The Rheinkalk limestone works in Flandersbach, Germany, lies at the heart of the limestone belt in the Rhenish Massif shale formation. The plant is the largest of its kind in Europe and has six shaft kilns and four rotary tubular kilns in which the limestone is fi red and then held ready for transport in limestone collection silos.

As part of a modernization project, the transport system between the kilns and the bunker silos was to be brought up to the state of the art. The aim was to automate the largely manual control of the 254 different route sections. These route sections were previously controlled by two control stations that had to communicate with each other constantly to coordinate collision-free transport of the lime.

For Kristijan Rajic, project manager at Rheinkalk, the main focus of the project was clear: “The routing should no longer be the control station operator’s job but should be controlled automatically by management software.”

New field of application for standard software

The Rheinkalk plant in Flandersbach was already using the Simatic PCS 7 process control system. Trips GmbH, which was contracted to execute the project, therefore considered using the PCS 7 Route Control option for the automatic routing. The Route Control package had been used only for liquids transportation up to this point; however, extensive analyses revealed that the functionality of Route Control was suitable for implementation in the limestone works. The integration of Route Control into PCS 7 ensures trouble-free updates for newer versions of the control system. Simatic PCS 7 offers optimum diagnostic capabilities during commissioning with the system in operation and therefore enables the shortest possible reconnection times of the individual drives. In addition, all the routes can be simulated so that less time is necessary to perform the commissioning. There is also less engineering effort because the assignment management can be implemented with pretested software modules.

Optimum utilization of transport capacity

With the previous control system, a new transport request could not be authorized until all the route sections concerned were free. This meant that some route sections ran empty for long periods and therefore limited the transport performance of the plant. The adaptation of the Route Control standard implemented by Trips prevents these time losses: as soon as there is no more material on the conveyor belt, the route section is released for another requested material transport and the times in which the conveyor belts run empty are minimized. Fast transport times also increase the productivity of the plant because the material can now be transported faster to the appropriate lime collection silos. This measure alone increases the productivity of the conveyor system by approximately 30 percent and helps eliminate bottlenecks in the plant. Thanks to the new solution, material jams can be prevented before they occur.

Targeted quality management

Simatic Route Control also allows detailed recording of different product qualities and tracks them from their production in the kilns along the transport routes to their storage in the silos. This enables qualityspecific storage of the products for the first time, which provides Rheinkalk with a much more flexible business model for the marketing of its products. The Route Control software receives the appropriate quality identifications via a link to the automatic sampler in the laboratory and therefore knows what product quality is under way on which transport route. These quality identifications are also displayed on the Route Control faceplate so that the control station operator can see which quality is coming from which source (kiln). In the event of a fault, he or she can then convey the material on the belts manually to the appropriate collection silo after eliminating the fault, unless an alternative route can be determined automatically. The operator can therefore ensure that storage of the products continues to be strictly separated

Efficient support

For project manager Rajic, the automation of the transport processes was a big step forward, also as far as the user-friendliness of the processes was concerned: “The operators can now concentrate more on the key business, which is the kiln operation. This shows in the improved quality of the products.” The project manager at Trips is also impressed by the functionality: “The Simatic Route Control software helped us to reduce the configuration effort for this project by 25 percent and to cut the commissioning time to 20 percent of the normal time, thanks to optimum diagnostic and simulation options.”