Effects of lignite dewatering treatment on the surface behaviour and NO emission characteristics during the combustion process.

Hailaer lignite (HLE) with a uniform particle size distribution (3–6 mm) was employed to investigate the parameters of the low‐temperature dewatering process influencing the emission of gaseous pollutants (NOx) during their combustion process. The combustion of HLE original/dried samples obtained from a COMBDry drying system were carried out in a fixed bed horizontal furnace under an air atmosphere at the reaction temperature of 1100 °C. The dewatering treatment led to the enhancement of the relative amount of the volatile and fixed carbon content in the upgraded coal sample. The deconvolution of the Raman spectra of each sample showed that the increased degree of drying led to an enhancement of the defects in aromatic structures, indicating an enhancement in the number of active sites or oxygen‐containing complexes on particle surface. The devolatilization and combustion experimental results showed the following: (1) with the increase in the degree of drying, more HCN and NH3 were released during the devolatilization process, and both HCN and NH3 molecules had positive effects on the consumption of NO under high temperature conditions; (2) due to the enhancement of the specific surface area and total amount of surface active sites (Cf) after the drying treatment, the combustion and reduction reactivity of the dried HLE samples increased significantly; and (3) the conversion ratio of fuel‐N to NO during the combustion process decreased significantly with the increase of the degree of dewatering. Therefore, it could be concluded that the removal of moisture content in lignite particles in advance had positive effects on lignite high efficiency combustion with low NO emission. [ABSTRACT FROM AUTHOR]