Numerical Simulation And Optimization Of The Combustion In A 1000MW Ultra Supercritical Boiler

Ultra supercritical power generation technology is recognized internationally as a clean-coal technology which has fine operation flexibility,good load flexibility,and has significant environmental protection performance.With the high parameter,large scale of the boiler and the large number of ultra supercritical boilers putting into operation,the combustion characteristics,operating stability,combustion efficiency and pollutant emission of the boiler have been paid much attention to.In this paper,a 1000 MW ultra supercritical swirl combustion boiler is selected as the research object,the numerical simulation software is used to simulate the combustion characteristics under basic and variable conditions,which has certain theoretical and social application value.First,this paper introduces the general situation of a ultra supercritical once-through boiler model DG3110/26.15-? 2,describes the characteristics of DBC-OPCC low NOx swirling pulverized coal burner and over-fire air regulator.Considering the influence of the structure and size of burner and over-fire air regulator on the combustion condition,the burner and over-fire air regulator are modeled and meshed respectively,the 48 burners and 16over-fire air regulators and boiler furnace are considered as a complete computational domain for full furnace modeling and mesh division.From top to bottom,the boiler is divided into different regions,and meshed respectively.Mesh refinement is applied in the burner area,which effectively improves the quality of the grid and reduces the influence of pseudo diffusion on the calculation results.Secondly,on the basis of selecting the appropriate geometric model and numerical model,the flow,combustion and NOx emission characteristics of the boiler under the basic operating conditions are simulated.It is found that the particle trajectory,velocity distribution,temperature distribution and distribution of each component are consistent with the burning law when burning the design coal.And the combustion effect is remarkable,the emission of NOx is obviously less,which can achieve the purpose of clean combustion to a large extent.Finally,on the basis of the basic working conditions,the variable working conditions simulation were carried out.And the combustion and NOx emission characteristics of the boiler under the variable load condition,the variable pulverizer condition,the variable secondary air swirling intensity and the variable over-fire air condition are studied.The results show that the reasonable reduction of the boiler load or the increase of the swirling strength can improve the combustion efficiency of fuel particles and reduce the emission of NOx in acertain degree.The discontinuation of the top burner is equivalent to increasing the air classification effect,which can significantly reduce the emission of NOx,while closing down the lower burner will weaken the air classification,which will lead to the increase of NOx emissions.Increasing the over-fire air is equivalent to enhancing air classification,which will largely reduce the generation of NOx.