Materials for Low pH Slurry at Elevated Temperatures?
Materials for Low pH Slurry at Elevated Temperatures?
(OP)
I am currently looking at an application using a dilute sulfuric acid slurry with a pH of less than 1.5. The process may reach 500F and 700psig for extended periods of time. I am searching for a cost efficient piping material for this application. Today a large range of products are available, Alloy 20, Hastelly (multiple grades), 904L, Duplex, Super Duplex, Zirconium and Tantilum. These materials all have different corrsion rates (well published at lower temperatures)and prices. The process will require extensive field welding.
I would like to hear from others about their experiences they have had with similar operating conditions. Also a publication that may compare corrosion rates at elevated temperatures for a dilute sulfuric acid application.
I would like to hear from others about their experiences they have had with similar operating conditions. Also a publication that may compare corrosion rates at elevated temperatures for a dilute sulfuric acid application.





RE: Materials for Low pH Slurry at Elevated Temperatures?
http://www.welding-advisers.com/
RE: Materials for Low pH Slurry at Elevated Temperatures?
RE: Materials for Low pH Slurry at Elevated Temperatures?
RE: Materials for Low pH Slurry at Elevated Temperatures?
RE: Materials for Low pH Slurry at Elevated Temperatures?
At this time we would like to avoid lined pipe.
RE: Materials for Low pH Slurry at Elevated Temperatures?
One early article from Advanced Materials & Processes March 2000, by James S. Grauman and Tony Say, detailed the selection and application of titanium for autoclaves used in the High Pressure Acid Leach process for nickel laterite ores. Since then it seems several newer developments like Detaclad and nanostructured titanium oxide have been tested in pilot plants. A Google search of 'high pressure acid leach' brings up 266 items of interest.
Field welding of titanium has its problems, mainly keeping the oxygen out of welding area. A medium vacuum glove box at the construction jobsite will allow some "field welding" of titanium spools, even if spools are not being welded in the final installed position.
RE: Materials for Low pH Slurry at Elevated Temperatures?
If it's a low-chloride system, there's at least some Fe in the solution and you're not in strongly reducing conditions, you may be into conventional "high pressure acid leach" type conditions as mentioned by the previous poster and commercially pure titanium will probably serve well. Acid addition dip tubes will need to be made of tantalum. Note that the ASME limit for Ti is 315 C, and the safe allowable stress is derated rapidly with temperatures approaching this limit.
If you have lots of chloride, you'll need titanium grade 7, and even that may not last forever. Crevice corrosion becomes a big problem.
Of course, your process may be nothing like HPAL for laterite ores and titanium might be a disastrous fit for your application. But at least this gives you a starting point for your materials selection research.
As to the welding of titanium, you don't need a glovebox- all you need is a skilled, knowledgeable titanium TIG welder with the right technique, an approved procedure, and suitable shield gas equipment.
RE: Materials for Low pH Slurry at Elevated Temperatures?
The use of Ta may be unavoidable, at least in the mixing section where high variations in concentration occur.
= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Materials for Low pH Slurry at Elevated Temperatures?