid van edelmetale is bestudeer ten opsigte van proseskinetika en herwinning as ʼn funksie van verskillende adsorpsieparameters soos oplossing-pH, koper, nikkel, vry sianiedioon, tiosianaat, aanvanklike edelmetaal (Pt, Pd, Rh en Au)-ioon en geaktiveerde koolstofkonsentrasies. Daar is aangetoon dat adsorpsietempo‟s binne die eerste 60 minute baie hoog was (het meer as 90% ekstraksie van edelmetale opgelewer) en daarna het die adsorpsie teen ʼn stadiger tempo voortgegaan totdat pseudo-ekwilibrium bereik is. Onder die verskillende adsorpsieparameters, by 95%-vertroubaarheidsinterval, het nikkel-konsentrasie die grootste invloed op die adsorpsieproses gehad, gevolg deur konsentrasie van die adsorbeermiddel. Daar is bevind dat die adsorpsie van Ni teen nagenoeg dieselfde tempo en met dieselfde herwinning as die edelmetale voortgegaan het, wat ná twee uur ʼn herwinning van nagenoeg 90% getoon het. Die kinetika van Cu-adsorpsie was stadiger, met minder as 30% wat teen die 120-minute-tydperk herwin is. Dit dui daarop dat die ko-adsorpsie van Cu tot die minimum beperk kan word deur verkorting van die verblyftyd. Daar is bevind dat die adsorpsie van Fe minder as 5% is, terwyl die herwinning van Rh onbeduidend klein was. Die uitwerking van die konsentrasie van die tiosianaatione was nie so belangrik as die uitwerking van die konsentrasie van vry sianiedione nie maar het steeds ʼn mate van invloed gehad. Die korrelasie tussen verskillende adsorpsieparameters is met behulp van meerveranderlike analise bestudeer. Die optimale eksperimentele toestande het gelei tot ʼn oplossing met ʼn pH van 9.5, [Cu(I)] van 10 dpm, [Ni(II)] van 10 dpm, [CN] van 132.44 dpm, [SCN] van 98.95 dpm, [EM‟e] van 2.03 dpm en [AC] van 10 g/L. Onder hierdie toestande was die voorspelde adsorpsiepersentasies van Pt, Pd en Au nagenoeg 98, 92 en 100%, op die vlak van 95%-waarskynlikheid binne twee uur as ʼn doeltreffende laaityd. Die negatiewe waardes van ΔG° vir alle ione onder optimale toestande dui op die uitvoerbaarheid en spontane aard van die adsorpsieproses. Daar is bevind dat chemiesorpsie die deurslaggewende meganisme by die adsorpsieproses van Pt(II), Pd(II) en Au(I) is. Gebaseer op hulle distribusiekoeffisiënte volg die affiniteit van geaktiveerde koolstof vir metaalione die selektiwiteitsvolgorde soos hieronder voorgestel. Au(CN) > Pt(CN) > Pd(CN) > Ni(CN) > Cu(CN) Laastens, dit is belangrik dat addisionele navorsing en ontwikkelingsaktiwiteite in die toekoms die ekonomiese haalbaarheid van die proses bewys. Werk in die toekoms is nodig om die adsorpsie van edelmetale (EM‟e) te ondersoek deur vergelyking van die doeltreffendhede en kinetika van adsorpsie wanneer natriumhidroksied (in hierdie studie) of kalk, onderskeidelik, gebruik word ten einde die pH te beheer

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Carbon dioxide (CO2) is seen as one of the main contributors to global warming. The use of fossil fuels for power production leads to large quantities of carbon dioxide being released into the atmosphere. The released CO2 can, however, be captured by retrofitting capture units downstream from the power plant called Post Combustion Carbon Dioxide Capturing. Post combustion CO2 capture can involve the reactive absorption of CO2 from the power plant flue gas steam. Reactive solvents, such as monoethanolamine (MEA), are used for capturing the CO2 and the solvent is regenerated in a desorber unit where the addition of heat drives the reverse reaction, releasing the captured CO2. However, the large energy requirement for solvent regeneration reduces the viability of employing CO2 capture on an industrial scale. This study focused on establishing a facility for CO2 capture studies – the main aim being the construction and validation of the results produced by the pilot plant facility. A secondary aim of this study was developing an Aspen Plus® Simulation method that would simplify simulating the complex CO2 capture process. Results from the simulation were to be compared to that of the pilot plant experiments. A pilot plant facility with a closed gas system, allowing gas recycling from both the absorber and the stripping columns, was set up. The absorber column (internal diameter = 0.2 m) was set up to allow one to obtain information regarding gas- and liquid temperatures and compositions at various column heights. Online gas analysers are used for analysing the gas composition at various locations in the absorber column. The pilot plant was initially commissioned with 20 weight % MEA in aqueous solution; however the main validation experiments were conducted with 30 weight % MEA in aqueous solution. 30 weight % MEA (aq) is generally used as the reference solvent for pilot plant studies. Pilot plant results with regards to the carbon dioxide concentration profiles for the absorber column as well as the regeneration energy requirement and capture rates compared well to literature data. The Aspen Plus® simulation was also set up and validated using published pilot plant data. The comparison of the pilot plant results from this study, to the results from the Aspen Plus® Simulation, showed good agreement between the two. The Aspen Plus® Simulation could further be used to validate pilot plant data that has been gathered outside the range of reported CO2 capture efficiencies. The Aspen Plus®model was evaluated at liquid-to-gas ratios of 1.7 and regeneration energies matching the pilot plant results. It was found that the model under predicts the capture efficiency of CO2 with an average of 4.0%. The model was corrected for this error at liquid-to-gas ratios of 2 and the fit of the model to pilot plant results improved considerably (R2-value = 0.965). Pilot plant repeatability was investigated with both 20 weight %- and 30 weight % MEA in aqueous solution. Temperature- and gas concentration profiles from the absorber column showed good repeatability. The maximum deviation of the regeneration energy and the capture efficiency from the calculation means were ±0.72% and ±1.40% respectively. The aims of this study have been met by establishing, and validating the results of a pilot plant facility for carbon dioxide capture studies. It has been shown that the pilot plant produces repeatable results. Results from the Aspen Plus® Simulation were validated and also match results from the established pilot plant setup. The simulation may prove to provide valuable information regarding the optimal operating conditions for the pilot plant and may aid in performing a full parametric study on the CO2 capture process. / AFRIKAANSE OPSOMMING: Koolstofdioksied (CO2) word geklassifiseer as een van die bekendste kweekhuisgasse wat ʼn groot bydra lewer tot aardverwarming. Die gebruik van fossielbrandstowwe om na die energiebehoeftes van die mens om te sien lei daartoe dat groot hoeveelhede koolstofdioksied, hoofsaaklik vanaf kragstasies, vrygestel word in die atmosfeer. Daar is verskeie maniere hoe die CO2 uit die uitlaatgas van kragstasies verwyder kan word – die vernaamste hiervan is bekend as die Na-verbranding opvangs metode. Die opvangs van CO2 na verbranding van fossielbrandstowwe vir kragproduksie kan vermag word deur van reaktiewe absorpsie tegnieke gebruik te maak. Mono-etanol-amien (MEA) kan vir hierdie doeleindes aangewend word deur dit, in ʼn absorpsiekolom, in kontak te bring met die CO2. Die gereageerde oplosmiddel word geregenereer deur die oplosmiddel te verhit in ʼn stropingskolom. ʼn Bykans suiwer CO2 stroom word vrygestel. Die implementering van hierdie opvangtegniek op industriële skaal lei egter tot groot energieverliese vir die kragstasies. Die hoofrede hiervoor is die hoeveelheid energie wat benodig word om die oplosmiddel te regenereer vir hergebruik. Die hoofdoel van hierdie studie was gemik op die oprigting en inwerkstelling van 'n navorsingsfasiliteit vir studies aangaande die na-verbranding opvangs van CO2. Dit het behels die ontwerp, konstruksie en stawing van gelewerde resultate met resultate in die literatuur. 'n Sekondêre doel van hierdie studie was die metode-ontwikkeling vir die opstel van 'n Aspen Plus® Model wat die simulasie van die CO2 opvangsproses met ʼn reaktiewe oplosmiddel, MEA, vereenvoudig. Gesimuleerde resultate is vergelyk met resultate uit die literatuur. Die toetsaanleg, met 'n geslote gas stelsel, maak voorsiening vir die hersirkulering van gas wat vir eksperimentele doeleindes gebruik word. Die absorpsie kolom (interne diameter van 0,2 m) is opgestel sodat informasie aangaande die gas- en vloeistof temperature, sowel as gas- en vloeistof komposisies vanaf verskillende kolomhoogtes, bekom kan word. ʼn Aanlyn CO2 analiseerder word gebruik om vir CO2 in die prosesgas te analiseer. Die toetsaanleg is aanvanklik in bedryf gestel met ʼn 20 massa % MEA in waterige oplossing; die hoof eksperimente is egter uitgevoer deur van 30 massa % MEA in waterige oplossing gebruik te maak. Die laasgenoemde oplosmiddel word algemeen gebruik in die CO2 opvangs verwante navorsingsveld. Die resultate van die toetsaanleg, vergelyk goed met resultate in die literatuur. Die gesimuleerde Aspen Plus® resultate is ook vergelyk met resultate in die literatuur en die gevolgtrekking is gemaak dat die simulasie gebruik kan word om redelike akkurate voorspellings van die werklike prosesresultate te gee. Die simulasie is verder ook gebruik om resultate, verkry vanaf die opgerigte toetsaanleg, te verifieer en ʼn goeie ooreenstemming tussen die gesimuleerde en die eksperimentele resultate is waargeneem. ʼn Verder gevolgtrekking aangaan die Aspen Plus® simulasie metode was dat dit in die toekoms ʼn groot doel kan dien in die optimeringsproses van toetsaanlegte waar navorsing aangaande die na-verbranding opvang van CO2 gedoen word. Die Aspen Plus® model is geëvalueer by ‘n vloeistof-tot-gas-verhouding van 1,7 en ooreenstemmende toetsaanleg resultate, aangaande die hoeveelheid energie wat ingesit is vir die regenerasie van die oplosmiddel. Die onakkuraathede in die model, met betrekking tot die voorspelling van die hoeveelheid CO2 wat vasgevang sal word, is hierdeur bepaal en die model is daarvoor aangepas. Resultate van die verbeterde model vergelyk baie goed met die toetsaanleg resultate – ʼn R2-waarde van 0.965. Die herhaalbaarheid van die toetsaanleg resultate is ondersoek en ʼn goeie herhaalbaarheid van die temperatuur- en CO2 konsentrasieprofiele is verkry. Die toetsaanleg dui ook goeie herhaalbaarheid met betrekking tot die effektiwiteit waarmee die CO2 uit ʼn gasstroom verwyder word (± 1,40%), sowel as die hoeveelheid energie wat benodig word vir regenerering van die oplosmiddel (± 0,72%). Die doelwitte van hierdie studie is bereik deur die oprigting en verifiëring van resultate gelewer deur 'n toetsaanleg vir studies aangaande die na-verbrandingsopvang van CO2. Die herhaalbaarheid van toetaanleg resultate is bewys. Resultate van die Aspen Plus® simulasie stem ooreen met resultate in die literatuur sowel as resultate van die toetsaanleg wat opgerig is in hierdie studie.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Whereas fuel used for transport and electricity production are mainly fossil–derived, there has recently been an increased focus on bio-fuels due to the impact of fossil derived fuel on the environment as well as the increased energy demand worldwide, concomitant with the depletion of fossil fuel reserves. Paper sludge produced by paper mills are high in lignocellulose and represents a largely untapped feedstock for bio-energy production. The aim of this study was to determine the composition, fermentability and optimum paper sludge loading and enzyme dosage for producing ethanol from paper sludge. This information was used to develop a model of the process in Aspen Plus®. The mass and energy balances obtained from the Aspen Plus® model were used to develop equipment specifications which were used to source equipment cost data. A techno-economic model was developed from the equipment cost data to assess the economic viability of the simultaneous saccharification and fermentation (SSF) process utilising paper sludge as feedstock. Nine paper sludge samples obtained from Nampak Tissue (Pty) Ltd. were evaluated in terms of ethanol production and those samples yielding the highest and lowest ethanol titres were selected for optimisation. This allowed for the determination of a range of ethanol concentrations and yields, expressed as percentage of the theoretical maximum, which could be expected on an industrial scale. Response surface methodology was used to obtain quadratic mathematical models to determine the effects of solid loading and cellulase dosage on ethanol production and ethanol yield from paper sludge during anoxic fed-batch fermentations using Saccharomyces cerevisiae strain MH1000. This approach was augmented with a multi response optimisation approach incorporating a desirability function to determine the optimal solid loading and cellulase dosage in fed-batch SSF cultures. The multi response optimisation revealed that an optimum paper sludge loading of 21% (w/w) and a cellulase loading of 14.5 FPU g-1 be used regardless of the paper sludge sample. The fact that one optimal enzyme dosage and