Research On The Optimization Of Swirl Inverse-jet Combustor Based On Stable Combustion Mechanism In The Recirculation Zone

Pulverized coal industrial boiler's double cone reverse injection pulverized coal combustion technology was developed byChina Coal Research Institute,it found that this technology caused certain influence to the ignition and combustion efficiency of the pulverized coal due to the weaker swirl strength of the secondary air in the early burner design.Therefore,a relatively mature bluff body recirculation zone stable combustion technology was introduced in this paper,to organically combines with the existing double-cone burners,in order to improve the combustion efficiency of the pulverized coal in the burner and reduce the fly ash residue of the boiler.Through this optimization and transformation,the pulverized coal is finally realized in an efficient,cyclic,and comprehensive utilization,achieving energy conservation,cost reduction,and efficiency reduction.Firstly,the rotary jet of the double cone burner is studied in this paper,and temperature field distribution inside the burner under different swirl intensity is simulated.The optimal swirl intensity in the double cone burner is 2.5~3.0,which provides the basis of parameter settings in the simulation study.Then the combustion mechanism of the bluff body was studied to provide a theoretical basis for the next step of installation of a blunt body.Drawing lessons from the four typical bluff bodies used on boilers in power stations,and through comparison analysis and type selection,a conical bluff body is the most optimal choice.Then reasonable values of three key parameters of a conical bluff body,including the cone angle,side width,and blocking rate were theoretical studied.It was determined that the taper angle was 60° to 90°,the relative width was 0.5~0.75,and the blocking rate was 0.The simulation study of three optimized transformation schemes of the original burner were carried out,and effects of the three schemes,including installing the blunt body,the guide vane,the bluff body and the deflector vane,were compared and analyzed.Installing the bluff body and the deflector vane is the most optimal choice,and the simulation study of four different size bluff bodies was performed.It was determined that a suitable cone angle of a conical bluff body on a double cone burner was 73.6°,and the ratio of edge to width was 0.65,the blocking rate is 0.Through the hot bench experiment,the effect of installing a bluff body in the burner was verified,and the degree of flame accumulation was increased.Further,the rigidity of the flame exiting the burner was enhanced.The optimization of the installation of a bluff body and covering of the guide vanes on a 14 MW burner has verified that the recirculation zone formed by the swirling reverse jet of the nested combustor in the recirculation zone formed by the bluff body at high swirling intensity,the double recirculation zone.The nesting reduces the average temperature of the burner to below 60°C,the average furnace temperature is increased by 50°C,the negative pressure fluctuation of the furnace is significantly reduced,the average steam production is increased by 2t/h,and the carbon content of fly ash is reduced below 15%.The pulverized coal combustion efficiency verified the simulation results.Finally,four different size bluff bodies were used for industrial tests and the appropriate dimensions for the 14 MW burner were determined,which are in agreement with the simulation results.