Situated in Anagni, a hilly environment some 100km southeast of Rome, the family-owned Marocca Costruzioni has exploited a limestone deposit since 1921. A wide variety of high quality aggregates are marketed for concrete, asphalt and roadworks along the Lazio and Toscana provinces.
The main challenge for Marocca is the large altitude difference between the new quarry face, situated 495m above sea level, and the stationary processing plant some 200m lower. The gradation along the quarry roads is more than 15 degrees.
Having tried conventional trucking to move the limestone after primary crushing down to secondary processing, it was quickly discovered that trucks were a costly solution, consuming many tyres and a lot of fuel. An alternative solution was crucial for the quarry?s future.
?Based on studies of available options, it became clear to us that Metso?s mobile primary crushing and conveying system would provide us with the biggest benefits and the capacity, economy and reliability we were looking for,? Marocca Costruzioni managing director Alberto Marocca said.
?With half a year?s experience now behind us, we are fully convinced of the benefits of the Metso mobile system. It works just as we expected and secures our profitable operation. As a bonus, we have gained a dust-free and safe quarrying environment.?
The 25 million tonne limestone reserve ensures Marocca?s operational future for several decades to come.
?The mobile system allows us to exploit our quarry with just minor modifications during the planned six phases, reaching up to the 525m level,? Marocca added. ?In fact, we have made a solid investment in our future.?
TRACKED CRUSHING SYSTEMS
Metso?s Lokotrack LT140 primary jaw plant started to crush the limestone feed in November 2012. The unit is connected to the two-piece LL12 series mobile conveyor system and further to the stationary, locally manufactured, 400m long field conveyor.
After just a week?s training, the Metso mobile system could reach a continuous crushing capacity of 800 tonnes per hour. The limestone feed contains a lot of fine materials. The LT140 was first run with a closed side setting of 160mm and was later increased to 200mm. With this, the fuel consumption of the primary unit fell by 10 litres per hour to 21 litres.
?Actually, the C140 jaw crusher can crush up to 1200 tonnes per hour,? Marocca said. ?Because of the steepness of our static conveyor, it gets overheated with bigger material volumes, so we limited the production to 800 tonnes per hour. As a side product, our static, downhill conveyor produces 220kW of electricity when operated.?
After the static conveyor, the limestone is fed to the secondary circuit by front-end loaders. When the tunnel feeder with new conveyors is completed, the Fosso della Foresta quarry will become truckless.