Comparison of DeNOx additives in SNCR fluidized bed boiler system

Due to decreasing BAT emission limits of NOx the owners of heating plant are looking for DeNOx solution, especially by solid fuel firing boilers. Fluidized-bed boil-ers combustion temperature is generally lower, and some primary precautions were sufficient. Nowadays lots of plants install secondary precautions (especially SNCR) into their boilers due to increasing periods of exceeding emission NOx limits. The article is about comparison of water solution of urea (41 % wt.), ammonium sulfate (33 % wt.) and am-monia (22 % wt.) and their utilization in SNCR technol-ogy. Laboratory determination specified exact content of functional substance and content of redox nitrogen. Also, significant content of heavy metals was not detected. Operational tests were realized in CFB coal-biomass boiler (steam parameters: 140 t·h-1, 525 °C, 12.5 MPa). Dosing of DeNOx additives were only during boiler per-formance higher than 92 %, for lower performance pri-mary precautions were sufficient. There was higher tem-perature through the combustion chamber during active SNCR dosing (877 °C, standard temperature 850 °C), alt-hough the amount of combustion air was increased. Com-plication connected with high emission of NH3 was not detected. Lower emission of CO was also detected. All three additives are suitable for application in SNCR technology. To reach emission limits were needed 3.7 l·h-1 of ammonia solution, 5.04 l·h-1 of urea solution and 5.74 l·h-1 of ammonium sulfate solution. After recal-culation it means 0.65 kg·h-1 (ammonia), 1.1 kg·h-1 (urea) and 0,38 kg·h-1 (ammonium sulfate) of redox nitrogen content.