Polymer Autoclaving (EPP)

Trying to produce pre-expanded PP beads using an autoclave (pressure of 600 PSI; Blowing Agent = Co2 ; Dispersing agent = h20; Temperature = 150 C).

Constant stirring @ 100 RPM ; Saturation Time = 1 Hr....

Have been having problems getting the beads to be released from the bottom of the autoclave. They all agglomerate, melt and are not pushed out with only water and steam being discharged. Have tried surfactant but same results...

Any potential solutions to resolve this (am using a 1 mm die for discharge - have tried bigger dia. but no success...polymer melt sticks to the stirrer).