An extruder that includes: an extruder barrel with an inlet end and a discharge end; a rotatable screw element disposed axially within the barrel with a screw inlet end proximate the inlet end and a screw discharge end proximate the discharge end of the barrel; a shaft extending axially through the screw element and comprising a central bore with an opening proximate to the inlet end of the barrel and extending through the shaft to a closed terminal end; and a coolant delivery conduit extending axially within the bore comprising a coolant inlet end proximate to the inlet end of the barrel and a coolant discharge end. The closed terminal end of the bore is located at a predetermined distance upstream from the screw discharge end. Further, the coolant discharge end is located within the bore and proximate to the closed terminal end of the bore.

A mixer for ceramic feedstock pellets includes a tank, a mixing device within the tank, and a heat exchanger including a cooler for cooling of the content of this tank. A controller controls the heat exchanger which includes a heater arranged to heat the content of this tank to a temperature comprised between a lower temperature (TINF) and a higher temperature (TSUP) stored in a memory for a specific mixture. The heater exchanges energy with a heat exchanger and mixing temperature maintenance circuit, external to this tank. The thermal inertia of this circuit is higher than that of this fully loaded tank.

A mixer for ceramic feedstock pellets with a tank, a mixing shaft, and a heat exchanger including a cooler for the cooling of the content of this tank is provided. A controller controls the heat exchanger which includes a heater arranged to heat the content of this tank to a temperature comprised between a lower temperature (TINF) and a higher temperature (TSUP) stored in a memory for a specific mixture, and the heater exchanges energy with a heat exchange and mixing temperature maintenance circuit, external to this tank, and wherein the thermal inertia of this circuit is higher than that of this fully loaded tank. The invention also concerns a method for mixing raw material for powder metallurgy, implementing a specific injection molding composition and a specific binder.

Mixer for ceramic feedstock pellets with a tank, a mixing means, and heat exchange means including cooling means for the cooling of the content of this tank.

Control means control the heat exchange means which include heating means arranged to heat the content of this tank to a temperature comprised between a lower temperature (TINF) and a higher temperature (TSUP) stored in a memory for a specific mixture, and the heating means exchange energy with a heat exchange and mixing temperature maintenance circuit, external to this tank, and wherein the thermal inertia of this circuit is higher than that of this fully loaded tank.

The invention also concerns a method for mixing raw material for powder metallurgy, implementing a specific injection moulding composition and a specific binder.

A process for the calcination of raw gypsum in a heatable extruder, wherein the raw gypsum is feed into the extruder and heated to a temperature of from 150 C. to 350 C. to thereby convert the raw gypsum to calcined gypsum with a content of calcium hemihydrate of at least 50 wt.-%. By using a heatable extruder for the calcination, calcined gypsum with a high content of calcium sulphate hemihydrate and low residual amounts of the respective dihydrate and anhydrite can be obtained. The present invention further concerns a system, which is adapted to such preparation of calcined gypsum and includes an appropriate heatable extruder and the use of a heatable extruder for the calcination of raw gypsum.

An extruder, preferably for calcining and extruding raw gypsum, including a calcination zone and a mixing zone, wherein the extruder is optionally configured to capture and/or retain water liberated in the calcination zone, apparatuses and processes employing such extruders and respective uses.