The aim of the PhD research project is to carry out techno-economic studies on innovative solutions for CO2 capture in cement plants and power plants by Calcium Looping (CaL) processes. CaL is an emerging technology for CO2 capture that uses CaO-based sorbent to remove CO2 from process flue gases, according to the carbonation reaction CaO+CO2 -> CaCO3. Starting from the initial configuration, proposed by Shimizu in 1999, the work carried out in this PhD thesis focuses on the following novel aspects with respect to the state-of-the-art: (i) the investigation of various novel process configurations for the integration of CaL process in cement plants, (ii) the opportunity of thermochemical storage of sorbent to improve the economic performance of flexibly operated power plants. In this thesis, the integration of Calcium looping (CaL) processes in a cement plant, through different plant solutions, is assessed. The configurations that constitute the core of the analysis are: (i) the Tail-end CaL configuration, where fluidized bed CaL reactors treats the flue gas downstream a cement burning process, and (ii) the Integrated entrained-flow (EF) CaL system, where the EF CaL reactors are integrated in the preheater and precalciner of the cement kiln. An in-depth analysis was conducted for these two configurations to assess the impact of the operating parameters on the overall system performance, followed by a technical-economic comparison to highlight the advantages and disadvantages of the two processes. From these two configurations, other alternative processes have been developed and analyzed to overcome some criticalities or exploit some peculiarities of both Tail-end CaL and Integrated EF Cal systems. All configurations and processes using CaL technology were then compared to two oxyfuel-based configurations, which are considered among the most promising for reducing CO2 emissions in cement plants: Full oxyfuel process and Partial oxyfuel process. This comparison was carried out from an energy, economic and semi-quantitative perspective. The analysis shows that processes based on CaL technology are competitive, from a technical and economic point of view, for the reduction of CO2 emissions in cement plants, even compared to technologies that are more invasive (such as full oxyfuel configuration). In the second part of this thesis, a new Calcium Looping system for the energy sector with high temperature sorbent storage was assessed. Initially, using a simplified model, the optimal size of the calciner and storage system was evaluated from an economic perspective. Starting with the results of this preliminary analysis, a second comprehensive techno-economic analysis of CaL plants without (Baseline) and with (Flexical) sorbent storage systems was performed, with detailed modeling of part-load performance from weekly cycling operations. The analysis was expanded by also considering the possibility of introducing a secondary storage system to further increase the system flexibility. Heat and mass balances were calculated for CaL plants at different loads, taking into account the off-design performance of heat exchangers and machines. Knowing the system performance derived from the detailed models of the CaL systems, the previous economic analysis was replicated to calculate and compare the economic performance of both systems, with and without the storage. From the analysis performed, it can be concluded that, through appropriate technical measures, the thermochemical energy storage of the CaL system sorbent, can be exploited to achieve the dual objectives of increasing plant flexibility and cost reduction. The advantage of the storage system is greater when the capacity factor of the system is lower and will therefore be increasingly advantageous in the coming years as the penetration of renewables for electricity production is expected to increase.
L'obiettivo del progetto di ricerca sviluppato in questo dottorato è quello di effettuare studi tecnico-economici su soluzioni innovative per la cattura di CO2 in cementifici e centrali elettriche mediante processi di Calcium Looping (CaL). Il CaL è una emergente tecnologia per la cattura della CO2 che utilizza un sorbente a base di CaO per rimuovere la CO2 dai gas di processo, secondo la reazione di carbonatazione CaO+CO2 -> CaCO3. Partendo dalla configurazione inizialmente proposta da Shimizu nel 1999, il lavoro svolto in questa tesi di dottorato si concentra sui seguenti aspetti innovativi rispetto allo stato dell'arte: (i) lo studio di varie nuove configurazioni di processo per l'integrazione del processo CaL nei cementifici, (ii) l'opportunità dell'immagazzinamento termo-chimico del sorbente per migliorare le performance economiche di centrali a combustibile fossile ad elevata flessibilità. In questa tesi si valuta l'integrazione dei processi di Calcium looping (CaL) in un cementificio, attraverso diverse soluzioni impiantistiche. Le configurazioni che costituiscono il nucleo dell'analisi sono: (i) la configurazione Tail-end CaL, dove i reattori CaL a letto fluido trattano i fumi a valle del processo produttivo del cemento, e (ii) il sistema integrato entrained-flow (EF) CaL, dove i reattori EF CaL sono integrati nel preriscaldatore e precalcinatore del processo per la produzione di clinker. Per queste due configurazioni è stata condotta un'analisi approfondita per valutare l'impatto dei parametri operativi sulle prestazioni complessive del sistema, seguita da un confronto tecnico-economico per evidenziare i vantaggi e gli svantaggi dei due processi. A partire da queste due configurazioni, sono stati poi sviluppati e analizzati altri processi alternativi per superare alcune criticità o sfruttare alcune peculiarità di entrambi i sistemi Tail-end CaL e Integrated EF Cal. Tutte le configurazioni e i processi che utilizzano la tecnologia CaL sono stati poi confrontati con due configurazioni basate sull'ossicombustione, che sono considerate tra le più promettenti per la riduzione delle emissioni di CO2 nei cementifici: Full oxyfuel process e Partial oxyfuel process. Questo confronto è stato effettuato da una prospettiva energetica, economica e semi-quantitativa. L'analisi mostra che i processi basati sulla tecnologia CaL sono competitivi, da un punto di vista tecnico ed economico, per la riduzione delle emissioni di CO2 nell’industria del cemento, anche rispetto a tecnologie più invasive (come la configurazione full oxyfuel). Nella seconda parte di questa tesi è stato valutato un nuovo sistema Calcium Looping per il settore energetico con stoccaggio di sorbenti ad alta temperatura. Inizialmente, utilizzando un modello semplificato, è stata valutata la dimensione ottimale del calcinatore e del sistema di stoccaggio da un punto di vista economico. Partendo dai risultati di questa analisi preliminare, è stata eseguita una seconda analisi tecno-economica completa degli impianti CaL senza (Baseline) e con sistemi di stoccaggio del sorbente (Flexical), con una modellazione dettagliata delle prestazioni a carico parziale su un ciclo di produzione settimanale. L'analisi è stata ampliata considerando anche la possibilità di introdurre un sistema di stoccaggio secondario per aumentare ulteriormente la flessibilità del sistema. I bilanci di calore e di massa sono stati calcolati per gli impianti CaL a diversi carichi, tenendo conto delle prestazioni di fuori progetto degli scambiatori di calore e delle macchine. Conoscendo le prestazioni del sistema derivate dai modelli dettagliati dei sistemi CaL, l'analisi economica precedente è stata replicata per calcolare e confrontare le prestazioni economiche di entrambi i sistemi, con e senza lo stoccaggio. Dall'analisi effettuata, si può concludere che, attraverso opportuni accorgimenti tecnici, l'accumulo termochimico di energia del sorbente del sistema CaL, può essere sfruttato per raggiungere il duplice obiettivo di aumentare la flessibilità dell'impianto e ridurre i costi. Il vantaggio del sistema di accumulo è maggiore quando il capacity factor dell'impianto è più basso e sarà quindi sempre più vantaggioso nei prossimi anni in quanto si prevede un aumento della penetrazione delle rinnovabili per la produzione di energia elettrica.
Advanced applications of Calcium-Looping for CO2 capture in cement plants and flexible power plants
De Lena, Edoardo
2021/2022
Abstract
The aim of the PhD research project is to carry out techno-economic studies on innovative solutions for CO2 capture in cement plants and power plants by Calcium Looping (CaL) processes. CaL is an emerging technology for CO2 capture that uses CaO-based sorbent to remove CO2 from process flue gases, according to the carbonation reaction CaO+CO2 -> CaCO3. Starting from the initial configuration, proposed by Shimizu in 1999, the work carried out in this PhD thesis focuses on the following novel aspects with respect to the state-of-the-art: (i) the investigation of various novel process configurations for the integration of CaL process in cement plants, (ii) the opportunity of thermochemical storage of sorbent to improve the economic performance of flexibly operated power plants. In this thesis, the integration of Calcium looping (CaL) processes in a cement plant, through different plant solutions, is assessed. The configurations that constitute the core of the analysis are: (i) the Tail-end CaL configuration, where fluidized bed CaL reactors treats the flue gas downstream a cement burning process, and (ii) the Integrated entrained-flow (EF) CaL system, where the EF CaL reactors are integrated in the preheater and precalciner of the cement kiln. An in-depth analysis was conducted for these two configurations to assess the impact of the operating parameters on the overall system performance, followed by a technical-economic comparison to highlight the advantages and disadvantages of the two processes. From these two configurations, other alternative processes have been developed and analyzed to overcome some criticalities or exploit some peculiarities of both Tail-end CaL and Integrated EF Cal systems. All configurations and processes using CaL technology were then compared to two oxyfuel-based configurations, which are considered among the most promising for reducing CO2 emissions in cement plants: Full oxyfuel process and Partial oxyfuel process. This comparison was carried out from an energy, economic and semi-quantitative perspective. The analysis shows that processes based on CaL technology are competitive, from a technical and economic point of view, for the reduction of CO2 emissions in cement plants, even compared to technologies that are more invasive (such as full oxyfuel configuration). In the second part of this thesis, a new Calcium Looping system for the energy sector with high temperature sorbent storage was assessed. Initially, using a simplified model, the optimal size of the calciner and storage system was evaluated from an economic perspective. Starting with the results of this preliminary analysis, a second comprehensive techno-economic analysis of CaL plants without (Baseline) and with (Flexical) sorbent storage systems was performed, with detailed modeling of part-load performance from weekly cycling operations. The analysis was expanded by also considering the possibility of introducing a secondary storage system to further increase the system flexibility. Heat and mass balances were calculated for CaL plants at different loads, taking into account the off-design performance of heat exchangers and machines. Knowing the system performance derived from the detailed models of the CaL systems, the previous economic analysis was replicated to calculate and compare the economic performance of both systems, with and without the storage. From the analysis performed, it can be concluded that, through appropriate technical measures, the thermochemical energy storage of the CaL system sorbent, can be exploited to achieve the dual objectives of increasing plant flexibility and cost reduction. The advantage of the storage system is greater when the capacity factor of the system is lower and will therefore be increasingly advantageous in the coming years as the penetration of renewables for electricity production is expected to increase.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/180314