Titanium equipment in the ionic membrane caustic soda industry advantages
Titanium oxide surface due to the poor infiltration of the surface smooth and non-corrosive, and therefore not easy scaling, better than other metals. The thermal conductivity of titanium is less than carbon steel and copper, similar to stainless steel, but titanium has excellent corrosion resistance. So the wall thickness can be significantly reduced, and the titanium surface and steam heat transfer mode drops condensate, reducing the thermal resistance, titanium surface scaling. So that the heat transfer performance of titanium significantly improved, very suitable for the production of corrosive media, heat exchange equipment. As titanium material can solve the corrosion of equipment and pipelines, to prevent corrosion of salt water and caustic soda due to equipment and pipeline corrosion.
Titanium ≤140 ℃ in the range of almost no corrosion in various concentrations of sodium chloride solution, stainless steel than 3 16L and copper-nickel alloy and so have much higher corrosion resistance; titanium has a strong passivation And has the ability to rapidly repair its damaged protective oxide film; Industrial titanium is not sensitive to contact corrosion, pitting corrosion, intergranular corrosion, stress corrosion, etc. Titanium is very resistant to corrosion in high-temperature and humidity chlorine, Titanium at room temperature in chlorine water, the corrosion rate of 0.000565mm / a; at a temperature of 80 ℃ in chlorine water, the corrosion rate of 0.00431mm / a; 95% of the wet chlorine at room temperature titanium corrosion rate 0. 00096mm / a.
Titanium corrosion resistance in alkali, titanium is stable in dilute alkali solutions (concentrations below 20%); in relatively concentrated alkaline solutions, especially when heated, it slowly releases and produces titanates. Titanium has excellent corrosion resistance in most alkaline solutions. The corrosion rate increases with the concentration and temperature of the solution. In the presence of oxygen, ammonia or carbon dioxide in the alkaline solution, titanium accelerates the corrosion of the titanium. in alkaline solution with hydrogen, the corrosion of titanium is poor. However, sodium hydroxide solution also has strong corrosion resistance. For example, the corrosion rate of titanium in 73% sodium hydroxide solution at 130 ℃ is only 0.18mm / a. Titanium is different from other metals in that it does not cause stress corrosion cracking in sodium hydroxide solution, but long-term exposure may Hydrogen embrittlement occurs. Therefore, the use of titanium in caustic and other concentrations of alkali solution temperature should be 93.33. Table 2-7 summarizes the corrosion resistance of titanium in a variety of environments. It is not difficult to see from the above, titanium is the chemical industry's most corrosion-resistant, the most promising corrosion-resistant materials, in particular, is that it is completely static and dynamic sea water and marine atmosphere corrosion, and even exceeded some of the resistance Erosion materials.
Ion-exchange membrane electrolysis process characteristics:
(1) Ion-exchange membrane electrolysis process has very high requirements on the quality of salt water getting into the tank. In addition to achieving a certain concentration (305 5g / L) and temperature (77.5 7.5) with extremely stringent requirements, brine must be refined and heated to meet production requirements.
(2) using ion-exchange membrane electrolysis technology, production to produce a lot of high-temperature wet chlorine, the temperature at 75 ~ 90, need to be cooled and dried to use.
(3) NaCl in brine and NaOH, Na2C03, ClO-, C1O3- and other impurities in high-temperature wet chlorine and caustic soda are extremely corrosive, and generally, metal materials cannot withstand such corrosion. These factors determine the ion-exchange membrane electrolysis process, we must carefully choose its production equipment and piping materials, or run in the production, run, drip, leakage and other phenomena that seriously affect the normal production and product quality, and will Significantly increase equipment maintenance and production costs.
(4) during the process of ion-exchange membrane electrolysis, NaOH, Na2C03, Ba2 +, ClO-, C1O3- and other impurities will exist in the diluted brine after electrolysis due to production reasons; the temperature of the light brine after electrolysis is 83-85 ° C ; Caustic soda production cathode concentration of 28% -32%, the temperature is about 85 ℃.
