阅读说明：本技术 一种利用菱镁矿制备氧化镁的方法 (Method for preparing magnesium oxide by using magnesite ) 是由 董振海 智慧 杨晓峰 付亚峰 满晓霏 刘剑军 于 2021-09-01 设计创作，主要内容包括：本发明涉及氧化镁制备技术领域,具体涉及一种利用菱镁矿制备氧化镁的方法。包括如下步骤：将菱镁矿的浮选精矿筛分为至少两种粒度的矿粉并分别进行流化态煅烧。本发明实施例的方法对菱镁矿浮选精矿进行粒径分级并分别流化态煅烧,避免细粒菱镁矿的过烧或粗粒菱镁矿的欠烧,提高氧化镁产品的活性,同时提升菱镁矿的资源利用率。(The invention relates to the technical field of magnesium oxide preparation, in particular to a method for preparing magnesium oxide by utilizing magnesite. The method comprises the following steps: the magnesite flotation concentrate is screened into mineral powder with at least two particle sizes and is respectively subjected to fluidized calcination. According to the method provided by the embodiment of the invention, the magnesite flotation concentrate is subjected to particle size classification and is respectively calcined in a fluidized state, so that overburning of fine-grained magnesite or under-burning of coarse-grained magnesite is avoided, the activity of a magnesium oxide product is improved, and the resource utilization rate of magnesite is improved.)

1. A method for preparing magnesium oxide by using magnesite is characterized by comprising the following steps: the magnesite flotation concentrate is screened into mineral powder with at least two particle sizes and is respectively subjected to fluidized calcination.

2. The method for preparing magnesium oxide by using magnesite according to claim 1, wherein the content of magnesium oxide after ignition weight loss of the flotation concentrate is not less than 44% in percentage by weight, the flotation concentrate is obtained by refining and flotation of raw magnesite, and the content of magnesium oxide after ignition weight loss of the raw magnesite is not more than 42%.

3. The method for preparing magnesium oxide by using magnesite according to claim 1, wherein the flotation concentrate particle size is 48-125 μm.

4. The method for preparing magnesium oxide by using magnesite as claimed in claim 1, wherein the flotation concentrate is screened into two kinds of ore powder, wherein the first ore powder has a maximum particle size of 70-80 μm and an average particle size of 50-60 μm, and the second ore powder has a minimum particle size larger than that of the first ore powder and an average particle size of 100-110 μm.

5. The method for preparing magnesium oxide by using magnesite as claimed in claim 4, wherein the first particle size ore powder is 48-74 μm in size, and the second particle size ore powder is 74-125 μm in size.

6. The method for preparing magnesium oxide by using magnesite as claimed in claim 4, wherein the calcination temperature of the ore powder is 820-870 ℃.

7. The method for preparing magnesium oxide by using magnesite as claimed in claim 4, wherein the calcination time of the ore powder with the first particle size is 4-6min, and the calcination time of the ore powder with the second particle size is 8-12 min.

8. The method for preparing magnesium oxide by using magnesite according to claim 1, wherein the fluidized calcining furnace or fluidized bed reactor is used for the fluidized calcining, and air with the air speed of 2.0-2.5m/s is introduced during calcining.

9. Magnesium oxide, characterized in that it is obtained by a process according to any one of claims 1 to 8.

Technical Field

The invention relates to the technical field of magnesium oxide preparation, in particular to a method for preparing magnesium oxide by utilizing magnesite.

Background

The magnesite resources in China are abundant, the proven reserves are about 31 hundred million t and account for one fourth of the total reserves in the world, the magnesite resources are mainly distributed in Liaoning provinces and Shandong provinces, the total reserves account for about 95.11% of the total reserves in the country, the Liaoning province is mainly concentrated in the south areas of Liaoning provinces, such as the sea city, the Yingkou and other areas, the proven mine areas are 12, the reserved reserves are 25.77 million t and account for about 85% of the total reserves in the country and account for 20% of the total reserves in the world.

