Study on the preparation of active magnesium oxide

Abstract

Description

A method for preparing active magnesium oxide

Technical Field

The present invention belongs to the field of inorganic material preparation, and specifically relates to the preparation technology of magnesium compounds, especially the preparation method of highly active magnesium oxide.

Background technology

As an important inorganic chemical product, magnesium oxide is mainly used in building materials, fertilizers, rubber, plastics, medicine and environmental protection, refractory materials and the preparation of magnesium metal. With the continuous development of science and technology, the application range of active magnesium oxide is getting wider and wider, especially the demand for high active magnesium oxide will further increase.

At present, the raw materials for the preparation of magnesium oxide are mainly sea salt, brine, magnesite, dolomite and so on. The methods of producing magnesium oxide from solid ore include calcination method, carbonization method, carbon and ammonia double-cycle method, acid digestion method, etc.; the methods of preparing magnesium oxide from brine or sea salt include emulsion of lime method, ammonia method, etc.

Li Wei-han (light burning magnesium oxide powder activity research, Wuhan Iron and Steel Institute Journal, 1992,15(1): 30-37) studied at 800 and 850 ℃ on the magnesite in Liaoning and Shandong for 2 hours of roasting, to get the active magnesium oxide, which the content of magnesium oxide in the 90% below, and to get the value of iodine adsorption of magnesium oxide in 80mgI/g MgO or so.

Wang Yafang (from magnesite preparation of high-purity magnesium oxide process research, mineral protection and utilization, 2005,6:17-20) to calcined magnesite produced light burned magnesium as raw material, after digestion, carbonation of magnesium bicarbonate solution, after the use of activated carbon as an adsorbent to remove calcium, iron and other impurities, and then pyrolysis, calcined to produce high-purity magnesium oxide.

Li Huan (the use of magnesite to prepare highly active magnesium oxide, refractories, 2006,40:294-296) studied magnesite as raw material, first calcined at 850 ℃ for 2h to obtain light burned magnesium oxide, and then hydrated into magnesium hydroxide, after drying at different temperatures (respectively, 450 ℃, 500 ℃, 550 ℃, 600 ℃) and holding time (respectively, 1h, 1.5h, 2h) Highly active magnesium oxide was prepared by decomposing magnesium hydroxide under light burning.

Chinese patent application 201110372850.0 disclosed that the raw material magnesium chloride solution as well as a mixture of NH3 and CO2 were passed into a supergravity reactor, and the gas-liquid rapid mixing reaction was carried out under the supergravity conditions, with the concentration of magnesium chloride solution of 0.2-0.5 mol/L, the volume ratio of NH3 and CO2 of (1.6-2.4):1, the reaction temperature of 70-80°C, the supergravity The reaction temperature is 70-80°C and the supergravity level is 150-960 g. The intermediate basic magnesium carbonate is obtained by reaction precipitation, filtration, washing and drying, and then the basic magnesium carbonate is calcined at the temperature of 500-900°C to obtain active magnesium oxide.

Chinese patent application 200510047743.5 discloses taking magnesite as raw material, through 600-800℃ light burning, 80-200℃ hydration, filtration, purification, drying, ball milling, 450-600℃ low-temperature calcination process to produce activated magnesium oxide, using this method can produce iodine adsorption value of 140-200mgI/g of highly activated magnesium oxide.

Chinese patent application 200410072343.5 discloses the use of natural water magnesite direct roasting to manufacture activated magnesium oxide, the process includes crushed water magnesite at 450 ~ 800 ℃ dynamic roasting 30 ~ 120 minutes, to obtain the iodine adsorption value of 80 ~ 120mgI/g of activated magnesium oxide.

Chinese patent application 200710065933.9 disclosed that under mechanical stirring conditions, adding a concentration of 15-20% of the milk of lime to the magnesium sulfate waste liquid, adjusting the pH at 12-13, stirring the reaction for a period of time to obtain a mixture of calcium sulfate and magnesium hydroxide, carbonization of the precipitate, filtration to obtain a magnesium bicarbonate solution, and pyrolysis of magnesium bicarbonate solution under the conditions of heating and stirring to get the Basic magnesium carbonate precipitate, after filtration, washing, drying and calcination at 950-1000 ℃ for 4-6 hours to obtain high activity of magnesium oxide.

All of the above methods for producing magnesium oxide methods have their own limitations, such as more by-products, large amount of energy consumption, cumbersome production methods, high cost, serious environmental pollution by NH3 and CO2, and other defects, which need to be improved.

Content of the invention

Aiming at the problems of long process flow, high production cost, complicated preparation process and high energy consumption of magnesium oxide production in the existing technology, the present invention provides a preparation method of active magnesium oxide.

The preparation method of active magnesium oxide provided by the present invention includes the following process steps:

(1) warming the closed heating device to 400 to 440°C;

(2) placing the magnesium hydroxide into the aforementioned closed heating device for roasting.

Preferably, said roasting time is 1.5-2 h. Highly active magnesium oxide is obtained by this process, during which the following chemical reaction occurs:

Mg(OH)₂→MgO+H₂O

Preferably, said magnesium hydroxide has a particle size of about 2.0 μm.

(3) The calcined magnesium oxide is cooled to room temperature in a drier.

In the present invention, the activity index of magnesium oxide is evaluated by the water law method, and the activity of magnesium oxide measured by the water law method is above 89%, which is a high activity magnesium oxide; and it is a well-dispersed granule. The method of the present invention has the advantages of relatively low calcination temperature, short roasting time and simple process, and the products obtained by the preparation have the characteristics of high activity, small particle size, etc., and the average particle size of the products is 4 μm. compared with the higher roasting temperature in the prior art, the present invention has a great advantage in terms of energy consumption, and there is no problem of decreasing the purity of the products because of the low-temperature roasting.

The magnesium oxide obtained by the method of the present invention can be used in fertilizers, plastics, environmental protection, refractory materials and metal magnesium extraction and other industries. The method of the present invention has a short industrial process, simple equipment, no pollution, easy to operate, and the product quality obtained by its preparation is high.

Specific implementation

Example 1:

Magnesium hydroxide with particle size D50 of 2 μm is put into a muffle furnace at a temperature of 440°C and roasted for 2 hours to obtain light-fired magnesium oxide powder. Then the magnesium oxide powder was put into a drier and cooled to room temperature. The magnesium oxide activity measured by water law in this test was about 89%, and the average particle size of the product was 4 μm, which was high activity magnesium oxide.

Example 2:

Put the magnesium hydroxide with a particle size D50 of about 2 μm into a muffle furnace at a temperature of 440°C for 1.5 hours to obtain lightly burned magnesium oxide powder. Then the magnesium oxide powder was put into a drier and cooled to room temperature. In this test, the activity of magnesium oxide measured by water law is about 90%, and the average particle size of the product is 4 μm, which belongs to high activity magnesium oxide.

Example 3:

Put the magnesium hydroxide with a particle size D50 of about 2 μm into a muffle furnace at a temperature of 350°C and roast and burn it for 2 hours to obtain lightly burned magnesium oxide powder. Then the magnesium oxide powder was put into a drier and cooled to room temperature. In this test, the magnesium oxide activity was measured by water lawfulness at about 51%, and the magnesium oxide activity was low.

Example 4:

Put the magnesium hydroxide with a particle size D50 of about 2 μm into a muffle furnace with a temperature of 400 ℃ and roast and burn for 1.5 hours, and get the lightly burnt magnesium oxide powder. Then the magnesium oxide powder was put into a drier and cooled to room temperature. In this test, the activity of magnesium oxide measured by water law is about 81%, and the activity of magnesium oxide is high.