Fibering Mechanism Of Modified Molten Blast Furnace Slag And Experimental Research

At present the water quenched process is the most extensive approach for blast furnace slag.However,during this process,it not only consumes large amount of water but also brings serious pollution to environment.Besides,the slag sensible heat is difficult to be recycled and the production is low value-added.Blast furnace slag has attracted attention of metallurgists as an available secondary resource,and how to recycle it and its heat has become an urgent concern for the steel industry.So,in order to efficiently use the slag sensible heat and produce high additional value products,the blast furnace slag was used to produce the slag wool by changing it chemical composition.However,so far it has few commercial applications because there were not enough studies about the effect of changing the blast furnace slag chemical composition on the slag wool production and the forming mechanism of slag wool.This paper discusses examined the mechanism of direct fiber formation of blast furnace slag.This paper the dynamics of slag flow on a roller surface,the dynamics of fiber formation process,and the rules of heat loss changes throughout the fiber formation process using the centrifugation method.It explores how the factors,such as gas pressure and volume and the nozzle type involved in the injection method,affect fiber formation.The thermal experiments were performed using a metallurgical slag comprehensive platform and a semi-industrial pilot test platform,with the assistance of microscopic testing tools,such as an ore microscope,electron microscope,X-ray diffractometer,energy spectrum analyzer,and differential scanning calorimeter(DSC).Based on the theory of boundary layer,the paper explores the flow mechanism of the slag on the roller surface involved in the centrifugal spinning method.The formation process of the slag boundary layer film was analyzed in detail and a local similarity solution model was established.A mathematical model and a wave model were developed for the boundary layer thickness distribution.The relationships of the boundary layer thickness distribution with the Reynolds number and the roller diameter were evaluated.By studying the factors affecting the boundary layer thickness,the relationships among the wavelength,the slag surface tension,the slag density,the roller speed,the roller diameter and thickness were obtained.By focusing on the formation of the bulge in the boundary layer film and the fiber formation process,the study found that the Rayleigh-Taylor instability was the maincausal factor of film instability and that the surface tension played a deciding role in the formation of the bulge.This explained the two methods of fiber formation,evolent spinning and boundary layer separation.Based on the slag fiber formation process,the heat loss rules during slag dripping were examined through three stages:stage of slag dripping before roller,roller-to-roller stage,and fiber formation stage.The functional relationship between the residual heat of the slag stream and the radius of the stream is established for the free dripping process of slag;the mathematical model of the inelastic collision energy loss between the slag and the centrifugal roller surface is established;the mathematical model for the three types of heat loss under the conditions of static stream,dynamic stream,and forced convection cooling revealed the law of heat transfer changes during the slag fiber formation process.Based on the principle of sprayed jet,the mechanism of jet fiber formation was explored with Fluent software simulation.The flow field of nozzles with different Mach numbers was analyzed.The formation process of liquid film and surface bulges in the blowing process was studied;the mechanism of filament breaking and fiber formation was revealed;this paper examines the effects of nozzle diameter,gas flow rate and pressure,and slag viscosity.Thermal tests were conducted using metallurgical slag comprehensive platform and a pilot experiment platform.For fibers prepared by centrifugal method at an acidity coefficient of 1.0?1.3,the variation in fiber diameter was small and the fiber surface was smooth.When the acidity coefficient exceeded 1.3,the fiber diameter increased significantly and the fibers turned coarser,accompanied by the presence of slag balls and reduced fiber quality.When the acidity coefficient is in the range of 1.2 to 1.4,the diameter of fibers formed using the spray method was less than 3?m,the content of slag ball was lower than 5.14%,and the rate of cotton formation was higher than 70%,reaching the associated national standard.The fiber products were also tested on the pilot experiment platform;the fiberboard obtained showed desirable thermal insul ation property and high-temperature tolerance.The operation temperature was found to be greater than 600? in compliance with the national standard requirement.