Calcination using liquid metal heat exchange fluid

A process for the indirectly heated calcination of a particulate material to convert it to its anhydrous state and to liberate the vaporizable portion of said material, comprising:

• a) fluidizing the particulate material with a gaseous fluidizing medium in a calcination apparatus housing a closed loop heat exchanger adapted to indirectly transfer heat to the particulate material by means of a liquid metal heat exchange fluid arranged to flow through the closed loop heat exchanger;
• b) heating the fluidized particulate material flowing through the calcination apparatus in indirect heat exchange with the closed loop heat exchanger at a temperature sufficient to liberate the vaporizable portion of said particulate material in the form of gaseous vapor which exits the calcination apparatus with the gaseous fluidizing medium, and wherein the particulate material is converted to its anhydrous state;
• and
• c) returning the gaseous vapor to the calcination apparatus to serve as the fluidizing medium for the particulate material entering the calcination apparatus.

A calcination apparatus comprising,

• a) a calcination vessel,
• b) a heat exchanger housed in the calcination vessel, the heat exchanger having a heat exchange loop pipe containing liquid metal heat exchange fluid and forming a conduit for the liquid metal heat exchange fluid, the conduit having an outer surface, whereby heat from the heat exchange loop pipe is transferred through the outer surface of the conduit by the liquid metal heat exchange fluid in the conduit to the material being calcined in the calcination vessel,
• c) a first opening in the upper portion of the calcination vessel adapted for entry of a particulate material to fall freely therein and become fluidized by a fluidizing gas,
• d) a second opening in the upper portion of the calcination vessel below the first opening adapted for the free-flowing fluidized particulate material to exit the calcination vessel,
• e) a third entry in the lower portion of the calcination vessel for entry of a fluidizing gas, and
• f) a fourth entry in the top portion of the calcination vessel for exit of the fluidizing gas.