Simulation Study On Ultra-low NO_x Emission Of 600MW Boiler Based On Controllable High Temperature Preheating Technology

Coal is an important basic energy and means of production in China,and the nitrogen oxide produced in the process of coal combustion is one of the main sources of pollution.In this paper,the ultra-low nitrogen combustion technology of the controllable high temperature preheating device is applied to the reconstruction scheme of 600MW boiler.The purpose is to further reduce the NOx emission and achieve the emission target of NOx?50mg/Nm3.In this paper,a 600MW Tangentially Fired Boiler of a power plant is taken as the research object.After a part of the air powder mixture of the self-made coal system is sent to the device for pretreatment by using the controllable high temperature preheating device,the reductive gas and residual fuel produced are sent to the reduction area of the furnace through the high temperature preheating product pipeline,and the combustion process of the fuel is reduced by using the product of the fuel itself As an ultra-low NOx high efficiency burnout technology,the specific research contents are as follows:First of all,according to the characteristics of the research object,according to the basic idea of numerical simulation and referring to the experience of relevant literature,by analyzing the mathematical models used in each numerical simulation calculation stage,the system's gas-phase turbulent flow model,wall function model,gas-solid two-phase turbulent flow model,gas-phase turbulent combustion model,radiation heat transfer model,radiation heat transfer model,volatilization analysis are established The model,coke combustion model and NOx generation calculation method are given.Secondly,this paper studies the design and operation of the boiler,uses fluent numerical simulation software as the research tool,uses gambit to model the whole boiler,and reasonably divides the grid according to the actual three-dimensional structure.After the pre-processing is completed,fluent software simulates the combustion process of the whole furnace.After that,the flue gas temperature at the outlet of each heating surface of the furnace,the volume concentration of 02 and NOx at the outlet of the furnace obtained from the simulation calculation are compared with the measured values of the actual operation of the on-site boiler,and the model is modified to obtain an accurate and reasonable simulation model of the benchmark working condition,which provides a reliable model reference for the subsequent reconstruction project.Then,a part of the whole fuel sent to the furnace is sent to the controllable high temperature preheating device for preliminary treatment,and the processed reburning fuel enters the reduction zone of the furnace through the preset reduction gas nozzle to participate in the whole combustion process.Other basic setting conditions remain unchanged,change the position of reduction nozzle,simulate and calculate the distribution cloud chart of NOx volume concentration and NOx concentration value at furnace outlet under various working conditions;compare the results with the actual working conditions,verify the effectiveness of ultra-low NOx emission technology of controllable preheating device,and find the best injection position of reburning fuel to provide guidance for field transformation.Finally,after determining the height of the pyrolysis fuel inlet in the reduction area,the relationship between the fuel ratio of the pyrolysis gas and the NOx concentration is obtained by simulating and calculating the conditions of installing the fuel inlet on the wall,the conditions of different controllable high-temperature preheating fuel device treatment,the conditions of different combination of coal mills and the conditions of different burn out air ratio,and the transformation test is carried out on site Provide the best operation plan.