Nowadays the progressive depletion of fossil fuels combined with their environmental impact requires new possible solutions for their replacement in the current energy scenario. Fast pyrolysis bio oil (FPBO) is a pyrolysis oil obtained starting from a very wide range of biomass as a raw material, like sawdust, forestry residues, bark, etc. It is supposed that FPBO can replace fuel oil specially in stationary applications like burners, furnaces and boilers. For this reason it is necessary to characterize its physicochemical properties and furthermore its evaporation and combustion behaviour. Due to the complex composition of the FPBO, a surrogate mixture needs to be defined for modeling purposes. A surrogate mixture able to describe FPBO has been developed within the EU H2020 Residue2Heat. This mixture includes acetic acid and ethylene glycol (EG), whose behaviour is investigated in this work. Experimental data from Istituto Motori–CNR about evaporation and combustion of isolated droplets of these two compounds have been compared to simulations results obtained using a 1D model able to describe droplet evaporation, ignition and combustion. Attention was paid to the effect of the suspending fiber on the droplet evaporation rate. Moreover, several numerical grids were evaluated to investigate the sensitivity of the results to the grid in terms of spatial discretization and extension of the computational domain, for both liquid and gas phases. Moreover, the effect of non-ideal VLE was investigated for the Acetic Acid/EG mixture. Finally, the EG pyrolysis and combustion mechanism has been significantly improved, on the basis of new recent experimental data obtained in a flow reactor at DLR-Germany. Trough the analysis of reactive flows it was possible to identify the reactions that mostly affect the reactivity of the system and their parameters were modified taking into account also the reaction rate parameters of the DLR kinetic mechanism. These modifications allowed to improve the agreement between model predictions and experimental results also in the single droplet combustion experiments.
Oggigiorno il progressivo esaurimento dei combustibili fossili combinato con il loro impatto ambientale richiede nuove possibili soluzioni per la loro sostituzione nell'attuale scenario energetico. Il bio olio da pirolisi veloce (FPBO) è un olio di pirolisi ottenuto a partire da una vasta gamma di biomassa come materia prima, come segatura, residui forestali, corteccia, ecc. Si suppone che il FPBO possa sostituire l'olio combustibile specialmente in applicazioni stazionarie come bruciatori, forni e caldaie. Per questo motivo è necessario caratterizzarne le proprietà fisico-chimiche ed anche il suo comportamento in evaporazione e combustione. A causa della complessa composizione dell'FPBO, è necessario definire una miscela surrogata a fini di realizzarne un modello. Una miscela sostitutiva in grado di descrivere l'FPBO è stata sviluppata all'interno dell'UE H2020 Residue2Heat. Questa miscela include acido acetico e glicole etilenico (EG), il cui comportamento è studiato in questo lavoro. Dati sperimentali dell'Istituto Motori-CNR sull'evaporazione e sulla combustione delle goccioline isolate di questi due composti sono stati confrontati con i risultati delle simulazioni ottenuti utilizzando un modello 1D in grado di descrivere evaporazione delle gocce, accensione e relativa combustione. È stata prestata attenzione all'effetto della fibra sospesa sulla velocità di evaporazione delle goccioline. Inoltre, sono state valutate diverse griglie numeriche per indagare la sensibilità dei risultati alla griglia in termini di discretizzazione spaziale ed estensione del dominio computazionale, sia per le fasi liquide che gassose. Inoltre, l'effetto del VLE non ideale è stato studiato per la miscela dei due composti. Infine, il meccanismo di pirolisi e combustione EG è stato notevolmente migliorato sulla base dei nuovi dati sperimentali recentemente ottenuti in un reattore di flusso presso il DLR-Germania. Attraverso l'analisi dei flussi reattivi è stato possibile quindi identificare le reazioni che maggiormente influenzano la reattività del sistema e i loro parametri sono stati modificati tenendo conto anche dei parametri della velocità di reazione del meccanismo cinetico DLR. Queste modifiche hanno permesso di migliorare l'accordo tra le previsioni del modello e i risultati sperimentali anche negli esperimenti di combustione a goccia singola.
Modeling ethylene glycol single droplet evaporation and combustion
BONANOMI, STEFANO
2016/2017
Abstract
Nowadays the progressive depletion of fossil fuels combined with their environmental impact requires new possible solutions for their replacement in the current energy scenario. Fast pyrolysis bio oil (FPBO) is a pyrolysis oil obtained starting from a very wide range of biomass as a raw material, like sawdust, forestry residues, bark, etc. It is supposed that FPBO can replace fuel oil specially in stationary applications like burners, furnaces and boilers. For this reason it is necessary to characterize its physicochemical properties and furthermore its evaporation and combustion behaviour. Due to the complex composition of the FPBO, a surrogate mixture needs to be defined for modeling purposes. A surrogate mixture able to describe FPBO has been developed within the EU H2020 Residue2Heat. This mixture includes acetic acid and ethylene glycol (EG), whose behaviour is investigated in this work. Experimental data from Istituto Motori–CNR about evaporation and combustion of isolated droplets of these two compounds have been compared to simulations results obtained using a 1D model able to describe droplet evaporation, ignition and combustion. Attention was paid to the effect of the suspending fiber on the droplet evaporation rate. Moreover, several numerical grids were evaluated to investigate the sensitivity of the results to the grid in terms of spatial discretization and extension of the computational domain, for both liquid and gas phases. Moreover, the effect of non-ideal VLE was investigated for the Acetic Acid/EG mixture. Finally, the EG pyrolysis and combustion mechanism has been significantly improved, on the basis of new recent experimental data obtained in a flow reactor at DLR-Germany. Trough the analysis of reactive flows it was possible to identify the reactions that mostly affect the reactivity of the system and their parameters were modified taking into account also the reaction rate parameters of the DLR kinetic mechanism. These modifications allowed to improve the agreement between model predictions and experimental results also in the single droplet combustion experiments.| File | Dimensione | Formato | |
|---|---|---|---|
|
2018_4_Bonanomi.pdf
non accessibile
Descrizione: Testo della tesi
Dimensione
10.15 MB
Formato
Adobe PDF
|
10.15 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/10589/139757