Marco Simone

Gasification of pelletized biomass in a pilot scale downdraft gasifier

This work presents a pilot-scale investigation aimed at assessing the feasibility and reliability of biomass pellet gasification. Wood sawdust and sunflower seeds pellets were tested in a 200 kW downdraft gasifier operating with air as gasifying agent. The gasification of pelletized biomass led to rather high and unstable pressure drops, reducing the gasifier productivity and stability. Furthermore the generation of fine residues compromised the operation of wet ash removal systems. On the other hand, good syngas compositions (H(2) 17.2%, N(2) 46.0%, CH(4) 2.5%, CO 21.2%, CO(2) 12.6%, and C(2)H(4) 0.4%), specific gas production (2.2-2.4 N m(3) kg(-1)) and cold gas efficiency (67.7-70.0%) were achieved. For these reasons pelletized biomass should be considered only as complementary fuel in co-gasification with other feedstock.

Suitability of giant reed (Arundo donax L.) for anaerobic digestion: Effect of harvest time and frequency on the biomethane yield potential

This study aimed to investigate the potential of giant reed for biomethane production by examining the influence of harvest time and frequency on the Biochemical Methane Potential (BMP), the kinetics of biomethane accumulation in batch reactors and the expected methane yield per hectare. The crop was cut at five different times, regrowths from early cuts were harvested in autumn and BMP of each cut was assessed. The highest BMP (392 NL kg VS(-1)) and the best kinetics of methane production were associated to juvenile traits of the crop. By coupling the early cuts with the corresponding regrowths (double harvest), the dry biomass (from 35 to 40 Mg ha(-1)) equaled that obtained by a single cut at end of the season (38 Mg ha(-1)), while the methane yield per hectare (11,585-12,981 Nm(3) ha(-1)) exceeded up to 35% the methane produced with a single harvest at crop maturity (9452 Nm(3) ha(-1)).

Assessment of syngas composition variability in a pilot-scale downdraft biomass gasifier by an extended equilibrium model

A new simplified approach based on equilibrium modeling is proposed in this work to describe the correlations among syngas species experimentally observed in a pilot scale downdraft biomass gasifier operated with different feedstocks (biomass pellets and vine prunings). The modeling approach is based on experimental evidence on the presence of devolatilization products in the syngas and fluctuations of syngas composition during stationary operation, accounted for by introducing two empirical parameters, a by-pass index and a permeability index. The simplified model correctly reproduces the correlations among the main syngas species (including methane and ethylene) resulting from experimental data of pilot tests with different feedstocks and under a wide range of operating conditions.

Numerical and experimental investigation of downdraft gasification of woody residues.

A pilot scale throated downdraft gasifier was operated with vine prunings as feedstock to assess the effect of biomass loading rate on process performance. A distributed 1D model of mass and heat transfer and reactions was applied to aid the interpretation of experimental evidence. The model takes into account peculiar gasifier design features (air inlets and throat) and it reproduces satisfactorily the temperature profiles and the mass fluxes of gaseous species at different biomass loading rates. The integration of pilot-scale experiments and numerical simulations provides sound indications for the gasifier operation. In particular, simulations performed at different loading rates and feedstock humidity show that steady state operation and stable performance of the gasifier rely on the thermal balance between the enthalpy of cold biomass moving downward and the counter-current radiative heat fluxes moving upward from the oxidation zone. This balance can be destabilized by high loading rate and moisture contents.

Gasification of woodchips from the San Rossore natural reserve maintenance for CHP application: A case study analysis

This work aims at analyzing a complete biomass gasification chain for CHP purposes. The biomass production step is related to an existing scenario, the woodchips produced from the maintenance of the S.Rossore natural reserve. Two different gas cleaning systems are taken into account, a wet gas clean-up and a hot gas clean-up (based on a dolomite bed with air injection for tar cracking). Performance indicators are calculated according to an inventory of the energy and mass fluxes. The results show that the most significant energy loss of the wet gas clean-up is due to syngas cooling, while for the hot tar clean-up part of the syngas sensible heat is recovered, however this is a benefit only if a suitable heat demand is available in the plant. Since part of the syngas chemical energy is lost in the dolomite bed in the hot clean-up, the overall energy efficiency of this chain is lower compared to the wet gas clean-up. The main advantage of the hot clean-up is the reduction of the wastewater.

A Comprehensive Approach to the Characterization of second Generation Biofuels

The thermochemical conversion of conventional and alternative biofuels is capable of supplying a wide range of energy vectors and chemicals. Peculiarities of such materials require a comprehensive and detailed characterization to provide the fundamental information and face with the issues of each process step. Innovative technologies, advanced model approaches, optimization procedures, need data which comply with relevant standards. The characterization tools described in this work range from lab-scale tools, used to provide the fuel fingerprint, to pilot scale facilities, which operate under industrial scale conditions. Protocols and procedures have been elaborated for all activities to provide reliable and qualified parameters for practical applications and comprehensive codes. The experimental activities have been supported with a broad set of on-line and off-line measurements and analyses, and coupled with modelling activities to qualify the experiments. Finally, a biofuel database, reporting the data collected in the last years, has been developed.

Biomass gasification: experimental and modelling activities at CRIBE

Biomass gasification can be operated in various reactor configurations and under different operating conditions. The process is versatile as for biomass input as well as for the product (electricity, cogeneration, syngas, hydrogen, Fischer-Tropsch fuels) and it is an option to promote distributed power generation. Despite this technology was proposed and studied starting from the mid 20 th century, it is still not widespread due to some technological barriers that need to be addressed [1]. The major technological barriers can be classified in two groups: