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Medium-grade magnesia to be more environmentally friendly and efficient

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Medium-grade magnesia to be more environmentally friendly and efficient

Date:2017-03-11 author:Hongkai Fire Resistance click:

The medium-grade magnesia industry is a typical resource-based industry. Since China's reform and opening up in the 1980s, due to the rapid increase in the demand for magnesium raw materials and the low entry threshold for primary raw materials processing, the rational development of magnesite has been seriously undermined. Due to economic reasons, the price of magnesite super-grade ore is about five times that of third-grade ore. Extensive mining, rich mining and abandonment of poverty are serious phenomena, resulting in a great waste of resources, and even more serious is the imbalance of mining and stripping. In 2005, the author participated in the "spot adjustment" of 12 key magnesite mines in Liaoning Province. It was estimated that the debts of rock stripping at that time were over 100 million tons. The situation has not changed fundamentally since then, resulting in difficulties in mining some high-quality ores. In recent years, the original meaning of the super-grade ore has been very rare, the first-grade ore shortage, ore quality decline led to the average MgO content of magnesia decreased by more than 0.5%.




Therefore, in order to make rational and effective use of limited resources, we must conscientiously implement relevant laws and regulations, further integrate magnesite mines and old mines with an annual mining volume of more than 300,000 tons, implement large-scale mining and intensive management, do a good job of detailed investigation of existing mining areas, mining according to mining design, make up for the debts of rock stripping in key mines, and prolong mines. Service life; Promotion of mineral processing technology, comprehensive utilization of low and medium grade ores. At present, the relevant enterprises have gradually realized that the production of high-quality raw materials can not be maintained by relying on raw materials only; only by beneficiation and purification of raw ore, can high-quality primary raw materials be produced and the normal production of raw materials be guaranteed. Following the successful start-up of flotation system in Haicheng Magnesium Mine General Plant, many enterprises have built flotation projects, and other enterprises have begun to prepare, at the same time, the comprehensive utilization of flotation tailings is also under study.




In the next three to five years, the promotion of magnesite flotation technology, the follow-up processing of high-purity Mg (OH) 2 produced by Tibetan cryptocrystalline magnesite and Qinghai Salt Lake Magnesium Extraction will provide high-quality raw materials for the production of magnesite in China.




Production of High Quality Light Burned Magnesium Oxide




According to foreign exchange data, the annual consumption of lightly burned magnesia (CCM) in the world is about 10 million tons. China is the world's largest producer of lightly burned magnesia, with an annual output of 3.5 million to 4 million tons. Japan, the United States and other countries used light-burnt magnesia for sintering magnesia and non-refractory materials in the 1990s, the proportion of 80:20, and then gradually changed to 70:30, now roughly 65:35. Large-scale light-burning plants built abroad have many kinds of products and wide uses. Therefore, we should not only pay attention to the development of light burnt magnesia (CCM) for refractories, but also vigorously cultivate new magnesite materials industry, such as magnesium chemical industry and magnesium building materials, in order to adjust the product structure of light burnt magnesia. Only by establishing large-scale concentrated production base of light-burning magnesia and forming scale effect can reasonable investment be made, so that advanced roasting technology and kilns can be adopted to solve the problems of energy saving and emission reduction, low-carbon economy and CO2 recovery from the source.




In order to produce high-purity magnesite with the "two-step calcination" process in southern Liaoning Province of China, not only the traditional reverberatory furnace was used to light-burn magnesite lump ore, but also the concentrate flotation powder from foreign suspension furnace was introduced to light-burn magnesite crushed ore in rotary kiln, fluidized bed furnace and new suspension furnace. For example, the commissioning of a multi-layer furnace (MHK) in an enterprise, as well as the large-scale airflow suspension furnace for roasting Al (OH) 3 in non-ferrous metals industry and the decomposition furnace outside cement industry kiln provide favorable conditions for the selection of light-burning magnesia kiln.




Developing low-cost and high-grade magnesia




It is generally believed that the global high-end refractory market requires high-grade magnesia with MgO content (> 98%), sintered magnesia with bulk density (> 3.40 g/cubic centimeter) and fused magnesia with bulk density (> 3.50 g/cubic centimeter). The annual consumption of high-grade magnesia in high-temperature industrial sectors such as steel and cement is about 1 million tons.




The total annual output of sintered magnesia in China is about 4 million tons. Around 1980, the export volume of cheap natural magnesia in China increased sharply, and it has occupied the international middle and low-end magnesia market. Generally speaking, the supply of middle and low-end magnesia in the market exceeds the demand. The output of this part of sintered magnesia should be controlled, especially the production of re-burned magnesia should be gradually reduced. Due to the decline of ore grade and the rise of fuel and labor prices, the quality of mid-grade magnesia and high-purity magnesia has decreased significantly. In the future, the market demand for mid-grade and high-purity magnesia will increase, because the trend of mid-grade sand replacing heavy burnt sand downwards and high-purity sand replacing part of fused sand upwards is obvious.




After more than 30 years of disorderly mining, it is an indisputable fact that the quality of magnesite ore and magnesite is reduced. At present, the related enterprises have gradually realized the importance of ore flotation and purification, and it is an inevitable trend to popularize mineral processing technology. Starting from beneficiation, the grade of ore is improved, high activity light-burning magnesia is produced by energy-saving and efficient light-burning equipment, and the quality of high purity sand is improved by means of dry high pressure dry ball and high temperature calcination of clean fuel. It is also necessary to explore new technology and process of magnesia production in order to produce high-grade sintered magnesia with low MgO content of 98% and bulk density of more than 3.40 g/cubic centimeter at low cost. Building a large-scale production plant integrating mineral processing and production of high-purity magnesia is in line with the future development direction.

Medium grade magnesia


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