CN113880479B - Method for preparing lightweight aggregate from magnesium-magnesium slag smelted by silicothermic process - Google Patents

Method for preparing lightweight aggregate from magnesium-magnesium slag smelted by silicothermic process Download PDF

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CN113880479B
CN113880479B CN202111330445.2A CN202111330445A CN113880479B CN 113880479 B CN113880479 B CN 113880479B CN 202111330445 A CN202111330445 A CN 202111330445A CN 113880479 B CN113880479 B CN 113880479B
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magnesium
slag
lightweight aggregate
ceramsite
magnesium slag
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CN113880479A (en
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朱苗淼
李辉
李妍
仁普亮
孙永民
黄琪
曹静
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Xian University of Architecture and Technology
Shaanxi Architecture Science Research Institute Co Ltd
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Shaanxi Architecture Science Research Institute Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/02—Treatment
    • C04B20/04—Heat treatment
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/02—Agglomerated materials, e.g. artificial aggregates
    • C04B18/027—Lightweight materials
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/14—Waste materials; Refuse from metallurgical processes
    • C04B18/141—Slags
    • C04B18/144—Slags from the production of specific metals other than iron or of specific alloys, e.g. ferrochrome slags
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/02—Treatment
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/02—Treatment
    • C04B20/023—Chemical treatment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Structural Engineering (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Civil Engineering (AREA)
  • Environmental & Geological Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)

Abstract

The invention discloses a method for preparing lightweight aggregate from magnesium slag produced by silicothermic process, which comprises the following steps: 1. putting the slowly cooled silicothermic magnesium-smelting slag into a ball mill, and grinding and sieving to obtain magnesium slag powder; 2. putting the magnesium slag powder into a granulator, spraying water to the magnesium slag powder, and performing rotary granulation to obtain magnesium slag ceramsite; 3. pre-curing the magnesium slag ceramsite to obtain pre-cured magnesium slag ceramsite; 4. and putting the pre-cured magnesium slag ceramsite into a closed container into which hot flue gas is introduced for carbonization, and naturally cooling to obtain the magnesium carbide slag lightweight aggregate. According to the invention, the magnesium slag ceramsite is prepared by taking the slowly-cooled magnesium slag smelted by the silicothermic process as a raw material, and is sequentially pre-cured and carbonized, so that a large number of small holes are generated in the magnesium slag ceramsite, the density of the magnesium carbide slag lightweight aggregate is reduced, the diffusion efficiency of carbon dioxide gas is improved, the carbonization time is shortened, uniform carbonization is realized, the carbonization degree is improved, the strength of the magnesium carbide slag lightweight aggregate is increased, and the high-strength and light-weight magnesium carbide slag lightweight aggregate is obtained.

Description

Method for preparing lightweight aggregate from magnesium-magnesium slag smelted by silicothermic process
Technical Field
The invention belongs to the technical field of building materials, and particularly relates to a method for preparing light aggregate from magnesium-magnesium slag smelted by a silicothermic process.
Background
Along with the expansion of the magnesium metal industry in China, on one hand, the output of magnesium slag produced by silicothermic process is increased year by year, which causes certain harm to the environment and human health, and the resource recycling of the magnesium slag is urgent; on the other hand, the greenhouse effect caused by the emission of carbon dioxide in the magnesium industry and other industrial waste gases is becoming more serious, the capture and utilization of carbon dioxide become the focus of industrial and scientific research in the world at present, and the carbonization of magnesium slag cementing materials is generated under the background. Meanwhile, as the sustainable development strategy of our country goes deep, the aggregate becomes increasingly scarce as a natural ore resource, and the price thereof is gradually increased, so that the research and development of substitutes for natural aggregates are urgently needed. The grindability and low price (only transportation cost) of the magnesium slag make the magnesium slag one of suitable substitute raw materials, but related reports and inventions are lacked at present.
In addition, the prior art has some non-negligible defects which limit the application of the magnesium slag lightweight aggregate in the actual production, such as: the low efficiency caused by overlong carbonization time, the density of the carbonized magnesium slag exceeds the requirement of national standard on light aggregate, the additional energy consumption brought by the steps of air cooling and the like in the magnesium slag pretreatment, the high energy consumption brought by the high-temperature and high-pressure environment of the carbonization subsequent treatment, the incomplete utilization of the heat energy carried by the flue gas in the carbonization process and the like. Therefore, it is important to propose a method for reducing the density of the magnesium slag aggregate while ensuring high strength.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for preparing lightweight aggregate from magnesium slag produced by silicothermic process magnesium smelting aiming at the defects of the prior art. The method takes the magnesium slag smelted by the silicothermic process after slow cooling as the raw material to prepare the magnesium slag ceramsite, and then the magnesium slag ceramsite is pre-cured and carbonized in sequence, so that a large number of small holes are generated inside the magnesium slag ceramsite, the density of the magnesium carbide slag lightweight aggregate is reduced, the diffusion efficiency of carbon dioxide gas is improved, the carbonization time is shortened, uniform carbonization is realized, the carbonization degree is improved, the strength of the magnesium carbide slag lightweight aggregate is greatly increased, and the high-strength and light-weight magnesium carbide slag lightweight aggregate is obtained.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a method for preparing lightweight aggregate from magnesium slag smelted by a silicothermic method is characterized by comprising the following steps:
step one, putting the slowly cooled magnesium-magnesium slag smelted by the silicothermic process into a ball mill for grinding, and then sieving to obtain undersize products, namely magnesium slag powder;
step two, putting the magnesium slag powder obtained in the step one into a granulator, and spraying water to the magnesium slag powder for rotary granulation to obtain magnesium slag ceramsite; the water content of the magnesium slag ceramsite is 16% -20%;
step three, performing accelerated hydration pre-curing on the magnesium slag ceramsite obtained in the step two to obtain pre-cured magnesium slag ceramsite;
step four, putting the pre-cured magnesium slag ceramsite obtained in the step three into a closed container into which hot flue gas is introduced for carbonization to obtain magnesium carbide slag ceramsite, and taking out the magnesium carbide slag ceramsite and naturally cooling to obtain magnesium carbide slag lightweight aggregate; the hot flue gas contains carbon dioxide with volume concentration of more than 20%.
According to the invention, the magnesium slag smelted by the silicothermic process after slow cooling is taken as a raw material, the raw material is ground and sieved to obtain magnesium slag powder, then water is sprayed and the magnesium slag powder is granulated in a rotating manner to obtain magnesium slag ceramsite, the magnesium slag powder is contacted with water and then begins a hydration reaction, and by controlling the water content of the magnesium slag ceramsite, on the premise of ensuring the formation of the magnesium slag ceramsite, the pores in the magnesium slag ceramsite are increased, the porosity is increased, a diffusion path is provided for the entry of carbon dioxide in the subsequent carbonization process, the carbonization degree is improved, the strength of the magnesium carbide slag light aggregate is further improved, and the density of the magnesium carbide slag light aggregate is reduced; then, performing pre-curing on the magnesium slag ceramsite, namely, continuously performing hydration reaction on the magnesium slag ceramsite, so that a large number of small holes are formed in the magnesium slag ceramsite, the density of the magnesium carbide slag lightweight aggregate is further reduced, and the large number of small holes are beneficial to improving the diffusion efficiency of carbon dioxide gas in the subsequent carbonization process, shortening the carbonization time, realizing uniform carbonization, improving the carbonization degree, greatly increasing the strength of the magnesium carbide slag lightweight aggregate, and obtaining the high-strength and light-weight magnesium carbide slag lightweight aggregate; meanwhile, the magnesium slag smelted by the silicothermic method is firstly molded into magnesium slag ceramsite, and then pre-cured and carbonized, so that the stability of the magnesium slag lightweight aggregate is improved, and the application range of the magnesium slag lightweight aggregate as a building product is expanded.
The method for preparing the lightweight aggregate by using the magnesium slag smelted by the silicothermic process is characterized in that a 100-mesh screen is adopted for sieving in the first step. The optimized screen mesh aperture effectively removes impurities in the magnesium slag from the silicothermic process, improves the screening efficiency, increases the content of magnesium oxide in the magnesium slag powder, and is beneficial to improving the strength of the lightweight aggregate of the magnesium carbide slag.
The method for preparing the lightweight aggregate by using the magnesium slag smelted by the silicothermic process is characterized in that the slow cooling in the step one is natural cooling.
The method for preparing the lightweight aggregate from the magnesium slag smelted by the silicothermic method is characterized in that the rotating speed of the rotary granulation in the step two is 18-22 r/min. The optimized rotating speed is beneficial to the rotation granulation of the magnesium slag powder to obtain the magnesium slag ceramsite.
The method for preparing the lightweight aggregate by smelting the magnesium slag through the silicothermic process is characterized in that the particle size of the magnesium slag ceramsite in the second step is 2cm. The magnesium slag ceramsite with the particle size can be completely carbonized within about 30min, so that the carbonization speed is increased; when the particle size of the magnesium slag ceramsite exceeds 2cm, repeated carbonization is usually needed to ensure the carbonization degree.
The method for preparing the lightweight aggregate by smelting the magnesium-magnesium slag through the silicothermic process is characterized in that the temperature of the pre-curing in the third step is 20-26 ℃, the humidity is 50-90%, and the time is 3-28 days. The pre-curing condition is easy to realize, can be achieved in a conventional construction site or a conventional factory, does not need heating equipment and humidifying equipment to adjust the pre-curing condition, and improves the practicability of the method.
The method for preparing the light aggregate from the magnesium-magnesium slag smelted by the silicothermic method is characterized in that the precasting in the third step is carried out at the temperature of 30-100 ℃, the humidity is 50-90% and the time is within 3 d. The temperature of the pre-curing condition is higher, the hydration speed of the magnesium slag ceramsite is accelerated, and the pre-curing time is reduced to be within 3 d.
The method for preparing the light aggregate from the magnesium-magnesium slag smelted by the silicothermic method is characterized in that in the fourth step, the hot flue gas contains carbon dioxide, the volume concentration of the carbon dioxide is 20-25%, the carbonization temperature is 130-150 ℃, the pressure is 0.25MPa, and the time is 30min. The carbonization degree of the magnesium carbide slag light aggregate is the highest at the optimal carbonization temperature, and is matched with the temperature range of the high-temperature industrial waste gas, so that the high-temperature industrial waste gas is directly adopted for carbonization, and the full utilization of resources is realized.
The method for preparing the lightweight aggregate by smelting the magnesium-magnesium slag through the silicothermic process is characterized in that the magnesium carbide slag ceramsite obtained in the fourth step is sequentially circulated and repeated with the pre-curing process in the third step and the carbonizing process in the fourth step, and then is taken out and naturally cooled. Usually, the magnesium carbide slag ceramsite is taken out and subjected to a color development experiment by adopting phenolphthalein, if the magnesium carbide slag ceramsite is not completely carbonized or is not uniformly carbonized after the phenolphthalein is developed, the pre-curing process and the carbonization process are continuously and circularly repeated until the magnesium carbide slag ceramsite is completely carbonized, and the high-strength magnesium carbide light aggregate is ensured to be obtained.
Compared with the prior art, the invention has the following advantages:
1. the magnesium slag ceramsite is prepared by taking the magnesium slag smelted by the silicothermic process after slow cooling as a raw material, and then the magnesium slag ceramsite is pre-cured and carbonized in sequence, so that a large number of small holes are generated inside the magnesium slag ceramsite, the density of the magnesium carbide slag lightweight aggregate is reduced, the diffusion efficiency of carbon dioxide gas is improved, the carbonization time is shortened, uniform carbonization is realized, the carbonization degree is improved, the strength of the magnesium carbide slag lightweight aggregate is greatly increased, the high-strength light magnesium carbide slag lightweight aggregate is obtained, and the application range of the magnesium carbide slag lightweight aggregate as a building product is expanded.
2. The invention adopts the slow-cooling magnesium slag smelted by the silicothermic process as the raw material, does not need to carry out quenching treatment of watering and air cooling after heating the magnesium slag smelted by the silicothermic process, reduces the pretreatment process steps of the magnesium slag, saves water resources and energy resources, simplifies the production process, greatly improves the production efficiency and reduces the production cost.
3. The invention reduces the water content of the magnesium carbide slag lightweight aggregate by controlling the water content of the magnesium slag ceramsite and combining the modes of hydration precaution and carbonization by adding water, forms a large number of pores, solves the problems of less pores and high density in the magnesium carbide slag aggregate, and the prepared magnesium carbide slag lightweight aggregate is close to GB17431 lightweight aggregate and GB17431For 1000g/m in test methods 3 The density requirement of the lightweight aggregate.
4. The invention increases the diffusion efficiency of carbon dioxide gas by increasing the carbonization temperature, realizes uniform carbonization under lower concentration of carbon dioxide gas, greatly increases the strength of the magnesium carbide slag lightweight aggregate, and meets the requirement of 1000g/m in GB17431 lightweight aggregate and test method thereof 3 The strength of the light aggregate is required, and the high-strength light magnesium carbide slag light aggregate is prepared under the carbon dioxide content of the hot flue gas of the existing factory, so that the energy waste caused by the temperature reduction of industrial waste gas (100-200 ℃) in the prior art is overcome.
