References of "Fraikin, Laurent"
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See detailAnalysis of shrinkage effect on mass transfer during the convective drying of sawdust/sludge mixtures
Li, Jie; Bennamoun, Lyes; Fraikin, Laurent ULg et al

in Drying Technology (in press)

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See detailInvestigation on Convective Drying of Mixtures of Sewage Sludge and Sawdust in a Fixed Bed
Li, Jie ULg; Fraikin, Laurent ULg; Salmon, Thierry ULg et al

in Drying Technology (2014)

This work is a part of a project aiming at developing a renewable fuel for gasification purposes, through convective drying of sludge/wood mixtures. The first step consists of characterizing the behavior ... [more ▼]

This work is a part of a project aiming at developing a renewable fuel for gasification purposes, through convective drying of sludge/wood mixtures. The first step consists of characterizing the behavior of sawdust/sludge mixtures during the application of convective drying. The influence of the mixing step (no mixing against 30 s at 40 rpm), as well as the sawdust/sludge ratio (1/9, 2/8, 3/7 and 4/6 on a dry basis) and the effect of the drying temperature (50 °C, 80 °C and 110 °C) have been investigated. In this study, X-ray tomography, a non-invasive imaging technique, is used to assess changes in the volume, void and exchange surface at the beginning and the end of the drying process. Results first confirm the importance of the mixing step on the drying behavior: the drying rate of the mixed sludge is lower than that of the original sludge. Nevertheless the addition of sawdust is shown to have a positive impact on the drying process from a mass ratio of 2/8, with drying rates higher than that of the original sludge. With increasing amount of sawdust, the initial and final bed volumes, initial and final total exchange surfaces, and initial void fraction increase linearly, but the bed volume shrinkage and final void fraction decrease linearly. [less ▲]

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See detailConvective drying of sawdust/sludge mixtures in a fixed bed: The effect of sludge origin
Li, Jie ULg; Fraikin, Laurent ULg; Salmon, Thierry ULg et al

Scientific conference (2014, August 26)

Sludges collected from Oupeye WWTP (MS=80%), Grosses Battes WWTP (MS=85.5%), and Embourg WWTP (MS=88%) in Belgium and presenting different properties were used. The influence of the sawdust/sludge ratio ... [more ▼]

Sludges collected from Oupeye WWTP (MS=80%), Grosses Battes WWTP (MS=85.5%), and Embourg WWTP (MS=88%) in Belgium and presenting different properties were used. The influence of the sawdust/sludge ratio on convective drying was investigated in a fixed bed. X-ray tomography was used to assess changes in volume, exchange surface and void fraction. Results showed that the average drying rates were 0.062 (Oupeye), 0.079 g/s (Grosses Battes) and 0.042 g/s (Embourg) respectively, using raw sludges. For sawdust/sludge mixtures with the mass ratio of 4/6, the average drying rates of sludges were improved (Oupeye: 0.092 g/s, Grosses Battes: 0.106 g/s, Embourg: 0.049 g/s). [less ▲]

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See detailConvective drying behavior of sawdust/sludge mixtures in a fixed bed
Li, Jie ULg; Fraikin, Laurent ULg; Salmon, Thierry ULg et al

Scientific conference (2014, May 27)

This work is part of a project aiming at developing a renewable fuel for gasification purposes, through the convective drying of sludge/wood mixtures. The first step consists in characterizing the drying ... [more ▼]

This work is part of a project aiming at developing a renewable fuel for gasification purposes, through the convective drying of sludge/wood mixtures. The first step consists in characterizing the drying behaviour of sludge/sawdust mixtures, in a convective fixed bed dryer. The influence of the mixing step (no mixing against 30 s at 40 rpm) and the sawdust/sludge ratio (1/9, 2/8, 3/7 and 4/6 on a dry basis) was investigated. X-ray tomography, a non-invasive imaging technique, was used to assess changes in volume and exchange surface during drying. The sawdust addition was shown to have a positive impact on the drying process from mass ratio of 2/8. Results showed that the volume and exchange surface increased with higher sawdust addition during the whole drying process. Moreover, a linear decrease of the exchange surface is observed with sludge, while a plateau is reached after a linear phase for sludge/sawdust mixtures. As expected, the drying rate of sludges or sludge/sawdust mixtures decreased nearly linearly with the exchange surface. For sawdust/sludge mixtures, the drying rate continued to decrease after the end of shrinkage, due to internal transfer limitations. These promising results open the way to new valorisation ways, especially for very pasty sludge. [less ▲]

