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Evaluation of different process designs for biobutanol production from sugarcane molassesVan der Merwe, Abraham Blignault 03 1900 (has links)
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
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Process development for the robust production of polyhydroxyalkanoatesFerré, Anna January 2018 (has links)
Polyhydroxyalkanoates (PHA) are a family of biodegradable polyesters naturally synthesised by some bacteria and archaea. PHA have high industrial value as bioplastics for packaging and biomedical applications. However, their broader use is hindered by high production costs and uncontrolled variation of polymer properties. The extreme halophile Haloferax mediterranei shows bioprocess advantages that can be exploited for the low cost production of the PHA copolymer Poly(3-hydroxbutyrate-co-3-hydroxyvalterate) (PHBV). The focus of this thesis is to identify process variables responsible for the uncontrolled variation of PHA properties in order to progress towards the robust production of PHBV using H. mediterranei. The outcome of the investigation is a novel cultivation strategy for the reliable synthesis of PHBV copolymers with controlled composition and microstructure showing minor differences in material characteristics. Initially, growth kinetics and PHBV synthesis were characterised under nitrogen-excess and nitrogen-limiting conditions in ammonium and for the first time, nitrate. The nitrogen source and concentration influenced PHBV accumulation and variations in polymer composition were observed with ammonium, highlighting the importance of the control of cultivation conditions. Volatile fatty acids (VFA) were found to be a more direct approach to determine PHBV composition and for the first time were used as substrates in H. mediterranei cultures. When the cells were grown in C4:0/C5:0 mixtures, the 3HV fraction in the PHBV was proportional to the percentage of C5:0 in the feed mixture, allowing the synthesis of copolymers with a predefined composition ranging from pure PHB to pure PHV. The cultivation strategy proved effective for the synthesis of HV rich PHBV, which is not easily obtained due to the 3HV precursor toxicity. The polymer microstructure was controlled using different feeding strategies: co-feeding generated random copolymers, while sequential feeding created block and blend copolymers. The synthesis of block copolymers is of interest because the materials show enhanced yield strength and mechanical strength, making such materials more suitable for commodity uses. Bespoke random, block, and blend copolymers with 0â100 mol% 3HV were synthesized and their thermal and mechanical properties studied. Lastly, high temperature cultivation and several surfactants were tested to enhance the production of bespoke PHBV from VFA. PHBV productivity and accumulation was greatly improved in a fed-batch bioreactor fermentation at 37°C with Tween-80 and the maximum PHBV content 58.9% was obtained. The polymers from shake-flasks and from bioreactors showed minor variations in their material properties, demonstrating the scalability and the robustness of the process developed. Further understanding of the different process variables affecting polymer synthesis and composition was gained in this thesis. It is now possible to produce PHBV with controllable composition, microstructure and minor differences in material characteristics. The novel and robust production strategy developed address the bioprocess challenge of minimising the uncontrolled variation of polymer characteristics that is currently hindering the wider use of PHA hence allowing the production of high quality polymers for commodity goods, packaging and biomedical applications.
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