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Heating the Cold Rolling Mill in a Climate-Friendly Manner

In order to change the metallurgical properties of products, they are heated up to 700 °C. The heat escaping during the subsequent cooling process often goes unused. As the first cold rolling mill to do so, the BILSTEIN company from Hagen now uses an ORC system (Organic Rankine Cycle) in order to exploit this energy to generate electricity and heat. This technical expansion has increased the energy efficiency of the annealing system by 39 per cent. This saves the plant around 1,300 tonnes of CO2 per year.

Although the ORC process has been around for quite a while, it is not consistently used in industry. BILSTEIN GmbH & Co. KG together with the Ascentec and DeVeTec companies has developed an ORC solution specifically designed for the cold rolling mill, which is both economical and climate-friendly. The new system removes heat from the gas circulating in the bell-type annealing system and transfers this heat to the working fluid of ethanol. Instead of the usual ORC turbine, the evaporating ethanol then drives a piston engine. Thermal energy is converted into mechanical energy, which drives a generator. This then converts the mechanical energy into electrical energy.

Engine for progress:

  • uses "waste heat" above 200 °C with the ORC process
  • 1,300 tonnes of CO2 saved per year
  • a perfectly tailored solution for small and medium-sized enterprises
  • saves 900,000 kWh of electricity and 4 million kWh of heating and process energy

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Photo: BILSTEIN GmbH & Co. KG

The ORC engine for generating power is found in the compact container on the right. The generator is fitted at the rear. The steam generator is in the left part, which is where the ethanol is evaporated.



Economic Opportunities for SMEs

The technology used here exploits the use of "waste heat" at temperatures of between 200 and 400 °C. Typically, this heat simply remains unused and is released into the surrounding environment. With the ORC system, a high level of efficiency can be achieved for a comparatively low investment. The piston engine in the ORC system can even work with discontinuous heat input, which is what distinguishes it from a turbine. For NRW, a state that is strongly characterised by industry and is home to many metal processing companies, this technology can play a key role in the economic reduction of greenhouse gases, especially in small and medium-sized enterprises.

Energy Used on Site

BILSTEIN uses the self-generated electricity exclusively on site. The company uses the thermal energy generated, for example, to heat the building. In total, the cold rolling mill saves up to 900,000 kilowatt-hours of electricity and four million kilowatt-hours of energy for heating and process heat annually thanks to the efficiency increases.


Photo: BILSTEIN GmbH & Co. KG

"Our goal was to catapult the efficiency of the bell-type annealing system we wanted to install to be state-of-the-art using cutting-edge automation technology and innovative energy technology. As a result, we see a system configuration that is unique worldwide, which achieves this goal and documents the future viability of our company in terms of competitiveness and environmentally-conscious behaviour."

Gerald Zwickel, Technical Director , BILSTEIN GmbH & Co. KG


 



Partners and sponsors


Partners:
  • BILSTEIN GmbH & Co. KG
  • DeVeTec GmbH
  • LOI Thermprocess GmbH
  • Ascentec GmbH
Sponsors:
  • Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit (BmUB)