Steam Turbocharger for coupling steam and compressed air networks

In industry, steam networks are operated for various applications. These networks often contain steam lines with different pressure levels, whereby the pressure reduction between two pressure levels is mainly achieved by mechanical throttling via control valves. At the same time, the demand for compressed air in these industrial enterprises is often high. Within the scope of this project, a new possibility of coupling these two supply networks will be realized – with the help of a newly developed turbo machine. The project partner is Turbonik GmbH from Herten, which specializes in the manufacture of efficient and compact micro steam turbines.

The previously energetically unused throttling of the pressure differences can be used via a steam turbine to directly drive an c air compressor. Based on the parallels to the automotive turbocharger, this application is referred to as "steam turbocharger". In high power ranges (several megawatts of mechanical power), such coupled turbomachines are already established. Otherwise, for the power range of significantly less than one megawatt- despite the high ecological relevance and the frequently encountered applications – economical and compact units and standardized integrations are not yet available. Small and medium-sized companies therefore do not yet have the opportunity to use their steam networks for coupled compressed air generation.

The modularized container design with integrated steam boiler and steam turbocharger demonstrated in the project "Steam Turbocharger - Increasing Efficiency in Industrial Companies by Coupling Steam and Compressed Air Networks" shows that both, the stand-alone use of the steam turbocharger to replace existing steam reduction valves and the installation of complete systems consisting of steam boiler and steam turbocharger are possible in a simple and space-saving way.

The advantage of a steam turbocharger is the reduction of losses in the energy conversion chains. Instead of using electrical energy from the power grid to drive the electric motor of an air compressor, the direct coupling of turbine and compressor significantly shortens the energy conversion chain. Gearless steam turbochargers can halve primary energy consumption and CO₂ emissions compared to compressors fed from the power grid. If the market were to be fully penetrated, this would result in a considerable savings potential of up to 1.3 million t CO₂ per year in Germany. Current publications show that the use of steam turbines as drive units is currently only recommended in the megawatt range due to economic restrictions. Nevertheless, direct drive by means of steam turbines is clearly superior to electric motors in all cases from an ecological point of view.

For steam turbochargers to be used in industry, they must therefore have low investment and operating costs in addition to high efficiency. This requires a simple and compact design as well as standardized interfaces for system integration at the operator, which are being developed in this project. The turbine and compressor must be specially developed for high speeds and adapted to each other in order to achieve high efficiencies. If this development succeeds, preliminary studies show that payback periods of two to three years are feasible, so that the enormous ecological potential can also be exploited in real terms due to the good economic efficiency. Tailored to the above-mentioned requirements, the prototype of a steam turbocharger coupled with a steam generator as a container solution is being developed, constructed and tested as part of the project.

• Turbonik GmbH