how can we freeze fruit pulps in 200 kg drums?

Answer 1

Calculate how much the pulp will expand when being frozen. You can do this by freezing a small container and measure the volume increase.
Fill the drums with the fruit pulp, just high enough to allow for the expected expansion.
Close the drums and freeze.

This question is too easy, or is there a catch?

Answer 2

You would need to place the drums in a walk-in freezer. Supermarkets and large butcher-shops use these. Perhaps they would allow you to use some space in their freezers when not filled to capacity.