CN110498621B

CN110498621B - Preparation method of superfine purified concentrate powder sintered magnesia

Info

Publication number: CN110498621B
Application number: CN201910823268.8A
Authority: CN
Inventors: 于景坤
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-09-02
Filing date: 2019-09-02
Publication date: 2021-11-05
Anticipated expiration: 2039-09-02
Also published as: CN110498621A

Abstract

The invention discloses a preparation method of superfine purified concentrate powder sintered magnesite, which adopts magnesite as a raw material, obtains superfine magnesite concentrate powder by two-stage crushing and grinding, and directly obtains the volume density of more than or equal to 3.40g/cm through compression molding and high-temperature calcination³High-density sintered magnesia. The invention cancels the light burning equipment and process required in the prior preparation process, so that the preparation process of the high-density sintered magnesia becomes simple and easy, the production period is shortened, and the equipment investment and the production cost are greatly reduced. Compared with the prior high-density sintered magnesite, the production period of the invention is shortened by 1/2, the equipment investment is reduced by 50%, the production cost is reduced by more than 40%, and the invention has good technical and economic values and wide market application prospect.

Description

Preparation method of superfine purified concentrate powder sintered magnesia

Technical Field

The invention relates to the technical field of refractory material manufacturing, in particular to a preparation method for preparing high-density sintered magnesia by two-stage superfine purification of concentrate powder.

Background

The sintered magnesia is used as a main raw material of the alkaline refractory material, and the volume density of the sintered magnesia has important influence on the slag erosion resistance and the high-temperature strength of the refractory material and directly influences the service life of the refractory material. The research result and the production practice show that when the volume density of the sintered magnesia is not less than 3.40g/cm³In the process, the service performance of the prepared refractory material is obviously improved, the service life of the refractory material is one time of that of common density sintered magnesia, and the refractory material can replace electric melting magnesia to be used as a refractory raw material. Therefore, not only can energy be saved and environmental pollution be reduced, but also the production cost of the refractory raw materials can be greatly reduced.

At present, the following two production processes for preparing high-density sintered magnesite are publicly reported.

The first preparation process is shown in fig. 1 as follows: magnesite → light burned magnesia obtained by primary light burning → magnesium hydroxide obtained by hydration treatment → light burned magnesia obtained by secondary light burning → pressure molding → high temperature burning → high density sintered magnesia (see the authorization notice No. CN1301228C 'a preparation method of sintered magnesia').

The second process is shown in fig. 2 as: magnesite → fine grinding and flotation purification → superfine grinding and grinding → light burning to obtain light burnt magnesia → press forming → high temperature calcination.

From the above two preparation processes, the first preparation process is to convert magnesite into magnesium hydroxide, and then to use the magnesium hydroxide as a raw material to manufacture high-density sintered magnesite. Although bulk densities greater than 3.40g/cm can be prepared using the above process³The high-density sintered magnesite, however, needs to be lightly burned twice and converted into raw materials, so that the production equipment and the process are complicated, and the production cost is greatly increased.

The second preparation process is to use magnesite as raw material, to obtain superfine magnesite concentrate powder through two-stage grinding and one-time flotation, purification and mineral separation, to obtain light-burned magnesia powder through one-time light burning, to obtain high-density sintered magnesia through compression molding and high-temperature calcination.

Compared with the first process, the second process method is much simpler, shortens the production period and greatly reduces the cost. However, in both the first and second processes, the light-burned magnesia needs to be prepared through a light-burned decomposition process. The light-burning decomposition of the magnesite needs a light-burning kiln and a series of auxiliary equipment, and a large amount of fuel is needed to heat the light-burning kiln to 850-1000 ℃ so as to ensure the complete decomposition of the magnesite. Therefore, a large energy supply is also required.

Generally, one shaft kiln or rotary kiln for calcining and sintering magnesite is provided with three light-fired kilns simultaneously to meet the production requirement. The cost for building three light-burning kilns and auxiliary equipment thereof is equivalent to the cost for building one vertical kiln or rotary kiln for calcining magnesia. In addition, the fuel cost for decomposing magnesite by light burning is 50% of that of magnesite calcined in a shaft kiln.

On the other hand, when the magnesite clinker is calcined and sintered, the temperature of the high-temperature zone of the calcining kiln is as high as 1800-2000 ℃. The heat discharged from the high-temperature zone is discharged out of the kiln for the most part except for a small part for preheating the sintering raw material. Not only causes great waste of energy, but also causes the temperature at the top of the calcining kiln to be overhigh, thereby greatly reducing the service life of the equipment.

