The Investigation Of Combustion And NO Formation Characteristics Of Blended Coal In O₂/H₂O Atmosphere

The situation that coal is the main energy in our country will not change in the short term,however,the huge amount of CO₂ and NO_x emissions caused by coal combustion is becoming a focus of attention.The novel oxy-fuel combustion technology:oxy-steam combustion technology which can control the emission of CO₂ and NO_x is with great potential;meanwhile,the blended-coal combustion technology is widely applied in our country.So the investigation of the combustion characteristics and NO_x formation characteristics of blended coals in oxy-steam atmosphere is of great importance.In this work,three types coals of different ranks:Jingcheng coal（JC）,Datong coal（DT）,Shenhua coal（SH）and two types of blended coals:SH/JC,SH/DT are selected to investigate the combustion characteristics and NO_x formation characteristics of blended coals in O₂/H₂O atmosphere.Firstly,the influences of combustion atmosphere,blending ratios,oxygen concentration,heating rate on blended coals combustion characteristics and interaction effects of blended coals are studied using a thermogravimetric analyzer.The results show that,（1）the ignition and burnout temperature of blended coals decreases and comprehensive combustion characteristics index increases in O₂/H₂O atmosphere compared to O₂/N₂ atmosphere;（2）the maximum interaction effect of SH/DT and SH/JC blended coals occurs when SH blending ratio reaches 50%in O₂/H₂O atmosphere;（3）the increase of oxygen concentration can increase the comprehensive combustion index of blended coals and enhance the interaction effect of blended coals;（4）the comprehensive combustion index of blended coals become larger with the increase of heating rate while the interaction effect of blended coals firstly increase and then decrease;（5）the interaction effect of SH/JC blended coal is stronger than that of SH/DT blended coal under different combustion conditions.Subsequently,the combustion characteristics of blended coal char and the interaction effect of blended coal char are studied on a thermogravimetric analyzer with the change of oxygen concentration in O₂/H₂O atmosphere.The results show that,（1）the comprehensive combustion characteristics index of blended coal char is also strengthened in O₂/H₂O atmosphere compared to O₂/N₂ atmosphere;（2）the comprehensive combustion index and interactions effect of blended coal char increases as the oxygen concentration increases;（3）the SH/JC blended coal char still have a stronger interaction effect than the SH/DT blended coal char.Finally,the effects of atmosphere,water vapor concentration,oxygen concentration,and temperature on NO formation characteristics of coal are studied on horizontal tube furnace and the interaction effect of NO formation of blended coal is discussed.The results show that（1）the addition of steam can reduce the NO generation.As the water vapor concentration increases,the NO generation of blended coal decreases gradually;（2）NO generation is higher than the linear weighted value at low water vapor concentration and gradually approaches the linear weighted value with the increase of water vapor concentration;（3）As the concentration of oxygen increases,the NO generation of blended coal char firstly increases and then decreases,NO generation is higher than linear weighted value at low oxygen concentration and lower than linear weighted value at high oxygen concentration;（4）the NO generation of blended increases with the increase of temperature,NO generation is higher than the linear weighted value at each temperature.