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See detailAnalysis of the Shrinkage Effect on Mass Transfer During Convective Drying of Sawdust/Sludge Mixtures
Li, Jie ULg; Bennamoun, Lyes; Fraikin, Laurent ULg et al

in Drying Technology (2014), 32

Convective drying of wastewater sludges and sawdust/sludge mixtures was studied. The first part of this work was an experimental study performed in a cross-flow convective dryer using 500 g of wet ... [more ▼]

Convective drying of wastewater sludges and sawdust/sludge mixtures was studied. The first part of this work was an experimental study performed in a cross-flow convective dryer using 500 g of wet material extruded through a disk with circular dies of 12 mm. The results showed that the sawdust addition has a positive impact on the drying process from a mass ratio of 2/8, on a dry basis, with observed drying rates higher than the original sludge. The second part of this work consisted of developing a drying model in order to identify the internal diffusion coefficient and convective mass transfer coefficient from the experimental data. A comparison was made between fitted drying curves, well represented by the Newton’s model, and the analytical solutions of the diffusion equation applied to a finite cylinder. Variations of dimensional characteristics such as the volume and exchange surface of the sample bed were obtained by X-ray tomography. This technique allowed confirm that shrinkage, which is an important phenomenon occurring during sludge and sawdust/mixture drying, must be taken into account. The results showed that both the internal diffusion coefficient and convective mass transfer coefficient were affected by mixing and sawdust addition. The internal diffusion coefficient changed from 7.77×10-9 m2/s for the original sludge to 7.01×10-9 m2/s for the mixed sludge and then increased to 8.35×10-9 m2/s for the mixture of a mass ratio of 4/6. The convective mass transfer coefficient changed from 9.70×10-8 m/s for the original sludge to 8.67×10-8 m/s for the mixed sludge and then increased to 12.09×10-8 m/s for the mixture of a mass ratio of 4/6. These results confirmed that sawdust addition was beneficial to the sludge drying process as the mass transfer efficiency between the air and material increased. Reinforcing the texture of sludge by adding sawdust can increase the drying rate and decrease the drying time, and then the heat energy supply will be reduced significantly. The study also showed that neglecting shrinkage phenomenon resulted in an overestimation for the internal diffusion coefficient for the convective drying of sludges and sawdust/sludge mixtures. [less ▲]

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See detailExperimental arguments concerning a hydraulic connection layer during limestone convective drying
Prime, Noémie ULg; Housni, Z.; Fraikin, Laurent ULg et al

in Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 (2014)

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See detailModeling and Simulation of Heat and Mass Transfer During Convective Drying of Wastewater Sludge with Introduction of Shrinkage Phenomena
Bennamoun, Lyes ULg; Fraikin, Laurent ULg; Léonard, Angélique ULg

in Drying Technology (2014), 32(1), 13-22

Wastewater sludge is dried in a convective dryer using air temperatures varying from 80°C to 200°C, velocities changing from 1 m · s−1 to 2 m · s−1, and humidities ranging from . The convective dryer is ... [more ▼]

Wastewater sludge is dried in a convective dryer using air temperatures varying from 80°C to 200°C, velocities changing from 1 m · s−1 to 2 m · s−1, and humidities ranging from . The convective dryer is equipped with a camera and an infrared pyrometer to follow respectively the external surface and the temperature of the product. The experimental results show that drying kinetic can be divided into three phases: two short first phases, called adaptation and constant drying phases, and a long third phase, called falling drying rate phase. As the moisture content decreases, the camera confirms simultaneous shrinkage effect with the volume reduction of the product of about 30–45% of the initial volume. Moreover, an increase of the product temperature towards air temperature was measured with the infrared pyrometer. In a second step of this study, the experimental results are modeled and simulated using heat and mass balances applied to the product and the heated air. The drying curve is rightly expressed with fourth-degree polynomial model with a correlation coefficient that approximates the unity and with low calculated errors. An outstanding determination of the heat transfer coefficient has permitted calculating the product temperature with good agreement with experimental results. The heat transfer coefficient expressed by means of Nusselt number is presented as a function of Reynolds and Prandlt numbers, changeable with air and product characteristics taking into account shrinkage effect. Moreover, as the applied air temperatures are sufficiently high, transfer by radiation is not neglected and is introduced in the mathematical model. [less ▲]

