Study On Technology Of Fiber Formation Of Molten Blast Furnace Slag And Fiber Products

Blast furnace slag(BF slag)is a by-product of iron-making, and its output is very high. However, current method of treating BF slag is a great waste of the heat produced by melted slag, and creates little added value for application. A feasible method to recover more heat and improve the added value of BF slag is proposed in the present article. By addition of a slag modifier, the chemical composition of BF slag is changed. The modified slag is then used to prepare slag fibers through centrifugal fiberizing. Finally, these slag fibers can be used to make fiber products. In view of the fiberization of molten BF slag and the preparation of fiber products, the author of this paper has done the following researches:The formation mechanism of slag fiber was described theoretically. Specifically, the fiber formation process was divided into two stages: fiber formation and tensile deformation of fiber. In the first stage, by centrifugal and nozzle-blow process, a unified form of expression of the most unstable wavelength during fiberization was obtained and verified. In the second stage, based on previous studies on fiber fracture, a hypothesis was proposed about a free liquid filament of arbitrary viscosity that can be used to study fiber drawing process. In this stage, the effects of shear-thinning viscosity of molten slag on the tensile deformation of fiber were analyzed.The fiberization process of molten BF slag was studied experimentally through centrifugal method. The optimal process parameters under experimental conditions were determined through centrifugal tests of molten BF slag with different acidity coefficients. Based on experiment results, factors that can affect the diameter and the length of slag fibers were analyzed, the unstable wavelength was defined, and the influence of such parameters as outlet slag temperature, roll diameter and roll speed on the centrifugal spinning process and the finished fibers.In the acid-alkali resistance experiment, slag fibers of varied acidity coefficients that had been obtained from centrifugal method were tested. It was found that the resistance ability of slag fibers tended to increase with the increase of acidity coefficient. Based on this finding, slag fibers with a coefficient of 1.3 were selected to prepare fiberboards for performance study. In the process of preparation, in order to overcome the adverse environmental and healthy impacts of phenolic resin, a kind of organic binder widely used in traditional preparation process, this study decided to use slag fiber as a main raw material for the production of fiberboards, with polyvinyl alcohol(modified by silica sol and borax) as a binder. Fiberboards of different binder ratio were obtained under orthogonal test. According to relevant standards, properties of fiberboards like thermal conductivity, compression strength, tensile strength, hydrophobicity and thermal shrinkage temperature under load were analyzed using thermal conductivity tester, electronic universal testing machine and other equipments. The influence of the type and amount of binder on the properties of slag fiberboards was also studied. Results showed that the addition of silica sol can improve the high temperature resistance of fiberboards, while the addition of borax can improve the hydrophobic rate and compression strength of fiberboards. By comparing the performance of all tested samples, it was found that the optimal applying amount of silica sol and borax depends on the concentration of polyvinyl alcohol.Finally, through the test of the strength and thermal conductivity and the analysis of the corresponding semi empirical model of the different bulk density fiberboards, the relationship between the strength of the fiber board, the thermal conductivity and the bulk density was studied, and the appropriate bulk density and porosity of slag fiber products were determined. It was found that the three-dimensional distribution of the fiber can improve the strength of the fiber board without increasing the thermal conductivity by testing the strength and thermal conductivity of slag fiber board with different structural forms.