The aim of this thesis is to conduct a techno-economic and energetic analysis of different sustainable production methods of liquefied natural gas (LNG) used as fuel for maritime transport. The processes covered mainly concern the production of synthetic natural gas (SNG) and biomethane: the first is produced by exploiting renewable electricity, the second from the anaerobic digestion of organic matter (biomass). It should be emphasized that the LNG produced by these processes (e-LNG and bio-LNG) belongs to the category of so-called zero carbon fuels or fuels with zero carbon emissions, as the CO2 produced by their combustion is captured and reused as feedstock; it follows that the net balance of CO2 produced/consumed is equal to zero (or almost), and this entails significant environmental benefits. Concerning the technical analysis, the mass and energy balances were evaluated using the Aspen Plus process simulator, taking as a reference the annual capacity of a port located in North-East Italy. Four different alternatives were considered, two involving e-LNG production and two involving bio-LNG production. The energy consumption associated with the different processes was evaluated in order to estimate the energetic efficiency of the different alternatives. From the simulation results, it was found that bio-LNG production with biogas upgrading by cryogenic distillation (alternative 3) is the most energy-efficient alternative. The economic analysis was conducted to evaluate the levelized cost of LNG, a useful metric for comparing the cost of renewable LNG (synthetic and bio) to the cost of conventional LNG obtained from fossil sources. Also in this case, the cheapest alternative is the third, as the LNG produced has a lower levelized cost (31.12 €/GJ) than the other alternatives. The cost of e-LNG is instead much higher (67.70 and 59.88 €/GJ, respectively, for alternatives 1 and 2): this shows that e-LNG can become cheaper than bio-LNG only if low-cost renewable electricity is available, capital costs are significantly reduced and high electrolyzer load factors can be achieved. Currently, the most cost-effective strategy to reduce shipping-related emissions is therefore to use bio-LNG blended in any ratio with fossil LNG. Finally, the results of the preliminary carbon footprint analysis show that the greenest alternative involves the production of bio-LNG with biogas upgrading by chemical methanation (alternative 4), while the production of e-LNG with CO2 capture from flue gases leads to the largest emissions (alternative 2).
Lo scopo di questa tesi è quello di condurre un'analisi tecnico-economica ed energetica di diversi metodi di produzione sostenibili di gas naturale liquefatto (GNL) usato come combustibile per il trasporto marittimo. I processi affrontati riguardano principalmente la produzione di gas naturale sintetico (GNS) e di biometano: il primo è prodotto sfruttando l'energia elettrica ottenuta da fonti rinnovabili, il secondo dalla digestione anaerobica della materia organica (biomasse). C'è da sottolineare che il GNL prodotto da tali processi (e-GNL e bio-GNL) appartiene alla categoria dei cosiddetti zero carbon fuels o carburanti a zero emissioni di carbonio, in quanto la CO2 prodotta dalla loro combustione viene catturata e riutilizzata come reagente; ne deriva che il bilancio netto di CO2 prodotta/consumata è pari a zero (o quasi), e questo comporta notevoli benefici ambientali. Per quanto riguarda l'analisi tecnica, i bilanci di massa e di energia sono stati valutati usando il simulatore di processo Aspen Plus, prendendo come riferimento la capacità annua di un porto nel nord-est italiano. Sono state inoltre considerate quattro diverse alternative per la produzione di GNL, due riguardanti l’e-GNL e due il bio-GNL. I consumi energetici associati ai diversi processi sono stati valutati al fine di stimare l'efficienza delle diverse alternative dal punto di vista energetico. Dai risultati delle simulazioni, è stato trovato che la produzione di bio-GNL con purificazione del biogas mediante distillazione criogenica (alternativa 3) è l’alternativa più conveniente dal punto di vista energetico. L’analisi economica è stata condotta per valutare il costo livellato del GNL, metrica utile per confrontare il costo del GNL rinnovabile (sintetico e bio) al costo del GNL convenzionale ottenuto da fonte fossile. Anche in questo caso, l’alternativa più economica è la terza, in quanto il GNL prodotto ha un costo livellato più basso (31.12 €/GJ) delle altre alternative. Il costo dell’e-GNL è invece molto maggiore (67.70 e 59.88 €/GJ, rispettivamente, per l’alternativa 1 e 2): questo dimostra che l’e-GNL può diventare più economico del bio-GNL solo se è disponibile elettricità rinnovabile a basso costo, i costi capitali si riducono sensibilmente e si possono ottenere elevati fattori di carico dell’elettrolizzatore. Attualmente, la strategia più conveniente per ridurre le emissioni legate al trasporto marittimo è quindi quella di usare GNL fossile e bio-GNL in proporzioni miste. Infine, i risultati dell’analisi preliminare dell’impronta di carbonio dimostrano che l’alternativa più green è quella che prevede la produzione di bio-GNL con upgrading del biogas mediante metanazione chimica (alternativa 4), mentre la produzione di e-GNL con cattura della CO2 dai gas di combustione comporta le emissioni maggiori (alternativa 2).
Utilizzo di GNL come combustibile per il trasporto marittimo: analisi tecno-economica ed energetica di diversi processi di produzione
ADINOLFI, MICHELE
2022/2023
Abstract
The aim of this thesis is to conduct a techno-economic and energetic analysis of different sustainable production methods of liquefied natural gas (LNG) used as fuel for maritime transport. The processes covered mainly concern the production of synthetic natural gas (SNG) and biomethane: the first is produced by exploiting renewable electricity, the second from the anaerobic digestion of organic matter (biomass). It should be emphasized that the LNG produced by these processes (e-LNG and bio-LNG) belongs to the category of so-called zero carbon fuels or fuels with zero carbon emissions, as the CO2 produced by their combustion is captured and reused as feedstock; it follows that the net balance of CO2 produced/consumed is equal to zero (or almost), and this entails significant environmental benefits. Concerning the technical analysis, the mass and energy balances were evaluated using the Aspen Plus process simulator, taking as a reference the annual capacity of a port located in North-East Italy. Four different alternatives were considered, two involving e-LNG production and two involving bio-LNG production. The energy consumption associated with the different processes was evaluated in order to estimate the energetic efficiency of the different alternatives. From the simulation results, it was found that bio-LNG production with biogas upgrading by cryogenic distillation (alternative 3) is the most energy-efficient alternative. The economic analysis was conducted to evaluate the levelized cost of LNG, a useful metric for comparing the cost of renewable LNG (synthetic and bio) to the cost of conventional LNG obtained from fossil sources. Also in this case, the cheapest alternative is the third, as the LNG produced has a lower levelized cost (31.12 €/GJ) than the other alternatives. The cost of e-LNG is instead much higher (67.70 and 59.88 €/GJ, respectively, for alternatives 1 and 2): this shows that e-LNG can become cheaper than bio-LNG only if low-cost renewable electricity is available, capital costs are significantly reduced and high electrolyzer load factors can be achieved. Currently, the most cost-effective strategy to reduce shipping-related emissions is therefore to use bio-LNG blended in any ratio with fossil LNG. Finally, the results of the preliminary carbon footprint analysis show that the greenest alternative involves the production of bio-LNG with biogas upgrading by chemical methanation (alternative 4), while the production of e-LNG with CO2 capture from flue gases leads to the largest emissions (alternative 2).File | Dimensione | Formato | |
---|---|---|---|
Adinolfi_Michele.pdf
accesso riservato
Dimensione
6.55 MB
Formato
Adobe PDF
|
6.55 MB | Adobe PDF |
The text of this website © Università degli studi di Padova. Full Text are published under a non-exclusive license. Metadata are under a CC0 License
https://hdl.handle.net/20.500.12608/45522