Production of synthesis gas from biomass residues by staged fixed-bed gasification - results from pilot test campaigns

Fluidized-bed and entrained-flow gasification systems are developed for large-scale synthesis gas applications with at least 100 MW biomass input. However, there is also a market need for smaller-scale plants, which could be better integrated into energy production systems and local biomass logistics. The staged fixed-bed (SXB) gasifier described in this paper targets a size range of 10-50 MW of feedstock input. The primary gasification stage occurs in an updraft fixed bed. The tar-containing updraft gas is further processed in the secondary gasification zone, where gas temperature is raised from 200-500 °C to 750-900 °C by feeding secondary oxygen through a specially designed catalytic distributor zone. The composition and tar content of the resulting raw gas is similar to that of fluidized-bed gasifiers. Consequently, hot gas filtration, catalytic reforming and final gas cleaning technologies, similar to those recently developed and demonstrated for fluidized-bed gasifiers, can be applied. The results from the 0.5 MW pilot gasification tests carried out with wood, bark and sunflower husk pellets are presented in this paper.