Converting waste heat into electricity: From steelworks to electricity works

Approximately 500 forging furnaces are operated in Germany – and this is already done very efficiently: approximately 35 per cent of the waste heat is sent back into the furnaces. By using the low temperature waste heat, even more would be possible – a research project with a forging company from Remscheid shows how electricity can be produced from this. A prestige project for Europe's largest steel-producing region, NRW.

At Grimm Edelstahlwerk in Remscheid, not everything revolves around steel: A steam turbine system transforms the low temperature waste heat produced into electricity. Organic fluids, vaporisable at lower temperatures, replace steam. "The technology is flexible, with low maintenance costs and start-up time", explains project leader Bernhart Stranzinger. "Which means it is exactly what we needed for the project."

Engine for progress:

  • the first system for converting waste heat into electricity at a forging company
  • net electricity yield of 200,000 kilowatt-hours in 2014 alone
  • savings of up to 570 tonnes of CO2 per year
  • reduction in electricity costs of up to 20,000 euro per month

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Photo: VDEh-Betriebsforschungsinstitut GmbH

Exterior view of the ORC plant at the Gustav Grimm Edelstahlwerke GmbH & Co. KG works: As ORC systems do not use water but rather organic fluids with a low evaporation temperature as fuel, they can also be used for the utilisation of low temperature waste heat. The procedure is used in particular, if the available temperature gradient between the heat source and the heat sink is too low to operate a turbine driven by steam.

The first plant of its type at a forging company, the highly complex installation has been successful

This first plant to generate electricity from low temperature waste heat at a forging company was erected by the Düsseldorf VDEh-Betriebsforschungsinstitut (BFI) together with the Grimm forging company: The procedure is called the "Organic Rankine Cycle", named after the Scottish physicist and engineer, William John Macquorn Rankine.

In the first step, the heat potential measurements were taken and a plant-wide energy management system was developed in order to be able to predict the waste heat capacity and the corresponding electricity production. In a further step, the researchers connected four of the five forging furnaces at Grimm to the system; no easy task: "The installation was highly complex", says the project team, "the ORC system, on the other hand, can be bought off the rack."

The procedure is transferred to further branches of industry

Now that the system is up and running, the climate is spared up to 570 tonnes of CO2 per year and Grimm saves up to 10,000 euro on electricity costs per month. Across the entire lifetime of the system, over 11,000 tonnes of CO2 can be saved. The BFI now wants to prepare a marketing strategy for further distribution. The ceramics, aluminium and cement industries are to use the procedure in the future. Other forging companies have already expressed an interest as well.

Photo: VDEh

"By converting waste heat from forging furnaces into electricity, up to 100,000 tonnes of CO2 could be saved in Germany alone."

Bernhart Stranzinger, VDEh Project Leader

Partners and sponsors

  • VDEh-Betriebsforschungsinstitut GmbH (BFI)
  • Gustav Grimm Edelstahlwerk GmbH & Co. KG
  • Bundesministerium für Bildung und Forschung (BMBF)