| In metallurgical process,a reasonable organized flow field is the key of improve product quality and production efficiency.But,in many circumstances,the furnaces used in the metallurgical process are working in high temperature environment.This makes it extremely difficult to obtain the flow field information.In recent years,with the development of computational fluid dynamics,computer technology and measurement technology,using the combinational method of CFD technology and hydraulic model experiment to research the flow phenomena in the process of metallurgy,becomes a mature and efficient new method to solve the problems above.The bottom blowing copper smelting process is a new method of independent intellectual property rights.It has the advantages of excellent flexibility to mineral,simple process,high oxygen enrichment rate and low energy consumption.With the increase of the scale of the production line and the size of the bottom blowing furnace,the gas quantity injected into the bottom blowing copper is increasing gradually.At present,mainly through three aspects to improve the gas-flow rate of bottom:increasing the gas injection speed,increasing the number of oxygen lance and increasing the size of the oxygen lance.It caused the serious wear and tear of oxygen lance and reduced service life of oxygen lance by increasing the gas-flow rate.Also,the flow and mixing characteristics of the whole furnace can be influenced by increasing the number of oxygen lance.In addition,the three methods will increase the melt spray increased in the smelting process.So,a reasonable organized flow field is the key of the regular production of the bottom blowing copper smelting furnace.In this paper,A typical bottom blowing furnace of a company with diameter of 4.8m and length of 21m is studied.And the combinational method of CFD technology and hydraulic model experiment is used to discuss the multiphase flow process in the bottom blowing copper smelting furnace.Above all,the main contents of the research are as follows:(1)The compressible flow model was carried out to discuss the change rule of main flow parameters in both two channels of oxygen lance,and the empirical expressions of main flow parameters at the exit of oxygen lance were obtained by data fitting.The error of static pressure,density,velocity and total pressure at oxygen lance outlet is not more than 3%,the calculation results are faithful.The three segment full buoyancy model was used to calculate the stirring energy of the original oxygen lance under three different gas flow conditions,and the ratio of the theoretical stirring energy to the actual stirring energy was defined as the oxygen lance efficiency.The efficiency of the outer channel of the original oxygen lance under three different gas flow conditions were 73.17%,66.41%and 60.6%,and the efficiency of the inner channel were 92.31%,89.02%and 85.37%.In addition,the efficiency of oxygen lance with three typical shapes was calculated by this model.The efficiency of the outer channel of oxygen lance under three different shapes were 68.21%?66.41%and 64.32%,and the efficiency of the inner channel were 89.77%?89.02%and 88.33%.(2)Based on the similarity principle,the hydraulic model of the bottom blowing furnace was built under the rule of equal corrected Fr number,and the hydraulic model was used to discuss the relationship between gas flow rate,structure of oxygen lance outlet and flow state.The experimental results show that the discontinuity of the gas jet near the exit of the oxygen lance was the main cause of the pressure fluctuation.It is also found that the relationship between the pressure fluctuation frequency and the gas flow rate is approximately linear,the greater the gas flow rate,the greater the pressure fluctuation frequency was.The influence of three important structural parameters on the flow state in the experimental table was analyzed by the orthogonal method,and the fuzzy judgment matrix and weight vector were carried out to discuss the weight of the two optimization indexes in the comprehensive evaluation index.Finally,the optimal combination of the oxygen lance spacing,the oxygen lance diameter and the oxygen lance angle is obtained by the analysis of the signal to noise ratio and range analysis.(3)The PIV system was used to measure and analyze the flow parameters in the hydraulic model of the bottom blowing furnace.Then,the macro instability in the bottom blowing furnace is studied by the method of frequency spectrum analysis.It is not possible to observe the macro-instability when the gas flow rate is low,and with the increase of the gas flow rate,the overwhelming influence of dominant frequency on the frequency spectrum is gradually increasing,when the ratio of the maximum amplitude and the background amplitude is greater than 30,the macro instability phenomenon occurs in the hydraulic model.In addition,in the 10 groups of different water depth of the experimental program,the macro instability was not observed when the water depth was in the range of 300mm?450mm and 650mm?700mm,but it can be found in the hydraulic model when the water depth was between 500mm and 600mm.It also found that the size of the hydraulic model was the main influencing factors of the MI frequency.When the ratio of the model to the prototype were 1:3,1:5 and 1:10(corresponding to the diameter of the hydraulic model were 1230mm,738mm and 369mm),the MI frequencies were 0.653Hz,0.871 Hz and 1.258Hz,respectively.The larger the diameter of the hydraulic model,the smaller the MI frequency.(4)The physical and mathematical model were founded to research the influence of gas flow rate and pool depth on the thermal flow process in the bottom blowing furnace.Then,the influence of three important structural parameters on the flow state was analyzed by the orthogonal method.The influence of three factors on the bottom blowing furnace is obtained by SNR.The factors affecting the bottom blowing process has the following sequence:oxygen lance spacing>oxygen lance lead bath diameter>oxygen lance inclination angle.The optimal combination is the oxygen lance diameter 6mm,the oxygen lance spacing 50mm,the oxygen lance angle 10°.Compared with the original scheme,the mean turbulent kinetic energy increased by 17.08%,the amount of splash reduced 14.59%. |
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