Decarbonizzazione e desolforazione del syngas proveniente dal processo di gassificazione per produrre idrogeno e tecnologie CTL

Il lavoro elaborato nella tesi riporta la valutazione della fattibilità tecnico-economica di un impianto di produzione dei combustibili liquidi che utilizza il processo Fischer Trospch integrato con tecnologie di cattura della CO2. L’analisi di sistema è stata sviluppata con l’ausilio del codice di simulazione impiantistica Aspen Plus. Pertanto si è analizzato un impianto di tipo dimostrativo collegato alle potenzialità della miniera del Sulcis e si è stimata una taglia impiantistica di circa 9000 barili/giorno di combustibili liquidi prodotti equivalenti ad un consumo di circa 4500 tonn/giorno di carbone. La valutazione della configurazione impiantistica si è sviluppata attraverso l’integrazione delle differenti sezioni al fine di ottimizzare gli scambi energetici. Si sono quindi stimate le prestazioni in termini di bilanci in massa ed energia di due tipologie di impianti senza CCS e con CCS, con l’obiettivo di analizzare l’impatto sull’efficienze dell’inserimento della cattura della CO2. I risultati indicano che più del 47 % dell’input energetico viene convertito in energia elettrica e prodotti liquidi con una differenza di due punti percentuali tra i due casi, ed un resa in combustibili liquidi del 40 %. ) Relativamente alla resa di prodotti liquidi si è ottenuta una selettività pari a SC5+=0,82. L’analisi economica e finanziaria è stata sviluppata stimando l’attualizzazione dell’investimento ovvero il valore attuale netto, il TIR ed il pay back. La struttura finanziaria e le assunzioni utilizzate scelte sono quelle tipiche per la valutazione di fattibilità economica in impianti di potenza. Considerato il petrolio come il prodotto concorrenziale si è stimata la convenienza delle due configurazioni analizzate individuando il valore minimo del prezzo del greggio al fine di ottenere un TIR del 20 %. Infine si è sviluppata un’analisi di sensitività variando i principali parametri di interesse. Ovvero si è parametrizzato il costo di mercato della quota CO2 al fine di individuare il valore che permette una convenienza economica nell’introduzione della cattura della CO2 rispetto alla sua emissione senza cattura. Un analisi parametrica in funzione del prezzo del greggio ha permesso di delineare la sensibilità dell’iniziativa rispetto a questa grandezza

Decarbonizzazione e desolforazione del syngas proveniente dal processo di gassificazione per produrre idrogeno e tecnologie CTL

Il lavoro elaborato nella tesi riporta la valutazione della fattibilità tecnico-economica di un impianto di produzione dei combustibili liquidi che utilizza il processo Fischer Trospch integrato con tecnologie di cattura della CO2. L’analisi di sistema è stata sviluppata con l’ausilio del codice di simulazione impiantistica Aspen Plus. Pertanto si è analizzato un impianto di tipo dimostrativo collegato alle potenzialità della miniera del Sulcis e si è stimata una taglia impiantistica di circa 9000 barili/giorno di combustibili liquidi prodotti equivalenti ad un consumo di circa 4500 tonn/giorno di carbone. La valutazione della configurazione impiantistica si è sviluppata attraverso l’integrazione delle differenti sezioni al fine di ottimizzare gli scambi energetici. Si sono quindi stimate le prestazioni in termini di bilanci in massa ed energia di due tipologie di impianti senza CCS e con CCS, con l’obiettivo di analizzare l’impatto sull’efficienze dell’inserimento della cattura della CO2. I risultati indicano che più del 47 % dell’input energetico viene convertito in energia elettrica e prodotti liquidi con una differenza di due punti percentuali tra i due casi, ed un resa in combustibili liquidi del 40 %. ) Relativamente alla resa di prodotti liquidi si è ottenuta una selettività pari a SC5+=0,82. L’analisi economica e finanziaria è stata sviluppata stimando l’attualizzazione dell’investimento ovvero il valore attuale netto, il TIR ed il pay back. La struttura finanziaria e le assunzioni utilizzate scelte sono quelle tipiche per la valutazione di fattibilità economica in impianti di potenza. Considerato il petrolio come il prodotto concorrenziale si è stimata la convenienza delle due configurazioni analizzate individuando il valore minimo del prezzo del greggio al fine di ottenere un TIR del 20 %. Infine si è sviluppata un’analisi di sensitività variando i principali parametri di interesse. Ovvero si è parametrizzato il costo di mercato della quota CO2 al fine di individuare il valore che permette una convenienza economica nell’introduzione della cattura della CO2 rispetto alla sua emissione senza cattura. Un analisi parametrica in funzione del prezzo del greggio ha permesso di delineare la sensibilità dell’iniziativa rispetto a questa grandezza

Influence of the catalyst support on the steam reforming performance of toluene as tar model compound

