Alessandro Manni

Spent coffee enhanced biomethane potential via an integrated hydrothermal carbonization-anaerobic digestion process

This study reports the implications of using spent coffee hydrochar as substrate for anaerobic digestion (AD) processes. Three different spent coffee hydrochars produced at 180, 220 and 250 °C, 1 h residence time, were investigated for their biomethane potential in AD process inoculated with cow manure. Spent coffee hydrochars were characterized in terms of ultimate, proximate and higher heating value (HHV), and their theoretical bio-methane yield evaluated using Boyle-Buswell equation and compared to the experimental values. The results were then analyzed using the modified Gompertz equation to determine the main AD evolution parameters. Different hydrochar properties were related to AD process performances. AD of spent coffee hydrochars produced at 180 °C showed the highest biomethane production rate (46 mL CH4/gVS.d), a biomethane potential of 491 mL/gVS (AD lasting 25 days), and a biomethane gas daily composition of about 70%.

Biomass furnace study via 3D numerical modeling

Purpose – In the recent years the interest toward the use of biomass as a fuel for energy conversion, along with the continuous tightening of regulations, has driven the improvement of accurate design techniques which are required to optimize the combustion process and simultaneously control pollutant emissions. In this paper the use of a 3D Computational Fluid Dynamics approach is analyzed to that aim by means of an application to an existing 50 MW biomass fixed-bed combustion furnace fueled by grape marc. The paper aims to discuss these issues. Design/methodology/approach – The studied furnace is an interesting example of biomass utilization as it may integrate biomass with organic residual by an industrial process. The numerical model has been implemented into an OpenFOAM solver, with an Eulerian-Lagrangian approach. In particular, the fully 3D approach here presented, directly solves for the gas and solid evolution in both the combustion bed and the freeboard. Special care has also been devoted to the...

Biomass pyrolysis modeling of systems at laboratory scale with experimental validation

Purpose Thermochemical conversion processes are one of the possible solutions for the flexible production of electric and thermal power from biomass. The pyrolysis degradation process presents, among the others, the interesting features of biofuels and high energy density bio-oil production potential high conversion rate. In this paper, numerical results of a slow batch and continuous fast pyrolyzers, are presented, aiming at validating both a tridimensional computational fluid dynamics-discrete element method (CFD–DEM) and a monodimensional distributed activation energy model (DAEM) represents with data collected in dedicated experiments. The purpose of this paper is then to provide reliable models for industrial scale-up and direct design purposes. Design/methodology/approach The slow pyrolysis experimental system, a batch of small-scale constant-pressure bomb for allothermic conversion processes, is presented. A DEM numerical model has been implemented by means of a modified OpenFOAM solver. The fast pyrolysis experimental system and a lab scale screw reactor designed for biomass fast pyrolysis conversion are also presented along with a 1D numerical model to represent its operation. The model which is developed for continuous stationary feeding conditions and based on a four-parallel reaction chemical framework is presented in detail. Findings The slow pyrolysis numerical results are compared with experimental data in terms of both gaseous species production and reduction of the bed height showing good predictive capabilities. Fast pyrolysis numerical results have been compared to the experimental data obtained from the fast pyrolysis process of spruce wood pellet. The comparison shows that the chemical reaction modeling based on a Gaussian DAEM is capable of giving results in very good agreement with the bio-oil yield evaluated experimentally. Originality/value As general results of the proposed activities, a mixed experimental and numerical approach has demonstrated a very good potential in developing design tools for pyrolysis development.