Pyrolysis Gas of Biomass and Coal as a NO_x-Reductive in a Coal Fired Test Facility

Abstract

To lower NO_x-emissions in pulverized coal combustion, pyrolysis gas from biomass and hard coal were used as reburn fuel. The results have been compared with synthetic reburn fuel mixtures. With pyrolysis gas as reburn fuel, minimum NO_x-emissions of 200 mg/m _n ³ (approx. 100 ppm) at 6% O₂ in the flue gas are possible. The main parameters are pyrolysis gas composition, stoichiometry and residence time in the reduction zone. Best minimizing results have been achieved with pyrolysis gas produced at about 800°C-900°C reactor temperature using coal as raw material. However, the pyrolysis temperature showed no distinct influence on NO_x-reduction using biomass as feedstock. The nitrogen concentration, especially in the tar components of the pyrolysis gas, appears to have a positive effect on NO_x-reduction in the reburn zone of the combustion reactor.

Keywords:

• Biomass
• coal combustion
• NO_x-reduction
• reburn
• pyrolysis