Nitrogen blanket conservation
Nitrogen blanket conservation
(OP)
There are two soybean oil silos getting filled from a railcar ~once a week. We keep a Nitrogen blanket on the silos in case the oil is held for a few weeks, even though that doesn't happen often. (Blanket maintained at 6-7" WC with pressure/vac relief valve)
Our nitrogen generator seems undersized for the application - we need high purity nitrogen on some of our other applications, and the purity drops significantly when we're emptying the railcar into the silos.
Nitrogen is added to maintain a blanket on the railcar.
Now with all that background - the question:
Has anyone got experience taking the Nitrogen from the silo and putting that back on the railcar? In effect it would be a closed loop, trading soybean oil for Nitrogen gas. I'm thinking about automatic shut-off valves and pretty big lines to persuade the gas into the railcar rather than venting to atmosphere as we do now.
Our nitrogen generator seems undersized for the application - we need high purity nitrogen on some of our other applications, and the purity drops significantly when we're emptying the railcar into the silos.
Nitrogen is added to maintain a blanket on the railcar.
Now with all that background - the question:
Has anyone got experience taking the Nitrogen from the silo and putting that back on the railcar? In effect it would be a closed loop, trading soybean oil for Nitrogen gas. I'm thinking about automatic shut-off valves and pretty big lines to persuade the gas into the railcar rather than venting to atmosphere as we do now.





RE: Nitrogen blanket conservation
We unload propane and butane by taking the vapors off the tank to pressure up and displace the liquid from the rail car.
RE: Nitrogen blanket conservation
RE: Nitrogen blanket conservation
Do the rail cars come in already inerted with nitrogen? If they contain air, that's going to defeat the purpose of your proposed line.
RE: Nitrogen blanket conservation
RE: Nitrogen blanket conservation
The vapor vent configuration you envision is commonly used with dangerous and/or volitile liquids. Offloading can be by pressure or by pumping, each has it's own advantages/disadvantages
As an example, see Figure #2 of this link:
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Most importantly, if you offload by pressure, ensure that your recieving tank has an emergency pressure vent. At the end of liquid delivery, there is commonly a pressure surge that can destroy a marginal tank.
My opinion only...
-MJC
RE: Nitrogen blanket conservation
Oh yeah....
Are these "silos" that you describe filled with oil,... are they really "storage tanks" ?
Is the bottom of the container flat, tapered, rounded or what ?
(The term silo is typically used for containers that store bulk solids, powders, etc)
-MJC
RE: Nitrogen blanket conservation
Thanks for all the input - seemed to make sense. I think there will be a common header & shut-off valve to the railcar. The silos still have the 3" breather valve to maintain low pressure - just need to make sure that the pressure drops through the line back to the railcar keep everything flowing correct.
RE: Nitrogen blanket conservation
make sure your breather conservation valve can handle ALL credible scenarios.