Energy losses due to elutriation in fluidized bed gasification of sugarcane bagasse

Sugarcane gasification in a fluidized bed gasification system, FBGS, has many unknown aspects, among which elutriation energy loss is important to energy efficiency. This paper reports energy losses due to elutriation quantified in pilot scale FBGS tests. The bagasse, supplied by a local sugar and alcohol cooperative, contained approximately 10% moisture (dry basis) and had a particle diameter (dp) whose most frequent size interval was 0.55 mm < d(p) < 1.25 mm. The tests were conducted in a cylindrical section FBGS with an internal diameter ratio of two between freeboard and bed sections. The pilot scale FBGS was fed approximately 167 kg/h of air dried bagasse with a bed temperature of 663-686 degrees C, and 134 kg/h when bed temperature was 709-913 degrees C. Air factors were 0.17 and 0.22, respectively, in these tests. Elutriated solids decreased from 6.8 to 2.6 kg/h, corresponding to carbon losses of 5.4-2.3%, as bed temperature was increased from the lower to the higher temperature range. It is concluded that temperature has a great influence on gasification of small bagasse particles and that at higher temperatures elutriation decreased.