Purge rate during volume change

[ThijsM]

Hello,

I hope you can help me with the following interesting question:

We are working in a batch process with fermentation and I have a vessel that contains a gas cap of CO2. When we empty the vessel, air or CO2 is sucked in and the vessel is cleaned. During cleaning, fumes and formed and the CO2 concentration decreases also due to reaction with NaOH. For this, I have assumed a certain consumption.

Now is the problem that if we fill the vessel, CO2 starts to be formed and the concentration increases. We want to purge the vessel untill the CO2 concentration is > 95% and then we want to collect it, but I am incapable of calculation the amount of CO2 that is needed to rinse the vessel. The Basic Room Purge Equation does not take into account the fact that my volume of the room (vessel in this case) changes in time, and this is something I have to do.

Does anybody have experience with this issue?

 

[ThijsM]

Nobody?

 

[Casimo5]

What is the maximum operating pressure of the vessel?

I'm not sure I fully understand your process. Are you saying that you fill the vessel and start fermentation, which generates CO2 which mixes with the air that is already in the vessel, then you want to purge the vessel of that CO2/air mixture until CO2 concentration is above >95%, at which point you will not just purge, but actually collect the CO2?

 

[ThijsM]

Yes Casimo5, you are right, above 95% we want to collect the CO2. The working pressure is atmospheric with a open connection to 2 CO2 headers between which we will switch at above 95%.
I have already solved the issue by calculating the concentration of CO2 in the vessel at different time intervals in Excel taking the produced CO2 in that interval into account.

Thanks anyway!