Influence of an Oxygen Carrier on the CH4 Reforming Reaction Linked to the Biomass Chemical Looping Gasification Process.

A major challenge in biomass chemical looping gasification (BCLG) is the conversion of CH4 and light hydrocarbons to syngas (CO + H2) when the goal is the use for bioliquid fuel production. In this work, tests were performed in a batch fluidized bed reactor to determine the catalytic effect on the CH4 reforming reaction of oxygen carriers used in the BCLG process. Three ores (ilmenite, MnGB, and Tierga), one waste (LD slag), and five synthetic materials (Fe10Al, Fe20Al, Fe25Al, Cu14Al, and Ni18Al) were analyzed. These results were compared to those obtained during ∼300 h of continuous biomass gasification operation in a 1.5 kWth BCLG unit. The low-cost materials (ores and waste) did not show any catalytic effect in the CH4 reforming reaction, and as a consequence, the CH4 concentration values measured in the syngas produced in the continuous prototype were high. The synthetic oxygen carriers showed a catalytic effect in the CH4 reforming reaction, increasing this effect with increasing temperature. With the exception of the Ni-based oxygen carrier (used as a reference), the Cu-based oxygen carrier, working at 940 °C, showed the best catalytic properties, in good agreement with the low CH4 concentration values measured in the syngas generated in the continuous unit. The tests performed in a batch fluidized bed reactor were demonstrated to be very useful in determining the catalytic capacity of oxygen carriers in the CH4 reforming reaction. This fact is highly relevant when a syngas with a low CH4 content is desired as a final product.

Biomass Chemical Looping Gasification of pine wood using a synthetic Fe2O3/Al2O3 oxygen carrier in a continuous unit.

Biomass Chemical Looping Gasification is a novel technology allowing high quality syngas production at autothermal conditions without CO2 emissions to the atmosphere and low tar generation. This work compiles gasification results corresponding to 38 h of continuous operation in a 1.5 kWth unit using pine wood as fuel and a synthetic Fe-based oxygen carrier, Fe20Al. The main operating conditions such as temperature (T = 820-940 °C), steam-to-biomass ratio (S/B = 0.05-0.65), and oxygen-to-biomass ratio (λ = 0.2-0.6) were analyzed at steady state conditions using a novel method for controlling oxygen in the process. A syngas composed by 37% H2, 21% CO, 34% CO2 and 7% CH4, and tars below 2 g/Nm3 could be obtained at autothermal conditions, leading to a syngas yield of 0.8 Nm3/kg dry biomass and a cold gas efficiency of 68%. The material maintained a high reactivity although some Fe lost was observed.