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See detailModeling of Wastewater Sludge Drying with Determination of Diffusivity Moisture
Bennamoun, Lyes ULg; Fraikin, Laurent ULg; Salmon, Thierry ULg et al

in Journal of Residuals Science and Technology [=JRST] (2013), 10(4), 165

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See detailConvective Drying of Mixtures of Sewage Sludge and Sawdust in a Fixed Bed
Li, Jie ULg; Fraikin, Laurent ULg; Salmon, Thierry ULg et al

Conference (2013, October 04)

This work is part of a project aiming at developing a renewable fuel for gasification purposes, through the convective drying of sludge/wood mixtures. The first step consists in characterizing the drying ... [more ▼]

This work is part of a project aiming at developing a renewable fuel for gasification purposes, through the convective drying of sludge/wood mixtures. The first step consists in characterizing the drying behaviour of sludge/sawdust mixtures, in a convective fixed bed dryer. In particular, the influence of the mixing step (no mixing against 30 s at 40 rpm) and the sawdust/sludge ratio (1/9, 2/8, 3/7 and 4/6 on a dry basis) have been investigated, as well as the drying temperature (50 °C, 80 °C and 110 °C). As showed in a previous work, the addition of dry matter into sludge has an impact on the initial 3D structure of the bed of extrudates to be dried. Moreover, it is well known that the volume shrinkage occurring during sludge drying will affect the drying velocity. In this study, X-ray tomography, a non-invasive imaging technique, is used to assess changes in volume, porosity and exchange surface between the beginning and the end of the drying process. Results first confirm the importance of the mixing step on the drying behaviour: the drying rate of the mixed sludge is slower than the one of original sludge. Nevertheless the addition of sawdust is shown to have a positive impact on the drying process from mass ratio of 2/8, with observed drying rates higher than for the original sludge. During the whole drying process, the volume and exchange surface of the sample increase and the porosity decreases as the mass ratio increases. These results indicate that the air and the sample contact more fully with more sawdust addition, resulting from bed expansion and exchange surface increase. Hence, the heat and mass transfer efficiency between the air and the material increases and consequently the drying rate. Further work will be done in order to assess the impact of the drying temperature and to characterize the behaviour of these samples during pyrolysis using thermo gravimetric analysis. [less ▲]

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See detailImpact of sludge storage duration on its dewatering and drying ability
Pambou, Yvon-Bert; Salmon, Thierry ULg; Fraikin, Laurent ULg et al

Poster (2013, October)

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See detailDifferent phases of water transfer during rock drying
Prime, Noémie ULg; Housni, Zakarya; Fraikin, Laurent ULg et al

Conference (2013, September 10)

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See detailHeat and mass transfer coefficient analysis during rock convective drying
Prime, Noémie ULg; Housni, Zakarya; Fraikin, Laurent ULg et al

Conference (2013, August)

This paper presents some experimental investigations about convective drying of rocks. Cylindrical samples made of limestone are dried from one their bases submitted to an air flow, while the other ... [more ▼]

This paper presents some experimental investigations about convective drying of rocks. Cylindrical samples made of limestone are dried from one their bases submitted to an air flow, while the other surfaces are hermetically covered. All other factors being equal, the influence of two parameters is looked after: the cylinder height, equivalent to the volume/surface ratio of the samples, and the direction of the air flow. The tests are interpreted both from the drying curves and from the values of water and heat transfer coefficients. Results first highlight that air flow incidence on the dried surface changes the kinetics and the transfer coefficient values. It can thus be supposed that the air flow direction would modify the thickness of the transfer limit layer at the surface and/or would make invalid the hypothesis of such a limit layer model for some flow configurations. Besides, the volume/surface ratio is shown to be correlated to the evaporation flux on the constant drying phase, and thus to the transfer coefficients. Nonetheless, this link tends to disappear from sufficiently high values of the volume/surface ratio since, in this case, the transfer coefficients reach constant values. This effect, in addition to other observations made on the drying curves, well fits with the hypothesis of a hydraulically connected layer below the drying surface, which would maintain during the constant drying rate phase. In the present case, this layer would have a thickness of around 20 to 30 mm. [less ▲]

