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2

# Pressure Drop Calculations In Ko Drum And Liquid Seal Drum

pressure drop in flare system

7 replies to this topic
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### #1 Marilena29

Marilena29

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Posted 13 May 2021 - 02:43 PM

Hello everybody,

Can anyone direct me how to calculate pressure drop in a knockout drum from a flare system? I mention that are known next parameters: temperature, pressure, molar mass and flowrate for the inlet stream in the KO drum. Also, after the KO drum there is a pipe systems that directs the gas from the KO drum to the liquid seal drum. For the liquid seal drum I know the temperature, pressure molar mass and flowrate for the exiting gas flow. It is required to calculate the pressure drop on each element on the system, namely: KO drum, pipes and liquid seal drum.

For the pipes I found the procedure in API 521, but for the KO drum and liquid seal drum I didn't find anything that refers to the pressure drop calculations for these to vessels.

Edited by Marilena29, 13 May 2021 - 02:43 PM.

### #2 Bobby Strain

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Posted 13 May 2021 - 07:54 PM

Is this for real?

Bobby

### #3 Marilena29

Marilena29

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Posted 14 May 2021 - 12:59 AM

Is this for real?

Bobby

Yes, is for real. I have also the technical drawings for the KO drums and for liquid seal drums, with all dimensions. Also I have the isometrics for the pipes. The main problem for me is I don't know what pressure is at the outlet of the KO, so to calculate the pressure upstream, up to the flare stack. The only point where there are sensors is after the seal drum, and the sensors measure as said before, temperature, pressure, molar mass and gas flowrate.

Should I calculate the condensation process in the KO drum, and starting from the equilibrium maybe I will obtain the pressure in the drum?

Edited by Marilena29, 14 May 2021 - 01:15 AM.

### #4 breizh

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Posted 14 May 2021 - 01:19 AM

Hi,

You need to perform the calculation backwards from the top of the flare to each piece of equipment .

Attached document to visualize the equipment.

My 2 cents

Breizh

Edited by breizh, 14 May 2021 - 08:08 PM.

### #5 Bobby Strain

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Posted 14 May 2021 - 09:34 AM

What is the purpose for this activity? And, Breizh is correct. Do you have access to a process simulator?

Bobby

### #6 Marilena29

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Posted 17 May 2021 - 03:30 AM

Thank you !

Hi,

You need to perform the calculation backwards from the top of the flare to each piece of equipment .

Attached document to visualize the equipment.

My 2 cents

Breizh

### #7 Marilena29

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Posted 17 May 2021 - 03:48 AM

Hello Mr. Strain,

It was requested to calculate the pressure drop for each equipment from KO drum up to the stack of the flare for two cases: 1. normal activity (when just a small amount of natural gas is burned to maintain the torch up to the flare, and in this case all the gases from the flare header are recovered) and 2. emergency case: when all the gases are sent through the system KO drum - pipes - liquid seal vessel to the flare stack to be burned. From these information I understand that the purpose of the activity is to determine if the flare system supports large amount of gas in case of emergency, taking into account that the capacity of some installations was increased.  Regarding the simulator, I have just PRO II 2020 from Aveva.

What is the purpose for this activity? And, Breizh is correct. Do you have access to a process simulator?

Bobby

### #8 Bobby Strain

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Posted 17 May 2021 - 09:10 AM

I don't know much about PRO II, but most simulators have tools to analyze flare systems. This analysis should have been conducted at the time the units were expanded. But, better late than never. Why is the analysis only covering these portions? Seems like the analysis should cover everything to the relief valves.

Bobby