Dear Brunusmcchunky;
You may try to do the next steps, but keep in mind:
We are still ready for future discussions and help.
Good Luck!
ARGOS++
Dear enhas;
I don’t believe that’s a real solution, then it would be much easier to warm the pipe to –78°C and let the CO2 sublimate and clean the pipe with much less N2 gas. That would be more effective.
Maybe with He you can do the same at -100°C or less, even when the pipe is partially closed, because its high diffusion coefficients, according to the phase diagram of CO2 (maybe with less pressure too):
http://scifun.chem.wisc.edu/chemweek/pdf/CarbonDioxide.pdf
Good Luck!
ARGOS++