36,450 research outputs found
Maria Bersani
No full textLa voce illustra la biografia e l'apporto letterario dato da Maria Bersani alla letteratura per l'infanziaThe headword explains the biography and the contribution of the author Maria Bersani to the children's literatur
Maria C. Manca de Nadra, Mario E. Arena and Fabiana M. Saguir
No full textIt is well known that lactic acid bacteria need multiple nutritional requirements for growth. They require numerous amino acids and other growth factors to develop in synthetic media. In this review the amino acid requirements, the effect of L-malic acid and citric acids metabolism on these requirements and the catabolism of amino acids by lactic acid bacteria from wine are discussed, with emphasis on arginine and its amino acid derivates: citrulline and ornithinFil: manca de Nadra, Maria C.. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Saguir de Zucal, Fabiana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Microbiología; ArgentinaFil: Arena, Mario Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentin
Carbon Nanotubes from Polyethylene: Experimental Study and Modelling Approach
No full textThe traditional methods for production of carbon nanotubes (CNTs) utilize graphite, carbon monoxide or hydrocarbons for the construction of the carbon skeleton of CNT, and different kinds of metals as catalysts. Moreover, all these methods usually require critical operating conditions that are very expensive, and then strongly restrict the fields of applications of these nanostructures This paper reports the experimental results obtained by applying a new technique for a continuous, mass production of high-quality multi-wall carbon nanotubes (MWCNTs), based on fluidized bed pyrolysis of different polymers [Arena et al., 2006]. Analytical characterization of the nano-structured materials obtained by feeding polyethylene has been carried out by means of TG-DTA, SEM and TEM, Raman and X-ray. The chemical mechanism of the CNTs synthesis is also described with reference to the catalytic effect of metal nanoparticles
The phenomenology of bed defluidization during the pyrolysis of a food-packaging plastic waste
No full textThe stability, in long-term operation, of fluidized bed reactors utilised to pyrolyse plastics waste can be seriously compromised by particle agglomeration phenomena. These phenomena can cause poor fluidization and eventually lead to defluidization. In order to investigate this phenomenon, a polypropylene waste from a food-packaging industry was utilised in a laboratory-scale bubbling fluidized bed reactor. The effect of the main operating variables (bed hold-up, size of inert material, fluidizing velocity, feed rate of plastic pellets) was investigated by means of experiments carried out under an inert atmosphere. The time at which defluidization occurred was correlated with some process variables by means of linear relationships. A new modelling approach was also proposed in order to predict the risk of defluidization under different operating conditions. © 2001 Elsevier Science B.V. All rights reserved
Defluidization phenomena during the pyrolysis of two plastic wastes
No full textA couple of commercially available packaging-derived fuels, both obtained as a result of mono-material recycling programs of polyethylene (PE) and polyethylene terephthalate (PET), were fed in a laboratory scale bubbling fluidized-bed reactor, made of quartz. The effect of the main operating variables (bed solids hold-up, inert material size, fluidizing velocity, plastics feed rate) on the agglomeration and the defluidization phenomena was investigated by means of experiments carried out in the bed temperature range of 450-650 °C. Different mechanisms of defluidization were identified and characterized. The time at which defluidization occurred was correlated to the ratio between the bed solids hold-up and the polymer feed rate by means of linear relationships. An increase of this ratio, as well as a decrease of the bed temperature, led to a decrease of the defluidization time for both the recycled polymers. No substantial effects were found in the tested range of fluidizing gas velocities. An operating criterion to avoid defluidization was finally proposed
A systematic approach to fixed carbon balance during the fluidized bed combustion of a packaging-derived fuel
No full textThe combustion of cylindrical pellets of a market-available, packaging-derived fuel, obtained from a mono-material collection of polyethylene terephthalate (PET) bottles, was investigated by means of two batchwise operated bench-scale fluidized bed combustors. After devolatilization, the fixed carbon was present in the bed in three phases: an A-phase, made of aggregates of sand and char, an S-phase, made of individual carbon-covered sand particles and an F-phase, made of elutriable carbon fines, abraded by the surfaces of A- and S-phases. A simple model was developed in order to quantify the role of different phenomena affecting the overall fixed carbon conversion. The algorithm was based on a network of paths representing the generation of the three phases from the parent fuel, the crumbling of A-phase, the attrition of S-phase, the combustion of the fixed carbon as well as the elutriation of carbon fines. The calculated data compared well with the experimental results. The role of the comminution phenomena was negligible. The kinetic parameters and the bed temperature appeared to have a remarkable influence on the fixed carbon combustion efficiency. Copyright (C) 2000 Elsevier Science S.A
