Kinetic Characterization of Tar Reforming on Commercial Ni-Catalyst Pellets Used for In Situ Syngas Cleaning in Biomass Gasification: Experiments and Simulations under Process Conditions

Abstract

Filtering-catalytic candles, filled with an annular packed-bed of commercial Ni-catalyst pellets (∼600 g), were successfully tested for in situ syngas cleaning in a fluidized-bed biomass steam gasifier [ Fuel Process. Technol. 2019 191 44 53 ]. Those tests enabled the macroscopic evaluation of gasification and gas cleaning as a whole, requiring a more specific assessment of the catalyst performance inside the filter candle. To this end, steam reforming tests of tar key compounds (naphthalene and toluene; thiophene in traces to observe sulfur deactivation) were performed with a laboratory-scale packed-bed reactor containing the same catalyst pellets (<7 g). A lumped kinetics was derived, referred to a pseudocomponent representing tars. This was then validated by simulation of the annular catalytic packed bed inside the filter candle, obtaining numerical results in fair agreement with gasifier outputs. As a result, the lab-scale investigation with a small amount of catalyst provides reliable predictions of tar catalytic reforming in industrial-scale filtering-catalytic candles.

Chemical Looping Combustion and Gasification: A Review and a Focus on European Research Projects

“…217 This reverberates on CLG, which is thought of as an innovative application to convert solid fuels into syngas and H 2 . 223 The chemical looping treatment of coal may be more complicated than that of gaseous fuels, as coal has a heterogeneous composition including a formerly living matrix (carbon, hydrogen, oxygen, nitrogen, sulfur) and mineral matter (named "ashes", as they are the solid residue of combustion): 83 the removal of ashes accumulation in a continuous operation inevitably causes a loss of OC; sulfur may be converted into syngas pollutants and negatively affect the OC reactivity (e.g., H 2 S which poisons Ni-based materials 224 ).…”

“…The complete development of BCLG, beneficial as a BECCS technology and in BtL chains, must face specific technical issues brought in by biomass nature, i.e., by its proximate and ultimate analyses . The usual high content of volatile compounds in biomass is related to higher reactivity with OCs, but also to a greater tendency to produce a large amount of sticky and acidic tar during gasification. ,,− Among solid fuels for gasification, terrestrial biomasses such as pine and straws show high C/H ratios, therefore producing syngas with high CO/H 2 molar ratio, which in turn may be not suitable depending on the downstream desired use (e.g., CO/H 2 molar ratio = 0.5 is recommended for Fischer-Tropsch , ); cogasification of biomass and solids with lower C/H (e.g., plastics such as polyethylene) may help to increase H 2 fraction in syngas. ,, With regard to syngas pollutants, N-derived ones (HCN, NH 3 , NO x ) must be considered in the gasification of terrestrial biomass (1–2 wt % of N in ultimate analysis) and waste materials as well . As to S, its content is usually very low in plant biomass, so S-derived pollutants (H 2 S, SO x ) are not of significant concern, whereas they are in the gasification of waste materials. , Mineral compounds in solid fuel ashes may negatively affect syngas quality and OC performances.…”