Abstract: A process for the preparation of a polyolefin in a slurry loop reactor provided with settling legs may include introducing olefin reactants, diluents, and polymerization catalyst into the reactor while circulating. The process may include polymerizing the olefin reactants to produce a slurry, continuously withdrawing the slurry, via the settling legs, and transferring withdrawn solid olefin polymer particles to a recovery section. Each settling leg may have an inlet connected to the reactor and an outlet connected to the recovery section. At least one settling leg is continuously open, allowing continuous withdrawal of slurry. Each outlet of the settling legs may be connected to the recovery section by a conduit provided with a pressure control device. The pressure in the reactor may be controlled by operating the pressure control device.