CFD Simulations in Mechanically Stirred Tank and Flow Field Analysis: Application to the Wastewater (Sugarcane Vinasse) Anaerobic Digestion

Anaerobic digestion is a widely used process for waste treatment and energy production. This natural process takes place in a controlled environment, anaerobic digesters. Mixing is one of the main operating parameters. The understanding of the flows during the agitation of the medium is crucial for the optimization of the process yield. In fact, the mass and heat transfers are enhanced by the agitation. However, the complex biochemical reactions can be inhibited with overly vigorous agitation. A detailed and in-depth understanding of the phenomena occurring during agitation requires modeling studies. In this chapter, we propose a general approach, based on computational fluid mechanics (CFD), to analyze the mechanical mixing of an anaerobic reactor. We apply this work to the anaerobic digestion of the sugarcane vinasse, which is a liquid waste generated during the production of alcohol. The single-phase Reynolds-averaged Navier-Stokes (RANS) simulations of mechanical agitation of Newtonian fluids for different rotational speeds are presented. The equations system is closed with the standard k-epsilon turbulence model. The flow field is analyzed with the velocity profiles, the Q and Lambda2 fields, the pressure and the vorticity

Altered splicing of Tau in DM1 is different from the foetal splicing process

AbstractAmong the different mechanisms underlying the etiopathogenesis of myotonic dystrophy type 1 (DM1), a backward reprogramming to a foetal splicing machinery is an interesting hypothesis. To address this possibility, Tau splicing, which is regulated during development and modified in DM1, was analyzed. Indeed, a preferential expression of the foetal Tau isoform, instead of the six normally found, is observed in adult DM1 brains. By using two cell lines, we show here that the cis-regulating elements necessary to generate the unique foetal Tau isoform are dispensable to reproduce the trans-dominant effect induced by DM1 mutation on Tau exon 2 inclusion. Our results suggest that the mis-splicing of Tau in DM1 is resulting from a disease-associated mechanism

Innovation thérapeutique dans le cancer du colon (intérêt de deux prodrogues orales du 5-fluorouracile, capecitabine (xeloda®) et tegafur-uracile (UFT®))

CHATENAY M.-PARIS 11-BU Pharma. (920192101) / SudocSudocFranceF

A Review on the Rheological Behavior of Organic Waste for CFD Modeling of Flows in Anaerobic Reactors

International audienceAnaerobic digestion is a widely used process for organic waste treatment and renewable energy production. This is a complex natural biodegradation of organic matter involving four main biochemical reactions through the action of four microbial groups. The performances of anaerobic digestion (biodegradation and biogas production) depend on the contact between the biodegradable materials and the microorganisms. Consequently, hydrodynamics phenomena have a significant impact on the anaerobic digestion. Computational Fluid Dynamics (CFD) simulations allow to simulate the flow field within anaerobic digesters. In these models, the waste are characterized by their physical properties, specifically their rheological properties. Rheology consists in the study of the flow of liquids or viscous materials. In this respect, it involves the properties related to the flow behavior of liquids and the temporary and/or permanent deformation of materials. The knowledge on the rheological properties of the biowaste is crucial in order to describe the flows using CFD models. The aim of this review is to present the physical properties of different type of waste, as well as the rheological models. In conclusion, the rheological behaviors of wastewater, manure, and sludge are described in literature. However the rheological behaviors of a mix of biowaste and solid food waste are poorly known. Research should focus on the experimental measurements of these biowaste. These data are necessary for CFD modeling of flows in anaerobic reactors treating this type of waste

Start-Up Strategy and Process Performance of Semi-Continuous Anaerobic Digestion of Raw Sugarcane Vinasse

International audienceThe sugarcane distillery waste water is generated throughout the sugarcane molasses fermentation and distillation. In Reunion Island, a part of the vinasse production is treated by methanisation process. However, the remaining part is diluted then discharged into the sea. The aim of this work is to study the anaerobic treatment of sugar cane vinasse, with energy recovery. Nonetheless, vinasse pollutant load is difficult to treat. Regarding the experimentations, the biochemical potential (BMP) test is used for the determination of the methanogen potential. The BMP is then modelled with the modified Gompertz and the first order kinetic models. Furthermore, a laboratory study is carried out for studying the methane production of vinasse in semi-industrial scale over a period of 130 days. The start-up strategy of the 16 L pilot is proposed, in particular the gradual increase of organic load. The physico-chemical analysis of the medium is needed to prevent and explain the failure of the process. Indeed, the biogas production and physico-chemical measurements during the digestion are presented and discussed. The maximum methane yield of the BMP is 185 NLCH4kg−1COD, obtained with I/S ratio in terms of volatile solids of 0.7. The outcomes showed that the first-order kinetic and modified Gompertz models fit well with the BMP test curves. Concerning the pilot, the start-up period lasted 45 days the maximum specific production was 151.00 NLCH4kg−1COD (232.31 NLbiogaskg−1COD ). In further studies, different mixing strategies will be studied

