All-solid waste light phosphogypsum artificial aggregate and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and particularly relates to an all-solid waste light phosphogypsum artificial aggregate and a preparation method thereof. The preparation method of the all-solid waste light phosphogypsum artificial aggregate comprises the following steps: (1) mixing, grinding and heating phosphogypsum and blast furnace slag to obtain a mixture; (2) uniformly mixing the mixture with rice hull ash, slaked lime and biochar to obtain a dry mixture; (3) adding water glass and water into the dry mixture, mixing to obtain a slurry material, then adding foam, and stirring to obtain a light slurry material; (4) granulating and curing the light-weight slurry, and then naturally airing to obtain aggregate particles; and (5) spraying an organic silicon water repellent on the surfaces of the aggregate particles treated in the step (4), and naturally placing to obtain the all-solid waste light phosphogypsum artificial aggregate. The all-solid waste light phosphogypsum artificial aggregate disclosed by the invention has the advantages of low density and low water absorption rate.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to an all-solid waste lightweight phosphogypsum artificial aggregate and a preparation method thereof. Background Art

[0002] Phosphogypsum is the main solid waste produced by the wet process of industrial phosphoric acid production. Its main chemical component is calcium sulfate dihydrate, and it contains a small amount of impurities such as phosphoric acid, calcium phosphate, fluoride, and heavy metals. It appears as a white or dark gray wet fine powder. my country is a populous country and a large agricultural country. Phosphate fertilizer production is extremely important for agricultural development. Therefore, the output of phosphoric acid has remained high for many years. According to statistics, 90% of phosphoric acid in the country is produced by wet process. Every ton of phosphoric acid produced will produce 4.5 to 5 tons of phosphogypsum, and the annual output of phosphogypsum is about 80 million tons. In recent years, with the advancement of science and technology and the increase in ecological and environmental protection efforts, the comprehensive utilization rate of phosphogypsum in my country has reached more than 50%, but it still faces huge challenges of concentrated production, large-scale storage and complex and difficult use.

[0003] At present, my country's phosphogypsum is mainly used as a resource in agriculture, industry and construction. Due to the huge scale of construction in my country, the strong demand for building materials in the market, and the current situation of insufficient supply of natural building materials, phosphogypsum has attracted widespread attention for the production of building materials and has great development potential. The application of phosphogypsum in the field of building materials mainly includes: replacing natural gypsum as a cement setting agent, producing gypsum building materials (such as gypsum powder, gypsum board, gypsum block, unburned bricks, sound-absorbing panels, etc.), preparing self-leveling mortar, producing high-strength gypsum, preparing artificial aggregates, etc. Since the amount of aggregate used in concrete is the largest, replacing natural aggregates with phosphogypsum artificial aggregates can not only significantly improve the utilization rate of phosphogypsum, but also solve the problem of shortage of natural sand and gravel aggregates in local areas. The conventional method of making phosphogypsum artificial aggregates is to mix phosphogypsum with cement, slag and other cementitious materials evenly into a slurry, and then prepare it into approximately spherical particles, which can be solidified and hardened through different curing systems. This type of preparation technology generally has shortcomings such as low utilization rate of phosphogypsum, high density of artificial aggregate, and poor water resistance of aggregate.

[0004] Therefore, it is necessary to provide an improved technical solution to address the above-mentioned deficiencies in the prior art. Summary of the invention

[0005] The object of the present invention is to provide a fully solid waste lightweight phosphogypsum artificial aggregate and a preparation method thereof, so as to help solve or improve the problem of high density or poor water resistance of the phosphogypsum aggregate in the prior art.

[0006] In order to achieve the above-mentioned object, the present invention provides the following technical scheme: a method for preparing all-solid waste lightweight phosphogypsum artificial aggregate, comprising the following steps: (1) mixing phosphogypsum and blast furnace slag, grinding and heating to obtain a mixture; (2) uniformly mixing the mixture with rice husk ash, slaked lime and biochar to obtain a dry mixture; (3) adding water glass and water to the dry mixture to obtain a slurry-like material, then adding foam and stirring to obtain a lightweight slurry; (4) granulating the lightweight slurry, curing it, and then naturally drying it to obtain aggregate particles; (5) spraying an organosilicon water repellent agent on the surface of the aggregate particles obtained by the treatment of step (4), and leaving it to stand naturally to obtain the all-solid waste lightweight phosphogypsum artificial aggregate.

[0007] Preferably, in the mixture, the mass percentage of phosphogypsum is 60%-80%, and the mass percentage of slag is 20%-40%; in step (1), the mixed grinding is carried out under heating conditions, and the heating temperature is 110-120°C; the particle size of the mixture is: the residue on a 0.08 mm square hole sieve is less than 10%.

[0008] Preferably, in step (2), the mass ratio of the mixture, rice husk ash, slaked lime and biochar is 100:(10-20):(0.5-1.0):(5-10).

[0009] Preferably, in step (3), the mass of the water glass is 3%-6% of the mass of the blast furnace slag in the dry mix; and the mass of the foam is 1%-3% of the total mass of the phosphogypsum and blast furnace slag.

[0010] Preferably, in step (4), the curing temperature is 20-40° C., the relative humidity is ≥90%, and the curing time is ≥14 days; and the natural drying time is 1-2 days.

[0011] Preferably, in step (5), the spraying amount of the organic water repellent is 0.3-0.5 kg / m 2 The temperature of the natural placement is 20-30°C, and the natural placement time is more than 3 days.

[0012] Preferably, the particle size of the phosphogypsum is ≤50 μm, the moisture content is ≤1.0%, and the sulfur trioxide content is ≥40%; the main components of the blast furnace slag are silicates and aluminosilicates, the average particle size is ≤20 mm, the moisture content is ≤1%, and the ratio of alkaline oxides to acidic oxides is >1.0.

[0013] Preferably, the rice husk ash is a fine powder obtained by burning rice husk, an agricultural waste, with an active silicon dioxide content of ≥80% and a specific surface area of ​​≥5000m 2 / kg; the slaked lime is first-class building slaked lime, with a CaO+MgO content of ≥70%, qualified volume stability, and a particle size that meets the requirement that the sieve residue on a sieve with an aperture of 0.125mm is ≤10%; the particle size of the biochar is 1-2mm.

[0014] Preferably, the modulus of the water glass is 1.6-1.8, and the solid content is ≥35%; the foam is obtained by frothing a mixed solution of a foaming agent and water, and the density of the foam is 50-60 kg / m 3 .

[0015] The present invention also provides an all-solid waste lightweight phosphogypsum artificial aggregate, which adopts the following technical scheme: an all-solid waste lightweight phosphogypsum artificial aggregate, wherein the all-solid waste lightweight phosphogypsum artificial aggregate is prepared by the method as described above.

[0016] Beneficial effects:

[0017] In the preparation method of all-solid waste lightweight phosphogypsum artificial aggregate of the present invention, by mixing and grinding phosphogypsum and blast furnace slag, and heating during the grinding process, part of the dihydrate gypsum in the phosphogypsum is dehydrated to generate hemihydrate gypsum, thereby having hydration reaction activity; at the same time, the phosphogypsum and blast furnace slag are mixed evenly, which is convenient for stimulating the hydration activity of the slag after subsequent water addition, thereby generating a matrix with higher strength; the mixture of phosphogypsum and blast furnace slag is used as the main strength source of the aggregate, and rice husk ash has high volcanic ash activity and will react with calcium-containing substances to generate hydrated calcium silicate gel to improve strength; at the same time, the rice husk ash will absorb Solidify the trace heavy metal elements in phosphogypsum; the role of slaked lime is to neutralize the small amount of acidic substances in phosphogypsum and provide the calcium-containing substances required for the volcanic ash reaction; the main role of biochar is to absorb harmful elements in the mixture and absorb moisture to provide internal curing effect, and the porous and lightweight characteristics of biochar will significantly reduce the density of the material; the main role of water glass is to stimulate blast furnace slag to produce strength; the main role of water is to mix the materials evenly and provide a medium for the hydration reaction of the ground phosphogypsum and the reaction between blast furnace slag and water glass; the main role of foam is to reduce the density of the material and provide basic conditions for the preparation of lightweight artificial aggregate. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0019] The present invention will be described in detail below in conjunction with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0020] Aiming at the problem that the existing phosphogypsum aggregate has high density or poor water resistance, the present invention provides a method for preparing a fully solid waste lightweight phosphogypsum artificial aggregate.

[0021] The method for preparing the all-solid waste lightweight phosphogypsum artificial aggregate of the embodiment of the present invention comprises the following steps: (1) mixing phosphogypsum and blast furnace slag, grinding and heating to obtain a mixture; (2) uniformly mixing the mixture with rice husk ash, slaked lime and biochar to obtain a dry mixture; (3) adding water glass and water to the dry mixture to obtain a slurry-like material, then adding foam and stirring to obtain a lightweight slurry; (4) granulating the lightweight slurry, curing it, and then naturally drying it to obtain aggregate particles; (5) spraying an organosilicon water repellent agent on the surface of the aggregate particles obtained by the treatment of step (4), and leaving it to stand naturally to obtain the all-solid waste lightweight phosphogypsum artificial aggregate.

