Influence des bulles gazeuses et des préparations fermentatives complexes sur la viscosité des mélasses de betterave à sucre

La mélasse est le coproduit de la fabrication du sucre de canne ou de betterave et dont la composition varie en fonction des conditions climatiques de production de la matière première et du processus de fabrication mis en place par la sucrerie. Elle se présente sous la forme d’un liquide épais, homogène, de couleur marron. Sa forte viscosité limite sa fluidité et son transport dans les tuyauteries et l’abaissement de cette viscosité par réchauffage engendre des coûts élevés d’énergie. L’objectif de cette étude est la mise en oeuvre d’une méthodologie efficace permettant de diminuer la viscosité de la mélasse par l’usage des solutions liquéfiantes (ferments) sans toutefois augmenter la température. Cette diminution évitera à l’usine de dépenser énormément d’énergie pour baisser sa viscosité et faciliter sa fluidité dans les tuyauteries. Les travaux ont été réalisés en utilisant cinq (5) différentes préparations fermentatives liquides de masse volumique 1,2 g/ cm³ fabriquées dans une firme Danoise Novo-Nordisk et qui sont destinées à la transformation des produits céréaliers pour la production des boissons. Il s’agit notamment de : Ultraflo-L, Cereflo- 200L, Thermamyl-120L, Fungamyl-800L et Ceremix- 6 XL. A travers cette recherche, il a été utilisé une mélasse, de pureté 55% laquelle, dans 100 kg de matière sèche retient 55 kg de saccharose et 45 kg de matières organiques et non organiques. Cette mélasse a été ensuite intensivement mélangée à l’aide d’un malaxeur mécanique, et périodiquement par intervalle d’un quart d’heure, des échantillons ont été prélevés et dont la masse volumique a été mesurée. Il ressort des expériences que les masses volumiques de ces échantillons diminuent respectivement en passant de 1,360 à 1,320 ; 1,250 et 1,200 g/ cm³. A la température constante de 60 °C, maintenue à l’aide d’un ultra thermostat, la viscosité des échantillons a été mesurée. Les résultats obtenus ont montré que les viscosités finales de la mélasse de concentration 60% ont varié dans l’amplitude 10,5 à 15,3 m.Pa.s. Pour une thermo stabilité de la mêlasse avec un pH neutre des préparations fermentatives comme l’ultraflo- L et le cereflo -200L permettent de diminuer la viscosité de la mêlasse de 20-35%.© 2016 International Formulae Group. All rights reserved.Mots clés: Mélasses, betterave, viscosité, température, fermentsEnglish Title: Influence of gaz bubbles and complex fermentative preparation on the viscosity of the sugar beet molassesEnglish AbstractMolasses is the product of the manufacture of sugar cane or beet whose composition changes depending on the climatic conditions of de production of the raw materials and of the process of manufacture set up by the sugar refinery. It comes as a thick, homogenous, and brown liquid. Its fluidity is limited by its strong viscosity,  hence the high cost of energy needed for its conveyance in the pipes, caused by the diminution of that viscosity through reheating. The aim of this study is the implementation of an efficient methodology allowing to lowering the viscosity of the molasses by the use of liquefying solutions without, however, increasing the temperature. This diminution will enable the factory not to use a lot of energy to lower the viscosity so as to ease fluidity in the pipes. The works have been carried out by using five (5) different liquid fermentative preparations of 1.2 g/cm³ relative density made in a Danish Novo-Nordisk firm intended to the transformation of cereal products for the production of drinks. It is basically about: Ultraflo-L; Cereflo- 200L; Thermamyl- 120L; Ffungamyl-800L and Ceremix-6XL. In carrying out this scientific research, we have used the molasses of beet, of 55% purity, which in 100 g of dried matters retain 55 kg of sucrose and 45 kg of organic and inorganic matters. This molasses has been then intensively mixed with a mechanic mixer, and periodically, at 15mn intervals, samples have been taken the relative density of which has been measured. It follows from our experiences that the relative densities of theses samples diminishes respectively , passing from 1.360 to 1.320; 1.250 and 1.200 g/cm³. Densities of these samples taken respectively reduce from 1,360; 1,320; 1,250; 1,200 g/cm3. At constant temperature of 60 °C, Kept by an Ultra thermostat, the viscosity of samples have been measured. The results have shown that final viscosities of molasses of 60% concentration have varied from 10.5 to 15.3 m. Pa in terms of amplitude. Thus, the thermo stability of the molasses with a neutral pH and a weak dose of fermentative preparations, like the Ultraflo-L and Cereflo-200L, allow the reduction of the viscosity of molasses to 20-35%.© 2016 International Formulae Group. All rights reserved.Keywords: Molasses, beet, viscosity, temperature, ferment

