Research On Stepped Ignition Combustion Technology And Its Application For Low Heat Value Gas

The blast furnace gas (BFG), which is a by-product in the process of ironmaking in iron and steel works, is difficult to get a better use of because of its poor combustion performances. And the dismissing of BFG causes the pollution problem as well as the waste of energy. Now with the reinforcement of energy saving and environmental consideration, the recycling of BFG has made great progress.It is a traditional machenism of flame stabilization that the heat in recirculation zone is used to improve the combustion performances of BFG. But the effect of flame stabilization is limited by the mismatch between the temperature field and the concentration field in the bluff body burner. The slitted bluff body burner, which is devoloped on the basis of bluff body burner, has a crack in the middle of the body. And the position of the flame can be adjusted to achieve flame stabilization under low load and to prevent the damage of nozzle burning, coking of the water-wall and high temperature corrosion etc under high load.The combustion characteristics of BFG, and the principle and measure of stabilized combustion are firstly analyzed in this text. Then the principle and the advantage of step combustion technology in recirculation zone are specially introduced. Finally, combustion performances of both the direct current burner and the slitted bluff body burner are simulated in FLUENT under the same initial conditions, from which the velocity vector, the contour diagrams of temperature, stream function and mixture fraction of the flow field are obtained.The simulation results show that the temperature is higher and more uniform in the slitted bluff body burner than in the direct current burner and low-speed recirculation zone allows the air flow in the furnace to mix sufficiently, to stay longer and to burn better; the flame length is shorter than that in the direct current burner, which provide a high temperature to ensure the continuance and stability of the flame. So the conclusion can be drew that the slitted bluff body burner is of great ignition characteristics and flame stabilization, which provides a good theory support and guidance for experimental and industrial applications.