Thesis (MScEng)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Can salts present in an aqueous industrial effluent be retained by the [me ash that is produced as a by-product of gasification or by power stations utilising coal as the raw material? In order to answer this question, the actual chemistry that occurs during the mixing and settling process, needs to be understood. At the Sasol Secunda petrochemical plants in South Africa, ash is produced as a byproduct from the gasification of coal, and by the coal-fired power stations (steam plants). The [me portion of the ash (± 50J.lm in diameter) is disposed of through the use of a closed loop wet ash disposal system. The ash is transported as a slurry to the disposal sites (ash darns). The industrial effluent used to transport the ash consists mainly of the recycled ash effluent, known as clear ash effluent (CAE), as well as a variety of process waste streams containing high concentrations of salts. This mixture of ash and water is pumped to ash dams, where the ash is allowed to settle and is therefore separated from the effluent. From the ash darns the effluent flows into evaporation dams, and finally into CAE dams before being returned to the ash plant in Sasol 2 and 3 to be mixed once again with the ash. During this contact time of the ash with the water certain chemical reactions may occur. If one understands what chemical reactions occur during this process, and under what conditions they occur, then it will be possible to utilise the ash disposal system to its full potential, possibly enhancing the salt retention ability. An investigation was thus conducted into what processes actually occurs during the entire ash water contact period. The overall aim of the project was to obtain an understanding of the functioning of the [me ash disposal system so that its efficiency can be improved upon, and furthermore, so that the ash darns can be utilised more effectively in retaining salts. This investigation focussed on the chemical reactions that occur when an industrial effluent is mixed with fine ash, and consisted of four main aspects: • A literature survey on related issues. • An analysis and evaluation of the changes that occur in the actual disposal system. • Laboratory column experiments to investigate, in more detail, the different chemical reactions, which occur during the different stages of the disposal process. • The drilling of boreholes into the ash dams to obtain core material at a variety of depths and locations for analysis purposes. From this investigation it was concluded that salts are retained in the ash dams; based on the results obtained from the laboratory column experiments and the production rate of the fine ash from Sasol 2 and Sasol 3, the potential amount of salts that can be removed from the system (either due to precipitation or water retention in the ash dams) is approximately 95 tons/day. The salts that were found to be most pertinent to the wet ash disposal system utilised at Sasol, Secunda, are Ca, S04, Na, and Cl. Of these, Ca, S04 and Na were identified in literature to be the components most commonly associated with fly ash leachate. The Ca chemistry, which occurs in the ash disposal system, was explored extensively. Is was found that Ca, which is initially present in the fresh fine ash as lime, is leached from the ash into the effluent, where it reacts with carbon dioxide in the atmosphere, and is therefore removed from the system due to the precipitation of calcite. Sodium, S04, and Cl were all found to be retained in the ash; the S04 appears to be retained in a stable form within the ash, not merely due to hydraulic retention, which suggests that the ash system has the potential to act as a salt sink for S04 ions. The mechanism of salt retention in the ash darns was found to be predominantly by means of hydraulic retention, and therefore the salts have the potential to be flushed out of the ash dams into the underlying soil material. However, results from the core drilling exercise revealed that there doesn't appear to be a significant seepage of elements from the ash fill material into the underlying vertisol material. Some components (AI, Fe, Na, K, Mg, Cr, P, Ti and V) from the older, and inactive ash dam, do appear to have percolated into the underlying material. However, a significant amount of water, and therefore salts, are still retained in the ash dam. In terms of the mineralogical composition of the ash dams, a significant difference was observed between the mineral phases present in the ash fill material of an active and an inactive ash dam. Ettringite was detected throughout the borehole drilled into the inactive ash darn, and was not evident at all in the core material from the two boreholes drilled into the active dam, which suggests that this mineral is formed in the ash darns over a long time period. The minerals quartz and mullite were found in the fresh [me ash as well as in most of the core material obtained from the drilling exercise. The mineralogical composition of the ash fill samples, from the boreholes drilled into the centre of the active and inactive ash darns, was found to be very consistent with depth. This finding, combined with the fact that the chemical composition of the core samples varied more significantly in the borehole located near the edge of the active fine ash darn, indicated that the lateral position of the ash in the ash dam influences the chemical reactions that occur. Overall, from this investigation it was concluded that although the chemistry, involved in the mixing of an industrial effluent with fine ash, is extremely complex and site-specific, it is possible to determine the most significant changes which occur within a wet ash disposal system. Besides providing one with a better understanding of the working of the Secunda ash disposal system, the results of this investigation have also provided the framework for future research on this topic and related issues, i.e. the construction of a pilot scale ash darn set-up; further column experiments to investigate the extent to which S04 ions can be removed from the system; the influence of the addition of CO2 to the system; and more extensive core drilling in the vicinity of the ash darns. / AFRIKAANSE OPSOMMING: Kan soute teenwoordig in 'n industriële uitvloeisel teruggehou word in fynas geproduseer as neweproduk van steenkoolkragsentrales? Om 'n antwoord op hierdie vraag te kry, moet die chemiese reaksies wat gebeur tydens die meng en wegdoening van die as en aswater verstaan word. By die Sasol petrochemiese aanlegte in Secunda, Suid Afrika, word fynas geproduseer as 'n neweproduk in die vergassing en die stoomopwekkingprosesse. Die fynas (50)lm diameter) word weggedoen deur 'n geslote nat asstelsel. Die industriële uitvloeisel wat gebruik word vir die vervoer van die as bestaan hoofsaaklik uit hergebruikte aswater (genoem CAE - clear ash effluent), asook 'n verskeidenheid ander prosesafvalstrome wat hoë konsentrasies soute bevat. Die mengsel van as en aswater word in 'n asflodder gepomp na die asdamme, waar die as besink en sodoende geskei word van die waterfase (aswater). Vanaf die asdamme vloei die aswater na verdampingsdamme, en daarna na die CAE damme, vanwaar die CAE weer na die Sasol aanleg teruggepomp word om weer met as gemeng te word. Gedurende die kontak tussen die CAE en as gebeur sekere chemiese reaksies. Indien hierdie reaksies verstaan word, en onder watter toestande dit plaasvind, kan die asdamstelsel tot volle kapasiteit benut word deur moontlik die soutretensie binne die asdam te verhoog. 