[0022] In the preparation method of all-solid waste lightweight phosphogypsum artificial aggregate of the present invention, by mixing and grinding phosphogypsum and blast furnace slag, and heating during the grinding process, part of the dihydrate gypsum in the phosphogypsum is dehydrated to generate hemihydrate gypsum, thereby having hydration reaction activity; at the same time, the phosphogypsum and blast furnace slag are mixed evenly, which is convenient for stimulating the hydration activity of the slag after subsequent water addition, thereby generating a matrix with higher strength; the mixture of phosphogypsum and blast furnace slag is used as the main strength source of the aggregate, and rice husk ash has high volcanic ash activity and will react with calcium-containing substances to generate hydrated calcium silicate gel to improve strength; at the same time, the rice husk ash will absorb Solidify the trace heavy metal elements in phosphogypsum; the role of slaked lime is to neutralize the small amount of acidic substances in phosphogypsum and provide the calcium-containing substances required for the volcanic ash reaction; the main role of biochar is to absorb harmful elements in the mixture and absorb moisture to provide internal curing effect, and the porous and lightweight characteristics of biochar will significantly reduce the density of the material; the main role of water glass is to stimulate blast furnace slag to produce strength; the main role of water is to mix the materials evenly and provide a medium for the hydration reaction of the ground phosphogypsum and the reaction between blast furnace slag and water glass; the main role of foam is to reduce the density of the material and provide basic conditions for the preparation of lightweight artificial aggregate.

[0023] In a preferred embodiment of the method for preparing all-solid waste lightweight phosphogypsum artificial aggregate of the present invention, in the mixture, the mass percentage of phosphogypsum is 60%-80% (for example, 60%, 65%, 70%, 75% or 80%), and the mass percentage of slag is 20%-40% (for example, 20%, 25%, 30%, 35% or 40%); in step (1), the mixed grinding is carried out under heating conditions, and the heating temperature is 110-120°C (for example, 110°C, 112°C, 114°C, 116°C, 118°C or 120°C); the particle size of the mixture is: the residue on the 0.08 mm square hole sieve is less than 10%.

[0024] In a preferred embodiment of the method for preparing all-solid waste lightweight phosphogypsum artificial aggregate of the present invention, in step (2), the mass ratio of the mixture, rice husk ash, slaked lime and biochar is 100:(10-20):(0.5-1.0):(5-10) (for example, 100:10:0.5:5, 100:20:1.0:10, 100:15:0.75:7.5, 100:10:1:10, 100:20:0.5:10, 100:15:0.5:10, 100:15:1:5, 100:20:1:5, 100:10:1:5, 100:15:0.75:5, 100:15:0.75:10 or 100:18:0.8:9, etc.).

[0025] In a preferred embodiment of the method for preparing all-solid waste lightweight phosphogypsum artificial aggregate of the present invention, in step (3), the mass of water glass is 3%-6% (for example, 3%, 4%, 5% or 6%) of the mass of blast furnace slag in the dry mix; the mass of foam is 1%-3% (for example, 1%, 2% or 3%) of the total mass of phosphogypsum and blast furnace slag.

[0026] In a preferred embodiment of the method for preparing all-solid waste lightweight phosphogypsum artificial aggregate of the present invention, in step (4), the curing temperature is 20-40°C (for example, 20°C, 25°C, 30°C, 35°C or 40°C), the curing relative humidity is ≥90%, and the curing time is ≥14 days; the natural drying time is 1-2 days.

[0027] Preferably, the granulation in step (4) can be carried out in a disc spheronizer to prepare nearly spherical particles of different sizes, or professional extrusion equipment can be used to make cylindrical particles of different sizes.

[0028] In a preferred embodiment of the method for preparing all-solid waste lightweight phosphogypsum artificial aggregate of the present invention, in step (5), the spraying amount of the organic water repellent is 0.3-0.5 kg / m 2 (For example, 0.3 kg / m 2 , 0.35kg / m 2 , 0.4kg / m 2 , 0.45kg / m 2 or 0.5kg / m 2 ); the natural placement temperature is 20-30°C (for example, 20°C, 22°C, 24°C, 26°C, 28°C or 30°C), and the natural placement time is more than 3 days.

[0029] In a preferred embodiment of the method for preparing all-solid waste lightweight phosphogypsum artificial aggregate of the present invention, the particle size of the phosphogypsum is ≤50 μm, the moisture content is ≤1.0%, and the sulfur trioxide content is ≥40%; the main components of the blast furnace slag are silicate and aluminosilicate, the average particle size is ≤20 mm, the moisture content is ≤1%, and the alkaline oxide (i.e., CaO+MgO ) to acidic oxide ratio>1.0.

