| The problem of using steel slag with a low hydraulic activity and using as cement admixture with low amount and utilization was settled for the content of hydraulic activity minerals were enhanced by removing the nonhydraulic minerals from steel slag powder. The nonhydraulic mineral product(mainly includes metal Fe, Fe3O4, RO phase) was the research object of this paper. In the paper a simple, quick and accurate method was identified to measure nonhydraulic minerals content in steel slag; the selective dissolution characteristic of RO phase was investigated to determine a kind of practical technical solution to enhance the iron quality and density of the nonhydraulic mineral product; the reached degree of the product index used as ironmaking raw materials or heavy medium powder for coal preparation was evaluated, and the weak technical indicators were improved by the practical technical solution to meet the requirements of product standards.The results show that for the quantitative determination of Fe, steel slag solids were firstly treated in I2-ethanol solution and then the residual mass of the treated sample was measured, and the content of Fe was calculated based on the unique soluble component of steel slag in the solution. The content of Fe3O4 was determined in a solution of 10% HNO3 based on the unique insoluble magnetic compound in steel slag, and the nonmagnetic refractory impurities existed in the insoluble solids were separated from Fe3O4 by magnetic separation. The content of Fe3O4 was determined via the mass of insoluble magnetic residue. To determine the content of RO phase, the sample was immerged into ethylene diamine tetraacetic acid disodium salt-diethylaminetriethanolamine(EDTA-DEA-TEA) solution. In the insoluble materials, the nonmagnetic refractory impurities were extracted from Fe, Fe3O4 and RO phase by magnetic separation. The content of RO phase was determined after subtracting the Fe and Fe3O4 from the total mass of the magnetic insoluble solids. To fully redissolve the particles of the soluble components, the sample was reground and the fineness of the ground product was < 6 or <8μm. The controlled temperature of the solutions was 30 ℃.The selective dissolution effect of RO phase sample in 20% acetic acid solution was remarkable dissolved 2h, the dissolution ratio of RO phase was 35.50%, the Mg O was 29.76% and the Fe O was 5.74% and Mg/ Fe was 9. The optimization scheme for quality improvement of RO phase was that 1g RO phase sample dissolved 2h in 100 m L of 20% acetic acid solution and insulated 60℃. The silicate materials and interstitial phases in steel slag can be dissolved by 20% acetic acid solution to reduce the gangue composition content in the sample and improve its iron grade.The performance indicators of the nonhydraulic mineral product can meet the five grade index requirements of ordinary concentrate in the YB/T 4267-2011 Classification of Grade of Iron Ore Products, and total iron content is 64.3%. Coarse powder, semi-product and end-product were dissolved 2h by 20% acetic acid solution to improve their quality to respectively reach five grade, two grade, one grade index requirements of ordinary concentrate. And total iron content of them is 63.77%, 70.09%,79.15% respectively.The performance indicators of the nonhydraulic mineral product can achieve the special fine-grained technical requirements in the MT/T 1017-2007 Coal Preparation Magnetite Powder, its density is 4.53g/cm3, and the content of magnetic mineral is 96.7%. Coarse powder, semi-product and end-product were dissolved 2h by 20% acetic acid solution, coarse powder and semi-product can reach the fine-grained technical requirements, end-product still meet the special fine-grained technical requirements and its density is 4.71g/cm3, and the content of magnetic mineral up to 98.5%. |
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