paper sludge loading is possible, regardless the paper sludge feed stock, is attractive since the SSF process can be controlled efficiently, while not requiring process alterations to optimize ethanol production when different batches of paper sludge are processed. At the optimum paper sludge loading and cellulase dosage a minimum ethanol concentration of 47.36 g l-1 (84.69% of theoretical maximum) can be expected regardless of the paper sludge used. An economic assessment was conducted to ascertain whether ethanol production from paper sludge using SSF is economically viable. Three scenarios were investigated. In the first scenario revenue was calculated from the ethanol sales linked to the basic fuel price, whereas in the second and third scenarios liquefied petroleum gas (LPG) consumption at the paper mill was replaced with anhydrous and 95% ethanol respectively. In all the cases, paper sludge feed rates of 15, 30 and 50 t d-1 were used. The production of ethanol from paper sludge for ethanol sales (scenario 1) resulted in higher IRR and NPV values, as well as shorter payback periods, compared to replacement of LPG at the paper mill (scenarios 2 and 3). At an assumed enzyme cost of $ 0.90 gal-1 (R 2.01 litre-1), IRR values of 11%, 22% and 30% were obtained at paper sludge feed rates of 15, 30 and 50 t d-1. A sensitivity analysis performed on the total capital investment and enzyme cost revealed that the SSF process is only economically viable at a paper sludge feed rate of 50 t d-1 irrespective of the variation in capital investment. For the SSF process to be economically viable the enzyme costs must be lower than $ 0.70 gal-1 (R 1.56 litre-1) and $ 1.20 gal-1 (R 2.68 litre-1) for paper sludge feed rates of 30 and 50 t d-1 respectively. The SSF process at a paper sludge feed rate of 15 t d-1 was not economically viable even assuming a zero enzyme cost. A Monte Carlo simulation revealed that the SSF process is economically viable at a paper sludge feed rate of 50 t d-1 as a mean IRR value of 32% were obtained with a probability of 26% to attain an IRR value lower than 25%. The SSF process at lower paper sludge loadings is not economically viable as probabilities of 70% and 95% were obtained to attain IRR values lower than 25% at paper sludge feed rates of 30 and 15 t d-1 respectively. From this study it can be concluded that paper sludge is an excellent feedstock for ethanol production for the sales of ethanol at a paper sludge feed rate in excess of 50 t d-1 with the added environmental benefit of reducing GHG emissions by 42.5%. / AFRIKAANSE OPSOMMING: Aangesien dat brandstof vir vervoer en energie meestal vanaf fossiel afgeleide bronne kom, is daar onlangs ʼn groter fokus op bio-brandstowwe as gevolg van die impak van fossiel afgeleide brandstowwe op die omgewing en 'n verhoogde aanvraag na energie wêreldwyd, gepaardgaande met die uitputting van fossielbrandstof-reserwes. Papier slyk geproduseer deur papier meule is hoog in lignosellulose en verteenwoordig 'n grootliks onontginde grondstof vir etanol produksie. Die doel van die studie was om vas te stel wat die samestelling, fermenteerbaarheid, optimale papier slyk en ensiem ladings is vir die vervaardiging van etanol uit papier slyk. Die inligting was gebruik om 'n model van die proses in Aspen Plus® te ontwikkel. Die massa-en energiebalanse wat verkry is van die Aspen Plus® model was gebruik om toerusting spesifikasies te ontwikkel wat gebruik was om toerusting kostes te bereken. ‘n Tegno-ekonomiese model is ontwikkel om die ekonomiese lewensvatbaarheid van die gelyktydige versuikering en fermentasie proses “SSF” wat gebruik maak van papier slyk as grondstof te assesseer. Nege papier slyk monsters verkry vanaf Nampak Tissue (Pty) Ltd. is geëvalueer in terme van etanol produksie. Die monsters wat die hoogste en laagste etanol konsentrasies opgelewer het, is geselekteer vir optimalisering omdat dit toegelaat het vir die vasstelling van etanol konsentrasies en opbrengste, uitgedruk as persentasie van die teoretiese maksimum, wat verwag kan word in industrie. Reaksie oppervlak metodologie “RSM” is gebruik om wiskundige modelle te ontwikkel om die impak van papier slyk lading en sellulase dosis op etanol produksie en etanol opbrengs te assesseer. Die RSM is aangevul met 'n multi effek optimiserings benadering wat 'n wenslikheid funksie inkorporeer om die optimale papier slyk lading en sellulase dosis in gevoerde-enkellading SSF kulture te bepaal. Die multi effek optimalisering het getoon dat 'n optimale papier slyk lading van 21% (w/w) en 'n sellulase dosis van 14.5 FPU g-1 gebruik moet word, ongeag van die papier slyk monster. Die feit dat die optimale ensiem dosis en papier slyk lading dieselfde is ongeag die papier slyk monster, is aantreklik aangesien die SSF proses meer doeltreffend beheer kan word omdat proses veranderinge nie nodig is om die proses te optimaliseer nie. By die optimale papier slyk lading en sellulase dosis kan 'n minimum etanol konsentrasie van 47.36 g l-1 (84,69% van die teoretiese maksimum) verwag word ongeag van die papier slyk wat gebruik word. 'n Ekonomiese evaluasie is gedoen om vas te stel of etanol produksie vanaf papier slyk met behulp van SSF ekonomies lewensvatbaar is. Drie moontlikhede is ondersoek. In die eerste moontlikheid is die inkomste bereken vanaf etanol verkope gekoppel aan die basiese brandstofprys, terwyl in die tweede en derde moontlikhede, LPG by die papier meul vervang is met anhidriese en 95% etanol onderskeidelik. In al die gevalle was daar gebruik gemaak van papier slyk voer tempo’s van 15, 30 en 50 t d-1. Die produksie van etanol uit papier slyk vir verkope (moontlikheid 1) het gelei tot hoër IRR en die NPV waardes, sowel as korter terugverdien tydperke, in vergelyking met die vervanging van LPG by die papier meul (moontlikhede 2 en 3). Met ʼn ensiem koste van $ 0.90 gal-1 (R 2.01 litre-1) is IRR-waardes van 11%, 22% en 30% verkry teen papier slyk voer tempo’s van 15, 30 en 50 t d-1 onderskeidelik. 'n Sensitiwiteitsanalise uitgevoer op die totale kapitale belegging en ensiem koste het aan die lig gebring dat 'n SSF proses slegs ekonomies lewensvatbaar is op 'n papier slyk voer tempo van 50 t d-1 ongeag van die variasie in die kapitale belegging. Vir die SSF proses om ekonomies lewensvatbaar te wees, moet die ensiem kostes laer wees as $ 0.70 gal-1 (R 1.56 liter-1) en $ 1.20 gal-1 (R 2.68 liter-1) vir papier slyk voer tempo’s van onderskeidelik 30 en 50 t d-1. Die SSF proses was op 'n papier slyk voer tempo van 15 t d-1 nie ekonomies lewensvatbaar nie, selfs teen 'n ensiem koste van nul. 'n Monte Carlo-simulasie het getoon dat die SSF proses ekonomies lewensvatbaar is met 'n papier slyk voer tempo van 50 t d-1 omdat 'n gemiddelde IRR-waarde van 32% verkry is met 'n waarskynlikheid van 26% om 'n IRR-waarde laer as 25% te verkry. Die SSF proses teen papier slyk voer tempo’s van 30 en 15 t d-1 is nie ekonomies lewensvatbaar nie omdat waarskynlikhede van 70% en 95% onderskeidelik verkry is om IRR-waardes laer as 25% te kry. Daar kan van die studie afgelei word dat papier slyk 'n uitstekende grondstof is vir die produksie van etanol mits 'n papier slyk voer tempo van meer as 50 t d-1 bereik kan word. Die produksie van etanol vanaf papier slyk het die bykomende voordeel dat kweekhuis gasse (GHG) met 42.5% verminder word.

Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: All process measurements contain some element of error. Typically, a distinction is made between random errors, with zero expected value, and gross errors with non-zero magnitude. Data Reconciliation (DR) and Gross Error Detection (GED) comprise a collection of techniques designed to attenuate measurement errors in process data in order to reduce the effect of the errors on subsequent use of the data. DR proceeds by finding the optimum adjustments so that reconciled measurement data satisfy imposed process constraints, such as material and energy balances. The DR solution is optimal under the assumed statistical random error model, typically Gaussian with zero mean and known covariance. The presence of outliers and gross errors in the measurements or imposed process constraints invalidates the assumptions underlying DR, so that the DR solution may become biased. GED is required to detect, identify and remove or otherwise compensate for the gross errors. Typically GED relies on formal hypothesis testing of constraint residuals or measurement adjustment-based statistics derived from the assumed random error statistical model. Classification methodologies are methods by which observations are classified as belonging to one of several possible groups. For the GED problem, artificial neural networks (ANN’s) have been applied historically to resolve the classification of a data set as either containing or not containing a gross error. The hypothesis investigated in this thesis is that classification methodologies, specifically classification trees (CT) and linear or quadratic classification functions (LCF, QCF), may provide an alternative to the classical GED techniques. This hypothesis is tested via the modelling of a simple steady-state process unit with associated simulated process measurements. DR is performed on the simulated process measurements in order to satisfy one linear and two nonlinear material conservation constraints. Selected features from the DR procedure and process constraints are incorporated into two separate input vectors for classifier construction. The performance of the classification methodologies developed on each input vector is compared with the classical measurement test in order to address the posed hypothesis. General trends in the results are as follows: - The power to detect and/or identify a gross error is a strong function of the gross error magnitude as well as location for all the classification methodologies as well as the measurement test. - For some locations there exist large differences between the power to detect a gross error and the power to identify it correctly. This is consistent over all the classifiers and their associated measurement tests, and indicates significant smearing of gross errors. - In general, the classification methodologies have higher power for equivalent type I error than the measurement test. - The measurement test is superior for small magnitude gross errors, and for specific locations, depending on which classification methodology it is compared with. There is significant scope to extend the work to more complex processes and constraints, including dynamic processes with multiple gross errors in the system. Further investigation into the optimal selection of input vector elements for the classification methodologies is also required. / AFRIKAANSE OPSOMMING: Alle prosesmetings bevat ʼn sekere mate van metingsfoute. Die fout-element van ʼn prosesmeting word dikwels uitgedruk as bestaande uit ʼn ewekansige fout met nul verwagte waarde, asook ʼn nie-ewekansige fout met ʼn beduidende grootte. Data Rekonsiliasie (DR) en Fout Opsporing (FO) is ʼn versameling van tegnieke met die doelwit om die effek van sulke foute in prosesdata op die daaropvolgende aanwending van die data te verminder. DR word uitgevoer deur die optimale veranderinge aan die oorspronklike prosesmetings aan te bring sodat die aangepaste metings sekere prosesmodelle gehoorsaam, tipies massa- en energie-balanse. Die DR-oplossing is optimaal, mits die statistiese aannames rakende die ewekansige fout-element in die prosesdata geldig is. Dit word tipies aanvaar dat die fout-element normaal verdeel is, met nul verwagte waarde, en ʼn gegewe kovariansie matriks. Wanneer nie-ewekansige foute in die data teenwoordig is, kan die resultate van DR sydig wees. FO is daarom nodig om nie-ewekansige foute te vind (Deteksie) en te identifiseer (Identifikasie). FO maak gewoonlik staat op die statistiese eienskappe van die meting aanpassings wat gemaak word deur die DR prosedure, of die afwykingsverskil van die model vergelykings, om formele hipoteses rakende die teenwoordigheid van nie-ewekansige foute te toets. Klassifikasie tegnieke word gebruik om die klasverwantskap van observasies te bepaal. Rakende die FO probleem, is sintetiese neurale netwerke (SNN) histories aangewend om die Deteksie en Identifikasie probleme op te los. Die hipotese van hierdie tesis is dat klassifikasie tegnieke, spesifiek klassifikasiebome (CT) en lineêre asook kwadratiese klassifikasie funksies (LCF en QCF), suksesvol aangewend kan word om die FO probleem op te los. Die hipotese word ondersoek deur middel van ʼn simulasie rondom ʼn eenvoudige gestadigde toestand proses-eenheid wat aan een lineêre en twee nie-lineêre vergelykings onderhewig is. Kunsmatige prosesmetings word geskep met behulp van lukrake syfers sodat die foutkomponent van elke prosesmeting bekend is. DR word toegepas op die kunsmatige data, en die DR resultate word gebruik om twee verskillende insetvektore vir die klassifikasie tegnieke te skep. Die prestasie van die klassifikasie metodes word vergelyk met die metingstoets van klassieke FO ten einde die gestelde hipotese te beantwoord. Die onderliggende tendense in die resultate is soos volg: - Die vermoë om ‘n nie-ewekansige