A catalyst preparation system comprising: (a) a metallocene or transition metal compound addition system configured to add a metallocene or transition metal compound to the catalyst preparation system at a controlled rate; (b) a co-catalyst addition system configured to add a co-catalyst to the catalyst preparation system at a controlled rate; (c) a continuous calcination vessel configured to add a calcined chemically-treated solid oxide to the catalyst preparation system at a controlled rate, wherein the continuous calcination vessel comprises: i. a substantially horizontal fluidized bed vessel; ii. a particulate material inlet capable of introducing inlet particulate material into the fluidized bed vessel; iii. a fluidizing gas inlet capable of introducing a fluidizing gas into the fluidized bed vessel; iv. a fluidizing gas path capable of directing the fluidizing gas from the fluidizing gas inlet into the fluidized bed vessel to fluidize the inlet particulate material; v. a heating zone (15, 20, 35) within the fluidized bed vessel, wherein the heating zone (15, 20, 35) within the fluidized bed vessel comprises a first heating zone and a second heating zone, wherein: the fluidizing gas in the first heating zone comprises air, nitrogen, argon, hydrogen, oxygen, carbon monoxide, water, or any combination thereof; and the fluidizing gas in the second heating zone comprises helium, neon, argon, nitrogen, or any combination thereof; vi. an outlet capable of removing outlet particulate material from the fluidized bed vessel, wherein the outlet particulate material comprises the calcined chemically-treated solid oxide; and vii. a cooling system downstream of the outlet of the fluidized bed vessel; and (d) a controller programmed with an algorithm to control the rate of addition of the metallocene or transition metal compound and the co-catalyst based on the rate of addition of the calcined chemically-treated solid oxide from the continuous calcination vessel. (a) a metallocene or transition metal compound addition system configured to add a metallocene or transition metal compound to the catalyst preparation system at a controlled rate; (b) a co-catalyst addition system configured to add a co-catalyst to the catalyst preparation system at a controlled rate; (c) a continuous calcination vessel configured to add a calcined chemically-treated solid oxide to the catalyst preparation system at a controlled rate, wherein the continuous calcination vessel comprises: i. a substantially horizontal fluidized bed vessel; ii. a particulate material inlet capable of introducing inlet particulate material into the fluidized bed vessel; iii. a fluidizing gas inlet capable of introducing a fluidizing gas into the fluidized bed vessel; iv. a fluidizing gas path capable of directing the fluidizing gas from the fluidizing gas inlet into the fluidized bed vessel to fluidize the inlet particulate material; v. a heating zone (15, 20, 35) within the fluidized bed vessel, wherein the heating zone (15, 20, 35) within the fluidized bed vessel comprises a first heating zone and a second heating zone, wherein: the fluidizing gas in the first heating zone comprises air, nitrogen, argon, hydrogen, oxygen, carbon monoxide, water, or any combination thereof; and the fluidizing gas in the second heating zone comprises helium, neon, argon, nitrogen, or any combination thereof; vi. an outlet capable of removing outlet particulate material from the fluidized bed vessel, wherein the outlet particulate material comprises the calcined chemically-treated solid oxide; and vii. a cooling system downstream of the outlet of the fluidized bed vessel; and i. a substantially horizontal fluidized bed vessel; ii. a particulate material inlet capable of introducing inlet particulate material into the fluidized bed vessel; iii. a fluidizing gas inlet capable of introducing a fluidizing gas into the fluidized bed vessel; iv. a fluidizing gas path capable of directing the fluidizing gas from the fluidizing gas inlet into the fluidized bed vessel to fluidize the inlet particulate material; v. a heating zone (15, 20, 35) within the fluidized bed vessel, wherein the heating zone (15, 20, 35) within the fluidized bed vessel comprises a first heating zone and a second heating zone, wherein: the fluidizing gas in the first heating zone comprises air, nitrogen, argon, hydrogen, oxygen, carbon monoxide, water, or any combination thereof; and the fluidizing gas in the second heating zone comprises helium, neon, argon, nitrogen, or any combination thereof; vi. an outlet capable of removing outlet particulate material from the fluidized bed vessel, wherein the outlet particulate material comprises the calcined chemically-treated solid oxide; and vii. a cooling system downstream of the outlet of the fluidized bed vessel; and (d) a controller programmed with an algorithm to control the rate of addition of the metallocene or transition metal compound and the co-catalyst based on the rate of addition of the calcined chemically-treated solid oxide from the continuous calcination vessel.