A comprehensive heat transfer model for rotary desorbers

Abstract

A model that describes the heat transfer processes within a rotary desorber is presented. This model has several advantages over previous models. The method for calculating the wall-to-bed heat transfer rate includes the effects of moisture in the feed solids and allows for evaporation from the bed before the bulk bed temperature reaches the saturation temperature of the moisture. The method for calculating radiative heat transfer in the desorber accounts for the real nature of the participating gas and the amounts of CO, and H,O in the gas phase from both combustion and evaporation. Results from experiments performed using a pilot-scale desorber are discussed, and the model is validated by comparing the predicted bed temperature profiles and evaporation rates to those found experimentally. A preliminary attempt to account for the effects of a non-uniform bed on the evaporation rate from the bed is also presented along with several parametric studies.On prksente un modtle d&rivant les procedks de transfert de chaleur dans un dispositif de dksorbtion rotatif. Ce modtle prksente plusieurs avantages sur les modbles pr6ddents. La mkthode de calcul du taux de transfert de chaleur entre la paroi et le lit tient compte des effets de I'humiditk dans les solides d'alimentation et permet I'kvaporation 2 1 partir du lit avant que la temp6rature en masse du lit n'atteigne la temp6rature de saturation de I'humiditk. La mkthode pour calculer le transfert de chaleur radiatif dans le dksorbeur tient compte de la nature rklle du gaz participant et des quanties de CO, et H,O dans la phase gazeuse issue de la combustion et de 1'6vaporation. On analyse les rksultats des exp6riences menks ?i I'aide d'un dispositif de dtsorbtion ?i l'khelle pilote, et on valide rksultats en comparant la praiction des profils de temp6rature du lit et des taux d'kvaporation et Zt des donnks exphimentales. On prksente dgalement un travail prkliminaire pour tenir compte des effets d'un lit non uniforme sur la vitesse d'kvaporation Zt partir du lit ainsi que plusieurs ktudes paramktriques.

Numerical Modeling of a Discontinuous Incineration Process with On-line Validation

“…When municipal and hospital wastes are involved, the choice usually goes to either a drum or a grate kiln. When either industrial toxic waste or sludge is available, a rotary kiln is often recommended. − With reference to drum and grate kilns, the most significant difference is waste movement along the combustion bed. In the former, movement is almost continuous while in the latter waste advances discontinuously.…”