Fluidized-bed pyrolysis of polyolefins wastes: Predictive defluidization model
No full textThe risk of defluidization during the low-temperature pyrolytic processes of polyolefins is one of the major constraints to a wider utilization of fluidized beds for the pyrolysis of plastic wastes. A predictive model can estimate the occurrence of defluidization under different operating conditions, taking into account the role of physical properties of the polymers and hydrodynamic variables of the reactor, together with that of the main operating parameters, like the process temperature and the plastic waste feed rate. The results agree well with the experimental data obtained by feeding recycled polypropylene and polyethylene in a laboratory-scale bubbling fluidized-bed pyrolyzer. An operating map allows to distinguish the region of reactor stable operation from that of defluidization
Carbon attrition during the circulating fluidized bed combustion of a packaging-derived fuel
No full textCylindrical pellets of a market-available packaging-derived fuel, obtained from a mono-material collection of polyethylene terephthalate (PET) bottles, were batchwise fed to a laboratory scale circulating fluidized bed (CFB) combustor. The apparatus, whose riser was 41 mm ID and 4 m high, was operated under both inert and oxidizing conditions to establish the relative importance of purely mechanical attrition and combustion-assisted attrition in generating carbon fines. Silica sand particles of two size distributions were used as inert materials. For each run, carbon load and carbon particle size distribution in the riser and rates of attrited carbon fines escaping the combustor were determined as a function of time. A parallel investigation was carried out with a bubbling fluidized bed (BFB) combustor to point out peculiarities of attrition in CFB combustors. After devolatilization, PET pellets generated fragile aggregates of char and sand, which easily crumbled, leading to single particles, partially covered by a carbon-rich layer. The injected fixed carbon was therefore present in the bed in three phases: an A-phase, made of aggregates of sand and char, an S-phase, made of individual carbon-covered sand particles and an F-phase, made of carbon fines, abraded by the surfaces of the A- and S-phases. The effects of the size of inert material on the different forms under which fixed carbon was present in the bed and on the rate of escape of attrited carbon fines from the combustor were investigated. Features of carbon attrition in CFB and BFB combustors are discussed
R&D for gas recovery systems and study of eco-friendly gas mixtures for new gas detectors for the Experiments at the CERN Large Hadron Collider
No full textLa tesi di dottorato dal titolo "R&D for Gas Recovery Systems and Study of Eco-Friendly Gas Mixtures for New Gas Detectors for the Experiments at the CERN Large Hadron Collider", tratta lo sviluppo e l’ottimizzazionedi sistemi di recupero su scala industriale per gas fluorurati ad alto GWP e lo studio di miscele di gas ecofriendly per i rivelatori di particelle utilizzati negli esperimenti al Large Hadron Collider (LHC) del CERN. Il lavoro di tesi si e’ incentrato sull'uso di gas fluorurati, responsabili di alte emissioni di gas serra, e sulle strategie per ridurne l'impatto ambientale, principalmente attraverso il recupero e il riutilizzo di questi gas. I processi sfruttano diversi metodi di separazione fisica, tra cui l'uso di membrane selettive e processi di distillazione, per il recupero di gas come CF4, C2H2F4 e C4F10, impiegati negli esperimenti CMS e LHCb. Viene inoltre analizzata l'importanza di sviluppare miscele di gas alternative a basso impatto ambientale e si illustrano i risultati dei analisi come ISE, UV-Vis e VUV volte a caratterizzare da un punto di vista chimico-fisico i gas attualmente impiegati nei rivelati e potenziali alternative piu’ ecofriendly.The doctoral thesis titled "R&D for Gas Recovery Systems and Study of Eco-Friendly Gas Mixtures for New Gas Detectors for the Experiments at the CERN Large Hadron Collider" focuses on developing and optimizing industrial-scale recovery systems for high GWP fluorinated gases. It also studies eco-friendly gas mixtures for particle detectors used in experiments at the CERN Large Hadron Collider (LHC). The thesis emphasizes using fluorinated gases responsible for high greenhouse gas emissions and strategies to reduce their environmental impact, primarily through gas recovery and reuse. Various methods of physical separation including selective membranes and distillation processes are utilized for the recovery of gases such as CF4, C2H2F4, and C4F10, which are used in the CMS and LHCb experiments. Additionally, it analyses the importance of developing alternative gas mixtures with low environmental impact and presents results of analyses such as ISE, UV-Vis, and VUV aimed at characterizing the gases currently used in detection and potential more eco-friendly alternatives from a physicochemical perspective
- …
