Leipzig, November 2, 2017 - The incineration of agricultural and biogenic residues in small and medium-sized plants requires special measures to reduce dust and nitrogen oxide emissions. The "SCR-Filter" project has successfully developed a combined process for removing dust from exhaust gases while simultaneously reducing nitrogen oxides.
In order to reduce the burning of wood, residual and waste materials are increasingly being used to generate energy. The thermal conversion of such wood-free biomass results in increased emissions. So far, corresponding exhaust gas purification processes have been available on the market for large-scale plants in the megawatt range, but not for plants with a thermal output of up to 1 MW. The consortium of the project "SCR-Filter - Demonstration of processes for the combined reduction of nitrogen oxides and fine dust in biomass furnaces" (FKZ-Nr. 03KB096), which the DBFZ Deutsche Biomasseforschungszentrum gemeinnützige GmbH as well as Industrietechnik Barleben GmbH, Fraunhofer IFF and Dr. Weigel Anlagenbau GmbH were involved, developed and tested a process for the reduction of dust and nitrogen oxides (NOX) in exhaust gases, which is also efficient and economical for plants in the low power range.
The gas exhaust purification system consists of a catalyzed coated fabric material that allows a combination of dust separation and the so-called selective catalytic reduction (SCR, see info box) of NOX. The dust is deposited on the outer surface of the filter, where the nitrogen is removed from the gas exhaust on the coated inside of the filter.
In the combustion tests, wood chips, straw and mixed pellets were used to achieve dust separation rates of 80-90%. For straw and mixed pellets, the current limit value of 20 mg/m3 (related to 6 Vol.%-O2) could be complied with, but not limited to the value required in future. In the case of NOX, reduction rates of 50-60 % were achieved by taking ammonia (NH3) slip into consideration. Optimal adjustment of the filter temperature and the amount of reducing agent makes it possible to fall well below the current NH3 limit value of the TA-Luft. In view of its future tightening, further adjustments are required in the cleaning process in order to be able to thermally recycle residual materials in the smaller and medium performance range.
The concrete results from the final report in the project profile can be found here.
SCR - Selective catalytic reduction
SCR is a chemical reaction in which nitrogen oxide (NOX) in the exhaust gas are converted into water (H2O) and elemental nitrogen (N2) by the addition of ammonia (NH3). The process is used to reduce nitrogen oxide in power plants and has been used in vehicle engines since 2003 with AdBlue® technology, whereby a 32.5% urea solution is injected into the exhaust gas stream.
Contact Program Support of the "Biomass energy use"
Diana Pfeiffer – Project coordination
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Angela Gröber – press relations
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