PU 15 Alumina Storage and Expedition
Alumina product is transported by means of airlift and air slides from calcination unit PU 21 into two silos where alumina is stored before further expedition.
Alumina for expedition is taken from these silos and by means of pneutransport is loaded into railway wagons.
The silos are designed for one month production of alumina.
PU 19 Aluminium Hydrate Storage
Covered aluminium hydrate storage serves for storing of aluminium hydrate in the case when calcination unit PU 21 is out of operation but the other units operate. The storage is designed for storing capacity of 14 days production. Supply and discharge of hydrate is solved by belt conveyers of PU 20.
PU 20 Outdoor Belt Conveyer of Hydrate
This unit secures the transport of hydrate from PU 17 hydrate filtration to PU 21 calcination, PU 19 hydrate storage and from PU 19 to PU 21 calcination and for loading into wagons or trucks.
PU 21 Calcination
In this unit the aluminium hydrate is calcined into aluminium oxide product of the alumina plant. Aluminium hydrate is transported to PU21 by belt conveyers either from PU17 or from PU 19 or from PU17 and PU 19 simultaneously. For calcination the Gas suspension calciner is used. The most important part of the unit is a rector what is a refractory lined cylindrical vessel with conical bottom. Preheated and partly calcined alumina enters the rector above the inlet of fuel and of preheated combustion air. The velocity of the air at the inlet is sufficient to ensure proper suspension of particles over the entire cross section of the reactor at full and partical capacity.
The calcined alumina is entrained from the reactor by the gaseous mixture of water vapour and combustion products after a few seconds retention time at approx. 1 150 – 1 250 °C. Calcinated Alumina is separated from the hot gases, stepwise cooled down by incoming air and cooling water (in last step) and by pneumatic transport delivered into alumina storage.