How to prepare basic magnesium carbonate_Industrial additives

How to prepare basic magnesium carbonate [Background and Overview]

Basic magnesium carbonate is also called “light magnesium carbonate”. Chemical formula xMgCO₃·yMg(OH)₂·zH₂O(x=3～5, y=1, z=3～7 ). The typical molecular formula is 3MgCO₃·Mg(OH)₂·3H₂O, with a molecular weight of 365.31. White crystal or amorphous light and loose powder. Proportion 2.16. Insoluble in water and ethanol, easily soluble in acid, and releases carbon dioxide at the same time. Decomposes when heated; releases carbon dioxide and water, and transforms into magnesium oxide at 700°C. It is obtained by the reaction of magnesium hydroxide emulsion and carbon dioxide or the mixing reaction of soluble magnesium salt and sodium carbonate at a certain concentration.

Hydrated basic magnesium carbonate exists stably in the air. Its chemical composition varies slightly due to different preparation methods and conditions. Its relative density is small and it can be used as an additive for rubber and plastic products. It also has the characteristics of non-burning and does not burn when heated. After decomposition, it can be used to prepare magnesium oxide, and food-grade basic magnesium carbonate can be used as a flour improver. Basic magnesium carbonate can be used as an excellent filler and reinforcing agent for rubber products and as a heat-insulating and high-temperature-resistant fireproof and thermal insulation material. It is also used to make magnesium salt, magnesium oxide, fire retardant coatings, printing inks, ceramics, glass, cosmetics, toothpaste, medicine and pigments, etc. For some special-purpose basic magnesium carbonates, the requirements for impurities contained are also different depending on their uses. For example, when used as a raw material for making high-purity magnesium oxide, a refractory material, the content of calcium oxide and boron impurities is required to be very low, because the B₂O₃ in the product It will form various eutectic compounds with impurities such as CaO and SiO₂ under high temperature conditions, thereby reducing the high temperature performance of refractory materials. Therefore, when basic magnesium carbonate is used as a raw material for preparing high-purity magnesium oxide, the content of CaO and CaO is one of the important indicators for evaluating the quality of the product. The lower the content, the better. For electronic grade basic magnesium carbonate, it must not only have high purity, but also have special physical properties. Therefore, when producing basic magnesium carbonate, the specific standards of the product must be determined according to the specific use of the product. However, generally speaking, the purity of the product determines the scope of application of the product.

How to prepare basic magnesium carbonate [Preparation]

Currently, the main production methods of basic magnesium carbonate in my country include: Nanshui soda ash method, magnesium sulfate ammonium bicarbonate method, dolomite carbonization method, light fired powder carbonization Law etc.

1. Nanshui Soda Ash Method

The brine soda ash method is the oldest method of producing basic magnesium carbonate and has a production history of sixty or seventy years in my country. Although the production method is ancient, it is still the production method with the largest output and the highest product grade of basic magnesium carbonate in my country. This method uses the southern water that has been sun-salted along the coast, and after a series of processes such as removing impurities and iron, prepares it to a certain degree of Baume, and reacts with the dissolved and impurity-removed soda ash solution at a certain temperature to generate alkali. Formula magnesium carbonate. After centrifugation or pressure filtration, wash repeatedly with deionized water until chloride ions meet the requirements. The filter cake is dried to obtain basic magnesium carbonate product; the filter cake is directly calcined to obtain magnesium oxide product. By controlling the reaction temperature and reactant concentration, products with different bulk densities can be obtained, that is, heavy magnesium carbonate or light magnesium carbonate can be obtained. It is understood that there are only two or three companies in Shouguang, Shandong Province that use this method for production. Two of them mainly produce light magnesium oxide, and one mainly produces heavy magnesium carbonate. Two companies produce light magnesium oxide. The production of light magnesium oxide does not exceed 2,000 tons, mainly because the production cost of this method is high and the market demand corresponding to its products is not large. The enterprises that produce heavy magnesium carbonate are almost workshop-style production, with an annual output of only a few hundred tons.

2. Magnesium sulfate ammonium bicarbonate method

Basic magnesium carbonate can be produced by reacting purified magnesium sulfate solution with ammonium bicarbonate solution. By adjusting the reactant concentration and reaction temperature, basic magnesium carbonate with different bulk densities can be obtained. The reaction product is washed and filtered repeatedly to ensure that the product meets quality requirements. At present, there are very few domestic companies using this method to produce basic magnesium carbonate. It is understood that only one company may be producing it. The product can be sold as a basic magnesium carbonate product, or the basic magnesium carbonate can be calcined into magnesium oxide for sale. This is the main method for producing pharmaceutical grade and food grade magnesium carbonate and magnesium oxide. However, the output is very small, with only more than a hundred tons a year, or at most a few hundred tons.

3. Dolomite carbonization method

The dolomite carbonization method is to calcine dolomite and then hydrate the resulting dolomite (mainly composed of calcium oxide and magnesium oxide) to obtain a mixed solution of magnesium hydroxide and calcium hydroxide. The tail gas of calcined dolomite is purified, and its carbon dioxide content is about 30%. After compression, it reacts with dolomite hydration liquid in the carbonization tower to obtain calcium carbonate precipitation and magnesium bicarbonate solution. After the reaction solution is precipitated and filtered, the magnesium bicarbonate solution is sent for pyrolysis to obtain basic magnesium carbonate. After filtering and washing the pyrolysis solution, a basic magnesium carbonate filter cake is obtained. The filter cake is dried to obtain basic magnesium carbonate product; the filter cake is calcined to obtain light magnesium oxide product. This is the production method with the highest energy consumption and the longest process route among all methods for producing basic magnesium carbonate.Method, there are probably only two to three companies in China using this process for production. In terms of magnesium oxide, some companies have an annual output of 1,000 tons, while others do not reach 1,000 tons, and product quality varies. The magnesium carbonate and magnesium oxide produced by this method have relatively large specific volumes. It is the main method for producing magnesium carbonate, light magnesium oxide and active magnesium oxide with large specific volumes. Some companies shape and dry the obtained basic magnesium carbonate filter cake, and process it into gymnastics magnesium blocks for sale at home and abroad, which have relatively high added value.