[0030] In a preferred embodiment of the method for preparing all-solid waste lightweight phosphogypsum artificial aggregate of the present invention, rice husk ash is a fine powder obtained by burning rice husk, an agricultural waste, with an active silicon dioxide content of ≥80% and a specific surface area of ​​≥5000m 2 / kg; the slaked lime is the first-class building slaked lime, with CaO+MgO content ≥70%, qualified volume stability, and particle size that meets the requirement that the sieve residue on the sieve with an aperture of 0.125mm is ≤10%; the particle size of biochar is 1-2mm.

[0031] In a preferred embodiment of the method for preparing all-solid waste lightweight phosphogypsum artificial aggregate of the present invention, the modulus of water glass is 1.6-1.8 (for example, 1.6, 1.7 or 1.8), and the solid content is ≥35%; the foam is obtained by frothing a mixed solution of a foaming agent and water, and the density of the foam is 50-60 kg / m 3 (For example, 50kg / m 2 , 53kg / m 2 , 55kg / m 2 , 58kg / m 2 or 60kg / m 2 ).

[0032] The present invention also provides an all-solid waste lightweight phosphogypsum artificial aggregate. The all-solid waste lightweight phosphogypsum artificial aggregate in the embodiment of the present invention is prepared by the method described above.

[0033] The all-solid waste lightweight phosphogypsum artificial aggregate and the preparation method thereof of the present invention are described in detail below through specific embodiments.

[0034] In the following examples: phosphogypsum is a powdered solid waste produced by a phosphorus chemical enterprise after producing phosphoric acid by a wet process, with a particle diameter of less than 50 μm, a moisture content of less than 1.0%, and a sulfur trioxide content of more than 40%;

[0035] Blast furnace slag is a product of the iron ore smelting process. Iron oxide is reduced to metallic iron at high temperature. Impurities such as silicon oxide and aluminum oxide in the iron ore react with lime and other substances to form a molten material with silicate and aluminosilicate as the main components. After quenching, it becomes a loose and porous granular material. The average particle size of the blast furnace slag used is less than 20 mm, the moisture content is less than 1%, and the ratio of basic oxides (CaO+MgO) to acidic oxides is greater than 1.0.

[0036] Rice husk ash is a fine powder obtained by high-temperature combustion of rice husk, an agricultural waste. It contains more than 80% active silicon dioxide and has a specific surface area of ​​5000m 2 / kg or more;

[0037] Hydrated lime is a first-class building slaked lime powder supplied in the building materials market, requiring the CaO+MgO content to be no less than 70%, the volume stability to be qualified, and the particle size to meet the requirement that the residue on the 0.125mm sieve is no more than 10%;

[0038] Water glass is a common liquid water glass product on the market, with a modulus of 1.6-1.8 and a solid content of more than 35%;

[0039] Biochar is a porous solid material obtained by high-temperature anaerobic pyrolysis of biomass materials such as rice husks, reed stalks, and bamboo at 500-600°C, with a particle size of 1-2 mm.

[0040] The foam is made by diluting the commercially available foaming agent with water into a uniform solution, and then produced by special foaming equipment. The density is controlled at 50-60kg / m 3 , the foam is rich in bubbles with a diameter of less than 1mm;

[0041] Silicone is a commercially available organosilane hydrophobic material that appears as a transparent liquid;

[0042] The water is ordinary tap water.

[0043] Example 1

[0044] The method for preparing the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment comprises the following steps:

[0045] (1) 60 parts of phosphogypsum and 40 parts of blast furnace slag are placed in a ball mill for mechanical mixing, crushing and grinding for 40-60 minutes, until the mixed fine powder reaches less than 10% of the residue on a 0.08 mm square hole sieve. During the mixing and grinding process, the temperature of the mixture can be raised to 110° C. by heating. Through mixing and grinding, part of the dihydrate gypsum in the phosphogypsum is dehydrated to form hemihydrate gypsum, which has hydration reaction activity; at the same time, the phosphogypsum and blast furnace slag powders are evenly mixed, which is convenient for stimulating the hydration activity of the slag after subsequent water addition, thereby producing a higher strength matrix.

[0046] (2) The fine powder obtained by mixing and grinding, rice husk ash, slaked lime, and biochar were weighed and mixed in a mass ratio of 100:20:0.5:5 to obtain a dry mix for preparing artificial aggregate.

[0047] (3) Add appropriate amounts of water glass and water to the above dry mix, with the amount of water glass being 1.2 parts (the mass of water glass added being 3% of the mass of slag in the dry mix) and the amount of water being 15 parts (the mass ratio of the amount of water added to the dry mix being 0.15); mix the above materials in a forced concrete mixer for 1-2 minutes to prepare a plastic mud-like material; at the same time, start a professional foaming equipment to prepare and weigh a good quality foam (the amount of foam is 1 part, i.e., 1% of the total mass of phosphogypsum and blast furnace slag), add the foam to the mixer, and stir for 2-3 minutes, so as to prepare a plastic, uniform, and bubble-rich lightweight mud material.

[0048] (4) The prepared lightweight slurry is loaded into a specific disc ball forming machine to prepare nearly spherical particles with a diameter of 10-20 mm, or a professional extrusion device is used to prepare cylindrical particles of different sizes. These particles are placed in an environment of 20°C and 90% relative humidity for natural curing for 14 days to prepare lightweight artificial aggregates with high mechanical strength.

[0049] (5) Dry the cured particles under natural conditions for 1 day to evaporate the free water in the surface pores; spray the organic silicon water repellent on the particle surface with a spray device, stir the particles appropriately during the spraying process to make the entire surface evenly absorbed, and control the spraying amount of the organic silicon water repellent to 0.4 kg per square meter of the particle outer surface. After the spraying is completed, place it naturally under the temperature of 20-30°C for 3 days to obtain the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment with good long-term stability and low water absorption.

[0050] Example 2

[0051] The method for preparing the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment comprises the following steps:

[0052] (1) 70 parts of phosphogypsum and 30 parts of blast furnace slag are placed in a ball mill for mechanical mixing, crushing and grinding for 40-60 minutes, until the mixed fine powder reaches less than 10% of the residue on a 0.08 mm square hole sieve. During the mixing and grinding process, the temperature of the mixture can be raised to 110°C by heating. Through mixing and grinding, part of the dihydrate gypsum in the phosphogypsum is dehydrated to form hemihydrate gypsum, which has hydration reaction activity; at the same time, the phosphogypsum and blast furnace slag powders are evenly mixed, which is convenient for stimulating the hydration activity of the slag after subsequent water addition, thereby producing a higher strength matrix.

[0053] (2) The fine powder obtained by mixed grinding, rice husk ash, slaked lime, and biochar were weighed and mixed uniformly in a mass ratio of 100:15:0.7:10 to obtain a dry mix for preparing artificial aggregate.

[0054] (3) Add appropriate amounts of water glass and water to the above dry mix, with the amount of water glass being 1.2 parts (the mass of water glass added being 3% of the mass of slag in the dry mix) and the amount of water being 15 parts (the mass ratio of the amount of water added to the dry mix being 0.15); mix the above materials in a forced concrete mixer for 1-2 minutes to prepare a plastic mud-like material; at the same time, start a professional foaming equipment to prepare and weigh a good quality foam (the amount of foam is 1 part, i.e., 1% of the total mass of phosphogypsum and blast furnace slag), add the foam to the mixer, and stir for 2-3 minutes, so as to prepare a plastic, uniform, and bubble-rich lightweight mud material.

[0055] (4) The prepared lightweight slurry is loaded into a specific disc ball forming machine to prepare nearly spherical particles with a diameter of 10-20 mm, or a professional extrusion device is used to prepare cylindrical particles of different sizes. These particles are placed in an environment of 20°C and 90% relative humidity for natural curing for 14 days to prepare lightweight artificial aggregates with high mechanical strength.

[0056] (5) Dry the cured particles under natural conditions for 1 day to evaporate the free water in the surface pores; spray the organic silicon water repellent on the particle surface with a spray device, stir the particles appropriately during the spraying process to make the entire surface evenly absorbed, and control the spraying amount of the organic silicon water repellent to 0.4 kg per square meter of the particle outer surface. After the spraying is completed, place it naturally under the temperature of 20-30°C for 3 days to obtain the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment with good long-term stability and low water absorption.

[0057] Example 3

[0058] The method for preparing the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment comprises the following steps:

[0059] (1) 80 parts of phosphogypsum and 20 parts of blast furnace slag are placed in a ball mill for mechanical mixing, crushing and grinding for 40-60 minutes, until the mixed fine powder reaches less than 10% of the residue on a 0.08 mm square hole sieve. During the mixing and grinding process, the temperature of the mixture can be raised to 110° C. by heating. Through mixing and grinding, part of the dihydrate gypsum in the phosphogypsum is dehydrated to form hemihydrate gypsum, which has hydration reaction activity; at the same time, the phosphogypsum and blast furnace slag powders are evenly mixed, which is convenient for stimulating the hydration activity of the slag after subsequent water addition, thereby producing a higher strength matrix.

[0060] (2) The fine powder obtained by mixing and grinding, rice husk ash, slaked lime, and biochar were weighed and mixed uniformly in a mass ratio of 100:10:1.0:5 to obtain a dry mix for preparing artificial aggregate.

