High Temp Sulfuric resistant materials

[twalicia]

I am looking for a material suitable for use to make an agitator in a pressure vessel operating at 4 bar, max 150oC, submerged in boiling H2SO4 at 20% concentration. The vessel contain abrasive clay slurry at 30% solids con. Would appreciate some recommendation on a suitable material. Currently we use a lead lined agitator but are trying to phase out the lead in our product.

Thanks for the input.

 

[kenvlach]

Due to the abrasive slurry, cannot recommend any coated material.

Metals Handbook, 9th. Edn., Vol. 13, Corrosion, pp. 1152-1153, and the corrosion resistance chart from Astro-Cosmos

http://www.astrocosmos.com/pdf/chart.pdf

both indicate that you can safely use zirconium or tantalum
(unalloyed) at the sulfuric acid boiling point.

 

[hacksaw]

what kind of pumps are you using?

 

[twalicia]

Hacksaw, we don't use a pump. As the vessel is pressurised, we relieve the pressure from 4 bar to about 1.5 - 2 bar, then the slurry is sort of push through into a holding tank where we quench it to lower temp.

However, there is a hast-C valve at the bottom of the vessel.

 

[hacksaw]

sounds like a laterite ore digester; that's pretty rough service

if the valve is holding up, then you have a starting point for your materials selection, but you may need some hardfacing. Hast.C(C-276) valves are generally cast and are a slightly different from the plate and bar stock you'd be using to fabricate an agitator.

 

[BRT549]

There are a number of coatings you can put on the agitator. Epoxy-based (or vinyl-ester) with silica sand filler might work for both corrosion and erosion.