Rheological characterization and CFD modeling of corn stover–water mixing system at high solids loading for dilute acid pretreatment

Zhang, Longping; Zhang, Jian; Li, Chuan-Hang; Bao, Jie

doi:10.1016/j.bej.2014.06.018

Cited by 28 publications

(9 citation statements)

References 29 publications

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“…Hennessey et al 5 noted that the yield stress is observed experimentally in stirred tank reactors by the stagnation of the biomass on the wall of the reactors. 25,26 The power law viscosity coefficients (K and n) are used for the CFD simulations. When we measured the viscosity in situ in the fed-batch stirred tank reactor, there was no observed stagnation of the biomass on its walls, indicating that the yield stress in the fed-batch reactor was minimal or even zero.…”

Section: Rheological Measurementsmentioning

confidence: 99%

“…The power law model has also been used by other researchers to analyze the viscosity data obtained from in situ viscosity measurements in stirred tank reactors for lignocellulose slurries. 25,26 The power law viscosity coefficients (K and n) are used for the CFD simulations.…”

Section: Rheological Measurementsmentioning

confidence: 99%

“…Their approach was based on measuring experimental torque data using reference fluids, as well as during enzymatic hydrolysis of Arundo. Their method resembles the mixing torque method used by Zhang et al 25 and Nguyen et al 26 The former authors also used a single-phase, steady-state CFD model to understand the effect of the rheological model on mixing with a helical impeller. This CFD model follows the initial work of Um and Hanley.…”

Section: Introductionmentioning

confidence: 99%

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Enhancing biomass hydrolysis for biofuel production through hydrodynamic modeling and reactor design

Gaona

Lawryshyn

Saville

2019

Energy Science & Engineering

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A computational fluid dynamics model was developed to represent high‐solids enzymatic hydrolysis. This model accounted for the transient and multiphase (solids‐slurry) nature of the high‐solids enzymatic hydrolysis process. The model investigated the effect of slurry viscosity, rotational speed, and two impeller configurations on the distribution of insoluble solids. Initial CFD results identified segregation of the velocity contours for the non‐Newtonian slurry, which could potentially affect the reactor performance. The multiphase, transient CFD simulations showed that the first impeller configuration delayed the distribution of solids, and compartmentalized mixing in the reactor. The second impeller configuration, meanwhile, improved solids mixing and hydrolysis, while using lower rotational speeds (and thus, energy). The second impeller configuration also expanded the size of the pseudo‐cavern between impellers, which is critical for better dispersion of the solids. The CFD trends of the second impeller configuration were experimentally verified by conducting fed‐batch, high‐solids enzymatic hydrolysis trials with pretreated lignocellulose. The experimental results showed that the second impeller configuration provided better mixing of the non‐Newtonian slurry and enhanced solids‐enzyme interactions, leading to improved glucan‐to‐glucose conversion. This work illustrates that a transient multiphase CFD model can provide valuable insights into the design and optimization of high‐solids enzymatic hydrolysis reactors. The CFD model has identified pathways to improve the distribution of solids while reducing the energy needed for mixing. The CFD model can also guide experimental and design work to scale up these reactors from the laboratory to pilot and commercial scale.

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Section: Rheological Measurementsmentioning

confidence: 99%

Section: Rheological Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhancing biomass hydrolysis for biofuel production through hydrodynamic modeling and reactor design

Gaona

Lawryshyn

Saville

2019

Energy Science & Engineering

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“…Especially when you should reach concentration of solid phase of more than 50% (Hou, 2016;Zhang, 2014). A high value of secondary circulation in the r-z plane in the mixer even at low rotational speeds of the stirrer effectively mixes the two phases without destroying the solid.…”

Section: Introductionmentioning

confidence: 99%

Optimization of geometric parameters of a ribbon impeller

Kuncewicz¹,

Stelmach²

2017

Chemical and Process Engineering

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Geometric parameters of a ribbon impeller were optimized on the basis of numerical calculations obtained from the solution of our own 3D/2D hybrid model. The optimization was made taking into account mixing power and homogenization time for ribbon impellers with a different number of ribbons and width operating in a laminar motion for Newtonian fluid. Due to minimum mixing energy required to stir a unit volume of liquid the most efficient impeller appeared to be that with one ribbon of width equal to 0.1 to 0.15 of the mixing vessel diameter. Impellers with more than one ribbon needed much higher mixing power but did not increase significantly secondary circulation in the vessel. These impellers increased first of all primary circulation, i.e. they increased only circular motion of liquid in the vessel.

