Coproduction of clean syngas and iron from woody biomass and natural goethite ore Shinji Kudo a , Keigo Sugiyama b , Koyo Norinaga a , Chun-Zhu Li c , Tomohiro Akiyama b , Jun-ichiro Hayashi a,⇑ a Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga 816-8580, Japan b Center for Advanced Research of Energy Conversion Materials, Hokkaido University, Sapporo 060-8628, Japan c Curtin Centre for Advanced Energy Science and Engineering, Curtin University, GPO Box U1987, Perth, Australia article info Article history: Received 21 December 2010 Received in revised form 20 April 2011 Accepted 13 June 2011 Available online 23 August 2011 Keywords: Biomass Reforming Tar Coke Goethite abstract Conversion of biomass into clean syngas was studied considering application of low-grade iron ore to reforming of tar. Chipped cedar with moisture content of 0.1–10.1 wt% was continuously pyrolysed at 550 °C, and the nascent volatiles were subjected to reforming at 690–800 °C in a bed of mesoporous hematite derived from a type of natural goethite. The yield of heavy tar (b.p. > 350 °C) decreased from 18.8 to less than 0.01 wt% during the reforming mainly by its oxidation by the ore and conversion into coke. The hematite was reduced completely to magnetite and further but incompletely to wustite. The formation of iron was inhibited by high CO 2 /CO and H 2 O/H 2 ratios of the gas phase. The coke-loaded mag- netite/wustite mixture was, however, an excellent precursor of iron. Reheating the spent ore up to 800 °C in the absence of the volatiles reduced the magnetite/wustite to wustite/iron obeying direct and indirect reduction mechanisms. Repeated cycles of such reheating and reforming converted the volatiles and ore into syngas with a total tar concentration as low as 10 mg Nm 3 -dry and coke-loaded iron, respectively. Contribution of the steam reforming with iron–wustite redox cycles became more important as the reforming-reheating cycles were repeated. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Pyrolysis is the primary step of biomass gasification, and forma- tion of condensable organic product, which is generally termed tar, is therefore inevitable. Complete conversion of tar into a major portion of the gaseous product, in particular, that inside the reactor system has been a most important engineering subject [1–3] since it can greatly enhance the process efficiency and reduce the imple- mentation/operating cost of the gasification. Direct use of product gas as a fuel for internal combustion engines is generally requested to reduce residual concentration of tar (except for light aromatic hydrocarbons such as benzene and alkylbenzenes) to a level below 50–100 mg Nm 3 on a steam-free basis [1]. Such a concentration corresponds to a mass yield around 0.01 wt%-dry-feedstock, though the volume of the product gas depends on gasifying agents. In application of product gas to Fischer–Tropsch (FT) synthesis, naphthalene concentration should be below 10–20 mg Nm 3 , while this process is normally tolerant to benzene and toluene [4]. It is known for complete or nearly complete conversion of the tar that non-catalytic reforming is needed to be operated at tem- perature as high as 1200 °C and therefore consumption of much O 2 or air, which is associated with a great heat penalty [5]. Partial oxidation of a mixed vapour of tar and lighter gases such as CO and H 2 at temperature as low as 800 °C results in preferential con- sumption of the latters and formation of refractory aromatics from the formers [1,6]. Catalytic reforming of the tar has been studied by a number of researchers. Performances of a number of Ni–Al 2 O 3 catalysts with and without promoters and other types of synthes- ised catalysts, for example, have been investigated [3,7–9]. How- ever, there still remain subjects to overcome problems of catalyst deactivation [10,11]. There have also been operating problems arisen from particulate matters such as ash, soot and char. As re- viewed comprehensively by Yung et al. [10], most of previous stud- ies on steam reforming of volatiles from biomass, specific light hydrocarbons or light aromatics over Ni-based catalysts and others employed steam-to-carbon molar ratios, S/C, of 0.5–5. Such high S/ C, which is impractical in consideration of heat demand of gasifica- tion and its thermal efficiency, suggests difficulty in preventing the catalysts from being deactivated by coking with limited supply of steam and/or oxygen. Another option of the tar reforming is to employ a catalyst or catalyst-like solid that can be used as material or fuel even after the loss of activity. An example is tar reforming over charcoal that is produced by the pyrolysis of biomass simultaneously with the volatiles to be reformed [12–14]. It has been demonstrated that tar vapour undergoes very fast thermochemical deposition onto micropore surface of the charcoal and then the deposited carbon 0016-2361/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2011.06.074 ⇑ Corresponding author. Tel./fax: +81 92 583 7793. E-mail address: junichiro_hayashi@cm.kyushu-u.ac.jp (J.-i. Hayashi). Fuel 103 (2013) 64–72 Contents lists available at SciVerse ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel