Experimental study on salt crystallization process of zero discharge treatment of hyperhaline mine water

According to the water quality characteristics of typical hyperhaline mine water in Pan'er Coal Mine, the salt separation crystallization process scheme was formulated in combination with the solubility change rule of sodium sulfate Na₂SO₄ and NaCl and the phase diagram of Na⁺//Cl^- and SO₄^2--H₂O ternary water salt system. The effects of salt concentration and stirring rate on crystallization separation were investigated. The experimental results show that the total dissolved solid TDS of by-product high concentrated brine is 109 018.15 mg/L, the temperature is controlled at 100 ℃, the stirring speed is 200 r/min, and the mass concentration of NaCl and Na₂SO₄ at the evaporation terminal point is 265.54 g/L and 64.98 g/L respectively; after that, the temperature is controlled at -5 ℃, the stirring speed is 150 r/min, the mass concentration of NaCl and Na₂SO₄ at the end of refrigeration is 278.30g/L and 6.67g/L respectively; then the temperature is controlled at 100 ℃, the stirring speed is 100 r/min, the mass concentration of NaCl and Na₂SO₄ at the end of evaporation is 302.68 g/L and 41.86 g/L respectively. Under this scheme, the separation purities of Na₂SO₄ and NaCl is 97.3% and 95.2% respectively, which meet industrial standards. Therefore, this study realizes the resource utilization of salt, and reduces the amount of hybrid salt production.