Low-carbon aggregate based on solid waste and preparation method

Abstract

The invention provides a low-carbon aggregate based on solid waste and a preparation method, and belongs to the technical field of solid waste resource utilization, the low-carbon aggregate comprises a solid waste layer, and a stable layer and a pressure bearing layer which sequentially wrap the solid waste layer from inside to outside; the low-carbon aggregate is designed into three layers, and the thickness of each layer is strictly controlled; the innermost layer is a solid waste layer, and waste residues are preliminarily fixed through a small amount of materials with hydration activity; then preparing a stable layer with relatively high compactness by utilizing steel slag, mineral slag, desulfurized gypsum and the like, and firmly wrapping the waste slag, so that harmful elements cannot be leached out; and finally, silica fume and cement are matched with steel slag, mineral slag, desulfurized gypsum and the like to prepare a pressure-bearing layer with relatively high strength, so that the strength is provided for the low-carbon aggregate.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource utilization, and specifically relates to a low-carbon aggregate based on solid waste and a preparation method thereof. Background Art

[0002] Hard-to-use solid wastes such as incineration fly ash, slag, phosphogypsum, tailings fines, and lithium slag have low utilization rates and are mostly stockpiled and landfilled, seriously polluting groundwater resources and the surrounding environment. Furthermore, the traditional method of producing aggregates by blasting rocks is no longer sustainable, leading to a gradual shortage of high-quality aggregates in the market and difficulties in ensuring project quality. Summary of the Invention

[0003] The embodiment of the present invention provides a low-carbon aggregate based on solid waste and a preparation method, which uses a low-carbon cementitious material with high density to seal the waste residue inside the aggregate in the form of a package, thereby realizing the disposal of industrial waste. At the same time, due to the high strength and good durability of the low-carbon cementitious material, the quality of the aggregate can be greatly improved, thereby achieving the purpose of treating waste with waste.

[0004] To achieve the above-mentioned object, the present invention adopts a technical solution: providing a low-carbon aggregate based on solid waste, comprising: a solid waste layer, and a stabilizing layer and a pressure-bearing layer sequentially wrapped around the solid waste layer from the inside out; based on the particle size range of the low-carbon aggregate, the thickness of the solid waste layer, the stabilizing layer, and the pressure-bearing layer are determined as follows:

[0005] When the particle size of the low-carbon aggregate is between 5.0 mm and 10.0 mm, the diameter of the solid waste layer is between 0.3 mm and 2.36 mm, the thickness of the stabilization layer is between 0.3 mm and 2.36 mm, and the thickness of the pressure-bearing layer is between 1.18 mm and 3.3 mm;

[0006] When the particle size of the low-carbon aggregate is between 10.0 mm and 20.0 mm, the diameter of the solid waste layer is between 0.6 mm and 4.5 mm, the thickness of the stabilization layer is between 0.6 mm and 4.5 mm, and the thickness of the pressure-bearing layer is between 2.36 mm and 8.0 mm;

[0007] When the particle size of the low-carbon aggregate is in the range of 20.0 mm to 40.0 mm, the diameter of the solid waste layer is 1.18 mm to 9.5 mm, the thickness of the stabilization layer is 2.36 mm to 8.0 mm, and the thickness of the pressure-bearing layer is 4.5 mm to 12.5 mm.

[0008] In combination with the first aspect, in one achievable manner, the solid waste layer comprises, by mass percentage, 10% to 25% of waste incineration fly ash, 13% to 30% of slag, 22% to 37% of red mud, 10% to 20% of carbide slag, and 10% to 26% of other components;

[0009] The other components are composed of one or more of phosphogypsum, tailings powder, stone powder, dust removal ash, phosphorus slag, mercury slag, chromium slag, boron slag, and lithium slag in any proportion;

[0010] The stabilization layer comprises, by mass percentage, 20% to 35% of steel slag, 30% to 55% of slag, 5% to 15% of desulfurized gypsum, 10% to 25% of fly ash, and 0.5% to 1.5% of Na2CO3;

[0011] The pressure-bearing layer comprises, by mass percentage, 15% to 25% silica fume, 10% to 25% steel slag, 30% to 50% slag, 5% to 15% desulfurized gypsum, and 5% to 15% cement.

[0012] In a second aspect, an embodiment of the present invention further provides a method for preparing the low-carbon aggregate based on solid waste, the method comprising the following steps:

[0013] Step 1: Preparation of the solid waste layer:

[0014] After the powder of the solid waste layer is mixed and stirred uniformly according to a certain proportion, X kg is weighed and evenly placed in a disc granulator. The turntable is turned on and the mixed powder is sprayed at the same time with a water amount of 0.27X to 0.32X until the spraying is completed; particles that do not meet the target particle size are sieved out and the mass m1 of the low-carbon aggregate primary product a is obtained by weighing;

[0015] Step 2: Wrapping the stabilizing layer on the surface of the low-carbon aggregate primary product a:

[0016] Mix the excess stabilization layer powder in proportion and stir evenly, then place it in the first hopper for later use;

[0017] The low-carbon aggregate primary product a is placed in the turntable of the disc granulator, and the angle θ between the turntable and the horizontal plane is adjusted to 38° to 43°; the disc granulator is turned on, and the first hopper is turned on at the same time, so that the stabilized layer powder in the first hopper falls into the turntable in batches, and the mass of the stabilized layer powder falling each time is controlled to be 0.15ml to 0.25ml; after each discharge, the sprayer is turned on, and the amount of water sprayed each time is 0.23 to 0.28 of the mass of the powder falling into the disc;

