Bp Chemicals Limited

Michel C Filippelli

David Newton

Jean-Claude Chinh

Michael Bernard Power

The invention relates to continuous gas fluidised bed polymerisation of olefins, especially ethylene, propylene, or mixtures of these with other alpha olefins, wherein the monomer-containing recycle gas employed to fluidise the bed is cooled to condense out at least some liquid hydrocarbon. The condensed liquid, which can be a monomer or an inert liquid, is separated from the recycle gas and is fed directly to the bed to produce cooling by latent heat of evaporation. The liquid feeding to the bed can be through gas-induced atomiser nozzles (FIG. 2), or through liquid-only nozzles. The process provides substantially improved productivity of gas fluidised bed polymerisation of olefins.

Polymerization process

The invention relates to continuous gas fluidized bed polymerization of olefins, especially ethylene, propylene, or mixtures of these with other alpha olefins, wherein the monomer-containing recycle gas employed to fluidize the bed is cooled to condense out at least some liquid hydrocarbon. The condensed liquid, which can be a monomer or an inert liquid, is separated from the recycle gas and is fed directly to the bed to produce cooling by latent heat of evaporation. The liquid feeding to the bed can be through gas-induced atomizer nozzles (FIG. 2), or through liquid-only nozzles. The process provides substantially improved productivity of gas fluidized bed polymerization of olefins.

A fluidized bed polymerization reactor which is a generally cylindrical vessel having a longitudinal axis and a fluidization grid located in the vessel generally perpendicular to the longitudinal axis of the vessel and defining a fluidized bed region above the fluidization grid. The reactor has an inlet for continuously introducing a gaseous stream of polymerizable monomers into the vessel below the fluidization grid at a gas velocity sufficient to maintain particles in the fluidized bed region in a suspended and fluidized condition; an outlet for removing polymer product from the fluidized bed region and an outlet for continuously removing an outlet stream of gaseous unreacted polymerizable monomer from the fluidized bed region. A cooling device cools at least a part of the outlet stream to a temperature at which liquid condenses out of the outlet stream, and a separating device separates at least a part of the cooled outlet stream into condensed liquid and a cooled gaseous stream. The separated cooled gaseous stream is returned to the inlet and an injection device injects at least a part of the condensed liquid into the fluidized bed region at a point where the gaseous stream of polymerizable monomers passing through the vessel has substantially reached the operating temperature of the polymerization reactor. The injection device includes at least one gas induced atomizing nozzle for injecting an atomized stream of the condensed liquid into the fluidized bed region in a direction generally perpendicular to the longitudinal axis of the vessel.

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Martigues, France

Michel C Filippelli