Publication | Peer reviewed papers | Synthesegas und Synthesen
Cold flow model study of continuous char separation in a fluidized bed system for electrically enhanced biomass gasification
Published 1 November 2025
Citation: Karte G, Hannl TK, Benedikt F, Pröll T, Pfeifer C. Cold flow model study of continuous char separation in a fluidized bed system for electrically enhanced biomass gasification. Applied Thermal Engineering. 2025. 278 (D): 127425.
Abstract
A cold flow model (CFM) study was conducted to investigate the operation and performance of a fluidized continuous biomass char separation unit (segregator). Char separation from a binary char/bed material stream is obtained through density-difference induced segregation and subsequent pneumatic discharge. The segregator is a substantial part of a novel multi fluidized bed reactor system for an electrically assisted sorption enhanced biomass steam gasification process (extension of the “classical” dual fluidized bed reactor concept). The process combines enhanced biomass-to-product gas conversion as well as extraction and discharge of concentrated CO2. Electric heating at certain positions in the process and the continuous char separation enable operation with high biomass conversion while avoiding/minimizing the need of oxy-combustion. In the CFM experiments the effect of the fluidization and the solid flowrate on the separation efficiency and purity of the separated char stream were determined. Our results indicate that char segregation is most effective under mild fluidization conditions (U/Umf < 3), achieving char separation efficiencies of approximately 90 %, while droping rapidly thereafter to 45 % at U/Umf = 4.1. With the chosen segregator design, no effect of the solid flowrate on the separation efficiency was identified. Bed material loadings carried with the separated char streams of 1.2–5.8 kgbed/kgchar – correlating positively with the applied gas velocity – have been determined. According to process simulation based on the empirically determined parameter ranges, a net electricity input of 0.17–0.39 kWel/kWLHV,org is required yielding a net cold gas efficiency of 0.75–0.77 kWLHV,PG/ kWLHV,org+el and a net carbon capture ratio of 0.29–0.46 kgC,capt/kgC,biomass.