Application of Jet Aerator in Highly Corrosive Wastewater

The customer in this project is a pharmaceutical and chemical company producing p-aminophenol. The production wastewater has a salinity of 18% (mainly chlorides) and is treated with ozone at a concentration of 150mg/L and a content of 10%, with ozone gas pressure of 0.1MPa. Both chlorides and ozone are corrosive.

Because chloride ions and ozone are corrosive, aeration equipment must resist corrosion from both chloride ions and ozone if it is to operate normally, stably and over the long term. Stainless steel has good corrosion resistance to ozone: 304 stainless steel can be used in low-concentration ozone environments, and 316L stainless steel can be used in high-concentration ozone environments. Chloride ions can reduce formation of the passivation film on 316L stainless steel and accelerate damage to that film, causing pitting and then local corrosion, which undermines long-term stable operation. Therefore, if aeration equipment needs to resist high-concentration chloride corrosion, higher-grade materials such as Hastelloy or titanium alloy are normally required.

The higher the material requirement for the equipment, the higher the material cost and fabrication requirement, which increases equipment price and is not conducive to promotion and use. After verification from many aspects, we solved this difficulty by spraying an anti-corrosion coating inside the equipment.

The coating we use is an ethylene and chlorotrifluoroethylene copolymer. It offers thermal stability, chemical corrosion resistance (resistant to acids, most strong alkalis, strong oxidants and other chemicals; with excellent stability against some inorganic salts including water and salt solutions), and low permeability.

GW aeration equipment with an internal anti-corrosion coating is manufactured from redesigned drawings. While ensuring that the equipment flow passage remains unchanged, the interior is uniformly sprayed with an anti-corrosion coating. Keeping the flow passage unchanged ensures that performance is not changed, while the ethylene-chlorotrifluoroethylene copolymer coating prevents corrosive substances from attacking the equipment, thereby solving the problem.