5. The method increases the diffusion efficiency of carbon dioxide gas by increasing the carbonization temperature, effectively shortens the carbonization time, does not need to carry out steam pressing subsequently, further shortens the preparation time of the magnesium carbide slag light aggregate, improves the preparation efficiency, reduces the condition requirement, and is beneficial to the wide application of the magnesium carbide slag light aggregate.
The technical solution of the present invention is further described in detail by the accompanying drawings and examples.
Drawings
FIG. 1 is a cross-sectional phenolphthalein color development test result chart of the magnesium carbide slag lightweight aggregate obtained in example 1 of the present invention.
FIG. 2 is a cross-sectional phenolphthalein color development test result chart of the magnesium carbide slag lightweight aggregate obtained in example 2 of the present invention.
FIG. 3 is a cross-sectional phenolphthalein color development test result chart of the magnesium carbide slag lightweight aggregate obtained in example 3 of the present invention.
FIG. 4 is a cross-sectional phenolphthalein color development test result chart of the magnesium carbide slag lightweight aggregate obtained in example 4 of the present invention.
FIG. 5 is a cross-sectional phenolphthalein color development test result chart of the magnesium carbide slag lightweight aggregate obtained in example 5 of the present invention.
FIG. 6 is a cross-sectional phenolphthalein color development test result chart of the magnesium carbide slag lightweight aggregate obtained in example 6 of the present invention.
FIG. 7 is a cross-sectional phenolphthalein color development test result chart of the magnesium carbide slag lightweight aggregate obtained in example 7 of the present invention.
FIG. 8 is a cross-sectional phenolphthalein coloration test result chart of the magnesium carbide slag lightweight aggregate obtained in example 8 of the present invention.
FIG. 9 is a cross-sectional phenolphthalein color development test result chart of the magnesium carbide slag lightweight aggregate obtained in example 9 of the present invention.
FIG. 10 is a cross-sectional phenolphthalein coloration test result chart of the magnesium carbide slag lightweight aggregate obtained in example 10 of the present invention.
FIG. 11 is a cross-sectional phenolphthalein color development test result chart of the magnesium carbide slag lightweight aggregate obtained in example 11 of the present invention.
FIG. 12 is a cross-sectional phenolphthalein color development test result chart of the magnesium carbide slag lightweight aggregate obtained in example 12 of the present invention.
FIG. 13 is a cross-sectional phenolphthalein coloration test result chart of the magnesium carbide slag lightweight aggregate obtained in example 13 of the present invention.
Detailed Description
The magnesium slag produced by silicothermic process in the embodiments 1-13 of the invention are all from magnesium factories in elm areas.
Example 1
The embodiment comprises the following steps:
step one, putting naturally cooled magnesium-magnesium slag smelted by a silicothermic method into a ball mill for grinding, and then sieving by a 100-mesh sieve to obtain undersize products, namely magnesium slag powder;
step two, putting the magnesium slag powder obtained in the step one into a granulator, and spraying water to the magnesium slag powder for rotary granulation to obtain magnesium slag ceramsite; the rotating speed of the rotary granulation is 18 r/min-22 r/min; the particle size of the magnesium slag ceramsite is 2cm, and the water content is 16% -18%;
step three, performing accelerated hydration pre-curing on the magnesium slag ceramsite obtained in the step two to obtain pre-cured magnesium slag ceramsite; the pre-curing temperature is 20-26 ℃, the humidity is 90%, and the time is 3d;
step four, putting the pre-cured magnesium slag ceramsite obtained in the step three into a closed container into which hot flue gas is introduced for carbonization to obtain magnesium carbide slag ceramsite, and taking out and naturally cooling to obtain magnesium carbide slag lightweight aggregate; the hot flue gas contains carbon dioxide, the volume concentration of the carbon dioxide is 100%, the carbonization temperature is 130-150 ℃, the pressure is 0.25MPa, and the time is 30min.
Example 2
The present embodiment is different from embodiment 1 in that: the pre-curing time is 7d.
Example 3
The present embodiment is different from embodiment 1 in that: the pre-curing time is 28d.
Example 4
The present embodiment is different from embodiment 1 in that: the water content of the magnesium slag ceramsite is 18% -20%.
Example 5
This embodiment is different from embodiment 4 in that: the pre-curing time is 7d.
Example 6
This embodiment is different from embodiment 4 in that: the pre-curing time is 28d.
