Two coal ashes (one with high-melting temperature and one with low-melting temperature) obtained at 600 °C in air were pressed into pellets and further treated for 1 h at different temperatures from 700 to 1200 °C at the interval of 100 °C in reducing atmosphere (mole ratio CO:CO 2 = 60:40) to investigate the melting behavior of typical ash particles. The final structures were characterized by XRD and SEM-EDX. The results showed that most Na, K, Ca, and Fe took the form of aluminosilicates. Although the low-melting particles (Na−K-enriched aluminosilicate particles and Ca−Fe-enriched aluminosilicate particles) were small in number percentage, these particles were already melted at 1000 °C. It is possible that Fe was enriched more readily in particles than Ca. The extent of fragmentation of calcite particle was closely related to the calcite type. The calcite particles with layered textures fragmented more. Gaussian distribution successfully simulated the calcite particle size distribution after calcite particle fragmentation. The detailed mechanism analysis showed that the Fe−O particle dissolution was primarily controlled by diffusion. The Fe−O crystals from pyrite and siderite showed similar patterns of crystal growth.

Two coals (one coal with high-melting temperature ash and one with low-melting temperature ash) were chosen to investigate the effect of residence time at high temperatures in a reducing atmosphere on coal ash behavior. Scanning electron microscopy linked with energy dispersive X-ray analysis (SEM-EDX) and X-ray diffraction (XRD) were used to characterize the ash behavior. The residence time has a great influence on the amount and composition of minerals, especially for the high-melting temperature ash. The diffraction peak intensities for most minerals formed in the high-melting temperature coal ash after heat treatment reach their maximum value after 2 min, and then, they decrease. This trend is not apparent for the low-melting temperature ash. The high-melting temperature ash also has a higher mineral content than the low-melting temperature ash for the same residence time. Formation of a large amount of mullite in the high-melting temperature ash after heat treatment indicates that mullite formation is rapid, but a high (Na 2 O + K 2 O + CaO) content can inhibit the formation of mullite. Different mineral compositions have been found in the ash samples under nonthermal equilibrium and thermal equilibrium conditions. Most minerals formed under thermodynamic equilibrium conditions are not observed under the nonequilibrium conditions. This is attributed to the low stability of minerals at high temperatures. The kinetic limitations of the dissolution of FeO particles must also be considered, especially for larger FeO particles.

Band keratopathy (BK) is a common complication in aphakic eyes with silicone oil tamponade for open-globe injury (OGI), characterized by the grayish-white opacities in the cornea, resulting in a significantly decreased vision when extending to the visual axis. To identify the risk factors for BK in aphakic eyes following vitreoretinal surgical treatment with silicone oil tamponade for OGIs, we performed a multicenter case-control study. The incidence of BK was 28% (28/100 eyes). The multivariate binary logistic regression revealed the silicone oil retention time (SORT) ≥6 months and zone III injury were significant risk factors for BK. From the hierarchical interaction, SORT ≥6 months had a significant risk for BK in eyes with rupture, aniridia, and zone III injury, while zone III injury had a significant risk for BK in eyes with rupture, incomplete/complete iris, and SORT ≥6 months. By using restricted cubic splines with three knots at the 25th, 50th, and 75th centiles to model the association of SORT with BK, we also found a marked increase in the risk for BK at ≥10 months and a slow increase after 6 months, but almost stable within 4–6 months.

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