fout op te spoor en te identifiseer is sterk afhanklik van die grootte asook die ligging van die fout vir al die klassifikasie tegnieke sowel as die metingstoets. - Vir sekere liggings van die nie-ewekansige fout is daar ‘n groot verskil tussen die vermoë om die fout op te spoor, en die vermoë om die fout te identifiseer, wat dui op smering van die fout. Al die klassifikasie tegnieke asook die metingstoets baar hierdie eienskap. - Oor die algemeen toon die klassifikasie metodes groter sukses as die metingstoets. - Die metingstoets is meer suksesvol vir relatief klein nie-ewekansige foute, asook vir sekere liggings van die nie-ewekansige fout, afhangende van die klassifikasie tegniek ter sprake. Daar is verskeie maniere om die bestek van hierdie ondersoek uit te brei. Meer komplekse, niegestadigde prosesse met sterk nie-lineêre prosesmodelle en meervuldige nie-ewekansige foute kan ondersoek word. Die moontlikheid bestaan ook om die prestasie van klassifikasie metodes te verbeter deur die gepaste keuse van insetvektor elemente.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: It was found that bacterial sludge from anaerobic water treatment systems is produced internationally at a rate of 60 grams per person per day and the accumulation of the potentially hazardous by-product has become of increasing concern. The produced bacterial sludge is frequently pumped into dams, dried out and used as agricultural fertilizer. This bacterial sludge is expected to have a relatively high heating value and as such, has the potential to produce energy from the biomass. It is, therefore, advisable to utilize this energy potential as an alternative to conventional sludge disposal. This project aimed to improve the yield of syngas by optimizing the reactor design to partially oxidize bacterial sludge using a sonochemical reactor that is operated at bulk atmospheric conditions. The effect of different conditions was investigated and the optimum settings for syngas production were found by investigating temperature, pressure and the effect of the amplitude of operation that regulates the energy input by the ultrasonic equipment. The optimum conditions were used to investigate the kinetics involved in this process as well as to determine the energy consumption by the process. It was also required to study the feasibility of partially oxidizing bacterial sludge using a sonochemical reactor instead of conventional steam gasification and also as an alternative means of sludge disposal. By eliminating this pollutant source, the future environmental threat posed by an increasing population size will be minimized and energy will be utilized from a thus-far wasted energy source. The syngas that is produced is used as a green alternative to fossil fuels in the Gas-to-Liquids (GTL) process to produce liquids fuels. A thus-far wasted energy source will be consumed and fossil fuels can be saved in the process. It was found that the maximum hydrogen mole percentage produced is 0.141 mole % of the vapour phase with the maximum carbon monoxide mole percentage in the vapour phase at 1.896 mole %. This shows an improvement on work conducted by Beyers (2011) of 59 % for hydrogen, 92% for carbon monoxide and a reduction of 49 % for carbon dioxide. A kinetic study of the process indicated that the rate equations that describe the hydrogen and carbon monoxide production are zero order and, therefore, independent of initial concentration of the sludge. The rate constants were 0.0146 (mol % hydrogen/s) and 0.0183 (mol % hydrogen/s) for hydrogen and carbon monoxide, respectively. It was found that the most severe change to the higher heating value of the feed was a mere 0.27 mJ/kg from an original value of 9.81 mJ/kg. This therefore confirms that the reaction has not proceeded to completion. The statistical model predicted a maximum value for hydrogen production at 0.151 mole % in the product gas, 0.01 mole % from the measured maximum. It was also found that hydrogen is produced during the sonolysis of distilled water and that this confirms that the hydrogen production during partial oxidation of the sludge sample comes mainly from the water present in the sludge. The hydrogen produced when only using water, was found to be 0.127 mole % and when using the active sludge, the value was 0.116 mole % hydrogen in the vapour phase. The thermal decomposition of calcium carbonate in the lime that is used to treat the pH of the unit where the sludge originates from, followed by the formation of carbon monoxide during the Boudouard reaction, led to an increased amount of carbon monoxide present in the product gas. Ultrasonic intensity is defined as the amount of energy that is transferred to the sample per cubic meter of the internal surface area of the reactor vessel. It was found that the intensity that was delivered to the reactant was lower than expected as the reactor was operating at an efficiency of only 36%. The design intensity was 1.44 W/m2 and the actual delivered intensity was 0.52 W/m2. Based on a maximum yield of 0.00012 Nm3/kg, the cost of syngas production under the conditions described by this study, would amount to R 19.98/Nm3. This cost only implicates the operational expenses and does not take further downstream processing and initial capital investment repayments into account. Conventional steam gasification at a yield of 0.67 Nm3/kg has an operational syngas production cost of R 1.48/Nm3. This process was therefore found to not be economically feasible as the cost of utilizing ultrasound as opposed to normal steam gasification is more than ten times more expensive. It was concluded that the process was successfully optimized by the redesigning of the reactor and that carbon dioxide production was limited by excluding oxygen from the feed gas. It was also concluded that the sonolysis of water and the thermal decomposition of calcium carbonate, followed by the conversion of carbon dioxide to carbon monoxide, supplements the syngas production under the current operational conditions. Based on the production of no methane during the course of this study, the sonochemical process can be tied into the GTL process after the steam reforming unit. Due to the relatively high carbon dioxide content, the process will need to join the main feed gas stream that is fed into the carbon dioxide removal unit before it enters the GTL process to correct the desired feed gas ratio. Based on the very low syngas yields, the low hydrogen to carbon monoxide ratio in comparison to the required ratio of 2 as well as the high energy intensity