Future-Oriented SNCR Technologies – Application and Advantages of Selective Cooling in Large Coal-Fired Boilers

摘要

The SNCR process was introduced in the eighties of the last century and became the Best Available Technology (BAT) for smaller and medium sized combustion plants like WtE plants approximately ten years later. For larger coal-fired power plants, however, the SNCR process was not considered sufficient to maintain the required NOx reduction at all boiler loads and operating conditions. Thus the SCR technology was applied in most cases. While both technologies, low NOx combustion and SNCR, developed rapidly, especially after the turn of the millennium, the application of the SNCR process became a technically and economically viable option to minimize the NOx emissions also in larger power plants. This paper addresses the different approaches in two power plants in Poland where similar boilers (Type OP 650) with a capacity of 225 MWel are installed. Operating experiences show that with the latest developments and improvements the current NOx levels imposed by the regulators can be assured, and that there is also potential to comply with expected more stringent requirements. The recent decision of the EU to lower the valid NOx limit for lignite-fired boilers above 100 MWth from 200 to 175 mg NOx/Nm3 opens the door for the application of the SNCR technology. In Germany for instance out of 28 power boilers in operation only four comply with the new regulation.