Dynamic pressure control in double loop reactor

1. A method for the slurry polymerization of olefins comprising:

providing a first loop reactor operated at a first pressure;

providing a second loop reactor operated at a second pressure controlled in real time by variations in the first pressure to maintain a predetermined pressure difference of from 0.5 bars to 2 bars, wherein the first loop reactor and the second loop reactor are connected in series via a line adapted for transferring growing polymer from the first loop to the second loop, wherein the line connecting two loops is subject to a dynamic pressure difference;

introducing olefin monomer into the first loop reactor;

contacting the olefin monomer with a first catalyst system within the first loop reactor to form a first polyolefin;

withdrawing the first polyolefin from the first loop reactor;

transferring the first polyolefin from the first loop reactor to the second loop reactor via the line;

contacting the first polyolefin with a second catalyst system within the second loop reactor to form a second polyolefin; and

withdrawing the second polyolefin from the second loop reactor.

2. The method of claim 1 , wherein the first and second loop reactors are linked by a by-pass line for connecting two points of the same loop reactor and by an alternate route having a different transit time than that of the main route, said by-pass line also collecting the growing polymer exiting the first loop reactor at exit points and sending said growing polymer to an entry point in the second reactor.

3. The method of claim 2 , wherein the velocity in the by-pass line connecting the two loop reactors is larger than 3 m/s.

4. The method of claim 1 , wherein the first loop reactor operates in batch operation.

5. The method of claim 4 , wherein the second loop reactor operates in continuous operation.