The high-activity magnesium oxide is an important functional inorganic chemical product, and has high specific surface energy, so that the high-activity magnesium oxide is widely used for preparing heat-resistant ceramics and special cement, is used as a catalyst in organic synthesis, and is used as a carrier of a medicament and an adsorbent of pollutants. It is also useful as an accelerator and activator for high-quality chloroprene rubber, butyl rubber, nitrile rubber and fluororubber because of its high activity. The existing calcining equipment for preparing high-activity magnesium oxide by using magnesite, such as a rotary kiln, a reflection kiln, a tunnel kiln and the like, is mostly limited to processing magnesite lump materials. In recent years, high-quality magnesite resources are consumed greatly, and low-grade magnesite utilization is emphasized for improving the utilization rate of the magnesite resources. Because the purity and activity of the magnesium oxide product obtained by directly calcining low-grade magnesite are not ideal enough, the low-grade magnesite needs to be subjected to flotation treatment to improve the magnesium grade, the flotation process necessarily comprises high dissociation of raw magnesite, the obtained magnesite concentrate is in a powder state, and the existing reactor is difficult to effectively treat. In addition, because the reaction in the existing reactor is lump material reaction, the heat and mass transfer efficiency is low, the calcination time is long, the calcination is not uniform, the activity of the magnesium oxide product is reduced, and the waste of magnesite resources is caused.

Disclosure of Invention

The present invention is based on the discovery and recognition by the inventors of the following facts and problems: the raw magnesite ore grade of the existing magnesium oxide product which can be directly fired is at least 45 percent, while the low-grade raw ore below 42 percent can be fired and utilized after ore dressing. Most of the existing calcining equipment and preparation process for preparing high-activity magnesium oxide by utilizing magnesite are only limited to treating magnesite lump materials with higher grade, and the magnesite powder with micro-fine particles obtained after flotation is difficult to treat, long in calcining time and uneven in calcining, so that the activity of a magnesium oxide product is reduced, and the waste of magnesite resources is caused; in addition, although raw magnesite is mainly made of lump materials, powder is still inevitably generated in the mining process, the powder enters calcining equipment such as a rotary kiln and the like to easily block an exhaust duct, and in order to prevent the powder from blocking the equipment, the prior art generally performs ball forming and blocking treatment on the powder, so that the process and the cost are increased.

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the embodiment of the invention provides a method for preparing magnesium oxide by using magnesite, which comprises the steps of carrying out particle size classification on magnesite by flotation and selection, respectively carrying out fluidized state calcination, strictly controlling calcination temperature and calcination time, avoiding overburning and underburning, and improving the activity of a magnesium oxide product.

The method for preparing magnesium oxide by using magnesite according to the embodiment of the invention comprises the following steps: the magnesite flotation concentrate is screened into mineral powder with at least two particle sizes and is respectively subjected to fluidized calcination.

According to the advantages and technical effects brought by the method for preparing magnesium oxide by using magnesite in the embodiment of the invention, 1, the method in the embodiment of the invention carries out particle size classification on magnesite flotation concentrate and respectively carries out fluidized calcination, thereby avoiding overburning of fine-grained magnesite or under-burning of coarse-grained magnesite, improving the activity of magnesium oxide products and simultaneously improving the resource utilization rate of magnesite; 2. the raw material used by the method provided by the embodiment of the invention is magnesite flotation concentrate, and the magnesite grade can be improved through ore dressing treatment including flotation, so that the method provided by the embodiment of the invention has lower requirements on magnesite raw ore, and can be used for firing magnesium oxide by using the magnesite raw ore with lower grade; 3. the method provided by the embodiment of the invention has the advantages of short calcination time, high heat and mass transfer efficiency, low energy consumption, stable process operation, and high activity and stable property of the sintered magnesium oxide product.

According to the method for preparing the magnesium oxide by utilizing the magnesite, disclosed by the embodiment of the invention, according to the weight percentage, the content of the magnesium oxide after ignition weight loss of the flotation concentrate is more than or equal to 44%, the flotation concentrate is obtained by refining and floating the magnesite raw ore, and the content of the magnesium oxide after ignition weight loss of the magnesite raw ore is less than or equal to 42%.

