Four-stage mobile crusher
Portuguese contractors Rosas Construtores recently opted for a Metso Minerals four-stage mobile crushing and screening operation for a highway renewal project.
With most north–south motorways completed, Portugal is now investing in highways facing towards the cities of Madrid and Barcelona in Spain.
One of these, south of Oporto, is the 200km long IP5 connecting the cities of Aveiro and Vilar Formosa, close to the Spanish border. Over a period of two years, the existing two-lane highway will be widened into a safer four-lane motorway.
Rosas Construtores are responsible for producing 65,000 tonnes of aggregate for a 9km section near Talhades. The end-product requirement specifies 0–50mm aggregate comprising at least 35% fines.
In order to meet the end-product and capacity demands, Metso Minerals Portugal recommended a fully mobile process comprising primary, secondary and tertiary crushing plants and a mobile screen; the tertiary unit being necessary to guarantee the required amounts of fines.
At the primary stage a Nordberg LT110 mobile jaw crusher operating with a 140–160mm setting is used to reduce the –800mm granite feed. A secondary LT300HP cone crusher operating with a 38–42mm setting is followed by a Nordberg ST356 mobile screening unit featuring a large, 4.8m x 1.5m, three-deck screen.
To secure the required amount of fines, the ST356, using a 56mm screen mesh, is equipped with a side conveyor that delivers oversized 50–100mm material into an LT300HP mobile tertiary cone crusher. After fine crushing at a 16mm setting, the material is fed back to the mobile screen.
A capacity of 210–290 tonnes/h is being achieved using this four-stage process, the capacity varying according to the amount of fines in the feed material.
‘We are very happy with the capacity of the mobile equipment, which is able to meet the special end-product requirements. In six months we have already produced 45,000 tonnes, which is more than expected,’ said Rosas Construtores’ quarry manager, José Antunes.
