Biosourced aromatics (BTX (benzene, toluene, xylene) and phenols) could be produced by lignin pyrolysis coupled with catalytic hydrodeoxygenation (HDO) of uncondensed pyrolysis vapors. Guaiacol is used as a model compound to study the catalytic HDO over Fe/SiO 2 catalyst. Experiments were conducted in a fixed bed reactor operated at 673 K (1 atm) with a gas mixture (guaiacol, H 2 , H 2 O, CO, CO 2 ) that mimics the real gas composition from lignin pyrolysis. Fe/SiO 2 catalyst was shown to be selective for guaiacol HDO into benzene and phenols because it does not catalyze the aromatic ring hydrogenation. Major and minor products are modeled by a semidetailed kinetic mechanism. A deactivation law is also determined. The kinetic model is then included in an Aspen Plus model of lignin to BTX process. Aspen Plus model handles (1) pyrolysis of lignin, including char, oligomers, gases and aromatic yields, (2) catalytic conversion of aromatics by the kinetic model, (3) heat exchangers, and (4) BTX vapors recovery by scrubbing with 1-methyl-naphthalene. Mass and carbon balances, heat demand, and selectivity in desired products are given for the overall process. The effect of gas dilution from pyrolysis reactor on BTX losses, heat demand, and scrubbing solvent flow rate is highlighted. High carrier gas flow rates (as required for biomass pyrolysis in fluidized bed) lead to the entrainment of fines and oligomers, dilute the products, and impact considerably the process intensification.
International audienceThis paper presents a theoretical assessment of energy, exergy, and syngas cleaning performances in a biomass gasification combined heat and power (CHP) plant with varying operating parameters. The analysis is carried out using a detailed model of a biomass gasification CHP plant developed with Aspen Plus. The model describes: wood drying and gasification in a dual fluidized bed (DFB) reactor, syngas cleaning, as well as combustion in a gas engine for electricity production. Heat is recovered from the CHP system for internal needs and for district and domestic water heating. An accurate prediction of tar and inorganic contaminants is developed for proper modeling of syngas cleaning efficiency. The influence of wood moisture content, drying conditions, flow rate of the sand circulating in the DFB reactor, catalyst and scrubbing agent efficiencies, as well as additional electricity production through steam turbine on the overall process performances is studied. On the basis of the comparative analysis of nine case studies, it is found that the highest energetic efficiencies are obtained when forced drying is not implemented in the CHP system. Lowering the inlet wood moisture content with natural drying (energy-free) prior to the CHP plant improves the electrical efficiency. An overall energeticefficiency of 74% (23% electric, 51% thermal; based on the lower heating value of wood on anhydrous basis) is then reached with wood fed at 30% moisture content. The best exergetic efficiency is reached when wood (naturally dried to 30%) is dried further to 15% by forced drying in the CHP plant and when some of the high-temperature heat is recovered for electricity production via steam turbine instead of district heating. In this case, the overall energetic efficiency is 63% (32% electric, 31% thermal). This model is a useful tool to assess process design improvements and life cycle inventory
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