Four-stage processing

Portuguese contractor rosas Construtores has bought a Metso Minerals four-stage mobile crushing and screening plant for its work on the renewal of the 200 km IP5 highway between Aveiro and Vilar Formosa. This involves widening the existing two-lane highway into a safer four-lane motorway over a period of two years.

Rosas Construtores is responsible for producing 65000 tonnes of aggregate for a 9 km section near Talhades. The end product requirement specifies 0 to 50 mm aggregate comprising at least 35% of fines. In order to meet the end product and capacity demands, Metso Minerals Portugal recommended a mobile process comprising a primary, secondary and tertiary crushing plant and a mobile screen; the tertiary being necessary to guarantee the required amounts of fines.

At the primary stage the Nordberg LT110 mobile jaw crusher reduces feed material as large as 800 mm on its 140 to 160 mm setting. A secondary LT300HP with the proven HP series secondary cone crusher, reduces the granite further on a 38 to 42 mm setting. It is then sorted by a 4,8 x 1,5 m three-deck Nordberg ST356 screen.

The ST356 uses a 56 mm screen mesh, equipped with a conveyor to take the oversized 50 to 100 mm materials to the LT300HP mobile crusher, equipped with an HP tertiary cone crusher. After fine crushing with a 16 mm setting, the material is fed back to the mobile screen.

A capacity of 210 to 290 tonnes/hour is being achieved using the four-stage process, and the capacity varies according to the amount of fines in the feed material.