[0061] (3) Add appropriate amounts of water glass and water to the above dry mix, with the amount of water glass being 1.2 parts (the mass of water glass added being 3% of the mass of slag in the dry mix) and the amount of water being 15 parts (the mass ratio of the amount of water added to the dry mix being 0.15); mix the above materials in a forced concrete mixer for 1-2 minutes to prepare a plastic mud-like material; at the same time, start a professional foaming equipment to prepare and weigh a good quality foam (the amount of foam is 1 part, i.e., 1% of the total mass of phosphogypsum and blast furnace slag), add the foam to the mixer, and stir for 2-3 minutes, so as to prepare a plastic, uniform, and bubble-rich lightweight mud material.

[0062] (4) The prepared lightweight slurry is loaded into a specific disc ball forming machine to prepare nearly spherical particles with a diameter of 10-20 mm, or a professional extrusion device is used to prepare cylindrical particles of different sizes. These particles are placed in an environment of 20°C and 90% relative humidity for natural curing for 14 days to prepare lightweight artificial aggregates with high mechanical strength.

[0063] (5) Dry the cured particles under natural conditions for 1 day to evaporate the free water in the surface pores; spray the organic silicon water repellent on the particle surface with a spray device, stir the particles appropriately during the spraying process to make the entire surface evenly absorbed, and control the spraying amount of the organic silicon water repellent to 0.4 kg per square meter of the particle outer surface. After the spraying is completed, place it naturally under the temperature of 20-30°C for 3 days to obtain the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment with good long-term stability and low water absorption.

[0064] Example 4

[0065] The method for preparing the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment comprises the following steps:

[0066] (1) 60 parts of phosphogypsum and 40 parts of blast furnace slag are placed in a ball mill for mechanical mixing, crushing and grinding for 40-60 minutes, until the mixed fine powder reaches less than 10% of the residue on a 0.08 mm square hole sieve. During the mixing and grinding process, the temperature of the mixture can be raised to 110° C. by heating. Through mixing and grinding, part of the dihydrate gypsum in the phosphogypsum is dehydrated to form hemihydrate gypsum, which has hydration reaction activity; at the same time, the phosphogypsum and blast furnace slag powders are evenly mixed, which is convenient for stimulating the hydration activity of the slag after subsequent water addition, thereby producing a higher strength matrix.

[0067] (2) The fine powder obtained by mixing and grinding, rice husk ash, slaked lime, and biochar were weighed and mixed in a mass ratio of 100:20:0.5:5 to obtain a dry mix for preparing artificial aggregate.

[0068] (3) Add appropriate amounts of water glass and water to the above dry mix, with the amount of water glass being 1.2 parts (the mass of water glass added being 3% of the mass of slag in the dry mix) and the amount of water being 15 parts (the mass ratio of the amount of water added to the dry mix being 0.15); mix the above materials in a forced concrete mixer for 1-2 minutes to prepare a plastic mud-like material; at the same time, start a professional foaming equipment to prepare and weigh a good quality foam (the amount of foam is 3 parts, i.e., 3% of the total mass of phosphogypsum and blast furnace slag), add the foam to the mixer, and stir for 2-3 minutes, so as to prepare a plastic, uniform, and bubble-rich lightweight mud material.

[0069] (4) The prepared lightweight slurry is loaded into a specific disc ball forming machine to prepare nearly spherical particles with a diameter of 10-20 mm, or a professional extrusion device is used to prepare cylindrical particles of different sizes. These particles are placed in an environment of 20°C and 90% relative humidity for natural curing for 14 days to prepare lightweight artificial aggregates with high mechanical strength.

[0070] (5) Dry the cured particles under natural conditions for 1 day to evaporate the free water in the surface pores; spray the organic silicon water repellent on the particle surface with a spray device, stir the particles appropriately during the spraying process to make the entire surface evenly absorbed, and control the spraying amount of the organic silicon water repellent to 0.4 kg per square meter of the particle outer surface. After the spraying is completed, place it naturally under the temperature of 20-30°C for 3 days to obtain the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment with good long-term stability and low water absorption.

[0071] Example 5

[0072] The method for preparing the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment comprises the following steps:

[0073] (1) 70 parts of phosphogypsum and 30 parts of blast furnace slag are placed in a ball mill for mechanical mixing, crushing and grinding for 40-60 minutes, until the mixed fine powder reaches less than 10% of the residue on a 0.08 mm square hole sieve. During the mixing and grinding process, the temperature of the mixture can be raised to 110°C by heating. Through mixing and grinding, part of the dihydrate gypsum in the phosphogypsum is dehydrated to form hemihydrate gypsum, which has hydration reaction activity; at the same time, the phosphogypsum and blast furnace slag powders are evenly mixed, which is convenient for stimulating the hydration activity of the slag after subsequent water addition, thereby producing a higher strength matrix.

