Evaluation of date palm residues combustion in fixed bed laboratory reactor: A comparison with sawdust behaviour Yassine Elmay a, b, c , Mejdi Jeguirim b, * , Sophie Dorge a , Gwenaëlle Trouvé a , Rachid Said c a Laboratoire Gestion des Risques, Environnement, 3 bis rue Alfred Werner, 68093 Mulhouse, France b Institut de Science des Matériaux de Mulhouse, UMR 7361 CNRS, 15 rue Jean Starcky, 68057 Mulhouse, France c Unité de Recherche d’Etude des Milieux Ionisés et Réactifs (UR EMIR), IPEIM, Avenue Ibn El Jazzar, Monastir 5019, Tunisia article info Article history: Received 19 April 2012 Received in revised form 18 May 2013 Accepted 3 July 2013 Available online 27 July 2013 Keywords: Date palm residues Sawdust Combustion Fixed bed reactor Gaseous emissions abstract Combustion tests of five date palm Tunisian residues, namely: Date Palm Leaflets (DPL), Date Palm Rachis (DPR), Date Palm Trunk (DPT), Date Stones (DS) and Fruit-stalk Prunings (FP), were performed in a laboratory scale furnace. Gaseous emissions such as CO 2 , CO, VOC, NO x and SO 2 , were analysed at 600  C under 30e60 NL/h flow rate. Obtained results were compared with sawdust combustion behaviour in order to select the most convenient biofuel for an application in domestic boiler installations. Combustion tests show that ignition delay and combustion time reaction are independent of the date palm residue. However, gaseous products emission rates and factors are correlated to the sample characteristics such as carbon, nitrogen and sulphur contents as well as fixed carbon and volatile matters contents. In order to optimize date palm residues combustion by decreasing unburnt gaseous emissions, special attention should be given to the design of the secondary air supply. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Expectation for the world energy demand and supply shows that fossil fuels such as oil, coal and natural gas will be depleted within the next 40e50 years [1]. Therefore, among renewable en- ergies, biomass production and utilisation is growing considerably since it offers the possibility to provide partial substitution of the non-renewable energy sources. In addition to the economic advantage, use of biomass for energy production incorporates many environmental benefits such as reduced CO 2 emissions from fossil fuels combustion [2]. In Tunisia, thousands tons of biomass in the form of olive resi- dues, wood waste, date palm residues and many other agriculture residues are generated every year. These resources could be easily used in energy production for replacing fossil fuels. Although en- ergetic valorization of olive waste has received considerable attention [3e5], few investigations on date palm residues com- bustion were found in literature. Date palm tree (see Fig. 1) is a typical cultivated tree in the arid and semi-arid regions of the world. It is especially abundant in several regions in the south of Tunisia [6e8](Fig. 2). Each year, important quantities of palm leaves, which are composed by the rachis (DPR) and the leaflets (DPL), become dry and are removed or fall from trees. Moreover, after many decades of cultivation, several date palms need to be substituted due to the decline of their production yield. Thus, the trunk (DPT) generated can be a potential source for energy recovery. After the date fruit harvesting, important quantities of fruit-stalk prunings (FP) are generated. Date stones (DS) are by-product usually produced from processing of based-date fruits in industrial sector. Estimations of annual amounts of these residues are not easily available. The main application for date palm residues in literature was found in wastewater treatment. For example, Date Stones and Palm-Trees Waste were tested for the removal of Cu(II) and Methylene Blue from aqueous solution [9,10]. Results showed that these residues are effective and alternative materials for waste- water management in industrial processes. Recently, thermogravimetric analyses under inert and oxidative atmospheres of five date palm residues have revealed that thermal degradation profiles are similar among the samples, except for date stone. Among the studied samples, date palm trunk was the most reactive material under both atmospheres, whereas date stone was the less reactive fuel [8]. Sait et al. have also determined pyrolysis and combustion kinetics of three date palm residues using ther- mogravimetric analysis [11]. Kinetics data have been obtained for thermal degradation for seed, leaf and leaf stem. Gasification of * Corresponding author. Tel.: þ33 389327658; fax: þ33 89327661. E-mail address: mejdi.jeguirim@uha.fr (M. Jeguirim). Contents lists available at SciVerse ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene 0960-1481/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.renene.2013.07.007 Renewable Energy 62 (2014) 209e215