Applicability of a kinetic model for catalytic conversion of tar and light hydrocarbons using process-activated ilmenite

This work evaluates further the applicability of a previously formulated kinetic model that describes the conversion of tar and light hydrocarbons during the catalytic upgrading of a raw gas derived via biomass gasification. The model is based on the mechanism through which tar and light hydrocarbons are converted, and the distribution of CO/CO2 and tar/light hydrocarbons as the products of the destruction of the parent tar and light hydrocarbons. Furthermore, the model uses a pseudo tar to represent all the in situ-formed tar and light hydrocarbons. The experiments used an ilmenite catalyst that was activated in the Chalmers 12-MWth boiler, and a mature tar-containing raw gas that was produced in the Chalmers 2-4-MWth dual fluidized bed biomass gasifier. The temperature levels (800 °C and 850 °C) and ilmenite particle size ranges (45-90 µm and 125-180 µm) were investigated. Through fitting the model to the experimental data, the composition of the upgraded gas as a function of gas-solid contact time was derived for the operating conditions studied. The previously proposed conversion network for tar and light hydrocarbons, and the empirical model coefficients for ilmenite (125-180 µm) at 850 °C were validated. Overall, the obtained results confirm that the proposed model is able to describe the upgrading process. Further development of the proposed model and application of the results obtained for ilmenite in designing gas upgrading strategies are discussed.