COMPARISON OF LARGE-SCALE AND SMALL-SCALE CIRCULATING FLUIDIZED-BED COMBUSTORS WITH RESPECT TO POLLUTANT FORMATION AND REDUCTION FOR DIFFERENT FUELS

To investigate the scale-up problem of circulating fluidized bed combu stors with particular respect to emissions, comparative combustion exp eriments have been performed in an industrial-size combustor (12 MWth, height 14 m, cross-sectional area 1.6 m x 1.6 m) and in a lab-scale f acility (:height 16 m, inner diameter 100 mm). A comparison of the axi al concentration profiles of oxygen, carbon monoxide, nitric oxide, ni trous oxide and ammonia along the riser height, obtained during the co mbustion of wood, pear and coal under conditions of equal fuel bed mat erial, solid holdup and gas residence time, shows a basic similarity. This indicates that suitably sized and operated lab-scale combustors m ay indeed be valuable tools for the investigation of combustion phenom ena. However, some significant deviations of the profiles can be recog nized, too. These deviations are caused by three-dimensional effects i n the large-scale combustor and indicate the limitations of small-scal e experiments. (C) 1998 Elsevier Science Ltd All rights reserved.