Papers by Leonardo Tognotti
Bioresource technology, 2013
A pilot scale throated downdraft gasifier was operated with vine prunings as feedstock to assess ... more 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 load...
Attualmente 8 linee sono griglie, 2 RK (Montale) Taglie tutte tra 100 e 300 t/giorno Impianti non... more Attualmente 8 linee sono griglie, 2 RK (Montale) Taglie tutte tra 100 e 300 t/giorno Impianti non più operativi: Castelnuovo, Falascaia, Rufina L'impianto di San Zeno (griglia raffreddata ad aria, taglia 120 t/g) si colloca nella categoria più ricorrente in Italia
A Computational Fluid Dynamics model of a pilot-scale entrained flow reactor is developed with th... more A Computational Fluid Dynamics model of a pilot-scale entrained flow reactor is developed with the aim to shed light into the cloud of solid fuel particles. An iterative procedure is suggested to derive devolatilization kinetics: particle average residence times and heating rates are estimated from the numerical model, and a linear dependence of the particle temperature with residence time is assumed. In this manner the volatile release equation can be integrated analytically and subsequently kinetic parameters can be obtained from experimental conversion data. The procedure is shown for a Sebuku type coal in oxy-fuel conditions. Introduction The development of clean and efficient technologies for power generation from solid fuels such as biomass and coal, would benefit of detailed simulations tools as Computational Fluid Dynamics, able to handle a turbulent reactive multiphase flow in a complex geometry without any need of scale-up procedures. Despite the huge increase in computati...
Energy Procedia, 2018
District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
Bioresource Technology, Apr 1, 2013
h i g h l i g h t s " Develop a tool which allows evaluating the effect of the biomass loading ra... more h i g h l i g h t s " Develop a tool which allows evaluating the effect of the biomass loading rate and moisture content. " The model satisfactorily represents the gasifier behavior. " As the cold wave overcomes the hot wave no throat stabilization occurs. " When the biomass loading rate is increased up to 87.5 kg/h, no throat stabilization occurs.
Biodiesel production facilities are widespread in the world as the demand for “green” fuels incre... more Biodiesel production facilities are widespread in the world as the demand for “green” fuels increase continuously. So, the number of accidents increases with the number and the capacity of plants. In this paper, the fire and explosion risks in biodiesel production facilities are discussed. Beside some evident risk sources such as flammable storage tanks, we have shown that process deviations may give a relevant contribution to the overall risk and that two critical aspects may be: the excess of the amount of residual methanol in the streams fed to the phase separation step (e.g. biodiesel/unreacted separation after reaction, or glycerin/fatty acids separation), which can affect separation efficiency, and the condensation of flammable vapour streams.
Computer Aided Chemical Engineering, 2000
Combustion and Flame, 1995
... There is still a need to understand better the temper 00102180 95 9.50 SSDI 00102180(95) 0008... more ... There is still a need to understand better the temper 00102180 95 9.50 SSDI 00102180(95) 00089O 182 V. COZZANI ET AL. ... 1. Electrodynamic thermogravimetric analyzer (EDTGA). 184 V. COZZANI ET AL. An optical microscope and a video camera allow particle viewing. ...
Environmental Science & Technology, 1991
International Journal of Molecular Sciences
The use of biopolyesters, as polymeric matrices, and natural fillers derived from wastes or by-pr... more The use of biopolyesters, as polymeric matrices, and natural fillers derived from wastes or by-products of food production to achieve biocomposites is nowadays a reality. The present paper aims to valorize mussel shells, 95% made of calcium carbonate (CaCO3), converting them into high-value added products. The objective of this work was to verify if CaCO3, obtained from Mediterranean Sea mussel shells, can be used as filler for a compostable matrix made of Polylactic acid (PLA) and Poly(butylene adipate-co-terephthalate) (PBAT). Thermal, mechanical, morphological and physical properties of these biocomposites were evaluated, and the micromechanical mechanism controlling stiffness and strength was investigated by analytical predictive models. The performances of these biocomposites were comparable with those of biocomposites produced with standard calcium carbonate. Thus, the present study has proved that the utilization of a waste, such as mussel shell, can become a resource for bio...
The prediction of NO emissions from industrial burners represents a key goal of Computational Flu... more The prediction of NO emissions from industrial burners represents a key goal of Computational Fluid Dynamics (CFD) aided design. Simplified NO formation mechanisms are usually desirable, to reduce the computational effort related to the numerical simulations; however, they must be able to capture the NO trends with acceptable accuracy. Simplified mechanisms for the thermal and prompt NO formation routes are generally available within the existing commercial CFD packages and they provide acceptable NO predictions at relatively high temperatures. However, when operating at lower temperatures and with hydrogen, other mechanisms can be relevant, such as those involving N 2 O and NNH intermediates. This can become particularly relevant in non traditional combustion regimes, such as flameless combustion, characterized by operating temperature far below the levels observed in traditional burners. The present work shows a numerical and experimental investigation of a flameless combustion burner operating with methane-hydrogen mixtures with a H 2 content up to 50% by wt. The work is focused on the requirements of the CFD model for the accurate prediction of the NO emissions from the burner. In particular, the influence of the combustion model and kinetic mechanism on the temperature fields on which the NO prediction is based is thoroughly discussed, together with the simplified NO formation paths to be included in the model. The approach based on the direct coupling of simplified NO mechanisms to the CFD calculation is compared to a different methodology, based on the post-processing of the CFD results with detailed kinetic mechanism for the gasphase combustion and pollutants formation. A validation methodology is also implemented to quantitatively assess the degree of agreement between the numerical results and the experiments and to guide the selection of the modeling parameters required for predicting NO emissions accurately.
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Papers by Leonardo Tognotti