Sulphuric Acid Pipework - Iron Pick-Up

[Sarah251]

I am currently extending an acid pipeline (pipe material: mild steel) approximately 500 metres. This is an acid transport line from a ship to a storage tank. The acid is 98% sulphuric acid. The acid has a strict iron content specification. I need to determine the amount of iron that the acid will "pick-up" through the pipework. Any ideas on how to go about this?

 

[kenvlach]

You can get a rough estimate from corrosion data. One source

http://www.resistoflex.com/sulfuric_graphs.htm#7

gives the corrosion rate of mild steel in 98% H₂SO₄ at 80^oF as 0.01 inch/year.
So, multiply by the interior surface area of the pipe and the transit time to get volume of dissolved Fe, convert to mass and then divide by the volume of acid to get Fe concentration.

But, the above value applies for unstirred acid. High flow rates will alter, also the initial flow of acid through the pipe may dissolve any existing rust, so the actual Fe may be higher. The acid flow rate in CS piping should not not exceed 0.5-0.6 m/s in order to not disturb the protective film formed on the CS.

Check out the info at this site:

http://www.sulphuric-acid.com