Combustion and Flame 142 (2005) 249–257 www.elsevier.com/locate/combustflame Particle–metal interactions during combustion of pulp and paper biomass in a fluidized bed combustor F. Eldabbagh a , A. Ramesh a , J. Hawari b , W. Hutny c , J.A. Kozinski a,∗ a Energy & Environmental Research Laboratory, McGill University, 3610 University Street, Wong Building, Room 2160, Montreal, QC, Canada H3A 2B2 b Biotechnology Research Institute, National Research Council of Canada, Ottawa, ON, Canada c Energy Technology Centre—Ottawa, Natural Resources Canada, Ottawa, ON, Canada Received 7 September 2004; received in revised form 5 March 2005; accepted 21 March 2005 Available online 30 April 2005 Abstract We compare interactions between metals and solid particles during the classic fluidized bed combustion (FBC) and a new low–high–low temperature (LHL) combustion of selected biomass. The biomass was a mixture of bark and pine wood residues typically used by a paper mill as a source of energy. Experiments, conducted on a pilot scale, reveal a clear pattern of surface predominance of light metals (Ca, Na, K) and core predominance of heavy metals (Cd, Cr) within the LHL-generated particles. No such behavior was induced by the FBC. Metal migration is linked to the evolution of inorganic particles. A composite picture of the metal rearrangements in the particles was obtained by a combination of independent analytical techniques including electron probe microanalysis, field emission scanning electron microscopy, inductively coupled plasma spectrometry, and X-ray diffractometry. It is suggested that the combination of (1) the high-temperature region in the LHL and (2) changes in the surface free energy of the particles is the driving force for the metal–particle behavior. Important practical implications of the observed phenomena are proposed, including removal of hazardous submicron particulate and reduction in fouling/slagging during biomass combustion. These findings may contribute to redesigning of currently operating FBC units to generate nonhazardous, nonleachable, reusable particles where heavy metals are immobilized while environmental and technological problems reduced.  2005 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Keywords: Biomass; Metals; Inorganic particles; Fluidized bed combustion 1. Introduction Biomass is a clean and renewable energy source, which stores and converts the solar energy via the photosynthesis process. Not only is it a plentiful fuel, * Corresponding author. Fax: +1 514 398 4492. E-mail address: janusz.kozinski@mcgill.ca (J.A. Kozinski). but its use also reestablishes the natural carbon cy- cle, helping mitigate greenhouse gas emissions. This renewable energy source is nearly CO 2 neutral [1]. An average heating value of biomass energy crops is comparable to that of a subbituminous coal. Overall, it is possible to achieve 93% reduction in net CO 2 emissions per unit heating value by switching from coal to biomass and 84% reduction by switching from natural gas-fired cogeneration to biomass [2]. Due to inherent advantages of the biomass in substitut- 0010-2180/$ – see front matter  2005 The Combustion Institute. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.combustflame.2005.03.013