Pipe material for 93% Sulfuric Acid at Ambient Temperature

[AlbertaMecchie]

Hello,

I am designing a piping system to handle 93% sulfuric acid at ambient temperature (no higher than 104 deg F) and am just wondering what is a suitable piping material.

Is 316L stainless good, or Hastelloy C-276 ? The pipe size will be 3/4" to 1".

Thanks,

Jon

 

[TugboatEng]

Our local refineries uses carbon steel for the straight runs with Carpenter 20 for any bends. Carbon steel forms a passive layer in the presence of strong sulfuric acid but they passive layer is very soft and sensitive to erosion by turbulence.

Edit: See Ed's correction based on concentration.

 

[EdStainless]

93% acid can be difficult, it is more aggressive than 98%.
I have seen the alloy choice default to either alloy 20 for everything, or a mixture with high Si austenitic stainless (A610). High Si cast iron is often used for pumps.
In 93% acid at 115F the erosion rate for carbon steel at 5ft/sec is 1"/yr, not quite manageable.
And 316L is right at its limits with the concentration and temp, it work with stronger acid or colder temps.


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[moltenmetal]

PVC, for sure, at those sizes. It will be corrosion immune. Polypropylene would be a 2nd option.

 

[MJCronin]

Look at Figure 10 of this guideline .... Seems that several materials may be acceptable

https://info.veolianorthamerica.com...industrial/sulfuric-acid-push-information.pdf

Looks to me that, at 93% and 104F , you can still use carbon steel, but you are just on the edge

I would contact some of the proprietary alloy vendors, do some cost studies and get their direct input

MJCronin
Sr. Process Engineer

 

[EdStainless]

I have never been in a plant that allowed sulfuric acid in unreinforced polymers.
The acid is highly oxidizing and causes accelerated aging in nearly everything that isn't a fluoropolymer.
And as the piping become more brittle the high thermal expansion can cause real issues.
I'll add this to this thread also.
[URL unfurl="true"]https://res.cloudinary.com/engineering-com/raw/upload/v1627427608/tips/H2SO4_r9eqzx.docx[/url]

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P.E. Metallurgy, consulting work welcomed

 

[shvet]

For piping see NACE RP0391.
For tanks&vessels see NACE SP0294.
Also relevant chapter #77 in ASM handbook vol. 13C.

https://dl.asminternational.org/han...sion-by-Sulfuric-Acid?redirectedFrom=fulltext

 

[MJCronin]

This is an important and very informative document regarding Nickel bearing alloys and sulfuric acid.

This useful research was developed by the Canadian Nickel Institute

https://nickelinstitute.org/media/4692/ni_inco_1318_corrosionresistsulphuric_relatedcompounds.pdf

MJCronin
Sr. Process Engineer

 

[moltenmetal]

@EdStainless: the line sizes here are 1". At those sizes, any metallic material you select is going to have very limited corrosion allowance against general corrosion. So sure, you could use plastic lined metallic piping- but when dealing with such small quantities of acid, nonmetallic materials are widely used. It likely comes to site delivered in an HDPE drum or tote tank...

 

[EdStainless]

Alloy 20 has a near zero corrosion rate in this application, same with a number of Ni alloys.
And with proper resil selection FRP piping could have a very long service life.
Using solid polymer in a highly oxidizing environment will eventually lead to unexpected catastrophic failure.
We used to get acid in poly totes, that were in metal boxes to support them, and had warning labels that they were for transport only and not for long term storage.

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P.E. Metallurgy, consulting work welcomed

 

[MJCronin]

I agree with EdStainless .... there are options here ...

But I would also suggest that a flanged, steel piping system with a PTFE or PVDF lining should also be explored.

Lined piping systems are described here:

https://www.mersen.it/sites/italy/f...6-ace-armylor-piping-ptfe-pfa-ansi-mersen.pdf

It would be probably less prone to catastrophic failure, as it will leak before rupture

More good information here:

https://onepetro.org/NACECORR/proceedings-abstract/CORR00/All-CORR00/NACE-00700/111692

Discussion here:

https://www.reddit.com/r/ChemicalEngineering/comments/4dr8vw/piping_lifespan_ptfe_lined_vs_ss/

MJCronin
Sr. Process Engineer

 

[MJCronin]

There are claims that CPVC is superior to both metallic and other types of plastic piping systems:

https://www.corzan.com/blog/can-cpvc-piping-systems-be-applied-in-sulfuric-acid-plants

Be very careful if you are switching back and forth between 93 and 98% sulfuric acid .... only one type of plastic piping seems suitable

https://www.waterworld.com/home/article/16192668/pipe-stands-up-to-high-acid-applications

Anyone else ???

MJCronin
Sr. Process Engineer

 

[EdStainless]

Correct MJ, different resins are very specific to acid concentrations (and impurities). With FRP there are some lining resins that have wider tolerance.
There are still many places where oxidizing acids are prohibited from being handled in solid polymer piping.

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P.E. Metallurgy, consulting work welcomed