Développement d'un simulateur de terres agricoles et de politiques pour promouvoir des politiques climato-intelligentes

International audienceFeeding 1.5 billion people by 2030, and 2 billion by 2050, while mitigating and adapting to climate change, is a daunting challenge that countries in Africa are attempting to address. In this paper we report in a project between Mohammed VI Polytechnic University (UM6P) and Climate Interactive (CI). Our tool, the Agriculture and Land Policy Simulator (ALPS) helps policy-makers and stakeholders make climate-smart decisions in their agriculture strategies. ALPS models the intersections among land, agriculture, and climate. We base our work on the Climate Smart Agriculture (CSA) concept, the three pillars of which are: food security, resilience to climate changes, and mitigation of emissions. Using System Dynamics, a multidisciplinary team of agronomists, agricultural economists, and system dynamics developed the causal relationships. We refined system structure and formulations based on discussion with experts, existing research, and analysis of strategic policy documents. The model parameters are set to fit historical data from a variety of sources. In this paper we present the Moroccan case of ALPS, incorporating significant improvements over prior work and fitted to the Morocco policy context. The Green Morocco Plan (known by the French acronym PMV) is specifically used for simulation and modeling exercise. The simulator allows the user to test assumptions and scenarios through varying levels on different policy components. ALPS has previously been used to simulate the Ethiopian context, and future development will improve both these cases and will be extended to cover several African countries. The causal loop below summarizes all interactions between the model variables that interlink agriculture sectors. Food Demand increases with population and living standards. The user makes choices to ensure Food Available-Production and Imports less Losses and Exports-can meet demand. Land use can change between five categories-Cropland, Pasture, Forest, Grassland, and Dessert. The availability and need for irrigation depends on rainfall and infrastructure. These physical limits enforce the constraints the agriculture system faces. Action to meet food demand also create undesirable consequences. Countries have goals such as reducing greenhouse gas emissions and deforestation. ALPS includes direct emissions from crop and livestock farming, as well as emissions from land-use changes and the stocks of carbon sequestered in soil and biomass. These help the user see the impact on other goals when meeting food needs

Intensification of phosphate fertilizers granulator using CFD: transition phenomenon investigation FuturE work & perspectives

International audienc

Modélisation et simulation CFD des écoulements complexes dans le procédé de production des engrais phosphatés : Unités de preneutralisation et de granulation

