Experimental and numerical evaluation of the transport behaviour of a moving fuel bed on a forward acting grate

Abstract

The objective of this study is to evaluate experimentally and numerically the transport behaviour of a moving bed on a forward acting grate. Therefore, the grate was operated with expanded clay and wood chips without combustion. Frequency and amplitude of the grate bars and feed rate were subject to change. Experimental findings showed that large particles have shorter residence times than small particles which is due to segregation on the grate. Additionally, the experiments indicated that increased frequencies of the grate bars lead to reduced residence times whereas the amplitude had no significant effect. The motion of a packed bed e.g., its particles was described numerically by the discrete element method (DEM). Thus, detailed data on all the particle’s paths and velocities are available. These data were used within the mean velocity method (MVM) and the tracking method (TM) to estimate the residence time of a packed bed. Both methods confirmed the dependency of the residence time on particle size, however, better predictions were obtained by the Tracking Method. The mean residence times varies from 40 to 120 min depending on the particle size.