Materials compatible with Hydrazine Hydrate and KOH. 1

[shankerm]

I'am working on designing a reactor for a process that uses KOH and Hydrazine hydrate upto 200C, highly basic and corrosive solutions.

Hydrazine hydrate is not compatible with metals containing Molebdenum. Thus, SS 316 IS RULED OUT. Any other suggesions, From sources, I've learnt that Nickel rich alloy would be suitable .

Any suggesions ???

Thank you !

 

[EdStainless]

How caustic will your system be?
Will there be any chlorides, at all?

What kind of equipment will you be building? (tanks, heat exchangers, piping??)
I have some thoughts, but would like detail first.

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Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[btrueblood]

Do you care if the hydrazine hydrate decomposes?

 

[shankerm]

Well, Firstly I'am designing a jacketed vessel, with hot oil and cooling in the jacket. A 500 litre vessel.

The solution is highly basic, about 13. And hydrazine hydrate is one of the reactants that yields another product at 150 C, that is condensed and separated out.

And no chlorides at all. The batch consists of 4 chemicals, which total to 500 kg, out of which only 40 kg is hydrazine hydrate and about 60 kg is KOH.

The other 2 chemcials are non corrosive in nature !

 

[btrueblood]

Shankerm,

200 C is getting close to the temperature at which you can expect some catalytic activity of metals with hydrazine/hydrazine hydrate. It is certainly hot enough to start a self-sustaining decomposition reaction with neat hydrazine, and strong hydrazine hydrate concentrations, with the platinum and iridium type noble metals. I know at more than 800F the reaction will be self-sustaining with Ni/Fe/Co metals and alloys, when above some limit of concentration of the hydrazine. See Eckhardt Schmidt's book _Hydrazine and Its Derivatives_ for details. An
Inconel (600) would probably work, provided some of the other guys on this forum tell you its okay with the KOH, if some degree of decomposition of hydrazine is okay with your process. In a former life, we used Inco 600, and sometimes 625, for hydrazine/hydrazine hydrate gas generator "reactors" (okay, they were rocket engines).

 

[EdStainless]

600 is a reasonable option for caustic service. Pure Ni200 has better corrosion resistance, but it is so soft that erosion is an issue.
400 (Monel 70Ni/30Cu) may be an option, but I would be hesitant with the hydrazine.
If you have piping or external heat exchangers to deal with consider E-Brite for those.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[pmureiko]

I remember hydrazine hydrate vendor literature lists 304L and 316L stainless steels as recommended materials of contruction. This recommendation for may be for ambient and not cover the high temperatures of your process.