required for this process, it can be concluded that the partial oxidation of biomass sludge in a sonochemical reactor is not feasible as an alternative technology to conventional steam gasification. The operating costs of the sonochemical unit would be nearly ten times that of steam gasification and is therefore concluded to not be a competitive technology to conventional steam gasification. It is recommended that the reactor design is reinvestigated to improve the delivered ultrasound intensity as well as the surface area where the ultrasonic waves are intensified. This would eliminate dead-zones. It was also recommended that the argon gas is continuously bubbled through the reactant mixture during experiments to eliminate the degassing effect caused when the ultrasound is initially emitted. The gas outlet of the process can then be connected to an online gas chromatograph (GC) with a thermal conductivity detector (TCD) and flame ionization detector (FID) methanizer in series as the TCD does not destroy the sample and this setup would improve the analytical process. The production of carbon monoxide from lime as well as the production of hydrogen from water during sonolysis needs to be investigated. The effect of radicals can also be studied by the addition of a radical scavenger to the process. It is recommended that the experimental design is reinvestigated and a design that will deliver similar information utilizing fewer data points should be chosen. Based on this model as well as further kinetic testing, it is recommended that a complete ASPEN model is developed to simulate the energy requirements to tie the ultrasonic process into the commercial plant. Based on this model, a complete feasibility study can then be conducted to determine the capital costs involved, the operating costs, the repayment period as well as taking the current costs of sludge disposal into account. / AFRIKAANSE OPSOMMING: Daar is gevind dat bakteriele slik internasionaal geproduseer word deur anaerobiese waterbehandelingseenhede teen ‘n tempo van 60 gram per person per dag en dat die opberging van hierdie gevaarlike byproduk ‘n groeiende probleem word. Die geproduseerde bakteriele slik word in damme gestoor, uitgedroog of gebruik as kunsmis in die landbou bedryf. Daar word vermoed dat hierdie baketriele slik oor ‘n hoe verwarmings waarde beskik en het daarom die potensiaal om energie te produseer uit die biomassa. Daarom is dit voorgestel om alternatiewe prosesse te ondersoek om van hierdie slik ontslae te raak en moontlik die energie wat beskikbaar is te gebruik. Die projek is daarop gefokus om die produksie van syngas te verbeter deur die reaktorontwerp te optimeer deur gebruik te maak van parsiele oksidasie van slik onder atmosferiese kondisies deur klankgolwe te gebruik. Die effek van verskillende operasionele kondisies is ondersoek en die optimale vlakke van syngas produksie is gevind deur temperatuur, druk en amplitude wat die hoeveelheid energie wat oorgedra word aan die reaktor reguleer, te ondersoek. Die optimale kondisies is ook gebruik om die kinetiese aspekte van die proses te ondersoek en ook om te kyk wat die sisteem se energie benodighede behels. Die haalbaarheid om baketriele slik parsieel te oksideer in ‘n sonochemiese reaktor is vergelyk met dit van konvensionele stoom vergassing van die biomassa en is ook ondersoek as ‘n alternatief om van die slik ontslae te raak. Deur die slik te verwyder as ‘n potensiele bron van besoedeling, kan die toekomstige omgewing’s risiko wat deur die toename in die bevolkkingsgroote tot gevolg is, verwyder word deur ‘n energie bron te gebruik wat tot dusver geignoreer is. Die syngas wat geproduseer word kan dan gebruik word in die “Gas-to-Liquids” (GTL) process om vloeistof brandstowwe te produseer. Dus sal ‘n omgewingsrisiko verminder word, ‘n energiebron word benuttig wat nooit van tevore benuttig is nie en fosiel brandstowwe kan gespaar word. Die maksimum waterstof wat geproduseer is, was 0.141 mol % in die gas fase met ‘n maksimum waarde vir koosltof monoksied van 1.896 mol % in die gas fase. Dit toon ‘n verbetering van 59 % vir waterstof, 92 % vir koolstof monoksied en ‘n vermindering van 49% in die koolstof dioksied wat deur Beyers (2011) geproduseer is. Die kinetiese studie het ondervind dat die “rate equation” van waterstof en koolstofmonoksied beskryf word deur nul-orde kinetika. Hierdie konstantes was 0.0146 (mol % waterstof/s) en 0.0183 (mol % waterstof/s) vir waterstof en koolstofmonoksied. Daar is ook gevind dat die grootste moontlik verandering in die hoe verwarmings waarde van die biomassa is ‘n skamele 0.27 mJ/kg van die oorspronklike waarde van 9.81 mJ/kg. Hierdie waarneming staaf dus die uitkoms dat die reaksie dus nie tot die einde verloop het nie. Die statistiese model het ‘n maksimum van 0.151 mol % voorspel wat 0.01 mol % meer was as die waarde wat gemeet is. Dit is ook gevind dat waterstof geproduseer word deur die sonoliese van water en dat hierdie bykomende waterstof deel uitmaak van die produkgas aangesien die slik grootliks uit water bestaan.Die hoveelheid waterstof in die gas fase wat geproduseer is tydens sonoliese van ‘n suiwer water monster, was 0.127 mol %. Die hoeveelheid waterstof in die gas fase wanneer die slik behandel is ten optimal kondisies, was 0.116 mol % gemiddeld. Die hitte degradering van kalsium karbonaat wat teenwoordig is in die kalk wat gebruik word om die pH van die produksie eenheid te reguleer, gevolg deur die Boudouard reaksie, het tot gevolg dat addisionele koolstof monoksied ook gevorm word. Ultrasoniese intensiteit kan gedefineer word as die hoeveelheid energy wat oorgedra word aan ‘n reaktant gebasseer op die oppervlak area aan die binnekant van die reaktor. Die intensiteit waarteen die voermateriaal blootgestel word aan die klankgolwe was laer as verwag met ‘n 36 % effektiwiteit. Die ontwerp spesifiseer ‘n intensiteit van 1.44 W/m2 en die intensiteit wat fisies gelewer is, was 0.521 W/m2. Die maksimum produksie van syngas was 0.00012 Nm3/kg, wat lei tot ‘n operasionele koste van R 19.98/Nm3 onder die kondisies van hierdie studie. Hierdie koste neem nie die oorsponkilke kapitaal vir die konstruksie, of die koste van verdere behandelik van die gas, in ag nie. Konvensionele stoom vergassing teen ‘n opbrengs van 0.67 Nm3/kg het ‘n operasionele koste van R 1.48/Nm3 tot gevolg. Die proses is dus ekonomies nie ‘n aantreklike opsie nie aangesien die kostes van syngas produksie met ultraklank meer as tien keer meer is as konvensionele stoom vergassing. Daar is tot die gevolgtrekking gekom dat die reaktor optimering suksesvol