Pyrrole (C4H5N) and pyrrolidine (C4H9N) are molecules that reflect the chemical functionalities of the nitrogen fraction of heavy-fuels such as coals, tar, biofuels or bio-oils, and therefore are typically used to represent their reactivity. Understanding the decomposition pathways of these model nitrogen compounds is important for quantifying the formation of nitrogen oxides (NOx) especially in coals and biomass combustion and conversion processes, where these pollutants are mainly formed by reactions involving the nitrogen chemically bound in the fuel (Fuel-N). The expected continuous increase in population and energy demand, which are the main source of emissions of these pollutants, pushed many countries to implement increasingly stringent emission control regulations. Therefore, a proper burner design and the implementation of proper primary control devices to minimize the Fuel-NOx formation are necessary factors. To achieve this goal chemical kinetics modelling, area in which this thesis work is placed, plays a fundamental role. In the first part of this thesis the foundations for the development of the kinetic model of these two molecules have been built: the kinetic constants of some of the most important reactions in which pyrrole (C4H5N) and pyrrolidine (C4H9N) are involved in pyrolytic and oxidative conditions (radical extractions and additions) have been determined by accurate electronic structure calculations. The new kinetic constants thus determined for pyrrole were used in the second part of this thesis to improve the pyrrole kinetic model previously proposed by the CRECK research group: the kinetic constants of the calculated reactions were included in this model and the effects of these changes have been analysed and discussed in detail. The reactions involving C4H9N are also a good starting point for the future development of the combustion model of this molecule that is attracting interest as an anti-knocking fuel additive of plant origin for gasoline engines. Concluding, this thesis work aims at the extension of the CRECK kinetic modeling framework through the description of the nitrogen fraction of liquid biomass fuels also providing a valuable basis for subsequent developments for nitrogen components of greater complexity and motivating further experimental, theoretical and modelling efforts.
Il pirrolo (C4H5N) e la pirrolidina (C4H9N) sono molecole che riflettono le funzionalità chimiche della frazione azotata di combustibili pesanti quali il carbone, i catrami, i biocarburanti o i bio-oli, e quindi vengono tipicamente utilizzate per rappresentarne la reattività. La comprensione delle vie di decomposizione di questi composti azotati modello è importante per quantificare la formazione di ossidi di azoto (NOx) specialmente nei processi di combustione e conversione di carbone e biomassa, in cui questi inquinanti si formano principalmente dalle reazioni che coinvolgono l'azoto chimicamente legato nel combustibile (Fuel-N). Il previsto continuo aumento della popolazione e della richiesta energetica, che sono la principale fonte delle emissioni di questi inquinanti, ha spinto molti paesi ad attuare normative sempre più stringenti sul controllo delle emissioni. Una corretta progettazione dei bruciatori e l'implementazione di adeguati dispositivi di controllo primario per ridurre al minimo la formazione di Fuel-NOx risultano quindi fattori necessari. Per raggiungere questo obiettivo la modellazione cinetica chimica, area in cui questo lavoro di tesi si colloca, gioca un ruolo fondamentale. Nella prima parte di questa tesi sono state costruite le basi per lo sviluppo del modello cinetico di queste due molecole: le costanti cinetiche di alcune tra le più importanti reazioni in cui pirrolo (C4H5N) e pirrolidina (C4H9N) sono coinvolte in condizioni pirolitiche e ossidative (estrazioni e addizioni radicaliche) sono state determinate mediante accurati calcoli di struttura elettronica. Le nuove costanti cinetiche così determinate per il pirrolo sono state utilizzate nella seconda parte di questa tesi per migliorare il modello cinetico del pirrolo precedentemente proposto dal gruppo di ricerca CRECK: le costanti cinetiche delle reazioni calcolate sono state inserite in questo modello e gli effetti di queste modifiche sono stati analizzati e discussi in dettaglio. Le reazioni che coinvolgono C4H9N costituiscono altresì un buon punto di partenza per il futuro sviluppo del modello di combustione di questa molecola che sta attraendo interesse come additivo antidetonante di origine vegetale per motori a benzina. Concludendo, questo lavoro di tesi mira all'estensione del quadro di modellazione cinetica CRECK tramite la descrizione della frazione azotata di combustibili liquidi da biomassa fornendo anche una base preziosa per successivi sviluppi per componenti azotati di maggiore complessità e motivando ulteriori sforzi sperimentali, teorici e di modellazione.
A theoretical and kinetic-modelling study of the OH/H/CH3/HO2-initiated gas-phase oxidation and pyrolysis of N-containing components from biomass fast pyrolysis : pyrrole and pyrrolidine
Giudici, Clarissa
2020/2021
Abstract
Pyrrole (C4H5N) and pyrrolidine (C4H9N) are molecules that reflect the chemical functionalities of the nitrogen fraction of heavy-fuels such as coals, tar, biofuels or bio-oils, and therefore are typically used to represent their reactivity. Understanding the decomposition pathways of these model nitrogen compounds is important for quantifying the formation of nitrogen oxides (NOx) especially in coals and biomass combustion and conversion processes, where these pollutants are mainly formed by reactions involving the nitrogen chemically bound in the fuel (Fuel-N). The expected continuous increase in population and energy demand, which are the main source of emissions of these pollutants, pushed many countries to implement increasingly stringent emission control regulations. Therefore, a proper burner design and the implementation of proper primary control devices to minimize the Fuel-NOx formation are necessary factors. To achieve this goal chemical kinetics modelling, area in which this thesis work is placed, plays a fundamental role. In the first part of this thesis the foundations for the development of the kinetic model of these two molecules have been built: the kinetic constants of some of the most important reactions in which pyrrole (C4H5N) and pyrrolidine (C4H9N) are involved in pyrolytic and oxidative conditions (radical extractions and additions) have been determined by accurate electronic structure calculations. The new kinetic constants thus determined for pyrrole were used in the second part of this thesis to improve the pyrrole kinetic model previously proposed by the CRECK research group: the kinetic constants of the calculated reactions were included in this model and the effects of these changes have been analysed and discussed in detail. The reactions involving C4H9N are also a good starting point for the future development of the combustion model of this molecule that is attracting interest as an anti-knocking fuel additive of plant origin for gasoline engines. Concluding, this thesis work aims at the extension of the CRECK kinetic modeling framework through the description of the nitrogen fraction of liquid biomass fuels also providing a valuable basis for subsequent developments for nitrogen components of greater complexity and motivating further experimental, theoretical and modelling efforts.| File | Dimensione | Formato | |
|---|---|---|---|
|
TESIDEFINITIVA_ClarissaGiudici1.pdf
Open Access dal 18/09/2022
Descrizione: Tesi di Laurea Magistrale
Dimensione
6.85 MB
Formato
Adobe PDF
|
6.85 MB | Adobe PDF | Visualizza/Apri |
I documenti in POLITesi sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/10589/180253