The primary aluminium reduction plant, where the actual metal production takes place, constitutes the main part of the SALCO project.
This part of the complex mainly comprises two potrooms, which are the buildings housing the group of cells in which aluminium is produced by electrolytic reduction. Each of the potrooms will be 888 meters long.
The two parallel potroom buildings will house two rows of electrolytic cells, known as potlines. Each potline consists of 252 cells, making 126 cells in each potroom .
The cells are being designed according to SAMI's SY-400 technology and will operate at 400 kA.This will provide a production capacity of 276,000 tonnes per annum. A sophisticated logistics system handles the raw materials in and the liquid metal out:
• Alumina is fed through a closed system
• A high-voltage system supplies electricity via busbars
• Anodes will be installed using advanced cranes
• Mobile tapping vehicles transport liquid aluminium to the casthouse
• Mobile pallets handle the spent anode butts
There will also be several utility functions associated with the plant, including:
• Rectifiers to supply DC current to the potlines
• Fume treatment plant, comprising dry and wet scrubbers
• Cell relining workshop
• Crane service workshop
Second Phase :
This part of the complex mainly comprises two potrooms, which are the buildings housing the group of cells in which aluminium is produced by electrolytic reduction. Each of the potrooms will be 1,070 meters long.
The two parallel potroom buildings will house two rows of electrolytic cells, known as potlines. Each potline consists of 288 cells, making 144 cells in each potroom .
The cells are being designed according to SAMI's SY-400 technology and will operate at 400 kA.This will provide a production capacity of 310,000 tonnes per annum.
The carbon plant manufactures carbon anodes, which are a vital part of the primary aluminium production process. It consists of a paste plant and an anode baking plant. From its start-up, the carbon plant will produce approximately 150,000 tonnes of anodes per year for 1st phase and 180,000 tonnes of anodes per year for 2nd phase for use in the potlines.
Anodes are made from petroleum coke, recycled butts and pitch. Butts are the residual carbon part of spent anodes. The coke and butts are crushed and screened before different quantities are mixed with pitch at about 180°C and formed into “green” anodes. Each anode weighs about one tonne.
The “green” anodes are baked at about 1200°C before being used in the electrolytic cells.
The production of one tonne of aluminium requires about 0.5 tonne anodes. Approximately 63,000 tonnes butts per year will be recycled at the plant.
Both the paste plant and the anode baking plant will be equipped with state of the art fume treatment plants to minimize emissions.
The anode service plant consists of the bath cleaning plant (BCP) and the anode rodding plant (ARP). Spent anodes are cleaned in the BCP. Bath residues are recycled to the potline and butts are recycled to the paste plant. Anode hangers are cleaned in the ARP and checked before new baked anode blocks are attached. The complete anode assemblies are then returned to the potline.
The SALCO casthouse has been designed to produce 320,000 tonnes of cast products for each phase per year. Its main products will be extrusion ingots and foundry alloys. The casthouse will also house equipment for producing standard primary ingots.
Molten aluminium from the potlines is transported to the casthouse in crucibles by special tapping vehicles. Before entering the casthouse, the molten aluminium is treated in fluxing stations where sodium and impurities are removed. Fluxing is carried out in the crucibles by means of a special patented process.
Using gas-fired furnaces
After the fluxing process, the molten aluminium is discharged from the crucibles into gas-fired mixing furnaces, alloying elements and some solid aluminium casting. The molten metal is quality checked and thereafter transferred through a launder system and a in-line filter refining unit for the effective removal of hydrogen and inclusions.
The molten metal is cast in the form of both foundry alloys and extrusion ingots. After the casting process, the ingots are automatically marked, stacked into bundles , weighed and packed for storage and shipment . Extrusion ingot casting takes place in vertical , direct chilled casting machines . consisting of water-cooled casting moulds of different sizes suitable for casting a large number of ingots, or logs, in the required lengths.
After casting, the logs are heat-treated in homogenizing furnaces, sawn to the required length, marked, bundled, weighed and transferred to the storage area ready for shipment.
The SALACO power plant will be a combined-cycle power plant with the capacity to supply 750 MW to the aluminium plant for 1st phase .
Since a power supply interruption of more than a few hours may result in severe damage to the aluminium production process.The power plant has to meet some very high requirements for power supply regularity, power plant design will therefore include spare capacity in the form of one generator unit. There will also of additional back-up from the national grid with 400 KV and 600 MW.
Gas and steam turbines
The configuration includes four gas turbines and two steam turbines operating in a combined cycle. Total installed capacity will be approx.750 MW.
The design is to be based on best available technology (BAT); i.e. low NOx burner technology, in combination with selective catalytic reduction (SCR), in order to comply with local emission standards. Furthermore, a cooling tower system has been selected that minimizes the plant’s total cooling water requirement.