Preparation Of High Purity Magnesium Oxide By Chloride Roasting Magnesite

High-purity magnesium oxide was prepared by roasting magnesite which mixed with the anhydrous magnesium chloride at a lower calcination temperature. The thermal decomposition of mixed powder was analyzed by thermogravimetric analysis and dynamic thermogravimetric analysis (TG-DTA). The characterization of roast product was investigated by X-ray diffraction (XRD), scanning electronic microscope (SEM), and purity analysis. Compared with roast product prepared by the traditional method, the results showed that adding magnesium chloride can improve the magnesium oxide's purity by reacting with calcium carbonate to generate calcium chloride and washing to remove calcium. Through mechanism, because of chloride ions penetration, magnesium chloride plays a role of partition to magnesite, it makes magnesite's specific surface area increase; this is helpful to reduce the calcination temperature.The purity of products by roasting magnesite which mixed with the anhydrous magnesium chloride was 99.3% and calcium carbonate content reduce to 0.07%, when roasting temperature was 650?, roasting time was 1h, feed ratio was 1.6:1. The purity of products by direct roasting magnesite which mixed with the magnesium chloride hexahydrate can reach to 99.25%, and calcium content dropped to 0.3%, when roasting temperature was 650?, roasting time was 1h, feed ratio was 2.6:1. The purity of the product have improved greatly compared with direct roasting by using indirect roasting magnesite which mixed with the magnesium chloride hexahydrate, the feed ratio was 2.2:1, when roasting mixed powder 3 h at 200?, then heating up to 650? roasting, the main content of product from 98.05% to 99.26%, calcium content from 0.62% to 0.29%, the utilization efficiency of the magnesium chloride hexahydrate was improved effectively.Only by roasting magnesite process is difficult to achieve the preparation of high purity magnesium oxide (main content> 99%), it usually need a further purification treatment to obtain high purity magnesium oxide; to roasting magnesite fully, roasting temperature at least above of 850-900?. The paper research the process of roasting magnesite which mixed with anhydrous magnesium chloride or magnesium chloride hexahydrate. It can get high-purity magnesium oxide directly through the roasting process, the technological process is simple and the products'purity is high. The magnesium chloride can promote magnesite thermal decomposition, reducing the production cost, saving energy and reducing consumption.