Can concentrated sulfuric acid of 98 concentration be stored in FRP tanks?

Sulfuric acid concentration of more than 70%, are called concentrated sulfuric acid, the largest concentration of sulfuric acid is 98%, also known as smoky sulfuric acid. Concentrated sulfuric acid storage tanks are usually made of A3 or Q235. Concentrated sulfuric acid has strong oxidation, and after contact with steel, it will generate an oxide film on the surface to passivate it, and itself is reduced to sulfur dioxide, so more than 70% concentrated sulfuric acid, ordinary steel is relatively resistant to sulfuric acid corrosion.

At the same temperature, the corrosion effect of sulfuric acid with different concentrations on steel is also different, the corrosion effect of sulfuric acid with about 85% concentration is the largest, and the corrosion effect of sulfuric acid with about 98% concentration is quite small.

At the same concentration, the lower the temperature, the smaller the corrosion effect. At higher than 50 ° C, carbon steel materials are generally not used. Therefore, the use of carbon steel tank to hold concentrated sulfuric acid, subject to the adjustment of temperature and concentration there is a certain uncertainty.

So, can fiberglass tank work? Glass reinforced plastic tank is made of corrosion resistant resin and glass fiber wound. Whether concentrated sulfuric acid resistance is mainly determined by the lining of the glass fiber reinforced plastic tank, at present, the domestic resin even if the corrosion resistance is strong vinyl resin, the concentration of sulfuric acid resistance can only go to 55%, more than 60% of the glass fiber reinforced plastic tank lining will be corroded off. Therefore, the conventional FRP tank is not resistant to concentrated sulfuric acid.

However, we can achieve the purpose of holding concentrated sulfuric acid in FRP tanks by making changes in the lining layer of FRP tanks. After many years of production and verification, the use of FRP composite tank to hold concentrated sulfuric acid has achieved good practical results. FRP composite tank, when the temperature of the storage tank medium does not exceed 60 ° C, PVC and PP materials are used to make the inner liner of the FRP tank, and the outside is wound with glass fiber to form the FRP composite tank. Over 60℃, we can use PVDF material to make the inner liner of FRP tank, and use glass fiber winding to form FRP composite tank outside. The PVC, PP, PVDF material used in the lining of the FRP composite pipe forming process not only meets the requirements of concentrated sulfuric acid on the corrosion of the lining layer of the FRP tank, but also meets the requirements of the strength of the storage tank through the glass fiber winding of the structural layer of the tank. Therefore, what is used to store concentrated sulfuric acid, with PVC, PP, PVDF material lined glass reinforced plastic composite tank is completely acceptable.