Mechanism and Kinetic Modeling of Catalytic Upgrading of a Biomass-Derived Raw Gas: An Application with Ilmenite as Catalyst

Abstract

A mechanism and kinetics to describe the catalytic upgrading of a biomass-derived raw gas is provided in this paper. The mechanism encompasses the principal trends in the evolution of tar and light hydrocarbons. Using this mechanism and a pseudotar that represents tar and light hydrocarbons formed in situ, a kinetic model is developed. The applicability of the kinetic model is demonstrated for a processactivated ilmenite. The experiments were conducted in a bench-scale, bubbling fluidized-bed reactor that was fed with a tar-rich raw gas stream from the Chalmers indirect biomass gasifier. The effects of the ilmenite on tar decomposition and total gas composition were evaluated at 800 °C for three different gas−solid contact times. Combing the experimental results and the proposed kinetic model, the evolutionary profiles of the different tar and light hydrocarbon groups can be evaluated in relation to the gas−solid contact time. The results form the basis of a process model for optimization and upscaling.

Negative CO2 emissions through the use of biofuels in chemical looping technology: A review

“…Considering the presence of CO 2 in biogas, another possibility is the use of the chemical looping dry reforming (CLDR) process as a means of biogas valorization [188]. The syngas In addition, CLR can be used as a secondary tar-cleaning process for upgrading biomassderived gas [174][175][176][190][191][192][193][194][195][196][197][198][199]. The idea behind the tar-cleaning method is to reform tar components (C n H m ) into useful gas molecules.…”

“…The tests were carried out in a continuous bench-scale CLR reactor at temperatures between 750 and 880 ºC. Bed materials tested included ilmenite [196,198,199], catalysts based on nickel [176] and manganese [175], and mixtures of ilmenite and NiO/Al 2 O 3 [197]. The main parameters to consider in the process were the efficiency of tar reforming in the fuel reactor, by analysing the tar content at the inlet and outlet streams, and regeneration after coke formation, by measuring the CO and CO2 concentrations at the air reactor outlet.…”

Importance of Decomposition Reactions for Catalytic Conversion of Tar and Light Hydrocarbons: An Application with an Ilmenite Catalyst

“…The raw gas consists of steam at a level of about 50–60 vol %. H 2 , CO, CO 2 , methane, and ethene are the main components of the permanent gas, and the tar composition is dominated by aromatic species. , Given the raw gas properties, representative reactions associated with the gas cleaning process were identified and investigated independently, so as to examine the individual effects of the reactions. Furthermore, the aggregate effects that are manifested during the real process were investigated by combining the reactions.…”

“…In the latter case, hydro-cracking and dry reforming reactions could also occur, because the reactant gases contained H 2 and CO 2 . Toluene was chosen as a tar representative because it is a major tar component of the given raw gas, i.e., it accounts for up to 12 wt % of the total tar. ,, Furthermore, benzene, which is one of the most stable tar species, can be produced from toluene, which provides further details about tar evolution. ,,, …”

“…The ability of ilmenite to reduce the tar content and adjust the final gas composition via WGS has been proven. , However, the detailed activity of ilmenite toward the different decomposition reactions and the contributions of these reactions to the overall gas cleaning process remain unclear. Furthermore, in a previous investigation by the same authors, the kinetic model for a gas cleaning process that was conducted under excess steam conditions and catalyzed by ilmenite required the identification of the most important reactions …”