Disclosure of Invention

The invention provides a method for preparing high-density sintered magnesia by purifying concentrate powder through two-stage superfine grinding, aiming at overcoming the defects of the prior art and the prior art in the process of preparing the high-density sintered magnesia. The preparation method of the invention takes magnesite as raw material, and directly prepares high-density sintered magnesite through first-stage fine grinding, flotation purification and mineral separation, second-stage ultrafine grinding and grinding, compression molding and high-temperature calcination.

The invention relates to a preparation method of superfine purified concentrate powder sintered magnesia, which adopts two-stage grinding and crushing to obtain superfine magnesite concentrate powder, and the superfine magnesite concentrate powder is pressed and molded and directly calcined at high temperature to obtain high-density sintered magnesia; the process comprises the following steps:

1) first-stage grinding concentrate powder purification and mineral separation, wherein first-stage grinding concentrate powder purification and mineral separation treatment is carried out, magnesite is used as a raw material, and the magnesite is ground to 200 meshes, namely magnesite powder with the fineness of 74 mu m; wherein, the content of-200 meshes of magnesite powder is more than or equal to 75 percent, and the magnesite concentrate powder with the required purity is obtained;

2) performing secondary ultrafine grinding and grinding, and performing further ultrafine grinding and grinding on the magnesite concentrate powder selected at the primary stage to obtain ultrafine magnesite concentrate powder with the fineness of less than or equal to 4 mu m;

3) pressing and forming, namely pressing and forming the superfine magnesite concentrate powder obtained by the two-stage superfine grinding and grinding by adopting a press under the pressure of more than or equal to 300 MPa;

4) calcining at high temperature, namely calcining the press-formed superfine magnesite concentrate at 1800-2000 ℃ for 2-3 hours, so that the magnesite can be directly completely decomposed in the high-temperature calcining process; or fully utilizing the waste heat at the upper part of the calcining kiln to complete the complete decomposition of the magnesite in the high-temperature calcining process, thereby obtaining the volume density of 3.40g/cm³～3.50g/cm³The high-density sintered magnesia product.

The wet flotation purification beneficiation treatment is preferably carried out in the invention, namely, the wet flotation purification beneficiation is carried out in a flotation tank of wet flotation equipment, and the magnesite concentrate powder with the required purity is obtained.

The fineness of the superfine magnesite concentrate powder can be further refinedTo 1-3 μm, and further leading the volume density of the high-density sintered magnesia product to reach 3.42g/cm³～3.50g/cm³。

The invention adopts a grinder and an ultrafine grinding device which can grind mineral powder with the fineness less than or equal to 4 mu m during grinding and ultrafine grinding. The ultrafine grinding equipment can adopt ultrafine grinding equipment such as an airflow mill, a high-speed mechanical impact mill, a stirring ball mill, a grinding and stripping machine, a sand mill, a vibration ball mill, a rotary barrel type ball mill, a planetary ball mill, a tower mill, a cyclone self-grinding machine, a high-pressure roller mill, a high-pressure water jet mill or a colloid mill and the like for ultrafine grinding and grinding. The calcining process of the invention can be carried out by adopting equipment such as a shaft kiln or a rotary kiln.

The preparation method of the invention obtains the superfine magnesite concentrate powder with the fineness less than or equal to 4 mu m by primary grinding and flotation purification and secondary superfine grinding and grinding, directly carries out high-temperature calcination after compression molding, and directly completes the complete decomposition of magnesite in the high-temperature calcination process, thereby directly obtaining the high-density sintered magnesite product. Therefore, light burning equipment and a light burning process for decomposing magnesite are completely cancelled, so that the whole process flow of sintering magnesite is very simple, and the production period is greatly shortened. Meanwhile, light burning equipment is saved, sintering process is reduced, equipment and site are saved, energy is saved, environment is protected, and production cost is greatly reduced.

The invention can also fully utilize the waste heat at the upper part of the calcining kiln to complete the complete decomposition of the magnesite in the high-temperature calcining process, thereby not only ensuring the complete decomposition of the magnesite, but also greatly reducing the heat emission of the waste heat and prolonging the service life of the calcining kiln.

Drawings

FIG. 1 is a schematic flow diagram of a first prior art manufacturing process;

FIG. 2 is a schematic flow diagram of a second prior art manufacturing process;

FIG. 3 is a schematic flow chart of the preparation process of the present invention.

Detailed Description

The invention is explained in detail below with reference to the figures and exemplary embodiments. Shown in the following drawings are preferred embodiments which do not limit other embodiments of the invention.

The invention is described in detail below with reference to the figures and exemplary embodiments.

Referring to fig. 3, the invention provides a preparation method for preparing high-density sintered magnesia by two-stage superfine purification of concentrate powder through multiple improvements and experiments, aiming at the complicated process that light-burned magnesia is prepared by light-burned magnesite and then high-density sintered magnesia is prepared through molding and high-temperature calcination processes in the prior art.

Research results show that the magnesite in China belongs to a coarse crystalline ore system, and magnesium carbonate, namely MgCO, remains in MgO generated after decomposition₃The "pseudomorphic" structure of (1). This "pseudomorphic" structure hinders the sintering of MgO. In the traditional sintered magnesia production process, the light burning process is mainly set to destroy the 'pseudo-crystal' structure, and simultaneously, the activity of magnesia and the compaction density of a formed blank are increased to improve the sintering performance of magnesia and further obtain the densified high-density sintered magnesia.

The inventor obtains unexpected experimental results through a large number of researches and experiments, namely the magnesite powder can destroy or partially destroy the pseudomorphic crystal structure of magnesium carbonate when the fineness of the magnesite powder reaches less than or equal to 4 mu m through ultrafine grinding and grinding, and meanwhile, the specific surface area of the magnesite powder can be increased through ultrafine grinding and grinding, so that the ultrafine concentrate powder with the energy required by magnesite sintering can be obtained.

The unexpected experimental result only needs to carry out ultrafine grinding, grinding and purification ore dressing to obtain ultrafine magnesite concentrate powder with the fineness less than or equal to 4 mu m, the ultrafine magnesite concentrate powder is directly calcined at high temperature after being pressed and formed, and the complete decomposition of magnesite and the direct obtaining of high-density sintered magnesite products are directly completed in the high-temperature calcination process, thereby laying a scientific theoretical foundation for completely canceling the light burning process.

Meanwhile, through a plurality of experiments and improved results, the invention can also fully utilize the waste heat at the upper part of the calcining kiln to complete the complete decomposition of the magnesite in the high-temperature calcining process. Because the temperature of the waste heat at the upper part of the calcining kiln is very high, not only can the complete decomposition of magnesite be ensured, but also the heat emission of the waste heat is greatly reduced, and the calcining kiln has good protection effect on long-term use.

The two experimental results of the invention fully prove the practical feasibility of the technology, and achieve the technical effect expected by the invention in actual operation.

On the basis of the research and the experiment, the invention innovatively provides a preparation method for preparing high-density sintered magnesia by using superfine purified concentrate powder, namely magnesite is firstly ground to 200 meshes, namely magnesite powder with the particle size of 74 mu m by using a grinder; wherein the content of-200-mesh magnesite powder is more than or equal to 75 percent; after primary grinding concentrate powder and wet flotation purification mineral separation, magnesite concentrate powder with required purity is obtained; and then the superfine magnesite concentrate powder with the fineness less than or equal to 4 mu m is obtained by secondary superfine grinding and grinding. Because the 'pseudo-crystal' structure of the screened superfine magnesite concentrate powder is destroyed, and meanwhile, the superfine magnesite concentrate powder with the fineness less than or equal to 4 mu m increases the specific surface area, and the densification and sintering performance of magnesite is greatly improved. Therefore, the powder is pressed and molded under the pressure of more than or equal to 300MPa, and then is calcined for 2-3 hours at the high temperature of 1800-2000 ℃, so that the volume density of 3.40g/cm can be obtained³～3.50g/cm³The high-density sintered magnesia product. Therefore, in the process for preparing the high-density sintered magnesite, light-burning equipment and a light-burning process are not needed.

In the preparation process, the magnesite powder has low viscosity and can be ground by a wet method, so the magnesite powder can be conveniently connected with the wet floatation process in the previous step, the superfine grinding and grinding process of the invention becomes simpler and more feasible, and the magnesite powder is water-saving and environment-friendly.

