Study On Ultra-fine Steel Slag Processed By Waste Heat Of Steel Mill

According to statistics,the output of waste steel slag has exceeded 1 billion tons in China,but its utilization ratio is less than 30%.Large amount of the emission of steel slag has caused land occupation and environmental pollution.Research shows that the ultrafine grinding of steel slag to D50 <10 ?m can effectively improve its activity and can be used as a mineral admixture to meet resource utilization.However,there are disadvantages such as low efficiency and small single-scale in the current ultrafine grinding technology,limiting the application of ultra-fine steel slag powder.This paper uses the waste heat of steel mills to achieve the ultrafine grinding of steel slag,thus provides a new process and equipment for the utilization of the waste heat of a steel mill and the low cost,large-scale of ultrafine grinding of steel slag.The numerical model of superheated steam jet mill(nozzle throat diameter d_c=3.5 mm)was established in CFD software to research the flow field and particle acceleration characteristics.According to the numerical model,the air flowing classifier and the dust collector were designed to establish the pilot test platform of superheated steam jet mill.Besides,experiments were conducted through the experimental platform.Based on the existing research,particle acceleration characteristics of the large flow nozzle was scaled and simulated to guide the magnification design of the superheated steam jet mill.The conclusions were as follows:(1)The velocity of the steam flow accelerated by the nozzle was greater than that of the air.And the particles of d=50~200 ?m were accelerated by the steam refrigerant,reaching the maximum dimensionless distance(the ratio of the air jet distance to the nozzle outlet diameter)of 15-21 times.And the larger the particle size was,the longer the acceleration distance was.The acceleration velocity of the particle groups in the axis was biggest,the relative volume fraction was the lowest,but the lower the acceleration rate along the axis of the jet,the higher the relative volume fraction was.(2)Superheated steam jet mill was easy to ultrafine the steel slag to D50(means 50% through the particle size)=4~10 ?m.When the classifier speed was kept constant and the grinding particle size is D50= 7.1?m,the larger the particle size was,the lower the grinding steel slag output was,indicating that the particle size of the feed had a significant effect on the output,which was consistent with the numerical simulation.(3)When the nozzle throat diameter was d_c=8 mm?d_c=16 mm?d_c=24 mm?d_c=32 mm respectively,the particle of d=100 ?m achieved the maximum dimensionless distance of about 17 times,similar to that of the nozzle throat diameter d_c=3.5 mm,indicating that when the nozzle throat diameter was increased,the dimensionless distance of particle acceleration was basically unchanged.Therefore,when superheated steam jet mill was scaled,the size of the crushing chamber and the relevant structural parameters could be determined by the dimensionless distance of the particles.Under the same conditions,the higher the inlet pressure of the superheated steam was,the higher the speed of the particles was,and the longer the acceleration distance was.The higher the inlet temperature was,the higher the speed of the particles was,but the acceleration distance was not changed.