According to the method for preparing magnesium oxide by utilizing magnesite, the granularity of the flotation concentrate is 48-125 mu m.

According to the method for preparing magnesium oxide by using magnesite, the flotation concentrate is sieved into mineral powder with two particle sizes, wherein the maximum particle size of the mineral powder with the first particle size is 70-80 μm, the average particle size is 50-60 μm, the minimum particle size of the mineral powder with the second particle size is larger than that of the mineral powder with the first particle size, and the average particle size is 100-110 μm.

According to the method for preparing magnesium oxide by using magnesite, the granularity of the mineral powder with the first granularity is 48-74 mu m, and the granularity of the mineral powder with the second granularity is 74-125 mu m.

According to the method for preparing magnesium oxide by using magnesite, the calcination temperature of the ore powder is 820-870 ℃.

According to the method for preparing magnesium oxide by using magnesite, the calcination time of the mineral powder with the first granularity is 4-6min, and the calcination time of the mineral powder with the second granularity is 8-12 min.

According to the method for preparing magnesium oxide by using magnesite, the fluidized state calcination adopts a fluidized state calcination furnace or a fluidized bed reactor, and air with the air speed of 2.0-2.5m/s is introduced during calcination.

A magnesium oxide according to an embodiment of the present invention is prepared by the method described in the above embodiment.

According to the advantages and technical effects brought by the magnesium oxide provided by the embodiment of the invention, the magnesium oxide product provided by the embodiment of the invention has high activity and good stability. The citric acid color development time of the magnesium oxide product is not more than 38 s.

Detailed Description

The following describes embodiments of the present invention in detail.

The method for preparing magnesium oxide by using magnesite according to the embodiment of the invention comprises the following steps: the magnesite flotation concentrate is screened into mineral powder with at least two particle sizes and is respectively subjected to fluidized calcination.

According to the advantages and technical effects brought by the method for preparing magnesium oxide by using magnesite in the embodiment of the invention, 1, the method in the embodiment of the invention carries out particle size classification on magnesite flotation concentrate and respectively carries out fluidized calcination, thereby avoiding overburning of fine-grained magnesite or under-burning of coarse-grained magnesite, improving the activity of magnesium oxide products and simultaneously improving the resource utilization rate of magnesite; 2. the raw material used by the method provided by the embodiment of the invention is magnesite flotation concentrate, and the magnesite grade can be improved through ore dressing treatment including flotation, so that the method provided by the embodiment of the invention has lower requirements on magnesite raw ore, and can be used for firing magnesium oxide by using the magnesite raw ore with lower grade; 3. the method provided by the embodiment of the invention has the advantages of short calcination time, high heat and mass transfer efficiency, low energy consumption, stable process operation, and high activity and stable property of the sintered magnesium oxide product.

According to the method for preparing the magnesium oxide by utilizing the magnesite, disclosed by the embodiment of the invention, according to the weight percentage, the content of the magnesium oxide after ignition weight loss of the flotation concentrate is more than or equal to 44%, the flotation concentrate is obtained by refining and flotation of raw magnesite, the content of the magnesium oxide after ignition weight loss of the raw magnesite is less than or equal to 42%, and the refining comprises crushing or grinding.

According to the method provided by the embodiment of the invention, the magnesite flotation concentrate is obtained by mineral separation of raw ores, the content of magnesium oxide is increased from a lower level to a higher level, and the grade requirement of the sintered magnesium oxide is met. The magnesite flotation concentrate adopted by the method provided by the embodiment of the invention has the main phase of MgCO₃Contains small amount of CaO, small amount of calcium and dolomite CaMg (CO)₃)₂Exist in the form of (1).

According to the method for preparing magnesium oxide by utilizing magnesite, the granularity of the flotation concentrate is 48-125 mu m. In the method of the embodiment of the invention, the raw material used for calcination is powdered magnesite powder, which is obtained by converting raw magnesite in lump form into powdered magnesite due to the refining process.

