Inspection and replacement of spherical tanks

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Gentlemen, I have a question for you: our propylene spherical tanks need to be regularly overhauled, and this is to be done without shutting down production, by carrying out the overhauls in batches. Our equipment has very high requirements regarding the quality of propylene; it must not contain water or non-condensable gases such as nitrogen. Our propylene storage tank has a design pressure of 2.16 Mpa and a capacity of 2,000 cubic meters. We used a pump to drain the storage tank to its lowest liquid level; at that time, there was still 1 left in the propylene storage tank. Propylene gas phase at 0 MPA. For more than 10 tons of liquid, I have an idea – I’m not sure if it’s feasible or not: in order to save energy, use high-pressure nitrogen to raise the pressure in the tank that is to be repaired to 1.70 MPa, then slowly open the valves to create a pressure difference that pushes the liquid into the designated tanks with lower liquid levels; once the pressures are almost equal, close the valves of the tank that is under repair. During the analysis of the nitrogen content in storage tanks with low liquid levels, it is discharged to the flare.