Mathematical modelling and numerical simulations are widely used in many chemical industries, such as petrochemical industry. Its used for operator training, design, and process optimization.However, there is a lack of rigorous numerical modeling and simulations in the phosphatefertilizer industry. There exist many challenges in the production systems of phosphatefertilizers including; multiple phases in the system such as liquids, solids and gas, particleswith different sizes and distributions, and variation in the physical properties including rheologyand thermodynamics properties. Despite the available resources, limited studies have beenfocused on the understanding of the hydrodynamics within the components of the manufacturing process, to enhance the production yield and to adapt the manufacturing process conditions to the quality of raw materials. Computational Fluid Dynamics (CFD) represents a valuable tool to validate phenomenological models and allows an exhaustive understanding of process sensitivity to operating conditions, and geometrical details effects on the flow hydrodynamics. Furthermore, CFD permits a better understanding of physical phenomena, as exchange mechanisms occurring in the studied processes, which is not possible on the industrial plant or by laboratory scale experiments that require many considerations for the scale up. The aim of this thesis is to i) investigate the fluid dynamics of the master pieces in Di Ammonium Phosphate fertilizer process, which are the preneutralization and the granulation unit operations, using commercial simulation software Ansys Fluent, ii) to identify the effects of the complex phenomena in the formation of heterogeneities of the multiphase flows, and iii) to evaluate the effect of the operating conditions on the flows hydrodynamics. On the light of the obtained results, we aim to optimize the design and control of the preneutralization and granulation units and propose new recommendations for a better process performance.This research work is composed of two different studies; on the one hand, the three-dimensional modeling and simulation of the preneutralizer reactor, based on the Euler-Euler multiphase approach, and theMultiple Reference Frame (MRF) is applied to consider the rotational movement of the agitator. The tailored gas-liquid CFD model accounts for the transfer mechanisms and chemical species exchange between phases. The finite rate turbulence chemistry interaction model is adopted to demonstrate the strong relation between turbulence and chemistry in reacting turbulent flows. We evaluated the baffles effect on the fluid dynamics in a simplified preneutralizer model, we studied the sensitivity of the reacting flow hydrodynamics to the operating conditions, and we conducted a geometrical optimization study, giving birth to a new preneutralizer design, with optimal gas spargers type and positions. On the other hand, a rotary drum granulator CFD model is tailored. Gas-solid flow is numerically simulated using the Euler-Euler approach, coupled to the Kinetic Theory of Granular Flow (KTGF). The effect of fertilizer particles size on their dynamics is evaluated. We studied the CFD granulation model sensitivity to the drag model subcomponent of the CFD model, and to the key operating conditions.In light of the present study, new operating conditions combinations are proposed for theindustrial plant to validate further by an experimental campaign. All the conducted simulationsare fully three dimensional with the industrial scale dimensions.La modélisation mathématique et la simulation numérique sont largement utilisées dans les industries chimiques, en occurence dans la pétrochimie, pour la formation des opérateurs, la conception et l’optimisation des procédés. Cependant, il y a un manque des travaux de modélisation et de simulations numériques rigoureuses dans l’industrie des engrais phosphatés. Il existe de nombreux défis dans les systèmes de production d’engrais phosphatés, notamment les systèmes multiphasiques, telles que les liquides, les solides et le gaz, les particules de différentes tailles et distributions, et la variation des propriétés physiques, y compris la rhéologie et la thermodynamique.Malgré les ressources disponibles, peu d’études ont été consacrées à la compréhensionde l’hydrodynamique au sein des lignes de production des engrais, afin d’augmenter le rendement de la production et d’adapter les conditions opératoires du procédé, de production à la qualité des matières premières. La dynamique des fluides numérique (CFD) représente un outil incountournable pour validerdes modèles rigoureux et permettre une compréhension exhaustive de la sensibilité du procédéaux conditions de fonctionnement, et des effets des détails géométriques sur l’hydrodynamiquede l’écoulement. De plus, la CFD permet une meilleure compréhension des phénomènes physiques, des mécanismes d’échange qui ont lieu dans les procédés étudiés, ce qui est casément pas possible par des expériences et dans les installations industrielles réelles ou pilote. C’est un outil efficace pour le scale up et pour l’optimisation des conditions de fonctionnement des unités chimiques. L’objectif de cette thèse est d’étudier la dynamique des fluides dans des pièces maîtresses duprocédé de production des engrais Di-Ammonium Phosphate: la preneutralisation et la granulation, n utilisant le logiciel commercial de simulation Ansys Fluent, en identifiant l’effetdes phénomènes complexes dans la formation d’hétérogénéités des flux multiphasiques, et enévaluant l’effet des conditions opératoires sur l’hydrodynamique des écoulements. De plus, à la lumière des résultats obtenus, optimiser la conception et le contrôle des unités de preneutralisation et de granulation et proposer de nouvelles recommandations pour une meilleure production.Ce travail de recherche est composé de deux études différentes; d’une part, la modélisation etla simulation tridimensionnelles du réacteur de preneutralisation, basées sur l’approche Euler-Euler multiphasique, et l’approche à référence multiple (MRF) qui est appliquée pour considérerle mouvement de rotation de l’agitateur. Le modèle CFD gaz-liquide adapté considèreles mécanismes de transfert et les échanges d’espèces chimiques entre les phases. Le modèled’interaction turbulence-chimie à taux fini est adopté pour montrer la relation forte entre laturbulence et la chimie dans les écoulements turbulents réactifs. Nous avons évalué l’effet deschicanes sur la dynamique des fluides dans le preneutralisateur simplifié, et nous avons étudié la sensibilité de l’hydrodynamique de l’écoulement réactif aux conditions de fonctionnement. Nous avons mené une étude d’optimisation géométrique, conduisant à un nouveau design de preneutralisateur, avec un type et des positions optimales des injecteurs de gaz.D’autre part, un modèle CFD de granulateur à tambour rotatif est développé. L’écoulementgaz-solide est simulé numériquement en utilisant l’approche Euler-Euler, couplée à la théoriecinétique des écoulements granulaires (KTGF). L’effet de la taille des particules d’engrais surleur dynamique est évalué. Nous avons étudié la sensibilité de la granulation au modèle detraînée, dans le developement d’un modèle CFD, et aux conditions de fonctionnement clès decette opération unitaire. A la lumière de la présente étude, de nouvelles combinaisons des conditions opératoires sont proposées pour l’installation industrielle afin de les valider par unecampagne expérimentale.Toutes les simulations effectuées sont réalisées en 3D, en respectant les dimensions à l’échelleindustrielle

In Silico CFD Investigation of the Granulation Hydrodynamics in Rotating Drum: Process Sensitivity to the Operating Parameters and Drag Models

Computational fluid dynamics (CFD) have been extensively used to simulate the hydrodynamics of multiphase flows (MPFs) in rotating machinery. In the presence of a granular dense phase, the Kinetic Theory of Granular Flow (KTGF) is usually coupled to Eulerian multi-fluid models to obtain tractable computational fluid models. In the present work, the hydrodynamic behavior of a three dimensional, industrial scale, and rotating drum granulator with gas–solid flows is assessed using the Eulerian–Eulerian approach coupled with the k-ε standard turbulence model. A Eulerian–Eulerian Two-Fluid Model (TFM) is used with the KTGF model for the granular phase. The sensitivities to different operating parameters, including the rotational speed (8, 16, and 24 rpm), inclination degree (3.57∘, 5.57∘, and 7.57∘), and degree of filling (20%, 30%, and 40%) are studied. Moreover, the impact of the drag model on the simulation accuracy is investigated. The flow behavior, regime transitions, and particle distribution are numerically evaluated, while varying the operating conditions and the drag models. The rotational speed and filling degree appear to have greater influences on the granulation effectiveness than on the inclination degree. Three drag models are retained in our analysis. Both the Gidaspow and Wen and Yu models successfully predict the two-phase flow in comparison to the Syamlal and O’Brien model, which seems to underestimate the hydrodynamics of the flow in both its axial and radial distributions (a fill level less than 35%). The methodology followed in the current work lays the first stone for the optimization of the phosphates fertilizer wet-granulation process within an industrial installation