The quarry, which employs 42 employees, covers 150 hectares between Metz and Thionville, markets around 800,000 tonnes of aggregates and receives 600,000 tonnes of inert soil per year. In its upper layer, it extracts Jaumont stone, yellow-gold in color, with which certain heritage works (such as the Metz Cathedral) were built in the region; and several strata of polystone limestone (crystalline and massive) in its lower layer, up to 300 meters deep.
Less jerky operation
“We had to commit to the path of decarbonization, consume less deposits and manufacture as many aggregates, and limit our use of water”indicates Jérémy Jean, the director of Vaglio. Historically, the Jaumont quarry used nine processing units, which were equipped with 11 heat engines. The most elaborate materials, such as washed sand, were transferred from one unit to another by truck.
From now on, a single installation is used for the manufacture of around fifteen products (washed sand, washed gravel for concrete, road gravel, stones, etc.) All the machines (crushers, screens, sand and gravel washing, sludge press .…) are interconnected. A controller assists the six operators, with 360 sensors, to optimize machine performance. Objective: put an end to load breaks, since some machines were going faster than others. Walkways, overhead cranes and closed buildings at the screening-crushing stations also help limit travel.
A more efficient sludge press
In addition to eliminating intermediate transport of products, La Grande ourse aims to rationalize the consumption of natural resources. The installation is equipped with three different scalping techniques which follow one another to remove as much clay as possible “and preserve as much lime as possible”. More stones can be processed. Furthermore, the dust generated inside the factory is now vacuumed up.
Another new feature is the installation of a more efficient sludge press, with the support of the Rhine-Meuse water agency. Injected under pressure, the clays recovered during the washing of the materials are compressed in the form of cakes in order to recover the water they contain. 17,000 cubic meters of water can be recovered each year and reinjected into the installation. The clay cakes are waiting for markets. Paths must be identified in the construction industry.
A very high voltage delivery point installed on site
By switching to electric, the quarry plans to avoid 1,000 tonnes of carbon per year. Enedis has installed a very high voltage delivery point (20,000 volts). Given the distance between the machines, up to 1.5 km or even 2 km apart, major earthworks and networks were carried out by NGE subsidiaries. “There was no real problem with integration into the electricity network, but we signed a load-shedding agreement, a voluntary approach on our part”specifies Jérémy Jean.
With the reduction in the number of mobile machines, the consumption of non-road diesel (NGR) has been reduced by 65%. Drilling-mining equipment, the transport of certain materials to the fixed installation (La Grande Ourse), and the loading of materials before leaving the factory still require the use of RNG. Faced with the change brought about by the transition from mobile machines to a fixed installation, certain machine operators are currently being trained to manage the entire process.
Source: www.usinenouvelle.com