'n Ondersoek is gedoen om te bepaal watter prosesse plaasvind gedurende kontak tussen die as en water. Die doel van die ondersoek was om 'n beter begrip te kry oor die funksionering van die fynas-wegdoeningstelsel en om te bepaal of die asdamme meer effektiefbedryfkan word om moontlik meer soute te akkommodeer. Die ondersoek het uit vier hoofaspekte bestaan: • Literatuuroorsig, • 'n Analise en evaluering van die veranderinge wat plaasvind oor die asdamstelsel, • Laboratoriumskaal kolomeksperimente om in meer besonderhede die chemiese reaksies wat 'n rol in die aswaterstelsel speel, te bepaal, en • Die boor van toetsgate op die bestaande asdamme om boorkerne te ontleed by bepaalde dieptes en liggings. Uit die ondersoek is bevind dat soute wel in die asdamme behou word. As die kolomtoetse as basis gebruik word, en die produksietempo van fynas vanaf Sasol 2 en 3, dan kan daar 'n potensiële 95 ton soute per dag deur die asstelsel verwyder word (deur hoofsaaklik waterretensie en presipitasie van soute). Die mees prominente soute wat in die Sasol asstelsel voorkom is Ca, S04, Na, en Cl. Vanhierdie soute, is Ca, S04, en Na deur die literatuur geïdentifiseer as komponente wat met vliegas loog geassosieer word. Die Ca chemie, wat in die asstelsel plaasvind, is in besonderhede ontleed. Dit is bevind dat Ca, teenwoordig in die vars fynas as kalk, vanuit die as in die aswater geloog word, waar dit dan met atmosferiese CO2 reageer en dan vanuit die stelselverwyder word deur die presipitasie van kalsiet. Natrium, S04 en Cl word in die as teruggehou. Dit wil voorkom asof die S04 in 'n stabiele vorm in die as teruugehou word, nie net deur die hidrouliese retensie nie en dat die asstelsel dalk as 'n potensiële sink vir S04 kan optree. Die meganisme van soutretensie in die asdamme is hoofsaaklik deur hidrouliese retensie, met die gevolg dat die soute potensieel in die onderliggende grond uitgewas kan word. Die resultate van die boorkernondersoek wys egter dat daar nie beduidende uitwassing van hierdie soute in die grond is nie. Dit wil voorkom of sekere komponente (Al, Fe, Na, K, Mg, Cr, P, Ti en V) van die ou en onaktiewe asdam in die grond geloog is. 'n Beduidende verskil was gevind tussen die minerale fases in die asmateriaal van die aktiewe en onaktiewe asdamme. Ettringiet was teenwoordig deur die hele diepte van die boorkern van die onaktiewe dam, maar was nie teenwoordig in beide boorkerns van die gate op die aktiewe asdam nie. Dit impliseer dat hierdie mineraaloor 'n langer tyd gevorm word. Kwarts en mulliet was deurentyd in al die boorkerne teenwoordig. Die mineralogie van die boorkern van die middel van die aktiewe asdam was baie konstant met diepte (in teenstelling met dié van die boorkern op die kant van die asdam) wat daarop dui dat die laterale posisie van die as in die asdam die chemiese reaksies wat mag plaasvind kan beïnvloed. Die ondersoek bevestig dat alhoewel die chemiese reaksies betrokke in die aswaterstelsel baie kompleks en liggingspesifiek is, die mees beduidende veranderinge wat in die asstelsel plaasvind, wel bepaal kan word. Die ondersoek het benewens 'n beter begrip van hoe die asdamme reageer, ook 'n raamwerk gegee vir verdere navorsing in hierdie veld, bv. die bou van 'n loodsskaal-asdam, verdere kolomtoetse om die vermoë van die asstelsel om S04 ione te verwyder te bepaal en die invloed van gemanipuleerde kalsiet presipitasie deur die byvoeging van CO2.

Thesis (MIng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Fouling is readily acknowledged as one of the most critical problems limiting the wider application of membranes in liquid separation processes. A better understanding of fouling layer formation and its monitoring is needed in order to improve on existing cleaning techniques. Plant operation can be optimised if fouling can be monitored by noninvasion means either on the plant itself or on an attached monitoring device. The overall scope of this research was to develop a non-destructive, real-time, in situ visualisation technique or device for concentration polarisation and fouling layer monitoring. Ultrasonic-time-domain-reflectometry (UTDR) was employed as a visualisation technique to provide real-time characterisation of the fouling layer. A 24 cm-long rectangular flat sheet aluminium cell was designed and used as separation device for a desalination system. The experimental results obtained using this module confirmed that there are an excellent correspondence between the flux decline behaviour and the UTDR response from the membrane. The ultrasonic technique could effectively detect fouling layer initiation and growth on the membrane in real-time. In addition to the measurement of fouling, the ultrasonic technique was also successfully employed for monitoring membrane cleaning. Since no real-time permeation data is available during cleaning operations in industrial applications, a UTDR monitoring device may prove to be a very valuable technique in optimising cleaning strategies. The technique was further tested on an 8-inch diameter spiral wrap industrial module and good results were obtained. Stagnant zones, as well as flux flow behaviour inside the module could be determined. However, more research IS needed to fully understand the complex phenomena inside a spiral wrap module. Overall, the UTDR technique and its use in monitoring devices have a major impact in the membrane industry due to its extremely powerful capabilities. / AFRIKAANSE OPSOMMING: Membraan-bevuiling of -verstopping is die grootste struikelblok wat die algemene aanwending van membrane vir verskillende watersuiweringsprosesse negatief beinvloed. 'n Beter begrip van membraan-bevuiling, asook beter metingsmetodes daarvan is nodig om op bestaande skoonmaaktegnieke te verbeter. Die hoofdoel van hierdie studie was die ontwikkeling van 'n nie-destruktiewe-in-lyn visuele tegniek vir die meting van konsentrasie polarisasie en membraan-bevuiling. Deur gebruik te maak van ultrasoniese klank golwe, is 'n tegniek ontwikkel wat 'n direkte visuele aanduiding kon gee van die toestand van membraan-bevuiling binnein die module. 