According to the method for preparing magnesium oxide by using magnesite, the flotation concentrate is sieved into mineral powder with two particle sizes, wherein the maximum particle size of the mineral powder with the first particle size is 70-80 μm, the average particle size is 50-60 μm, the minimum particle size of the mineral powder with the second particle size is larger than that of the mineral powder with the first particle size, and the average particle size is 100-110 μm. The method of the embodiment of the invention optimizes the average particle size of the fine and coarse particle mineral powder, the mineral powder with concentrated particle size distribution is heated more uniformly and fully during calcination, and the high activity of the magnesium oxide product is ensured.

According to the method for preparing magnesium oxide by using magnesite, the granularity of the mineral powder with the first granularity is 48-74 mu m, and the granularity of the mineral powder with the second granularity is 74-125 mu m. According to the method provided by the embodiment of the invention, the magnesite is screened into fine and coarse grain mineral powders with different grain sizes, and the grain size boundary values of the fine and coarse grain mineral powders are optimized, so that the calcination temperature and the calcination time of the mineral powders with two grain sizes can be conveniently and respectively controlled subsequently.

According to the method for preparing magnesium oxide by using magnesite, the calcination temperature of the ore powder is 820-870 ℃. It should be noted that the calcination temperature of the ore fines of the first particle size and the calcination temperature of the ore fines of the second particle size may be the same or different. The method of the embodiment of the invention optimizes the calcination temperature and ensures the generation of magnesium oxide crystals.

According to the method for preparing magnesium oxide by using magnesite, the calcination time of the mineral powder with the first granularity is 4-6min, and the calcination time of the mineral powder with the second granularity is 8-12 min.

In the method of the embodiment of the invention, the calcination time of magnesite ore powder with smaller granularity is shorter. On one hand, under the same calcination temperature, the magnesite ore powder with smaller granularity has better heat and mass transfer effects, the time for obtaining the growth energy of crystal grains is shorter, the crystal defects are reduced due to the overlong calcination time, and the activity of a magnesium oxide product is reduced. On the other hand, as magnesite is decomposed to generate carbon dioxide or water during calcination, the carbon dioxide or water is adsorbed on the surfaces of magnesium oxide crystal grains to enable the crystal grains to grow orderly, so that crystal defects are reduced. Therefore, the method provided by the embodiment of the invention is used for grading the particle sizes of the magnesite powder raw materials with different particle sizes and respectively carrying out fluidized calcination, and simultaneously strictly controlling the calcination time, so that over-calcination or under-calcination of the magnesite powder is prevented, and the magnesite powder with different particle sizes can be calcined into a magnesium oxide product with small grain size, more crystal defects and high reaction activity.

According to the method for preparing magnesium oxide by using magnesite, the fluidized state calcination adopts a fluidized state calcination furnace or a fluidized bed reactor, and air with the air speed of 2.0-2.5m/s is introduced during calcination. In the method of the embodiment of the invention, the fluidized bed reactor is heated by heating equipment such as an electric furnace during fluidized calcination. In order to ensure the accuracy of the calcination time, the method provided by the embodiment of the invention preheats the electric furnace or the fluidized calciner to the calcination temperature before calcination, loads the mineral powder, starts timing after the temperature in the furnace is raised to the calcination temperature again, and carries out fluidized calcination.

According to the method for preparing magnesium oxide by using magnesite, the sample is taken out under the protection of nitrogen after calcination is finished, and the sample is naturally cooled.

The method for preparing magnesium oxide by using magnesite according to the embodiment of the invention preferably comprises the following steps: refining raw magnesite, and performing flotation treatment to obtain magnesite flotation concentrate with granularity of 48-125 mu m; screening the magnesite flotation concentrate into fine-grained mineral powder with the granularity of 48-74 mu m and mineral powder with the coarse granularity of 74-125 mu m, and respectively carrying out fluidized state calcination, wherein the calcination temperatures of the two kinds of grained mineral powder are respectively 820-870 ℃, the calcination times are respectively 4-6min and 8-12min, and the calcination equipment is a fluidized state calciner or a fluidized bed reactor; wherein, the content of the magnesium oxide after ignition weight loss of the flotation concentrate is more than or equal to 44 percent, and the content of the magnesium oxide after ignition weight loss of the magnesite raw ore is less than or equal to 42 percent.

