Monetary Benefits by Reduction in Extraneous Dilution to Alumina Refinery

Hi Friends,

In present post, we will discuss the monetary impact of extraneous dilution to Bayer process in production of alumina and possible steps to control and minimize the extra water intake to process for converting the losses into monetary benefits. To analyse the dilution problems in Alumina refineries, let us run through the various process areas for identifying the major sources of extraneous dilution to process. The major sources are listed below-

1. High moisture in Bauxite fed to grinding unit,
2. Direct injection of steam to desilication tanks, digesters and causticizers,
3. Ingress of rain water to process areas,
4. Equipment flushing water to process,
5. Entry of gland seal water of rotating equipment,
6. Occasional hosing of floors of process areas,
7. Extra water intake for residue washing,
8. Extra water draw for hydrate washing,
9. Leakages in valves of fresh water line provided for intermittent washing of sight glasses and demisters of evaporators,

Extra dilution to process means additional evaporation load and thus high fuel consumption for meeting additional steam requirement. In earlier posts, we have already discussed in detail break up of water required for various process areas of Alumina refineries. 

Now let us assume a hypothetical and small reduction in fresh water to plant by 0.25 m3 per tonne of alumina which can easily be achieved, if we so desire, in any operative Alumina refineries of the World. Other assumptions for evaluating the monetary benefits are listed below-

(i) Fuel for steam raising is coal,

(ii) Calorific value of coal is around 5500 k.cal per kg,

(iii) Steam coal ratio in Boilers = 5.0,

(iv) Coal for bank firing = 4%,

(v) Issue price of coal = US$ 80 per tonne,

(vi) Steam economy in Evaporators = 4.0 .

With these assumptions, direct monetary benefits for a 1.0 Mtpa Alumina refinery works out to around US$ 1.04 Million per year. In addition to this indicated monetary benefits, there are many indirect advantages like higher liquor productivity across precipitators because of higher concentration profile which will result in reduction in specific electrical energy consumption per tonne of alumina production. Thus, it's worth taking steps to minimize extraneous dilution to process for substantial savings.

It is evident from above discussions that awareness of plant operating personnel and constant vigil of managerial staffs irrespective of their area of activities can contribute a lot in dilution control to process resulting in improving the profitability of the plant. 


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Thanks and regards.

Kunwar Rajendra