'n Reghoekige aluminium-module, 24 cm lank, is ontwerp en gebou waarbinne die membraan geplaas is vir die skeidingsproses. Resultate dui daarop dat daar 'n uitstekende verband bestaan tussen die afname in permeaatvloei en die ultrasoniese eggo vanaf die membraan. Die ultrasoniese tegniek kon die vorming van en toename in membraan-bevuiling doeltreffend karakteriseer. In teenstelling hiermee, is die tegniek ook suksesvol aangewend om die skoonmaak-proses van membrane te ondersoek. Met min of geen data beskikbaar vir die skoonmaak-proses van membrane in die industriële sektor, het die tegniek enorme potensiaal in die optimisering van bestaande skoonmaak-tegnieke. Die tegniek is verder aangewend op 'n industriële 8-duim deursnee spiraal-module en goeie resultate is verkry. Stagnante sones asook vloed-vloei-patrone binne-in die module kon suksesvol bepaal word. Baie navorsing is egter nog nodig om die ingewikkelde data wat gegenereer word tydens die ondersoek van 'n spiraal-module ten volle te verstaan. Die enorme potensiaal en moontlikhede van die ultrasoniese tegniek kan die begin wees van 'n revolusie in die membraan-industrie.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2005. / Although selective oxidation catalysts are widely used and extensively studied for their industrial and academic value, their complex mechanisms are, to a large extent, still unclear. The field of so-called allylic (amm)oxidations reactions was chosen for further investigation, in particular the simplistic selective oxidation of propene to acrolein over an α-Bi2Mo3O12 catalyst. One of the most important approaches in selective oxidation is to try to correlate the physicochemical properties of catalysts with their catalytic performance (activity and selectivity). The most interesting, and seemingly most widely invoked parameter, is lattice oxygen mobility. The problem, however, is the difficulty encountered in measuring oxygen mobility. It is hypothesised that the depth of oxygen utilisation and lattice oxygen mobility of bismuth molybdate during the partial oxidation of propene to acrolein may be determined by measuring the rate of acrolein formation and lattice oxygen usage over a range of discrete particle sizes that could be synthesised using reverse micelle technology. Catalyst Preparation A preliminary investigation into the reverse micelle technique showed that discrete nanosized particles could be synthesised, but that there was no size control over the outcome and that, in most cases there were some degree of particle agglomeration. It was also found that nanorod formation occurred due to adsorbtion of surfactant. More in-depth investigation had to be done in order to achieve particle size control and the liberation of the calcined α-Bi2Mo3O12 catalyst particles required for kinetic experiments. Simple precipitation methods, the catalyst calcination step, and the formation and stability of reverse micelles were investigated. A simple precipitation method to prepare α-Bi2Mo3O12, suitable to be integrated into the reverse micelle technique was found by buffering the mixture of bismuth nitrate and ammonium molybdate solutions with an excess of molybdate. This prevented the pH from decreasing below a critical value of 1.3 (at which β-Bi2Mo2O9 forms as an impurity). The excess molybdenum caused the formation of MoO3 in the calcined product, which was selectively and successfully removed using a warm ammonium wash followed by a water rinse and a recalcination step. XRD of a temperature range calcination shows that the calcination starts at temperatures as low as 200°C and almost complete calcination of the catalyst at 280°C. DSC analyses show a 47.15 J/g crystal formation peak only at 351°C. The Mo18O56(H2O)8 4- anion or its double, Mo36O112(H2O)16 8-, is responsible for the formation of α-Bi2Mo3O12 in the precipitation calcination reaction. Reverse micelles were investigated using a Malvern Zetasizer and showed a complex dynamic system in which the reverse micelle sizes and size distributions change over time as a function of surfactant and aqueous concentrations, the salt used and aqueous phase salinity. Although much was accomplished in this study, more investigations into the constituent steps of the reverse micelle technique are needed to develop a method to synthesise the range of discrete catalyst particle sizes required for kinetic studies. Kinetic Studies For the purpose of kinetic experiments a metal reactor was found to be superior to that of a glass reactor. The reactor rig was adequate for these kinetic studies but do not meet the requirements for detailed reaction order experiments. The analysing apparatus could not measure CO2 formation accurately and it had to be calculated using a carbon balance. Only the model proposed by Keulks and Krenzke [1980a] was able to describe the kinetic result, but the model parameter describing the oxidative state of the catalyst surface could not be calculated due to the lack compatibility between published data. Values were awarded to this parameter so to give an Arrhenius plot which corresponded to published data. The parameter describing the oxidative state vs. temperature took on a function that was consistant with the reasoning of Keulks and Krenzke [1980a]. Comprehensive preliminary kinetic studies are needed, both in catalyst reduction and reoxidation, in order to determine the reaction conditions, explore more advanced kinetic models and investigate model parameters that are theoretically and/or empirically obtainable and quantifiable.

Thesis (MEng.)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The aim of the thesis was to investigate the use of flow destabilization methods, combined with permeate backflushing (BIF) or on their own, on flux recovery and maintenance in capillary UF membrane systems under cross-flow (XF) and dead-end (DE) operating conditions. Various hydraulic and mechanical methods have been used to remove the accumulated cake layer and improve steady state process flux. Permeate backflushing (B/F) is the most widely used but the drawbacks are loss of product and extensive down-time. In a pilot plant study for ultrafiltration of surface waters containing high NOM, turbidity and cation loads, the use of flow destabilization, or feed flow reversal (FFR) combined with cross-flow B/F was able to improve the normalised flux by 10.7 ± 3.4 %, compared with 3.2 ± 1.6 % improvement for BIF without FFR. When a second B/F included FFR, the flux improvement was 7.0 ± 2.0 % compared with 4.3 ± 2.5 % for a B/F without FFR. The hypothesis was proposed that the flow destabilization caused slight lifting of the oriented cake layer, while the cross-flow B/F was able to sweep the lifted cake out of the lumen. If the flow destabilization may be effected by a simple but effective and low-cost method, and if this flow destabilization may be combined with reverse flow for short durations, the "lift-and-sweep" approach will be the ideal method of maintaining process flux and increasing membrane life. Such a flow destabilization method, now named "reversepressure pulsing" (RIP), was developed. The method involves circulation of feed water in a recycle loop for 2 s to gain momentum, followed by closure of a fast-action valve upstream of the modules. The momentum of the water in the concentrate loop carries it into an air-filled feed accumulator, while concentrate and reverse-flow