Effect Of Iron-bearing Minerals On High-temperature Ash Behaviors In Reducing Atmosphere

Based on remarkably different Fe2O3content in coal ash, three typical Chinese coal samples were selected and added with iron-bearing minerals (pyrite-FeS2and iron powder-Fe) to study how Fe affects the high-temperature ash behavior in reducing atmosphere. The coal ash chemical composition and mineral components in coal, ash and slag samples were measured by X-ray fluorescence spectrometer and X-ray diffractometer respectively. The ash fusion temperatures were tested and collected by5E-ⅡF type instrument. The effect of iron-bearing minerals on liquid molten slag and solid crystals was studied by the thermodynamic equilibrium software. Mineral Factor (MF) combined with analogous ternary phase diagram illustrated the influence of mineral species and relative contents on ash fusion characteristics. Summarize the whole thesis, the following conclusions were summed up:(1) Compare the option adding FeS2with that Fe at the same condition, and then discover:the flowing temperature (FT) of the former is a little higher than that of the latter; XRD patterns show that the diffraction peak of Fe is more dispersing of option adding FeS2; some cementite (Fe3C) and ferro-silicate minerals exit in ash high-temperature minerals and constrained the formation of Fe. Integrate all the three points to reflect that S element increases the fusion temperatures but can also cut the odds of iron precipitation problem to a certain extent.(2) From the semi-quantitative results of slag samples, Fe2O3and CaO contents change after adding iron-bearing minerals and calcium-bearing minerals. When the ratio of Fe2O3/CaO (ie, C value) comes closer to1.0, the content of iron becomes lower, so if only takes iron precipitation content into account, the slagging orientation is smaller.(3) Iron-bearing minerals (FeS and ferro-cordierite) will be precipitated first from the liquid slag system after adding FeS2, Fe. The precipitated minerals cut down the liquid temperature (LT). When the system temperature is higher than LT, the C value approaches the original C in coal ash, meantime, below the LT, the C value curves of different two options with the same C value come closer. Therefore, it has its own limitation to observe the properties of viscosity-temperature if ash chemical composition is the only factor to be considered, it is essential to consider minerals too. (5)After adding iron-bearing minerals, the ratio of Fe2O3/CaO is higher, the temperature, which means the slag system viscosity achieves25Pa·s (ie, T25Pa·s), is higher. The best Fe2O3/CaO ratio range satisfies the require of viscosity will be calculated in this way and a simple and practical method to predict the T2sPa·s will also be provided.