Oxidation mechanism of ammonia-N/coal-N during ammonia-coal co-combustion.

Ammonia-coal co-combustion is a feasible approach to reduce CO 2 emissions during thermal power generation, it is necessary to study NO formation mechanism in ammonia-coal co-firing to realize low-carbon and low-nitrogen combustion. The experimental results showed that temperature and ammonia ratio have a significant effect on the NO formation. Under the same ammonia blending amount, the NO production increased first and then decreased with temperature increasing. Theoretical calculations revealed that the formation of NH in NH 3 →NH→NO is one of the factors restricting ammonia combustion. NH oxidation on the char surface first occurred in the NH/coal/O 2 combustion system, and realized the conversion of N to NO, HNO and NO 2 through different reaction paths. Combined with the experimental and theoretical calculation results, it was concluded that the reduction of NO by ammonia/char is enhanced at high temperature (>1300 °C), which reduces the conversion of ammonia-N/coal-N to NO. • Temperature and ammonia blending ratio significantly influenced the NO emissions. • NO increased first and then decreased with temperature increasing at same ammonia mixing ratio. • Theoretical calculation results show that NH oxidation first in the co-firing system. • NH formation was one of the limiting factors of ammonia combustion speed. • Intermediate HNO played a key role in NO formation in NH 3 and coal co-firing. [ABSTRACT FROM AUTHOR]