Reduced power consumption compared to a traditional stirred tank reactor (STR) for enzymatic saccharification of alpha-cellulose using oscillatory baffled reactor (OBR) technology

Abbott, Matthew S.R.; Perez, Gustavo Valente; Harvey, Adam P.; Theodorou, Mike K.

doi:10.1016/j.cherd.2014.01.020

Cited by 27 publications

(12 citation statements)

References 29 publications

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“…In fact, the OBR could achieve the highest conversion achieved in the STR at »1/20th the power consistent with the findings of Abbott et al [41] when they observed a reduction of 94À99% power in the OBR (2.36 Wm ¡3 ) compared with the STR (37.2À250 Wm ¡3 ) in the saccharification of 5.2% a-cellulose.…”

Section: Resultssupporting

confidence: 89%

Enzymatic saccharification of cellulose: a study of mixing and agitation in an oscillatory baffled reactor and a stirred tank reactor

Ikwebe

Harvey

2015

Biofuels

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Cellulose saccharification has been shown to be a function of agitation. Here, the effect of agitation by oscillatory mixing in an oscillatory baffled reactor (OBR) has been assessed and contrasted with a stirred tank reactor (STR). After 168 h of saccharification at 200 Wm ¡3 , 91% conversion of the cellulose (»25 g/L glucose) was observed in the OBR, as against 74% conversion (»21 g/L glucose) in the STR. At 120 Wm ¡3 in both systems, the conversion in the OBR was 69% (»19 g/L glucose) within the first 24 h, and 88% conversion (24 g/L glucose) after 168 h. The STR yielded 55% (15.3 g/L glucose) and 67% (»18.6 g/L glucose) within the same time scale respectively, differences of 14 and 21% respectively. At equivalent power density of 10 Wm ¡3 , the two reactors exhibited the same mean strain rates of 6.65 s ¡1 , but as the power densities increased the mean strain rates in the STR became significantly higher than that in the OBR. This observation could be partly responsible for the seemingly better saccharification observed in the OBR. Although agitation is essential for optimum saccharification, the nature of the agitation is perhaps a more important factor owing to shear stresses on enzymes. BackgroundMixing is a physical process that governs the rate of change of a chemical environment. To achieve suitably high ethanol titres during fermentation, adequate levels of mixing are very important. Adequate mixing can increase the overall rate by reducing external mass transfer resistance in the rate-limiting saccharification step. This is even more imperative in the saccharification of cellulosic materials. With the projected decline in petroleum reserves and the attendant global energy crises, cellulosic materials have been recognised as some of the most promising alternative resources to supply our chemical and energy needs sustainably.[1] Cellulose is the most abundant carbohydrate polymer in nature,[2] probably the most abundant organic compound on earth,[3] and as a result has evoked long-term interest as a potential source of plentiful food and energy.[4] Cellulose is a linear homopolymer of anhydroglucose units linked by b-(1-4)-glycosidic bonds, with amorphous and crystalline regions. [5,6] It is hydrolysed into glucose during saccharification by enzyme complexes referred to as "cellulases".The hydrolysis of cellulose, however, is difficult. It is influenced by a number of factors, including the structural characteristics of the cellulosic substrate, the amorphous, easily hydrolysable and recalcitrant crystalline regions, [7] sugar inhibition,[8À11] the quality of the enzyme complex which determines the relative performance of its individual components (i.e. the speed of enzyme action), [9,12À15] enzyme and substrate concentrations,[12,14] temperature,[13] pH,[16] the degree of agitation,[17] and

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Section: Resultssupporting

confidence: 89%

Enzymatic saccharification of cellulose: a study of mixing and agitation in an oscillatory baffled reactor and a stirred tank reactor

Ikwebe

Harvey

2015

Biofuels

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“…It is also pointed out that both models were developed for pulsed flow in tubes and columns without a net flow (i.e. equivalent to batch OBRs) and that they have been used to compare performances between classic stirred-tank reactors and OBR in different applications, as bioprocess and crystallization (Abbott et al, 2014;Ni et al, 2004). However, there is a very limited number of fundamental studies of energy dissipation rate in COBRs, therefore impeding the validation of these models.…”

Section: Introductionmentioning

confidence: 99%

Predicting power consumption in continuous oscillatory baffled reactors

Avila

Fletcher

Poux

et al. 2020

Chemical Engineering Science

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Continuous oscillatory baffled reactors (COBRs) have been proven to intensify processes, use less energy and produce fewer wastes compared with stirred tanks. Prediction of power consumption in these devices has been based on simplistic models developed for pulsed columns with single orifice baffles several decades ago and are limited to certain flow conditions. This work explores the validity of existing models to estimate power consumption in a COBR using CFD simulation to analyse power density as a function of operating conditions (covering a range of net flow and oscillatory Reynolds numbers: !" #$% = 6 − 27 / !"-= 24 − 96) in a COBR with a single orifice baffle geometry. Comparison of computed power dissipation with that predicted by the empirical quasi-steady flow models shows that this model is not able to predict correctly the values when the flow is not fully turbulent, which is common when operating COBRs. It has been demonstrated that dimensionless power density is inversely proportional to the total flow Reynolds number in laminar flow and constant in turbulent flow, as is the case for flow in pipes and stirred tanks. For the geometry studied here (1/2) * = 330 !" 7 ⁄ in laminar flow and (1/2) * = 1.92 in turbulent flow.

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“…Vortices form down the length of the OBR as material is forced through periodically spaced orifice plates (baffles). The advantages of this agitation type include uniform mixing at low shear (Ni et al, 2000), enhanced mass (Hewgill et al, 1993, Ni et al, 1995 and heat (Mackley and Stonestreet, 1995) transfer, the possibility of linear scale-up (Smith andMackley, 2006, Smith, 1999) and power efficient agitation (Abbott et al, 2014b, Jambi et al, 2013. The mixing intensity is also decoupled from the net flow rate which enables plug flow to be achieved in substantially shorter reactors compared to conventional tubular designs where high net flows are required for turbulence (Stonestreet and van der Veeken, 1999, van Vliet et al, 2005, Stonestreet and Harvey, 2002, Abbott et al, 2014a.…”

Section: Cultivation Of Microalgae Currently Occurs In Either Open Ormentioning

confidence: 98%

Liquid culture of microalgae in a photobioreactor (PBR) based on oscillatory baffled reactor (OBR) technology – A feasibility study

Abbott

Brain

Harvey

et al. 2015

Chemical Engineering Science

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Reduced power consumption compared to a traditional stirred tank reactor (STR) for enzymatic saccharification of alpha-cellulose using oscillatory baffled reactor (OBR) technology

Cited by 27 publications

References 29 publications

Enzymatic saccharification of cellulose: a study of mixing and agitation in an oscillatory baffled reactor and a stirred tank reactor

Enzymatic saccharification of cellulose: a study of mixing and agitation in an oscillatory baffled reactor and a stirred tank reactor

Predicting power consumption in continuous oscillatory baffled reactors

Liquid culture of microalgae in a photobioreactor (PBR) based on oscillatory baffled reactor (OBR) technology – A feasibility study

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