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Control and regulation of a tunnel kiln

The company

WISTRA GmbH, based in Düren, Germany, is a major plant manufacturer for sintering lines and industrial kiln plants for the production of technical ceramics. For more than 90 years, the company has been building complete firing lines and turnkey plants for the ceramics industry.

For the product "electroporcelain" alone, WISTRA has built more than 130 kiln lines. Other products include structural and electronic ceramics, LTCC ceramics, medical ceramics, grinding wheels and cutting tools.

In addition, WISTRA builds refractory sintering lines for silica, fireclay, ceramic-bonded magnesite or dolomite.

The customer base of WISTRA GmbH is distributed worldwide. Among others, the company has commissioned plants in Russia, USA, China as well as in the European area.

Task and solution

For the Brazilian company Magnesita, WISTRA built a tunnel kiln at the Kruft plant (Rhineland-Palatinate) in which refractory bricks are fired. In each of the six firing zones of the tunnel kiln, up to six burners are controlled to heat the zone according to the set temperature setpoint. The batches are fed through all zones via a hydraulic pusher. The bricks then pass through a cooling zone. A comprehensive, flexible automation solution was required for monitoring and controlling the individual temperature control zones and firing positions as well as the overall process.

To implement this task, a SIMATIC S7-300 is used as the control system. The PLC program is based on the standard library developed by focus (predefined blocks for controllers, motors, etc. of any kind). The visualization was created with SIMATIC WinCC V7.0. Standard elements from focus are also used here. By using the standards, the development time of the control program and visualization could be kept as short as possible.

In addition, project-specific modules were developed, e.g. for the control and operation of the so-called burner rotation. In this process, the individual burners of a zone are automatically controlled as required or according to the level of the set temperature. The aim here is to heat the burner zones as evenly as possible and to utilize the burners evenly. The system also controls the pressure for the induced draft and the forced drafts.

A SIMATIC Panel PC Touch, which is mounted on the outside of the furnace, enables the operating personnel to completely monitor the furnace and to change the corresponding parameters. This allows direct intervention in the processes of the plant depending on the user level. The coupling between control and visualization is done via TCP/IP.

The project in compact

Control and regulation of a tunnel kiln

  •     6 firing zones
  •     draught and thrust air control
  •     automatic door control
  •     hydraulic pusher
  •     monitored gas line

Automation technology

  •     SIMATIC WinCC as control system
  •     control system of the SIMATIC S7-300 series
  •     connection via Ethernet
  •     SIMATIC Panel PC