1309-48-4

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Questions And Answer

• Chemical Properties

  Magnesium oxide is a typical alkaline earth metal oxide, chemical formula MgO. White powder, melting point 2852 ℃, boiling point 3600 ℃, the relative density of 3.58 (25 ℃). It is soluble in acid and ammonium salt solution. Its slow action with water can produce magnesium hydroxide. It can be dissolved in carbon dioxide aqueous solution to produce magnesium bicarbonate. In the air, it can gradually absorb moisture and carbon dioxide. Heating releases irritating fumes. Magnesite (MgCO3), dolomite (MgCO3 ? CaCO3) and seawater are the main raw materials for the production of magnesium oxide. ;

• Production of Magnesium Oxide

  Thermal decomposition of magnesite or dolomite generates magnesium oxide. Magnesium hydroxide precipitate is obtained first by treating seawater with hydrated lime; magnesium oxide is obtained by burning magnesium hydroxide. Alternatively, we can take the magnesium chloride lumps or brine after bromination as raw material during the comprehensive utilization of seawater; add sodium hydroxide or sodium carbonate to generate magnesium hydroxide or basic magnesium carbonate precipitation, and then burn to obtain magnesium oxide. At present, China mainly uses magnesite, dolomite, brine or halogen as raw material.
  Magnesium oxide accounts for the largest amount of magnesium compounds, accounting for about 3/4 of the total magnesium industry. Magnesia made at temperatures below 900 ° C is light magnesia with low density, having large specific surface area and strong absorbability. Can be used as a catalyst, rubber filler and improve the performance of rubber accelerator. Mixing with magnesium chloride solution can make magnesia cement. It can also be used as flame retardant for building materials. It can be medically used as antacids and laxatives for the treatment of hyperacidity and stomach and duodenal ulcer disease, often combined with calcium carbonate easy to cause constipation. For animal feed additives and plant fertilizers. The light magnesium oxide obtained at 950 ~ 1050 ℃has high density with particle distribution having a certain range and being easier to hydrate.
  Use it to react with the silica on the silicon steel surface at high temperature to produce magnesium silicate film-like product; it can be used as a silicon steel separator to prevent the sintering of silicon steel upon high-temperature sintering. The heavy magnesium oxide prepared at high temperature of 1500-1800 ℃ has high density, small specific surface area, be difficult to be decomposed by heat, has low chemical activity, not easily to react with acid and low hydration rate. It can be used as high temperature refractory materials and the binder during manufacturing refractory crucible and the furnace lining. ;

• Application

  • Light magnesium oxide is used in ceramics, enamel, refractory crucible, refractory bricks, etc., also used as polishing agent, binder, paint and paper filler, neoprene accelerator, activator. In medicine, it can be used as antacids, laxatives, for the treatment of hyperacidity and duodenal ulcer disease, but also for glass, phenolic, plastics and other industries.
  • Dead-roasted magnesium oxide, namely magnesite, has granular type and brick type, being widely used as the refractory materials of steel furnace, cement kiln and glass furnace.
  • Alkaline granular refractory, mainly used for metal refining industry, with massive refractory for the furnace, or granular material for maintenance; Use spray, coating method to have it attached to the furnace wall in order to enhance the furnace fire resistance.
  • Magnesium oxide produce a positive charge inside the water with most of the suspended material being negatively charged, acting absorption role, can improve the filtration effect.
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• Industrial production of light magnesium oxide

  In the salinization industry of sea salt, it is mainly used of bitter brine, heavy brine and high temperature salt as raw materials to produce light magnesium carbonate or light magnesium oxide. Industrialized production methods include soda ash method, lime and carbon ammonia.
  (1) Soda ash process include: 1. Ingredients 2. Reaction 3. Washing 4. Pyrolysis 5. Filter 6.Roasting 7. Crushed packaging. Soda ash production of light magnesium carbonate or light magnesium oxide has mature technology, higher product quality. However, consumption of soda ash, fresh water consumption is also large.
  (2) Lime method uses lime milk instead of soda ash. Its reaction with magnesium chloride in brine to generate magnesium hydroxide, followed by carbonation using carbon dioxide gas, generating magnesium bicarbonate. When using the lime method, the sulfate in the brine should be minimized, otherwise large deposits of calcium sulphate are formed and mixed in the product. The advantage of this method is the use of lime instead of soda ash, reducing costs. The disadvantage is that the process and equipment is more complicated than soda ash method, and by-produces large number of CaCl2 solution to be managed.
  (3) Raw materials of carbon ammonia method are the high concentrations of bitter brine, brine or salt immersion thick solution. Carbon ammonia used is ammonia bicarbonate, carbonized ammonia or sending ammonia and carbon dioxide gas directly into the brine, with carbon ammonia instead of soda ash being reacted with the magnesium chloride or magnesium sulfate in the brine to generate the corresponding magnesium carbonate. The reaction is as follows:
  1. Brine containing MgCl2 and MgSO4 reacts with NH4HCO3 solution: MgCl2 + 2NH4HCO3 = Mg (HCO3) 2 + 2NH4Cl MgSO4 + 2NH4HCO3 = Mg (HCO3) 2+ (NH4) 2SO4
  2. Directly send ammonia and carbon dioxide to the brine.
  3. The generated MgCO3 • 3H2O and Mg (HCO3) 2 are subject to pyrolysis to generate alkaline magnesium carbonate: Mg (HCO3) 2 + 2H2O = MgCO3 • 3H2O + CO2 ↑ 5 {MgCO3.3H2O} = 4MgCO3.Mg H2O + CO2 ↑ + 10H2O
  4. Alkaline magnesium carbonate is roasted to generate light magnesium oxide: 4MgCO3.Mg (OH) 2.4H2O = 5MgO + 4CO2 ↑ + 5H2O
  Control of carbon ammonia process: 1. Raw material concentration and reaction temperature 2. Pyrolysis temperature; 3. Dehydration, washing and drying; 4. Roasting; 5. Mother liquor treatment.
  Compared with the soda ash method, the production of light magnesium carbonate and light magnesium oxide by the carbon ammonia process is simple, the product has a high specific volume, and the supply channel of the ammonium bicarbonate is more and the cost is lower. However, the mother liquor evaporation and concentration process is of high energy consumption. ;

• Toxicity

  Magnesium oxide is mildly irritating to the conjunctiva and nasal mucosa. Vapors can cause ulcer disease. Dust can cause breathing problems, chest pain, coughing, diffusive interstitial fibrosis and emphysema. The maximum allowable concentration in the United States is 10 mg / m3. ;

• Usage limit

  FAO / WHO (1984): milk powder 10 g / kg; cream powder 1 g / kg (both limited for vending machines).
  FDA, § 184.143l, 2000: use GMP as limit.
  Japan limits its usage for adsorption. ;

• Uses

  Magnesium oxide (MgO,1309-48-4) is used as a lining for steel furnaces, as a component in ceramics, as food additives and pharmaceuticals, and to make strong window glass, fertilizers, paper, and rubber manufacturing. ;

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