Study On Combustion Characteristics Of Oxygen-enriched For Gas Boiler In Power Plants

In China, the main source of greenhouse gas emissions was from thermal power plants based on burning fossil fuels, which can be effectively reduce greenhouse gas emissions, by using oxygen-enriched combustion technology. In recent years, the numbers of gas boilers were increased among China's power plants, and the current researches for combustion characteristics of oxygen-enriched in power plant's gas boilers were few. This paper investigated a 325MW gas power plant boiler, whose characteristics of gas oxygen-enriched combustion were studies by the methods of experimental and numerical simulation.The characteristics of natural gas for oxygen-enriched combustion were studies in the atmosphere of O2/N2.The results showed that, with the increasing of oxygen concentration from 21% to 30%, the flame temperature increased, the distribution of high temperature area was more concentrated. When the oxygen concentration was greater than 27%, the rising of temperature slowed down. Mathematical models of combustion process were set up for natural gas boiler, and this model was applied to simulate the test bed, which was proved to be accurate.The combustion characteristics of natural gas boiler in power plant were studied by the method of numerical simulation, both by the traditional approach and the oxygen-enriched combustion technology (O2/CO2 combustion technology). The results showed that, when the oxygen concentration was 25%, the temperature distribution and flue gas radioactive properties in the furnace were close to the traditional combustion. When the oxygen concentration is increased from 21% to 40%, the amount of smoke decreased by 41%, the temperature of furnace flue was found to have more significant improvement, the average temperature in the burner section increased more than 300K, volume accounts of the flame in furnace became worse, the burnout rate slightly decreased, gas radiation increased, and heat flux of the radiation heat transfer from the furnace wall increased by 26%.The combustion characteristics of oxygen-enriched for nature gas were examined by numerical method, in various air supplying conditions. The results show that, compared with oxygen blown by the secondary air and the graded air, when oxygen blown uniformly, the temperature of flue was slightly higher, the distribution of the gradient O2 concentration changed larger, radiation heat decreased by 1%. When the rate of primary air reduced from 15% to 10%, the level of the gas recirculation enhanced, the furnace temperature increased more than 40K, volume accounts of the flame in furnace became better, the uniformity of radiation heat transfer from the furnace wall was improved. When the rate of the secondary air reduced from 59% to 54%, the region of the flue recirculation enlarged, the velocity of the flue recirculation decreased by more than 13%, the average temperature in the burner section slightly decreased, and the radiation heat transfer from the wall was increased by 1%. Comparison of the results in different condition, the combustion characteristics in furnace was better when the oxygen supplying was uniform, with a primary air rate of 10% and a secondary air rate of 54%. Then the boiler efficiency can be increased by about 4.8%, compared with the traditional combustion,The results of this study can provide an important basis and reference with improve natural gas boilers'structure using oxygen-enriched combustion for the power plant and the design of air distribution methods.