was en deur geen stuurstof te voer nie, die koolstofdioksied persentasie verminder is. Daar is ook tot die gevolgtrekking gekom dat die sonoliese van water, en die hitte degradering van kalsium karbonaat, gevolg deur die Boudouard reaksie, die syngas produksie supplementeer. Aangesien geen metaan gedurende hierdie studie geproduseer is nie, kan die sonochemiese proses inskakel by die GTL aanleg na die stoom hervormingseenhed. As gevolg van die hoe koolstofdioksied konsentrasie, sal die prosesstroom gemeng moet word met die produk stroom uit die stoom hervormings proses, wat gevoer word na die koolstofdioksied verwyderings eenheid. Hierdie eenheid is daarvoor verantwoordelik om die korrekte verhouding van gasse vir die GTL voer stroom te reguleer. Gebasseer op die baie lae syngas opbrengs, die lae waterstof tot koolstofmonoksied verhouding en die hoe energie behoeftes, is daar tot die gevolgtrekking gekom dat die parsiele oksidasdie van die biomassa in ‘n sonochemiese reaktor nie ‘n haalbare alternatief is vir konvensionele stoom vergassing nie. Die operasionele koste van die sonochemiese eenheid is ongeveer tien keer meer as die van stoom vergassing en daarom is die proses nie kompeterend nie. Daar word voorgestel dat die reaktor ontwerp hersien word om die gelewerde intensiteit te verbeter, sowel as om die kontak area waar die klankgolwe gekonsentreer is, te vergroot. Dit sal dooie sones uitskakel. Daar word ook voorgestel dat argon gas gedurende die eksperiment aanhoudende geborrel word deur die reaktant vloeistof in die reaktor om die ontgassingseffek uit te skakel sodra die klankgolwe aangeskakel word. Die gas uitlaat kan dan inlyn gekoppel word aan ‘n gas chromatograaf met ‘n termiese geleidings detektor (TCD) en ‘n vlam ionisasie detektor (FID) met metaan omskakeling, aangesien die TCD nie die monster vernietig nie. Hierdie opstelling behoort analitiese methodes te verbeter. Die produksie van koolstofmonoksied uit kalk sowel as die produksie van waterstof uit water gedurende sonoliese, moet verder ondersoek word. Die effek van radikale kan ook verder bestudeer word deur die gebruik van ‘n radikaal rower gedurende die proses. Daar word ook voorgestel dat die statistiese ontwerp herondersoek word sodat minder eksperimente gebruik kan word om soortgelyke resultate te bekom met minder data punte. Gebasseer op hierdie nuwe model en ‘n kinetiese studie, word dit aangeraai dat ‘n volledige ASPEN model gebou word om te simuleer hoe hierdie sonochemiese eenheid sal inskakel met die kommersiele eenheid. Dit sal dan moontlik wees om die energie benodighede van die proses te verstaan en gebasseer daarop, kan ‘n volledige haalbaarheid studie gedoen word wat kyk na oorspronklike installasie kostes, onderhouskostes, operasionele kostes sowel as die terugbetaling van die konstruksie kostes. Dan kan ‘n vergelyking getref word met die huidige kostes om van hierdie slik ontslae te raak en om die slik as ‘n brandstof te benut.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The Platreef ore deposit, situated in the Bushveld Igneous Complex, is one of the world’s largest platinum group metal (PGM) resources. The mineralogy of this resource is, however, unique as it consists of complex PGM mineralization with mainly copper and nickel, at very low PGM grades. The PGMs are mainly present in the ore as slow floating refractory minerals resulting in marginal process economics when processing via traditional mill-float-smelt processes. A new process is currently being investigated to extract PGMs from low grade Platreef ore and concentrate using a sequential heap leach process entailing heap bioleaching and high temperature cyanide leaching. The heap bioleach extracts the base metals in an acidic sulphate medium using a mixed culture of mesophiles and thermophiles. After heap bioleaching, the heap will be reclaimed, rinsed and restacked for high temperature cyanide leaching where the cyanide liquor is directly heated via solar energy in panels. Platinum, palladium and gold are extracted during the cyanide leaching stage and then recovered from the pregnant liquor either by adsorption onto activated carbon or ion exchange resins. Final metal recovery will proceed by techniques such as electrowinning and precipitation. In this thesis, process options for the recovery of platinum group metals from cyanide solutions were identified with different flowsheet alternatives developed utilizing these options. Simulations were made for the different processing alternatives with the objective of finding the alternative flowsheet to maximise net present value. The various processing options were simulated, combining data from concurrent experimental studies and data reported in literature with kinetic adsorption models. This was combined with economic models to arrive at an optimum design for each flowsheet alternative. Seven different processing alternatives for the recovery of platinum group metals from cyanide solutions were developed and investigated. These included two different activated carbon flowsheets as well as five different ion exchange resin flowsheets. The flowsheets differ in the elution procedures as well as the use of single or multiple resins. The well-known Merrill Crowe precipitation process was investigated but was found to yield unsatisfactory results. In each alternative, the cyanide solution is sent to a SART (sulphidization, acidification, recycling and thickening) plant to remove copper, nickel and zinc from solution prior to upgrading by means of adsorption onto activated carbon or ion exchange resins and subsequent elution. The platinum group metals are recovered from the eluate by precipitation using an autoclave, producing a solid product consisting of base and precious metals, while gold is recovered by electrowinning. It was found that the overall performance of the resin-in-solution (RIS) flowsheets were superior to that of the carbon-in-solution (CIS) flowsheets, from an overall PGM recovery perspective and product grades. The superior adsorption kinetics and high selectivity of the resins for the PGMs resulted in excellent overall plant performances, with PGM extractions in excess of 97%. Gold extraction efficiencies with resins were found to be lower than those achieved in the CIS flowsheets, mainly due to the higher selectivity of the resins for the divalent platinum and palladium cyanide complexes and poor gold elution efficiencies. The gold concentrations in the feed streams to these processes were, however, very low, at only 8.5% of the total precious metal content. The overall