Temperature Simulation And Optimization Research On The Processes Of The Ladle Regenerative Preheating And Turnover

The temperature of molten steel is significantly influenced by the ladle,the thermal state of which is the load and smelting container of molten steel at the interface from the converter to the continuous casting.Enhancing the thermal state of ladle,which could decrease the temperature drop of molten steel during the turnover period and the tapping temperature of converter,is of important meaning to the steelmaking process.The main technologies applied to steelmaking plants include the regenerative preheating technology,ladle cover technology,online preheating technology and real-time tracking and dispatching management of ladle.The optimizing research of numerical simulation on the regenerator and nozzle,which are the core components of the regenerative preheating system,was conducted in this research to the problems of low heating-up speed and uneven temperature in the preheating process.This research provided guidance for optimized selection of regenerators and structure design of nozzles.The finite-volume software,Fluent,was adopted to develop the transient fluid-solid coupling heat transfer model of regenerator and turbulence and combustion reacting model of jet flame from the nozzle.The effect of cell opening shapes,cell opening side length of regenerator and switching time on the air-preheating temperature,time requirements for regenerator arriving the steady thermal state,pressure loss and energy recovery ratio was studied.In case of enough pressure supply from the air blowers,the square cell opening,cell opening side length of 2mm and switching time of 15s are the best design and operating parameters.The effect of the number of gas orifices and gas injecting angle on flame fields inside and outside the nozzle was studied.The nozzle with the 20° gas injecting angle and 4 gas orifices,in which the flame length and width at the rear of flame temperature field reach the maximum values,was the best structure parameters for large ladle preheating.To the status of disconnected researches on heat transfer among preheating,ladle and molten steel,the steady and transient coupling calculation models of regenerative preheating,heat transfer in the ladle and molten steel were established.The effect of air-preheating temperature,gas flow rate and air flow rate during the ladle preheating at the cold repair process on the thermal state of ladle and temperature drop of molten steel.The temperature drop rate decreased by about 0.022K/min when air-preheating temperature increased from 925K to 1225K.The preheating gas flow rate and air flow rate that could minimize the temperature drop of molten steel during the heavy ladle period were 260Nm3/h and 1500Nm3/h respectively.The capping and online preheating are two important methods for improve the thermal state of the ladle.The heat transfer models of the empty and heavy ladle with or without the cover and online preheating were established for the turnover period of ladle.The effect of using cover and online preheating time on the thermal state of ladle and temperature drop of molten steel was studied.There was a similar effect between the capping of empty and heavy ladle and the online preheating of 30min on the keeping ladle temperature and decreasing the temperature drop of molten steel,and the decrease of temperature drop rate of molten steel during heavy ladle period was 0.11 K/min.The temperature measurement was adopted to verify the calculation model,and was adopted to verify the effect of the above research on the preheating process and decreasing temperature drop of molten steel and tapping temperature in the steelmaking plant together with the production data.For different steels,the decrement of tapping temperature is 5.8K～50.1K lower in 2017 than in 2015 without the optimizing.