Numerical Simulation Of Flow Field In A Multi-layer Smelting Reduction Reactor

In the smelting reduction process,the thick slag layer can separate the oxidation zone from the reduction zone,avoiding the reoxidation of reduced iron and increasing the consumption of pulverized coal.The temperature of each area in the slag iron bath reactor is high,and the smelting environment is complex,and many internal phenomena cannot be observed directly.Therefore,it is necessary to study the slag and iron bath molten pool flow phenomenon by physical simulation and numerical simulation and other main means,so as to provide a basis for further improvement of thick slag layer iron bath molten reduction process.Based on the water model experiment of an iron bath smelting reduction reactor with thick slag layer,numerical simulation is token out to study the stirring characteristics of the molten bath by double-layer side blowing lance under different injection angles(40°,45°,50°)and different horizontal insertion depths(60mm,120mm,180mm),and the accuracy of numerical simulation is verified by the results of water model experiment.By observing the flow field of the molten pool in the gas-liquid two-phase flow and the diffusion of the tracer,the proportion of the weak flow zone and the dead zone and the mixing time under different side-blowing conditions are analyzed,and the mixing time of molten bath under different gas flow rates are also studied.By comparing the flow field of molten pool with single nozzle,double nozzles(symmetrical and asymmetrical)and four nozzles(symmetrical and asymmetrical),the proportion of dead zone,average turbulent kinetic energy and mixing time,(1)The horizontal insertion angle of the side blowing lance has a more significant influence on the stirring characteristics of the molten pool than the horizontal insertion depth.The horizontal injection angle and insertion depth of the side blowing lance affect the swirling flow area and the number of swirling flows generated in the molten pool.When the horizontal injection angle of the side blowing lance is larger and the horizontal insertion depth is deeper,the volume of the weak flow zone or the dead zone in the molten pool is smaller,which is more conducive to the stirring and mixing of the molten pool.The best injection conditions are obtained from the numerical simulation:the upper injection angle is 50°,the insertion depth is60 mm,the lower injection angle is 50°,and the insertion depth is 120 mm.In addition,the mixing time of molten bath under different gas flow rates are also studied.It is obtained that the mixing time of molten bath is the shortest when the single gas flow rates of upper and lower lance are 8.58 and 10.43 Nm~3/h,respectively.(2)Asymmetrical bottom blowing is better than symmetrical bottom blowing,and the effect of double nozzles bottom blowing was better than four nozzles bottom blowing.The mixing effect is worst under the condition of single nozzle.When the bottom blowing is asymmetrical with double nozzles,the mixing time is the shortest.Under the condition of double nozzles asymmetrical bottom blowing,when the insertion angle and depth of side lance are larger and deeper,the whole molten pool is fully stirred.When the insertion depth of the side lance is deeper,the gas holdup in the molten pool is greater and the stirring of the molten pool is more intense,while the insertion angle has little effect on the gas holdup.By comparing the influence of different side blowing conditions on the slag layer,it is found that the slag layer is divided into two layers by double-layer side lance,and the critical surface of the slag layer is about 200～260mm from the bottom,and the insertion depth of the lower side lance has a greater influence on the layering of the slag.