Energy recovery of date palm residues in a domestic pellet boiler

This work presents a preliminary study on the energy recovery of two date palm residues (date stone and date rachis) provided from Tunisia. Rachis residues were transformed into pellets while date stones were used as received. Physicochemical characteristics such as ultimate and proximate analyses and calorific values were determined. Date palm residues were combusted in a domestic pellet boiler according to European EN 303-5 standard. High calorific values of both residues as well as combustion efficiencies close to 80% obtained during combustion tests indicate that these residues are a promising alternative to produce renewable energy in Tunisia. Further adjustments (airflow and fuel feed rates) are necessary to improve boiler efficiencies. High air excess were observed and consequently cooled down the fume temperature. dust emission factors were in the same order of magnitude than expected for EN 303-5 certification. Bottom and fly ashes were characterized by DRX and Fluorescence X. With high contents of chlorine and ash in the rachis pellets, combustion of this sample leads to high emission factors of dust. Further investigations are required for rachis pellets to reach biofuel standards. Elemental chlorine remains in solid residues as bottom and fly ashes under Halite and Sylvite species.