Effects of oxygen partial pressure on physical and chemical characteristics of fuel and deep low NOx emission

The high efficient and clean coal combustion with fundamental deep low pollution emission is extensively explored worldwide. In this work, the Shenmu bituminous coal was preheated in a circulating fluidized bed (CFB) and this modified fuel including the preheated fuel and the coal gas was burned in a down-fired combustor (DFC) under the O-2/CO2 atmospheres. The coal char and coal gas produced by preheating raw coal were measured and analyzed to obtain the changes of physical and chemical characteristics and the reduction of NOx original emissions. The results showed that both G band FWHM and I-G/I-ALL of the preheated fuel were lower than those of raw coal, respectively, while both I-D1/I-G and ID3+D4/I-G were significantly higher than those of raw coal, and the intensity of quartz, the anhydrite peaks and the fuel particle size were significantly reduced after preheating process. During the oxygen partial pressure of primary air increasing from 28.6% to 36.0%, and the increase of NH3/HCN from 0.61 to 1.26, NOx emissions decreased from 39.6 mg/MJ to 37.3 mg/MJ (@6%O-2). The increased oxygen partial pressure of primary air improved the conversion ratio of fuel-N to coal gas-N. In the period of pulverized bituminous coal preheating, it destroyed and reconstructed the stability of carbon molecular micro-structure and the regularity of crystal structure for modified fuel microphysical morphology.

Automated summary

Research on high efficient and clean coal combustion involves preheating fuel in a circulating fluidized bed to reduce NOx emissions. The preheated fuel undergoes changes in physical and chemical properties during combustion, with increased oxygen partial pressure improving fuel-N conversion and reducing NOx emissions.