International Flame Research Foundation

Livorno, Italy

International Flame Research Foundation

Livorno, Italy
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Simone M.,Centro Of Ricerca Interuniversitario Sulle Biomasse Da Energia | Nicolella C.,Centro Of Ricerca Interuniversitario Sulle Biomasse Da Energia | Tognotti L.,Centro Of Ricerca Interuniversitario Sulle Biomasse Da Energia | Tognotti L.,International Flame Research Foundation
Chemical Engineering Transactions | Year: 2011

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. © 2011, AIDIC Servizi S.r.l.


Li J.,KTH Royal Institute of Technology | Biagini E.,International Flame Research Foundation | Yang W.,KTH Royal Institute of Technology | Tognotti L.,International Flame Research Foundation | And 2 more authors.
Combustion and Flame | Year: 2013

In this work, the flame characteristics of torrefied biomass were studied numerically under high-temperature air conditions to further understand the combustion performances of biomass. Three torrefied biomasses were prepared with different torrefaction degrees after by releasing 10%, 20%, and 30% of volatile matter on a dry basis and characterized in laboratory with standard and high heating rate analyses. The effects of the torrefaction degree, oxygen concentration, transport air velocity, and particle size on the flame position, flame shape, and peak temperature are discussed based on both direct measurements in a laboratory-scale furnace and CFD simulations. The results primarily showed that the enhanced drag force on the biomass particles caused a late release of volatile matter and resulted in a delay in the ignition of the fuel-air mixture, and the maximum flame diameter was mainly affected by the volatile content of the biomass materials. Furthermore, oxidizers with lower oxygen concentrations always resulted in a larger flame volume, a lower peak flame temperature and a lower NO emission. Finally, a longer flame was found when the transport air velocity was lower, and the flame front gradually moved to the furnace exit as the particle size increased. The results could be used as references for designing a new biomass combustion chamber or switching an existing coal-fired boiler to the combustion of biomass. © 2013 The Combustion Institute.


Li J.,KTH Royal Institute of Technology | Bonvicini G.,International Flame Research Foundation | Tognotti L.,International Flame Research Foundation | Tognotti L.,University of Pisa | And 2 more authors.
Fuel | Year: 2014

Torrefied biomass is a coal-like fuel that can be burned in biomass boilers or co-fired with coal in co-firing furnaces. To make quantitative predictions regarding combustion behavior, devolatilization should be accurately described. In this work, the devolatilization of three torrefied biomasses and their parent material were tested in an isothermal plug flow reactor, which is able to rapidly heat the biomass particles to a maximum temperature of 1400 C at a rate of 104 C/s, similar to the conditions in actual power plant furnaces. During every devolatilization test, the devolatilized biomass particles were collected and analyzed to determine the weight loss based on the ash tracer method. According to the experimental results, it can be concluded that biomass decreases its reactivity after torrefaction, and the deeper of torrefaction conducted, the lower the biomass reactivity. Furthermore, based on a two-competing-step model, the kinetic parameters were determined by minimizing the difference between the modeled and experimental results based on the least-squares objective function, and the predicted weight losses exhibited a good agreement with experimental data from biomass devolatilization, especially at high temperatures. It was also detected that CO and H2 are the primary components of the released volatile matters from the devolatilization of the three torrefied biomasses, in which CO accounts for approximately 45-60%, and H2 accounts for 20-30% of the total volatile species. © 2014 Elsevier Ltd. All rights reserved.


