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

How Refined Surgical Technical Solutions Can Make Bentall Operation a Low-Risk Procedure: 20-Year Personal Experience at the “Root” of the Aortic Diseases—It Is Time to Change Surgical Guidelines

(1) objective: twenty years' experience of bentall-de bono operations by one surgeon. (2) methods: from January 2003 to september 2023, four-hundred-and-two patients aged 65.9 +/- 15 years underwent a bentall operation. the euroScore-2 was 5.0% +/- 3.8%. associated procedures were performed on 113 patients (28.1%). results: operative mortality was 1.2% (n = 5), in particular 0.69% (n = 2/289) for isolated bentall operation, 2.65% (n = 3/113) for combined procedures (p < 0.05). postoperative acute heart failure occurred in 38 patients (9.45%). preoperative pulmonary hypertension (44 +/- 14 vs. 33 +/- 7 mmHg), cardiopulmonary bypass time (169 +/- 61 min. vs. 124 +/- 42 min.) and aortic cross-clamp time (133 +/- 45 min. vs. 107 +/- 34 min.) have been recognized as independent predictors of mortality and cardiac complications (p < 0.05). conclusions: In our experience, the bentall operation was associated with low operative mortality and low rate of complications. for this reason, in agreement with the patients, we have modified surgical indication for ascending aortic aneurysms and now we think that it is time to change surgical guidelines

The role of the female gender on mid-term outcome after coronary artery bypass grafting: a retrospective study

Background: data on female gender differences on clinical prognosis after coronary artery bypass grafting (CABG) are still controversial. we evaluated retrospectively the impact of women patients in comparison with men undergoing CABG on mid-term outcome. methods: between december 2014 and march 2022, 1,044 consecutive patients (162 females, 15.5%, 882 males, 84.5%) underwent isolated CABG. the mean follow-up was 40±27 (median 38) months. Logistic and cox model analysis regressions were used to assess the risk of female gender and other variables, kaplanMeier estimates to assess survival rates. results: women did not have a significant higher operative mortality than men (3.09% vs. 1.93%; P=0.37). there was no difference in the use of left internal mammary artery (97.5% vs. 94.9%; P=0.85). Independent predictors of early mortality were emergency CABG (P<0.0001), percutaneous coronary intervention (PCI) within 30 days (P=0.0026), and higher EuroSCORE II (P=0.0155). At 7.5 years, actuarial survival was 87%±3.6% for female gender vs. 88%±1.9% in male gender (P=0.41), freedom from cardiac death 97%±1.8% vs. 96.6%±1.0% (P=0.6), freedom from major adverse cardiac events (MACE) 87%±6.2% vs. 89.7%±2.5% (P=0.96). Independent predictor of all-causes death and cardiac death was the advanced age (74 years in dead patients vs. 67 years in survivors) (P<0.0001). female gender was not a predictor of either operative mortality (P=0.34) or worse mid-term outcome (P=0.41). conclusions: women undergoing CABG with the same surgical techniques currently adopted for men, do not appear to be associated with worse early prognosis. freedom from late all-causes mortality, cardiac death and adverse cardiac events are comparable and equally satisfactory, highlighting the positive protective effect of CABG over time also in women

Bentall Operation: Early Surgical Results, Seven-Year Outcomes, and Risk Factors Analysis

