The Evolution of Soderberg Aluminum Cell Technology in North and South America

In the 1940s, the horizontal stud Soderberg cells were considered to be superior to the small 30-kA Hall prebake cells, which at that time operated at a lower current efficiency and higher energy consumption. The amperage was first increased on the Soderberg cells from 30 kA to 50-60 kA and then later to 90-120 kA by basically increasing the anode length and the number of anode studs. Due to the increase in demand for aluminum metal, the less expensive Soderberg smelters proliferated in the 1940s to the 1970s in North and South America. In the 1970s, 24 Soderberg smelters located in North and South America had a primary aluminum capacity over 3 million tpy. The largest operating Soderberg smelter, Companhia Brasileira de Aluminio, has a plant capacity over 470000 tpy and started the last new Soderberg potline in 2007. However, poor magnetics inherent with end-to-end Soderberg cell busbar design limited any further increase in amperage while the side-to-side prebake cells were able to operate more efficiently at 200 kA and higher. Compared with prebake technology, Soderberg cells are now less efficient and have higher production costs, they are more difficult to automate and they have the greatest environmental and health challenges. Health studies from the middle of the 1970s showing a clear link between Soderberg tar fume exposure and the incidence of various types of cancer lead companies to propose a program of replacement. As a result, today there are only five Soderberg smelters operating in North and South America with a capacity of < 1 million tpy.