In order to improve the mass transfer efficiency of the high‐temperature molten pool area in the oxygen coal combustion melting and separating furnace, water model experiment and VOF model were used to study the mechanism of bubble formation in the area, investigate the changing rules of oxygen lance parameters on the shape and frequency of bubbles. The results show that the basic law of bubble generation is the transition from lateral injection to longitudinal growth, and the bubble generation frequency is 7.5 Hz under standard conditions. Increasing the oxygen lance mass flow will reduce the generation frequency, but the local bubble distribution is more compact. Increasing the oxygen lance inclination angle increase the generation frequency, but it will cause local gas phase accumulation, if too close to the bottom of the furnace. Small oxygen lances diameter is beneficial to increase the generation frequency and enhance mass transfer efficiency. Increasing the oxygen lance immersion depth is conducive to increasing the generation frequency, the gas‐liquid interface and improving molten and separation efficiency. On the other hand, it will weaken the effect of “adherence to the wall” and reduce the erosion of furnace lining by inhibiting the flow of bubbles and slag.
A new process of prereduction of rotary kiln-oxygen coal combustion and melting ironmaking was developed. The core is to realize the conversion of mass and energy of pulverized coal through high-density injection of pulverized coal and high-density combustion in the molten pool to provide the required energy for the ironmaking process. By calculating the combined energy values of working conditions under different metallization rates (η), gas oxidation degrees (α) and blast oxygen content (μ), the pulverized coal consumption, exergy income, exergy expenditure, four gas exergy values, and process of the process system under different working conditions were analyzed. Exergy using efficiency, quantitatively evaluated the interaction between the mass-energy conversion efficiency of coal powder and process parameters and used orthogonal analysis to determine the combination of working conditions with the highest energy utilization rate. The results show that increasing the metallization rate, gas oxidation degree, and blasting oxygen content will change the exergy value, and the exergy utilization efficiency will increase with the increase of metallization rate, gas oxidation degree, and blast oxygen content, but the various parts exergy the value does not reach the optimum with the increase of the process operating parameters. After comparing and analyzing the overall working conditions, it can be known that when the charge metallization rate is 70%, the melting furnace gas oxidation degree is 12% and the blast oxygen content is 98%, the rotary kiln-oxygen coal combustion melting furnace has the best operating conditions and the highest energy utilization efficiency. A mathematical relationship model including metallization rate, gas oxidation degree, blast oxygen content, and process exergy utilization efficiency was established: y = η × 0.1908+α × 0.467227383+μ × 0.137069+0.522508.
Through visualization experiments, the macroinstability behaviour in the molten pool of the oxygen coal combustion melting and separation furnace was analysed by a physical simulation. In the experiment, images were acquired using a high-speed camera and an image processing system was used to track the gas-phase change in the local area of the molten pool and regular fluctuation of the molten pool in real time. Among them, bubble as the carrier of jet energy transfer and liquid level fluctuation. A close connection was observed between the local area bubble motion, jet behaviour, and macroinstability characteristics of the liquid level. The effects of different variables on the local stirring of the molten pool and overall macroinstability were compared. The developed ironmaking process parameters were optimized. The optimal immersion depth of the oxygen lance was 15 mm, while the optimal diameter of the oxygen lance was 4 mm.
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