Material for Chemical Reactor Vessel

[isoca]

A customer wants to change a chemical reactor vessel that works with a solution of: 20% methanol, 60% glycerin, 3% sodium chloride, 1% hydrochloric acid and 3% fatty acids. The reactor works between 70ºC and 80ºC.
Currently the equipment is made of carbon steel with an internal PVDF coating. Due to the thermal expansion cycles the coating fails and the carbon steel is quickly attacked.
The idea is to replace the material with another (uncoated) capable of withstanding the conditions mentioned above for at least 15 years
Could someone guide me in which alloys would be appropriate? For now I have ruled out titanium or zirconium alloys due to the risk of SCC in media with HCl and methanol.
Could the C276 or C22 hastelloy be an alternative?
Thank you!

 

[moltenmetal]

At first glance it looks like an easy application for any C alloy.

At 70-80 C, a better lining method on a properly prepared carbon steel shell should also do the job, and for less money. That assumes it needs to withstand substantial pressures, because if it doesn't, the obvious solution is FRP.

 

[MJCronin]

I agree with MM .... the thermal cycles seem modest and a reputable coatings vendor should have something

A vessel made from C276 or C22 will be expensive and may have a problem with the 3% sodium chloride

Can you post a design outline drawing and give us other details ?

MJCronin
Sr. Process Engineer

 

[isoca]

First of all, thank you very much for your comments.
I completely agree that the best solution is to use a suitable coating.
Unfortunately, it is our client's wish to use an alloy that does not need the use the coating. I estimate that when they see what it costs they will rethink your idea. For now I can't get the drawing, but it's just a mixing tank with two flanges, which operates at atmospheric pressure.

 

[MJCronin]

Yeah, yeah ..... we are all familiar with that tune ...

Client's young MBA engineer comes up with a "brilliant idea" and demands that you implement it.

When all of the costs are in, he blanches, says he never suggested it and demands that you "brainstorm" and "think outside the box".... Oh, and he needs this yesterday ....

If you have enough time, I suggest that if you can make/get a sketch of the vessel, send it to a fabricator and ask for a budgetary quote in each of the following:

1) Carbon steel with a vendor GUARANTEED Kynar (or other) lining
2) 100% C276 material (none of the other materials will hold up)
3) 100% Wrought Nickel (UNS N02200 is used in the chemical industry for its corrosion resistance)

The Nickel will be the most expensive ... But many fab shops will shy away from this material ...

By the way, if the vessel is going to hell with your corrosive witches brew, how is your interconnected piping system doing ? What piping materials are you using and how is the corrosion just downstream of the valves ??

What are the materials of any pumps ???.... Are they Teflon lined ?

Tell us more... What size is this tank ?

What are the dimensions

MJCronin
Sr. Process Engineer

 

[EdStainless]

If this is fairly large you might also toss explosively clad plate into the construction mix.
But a lot more info in needed.
What is the pH of this solution?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[Dhurjati Sen]

Dear isoca,

Are you the designer of the vessel or the licensor for this particular plant?

Anyway, you can suggest FRP or GRE for the tank material. It would be quite ingenious.

ingenious (adjective)
(of a person) clever, original, and inventive.
(of a machine or idea) cleverly and originally devised and well suited to its purpose.

Regards.



DHURJATI SEN
Kolkata, India

 

[MJCronin]

I agree with EdStainless ....

Clad plate may be an option ...... but without any more details of the tank size, nozzles and construction, it is impossible to determine this.

MORE INFORMATION = BETTER ANSWERS !!!!!


MJCronin
Sr. Process Engineer

 

At first sight this looks like a job for one of the elite C alloys: C276, C22, C2000, I-686, Alloy 59. Both the temperature and the process fluids certainly put this beyond the capability of any stainless steel.

Have you thought of inserting corrosion coupons?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[isoca]

First of all many thanks for your useful answer.
Regarding the pH, it varies between 1.5 and 2.
The vessel is a cylinder with two semi-spherical caps and its dimensions are 3 m high and 1.5 m in diameter. It has a top loading lid, a solution outlet flange and a hole for measuring temperature and pH.
Taking into account your comments and the information obtained from literature, I still have some doubts about using an alloy such as c22 or c276. On other hand I have some concern about welds behavior in this conditions.
The work for now is for advice only, we are not the vessel designers.
For now my suggestion will be to work on the improvement of the coating (although I don't think it's welcome ..)
Many Thanks!

 

I suggest you contact the Nickel Development Institute and engage one of their consultants, who are top people in the corrosion field. Meanwhile, get hold of some corrosion coupons and put them to work.
And you are right to be concerned about welding these alloys, which is all about matching the corrosion resistance of the base metal.

(Disclaimer: I receive no consideration from NiDI.)

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

Resistance of Nickel and High-Nickel Alloys to Corrosion by Hydrochloric Acid, Hydrogen Chloride and Chlorine (279)

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[isoca]

Estimados,
muchas gracias por sus muy útiles comentarios y recomendaciones. Me han sido de mucha ayuda.
Estoy de acuerdo en que antes de tomar cualquier desición lo mejor es hacer pruebas de corrosion con cupones soldados para verificar la aptitud del material.
Los mantengo al tanto de los resultados.
Saludos cordiales

 

de nada

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."