Coraggio G.,International Flame Research Foundation | Tognotti L.,International Flame Research Foundation | Cumbo D.,ENEL S.p.A | Rossi N.,ENEL S.p.A | Brunetti J.,ENEL S.p.A
Proceedings of the Combustion Institute | Year: 2011

This paper reports part of the results of the campaigns performed on a low NOx burner, firing natural gas in oxy-fuel conditions. The results of combustion tests on burning natural gas with different flue gas recycle rates are presented, with a particular emphasis on NOx production that might affect retrofitting of oxy-fuel technology in conventional boilers. The process and flame characterisation performed on natural gas provides a valuable set of experimental data for the technological development of oxy-combustion burner technology with recycled flue gas, especially in retrofitting scenarios. The data can be used to develop a better understanding of the chemical and physical phenomena involved in oxy-fuel combustion and can provide modellers with a valuable hint for the development of specific sub-models for oxy-combustion simulation. Since is seems technologically unfeasible to reduce down to zero the presence of nitrogen in recycled flue gases, due to air in-leakages, the presence of relatively small amounts of nitrogen in crucial location in the burner provides a thermal NOx source, depending on local levels of temperature and oxygen concentration. © 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.


Karlstrom O.,Åbo Akademi University | Brink A.,Åbo Akademi University | Hupa M.,Åbo Akademi University | Tognotti L.,University of Pisa | Tognotti L.,International Flame Research Foundation
Combustion and Flame | Year: 2011

In industrial pulverized fuel combustion, char oxidation is generally limited by the combined effects of chemical reactions and pore diffusion. Under such conditions, char oxidation is frequently predicted by power law models, which despite their simplicity, are widely used in the comprehensive CFD modeling of pulverized coal boilers. However, there is no consensus on the apparent reaction order given by such models. This study developed a systematic approach which gives consistent values over a range of conditions. Apparent reaction orders for 10 bituminous coal chars were investigated with three different oxygen concentrations, ranging from 4 to 12vol.%, and a gas temperature of 1223K for each char. Experimental burnout profiles of the chars were obtained by means of an Isothermal Plug Flow Reactor operating at industrially realistic heating rates (104K/s). For various reaction orders between 0.05 and 2.00, kinetic parameters were independently determined, following numerical procedures recently suggested in the literature. The resulting values were incorporated into an empirical power law model and compared to experimental data for the 10 chars, over a burnout range of 0-75%. The best fit to the experiments occurs with apparent reaction orders of around one for all the chars. © 2011 The Combustion Institute.


Galletti C.,University of Pisa | Coraggio G.,International Flame Research Foundation | Tognotti L.,University of Pisa | Tognotti L.,International Flame Research Foundation
Fuel | Year: 2013

The modeling through computational fluid dynamics of oxy-natural-gas combustion experimental tests in a 3 MW semi-industrial furnace equipped with alow NOx burner is discussed. Since the complex geometry of the burner and the size of the furnace, a modeling strategy has been adopted to diminish the computational time and thus to make the simulations affordable. The model aims at validating different sub-models (e.g. combustion/kinetics, radiation/spectral) for oxy-natural-gas fired conditions through the comparison of predictions and in-flame measurements of temperature and chemical species. It is found that fast chemistry approaches are unable to predict the temperature field. The spectral model was also found to play a fundamental role for the correct analysis of such scale devices. Uncertainties in experimental and modeling results are discussed and compared. © 2013 Elsevier Ltd. All rights reserved.


Karlstrom O.,Åbo Akademi University | Brink A.,Åbo Akademi University | Biagini E.,Consorzio Pisa Ricerche | Hupa M.,Åbo Akademi University | And 2 more authors.
Proceedings of the Combustion Institute | Year: 2013

The influence of concentration of oxygen on the oxidation rates of 5 anthracite chars is investigated at gas temperatures ranging from 1223 K to 1673 K. Reaction orders and kinetic parameters are determined with a multivariable optimization method in which modeled burnout profiles are fitted to experimental burnout profiles from a 4 m isothermal plug flow reactor operating at industrially realistic heating rates, i.e., 104-105 K/s. The determined reaction orders are compared to reaction orders of 10 bituminous coal chars investigated at similar conditions in a previous study. The results show that the optimized reaction order of the anthracite chars is zero, while the reaction order of the bituminous coal char is one. The difference in the reaction orders cannot be explained by using the two semi-global oxidation reactions: C(O) + O2 → CO/CO2 and C(O) → CO. However, by also considering 2C(O) → CO2 + C as a possible reaction step, the reaction order difference between the anthracite chars and the bituminous coal chars can be explained. In addition, a first attempt to apply the same multivariable optimization method to determine the reaction order for a biomass char is presented. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.