permeate (which also lifts the fouling layer) are discharged to the atmosphere using the recycle pump for 15 s. When the valve opens again, the air in the accumulator forces the water under pressure through the membrane lumens, causing a pressure pulse and flow perturbations that lift, shift and break up the fouling layer. During 3 such "lift-and-sweep" events, the cake is lifted and the debris is swept out of the lumen. Experimental results for uninterrupted dead-end filtration at a UF pilot plant using RIP only on a severely fouled membrane, indicated that the RIP increased the flux by 18.4 % and decreased the dP by 8.2 % over a 7.2 h period. The method is effective in removing the cake layer intermittently and no long-term flux decline occurred for a period of 555 h since the previous chemical cleaning. / AFRIKAANSE OPSOMMING: Die doel van die tesis was om die gebruik van vloei-destabiliserings metodes, alleen of gekombineer met permeaat-terugwas, op vloed-herwinning en instandhouding in kapillêre UF membraan-stelsels tydens kruisvloei en doodloop bedryf, te ondersoek. Verskeie meganiese en hidrouliese metodes word gebruik in membraan stelsels om die koeklaag op die membraan se oppervlak te verwyder en die gestadigde-toestand vloed te verbeter. Vanhierdie metodes word permeaat-terugwas die meeste gebruik, maar het sy nadele insluitend verlies van produk en produksietyd. In 'n loodsstudie vir die ultrafiltrasie van oppervlakwaters wat hoë beladings NOM, turbiditeit en katione bevat, is die waarneming gemaak dat kruisvloei terugwas met vloeidestabilisering (voerrigting-verandering) die genormaliseerde vloed met 10.7 ± 3.4 % kon verbeter, vergeleke met 'n 3.2 ± l.6 % verbetering sonder voerrigting-verandering. Vir 'n tweede terugwas was die verbetering 7.0 ± 2.0 % vergeleke met 4.3 ± 2.5 % sonder voerrigtingverandering. Die hipotese was voorgestel dat die vloei-destabilisering die geoiënteerde koeklaag van die oppervlak gelig het, en die kruisvloei terugwas die geligde koeklaag uit die lumen kon vee. Indien hierdie vloei-destabilisering bewerk kan word deur 'n eenvoudige maar effektiewe manier, en indien dit gekombineer kan word met terugvloei van produk vir kort tydperke, sal hierdie "lig-en-vee" benadering die ideale metode wees om die membrane se vloed te verbeter en leeftyd te verleng. So 'n vloei-destabiliseringsmetode, nou genoem "terugdruk-pulsering", is ontwikkel. Die metode behels die sirkuiering van voer-water vir 2 s in 'n hersirkulasielus om momentum op te bou, gevolg deur die toemaak van 'n snel-aksie klep stroom-op van die modules. Die water in die konsentraat-lus se momentum dra dit vorentoe tot in In lug-gevulde voer-akkumulator, terwyl konsentraat en terug-vloei permeaat (wat ook tot 'n mate die koeklaag lig) ook na die atmosfeer gewend word vir 15 s deur die hersirkulasiepomp. As die klep weer oopgaan, ontspan die lug in die akkumulator, en forseer die water daarin onder druk deur die membraan-lumens. Die druk-puls en vloei-perturbasies lig, skuif en breek die koeklaag op. Tydens 3 agtereenvolgende "lig-en-vee" aksies word die koeklaag effektief opgebreek en uit die lumen gevee. Eksperimentele uitslae vir ononderbroke doodloop bedryf op uitermate aangevuilde membrane van 'n ultrafiltrasie loodsaanleg toegerus met terugdruk-pulsering, het getoon dat die vloed met 18.4 % verbeter kon word en die dP met 8.2 % verminder kon word in slegs 7.2 h. Die metode breek die koeklaag effektief op, en geen langtermyn vloed-afname is waargeneem vir meer as 555 h sedert die vorige chemiese was-prosedure nie.

Thesis (MScEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Supercritical extraction is being investigated as a possible alternative to the processes currently used in the fractionation of paraffinic waxes. By removing the lighter carbon fractions from the wax, the wax hardness will be improved and its melting temperature range reduced, hence improving the performance of the wax product in certain applications. In order to evaluate and operate such an extraction process optimally, it is necessary to have a thermodynamic model that accurately represents the process system. There are, however, currently no predictive models available for these systems. In order to fit present models to the systems, accurate phase equilibrium data of the supercritical solvent - n-alkane systems are needed. Unfortunately, the amount of reliable published data on these systems in the required operating range is very limited. A view cell was designed and developed with which these high pressure equilibria could be studied. The binary phase equilibria of supercritical CO2 with n-CI2, n-CI6, n-C20, n-C24, n-C28 and n-C36 and of supercritical ethane with n-CI6, n-C24 and n-C28 were measured in the temperature range 313 - 367 K. It was found that the systems with these two solvents have very different types of phase behaviour. The n-alkane solubility is much higher in ethane, but supercritical CO2 will provide a much better degree of control over the selectivity achieved in an extraction process. Of the various equations of state investigated, it was found that the Patel Teja equation of state provided the best fit of the CO2 - n-alkane systems and that the Soave-Redlich- Kwong equation fitted the ethane - n-alkane systems the best. The interaction parameters of both these equations of state display a functional relationship with temperature and nalkane acentric factor, making it possible to determine parameter values for application at other operating temperatures and with other n-alkane systems. It was found that the current equations of state were not able to represent the phase equilibria accurately over the entire range of operating conditions. The poor performance of the equations of state can be attributed to inherent flaws in the existing equations of state. / AFRIKAANSE OPSOMMING: Superkritiese ekstraksie word tans ondersoek as 'n moontlike altematief vir die prosesse wat huidiglik gebruik word om paraffiese wasse te fraksioneer. Die Iigter koolstofwasse word verwyder om die washardheid te verhoog en die temperatuurgebied waaroor die was smelt te verklein. Dit verbeter dan die was se kwaliteit en werkverrigting. Modelle wat die superkritiese ekstraksie proses akkuraat kan voorstel word egter benodig om die ekstraksie proses te kan evalueer en optimaal te bedryf. Daar is tans geen modelle beskikbaar wat die proses direk kan voorstel nie. Akkurate fase-ewewigsdata word benodig om bestaande modelle aan te pas vir gebruik in hierdie sisteme. Daar is egter baie min betroubare faseewewigsdata vir die superkritiese oplosmiddel - n-alkaan sisteme beskikbaar in die literatuur. 