Decreasing triboelectric charging of, and/or reactor fouling by, polyolefin particles

A method for decreasing triboelectric charging of, and/or reactor fouling by, polyolefin particles in a fluidized bed-type gas phase polymerization reactor (FBT-GPP reactor) comprising a distributor plate and a wall defining a reaction zone, wherein the polyolefin particles are located in the reaction zone and the reaction zone is located above and in fluid communication with the distributor plate, the method comprising:

• feeding an argon gas/nitrogen gas mixture upward through the distributor plate into the reaction zone to fluidize the polyolefin particles in the reaction zone, wherein the argon gas/nitrogen gas mixture consists of from 5 volume percent (vol %) to no more than 65 vol % argon gas, from 95 vol % to no less than 10 vol % nitrogen gas, and from 0 vol % to no more than 5 vol % helium gas, wherein the sum of all these vol % equals 100 vol % of the argon gas/nitrogen gas mixture.