Nowadays, the worldwide energy demand is met mainly by fossil fuels. These fuels, however, release into the atmosphere carbon dioxide and other pollutants, increasing the greenhouse effect and the acid rainfall phenomenon; therefore, other sources of energy are being sought. The use of biogas as an energy source is becoming increasingly important in Europe and especially in Italy and Germany where more than 1400 biogas plants are already active for each country. Since it is generated by anaerobic digestion of agricultural residues or sewage, if burned, biogas does not introduce new CO2 into the atmosphere. Biogas is currently used to produce electricity and heat in Combined Heat and Power (CHP) plants. This technology is being used by more and more biogas producers as, thanks to the incentives, the process is economically convenient. However, because of this, these incentives are decreasing and they are going to run out, making the CHP plant unsustainable. There is therefore a need to address the use of biogas to new processes capable of self-sustaining. The aim of this thesis is to develop a process diagram for the production of diesel from biogas and to verify its sustainability. Biogas has been purified from H2S through an absorption with MDEA and subsequently converted into syngas in a reforming section. Through the FT (Fischer-Tropsch) synthesis this syngas has been converted into diesel. Once productivity in terms of liquid hydrocarbons (e.g. gasoline, diesel and wax) has been estimated an economic analysis has been conducted in order to verify the sustainability of the process. The results obtained show that some of the analyzed configurations can also be a viable alternative to the CHP solution.
Oggigiorno, la richiesta mondiale di energia è soddisfatta principalmente da combustibili fossili. Questi carburanti, tuttavia, rilasciano nell’atmosfera anidride carbonica e altri inquinanti, aumentando l’effetto serra e il fenomeno delle piogge acide; pertanto, si ricercano altre fonti di energia. L’utilizzo del biogas come fonte energetica sta assumendo sempre più importanza in Europa ed in particolare in Italia e in Germania dove per ciascuna nazione più di 1400 impianti biogas sono già attivi. La combustione del biogas non introduce nuova CO2 nell’atmosfera essendo prodotto dalla digestione anaerobica di residui agricoli o di reflui vari. Attualmente il biogas viene utilizzato per produrre elettricità e calore in impianti CHP (Combined Heat and Power). Questa tecnologia viene sfruttata sempre da più produttori di biogas in quanto prevede incentivi sull’energia elettrica prodotta e rivenduta. A causa di ciò, questi incentivi stanno diminuendo e sono destinati ad esaurirsi, rendendo un impianto CHP non sostenibile. Vi è dunque la necessità di indirizzare l’utilizzo del biogas verso nuovi processi in grado di auto-sostenersi. Lo scopo di questa tesi è quello di sviluppare uno schema di processo per la produzione di diesel da biogas e verificarne la sostenibilità. Il processo consiste nella purificazione del biogas dall’H2S tramite assorbimento con MDEA e una successiva conversione in syngas in una sezione di reforming. Tramite la sintesi di FT (Fischer-Tropsch) questo syngas è poi convertito in diesel. Stimata la produttività in termini di idrocarburi liquidi prodotti (e.g. benzine, diesel e cere) è stata condotta un’analisi economica per verificare la sostenibilità del processo. I risultati ottenuti dimostrano che alcune delle configurazioni analizzate possono essere anche attualmente una valida alternativa alla soluzione CHP.
Diesel production from biogas. Design and economic assessment
GHEZZI, STEFANO;IANNACE, GIULIO
2016/2017
Abstract
Nowadays, the worldwide energy demand is met mainly by fossil fuels. These fuels, however, release into the atmosphere carbon dioxide and other pollutants, increasing the greenhouse effect and the acid rainfall phenomenon; therefore, other sources of energy are being sought. The use of biogas as an energy source is becoming increasingly important in Europe and especially in Italy and Germany where more than 1400 biogas plants are already active for each country. Since it is generated by anaerobic digestion of agricultural residues or sewage, if burned, biogas does not introduce new CO2 into the atmosphere. Biogas is currently used to produce electricity and heat in Combined Heat and Power (CHP) plants. This technology is being used by more and more biogas producers as, thanks to the incentives, the process is economically convenient. However, because of this, these incentives are decreasing and they are going to run out, making the CHP plant unsustainable. There is therefore a need to address the use of biogas to new processes capable of self-sustaining. The aim of this thesis is to develop a process diagram for the production of diesel from biogas and to verify its sustainability. Biogas has been purified from H2S through an absorption with MDEA and subsequently converted into syngas in a reforming section. Through the FT (Fischer-Tropsch) synthesis this syngas has been converted into diesel. Once productivity in terms of liquid hydrocarbons (e.g. gasoline, diesel and wax) has been estimated an economic analysis has been conducted in order to verify the sustainability of the process. The results obtained show that some of the analyzed configurations can also be a viable alternative to the CHP solution.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/136154