The LCLL Process: A Sustainable Solution for the Treatment and Recycling of Spent Pot Lining

摘要

Spent pot lining (SPL) is a hazardous waste generated from the internal lining of Al electrolytic pots consisting of carbon and refractory bricks. This residue is classified as a dangerous waste mainly because of its contamination by fluorides and cyanides, and its reactivity with water, generating explosive gases. Over the last several years, the aluminum industry has made some progress on the SPL issue by recognizing that landfilling in unlined sites is no longer acceptable to most local communities. In 2008, Rio Tinto inaugurated a new plant in Jonquiere, Quebec for the treatment of spent pot lining, based on the "Low-Caustic Leaching and Liming" process (LCL&L) developed at the Rio Tinto Arvida Research and Development Centre in the early 1990s. This plant treats 80 kt of stored and fresh SPL annually. The hydrometallurgical treatment detoxifies SPL and produces inert by-products, which are then used as raw materials in industries such as the cement industry. This paper describes the LCL&L process characteristics, including valorization routes for its by-products and some recent process improvements to reduce treatment costs with improved energy efficiency.