Research on the Integration of Magnesium Chloride and Magnesium Sulfate Pyrolysis Processes
Hebei Messi Biology Co., Ltd. states that high-purity magnesium oxide, as a key inorganic functional material, is widely used in high-end fields such as electronics, ceramics, refractories, and environmental flame retardants. For a long time, China’s high-purity magnesium salt materials relied heavily on imports. With the increasing demand for clean production and high-value resource utilization, pyrolysis methods using magnesium salts as raw materials have gradually become a mainstream technical route. This article integrates the magnesium chloride pyrolysis method, the direct magnesium sulfate pyrolysis method, and magnesium sulfate derivative processes to systematically review efficient, low-consumption, and environmentally friendly preparation technologies for high-purity magnesium oxide.
The magnesium chloride pyrolysis process is one of the early methods to achieve continuous production in China. Through integrated technology involving spray drying, continuous pyrolysis, and dynamic calcination, it addresses the technical challenges of high-temperature gas-solid separation and equipment corrosion protection. This allows for the efficient utilization of waste heat, combining energy conservation, environmental protection, and production efficiency. This process features a short production route, low operating costs, and high product added value, enabling the direct preparation of high-purity magnesium oxide powder from magnesium chloride raw materials. The technology has reached a highly competitive international standard, helping to reduce long-term reliance on imports of high-end magnesium-based materials while promoting marine chemical engineering and the refined, comprehensive utilization of magnesium resources.
The direct pyrolysis of magnesium sulfate is another mature and controllable preparation route. Research indicates that magnesium sulfate heptahydrate completes dehydration at 60–300°C, and anhydrous magnesium sulfate completes pyrolysis to generate magnesium oxide at 950–1100°C. By optimizing parameters such as temperature, time, and particle size, the dehydration and pyrolysis stages can be separated to achieve precise control. Under optimized conditions, magnesium sulfate with an appropriate particle size can undergo low-temperature dehydration followed by high-temperature isothermal pyrolysis to produce cubic-phase high-purity magnesium oxide with a purity of up to 99.9%. The resulting product exhibits a regular crystal structure and stable performance, meeting the requirements of high-end applications.
Magnesium sulfate-based processes also extend to several green co-production and resource utilization pathways. Using magnesium sulfate as a raw material, magnesium oxide can be directly prepared via reduction in the presence of catalysts and carbonaceous reducing agents. For industrial magnesium sulfate waste liquid, active magnesium oxide can be prepared through milk of lime precipitation, carbon dioxide carbonation, and pyrolysis calcination. This achieves waste liquid resource utilization with advantages such as high magnesium yield, environmental friendliness, and low cost. Additionally, utilizing magnesium sulfate heptahydrate—a by-product of boromagnesium ore—and reacting it with ammonium bicarbonate can prepare basic magnesium carbonate, which is then calcined to obtain light magnesium oxide, expanding the value of the boron-magnesium industrial chain.
Overall, the magnesium chloride and magnesium sulfate pyrolysis processes, along with their derivative methods, jointly construct a magnesium oxide production system characterized by diversified raw materials, clean processes, and high-end products. Continuous pyrolysis improves efficiency and purity, staged temperature control optimizes crystal form and performance, and resource utilization reduces costs and pollution, aligning with the development directions of high-end manufacturing and green chemical engineering. With continuous technological iterations, the preparation of high-purity magnesium oxide via magnesium salt pyrolysis will further support the upgrading of industries such as electronics, cables, and refractories, supporting the advancement of China’s magnesium resource utilization toward high international standards.