George William Morgenthaler
Engineers at Lakeridge Trl, Boulder, CO

5222448, Jun 29, 1993

Apr 13, 1992

7/868024

George W. Morgenthaler - Boulder CO
Jeffrey L. Struthers - Falls Church VA
George W. Carter - Gloucester, CA

Columbia Ventures Corporation - Vancouver WA

F23G 704

110346

Spent potliner from aluminum reduction cells includes carbon, inorganic brick and refractory material, and fluoride, sulfur, and cyanide compounds, and is considered hazardous. It is treated by introducing it into a vessel, and exposing it to the heat of a plasma torch at a temperature of at least 1000. degree. C. As a result, carbon is gasified and converted to combustible carbon monoxide or hydrocarbons, or to carbon dioxide; inorganic material is melted form slag; fluoride compounds are melted, vaporized, or reduced to gaseous HF; cyanide compounds are destroyed; and all other materials, including sulfur compounds, are either melted or gasified. As a result, the spent potliner is rendered non-hazardous, and the quantity of remaining slag has both its solid volume and mass substantially reduced by a factor of at least 1. 5:1 in mass and at least 3:1 in volume relative to the input spent potliner. The process allows gaseous fluoride compounds to be captured and thermal energy produced in the process to be extracted.