Bubbling fluidized bed biomass gasification—Performance, process findings and energy analysis

Bubbling fluidized bed gasifiers (BFG) has potential for rural electrification projects especially in third world countries where biomass supplies are abundant from agricultural, wood industries and where electricity supply from the grid is not available. In this paper the performance of a BFG was observed in terms of its thermal output. Gas chromatography (GC) was used to check the gas composition. The size of the wood chips was irregular but mostly falls in the range of 30 mm in both length and width, with the thickness at an average of 3.0 mm. It showed that the gas produced had an energy content of 4.74 MJ/m3 at a bed temperature of 733 °C, with the equivalence ratio at 0.23. The resulting thermal efficiency was 61.32% with a thermal output of 355.55 kWth. For village electrification projects, this thermal output is able to supply 100 kWe through a diesel generator, enough for electricity consumption in 100 households. An energy balance of the system was done to determine its work potential. It was found that the heat loss was 29.64%. A Shankey diagram of the energy distribution of the BFG system shows that the rest of the thermal output is not utilized and exits the system in the form of char and tarry liquids. Condensates were collected for high-performance liquid chromatograph (HPLC) analysis. It was found that phenol was high when the bed temperature was 450 °C, which makes the outlet condensate very soluble in water and can cause water contamination.