Polymer powder storage and/or transport and/or degassing vessels

Polymer powder vessel comprising:

• a silo comprising a main vertical cylinder and a hopper at the bottom of the cylinder,
• a polymer powder which occupies the full volume of the hopper and at least a part of the volume of the cylinder,
• a polymer powder silo inlet pipe connected to the silo at a height located above the polymer powder, preferably connected to the top of the silo, and
• a polymer powder hopper withdrawal pipe connected to the hopper, preferably connected to the bottom of the hopper,
• characterised in that the polymer powder hopper withdrawal pipe is also connected to the silo at a location above the polymer powder for recirculating a part of the polymer powder within the silo.

Process for operating a polymer powder vessel which comprises

• a silo comprising a main vertical cylinder and a hopper at the bottom of the cylinder,
• a polymer powder which occupies the full volume of the hopper and at least a part of the volume of the cylinder,
• a polymer powder silo inlet pipe connected to the silo at a height located above the polymer powder, preferably connected to the top of the silo, and
• a polymer powder hopper withdrawal pipe connected to the hopper, preferably connected to the bottom of the hopper,
• characterised in that at least a part of the polymer powder which is withdrawn from the hopper is recirculated via the polymer powder hopper withdrawal pipe to a location upstream of the silo or to the silo at a height located above the polymer powder, preferably located at the top of the silo.

Process for operating a polymer powder degasser vessel used in a continuous polymerisation process wherein

• said degassing vessel is located downstream of a polymerization reactor,
• said degassing vessel is located upstream of a polymer powder extruder, and
• said polymer powder extruder is shutting down, and
• wherein said degassing vessel further comprises
• a silo comprising a main vertical cylinder and a hopper at the bottom of the cylinder,
• a polymer powder which occupies the full volume of the hopper and at least a part of the volume of the cylinder,
• a polymer powder silo inlet pipe connected to the silo at a height located above the polymer powder, preferably connected to the top of the silo, and
• a polymer powder hopper withdrawal pipe connected to the hopper, preferably connected to the bottom of the hopper,
• characterised in that at least a part of the polymer powder which is withdrawn from the hopper is recirculated via the polymer powder hopper withdrawal pipe to a location upstream of the silo or to the silo at a height located above the polymer powder, preferably located at the top of the silo.