What You Need to Know About Storing Sulfuric Acid in FRP Tanks

Due to its highly corrosive nature, sulfuric acid presents a number of handling and storage problems for plant operators. Knowing what these problems are and how to account for them is absolutely crucial for plant operators to ensure safe storage of the chemical at the worksite.

Facility owners who use Fiberglass-Reinforced Plastic (FRP) tanks for storing sulfuric acid should especially be wary of their storage practices.

Sulfuric acid stored in FRP tanks needs to be of low concentration to avoid tank failure. Ideally, you’re looking at concentrations of 70% or lower; however, a solution with a concentration of 75% also works fine. Anything above that is not safe.

Besides concentration, you should also be wary of the temperature at which you’re storing the acid in your FRP tanks.

For batches of sulfuric acid prepared with concentration of 75%, the recommended storage temperature range is 100 degrees to 120 degrees Fahrenheit. As the concentration decreases, the allowable storage temperature limit increases.

Diluting sulfuric acid for storage

Okay, so what’s the proper way of diluting sulfuric acid so that you can store it safely in your FRP tanks?

First and foremost, decide on a concentration. This will be dictated by your manufacturing needs.
Next, add the entire amount of water to the storage tank required to achieve the concentration you decided on in step 1.
Now, slowly start adding the acid to the center of the tank. Why add the acid to the center of the tank? So as to avoid contact with the tank walls. You can use a PVC or stainless steel coupling for the purpose.
While adding the acid to the tank, keep agitating the solution with the help of a mechanical agitator to prevent the acid from settling at the bottom of the tank.
Once the dilution is complete, take a test sample to ensure the concentration is on the mark.

Also, when diluting the acid, be mindful of the heat that is generated as a result of the process. The reaction between sulfuric and water is highly exothermic, and it generates a considerable amount of heat. This heat should be expelled, otherwise it can raise the temperature of the tank and lead to product degradation or, worse, tank failure.

A final piece of advice: use above-ground, non-insulated FRP tanks for storing sulfuric acid at your plant. Avoid underground storage tanks as they make temperature control harder.

And if you ever need help with installing, modifying or repairing your FRP tanks, contact Hudson Fiberglass; we offer expert FRP tank installation, inspection, modification, field welding for tank and repair services to businesses in Florida.

Learn more about fiberglass tank repair here