Chemical Looping Gasification of Biomass in a 20 kWth pilot plant

Abstract

The increasing demand for carbon neutral fuels to reduce carbon emissions highlights the need for novel, efficient, and scalable processes for converting low grade biomass into bio fuels. This study investigates the influence of operating conditions on biomass gasification for methanol production using Chemical Looping Gasification (CLG). Experiments were conducted in a 20 kWth pilot plant using ilmenite as the oxygen carrier. The effects of air supply, operating temperature, and gasifying agent composition on process performance were investigated using two different biomass fuels: Waste Wood type B (WWB) and Microalgae (MA). An increased air-to-fuel ratio resulted in a higher degree of combustion, which reduced the concentrations of syngas components (CO and H2) and consequently decreased syn gas production. A decrease in temperature reduced the fuel conversion rate, resulting in a greater fraction of carbon being converted in the Air Reactor rather than the Fuel Reactor. Comparing the achieved gas equilibrium and the theoretical according to the water gas shift equilibrium indicates a temperature dependent catalytic effect the final gas composition. An increased fraction of CO2 in the gasifying agent did not significantly affect fuel reactivity or conversion. However, it increased the amount of carbon introduced into the system and consequently increased the fractions of CO and CO2 in the product gas. Comparison of the two biomass fuels indicates that WWB provides more stable operation and produces lower concentrations of pollutants in the form of NOx than MA. WWB therefore appears to be the more favorable fuel under the investigated conditions.