The shelf life of energetic materials (EMs) is directly associated with safety and functionality. Therefore, a priori knowledge of this parameter is essential. The standard approach for predicting the shelf life of EMs is tremendously time and money consuming. It involves massive accelerated aging tests at temperatures typically between 40 and 80 °C for relatively long time periods--from months to years--with different aging time intervals, followed by analysis of the aging-induced changes. A subsequent kinetic analysis with Arrhenius evaluation provides the effective activation energy for calculating shelf life at lower storage temperatures. In this work, a much less time- and resource-intensive approach based on the kinetic analysis of decomposition data gathered by using thermal analysis techniques is discussed as a possible alternative for the shelf life prediction of EMs. The discussion is placed in the context of the few but promising works of literature on the subject that provide evidence and examples. On the path towards the practical application of this approach, the definition of procedures that allow for a realistic simulation of storage conditions not only in the accelerated aging tests--still needed but limited to the validation of the decomposition kinetics--but also in the thermal analysis experiments is highlighted as one of the main issues to be addressed. © 2023 by the authors.

As the use of biomass as a carbon-neutral energy source increases, so does the need for storage facilities, especially for those that are highly seasonal. Consequently, the stored materials may be subject to a natural ageing process before they are used. Such ageing can modify the deflagration parameters of the materials since it can reduce hygroscopicity, increase stiffness and brittleness and change chemical composition in terms of cellulose, hemicellulose and lignin contents. Hydrothermal treatment is a process that accelerates the ageing of wood and lignocellulosic materials. In this work, several lignocellulosic powders from industrial processes were subjected to accelerated ageing to investigate their influence on flammability properties. Grape marc, cork flour, olive pomace, wood dust and lignocellulosic residues from processing waste were selected based on their morphology, chemical characterization and lignin/cellulose content. Based on literature data, ageing conditions in terms of temperature and humidity were chosen to reproduce naturally aged materials. In this study, the effects of ageing on the minimum ignition energy (MIE) and combustion/pyrolysis behaviour were investigated by chemico-physical screening and thermogravimetric analysis and differential scanning calorimetry (TGA and DSC) in an inert and oxidative atmosphere. Results showed how ageing can change the risk of ignition. For example, the MIE of grape marc decreases, while wood-based samples do not ignite after ageing. The decrease in the case of grape pomace is consistent with the decrease in lignin content and moisture. At the same time, passivation of the particle surface could explain the behaviour of the wood samples.

Humic acids (HA) consist in a multitude of heterogeneous organic molecules surviving the biological and chemical degradation of both vegetal and animal biomasses. The great abundance and chemical richness of these residues make their valorisation one of the most promising approaches to move towards a circular economy. However, the heterogeneity of the biomass from which HA are extracted, as well as the production process, significantly affects the nature and the relative content of functional groups (i.e. quinones, phenols and carboxylic and hydroxyl moieties), eventually changing HA reactivity and ultimately determining their application field. Indeed, depending on their properties, these substances can be used as flame retardants in the case of pronounced resilience degree (i.e., absent or low reactivity), or as antioxidant or antimicrobial agents in the case of pronounced reactivity, thanks to their redox behaviour. In this work we investigated the flammable, the thermal and the physico-chemical features of HA extracted from different composted biomasses to identify the reactivity or the resiliency of these moieties. Several techniques, including flammability characterization (LIT and MIE), laser diffraction granulometry, TG, XRD analyses, FTIR spectroscopy on both solid and gaseous phases, and Raman spectroscopy were integrated to investigate the correlation among the safety parameters, the distributions of particle sizes, as well as the thermal, the chemical properties of HA powders and the influence of post-extraction processes on HA final properties.

This paper presents in detail a novel course introduced in the academic year 2021/2022 in the Master's degree program in Chemical Engineering at the University of Naples Federico II. The course, called Safety of Dusts and Liquids and Lab Activities, aims to educate students on the industrial safety issues of combustible dusts and flammable liquids. The course was structured with lectures, classroom exercises and laboratory activities aimed at characterizing the ignition sensitivity and explosion severity of certain gaseous fuels, liquids and dusts. Each laboratory activity was preceded by a video tutorial, designed and prepared by the lecturers, in order to introduce the students to the activities and prepare them for all the procedures to be performed. Students' satisfaction was assessed through the compilation of several anonymous surveys. Results showed a high level of student satisfaction with the course topics and laboratory activities and they will also be used to introduce some improvements for next year.

