Numerical Study On Operation Characteristics Of Hierarchical Fuelpartial Oxygen-enriched Swirl Pulverized Coal Burner

Coal is the main fuel in the energy industry structure of China,which is especially limited but crucial.Hence,the price of coal keeps increasing and most thermal power plant have to use low-quality-coal which is cheap but poor in quality as fuel to avoid deficit.The most important issue in the process of low-qualitycoal combustion is combustion stabilized.And with the development of technology,the oxygen manufacturing technology is improved.Higher oxygen concentration and lower oxygen production cost make it possible that to solve the combustion stabilized problem of low-quality-coal with oxygen-enriched combustion technology.Based on the above ideas,this paper presented a new type of combustion equipment using partial oxygen-enriched and fuel classification technology to burn low-quality-coal and be conducive to its stable combustion,which is hierarchical fuel partial oxygen-enriched swirl pulverized coal burner.Then the thermodynamic calculation and structural design were carried out.The main characteristics of the burner are: The fuel is sent in by inner and outer primary air to form graded combustion;Swirl blades are set in the oxygen-enriched air conduit and auxiliary air channel,which can cause swirl combustion and increase the residence time of the fuel in the high temperature zone;The inner combustion,whose fuel is less,is in an oxygen-enriched environment.And its main purpose is to form the central high temperature reflux area accompanied by swirl blades in the oxygen-enriched channel;The high temperature reflux area formed in the inner combustion is used for combustion stabilized of whole burning area.Then,after selecting the appropriate numerical calculation model,the cold flow field of the burner was carried out by means of numerical simulation.And the influence of the angle between the swirl blades in both oxygen-enriched air channel and auxiliary air channel and the burner axis to the flow field of the burner outlet was researched.According to the results: If the angle between the swirl blades and the burner axis was too small,after flowing across the swirl blades,the axial velocity component was large.And if the angle between the swirl blades and the burner axis was too large,the circumferential velocity component was large.And both in these two conditions,there cannot be enough radial velocity component to form stable reflux area.While the angle between the swirl blades in oxygen-enriched air channel and the burner axis was between 20 degrees and 45 degrees,and the angle between the swirl blades in auxiliary air channel and the burner axis was between 30 degrees and 60 degrees,the reflux area could be formed near the burner outlet.In addition,according the numerical simulation results,while the angle between the swirl blades in oxygen-enriched air channel and the burner axis was 30 degrees,and the angle between the swirl blades in auxiliary air channel and the burner axis was 45 degrees,the flow field of the combustion chamber out of the burner outlet was the best.According to the results of cold flow field simulation results,the hot burning field of the burner was carried out.And the influence of the oxygen concentration in the oxygen-enriched air channel to the temperature and species distribution in the combustion chamber out of the burner outlet was researched.According to the results: With the rise of the oxygen concentration in the oxygen-enriched air channel,the temperature in the combustion chamber out of the burner outlet increased,the volatile content decreased,the carbon dioxide and the water vapor content increased.The oxygen concentration discrepancy between the combustion chamber and the oxygenenriched air channel increased,the combustion tended to completed.However,after the oxygen concentration was higher than 30 percent,the trend of change was slow down.And while the oxygen concentration of the oxygen-enriched air channel was lower than 30 percent,with the rise of distance from the entrance of the combustion chamber,the temperature increased firstly and then decreased,the highest temperature was at the 3m from the entrance of the combustion chamber;And while the oxygen concentration was higher than 30 percent,high temperature was formed near the outlet of the burner,and then with the rise of distance from the entrance of the combustion chamber,the temperature decreased.Hence,taking into account the above results and the impact of economy and safety,setting the oxygen concentration of the oxygen-enriched air channel in 30 percent was the best.