The Innovation:

Hybrid Boilers or Self-Fired Waste Heat Boilers

The hybrid boiler is the extremely well thought-out combination of steam boiler and waste heat boiler and has an additional flue tube pass for waste heat utilisation in addition to the design known from the flame tube boiler.

The conventionally fired boiler section generates heating or process heat while simultaneously utilizing the heat potential from waste heat sources (waste heat section).

Hybrid boilers with burners enable continuous and efficient steam generation from process heat if the waste heat is not continuously available. This type of boiler is mainly used in combination with cogeneration plants (CHP), gas turbines or TNV/RNV air purification systems.

In the waste heat pass, the hot flue gases from the upstream combustion process are used to support the generation of heating or process heat. This was also the starting point for the development of the hybrid boilers: Biogas plants with their special requirements:

  • If the biogas CHP plant fails, the steam output should be provided by a "normal" burner. With natural gas or biogas firing.
  • For peak loads, which cannot be achieved with CHP units, the missing energy is generated with an industrial burner (CHP unit only runs base load).
  • General increase in performance through hybrid performance.

If the exhaust gas flow fails or is insufficient at peak load, the part fired by oil or gas automatically takes over the steam generation or controls the peak load.

The Main Advantages of Hybrid Boilers

More Efficiency:

  • Only one boiler required – this saves space and installation costs.
  • The system is less expensive, has a longer service life and the need for spare parts is lower.
  • Maintenance by the operator and the manufacturer is less time-consuming.
  • A boiler sequence control is not required. The hybrid boiler "organises itself".
  • Increase efficiency and environmental friendliness by using waste heat sources. If the exhaust gas flow fails, the fossil-fueled part automatically takes over the steam supply. As soon as exhaust gas is available again, it can be used again to generate steam within seconds.

More Safety and Longevity:

  • Due to its hybrid function, the boiler is constantly at operating temperature. Dangerous, corrosion-inducing dew point undershoots are minimized.
  • If a cold start is necessary, you can start the boiler with fuel. The flue gas flow, which can cause stronger corrosion when cold, is switched on as soon as the operating temperature is reached.

Higher Overall Efficiency:

  • Installation of feed water preheating for both power units only in the more efficient waste heat flow. This improves the overall efficiency of the system. The feed water can be heated more strongly than in two systems. Feed water preheating of both power units only in the exhaust gas flow of the combined heat and power (CHP) improves the efficiency in the CHP area.
  • This also results in a better overall utilisation of the storage heat in the boiler and feed water tank than with two separate units.

Achenbach Hybrid Steam Boilers: Robust, reliable, durable and efficient

Are you interested in Achenbach's services? We are looking forward to your questions.

Simply send an e-mail to or call us +49 2391 9591-0.

Contact us