The problem of molten salt corrosion objectively exists and requires multiple ways to alleviate it

2024-06-13 10:02:30

Molten salt has good thermal stability, fluidity, high thermal conductivity, and high electrical conductivity, and has been widely used in industry. With the continuous development of the solar thermal power generation industry in the global field, the dependence of the solar thermal power generation industry on binary molten salts mainly composed of sodium nitrate and potassium nitrate, and ternary molten salts mainly composed of sodium nitrate, potassium nitrate, and Sodium Nitrite as heat transfer and storage media is also increasing. According to statistics from the CSPPLAZA Research Center, there are over 20 solar thermal power plants that have been put into operation worldwide that use molten salt for heat transfer or storage. Based on rough estimates, the total amount of molten salt used has reached over 700000 tons.

According to the technical specifications (trial) for solar thermal power generation demonstration projects released by the Energy Bureau in September last year, for China, which is about to launch a solar thermal demonstration project of about 1GW, the molten salt heat storage system will become a necessary configuration except for some disc projects. But will the extensive use of molten salt Products cause serious corrosion to the Equipment and Pipelines of the photothermal system? To explore the answer to this question, the reporter recently interviewed some industry enterprises related to molten salt products.

The problem of molten salt corrosion is inevitable

The reporter found that all interviewees believe that the corrosiveness of molten salt to equipment and pipelines objectively exists. Because whether it is sodium nitrate, potassium nitrate, or sodium nitrite used in photothermal products, the presence of chlorides cannot be completely eliminated, and the chloride ions contained in chlorides have a strong corrosive effect on metals.

According to relevant data, the impact of chloride ions on metal corrosion is manifested in two aspects: firstly, it reduces the possibility of passive film formation on the material surface or accelerates the damage of passive film, thereby promoting local corrosion; On the other hand, it reduces the solubility of H2S and CO2 in aqueous solutions, thereby alleviating material corrosion.