Thesis (MScEng (Process Engineering))--Stellenbosch University, 2010. / ENGLISH ABSTRACT: Recently, improved technologies have been developed for the biobutanol fermentation process: higher butanol concentrations and productivities are achieved during fermentation, and separation and purification techniques are less energy intensive. This may result in an economically viable process when compared to the petrochemical pathway for butanol production. The objective of this study is to develop process models to compare different possible process designs for biobutanol production from sugarcane molasses. Some of the best improved strains, which include Clostridium acetobutylicum PCSIR-10 and Clostridium beijerinckii BA101, produce total solvent concentrations of up to 24 g/L. Among the novel technologies for fermentation and downstream processing, fedbatch fermentation with in situ product recovery by gas-stripping, followed by either liquid-liquid extraction or adsorption, appears to be the most promising techniques for current industrial application. Incorporating these technologies into a biorefinery concept will contribute toward the development of an economically viable process. In this study three process routes are developed. The first two process routes incorporate well established industrial technologies: Process Route 1 consist of batch fermentation and steam stripping distillation, while in Process Route 2, some of the distillation columns is replaced with a liquid-liquid extraction column. The third process route incorporates fed-batch fermentation and gas-stripping, an unproven technology on industrial scale. Process modelling in ASPEN PLUS® and economic analyses in ASPEN Icarus® are performed to determine the economic feasibility of these biobutanol production process designs. Process Route 3 proved to be the only profitable design in current economic conditions. For the latter process, the first order estimate of the total project capital cost is $187 345 000.00 (IRR: 35.96%). Improved fermentation strains currently available are not sufficient to attain a profitable process design without implementation of advanced processing techniques. Gas stripping is shown to be the single most effective process step (of those evaluated in this study) which can be employed on an industrial scale to improve process economics of biobutanol production. / AFRIKAANSE OPSOMMING: Onlangse verbeteringe in die tegnologie vir die vervaardiging van butanol via die fermentasie roete het tot gevolg dat: hoër butanol konsentrasies en produktiwiteit verkry kan word tydens die fermentasie proses, en energie verbruik tydens skeiding-en suiweringsprosesse laer is. Hierdie verbeteringe kan daartoe lei dat biobutanol op ʼn ekonomiese vlak kan kompeteer met die petrochemiese vervaardigings proses vir butanol. Die doelwit van die studie is om proses modelle te ontwikkel waarmee verskillende proses ontwerpe vir die vervaardiging van biobutanol vanaf suikerriet melasse vergelyk kan word. Verbeterde fermentasie organismes, wat insluit Clostridium acetobutylicum PCSIR-10 en Clostridium beijerinckii BA101, het die vermoë om ABE konsentrasies so hoog as 24 g/L te produseer. Wat nuwe tegnologie vir fermentasie en skeidingprosesse behels, wil dit voorkom of wisselvoer fermentasie met gelyktydige verwydering van produkte deur gasstroping, gevolg deur of vloeistof-vloeistof ekstraksie of adsorpsie, van die mees belowende tegnieke is om tans in die nywerheid te implementeer. Deur hierdie tegnologie in ʼn bioraffinadery konsep te inkorporeer sal bydra tot die ontwikkeling van ʼn ekonomies lewensvatbare proses. Drie prosesserings roetes word in die studie ontwikkel. Die eerste twee maak gebruik van goed gevestigde industriële tegnologie: Proses Roete 1 implementeer enkellading fermentasie en stoom stroping distillasie, terwyl in Proses Roete 2 van die distilasiekolomme vervang word met ʼn vloeistof-vloeistof ekstraksiekolom. Die derde proses roete maak gebruik van wisselvoer fermentasie met gelyktydige verwydering van produkte deur gas stroping. Die tegnologie is nog nie in die nywerheid bewys of gevestig nie. Om die ekonomiese uitvoerbaarheid van die proses ontwerpe te bepaal word proses modellering uitgevoer in ASPEN PLUS® en ekonomiese analises in ASPEN Icarus® gedoen. Proses Roete 3 is die enigste ontwerp wat winsgewend is in huidige ekonomiese toestande. Die eerste orde koste beraming van die laasgenoemde projek se totale kapitale koste is $187 345 000.00 (opbrengskoers: 35.96%). Die verbeterde fermentasie organismes wat tans beskikbaar is, is nie voldoende om ʼn proses winsgewend te maak nie; gevorderde proses tegnologie moet geïmplementeer word. Gasstroping is bewys as die mees effektiewe proses stap (getoets in die studie) wat op industriële skaal geïmplementeer kan word om die winsgewendheid van die biobutanol proses te verbeter. / Centre for Renewable and Sustainable Energy Studies