Sodium.nitrate and.potassium nitrate salts

[Sojournerman]

Hi guys I want to know what metals I can use for heating a 60_40 mix of sodium and potassium nitrates .
What will not react with this is mix?
Thanks

 

[EdStainless]

How hot are you going?

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

http://web.ornl.gov/info/reports/1989/3445605663145.pdf

http://large.stanford.edu/publications/coal/references/docs/10141843.pdf

 

[Sojournerman]

Hi Ed at the moment its a guess , I would guess to the mixtures melting point ? 400deg ish celcius I am thinking of going to salt but thats up.at like I think 801° cel

 

[metengr]

The melting point for sodium/potassium salts ranges from 130 deg C to 270 deg C . This is why they are used for thermal heat systems that operate at up to 600 deg C.

What is your application?

 

[Sojournerman]

Metengr cant say to much but it is for a heat sink . At what temperature does this mix start to break down?

 

[moltenmetal]

800 C is far too hot for a nitrate or nitrate-nitrite salt bath. Both the nitrate and nitrite salts are freely decomposing at this temperature.

http://www.parkthermal.com/Technical Bulletins/A Guide To The Safe Use Of Molten Salt Baths.pdf

Metallic materials aren't going to be a good choice for a molten chloride bath.

 

[EdStainless]

In closed high purity systems you can push the temps (read the ORNL paper) but 800C is not going to work.
As long as the Cl impurities are kept low (low ppm levels) there are many alloys that work. These salts are used in some of the solar thermal power plants.

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P.E. Metallurgy, Plymouth Tube

 

[Sojournerman]

Thanks ed and molten for.the info appreciate the time will.have a.look at the solar thermal.plants you mentioned .
If I had a 44 gallon drum of 60/40 (using it as an example)sodium/potasium nitrate heated to 600 deg celcius how do I work out how much energy is stored in it? Need it to recover heat to boil water for.steam.cleaning and a couple of other applications as well

 

[metengr]

Sojournerman;
Look up the heat capacity of the molten salt and based on the volume of salt convert to mass you can calculate the heat absorbed. You better be sure you understand the safety implications of handling this stuff.

 

[EdStainless]

When these start to decompose oxygen is liberated, and then things start to burn, and this all happens very abruptly. People have blown these systems up in the past.

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P.E. Metallurgy, Plymouth Tube

 

[moltenmetal]

Heat capacity can be used- heat of fusion cannot be used, as the initial film of solidifying material on the coil or other heat transfer surface will rapidly prevent recovery of the balance of the heat of fusion.

Too hot is very dangerous with this stuff as EdStainless has indicated.

Again, I have nothing to recommend to you for a metallic material for use in contact with molten chloride salts capable of > 800 C temperatures. The nitrate/nitrite mixtures are NOT capable of those temperatures- they will blow up.

 

[Sojournerman]

You guys rock and are the salt of the earth(pun intended)appreciate the help and advice .Certainly dont want to cause a very rapid burn leading to a very quick disintergration . might miss out on a few beers this christmas .
Should I trust the info on wiki?
There seems to be quite abit there.
Thanks guys

 

[EdStainless]

Don't trust the WIKI article, but go to the sited sources for the real dope.

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P.E. Metallurgy, Plymouth Tube

 

[Sojournerman]

Hi guys merry christmas
Couple of questions
how.much does the sodium/potasium mix expand when heated? 20-30%
Does pressure increase the "boiling" point of these chemicals? I suspect not
Appeciate the help guys

 

[metengr]

Read here for information

https://intraweb.stockton.edu/eyos/...fficient_Soultions_using_short_term_TES/4.pdf