The first full scale Atoll metal recovery plant (MRP) in the USA commenced construction in Johnstown, Pennsylvania in November 2007 and was completed in 2008.
Known as Riders, the plant, which produces 500 t/month of high carbon ferromanganese (FeMn), is wholly owned by Atoll.
The Riders project is also significant in terms of its environmental benefits as it processes slag from a stockpile which, since its closure in 1977, has had no economically viable treatment options. With all of the slag a saleable product, both as metal and crushed slag, on project completion all of the stockpiled material will have been sold into the market, returning the area to its original contour and vegetation. The processing of the reserve in this manner therefore complies with the environmental objective of the Pennsylvania Department of the Environment to promote recycling of materials.
Furthermore, this zero effluent plant employs co-disposal of the slimes with the main aggregate tails stream, thus requiring no slimes dam. The crushing circuit is designed to minimise fines generation and the beneficiation process takes place in water, using no hazardous chemicals.
With a low operating and capital cost, the plant has an expected life of 10 to 15 years and processes some 25,000 t/month of slag. The technology employed in the plant comprises crushing, screening, jigging, classification and material handling, with the feed capacity of the crushing circuit being an average of 150 t/h and of the processing plant an average of 65 t/h. Of the product reclaimed, the metal is sold to the steel industry and the slag aggregate into the aggregate market and also possibly for use in acid mine water treatment.