'n Sig-sel, waarrnee hierdie hoe druk data gemeet kan word, is ontwerp en ontwikkel. Die volgende binere fase ewewigte is in die temperatuur gebied 313 - 367 K gemeet: superkritiese CO2 met n-CI2, n-CI6, n-C20, n-C24, n-C28 en n-C36, en superkritiese Etaan met n-CI6, n-C24 en n-C28. Daar is gevind dat hierdie twee superkritiese oplosmiddelsisteme verskillende tipes fase-ewewigsgedragte openbaar. Die n-alkane het 'n baie boer oplosbaarheid in Etaan, maar deur superkritiese C02 in 'n ekstraksie kolom te gebruik, sal tot beheer oor die selektiwiteit van die ekstraksieproses lei. Uit die verskillende toestandsvergelykings wat ondersoek is, is daar gevind dat die Patel- Teja vergelyking die CO2 sisteme die beste kon beskryf en dat die Soave-Redlich-Kwong vergelyking die beste vergelyking was om die Etaan sisteme mee te modelleer. Beide die toestandsvergelykings se interaksie parameters het 'n funksionele verband met temperatuur en die n-alkaan asentrise faktor getoon. Dit is dus moontlik om waardes vir die parameters vir sisteme by ander temperature en met ander n-alkaan tipes te bepaal. Daar was gevind dat die bestaande toestandsvergelykings nie die die fase-ewewigte oor die hele eksperimenele gebied akkuraat kon voorstel nie. Dit kan toegeskryf word aan foute wat inherent is aan die vergelykings.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The growth in intelligent control has primarily been a reaction to the realisation that nonlinear control theory has been unable to provide practical solutions to present day control challenges. Consequently the chemical industry may be cited for numerous instances of overdesign, which result as an attempt to avoiding operation near or within complex (often more economically viable) operating regimes. Within these complex operating regimes robust control system performance may prove difficult to achieve using conventional (algorithmic) control methodologies. Biological neuronal control mechanisms demonstrate a remarkable ability to make accurate generalisations from sparse environmental information. Neural networks, with their ability to learn and their inherent massive parallel processing ability, introduce numerous opportunities for developing superior control structures for complex nonlinear systems. To facilitate neural network learning, reinforcement learning techniques provide a framework which allows for learning from direct interactions with a dynamic environment. lts promise as a means of automating the knowledge acquisition process is beguiling, as it provides a means of developing control strategies from cause and effect (reward and punishment) interaction information, without needing to specify how the goal is to be achieved. This study aims to establish evolutionary reinforcement learning as a powerful tool for developing robust neurocontrollers for application in highly nonlinear process systems. A novel evolutionary algorithm; Symbiotic, Adaptive Neuro-Evolution (SANE), is utilised to facilitate neurocontroller development. This study also aims to introduce SANE as a means of integrating the process design and process control development functions, to obtain a single comprehensive calculation step for maximum economic benefit. This approach thus provides a tool with which to limit the occurrence of overdesign in the process industry. To investigate the feasibility of evolutionary reinforcement learning in achieving these aims, the SANE algorithm is implemented in an event-driven software environment (developed in Delphi 4.0), which may be applied for both simulation and real world control problems. Four highly nonlinear reactor arrangements are considered in simulation studies. As a real world application, a novel batch distillation pilot plant, a Multi-Effect Batch Distillation (MEBAD) column, was constructed and commissioned. The neurocontrollers developed using SANE in the complex simulation studies, were found to exhibit excellent robustness and generalisation capabilities. In comparison with model predictive control implementations, the neurocontrollers proved far less sensitive to model parameter uncertainties, removing the need for model mismatch compensation to eliminate steady state off-set. The SANE algorithm also proved highly effective in discovering the operating region of greatest economic return, while simultaneously developing a neurocontroller for this optimal operating point. SANE, however, demonstrated limited success in learning an effective control policy for the MEBAD pilot plant (poor generalisation), possibly due to limiting the algorithm's search to a too small region of the state space and the disruptive effects of sensor noise on the evaluation process. For industrial applications, starting the evolutionary process from a random initial genetic algorithm population may prove too costly in terms of time and financial considerations. Pretraining the genetic algorithm population on approximate simulation models of the real process, may result in an acceptable search duration for the optimal control policy. The application of this neurocontrol development approach from a plantwide perspective should also have significant benefits, as individual controller interactions are so doing implicitly eliminated. / AFRIKAANSE OPSOMMING: The huidige groei in intelligente beheerstelsels is primêr 'n reaksie op die besef dat nie-liniêre beheerstelsel teorie nie instaat is daartoe om praktiese oplossings te bied vir huidige beheer kwelkwessies nie. Gevolglik kan talle insidente van oorontwerp in die chemiese nywerhede aangevoer word, wat voortvloei uit 'n poging om bedryf in of naby komplekse bedryfsgebiede (dikwels meer ekonomies vatbaar) te vermy. Die ontwikkeling van robuuste beheerstelsels, met konvensionele (algoritmiese ) beheertegnieke, in die komplekse bedryfsgebiede mag problematies wees. Biologiese neurobeheer megamsmes vertoon 'n merkwaardige vermoë om te veralgemeen vanaf yl omgewingsdata. Neurale netwerke, met hulle vermoë om te leer en hulle inherente paralleie verwerkingsvermoë, bied talle geleenthede vir die ontwikkeling van meer doeltreffende beheerstelsels vir gebruik in komplekse nieliniêre sisteme. Versterkingsleer bied a raamwerk waarbinne 'n neurale netwerk leer deur direkte interaksie met 'n dinamiese omgewing. Versterkingsleer hou belofte in vir die inwin van kennis, deur die ontwikkeling van beheerstrategieë vanaf aksie en reaksie (loon en straf) interaksies - sonder om te spesifiseer hoe die taak voltooi moet word. Hierdie studie beaam om evolutionêre versterkingsleer as 'n kragtige strategie vir die ontwikkeling van robuuste neurobeheerders in nie-liniêre prosesomgewings, te vestig. 