The present invention relates to a process for operating a polymer powder degasser vessel, and in particular provides a process for operating a polymer powder degasser vessel which vessel comprises a silo comprising a main vertical cylinder and a hopper at the bottom of the cylinder, there being a polymer powder withdrawal pipe connected to the hopper by which polymer powder is withdrawn from the hopper, and wherein the silo contains a polymer powder which occupies less than 45% of the volume of the silo and the polymer powder passes through the polymer powder degasser vessel in a mass flow manner, further wherein at least one of the following is applied: i) polymer powder is withdrawn from the hopper and recirculated to the silo, wherein the recirculation rate of the polymer powder is at least 30 percent per hour of the polymer powder present in the silo, and ii) a purge gas is provided to the silo via the polymer powder withdrawal pipe or via an inlet located on the hopper at a vertical height which is less than half of height of the hopper from its bottom end.