Paola Brachi

Investigation of Char–Slag Interaction Regimes in Entrained-Flow Gasifiers: Linking Experiments with Numerical Simulations

Entrained-flow gasifiers are characterized by operating conditions that promote ash migration/deposition onto the reactor walls, whence the ash is drained as a molten phase. Experimental investigation on ashes generated by full-scale plants suggested that both char entrapment inside the melt and carbon-coverage of the slag can occur. Because of the wide range of spatial and temporal scales involved in these phenomena, numerical simulation of the fate of the flying fine char particles is a very difficult task. Simulations based on a Eulerian large eddy simulation (LES) approach for the turbulent gas phase and a Lagrangian particle tracking (LPT) approach for the solid phase have been performed to explore, in a simplified flow configuration, near-wall particle segregation and the role of relevant parameters (in particular, particles’ inertia and slag layer restitution coefficient). Results of numerical simulations have been critically discussed with reference to the experimental observations. Numerical results confirm that near-wall accumulation of particles may be extensive, and promoted by large Stokes numbers and by small restitution coefficients.

Segregation and fluidization behavior of poly-disperse mixtures of biomass and inert particles

Segregation and Fluidization Behavior of Poly-disperse Mixtures of Biomass and Inert Particles Paola Brachi , Riccardo Chirone, Francesco Miccio b, Michele Miccio ,Giovanna Ruoppolo Institute for Research on Combustion, (IRC-CNR), P.le Tecchio 80, 80125 Napoli, Italy Institute of Science and Technology for Ceramics (ISTEC-CNR), via Granarolo 64, 48018 Faenza (RA), Italy Department of Industrial Engineering, University of Salerno, via Giovanni Paolo II 132, 84084 Fisciano (SA), Italy p.brachi@cnr.irc.it

Simulation and flowsheeting of agro industrial residues torrefaction: the case of tomato peels waste

Torrefaction is a thermal pretreatment for biomass feedstocks of various origin, which is usually carried out in an inert atmosphere, at ambient pressure and in a temperature range of 200-300 °C. It has the ability to reduce the main logistic and application limitations of biomass, arising from its heterogeneity, low bulk density, low energy density, hygroscopic behavior and fibrous nature. During torrefaction a combustible gas (‘torgas’) consisting of different organic compounds is also produced in addition to the torrefied solid product. In a properly designed and operated torrefaction system the torgas may be combusted to generate heat for the drying and torrefaction steps, thus increasing the overall process efficiency. This paper focuses on the valorization of biomass made available from low-value, wet agro-industrial residues. The aim of this work is to provide the conceptual design and technical analysis of a torrefaction process for recovery and upgrade of wet tomato peels, which are a typical industrial waste in the Campania region (IT). The Aspen Plus software was used to depict the flowsheeting of the investigated torrefaction process, to develop and solve material and energy balances of the whole process, to carry out the internal heat integration steps. A novel aspect is the modeling of the torrefaction reactor, which was carried out by taking advantage of experimental correlations available in the literature from authors’ previous work. Drying of the wet biomass feedstock results a very energy-demanding operation. The main output of this study is the calculation of the process energy demand from external sources. Therefore, the paper discusses how far the torrefaction process of high-moisture tomato peel residues is from autothermal operation, provided the best available process design options and internal heat integration steps.

Fluidized Bed Combustion of a Lignin-based Slurry

Fluidized Bed Combustion of a Lignin-based Slurry Francesco Miccio, Roberto Solimene, Massimo Urciuolo, Paola Brachi, Michele Miccio a Institute for Research on Combustion CNR, P.le Tecchio 80, 80125 Napoli, Italy b Institute of Science and Technology for Ceramics CNR, via Granarolo 64, 48018 Faenza (RA), Italy c Department of Industrial Engineering, University of Salerno, via Giovanni Paolo II 132, 84084 Fisciano (SA), Italy francesco.miccio@cnr.it