Influence of Coal Blending on Ash Fusibility in Reducing Atmosphere
Coal blending is an effective way to organize and control coal ash fusibility to meet different requirements of Coal-fired power plants. This study investigates three different eutectic processes and explains the mechanism of how coal blending affects ash fusibility. The blended ashes were prepared by hand-mixing two raw coal ashes at five blending ratios, G:D = 10:90 (G10D90), G:D= 20:80 (G20D80), G:D = 30:70 (G30D70), G:D = 40:60 (G40D60), and G:D = 50:50 (G50D50). The samples were heated at 900 °C, 1000 °C, 1100 °C, 1200 °C, and 1300 °C in reducing atmosphere. XRD and SEM/EDX were used to identify mineral transformations and eutectic processes. The eutectic processes were finally simulated with FactSage. Results show that the fusion temperatures of the blended ashes initially decrease and then increase with the blending ratio, a trend that is typical of eutectic melting. Eutectic phenomena are observed in D100, G10D90, and G30D70 in different degrees, which do not appear in G100 and G50D50 for the lack of eutectic reactants. The main eutectic reactants are gehlenite, magnetite, merwinite, and diopside. The FactSage simulation results show that the content discrepancy of merwinite and diopside in the ashes causes the inconsistent eutectic temperatures and eutectic degrees, in turn decrease the fusion temperature of the blended ash and then increase them with the blending ratio.
Problems with utilisation of engineering wood for energy purposes
Waste engineering wood in the form of chipboard and plywood is a potential source of renewable energy in boilers for biomass combustion. The conditions causing the silicate melt slagging during combustion were studied by proximate analysis, mineralogical analysis using X-ray diffraction, scanning electron microscope with energy dispersive analyser and thermogravimetry. Slags are formed by refractory mineralogical phases of Ca, Si, Ti and Al.
Effect of coal slag on the wear rate and microstructure of the ZrO2-bearing chromia refractories
Abstract The typical properties of slag and refractories for slagging coal gasifier were investigated. In the range of 0–25% CaO/ash, the characteristic ash-fusion temperatures (AFTs) and viscosity of a coal-ash slag decreased with an increase of CaO additive. When the CaO/ash ratio was greater than 25% in the mixture of the coal and limestone, AFTs no longer reduced. The slag viscosity for limestone addition with CaO/ash = 25% was very low and in a narrow range (4–13 Pa.s) at coal gasification temperatures between 1300 °C and 1500 °C. However, corrosion resistance of the ZrO2-bearing chromia refractories reduced with increasing CaO content in coal slag, especially for a slag with more than 30% CaO content. Increased chromia in three kinds of the ZrO2-bearing chromia refractories resulted in increased corrosion resistance. The higher the Cr2O3 content and the lower the SiO2 content, the less the deterioration of microstructures in the materials. Thermochemical spalling of the ZrO2-bearing 80% Cr2O3 refractory after 807 operating hours of a coal gasifier was considered as the primary attack mechanism.