The analysis of gaseous products reveals the characteristics, mechanisms, and kinetic equations describing the dehydroxylation and decarburization in coal series kaolinite. The results show that the dehydroxylation of coal series kaolinite arises from the calcination of kaolinite and boehmite within the temperature range of 350–850 °C. The activation energy for dehydroxylation is 182.71 kJ·mol−1, and the mechanism conforms to the A2/3 model. Decarburization is a two-step reaction, occurring as a result of the combustion of carbon and the decomposition of a small amount of calcite. The temperature range in the first step is 350–550 °C, and in the second is 580–830 °C. The first step decarburization reaction conforms to the A2/3 mechanism function, and the activation energy is 160.94 kJ·mol−1. The second step decarburization reaction follows the B3 mechanism function, wherein the activation energy is 215.47 kJ·mol−1. A comparison with the traditional methods proves that the kinetics method utilizing TG-FTIR-MS is feasible.

Coal gangue is used to replace cement clinker to prepare cementitious material via activation techniques. Thus, the solid waste can be effectively disposed, and the carbon emission from cement production processes can be significantly reduced. In this paper, the product transformation, reaction mechanism, and thermal activation kinetics of coal gangue were analyzed by X-ray diffraction, thermal analysis, infrared analysis, and scanning electron microscopy. We employed a suspension calcination process to prepare high-activity metakaolin. A cementitious material was prepared from the metakaolin and cement, and the mechanical properties and hydration products were analyzed. The results show that metakaolin was formed by the dehydroxylation of kaolinite in the coal gangue during calcination, and the reaction was based on the Z–L–T three-dimensional diffusion mechanism with an activation energy of 190.2 kJ/mol. Metakaolin with dissolution rates of 69.5%–76.3% and 44.5%–52.3% of activated alumina and silica, respectively, were synthesized by calcining the coal gangue at 750°C–850°C for approximately 5 s via suspension calcination. The prepared cementitious material showed 28-days compressive strength of 57.5–61.5 MPa and an activity index of 114%–135%. The cementitious material participated in the hydration of cement and formed a structurally dense hardened body, which resulted in a high replacement volume and high strength of the specimens. The preparation of low-carbon cementitious materials by activating gangue via suspension calcination provides a basis for gangue utilization and reduction of carbon emissions during cement production.

A new roasting process with a conveying bed was constructed and used to remove sulfur of high-sulfur bauxite. Roasting temperature, phase transformation, microcrystal, specific surface area of high-sulfur bauxite, and the mechanism of the reaction during the roasting process were analyzed. The digestion properties of roasted bauxite were also investigated. The results showed that the sulfur in high-sulfur bauxite can be efficiently removed by roasting in the conveying bed at 520‒720 °C for 2 s. Major reactions of high-sulfur bauxite during roasting were the dehydration of minerals, desulfurization of pyrite, sulfation of SO2, and decomposition of sulfate. The rate of mineral dehydration reaction was significantly slower than that of the desulfurization reaction. The specific surface area of roasted ore greatly increased, and the microcrystal of Al-O mineral was refined, which was conducive to Al2O3 digestion. The mass fraction of sulfide sulfur in high-sulfur bauxite was reduced from 1.20% to 0.01%, and the relative digestibility of alumina reached more than 99% when roasting at 600 °C for 2 s. This paper provides revelations and instructions for the process development and application of high-sulfur bauxite.

Steel is one of the most important industrial materials, which mainly comes from the smelting of iron ore. In view of the huge steel consumption every year, the exploitation of vast reserves of siderite ores is significant for improving the self-sufficiency rate of iron ore resources and ensuring the strategic security of the iron and steel industries. This paper investigated the influence of temperature, time, and other parameters on the magnetic properties of roasted siderite ores using the method of suspended roasting and analyzed the washability of roasted ores under weak-magnetic-field conditions using the magnetic separation tube experiment. The findings of the study explained the iron phase transformation process, i.e., FeCO3 was transformed into Fe3O4 by suspension magnetization roasting. Furthermore, the saturation magnetization of the roasted ore increased in due time at a constant temperature range of 550–750 °C and a roasting time of less than 5 s. It also increased with increasing temperature and constant time. The roasted ore achieved the best magnetic characteristics after roasting at 750 °C for 5 s. After low-intensity magnetic separation, the iron grade of the concentrate changed to 55.12%, with a recovery rate of 90.34%. The study results provide a reference for the development and application of siderite suspension magnetization roasting technology.

Upgrading and utilizing low-grade iron ore is of great practical importance to improve the strategic security of the iron ore resource supply. In this study, a thermal analysis–infrared (IR) analysis–in-situ IR method was used to investigate the reaction mechanism and kinetics of Daxigou siderite. Experiments were conducted using a conveyor bed magnetization roasting process (CBMRP) to investigate the magnetization of siderite. Multi-stage magnetic separation processes were adopted to extract magnetite. The results show that simultaneously the iron carbonate in siderite decomposes, and magnetite is formed between 364 °C and 590 °C under both inert and reducing atmospheres. The activation energy of the magnetization roasting reaction is 106.1 kJ/mol, consistent with a random nucleation and growth reaction mechanism. Magnetization roasting at 750–780 °C for approximately 3.5 s in the CBMRP results in a magnetic conversion rate of >0.99% of the iron minerals in the siderite. A beneficiation process of one roughing, one sweeping, and three cleaning processes was adopted. A dissociation particle size of −400 mesh accounting for 94.78%, a concentrate iron grade of 62.8 wt.%, and a recovery of 68.83% can be obtained. Overall, a theoretical and experimental basis is presented for the comprehensive utilization of low-grade siderite.