Combustion characteristics and kinetics of torrefied olive pomace Chamseddine Guizani a , Khouloud Haddad b , Mejdi Jeguirim b, * , Baptiste Colin c , Lionel Limousy b a University of Grenoble Alpes, LGP2, F-38000, Grenoble, France b IS2M, UMR 7361 CNRS, 15, rue Jean Starcky, Mulhouse, France c RAPSODEE, Mines Albi, Route de Teillet, 81013, Albi CT Cedex 09, France article info Article history: Received 16 November 2015 Received in revised form 13 February 2016 Accepted 7 April 2016 Keywords: Olive pomace Torrefaction Biomass reactivity Combustion Kinetics abstract This investigation aims to examine the OP (olive pomace) recovery as a fuel in heat production systems. A two-steps process is proposed to adapt OP for such application. Firstly, the OP torrefaction is performed for various temperatures in order to improve the combustion properties. It is seen that, in addition to the hydrophobic character, the higher heating value of the samples increased with the torrefaction severity. Secondly, the reactivity in air of TOP (torrefied olive pomace) using thermogravimetric analyses is examined. The results show a decrease in the TOP reactivity with the increase of the torrefaction tem- perature. This behaviour is attributed to the degraded proportion of the three macro-components: Hemicellulose (HC), Cellulose (C), Lignin (L). A kinetic model based on the HC, C and L thermal degra- dation is applied to simulate the combustion of OP and TOP samples. The activation energies of the macro-components degradation and char combustion reactions are determined. In addition, the pro- portions of HC, C and L left in the TOP samples after the torrefaction step are extracted. This modelling part brings understanding keys on both torrefaction and combustion steps. It also provides kinetic pa- rameters concerning OP and TOP combustion, which are necessary for combustor sizing. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Currently, the main challenge in the energy policy is to reduce fossil fuel dependence and to attain a sustainable, competitive and renewable energy supply. Biomass energy is designed as renewable energy since the carbon dioxide emitted during conversion belongs to the carbon cycle [1]. The biomass use for energy production can help to decrease GHG (greenhouse gas) emissions and to meet the targets established in the European Union Energy Strategy 2020 and the Kyoto Protocol [2]. Thermochemical conversion processes such as combustion, gasification, and pyrolysis are promising routes to convert biomass to fuel, chemicals, and renewable power [3]. However, the recovery of raw biomass feedstock has significant technical barriers such as low energy density, high moisture con- tent, fibrous nature and hydrophilic character. These barriers impact strongly logistics (mill, handling, transport), the final energy efficiency and therefore the biomass competitiveness in the energy generation market [4,5]. To overcome these issues, a process for feedstocks homogeni- zation, stabilization and energetic densification is required. This task could be performed through a pretreatment technique called torrefaction [5]. Torrefaction is a mild pyrolysis process in which the biomass is heated at temperatures ranging from 200 to 300  C for duration of generally 1 h or less. The heating is generally per- formed under inert conditions at atmospheric pressure. The state of the arts and prospects of the different torrefaction technologies was detailed recently by Batidzirai et al. [5]. During torrefaction, in addition to the water removal, the major decomposition reactions affect the hemicellulose. Cellulose and Lignin degrade slightly depending on the torrefaction temperature [6]. Torrefied biomass retains 60e80% of the initial mass, loses its hygroscopic properties and preserves 70e90% of its energy contents [7]. The torrefied biomass has a lower O/C (oxygen-to-carbon) ratio, high energy density and hydrophobic character [8]. In addition, several in- vestigations showed that torrefaction process improves the grind- ability and the compaction properties [9]. These different properties of torrefied biomass are attractive for several applica- tions such as heating and electricity production as well as gasification. * Corresponding author. Tel.: þ33 3 89608661. E-mail address: mejdi.jeguirim@uha.fr (M. Jeguirim). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2016.04.034 0360-5442/© 2016 Elsevier Ltd. All rights reserved. Energy 107 (2016) 453e463