Optimering av SNCR-system i en biobränsleeldad panna : möjligheter till minskade NOx-utsläpp för ENA Energi

Sammanfattning: Emission of nitrogen oxides as well as carbon monoxides is an inevitable result of combustion. A Swedish law "Law of environmental fee for emissions of nitrogen oxides as a result of energy production" (lagen om miljöavgift på utsläpp av kväveoxider vid energiproduktion (SFS 1990:613)) controls the emission of NOx from energy production by a system of fees. The system has resulted in a strong approach toward less emissions of NOx among the energy production plants. High emission levels, today exceeding 52 mg/MJsupplied fuel, leads to costs for energy production companies. This paper examines possibilities to reduce the emissions of NOx by optimization of the SNCR-technique in a biofuel fired heat and power plant. SNCR (Selective Non Catalytic Reduction) involve supply of an NOx reducing reagent in the furnace. The project is carried out on a 80 MWt grate fired boiler at ENA Energi AB, Enköping, Sweden. Tests have been worked out to find new strategies for the operation of the SNCR- system. The project comprised getting acquainted with the plant in Enköping, especially the function and ammonia supply positions of the SNCR-system. Analyses have been focused on periods or loads with high emissions of nitrogen oxides. Tests of the existing ammonia supply positions, of the angle of diffusion and of one new ammonia supply position, have been performed. The result shows that today's operation is good. However, a good reduction of NOx can also be achieved by using other combinations of the ammonia supply positions then what is used today. Also, the results show that the carrying air is of great importance.