1,720,970 research outputs found
Mechanical activation of alkaline residues in view of the application of accelerated carbonation
No full textMineral carbonation is a permanent and safe way for the sequestration of anthropogenic CO2. Carbonation reactions of metal oxides- and hydroxides-bearing alkaline solid waste occur spontaneously at atmospheric temperature and pressure, but proceed slowly to obtain an industrial viable process. In order to enhance mineral carbonation it is necessary a careful selection of the process routes and the process conditions and to use pre-treatments that increase the material reactivity. Mechanical activation is a pre-treatment method that increases mineral dissolution rates due to particle size reduction, specific surface increase and structural disorder production. Many experiments were conducted by increasing the grinding time and the carbonation time of the selected materials (steelmaking slag, incinerator ashes and track ballast) to evaluate how increasing grinding time influences the carbonation rate. The two key factors for the selection of the materials for the laboratory tests were the presence of alkali metals and alkaline earth metals and the time of mechanical activation. A jaw crusher and a continuous ring mill were used to reduce the samples size and / or to obtain homogeneous samples, while a disc mill and a vario-planetary mill were used for mechanical activation. The chemical composition of the samples was determined with X-ray fluorescence, a simultaneous DSC / TGA analyzer was utilized to define the carbonate content, the CO2 uptake and the calcium conversion efficiency and X-ray diffraction was used to determine the mineralogical composition of the materials and the changes in the crystal structure after the experiments. X-ray diffraction and thermogravimetric analyses of mechanically activated alkaline residues show respectively that with increasing the grinding time the crystallinity of the materials decreases and the carbonate content, the CO2 uptake and the calcium conversion efficiency generally increase
Fuels from citrus wastes: recovery of wastes from juice industry for the production of "biopellets"
No full textThe reuse of agricultural waste mainly interests the regions of Southern Italy; in particular, Sicily produces 70% of national citrus (annually about 700,000 tonnes of citrus fruits), consequently many waste are generated from production and use of citrus fruits. More than 300,000 tonnes of waste derived from industrial use of citrus fruits end up in landfill sites with considerable problems of disposal, rising chain costs and leading to lower profit margins for the agriculture and manufacturing sectors. The idea exposed in this paper is to use a low cost technology to recovery the waste as raw material for the production of "Biopellets”, i.e. home heating products, healthier than wood pellets, with a higher calorific value. The technology utilized, in order to produce the Biopellets, is based on the use of a mechanochemical refining system named “Refolo”. The system, consisting in a micronizer mill for ligno-cellulosic and polymeric materials, is composed of an innovative device able to obtain a dry powder from any organic and polymeric waste. This technology has passed laboratory tests and was realized a little demonstrator, that gave considerable results in terms of calorific quality and sterility of the final product. The work focuses on this technology and discusses the possibilities of use
Analisi di Aree contaminate mediante spettrometri VIS-NIR aerotrasportati su droni e microdroni: esperienze pratiche su aree sperimentali
No full textNel lavoro vengono riportati i risultati preliminari dell'attività di messa a punto di una piattaforma di ricognizione chimica aerea basata sull'impiego di microspettrometri UV-VIS-NIR montati su UAV (Unmanned Aerial Veichle). In questo lavoro abbiamo utilizzato una discarica in attività come fonte di dati certi per costruire un data base di risposte analitiche, analizzando le aree della discarica con gli spettrometri montati su UAV. In discarica i rifiuti (principalmente terre contaminate) sono disposti secondo uno schema di celle ben definito; ciò ha permesso di individuare i parametri geometrici dell'osservazione e di ottimizzare la ripresa delle caratteristiche ottiche delle terre nell'intervallo VIS-NIR. Nel lavoro vengono discussi i pregi e difetti e le possibilità di espansione del metodo di ricognizione per siti contaminati, basata su UA
Asbestos on railway ballast: analyses, monitoring and management
