Method for supplying granulated material to a polymerisation reactor

Polyolefin producing unit, comprising:

• means for feeding monomer, co-monomer, and optionally diluent to at least one polymerization reactor, means for feeding a polymerization catalyst to said at least one polymerization reactor;
• a reactor system comprising at least one polymerization reactor,
• one or more monomer and/or diluent recovery system configured to recover unreacted monomer and/or diluent discharged from the polymerization reactor;
• and
• a polyolefin processing system configured to process polyolefin particles produced in said polymerization reactor,
• wherein said means for feeding a polymerization catalyst comprises a first conduit having a catalyst inlet, the first conduit being operably connected to a pocket ball valve comprising at least one pocket, said pocket ball valve comprising an elastic member operably affixed at the bottom of said at least one pocket, said pocket ball valve being operably connected to a second conduit, said second conduit being operably connected to said polymerization reactor, and wherein said at least one pocket has a volume ranging from about 1 to about 100 cm3 and wherein the first conduit and second conduit are under pressure.