Numerical Simulation Of Thick Layer Sintering Process

Iron ore sintering is a critical process influencing the productivity,quality and enrgy consumption of the integrated iron and steel industry.In order to satisfy the production capacity of blast furnace,more and more sintering equipment were modificated to adopt new sintering process,which can increase sinter output significantly.However,the increase of layer thickness disrupts the temperature filed and the burning through point was delayed.The distribution of temperature filed affects the quality of sinter production directly.There will be practical significance to improve the thickness of layer on the premise of ensuring the sintering yield and sinter quality.Aiming at this problem,numerical simulation method was adopted in this paper to analysis temperature field in sinter layer.The effect of layer thickness and double ignition sintering process on burn through point and temperature field in layer was discussed.Based on the parameters of a sintering machine area 360 m2,a CFD software(computational fluid dynamics,Fluent)was adapted to simulate the distribution and change of temperature field.Sintering bed was treated as porous media.Heat and mass transfer mathematical model were established based on basal conservation equation.Ergen equation was introduced to express the pressure change caused by the gas passing through the layer.Mass source,energy source,momentum source term were coded as user defined function to import program to slove the calculation.Some relevant reactions and parameters which has greater impact on the temperature field were considered,such as coke combustion,calcium carbonate decomposition,carbon monoxide generation.Temperature field and burn through point was calculated.(1)Measured results and calculated results were compared to verify the correctness of model.The result shows that simulation results consistent with the actual production,and the error is 4.17%,which can be a good representation of the sintering process.The simulation method was used to analysis the effect of layer thickness on temperature field and burn through point,and the production index was analysised.The results show that the trend of layer thickness between 1473K and 1673K was firstly increases and then decreases when the layer thickness was increased to 1000mm,and reaches the maximum value at 800mm.(2)In view of the problem that the bottom temperature of the layer is too high and the burn through point was delayed when the thickness increased,layer thickness 1000mm was chosed and carbon content and premeability were changed to analysis the effect on thick layer sintering process.The results show that sinter output increase to the greatest degree when the carbon content is 4.0%,and fuel consumption decreased about 6.98%compared with 800mm.Vertical sintering velocity increases gradually as the porosity increases,and the temperature field within the layer tends to be uniform.(3)In order to shorten sinterng time and obtains a reasonable temperature field while increasing the thickness of layer,a new sintering process named double-layer sintering(double layer burden and double ignition sintering process)was simulated.The results show that double layer sinteirng feed process increased the layer thickness between 1473K and 1673K by 57.84%,and the thickness of layer less than 1473K is reduced by about 57.61%.Double ignition process has two combustion zones in layer which shorten the sintering time about 950 seconds,and the burn through point was 42.60%in advance.Coke combustion rate was increase when oxygen content enrich and temperature in layer was increased,which beneficial to improve sinter quality.