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# Isenthalpic Expansion Valve Calculation

jt valve

2 replies to this topic
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### #1 Bitan729

Bitan729

Junior Member

• Members
• 14 posts

Posted 13 September 2021 - 04:17 PM

Hello Everyone,

In our Gas sweetening Unit C2+ liquid is produced from available natural gas at around 25 Kg/CM2G pressure. We then store the liquid hydrocarbon to 5 of our C2+ sphere to cater it as feed to Ethylene Cracking unit (ECU) at 30 Kg/Cm2G pressure (Temperature of sphere are around 32 Deg.C) via pump. Then the liquid pressure at ECU led down to 8 Kg/Cm2G by control valve, and due to which the liquid temperature falls to -20Deg.C (approx). This cold liquid then is used as a heat exchanging medium in Tertiary Refrigeration unit , before being feed to cracking furnace pre heater. The composition(wt%) of C2+ liquid is as follows :

C1: 1.4%

C2: 63.83%

C3 :21.21 %

I-C4: 4.78%

n-C4 :4.76%

n-C5 : 1.1%

C6+: 0.97%

Specific gravity: 0.4333

Now I want to calculate the isenthalpic expansion of the liquid feed (feed condition , feed VLE composition etc) in MS Excel for personal interest only. It can be done rigorously by PR EOS or any other EOS.

I have found some reference to do so in DWSIM manual where they have mentioned about 'Goldzberg correlation' for the same. But I have not found any more reference about the correlation in internet or anywhere.

If you have any extra reference about the equation please share. Also if anyone having Excel sheet or algorithm for such isenthalpic expansion calculation, please share.

With regards,

Bitan729

Edited by Bitan729, 13 September 2021 - 04:20 PM.

### #2 PaoloPemi

PaoloPemi

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Posted 14 September 2021 - 01:04 AM

your question is not clear, I assume that as isenthalpic expansion you mean solving a H-P flash operation,
you can do that in Excel (or Libre Office or similar tools available for Windows  and Linux) with a thermodynamic library.

I have Prode Properties (there are free versions for students available) or a process simulator or similar tools...
If you know the composition I suggest to adopt a EOS or similar accurate methods, the mentioned library includes analytical derivatives for most properties including Joule–Thomson coefficient (for vapor and liquid phases) etc.
As alternative you can adopt simplified formulations as, for example,
Goldzberg, V., McKee, F., 1984 Oil Gas J. (July)
Real properties of natural gas provide base for thermal hydraulic analysis of pipelines

### #3 breizh

breizh

Gold Member

• 5,112 posts

Posted 14 September 2021 - 01:07 AM

Hi,

You can also use this application available on Internet to support your work:

Properties with Variant Fina Pressure – Quest Consultants

Note : I encourage you to develop your own spreadsheet using EOS .

Good luck

Breizh