Low-temperature steam gasification of wood using a two-stage gasification process to avoid bed agglomeration in a fluidized bed gasifier and tar problems

Steam gasification of wood was conducted using a two-stage gasification process with fluidized bed and tar cracking reactors connected in series. This research explores the possibility of producing a H₂-rich syngas while avoiding bed agglomeration and tar problems at the same time. In the current study, a low fluidized bed temperature was performed with activated carbon as a tar removal additive. Experiments at a fluidized bed temperature of about 600 °C successfully produced low-tar and H₂-rich syngases without any operational problems. When activated carbon was applied, the tar concentration in syngas sharply decreased from 3120 to 48–215 mg/Nm³ (reduction rate: 93.1–98.5 %). Activated carbon also increased syngas and H₂ yields. The maximum syngas and H₂ yields were 1.7 Nm³/kg_{dry_wood} and 68 g/kg_{dry_wood}, respectively. Further, with activated carbon, the condensed tar yield drastically decreased from 26.9 to 2.9–9.5 g/kg_{dry_wood}. A long-term wood gasification was performed for 3 h to test the stability of the two-stage gasification operation. The syngas development was stable at this reaction time, and the H₂ yield was still high at 47.2 g/kg_{dry_feed}. Additionally, toluene, which can be used a fuel source, was the sole tar component produced in the 3-h gasification.