Effect of S0₂ and NO on the Conversion of Fuel Nitrogen to N₂0 and NO in Single Particle Combustion of Coal

ABSTRACT

The effects S0₂ and NO concentrations on the emissions of N₂0 and NO from a single particle of coal burning in a fluidized bed combustor is reported. The experiments were carried out in a laboratory scale quartz glass fluidized bed reactor in the temperature range 1023-1123 K. Since the combustion processes for the volatiles and char are consecutive, the effects of added NO and SO₂ occurring during the volatiles combustion can be distinguished from those occurring during the subsequent char combustion. During the combustion of the volatiles, addition of NO (250 ppm) results in an increased formation of N₂0, whereas the net NO formation decreases. This effect is enhanced when both NO (250 ppm) and SO₂ (900 ppm) are included in the fluidizing gas mixture. The effect of NO can be explained by the generally accepted gas phase mechanism of NO and N₂O formation and destruction. The role of SO₂ is less clear, but is likely to involve its impact on the radical concentrations. During the char combustion stage, similar effects are seen, i.e., the N₂O formation increases in the presence of NO, and is further increased in the presence of both NO and SO₂ 0ver the temperature range investigated, the addition of NO, resulted in an increased emission of N₂O: whereas the effect of SO₂ decreased with increasing temperature.

Key Words:

• Pollutants
• coal combustion
• fluidized beds
• N₂O
• SO₂
• NO