Among the new challenges that Chemical and Industrial Engineering are facing, the exploitation of alternative energy sources, especially biomass and waste molecules (such as carbon dioxide and sulfur compounds), clearly emerges. Biomasses are a valuable alternative source of biogas that, due to its versatility, can be converted into several bulk chemicals such as (bio)methanol and dimethylether (DME). On the other hand, since the 1990s, carbon dioxide has sparked increasing interest as a raw material for chemical processes. The usefulness of biomass and other techniques for the capture and use of CO2 is twofold: on one hand it enables and incentives the sequestration of a greenhouse gas and on the other hand it fixes a very volatile molecule in a more stable one which has several applications in industry. The purpose and benefit are clear: use emissions to produce valuable molecules (this is the concept of negative net emissions). It should not be forgotten that methanol is a basic chemical compound widely used as an intermediate in many industrial processes and applications. Not least, (bio)methanol is already currently employed as an additive in gasoline. Actually, the diesel engine is able to properly work only with (bio)methanol without the need for any technological modification. An economy based on methanol molecule had already been theorized by Prof. George Olah (Nobel Prize for Chemistry 1994). In his detailed analysis, he showed how methanol could be an excellent solution in both environmental - technological and energy perspective: (1) it can be easily transported and produced unlike hydrogen, (2) it can be produced according to different chemical pathways (biogas, natural gas, coal gasification and so on), both from conventional feedstock and alternative carbon sources, (3) it allows to remove and fix CO2 in a stable molecule with a booming-trend world market and finally (4) methanol, besides being a widely used chemical intermediate, is also a valid alternative to fossil fuels. In this perspective of biomass exploitation as a potential candidate to replace a market share currently occupied by fossil fuels, our work aims to develop a valid technology for the production of (bio)methanol. Indeed, starting from a multiscale approach, we have proposed a new kinetics of methanol that would allow to operate at low pressures (microscale and mesoscale). Starting from this tool, we proceeded to model a reactor for the synthesis of (bio)methanol of more compact dimensions compared to Lurgi technology (macroscale). The choice of redesigning the reactor leaner and more compact was dictated by the need of using directly in situ the produced biogas (farm) without taking away space for agricultural activity. The proposed solution also allows the reactor to be efficient from an energy point of view. Finally, the reactor has been included in an Aspen HYSYS V.10 simulation to verify its performance and economic feasibility.
Tra le nuove sfide che l’ingegneria chimica ed industriale stanno affrontando, emerge chiaramente lo sfruttamento di fonti energetiche alternative, in particolare le biomasse e molecole di scarto (quali diossido di carbonio e composti solforati). Le biomasse sono una valida fonte di biogas che, data la sua versatilità, può essere convertito in diverse altre molecole di base quali ad esempio (bio)metanolo e dimetil-etere (DME). D’altro canto, a partire dagli anni 90 dello scorso secolo, il diossido di carbonio ha suscitato un interesse sempre più crescente come materia prima per i processi chimici. L’utilità delle biomasse ed altre tecniche di cattura e utilizzo della CO2 è duplice: da un lato si favorisce il sequestro di un gas serra e dall’altro si fissa una molecola molto volatile in una molecola più stabile con numerose applicazioni in ambito industriale. Lo scopo e beneficio sono chiari: utilizzare emissioni per produrre molecole utili (negative net emissions). Non bisogna infatti dimenticare che il metanolo è un composto chimico di base largamente utilizzato come intermedio in tantissimi processi ed applicazioni industriali. Non di meno, il (bio)metanolo è già attualmente aggiunto come additivo nelle benzine. In realtà, il motore diesel è in grado di funzionare perfettamente solo a (bio)metanolo senza la necessità di alcuna modifica tecnologica. Un’economia basata sulla molecola metanolo era già stata teorizzata dal Prof. George Olah (premio Nobel per la Chimica 1994). Nella sua analisi dettagliata, mostrava come il metanolo potesse essere un’ottima soluzione sia dal punto di vista ambientale/tecnologico sia energetico: (1) può essere facilmente trasportato e prodotto a differenza dell’idrogeno, (2) può essere prodotto secondo diversi cammini chimici (biogas, gas naturale, gassificazione del carbone etc.), (3) permette di rimuovere e fissare la CO2 in una molecola stabile e con un mercato mondiale in forte espansione ed infine (4) il metanolo, oltre ad essere un intermedio chimico largamente sfruttato, è anche una valida alternativa ai combustili fossili come carburante. In questa prospettiva di sfruttamento delle biomasse come potenziale candidato a sostituire una quota di mercato al momento occupata dai combustili fossili, il nostro lavoro punta a sviluppare una tecnologia valida per la produzione di (bio)metanolo. Infatti, partendo da un approccio multi-scala, abbiamo riproposto una nuova cinetica del metanolo che consentisse di operare a basse pressioni (micro-scala e meso-scala). Partendo da questo strumento, si è proceduto a modellare un reattore per la sintesi del (bio)metanolo di dimensioni più compatte rispetto alla tecnologia Lurgi (macro-scala). La scelta di ridisegnare il reattore più snello e compatto è stata dettata dalla necessità di utilizzare direttamente in sito il biogas prodotto (fattoria) senza sottrarre spazio all’attività agricola. La soluzione proposta inoltre permette di efficientare il reattore anche da un punto di vista energetico. Infine, il reattore è stato inserito in una simulazione Aspen HYSYS V.10, per verificarne performance e fattibilità economica.
Biogas to methanol : a multiscale approach. From the kinetics and reactor design to the plant scale and economic feasibility
Gallo, Veronica;CAUTERUCCIO, MARTINA
2019/2020
Abstract
Among the new challenges that Chemical and Industrial Engineering are facing, the exploitation of alternative energy sources, especially biomass and waste molecules (such as carbon dioxide and sulfur compounds), clearly emerges. Biomasses are a valuable alternative source of biogas that, due to its versatility, can be converted into several bulk chemicals such as (bio)methanol and dimethylether (DME). On the other hand, since the 1990s, carbon dioxide has sparked increasing interest as a raw material for chemical processes. The usefulness of biomass and other techniques for the capture and use of CO2 is twofold: on one hand it enables and incentives the sequestration of a greenhouse gas and on the other hand it fixes a very volatile molecule in a more stable one which has several applications in industry. The purpose and benefit are clear: use emissions to produce valuable molecules (this is the concept of negative net emissions). It should not be forgotten that methanol is a basic chemical compound widely used as an intermediate in many industrial processes and applications. Not least, (bio)methanol is already currently employed as an additive in gasoline. Actually, the diesel engine is able to properly work only with (bio)methanol without the need for any technological modification. An economy based on methanol molecule had already been theorized by Prof. George Olah (Nobel Prize for Chemistry 1994). In his detailed analysis, he showed how methanol could be an excellent solution in both environmental - technological and energy perspective: (1) it can be easily transported and produced unlike hydrogen, (2) it can be produced according to different chemical pathways (biogas, natural gas, coal gasification and so on), both from conventional feedstock and alternative carbon sources, (3) it allows to remove and fix CO2 in a stable molecule with a booming-trend world market and finally (4) methanol, besides being a widely used chemical intermediate, is also a valid alternative to fossil fuels. In this perspective of biomass exploitation as a potential candidate to replace a market share currently occupied by fossil fuels, our work aims to develop a valid technology for the production of (bio)methanol. Indeed, starting from a multiscale approach, we have proposed a new kinetics of methanol that would allow to operate at low pressures (microscale and mesoscale). Starting from this tool, we proceeded to model a reactor for the synthesis of (bio)methanol of more compact dimensions compared to Lurgi technology (macroscale). The choice of redesigning the reactor leaner and more compact was dictated by the need of using directly in situ the produced biogas (farm) without taking away space for agricultural activity. The proposed solution also allows the reactor to be efficient from an energy point of view. Finally, the reactor has been included in an Aspen HYSYS V.10 simulation to verify its performance and economic feasibility.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/169384