Application of Titanium Equipment in the Ion-Membrane Caustic Soda Industry

1. Application of Titanium Equipment

   In ion-exchange membrane caustic soda production plants, titanium is primarily used in equipment and pipelines for secondary brine purification, electrolytic dechlorination, and residual chlorine treatment.

2. Precautions for Using Titanium Equipment in the Chlor-Alkali Industry

   (1) Titanium must not be used in dry chlorine. Titanium reacts violently with chlorine gas, even at temperatures below 0°C, forming titanium tetrachloride, which then decomposes into titanium dichloride, leading to corrosion and combustion. To ensure the reliable stability of titanium in chlorine gas, the water content in the chlorine gas should be no less than 0.5%.

3. (2) Generally, titanium does not suffer from pitting, intergranular corrosion, or stress corrosion. However, titanium is more prone to crevice corrosion, particularly in gaps of about 0.5 mm in width. Crevice corrosion often occurs at the connections between heat exchanger tubes and tube sheets, as well as at the contact points between titanium and non-metal gaskets. Additionally, crevice corrosion is likely to occur in saturated brine at temperatures above 120°C. The following measures can be taken to prevent crevice corrosion:

   • Avoid gaps and stagnant areas in the equipment;
   • Use titanium-palladium alloy flange weld rings, or titanium gaskets and titanium-clad gaskets;
   • Use strength expansion and seal welding for connections between titanium tubes and tube sheets in heat exchangers.

4. (3) After titanium equipment is contaminated by iron, its corrosion resistance decreases, and hydrogen absorption can lead to embrittlement. The more severe the iron contamination, the more hydrogen the titanium absorbs. Therefore, during the processing, maintenance, and repair of titanium equipment, steel tools should be avoided as much as possible.

It is foreseeable that with the development of the chlor-alkali industry, titanium equipment will have even broader application prospects.