The use of CO2 as raw material is currently gaining interest in the perspective of reducing world greenhouse gasses emissions and mitigate the effects of the climate change. Among the greenhouse gases, CO2 is the most problematic one because, despite its relatively weak radiative force, it is emitted in huge amounts. In the present work, its exploitation for the production of an alternative promising fuel, dimethyl ether (DME), was analysed. In particular, this study focuses on the techno economic assessment of a membrane reactor assisted process for the direct conversion of CO2 into dimethyl ether and the quantification of the CO2 abatement. The production of DME through methanol dehydration is a very well-known and established process and it is commonly carried out in two steps starting from a syngas feedstock. Methanol is first produced in a reactor, then it is dehydrated in a second reactor after its purification from water and the unconverted gases. Studies proved that the direct synthesis of dimethyl ether in a single reactor is preferable for large scale production because of the higher performance and the lower overall costs related to the easiness of the single reactor management. However, the more complex heat management and the water accumulation, especially at higher CO2 concentration in the feeds, are still challenges to be solved prior to the establishment of this technology at industrial practice. The integration of membranes in the reactor technology for the in-situ water separation was proposed as a solution for this purpose. In this reactor configuration, called membrane reactor, reaction and separation (i.e. in this case product removal) occur simultaneously, allowing to overcome the thermodynamic limitations and improving the thermal management. Several modelling studies have already demonstrated the feasibility of this type of reactor for the direct conversion of CO or CO2 rich feeds to DME. In this work, besides the technical analysis, an economic assessment of the membrane reactor assisted process was carried out to determine the DME minimum selling price (MDSP) to be compared with the MDSP obtained with the conventional process and current DME market price. A carbon footprint analysis was also performed to demonstrate the potential CO2 abatement provided by this process. ASPEN Plus software was used to simulate the process and predict the DME production of the conventional reactors while a phenomenological membrane reactor model was used to describe the membrane reactor performance. ASPEN environment was also used to describe the downstream separation necessary to recover DME with the purity required for fuel application and the upstream compression section (i.e., feed conditioning), to bring the reactants to the reactor operating conditions. CAPEX were estimated by means of a factorial methodology based on the Purchase Equipment Cost (PEC). Cost correlations from literature were used to determine the cost of each component. OPEX were calculated via the sum of fixed operating costs and variable operating costs. Fixed operating costs were estimated similarly to CAPEX, by the determination of the labour costs and all the other cost components were calculated by means of explicit default factors. On the other hand, variable operating costs were obtained directly from the plant consumptions (i.e. feedstock and utilities). Finally, the MDSP was calculated as the minimum price at which DME need to be sold in order to have NPV=0 (or equally IRR= discount rate) at the end of the project life.
L’utilizzo della CO2 come materia prima in processi di sintesi è una soluzione che sta riscontrando molto interesse nella prospettiva di ridurre le emissioni mondiali di gas serra e mitigare gli effetti del cambiamento climatico. Nel presente lavoro, viene analizzato il suo utilizzo per la produzione di un combustibile alternativo, dimetiletere (DME). In particolare, questo studio si concentra sulla valutazione tecnico-economica di un processo di conversione diretta della CO2 in dimetiletere basato su reattore a membrana e la quantificazione dell'abbattimento anidride carbonica. La produzione di DME attraverso la disidratazione del metanolo è un processo noto e consolidato e viene comunemente svolto in due fasi partendo da syngas. Studi però hanno mostrato le potenzialità della sintesi diretta del dimetiletere. Le migliori performance e i minori costi complessivi la farebbero preferire nel caso di produzioni su larga scala. Tuttavia, la gestione del calore più complessa e l'accumulo di acqua, specialmente al crescere delle concentrazioni di CO2 nei reagenti, rappresentano gli ostacoli principali all’applicazione industriale. A tal fine, è stata proposta l'integrazione di membrane nella tecnologia del reattore in una configurazione chiamata reattore a membrana. In questo tipo di reattore, reazione e separazione (dei prodotti) avvengono simultaneamente, consentendo di superare i limiti termodinamici e migliorando la gestione termica. Diversi studi hanno già mostrato la fattibilità di questo tipo di reattore per la conversione diretta di miscele di CO e CO2 in DME. In questo lavoro, oltre all'analisi tecnica, è stata effettuata una valutazione economica del processo al fine di determinare il prezzo minimo di vendita DME (MDSP) da confrontare con quello del processo convenzionale e l'attuale prezzo di mercato del DME. È stata inoltre eseguita un'analisi della carbon footprint per dimostrare il potenziale abbattimento di CO2 fornito da questo processo. ASPEN Plus software è stato utilizzato per simulare il processo di produzione in reattori convenzionali, mentre un modello Matlab di reattore a membrana è stato utilizzato per descrivere le prestazioni del reattore a membrana. L'ambiente ASPEN è stato utilizzato anche per descrivere la separazione a valle necessaria per recuperare il DME con la purezza necessaria per l'applicazione come carburante e la sezione di compressione a monte per portare i reagenti alle condizioni di funzionamento del reattore. I CAPEX sono stati stimati mediante una metodologia fattoriale basata sul costo di acquisto dei componenti (PEC). Per la determinazione del costo di ogni componente sono state utilizzate delle correlazioni da letteratura. Gli OPEX sono stati calcolati sommando i costi operativi fissi e i costi operativi variabili. I costi operativi fissi sono stati stimati in modo analogo ai CAPEX, determinando prima il costo del lavoro e poi tutte le altre componenti di costo mediante fattori. I costi operativi variabili invece sono stati ottenuti direttamente dai consumi dell'impianto (feedstock e utilities). Infine, l'MDSP è stato calcolato come il prezzo minimo al quale il DME deve essere venduto per avere NPV = 0 (o ugualmente IRR = tasso di sconto) alla fine della vita del progetto.
Techno economic assessment of a membrane reactor based process for the direct conversion of CO2 to dimethyl ether
Gazzola, Alessandro
2019/2020
Abstract
The use of CO2 as raw material is currently gaining interest in the perspective of reducing world greenhouse gasses emissions and mitigate the effects of the climate change. Among the greenhouse gases, CO2 is the most problematic one because, despite its relatively weak radiative force, it is emitted in huge amounts. In the present work, its exploitation for the production of an alternative promising fuel, dimethyl ether (DME), was analysed. In particular, this study focuses on the techno economic assessment of a membrane reactor assisted process for the direct conversion of CO2 into dimethyl ether and the quantification of the CO2 abatement. The production of DME through methanol dehydration is a very well-known and established process and it is commonly carried out in two steps starting from a syngas feedstock. Methanol is first produced in a reactor, then it is dehydrated in a second reactor after its purification from water and the unconverted gases. Studies proved that the direct synthesis of dimethyl ether in a single reactor is preferable for large scale production because of the higher performance and the lower overall costs related to the easiness of the single reactor management. However, the more complex heat management and the water accumulation, especially at higher CO2 concentration in the feeds, are still challenges to be solved prior to the establishment of this technology at industrial practice. The integration of membranes in the reactor technology for the in-situ water separation was proposed as a solution for this purpose. In this reactor configuration, called membrane reactor, reaction and separation (i.e. in this case product removal) occur simultaneously, allowing to overcome the thermodynamic limitations and improving the thermal management. Several modelling studies have already demonstrated the feasibility of this type of reactor for the direct conversion of CO or CO2 rich feeds to DME. In this work, besides the technical analysis, an economic assessment of the membrane reactor assisted process was carried out to determine the DME minimum selling price (MDSP) to be compared with the MDSP obtained with the conventional process and current DME market price. A carbon footprint analysis was also performed to demonstrate the potential CO2 abatement provided by this process. ASPEN Plus software was used to simulate the process and predict the DME production of the conventional reactors while a phenomenological membrane reactor model was used to describe the membrane reactor performance. ASPEN environment was also used to describe the downstream separation necessary to recover DME with the purity required for fuel application and the upstream compression section (i.e., feed conditioning), to bring the reactants to the reactor operating conditions. CAPEX were estimated by means of a factorial methodology based on the Purchase Equipment Cost (PEC). Cost correlations from literature were used to determine the cost of each component. OPEX were calculated via the sum of fixed operating costs and variable operating costs. Fixed operating costs were estimated similarly to CAPEX, by the determination of the labour costs and all the other cost components were calculated by means of explicit default factors. On the other hand, variable operating costs were obtained directly from the plant consumptions (i.e. feedstock and utilities). Finally, the MDSP was calculated as the minimum price at which DME need to be sold in order to have NPV=0 (or equally IRR= discount rate) at the end of the project life.| File | Dimensione | Formato | |
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Descrizione: Techno economic assessment of a membrane reactor based process for the direct conversion of CO2 to dimethyl ether
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https://hdl.handle.net/10589/174984