The ultrafine grinding equipment can adopt ultrafine grinding equipment such as an air flow mill, a high-speed mechanical impact mill, a stirring ball mill, a grinding and stripping machine, a sand mill, a vibration ball mill, a rotary barrel type ball mill, a planetary ball mill, a tower type mill, a cyclone self-grinding machine, a high-pressure roller mill, a high-pressure water jet mill or a colloid mill. The high-temperature calcination of the invention can adopt equipment such as a shaft kiln or a rotary kiln.

The invention directly obtains the high-density sintered magnesite by using the superfine magnesite concentrate powder obtained by two-stage crushing and grinding as the raw material and through compression molding and high-temperature calcination, and omits light-burning equipment and procedures required in the prior preparation process, so that the preparation process of the high-density sintered magnesite becomes simple and easy, the production period is shortened, and the equipment investment and the production cost are greatly reduced. Compared with the prior art for preparing high-density sintered magnesia, the production period is shortened by 1/2, the equipment investment is reduced by about 50 percent, and the production cost is reduced by more than 40 percent.

Example 1

Referring to fig. 3, in the embodiment, low-grade magnesite produced by domestic large bridges is used as a raw material, the main mineral is magnesite, and meanwhile, the low-grade magnesite also contains dolomite, a small amount of talc and other minerals. The main chemical composition is shown in table 1.

TABLE 1 composition of main chemical components

Components	MgO	SiO₂	CaO	Fe₂O₃	Al₂O₃	Others
							％	46.56	1.89	0.67	0.31	0.05	50.52

Firstly, carrying out purification and mineral separation treatment on primary grinding concentrate powder, and grinding magnesite raw materials to 200 meshes by adopting a common grinder, namely magnesite powder with the granularity of 74 mu m; wherein the content of-200-mesh magnesite powder is 82%. The finely ground magnesite powder is put into a flotation tank for wet flotation, purification and mineral separation to obtain magnesite concentrate powder, and the main chemical composition is shown in table 2.

TABLE 2 main chemical composition of magnesite concentrate powder

Components	MgO	SiO₂	CaO	Fe₂O₃	Al₂O₃	Others
							％	47.35	0.01	0.42	0.15	0.03	52.04

The main chemical composition of table 2 shows that the MgO content of magnesite concentrate powder after the purification and beneficiation treatment is significantly increased, from 46.56% to 47.35%.

And (3) carrying out secondary ultrafine grinding and grinding on the magnesite concentrate powder selected by the primary process. Carrying out ultrafine grinding and grinding on the primary magnesite concentrate powder by adopting a stirring ball mill to obtain ultrafine magnesite concentrate powder with the fineness of 2-3 mu m, and then pressing and molding the ultrafine magnesite concentrate powder under the pressure of 350 MPa; loading the superfine magnesite concentrate into rotary kiln, calcining at 1900 deg.C for 2.5 hr, decomposing magnesite directly in high-temp calcining, further sintering in high-temp calcining region to densify it and obtain the magnesite product with volume density of 3.43g/cm³The high-density sintered magnesite.

Example 2

Referring to fig. 3, the present embodiment also uses the low-grade magnesite of example 1 as raw material, and the preparation steps are as follows:

1) grinding magnesite to 200 meshes of magnesite powder by using a mill, and carrying out primary grinding and mineral separation treatment on the magnesite powder, wherein the content of-200 meshes of magnesite powder is 85%; carrying out wet flotation, purification and mineral separation on the levigated magnesite powder in a flotation tank to obtain magnesite concentrate powder with 47.21 percent of MgO;

2) carrying out secondary ultrafine grinding and grinding on the primary magnesite concentrate powder, and carrying out ultrafine grinding and grinding on the primary magnesite concentrate powder by adopting a high-speed mechanical impact mill to obtain ultrafine magnesite concentrate powder with the fineness of 1-2 mu m;

3) pressing and molding the secondary superfine magnesite concentrate powder by a press under 400 MPa;

4) compression molded superfineThe magnesite concentrate is calcined in a shaft kiln at 1950 ℃ for 2.5 hours, the decomposition process is directly finished by utilizing the waste heat discharged from a high-temperature area at the upper part of the shaft kiln, and the magnesite concentrate enters the high-temperature area for densification sintering to obtain the bulk density of 3.45g/cm³The high-density sintered magnesia product.

