In-Situ Salt Cake Recycling
Aluminium is, due to its properties, the second most used metal after iron. It is used in a wide number of products and sectors, either alone or as an alloy. Recycling is a major aspect of continued aluminium use, as more than a third of all the aluminium currently produced globally originates from old, traded and new scrap. The global aluminium recycle volume in 2009 was 18 million metric tons, and regardless of the recession these volumes continue to grow 5-6% a year.
Traditionally, the recovery of the aluminium metal has been performed using the rotary salt furnace (RSF) process, which produces salt cake as a bi-product. Typically, salt cake contains aluminium metal (5-20%), a salt-flux (NaCl+KCl) mixture (40- 55%), and aluminium oxide (20- 50%) and other non metallic products (NMP 2-8%)6. Depending on the quality of scrap or dross between 300kg and 1,000kg of salt cake is produced for each 1,000 kg processed.
Every year, several million tonnes of salt cake is produced globally and this number is growing with the increasing use of aluminium, particularly recycled aluminium.
Around 95% is landfilled, costing an estimated €80 million. In the UK alone, where costs are spiralling as a result of tighter.
Salt cake is a growing environmental problem. It has to be cooled in house to reach a safe temperature for transportation before being able to be transported to salt cake recycling facilities.