Galletti C.,University of Pisa | Coraggio G.,International Flame Research Foundation | Tognotti L.,University of Pisa | Tognotti L.,International Flame Research Foundation
IFRF Combustion Journal | Year: 2014

Computational Fluid Dynamics (CFD) simulations of oxy-coal combustion experiments conducted at the IFRF at the semi-industrial scale with two different burners, i.e. the Aerodynamically Air Staged Burner (AASB) and the low-NOx TEA-C burner, were performed in order to investigate the performance of different sub-models for oxy-fired conditions. Special attention was devoted to the reduction of computational cost by using proper modelling strategies based on reduced and complete computational domains. The uncertainties due to the choice of different sub-models and boundary conditions are discussed, highlighting the need for accurate and comprehensive experimental datasets to validate computational models. Discussion is made of the use of proper validation metrics to quantify the level of agreement between predictions and experiments. © International Flame Research Foundation, 2014.


Galletti C.,University of Pisa | Giovannini L.,University of Pisa | Coraggio G.,International Flame Research Foundation | Tognotti L.,University of Pisa | Tognotti L.,International Flame Research Foundation
Chemical Engineering Transactions | Year: 2013

Coal combustion is investigated in both air and oxy-fuel conditions in a pilot-scale entrained flow reactor able to provide high temperatures, heating rates and residence times. Measurements are carried out with different levels of complexity and are aimed at: assessing the thermal field inside the reactor; evaluating conversions of devolatilization or char combustion tests; identifying phenomena such as volatiles ignition and measuring the ignition delay time. Computational Fluid Dynamics was also used in order to provide a better understanding of the experimental evidences. Among the results, the ignition delay time was found to be larger in oxy-fuel conditions than in air, mainly because of the larger specific heat of the oxy-fuel environment. The proposed investigation may help the qualification of advanced experimental apparatus as entrained flow reactors, with the purpose to make them suitable for heterogeneous kinetics studies in oxy-fuel conditions. Copyright © 2013, AIDIC Servizi S.r.l.


Karlstrom O.,Åbo Akademi University | Brink A.,Åbo Akademi University | Hercog J.,Polish Institute of Power Engineering | Hupa M.,Åbo Akademi University | And 2 more authors.
Energy and Fuels | Year: 2012

In this study, the oxidation of 22 bituminous coal chars is modeled with (i) an individual activation energy for each char and (ii) constant activation energy for all the chars. Modeled burnout profiles, from 0 to 75% of burnout, are compared to experimental measurements from a 4 m isothermal plug flow reactor operating at temperatures and heating rates typical of pulverized fuel industrial combustion. The fuel and the gas rates are chosen such that temperature gradients in the radial direction and along the centerline of the reactor are minimized. In this study, the objective is to predict the burnout profiles with a model suitable for the comprehensive computational fluid dynamics (CFD) modeling of pulverized fuel boilers. Therefore, a power law model that takes into account external diffusion and apparent kinetics is used. The kinetic parameters that are used in the model are determined with a suggested multivariable optimization method. The results show that the experimental burnout profiles of the 22 individual chars are not predicted with a significantly higher accuracy using separately determined activation energy for each char than they were using a constant activation energy for all the chars. Thus, only one fuel specific parameter (i.e. the pre-exponential factor) is needed to model the burnout profiles. These findings are in agreement with some previous studies but are important considering the significant amount of experimental data and the large number of coal chars investigated using a systematic approach. © 2012 American Chemical Society.

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