Rapid mixing polymerization process

A process for polymerization of at least one olefin monomer in a polymerization reactor assembly, the polymerization reactor assembly comprising a reactor (1) having a housing (2) defining an inner space (3), the reactor (1) comprising

• a) at least one inlet (4);
• b) at least one outlet (5);
• c) a draft tube (6) having a substantially cylindrical shape and an inner space (7), wherein the draft tube (6) is located within the inner space (3) of the reactor (1) so that an upper opening (10) and a lower opening (11) of the draft tube (6) are fluidly connected with the inner space (3) of the reactor (1), and
• d) a stirrer (12) located within the inner space (3) of the reactor (1) and comprising a stirrer blade (14) having a helical shape, wherein the axis (8) of the draft tube and the axis (15) of the stirrer blade (14) are coinciding, the stirrer blade (14) extending concentrically with respect to the draft tube (6) and the housing (2) of the reactor (1), and
• e) secondary mixing means (23) for mixing the fluid inside the reactor (1) by rotating motion,
• wherein the inner space (3) of the reactor (1) comprises sections A, B, C, and D, wherein
• section A is the space defined by the upper end of the housing (2) of the reactor (1) and a first plane (10a) oriented transversally to the axis (8) of the draft tube and arranged at the upper end of the stirrer (12),
• section B is the space defined by the housing (2) of the reactor (1), the outer surface of the draft tube (6), the first plane (10a) and a second plane (11a) oriented transversally to the axis (8) of the draft tube and arranged at the lower opening (11) of the draft tube (6),
• section C is the space defined by the lower end of the housing (2) of the reactor (1) and the second plane (11a), and
• section D is the inner space (7) of the draft tube (6),
• wherein the stirrer (12) is rotatable inside the housing (2) of the reactor (1) to provide a mixing motion to fluids if present inside the reactor (1), the process comprising the steps of
• I. introducing the at least one olefin monomer, at least one polymerization catalyst, and at least one solvent via the at least one inlet (4) into section C to form a reaction mixture,
• II. rotating the stirrer (12) to force at least a part of the reaction mixture from section C via section B to section A and from section A via section D to section C,
• III. thereby polymerizing the at least one olefin monomer forming a polymer in said reaction mixture,
• IV. withdrawing at least a part of the reaction mixture via the at least one outlet (5) from section A to obtain an olefin polymer as a product.