Process description：

The caustic soda waste water (10% solution) from sulphonation would be discharged into 38C1 crystallization tank. 38P1 recycling pump pumps the waste water into 38T1 evaporating tower to evaporate the moisture in that. The temperature would be controlled between 37-42℃, and concentration of salt between 29-33%; it crystallizes itself constantly.

The hot air (≥100℃) for evaporation is from third stage waste heat recovery (68E2/E2). It goes into 38T1 from the bottom to exchange heat with caustic soda liquid, evaporate moisture in it and also oxidize the NaSO₃ in waste water to Na₂SO₄. Temperature of the air exiting 38T1 is controlled at 50℃. Na₂SO₄ crystal forms in 38C1, drawn by mud pump;then filter and pack. Filtrate goes back to 38C1 crystallization tank.

Unit 38 (caustic soda liquid oxidation, evaporation and crystallization) evaporates the moisture in 10% caustic soda solution, make the salt crystallizes in 38C1 (using the principle that Na₂SO₄ has different solubilities in difficult temperature. Also, waste heat air is balanced and surplus.

Related link:

China Unit 38 Waste Water Crystallization, Unit 38 Waste Water Crystallization Supplier - njweixian.com