[0074] (2) The fine powder obtained by mixed grinding, rice husk ash, slaked lime, and biochar were weighed and mixed uniformly in a mass ratio of 100:15:0.7:10 to obtain a dry mix for preparing artificial aggregate.

[0075] (3) Add appropriate amounts of water glass and water to the above dry mix, with the amount of water glass being 1.2 parts (the mass of water glass added being 3% of the mass of slag in the dry mix) and the amount of water being 15 parts (the mass ratio of the amount of water added to the dry mix being 0.15); mix the above materials in a forced concrete mixer for 1-2 minutes to prepare a plastic mud-like material; at the same time, start a professional foaming equipment to prepare and weigh a good quality foam (the amount of foam is 3 parts, i.e., 3% of the total mass of phosphogypsum and blast furnace slag), add the foam to the mixer, and stir for 2-3 minutes, so as to prepare a plastic, uniform, and bubble-rich lightweight mud material.

[0076] (4) The prepared lightweight slurry is loaded into a specific disc ball forming machine to prepare nearly spherical particles with a diameter of 10-20 mm, or a professional extrusion device is used to prepare cylindrical particles of different sizes. These particles are placed in an environment of 20°C and 90% relative humidity for natural curing for 14 days to prepare lightweight artificial aggregates with high mechanical strength.

[0077] (5) Dry the cured particles under natural conditions for 1 day to evaporate the free water in the surface pores; spray the organic silicon water repellent on the particle surface with a spray device, stir the particles appropriately during the spraying process to make the entire surface evenly absorbed, and control the spraying amount of the organic silicon water repellent to 0.4 kg per square meter of the particle outer surface. After the spraying is completed, place it naturally under the temperature of 20-30°C for 3 days to obtain the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment with good long-term stability and low water absorption.

[0078] Example 6

[0079] The method for preparing the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment comprises the following steps:

[0080] (1) 80 parts of phosphogypsum and 20 parts of blast furnace slag are placed in a ball mill for mechanical mixing, crushing and grinding for 40-60 minutes, until the mixed fine powder reaches less than 10% of the residue on a 0.08 mm square hole sieve. During the mixing and grinding process, the temperature of the mixture can be raised to 110° C. by heating. Through mixing and grinding, part of the dihydrate gypsum in the phosphogypsum is dehydrated to form hemihydrate gypsum, which has hydration reaction activity; at the same time, the phosphogypsum and blast furnace slag powders are evenly mixed, which is convenient for stimulating the hydration activity of the slag after subsequent water addition, thereby producing a higher strength matrix.

[0081] (2) The fine powder obtained by mixing and grinding, rice husk ash, slaked lime, and biochar were weighed and mixed uniformly in a mass ratio of 100:10:1.0:5 to obtain a dry mix for preparing artificial aggregate.

[0082] (3) Add appropriate amounts of water glass and water to the above dry mix, with the amount of water glass being 1.2 parts (the mass of water glass added being 3% of the mass of slag in the dry mix) and the amount of water being 15 parts (the mass ratio of the amount of water added to the dry mix being 0.15); mix the above materials in a forced concrete mixer for 1-2 minutes to prepare a plastic mud-like material; at the same time, start a professional foaming equipment to prepare and weigh a good quality foam (the amount of foam is 3 parts, i.e., 3% of the total mass of phosphogypsum and blast furnace slag), add the foam to the mixer, and stir for 2-3 minutes, so as to prepare a plastic, uniform, and bubble-rich lightweight mud material.

[0083] (4) The prepared lightweight slurry is loaded into a specific disc ball forming machine to prepare nearly spherical particles with a diameter of 10-20 mm, or a professional extrusion device is used to prepare cylindrical particles of different sizes. These particles are placed in an environment of 20°C and 90% relative humidity for natural curing for 14 days to prepare lightweight artificial aggregates with high mechanical strength.

[0084] (5) Dry the cured particles under natural conditions for 1 day to evaporate the free water in the surface pores; spray the organic silicon water repellent on the particle surface with a spray device, stir the particles appropriately during the spraying process to make the entire surface evenly absorbed, and control the spraying amount of the organic silicon water repellent to 0.4 kg per square meter of the particle outer surface. After the spraying is completed, place it naturally under the temperature of 20-30°C for 3 days to obtain the all-solid waste lightweight phosphogypsum artificial aggregate of this embodiment with good long-term stability and low water absorption.

[0085] Comparative Example 1

[0086] The difference between this comparative example and Example 1 is that slag is not used, and the rest is consistent with Example 1.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 2 is that no foam is used; the rest is consistent with Example 2.

[0089] Comparative Example 3

[0090] The difference between this comparative example and Example 3 is that water glass is not used; the rest is consistent with Example 3.

