PU 01 Bauxite Receiving and Crushing
Bauxite with maximum lump size 1000 x 800 x 800 mm is transported to the plant by Lorries. Bauxite is crushed primary in jaw crusher, after that is transported to vibratory rough sorter where particles bigger than 20 mm are separated and crushed in impact hammer crusher. The crushed Bauxite with grain size up to 20 mm is by means of conveyors of up 01A delivered into the covered Bauxite storage PU 02.
PU 01A Belt Conveyer Transport
This unit secures the transport of crushed Bauxite from PU 01 to PU 02 (Bauxite storage), homogenization purposes and transport of homogenized Bauxite from storage PU 02 to PU 08 Bauxite wet grinding.
PU 02 Bauxite Storage
The maximum Storage capacity is 66000 t what means one month consumption provided that the plant is supplied by Bauxite with stable or very little changing composition. If the composition is changing what is usual situation the Bauxite should be homogenized. Therefore the storage is divided into three stockpiles with storage capacity of 10 days each. The operation of the unit is as follows:
Bauxite after crushing is conveyed to one of the stockpiles. During this time no Bauxite is taken from this stockpile.
Bauxite for homogenization and for feeding of PU 08 Bauxite wet grinding is taken form the remaining two stockpiles.
In such way the stock of homogenized Bauxite for 10 days operation is created.
PU 03 Limestone Storing
The crushed limestone of two sizes – 30-70 and 70-160 is stored in this unit. To that unit the limestone is transported from crushing unit located outside the plant.
The unit PU 03 is APPI's delivery and responsibility.
PU 04 Limestone Burning
Two parallel ordered two-shaft regenerative kilns represent a unit for limestone burning. The burning cycle in both shafts is alternated in regular time intervals exactly adjusted to the kiln output capacity.
The normal capacity of the kiln is 310 t/day (max 380 t/day) when burning fraction 70-160mm and approx. 240 t/day (max 260 t/day) when burning fraction 30-70 mm. lime is used for lime milk preparation in PU 05 and in wet grinding unit PU 08.
PU 04B Burnt lime Store
This Unit serves for storing of burnt lime. In case of maintenance of one limestone burning kiln the burnt lime is taken from this store and used together with lime from the kiln which is in operation. The unit consists from covered store and transporting facilities. The stock of lime is sufficient for 20 days shut down of one kiln.
PU 05 Lime Milk Preparation
For preparing of lime milk 4 individual lines are designed. the burned lime is stored in storage tanks with capacity of 1.5 operating days of shaft kilns.
The lime is transported from these tanks by means of vibratory feeders in to a lime slaking tanks where slaking process takes place by reaction with process water. The lime milk flows from the slacking tanks through classifiers into maturing tanks from where it goes to consumers – red mud caustification PU 14 and calcium aluminate preparation in PU 13.
PU 08 Bauxite Wet Grinding
There are three limed for bauxite wet grinding, two lines are in operation, the third is stand-by.
In these unit the bauxite is grinding down to max. 5% particle size over 0.09 mm and bauxite slurry is prepared.
Bauxite is transported from bauxite storage PU02 by belt conveyers to the inlet hopper from where it is fed into the ball mill .weak caustic liquor from PU17A and lime from PU05 are also fed into ball mill.
Grinded bauxite slurry is pumped to PU09 predesilication.