Process
Acid Plant
The Acid plant complex consists of production facilities to produce 0.6 million tons of phosphoric acid and 2 million tons of sulphuric acid per year. Acid site units, known as Darou 1 and Darou 2 are located at Darou near Mboro, approximately 100 km from Dakar. The acid site is located ~100 km north of Dakar. It is well connected by road. A rail line connects the mine site & Dakar port for transport of Acid, Sulphur & concentrate.
The main steps in the manufacture of Sulphuric Acid from elemental Sulphur consists of burning of elemental Sulphur to Sulphur dioxide; then converting Sulphur dioxide to Sulphur trioxide in the presence of Vanadium Pentoxide catalyst and finally absorbing Sulphur trioxide in the Absorption towers to form strong Sulphuric Acid which is diluted to 98.5% concentration by addition of water.
Process Diagram
Facilities at a Glance:
| DAROU 1 |
|---|
| Commissioning : 1984 |
| Engineering : KREBS and Cie. |
| Nominal Capacity : 300,000 Tons P2O5 / year |
| 1 Sulphuric plant. Capacity : 3000 tH2SO4/day |
1 Phosphoric plant. Capacity : 1015 tP2O5/day.
|
| 1 Utility plant with 2 turbo Generators |
| DAROU 2 |
|---|
| Commissioning : 2001 |
| Engineering : KREBS-SPEICHIM / TECHNIP |
| Nominal Capacity : 300,000 Tons P2O5/year |
| 1 Sulphuric plant. Capacity : 3000 tH2SO4/day |
1 Phosphoric plant. Capacity : 1015 tP2O5 / day
|
| 1 Utility plant with 1 turbo Generator |
Process description:
Both Phosphoric Acid plants are Rhône-Poulenc Di Hydrate based process. Belt conveyors transport rock phosphate concentrate from the flotation plant to the acid site battery limit. The rock phosphate and a measured quantity of 98.5% sulphuric acid get charged into the reactors. Over flow slurry from the reactors gets fed to the UCEGO table vacuum filter. The weak acid (28% P2O5) from the filter is sent for clarification & the overflow from the clarifiers is sent to the evaporators to produce merchant grade phosphoric acid (52% P2O5).
Gypsum is conveyed & stacked through advanced gypsum thrower equipment.
Merchant phosphoric acid is transported through rail cars to sea for export.