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Based on the preliminary tests of the CRIBE downdraft gasifier, that successfully operated with wood chips, wood pellets and sunflower residues, a model of the reactor and the process is developed to predict the most important process performances (syngas composition, tar content, biomass conversion, maximum temperature achieved). A commercial software (Aspen Plus®) is used to develop a detailed model and relate operating conditions, biomass characteristics and reactor parameters. Although many literature works modeled all gasifiers like equilibrium reactors, here an originally procedure is applied to evaluate the effect of the operating conditions, quantify the gasification by-products (CO2, CH4, tar), and finally optimize the gasifier performance in view of different applicative processes. A sensitivity analysis is carried out to evaluate the effect of the operating conditions and the biomass composition and predict the outputs even in ranges of operability different from those operated with the CRIBE plant. Different process configurations are studied to efficiently produce syngas, electricity, hydrogen or Synthetic Natural Gas., Proceedings of the 19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany, pp. 1463-1468

Downdraft gasifiers are recognized as the most suitable gasification technology on a small scale due to the very low tar content of the syngas and the high fuel conversion. However some technological issues limit the reliability and diffusion of this technology, in particular tight feedstock specifications such as low moisture content and narrow size distribution. These specifications are hardly met by biomass residues from agriculture and agro­industries, which therefore need to be conditioned before being processed in downdraft gasifiers. Pelletization is a suitable option for biomass conditioning, allowing production of stable dry fuels of uniform size from different biomass residues. In this work pelletized residues obtained from sunflower seeds pressing are mixed with wood pellets and tested in a downdraft gasifier. The testing facility is a 200 kWth downdraft gasifier operating with air as a gasifying agent. The paper reports the results of the gasification tests along with samples characterization and plant performance indicators, providing a discussion about the evolution of the operating parameters., Proceedings of the 19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany, pp. 1384-1398

The devolatilization of solid fuels is of crucial importance for all thermo­chemical processes and is the basic step in gasification and combustion models. Here a structural model is developed to provide an Advanced tool for Biomass and Coal Devolatilization (ABCD model), even in blend. The main features are founded on the original approach of the CPD (Chemical Percolation Devolatilization) model by Fletcher [1]. The ABCD model extends the approach also to biomass fuels. Further improvements of the ABCD model are: (i) a population balance between n­mers in liquid metaplast; (ii) elemental balance closure with the speciation of light gases, hetero­species and tar composition; (iii) introduction of secondary reactions of tar­cracking and crosslinking. The ABCD model results agree with a selection of experimental data (from homemade and literature works) on different biomasses. The results reported in this paper encouraged IFRF in continuing the experimental campaign for the validation of the model by extending the Solid Fuel DataBase SFDB. The inclusion of ABCD in comprehensive codes (e.g., Reactor Network Analysis, RNA [2]) and process models is valuable because it gives detailed distribution of pyrolysis products in a wide range of conditions with a low computational cost., Proceedings of the 18th European Biomass Conference and Exhibition, 3-7 May 2010, Lyon, France, pp. 923-930

The optimization of biomass gasification should be studied with advanced models to evaluate the effect of the operating conditions, quantify the by-products (CO2, CH4, tar) and compare different reactor configurations. In this work different gasifiers (fixed beds, fluidized beds, entrained flow reactors) are modeled with Aspen Plus® according to an originally developed procedure. The innovative feature of the modeling procedure for all cases consists in the separation of the steps of solid fuel gasification (devolatilization, oxidation, gasification of the char, homogeneous reactions and tar cracking) and the development of dedicated sub-models (by adapting conventional blocks of the software or implementing dedicated sub-models). All steps are connected to respect material and heat balances according to the gasifier configuration. In addition a detailed description of the downdraft gasifier is realized as a distributed domain of several CSTRs and solving energy and mass equations for gas and solid phases with gPROMS software. The entrained flow reactor is also developed with Aspen HYSYS® to give a more comprehensive and automatic solution. All gasifier models developed in this work are powerful tools to be integrated in process study and optimization analysis., Proceedings of the 18th European Biomass Conference and Exhibition, 3-7 May 2010, Lyon, France, pp. 838-846