Indian Aluminium Company Limited, Alupuram Smelter Eloor.

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The Dorr Oliver single tank reaction system is employed here.
The slurry formed during the reaction is fed to the filter for separation of gypsum
from phosphoric acid.
Counter-current washing of the cake is carried out with 10 to 12% acid, secondly 3 to
5% acid and finally with water. Wash acid of strength 19%is returned to the reaction
system. The filtrate of strength 20 to 22% is sent to storage.
The byproduct gypsum is slurried with water and pumped to the Sulphate plant.
4.Ammonium Phosphate
Phosphoric acid, Sulphuric acid and gaseous ammonia are fed to a saturator and
agitated. Further addition of ammonia is done in the second saturator. The neutralized
product is a thick slurry and flows to a blunger where it is mixed with undersized
granules; crashed granules and recovered dust, along with some urea. The granulation
takes place in the blunger.
The liquid ammonia at a pressure of 15 psi (g) and 18 o C is injected to the blunger to
adjust the mole- ratio to 1.8.The amount of dry material recycled to the blunger is
about 6 to 10 tonnes per tonne of dry material produced .The blunger which operates
which on fludisation technique is of a double shat paddle mixer set on a slope .The
granulated wet product from the blunger flows through a chute to rotary co-current
drier when the material is dried by a current air along with combustion products from
a combustion chamber. The material leaving the drier is conveyed to set of vibrating
screens with 8 and 14 mesh screens. The –8 and +14 material is taken out as the
product. The +8 material is crushed and, along with –14-mesh material is fed back
into the blunger .The hot airflow is maintained through the driver by fan. The dustladen
air leaving the drier fan passes through a multiple cyclone where the bulk of the
dust separates out. The dust coming from the screens and other equipments is driven
out by a dust fan through a cyclone. The air from the drier cyclone and dust cyclone
along with the fumes leaving the reaction tank enter the scrubbers for removal and
recovery of ammonia and dust. The scrubbing is done with phosphoric acid. The
scrubber solution is fed back to the reaction tank. The product is bagged and sent to
storage.
5.Ammonium Sulphate
The Ammonium sulphate solution fed to the unit consisting of two separate streams
from the Caprolactum Plant of Petrochemical Division .One feed stream is Lactum
ammonium sulphate solution and the other feed stream is Oxime ammonium sulphate
solution. This plant consists mainly of the following four sections.
1. Concentration and crystallization section
2. Dewatering section
3. Drying and cooling section
4. Storage and bagging section.