The promotion of renewable energies: a sustainable answer to the energy problems of the rural households in Chad

peer reviewedLa promotion des énergies renouvelables est un thème d’actualité de par le monde. Chaque pays essaie d’apporter des solutions à son bilan énergétique compte tenu de ses paramètres dits de 3E (Énergie-Économie-Environnement). Cet article privilégie une approche scientifique en l’appliquant au contexte tchadien. Le but assigné à cet article est de mettre en exergue l’ampleur du patrimoine naturel tchadien en énergies renouvelables (biomasse, éolien, solaire, etc.) en le conciliant avec la nouvelle technologie afin de répondre aux besoins énergétiques des ménages n’ayant pas accès à l’énergie électrique. On abordera ce sujet avec une approche descriptive (état des lieux de la situation énergétique du Tchad, élaboration d’une carte des potentiels en énergies renouvelables, bilan environnemental, enquête réalisée sur des sites, etc.). L’article montre que le Tchad possède un potentiel renouvelable important, notamment le solaire et la biomasse auquel la population est favorable à son développement. L'exploitation de ce potentiel renouvelable nécessite un effort particulier de la part du gouvernement dans sa politique énergétique globale en matière d’investissements.Thèse de Doctorat en Science

Petrography and Geotechnical Characteristics of Aggregates from the Oyo and Mongo Massifs (Chad): Implications for the Construction of Structures

The present study focused on the petrography and geotechnics of aggregates of two sites around the city of Mongo for their use in construction. The study area is located in central Chad, in the Guéra province, at the eastern and north-western entrance to the city of Mongo. The area corresponds to a crystalline basement, and granitic massifs are abundant. Two deposits were studied: the Mongo massif, closest to the town of the same name, and the Oyo massif at the eastern exit of Mongo. The petrographic analysis showed that the studied materials are granites, light grey in color, composed of 30% quartz, 15% biotite, 20% feldspar, 30% plagioclase and 5% other minerals. From the geotechnical point of view, the materials of the Mongo site are more resistant to wear compared to those of Oyo which are less resistant. According to the results of micro-Deval and Los Angeles tests, the use of aggregates obtained from the Mongo site granites are usable in base courses for T1–T3 traffic admitting an axle of 8 to 10 tons and in surface dressings, contrary to those of Oyo, which are not favorable in road construction

Petrography and Geotechnical Characteristics of Aggregates from the Oyo and Mongo Massifs (Chad): Implications for the Construction of Structures

The present study focused on the petrography and geotechnics of aggregates of two sites around the city of Mongo for their use in construction. The study area is located in central Chad, in the Guéra province, at the eastern and north-western entrance to the city of Mongo. The area corresponds to a crystalline basement, and granitic massifs are abundant. Two deposits were studied: the Mongo massif, closest to the town of the same name, and the Oyo massif at the eastern exit of Mongo. The petrographic analysis showed that the studied materials are granites, light grey in color, composed of 30% quartz, 15% biotite, 20% feldspar, 30% plagioclase and 5% other minerals. From the geotechnical point of view, the materials of the Mongo site are more resistant to wear compared to those of Oyo which are less resistant. According to the results of micro-Deval and Los Angeles tests, the use of aggregates obtained from the Mongo site granites are usable in base courses for T1–T3 traffic admitting an axle of 8 to 10 tons and in surface dressings, contrary to those of Oyo, which are not favorable in road construction

Wind and solar assessment in the Sahelian Zone of Chad

Renewable energy sources have long been renowned as potential sources of free, clean and inexhaustible energy. However, energy in Chad is still exploited from non-renewable sources due to lack of comprehensive wind and solar maps, skills and public awareness pertaining to its significance in the country. This study is therefore set out to provide assessments of both wind and solar energies in the Sahelian zone in Chad, using the statistical twoparameter Weibull distribution function and Angstrom-Prescott model, respectively for a ten-year period. The evaluation of wind potential shows that the annual mean of the shape and scale parameters for all stations under study varied in the range of 1.26 – 1.56 and 2.49 m/s – 3.91 m/s, respectively. Stronger wind speed was observed during the dry season and a relatively slower wind speed was perceived during the wet season. Among the four stations, N’Djamena showed the highest power density compared to the other three stations with a mean power density that ranges between 100 W/m2 – 220 W/m2 . The prediction of solar potential in this region indicates that the global solar radiation for all stations is promising with station Abeche however, to show the highest solar energy density on average. A good agreement between Angstrom model and NASA data was also observed

Measurement of refraction index of thick and nontransparent isotropic material using transmission microwave ellipsometry

International audienceThis article introduces an original microwave ellipsometry method for the characterization of dielectric materials. It is a non-destructive technique based on the interaction between wave and material in the 26–40 GHz frequency range. The refraction index is obtained by measuring the rotation angle of the refracted wave polarization for different angular positions of the sample. The technique is then validated with polytetrafluoroethylene samples which refraction index is known

Caractéristiques des peuplements ligneux du tracé de la grande muraille verte des provinces de Wadi-Fira Est et de l’Ennedi Est du Tchad: Characteristics of the woody stands of the route of the great green wall of the provinces of Wadi-Fira East and Ennedi East of Tchad

