Process and apparatus for the gas-phase polymerisation

A process for catalytic polymerization in the gas phase, carried out in at least two interconnected polymerization zones, the process comprising introducing one or more monomers, in said polymerization zones, in the presence of catalyst, under conditions of reaction and the collection of the polymer product, from said polymerization zones, in which process, the particles of the growing polymer, flow up, through one of the said polymerization zones (ascending zone) under conditions of rapid fluidization or transport, they leave said ascent zone, and enter another polymerization zone (descending zone), through which they flow, in the downward direction, under the action of gravity, they leave the aforementioned zone of descent, and reintroduce themselves into the zone of ascent, thus establishing a circulation of the polymers, between the area of ​​ascent and the zone of descent, the procedure being further characterized by the fact that: - means are provided, which are capable of totally or partially avoiding which, the gas mixture present in the ascending zone, penetrates in the descending zone, and - a gaseous and / or liquid mixture, which has a different composition of the gas mixture present in the ascending zone, is introduced into the descending zone.