Research On Wall Fired Low NO_x Combustion Technology For 600MW Bituminous Firing Boiler

With gradually increasing atmospheric pollution,the national environmental protection consciousness is more and more strong.From coal-fired power plants pollutant emission is more and more serious,causing the attention of everyone.In China,thermal power generation own a large proportion.As a new environmental protection rules was proposed,early coal boiler can not meet the new standard.Therefore,there are quite a number of boilers requiring low NO_x combustion technology.In this paper 2×600 MW supercritical coal-fired boilers were modified to further reduce NO_x emissions from initial condition to meet the new.environmental protection rules.After a large number of literature research and on the basis of engineering design experience,the modification plan was put forward,which included the apply of new ultra low NO_x burner and secondary air staging adjustment.In the plan,the OFA ports will be 3600 mm higher than before,and distance from top burner to OFA ports will be 7260 mm instead of 3660 mm,which increase the deoxidation distance.In addition,Stoichiometry in main burner zone will be decreased to reduce the air flow in main burner zone,and increase the air flow of OFA ports,thus to form a deoxidation environment in main burning zone to reduce the NO_x emission in gas,advance air staging will further reduce the NO_x formation to meet the higher environmental protection requirement.In this paper,the temperature field uniformity and CO and O₂ distribution in furnace was analysed by CFD,which applied the basis to avoid the slagging and erosion after retrofit.From the commissioning,it was known that the new ultra low NO_x burner-AireJet^TM burner can further reduce the NO_x emission.For AireJet^TM burner,the core air flow and swirl strength for inner secondary air and outer secondary air can be adjusted,the ignition point can be adjusted by different combination to adopt the fuel change,control the NO_x formation and ensure the efficient combustion.The influence of OFA ports location and OFA flow was known during commissioning and tuning.The NO_x emission was reduced by advance air staging.After the detail introduction of retrofit plan and the performance after retrofit,it is concluded that it is practicable to reduce the NO_x emission of current boiler by the methods of adjusting the OFA ports location,low NO_x burner replacement and air staging adjustment.Hot test after retrofit indicates that boiler load is 660 MW when fueling designed coal with its efficiency of 94.41%,higher than 93.63% as guarantee value.NO_x concentration?translated into 6% oxygen?is 227mg/m³,lower than 240mg/m³ of contractual requirement.CO emission around SCR inlet is 58?L/L,lower than 100?L/L of contractual requirement.Each guarantee value has been achieved,exceeding customer's expectation of NO_x emission.