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Author: David Michael Lavenson
Publisher:
ISBN: 9781267657190
Category :
Languages : en
Pages :
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Book Description
Enzymatic conversion of lignocellulosic substrates is an important step in the biorefining process for the production of fuels and chemicals. Industrial implementation of cellulosic ethanol processes has been hindered by the lack of an economic and efficient way of digesting the cellulosic biomass feedstock. In order to reduce unit operations costs in the areas of mixing, handling, pumping, and separations, mass solids contents of the feed biomass must exceed approximately 20%. Above approximately 10% solids concentrations, cellulosic suspensions behave as non-Newtonian slurries while most of the moisture is retained within the substrate walls, making mixing and homogenization challenging. The underlying transport phenomena that govern these suspensions are complex and not completely understood. In this work, mass transfer and rheological behavior of high solids cellulose substrates are investigated. These studies use magnetic resonance imaging (MRI) to measure: 1. diffusion and adsorption in cellulosic fiber beds using labeled paramagnetic tracers; 2. velocity flow profiles of suspensions in tube flow to obtain pertinent rheological parameters; and 3. effects of mixing on the rates of liquefaction and saccharification in highly concentrated cellulose suspensions. MRI is a non-invasive technique which has been used for flow-imaging, diffusion, and adsorption studies. It is highly advantageous for the opaque biomass system which cannot be examined using light microscopy or other optical methods. Other techniques are used to probe the effects of fiber properties on diffusion-adsorption, liquefaction, and saccharification. Diffusion coefficients for MnCl2 and Gd-BSA are reported for various cellulosic suspensions, including delignified cellulose and dilute-acid pretreated lignocellulosic biomass. Diffusion is found to be highly dependent on the rate of adsorption in the fiber beds. The adsorption behavior of BSA on various cellulosic substrates, both lignocellulosic and delignified, is also investigated. Biomass suspension yield stress values are measured using MRI, and the resolution and uncertainty of the MRI technique are compared quantitatively with literature data collected from conventional rheometers. The MRI technique compares well with conventional techniques and offers improvements in sampling size, sampling error, measurement time, and uncertainty. Lastly, rates of liquefaction and extent of saccharification are measured for high solids content fiber suspensions undergoing enzymatic hydrolysis. A significant difference in the rates of liquefaction and saccharification is attributed to initial homogenization of enzyme, indicating the benefits of mixing enzyme and substrate on the centimeter scale. Application of these results to future work and industrial implications is also discussed.
Author: David Michael Lavenson
Publisher:
ISBN: 9781267657190
Category :
Languages : en
Pages :
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Book Description
Enzymatic conversion of lignocellulosic substrates is an important step in the biorefining process for the production of fuels and chemicals. Industrial implementation of cellulosic ethanol processes has been hindered by the lack of an economic and efficient way of digesting the cellulosic biomass feedstock. In order to reduce unit operations costs in the areas of mixing, handling, pumping, and separations, mass solids contents of the feed biomass must exceed approximately 20%. Above approximately 10% solids concentrations, cellulosic suspensions behave as non-Newtonian slurries while most of the moisture is retained within the substrate walls, making mixing and homogenization challenging. The underlying transport phenomena that govern these suspensions are complex and not completely understood. In this work, mass transfer and rheological behavior of high solids cellulose substrates are investigated. These studies use magnetic resonance imaging (MRI) to measure: 1. diffusion and adsorption in cellulosic fiber beds using labeled paramagnetic tracers; 2. velocity flow profiles of suspensions in tube flow to obtain pertinent rheological parameters; and 3. effects of mixing on the rates of liquefaction and saccharification in highly concentrated cellulose suspensions. MRI is a non-invasive technique which has been used for flow-imaging, diffusion, and adsorption studies. It is highly advantageous for the opaque biomass system which cannot be examined using light microscopy or other optical methods. Other techniques are used to probe the effects of fiber properties on diffusion-adsorption, liquefaction, and saccharification. Diffusion coefficients for MnCl2 and Gd-BSA are reported for various cellulosic suspensions, including delignified cellulose and dilute-acid pretreated lignocellulosic biomass. Diffusion is found to be highly dependent on the rate of adsorption in the fiber beds. The adsorption behavior of BSA on various cellulosic substrates, both lignocellulosic and delignified, is also investigated. Biomass suspension yield stress values are measured using MRI, and the resolution and uncertainty of the MRI technique are compared quantitatively with literature data collected from conventional rheometers. The MRI technique compares well with conventional techniques and offers improvements in sampling size, sampling error, measurement time, and uncertainty. Lastly, rates of liquefaction and extent of saccharification are measured for high solids content fiber suspensions undergoing enzymatic hydrolysis. A significant difference in the rates of liquefaction and saccharification is attributed to initial homogenization of enzyme, indicating the benefits of mixing enzyme and substrate on the centimeter scale. Application of these results to future work and industrial implications is also discussed.