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The model gives the temperature and moisture distributions of the air, and of the moist sheet, as a function of time and distance in the dryer. The influence of the sheet's velocity and that of the radiant energy on the dryer performance as well as the effect of the moisture content of the entering sheet have been studied. A set of 27 experiments was carried out using the infrared dryer in order to calibrate the model. In these, the following three variables each had three operational levels: web velocity, initial web moisture and heating power. The model predictions agreed very well with the experimental data. Model predictions using arithmetic averages for the parameters, and parameters correlated with operational variables, are also presented and discussed. ~~~ ~Le modkle permet le calcul de la distribution de la temperature et de I'humidite de I'air ainsi que de la nappe en fonction du temps et de la position dans le sechoir. L'influence de la vitesse de defilement de la nappe, de I'energie radiante ainsi que de I'effet de I'humidite de la nappe a I'entrke sur le skchage a Cte etudik. Un ensemble de 27 exfiriences fut realise avec le stchoir B infrarouges afin d'obtenir les donnees nkcessaires a la calibration du modkle. Chacune des trois variables choisies, soit la vitesse de defilement de la nappe. I'humidite de la nappe a l'entree ainsi que la puissance de chauffe, furent operees a trois niveaux distincts. Les predictions du modkle rksultant de I'utilisation de ces paramktres correspondent relativement bien aux donnees. Les predictions du modkle utilisant la moyenne arithmttique des parametres ainsi que celles des parametres correlCs avec les variables opirationnelles sont egalement presentees et discutees.

A mathematical model of biomass gasification in a fluidized bed has been developed. It considers axial variations of concentrations and temperature in the bubble and emulsion phases. The mass balance involves instantaneous oxidation and equilibrium devolatilization of the biomass, kinetics of solid-gas gasification reactions as well as of gaseous phase reactions and interphase mass transfer and gas convection. The energy balance is solved locally for each vertical volume element, and globally on the reactor by iteration on the temperature at the bottom of the bed. Three parameters have been adjusted based on the experimental results: the heat transfer coefficient at the wall, the weighting of the kinetics of the water-gas shift reaction and the fraction of biomass carbon remaining as char after devolatilization. The model is used to simulate a pilot scale (50 kg/h) biomass gasifier, and its predictions compared to experimental measurements. The temperature and gaseous concentrations are estimated with good accuracy for the experiments using a wood feedstock, except for the concentration of hydrogen which is overestimated.Un modkle mathematique de gazbification de la biomasse en lit fluidisk a ktk dCvelopp6. Les variations axiales de concentrations et de tempirature sont considirkes, dans les phases bulle et Cmulsion. Le bilan massique considkre les apports suivants: oxydation et dkvolatilisation B I'kquilibre du combustible instantankes, cinktique des reactions de gazkification en phase gazeuse et gaz-solide, transfert de masse interphase et convection du gaz. Le bilan d'knergie est rksolu localement pour chaque Clkment de volume vertical, et globalement sur le rkacteur par itCration de la tempkrature B la base du lit. Trois paramktres ont 6tk ajust6s a partir de rksultats expkrimentaux: Le coefficient de transfert de chaleur B la paroi, la ponderation de la cinktique de la reaction de transfert eau-gas et la fraction du carbone de la biomasse formant le rCsidu carbonk h la dkvolatilisation. Le programme a Ctk appliquk h la simulation d'un gazogkne B 1'Cchelle pilote (50 kglh), et les prkdictions obtenues comparkes aux mesures expkrimentales. Les tempkratures et concentrations gazeuses sont estimees avec une bonne prkision pour les expiriences utilisant du bois comme combustible, sauf pour le cas de la concentration d'hydrogkne qui est surestirnee.luidized bed gasification of biomass has been widely F investigated since 1975. This generic technology provides high heat and mass transfer rates when compared to fixed beds, and requires relatively simple equipment. The transfer rates ensure efficient solid-gas contacting and favor gas phase and gas-solid reactions. The temperature and concentration gradients are also kept to a minimum, allowing efficient control of the operating conditions and good turndown ratios. The industrial application of biomass gasification has only been slowed down by the low cost of readily available energy sources (i.e. natural gas and petroleum).The high costs of municipal solid waste dis...

A 100% cotton fabric was impregnated with an alkaline solution of a reactive dye and reaction with the cellulose achieved by heating using electric infrared emitters or hot air. The conditions gave temporal variations of fabric humidity and temperature that were similar for each heating method. Fixation yields and color strengths for the dyed fabrics were measured as a function of heating time. Infrared dye fixation yields were higher, and obtained in much shorter times, than those for dyeings produced by heating in air, particularly for dyes of lower reactivity. When using hot air for fixation, evaporation of water at the yarn surfaces during the initial phase of drying causes dye solution migration to the surface and an increased color yield of the final dyeing. The lower color yields of dyeings produced by infrared fixation were interpreted in terms of the suppression of this type of migration. Reaction of dye with the cotton at room temperature, under conditions preventing any drying, was assumed to occur without any migration of the initially unfixed dye. Fully continuous dyeing trials showed that the infrared fixation process gave high fixation yields with no visible color variation. Infrared fixation of reactive dyes on cotton could be valuable for reducing the environmental impact of unfixed dyes and dyeing assistants in the dyehouse effluent.

We developed an Internal Model Control (IMC) algorithm for drying a thin textile fabric, continuously passing through an electric infrared dryer, based on a reduced linear model of the drying dynamics. This model relates the controlled variables, the humidity and temperature of the web at the dryer outlet, to the manipulated variables, the electrical power supplied to the sources and the web speed through the dryer, and also to changes in the initial humidity of the web at the dryer inlet. The control algorithm was first tested by simulation using the model in regulation mode, and in set-point tracking mode, to vary the manipulated variables so as to maintain the controlled variables at their respective set-points when the inlet web temperature and humidity were changed. The performance under simulated operational conditions was compared to that of a conventional feedback proportional-integral (PI) controller coupled with a feedforward control. The IMC controller was then tested directly in regulation mode using a pilot scale infrared dryer, acting simultaneously on the manipulated variables, the emitter power and the web speed, to control the fabric temperature and humidity at the dryer outlet. The experimental results were compared with those from the above feedback-feedforward controller, on the pilot scale dryer. The results have indicated that the closed-loop stability of the process is assured simply by choosing a stable IMC controller. Also, such a controller does not require the design of specific compensators for the strong interactions between variables of the drying process.Utilisant un modele lineaire reduit de la dynamique de sechage d'une nappe mince dans un four a infrarouges, un algorithme de commande a modele interne (IMC : Internal Mode Control) a ete developpe pour I'operation du four lorsqu'une nappe textile y defile en continue. Ce modele relie les variables contrdees que sont I'humidite et la temperature de la nappe a la sortie du four aux variables manipulees que sont la puissance electrique et la vitesse de defilement de la nappe dans le four ainsi qu'a la variable de perturbation que constitue I'humidite de la nappe a I'entree. L'algorithme de commande fut tout d'abord teste par simulation en utilisant le modele en mode regulation et en mode asservissement en agissant sur les variables manipulees afin de respecter les consignes appliquees sur les variables contrdees face a des perturbations effectuees dans la temperature et I'humidite de la nappe a I'entree. Les performances sous des conditions simulees de fonctionnement furent comparees a celles obtenues d'un contrbleur conventionnel par retroaction proportionnelle-integrale (PI) couplee a une commande par anticipation (feedforward). Les performances de I'algorithme de commande a modele interne furent alors testees directement sur le banc d'essai en mode regulation en operant simultanement sur les variables manipulees que sont la puissance electrique et la vitesse de defilement de la nappe afin de contrder a la fois I'humidite et la tem...