[0091] Comparative Example 4

[0092] The difference between this comparative example and Example 4 is that no heating means is used during the mechanical mixing, crushing and grinding of phosphogypsum and blast furnace slag; the rest is consistent with Example 4.

[0093] Comparative Example 5

[0094] The difference between this comparative example and Example 5 is that no organic silicon water repellent agent is used for spraying treatment on the particle surface; the rest is consistent with Example 5.

[0095] Experimental example

[0096] The properties of the all-solid waste lightweight phosphogypsum artificial aggregate prepared in Examples 1-6 and the artificial aggregate prepared in the comparative example were tested.

[0097] Test method: The test shall be carried out in accordance with the requirements of the national standard “Light aggregate and its test methods (Part 2): Light aggregate test method” (GB / T 17431.2-2010).

[0098] The test results are shown in Table 1 below:

[0099] Table 1

[0100]

[0101]

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing all-solid waste lightweight phosphogypsum artificial aggregate, characterized in that: The steps include: (1) mixing phosphogypsum and blast furnace slag, grinding and heating to obtain a mixture; (2) uniformly mixing the mixture with rice husk ash, slaked lime and biochar to obtain a dry mix; (3) adding water glass and water to the dry mix to obtain a slurry-like material, and then adding foam and stirring to obtain a light slurry; (4) granulating the lightweight slurry, curing, and then naturally drying to obtain aggregate particles; (5) Spraying an organic silicon water-repellent agent onto the surface of the aggregate particles obtained by the treatment in step (4), and leaving the particles to stand naturally, thereby obtaining the all-solid waste lightweight phosphogypsum artificial aggregate.

2. The method for preparing all-solid waste lightweight phosphogypsum artificial aggregate according to claim 1, characterized in that: In the mixture, the mass percentage of phosphogypsum is 60%-80%, and the mass percentage of slag is 20%-40%; In step (1), the mixing and grinding is carried out under heating conditions, and the heating temperature is 110-120° C.; The particle size of the mixture is: the residue on a 0.08 mm square hole sieve is less than 10%.

3. The method for preparing all-solid waste lightweight phosphogypsum artificial aggregate according to claim 1, characterized in that: In step (2), the mass ratio of the mixture, rice husk ash, slaked lime and biochar is 100:(10-20):(0.5-1.0):(5-10).

4. The method for preparing all-solid waste lightweight phosphogypsum artificial aggregate according to claim 1, characterized in that: In step (3), the mass of the water glass is 3%-6% of the mass of the blast furnace slag in the dry mix; The mass of the foam is 1%-3% of the total mass of the phosphogypsum and blast furnace slag.

5. The method for preparing all-solid waste lightweight phosphogypsum artificial aggregate according to claim 1, characterized in that: In step (4), the curing temperature is 20-40° C., the relative humidity is ≥ 90%, and the curing time is ≥ 14 days; The time of natural drying is 1-2 days.

6. The method for preparing all-solid waste lightweight phosphogypsum artificial aggregate according to claim 1, characterized in that: In step (5), the spraying amount of the organic water repellent is 0.3-0.5 kg / m 2 ; The temperature of the natural placement is 20-30° C., and the time of the natural placement is more than 3 days.

7. The method for preparing all-solid waste lightweight phosphogypsum artificial aggregate according to any one of claims 1 to 6, characterized in that: The particle size of the phosphogypsum is ≤50 μm, the moisture content is ≤1.0%, and the sulfur trioxide content is ≥40%; The main components of the blast furnace slag are silicate and aluminosilicate, the average particle size is ≤20mm, the water content is ≤1%, and the ratio of basic oxide to acidic oxide is greater than 1.

0.

8. The method for preparing all-solid waste lightweight phosphogypsum artificial aggregate according to any one of claims 1 to 6, characterized in that: The rice husk ash is a fine powder obtained by burning rice husk, an agricultural waste, with an active silicon dioxide content of ≥80% and a specific surface area of ​​≥5000m 2 / kg; The slaked lime is first-class building slaked lime, with a CaO+MgO content of ≥70%, qualified volume stability, and a particle size that meets the requirement that the residue on a sieve with an aperture of 0.125 mm is ≤10%; The particle size of the biochar is 1-2 mm.

9. The method for preparing all-solid waste lightweight phosphogypsum artificial aggregate according to any one of claims 1 to 6, characterized in that: The modulus of the water glass is 1.6-1.8, and the solid content is ≥35%; The foam is obtained by frothing a mixed solution of a foaming agent and water, and the density of the foam is 50-60 kg / m 3 .

10. A fully solid waste lightweight phosphogypsum artificial aggregate, characterized in that: The all-solid waste lightweight phosphogypsum artificial aggregate is prepared by the method according to any one of claims 1 to 9.

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