A magnesium oxide according to an embodiment of the present invention is prepared by the method described in the above embodiment.

The magnesium oxide product prepared by the embodiment of the invention has high activity and good stability.

The present invention will be described in detail below by way of examples.

In the examples of the present invention and the comparative examples,

(1) the magnesite powder raw material is magnesite flotation concentrate with the granularity of 48-125 mu m, the magnesite flotation concentrate has the magnesia content of about 44 percent after ignition loss and the main phase of MgCO₃Contains small amount of CaO, small amount of calcium and dolomite CaMg (CO)₃)₂Exists in the form of (1); the flotation concentrate is obtained by refining and flotation of raw magnesite, and the content of magnesium oxide after the raw magnesite is burned, reduced in weight and reduced in weight is 41%.

(2) The activity of the magnesium oxide product is determined by a citric acid color development method, and the specific test method comprises the following steps: measuring 100ml of 0.1mol/L citric acid solution, placing the citric acid solution in a 250ml beaker, adjusting the temperature of the citric acid solution to 25 ℃, adding 5 drops of phenolphthalein indicator, placing the beaker in an ultrasonic cleaner, turning on the ultrasonic, weighing 2.030 +/-0.001 g of magnesium oxide sample, quickly pouring the magnesium oxide sample into the citric acid solution, starting timing by using a stopwatch, quickly stirring the solution by using a glass rod, and recording the color development time when the solution just turns red, namely the end point. The shorter the development time, the higher the activity of the magnesium oxide sample.

Example 1

(1) Screening: dry screening the magnesite flotation concentrate incoming material of the same batch, and obtaining fine mineral powder with the granularity of 48-74 mu m and the average grain size of 55.2 mu m and coarse mineral powder with the granularity of 74-125 mu m and the average grain size of 110.3 mu m by using a standard sleeve dry screening method.

(2) Calcining and cooling fine-grained mineral powder: preheating a first temperature-controlled electric furnace to 850 ℃, then placing a first quartz tube fluidized bed reactor filled with fine-grained mineral powder into the first temperature-controlled electric furnace, introducing air at the air speed of 2.0m/s under the working condition, starting timing after the temperature in the furnace rises to 850 ℃, and calcining for 5 min. And after the calcination is finished, switching nitrogen in the furnace, taking out the first quartz tube fluidized bed reactor, and naturally cooling in air to obtain a first magnesium oxide product.

(3) Calcining and cooling coarse-grained mineral powder: preheating a second temperature-controlled electric furnace to 850 ℃, then placing a second quartz tube fluidized bed reactor filled with coarse-grained mineral powder into the second temperature-controlled electric furnace, introducing air at the air speed of 2.0m/s under the working condition, timing after the temperature in the furnace rises to 850 ℃, and calcining for 9 min. And after the calcination is finished, switching nitrogen in the furnace, taking out the second quartz tube fluidized bed reactor, and naturally cooling in the air to obtain a second magnesium dioxide product.

Example 2

(1) Screening: dry screening the magnesite flotation concentrate incoming material of the same batch, and obtaining fine mineral powder with the granularity of 48-74 mu m and the average grain size of 55.2 mu m and coarse mineral powder with the granularity of 74-125 mu m and the average grain size of 110.3 mu m by using a standard sleeve dry screening method.

(2) Calcining and cooling fine-grained mineral powder: preheating a first temperature-controlled electric furnace to 820 ℃, then placing a first quartz tube fluidized bed reactor filled with fine-grained mineral powder into the first temperature-controlled electric furnace, introducing air at the air speed of 2.0m/s under the working condition, starting timing after the temperature in the furnace rises to 820 ℃ again, and calcining for 6 min. And after the calcination is finished, switching nitrogen in the furnace, taking out the first quartz tube fluidized bed reactor, and naturally cooling in air to obtain a first magnesium oxide product.

