This thesis delves into the context of the energy transition, focusing on renewable energy, specifically solar energy used in the Concentrated Solar Power (CSP) technology. Over time, CSP technology has undergone improvements to reduce the complexity of turbomachinery and enhance efficiency. Despite these advances, the cost of electricity produced by this technology remains non-competitive in the market. An innovative approach to cost reduction involves using supercritical carbon dioxide (sCO2) mixtures as the working fluid, instead of water vapor or pure supercritical CO2. The primary aims of this research are to address the challenge of the compatibility of metallic materials, such as Fe and Ni-based alloys, with high-temperature CO2 mixtures, with a focus on high-temperature corrosion resistance and to explore new, efficient and thermally stable mixtures to blend with CO2. While high-temperature sCO2 corrosion is extensively discussed in the literature, research on sCO2 mixtures are limited. First, in the study, various potential CO2 mixtures, including C6F6, C4F10, TiCl4, SiCl4, SO2 and Novec4710 as dopants, underwent a preliminary efficiency evaluation using Aspen Plus software to assess their potential application as working fluids in power cycles. Then, the experimental apparatus used for metallographic analyses has been refined over the years and in its final version includes a disassemblable cylinder made of Inconel 625 to evaluate the corrosion kinetic of the material as it allows to extract the samples during the test. This cylinder is filled with the sCO2 blend and a support containing perforated disks of various materials, heated in a muffle furnace. This approach enables the study of the thermal stability of the fluid and high-temperature corrosion of alloys. The selected temperatures for the study aim to identify the most suitable materials for different parts of a pilot CSP plant, which may range from 120°C to 550°C. Characterization of oxide layers was conducted using optical microscopy, SEM-EDS technique and metallographic analysis. Regarding two mixtures, those containing SiCl4 and SO2, promising materials and coatings have been identified after a test of 2000h. This research is part of the H2020 European projects Sarabeus and Desolination, providing an initial contribution to understanding and optimizing materials used in the new CSP technology.
Questa tesi approfondisce il contesto della transizione energetica, concentrandosi sulle energie rinnovabili, in particolare sull'energia solare utilizzata nella tecnologia CSP. Nel corso del tempo, la tecnologia CSP è stata perfezionata per ridurre la complessità delle turbomacchine e migliorarne l'efficienza. Nonostante questi progressi, il costo dell'elettricità prodotta da questa tecnologia rimane non competitivo sul mercato. Un approccio innovativo per ridurre i costi coinvolge l'uso di miscele di anidride carbonica supercritica (sCO2) come fluido di lavoro, invece di vapore d'acqua o anidride carbonica supercritica pura. Gli obiettivi principali di questa ricerca sono affrontare la sfida della compatibilità dei materiali metallici, come leghe di Fe e Ni, con miscele di CO2 ad alta temperatura, focalizzandosi sulla resistenza alla corrosione ad alta temperatura, e esplorare nuove miscele efficienti e termicamente stabili da mescolare con la CO2. Mentre la corrosione sCO2 ad alta temperatura è ampiamente discussa in letteratura, le ricerche sulle miscele di sCO2 sono limitate. Nel corso dello studio, diverse potenziali miscele di CO2, tra cui C6F6, C4F10, TiCl4, SiCl4, SO2 e Novec4710 come dopanti, sono state sottoposte a una valutazione preliminare dell'efficienza mediante il software Aspen Plus per valutarne l'applicazione potenziale come fluidi di lavoro in cicli di potenza. Successivamente, l'apparato sperimentale utilizzato per le analisi metallografiche è stato perfezionato nel corso degli anni e nella sua versione finale include un cilindro smontabile realizzato in Inconel 625 per valutare la cinetica di corrosione del materiale, consentendo l'estrazione dei campioni durante il test. Questo cilindro è riempito con la miscela sCO2 e un supporto contenente dischetti forati di vari materiali, riscaldato in un forno a muffola. Questo approccio consente lo studio della stabilità termica del fluido e della corrosione ad alta temperatura delle leghe. Le temperature selezionate per lo studio mirano a identificare i materiali più adatti per diverse parti di un impianto CSP pilota, che possono variare da 120°C a 550°C. La caratterizzazione degli strati di ossido è stata condotta utilizzando la microscopia ottica, la tecnica SEM-EDS e l'analisi metallografica. Riguardo a due miscele, quelle contenenti SiCl4 e SO2, sono stati identificati materiali e rivestimenti promettenti dopo un test di 2000 ore. Questa ricerca fa parte dei progetti europei H2020 Sarabeus e Desolination, fornendo un contributo iniziale alla comprensione e all'ottimizzazione dei materiali utilizzati nella nuova tecnologia CSP.
Experimental material compatibility analysis for innovative CO2 blends to be adopted as working fluid in high-efficiency CSP power plants / Putelli, Lorenza. - (2024 May 07).
Experimental material compatibility analysis for innovative CO2 blends to be adopted as working fluid in high-efficiency CSP power plants.
PUTELLI, LORENZA
2024-05-07
Abstract
This thesis delves into the context of the energy transition, focusing on renewable energy, specifically solar energy used in the Concentrated Solar Power (CSP) technology. Over time, CSP technology has undergone improvements to reduce the complexity of turbomachinery and enhance efficiency. Despite these advances, the cost of electricity produced by this technology remains non-competitive in the market. An innovative approach to cost reduction involves using supercritical carbon dioxide (sCO2) mixtures as the working fluid, instead of water vapor or pure supercritical CO2. The primary aims of this research are to address the challenge of the compatibility of metallic materials, such as Fe and Ni-based alloys, with high-temperature CO2 mixtures, with a focus on high-temperature corrosion resistance and to explore new, efficient and thermally stable mixtures to blend with CO2. While high-temperature sCO2 corrosion is extensively discussed in the literature, research on sCO2 mixtures are limited. First, in the study, various potential CO2 mixtures, including C6F6, C4F10, TiCl4, SiCl4, SO2 and Novec4710 as dopants, underwent a preliminary efficiency evaluation using Aspen Plus software to assess their potential application as working fluids in power cycles. Then, the experimental apparatus used for metallographic analyses has been refined over the years and in its final version includes a disassemblable cylinder made of Inconel 625 to evaluate the corrosion kinetic of the material as it allows to extract the samples during the test. This cylinder is filled with the sCO2 blend and a support containing perforated disks of various materials, heated in a muffle furnace. This approach enables the study of the thermal stability of the fluid and high-temperature corrosion of alloys. The selected temperatures for the study aim to identify the most suitable materials for different parts of a pilot CSP plant, which may range from 120°C to 550°C. Characterization of oxide layers was conducted using optical microscopy, SEM-EDS technique and metallographic analysis. Regarding two mixtures, those containing SiCl4 and SO2, promising materials and coatings have been identified after a test of 2000h. This research is part of the H2020 European projects Sarabeus and Desolination, providing an initial contribution to understanding and optimizing materials used in the new CSP technology.File | Dimensione | Formato | |
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