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LOW EMISSION CO-COMBUSTION OF DIFFERENT WASTE WOOD SPECIES AND LIGNITE DERIVED PRODUCTS IN INDUSTRIAL POWER PLANTS

Objective

Demonstration on an industrial scale that the following demands can be met :
- demonstration of the feasibility of co-combustion of contaminated waste wood lignite in industrial power plants with circulating fluidized bed combustion (CFBC) in combination with the co-generation principle yielding a high energy efficiency (>85%). Testing of pneumatic conveyance (including impurity extraction) of different and differently prepared waste wood (i.e. wood chips with 5 to 30 mm size) to the combustion chamber of a CFBC boiler. Indication of a practicable, economically and ecologically advantageous decentralized alternative for the use of waste wood. Demonstration of adherence to strict emission levels without costly waste gas scrubbing.
- proof that already existing moving stoker firing systems mainly in south-east Europe can thermally recycle a fraction of waste wood (mainly uncontaminated) to save fossill fuel.
Equipment for the Waste Wood Delivery and Handing Station of the Berrenrath power plant: The values guaranteed by the plant supplier regarding the amount to be covered by the pneumatic conveying system into the CFB boiler (8 t/h), the unloading capacity during truck unloading as well as storage volume of the buffer silo were attained. The pneumatic conveying system is capable of handling wood chips with a size of 3-50 mm according to the design specification without any problems; coarser wood chips of up to 100 mm length were smoothly transported as well. In the reporting period, a total of 1700 t of waste wood (waste wood from bulky refuse collection, constructional timber and demolition wood, railway sleepers) had been co-combusted. All emission limit values were adhered to both with and without adsorptive flue-gas cleaning.
Co-combustion of lignite and waste wood at the moving stoker of Pindos S.A. was started.
The demonstration phase of the co-combustion of contaminated waste wood and lignite in CFBC-boilers is to be implemented at the Berrenrath power plant belonging to Rheinbraun AG. The power plant (235 MWth) operates on the cogeneration technology, i.e. it supplies electricity and process heat. The high-pressure steam (90 bar, 500°C, 560 t/h) is produced by two steam generators of identical design.
The power generated is mainly for own requirements. But the power plant is linked to the public grid. The process heat in the form of 5 bar saturated steam is required for coal drying. The power plant is operated all the year round. Because no commercial experience exists as yet when it comes to pneumatically feeding shredded waste wood into fluidized bed boilers the following points will be examinated within the scope of the demonstration project:
- permissible grain size distribution in the processed waste wood,
- permissible impurity content in the processed waste wood which the nozzle size and the ash extraction and cooling equipment in fluidized bed combustion systems for lignite as standard fuel can tolerate,
- number of feeding stations,
- height of the feeding station above the nozzle grate,
- adjustments to the combustion air distribution,
- examination ,of deposit formation and corrosion behaviour.
During the demonstration phase at Rheinbraun's facilities, a series of tests will be performed with Greek lignite to demonstrate the possibility of operation of CFBC plants when firing mixtures of waste wood with poor quality lignite. Therefore, a suitable quantity of Greek lignite will be transported to the Berenrath plant to investigate the potential of implementing the CFBC technology for waste wood co-combustion with lignite in Greece.
The evaluations of the results from the demonstration in industrial scale will be based upon series of measurements during the monitoring process.

Call for proposal

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Coordinator

Rheinbraun AG
EU contribution
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Address
Stüttgenweg 2
50935 Köln
Germany

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Total cost
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