Intrinsic reactivity of biomass-derived char under steam gasification conditions-potential of wood ash as catalyst Pavlina Nanou, Héctor E. Gutiérrez Murillo, Wim P.M. van Swaaij, Guus van Rossum ⇑ , Sascha R.A. Kersten Sustainable Process Technology, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands highlights " Steam gasification of biomass char was studied in a thermo-gravimetric analyzer. " Biomass gasification can be catalytically enhanced by its own ash. " Char can be completely gasified within 12 min at 700 °C. " Ash loading and distribution are important for obtaining high gasification rates. " CO and H 2 in the gasifier can inhibit char gasification by a factor 2. article info Article history: Received 30 August 2012 Received in revised form 17 November 2012 Accepted 3 December 2012 Available online 8 December 2012 Keywords: Char Biomass Steam gasification Ash Potassium Distribution abstract The influence of ash on the steam gasification rate of pine wood derived char particles in the temperature range 600–800 °C is investigated. Ash derived from pine wood or specific ash components were added to the pine-wood (before pyrolysis) or to the produced char (after pyrolysis) via physical mixing or impreg- nation. The addition method and the amount and type of ash/ash component have been studied and the obtained gasification rates are compared. Impregnation of ash/ash components by 10 wt% or more (in the original pine wood) always resulted in a significant increase in the (initial) gasification rate. At 700 °C, e.g., impregnating 9.5 wt% KOH in pine wood resulted in complete char conversion within 12 min, corre- sponding to an increase in (initial) gasification rate by a factor 30 compared to char without impregna- tion. SEM images of the chars showed that impregnating the wood with concentrations up to 14 wt% resulted in unevenly distributed ash (components) in the particles. Based on this, the hypothesis is that besides the overall amount of ash also its distribution among and inside the char particles is important for enhancement of the reaction rate. A biomass gasification concept in which the steam gasification reaction of char is catalyzed by concentrating the ashes in the biomass is feasible. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Biomass gasification has drawn a lot of attention over the past decades as a process for power generation, for gaseous and liquid fuels production, as well as for chemicals [1]. The most important heterogeneous gasification reactions taking place during the gasifi- cation process which involve solid carbon are: the water–gas reac- tion (1), the Boudouard reaction (2) and the heterogeneous methanation reaction (3). C þ H 2 O $ CO þ H 2 ð1Þ C þ CO 2 $ 2CO ð2Þ C þ 2H 2 $ CH 4 ð3Þ In this paper, these reactions are studied and in particular the effect of ash additives on the reaction (gasification) rates. The work presented in this paper is part of a larger research program dealing with methane production from biomass via thermal gasification [2,3]. In this concept, alkali(ne earth) metals contained in the bio- mass are intended to catalyze pyrolysis, gasification, methanation and tar cracking/reforming. Char steam gasification has been a research topic for many years, especially in the coal gasification research of the 1980s. A lot of work is available on the steam gasification of coal char with various mixed or impregnated alkali metals such as: K 2 CO 3 [4–18], KOH [5,6,14,18], KCl [6,9,14,18], KHCO 3 [18], KNO 3 [15,18],K 3 PO 4 [15], Na 2 CO 3 [7,9,14], NaOH [11,14], NaCl [6,9,14]. Calcium has also been studied for coal char steam gasification as a cheap alternative to alkali metals: CaO [9,17], Ca(OH) 2 [13], CaCl 2 [9], as well as iron 1385-8947/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2012.12.012 ⇑ Corresponding author. Tel.: +31 53 489 3902. E-mail address: g.vanrossum@utwente.nl (G. van Rossum). Chemical Engineering Journal 217 (2013) 289–299 Contents lists available at SciVerse ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej