This work concerns the topic of different technologies for the capture of CO2 in cement factories. Among the different techniques studied in the European CEMCAP project, there is the oxy-combustion (oxy-fuel) process that represents the focus of this thesis. It involves replacing the inlet air to the plant with a mixture of pure oxygen and carbon dioxide to obtain combusted gases formed in large part by CO2 which is easier to be compressed and stored. A fraction of the burnt gases is recirculated with the pure oxygen produced by an air separation unit to control the high temperatures reached in the furnace due to the high oxygen content. The model of the reference cement plant, without the CO2 capture system, is based on a model previously developed and calibrated from the data provided by the European partner VDZ GmbH. Two different oxy-combustion configurations are obtained: the first one maintains the air leakages, while in the second one they are null. Then the two layouts obtained are compared with two different examples of oxy-combustion from two different reports, dating back to 2008 and 2018 respectively. The objective is to observe in the various cases the increases in energy consumption required to make possible the oxy-combustion compared to the reference case. Later a SPECCA analysis is conducted in order to determine the capture effectiveness compared to the consumptions involved. The results obtained confirm the potential of the oxy-combustion in the cement production field about the capture of CO2. At the same time, however, the additional energy costs that the new structure entails are highlighted. In particular, the air separation units (ASU) to guarantee the oxygen intake and the CO2 compression and purification unit (CPU) entail not negligible energy consumption. For these reasons the technology is still not available on a commercial scale, although the studies carried out by CEMCAP have achieved good results in modelling and analyzing a prototype in view of the test of a pilot plant.
Il presente lavoro si colloca nell’ambito delle diverse tecnologie per la cattura della CO2 nei cementifici. Tra le diverse tecniche studiate nel progetto europeo CEMCAP, vi è il processo ad ossi-combustione (oxy-fuel) che rappresenta il focus di questa tesi. Essa comporta la sostituzione dell’aria in ingresso all’impianto con una miscela composta da ossigeno puro e anidride carbonica per ottenere gas combusti formati in gran parte da CO2 che risulta essere più facile da comprimere e stoccare. Una frazione dei gas combusti viene ricircolata con l’ossigeno puro prodotto da una unità di separazione dell’aria per controllare le alte temperature raggiunte nel forno a causa dell’alto tenore di ossigeno. Il modello del cementificio di riferimento, privo dell’impianto di cattura della CO2, si basa su di un modello precedentemente sviluppato e calibrato a partire dai dati forniti dal partner europeo VDZ GmbH. Vengono ottenuti due diverse configurazioni ad ossi-combustione: una mantiene le rientrate di aria, mentre nella seconda sono rese nulle. Successivamente i due layout ottenuti vengono messi a confronto con due diversi esempi di ossi-combustione provenienti da due diversi rapporti, risalenti rispettivamente al 2008 e al 2018. L’obiettivo è osservare nei diversi casi gli aumenti dei consumi energetici necessari a rendere possibile l’ossi-combustione rispetto al caso di riferimento. Successivamente viene condotta un’analisi SPECCA volta a determinare l’efficacia di cattura rispetto ai consumi coinvolti. I risultati ottenuti confermano le potenzialità che ha in ambito della produzione del cemento l’ossi-combustione per la cattura della CO2. Allo stesso tempo però vengono messi in evidenza le spese energetiche aggiuntive che il nuovo assetto comporta. In particolare le unità di separazione dell’aria (ASU) per garantire l’apporto di ossigeno e l’unità di compressione e purificazione della CO2 (CPU) comportano consumi energetici non trascurabili. Per questo motivo la tecnologia non risulta ancora disponibile su scala commerciale, benché gli studi portati avanti da CEMCAP abbiano raggiunto buoni risultati nella modellizzazione ed analisi di un prototipo in vista del test di un impianto pilota.
Sistemi ad ossi-combustione nell'industria del cemento : modellizzazione e analisi energetico-ambientale
CORTI, CAMILLA PAOLA
2018/2019
Abstract
This work concerns the topic of different technologies for the capture of CO2 in cement factories. Among the different techniques studied in the European CEMCAP project, there is the oxy-combustion (oxy-fuel) process that represents the focus of this thesis. It involves replacing the inlet air to the plant with a mixture of pure oxygen and carbon dioxide to obtain combusted gases formed in large part by CO2 which is easier to be compressed and stored. A fraction of the burnt gases is recirculated with the pure oxygen produced by an air separation unit to control the high temperatures reached in the furnace due to the high oxygen content. The model of the reference cement plant, without the CO2 capture system, is based on a model previously developed and calibrated from the data provided by the European partner VDZ GmbH. Two different oxy-combustion configurations are obtained: the first one maintains the air leakages, while in the second one they are null. Then the two layouts obtained are compared with two different examples of oxy-combustion from two different reports, dating back to 2008 and 2018 respectively. The objective is to observe in the various cases the increases in energy consumption required to make possible the oxy-combustion compared to the reference case. Later a SPECCA analysis is conducted in order to determine the capture effectiveness compared to the consumptions involved. The results obtained confirm the potential of the oxy-combustion in the cement production field about the capture of CO2. At the same time, however, the additional energy costs that the new structure entails are highlighted. In particular, the air separation units (ASU) to guarantee the oxygen intake and the CO2 compression and purification unit (CPU) entail not negligible energy consumption. For these reasons the technology is still not available on a commercial scale, although the studies carried out by CEMCAP have achieved good results in modelling and analyzing a prototype in view of the test of a pilot plant.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/144257