3 replies to this topic

[Mohamed Selim]

the question is related to natural gas dehydration unit?

 

Why increasing the design gallons of Glycol Circulated/lb water removed, will decrease the Reboiler Heat duty Btu/Gal of circulated Glycol ?

 

Help in this please..

[Pilesar]

An analogy is heating a gallon of glycol to boil the water out. If there is less water in the glycol, then the glycol is closer to being pure and so needs less heat added.

[Art Montemayor]

The response given by Pilesar is technically correct.  It responds to the basic question about an increase in glycol (TEG?) circulation causing a decrease in the related reboiler duty expressed as Btu/Gal of circulated Glycol.

 

However, I would point out that the question raised does not reflect what is taken as the correct manner of expressing a reboiler's duty.  A reboiler duty is normally rated on a RATE basis and not on a volume basis.  In other words, the reboiler rating should be the Btus/hr that the reboiler requires to heat up the flow rate of glycol circulated through it.  It is not the Btu/gal of glycol required.  The query is worded incorrectly, I suspect, and the correct answer cannot be applied to the actual field application of regenerating an increased flow rate of glycol within the reboiler.

 

The Original Poster (OP) seems to be asserting a fact when he/she states "Why increasing the design gallons of Glycol Circulated/lb water removed, will decrease the Reboiler Heat duty Btu/Gal of circulated Glycol?"  This assertion is not true if what is meant is really:
Will increasing the flow rate of glycol circulated in a natural gas dehydration unit cause a required increase in the reboiler duty?

 

If that is the real query, then the answer is Yes.  If you circulate more glycol (in gal/hr), you will have to furnish more heat input at the reboiler (in Btu/hr) to regenerate the circulated glycol.  However, the OP does not express the question in that manner.  That is why Pilesar answers the query correctly - but as it applies to a gal of glycol, not to the rate of glycol flow.

Perhaps I have mis-read the query or not understood what the OP tries to explain; however, I don't want readers to misinterpret what Pilesar has correctly stated.  Truly, if there is less water in the glycol, then the glycol is closer to being pure and so needs less heat added - to the water that is boiled out - but the increased glycol flow requires more heat.

[Mohamed Selim]

Thank you very much; I have understood your answers.