Sono stete effettuate misure di Resistività Elettrica di Volume e l'Energia MInima di Innesco (MIE) di una polvere organica di Interesse Industriale

In this work, a three-layers Mallard-Le Chatelier inspired theoretical model is developed to fully characterise the steps occurring during the flame propagation of combustible dusts/air. The model is based on the hypothesis that the dust flame propagation follows a homogeneous path: the dust-air mixture is pre-heated up to the volatile point ( VP ), at which production of volatiles occurs, thanks to the backdiffusion of heat from the combustion zone of the flame to the colder zones. The volatiles produced are then heated up to the ignition temperature and enter in the combustion zone. The flame burning velocity is the results of the coupling between heating rate, pyrolysis and/or evaporation/sublimation rate and volatiles combustion rate. The rate of formation of volatiles was measured by means of TG/DSC analysis. The laminar burning velocity of gases was computed by simulating the gas flame propagation in a tube starting from the measured gas compositions (by literature data or FTIR analysis). (c) 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

According to the current international standards, to perform the correct evaluation of the explosion and flammability parameters, a uniform distribution of the dust particles should be achieved inside the 20 L and/or 1 m3 standard vessels.CFD simulations have shown that in both standard test vessels (20 L and 1 m3), the dust particles are not uniformly dispersed, being mostly concentrated at the edge of the macro-vortices generated by the injection of the fluid and particle through the nozzle. In addition, only a partial fed of the particles is obtained, and dust particles sedimentation phenomena can occur.As a result, the dust participating to the reactive process may be much lower than the expected nominal concentration in the vessel due to sedimentation and incomplete feeding. Consequently, misleading values of the flammability/explosion parameters could be measured. Particle sedimentation and incomplete feeding depends both on the Stokes number and on the Reynolds number, whereas the concentration distribution depends on the turbulence level, the fluid flow maps, and the number of particles which enter into the vessel through the nozzle.The aim of this work is to evaluate the key parameters (particle size, particle density, and fluid velocity) affecting sedimentation and incomplete feeding in 20 L vessel. To this end, CFD simulations of dust dispersion are performed at varying the particle density and size. Operating maps, in terms of the key parameters and/or their dimensionless combinations, are developed and a correlation for correction of the data is proposed.

Against dust explosions, all the flammability and explosibility parameters must be evaluated following standard procedures using the 20 L and/or the 1 m(3) vessel. Previous results comparing the dust dispersion in the 20 L sphere equipped with rebound or perforated annular nozzle showed that the initial turbulence level, the dust concentration, and the feeding are affected by the type of nozzle used. In this work, a similar investigation was performed on the 1 m(3) vessel, simulating the fluid flow evolution which is obtained with the rebound nozzle. Results showed that the 1 m3 vessel equipped with rebound nozzle presents a less uniform degree of turbulence and a higher amount of dust fed, compared to the case of perforated annular nozzle. However, the greatest effect on the initial level of turbulence and turbulent combustion regime is determined by the size of the vessel and not by the type of nozzle used.

Safety parameters assessment is not sufficient to fully understand the flammable and explosive behaviour of a combustible dust and correctly manage potential risk. A correct evaluation requires the identification of flame propagation path as well as the limiting step controlling fire propagation, through evaluation of dimensionless numbers (Biot, Damko center dot hler, Thiele, Sherwood, Thiele modulus numbers). Herein, these aspects were investigated for non-traditional dusts, made of nylon 6,6 short fibers. To this purpose, flammability parameters including minimum ignition energy (MIE), the maximum pressure of explosion and the deflagration index were assessed and combined with results of extensive physical-chemical characterization, by means of several techniques (TGA/DSC, FTIR, XRD). In particular, thermogravimetric analysis highlighted the presence of homogeneous and heterogeneous phase phenomena activated at different temperatures and heating rates. The homogeneous phase processes are controlled by the pyrolysis process strictly dependent on the dust size and its decomposition kinetics. The most flammable sample is characterized by smaller dimensions and a fast decomposition kinetics at low temperature. Heterogeneous flame propagation is controlled by the intrinsic heterogeneous reaction. The most reactive sample is characterized by the highest value of specific surface area and by intense exothermic phenomena at low temperature, as evidenced by the analysis of the solid residue. As a main conclusion, the processes involving nylon fibres that may modify the key parameters influencing the flammable/explosive behaviour are also discussed.

