Application of titanium equipment in ion-exchange membrane caustic soda industry
1. Application of titanium equipment
In ion-exchange membrane caustic soda production unit, titanium is mainly used in brine secondary refining, electrolytic dechlorination, residual chlorine treatment and other equipment and pipelines.
2. Precautions for using titanium equipment in chlor alkali industry
(1). Titanium cannot be used for dry chlorine. Titanium is in chlorine. Even if the temperature is below 0 ℃, violent chemical reaction will occur to produce titanium tetrachloride, which will be decomposed into titanium dichloride, and even corrosion and combustion. In order to maintain the reliable stability of titanium in chlorine, the water content in chlorine shall not be less than 0% and 5%.
(2). In general, titanium will not have pitting corrosion, intergranular corrosion and stress corrosion, but titanium is more prone to crevice corrosion, especially in crevices with a width of about 0 and 5mm. Crevice corrosion often occurs at the joint of heat exchanger tube and tubesheet, and at the contact between titanium and non-metallic gasket. In addition, crevice corrosion is also easy to occur in saturated brine above 120 ℃.The following measures can be taken to prevent crevice corrosion:
① Avoid gaps and retention areas on the equipment;
② Use titanium palladium alloy flange welding ring, or use titanium gasket and titanium clad gasket;
③ Titanium tube and tubesheet are used for heat exchange connection, and strength expansion seal welding is used.
(3) After titanium equipment is polluted by iron, its corrosion resistance will be reduced, and hydrogenation will cause embrittlement. The more serious the iron pollution is, the more hydrogen titanium absorbs, so it is being processed. When repairing and maintaining titanium equipment, try not to use steel tools.
It can be predicted that with the development of chlor alkali industry, titanium equipment has a broader application prospect.
