Title page for ETD etd-08292008-175601


Document Type Master's Dissertation
Author Kalenga wa Kalenga, Michael
Email michkale@twr.ac.za
URN etd-08292008-175601
Document Title Investigation into the influence of magnesia content, alumina content, basicity and ignition temperature on the mineralogy and properties of iron sinter
Degree MSc
Department Materials Science and Metallurgical Engineering
Supervisor
Advisor Name Title
Prof A M Garbers-Craig Supervisor
Keywords
  • sinter mineralogy
  • chemicals
Date 2007-09-05
Availability unrestricted
Abstract

The sinter quality is dependent on sinter mineralogy, which in turn depends on the chemical compositions of the sinter mix. Although many research works have been conducted, further investigation on the effect of chemical compositions (MgO, A2O3, Basicity) on the sinter quality is still required for further improvement of the sinter and more alternative additives are still being tested. In this project, a sinter pot has been used to manufacture sinters, which were characterized using point-counting to quantify the different phases and X-Ray diffraction to identify the polymorphic forms of Ca2SiO4 of the silicate phases. The produced sinters were evaluated with respect to reducibility index (RI), reduction degradation index (RDI), physical breakdown (TI and AI), and production properties (yield, coke breeze rate and production rate). The influence of ignition temperature, magnesium oxide, alumina addition and basicity on the mineralogy as well as physical and chemical properties of iron ore sinters were investigated.

Results were obtained as follows:

  1. For the Base case with a basicity of 2, 2.8 mass% MgO content, 1.7 mass % Al2O3 and 10 mass% CaO, the effect of ignition temperature, which ranged between 864oC and 1100oC, on the sinter quality was investigated. Results showed that the ignition temperature had an effect on the sinter properties: reducibility (RI), physical strength (TI and AI), production properties (yield, coke breeze rate and production rate). The temperature 1053oC was the best ignition temperature for an economically acceptable sinter. A further increase in ignition temperature was found to form melt on the surface of the sinter produced, leading to a sinter of low quality. Also, X-rays diffraction pattern showed that the allotropic transformation of the Ca2SiO4did not take place.
  2. The Low SiO2 Low Al2O3 sinter had the highest reducibility index and had the highest Abrasion index and the lowest coke breeze rate at 2.8 mass% MgO content compared to all the sinters produced in this project.
  3. For the High SiO2 Low Al2O3 sinter MgO was added through dolomite and fused magnesia. A comparative study on the effect of dolomite and fused magnesia was conducted. The sinter to which fused magnesia was added had lower reducibility, higher reduction degradation, higher tumble index, lower abrasion index and lower coke breeze rate than the sinter to which dolomite was added.
  4. High SiO2 High Al2O3 sinter had the lowest reducibility index, the lowest reduction degradation, the lowest tumbler index and the highest coke breeze rate.
  5. The increase in MgO content in all the sinters produced increased the coke breeze rate.

University of Pretoria 2007

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