JCF is recultivating the decommissioned Oberegg quarry
What do cement manufacturers do with their quarries once the limestone they contain has all but run out? Move on and simply dig the next hole elsewhere? That was out of the question for Jura-Cement-Fabriken AG (JCF). Although the company needs to develop new quarrying areas, it is committed to sustainability and also to transparency and close consultation in dealings with the neighboring communities. To minimize the open limestone quarrying area, JCF has undertaken to fill in decommissioned quarries in the future and then to recultivate these for use as local recreation areas or arable land. Furthermore, the company has promised to significantly reduce the energy consumption and CO2 emissions of its plants.
JCF’s first big project to fill in a quarry is Oberegg, which belongs to the Wildegg cement plant. Limestone extraction started there at the end of the 1960s. The quarry is now exhausted and the hole, which is currently 3 million cubic meters in size, is gradually to be filled in again over the next 15 – 20 years.
Most of the fill material comes from rail tunnel projects in the region
There is no lack of suitable clean fill material in a country like Switzerland, where numerous tunnel projects and other construction sites generate large quantities of excavated material. Why should excavated rock, rubble and earth end up simply being dumped when it can be put to good use elsewhere as fill material? After all, both tunnel construction and mining operations benefit if excavated/extracted material becomes sought-after fill material.
This fill material is transported by rail directly from the tunneling machine to the cement plant, where it continues its journey on a 2.5 kilometer conveyor line leading to its final destination deep in the quarry. In addition to the trackside loading station, the conveyor system itself has four loading stations – one for the train bringing the excavated tunnel material, one for trucks delivering excavated material from smaller building sites (home-building projects, for example) and two buffer stations for material that needs to be processed (mixed and/or dried). The problem with this is that the loading stations are not necessarily all running at the same time. The amount of material being sent to the quarry varies depending on where the material is coming from and how it is being supplied, and the four stations load different volumes of material onto the belt.
Fully automatic control of the belt speed
The two mechatronic industrial gear units are installed on the drum of the penultimate belt in the conveyor line and drive the belt via a joint drum. Fully automatic control of the speed ensures that the different volumes of material always reach the delivery point deep in the quarry with a consistent belt fill level.
Jürg Hitz, who is in charge of maintenance and engineering at the JURA Materials Group, is highly satisfied with the result:
“For many years now, jura cement conveyor systems have been equipped with drives from SEW-EURODRIVE. Based on our measurements to date, the two new mechatronic industrial gear units and fully automatic control of the belt speed are delivering energy savings of up to 40%. Let’s see when we switch the rest of the system to SEW-EURODRIVE’s mechatronic industrial gear units.”
In a mechatronic industrial gear unit, all components – from electric drive and gear unit to decentralized control electronics – are combined in one single self-contained industrial gear unit and are connected and networked when they leave the factory. This means there is just one power connection. There is no easier or quicker way of installing an inverter-controlled industrial gear unit solution.
The main advantage, though, is that the linked sensor technology can monitor, evaluate and thus flexibly influence the status of both the drive and the conveying process. This is ideal for optimizing the customer process by controlling the belt speed fully automatically, for example.
For the conveyor system in the quarry, this means the following:
- In contrast to the industry-standard S1 duty cycle with a constant speed, cement plant operators can now control the belt speed fully automatically in line with their requirements.
- JCF can thus significantly reduce its energy consumption and save on annual costs, not to mention benefiting from lower CO2 emissions.
- The adapted belt speed also results in far lower noise emissions.