Polymerization in several stages of alpha-olefins in the gas phase

Apparatus for the gas phase polymerization of alpha-olefins comprising, at least first and second serially disposed reactors, each of said reactors having cooling means associated therewith and recycle means;

• said first reactor having catalyst inlet means, an olefin inlet means at a lower end thereof, an outlet means at an upper end thereof and said recycle means of said first reactor being connected to said inlet and outlet means of said first reactor;
• olefin feed means connected to said recycle means of said first reactor;
• said second reactor having an outlet at the upper end connected to said recycle means of said second reactor, said second reactor recycle means connected to said second reactor at bottom and side inlets thereof;
• powder transfer means connected to said first reactor means at a first end thereof;
• said powder transfer means comprising in seriatim, a first conduit section, a first valve means, a discharge vessel, a second valve means, a decompression means having an upper discharge connection connected to the recycle means of said first reactor and a lower discharge connection connected via a third valve to a compression chamber, said compression chamber having first and second outlet members, said first outlet member connected to and communicating with said recycle means of said second reactor;
• fourth and fifth valve means in said recycle means of said second reactor upstream and downstream of the point of connection of said first outlet member;
• and, said second outlet member connected and communicating directly with said side inlet.