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Water / Wastewater / Environment

Herhof GmbH

Renewal of the automation technology of a plant for the mechanical-biological waste treatment

The company

Herhof GmbH, based in Solms/Niederbiel, is the developer and manufacturer of the innovative "Herhof dry stabilate process" for the treatment and recycling of residual waste.

In the dry stabilate process, the amount of residual waste is reduced by removing water via biological drying processes. The mechanical separability of the material is also significantly improved. This novel process step distinguishes the dry stabilate process from all conventional processing technologies.

Inert materials (stones, glass, ceramics) as well as ferrous/non-ferrous metals and batteries are separated. This is associated with a significant reduction in the given contaminant content of the remaining dry stabilate.

Through this consistent removal of non-combustible materials, the remaining quantity - the dry stabilate - is at the same time decisively upgraded in its energetic properties. It is now comparable with fossil fuels.

The use of dry stabilate as a fuel sustainably conserves resources and reduces the impact on the climate.

Task and solution

The task was to replace the existing automation solution with 42 ifm controls, which regulate the complete rotting technology, the air management and the cooling circuit. Together with the Herhof process engineers, a solution with Siemens S7 components was developed.

The solution is implemented with a central control system (Siemens S7-400), whereby the I/O level is connected by means of decentralized peripherals (ET 200S) via PROFIBUS-DP and PROFInet-IO. The central control is connected to the server of the control system (Wizcon) via "Industrial Ethernet". The plant personnel can thus operate and monitor the complete plant from the control system in the central control room. Changes to plant parameters (setpoints) are also made via this.

An overview of the running time and the status of the five boxes is provided to the operating personnel via a graphic box calendar specially implemented in the control system. Important data such as throughput quantities, temperatures, etc. are written to a Microsoft SQL database via ODBC for evaluation purposes. With the integrated browser technology of the control system, access from the company headquarters in Solms via the Internet is also possible. Since the plant was already in operation, the complete conversion of the control technology had to be carried out during ongoing operation. Therefore, already in the planning phase, special attention was paid to design the distribution of the decentralized periphery in such a way that the existing ifm controls could be replaced 1:1 by the decentralized periphery without replacing the complete wiring in the control cabinet. This resulted in a significant time advantage during the conversion phase, as the installation work could be reduced considerably.

Thus, according to the specifications of the Herhof process engineers, individual plant sections could always be rebuilt and put back into operation without having to shut down the entire plant.

The complete rebuild phase took only 14 days and this without interrupting ongoing operation.

The project in compact

MBS plant

  •     investment 25 million
  •     capacity 90.000 t residual waste per year
  •     5 rotting boxes

Automation technology

  •     Siemens S7 400
  •     decentralized periphery with PROFIBUS-DP and PROFInet-IO
  •     connection to the control system via Industrial Ethernet