(3) Calcining and cooling coarse-grained mineral powder: preheating a second temperature-controlled electric furnace to 820 ℃, then placing a second quartz tube fluidized bed reactor filled with fine-grained mineral powder into the second temperature-controlled electric furnace, introducing air at the air speed of 2.0m/s under the working condition, timing after the temperature in the furnace rises to 820 ℃, and calcining for 12 min. And after the calcination is finished, switching nitrogen in the furnace, taking out the second quartz tube fluidized bed reactor, and naturally cooling in the air to obtain a second magnesium dioxide product.

Example 3

(1) Screening: dry screening the magnesite flotation concentrate incoming material of the same batch, and obtaining fine mineral powder with the granularity of 48-74 mu m and the average grain size of 55.2 mu m and coarse mineral powder with the granularity of 74-125 mu m and the average grain size of 110.3 mu m by using a standard sleeve dry screening method.

(2) Calcining and cooling fine-grained mineral powder: preheating a first temperature control electric furnace to 870 ℃, then placing a first quartz tube fluidized bed reactor filled with fine-grained mineral powder into the first temperature control electric furnace, introducing air at the air speed of 2.0m/s under the working condition, timing after the temperature in the furnace rises to 870 ℃, and calcining for 4 min. And after the calcination is finished, switching nitrogen in the furnace, taking out the first quartz tube fluidized bed reactor, and naturally cooling in air to obtain a first magnesium oxide product.

(3) Calcining and cooling coarse-grained mineral powder: preheating a second temperature-controlled electric furnace to 870 ℃, then placing a second quartz tube fluidized bed reactor filled with fine-grained mineral powder into the second temperature-controlled electric furnace, introducing air at the air speed of 2.0m/s under the working condition, timing after the temperature in the furnace rises to 870 ℃, and calcining for 8 min. And after the calcination is finished, switching nitrogen in the furnace, taking out the second quartz tube fluidized bed reactor, and naturally cooling in the air to obtain a second magnesium dioxide product.

Comparative example 1

The magnesite powder raw material and equipment used in this comparative example are the same as those used in example 1, except that no fluidized bed reactor is used, and the powder is separately and directly loaded into an electric furnace for calcination.

Comparative example 2

The magnesite powder raw material and equipment adopted in the comparative example are the same as those in the example 1, except that the magnesite powder raw material is not screened and is loaded into the same quartz tube fluidized bed reactor for fluidized calcination for 9 min.

Comparative example 3

The magnesite powder raw material and equipment adopted in the comparative example are the same as those in the example 1, except that the magnesite powder raw material is not screened and is loaded into the same quartz tube fluidized bed reactor for fluidized calcination for 6 min.

The magnesium oxide products prepared in the above examples and comparative examples were subjected to a citric acid color development test, and the color development time thereof is shown in Table 1.

TABLE 1 citric acid development time of magnesium oxide products of each example and comparative example

As can be seen from Table 1, the citric acid color development time of the magnesium oxide products prepared in the above examples does not exceed 38s, and it can be seen that the magnesium oxide prepared by the method of the present invention examples has high activity and stable product properties.

In the comparative example 1, because a fluidized state calcination mode is not adopted, part of fine-particle mineral powder is over-burnt, while the coarse-particle mineral powder is under-burnt, the whole mineral powder is unevenly heated, and the activity of a magnesium oxide product is reduced. Comparative examples 2 and 3 the magnesite powder raw material was calcined directly without screening. The magnesite powder raw material has a large particle size range, and the mineral powder with different particle sizes is difficult to simultaneously reach a proper calcination state. In the comparative example 2, the magnesite ore powder with smaller granularity is over-burnt due to overlong calcination time, the number of crystal defects is reduced, and the activity of the obtained magnesium oxide product is reduced; comparative example 3 insufficient calcination time caused under-burning of magnesite ore powder with larger particle size, and also MgCO₃Does not convert into MgO, and also causes the reduction of the activity of the magnesium oxide product. Therefore, the method provided by the embodiment of the invention screens the magnesite powder raw materials and respectively performs fluidized calcination, can control calcination time of mineral powder with different particle sizes in a targeted manner, prevents over-burning or under-burning, and ensures high activity of magnesium oxide products.

In the present disclosure, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" and the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.