Demonstration plant Wet steam turbine (WST) in Ronneby - Sörbyverket

Ronneby Miljö & Teknik AB is a municipal company that is wholly owned by the municipality of Ronneby. Their goal is to combine environmental responsibility with economic efficiency. 

Ronneby Miljö & Teknik AB is a municipally owned company, which is wholly-owned by the municipality of Ronneby. They manage power, heat, water, sewage, garbage collection, fiber optic networks and broadband. Sörbyverket, the regional district heating plant, is operated by the subsidiary company, Ronneby Miljöteknik Energi AB. 

Sörbyverket in Ronneby has built a plant for wet steam, a steam turbine for electricity production at an existing district heating plant 

Compared to ordinary steam turbines, a wet steam turbine (WST) can operate at lower pressures and temperatures, with saturated steam. The wet steam turbine is a more robust but not as efficient as conventional turbines. But unlike them, the WST can handle some water particles.

The wet steam turbine is based on the same principle as a conventional steam turbine, which means that it needs to be cooled to condense and release heat. Although the WST does not need to have superheated steam, the boiler needs to produce steam and if a wet turbine is installed in an existing plant, it is most economically advantageous if the boiler is already equipped with a steam turbine. The electrical efficiency of a wet steam turbine is up to about 15%.

Lessons learned

To install a new technology in an old system and get the technologies to communicate and to function optimally can be difficult, especially if the supplier of the turbine focuses on generating as much electricity as possible without taking the entire system into account.

For a wet steam turbine to function optimally and with the best system efficiency for district heating deliveries, the conclusion is that a turbine that requires as much intervention in an existing plant as a wet steam turbine does, should work best if the entire system is adapted from the beginning.

The demonstration of the wet steam turbine had initial problems due to a design error, but when they were solved, the availability of the turbine was high. It would therefore be interesting to test a wet steam turbine on the same scale in a new construction of a combined heat and power plant to be able to evaluate the plant from that perspective.