Dynamic characteristics of solids mixing between coal and limestone were studied. Experiments were carried out in a 0.203 m diameter cold fluidized bed with coal and limestone of different sizes as the fluidized particles. Experimental parameters examined included operation time, air Row rate, bed height, initial bed setup, relative particle size and relative amount of the two particles. The coal concentration profile was analyzed through bed sectioning, and a mixing index was used to describe the profile. The observed results were presented graphically and in correlation forms. The steady state results were also compared with those available in the literature.

A model based on the Monte Carlo approach was developed to simulate the mixing and combustion behavior of a shallow coal-limestone fluidized bed combustor. The model involved the coupling of two sub-models: a combustion sub-model based on the two-phase concept of fluidization and a mixing sub-model based on our previously developed dynamic mixing model.The combustion sub-model considered both the volatile and char combustion. It assumed that the combustor consisted of three distinct phases, i.e., jet, bubble and emulsion, with combustion occurring only in the emulsion phase. The mixing sub-model considered the upward or downward movement of a coal particle in the bed as being governed by certain probability laws; these laws were, in turn, affected by the bubbling hydrodynamics.In all, the combustor simulation model took into consideration the effects of coal feed rate, coal size distribution, limestone size, air flow rate and combustor temperature on the combustor behavior. The simulation results included the dynamic response of coal concentration profile, coal size distribution, coal particle elutriation rate as well as the mixing status between the coal and limestone particles. Un modkle bast sur la mtthode Monte Carlo a ttt mis au point pour simuler le comportement de mtlange et de combustion du combusteur a lit fluidist de charbon et de chaux peu profond. Ce modble est bast sur le couplage de deux sous-modkles: un sous-modble de combustion utilisant le concept de fluidisation diphasique et un sous-modkle de mtlange bast sur le modble de mtlange dynamique que nous avons mis au point anttrieurement.Le sous-modkle de combustion considere la combustion volatile et la combustion du charbon. II suppose que le combusteur est constitut de trois phases distinctes, B savoir le jet, les bulles et I'tmulsion, la combustion survenant seulement dans la phase tmulsiont. On considere dans le sous-modMe de mtlange que le mouvement ascendant et descendant d'une particule de charbon dans le lit est rtgi par certaines lois de probabilitt; ces lois sont, h leur tour, influencts par I'hydrodynarnique du bullage. Globalement, le modble de simulation du combusteur prend en considtration les effets de la vitesse d'alimentation en charbon, de la distribution de taille des particules de charbon, de la taille des particules de chaux, du dtbit de l'air et de la temptrature du combusteur sur le comportement du combusteur. Les rtsultats de simulation comprennent la rtponse dynarnique du profil de concentration du charbon, la distribution de taille des particules de charbon, la vitesse d'tlution des particules de charbon ainsi que I'ttat du mtlange entre les particules de charbon et de chaux.