Plasma Vacuum-Arc Treatment Technology for the Metal Pipe Surfaces of Solar Thermal Power Plants

Abstract

Currently, there is widespread interest in developing efficient technologies for harnessing solar energy, both in direct conversion of solar energy into electrical energy and in solar thermal power plants (STPPs). STPPs are sustainable sources of electricity due to the accumulation of heat in a heat carrier, which can be water, molten salt, or oil. The key to increasing the attractiveness of this technology lies in replacing the method of directly generating steam by heating water with solar radiation, with a receiver method using an intermediate heat transfer fluid. The technology of transferring heat obtained from solar radiation through liquid salt (a mixture of potassium nitrate and sodium nitrate, among others) imposes high demands on the pipes of this system that carry the heat transfer fluid, particularly regarding their corrosion resistance and service life. Using pipes made of ordinary steel grades with a special anti-corrosion coating applied to their inner surface can significantly reduce costs and increase the service life of the pipes, as well as the efficiency and reliability of STPPs. The study demonstrates that the method of comprehensive plasma vacuum arc treatment of the inner surface of metal pipes of various configurations, and the application of special coatings, ensures high anti-corrosion protection. For instance, applying a thin-layer coating of austenitic steel with a high chromium content (up to 28%) to samples of martensitic steel pipes resulted in 100% retention of the original sprayed material composition. Thus, the mechanical strength of the base material of the metal pipes in salt STPPs is combined with the high anti-corrosion properties of the applied material. Recommendations are provided for using plasma vacuum arc technology to ensure high operational properties of the circulating pipe systems in salt STPPs.