Optimization Research On Bottom Blowing Of 2.5t Silicon Ladle

Ladle metallurgy is an economical and simple method of silicon purification,which can effectively remove the harmful impurities(such as Al and Ca),and homogenize the composition of liquid silicon.At present,most factory uses the ladle with a single centered nozzle to refine silicon.This design is easy to produce the dead zone of silicon melt in the refining process.The refining time is longer and the heat loss is much,thus affecting the quality of the product silicon after refinement.In this paper,the physical simulation and numerical simulation are used to study the process of ladle refining.The effects of different nozzle arrangement and the amount of refined gas on the flow characteristics in the silicon ladle are discussed.The main contents and conclusions are as follows:(1)The 2.5t ladle refining technology of a silicon factory in yunnan province was employed as the research object.On the basis of the similarity principle,a physical model of silicon ladle with copper nozzle was established according to the model and the prototype of 1:3.The influence of the number of nozzle,the nozzle position and different gas blowing on the mixing time were studied using water model experiment.The experimental results showed that the nozzle was located at off-centered 0.3r,which had the shortest mixing time in single nozzle ladle refining system.For the double nozzles ladle refining system,the mixing time was shortened with the increased of the spacing between the two nozzles.When the two nozzles were located at off-centered 0.7r with 180° symmetric distribution,showing the shortest mixing time.(2)The VOF model,standard k-? turbulence model,no slip wall and standard wall function were adopted to build the mathematical model of copper nozzle ladle refining.The physical simulation results were verified by the numerical simulation.The simulation results showed that compared with the original centered nozzle ladle refining,the average velocity and turbulent energy of liquid silicon in the single nozzle off-centered 0.3r ladle and the double nozzles off-centered 0.7r ladle were increased,and the dead area was reduced.Which is conducive to a good contact between liquid silicon and enriched oxygen,shorten the refining time,improve the efficiency of ladle refining.Among them,the double nozzle off-centered 0.7r had the best effect,and thesingle nozzle off-centered 0.3r was the second.Which is consistent with the experimental results of the water model.(3)The water model and numerical simulation results of the silicon ladle with the copper nozzle were presented,and the numerical simulation and industrial tests were carried out for the existing brick nozzle ladle.The content and distribution of impurities in the product silicon of the primitive and optimized ladle refining were analyzed.It showed that the Al and Ca contents in the product silicon of the optimized ladle refining were further reduced.Compared with the primitive ladle,which were reduced by 13.22% and 25.87% respectively.At the same time,the Si,Fe,Al,Ca elements in different parts of silicon ingot were distributed more evenly.The results were consistent with the numerical simulation results of the better turbulent performance and the smaller dead zone,which provided the guiding for the optimization of the ladle refining technology.