Valorisation énergétique des résidus agricoles

Le projet VERA a pour ambition d’optimiser et de valider par des tests un procédé intégré de valorisation énergétique de déchets agricoles et notamment des grignons d’olive. Le procédé global comporte i) la phase de préparation des résidus pour la combustion, et notamment de séchage des grignons en utilisant l’énergie solaire thermique ; ii) leur combustion dans un système approprié pour la production de la chaleur ; iii) l’utilisation de la chaleur pour la production de vapeur d’eau et éventuellement de l’électricité. Les deux premières phases de ce procédé seront étudiées dans le présent projet ; pour la dernière phase, seules des études d’optimisation seront effectuées pour déterminer les conditions optimales de valorisation énergétique de la chaleur de combustion, notamment pour sa transformation en électricité. Le travail soumis reprend les résultats préliminaires de deux tâches : 1) L’étude du processus de séchage des grignons par énergie solaire. Les vitesses de séchage étudiées ont été déterminées, grâce à la méthode de dérivation de la courbe de perte de masse en fonction du temps. Quant à la courbe caractéristique de séchage, elle est déterminée avec une approximation polynômiale de degré 3. Les résultats obtenus notent une faible dispersion de la majorité des courbes caractéristiques calculées autour de la courbe moyenne, et montrent que la capacité évaporatoire dépend linéairement du flux massique, ce qui indique qu’une partie essentielle de séchage est contrôlée par des limitations extragranulaires. 2) La modélisation en vue de déterminer les conditions optimales d’utilisation des résidus d’extraction d’huile d’olive dans des brûleurs et chaudières spécifiques et surtout dans leur environnement humain. Elle considère un système à lit fluidisé pour la combustion des grignons et cherche à déterminer les performances d’un tel système. Leur traitement après extraction de l’huile dans les presses artisanales et en particulier leur degré de séchage (entre 25 % et 35 % d’humidité) peut influer de manière importante sur les processus de fluidisation/défluidisation du combustible. Son pouvoir calorifique Inférieure (PCI) varie aussi selon son taux d’humidité résiduel (sensible à la méthode d’extraction) et de sa taille après le broyage

Moisture Sorption Isotherms And Thermodynamic Properties Of Urtica Dioica Leaves

Urtica dioica is a Moroccon endemic plant of used for its virtues in traditional medicine. Thus, it is necessary to study the effect of preservation processes on the storage conditions of the plant. The static gravimetric method was used to determine sorption isotherms of Urtica dioica leaves at three temperatures (40, 50 and 60 °C) and in the range of water activity ( w a ) ranging from 0.0572 to 0.898. Six mathematical models were used to fit the experimental data. The Enderby and Peleg models were found to be the most suitable for describing the sorption curves. The optimal water activity for conservation of Urtica dioica leaves was determined. Isosteric heats of desorption and adsorption were calculated by applying the Clausius- Clapeyron equation to the sorption isotherms at different temperatures; it decreased with increasing moisture content. A linear relation exists between the enthalpy and entropy of the sorption reaction

Thermodynamic Analysis of Moisture Adsorption of Taraxacum Officinale’ Powder

This work aims to model the adsorption isotherms and study the essential thermodynamic properties of Taraxacum Officinale’ powder during the moisture adsorption phenomenon at three temperatures 30, 40, and 50°C. The results have been determined by the application of the thermodynamics physical principles to the equilibrium data, which are experimentally measured. The estimated values of the isokinetic and harmonic temperatures and the Gibbs free energy change revealed that the sorption process is non-spontaneous and enthalpy driven

Thermodynamic Analysis and Mathematic Modeling of Waste Sludge from Drinking Water Treatment Plants

Water treatment annually produces a huge amount of Drinking Water Treatment Sludge (DWTS) wastes. The latter causes environmental problems in Morocco in terms of energy and pollution. Therefore, cost-effective and eco-friendly solutions for managing them should be proposed in order to reduce the frequency of storage along with transportation costs. In this paper, a thermodynamic analysis of DWTS wastes was conducted based on the isosteric heat and compensation theory. Different results concerning the mineralogical identification of sludges were established. Findings revealed that the by-product of water purification was mainly composed of aluminum, silica and iron hydroxides, with pH varying between 6.23 and 6.85. The suspended matter was between 18.3 and 19.6 m/l. The volatile matter of the three sludge samples was between 18 and 21%. The measured dry matter content was between 13.41 and 15.23%. The experimental tests were performed under temperatures from 45 and 60 °C, the experimental data of the sorption curves were fitted by using several models of correlation. Furthermore, the analysis showed that the Peleg’s model perfectly described the isotherm curves in the activities ranging from 0 to 90%. The net isosteric heats of sorption of the three hydroxide sludge from the Moroccan treatment station: $S_k$, $S_m$ and $S_s$, were determined for desorption and adsorption. Moreover, it was revealed that the equilibrium water content rising lead contributed to the reduction of the net isosteric heat and the entropy of sorption. Finally, the enthalpy-entropy compensation showed that the sorption mechanism involved was enthalpy driven

Comportement rhéologique et caractérisation des boues de traitement d'eau potable du Maroc

peer reviewedDrinking water treatment generates a high amount of pasty by-product known as drinking water treatment sludge (DWTS). The chemical composition, microstructure and rheological behavior of DWTS are of utmost importance in the calculation, design, optimization, commissioning and control of its treatment processes. The purpose of this research was to characterize the DWTS from the drinking water treatment plant of Marrakech (Morocco), aiming to help future researchers and engineers in predicting its hydrodynamic behavior. The first part of this study was devoted to the physical structure and the chemical composition of sludge. The second part was oriented towards the study of the mechanical properties; a penetration test and a rotational rheology test were performed. For the first test, a force–length penetration diagram was plotted in order to calculate the hardness, the cohesiveness and the adhesiveness of DWTS. For the second test, the shear stress and the apparent viscosity were plotted and fitted to five rheological models, as function of the shear rate, aiming to describe the rheological behavior of samples. The obtained results reveal that the drinking water treatment sludge from Marrakech is a porous, amorphous and highly adhesive material, with a shear-thinning (pseudoplastic) rheological behavior that can be described according to the Herschel–Bulkley model (better in low-rate stresses, R² = 0.98) or the Windhad model (better in high shear rates, R² = 0.96) and is mainly composed of silica, aluminum and iron oxides.T.0159.20-PD

Experimental and Numerical Investigations on Conductive Drying of Phosphate Washing Waste Clay

Morocco is the leading producer of phosphate and its derivatives in the world with a total production of 35 Mt. However, the extraction and the valorization of this mine generate huge quantities of phosphate washing waste clay (PHWWC) that constitute a main environmental and economic concern. To facilitate this waste clay storage and handling, it is necessary to decrease its moisture content that represents 80% of PHWWC. The present paper is devoted to studying the conductive drying of PHWWC. Drying experiments were conducted in a laboratory pilot. Afterwards, the experiment results were implemented in a one-dimensional numerical model of heat and mass transfer in a porous media to identify the drying parameters and performances. It was found that most of the water contained in PHWWC is free water that is removed with a constant drying rate. The volume reduction with a marked cracks phenomenon attained 65% without any significant effect of drying temperature and sample thickness. The effective moisture diffusivity of the PHWWC for a conductive drying process is ranged between 10−9 and 1.1 × 10−8 m2·s−1. The thermal efficiency of the drying system is up to 86%. The results could be used for the purpose of design and scale-up of the industrial dryer based on laboratory-scale experiments