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An optimized model is developed for the production of bio-fuels from biomass using a SuperPro Designer tool. Four types of Tunisian biomass feedstocks including date palm rachis, olive stones, vine stems and almond shells were selected for the fast pyrolysis process simulation. Simulation tests were performed at different temperatures ranging from 450 to 650 C, and residence times ranging from 0.1 to 10 s and the products yield were determined. The obtained results indicate that a temperature of 575 C and 0.25 s vapor residence time are the optimum parameters to maximize the bio-oil yield. Comparison between the different feedstocks indicates that a higher bio-oil fraction was obtained from the date palm rachis and vine stem. However, the difference between the samples is not significant and further investigations on the bio-oil properties are requested to select the suitable biomass for bio-oil production in Tunisia.

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In this work, six Tunisian local biomasses, namely ziziphus wood (ZW), almond shells (AS), olive stones (OS), vine stems (VS) and date palm leaflets (DPL) and trunks (DPT) were slowly pyrolyzed under inert atmosphere at a heating rate of 5 °C/min through thermogravimetric (TG) analyses. The thermal degradation of samples involves the interaction in a porous media of heat, mass and momentum transfer with chemical reactions. Heat is transported by conduction, convection and radiation and, mass transfer is driven by pressure and concentration gradients. Thermal degradation curves have been studied with minute details for each degradation step. The Coats-Redfern model was used to extract the kinetic parameters from the TG data, then the kinetic parameters such as the activation energy, the pre-exponential factor and the order of the reaction were calculated. Results showed that the total mass losses amounts and kinetics are dependent on the type of the used biomass. Moreover, the devolatilization could be described by the first order model, while the char formation stage was better described by the second and third order reactions model. The physicochemical characteristics of these samples were also determined. The volatile matter (VM) content varies considerably, with values ranging from 67.19% for AS to 77.4% for ZW. The maximum values were obtained for ZW and VS with values of 77.4% and 71.9%, respectively. The lowest value (67.19%) was determined for AS. In addition, the ash contents vary between 0.8% for OS and 5.66% for DPT.