Research Of Flow Field And Reduction Process In The Hydrogen Direct Reduction Shaft Furnace

As a kind of clean energy with strong reducibility,hydrogen is used in direct reduction process to effectively reduce carbon dioxide emissions.With the maturity of hydrogen production technology,the study of hydrogen direct reduction process has become very significant.Based on the chemical and thermal equilibrium equations of hydrogen reduction iron ore,the minimum gas requirement of reducing gas is calculated.The results show that when pure hydrogen is used as reducing agent,the amount of gas needed increases significantly and the utilization ratio of hydrogen decreases compared with the traditional direct reduction process,and when nitrogen or methane is added to the reducing gas,the amount of required gas decreases.However,the amount of gas needed when methane is added is significantly reduced,resulting in a very low hydrogen content in the reducing gas.Based on the CFD three-dimensional shaft furnace model,the iron oxide ore layer is simplified into porous medium to simulate that the seven factors of the outlet pressure of top reduction tail gas,the outlet size of furnace top reducing tail gas,the height of shaft furnace reduction section,the diameter of branch pipe,the length of branch pipe,the outlet of single and double reduction tail gas at the top of furnace and the inlet of single and double reduction gas in the reduction section of shaft furnace,make an effect on flow field in the reduction section of the shaft furnace.Then according to the previous research results,the three-dimensional shaft furnace model is approximately simplifies as a two-dimensional slice model.In order to more accurately study the flow field in the reduction section,The coupling method of computational fluid dynamics and discrete element method?CFD-DEM?is used.The particle size of the pellet is magnified by four times according to the principle of similarity.And the effects of four factors,such as the diameter of the reduction section of the shaft furnace,the amount of gas entering into the reduction section,the angle of the shaft of the reduction section of the shaft furnace and the inclined angle of the branch pipe of the shaft furnace,on the flow field of the furnace are further simulated and analyzed.The influence of the equipment parameters and process parameters on the airflow distribution in the reduction section of the shaft furnace is obtained,which provides a reference for the design of the shaft furnace.Finally,this paper assumes that the pellets contain the 100%of Fe₂O₃ and the reduction reaction is divided into three steps.The CFD two-dimensional shaft furnace model is established and the effect of nitrogen or methane on the metallization rate and temperature field of reducing gas?pure H₂?is studied by using sliding grid instead of material descending approximate simulation.The results show that the metallization rate of the material along the height is decreased and the outlet temperature of the tail gas is increased with the addition of nitrogen or methane in the reducing gas.The metallization rate and the reduction temperature of the material are greatly affected by the addition of CH₄.