Example 7
The present embodiment is different from embodiment 2 in that: the humidity of the pre-curing is 50%.
Example 8
The present embodiment is different from embodiment 2 in that: the pre-curing humidity is 70%.
Example 9
The present embodiment is different from embodiment 2 in that: the volume concentration of carbon dioxide in the hot flue gas is 50%.
Example 10
The present embodiment is different from embodiment 2 in that: and the volume concentration of carbon dioxide in the hot flue gas is 20%, the magnesium carbide slag ceramsite obtained in the fourth step is sequentially and circularly repeated for 2 times of the pre-curing process in the third step and the carbonizing process in the fourth step, and then the magnesium carbide slag ceramsite is taken out and naturally cooled.
Example 11
The present embodiment is different from embodiment 1 in that: the temperature of the pre-curing in the third step is 30 ℃, and the time is 2d.
Example 12
The present embodiment is different from embodiment 1 in that: in the third step, the temperature of the pre-curing is 100 ℃, and the time is 2d.
Example 13
The present embodiment is different from embodiment 1 in that: the temperature of the pre-curing in the third step is 65 ℃, and the time is 2d.
Samples of the magnesium carbide slag lightweight aggregate obtained in the embodiments 1 to 13 of the invention are respectively prepared to carry out a section phenolphthalein color development experiment, the carbonization degree is examined by utilizing the characteristic that phenolphthalein reagent is red when being mixed with alkali, and the results are shown in figures 1 to 13.
FIGS. 1 to 13 are graphs showing the results of phenolphthalein color development experiments on cross sections of the magnesium carbide slag lightweight aggregates obtained in examples 1 to 13 of the present invention, and none of the magnesium carbide slag lightweight aggregates obtained in examples 1 to 13 of the present invention has an obvious color development phenomenon, which indicates that the magnesium carbide slag lightweight aggregate prepared by the method of the present invention has complete and uniform carbonation; it can be seen from fig. 1 to 3 and fig. 4 to 6 that, under the condition of the water content of the present invention, the magnesium slag ceramsite can be completely carbonized, and meanwhile, under the condition of the same water content, the shorter the pre-curing time is, the more the magnesium slag ceramsite is easily carbonized uniformly, which indicates that the short pre-curing time causes more macropores generated in the magnesium slag ceramsite, so that carbon dioxide is more easily diffused into the magnesium slag ceramsite during the carbonization process to realize uniform carbonization.
The results of examining the bulk density and the barrel pressure strength of the magnesium carbide slag lightweight aggregates obtained in examples 1 to 13 of the present invention are shown in table 1.
TABLE 1
Figure BDA0003348617170000081
Figure BDA0003348617170000091
As can be seen from Table 1, examples 1 and 4, examples 2 and 5, and examples 3 and 6 were divided intoIt can be seen that, under the same pre-curing time, the increase of the water content of the magnesium slag ceramsite reduces the bulk density and the barrel pressure strength of the magnesium carbide slag lightweight aggregate, which indicates that the higher the water content of the magnesium slag ceramsite is, the more complete the hydration reaction in the magnesium slag ceramsite is, and the more free water in the pores of the magnesium slag ceramsite is, the lower the diffusion efficiency of carbon dioxide in the carbonization process is caused, and the carbonization degree is influenced, so that the bulk density and the barrel pressure strength of the magnesium carbide slag lightweight aggregate are reduced; comparing examples 1 to 3 and 4 to 6, respectively, it can be seen that the bulk density and the barrel pressure strength of the magnesium carbide slag lightweight aggregate are higher than those of 1000g/m in GB17431 lightweight aggregate and test method thereof 3 The cylinder pressure strength requirement (1.5 MPa) of the light aggregate indicates that the hydration degree of the magnesium slag ceramsite is increased along with the increase of the pre-curing time, and the densities of calcium hydroxide and hydrated calcium silicate generated in the hydration process are higher than those of calcium oxide and dicalcium silicate, so that the density of the magnesium slag ceramsite is increased, most of the hydrated calcium silicate is reserved after the subsequent carbonization, the calcium hydroxide is converted into calcium carbonate with higher density and volume, and the pores generated in the magnesium slag ceramsite are further reduced, so that the stacking density of the carbonized magnesium slag light aggregate is increased, and the increase of the stacking density causes the increase of the strength.