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Rheological and mass transfer properties of non-Brownian fiber suspensions are affected by fiber characteristics, fiber interactions, and processing conditions. In this thesis we develop several simulation methods to study the dynamics of single fibers in simple shear flow, as well as the rheology and mass transfer of fiber suspensions. Isolated, rigid, neutrally-buoyant, non-Brownian, slightly curved, nonchiral fibers in simple shear flow of an incompressible Newtonian fluid at low Reynolds number can drift steadily in the gradient direction without external forces or torques. The average drift velocity and direction depend on the fiber aspect ratio, curvature and initial orientation. The drift results from the coupling of rotational and translational dynamics, and the combined effects of flipping, scooping, and spinning motions of the fiber. Irreversible fiber collisions in the suspensions cause shear-induced diffusion. The shear-induced self-diffusivity of dilute suspensions of fibers increases with increasing concentration and increasing static friction between contacts. The diffusivities in both the gradient and vorticity directions are larger for suspensions of curved fibers than for suspensions of straight fibers. For suspensions of curved fibers, significant enhancements in the diffusivity in the gradient direction are attributed to fiber drift in the gradient direction. The shear-induced self-diffusivity of concentrated suspensions of fibers increases with increasing concentration before fiber networks or flocs are formed, after which the diffusivity decreases with increasing concentration. The diffusivity increases with increasing fiber equilibrium bending angle, effective stiffness, coefficient of static friction, and rate of collisions. The specific viscosity of fiber suspensions increases with increasing fiber curvature, friction coefficient between mechanical contacts, and solids concentration. The specific viscosity increases linearly with concentration in the dilute regime, and increases with the cube of the concentration in the semi-dilute regime. Concentrated fiber suspensions are highly viscous, shear thinning, and exhibit significant yield stresses and normal stress differences. Yield stresses scale with volume concentration and fiber aspect ratio in the same way as that observed in experiments. The first normal stress difference increases linearly with shear rate. The shear-induced diffusivity increases linearly with the derivative of the particle contribution to stress for dilute suspensions with respective to concentration. This correlation between rheology and shear-induced diffusion makes it possible to predict diffusivity from easily measured rheological properties.
Author: Miguel Angel Bibbó
Publisher:
ISBN:
Category :
Languages : en
Pages : 680
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Book Description
Author: N. Pan
Publisher: Woodhead Pub Limited
ISBN: 9781845691639
Category : Technology & Engineering
Languages : en
Pages : 93
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Book Description
The Textile Progress monograph series provides a critical and comprehensive examination of the origination and application of developments in the textile industry and its products. This issue reviews recent developments in the understanding of the fundamentals of liquid transport phenomena in fibrous materials, and deals with a wide range of issues, many of which are complex and thus still inadequately understood.
Author: Richard O. Maschmeyer
Publisher:
ISBN:
Category :
Languages : en
Pages : 27
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Book Description
The viscosities of concentrated suspensions of glass fibers in high viscosity silicone oil were measured with a capillary viscometer using 1/4 inch and 1/8 inch diameter capillaries. Suspension fiber length distributions and rheological properties were highly dependent on mixing technique. The viscosity of the suspensions was strongly dependent on fiber length distribution--a few percent of relatively long fibers in the distribution doubled or tripled the suspension viscosity. Special attention was paid to wall effects which complicate the interpretation of suspension viscosity data. Yield stresses, squeeze-through, the capillary entrance exclusion were observed; their magnitudes increased with fiber length and depended strongly on fiber length distribution.
Author: Jan Mewis
Publisher: Cambridge University Press
ISBN: 0521515998
Category : Science
Languages : en
Pages : 417
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Book Description
Presented in an accessible and introductory manner, this is the first book devoted to the comprehensive study of colloidal suspensions.
Author: Mohamed Naceur Belgacem
Publisher: John Wiley & Sons
ISBN: 1118773551
Category : Technology & Engineering
Languages : en
Pages : 1289
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Book Description
This book will focus on lignocellulosic fibres as a raw material for several applications. It will start with wood chemistry and morphology. Then, some fibre isolation processes will be given, before moving to composites, panel and paper manufacturing, characterization and aging.
Author:
Publisher:
ISBN:
Category : Rheology
Languages : en
Pages : 748
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Book Description
Author: Richard O. Maschmeyer
Publisher:
ISBN:
Category :
Languages : en
Pages : 36
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Book Description
Capillary viscometer measurements were made on a series of concentrated suspensions with the same fiber length distribution. Shear stress-shear rate data are reported for 0, 15, and 30 vol.% glass fiber suspensions in 100, 600, and 1000 P silicone oil. Yield stresses, wall effects, concentration defects, squeeze-through, and capillary entrance exclusion were not significant in the measurements. With other parameters held constant, the suspension viscosity increased with oil viscosity. The data were fit by a dimensionless plot of the form F(fRe, De) = 0 where f is the friction factor for tube flow and Re and De are the Reynolds and Deborah numbers of the system. The suspension viscosity increased with fiber concentration, but the magnitude of the increase was highly shear rate dependent. The data are compared with literature predictions for the dependence of suspension viscosity on fiber concentration and shear rate.
Author: Lan Tang
Publisher:
ISBN:
Category : Multiphase flow
Languages : en
Pages : 330
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Book Description