aim: to analyze early and mid-term outcomes of the bentall operation. methods: two hundred and seventeen patients (mean age 65.6 ± 15.9 years, males/females 172/45) underwent Bentall operation in a 7-year period (january 2015−december 2021), on average, 30 bentall operations occurred per year, using biological (n = 104) or mechanical (n = 113) valved conduits for the treatment of ascending aorta−aortic root aneurysms. associate procedures were performed in 58 patients (26.7%); coronary artery bypass grafting (CABG) in 35 (16%). mean follow-up was 55.2 ± 24 (median 60.2) months. cox model analysis was used to assess risk factors, kaplan−meier and log-rank tests were used to assess different survival rates. results: operative mortality was 1.38%. At 7 years, survival, freedom from cardiac death, and event-free survival were 93% ± 2%, 99% ± 1%, and 81% ± 5%. NYHA class (p < 0.0001), trans-aortic valve mean (p < 0.0001) and maximum (p < 0.000) gradients, left ventricular hypertrophy (p < 0.05), and pulmonary arterial pressure (p = 0.002) significantly improved vs. preoperative values. concomitant CABG during bentall operation independently affected late outcomes (HR 1.9−2.3; p-values < 0.05). late survival was affected by concomitant CABG (84% ± 8% vs. 95% ± 2%, p = 0.04), preoperative myocardial infarction (91% ± 9% vs. 97% ± 2%, p = 0.02), and biological vs. mechanical prostheses valved conduits (91% ± 9% vs. 95% ± 3%, p = 0.02). Event-free survival also was affected by concomitant CABG (62% ± 14% vs. 85% ± 5%, p = 0.005) and biological prostheses (78% ± 8% vs. 84% ± 6%, p = 0.06). Freedom from endocarditis−redo operation was 83% ± 9% for biological prostheses vs. 89% ± 6% for mechanical prostheses (p = 0.49). conclusions: Low rates of operative mortality and late complications make bentall operation the gold standard for the treatment of ascending aorta−aortic root aneurysms. coronary ischemic disease affects late outcomes. biological prostheses should be preferred for the elderly

Perceval sutureless bioprosthesis versus Trifecta sutured bioprosthesis for aortic valve replacement: immediate results of the Perfecta study

introduction: the perceval sutureless biological prosthesis for aortic valve replacement has been introduced with the rationale for shortening surgical, extracorporeal circulation and aortic cross-clamping times, in order to reduce postoperative complications. aim: to evaluate early hemodynamic performance and immediate outcomes of implantation of the perceval sutureless bioprosthesis in comparison with the St. Jude trifecta sutured bioprosthesis for aortic valve replacement (Perfecta study). material and methods: between december 2014 and June 2023, 281 patients underwent St. Jude Trifecta implantation (n = 220, mean age: 75.2 ±6.5 years) and Perceval implantation, when indicated (n = 61, mean age: 77.9 ±5.1 years). concomitant CABG was performed in 73 (33%) and in 27 (44%) patients, respectively. results: extracorporeal circulation and cross-clamp times were significantly shorter in perceval patients in all aortic valve replacements (61 ±23 and 49 ±18 minutes vs. 96 ±36 and 67 ±21 minutes), and in isolated procedures (54 ±10 and 43 ±8 minutes vs. 84 ±28 and 66 ±21 minutes) (p < 0.0001, for all comparisons). operative mortality was absent and 2.7%, respectively (p = 0.2). postoperatively, low output cardiac syndrome (0% vs. 4.5%) and total rate of major cardiac and non-cardiac related complications (6.6% vs. 18.6%) were significantly lower in perceval patients (p = 0.01). echocardiography at discharge in comparison with preoperatively showed a relevant and similar decrease of mean and peak trans-aortic valve gradients for the trifecta prosthesis (11.6 ±4.3 vs. 50 ±15.2 mm Hg; 21.6 ±7.3 vs. 78.8 ±24 mm Hg) and for the perceval prosthesis (12.6 ±4.8 vs. 52 ±12.5 mm Hg; 22.6 ±7.9 vs. 77.8 ±16 mm Hg) (p < 0.00001, for all comparisons). Better global cardiac function was observed in perceval patients. concomitant multi-vessel and left main coronary artery disease (p = 0.046; HR = 4.6) and chronic pulmonary disease (p = 0.006; HR = 5.6) were detected as independent predictors of death and postoperative major complications. conclusions: early hemodynamic performance appears to be satisfactory with the use of trifecta sutured and perceval sutureless bioprostheses. perceval implantation allows reduction of surgical times, better preservation of myocardial contractile function and, consequently, reduction of the risk of postoperative complications

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