Innovative German biomass plant begins operations

Germany has started operating a new biomass heating and power station that uses finely chopped material to generate eco-friendly energy.

The Zweckverband Restmuellheizkraftwerk Boeblingen (RBB) plant in Baden-Wuerttemberg completed successful trials this May.

Siemens’ Industry Solutions Division supplied a Reject Power system that enables the use of fuels with a high water content such as screenings from wood-chip processing. The new plant will be able to supply enough electricity to meet the needs of around 5,200 people. At the same time, the heat produced can be fed into the district heating network. Compared to the use of fossil fuels for the generation of electricity and heat, CO2 emissions are reduced by 10,200 metric tonnes per year.

The new power station supplements existing facilities for the thermal exploitation of residual materials. With the help of the Reject Power system for power generation, around 20,000 metric tonnes of finely chopped material that couldn’t otherwise be incinerated in conventional facilities can be utilised every year. The finely chopped material consists of natural-wood screenings that are produced when green waste, residual wood from forests and wood left over from landscape conservation, for example, are cut up into small chips.

“This facility is new territory for us,” said Wolf Eisenmann, managing director of RBB. “For the first time in Germany, we are producing electricity and heat from finely chopped material.”

The Reject Power system consists of the combustion chamber, the waste heat boiler, a flue gas cleaning unit and the chimney as well as the electrical equipment. The heart of the system is a spinning wheel, which throws the fine wood screenings into the combustion chamber at high speed, ensures better distribution of the combustion material and thus guarantees complete incineration. At a temperature of up to 950 degrees Celsius, the combustion chamber converts the screenings into usable energy. With the help of the spinning wheel method, fuels with a high water content can also be used.

The Reject Power installation is designed for the thermal conversion of around 20,000 metric tonnes of screenings, and produces 6.4 metric tonnes of steam per hour. A steam turbine uses the steam to generate electrical energy and provide heat for the district heating network. A power generator with an output of 700 kilowatts supplies the public grid of the community. The heat is fed into the district heating network via a district heat exchanger.

Due to the combination of power and heat that is produced, a fuel utilisation ratio of around 80 per cent is achieved.