Corrosive effects of chloride ions on strippers
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There is one stripping tower in the unit, made of 304 material. The stripping tower is to be used temporarily for treating wastewater; the chloride content in the wastewater is 3000 ppm, and it is to be reduced to less than 180 ppm after treatment, using 5 kg of stripping vapor. Under such operating conditions, how significant is the impact of chloride ions on the 304 material of the equipment? What level of damage will the equipment suffer in the short and long term over a 7-day cycle? Operating temperatures above 158°C may lead to pitting corrosion and stress corrosion cracking. Stress corrosion cracking may be short-term and transient, or it may last for a relatively long time. There is a high risk of leakage and cracking. With a cycle of 7 days, the equipment is likely to crack quickly, both in the short term and in the long term. It is better to keep the pH value of wastewater above 10, as this reduces its sensitivity to cracking.
Simply put, your situation carries a high level of risk. With a chloride ion concentration of 3000 ppm and a temperature above 158°C, 304 stainless steel is highly susceptible to corrosion under such conditions. Although you only plan to use it for 7 days, pitting corrosion may occur in a short period of time, or even cracking might happen – especially if there are residual stresses in the equipment itself; stress corrosion cracking can occur within just a few days. Raising the pH to above 10 does help by reducing the corrosion rate, but it cannot completely eliminate the risk. After 7 days, the device is likely to be damaged already; continuing to use it will cause further corrosion, and it may start leaking in not much time. It is recommended to either use more corrosion-resistant materials (such as 316L or duplex steel), or to strictly control the operating time; it is advisable to conduct a thorough inspection after use. .