Axial transport and residence time of MSW in rotary kilns - Part I. Experimental

Experiments on the influences of operational variables on the axial transport of both heterogeneous municipal solid waste (MSW) and homogenous sand are conducted in a continuous lab-scale rotary kiln cold simulator. Compared with sand, the residence time of MSW has a relatively large discrepancy with the ideal normal distribution due to the trajectory segregation of MSW components. The residence time at different axial zone is quite different due to the varied bed depth profile along the kiln length. MSW has a longer mean residence time (MRT) and a lower material volumetric flow (MVF) than sand because of the higher theta(d) than sand. The increment of both rotating speed and kiln slope reduces MRT, and increases MVF. Exit dam has a significant impact on the MRT and the influence of internal structure group consisting of various axial ribs and circular ribs is mainly determined by the height of circular ribs. Inside wall roughness also has effect on MRT through changing the bed regimes. For a case with the certain inlet and exit bed depths, the product of MRT and MVF holds at a constant within the limits of experimental errors in spite of the changing experimental variables. (C) 2002 Published by Elsevier Science B.V.