Waste Heat Recovery


Industrial exhaust gases from industrial combustion processes or hot exhaust air have a high potential for waste heat recovery. Both the temperature and the volumetric flow of the exhaust gases are decisive. The higher these values, the more energy can be recovered. Whether the heat released can also be fully utilized depends on the process medium. Within the scope of our plant engineering we develop innovative, functional and reliable systems tailored to your requirements – even for particularly demanding and extremely complex plants, including the necessary control engineering. The project planning, design, development and construction are based on our own process expertise and created using CAD systems. Individual process engineering components and devices are also built to order.

Under the umbrella of ROTAMILL GmbH, we bundle the comptences of energy recycling and exhaust air purification. With the expert knowledge of the former Schirm Wärmetechnik, our experts develop efficient solutions for energy- and waste heat recovery.

Potential for waste heat recovery


Cogeneration uses waste heat or steam, i.e. for heating purposes, as local and district heat or as process heat. Heat and power are generated simultaneously. Thus, the primary energy consumption can be considerably reduced.

Even at waste heat temperatures of 200 °C, cogeneration is sensible. Let our experts inform you about the latest trends at our energy audits.

Example: KWK plant at Euroglas in Osterweddingen

  • Exhaust gas: 100,000 Nm³/h, 550 °C
  • Steam: 16.2 t/h, 42 bar, 425 °C
  • Power generation: 3.1 MW

Exhaust gases can be used to preheat water. The simplest form is by supporting the heating system. The return water of the heating circuit with a temperature of about 60 °C is raised to 80 °C in a controlled manner by means of an exhaust gas heat exchanger. The boiler requires less fuel and can often even be switched off completely.

Example Warm Water Generation:

  • Exhaust gas: 8,000 Nm³/h, 300 °C
  • Warm water: 20 t/h, 90 °C, 3 bar
  • Power: 450 kW

It is also possible to generate hot water. In this case, the water is raised to more than 110 °C at a higher pressure and can also be used for heating purposes. It is also possible to operate adsorbers for cooling or compressors.

Example Hot Water Generation:

  • Exhaust gas: 38,000 Nm³/h, 470 °C
  • Warm water: 110 t/h, 190 °C, 24 bar
  • Power: 3,800 kW
Steam generation

Higher temperature exhaust gases can be used to produce steam. Due to its high temperature, the steam can be used in many different ways for heating processes.

Example Steam Generation: KWK plant at Euroglas in Osterweddingen

  • Exhaust gas: 100,000 Nm³/h, 550 °C
  • Steam: 16.2 t/h, 42 bar, 425 °C
  • Power generation: 3.1 MW

Why does steam contain so much energy?

To find out how much energy is in steam, you can conduct a short experiment: Take a saucepan filled with 2 litres of water and place it on a hotplate. Set the hotplate to the highest heating level. After a few minutes the water has warmed from 10°C to 100°C and starts to evaporate. Now wait until all the water has evaporated. It is highly likely that you will have to wait longer than half an hour.

The energy required for evaporation is much higher than the energy required for heating. This effect can also be used the other way around. If the steam is collected and led to different consumers, it can condense there. The thus set free energy is very high. The condensate will remain and will be carried back to the steam generator to be used again.

Thermal Oil

Thermal oil is a suitable heating medium wherever heat can be thermally converted into power in a power range of approx. 5,000 – 9,000 kW. Below this range, the plants are no longer profitable. Above this range, power generation using a steam turbine is more effective.


  • Power generation with ORC modules
  • Preheating
  • Heating of buildings

Range of use:

  • Ventilation and process systems for polluted and aggressive exhaust air
  • Air / air for process air
  • Air / water for hall heating
  • Air / water for process water heating

Heat recovery systems recover energy from the exhaust air via air/air and air/water heat exchangers and return it to the process as warm air for machine and hall ventilation. The heat recovery systems we supply recycle the sensitive and latent heat. Glass tubes or stainless steel tubes mounted in special seals are used as heat exchanger surfaces. These guarantee a long service life and easy cleaning.

Waste Heat recovery, according to temperature ranges: