Study On Low Nitrogen Combustion Of 140t/h Circulating Fluidized Bed Boiler Based On CPFD Method

In order to make better use of various coal types,circulating fluidized bed boiler technology emerged as the times require and has been widely used in China.However,in practical applications,the circulating fluidized bed has a series of problems such as unbalanced feedstock,serious coking and slagging,severe furnace wear and high nitrogen oxide emissions.In this paper,a Pyroflow type 140t/h high temperature and high pressure circulating fluidized bed boiler is taken as the research object.Combined with the characteristics of the boiler and the problems existing in the actual combustion,the secondary air layout,distribution,bed material particle size and coal feeding offset are set.The numerical simulation study was carried out,and the effects of various factors on the stationary combustion and NOx emissions of the boiler were analyzed.This paper first studies the influence of meshing method on mesh quality and the influence of mesh number on calculation accuracy.Then the theoretical analysis of the main models involved in the numerical simulation is carried out,and the specific numerical simulations are compared and analyzed for various drag models.Finally,all the mathematical models used in this paper are determined.In this paper,the current situation of combustion and pollutant discharge of a 140t/h high temperature and high pressure circulating fluidized bed boiler is analyzed by numerical simulation combined with the actual operation data of the site.The secondary air arrangement,distribution and bed size of the secondary air system are analyzed.In-depth study on the effects of key factors such as coal offset on low-nitrogen stationary combustion.The results show that the secondary air reform has resulted in good air classification,and the nitrogen oxide emissions have been well controlled.The NOx content has been reduced from 270 mg/m3 to 160 mg/m3,and due to its own cycle.The combustion characteristics,the carbon content of fly ash is not obvious.In the study of the influence of particle size on combustion,it is found that the bed material with excessive particle size has poor fluidization effect in the furnace,and it is easy to slag,and the inner circulation effect in the furnace is not obvious.At the same time,the larger the particle size of the bed material,the smaller the amount of coal powder carried,resulting in higher temperature in the upper dilute phase region.By comparing and analyzing the different coal supply settings,it is found that the most effective offset setting is left: medium: right = 1.93: 2.93: 3.93,wherein the coal offset setting has little effect on the furnace temperature field.The reason for the imbalance of the series of cyclones is that there is eddy current inside the furnace,and changing the coal supply is an effective method to solve the imbalance of the left and right cyclones and keep the boiler burning smoothly.