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In the present study reduction of nitrogen oxides using reburning technology, during combustion of sewage sludge (fuel I) and the mixture of sewage sludge, wasted bleaching earth and CaO (fuel II), was carried out. The experimental works were conducted in a laboratory-scale fluidized bed reactor (power up to 10 kW) with application of two types of beds: chemically inert bed (sand) and chemically active bed (CaO). The second combustion (reburning) zone in the reactor was formed by dosing into an area above the bed, additional gaseous fuel (propane). Obtained reduction in emissions of nitrogen oxides in both types of beds was at a level 70% - 79%. Additionally bed of CaO has the desulfurizing effect and also reduces the CO concentration in the exhaust fumes. A significant drawback of active bed is the adverse effect on increase of the primary NO which enters the second combustion zone. The result of this fact is higher NO_x emission during combustion of the same fuel in bed of CaO in comparison to the combustion of this fuel in the sand bed, when the same maximum degree of reduction of NO_x will be obtained for both types of beds.

Combustion processes of alternative fuels with high nitrogen content can cause nitrogen oxides emission which is unacceptable from an environmental and legal point of view. Reactions of nitrogen compounds, e.g. ammonia or heterocyclic compounds, are complex and there is a lack of specialized complete knowledge about them. This paper reports processes of propane combustion in a fluidized bed reactor without and with ammonia or pyridine addition into the reaction zone, especially nitrogen compound conversion into N x O y. Ammonia is converted into N x O y up to 78%, and pyridine up to 93%. The main product of their reactions is NO (average 97%). Residual C 5 H 5 N or NH 3 are converted to N 2. Nitrogen compounds' influence on processes involving CO and VOC. The effect of pyridine addition to the reaction zone on the kinetics of combustion process is practically negligible. The effect of ammonia addition is noticeable but limited.

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