Numerical Simulation Of Characteristics Of NOx Formation In Pulverized Coal And The Electronic Waste Flue Gas Combustion Process

Air pollution problem has become increasingly serious in recent years, and NOx is one of the important atmospheric pollutants, which is getting a worldwide attention due to their harmful impact upon the environment and human health. Fuel combustion is the main source of the formation of NOx, and coal combustion and industrial boiler combustion are two of the important aspects in our country. Therefore, numerical simulation of pulverized coal jet combustion and NOx emission characteristics under different factors as well as organic matter’s combustion characteristics and NOx emissions of heat recovery steam generator under different stratified combustion conditions have been conducted.For pulverized coal jet combustion, the effects of different factors on gas pollutant NOx formation during coal combustion have been studied. These factors include the different coal (bituminous, lignite and anthracite), the different particle size (d=10-80um) and the different combustion atmosphere (O2/CO2, O2/N2with oxygen concentration from21%to60%). The CPD pyrolysis model is used to fit the rate constant of single reaction rate model for different coals. On the basis of simulation results are basically consistent with pulverized coal jet combustion experiments for both the non-reactive and reactive cases, the characteristics of NOx formation have been analyzed under different factors. The simulation results show that the difference of coals, particle sizes, combustion atmosphere, and the different of distribution of fuel N in volatile and char as well as soot model in simulation have important effects on the formation of NOx formation.For the electronic waste flue combustion in waste heat boiler, combustible organics flue gas will be produced in the process of smelting electronic waste. These unburned organics flue gas and will be burned in the waste heat boiler, in order to prevent them into the flue treatment system and to reducing the difficulty and cost of flue gas treatment. In this parper, considering the situation of the concentration of organic matter in waste heat boiler entrance flue gas which produced by the smeltment of electronic waste changed, numerical simulations of organic matter’s combustion characteristics and NOx emissions of heat recovery steam generator under different stratified combustion conditions have been conducted, in order to optimize the boiler nozzles’stratified arrangement. The verification of two outlet boundary conditions (pressure outlet boundary and the outflow boundary conditions) and the different treatment methods of complex organics in entrance flue gas have been conducted firstly, then the effect of different layers of nozzles (2layers,3layers and4layers) and different nozzles’ position on organic matter’s combustion characteristics and NOx emissions have been analyzed in detail under different conditions of mass fraction of organic matter contained in the flue gas(2.655%,5%and10%) in this works. Considering the situation of NOx formation and the use of waste heat in waste heat boiler, the optimal of the boiler nozzles’ stratified arrangement for different concentration of organics have been obtained. Studies show that the optimal nozzle arrangement scheme is different when the concentration of organics in entrance flue change, in order to ensure that keep stable combustion in waste heat boiler and prevent local high temperature as well as control NOx formation.