| Sintering is one of the critical procedures in steel industry,and the domestic overall output of sintering is 1.28 billion tons in 2016.It has a poor adaptability performance when flaws are detected in the structure of the swirl burner,so some problems such as the flame length fluctuation,the high temperature zone dispersed over the sintering surface,the high fuel unburn rate even the off-fire issues and others,could be caused when the air or gas pressure fluctuated.The negative pressure level inside the furnace and the burner inlet pressure must be reasonable controlled,in order to maintain a reasonable flame length,ensuring the sintering surface temperature level.The swirl burner is operated in micro-negative pressure condition within the sintering ignition furnace,and the surface of sinter layer is directly heated by the flame,the characteristics of process and operating conditions are different from those of other swirling burners.Therefore,the flow and combustion characteristics of swirl burners in the ignition furnace were studied by the paper based on previous research results.The flow characteristics of swirling burner in the ignition furnace are firstly studied using the experiment and numerical simulation,after that an experiment table including dual-swirling burner that has a 1:1 ratio of the burner model of the production site was set up,the velocity distribution of the non-reacting flow through the burner was measured using the particle image velocimetry(PIV),there were little difference between the measurement results and numerical simulation results with respect to the local velocity and flow field locations,verifying the accuracy of the numerical simulation,then the affection on the CO unburn rate and sintering surface temperature were acquired after having analyses for the characteristics of the flow field,the temperature field and the burner parameters;Secondly,the influence of the bluff body structure on the burner flame stability was studied,and the heat-flow-solid coupling model was established to analyze the combustion characteristics of the burner on the thermal impact of the firebrick brick using the response surface method.Finally,the double-swirling burners were produced and installed in an industrial ignition furnace to complete the industrial experiment,as well as a live thermal meter testing was performed and the results indicated that the sintering material surface temperature level was increased from 1088°C to 1202 °C,the fuel consumption was also decreased by nearly 15%,after having an analysis of the two-month operating data.Experimental results indicated that:(1)Both the structural parameters and operating conditions had some effects on the combustion characteristics of the single swirl burner.The sintering surface temperature level was maintained at around 1080°C,and the CO unburn rate was kept at about 23.8%,which was not conducive to sintering production and energy saving.(2)Compared with single-swirling burner,the double-swirling burner has better performance in terms of sintering surface temperature level and CO unburn rate under the same conditions.When the double-swirling burner was operated stably,the sintering surface temperature level was maintained near 1210°C,the CO unburn rate was maintained at around 5%,which significantly reduced the sintering ignition energy consumption.(3)Both the PIV measurement results and numerical simulation results showed that the swirling flow structure in the furnace is similar in general,the average relative error of the tangential velocity was 5.38% and the maximum relative error was 6.5%.(4)The double-swirling burner installed with "一" shaped bluff body formed a stable ignition source on the left and right sides of the bluff body,and the ignition temperature reaches 1050°C,improving the combustion efficiency of burner to 93%,as well as reducing ignition energy consumption.(5)As for the rectangular refractory bricks with bell mouths,the maximum strain with a value of 1.22%,was distributed symmetrically at the end of the bell.(6)The double-swirl burner with a “一” shape blunt body was installed on the ignition furnace,then a live thermal meter testing was performed and the results indicated that the sintering material surface temperature level was increased from 1088°C to 1202 °C,it also indicated that the relative error between the test results and the numerical simulation results was about 3.4%.Having an analysis of operating data for the past two months,it was found that the double swirl burner with a “一” shape blunt body reduced fuel consumption by nearly 15%,compared to the conventional single-swirl burner and completely solving the problem of off-fire. |
PDF Full Text Request