Need Recommendation for vessel holding 28% Sulfuric Acid

[DougW]

I have an application requiring a 3000 gallon batch neutralizer that starts with 28% sulfuric acid in water. The acid is slowly consumed to form a sodium sulfate solution.

Conditions in the vessel are 50 psi pressure, 130 degrees Fahrenheit (55 C). I am considering an Alloy 20 pressure vessel but it is rather pricy ($48K). A glass lined reactor is double that!

The corrosion books recommend: Glass, Polypropylene, PVC, Alloy 20, Hastelloy C, fiberglass. No stainless or carbon steel is recommended.

I want to be able to sleep nights not worrying about leaks.

What would you specify for the vessel, piping and pump materials of construction in this service? Do you agree with the Alloy 20 spec for the vessel/pump and lined polypropylene steel pipe for the piping?

 

[TrevorP]

Unfortunately, sulphuric acid is in the 'high corrosion' range in this region. Hence, I would agree with you and tend towards a high-alloyed steel (e.g. 904L etc.) for this application. I have no personal experience with Alloy 20 on sulfuric acid, but charts I have seen indicate it is OK, so would agree on that. This is a useful link for suitable steels:

http://www.avestapolarit.com/upload/documents/technical/datasheets/AVPHighAlloyed.pdf

For pipework, again a high alloyed steel would be OK, although I personally prefer to use lined carbon steel. I normally specify PTFE lined, but this is primarily due to higher operating temperatures (>90°C). From charts, CPVC or PVDF lined should be just as effective up to 90°C as polypropylene lined (Although personally I wouldn't feel comfortable above about 75°C for these), and may be cheaper. PVC (i.e. not Chlorinated PVC) has a max. temperature of about 60°C (140°F), so is probably too close for this application.

 

[MJCronin]

DougW,

Have you considered "high performance" coatings on a carbon steel vessel ?

A google search with "sulfuric acid" coatings tanks, should yield some good candidates.

The tanks should be an ASME code stamped vessel equipped with a RV and manway.... I would make it about 72 to 84 inches diameter. at about $3.00/gallon, the tank alone should cost about $9K or less.

With about 370 sq ft of surface, you could spend up to $50/sq foot for a premium coating and still have the tank cost less than the alloy 20 version...

Also, have you considered a CS tank with 3/16ths alloy 20 cladding ? ( acompany called DETACLAD offers this) Several vessel vendors and fabricators offer this configuration as an option...

Come back with more details of your application...

MJC

MJC

 

[ssudhir49]

You can consider a hard rubber (Ebonite) lined carbon steel vessel as it will stand the sulfuric acid concentration at the temperature you have mentioned and a suitable vessel with dished ends can withstand the pressure.
Sudhir Sirdesai

 

[hacksaw]

a word about Alloy 20: its patent has run out, so you will find quite a variation in composition and performance. it does not work well in reducing environments. Hast. C/Carpenter 20 remain useful in such acids. FRP is going to have a problem at 50 psi. Cladding might be useful but I would recommend against any lining that was not mechanically robust especially where you might have mechanical agitation.

Most neutralization processes such as you have described can be done in atmospheric tanks as long as you have some means for fume collection and scrubbing.

You might give some thought to an atmospheric two stage \neutralization process.

More tankage, more square feet, and a little more complex, but more along the lines of established practice.

 

[BRT549]

A fiberglass tank made with a good Hetron or Atlac resin, and a class C glass veil on the inside surfaces. This will be cheaper than alloy 20 by at least 1/2.

If you think the temperature of the neutralization won't ever get above 130F, you could consider HDPE or cross-linked PE. It's not that big of a tank (3000 gal).

The only reason for an alloy vessel in this application should be if it's going to be pressurized.

 

[ghopkins]

I would go with the fiberglass option using a Section X, Class 2 code stamp (if you're in one of the 28 states that requires a Section X stamp on pressure vessels). Even if you're not in one of the states that requires it, I would still go with a code stamp if the vessel was in my plant... The fiberglass (using a premium vinylester resin) will hold up for 15-20 years (at least) and you never have to worry about a breach in the liner corroding the structure - as you do with steel constructions. Likewise, you don't have to worry about that troublesome external corrosion problem so many plants are faced with in steel constructions. I have a few case histories of fiberglass vessels built for this service and of fiberglass vessels (of this size) being code stamped at design pressures above 100 psig.

Let me know if you want them: ghopkins@rl-industries.com

Thanks, Greg

 

[patrickraj]

For this application you have to go for TEFLON lining.This is what my experience is.

 

[ghopkins]

DougW: more information to digest:

Please see following links for corrosion recommendations of vinyl ester resins used in fiberglass constructions:

Accessed through (

http://www.hetron.com):

http://www.ashchem.com/ascc/compoly/cg.asp?nCountNumber=281&alpha=S&is_header=N

I would recommend Hetron 922 or DERAKANE 411 in the corrosion liner and structure. A fire retardent layer can be applied externally with Hetron 992FR or DERAKANE 510C-350.

You can go to

http://www.derakane.com

to download Dow Chemical's corrosion guide. Flouropolymer linings work well for fiberglass or steel structures if the service environment requires it. However, you'll pay an unnecessary premium in this case. Teflon linings cost from $35-$100 per square foot depending on type (PFA, FEP, or PTFE) - that's just the material purchase cost. Then you have the labor to install/weld the thermoplastic liner. Of the flouropolymers, Kynar PVDF is the most economical at roughly $20/ft2 purchase cost and would work superbly for your service - although still overkill.

Again, you can design and stamp according to ASME Section X ("RP" stamp symbol) for fiberglass vessels if above 15 psig (as in this case). There's also a standard that ASME has called RTP-1 ("RTP" stamp symbol) that covers fiberglass applications from full vacuum up to 15 psig.

There are 10 companies that can provide the "RTP" stamp and two companies that can provide the "RP" stamp for Section X, Class 2 vessels.

Greg

 

[DougW]

Thanks to everyone's useful comments. I have purchased a surplus (used) 3000 gallon Alloy 20 vessel for this service. Last owned by Rohm & Haas Deer Park, Texas. 100 psi design, lethal service. It was $13,000 delivered. I did check out several coating (Plasite, etc) and they did seem like they would work. But, for $13K I have an Alloy 20 pressure vessel and no need for spark tests. Thanks everyone.

Doug

 

[hacksaw]

So far the odds are three for and five against, interesting.

What corrosion allowance are you taking?