The large amount of tar produced along with the syngas during biomass gasification is one of the major obstacle for the diffusion of gasifiers at industrial scale. Catalytic cracking and reforming are the most suitable processes for the transformation of tar into lighter gases. The selection of suitable catalysts is a critical step. The catalysts must own high activity and high resistance to deactivation for coke deposition. In this work the effect of two different supports, mayenite and aluminium oxide, on the activity of the nickel was investigated in the steam reforming of toluene that was used as tar model compound. In particular, the performed experimentations aimed to test the mayenite in terms of improvement of resistance to carbon deposition in conditions similar to those of gasification reactors. The obtained results indicate that Ni /mayenite catalyst needs higher temperature to activate and leads to lower value of toluene conversion with respect to Ni / alumina. However, mayenite, which is known from literature to have higher resistance to coke deposition due to the presence of free oxygens in the lattice which oxidize the coke deposited on the catalyst surface showed higher resistance to deactivation especially for low steam to carbon ratios

Non-Markovianity by undersampling in quantum optical simulators

We unveil a novel source of non-Markovianity for the dynamics of quantum systems, which appears when the system does not explore the full set of dynamical trajectories in the interaction with its environment. We term this effect non-Markovianity by undersampling and demonstrate its appearance in the operation of an all-optical quantum simulator involving a polarization qubit interacting with a dephasing fluctuating environment.Comment: Accepted versio

Toward green steel: Modeling and environmental economic analysis of iron direct reduction with different reducing gases

The objective of the paper is to simulate the whole steelmaking process cycle based on Direct Reduced Iron and Electric Arc Furnace technologies, by modeling for the first time the reduction furnace based on kinetic approach, to be used as a basis for the environmental and techno-economic plant analysis by adopting different reducing gases. In addition, the impact of carbon capture section is discussed. A complete profitability analysis has been conducted for the first time, adopting a Monte Carlo simulation approach. In detail, the use of syngas from methane reforming, syngas and hydrogen from gasification of municipal solid waste, and green hydrogen from water electrolysis are analyzed. The results show that the Direct Reduced Iron process with methane can reduce CO2 emissions by more than half compared to the blast furnace based-cycle, and with the adoption of carbon capture, greenhouse gas emissions can be reduced by an additional 40%. The use of carbon capture by amine scrubbing has a limited economic disadvantage compared to the scenario without it, becoming profitable once carbon tax is included in the analysis. However, it is with the use of green hydrogen from electrolyzer that greenhouse gas emissions can be cut down almost completely. To have an environmental benefit compared with the methane-based Direct Reduced Iron process, the green hydrogen plant must operate for at least 5136 h per year (64.2% of the plant's annual operating hours) on renewable energy. In addition, the use of syngas and separated hydrogen from municipal solid waste gasification is evaluated, demonstrating its possible use with no negative effects on the quality of produced steel. The results show that hydrogen use from waste gasification is more economic with respect to green hydrogen from electrolysis, but from the environmental viewpoint the latter results the best alternative. Comparing the use of hydrogen and syngas from waste gasification, it can be stated that the use of the former reducing gas results preferable, from both the economic and environmental viewpoint

Initial Surgical Strategy for the Treatment of Type A Acute Aortic Dissection: Does Proximal or Distal Extension of the Aortic Resection Influence the Outcomes?

(1) Background: We sought to analyze and compare the outcomes in terms of early and late mortality and freedom from a redo operation in patients undergoing surgical treatment for a type A acute aortic dissection in relation to the initial surgical treatment strategy, i.e., proximal or distal extension of the aortic segment resection, compared with isolated resection of the supracoronary ascending aorta. (2) Methods: This is a retrospective study in which we included 269 patients who underwent operations for a type A acute aortic dissection in the Department of Cardiac Surgery of Tor Vergata University from May 2006 to May 2016. The patients were grouped according to the extent of the performed surgical treatment: isolated replacement of the supracoronary ascending aorta (NE, no extension), replacement of the aortic root (PE, proximal extension), replacement of the aortic arch (DE, distal extension), and both (BE, bilateral extension). The analyzed variables were in-hospital mortality, postoperative complications (incidence of neurological damage, renal failure and need for prolonged intubation), late mortality and need for a redo operation. (3) Results: Unilateral cerebral perfusion was performed in 49.3% of the patients, and bilateral perfusion-in 50.6%. The overall in-hospital mortality was 31.97%. In the multivariate analysis, advanced age, cardiopulmonary bypass time and preoperative orotracheal intubation were independent predictors of in-hospital mortality. In the population of patients who survived the surgery, the probability of survival at 92 months was 70 +/- 5%, the probability of freedom from a redo operation was 71.5 +/- 5%, the probability of freedom from the combined end-point death and a redo operation was 50 +/- 5%. The re-intervention rate in the general population was 16.9%. The overall probability of freedom from re-intervention was higher in patients undergoing aortic root replacement, although not reaching a level of statistical significance. Patients who underwent aortic arch treatment showed reduced survival. (4) Conclusions: In the treatment of type A acute aortic dissection, all the surgical strategies adopted were associated with satisfactory long-term survival. In the group of patients in which the aortic root had not been replaced, we observed reduced event-free survival

