Physical And Chemical Properties Test And Comparative Experimental Study Of Quaternary Mixed Nitrate And Solar Salt

Heat transfer and storage technology is a key link in the development of renewable energy utilization technology.Molten salt as a new medium and high temperature heat transfer and storage medium has become a research hotspot in recent years.Commercial salt Solar salt has been widely used in solar thermal power plants at home and abroad as a heat transfer heat storage medium,but it has a high melting point,a low decomposition temperature,there is easy freezing and blocking during use,the insulation cost is large and narrow temperature range.The research group has developed a new type of quaternary nitrate,which has the advantages of low melting point and high decomposition temperature.In order to gain a deeper understanding of the physicochemical properties,stability and corrosiveness of quaternary salt and Solar salt under various working conditions,as well as the performance of the two nitrates under the same working conditions,quaternary salt and Solar Salt is the research object,and its thermal properties,stability and corrosion are explored separately.The high temperature melting method is used to prepare quaternary salt and solar salt base salt.The physical properties such as the melting point,decomposition temperature,specific heat,and thermal conductivity of the two nitrates are measured,and the heating rate and gas atmosphere during the measurement are changed to explore the influence of the heating rate and gas atmosphere on melting point and decomposition temperature.The results show that the quaternary salt has a lower melting point,a higher decomposition temperature,and stronger specific heat and thermal conductivity;the melting points of the quaternary salt and Solar salt increase first and then tend to balance with the increase of the heating rate due to the temperature lag phenomenon;The melting point and decomposition temperature of Solar salt vary with the reaction of NO₃^-/NO₂^-and N₂/O₂.In order to avoid the reaction between the components and the atmosphere,argon should be used as the protective atmosphere during the measurement of thermal physical properties.After the quaternary salt and Solar salt were kept at 500?/565?/600?for1000h and 500 times of cold and hot shock,the melting point,decomposition temperature,specific heat,thermal conductivity and viscosity of the sample were measured by Simultaneous thermal analyzer,laser thermal conductivity meter and viscometer and compared.The thermophysical parameters and the fluctuation range of the thermophysical parameters to investigate the stability of the two nitrates.The results show that the constant temperature and thermal shock conditions have a positive effect on the improvement of specific heat and thermal conductivity.At the same time,the thermal physical properties under thermal shock conditions are closer to the base salt;under two different conditions,the quaternary salt The melting point and primary crystal point are still lower than Solar salt,and the decomposition temperature,specific heat and thermal conductivity are higher than Solar salt;except for the constant temperature condition of 565?,the fluctuation of the specific heat and thermal conductivity of Solar salt is greater than the quaternary salt,four The stability of meta salt is obviously higher than that of Solar salt;the viscosity of quaternary salt is closer to that of Solar salt as the constant temperature time/impact times increase.Using the immersion method,the five kinds of steel were placed in a quaternary salt and Solar salt at 300?/570?for a constant temperature of 500h,and the unit corrosion amount and corrosion rate of the steel were calculated.The results showed that under high temperature(570?)working conditions,Quaternary salt is less corrosive than Solar salt,of which stainless steel 321 has the strongest corrosion resistance.Under low temperature(300?)working conditions,the two nitrates have little corrosiveness to the four types of stainless steel,and the corrosion rate to low carbon steel is lower than 0.1mm/a,low-carbon steel at low temperature can greatly reduce the actual engineering cost.