precious metal recoveries of the RIS flowsheets were thus higher than the CIS flowsheets due to the superior PGM extractions. From the cost analyses performed it was found that the RIS flowsheets requires lower initial capital costs, almost 28% lower than that require for the CIS flowsheets, while the operating cost requirements were found to be ±10% lower. This, combined with the high overall precious metal extractions, resulted in the RIS flowsheets to achieve higher net present values than those of the CIS flowsheets over an assumed project life of 15 years. The optimum flowsheet proposed for the recovery of precious metals from cyanide leach solutions was a RIS flowsheet option that employed the Amberlite PWA 5 resin, capable of extracting platinum, palladium and gold from solution, with elution being performed with a zinc cyanide solution. This process option had the lowest capital and operating cost requirements while achieving similar overall precious metal recoveries as the other flowsheets. Economic analysis of this process yielded the highest net present value, with a 31% increase in the overall return on investment compared to the optimal CIS flowsheet. Based on this, it was concluded that resin technology would be the best process option for recovering precious metals from cyanide leach solutions, however, additional research is required as the current level of process development is only at a concept phase. / AFRIKAANSE OPSOMMING: Die Platrif-erts, geleë in die Bosveld Kompleks, is een van die wêreld se grootste platinum groep metaal (PGM) reserwes. Die mineralogie van hierdie reserwe is uniek en bestaan uit komplekse PGM mineralisasie met hoofsaaklik koper en nikkel, teen baie lae PGM inhoud. Die PGMe is hoofsaaklik teenwoordig in die erts as stadig drywende minerale en dit lei tot marginale ekonomiese uitsigte wanneer hierdie reserwe deur tradisionele metodes verwerk word. Tans word ʼn nuwe proses ondersoek om die PGMe vanuit lae graad Platrif-erts en konsentraat te ontgin deur gebruik te maak van ʼn sekwensiële hooploogproses wat uit ʼn bio-loog en hoë temperatuur sianied loog stappe bestaan. Die bio-loog stap is verantwoordelik vir die ontginning van die basis metale deur gebruik te maak van ʼn suur sulfaat medium bestaande uit ʼn gemengde kultuur van mesofiele en termofiele. Nadat die bio-hooploog stap voltooi is, word die hoop herwin, gewas en herpak vir die daaropvolgende hoë temperatuur sianied loog, waar die sianied oplossing direk verhit word deur die gebruik van son panele. Platinum, palladium en goud word tydens hierdie stap ontgin en kan dan herwin word vanuit die loog oplossing deur gebruik te maak van adsorpsie deur geaktiveerde koolstof of ioon-uitruilings harse. Finale metaal herwinning kan deur elektroplatering en presipitasie vermag word. In hierdie tesis word verskeie proses opsies vir die ontginning en herwinning van PGMe vanuit sianied loog oplossings ondersoek waarna verskeie proses vloei diagram alternatiewe ontwikkel is met die doel om die opsie te vind wat die hoogste netto ekonomiese waarde sal oplewer. Die verskillende opsies is gesimuleer deur gebruik te maak van eksperimentele data gepubliseer in die literatuur en dit te kombineer met kinetiese adsorpsie modelle. Dit was dan gekombineer met ekonomiese modelle om ʼn optimum ontwerp van elke proses te verkry. Sewe verskillende proses vloei diagramme vir die herwinning en ontginning van PGMe vanuit sianied loog oplossings is ontwikkel en ondersoek. Hierdie het twee verkillende geaktiveerde koolstof prosesse en vyf verskillende ioon-uitruilings hars prosesse beslaan. Die opsies het verskil van eluerings metodes en adsorpsie medium. Die alombekende Merrill Crowe presipitasie proses is ook ondersoek, maar daar is gevind dat hierdie proses oneffektiewe resultate oplewer met betrekking tot die herwinning van die drie edel metale. In elke alternatief word die sianied oplossing in ʼn SART proses verwerk, waar die basis metale herwin word, gevolg deur die opgradering van die edel metale d.m.v. geaktiveerde koolstof adsorpsie of ekstraksie m.b.v. ioon-uitruilings harse, gevolg deur eluering. Die PGMe word dan herwin vanuit die eluerings oplossing deur termiese degradering van die metaal sianied komplekse, wat ʼn hoë graad presipitaat lewer bestaande uit die basis en edel metale. Goud word herwin d.m.v. elektroplatering. Daar is bevind dat die algehele verrigting van die ioon-uitruilings hars opsies beter was as die van die geaktiveerde koolstof opsies, beide van ʼn algehele edel metaal herwinnings en produk suiwerheid perspektief. Die verhoogde adsorpsie kinetika en hoër PGM selektiwiteit van die harse het daartoe gelei dat uitstekende algehele PGM herwinning verkry is in hierdie opsies, meer as 97%. Goud ekstraksie deur die harse was laer as wat verkry was deur die geaktiveerde koolstof opsies, weens die hoër selektiwiteit van die harse vir die divalente platinum en palladium sianied komplekse en laer hars eluering effektiwiteit. Die goud konsentrasies in die voer strome na die prosesse was laag, en het sowat 8.5% van die totale edel metale uitgemaak, wat bygedra het tot die lae goud herwinning. Algeheel was die edel metaal herwinning van die hars prosesse beter as die van die koolstof prosesse a.g.v. die hoër PGM adsorpsie. Koste evaluerings van die verskillende vloeidiagramme het getoon dat die hars opsies laer kapitaal kostes benodig, omtrent 28% minder as die koolstof opsies, terwyl bedryfskostes omtrent 10% minder was. Dit het bygedra tot die feit dat die ioon-uitruiling hars opsies ʼn hoër algehele netto ekonomiese waarde oor ʼn projek leeftyd van 15 jaar sal hê, aangesien de PGM ekstraksie, en dus die jaarlikse inkomste, ook hoër was. Die algehele proses vloei diagram wat voorgestel is vir die herwinning van edel metale vanuit sianied loog oplossings is die hars opsie wat gebruik maak van die Amberlite PWA 5 hars, wat in staat is om platinum, palladium en goud terselfdertyd te absorbeer, gevolg deur die eluering van die hars deur die gebruik van ʼn sink sianied oplossing. Hierdie proses het die laagste kapitaal en bedryfskostes getoon terwyl algehele PGM herwinning om en by dieselfde was as al die ander opsies. Hierdie proses sal verder ʼn 31% verhoging in die opbrengs op belegging lewer in vergelyking met die optimum geaktiveerde koolstof opsie. Die algehele gevolgtrekking is dat hars tegnologie die beter opsie sal wees vir die herwinning van edel metale vanuit sianied loog oplossings. Addisionele navorsing is dus nodig om resultate te verbeter aangesien hierdie studie slegs op ʼn konsep fase benadering was.