Enhanced performance of gasification by blending coal into biomass in a fluidized bed two-stage system

• Gasification of biomass blending coal was carried out in a fluidized bed two-stage system. • As the weight ratio of coal to biomass increased, carbon and hydrogen conversion increased. • The fluidized bed two-stage system run stably by separating the alkalis and coal char stream. • The tar content in producer gas reached its lowest level of 0.012 g/Nm 3 d . Biomass, blended with a small amount of coal, was fed into a fluidized bed two-stage gasifier to produce low-tar H 2 -rich gas through O 2 -rich gasification. The blended coal improved the energy density of biomass fuel and also worked as the bed material. For the fluidized bed two-stage gasification, large char particles of biomass and coal tend to accumulate at the bottom of the gasifier (a riser) to form a carbon-rich reaction zone there. Then, the O 2 coming from the bottom of the gasifier mainly reacts with such char, consequently suppressing its interaction with the gases including H 2 from pyrolyzer. Using O 2 -rich air with an ER of 0.35 and at gasification temperatures of about 890 °C, gasifying biomass blending 10 wt% coal produced gas containing 13.3 vol% CO, 20.1 vol% CO 2 , 4.3 vol% CH 4 , and 9.8 vol% H 2 , giving an LHV of 4.9 MJ/Nm 3 d . Tar content in the produced gas gradually decreased with time, and over the last 6 h the measured content was 0.012 g/Nm 3 d . Steady operation was well achieved, showing the performance without ash agglomeration for the O 2 -rich gasification of biomass.