How to use liquid nitrogen in S&T heat exchanger 1

[MTQ80]

Hi
I am new member and want to discuss one process development problem.

We are in the phase of developing some type of process to utilize excess liquid nitrogen to cool utility water. Can liquid nitogen be used to cool water from 110 degF to 41 degF in S&T type Heat Exchanger? Due to very low temperature of N2 i.e. -283degF, water in tubes of exchanger can freeze. Please help how liquid N2 can be utilized to cool water.

 

[ash9144]

Would be better to use the nitrogen to cool a heat transfer fluid (glycol) then use another exchanger to cool water with glycol.

Although I can't say I've ever heard of excess liquid nitrogen.

 

[MTQ80]

It is true that glycol is better option. But it will add one new exchanger and economically it is not advisable as this is existing sea water treatment plant which is producing excess liquid N2 which they want to use to cool sea water being used in the inter cooler of air compressor.

Therfore only oprtion is to use some S&T heat exchanger or some vertical tube vaporizer to cool water with out causing water freezing. Is there any one who did the same of type of study.How can I confirm that wich option is sutiable?

 

[gr2vessels]

You could use the vaporized N2 at a reasonable low temperature, mix it with air to control the temperature and using a back throttling valve, let it go through a shell and tube exchanger to cool directly your ...water?? Why don't you let the cold nitrogen gas cool directly the intercooler (or one suitable with nitrogen), perhaps an aftercooler also? why do you need the sea water and other intermediate fluids for your cooling?
cheers,
gr2vessels

 

[MTQ80]

Thx gr2. Actually this is existing facility and existing intercoolers (2+1) are not compatible for cryogenic conditions. That's why we hace to cool sea water going to intercoolers. Sea water can be cooled in S&T type HE or in vaporizer as other options like using glycol or mixture of water & glycol as a media, is not economical.

 

[25362]

Is there a cheap way to heat the cold nitrogen vapors before entering the water coolers ?
The overal heat transfer coefficient would be around 0.05 kW/(m^2oC)

 

[EdStainless]

Do you need to keep Nitrogen?
If not, then direct injection of the LN into the cooling water is possible. And yes, people build equipment for this.

If you want to use a S&T HX then it needs to be designed like the LNG vaporizers. The LN will be tubeside, the units will sit vertical, and the tubing has to be an austenitic stainless. Which stainless depends on the water chemistry.

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Plymouth Tube

 

[MTQ80]

Thx. I thnk option to use LNG vaporizer is quite feasible. Is there any one who have calculation procedure for verticle vaporizer. Help out on this plese.

 

[BenThayer]

what is the site that has you producing excess liquid nitrogen? it would seem that it has value.

we purchase some liquid nitrogen for extreme cooling but would never consider it for cooling water. liquid N2 is too expensive/valuable.

 

[dramarc]

Another approach:
Use gaseous N2 to cool the water in a heat ex. Use liquid N2 to directl cool recycled gasous N2 to desired temp.

Although I would go for direct cooling with N2 into the water as suggested above is it's possible.

 

[EdStainless]

I have seen S&T LNG units designed by CP&P in Chicago.

http://www.chicagopowerandprocess.com/Company_Profile.htm#Top of Page

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