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This research aims to study the degradation and the changes in physicochemical properties of a ternary molten salt mixture, commercially known as Hitec, in contact with a nitrogen and an air atmosphere. The degradation of the salt was determined by chemical analysis of the NO3- and NO2- anions and DSC determination of the melting and freezing point of the mixture. To this end, isothermal tests at 500 °C were performed for 1000 h. A deeper study of the evolution of the salt under air atmosphere was carried out until 2000 h. It was found that the mixture properties studied remain invariable when it was operated under N2 atmosphere. The use of atmospheric air resulted in a progressive increase in melting and freezing points due to the nitrite transformation to nitrate. The effect of the degradation could be observed in the early hours of the test and after 2000 h of test, the system had not reached and steady state and the degradation progress was still ongoing. [ABSTRACT FROM AUTHOR]

In the present work, the behaviour of a ferritic-martensitic steel, VM12, in Solar Salt was monitored by EIS. To this end corrosion tests at 580ºC were carried out for 1000 h. According to the EIS results, a diffusion-controlled reaction occurred during test, which indicates the formation of a porous corrosion layer. The EIS results also shown a corrosion rate of 50 µm·year-1 after 1000 h of testing. Results obtained by EIS were in agreement with the ones obtained by gravimetric and SEM-EDX analysis. Thus, results showed the possible suitability of EIS for monitoring corrosion processes in realtime of steels in CSP plants. [ABSTRACT FROM AUTHOR]

In the present work, the environmental damage of two types of molten salts and synthetic oil has been evaluated with the aim of deciding whether the use of molten salts is more suitable than synthetic oil from an environmental point of view. To this end Life Cycle Assessment has been used, since it offers numerous advantages in the assessment of aspects associated with the development of a product and its potential impact throughout the life of a given product from raw material acquisition, processing, manufacturing, use and finally its disposal. According to the results, the replacement of the VP-1 like thermal oil by molten salts is absolutely recommended from an environmental perspective, since the environmental impact of molten salts appear to be reduced in comparison to Therminol®VP-1. Thus, direct systems, in which thermal storage and heat transfer fluid are unified using molten salts, emerge to improve the power cycle performance, these being a good option not only from the known technical point of view, but also from the environmental point of view. Life Cycle Assessment seems to be a suitable and necessary methodology to quantify the environmental impacts of fluids, materials, and O&M in CSP plants. [ABSTRACT FROM AUTHOR]

In the present work, the behaviour of ZrO2 – Y2O3 coatings in contact with molten salts at 500 °C has been studied. The coatings were prepared by sol-gel and deposited by dip-coating on AISI 304 specimens previously prepared by sanding and polishing. The behaviour in contact with molten salt was studied through static corrosion tests by the immersion of the coated samples in an alkali-nitrate mixture with a composition of 60 wt.% NaNO3/40 wt.% KNO3 (commonly known as Solar Salt). Prior to test, the deposited coatings were characterized using Scanning Electron Microscopy and X-Ray Diffraction, showing a compacted, homogeneous and uniform aspect and t-YSZ as main component. After corrosion tests, the samples were characterized via gravimetric, Scanning Electron Microscopy and X-Ray Diffraction. The results show a good behaviour of the coated samples compared with the bare coupon samples. However after 1000 h of testing m-ZrO2 appears in the composition,. At this preliminary study, results confirm the suitability of ZrO2 -Y2O3 coatings in solar applications after those working hours, although it is necessary to optimize the coating and study its behaviour at longer times. [ABSTRACT FROM AUTHOR]