Inherent Metal Elements in Biomass Pyrolysis: A Review

One of the main drawbacks of using biomass as pyrolysis feedstock consists of the huge variability of the different biomass resources which undermines the viability of downstream processes. Inherent inorganic elements greatly contribute to enhance the compositional variability issues due to their catalytic effect (especially alkali and alkaline earth metals (AAEMs)) and the technical problems arising due to their presence. Due to the different pretreatments adopted in the experimental investigations as well as the different reactor configurations and experimental conditions, some mechanisms involving interactions between these elements and the biomass organic fraction during pyrolysis are still debated. This is the reason why predicting the results of these interactions by adapting the existing kinetic models of pyrolysis is still challenging. In this work, the most prominent experimental works of the last 10 years dealing with the catalytic effects of biomass inherent metals on the pyrolysis process are reviewed. Reaction pathways, products distributions and characteristics, and impacts on the products utilization are discussed with a focus on AAEMs and on potential toxic metallic elements in hyperaccumulator plants. The literature findings are discussed in relation to the applied laboratory procedures controlling the concentration of inherent inorganic elements, their capability of preserving the chemical integrity of the main organic components, and the ability of resembling the inherent inorganic elements in the raw biomass. The goal is to reveal possible experimental inconsistencies and to provide a clear scheme of the reaction pathways altered by the presence of inherent inorganics. This analysis paves the way for the examination of the proposed modifications of the existing models aiming at capturing the effect of inorganics on pyrolysis kinetics. Finally, the most relevant shortcomings and bottlenecks in existing experimental and modeling approaches are analyzed and directions for further studies are suggested

Caratterizzazione di un suolo inquinato da metalli pesanti

Per i privati imprenditori che producono rifiuti di vario tipo, indubbiamente l’attività di raccolta, selezione e smaltimento dei rifiuti costituisce un elemento di costo che incide sulla capacità e sulla qualità di presenza nel mercato. Per tale ragione, l’imprenditore è portato a ridurre al minimo le spese da sostenere per mantenere inalterata, garantire o potenziare, la sua presenza nel mercato. In questa logica esclusivamente economica è evidente che l’impresa che si libera illegalmente dei propri rifiuti, conseguendo consistenti economie di costo, acquisisce posizioni di vantaggio rispetto ad un’impresa analoga che invece, rispettosa delle normative, affronta tutti gli oneri previsti. L’operare in dispregio delle normative in tema di rifiuti genera quindi, non solo gravissimi e spesso irreversibili danni all’ambiente, ma causa anche una catena ininterrotta di atti emulativi da parte di altre imprese che giustificano il loro operare quale "comportamento obbligato" a difesa della loro competitività. In questo studio sono stati esaminati dei materiali scaricati abusivamente in località Portillo nel comune di S. Maria la Fossa, materiali che erano in origine scorie di fonderia contenenti rilevanti concentrazioni di metalli pesanti, ma che sono state camuffate per miscelazione con normale terreno. Con questa miscela presentata come terriccio, la malavita ha disseminato il territorio casertano di cumuli e di spianate. In particolare nel sito in oggetto questo materiale è stato utilizzato per formare il fondo stradale, coprendo uno spessore di almeno 30 cm per una larghezza di circa 4 m e per una lunghezza di circa 500 m

Effects of mixture composition, dilution level and pressure on auto-ignition delay times of propane mixtures

he auto-ignition process of propane/oxygen mixtures has been widely studied in several facilities. Literature on shock tubes and tubular flow reactors has shown a change in the activation energy of the ignition process in the transition region from intermediate to high-temperature chemistry. Although fuel ignition chemistry has been widely exploited at low and high temperatures, further studies are required at intermediate temperatures. Based on previously published experimental results, this paper aimed to investigate the kinetics responsible for such a phenomenology, through a detailed kinetic analysis of the main pathways involved in the ignition process of propane mixtures. Simulations were performed over a wide range of temperatures (from low to high), changing the dilution levels of the mixture from "air" conditions to 97%, the pressure from 0.1 up to 3. MPa, and the mixture compositions from lean in fuel to rich in fuel. The analysis suggests that the phenomenology strongly depends on the mixture dilution levels and pressure. In particular, the differences in the ignition chemistry between low to intermediate temperatures and between intermediate to high temperatures is more evident for systems that are highly diluted and at low pressure. Such results are supported by data from the literature.This aspect explains why such a behavior is not reported for any experimental configurations and partially justifies the differences among the data obtained in several facilities, which is commonly addressed by the non-idealities of systems

Oxidation in fish lipids during thermal stress as studied by 13C nuclear magnetic resonance spectroscopy

8 páginas, 2 tablas, 7 figuras13C Nuclear magnetic resonance spectroscopy has been applied to elucidate the mechanism of lipid oxidation occurring during thermal treatment of fish. Effects of temperature and time of processing have been studied by means of a model system of lipids, extracted from salmon (Salmo salar) muscle, to simulate industrial conditions of canning. Unsaturated fatty acids located at the sn-2 position of the glycerol moiety were the most prone to oxidative damage. Regarding the mechanism of the reaction, results inferred from olefinic and methylenic resonances indicated a higher susceptibility of the allylic sites closest to the carbonyl group, followed by those placed near the methyl terminal group. Unsaturations located in the middle of the carbon chain did not show much damage. The glyceryl region provided an unusual resonance at 53.4 ppm, which could be assigned to a hydroxylic compound formed during process. JAOCS 75, 147–154 (1998).We acknowledge financial support for Research Project ALI 90- 0773 provided by the Comisión Interministerial de Ciencia y Tecnología (CICYT), Research Project CEE UP. 3-783 (of DG XIV), and a research grant from the Departamento de Postgrado (CSIC) (to IM).Peer reviewe

Impiego delle acque di vegetazione dell’industria olearia per la rimozione di metalli pesanti da suoli inquinati

E’ stata sviluppata un’indagine su alcuni siti della provincia di Caserta, Campania, che risultano inquinati in seguito all’abbandono di notevoli quantitativi di rifiuti pericolosi. Lo studio, in coerenza con la normativa vigente all’epoca della sua realizzazione e relativa alla bonifica e al ripristino ambientale di siti inquinati (DM 471/99), si è posto i seguenti obiettivi: 1. valutare natura, concentrazioni delle componenti tossiche e quantità complessive dei materiali pericolosi abbandonati; 2. sviluppare un modello concettuale capace di fornire delle linee guida alla successiva fase di intervento di bonifica; 3. fare una previsione della dispersione del pennacchio di inquinanti nel suolo e nel sottosuolo sottostanti i cumuli e gli strati di rifiuti pericolosi tramite un opportuno modello matematico; 4. studiare in laboratorio delle tecniche di bonifica mirate alla problematica specifica; 5. applicare in campo le tecniche elaborate in laboratorio