Basic Technical Data Often Used in Design Calculations of Alumina Refinery

Hi Friends,

In this paper, we will present a few important data which are essentially required for carrying out process design calculations including material balance, thermal energy balance and sizing calculations for various equipment including pipelines of Alumina refinery as outlined here under:

·         Alumina means Al₂O₃ having molar mass = 2x27+3x16=102 g per mole.

·         Hydrated alumina means Al₂O₃.3H₂O having molar mass= 102+3x18=156 g per mole.

·       Thus 156 tonnes of Hydrate alumina = 102 tonnes of Alumina, this implies 1 tonne of Hydrate is equal to 102/156 = 0.65385 tonne of alumina.

·         Specific gravity of dry hydrate = 2.42

·         Specific gravity of dry Bauxite = 2.55 to 2.80

·         Bulk density of alumina = 0.95 to 1.05 tonne per m³.

·         Bulk Density of Bauxite = 1.20 - 1.30 t/m³.

·         Molar mass of Na₂CO₃ =106 gm/mole;

·         Static Angle of Repose of Bauxite = 30 to 32 degree

·         Dynamic angle of repose of Bauxite = 19 to 20 degree

·         Molar mass of Na₂O = 62 gm/mole

·         Molar mass of NaOH = 40 gm/mole

·         Hardness of Bauxite = 2.5 to 3.0 Moh

·         Bond Index = 10.5 t0 18 kW/st

·         Specific Gravity of dry bauxite residue (redmud) = 2.30

·         Velocity of slurry in pipe line = 1.5 to 2.44 m/sec.

·         Design velocity of steam in pipeline = 20 to 40 metres per sec.

·         Domestic Water requirement in township = 135 litres / capita.day

·         Potable Water requirement in Industries = 65 litres / capita.day

·         Sewage generation rate = 96 litres/capita.day.

·         Solid waste generation = 0.90 kg/ capita.day

·         Stack Height (in metres) = 14 x (Q)^0.3;  where Q = Emission rate of SO₂ in kg/hr.

·         Total water for Alumina Plant = 6.5 to 10 m³/tonne alumina

·         Norms for Green belt = 25% of total plant area (min.)

·     Residue Factor is the ratio of sum total oxides in Bauxite to sum total oxides in residue (red mud) which gives tonnes of residue generated per tonne of Bauxite processed. Residue generation rate with respect to alumina production varies from 1.10 - 1.35 tonnes residue per tonne of alumina. Higher residue factor signifies either poor quality of bauxite or lower alumina recovery or both.

Hope, all major input data have been covered here. We will appreciate your valuable remarks / comments, if any.

Best regards.

Rajendra Kunwar

www.ceti.co.in