HCl Application 2

[dragos12]

Does anyone has a literature for high temperature hcl application?
A:Temp: 400ºC to 600ºC ; B:Max Pressure = 5Bar ; C: corrosive internal condition : gas of 5%HCl- Water – Hydrogen
I try to select correct material but for such elevated tempratures, I could not find any source.

 

[Guest102023]

Pretty nasty conditions, your best hope is that the fluid remains gaseous at all times.
What is this application?

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[dragos12]

I was not informed. I came to an idea that regular alloys may not be resistant. I am investigating ceramic lining.

 

[moltenmetal]

If you can scrupulously avoid condensation, Inconel 600 or 625 have a shot. If you allow it to condense, you'll be in big trouble.

 

[dragos12]

Thanks moltenmetal.
What about Hastelloy?Do you have any experience?

 

[moltenmetal]

Which Hastelloy? Hastelloy B is an amazing material in reducing aqueous conditions but you're probably too hot for it. C is a good all-around grade, but 600/625 are superior to it in resisting high temperature halogens and halogen acid vapours at high temperature.

http://www.stainless-steel-world.net/pdf/10020.pdf?resourceId=320

 

[dragos12]

Thanks again. I will study 600/625 as well.

 

[lganga]

dragos12
Did you try with carbon and antiacid ceramic bricks? .But nozzles will be a problema, graphite made, perharps?.
There was an old company, may be is not active nowadays, that is why a write the name (Keramchemie).Those were working with HCL 5% but 200°C as I know.The problem is the resin able to support 600°C to fix the bricks.Perhaps you can get some information from Steuler KCH.
Regards
Luis

 

[Guest102023]

I think you are looking at the elite Ni-Cr-Mo alloys, which are VDM Alloy 59, Inconel 686, Hastelloy C-276 and C-2000. No guarantees of anything though. Suggest you contact the corrosion experts at Special Metals or Haynes.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[EdStainless]

As long as you stay over 150C you are dealing with hydrogen chloride gas.
With no condensation it is a lot like handling wet chlorine.
Alloys such as 600 and 825 (both over 21% Cr) can be used in this service.
I know that both 310 and S28 (25% Cr) are used in liquid HCL service, I couldn't find any high temp data offhand.
Do you know the actual amount of water in this system?
The corrosion rates will not be zero. You will be picking up some Ni in the solution.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[Raspberry]

We used to work with Concentrated HCl at elevated temperatures using borosilicate glassware as the material of construction.

We would operate under a partial pressure to reduce the boiling point otherwise the temperature would be simply too much for the glass - which I believe can withstand up-to 200°C.

The re-boilers were steam bayonets made from tantalum. If you need a metal that can withstand high temp, high corrosive (HCl) conditions then I recommend tantalum (but it isn't cheap!!)

 

[dragos12]

Moltenmetal,
what would be the consequences of condensation?

 

[moltenmetal]

Any water you form will be concentrated HCl...

 

[dragos12]

One further point,
could you compare C276 and Alloy 625?
Could we say C276 is superior to 625?

 

[moltenmetal]

625 will be more resistant to hot dry HCl. C276 will be more resistant to condensate. You can't have it both ways.

 

[dragos12]

thanks molenmetal, however I could not still reach to a point that I am sure C276 or 625 is better for the application.
Acc. to Haynes website, as concentration of HCL increases, c276 has better corrosion rate than 625.
Any final comments?

 

[moltenmetal]

At ANY CONCENTRATION, 625 will be more resistant to hot, dry HCl vapour (no LIQUID water, hence no aqueous hydrochloric acid), while C276 will be more resistant to the aqueous condensate from a hydrochloric acid stream should the system ever cool down without being thoroughly purged of both HCl and liquid water FIRST. So: if your stream ever condenses, C276 is a better choice, but may be attacked by the hot, dry conditions... If your stream NEVER CONDENSES but rather stays HOT AND DRY at high temperatures (greater than 400 C) all the time, 625 will last longer than C276 under those conditions- maybe substantially longer. You state that the service is 400-600 C, in which case for THOSE CONDITIONS, 625 is a much more resistant alloy. If the stream is allowed to condense and the condensate comes in contact with the 625, it will probably be attacked, and the attack will be localized- bottom of pipes, low spots etc. Can that be avoided by design? Then 625 is probably the better choice.

Will C276 give adequate resistance to your the hot, dry conditions? That depends on how much HCl is present in the stream on average and in peak, how hot the metal gets (including any localized hot-spots), how the equipment is fabricated and annealed, as well as what else is in the stream, whether the conditions cycle between oxidizing and reducing, and many other factors.

So, let's say we're talking about some application that makes hot, dry HCl and then quenches it with water or an alkaline solution in a scrubber of some sort. You would typically see something like 600 or 625 in the hot parts, then a transition to C276 or another C alloy just above the quench.

If this really matters, get the advice of a professional corrosion service metallurgist- don't try to make the selection based on the advice of people providing advice for free on an internet forum, as smart as they may be! And while people like Haynes and other manufacturers can be a useful source of information if properly used, they are obviously subject to bias toward what they sell.

 

[dragos12]

Moltenmetal, thanks again for your valuable time and words.
You are right however this is not for an application in my country and I am afraid no pro-metallurgist in my country can comment even close to what you write. Appreciate your input and experience !

 

[MagBen]

Do you have any strength level to consider? There are three versions of 625:
1.normal 625 is solid solution hardenable.
2.custom age 625 plus is precipitation hardenable, high strength can be obtained by aging without prior warm or cold working. this is important in appications where large-section size precludes warm working.
3. custom age 625 plus high strength

 

[MagBen]

From the composition standpoint, C276 has less Cr, but higher Mo than 625, so C275 will have a better corrosion resistance at reducing environments, but worse at oxidzing environments. Higher Cr is not a good thing at reducing agents, but will very helpful against oxiditation.

If your condition is more of reducing, you may want to try Hastelloy B-2 wiht very high Mo, and only 1% Cr. this alloy is not good at oxidizing media.