Example 3

Example 3 the low grade magnesite of example 1 is used as raw material, the magnesite is ground to 200 mesh magnesite powder with-200 mesh magnesite powder content of 88%; carrying out wet flotation, purification and mineral separation on the levigated magnesite powder in a flotation tank to obtain magnesite concentrate powder with 48.03 percent of MgO component;

performing secondary ultrafine grinding and grinding on the primary magnesite concentrate powder by using an air flow mill to obtain ultrafine magnesite concentrate powder with the fineness of 1-2 mu m; calcining superfine magnesite concentrate powder which is formed by compression under 380MPa in a shaft kiln at 1850 ℃ for 3 hours, directly completing the decomposition process of magnesite in the high-temperature calcination process, and obtaining the bulk density of 3.50g/cm through densification sintering in a high-temperature area³The high-density sintered magnesite.

In the three embodiments, two wet processes are mutually connected in the process of superfine grinding and wet flotation purification ore dressing, so that water sources are saved, and the purpose of environmental protection without environmental pollution is achieved.

The fineness of the superfine magnesite concentrate powder adopted in the three embodiments is 1-3 mu m, so that the pseudomorphic structure of magnesium carbonate is destroyed, the specific surface area of the powder is increased, and the volume density of the prepared high-density sintered magnesite is 3.42g/cm³Above, the final purity reaches 98.22%. The refractory material produced by the high-density sintered magnesia shows good service performance and service life in the use process, the service life of the refractory material is more than doubled compared with the service life of the existing refractory product, but the equipment investment and the production cost are only about 50 percent of the equipment investment and the production cost of the prior art.

The implementation process and the implementation effect obviously show that the method is particularly suitable for processing low-grade magnesite to obtain high-density sintered magnesite with high added value, can effectively improve the cost performance of the product, and has good technical and economic values and wide market application prospects.

The foregoing is merely a preferred embodiment of the present invention and is not intended to limit other embodiments of the invention. Various modifications may be made by those skilled in the art without departing from the principles of the invention and should be considered within the scope of the invention.

Claims

1. A preparation method of superfine purified concentrate powder sintered magnesite is characterized in that two-stage grinding and crushing are adopted to obtain superfine magnesite concentrate powder, high-density sintered magnesite is obtained by compression molding and direct high-temperature calcination, and the following process steps are adopted:

1) first-stage grinding concentrate powder purification and mineral separation, firstly, first-stage grinding concentrate powder purification and mineral separation treatment is carried out, magnesite is used as a raw material, and the magnesite is ground to 200 meshes, namely 74 mu m magnesite powder; wherein the content of-200 meshes of magnesite powder is more than or equal to 75 percent, and magnesite concentrate powder with required purity is obtained by mineral separation;

3) pressing and forming, namely pressing and forming the superfine magnesite concentrate powder selected by the second stage by adopting a press under the pressure of more than or equal to 300 MPa;

4) calcining at high temperature, calcining the press-formed superfine magnesite concentrate for 2-3 hours at 1800-2000 ℃ to obtain the bulk density of 3.40g/cm³～3.50g/cm³The high-density sintered magnesia product;

the decomposition process of magnesite is directly finished in the high-temperature calcination process.

2. The method of claim 1, wherein the purification beneficiation is a wet flotation purification beneficiation process.

3. The method as claimed in claim 1, wherein the fineness of the ultra fine magnesite concentrate powder is 1 to 3 μm.

4. A method as claimed in any one of claims 1 to 3 or any other claim, characterised in that the decomposition of magnesite is performed directly by using the waste heat from the upper part of the calciner during the high temperature calcination.

5. The method of claim 1, wherein the high-density sintered magnesite product has a bulk density of 3.42g/cm³～3.50g/cm³。

6. A method of preparation according to claim 2, characterized in that the wet flotation purification beneficiation process is performed in a flotation cell.

7. The method according to claim 1, wherein the grinding and the ultra-fine pulverization are carried out by using a grinder and an ultra-fine pulverization device which pulverizes a fine ore having a fineness of 4 μm or less.

8. The preparation process according to claim 7, wherein the ultrafine pulverization apparatus may employ a jet mill, a high-speed mechanical impact mill, an agitating ball mill, a milling and flaking machine, a sand mill, a vibration ball mill, a rotary barrel ball mill, a planetary ball mill, a tower mill, a cyclone autogenous mill, a high-pressure roller mill, a high-pressure water jet mill or a colloid mill.

9. The method of claim 1, wherein the calcining is performed in a shaft kiln or a rotary kiln.