Thermodynamic and economic analysis of advanced systems for CO2 capture

The final goal of the PhD research activity was the techno-economic assessment of fossil fuelled power plants with carbon capture by two different innovative technologies: one based on advanced sorbents (Sorption Enhanced Water Gas Shift) and one based on membranes (hydrogen selective membranes). Both the technologies were developed in two FP7 projects: Caesar and Cachet II. The PhD work was exclusively theoretical but with input from experiments carried out by the projects partners (ECN, SINTEF). In order to study advanced technologies together with innovative power production configurations, different investigation levels have been considered: detailed reactor model, specific process model and overall techno-economic plant simulation. SEWGS technology has shown good thermodynamic results both in NGCC and IGCC power plant with a consequent efficiency gain of about 3 percentage points when compared to the commercial ready CO2 capture technology. From an economic point of view, the application of SEWGS to NGCC does not show evident advantages compared to commercial ready technology. On the other hand, its application to IGCC leads to a decrease in the cost of CO2 avoided in the order of 35%. SEWGS adoption in integrated steel plant features substantial thermodynamic benefits compared to other technologies. Hydrogen membrane application to IGCC showed an efficiency improvement in the order of 3-4 percentage points compared to the reference pre-combustion technology. The economic evaluation underlined that the cost of CO2 capture through this technology with the present features is higher than the commercial ready process. Nevertheless there are several future possibilities to reduce the membrane performances which would make this technology more competitive.

La tesi di dottorato rientra nell'ambito della produzione di energia elettrica da fonti fossili con limitate emissioni di gas serra. L'obbiettivo della tesi è di sviluppare un'analisi tecnico-economica di sistemi avanzati per la cattura di gas serra (CO2) in impianti a gas naturale, carbone ed acciaierie integrate. Le tecnologie considerate sono il reattore di Sorption Enhanced Water Gas Shift e membrane al palladio per la separazione d’idrogeno. Entrambe sono state sviluppate in due progetti europei FP7, rispettivamente il progetto CAESAR ed il progetto CACHET-II. Il lavoro di tesi è basato su tre diversi livelli di simulazioni: simulazioni dettagliate di un singolo reattore, simulazioni dettagliate di un singolo processo e simulazioni di sistema. Il reattore SEWGS ha dimostrato ottime potenzialità sia dal punto di vista termodinamico che economico, soprattutto qualora applicato ad impianti a carbone o in acciaierie integrate. L’utilizzo di membrane permette di ottenere performance termodinamiche eccellenti. D’altra parte questa tecnologia richiede una sostanziale diminuzione dei costi di fabbricazione.