Modelling and simulation of a residual lignocellulosic biomass pyrolysis pilot plant

The present work has been devoted to the study, modelling and simulation of a pilot scale pyrolysis plant feed with residual agricultural residues located in Catania, Sicily. A global model representing the process flowsheet was created with Aspen Plus® software and was fed with actual experimental data obtained in the existing pilot plant. The aim has been to develop a flexible simulation model in which different types of local agricultural residues could be fed to the reactor and stablish the optimal conditions for each case. Raw materials’ characterization included ultimate and proximate analysis, and biochemical composition (cellulose, hemicelluloses, lignin, and inorganics contents). All these data were implemented in the simulation for the feedstock definition. The base scenario was established by feeding 35 kg/h of biomass under a pyrolysis temperature between 500 and 900°C. The decomposition of the organic matter was defined as a two-stage process: a first decomposition of the organic fraction into a residual solid fraction (char) and a gaseous mixture, and a subsequent cooling of the mixture to separate the condensable part and to obtain the pyro-oil and the permanent gas stream. This latter stream of gas was used to generate thermal power that could be used to support the energy requirements of the pyrolysis process. To reproduce the degradation of biomass and the resulting evolution of chemical species, a mathematical model, based on the operative temperature and the reaction kinetics was developed. The simulations were designed in order to maximize the gas fraction and minimize the char one. The obtained results were discussed in terms of compound yields, and energetic content of the generated pyro-gas.