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“…While viscosity provides useful information, rheological characterization can further this understanding through parameters, such as yield stress and viscoelastic properties (Funk and Dinger, 1994). Yield stress, the minimum stress required to induce flow in a material, has been studied substantially for both pretreated (Pimenova and Hanley, 2003;Knutsen and Liberatore, 2009;Stickel et al, 2009;Ehrhardt et al, 2010;Lavenson et al, 2011;Senturk-Ozer et al, 2011;Wiman et al, 2011;Samaniuk et al, 2012;Zhang et al, 2014) and enzymatically hydrolyzed (Roche et al, 2009;Viamajala et al, 2009;Geddes et al, 2010;Knutsen and Liberatore, 2010) feedstocks. But this parameter can be measured only on offline samples and not always in real time.…”

Section: Introductionmentioning

confidence: 99%

In Situ Rheological Method to Evaluate Feedstock Physical Properties Throughout Enzymatic Deconstruction

et al. 2018

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Feedstock physical properties determine not only downstream flow behavior, but also downstream process yields. Enzymatic treatment of pretreated feedstocks is greatly dependent on upstream feedstock physical properties and choice of pre-processing Technologies. Currently available enzyme assays have been developed to study biomass slurries at low concentrations of ≤1% w/w. At commercially relevant biomass concentrations of ≥15% w/w, pretreated feedstocks have sludge-like properties, where low free water restricts movement of unattached enzymes. This work is an account of the various steps taken to develop a method that helps identify the time needed for solid-like biomass slurries transition into liquid-like states during enzymatic hydrolysis. A pre-processing technology that enables feedstocks in achieving this transition sooner will greatly benefit enzyme kinetics and thereby overall process economics. Through this in situ rheological properties determining method, we compared a model feedstock, Avicel ® PH101 cellulose, with acid pretreated corn stover. Novozymes Cellic ® CTec2 (80 mg protein/g glucan) can reduce 25% (w/w) Avicel from solid-like to liquid-like state in 5.5 h, as the phase angles rise beyond 45 • at this time. The same slurry needed 5.3 h to achieve liquid-like state with Megazyme endoglucanase (40 mg protein/g glucan). After 10.8 h, CTec2 slurry reached a phase angle of 89 • or complete liquid-like state but Megazyme slurry peaked only to 64.7 • , possibly due to inhibition by cello-oligomers. Acid pretreated corn stover at 30% (w/w) with a CTec2 protein loading of 80 mg/g glucan exhibited a solid-like to liquid-like transition at 37.8 h, which reflects the combined inhibition of low water activity and presence of lignin. The acid pretreated slurry also never achieved complete liquid-like state due to the presence of biomass residue. This method is applicable in several scenarios comparing varying combinations of pre-processing technologies, feedstock types, pretreatment chemistries, and enzymes. Using this method, we can generate a process chain with optimal flow behavior at commercially-relevant conditions.

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Rheological characterization and CFD modeling of corn stover–water mixing system at high solids loading for dilute acid pretreatment

Cited by 28 publications

References 29 publications

Enhancing biomass hydrolysis for biofuel production through hydrodynamic modeling and reactor design

Enhancing biomass hydrolysis for biofuel production through hydrodynamic modeling and reactor design

Optimization of geometric parameters of a ribbon impeller

In Situ Rheological Method to Evaluate Feedstock Physical Properties Throughout Enzymatic Deconstruction

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