Numerical Simulation And Refractories Selection Analysis On Freeze Lining Of Submerged Arc Furnace

Freeeze lining of submerged arc furnace (SAP) is an effective measure of prolonging lining campaign, which is still at the beginning stage in China. In this thesis, technical status and refractory selection of SAF freeze lining were studied.The water-cooled tap hole of freeze lining in SAF smelting Si-Ca ferroalloys was simulated. Impact of some relevant design parameters to tap-hole life time was analyzed. Results showed that water-cooled tap hole could be applied in SAF smelting Si-Ca ferroalloys to slove the short lifetime problem of tap-hole. The proper velocity and temperature of cooling water were1.5m/s and40℃. Thermal conductivity of ramming paste between copper cooler and carbon brick is less than3W/(m·℃).Alumina-paraffin composite material was developed in cold model experiment for simulating the lining erosion process, thermal conductivity and melting point of which were5.15W/(m·℃) and56℃. The computing result of1D model was validated. The compatibility of1D model is poor when the temperature field is unstable. The thermal conductivity of refractories should be controlled when employing the1D model. The scope of thermal conductivity was defined by the value of lining heat release."BEM-Nelder Mead simplex Method"2D inverse heat conduction model for monitoring erosion profile of freeze lining in SAF smelting ferronickel was programed. When the erosion profile was obtained, temperature difference between measured and computed was within4℃. Result of erosion profile was validated by comparing lining heat release with industrial data and the relative error was about11%. The impact of thermal conductivity on computing results of erosion profile was analyzed. The thermal conductivity decrease23%and the thickness of lining would reduce around4.56%.Some physical-chemical indexes of hot preesed carbon brick, HP brick for short, were detected. Results showed that the imported NMA UCAR HP brick could be replaced by domestic SLTA HP brick as the refractories for producing ferro-manganes and ferro-chrome. Technical schemes that improving thermal conductivity was to increase percentage of pore diameter distribution in interval (0.1μm,1μm) and decrease percentage of that in interval (1μm,+∞). The carbon brick was not fit to use in the SAF smelting low Si ferronickel and the reason why the lifetime of SAF smelting ferronickel is short in China. The proportion of high alumina brick in liquid system of slag-refractory was calculated by ternary phase diagram, which was higher than50%. The high alumina brick was not fit to use in the SAF smelting ferronickel too. The anti ferronickel slag property of magnesia chrome brick and chrome-alumina brick were evaluated by static slag corrosion test. The reasonable component of ferro-nickel slag was determined by orthogonal test. Affecting factors to permeability and erosion were ranked and the proper furnace wall refractory was raised.Results of static slag corrosion test showed that permeability and erosion of Fe-Ni slag to refractories was proportionate to the temperature. The rank of factor about erosion degree was showed as follows, refractory type>FeO content> alkalinity and SiO2/MgO. The order of factor about permeability degree was listed below, Refractory type> FeO content> SiO2/MgO> alkalinity. The anti slag-erosion property of chrome alumina brick was better than that of magnesia chrome brick and the latter has better property of anti slag-permeability. The oxide permeating chrome alumina brick were mainly MgO and FeO and what permeating magnesia chrome brick were mainy FeO. The reasonable component of Fe-Ni slag was obtained. In this slag system, SiO2/MgO was about1.7, FeO content was less than15%and the alkalinity was0.85. The compression strength of chrome alumina brick is about190.34Mpa and this value was around66.44Mpa after slag permeability, which was higher than45Mpa of magnesia chrome brick. The thermal conductivity of chrome alumina brick was1.8times more than magnesia chrome brick. It was can concluded that chrome alumina brick was more suitable than magnesia chrome brick to be applied in the SAF smelting Fe-Ni ferroalloys.