A priori knowledge of the shelf life of energetic materials (EMs) is relevant due to its direct association with safety and functionality. This paper proposes a quick and reliable approach to predicting the shelf life of EMs whose thermal decomposition is an autocatalytic process once their failure threshold has been defined as a function of the limiting extent of conversion. This approach is based on the assumption of a kinetic law consistent with the autocatalytic behavior and on the subsequent extraction, via a suitable procedure of parameter identification, of the kinetics of thermal decomposition from differential scanning calorimetry (DSC) data gathered under dynamic conditions at three different heating rates. Its reliability is proven for picric acid (PA) through the comparison of kinetic predictions with evaluations of conversion obtained by using high performance liquid chromatography (HPLC) analysis for samples subjected to isothermal and non-isothermal accelerated aging tests, as well as for a sample of naturally aged material, i.e., PA, stored at room temperature for more than 10 years.

Mediante prove sia di tipo dinamico che in modalità Heat Step Scan, sono stati determinati tramite calorimetria differenziale la temperatura di transizione Vetrosa ed il Calore specifico di una resina di natura Vegetale

An unexpected promoting effect of KBr, used as a diluting salt, on the degradation of picric acid (PA) was observed during in situ diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy experiments performed here under accelerated ageing conditions--at 80 C and under an inert or oxidative atmosphere. While the formation of potassium picrate was excluded, this promoting effect--which is undesired as it masks the possible effects of test conditions on the ageing process of the material--was assumed to favor a first step of the decomposition mechanism of PA, which involves the inter- or intramolecular transfer of hydrogen to the nitro group, and possibly proceeds up to the formation of an amino group. An alternative diluting salt, ZnSe, which is much less commonly used in infrared spectroscopy than KBr, was then proposed in order to avoid misleading interpretation of the results. ZnSe was found to act as a truly inert diluting salt, preventing the promoting effect of KBr. The much more chemically inert nature (towards PA) of ZnSe compared to KBr was also confirmed, at much higher temperatures than DRIFT experiments, by dynamic differential scanning calorimetry (DSC) runs carried out on pure PA (i.e., PA without salt) and PA/salt (ZnSe or KBr) solid mixtures.

Il lavoro commissionato dalle società Ramoil ha riguardato la determinione del calore specifico tramite tecniche di calorimetria differenziale in scansione (DSC) in funzione della temperatura di alcuni oli minerali paraffinici di interesse Industriale

Some flammability characteristics of some dusts of industrial interest have been evaluated and measured

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Featured Application This work will help to identify and assess the dust explosion risk related to biomasses intended for energetic purposes. The concern about global warming issues and their consequences is more relevant than ever, and the H2020 objectives promoted by the EU are oriented towards generating climate actions and sustainable development. The energy sector constitutes a difficult challenge as it plays a key role in the global warming impact. Its decarbonization is a crucial factor, and significant efforts are needed to find efficient alternatives to fossil fuels in heating/electricity generation. The biomass energy industry could have a contribution to make in the shift to renewable sources; the quest for a suitable material is basically focused on the energy amount that it stores, its availability, logistical considerations, and safety issues. This work deals with the characterization of a wine-waste dust sample, in terms of its chemical composition, fire behavior, and explosion violence. This material could be efficiently used in energy generation (via direct burning as pellets), but scarce information is present in terms of the fire and explosion hazards when it is pulverized. In the following, the material is analyzed through different techniques in order to clearly understand its ignition sensitivity and fire effects; accelerating aging treatment is also used to simulate the sample storage life and determine the ways in which this affects its flammability and likelihood of explosion.

There are at least two main requirements for repeatable and reliable measurements of flammability and explosibility parameters of dusts: A uniform dispersion of solid particles inside the test vessel and a homogeneous degree of turbulence. Measurements of these parameters are performed in spherical vessels (20 L sphere or 1 m3 sphere). In several literature works, it has been shown that, in the standard 20 L sphere, the dust injection system generates a non-uniform dust cloud, while high gradients characterize the turbulent flow field. In our recent work, CFD simulations of flow field and dust concentration distribution in the 1 m3 spherical vessel were carried out and the results compared to the data previously obtained for the 20 L. It has been found that in the 1 m3 vessel, the spatial distribution of the turbulent kinetic energy is lower and much more uniform. Concerning the dust distribution, as in the case of the 20 L, dust is mainly concentrated at the outer zones of the vortices generated inside the vessel. In this work we use the previously validated CFD model to simulate the dust dispersion inside the 1 m3 vessel at different dust diameters. Results show that on increasing the dust diameter, the dust paths are different from those of the fluid flow until the sedimentation effect prevails and the turbulence field becomes similar to the dust-free air case. Since the spatial distribution of the turbulent kinetic energy is lower and much more uniform than in the 20 L sphere, the 1 m3 vessel is less susceptible to variations in the dust intrinsic properties, making parameter measurements more reliable and repeatable.

