Entrained Flow Gasification of Hardwood Bark: Experimental Characterization of Inorganic Matter versus Equilibrium and Viscosity Predictions

Hardwood bark (HW bark) containing a high ash yield (6.5 wt %) was gasified on a pilot scale in a pressurized entrained flow reactor (EFR, 250 kW_th) in allothermal conditions. Conventional physical–chemical characterizations were performed on the ash/slag (ash yield, weight and sieving, inductively coupled plasma, scanning electron microscopy with energy-dispersive spectroscopy, and X-ray diffractometry) and water (pH and ionic chromatography) both collected at the bottom of the EFR. Simulations were performed to predict the phase speciation (solid + liquid + gas) at equilibrium with FactSage 7.3 and its databases and to predict the viscosity with the FactSage “melt” and Thomas models above and below the liquidus temperature, respectively. Results showed that the inorganic matter collected could be characterized with a well closed overall and elemental mass balance. Slight pollution by the alumina wall of the reactor was observed. A very small amount (<4%) of fly ash was noticed. The quench water was acidic as a result of the oxidation of injected N₂ (and not as a result of N biomass). A good consistency was observed between experimental results of the main condensed phases and the prediction either from a simple phase diagram or with global calculations but for only ¹/₄ of the collected ashes. The remaining ashes, i.e., ³/₄, contained unpredicted phases, such as SiO₂ (from soil contaminant) and CaCO₃ (from raw HW bark), that did not react together. The viscosity was predicted to be between 1 and 10 Pa s in the 1300–1400 °C temperature range. This viscosity is below the 25 Pa s criteria to have a slag flowing adequately along the EFR wall.