AP Technology
AP technology surpasses all records for reliability, efficiency and productivity. Offering world class environmental, health and safety improvements, AP technology is the aluminum industry's cleanest technology with the lowest cost.
World wide, Rio Tinto Alcan delivers the industry's most comprehensive smelting AP technology and engineering with a century of aluminum production.
The result is a technological powerhouse with unrivalled expertise in operating smelters with sustainable, reliable and proven per tonne cost.
With its complete and bankable power-to-product solution, Rio Tinto Alcan is the company of choice for the world's leading aluminum manufacturers, enabling competitive operating cost for the industry.
Benefits:
- Rio Tinto Alcan holds a significant advantage through technology both for efficiencies and external sales.
- GHG emissions in AP technology, based on IAI 2003 Survey results, generated by this technology are among the lowest in the world.
- Technological leadership is supported through Rio Tinto Alcan's investment and economic cost reduction.
Rio Tinto Alcan technological leadership is realized in all aspects of our smelters operations and performance as it sustains industry benchmark in energy efficiency, productivity, high amperage cell technology. It has been the premier feature of many successful financing schemes of smelting technology available today.
Today AP technology is leading in all aspects of operations. Operating cost is at the lowest part of the industry cost curve; Installed capacity outside of China over the last two decades primarily uses AP technology; AP technology is the industry benchmark for energy productivity and sustainability creating exceptional value and competitiveness.
GHG emissions in AP technology based on IAI 2003 Survey results, generated by this technology are among the lowest in the world.
Rio Tinto Alcan holds a significant and unique advantage through technology both for internal use and development which leads to external sales.
The sale of AP technology offers Rio Tinto Alcan cash flow benefits as the technology licensing fees are usually paid in the beginning of a project.
By leveraging our technological and industry leadership through the development of a new path of ownership configuration for investment purposes, the risk is minimized for Rio Tinto Alcan.
Aluminum Production Process
How Aluminum is made
Aluminum is produced by the electrolytic reduction of alumina through a process known as the Hall-Heroult process. In this process, an electric current breaks down the alumina, causing the aluminum and oxygen molecules to separate. This reaction takes place in large cells or "pots", through which an electrical current is passed. The bottom and sides of each pot act as the cathode or negative electrode and contain the molten bath, composed mostly of cryolite and aluminum fluoride, in which the alumina is dissolved. Carbon blocks suspended just above the cathode, serve as the anode or positive electrode. When the electrical current passes through the mixture, flowing from the anode to the cathode, the molten aluminum molecules settle to the bottom of the "pot" while the oxygen combines with the carbon of the anode. The carbon anode is continuously depleted by the reaction and must be replaced. The molten aluminum deposited at the bottom of the "pot" is removed regularly using a vacuum siphon. It is then transferred to a holding furnace where it is alloyed, fluxed and degassed to remove trace impurities. From the holding furnace, the aluminum is cast in different shapes depending on end use and customer requirements.
There are two different technologies of the Hall-Heroult process - Soderberg technology (originally used in Kitimat) "Creates and Bakes" the anodes in place in each pot. The tops of the pots are uncovered and the sides, although normally closed, must be opened regularly for variety of process operations. Pre-bake technology "Creates and Bakes" the anodes in a separate facility. The pots are totally enclosed and most process operations occur without opening the pot enclosure.
Smelter expansion technology
The Kitimat Modernization Project Team will use the newest most modern AP pre-bake technology, originally developed by Pechiney (AP) and acquired by Alcan Inc. in 2004, and more recently by Rio Tinto Plc. for the modernization of Kitimat Works. High energy efficiency, computer control, low emissions, efficient dry scrubbing (cleaning) systems, and high levels of material recovery are features of this technology.
The modernization will consist of up to 366 pots housed in six buildings, increasing Kitimat’s current production capacity by 125,000 tonnes per year. The pots would operate better than 360,000 kA. They would be serviced by overhead cranes. By way of comparison, the existing Kitimat Smelter has a total of 900 smaller pots in 15 buildings with a total rated capacity of about 275,000 tonnes per year.
Raw materials that would be used in the process include: alumina from Australia; liquid pitch from Korea; and calcined coke from our Strathcona Plant in Edmonton, Alberta.
Alumina is stored in silos until it is required. Before being used in the process, the alumina is fed through devices known as dry scrubbers where it functions as a scrubbing medium to clean emissions.
The petroleum coke (carbon) and liquid pitch will be mixed together to form green anodes. Emissions from this process will be collected and dry scrubbed (cleaned) using coke as a scrubbing medium. The coke would then be reused in the process.
The green anodes will be baked using natural gas fires. All emissions will be collected, and any tars present, incinerated in the natural gas fires, then dry scrubbed using alumina. The alumina will then be reused in the process.
The baked anodes will be used to replace those that have been consumed in the pot. Partly consumed anodes (called butts) would be recycled back into the process as carbon.
In a pre-bake pot, alumina additions and anode effect treatments will take place within the totally enclosed pot. Removable doors will provide access for anode replacement. Emissions generated by the process will be contained within the enclosed pot and drawn off by an emission collection system. Treatment will be carried out in dry scrubbers. Emissions captured by the scrubbing process will be returned to the production process for re-use.
Aluminum smelting is a dry process with water being used only for cooling purposes. Sanitary sewage discharge will be pumped into the District of Kitimat sewage treatment facility while the surface runoff will be collected in retention ponds and then released.