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See detailDetermination of Moisture Diffusivity During Drying of Mortar Cement: Experimental and Modeling Study
Bennamoun, Lyes ULg; Kahlerras, Loubna ULg; Michel, Frédéric ULg et al

in International Journal of Energy Engineering (2013), 3(1), 1-6

The aim of this study is the experimental characterization of the behaviour of a mortar during convective drying. We focalise on mortar that has a rate water-cement of 0.5. The drying tests are developed ... [more ▼]

The aim of this study is the experimental characterization of the behaviour of a mortar during convective drying. We focalise on mortar that has a rate water-cement of 0.5. The drying tests are developed in a micro-convective dryer that can use samples weighing from 0 to 8g. The advantage of these experiments is to reproduce the natural conditions that can be found during the treatment of the mortar-atmosphere problems. The response of the drying curve or the drying kinetic depends on the applied drying conditions. So, the temperature of the air varies from 60°C to 130°C, the velocity of the air is changed from 2 m.s-1 to 5 m. s-1and the relative humidity is kept less than 1.7%. The comparison between the experimental results and the proposed analytical solutions of the equation of diffusion represented by Fick’s law, applied for a finite shape, allows determination of the values of the diffusion coefficient. It has a value of 1.71×10-10 m2.s-1 at 60°C, 13.69×10-10 m2.s-1 at 90°C and 16.27×10-10 m2.s-1 at 130°C. Calculation of the activation energy and the D0 constant are also possible. [less ▲]

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See detailImpact of sludge storage on dewatering and convective drying
Pambou, Yvon-Bert ULg; Salmon, Thierry ULg; Fraikin, Laurent ULg et al

Scientific conference (2012, November 10)

Annual production of sewage sludge in Europe is estimated at more than ten million tons of dry matter. Use in agriculture and incineration are the main ways of valorization. In this context, sludge drying ... [more ▼]

Annual production of sewage sludge in Europe is estimated at more than ten million tons of dry matter. Use in agriculture and incineration are the main ways of valorization. In this context, sludge drying appears as an essential step after mechanical dewatering. It reduces the costs of storage and transport, allows the stabilization and the hygienization of sludge while increasing its calorific value. However, this process is highly energy consuming and still needs to be optimized as it constitutes an important economic and environmental issue. This implies the improvement of knowledge about sludge drying, including the impact of the mechanical dewatering step. Before studying experimentally the influence of polymers type and dosage use for dewatering on the rheological properties and the drying process, it is necessary to assess the stability of the sludge during of the storage. Because sludge is a living material that can rapidly change, we use the method of experimental design in order to get maximum information with minimal testing, regarding sludge stability during storage. [less ▲]

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See detailMODELING WASTEWATER SLUDGE DRYING WITH DETERMINATION OF DIFFUSIVITY MOISTURE
Bennamoun, Lyes ULg; Fraikin, Laurent ULg; Salmon, Thierry ULg et al

Scientific conference (2012, September 06)

Convective drying of two different types of wastewater sludges is investigated. Experiments are realised in a micro-dryer, for air temperatures of 80 °C, 140 °C and 200 °C, the velocity and humidity ... [more ▼]

Convective drying of two different types of wastewater sludges is investigated. Experiments are realised in a micro-dryer, for air temperatures of 80 °C, 140 °C and 200 °C, the velocity and humidity remaining the same. The product drying kinetics presents, for all studied cases, three main phases, which are: adaptation phase, constant drying rate phase and falling drying rate. A comparison between two mathematical approaches allows determination of the diffusion coefficient. The value of this coefficient depends on the origin of the wastewater sludge and the operating temperatures. Physical changes such as shrinkage are introduced into the mathematical model. [less ▲]

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See detailInfluence du stockage des boues de STEP sur les émissions de NH3 et de COV durant leur séchage
Fraikin, Laurent ULg; Salmon, Thierry ULg; Herbreteau, Benjamin et al

