Catalytic gasification of woody biomass in an air-blown fluidized-bed reactor using Canadian limonite iron ore as the bed material Scott Hurley a , Chunbao (Charles) Xu a,b,⇑ , Fernando Preto c , Yuanyuan Shao b , Hanning Li a , Jinsheng Wang c , Guy Tourigny c a Dept. of Chem. Eng., Lakehead University, Thunder Bay, Ontario, Canada P7B 5E1 b Dept. of Chem. & Biochem. Eng., University of Western Ontario, London, Ontario, Canada N6A 5B9 c CanmetENERGY, Natural Resources Canada, Ottawa, Ontario, Canada K1A 1M1 article info Article history: Received 27 August 2010 Received in revised form 7 July 2011 Accepted 14 July 2011 Available online 30 July 2011 Keywords: Biomass Air-blown gasification Fluidized bed Tar reduction Catalyst abstract A Canadian limonite iron ore was tested for the first time as a catalytic bed material for air-blown gas- ification of pine sawdust at various equivalence ratios (ER, 0.20–0.35) on a pilot-scale fluidized bed gas- ifier, in comparison to a conventional olivine bed material. Effects of bed materials (iron ore and olivine) on tar formation and gasification efficiencies were comparatively investigated. The use of Canadian limo- nite iron ore as the bed material was found to be more active than olivine for tar reduction in the fluidized bed gasification of biomass at a small ER (60.3), leading to a very low tar yield of 15–25 g/kg biomass at ER = 0.30. The yields of combustible gas (carbon monoxide hydrogen, methane and C 2 hydrocarbon gases) and cold gas efficiency were generally the highest at medium values of ER (0.25–0.30) for both bed mate- rials. The iron ore was less active than olivine for producing combustible gases, leading to a lower cold gas efficiency (50% at ER = 0.30) compared to 75% for olivine. However, the use of the iron ore produced a higher yield of hydrogen than that of olivine in the gasification: 5.0 mol hydrogen per kg of biomass with the iron ore at ER = 0.30 which was about 25% higher than that with olivine. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Biomass gasification is a viable thermochemical conversion technology using gasification agents such as air/oxygen, steam or CO 2 for conversion of biomass, in particular recalcitrant lignocellu- losic biomass and agricultural/forestry waste streams, into low to medium Btu fuel gases (5–15 MJ/N m 3 ). The gases produced (e.g. H 2 , CO, CO 2 , CH 4 and C 2+ ) can be utilized directly as fuels for heat and electricity generation, or as feedstocks for the productions of methanol, ethanol, dimethyl ether, and Fischer–Tropsch oils, etc. [1]. Biomass gasification offers several advantages over other con- version processes such as combustion, pyrolysis and bio-conver- sions, with respect to the compact equipment required and its high thermal efficiency. The major challenge of biomass gasification is related to the for- mation of tar, a highly variable mixture of condensable aromatic hydrocarbons (1–5 ring aromatic compounds) along with other oxygen-containing hydrocarbons and complex polycyclic aromatic hydrocarbons (PAH). In an air-blown fluidized bed gasifier, typical tar contents in the producer gas have been reported between 0.5 and 100 g/m 3 [2–5]. Formation of tar not only results in a lower heating value of the fuel gas produced, but causes some operating issues such as downstream fouling due to condensation of the tars at temperatures below 350 °C [3,5]. For many applications, with the exception of direct and immediate syngas combustion for heat or electricity production, these tar levels must be reduced, often to below 50 mg/N m 3 [3]. The reduction of tar in biomass gasification has been the subject of a great number of studies [2,3,6–13]. Tar elimination approaches can be classified into two categories: primary measures and sec- ondary treatments. Primary measures are in-furnace approaches to reduce tar formation by varying the operating conditions or by adding catalysts to the feedstocks, or using reactive bed materials (such as dolomite, olivine) in fluidized bed gasifiers [8,9]. Second- ary treatments include cold-gas mechanical methods to remove tar from the cooled producer gas (using filter, scrubbers, etc.) and hot- gas catalytic processes to crack tar into gaseous products at a high temperature in a down-stream reactor (fixed bed or fluidized bed) which can be operated under different conditions than those of the gasifier [3,7,10–14]. Secondary catalytic treatment may also be re- garded as hot gas cleanup. Common catalysts for hot gas cleanup include nickel/iron-based catalysts [10,12,14], biomass chars and other catalysts such as dolomite and olivine [12]. The most widely used catalysts for hot gas cleanup and tar cracking are alumina- supported nickel catalysts such as commercial nickel-based steam reforming catalysts [15–18]. A major problem that has however 0016-2361/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2011.07.016 ⇑ Corresponding author at: Dept. of Chem. & Biochem. Eng., University of Western Ontario, London, Ontario, Canada N6A 5B9. E-mail address: cxu6@uwo.ca (Chunbao (Charles) Xu). Fuel 91 (2012) 170–176 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel