A process and apparatus is disclosed for heating or cooling polymer solids
in a dispensing section of a solid-state polycondensation reactor. Gas is
delivered to the dispensing section of the reactor in which it cools
polymer solids in the dispensing section by direct heat exchange. Part of
the gas is withdrawn at a point proximate to the dispensing section of the
reactor and is cooled. The rest of the gas ascends through a reactive
section of the reactor and purges polymer solids of impurities. The gas
withdrawn from the reactive section of the reactor is oxidized of
impurities and dried and then combined with the gas withdrawn proximate to
the dispensing section of the reactor. To achieve uniform heating or
cooling of the polymer solids in the dispensing section, a preferred ratio
of mass flow rate of gas to the mass flow rate of solids is recommended.
