Internal Tank Coating Question 2

[bboysen]

I have specified a baked phenolic coating for a steel 93% sulfuric acid storage tank. I have been considering switching to a high build flouropolymer lining. We use dryers on the tank vent and the acid will be stored in a conditioned room. Is there a compelling reason to specify the flouroploymer liner over the baked on phenolic system?

 

[ash9144]

Why line it at all? Is there some mixing or high temperature involved?
A plain carbon steel tank would work fine. If the liner develops a leak it will eat through the tank very quickly.

 

[JimCasey]

Most all the tables I have seen show that 316 0r 304 stainless is compatible with 93% or >higher< concentrations of H2SO4. An all stainless tank is going to be much less fragile than a phenolic-lined tank. Probably price-competitive, too since there is a lot of labor involved with lining the tank.

One thing to think about is letting the tank breathe through a dessicant dryer. Otherwise the incoming humidity might dilute the acid at the surface,and you could get corrosion at the normal level in the tank.

 

[MJCronin]

bboy....

My opinion:

- I agree that the SS tank is a good option when compared to an expensively lined CS tank. Using SS ensures that there will be no iron in the stream from the tank. This may or may not be important to you

- The dessicant dryer arrangement is to protect the contents from corrosion due to a "dilute sulfuric acid" layer, which forms on top of the concentrated acid. This is much more important in CS tanks (which have a history of corrosion because of this dilute acid) than for SS tanks.


There is an informative and well-writen FAQ on sulfuric acid systems on this website.

My opinion only

_MJC

 

[bboysen]

Thanks guys. The vent line has dryers, dilution was considered. This system is going in upstream of an RO facility so iron was a concern. I hadn't considered SS as an alternative although it is definately worth suggesting to the design team.

 

[MJCronin]

bboy,

A used stainless tank may be just what you are looking for. There seems to always be several available in the "used process equipment" marketplace.

If you compare the cost of a CS tank with a fancy coating, it will be about the same as a bare SS tank.....especially in the smaller (< 5000 g) sizes.

My opinion only

-MJC

 

[bboysen]

Thank you all very much for the help.