Abstract: Process for preparing a polyolefin polymer comprising the steps of a) forming a particulate polyolefin polymer by polymerizing one or more olefins in the presence of a polymerization catalyst system in a polymerization reactor; b) discharging the formed polyolefin particles from the polymerization reactor; c) degassing the polyolefin particles by a process comprising at least a final step of contacting the polyolefin particles with a nitrogen stream in a degassing vessel; and d) transferring the polyolefin particles from the vessel, in which the contacting of the polyolefin particles with the nitrogen stream is carried out, to a melt mixing device, in which the polyolefin particles are melted, mixed and thereafter pelletized, without passing the particles through a buffering device, wherein the degassing vessel is only partly filled with polyolefin particles and the empty volume within the degassing vessel is sufficient to take up additional polyolefin particles for at least 3 hours if the transfer of pol

Abstract: Process for treating polyolefin particles obtained by gas-phase polymerization of one or more olefins in the presence of a polymerization catalyst system and a C3-C5 alkane as polymerization diluent in a gas-phase polymerization reactor, the process comprising the steps of a) discharging the polyolefin particles continuously or discontinuously from the gas-phase polymerization reactor and transferring the particles to a first degassing vessel; b) contacting therein the polyolefin particles with a gaseous stream comprising at least 85 mol-% of C3-C5 alkane while the polyolefin particles have an average residence time in the first degassing vessel of from 5 minutes to 5 hours; c) transferring the polyolefin particles to a second degassing vessel; d) contacting therein the polyolefin particles with a stream comprising nitrogen and steam while the polyolefin particles have an average residence time in the second degassing vessel of from 5 minutes to 2 hours, wherein the contacting is carried out at conditions un

Abstract: Process for treating polyolefin particles obtained by gas-phase polymerization of one or more olefins in the presence of a polymerization catalyst system and a C3-C5 alkane as polymerization diluent in a gas-phase polymerization reactor, the process comprising the steps of a) discharging the polyolefin particles continuously or discontinuously from the gas-phase polymerization reactor and transferring the particles to a first degassing vessel; b) contacting therein the polyolefin particles with a gaseous stream comprising at least 85 mol-% of C3-C5 alkane while the polyolefin particles have an average residence time in the first degassing vessel of from 5 minutes to 5 hours; c) transferring the polyolefin particles to a second degassing vessel; d) contacting therein the polyolefin particles with a stream comprising nitrogen and steam while the polyolefin particles have an average residence time in the second degassing vessel of from 5 minutes to 2 hours, wherein the contacting is carried out at conditions un

Abstract: Process for preparing a polyolefin polymer comprising the steps of a) forming a particulate polyolefin polymer by polymerizing one or more olefins in the presence of a polymerization catalyst system in a polymerization reactor; b) discharging the formed polyolefin particles from the polymerization reactor; c) degassing the polyolefin particles by a process comprising at least a final step of contacting the polyolefin particles with a nitrogen stream in a degassing vessel; and d) transferring the polyolefin particles from the vessel, in which the contacting of the polyolefin particles with the nitrogen stream is carried out, to a melt mixing device, in which the polyolefin particles are melted, mixed and thereafter pelletized, without passing the particles through a buffering device, wherein the degassing vessel is only partly filled with polyolefin particles and the empty volume within the degassing vessel is sufficient to take up additional polyolefin particles for at least 3 hours if the transfer of pol

Abstract: Process for transferring polyolefin particles from a first gas-phase polymerization reactor to a second gas-phase polymerization reactor in a multistage polymerization of olefins carried out in at least two serially connected gas-phase polymerization reactors, wherein the first gas-phase reactor is a fluidized-bed reactor comprising a gas distribution grid and a settling pipe, which is integrated with its upper opening into the distribution grid and contains a bed of polyolefin particles which moves from top to bottom of the settling pipe, the process comprising the steps of introducing a fluid into the settling pipe in an amount that an upward stream of the fluid is induced in the bed of polyolefin particles above the fluid introduction point; withdrawing polyolefin particles from the lower end of the settling pipe; and transferring the withdrawn polyolefin particles into the second gas-phase polymerization reactor, process for polymerizing olefins comprising such a process for transferring polyolefin p

Abstract: Process for transferring polyolefin particles from a first gas-phase polymerization reactor to a second gas-phase polymerization reactor in a multistage polymerization of olefins carried out in at least two serially connected gas-phase polymerization reactors, wherein the first gas-phase reactor is a fluidized-bed reactor comprising a gas distribution grid and a settling pipe, which is integrated with its upper opening into the distribution grid and contains a bed of polyolefin particles which moves from top to bottom of the settling pipe, the process comprising the steps of introducing a fluid into the settling pipe in an amount that an upward stream of the fluid is induced in the bed of polyolefin particles above the fluid introduction point; withdrawing polyolefin particles from the lower end of the settling pipe; and transferring the withdrawn polyolefin particles into the second gas-phase polymerization reactor, process for polymerizing olefins comprising such a process for transferring polyolefin partic