1,720,975 research outputs found
Ammonia as a hydrogen carrier: energetic assessment of processes integrated with fuel cells for power generation
No full textAmmonia as a hydrogen carrier: energetic assessment of processes integrated with fuel cells for power generatio
Hydrogen production via steam reforming of different fuels: thermodynamic comparison
Full text linkHydrogen, a sustainable energy source, has potential to address climate change. However, traditional steam reforming processes produce CO2. Alternative fuels like bio-alcohols, biogas, and LPG are being adopted for steam reforming processes. This study presents a thermodynamic comparative examination of steam reforming processes employing different fuels, including methane, methanol, ethanol, propane, glycerol, and biogas. The analysis focuses on the hydrogen yield, environmental impact, and energy requirements of these processes and a comparison with experimental results. The analyses were conducted using AspenPlus® software, minimizing the Gibbs free energy under specified conditions (T = 25–1000 °C, n = 1–10, P = 1–40 bar). Among the fuels examined, methanol, biogas, and methane exhibited the highest hydrogen yields, reaching maximum values of 96.10 %, 95.86 %, and 95.26 % respectively at 600 °C, 1 bar, and a water-to-fuel ratio of 10. Ethanol, glycerol, and propane achieved yields of 89.66 %, 86.55 %, and 84.03 % respectively at 700 °C and the same pressure and water-to-fuel ratio
Prevention and Control of the Spread of Pathogens in a University of Naples Engineering Classroom through CFD Simulations
Full text linkThe design of ventilation and air conditioning systems in university classrooms is paramount to ensure students’ correct number of air changes per hour and an optimal thermal profile for their comfort. With the spread of the COVID-19 virus, these systems will inevitably need to evolve to cope with the current virus and any new airborne pathogens. The aim of this study is to analyze the quality of the ventilation system and the importance of the use of PPE in Lecture Hall C of the University of Naples Federico II compared to the premises in Piazzale Tecchio. After dimensioning the lecture theatre with the Autodesk software AutoCAD 2021, CFD simulations were carried out with the Computational Fluid Dynamics program Ansys 2021 R2. To study the trajectory of virus droplets released by a potentially infected student in the center of the classroom, the multispecies model was used, with carbon dioxide serving as the tracer gas for the virus cloud. After determining the CO2 contour zones at fifteen-minute intervals for a total duration of two hours, the probability of infection was calculated using the Wells–Riley equation
Dust explosion risk in polymer powder processing: Review and testing
No full textThe plastics industry, a global giant employing over 1.5 million people in Europe, faces a formidable challenge. Almost all plastic is combustible, and generating fine particles during processing (such as mechanical operations or recycling) can cause a potential explosion hazard. There is a wealth of literature on polymer powders in their 'pure' form, exploring the basic principles of dust explosions or measuring the effectiveness of inert dust in suppressing or preventing explosions. However, despite their frequent presence in the industry, there is a significant gap in research on polymer powder mixture, and actual industrial samples conditions. Which needs to be investigated urgently. The paper overviews relevant polymer dust explosions and accident dynamics and includes experimental testing and results. Statistical data on polymer dust explosions worldwide were examined to obtain a detailed picture of the materials involved and the severity of the explosion in terms of immediate damage and interruption of operations, furtherly, discussing lessons learned concerning dust explosion risks. Finally the experimental results presented here showed that more than 90% of the samples were combustible according to ISO 80079 and should therefore be considered “explosive.” Polyolefins have more severe explosive properties (regarding maximum explosion pressure and KSt) than more complex molecules (resins or polyesters). The highest value was shown by a mixture of PS/PPE dust collected in a recycling plant. These results revealed information on the likely synergistic effect of some polymers in a mix and the potential hazard that may affect different plastics industry sectors
Learning Safety of Dusts and Liquids by a Combined Experimental Lessons and Lectures Approach
Full text linkHumic acids on fire? Physico-chemical, thermal, flammability features and extraction process of different humic acids in support of their possible applications
Full text link: 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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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