Pour faire des propositions de stratégies de gestion durable de la grande muraille verte, la connaissance des caractéristiques du peuplement ligneux du tracé du Tchad est capitale. L’étude a pour objet de caractériser la flore et la végétation ligneuse sur le tracé de la GMV du Tchad, précisément au Wadi Fira Est et à l’Ennedi Est. La méthodologie utilisée a consisté à déterminer la composition floristique et la structure du peuplement ligneux dans les deux sites. Les inventaires floristiques ont permis de recenser 8 espèces reparties en 7 genres et 4 familles dans le site de Wadi Fira Est tandis que dans le site de l’Ennedi Est nous avons recensé 7 espèces reparties en 6 genres et 4 familles. La flore ligneuse est dominée par les Mimosaceae. La densité des ligneux (39,43 ind.ha-1) est plus importante dans l’Ennedi Est que dans le Wadi Fira Est (36,62 ind.ha-1) ; Cependant, le recouvrement au Wafi Fira Est (559,428 m².ha-1) est plus important que celui de l’Ennedi Est (499,844 m².ha-1). Les résultats obtenus montrent que les espèces les plus adaptées aux conditions écologiques pour la réussite de la GMV sont Acacia raddiana et Balanites aegyptiaca qui conviennent pour la restauration de ces écosystèmes. To make proposals for sustainable management strategies for the Great Green Wall, knowledge of the characteristics of the woody population along the Chad route is essential. The purpose of the study is to characterize the flora and woody vegetation along the route of the GGW of Chad, specifically in Wadi Fira East and Ennedi East. The methodology used consisted in determining the floristic composition and the structure of the woody stand in the two sites. Floristic inventories made it possible to identify 8 species divided into 7 genera and 4 families in the Wadi Fira East site while in the Ennedi East site we have identified 7 species divided into 6 genera and 4 families. The woody flora is dominated by Mimosaceae. The density of woody plants (39.43 ind.ha-1) is higher in Ennedi East than in Wadi Fira East (36.62 ind.ha-1); However, the overlap at Wafi Fira East (559.428 m².ha-1) is greater than that at Ennedi East (499.844 m².ha-1). The results obtained show that the species most suited to ecological conditions for the success of GMV are Acacia raddiana and Balanites aegyptiaca which are suitable for the restoration of these ecosystems

Comparative Analysis of Hybrid Renewable Energy Systems for Off-Grid Applications in Chad

In this study, a techno-economic feasibility analysis of hybrid renewable energy systems for four household categories in rural areas of Chad was studied based on the multi-criteria assessment technique. The problem of this study is to know the best optimal solution in the technical and economic feasibility study of the decentralized mini-grids for the rural electrification of isolated villages in Chad. The main objective of the work is to assess technically, economically and environmentally the feasibility of six scenarios of hybrid systems in five isolated sites in Chad. The performance analysis involved six scenarios of possible hybrid solutions while achieving a supply-demand balance for sustainable electrification of the remote villages, using the HOMER software. The results have shown that the optimum combination of the hybrid system was the photovoltaic/battery system with a Net Present Cost (NPC) of US $328,146 and it was found at Etena village. The photovoltaic/Wind/Diesel/Battery hybrid configuration was the least optimum system and it has appeared in Mandelia village. In terms of energy cost, the lowest Levelized Cost of Energy (LCOE) was estimated at US$ 0.236/kWh in a photovoltaic/Wind/Battery configuration at Koundoul site and the highest costs US $ 0.363/kWh in the photovoltaic/Battery configuration at the Linia site. It is established that hybrid solutions can be developed to make electricity available and accessible to the population of the remote rural areas in Chad. However, it is imperative that the local government must subsidize the diesel price to promote the adaptation of the abundant renewable solutions

Techno-economic feasibility of a remote PV minigrid electrification system for five localities in Chad

This study presents a techno-economic analysis of a mini-grid solar photovoltaic system for five typical rural communities in Chad while promoting renewable energy systems adaptation and rural electrifica�tion. The assessment techniques include the establishment of the socio-economic state of the rural communities through a field survey. The costs of system development, electricity tariff and sizing of energy production are realised via the Levelized Cost of Electricity (LCOE) technique. Sensitivity analysis was carried out to identify the parameters that affect the evolution of the LCOE during the life cycle of the project. The results have shown that the annual energy production at all sites varies between 233 MWh/ year and 3585 MWh/year. The highest amount of energy production is estimated at Guelendeng at a rate of 3218 MWh/year and a capacity of 2041 kW, while the lowest is predicted at Mombou at a rate of 211 MWh/year and a capacity of 134 kW. The standard LCOE for the system during the 25-year lifespan in the five villages is estimated at 0.30 €/kWh except at Mailo which was 0.31 €/kWh. This cost per kilowatt-hour is more attractive and competitive compared with the current rate charged by the national electricity company