Research On Mechanical Centrifugal Granulation Characteristics Of Blast Furnace Slag

As the main by-product of the ironmaking process,blast furnace slag(BF slag)is a high-grade heat source.The traditional water quenching method of BF slag treatment has the problems of large water consumption and environmental pollution.At the same time the BF slag mechanical centrifugal granulation and heat recovery process has the advantages of low energy consumption and no water consumption.It can recover waste heat from BF slag efficiently.Therefore,the mechanical centrifugal granulation and heat recovery process have become the matter of blast furnace slag treatment.Mechanical centrifugal granulation is the key of the entire process.Based on this,the dissertation starts with the research on the mechanism of BF slag mechanical centrifugal granulation.The relationship between the slag particle size and the operating conditions,the physical properties of the fluid and other physical quantities were studied.The experimental platform for BF slag mechanical centrifugal granulation was designed and developed.BF slag granulated simulation experiment and hot state experiment were carried out on the platform.The main point of the article is as follows:(1)The characteristics of the centrifugal motion of fluids were studied.A physical model of fluid centrifugal motion is established.Clarify the laws of fluid motion in each link of the centrifugal granulation process-liquid film tiling,liquid film edge protrusion,liquid film splitting,and separation into particles.Also based on the mathematical model of liquid film motion,the relationship between slag particle size and flow rate,granulator radius,granulator speed,density,viscosity,surface tension was derived.(2)BF slag mechanical centrifugal granulation experiment platform was established.Based on the analysis of the characteristics of centrifugal movement of fluid and the mechanism of granulation,in order to control blast furnace slag splitting mode in filamentous splitting,the saw tooth edge granulator structure is designed preliminary.The regulation method of the granulator speed was studied.Adjusting the speed of granulator in real time by using PLC and frequency converter,and add particle size feedback to achieve automatic adjustment of granulator speed control.At the same time,the slag flow control method is studied.The position of stopper rod is adjusted by using PLC and stepper motor,and then,the opening and closing of the slag outlet is changed,indirectly controlling the size of the slag flow.(3)Experimental study on centrifugal granulation of blast furnace slag was carried out.In the cold simulation experiment,a rosin and paraffin mixture-with the same physical properties-is used to substitute of BF slag.Comparing the experimental measured value of the particle size during the granulation process with the predicted value of the model.The results show that the two data are basically consistent.The accuracy of the established mathematical model of slag particle size was verified.The effect of the saw tooth edge granulator on the granulation effect was studied.It was found that the granulation effect of the saw tooth edge granulator was better than the disc-shaped granulator in the same working condition whether it was cold or hot.At the same time in the hot experiment of BF slag,experimental data shows that when the speed of the granulator is controlled below 1600 rpm,the generation of residue cotton can be effectively avoided.