Abstract: A fluid bed reactor system and process employing a silyl chromate catalyst therein wherein the reactor system comprises a vertical reactor having a fluidizing medium permeable distribution plate towards the base thereof, a fluidizing medium supply line to supply fluidizing medium to the base of the reactor, a catalyst injection means to supply particulate catalyst to the side of the reactor, a polymer product recovery means to recover polymer product from the reactor and beneath the distribution plate, a fluidizing medium recycle line to recycle the fluidizing medium from and to the reactor, and a heat exchanger in the recycle line to remove heat of reaction from the recycled fluidizing medium.