16 replies to this topic

[charlesivor]

Greetings to all

 

I am trying to model a simple truck loading facility in hysys and continue to struggle.

 

The system is fairly simple.  Trucks discharge into a bullet tank.  The product is then injected into a crude oil pipeline.

This is an existing system the client is experiencing issues with.

 

System details

Product - Stabilized Condensate

VP = 9.64

SG = .66

IC4 - 0.084% (mol%)

NC4 - 1.221%

IC5 - 17.930%

NC5 - 20.33%

C6+ - 60.43%

 

P-1102 is a vertical can pump TDH = 1186 @ 100gpm. (32hp)

 

V-1000

Diameter - 10.83 ft

Length - 123.5 ft

MAWP - 202 psig

 

PCV-1103 is used to recycle product back to tank and to maintain min critical flow.

 

Currently there is no nitrogen pad on the tank.  This is the primary reason for the current issues.  

I was able to model the process with a constant 6psig on the vessel and was able to drain it dry basically.

 

The current operation offloads 13 trucks in a 24 hour period.  185 barrels each @ 350 barrels per hour per FE.

 

My issue is I can not get hysys to hold the 350 bph into the vessel.  I had valves on inlets and outlets originally. 

 

Can hysys schedule these 13 loads possibly as batches?

Is there a way to inject a nitrogen pad to maintain pressure in the vessel to prevent vacuum?

As trucks are coming into the vessel and product is injecting into pipeline plus recycling back to the tank, is there a way to quantify the mass flow that is vented to the flare?.  Also the volume of N2 needed for a month?

Will API 2000 apply with 6 psig on the vessel?

 

I know what the system should look like.  A N2 regulator for the pad with a PCV on the outlet bleeding to the flare as needed to maintain the set point.

 

Attached Files

•  hysys.png   19.55KB   0 downloads

[charlesivor]

I also have actual data from scada for Pressure, flow and temp up an downstream of the pump.  Also vessel data.

[Bobby Strain]

You should just let the tank pressure. Or, you can control the flow to the pipeline to hold the pressure between high and low limits. With this, you need very little makeup gas an minimal venting.

 

Bobby

[latexman]

As Bobby said, let the tank "ride the bubble", if possible.

[charlesivor]

They have been letting it ride but continue to have operational issues.

The trucks do add pressure but the pipeline injection eventually trumps it.
I am learning Hysys and was hoping it could simulate this.
Thanks for the comments.

[latexman]

They have been letting it ride but continue to have operational issues.

Such as?

[charlesivor]

They have been letting it ride but continue to have operational issues.

Such as?

[charlesivor]

Pulling vacuum in a tank not rated for vacuum.
Pump cavitating when the vessel goes into vacuum

[latexman]

If you added an inert gas to the tank when near empty, so it would be atmospheric pressure or slightly above, such that the tank runs successfully when near full (inert gas compressed), how long until the inert gas is dissolved and pumped out that the problems come back?  

 

I understand the tank is not rated for FV.  Bummer, and, IMHO,  shame on the Engineer(s) that did that!  I bet it would have not cost much more, or it could have been free, to get the FV rating when that long tank was being constructed.  Can it be re-rated to get the FV rating?

[Bobby Strain]

This is what I call a "Rube Goldberg" operation. You can easily add a pressure controller on the tank to regulate a control valve on the pump discharge. And, you are wasting your time using HYSYS to simulate the operation. You already know how to fix it.

 

As Latexman suggested, that can be used, too. And you can add a valve to supply gas to maintain pressure above atmospheric.

 

Bobby

[latexman]

As Latexman suggested, that can be used, too. And you can add a valve to supply gas to maintain pressure above atmospheric.

 

 

Yep, break vacuum with inert gas.  If you do that, and the pressure from filling/compressing up to a full tank (85-90% level) can be handled by the existing equipment without releasing pressure to vent, you may have an economical solution with minimal loss of inert gas.

[charlesivor]

If you added an inert gas to the tank when near empty, so it would be atmospheric pressure or slightly above, such that the tank runs successfully when near full (inert gas compressed), how long until the inert gas is dissolved and pumped out that the problems come back?

I understand the tank is not rated for FV. Bummer, and, IMHO, shame on the Engineer(s) that did that! I bet it would have not cost much more, or it could have been free, to get the FV rating when that long tank was being constructed. Can it be re-rated to get the FV rating?

It should’ve been. There are a few issues all around.
I really was using this to try to expand my Hysys knowledge as I am still new to the software.
My initial thought is to but a 12-24 pack of N2 or more likely a mini bull tank with a regulated set at a few PSI.
As the trucks load throughout the day it will “replace” the makeup gas. Truck drivers are a variable on their own and can’t be reliably depended on.
Then a PCV on the outlet gas side set just under the max pressure the trucks can put out.
I wanted to used Hysys to schedule multiple scenarios for say a months supply of N2 and for waste gas to the flare for perMitting.
Hysys isn’t playing nice

[charlesivor]

This is what I call a "Rube Goldberg" operation. You can easily add a pressure controller on the tank to regulate a control valve on the pump discharge. And, you are wasting your time using HYSYS to simulate the operation. You already know how to fix it.

As Latexman suggested, that can be used, too. And you can add a valve to supply gas to maintain pressure above atmospheric.

Bobby

There is a PIC on the tank that will shut the pump down once it gets to low.
The vacuum on the tank turns into an NPSHa issue on the pump as well.
You’re right I didn’t need Hysys to fix the problem. I am self teaching myself Hysys and really wanted to recreate the real world scenario. Maybe it’s it’s my OCD.
I just thought I could schedule trucks and be able to send them at 350 bph.
Then show the min flow recycle and N2 inlets on the tank
While showing the pump injecting into the pipeline
Wishful thinking maybe

[charlesivor]

As Latexman suggested, that can be used, too. And you can add a valve to supply gas to maintain pressure above atmospheric.

Yep, break vacuum with inert gas. If you do that, and the pressure from filling/compressing up to a full tank (85-90% level) can be handled by the existing equipment without releasing pressure to vent, you may have an economical solution with minimal loss of inert gas.

I agree. Just using excel I came up with 500ish scf per day N2.
The flare pcv/py will need a set point under the truck out put.

[charlesivor]

Additional Hysys question.
When entering the composition exactly as above
It comes up with a different VP then what the sample shows.
Again could by my Hysys ignorance

[Bobby Strain]

Excel is but a fancy calculator. It does not add credibility to your work.

 

Bobby

[charlesivor]

Excel is but a fancy calculator. It does not add credibility to your work.

Bobby

Using a fancy calculator I came up with 500ish!