8 replies to this topic

[nivedita12]

Dear members

 

I am trying to cool down Boil Off Gas (natural gas from an LNG Tank)  coming from a tank to BOG compressor.

i need to use a 50% vol propylene  glycol for cooling the Boil off gas in a shell and tube exchanger

.

It seems that the propylene glycol forms slush in the Exchanger if it reaches its freezing point estimated to be -29.74 deg F.

 

How can i know the time when the glycol water will reach its freezing point from a ambient temperature of 95 F

 

Is there any article referring to the time the GW freezes in the shell and tube exchanger.

 

 

 

Thank you

Nivedita 

 

 

[Art Montemayor]

Nivedita:

 

Either you are having trouble with your use of the English language, or with your way of explaining what you are doing.  Boil off gas from an LNG tank is gas at cryogenic temperature (-260 ^oF).  It is impossible for you to “cool” this down using a solution of glycol and water.  I cannot understand what you are writing and I’m sure other members can’t either.

 

Of course the glycol solution will form “slush” when contacted with a cryogenic temperature!  What did you expect????

The only way to generate an intelligent and useful response from our members is to furnish an accurate, detailed flow diagram, showing the equipment involved and all the basic data - such as flow rates, temperatures, pressures, and compositions.  Otherwise, everyone trying to respond is only going to be guessing as to what you are proposing or doing.

 

What you are asking - the “time” that it takes for the glycol solution to freeze solid - is a ridiculous question, given the information that you furnish.  Don’t you know that allowing a water solution to freeze will essentially rupture any exchanger tube and create a hazardous situation?  Water expands when frozen into the solid state.  It can (and will) move buildings.  You should know this as elementary information.  Are you a student?  Please respond because I think this post belongs in the Student Forum.

[nivedita12]

Sorry i should have used heated instead of cooling . My verbage with english is not that good.

Also i do not have a flow diagram readily available with me. but will furnish the drawing once i am done. 

Thank you 

nivedita 

[Art Montemayor]

Please answer all my basic questions.  Are you a student?

[nivedita12]

yes i am a student 

[nivedita12]

Attached is the sketch for your reference

 

I have the BOG to be heated from -255 F to -20 F using glycol water.The glycol water flow rate if reduced in the Process gas heaters -1 and 2 shown in the sketch it will freeze in the Exchangers  depending upon the flow rate and velocity . at 50 gpm it will freeze in the exchangers hence have increased the flow rate to 100 gpm. 

 

I cannot show the flow rates of BOG now.

 

I needed to know the basis of the low flow rate or higher flow rate basis 

 

Attached is the sketch.

 

Thank you

Nivedita 

Attached Files

•  sketch.pdf   158.85KB   25 downloads

[Bobby Strain]

 

The sketch does not show on the PDF. But the low flow of glcol-water results in an inside film temperature below the freezing point.

 

Bobby

 

[nivedita12]

Thank u Bobby .The sketch i drew is on bluebeam. 

[Bobby Strain]

Here is one for all to read.

 

Bobby

 

 

 

 

Attached Files

•  sketch1.pdf   12.92KB   22 downloads