ANAEROBIC DIGESTION OF VINASSE AND CFD MODELLING APPROACH CONTEXT AND OBJECTIVES OF THE WORK

International audienceThe study’s ultimate goal consists of modelling and optimising the co-digestion of particulate substrates like sewage sludge, biowaste and vinasse from sugar cane. Given these substrates, the medium is highly heterogeneous and has particular physical characteristics and behaviour. Moreover, anaerobic digestion could be lead in wet-mode or in dry-mode, thus we want to develop a model valid for both configurations. In this context, the fluid flow modelling is of interest. Indeed, the contact between substrates and microorganisms has a significant influence on the anaerobic digestion process. It is directly correlated to the flow inside the digester. The research question is therefore the following: Is it possible to predict the spread of microorganisms inside the digester for both liquid and solid digestion? In this paper, we present the context of the work and the mathematical model based on Navier-Stokes equations with the Boussinesq approximation. Large-eddy simulation (LES) is used for the turbulence modelling. The sliding mesh method is used to characterise the impeller rotation. In further work, we will present the simulation results validated with the literature data. The differential equations will be solved on OpenFOAM software using the finite volume method. The flow will be simulated for both Newtonian (vinasse) and non-Newtonian fluids (manure) and at different total solid (TS) rates for non-Newtonian fluids. The obtained results will be the velocity and temperature profiles within the digester. It will hence be possible to optimise the process through both the medium physical properties (TS rate and viscosity) and the digester configuration. We will also consider the multiphase flow. Alongside numerical simulations, experiments are carried out on the substrates studied in order to estimate the methane production. In this poster, we present the results of experiments on the vinasse and the development of the CFD model

Anaerobic digestion of vinasse and cfd modelling approach

International audienceThe study's ultimate goal consists of modelling and optimising the co-digestion of particulate substrates like sewage sludge, biowaste and vinasse from sugar cane. Given these substrates, the medium is highly heterogeneous and has particular physical characteristics and behaviour. Moreover, anaerobic digestion could be lead in wet-mode or in dry-mode, thus we want to develop a model valid for both configurations. In this context, the fluid flow modelling is of interest. Indeed, the contact between substrates and microorganisms has a significant influence on the anaerobic digestion process. It is directly correlated to the flow inside the digester. The research question is therefore the following: Is it possible to predict the spread of microorganisms inside the digester for both liquid and solid digestion? In this paper, we present the context of the work and the mathematical model based on Navier-Stokes equations with the Boussinesq approximation. Large-eddy simulation (LES) is used for the turbulence modelling. The sliding mesh method is used to characterise the impeller rotation. In further work, we will present the simulation results validated with the literature data. The differential equations will be solved on OpenFOAM software using the finite volume method. The flow will be simulated for both Newtonian (vinasse) and non-Newtonian fluids (manure) and at different total solid (TS) rates for non-Newtonian fluids. The obtained results will be the velocity and temperature profiles within the digester. It will hence be possible to optimise the process through both the medium physical properties (TS rate and viscosity) and the digester configuration. We will also consider the multiphase flow. Alongside numerical simulations, experiments are carried out on the substrates studied in order to estimate the methane production. In this article, we present the results of experiments on the vinasse and the development of the CFD model

Le télétravail dans les bibliothèques d\u27ESR

Comment le télétravail règlementé et régulier, hors contexte exceptionnel et hors contexte de crise, se déploie-t-il dans les bibliothèques de l’enseignement supérieur ? C’était l’objet de l’enquête conduite en janvier 2022 par la commission “Évolution des métiers et des compétences” de l’ADB

Kinetic study of anaerobic co-digestion, analysis and modelling

International audienceAnaerobic digestion in insular context can be a good way to treat organic wastes and to dispose of a clean and constant renewable energy. However, insular context implies that waste volumes can be not important enough to provide efficient stocks, so treating mixed wastes is important. In another hand, french regulations obliges big producers of biowaste (kitchen, supermarkets ...) to find a way to recycle the biowaste and can in certain cases prohibit the mixes of waste. This study presents the modelling of household waste biomethane potential measurements, as a mix of pure waste, and the modelling of the different phases of anaerobic digestion via first order and Gompertz models. Results are analyzed. The disintegration coefficients are then used in various model of anaerobic digestion for mixed wastes