Estimating Vapor Flow Rate from Internal Floating Roof Tank

[sid9999]

We are building a tank farm with five 250k BBL internal floating roof tanks. Each tank has 50000 cubic feet vapor head space and will be landed on legs before being refilled. We will be required to install vapor destruction unit to control vapor head space during tank refill and when tank is empty and sitting on the legs. I am trying to calculate the minimum vapor flo rate that will be required from each tank that is off of float in order to size the blowers, bladders and combustor. I do not want to oversize the equipment and at the same time under size it.

Your input is well appreciated.

Thanks
Sidney

 

[IFRs]

When the tank is filled and the floating roof is on it's legs, the air/vapor flow rate through the floating roof will be equal to the liquid fill rate. But, that is too simple an answer so I must not be understanding the question.

 

[sid9999]

During tank refill the volume is the vapor displaced by filling rate and US Coast guard requires 125% of the maximum fill rate for the design. But in addition to the fill, there will be four other tanks empty and in breathing mode and we are required to vapor control those tanks in addition to the tank being refilled.