The Fine Application and Processing of Dolomite are The Directions For Its Development
2023-08-21
Dolomite is a non-metallic mineral composed primarily of magnesium calcium carbonate and other compounds, with MgCO3·CaCO3 being the predominant component. Currently, dolomite finds extensive applications in various industries including metallurgy, chemical industry, and construction. It serves as a refractory material in the metallurgical industry and can also function as a flux. Moreover, dolomite can be utilized for producing magnesium-containing cement and building stone in addition to manufacturing magnesium compounds in the chemical industry. Furthermore, it can be employed as calcium-magnesium phosphate fertilizer and granular fertilizer for soil acidification transformation purposes. Additionally, dolomite acts as fillers in rubber, plastic, pharmaceuticals industries among others. In the glass and ceramic industries, it functions as an ingredient that enhances the chemical stability and robustness of glass while improving the luster of ceramics. Lastly, dolomite serves as a raw material for producing metallic magnesium.
Dolomite is Used In The Field of Chemical Raw Material Preparation
Dolomite is a mineral consisting of calcium magnesium carbonate, which can be found in sedimentary rocks and extracted from quarries or natural deposits. The high concentrations of CaO and MgO in dolomite render it a significant source of these minerals, crucial for various industrial processes such as cement production, glass manufacturing, ceramics fabrication, fertilizer synthesis, and pharmaceutical formulation. Dolomite can undergo processing to extract these minerals and serve as a raw material for their production. Apart from its industrial applications, dolomite also possesses agricultural uses as a soil amendment to enhance soil pH levels. Its inherent properties make it an ideal construction material for projects like road building and concrete production due to its exceptional hardness and durability that effectively withstand weathering and erosion. The global abundance of dolomite deposits establishes it as a substantial resource capable of meeting the escalating demand for calcium- and magnesium-based products across diverse industries.
(1) Preparation of MgO High purity MgO
Refers to products with a magnesium oxide (MgO) content greater than 98% (w), which possesses excellent thermal conductivity, a large thermal expansion coefficient, outstanding light transmittance, alkali resistance at high temperatures, and superior electrical insulation properties. In the past, the production of high-purity MgO mainly relied on magnesite as the raw material. However, due to years of excessive mining activities, the ore grade has been declining and it has become challenging to produce products with a purity exceeding 98%. Currently, there are three methods for producing MgO from dolomite: carbonization method, acid leaching method, and ammonium leaching method. Nano-MgO exhibits distinct optical properties, electrical properties, thermal properties,magnetic properties,and chemical properties compared to non-nano materials. It finds wide applications in ceramics,re- fractories ,environmental purification ,medicine,and catalysis.
(2) The preparation of Mg(OH)2
Mg(OH)2 can serve as an inorganic flame retardant product with excellent flame retardancy and environmental protection characteristics. In comparison to other inorganic flame retardants, it boasts a low cost, good thermal stability, and does not generate toxic substances during production and usage processes. It possesses the ability to neutralize acidic substances produced during combustion and has been increasingly employed in polymer materials and various other fields. Nevertheless, traditional preparation methods suffer from drawbacks such as low product purity, complex procedures, and challenges in achieving industrialization. Changjiang et al., however, utilized dolomite as the raw material along with a brine precipitation method to produce flake-like Mg(OH)2 with a purity exceeding 98%, rendering it suitable for use as an additive flame retardant. This method offers advantages over the conventional brine approach including reduced costs, simplified processes with easier parameter control, environmental friendliness, lower impurity content, and certain industrial applicability.
(3) Preparation of Magnesium Carbonate
Basic magnesium carbonate is a versatile inorganic chemical product that can be used as an ingredient in high purity magnesia and magnesium salt series products, as well as rubber, insulation material, high grade glass, pharmaceutical and food additives and amendments.
(4) Preparation of Calcium Carbonate (CaCO3)
With the advancement of ultra-fine, intricate structural, and surface modification technologies for CaCO3, nano-ultrafine calcium carbonate has gained extensive utilization as a novel solid material. Employing dolomite as the raw material, Tong Mengliang successfully synthesized CaCO3 nanorods through secondary carbonization method with an average diameter of 150nm, an average length of 1μm, and an average aspect ratio ranging from 6 to 8. The optimized secondary carbonization process involved a temperature of 20℃, w(Ca(OH)2)=6%, w(crystal control agent)=2%, while polyvinyl alcohol was chosen as the dispersant.
Dolomite Separation Calcium Magnesium Method
The separation of calcium and magnesium, as well as the preparation of calcium and magnesium products, pose significant challenges in dolomite application. Currently, prominent methods for dolomite separation include acid hydrolysis, carbonization, ammonium leaching, and brine dolomite extraction.
Ammonium Leaching Process
The ammonium leaching method involves using light burnt white cloud lime obtained after calcination as a raw material. It is then digested with distilled water in a specific proportion, and ammonium salt is used as the leaching agent to extract calcium and magnesium ions from dolomite. Since ammonium salt is an acidic solution, it reacts with white cloud lime when heated to obtain refined calcium salt and magnesium salt. In this process, magnesium hydroxide precipitation can be generated in the presence of NH3, while calcium carbonate precipitation can be formed with CO2, achieving the purpose of separating calcium and magnesium.
Brine Dolomite Process
The dolomite (Ca(OH)2, Mg(OH)2) is introduced into the brine (MgCl2) at a specific temperature to facilitate the production of magnesium hydroxide. Subsequently, the resulting suspension undergoes filtration and drying processes in order to obtain powdered Mg(OH)2. The filtrate can be further subjected to reactions for the synthesis of CaCO3. Key features: This process offers cost-effectiveness and minimal environmental impact, while ensuring optimal utilization of calcium and magnesium resources present in both brine and white cloud lime, thereby achieving complete separation between calcium and magnesium within dolomite. However, challenges arise due to the generation of significant amounts of by-products which hinder efficient recovery of calcium chloride.
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