Sewage sludge drying with High-End-Technology
SPANGLER – the Plus of energy generation.
Sewage sludge must not be used any longer as fertilizer in agriculture due to nitrate contamination. In dried form, however, it can be used as fuel, for example, for energy generation. For this reason, Stadtentwässerung Mannheim (urban drainage) modernizes the sewage sludge drying plant of its sewage treatment plant. Three belt dryers replace two existing drum dryers and thus at the same time expand the drying capacities.
The first drying line was put into operation in July 2020, the other two should follow after dismantling of the drum dryer by the end of 2021, respectively summer 2022.
Performance for permanent availability
By order of HUBER SE, SPANGLER Automation planned, programmed and produced the switch and control system for all three drying streets, including conveyor system and exhaust air treatment. A redundantly designed process control system ensures that the processes are permanently monitored, and the plant is permanently available.
High operational reliability
The main control, a Siemens PLC S7-400, is also redundantly designed as the process control system Siemens SIMATIC PCS7, with which the plants are operated per HMI. A generously dimensioned power supply buffers so much electrical energy that all required PCs can continue their operation without any interruption in case of voltage breakdown. Furthermore, a low voltage main distribution takes care that the power supply plant in case of failure automatically switches to the second power supply to avoid any interruptions. For control of all drying streets, forty control cabinet fields, ten sub-distribution boxes directly at the machines, four control cabinets for the low voltage main distribution, and two IT panels were installed. Compliance with the machine safety directive is ensured by a
PROFIsafe bus system (210 nodes) to which all frequency converters are connected.
“The Siemens PCS7 and the redundant systems are highly available equipment and in connection with the bus system provide a very high safety level, “ Spangler project manager Anton Höcker describes the result of the high effort.