Food and drink supply chains have significant environmental impacts due to their use of resources, emissions, and waste production. An efficient method to reduce this impact is the valorisation of biomass waste through energy recovery by using it as a source of heat. The European energy system faces several fundamental challenges being currently the largest emitter of greenhouse gases due to its large dependence on fossil fuels (mostly natural gas). Therefore, the energy sector's decarbonization will play a central role in achieving a climateneutral economy in Europe. Identifying the suitable material for biofuel is basically focused on the amount of energy that the material stores, availability, and logistic considerations. Sawdust and wood chips have been extensively used as biofuel in recent years, but other promising raw and waste materials could be adopted (with the positive effect of reducing the impact on forestry soil and the food chain). Novel materials bring consequently novel challenges, also regarding their safe use. As an example, a relevant waste flow is produced from wine manufacturing. A solid with high moisture content is obtained from grapes pressing, and it could be reused to produce distillates. The obtained exhausted pomace could be considered among the materials potentially involved in energy recovery. It is also carrying dust explosion hazard, as solid residues could be present in the form of coarse and fine powders. In this work, grape pomace is examined: its explosion safety-related properties are evaluated to define the severity of events in which this material could be ignited. Minimum Ignition Energy (MIE), explosion pressure peak (Pmax), deflagration severity index (KSt), autoignition temperature (MIT), and Volatile Point (VP) are measured according to standard procedures. This material's thermal susceptibility and ignition sensitivity are studied and compared with biomasses from different sources (ligneo-cellulosic and herbaceous).

In this work, the effect of spatial distribution and values of the turbulent kinetic energy on the pressure-time history and then on the explosion parameters (deflagration index and maximum pressure) was quantified in both the standard vessels (20 L and 1 m). The turbulent kinetic energy maps were computed in both 20 L and 1 m vessels by means of CFD simulations with validated models. Starting from these maps, the turbulent flame propagation of cornstarch was calculated, by means of the software CHEMKIN. Then, the pressure-time history was evaluated and from this, the explosion parameters. Calculations were performed for three cases: not uniform turbulence level as computed from CFD simulations, uniform turbulence level and equal to the maximum value, uniform profile and equal to the minimum value. It was found that the cornstarch in the 20 L vessel get variable classes (St-1, St-2, St-3) with respect to the 1 m (St-1). However, simulations performed on increasing the ignition delay time, shown that the same results can be attained only using 260 ms as ignition delay time in the 20 L vessel.

Several phenomena (e.g., initial turbulence level, overdriving, underdriving, etc.) affect the measurement of dust explosion parameters in the 20 L and 1 m standard test vessels. Estimating the role of each phenomenon is crucial to understand the discrepancies observed over the years between the data collected using these vessels. In this work, we focus on the role of the pyrotechnic ignitors on the pressure trend and the temperature distribution. We run explosion tests in the 20 L vessel to measure the pressure-time history generated by the explosion of pyrotechnic ignitors. Moreover, we performed CFD simulations to simulate the spatial/temporal evolution of the temperature map from the hot core due to the igniter explosion toward the vessel walls. The explosion of the pyrotechnic ignitors shows a significant increase of pressure in the 20 L vessel, suggesting that flame propagation is occurring inside the vessel. Furthermore, the localized increase of temperature due to the ignitor explosions, diffuse, and then uniformize much more rapidly in the 20 L vessel than in the 1 m vessel. The flame propagation generated by the ignitors is very relevant in the 20 L sphere leading to the overdriving phenomenon. This result justifies the fact that for many organic dusts, the deflagration index values measured in the 20 L are much higher than those measured in the 1 m vessel. CFD simulations show that the hot core generated by the ignitors dissipate much faster in the 20 L vessel than in the 1 m vessel, due to the higher turbulence level of the smaller vessel. Therefore, dusts whose combustion is controlled by particle heating are more prone to sustain combustion in the 1 m than in the 20 L vessel.