Experimental Research On Transforming Characteristics Of Fuel-n Under Oxy-fuel Condition

Oxy-fuel combustion technology has its unique advantages in terms of CO2 capture,anr it's easy to achieve industrial applications. A lot of pilot-scale study shows its unique advantages in reducing NOX emissions.The changes of atmosphere under oxy-fuel conditions has great impact on the pyrolysis of pulverized coal and burnout of char, lead to differences in transforming characteristics of nitrogen. In this article we use a one-dimensional drop-tube furnace to carry out research on transforming characteristics of fuel-N during the pyrolysis and combustion of pulverized coal.Pyrolysis experiments of pulverized coal were carried out in the one-dimensional drop-tube furnace under Ar and CO2 atmosphere to study the effects of temperature and coal rank on the release of volatile-N and further investigate.the transformation path of nitrogen-containing functional groups. The results show that CO2 can promote NH3 release and secondary reaction of HCN. As the temperature or coal rank increases, the release of HCN will decrease, but the changes of NH3 release are complicated, depending on the reciprocal effect of temperature and coal rank. The XPS analysis of coal and char show that quaternary nitrogen will completely converted to pyrrole by the reactin with oxygen radical.Pyrrole can be further oxidized to pyridine.High concentration of CO2 will promote the conversion of functional groups.Combustion experiments were done in the one-dimensional drop-tube furnace under O2/N2, O2/Ar, O2/CO2 and O2/RFG atmosphere to study the effects of temperature and oxygen concentration on the conversion characteristics of fuel-N and further discuss the changes in contribution ratios of separate effects that reduce NO conversion ratios under oxy-fuel combustion. The results show that the increased temperature, oxygen concentration and coal rank all lead to higher NO conversion ratios.The contribution of recycled-NO reduction is dominant for reduce NO conversion ratio under oxy-fuel condition, accounting for more than 50% and will increase with increased recycled-NO concentration.Then the contribution for the high CO2 concentration in the furnace accounted for 20%~30%. The contribution for the removal of atmospheric nitrogen accounted for less than 20%.The main factors that can effect the contribution ratios of separate effects will vary depending on the coal rank. Low rank coal is mainly affected by the oxygen concentration and for high rank coal is the temperature.