'n Nuwe evolutionêre algoritme; Simbiotiese, Aanpasbare, Neuro-Evolusie (SANE), word aangewend vir die onwikkeling van die neurobeheerders. Hierdie studie beoog ook die daarstelling van SANE as 'n weg om prosesontwerp en prosesbeheer ontwikkeling vir maksimale ekonomiese uitkering, te integreer. Hierdie benadering bied dus 'n strategie waardeur die insidente van oorontwerp beperk kan word. Om die haalbaarheid van hierdie doelwitte, deur die gebruik van evolusionêre versterkingsleer te ondersoek, is die SANE algoritme aangewend in 'n Windows omgewing (ontwikkel in Delphi 4.0). Die Delphi programmatuur geniet toepassing in beide die simulasie en werklike beheer probleme. Vier nie-liniêre reaktore ontwerpe is oorweeg in die simulasie studies. As 'n werklike beheer toepassing, is 'n nuwe enkelladingsdistillasie kolom, 'n Multi-Effek Enkelladingskolom (MEBAD) gebou en in bedryf gestel. Die neurobeheerders vir die komplekse simulasie studies, wat deur SANE ontwikkel is, het uitstekende robuustheid en veralgemeningsvermoë ten toon gestel. In vergelyking met model voorspellingsbeheer implementasies, is gevind dat die neurobeheerders heelwat minder sensitief is vir model parameter onsekerheid. Die noodsaak na modelonsekerheid kompensasie om gestadigde toestand afset te elimineer, word gevolglik verwyder. The SANE algoritme is ook hoogs effektief vir die soek na die mees ekonomies bedryfstoestand, terwyl 'n effektiewe neurobeheerder gelyktydig vir hierdie ekonomies optimumgebied ontwikkel word. SANE het egter beperkte sukses in die leer van 'n effektiewe beheerstrategie vanaf die MEBAD toetsaanleg getoon (swak veralgemening). Die swak veralgemening kan toegeskryf word aan 'n te klein bedryfsgebied waarin die algoritme moes soek en die negatiewe effek van sensor geraas op die evaluasie proses. Vir industriële applikasies blyk dit dat die uitvoer van die evolutionêre proses vanaf 'n wisselkeurige begintoestand nie koste effektief is in terme van tyd en finansies nie. Deur die genetiese algoritme populasie vooraf op 'n benaderde modelop te lei, kan die soek tydperk na 'n optimale beheerstrategie aansienlik verkort word. Die aanwending van die neurobeheer ontwikkelingstrategie vanuit 'n aanlegwye oogpunt mag aanleiding gee tot aansienlike voordele, aaangesien individuele beheerder interaksies sodoende implisiet uitgeskakel word.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Peach and apricot shells are agricultural waste products. These waste products accumulate around canneries and food-processing plants in South Africa. No effort is being made to utilise these waste products. This study is the first part of the product development from these products i.e. peach shell activated carbon and apricot shell activated carbon. By producing activated carbon from peach and apricot shells the solid waste problem is addressed, but most of all a profit can be made. But why activated carbon? Activated carbons are unique and versatile adsorbent with a vast amount of adsorption applications. It can be produced via a simple oxidation reaction with steam and the nature of peach and apricot shells are such that it is expected that activated carbons with good adsorption properties can be produced from it. The single largest consumer of activated carbon in South Africa is the gold mining industry that uses imported coconut shell activated carbon for gold adsorption in the gold recovery process. Activated carbon is also used as water purification adsorbents. During this study activated carbons were produced in a fluidized bed reactor at various activation conditions: 700 - 900°C, 0.0425 - 0.0629 g steamlg char.min and 30 - 60 min. This was done in order to find the optimum activation conditions within the activation parameter range. The optimal activated carbons were defined as peach and apricot shell activated carbons that showed good microporous as well as mesoporous character. The optimal activated carbons produced are: peach shell activated at 875°C, 0.0533 g stearnlg char. min, 60 min and apricot shell activated carbon at 850°C, 0.0533 g steamlg char.min, 60min. The possible use of these optimal activated carbons and two other activated carbons produced (Peach shell activated carbon 900°C, 0.0425 g steamlg char. min, 60 min and apricot shell activated carbon 900°C, 0.0425 g steamlg char.min, 60min) were tested in gold recovery and water purification. The gold adsorption properties of peach and apricot shell activated carbons were found to be better than two commercial coconut shell activated carbons (Chemquest 650 and GRC 22). No definite conclusions could, however, be drawn about the replacement of coconut shell activated carbon with peach or apricot shell activated carbon, because abrasion test work and thermal regeneration of the experimental carbons still have to be performed. The experimental activated carbons displayed good phenol adsorption characteristic, although further test work is required. / AFRIKAANSE OPSOMMING: Perske- en appelkoospitte is landbouafvalprodukte. Hierdie afvalprodukte versamel rondom inmaakfabrieke en voedselververkingsaanlegte. Tans word daar geen poging in Suid-Afrika aangewend om hierdie afvalprodukte te benut nie. Hierdie studie is die eerste deel van die ontwikkeling van die produkte: Perskepitdop-geaktiveerde koolstof en appelkoospitdop-geaktiveerde koolstof. Deur geaktiveerde koolstof van die perske- en appelkoospitdoppe te maak, word nie net 'n antwoord op die vastestofafvalsprobleem gevind nie, maar daar kan ook geld gemaak word. Hoekom geaktiveerde koolstof? Aktiveerde koolstowwe is veelsydige en unieke adsorbente met 'n groot verskeidenheid adsorpsie toepassings. Dit kan vervaardig word via 'n eenvoudige oksidasie reaksie met stoom en die aard van die perske- en appelkoospitdoppe is sodanig, dat verwag kan word om geaktiveerde koolstowwe met goeie adsorpsie eienskappe daarvan te kry. Die grootste enkelverbruiker van geaktiveerde koolstof in Suid-Afrika is die goudmynbedryf, wat kokosneutdop geaktiveerde koolstof invoer om goud te herwin. Geaktiveerde koolstof word ook gebruik vir watersuiwering. Tydens hierdie studie IS geaktiveerde koolstowwe by verskillende aktiveeringskondisies in 'n gevloeïdiseerde bed vervaardig: 700 - 900oe, 0.0425 - 0.0629g stoornlg gepiroliseerde pitdoppe.min en 30 - 60 mm. Die aktiveringskondisies is gevarieer om sodoende die optimale aktiveringskondisies binne die aktiveringsparameterreeks te kry. 'n Geaktiveerde koolstof is as optimaal geklassifiseer as dit 'n goeie mikro- sowel as mesostruktuur getoon het. Die optimaal geaktiveerde koolstowwe is: geaktiveerde koolstof vervaardig van perskepitdoppe by 875°e, 0.0533 g stoornlg gepiroliseerde pitdoppe.min, 60 mm en geaktiveerde koolstof vervaardig van appelkoospitdoppe by 850oe, 0.0533 g stoornlg gepiroliseerde pitdoppe.min, 60min. Die gebruik van die twee optimale geaktiveerde koolstowwe sowel as twee ander geaktiveerde koolstowwe (perskepitdop-geaktiveerde koolstof, 900oe, 0.0425 g stoornlg gepiroliseerde pitdoppe.min, 60 min en appelkoospitdop-geaktiveerde koolstof, 850°C, 0.0533 g stoom/g gepiroliseerde pitdoppe.min, 60min) is VIr goudadsorpsie en watersuiwering ondersoek. Die goudadsorpsie eienskappe van die perske-en appelkoospitdop-geaktiveerde koolstowwe was beter as die van twee kommersiële kokosneutdop-geaktiveerde koolstowwe (Chemquest 650 and GRC 22). Daar kan egter geen definitiewe gevolgtrekkings gemaak word oor die vervanging van kokosneutdop geaktiveerde koolstowwe met dié van perske of appelkoospitdoppe nie, aangesien daar nog toetsresultate oor die slytweerstand en reaktiverings eienskappe van die eksperimentele geaktiveerde koolstowwe uitstaande is. Die eksperimentele geaktiveerde koolstowwe toon goeie adsorpie ten opsigte van fenol, maar verdere toetswerk is egter nodig.

