Effect of Radiative Transfer on Syngas Characteristics during Oxy-Steam Gasification of Lignite in a Fluidized Bed

Phase-averaged radiative properties in the P-1 radiation model were employed in conjunction with the Euler-Euler multiphase model to simulate oxy-steam gasification of lignite in an atmospheric pressure fluidized bed gasifier at oxygen to carbon (O/C) ratios in the range 0.8–1.6. By accomplishing a tighter coupling of gas phase radiative transfer with multiphase flow hydrodynamics than previously possible, the impacts of this modeling enhancement on the syngas composition predictions were assessed by comparing against measurements. A gray Weighted-Sum-of-Gray-Gases-Model (WSGGM) that considered only H ₂ O, CO ₂ to participate in radiation as well as a Planck mean absorption coefficient based model that included the participation of CO were employed to compute the gas radiation properties within the gasifier and along the syngas sampling train. The H ₂ O/CO ₂ ratio varied significantly within the gasifier. The WSGGM and Planck mean absorption coefficients differed by nearly an order of magnitude. Nevertheless, the choice of the gas radiative property model or the inclusion of radiation did not significantly alter the gas temperature or syngas composition at the gasifier exit. However, the temperature and composition profiles along the sampling train were impacted by the radiation modeling options employed. CO accounted for ~ 10% of the radiative transfer along the sampling train. The water-gas-shift (WGS) reaction persisted throughout the gasifier and along the syngas sampling train. Accounting of WGS kinetics and radiative transfer during syngas cooling improved its composition predictions for two out of the three operating conditions considered.