Investigation On Ignition,Combustion And Emission Characteristics Of Waste Tire Pellets In Oxy-fuel

With the rapid development of the automotive industry,how to reasonably treat waste tires has caused great concern worldwide.Concerning a large production of waste tires in China,direct landfill or disposal will aggravate environmental pollution and thus traditional disposal methods can no longer meet the needs.Waste tires with the higher heating value can be used as a promising alternative energy source for research and use,and this way will make more full use of resources.To achieve the clean combustion of waste tires in the circulating fluidized bed,this work studies the combustion characteristics and the formation of pollutant gas of waste tires based on the research of single pellet.Firstly,the proximate analysis,ultimate analysis,ash analysis and thermogravimetric analysis of the waste tire powder are carried out to obtain the typical combustion characteristics of waste tire as a kind of fuel.Then,the waste tire pellets are obtained by processing and pelletizing the powdered waste tires using a model.Then,the background gas environment is set to the CO2/O2 in the vertical electrical heating furnace and the influence of the operating conditions(temperature,airflow velocity and oxygen concentration)on the ignition,combustion and emission characteristics of the waste tire pellets are studied.Under all operating conditions in the vertical electrical heating furnace,the waste tire pellets always show the homogeneous ignition mode of volatile matter.The ignition and combustion of waste tire pellets are very rapid,and no black smoke is generated during the combustion process.With the increase of temperature,air flow speed and oxygen concentration,the flame spraying phenomenon is intensified,which means the more intense combustion.The distinct pores and cracks are found on the surface of char during the char combustion.Increasing oxygen concentration and temperature will shorten the ignition delay time and reduce the internal ignition temperature.At low oxygen concentration,the ignition delay time decreases first and then increases with the increase of the airflow velocity,while at high oxygen concentration,the ignition delay time keeps decreasing slowly with increasing airflow velocity.The increase of the airflow velocity can enhance the effect of oxygen concentration on the internal ignition temperature.NO emissions mainly exist in the volatile combustion stage,and SO2 emissions are mostly presented in the char combustion stage.With the increase of temperature,the emission of NO and SO2 was increased but NO2 emission was decreased.Besides,elevated temperature have no effect on the shape and peak position of NO and NO2 emission curves,but can change the curve shape of SO2 emission.Increasing the oxygen concentration and gas flow rate will reduce the increase of NO,NO2 and SO2 yield.