Numerical Simulation Of Coal-bed Methane Used For 2027t/h Coal-fired Boiler

Generally in coal mine production,methods of extensive ventilation can be used to discharge gas in order to improve the safety of production.The greenhouse effect of methane was 25 times as much as that of carbon dioxide,and the destruction of the ozone layer of it was 7 times as much as that of carbon dioxide.If methane is directly discharged into the atmosphere,it will not only result in climate change and environmental degradation,but also create a huge waste of energy.As the contents of VAM?Ventilation Air Methane?are very low?typically less than 1%?,it is limited to directly utilize VAM as the main fuel.The combination of VAM and thermal power generation can not only save energy,but also protecte the environment,which is in line with the national sustainable development strategy.In this thesis,2027t/h tangentially coal fired boiler in a power plant was the research object.VAM was used as the boiler supply wind,and the effect of VAM on the combustion characteristics of the furnace was studied by the numerical simulation method.The research object was modeled and meshed through FLUENT dedicated preprocessing software Gambit.Considering the heat transfer and mass transfer characteristics in the boiler,suitable mathematical models were set up,and the distribution of velocity,temperature,component and NO in each working condition were calculated by numerical calculation.The combustion characteristics under the working condition were analyzed with BMCR working condition as the basic working condition.The model was verified by simulating the basic conditions and used as the reference condition with VAM.Compare with the actual measurement results,the error of the temperature and oxygen content at the furnace exit is less than 5%,so the calculation model was reasonable and could truly reflected the operation of the furnace.In this thesis,the concentrations of methane in VAM,the ways that VAM entered the furnace and the effects of loads on the combustion characteristics of the boiler were studied.The results showed that with the increasing of methane concentration in VAM,the average temperature in the furnace was increased,and the maximum value was 53 K.The burning rate of pulverized coal decreased,the O₂ concentration in the furnace reduced,the CO concentration increased,and the reducing atmosphere enhanced.Methane would inhibited the formation of nitrogen oxides in furnace,so that the NO emission at the furnace exit was reduced from 388.21 mg/Nm³ to 318.88 mg/Nm³?convert to O₂ content6%?,and the reduction was 17.8%.When the methane concentration in VAM was 1%,the average temperature of the furnace decreased with only the primary air and only the secondary air separately replaced by VAM.The concentration of NO decreased from 388.21 mg/Nm³ to 328.7 mg/Nm³ when the primary air and only the secondary air simultaneously replaced by VAM.When the load dropped from 600MW to 410MW,the average cross-sectional temperature at A-layer burners decreased from 1507K to 1314K.The concentration of NO decreased from 388.21 mg/Nm³ to 289.6mg/Nm³.The boiler saved fuel after burned with VAM.When the methane concentration was 1%,the boiler saved standard coal 18.2 tons per hour when the primary air and the secondary air were replaced by VAM and burned under the full load.