Biomass gasification in dual fluidized bed gasifier

Abstract

The dual fluidized bed gasification technology is prospective because it produces high caloric product gas free of N2 dilution even when air is used to generate the required endothermic heat via in situ combustion. This study is devoted to providing the fundamentals for development of a bubbling fluidized bed (BFB) gasifier for biomass fuels coupled to a pneumatic transported riser (PTR) char combustor. Gasification test of 1.0 g dried coffee grounds containing 10.5 wt.% water using steam-blown fluidized bed clarified first the characteristics of fuel pyrolysis and steam gasification at 1073 K. With this clarification as the known input, a process simulation using the software package ASPEN then revealed that the dual bed gasification plant is able to sustain its independent heat and mass balances to allow cold gas efficiencies higher than 75%. The experiment using 5.0 kg/h dual fluidized bed pilot gasification facility was held according to the operation condition obtained from the simulation. Stable operation can be achieved and syngas with higher heating value can be produced. It was revealed that the necessary reaction time for the fuel can be lower than 160 s. Also it was found that impregnation of Ca catalysis will further increases the carbon conversion of the fuel compared with the gasification by simple mixing of fuel and catalysis.