4. Light burning powder carbonization method

Light burnt powder is also called light burnt magnesium oxide. The light-burning powder carbonization method is actually similar in principle to the dolomite carbonization method. By calcining magnesite and controlling the calcination temperature within a certain range, light-burned magnesium oxide can be obtained. Lightly burned magnesium oxide is hydrated with water to obtain magnesium hydroxide slurry. The tail gas after calcining magnesite ore is purified, compressed and sent to the carbonization tower, where it reacts with the hydrated slurry of light-burned powder to obtain a magnesium bicarbonate solution. After further precipitation and filtration, the magnesium bicarbonate solution is sent to pyrolysis to obtain alkali. formula magnesium carbonate, and then filtered and washed to obtain basic magnesium carbonate filter cake. There are currently one or two companies in China using this method to produce basic magnesium carbonate or magnesium oxide, with an annual output of about one to two thousand tons. There were several companies in Liaoning, my country, that built factories near magnesite mines to produce basic magnesium carbonate. Despite the advantages of raw materials and fuels, production had to be stopped in the end due to the small market.

How to prepare basic magnesium carbonate [identification]

The picture below shows the XRD spectrum of the sample.

How to prepare strontium carbonate from basic magnesium carbonate [Application]

Basic magnesium carbonate can be roughly divided into three aspects according to its uses. (1) Used as additives and improvers in food and various chemical products; (2) Used as raw materials for the preparation of magnesium series chemical products; (3) Used in pharmaceuticals and medical auxiliary therapeutic drugs. According to reports, taking basic magnesium carbonate into aluminum magnesium carbonate double salt and taking it together with ranitidine capsules, amoxicillin capsules, metronidazole tablets, etc. can greatly improve the cure rate of peptic ulcer in the elderly. Aluminum magnesium carbonate also plays an important role in treating ulcers. It increases the pH of the stomach and promotes tissue regeneration and repair. Since the regeneration and repair of ulcer tissue in the elderly is slow, taking aluminum magnesium carbonate can directly act on the ulcer surface to promote tissue regeneration and improve the ulcer healing rate. High-purity basic magnesium carbonate is non-toxic, tasteless and harmless to human health. Magnesium can enhance the heart function of the human body and has good fluidity. Therefore, adding it to flour as an auxiliary ingredient can It improves the dispersion and fluidity of flour and can supplement the human body’s demand for electrolytes such as inorganic salts. The addition amount is generally 10% to 15%. In chemical metallurgy, basic magnesium carbonate can also be added as an additive to some alloys to change the mechanical properties of the alloy.

Basic magnesium carbonate can also be used as an excellent filler and reinforcing agent for rubber products, which can improve the output and quality of rubber products. Refined transparent basic magnesium carbonate can also be used in transparent or light-colored rubber products. After it is mixed with rubber, it hardly changes the refractive index of the rubber itself, and can enhance the wear resistance, bending resistance and tensile strength of the rubber. strength. Because basic magnesium carbonate has the characteristics of non-burning and light and loose texture, it can also be used as heat insulation and high temperature resistant fireproof insulation material. Asbestos lightweight magnesium carbonate is an excellent insulation material and is used in shipbuilding, boiler manufacturing and other departments. In addition, it can also be used in paint, ink and coating industries.

How to prepare basic magnesium carbonate [Market Outlook]

As a direct product, the annual demand for methyltetrahydrofuran in my country’s basic magnesium carbonate market is only one to two thousand tons, which includes all light and heavy basic magnesium carbonate products. The biggest use of basic magnesium carbonate is to further calcine it and sell it as magnesium oxide product. In recent years, several large magnesium salt companies in Qinghai, my country, have produced high-quality, low-cost magnesium hydroxide products, with an output of hundreds of thousands of tons. These magnesium hydroxides are mainly processed into magnesium oxide products and sold on the market, forming strong competition for the magnesium oxide produced by basic magnesium carbonate. Under such competition, many basic magnesium carbonate production companies have shut down in recent years, and the existing basic magnesium carbonate production companies are also struggling, and most of them are in half-load production. Since low-cost, high-quality magnesium hydroxide is still competing strongly, it is expected that basic magnesium carbonate companies will not have an easy time in the next few years. I believe that some companies will still go bankrupt and close down.

How to prepare basic magnesium carbonate [Main reference materials]

[1] Chang Ruixuan, Ding Ke, Sun Xiaojun, Li Huijie, Huang Nana, Qiu Long, Gao Enjun, Liu Yunyi, Li Xue. Preparation of basic magnesium carbonate with different morphologies by pyrolysis [J]. Journal of Silicates, 2018 ,46(07):922-928.

[2] Zhang Shijie. Production and Prospects of Basic Magnesium Carbonate in my country [A]. China Inorganic Salt Industry Association Magnesium Compound Branch. 2016 Magnesium Compound Branch Annual Meeting and Magnesium Compound Industry Development Forum Special Edition [C]. China Inorganic Salts Magnesium Compound Branch of Industry Association: Calcium and Magnesium Salt Branch of China Inorganic Salt Industry Association, 2016: 2.

[3] Yuan Chunhua, and Li Haimin. “Application and synthesis method of basic magnesium carbonate.” Salt Lake Research 13.2 (2005): 40-44.

The role of magnesium carbonate