Operation and results of a 200-kW_th dual fluidized bed pilot plant gasifier with adsorption-enhanced reforming

Adsorption-enhanced reforming (AER) is a calcium-based process utilizing the benefits of the reversible carbonation reaction (CaO + CO₂ ⇔ CaCO₃ + heat) to capture CO₂ in situ in a gasifier, thereby shifting product gas distribution toward higher hydrogen yields which can be further combusted in a gas motor for electricity generation or further processed for pure hydrogen or synthetic natural gas production. Following successful EU projects and lab-scale experimentation, a 200-kW_th dual fluidized bed pilot plant (consisting of an interconnected gasifier and sorbent regenerator) was designed and constructed to investigate the AER process for purposes of commercialization. The operational pilot plant is hereby described and the designed operating range presented. Detailed characterization of the gasifier and regenerator (e.g., axial temperature and pressure profiles) is shown. The facility operates in a robust manner with constant and controllable temperatures and gas concentrations. Material loss due to attrition is low and the median particle size of the bed only decreases from 450 μm (raw material) to 350 μm (bed) over many days of operation. Selected results of a long-term experiment are presented, where the gasifier temperature is held for 18 h at 650 °C, achieving an average hydrogen concentration of 72 vol% and a carbon dioxide concentration of only 5 vol%. The results from the pilot plant are consistent with previously published dual fluidized bed AER lab-scale results with respect to product gas composition, lower heating value, and tar concentration.