Bubbling fluidized bed biomass gasification using a two-stage process at 600 °C: A way to avoid bed agglomeration

Air gasification of wood pellet was conducted using a two-stage gasifier consisting of a fluidized bed gasifier and a tar-cracking reactor filled with active carbon. The main aim of this study was to show that smooth gasification was possible at about 600 °C, where bed agglomeration could be avoided. Another important part of this study was to observe whether the low-temperature gasification could produce a producer gas with a similar gas quality to those obtained at high gasification temperatures. In the two-stage air gasification of wood pellet, active carbon showed an excellent performance in both removing tar and increasing H2 production. The gas quality of the producer gas obtained at the fluidized bed gasifier temperature of about 600 °C proved to be similar to that obtained at about 800 °C. Further, the gas quality of the producer gas obtained without an electrostatic precipitator turned out to be comparable to that obtained with an electrostatic precipitator A long-term two-stage gasification (200 min) was conducted successfully without any operational problems, producing a H2-rich (15 vol%) gas. The sole tar component of the producer gas from the long-term gasification was toluene, the content of which in the gas was only 8 mg/Nm3.