6 replies to this topic

[engtariq]

Hi,
I have cumene storage tank where I need to control tank pressure through pressure control also this system has a partial condenser to condense cumene vapor back to the tank. My concern is about the condenser vent, which is having a %LEL measuring device which it shows 100% LEL all the time. I need to dilute the cumene vapor by increasing the nitrogen blanket. Now the tank working pressure 0.035Kg/cm2 and tank level 45% and nitrogen blanket is 30 Nm3/hr. is that possible or not?

[DB Shah]

Kindly give a sketch indicating exactly the location of vent condenser.

[engtariq]

dear DB Shah,

I attached below link to get clear picture about my concern.

https://docs.google....K9vthg-oGw/edit


thank you

[DB Shah]

Dear engtariq,
I think the problem with your system is floating condenser on top without any control. At all the time the N2 will be full open to generate pressure where as unrestricted flow from condenser may be so high that it does not allows the pressure to build up.

I am attaching a file with two options.
For my personal interest also I will like to have merits/demerits of both the options from experts. I am presently on a assignment to finalize the chiller & PSV installation options.

Attached Files

•  Chiller On Storage Tank.xlsx   22KB   61 downloads

[engtariq]

Dear DB Shah,

i really thank you for replaying to my concern.

actually, the drawing which i attached for you before a little pit hazy.

we have at the tank two breathers PZV which are independent of the chiller.

we do have a U seal with 0.045kg/cm2 "500 mm" refer to attached and PZV'S having set pressure of 0.07 kg/cm2.

you mentioned in the attached excel file that The U seal should match the set point of the PVZ. is this philosophy can be applied in my case or not?


https://docs.google....fMTBjanc3NWZmZw

[DB Shah]

Dear enqtariq,

Vent PV & inert inlet PV both are set at same pressure ie 0.06 kg/cm2g. You need to have a reasonable difference between vent & inert set point. I will suggest following-
Reduce your inert inlet set point to ~ 20% less of vent ie 0.06*(1-0.2) = ~ 0.0480 kg/cm2g. This will ensure that the N2 stops quite early then the vent opens. Another point I suggest is -put the vent valve of 0.06 kg/cm2 on inlet of chiller. Thus a constant source of vacuum is eliminated. Your final figures should look like- (kg/cm2g)
Tank design press = more than 0.07
PZV set point =0.07
PV vent on chiller opens at press> 0.06
Inert opens when press is < 0.048
Vacuum inlet breather opens at = -x mmWCg + some margin (typical set point -25 mmWCg)
Tank design press in vacuum side= - x mmWCg (typical value = -50 mmWCg)
Hope this helps

DB Shah

[DB Shah]

One more thing I missed, inert gas injection should be on tank and not in downstream of chiller as you indicated in your drawing. In case chiller is under maintenance and its in/out are blinded, inert make up will be isolated.