Efficient generation of power from finely chopped material: Operation of biomass heating and power station completed successfully

Wednesday, Jul 01, 2009

The new biomass heating and power station of the Zweckverband Restmuellheizkraftwerk Boeblingen (RBB) in the German Land of Baden-Wuerttemberg has now started regular operations, using finely chopped material to generate energy in a manner which is most compatible with protection of the environment. After starting in February, trials were completed successfully at the beginning of May when the performance test was carried out. The Siemens Industry Solutions Division supplied a Reject Power installation for the heating and power station. The Reject Power system also enables the use of fuels with a high water content such as screenings from wood-chip processing. The new biomass heating and power station supplies electrical energy for 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 tons per year.

The new biomass heating and power station of RBB 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 tons of finely chopped material that it would not be possible to incinerate in conventional facilities can be utilized 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”, explained Wolf Eisenmann, managing director of RBB. “For the first time in Germany, we are producing electricity and heat from finely chopped material.” We decided in favor of the Reject Power concept from Siemens, continued Eisenmann, because an Austrian paper manufacturer had already achieved very promising results with this special incineration technique.

The Reject Power installation supplied by Siemens for the biomass heating and power station 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 heterogeneous 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 tons of screenings. It produces 6.4 metric tons of steam per hour with a pressure of 40 bars and a temperature of 390 degrees Celsius. 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, thus supplying approximately 5,200 people with electricity. 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 utilization ratio of around 80 per cent is achieved.

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The Siemens Industry Sector (Erlangen, Germany) is the world’s leading supplier of production, transportation, building and lighting technologies. With integrated automation technologies as well as comprehensive industry-specific solutions, Siemens increases the productivity, efficiency and flexibility of its customers in the fields of industry and infrastructure. The Sector consists of six Divisions: Building Technologies, Drive Technologies, Industry Automation, Industry Solutions, Mobility and Osram. With around 222,000 employees worldwide Siemens Industry posted in fiscal year 2008 a profit of EUR3.86 billion with revenues totaling EUR38 billion.

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