Thesis (PhD)--University of Stellenbosch, 2004. / 271 Leaves printed single pages, preliminary pages i-xviii and 253 numberd pages. Includes bibliography. List of figures, List of tables. / ENGLISH ABSTRACT: A Neurocontrol Paradigm for Intelligent Process Control using Evolutionary Reinforcement Learning Balancing multiple business and operational objectives within a comprehensive control strategy is a complex configuration task. Non-linearities and complex multiple process interactions combine as formidable cause-effect interrelationships. A clear understanding of these relationships is often instrumental to meeting the process control objectives. However, such control system configurations are generally conceived in a qualitative manner and with pronounced reliance on past effective configurations (Foss, 1973). Thirty years after Foss' critique, control system configuration remains a largely heuristic affair. Biological methods of processing information are fundamentally different from the methods used in conventional control techniques. Biological neural mechanisms (i.e., intelligent systems) are based on partial models, largely devoid of the system's underlying natural laws. Neural control strategies are carried out without a pure mathematical formulation of the task or the environment. Rather, biological systems rely on knowledge of cause-effect interactions, creating robust control strategies from ill-defined dynamic systems. Dynamic modelling may be either phenomenological or empirical. Phenomenological models are derived from first principles and typically consist of algebraic and differential equations. First principles modelling is both time consuming and expensive. Vast data warehouses of historical plant data make empirical modelling attractive. Singular spectrum analysis (SSA) is a rapid model development technique for identifying dominant state variables from historical plant time series data. Since time series data invariably covers a limited region of the state space, SSA models are almost necessarily partial models. Interpreting and learning causal relationships from dynamic models requires sufficient feedback of the environment's state. Systemisation of the learning task is imperative. Reinforcement learning is a computational approach to understanding and automating goal-directed learning. This thesis aimed to establish a neurocontrol paradigm for non-linear, high dimensional processes within an evolutionary reinforcement learning (ERL) framework. Symbiotic memetic neuro-evolution (SMNE) is an ERL algorithm developed for global tuning of neurocontroller weights. SMNE is comprised of a symbiotic evolutionary algorithm and local particle swarm optimisation. Implicit fitness sharing ensures a global search and the synergy between global and local search speeds convergence.Several simulation studies have been undertaken, viz. a highly non-linear bioreactor, a rigorous ball mill grinding circuit and the Tennessee Eastman control challenge. Pseudo-empirical modelling of an industrial fed-batch fermentation shows the application of SSA for developing partial models. Using SSA, state estimation is forthcoming without resorting to fundamental models. A dynamic model of a multieffect batch distillation (MEBAD) pilot plant was fashioned using SSA. Thereafter, SMNE developed a neurocontroller for on-line implementation using the SSA model of the MEBAD pilot plant. Both simulated and experimental studies confirmed the robust performance of ERL neurocontrollers. Coordinated flow sheet design, steady state optimisation and nonlinear controller development encompass a comprehensive methodology. Effective selection of controlled variables and pairing of process and manipulated variables were implicit to the SMNE methodology. High economic performance was attained in highly non-linear regions of the state space. SMNE imparted significant generalisation in the face of process uncertainty. Nevertheless, changing process conditions may necessitate neurocontroller adaptation. Adaptive neural swarming (ANS) allows for adaptation to drifting process conditions and tracking of the economic optimum online. Additionally, SMNE allows for control strategy design beyond single unit operations. SMNE is equally applicable to processes with high dimensionality, developing plant-wide control strategies. Many of the difficulties in conventional plant-wide control may be circumvented in the biologically motivated approach of the SMNE algorithm. Future work will focus on refinements to both SMNE and SSA. SMNE and SSA thus offer a non-heuristic, quantitative approach that requires minimal engineering judgement or knowledge, making the methodology free of subjective design input. Evolutionary reinforcement learning offers significant advantages for developing high performance control strategies for the chemical, mineral and metallurgical industries. Symbiotic memetic neuro-evolution (SMNE), adaptive neural swarming (ANS) and singular spectrum analysis (SSA) present a response to Foss' critique. / AFRIKAANSE OPSOMMING: 'n Neurobeheer paradigma vir intelligente prosesbeheer deur die gebruik van evolusionêre versterkingsleer Dit is 'n komplekse ontwikkelingstaak om menigte besigheids- en operasionele doelwitte in 'n omvattende beheerstrategie te vereenselwig. Nie-lineêriteite en vele komplekse prosesinteraksies kombineer om ingewikkelde aksie-reaksie verwantskappe te vorm. Dit is dikwels noodsaaklik om hierdie interaksies omvattend te verstaan, voordat prosesbeheer doelwitte doeltreffend gedoen kan word. Tog word sulke beheerstelsels dikwels saamgestel op grond van kwalitatiewe kriteria en word ook dikwels staatgemaak op historiese benaderings wat voorheen effektief was (Foss, 1973). Dertig jaar na Foss se kritiek, bly prosesbeheerstelsel ontwerp 'n heuristiese saak. Die biologiese prosessering van informasie is fundamenteel verskillend van metodes wat gebruik word in konvensionele beheertegnieke. Biologiese neurale meganismes (d.w.s., intelligente stelsels) word gebaseer op gedeeltelike modelle, wat grotendeels verwyderd is van die onderskrywende natuurwette. Neurobeheerstrategieë word toegepas sonder suiwer wiskundige formulering van die taak of die omgewing. Biologiese stelsels maak eerder staat op kennis van aksie-reaksie verhoudings en skep robuuste beheerstrategieë van swak gedefineerde dinamiese stelsels. Dinamiese modelle is of fundamenteel of empiries. Fundamentele modelle word ontwikkel vanaf eerste beginsels en word tipies uit algebraïese en differensiële vergelykings saamgestel. Modellering vanaf eerste beginsels is beide tydrowend en duur. Groot databasisse van historiese aanlegdata maak empiriese modellering aantreklik. Singuliere spektrumanalise (SSA) maak die vinnige ontwerp van empiriese modelle moontlik, waardeur dominante veranderlikes vanaf historiese tydreekse onttrek kan word. Aangesien tydreeksdata slegs 'n gedeelte van die prosesomgewing verteenwoordig, is SSA modelle noodwendig gedeeltelike modelle. Die interpretasie en aanleer van kousale verhoudings vanaf dinamiese modelle vereis voldoende terugvoer van omgewingstoestande. Die leertaak moet sistematies uitgevoer word. Versterkingsleer is 'n ramingsbenadering tot 'n doelwit-gedrewe leerproses. Hierdie tesis bewerkstellig 'n neurobeheerparadigme vir nie-lineêre prosesse met hoë dimensies binne 'n evolusionêre versterkingsleer (EVL) raamwerk. Simbiotiese, memetiese neuro-evolusie (SMNE) is 'n EVL algoritme wat ontwikkel is vir globale verstelling van die gewigte van ‘n neurobeheerder. SMNE is saamgestel uit 'n simbiotiese evolusionêre algoritme en 'n lokale partikelswerm-algoritme. Implisiete fiksheidsdeling verseker 'n globale soektog en die sinergie tussen globale en lokale soektogte bespoedig konvergensie.Verskeie simulasie studies is onderneem, o.a. die van 'n hoogs nie-lineêre bioreaktor, 'n balmeulaanleg en die Tennessee Eastman beheer probleem. Empiriese modellering van 'n industriële enkelladingsfermentasie demonstreer die aanwending van SSA vir die ontwikkeling van gedeeltelike modelle. SSA benader die toestand van 'n dinamiese stelsel sonder die aanwending van fundamentele modellering. 'n Dinamiese model van 'n multi-effek-enkelladingsdistillasie (MEBAD) proefaanleg is bewerkstellig deur die gebruik van SSA. Daarna is SMNE gebruik om 'n neurobeheerder te skep vanaf die SSA model vir die beheer van die MEBAD proefaanleg. Beide simulasie en eksperimentele studies het die robuuste aanwending van EVL neurobeheerders bevestig. Die gekoördineerde ontwerp van vloeidiagramme, gestadigde toestand-optimering en nie-lineêre beheerderontwikkeling vereis 'n omvattende metodologie. Beheerveranderlikes en die koppeling van proses- en uitvoerveranderlikes is implisiet en effektief. Maksimale ekonomiese aanwins was moontlik in hoogs nie-lineêre dele van die toestandsruimte. SMNE het besondere veralgemening toegevoeg tot neurobeheerderstrategieë ten spyte van prosesonsekerhede. Nietemin, veranderende prosestoestande mag neurobeheerderaanpassing genoodsaak. Aanpasbare neurale swerm (ANS) algoritmes pas neurobeheerders aan tydens veranderende proseskondisies en volg die ekonomiese optimum, terwyl die beheerder die proses beheer. SMNE bewerkstellig ook die ontwikkeling van beheerstrategieë vir prosesse met meer as een eenheidsoperasie. SMNE skaal na prosesse met hoë dimensionaliteit vir die ontwikkeling van aanlegwye beheerstrategieë. Talle kwelvrae in konvensionele aanleg-wye prosesbeheer word deur die biologies gemotiveerde benadering van die SMNE algoritme uit die weg geruim. Toekomstige werk sal fokus op die verfyning van beide SMNE en SSA. SMNE en SSA bied 'n nie-heuristiese, kwantitatiewe benadering wat minimale ingenieurskennis of oordeel vereis. Die metodologie is dus vry van subjektiewe ontwerpsoordeel. Evolusionêre versterkingsleer bied talle voordele vir 'n ontwikkeling van effektiewe beheerstrategieë vir die chemiese, mineraal en metallurgiese industrieë. Simbiotiese memetiese neuro-evolusie (SMNE), aanpasbare neurale swerm metodes (ANS) en singulêre spektrum analise (SSA) gee antwoord op Foss se kritiek.

Thesis (MScEng (Process Engineering))--Stellenbosch University, 2008. / Please refer to full text to view abstract.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Recently concern has been raised regarding effluent from wine cellars, as it often does not comply with environmental legislation. It was with this in mind that the effluent problem at Ashton Cellars was addressed. After carrying out a water audit of the plant, described in Chapter 3, it was concluded that the ion exchange plant is a significant contributor to the low pH and high conductivity of the effluent dam. Decreasing the effluent from the ion exchange plant should therefore help in improving the total effluent quality. During the water audit opportunities to improve the effluent by making small process changes in the cellar were identified. The primary objective of this study was to provide guidelines to improve the quality and decrease the volume of the effluent from the ion-exchange plant to more environmentally acceptable levels, whilst maintaining product specifications and production rates. This was achieved by studying the operation of the plant (Chapter 4) and testing the characteristics of the current and alternative resins (Chapter 5). Auditing of the ion exchanges plant included a detailed analysis of the regeneration and loading of the ion exchange columns. It was concluded that the operation of the plant can only be optimised once pH and/or conductivity meters, and preferably an automated control system, are installed on the plant. The results given in this thesis can be used as a guide when setting up such a control system. Laboratory testing of the resins revealed that the cation resin currently being used on the plant has been fouled and loads at a slow rate. When the resins are replaced, the use of Purolite CISO and Purolite A103S should be considered as these resins gave the most favourable results. Some alternative treatment methods for the processing of grape must, have been mentioned in Chapter 6. / AFRIKAANSE OPSOMMING: Al meer kornrner word deesdae uitgespreek oor wynkelders se afvalwater, omdat dit meerendeels nie aan die vereistes van omgewingswetgewing voldoen nie. Dit was met hierdie probleem in die oog dat die afvalwater probleem by Ashton Kelders ondersoek IS. Nadat 'n wateroudit van die fabriek, soos beskryf in Hoofstuk 3, uitgevoer is, is daar tot die slotsom gekom dat die ioonuitruilsisteem 'n groot bydra tot die lae pH en hoe konduktiwiteit van die afvaldam lewer. Indien die ioonuitruilsisteem se uitvloeisel verminder kon word, sou dit tot 'n groot mate bydrae tot 'n verbetering van die totale uitvloei kwaliteit. Gedurende die wateroudit is verskeie moontlikhede vir die verbetering van die uitvloei deur klein prosesveranderinge aan te bring, geidentifiseer. Hierdie studie het as hoof oogmerk die daarstelling van riglyne vir die verbetering van die kwaliteit en grote van die afvalstrome van die ioonuitruilsisteem om sodeende aan omgewingswetgewing te voldoen, maar ter selfder tyd die produk spesifikasies en tempos te handhaaf. Dit is gedoen deur die huidige bedryf van die fabriek te bestudeer (Hoofstuk 4) en die eienskappe van die huidige en altematiewe ioonuitruilharse te toets (Hoofstuk 5). Die oudit van die ioonuitruilsisteem het 'n gedetaileerde anaIiese van die hergenerasie en lading van die ioonuitruilkolornrne ingesluit. Daar is tot die slotsom gekom dat die bedryf van die sisteem alleenlik geoptirniseer kon word indien pH en/of konduktiwiteitsmeters, en verkieslik 'n automatiese kontrolesisteem geinstalleer word. Die resultate van hierdie tesis kan as basis vir so 'n kontrole sisteem gebruik word. Die laboratoriumtoetse op die harse het aan die lig gebring dat die katioonhars wat tans in gebruik is, baie vervuil is en net teen 'n lae tempo belaai kan word. Wanneer die harse vervang word, word die gebruik van Purolite el50 en Purolite A103S aangeraai, aangesien hierdie harse die beste resultate gelewer het. Altematiewe behandelingsmetodes van druifmos is in Hoofstuk 6 genoem.