Tank Blanket Gas Requirement

[Berenger]

Hi all,

I am trying to estimate the flue gas requirement for a proposed plant. I have been able to determine all FG needed for all processes except tank blanketing purposes.

People have directed me to API 2000, but it doesn't give you the blanket gas needed. API 2000 is used to calculate vent sizes and flowrate.

Can anyone explain how I can estimate the daily blanket gas requirement for tanks? Currently, I am estimating the daily withdrawal from the tanks and using that volume as the requirement. For example, if 10 pounds of slop was pumped out a day, the blanket gas required will be 10 pounds converted into cubic ft. Same thing for amine and glycol (using amine and glycol make-up values from promax simulations). However, I am coming up with a small value - 60 cubic feet a day.

Is my approach right? Does the figure look reasonable for a 60 mmscfd plant? Make-up of amine is 1.12 lb/hr, glycol is 2.85 lb/hr, water is 144.53 lb/hr and slop is 0.55 lb/hr. Using their densities, I converted into cubic feet/day. Density for slop is 62.06 lb/cubic ft.

Thank you all for your help.

 

[bimr]

You also need to consider the thermal effects of the tank in the sun.

http://www.cheresources.com/content/articles/safety/tank-blanketing-basics-covered

 

[maddocks]

Figure out your pumpout rates and how the product could be moved out of the tanks - that's your blanket rate. Then, size the system generously so you never run out of blanket gas - ever.

 

[shahyar]

Using API2000 for calculation of required blanket gas is too conservative. The respective API committee clearly prevented the designers from using API 2000 for that purpose( I have the document but it is not handy now). API2000 is standard to size "safety" devices.
Hope this help

 

[silebi66]

Hi Berenger
Sorry I can't answer you detail of this blanket gas requirement but you may refer to follow forum post , and
there is very useful excel spreadsheet for your reference.

http://www.cheresources.com/invision/topic/573-sizing-of-vacuumrelief-valve-on-storage-tank/page-3

Thank you.