Circulating Levels of Ferritin, RDW, PTLs as Predictive Biomarkers of Postoperative Atrial Fibrillation Risk after Cardiac Surgery in Extracorporeal Circulation

Postoperative atrial fibrillation (POAF) is the most common arrhythmia after cardiac surgery in conventional extracorporeal circulation (CECC), with an incidence of 15-50%. The POAF pathophysiology is not known, and no blood biomarkers exist. However, an association between increased ferritin levels and increased AF risk, has been demonstrated. Based on such evidence, here, we evaluated the effectiveness of ferritin and other haematological parameters as POAF risk biomarkers in patients subjected to cardiac surgery. We enrolled 105 patients (mean age = 70.1 +/- 7.1 years; 70 men and 35 females) with diverse heart pathologies and who were subjected to cardiothoracic surgery. Their blood samples were collected and used to determine hematological parameters. Electrocardiographic and echocardiographic parameters were also evaluated. The data obtained demonstrated significantly higher levels of serum ferritin, red cell distribution width (RDW), and platelets (PLTs) in POAF patients. However, the serum ferritin resulted to be the independent factor associated with the onset POAF risk. Thus, we detected the ferritin cut-off value, which, when >= 148.5 ng/mL, identifies the subjects at the highest POAF risk, and with abnormal ECG atrial parameters, such as PW indices, and altered structural heart disease variables. Serum ferritin, RDW, and PTLs represent predictive biomarkers of POAF after cardiothoracic surgery in CECC; particularly, serum ferritin combined with anormal PW indices and structural heart disease variables can represent an optimal tool for predicting not only POAF, but also the eventual stroke onset

Kinetics of CO2methanation on a Ru-based catalyst at process conditions relevant for Power-to-Gas applications

In this paper we show that a 0.5 wt.% Ru/γ-Al2O3catalyst is appropriate to carry out the Sabatier reaction (CO2methanation) under process conditions relevant for the Power-to-Gas application and we provide a kinetic model able to describe the CO2conversion over a wide range of process conditions, previously unexplored. To achieve these goals, the effects of feed gas composition (H2/CO2ratio and presence of diluents), space velocity, temperature and pressure on catalyst activity and selectivity are investigated. The catalyst is found stable when operating over a wide range of CO2conversion values, with CH4selectivity always over 99% and no deactivation, even when working with carbon-rich gas streams. The effect of water on the catalyst performance is also investigated and an inhibiting kinetic effect is pointed out. Eventually, the capacity of kinetic models taken from the literature to account for CO2conversion under the explored experimental conditions is assessed. It is found that the kinetic model proposed by Lunde and Kester in 1973 (J. Catal. 30 (1973) 423) is able to describe satisfactorily the catalyst behavior in a wide range of CO2conversion spanning from differential conditions to thermodynamic equilibrium, provided that a new set of kinetic parameters is used. It is shown however that a better fitting can be achieved by using a modified kinetic model, accounting for the inhibiting effect of H2O on CO2conversion rate

Integration of SNG plants with carbon capture and storage technologies modeling

Several power plant configurations have been recently studied as an alternative to conventional technologies in the field of energetic conversion of coal. The price of natural gas shows a volatile trend and when at its maximum promotes a renewed interest in technologies converting coal into synthetic natural gas (SNG). Moreover, in an low-carbon economy these processes include the capture of CO2 in the base plant configuration. This paper analyzes the possible integration of SNG plants with Carbon Capture and Storage Technologies (CCS). The studied SNG facilities are based on commercial coal gasification and methanation technologies currently available worldwide. The major problem in optimizing the methanation reaction, one of the most important stages of the whole process, is to achieve an efficient removal of the reaction heat to avoid catalyst sintering and prevent carbon particle formation. For this reason, in this study two different process configurations were compared. In the first configuration (case A), the removal of CO2 is operated before the methanation section and the reaction is carried out in a series of adiabatic fixed bed reactors with inter-cooling and product recycle. In the second configuration (case B) the dilution of the methanation feed with CO2 and steam controls the heat of reaction, being CO2 captured downstream the process. For both the plant configurations, performance is analyzed and the energy penalty caused by the introduction of CCS is evaluated. Particular attention is devoted to heat integration between different sections of the plant. Results show similar efficiency in both the cases and that more than 50% of the input energy can be converted to synthetic natural gas. The CCS integration leads to a slight efficiency reduction of about 1 percentage point. The selected plant configurations were tested and performance evaluated and compared in the Aspen Plus v. 8 simulation environment

Analisi economica ed ambientale per un impianto di teleriscaldamento a biomassa nel comune di Varese Ligure

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 , Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal