CO2 is an acid gas and one of the most undesirable greenhouse gas that contributes to anthropogenic climate change. The largest amount of CO2 released into the atmosphere is produced by combustion of fossil fuels in power plants to produce electricity. The absorption of CO2 with aqueous amines is the most mature capture technology suitable for post-combustion capture. However, the energy requirement for CO2 capture and compression is relatively large, specially the reboiler duty of the regeneration column. The desorption process needs energy, that is supplied by steam, to regenerate the solvent and separate the CO2 absorbed in the aqueous solution. Therefore, adding a CCS system to a power plant decreases significantly the power output. In the last years, new solutions to increase CO2 capture investment value while maintaining substantial CO2 emissions reductions have been considered. One of the possibilities is to operate the CO2 removal plant in flexible mode. Adding flexibility to the CO2 capture systems allows to temporary increase the electrical output during peak demands or when electricity prices are high. Post-combustion amine scrubbing is well-suited for flexible operations due to its relative independence from the power system. This work has been focused on the design of the CO2 capture system integrated in a 630 MW advanced natural gas combined cycle (NGCC). The capture has been obtained by absorption with aqueous monoethanolamine solutions (30%wt MEA), with a CO2 capture rate fixed at 95% at base load. The plant simulations have been performed with ASPEN Plus® integrated with an external Fortran subroutine developed by the GASP group of Politecnico di Milano. The absorption and desorption columns of the CO2 removal plant have been designed and then simulations have been carried out to determine the performance of different flexible CO2 capture modes. The economic analysis and the comparison with the fixed capture level configuration have also taken into account the influence of the carbon tax. The study on flexible operations has been carried out with the aim of determining the best compromise between the minimization of the energy required for the operation and the reduction of CO2 emissions.
L’anidride carbonica è uno dei gas serra più indesiderabili che contribuisce fortemente al cambiamento climatico. La maggior parte della CO2 rilasciata in atmosfera è generata dalla combustione nelle centrali di potenza per la produzione di energia elettrica. L’assorbimento della CO2 mediante soluzioni amminiche è la tecnologia attualmente più matura ed adatta alla cattura post-combustione. La richiesta energetica per la cattura della CO2 e successiva compressione è però ingente, specialmente la quantità di calore richiesta al ribollitore nella colonna di rigenerazione del solvente. Catturare la CO2 nelle centrali elettriche comporta quindi un aumento dei costi di produzione dell’elettricità. Negli ultimi anni, sono state sviluppate nuove soluzioni per aumentare l’efficienza dell’impianto mantenendo una sostanziale diminuzione delle emissioni e una di queste propone di operare la cattura in modo flessibile. Questo permette un temporaneo aumento della potenza elettrica fornibile durante i picchi di domanda o quando i prezzi dell’elettricità sono elevati. Il sistema di assorbimento è adatto ad operazioni flessibili grazie alla sua relativa indipendenza dall’impianto di potenza. Questa tesi si è focalizzata sul design di un sistema di cattura della CO2 integrato con un impianto da 630 MW a ciclo combinato alimentato a gas naturale (NGCC). La cattura è stata ottenuta attraverso assorbimento con soluzione acquosa di MonoEtanolAmmina (30%wt MEA), con una percentuale di cattura del 95%. Le simulazioni sono state sviluppate tramite ASPEN Plus® integrato con un subroutine Fortran sviluppata del gruppo GASP del Politecnico di Milano. Dopo aver progettato l’impianto di cattura della CO2, sono state valutate le performance delle configurazioni flessibili di assorbimento della CO2. Il confronto con il sistema di cattura a carico fisso e l’analisi economica hanno preso in considerazione l’influenza della carbon tax, con l’obiettivo di determinare il miglior compromesso tra la minimizzazione dell’energia richiesta per la cattura e quello di riduzione delle emissioni di CO2.
Study of flexible post-combustion CO2 capture applied to a natural gas power plant
PATRUNO, ELEONORA
2015/2016
Abstract
CO2 is an acid gas and one of the most undesirable greenhouse gas that contributes to anthropogenic climate change. The largest amount of CO2 released into the atmosphere is produced by combustion of fossil fuels in power plants to produce electricity. The absorption of CO2 with aqueous amines is the most mature capture technology suitable for post-combustion capture. However, the energy requirement for CO2 capture and compression is relatively large, specially the reboiler duty of the regeneration column. The desorption process needs energy, that is supplied by steam, to regenerate the solvent and separate the CO2 absorbed in the aqueous solution. Therefore, adding a CCS system to a power plant decreases significantly the power output. In the last years, new solutions to increase CO2 capture investment value while maintaining substantial CO2 emissions reductions have been considered. One of the possibilities is to operate the CO2 removal plant in flexible mode. Adding flexibility to the CO2 capture systems allows to temporary increase the electrical output during peak demands or when electricity prices are high. Post-combustion amine scrubbing is well-suited for flexible operations due to its relative independence from the power system. This work has been focused on the design of the CO2 capture system integrated in a 630 MW advanced natural gas combined cycle (NGCC). The capture has been obtained by absorption with aqueous monoethanolamine solutions (30%wt MEA), with a CO2 capture rate fixed at 95% at base load. The plant simulations have been performed with ASPEN Plus® integrated with an external Fortran subroutine developed by the GASP group of Politecnico di Milano. The absorption and desorption columns of the CO2 removal plant have been designed and then simulations have been carried out to determine the performance of different flexible CO2 capture modes. The economic analysis and the comparison with the fixed capture level configuration have also taken into account the influence of the carbon tax. The study on flexible operations has been carried out with the aim of determining the best compromise between the minimization of the energy required for the operation and the reduction of CO2 emissions.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/131682