Preparation And Study On Thermal Properties Of Multiple Mixed Molten Salt For High Temperature Heat Storage Of Solar Energy

Energy plays an important role in domestic economic and social development.With the development of economy and technology growing fast,the energy consumption of our country increases sharply.For example,the coal,oil,natural gas are being exploited and used excessively.At the same time,it will produce a large amount of greenhouse gas,which causes serious harm to the ecological environment.Our country must carry out effective adjustments of the energy structure by the way of developing renewable energy.The solar energy as a new type of energy,has the advantages of richness,less geographical effects,cleanliness and pollution-free.Solar thermal power generation technology can make good use of solar energy.Heat transfer and heat storage technology are the core of the solar thermal power generation technology.Choosing the appropriate heat storage material is very important.Molten salt used as heat storage material has the advantages of high temperature,low viscosity,high heat capacity and low cost.It is often referred to as the best heat storage material.When chlorate and carbonate are mixed alone,its phase transition temperature and phase change latent heat are low.When chlorate and carbonate are mixed,the phase change temperature and phase change latent heat are higher than the former,which is more advantageous to be used in solar heat storage technology.This article makes two kinds of binary mixture of molten salt,such as NaCl-Li Cl and NaCl-Na₂CO₃,and ternary mixture of molten salt,for example,KCl-Na₂CO₃-K₂CO₃.The experiment studies the binary mixed molten salt NaCl-Na₂CO₃ and ternary mixed molten salt KCl-Na₂CO₃-K₂CO₃.We prepare nine kinds of binary molten salt and thirty-six kinds of ternary molten salt,and make a comparison and analysis between ternary molten salt and Li₂CO₃-Na₂CO₃-K₂CO₃.The experiment uses DSC to study the thermal properties of mixed molten salt including melting point,freezing point and latent heat storage and thermal stability.The experimental results show that the melting point of NaCl-Li Cl which can co-melt are about 580? and the latent heat are mainly between 200-400J/g.The optimal proportion is 5:5,whose solidification temperature is 578.7? and crystallization latent heat is 320.2J/g.The melting point and crystallization latent heat of KCl-LiCl are respectively about 350?and mainly between 60-200J/g.They fail to melt under 600?.The sample of ternarymixture of molten salt whose melting point is 570?-580? and freezing point is550?-570?.The best sample is KCl-Na₂CO₃-K₂CO₃=2:3:5,whose melting point is568.9? and freezing point is 545.3?.Molten salt has a good thermal stability.This paper also studies the mixed molten salt corrosion.The experiment studies the corrosion of molten salt under the static,when puts 304 and 316 L stainless steel into NaCl-Li Cl?50%-50%?,KCl-LiCl?50%-50%?,KCl-Na₂CO₃?50%-50%?,NaCl-Na₂CO₃?50%-50%?,KCl-K₂CO₃?50%-50%?and KCl-Na₂CO₃-K₂CO₃?30%-30%-30%?.The result shows the corrosion resistance of 316 L stainless steel is better than 304.Under the same amount and the same proportion,the corrosion of carbonate is stronger than chlorate.