No full textThe material for rail ballast is normally obtained from the crushing of rocks with high mechanical strength, such as basalt, trachyte, gneiss and "green rocks", as ophiolites (serpentinites, amphibolites, gabbros, prasinites, etc.). Green rocks often contain discrete quantities of heavy metals and asbestos-like minerals, as chrysotile and amphibole asbestos. In Italy, the chrysotile asbestos mine in Balangero (Turin) has produced railroad ballast, over 5 million of tons, which was used for the railways of Piedmont, Liguria, Lombardy and, partially, Tuscany and, partially, Emilia Romagna, from 1930s up to 1990. In addition to Balangero, several other serpentinite quarries provided the railways ballast from the 1940s to 2000. As a result, many railway lines are now contaminated with significant quantities of asbestos. Since 2005 it was started a very complex and ambitious monitoring project alongside the Rete Ferroviaria Italiana - Italian Railway Network S.p.A. in order to detect the exact contours of the problem and to find the most appropriate methods to solve it
Recupero di catalizzatori petrolchimici esausti da rifiuto a risorsa
No full textI catalizzatori FCC, utilizzati nella reazione di cracking del petrolio grezzo e composti di un impasto di argilla e zeoliti Y caricate con lantanio, esauriscono la loro attività a valle dei processi petrolchimici e divengono rifiuti. La classificazione di tali rifiuti varia da non pericolosi a pericolosi in funzione sopratutto dei tenori in antimonio, nichel e molibdeno. Per trasformare tali rifiuti in risorse abbiamo studiato un processo basato su un trattamento meccanico di attivazione seguito da una cristallizzazione del prodotto attivato e contemporanea espulsione del lantanio, che è recuperato mediante una lisciviazione e successiva precipitazione con acidi organici (tartarico e citrico). E' così possibile recuperare il 96 % del materiale di rifiuto in due prodotti: un concentrato di lantanio carbonato e un altro di zeolite X e zeolite P.The FCC catalysts, used in the reaction of cracking of crude oil and consisting of a mixture of clay and zeolite Y loaded with lanthanum, end their activity downstream of petrochemical processes. The classification of these wastes varies from not dangerous to dangerous, the latter ones with very high levels in antimony, nickel and molybdenum. To transform this waste into resources, we studied a process based on a mechanical treatment of activation followed by a crystallization of the product activated and contemporary expulsion of lanthanum, which is recovered by a leaching and subsequent precipitation with organic acids (tartaric and citric acids). In this way it is possible to recover 96% of the waste material in two products: a concentrate of lanthanum carbonate and another concentrated product of zeolite X and zeolite P
Recycling of slag from steel industry and incineration for hydrogen production and CO2 sequestration
No full textEvaluation of Activation Efficiency and Quality of Slag Carbonation
No full textThe capacity of some industrial waste to sequester carbon dioxide is well known and it is also noted that to achieve the carbonation reaction it is necessary to activate the precursors overcoming the initial energy barrier through processes of dissolution in an autoclave at high temperature and pressure. To develop the direct carbonation, without autoclaving, our research group uses the mechanical activation of precursor minerals realized through an intense grinding made with friction mill (ring mill). We can estimate the timing of activation of mineral phases using a calculation model realized by us. Knowing the mechanical parameters of the grinding machines, the thermodynamic parameters of the material and the amount of radicalic sites obtained by grinding, we can evaluate the rate of carbonation for each type of mineral. The results show a good correlation between the activation level of the materials and the efficiency of carbon dioxide fixation: at ambient temperature and pressure a yield of up to 98% can be achieve
Bonifica di Aree Ferroviarie: inquinanti tipici, metodologie analitiche ed esperienze di cantiere
No full textNel lavoro vengono evidenziati i componenti inquinanti tipici delle massicciate ferroviarie, quali in particolare amianto, metalli pesanti e idrocarburi e le problematiche legate alla loro rilevazione e quantificazione. In particolare vengono evidenziati gli avanzamenti nella tecnica analitica dell'amianto a seguito dell'utilizzo della tecnologia μ-RAMAN. Nel lavoro vengono anche esposti gli aspetti essenziali del lavoro di bonifica delle massicciate e le problematiche legate alla rimozione in sicurezza di ballast contaminati da amiant
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