Comparing example 2 with examples 7 to 8, it can be seen that under the condition of other conditions being unchanged, the proper reduction of the pre-curing humidity can reduce the bulk density and the barrel pressure strength of the magnesium carbide slag lightweight aggregate, which also shows that the hydration reaction completion degree in the magnesium slag ceramsite is reduced, and calcium hydroxide and calcium silicate hydrate with strength are reduced, so that the bulk density and the barrel pressure strength of the magnesium carbide slag lightweight aggregate are reduced.
Comparing example 2 with example 9, it can be seen that, under the condition of keeping other conditions unchanged, the concentration of carbon dioxide in the carbonization step is adjusted downwards, so that the shortage of the reactant carbon dioxide is caused, and the carbonization degree is influenced, thereby reducing the bulk density and the cylinder pressure strength of the magnesium slag lightweight aggregate; comparing example 2 with example 10, it can be seen that the carbon dioxide concentration in the carbonization step is adjusted downward under the condition that other conditions are not changed, but the carbonization step is repeated, and the carbon dioxide concentration in the carbonization step is supplemented to a certain extent, so that the magnesium slag raw material which is not subjected to carbonization reaction is further carbonized, and further the bulk density and the cylinder pressure strength of the magnesium carbide slag lightweight aggregate are improved.
Comparing example 1 with examples 11 to 13, it is understood that the pre-curing time is shortened and the pre-curing temperature is increased under the condition that other conditions are not changed, so that the progress of the hydration reaction is promoted to a certain extent, the effect of long-time normal temperature curing is achieved, and the stacking density and the cylinder pressure strength of the magnesium slag light aggregate are improved.
In conclusion, the method adjusts the bulk density and the cylinder pressure strength of the magnesium carbide slag lightweight aggregate by adjusting the water content in the magnesium slag ceramsite and the pre-curing time of the magnesium slag ceramsite, thereby obtaining the magnesium carbide slag lightweight aggregate meeting the use requirement.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any simple modification, change and equivalent changes of the above embodiments according to the technical essence of the invention are still within the protection scope of the technical solution of the invention.

Claims (7)

1. A method for preparing lightweight aggregate from magnesium slag smelted by a silicothermic method is characterized by comprising the following steps:
step one, putting the slowly cooled magnesium-magnesium slag smelted by the silicothermic process into a ball mill for grinding, and then sieving to obtain undersize products, namely magnesium slag powder; the slow cooling is natural cooling;
step two, putting the magnesium slag powder obtained in the step one into a granulator, and spraying water to the magnesium slag powder for rotary granulation to obtain magnesium slag ceramsite; the water content of the magnesium slag ceramsite is 16% -20%;
step three, performing accelerated hydration pre-curing on the magnesium slag ceramsite obtained in the step two to obtain pre-cured magnesium slag ceramsite;
step four, putting the pre-cured magnesium slag ceramsite obtained in the step three into a closed container into which hot flue gas is introduced for carbonization to obtain magnesium carbide slag ceramsite, and taking out and naturally cooling to obtain magnesium carbide slag lightweight aggregate; the hot flue gas contains carbon dioxide, the volume concentration of the carbon dioxide is 20-25%, the carbonization temperature is 130-150 ℃, the pressure is 0.25MPa, and the time is 30min.
2. The method for preparing lightweight aggregate from the silicothermic magnesium-smelting slag according to claim 1, wherein the screening in the first step is performed by using a 100-mesh screen.
3. The method for preparing the lightweight aggregate from the silicothermic magnesium-smelting slag according to claim 1, wherein the rotation speed of the rotary granulation in the second step is 18 r/min-22 r/min.
4. The method for preparing the lightweight aggregate from the magnesium slag obtained by silicothermic process according to claim 1, wherein the particle size of the magnesium slag ceramsite in the second step is 2cm.
5. The method for preparing the lightweight aggregate from the magnesium-magnesium slag smelted by the silicothermic method according to claim 1, wherein the temperature of the pre-curing in the third step is 20-26 ℃, the humidity is 50-90%, and the time is 3-28d.
6. The method for preparing the lightweight aggregate from the magnesium slag obtained by silicothermic magnesium smelting according to claim 1, wherein the pre-curing in the third step is carried out at a temperature of 30-100 ℃, at a humidity of 50-90% and for a time within 3 d.
7. The method for preparing the lightweight aggregate from the magnesium slag smelted by the silicothermic method according to claim 1, wherein the magnesium carbide slag ceramsite obtained in the fourth step is sequentially and cyclically repeated with the pre-curing process in the third step and the carbonizing process in the fourth step, and then is taken out and naturally cooled.
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