Rheological characterization of raw and anaerobically digested cow slurry

Hreiz, Rainier; Adouani, Nouceiba; Fünfschilling, Denis; Marchal, Philippe; Pons, Marie‐Noëlle

doi:10.1016/j.cherd.2017.01.005

Cited by 27 publications

(16 citation statements)

References 24 publications

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“…Furthermore, Ansys Fluent provides a power law model (includes η 0 ) to describe the shear‐thinning fluid properties. Hereby, the fluid properties correlate by approximation to a fermenter slurry with a solid content of about 9 % . Tab.…”

Section: Cfd Simulationmentioning

confidence: 96%

A Scale‐up Strategy for the Fluid Flow in Biogas Plants

et al. 2018

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The mixing process in biogas plants is fundamental for effectiveness. Unfortunately, difficulties at full scale mean that research must usually be performed at lab‐scale and the results up‐scaled. This study presents a scale‐up strategy for the fluid flow in shear‐thinning non‐Newtonian fluids. Dimensional analysis was applied to connect the influencing parameters, i.e., geometric dimensions, rotational speed, and rheological properties, to key figures. By using the Reynolds and Hedström number, standards for adapting the rotational speed and rheological properties were defined as a function of the scale. A sliding‐mesh model was selected for numerical simulations of a plant with a paddle agitator at two different scales. The scale‐up approach leads to similar velocity fields, which result in equal normalized mixing times.

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Section: Cfd Simulationmentioning

confidence: 96%

A Scale‐up Strategy for the Fluid Flow in Biogas Plants

et al. 2018

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“…Rheological behavior and bioreactor hydrodynamics are the key parameters that determine the efficiency of any mixing equipment [27]. The rheological properties of slurry at various temperatures, TS content, and the type of substrate have been extensively studied by many researchers [49][50][51][52][53][54][55][56][57][58]. According to literature results, cattle manure and waste water sludges are non-Newtonian fluids because there is no linear relation between their shear rates and shear stresses [59].…”

Section: Effect Of Viscosity Shear Stress and Ts Contentmentioning

confidence: 99%

“…It has been noted that the fine particles dramatically reduce the slurry's apparent viscosity. Accordingly, grinding of solid manure before feeding it into the digester will decrease the mixing cost and enhance mixing and digestion efficiency [53]. Another method to decrease viscosity is filtration, which results in an improvement of the mixing efficiency of a Rushton turbine.…”

Section: Effect Of Viscosity Shear Stress and Ts Contentmentioning

confidence: 99%

Impact of mixing intensity and duration on biogas production in an anaerobic digester: a review

Singh

Szamosi

Siménfalvi

2020

Critical Reviews in Biotechnology

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This paper is a critical evaluation of the effect of mixing on biogas production rates in an anaerobic digester. Mixing plays a prominent role in determining the efficiency of the anaerobic digestion process. This review analyzes the miscellaneous effects of mixing (on the microbial community, methane content and volatile fatty acids) at various mixing intensities and during different stages of the digestion process. Intermittent mixing (mixing at intervals) seems preferable in terms of the quality and quantity of biogas produced, and results in lower power consumption and maintenance costs associated with large-scale biogas production. Preferable mixing time (the length at intervals) and the intensity depends on the geometry of the digester and impeller. The conclusion is drawn that the study of the slurry rheology is very crucial in the designing of the mixing equipment, the shape and size of the digester, and the pipe transport system which can assist in minimizing the initial investment and operational costs. Accordingly, this paper focuses on the parameters which determine the potency of mixing, such as viscosity, total solid content and digester design. Empirical data demonstrated by various researchers regarding rheological characteristics is compared and reviewed. Consequently, close attention should be paid toward the optimization of mixing in terms of its speed, mixing time and impeller geometry, especially during different stages of the digestion process (hydrolysis, acidogenesis, acetogenesis and methanogenesis). Finally, readers will be guided to the extensive publications regarding optimization, directions of future research, and troubleshooting of the mixing operation in an anaerobic digester. This investigation will help to improve mixing efficiency with biogas plants. HIGHLIGHTSEffect of shear rate on different stages of an anaerobic digestion process. Methane content varies with the variation in mixing speeds. Mixing effect is significant when the total solid content is higher. Intermittent mixing is favorable when compared to continuous mixing. The geometry of the digester and mixer is essential to evaluate digester mixing. ARTICLE HISTORY

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“…According to different authors, fermenting agricultural biomasses has been shown to have a rheofluidifying behavior characteristic of non-Newtonian fluids [33,[35][36][37]56] where viscosity decreases non-linearly under a shear stress. Conventional methods for measuring rheological properties are mostly performed with rotational or tubular rheometers in order to build a rheogram and, consequently, to identify the behavior fluid model [56].…”

Section: Rheological Propertiesmentioning

confidence: 99%

Methods for the Evaluation of Industrial Mechanical Pretreatments before Anaerobic Digesters

Fernandez¹,

Ramirez²,

Franco³

et al. 2020

Molecules

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Different methods were tested to evaluate the performance of a pretreatment before anaerobic digestion. Besides conventional biochemical parameters, such as the biochemical methane potential (BMP), the methane production rate, or the extent of solubilization of organic compounds, methods for physical characterization were also developed in the present work. Criteria, such as the particle size distribution, the water retention capacity, and the rheological properties, were thus measured. These methods were tested on samples taken in two full-scale digesters operating with cattle manure as a substrate and using hammer mills. The comparison of samples taken before and after the pretreatment unit showed no significant improvement in the methane potential. However, the methane production rate increased by 15% and 26% for the two hammer mills, respectively. A relevant improvement of the rheological properties was also observed. This feature is likely correlated with the average reduction in particle size during the pretreatment operation, but these results needs confirmation in a wider range of systems.

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Rheological characterization of raw and anaerobically digested cow slurry

Cited by 27 publications

References 24 publications

A Scale‐up Strategy for the Fluid Flow in Biogas Plants

A Scale‐up Strategy for the Fluid Flow in Biogas Plants

Impact of mixing intensity and duration on biogas production in an anaerobic digester: a review

Methods for the Evaluation of Industrial Mechanical Pretreatments before Anaerobic Digesters

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