Abstract:

Using the Na₂SO₄, K₂SO₄ and MgSO₄ as raw materials. A new type of ternary sulfate molten salt was prepared by adding different content of MgSO4 in the range from 10% to 40% (weight ratio) to the binary eutectic salt of Na₂SO₄-K₂SO₄ The melting temperature, latent heat value, thermal conductivity, specific heat, decomposition temperature and thermal stability were tested by means of thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), Thermal constants analyzer, X ray diffraction and thermal cycle tests. Experimental results showed that the ternary sulfate molten salt had a melting point which was distributed between 667.5 ℃ and 669.7 ℃. Whose melting point were 160 ℃ lower than that of binary sulfate molten salt, the ternary sulphate molten salt with 30% (weight ratio) MgSO₄, had the highest latent heat value 94.3 J·g^-1, the maximum specific heat capacity was 1.13 J·(g·K) ^-1 between 720 ℃ to 800 ℃, thermal conductivity was 0.41 W·(m·K) ^-1, and the decomposition temperature was 1070 ℃, after 50 times thermal cycle tests, the latent heat value slightly declined by 4.34%, the melting temperature and phase composition maintained the constant, indicated the ternary sulphate molten salt with 30% (weight ratio) MgSO4 had good thermal stability. The research provided basis for sulphate salt, which could be applied to high temperature heat transfer and heat storage medium.

Key words: molten salt, melting point, decomposition temperature, thermal stability