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Process for preparing high-purity activated magnesium oxide from magnesium carbonate trihydrate

Hebei Messi Biology Co., Ltd. stated that high-purity activated magnesium oxide is an important chemical raw material in modern industry. It is a fine product of magnesium salt and is widely used in various fields. Although my country is a major producer of magnesium oxide, it still exports a large amount of low-purity, low-grade magnesium oxide primary products. This is inconsistent with the needs of high-tech and high value-added magnesium oxide products. This article proposes the corresponding industrial production technology for developing high-purity and highly active magnesium oxide based on the magnesium carbonate trihydrate method in practical application.

High reactive magnesium oxide
  1. Process principle of magnesium carbonate trihydrate method
    This technology mainly uses high-concentration magnesium chloride solution (bromine production mother liquor by-product in the salt chemical production process) as the raw material, uses ammonium carbonate as the precipitant, reacts to generate MgCO3·3H2O precipitate, and calcines the produced material to produce High purity active magnesium. The by-product is mother liquor containing NH4CL. The mother liquor is evaporated, cooled, crystallized and separated to obtain solid NH4CL.
  2. Process application analysis
    The process mainly includes the preparation and calcination of MgCO3·3H2O. Generally, the high-concentration MgCl2 in the bromine production waste liquid is converted into MgCO3·3H2O, and then calcined to produce high-value-added high-purity activated magnesium oxide, which can greatly increase the added value of the product. The calcination temperature only needs about 750 degrees, the reaction conditions are mild, and the safety factor is high.
  3. Main equipment for preparation
    Generally, it can be divided into drying equipment (drying MgCO3·3H2O wet materials) and calcining equipment, which mainly include swirling dynamic calcining furnace, internal heating rotary furnace, external heating rotary furnace, etc. During preparation, equipment should be inspected to check that it is safe.
  4. Process of process preparation
    4.1 Purification treatment of bromine production waste liquid. Heat the brine to boiling, add a certain amount of sodium hypochlorite solution or hydrogen peroxide solution, stir, then add a small amount of soda ash solution, stir evenly, leave it overnight, and use the supernatant liquid as the raw material liquid. After precipitation and separation, the raw material mother liquor containing SO4 can be obtained. According to research, a saturated solution of CaCL2 is selected as the sulfur removal agent for the bromine production mother liquor to remove sulfur. The best effect is when the addition amount is 1.2 times the equivalent.
    4.2 Preparation process reaction. Add the purified high-concentration magnesium chloride solution (bromine production mother liquor) to the crystallizer, and use deionized water to prepare 1000 ml of reaction bottom liquid with a concentration of 0.5 mol/L. Heat the solution to maintain it at 30°C, and stir 53 g of it. (NH4)3CO3 solid powder was added slowly. During the reaction process, the following aspects should be paid attention to: (1) The feeding speed should be uniform; (2) The pH value of the reaction solution should be between 7.5 and 9.0; (3) The ideal aging time should be controlled between 1.5 and 2.5 hours. .
    4.3 Separation and washing. After the reaction is completed, the MgCO3·3H2O slurry obtained by the reaction is subjected to solid-liquid separation. The plate and frame filter press is selected as the filtration equipment. It has a simple structure, is easy to manufacture, has a small footprint and a large filtration area, high operating pressure, strong adaptability, and can realize two-step operations of filtration and washing. The level of CL content in the product is an important indicator to determine the quality of high-purity activated magnesium oxide. For this reason, in order to obtain qualified high-purity activated magnesium oxide, the MgCO3·3H2O obtained after the reaction must be fully washed so that the entrained CL can be fully removed.
    4.4 Drying. The drying process uses heating to vaporize the moisture in the washed MgCO3·3H2O wet material, thereby removing the MgCO3·3H2O wet material. Depending on the operating pressure, drying can be divided into normal pressure drying and vacuum drying. According to different operating methods, drying can be divided into continuous drying and intermittent drying. Continuous drying has the advantages of large production capacity, uniform product quality, high thermal efficiency and good working conditions. Intermittent drying is suitable for drying small batches, multiple varieties or materials that require a long drying time.
    4.5 Calcination. The relationship between calcination temperature and product quality. The key to the preparation of high-purity activated magnesium oxide lies in the control of calcination temperature. In general, the higher the temperature, the lower the activity of the resulting magnesium oxide product. In order to ensure that the quality of the obtained products meets the requirements, experiments were conducted on product quality at different calcination temperatures in order to obtain the best process parameters. It can be seen from the experimental data that when the calcination temperature is controlled at 750°C, the final product obtained can meet the needs of this process. Further increasing the calcination temperature can further increase the magnesium oxide content of the product, but the relative increase in content is not large. During the calcination process, attention should be paid to the following aspects: (1) The calcination temperature should be maintained at 750°C to allow complete and sufficient reaction: (2) When the calcination temperature is 750°C, the calcination time should be controlled at 60 seconds. The magnesium oxide content has exceeded 99.50%, which has reached the purpose of this process research. (3) Appropriate reaction conditions should be maintained to allow a complete reaction.
  5. Three wastes treatment
    Recycling technology is adopted for the treatment of process waste liquid. The mother liquor after separation of MgCO3·3H2O and the washing liquid of MgCO3·3H2O wet material are evaporated, crystallized, and the by-product NH4CL is separated: direct-fired calcination is changed to gas calcination. Put an end to the phenomenon of black smoke; when coal is used as the calcining heat source, a small amount of cinder will be produced, which can be stacked together and used as building materials for export. It does not cause pollution to the environment.
    Hebei Meixi Biological Co., Ltd. stated that the production of high-purity activated magnesium oxide by the magnesium carbonate trihydrate method is an effective production and application model based on sustainable development. Its process is reasonable and the conversion rate is high, and it has high promotion value. The use of mother liquor recycling process improves the utilization rate of minerals in brine and the acquisition rate of NH4CL in mother liquor. It can not only reduce material consumption, but also eliminate three wastes. It is a feasible green preparation method.

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