CaO- and MgO-rich fly ash derived from low-grade coals is typically discarded due to its incompatibility with existing large-scale valorisation technologies. This study demonstrates the potential of such low-grade fly ash as a substitute for flux and MgO sources in the iron-ore sintering process, a critical step in producing feedstock to yield ∼1 Gt/yr of crude steel globally. X-ray diffraction (XRD) analysis confirmed the supply of fine MgO particles from fly ash via thermal decomposition. Aligned with other MgO sources, fly ash suppressed the formation of calcium ferrites while increasing spinel content. Notably, the addition of fly ash enhanced the physical strength of sinter tablets due to the high reactivity of the MgO particles, which is in marked contrast to the detrimental effect of conventional MgO sources. Removal of sulphur from the fly ash further augmented the physical strength of the tablets by enhancing the reactivity of MgO. Further, detrimental elements for sintering, i.e., Na, K, P, and Cl, were negligible in the fly ash. These findings highlight the potential role of fly ash in supplying MgO without compromising the physical strength of the sinter, offering insights into sustainable steel production.

中文翻译：

---

低品位粉煤灰作为铁矿石烧结可持续氧化镁来源的增值潜力：原位 X 射线衍射和片剂研究的见解

源自低品位煤的富含 CaO 和 MgO 的粉煤灰通常会被丢弃，因为它与现有的大规模增值技术不兼容。这项研究证明了这种低品位粉煤灰在铁矿石烧结过程中作为熔剂和氧化镁来源的替代品的潜力，铁矿石烧结过程是全球生产约 1 Gt/年粗钢的原料生产的关键步骤。 X 射线衍射 (XRD) 分析证实，飞灰中通过热分解提供了细小的 MgO 颗粒。与其他氧化镁来源一致，飞灰抑制了铁酸钙的形成，同时增加了尖晶石含量。值得注意的是，由于 MgO 颗粒的高反应性，飞灰的添加增强了烧结片的物理强度，这与传统 MgO 源的有害影响形成鲜明对比。从飞灰中去除硫可以增强氧化镁的反应性，从而进一步增强片剂的物理强度。此外，飞灰中对烧结有害的元素，即Na、K、P和Cl可以忽略不计。这些发现强调了粉煤灰在不影响烧结矿物理强度的情况下提供氧化镁的潜在作用，为可持续钢铁生产提供了见解。