Poster (2011, November 29)

Le séchage constitue une étape importante en aval de la déshydratation mécanique en vue de la valorisation agricole ou énergétique des boues de station d’épuration. La teneur en eau peut être réduite à ... [more ▼]

Le séchage constitue une étape importante en aval de la déshydratation mécanique en vue de la valorisation agricole ou énergétique des boues de station d’épuration. La teneur en eau peut être réduite à moins de 5%, diminuant ainsi la masse et le volume des boues et, par conséquent, le coût pour le stockage, la manutention et le transport. L'élimination de l'eau augmente considérablement le pouvoir calorifique inférieur, transformant les boues en un combustible convenable. En outre, les boues séchées peuvent être stabilisées et exemptes d'agents pathogènes en fonction de la température et de la durée de traitement. Les technologies convectives sont largement utilisées pour le séchage des boues. Le principal avantage est la simplicité de la technologie et l’inconvénient majeur résulte de la grande quantité d'air à épurer et désodoriser. Le but des travaux menés par l'Université de Liège et VEOLIA Environnement est d'effectuer une caractérisation en laboratoire des émissions gazeuses en fonction des conditions de séchage. Pour ce faire, il est primordial de garantir une qualité constante de l'échantillon initial tout au long des mesures. En effet, même si elles sont conservées à basse température, les boues peuvent être le siège de dégradations biologiques et les propriétés de séchage peuvent être modifiées. Ainsi, la première partie de ce travail est consacrée à l’étude de l'influence de la durée de stockage des boues à 4°C sur les émissions gazeuses produites au cours de leur séchage convectif. Deux types de boues, l’une ayant subi une digestion et l’autre pas, sont étudiés. L’échantillonnage est effectué après la déshydratation mécanique dans deux stations de traitement des eaux usées situées à proximité de l'Université de Liège. Les échantillons sont stockés dans le laboratoire à 4°C dans un récipient hermétique. Pour effectuer les essais, 300 g de boue sont déposés dans le sécheur sous la forme d’un lit d'extrudés de 6 mm de diamètre. La masse de boue, la concentration en ammoniac et la concentration en composés organiques volatils sont mesurées en ligne respectivement par une balance, un analyseur infrarouge et un détecteur à ionisation de flamme. Des thermocouples permettent le suivi de la température en amont, au sein et en aval du lit de boue. Des essais de séchage sont effectués au jour 0 (= jour du prélèvement), et après 1, 2, 4, 10, 17 et 20 jours sous les conditions suivantes : température de l'air = 140°C; vitesse superficielle de l'air = 1 m/s; humidité absolue = 0,005 kgeau/kgair sec. La seconde partie du travail a été réalisée sur un échantillon de boue non digérée conservé à 12°C pour simuler des conditions réelles de stockage. Les essais de séchage ont été menés le jour de prélèvement et après 4, 10 et 20 jours, avec des conditions opératoires similaires. L’étude réalisée avec un stockage à 4°C montre que les émissions gazeuses sont maximales le jour du prélèvement, diminuent fortement durant les deux premiers jours de stockage pour atteindre un niveau constant durant deux semaines avant d’augmenter. Lors du stockage à 12°C, les émissions d’ammoniac et de COV sont multipliées respectivement par un facteur 40 et 4 entre le jour 0 et le jour 20. Ces résultats mettent en évidence l’impact des conditions et de la durée de stockage sur les émissions lors du séchage des boues et montrent l’importance de sécher les boues le plus rapidement possible pour limiter les nuisances. [less ▲]

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See detailImpact of Storage Duration on the Gaseous Emissions during Convective Drying of Urban Residual Sludges
Fraikin, Laurent ULg; Salmon, Thierry ULg; Herbreteau, B. et al

in Chemical Engineering and Technology (2011), 34(7), 1172--1176

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See detailImpact of storage duration on the emissions of ammonia and VOC during the convective drying of urban residual sludges
Fraikin, Laurent ULg; Herbreteau, Benjamin; Chaucherie, Xavier et al

in Tsotsas, E.; Metzger, T.; Peglow, M. (Eds.) Proceedings of IDS 2010 - Drying 2010 (2010, October)

Detailed reference viewed: 79 (20 ULg)