[0018] Then, the first hopper is opened again to discharge the material, and the above steps are repeated until more than 80% of the particles reach the diameter of the stable layer. The disc is kept rotating for 5 to 8 minutes, and then the disc granulator is closed; particles that do not meet the target particle size are screened out to obtain a low-carbon aggregate primary product b, which is weighed to obtain a mass m2 of the low-carbon aggregate primary product b;

[0019] Step 3: Wrapping the pressure-bearing layer on the surface of the low-carbon aggregate primary product b:

[0020] Mix the excess pressure-bearing layer powder in proportion and stir evenly, then place it in the second hopper for later use;

[0021] The low-carbon aggregate product b is placed on the turntable of the disc granulator; the angle θ between the turntable and the horizontal plane is adjusted to 30° to 36°; the disc granulator is turned on, and the second hopper is opened at the same time, so that the pressure layer powder in the second hopper falls into the turntable in batches.

[0022] Then, the second hopper is opened again to discharge the material, and the above steps are repeated until more than 80% of the particles reach the diameter of the pressure-bearing layer. The turntable is kept rotating for 6 to 10 minutes, and then the disc granulator is closed. Particles that do not meet the target particle size are screened out to obtain the low-carbon aggregate product C;

[0023] Step 4: After curing the low-carbon aggregate product c in a curing box, the product is placed in an autoclave for autoclave curing. After the pressure and temperature in the autoclave drop to normal pressure and room temperature, the product is taken out to obtain the low-carbon aggregate product d.

[0024] Step 5: placing the low-carbon aggregate primary product d in a rapid carbonization box for carbonization to obtain a low-carbon aggregate finished product.

[0025] In conjunction with the second aspect, in one achievable manner, in step 1, the rotation speed of the disc granulator is controlled at between;

[0026] Where n is the speed, unit is r / min;

[0027] θ is the angle between the turntable and the horizontal plane, which is the inclination angle and is controlled to be between 40° and 45°;

[0028] d is the diameter of the turntable, and its value is controlled to be 0.5m~8.5m.

[0029] In combination with the second aspect, in one feasible method, in step one, after spraying with water, keep the disc rotating and observe. When more than 80% of the particles reach the diameter of the solid waste layer, continue to keep the disc rotating for 3 to 5 minutes and then turn off the disc granulator.

[0030] In combination with the second aspect, in one feasible manner, in step 2, the angle θ between the turntable and the horizontal plane is adjusted to 38° to 43°, and the rotational speed is calculated according to the rotational speed control formula.

[0031] In combination with the second aspect, in one feasible method, in step 2, the mass of the powder falling into the stabilization layer each time is controlled at 0.15ml~0.25ml. After each discharge, the sprayer is turned on, and the amount of water sprayed each time is 0.23~0.28 of the mass of the powder falling into the disc.

[0032] In combination with the second aspect, in a feasible method, in step three, the angle θ between the turntable and the horizontal plane is adjusted to 30°~36°, and the speed is calculated according to the speed control formula; the mass of the pressure-bearing layer powder falling into the turntable each time is controlled at 0.20m2~0.30m2, and after each discharge is completed, the sprayer is turned on, and the amount of water sprayed each time is 0.19~0.24 of the mass of the pressure-bearing layer powder falling into the turntable.

[0033] In combination with the second aspect, in one feasible method, in step four, after curing in the curing box at a temperature of 20°C ± 1°C and a humidity ≥ 90% for 16 hours to 24 hours, the product is placed in the autoclave at 2.0 MPa to 3.5 MPa and 170°C to 200°C for autoclave curing for 2 hours to 5 hours. After the autoclave curing is completed, the exhaust valve is opened to exhaust.

[0034] In combination with the second aspect, in one feasible manner, in step five, the low-carbon aggregate product d is carbonized at 20°C ± 5°C, a carbon dioxide concentration of 0.85-1.50%, and a relative humidity of 65%-75% for 72h-144h to obtain a low-carbon aggregate finished product.

[0035] Compared with the prior art, the low-carbon aggregate based on solid waste and the preparation method provided by the present invention have the following beneficial effects:

[0036] (1) The low-carbon aggregate is designed to be divided into three layers, and the thickness of each layer is strictly controlled; the innermost layer is the solid waste layer, and a small amount of hydration-active materials are used to preliminarily fix the waste residue; then, steel slag, slag, desulfurization gypsum, etc. are used to prepare a high-density stabilization layer, which firmly wraps the waste residue to prevent harmful elements from leaching; finally, silica fume, cement, steel slag, slag, desulfurization gypsum, etc. are used to prepare a high-strength pressure-bearing layer to provide strength for the aggregate.

[0037] (2) The solid waste ratio of the present invention is high, about 92.5% to 97.5%, which not only achieves the harmless treatment of waste residues, but also ensures the strength of aggregates; at the same time, it realizes the concept of treating waste with waste, and is also in line with the national low-carbon development strategy.

[0038] (3) The stabilization layer uses steel slag, slag, and desulfurization gypsum to provide a certain strength, and uses the secondary hydration characteristics of fly ash to make the stabilization layer denser. At the same time, Na2CO3 is added, which can react with Ca(OH)2 produced by hydration to generate NaOH, continuously providing a strong alkaline environment, so that hydration continues and the density continues to increase, thereby tightly wrapping the industrial waste slag inside the stabilization layer. Harmful ions such as heavy metal ions are not easily leached, thus achieving harmless treatment of industrial waste slag.

[0039] (4) The aggregate particle size is closely related to the rotation speed and inclination angle of the disc granulator. According to the target particle size of the low-carbon aggregate, adjusting the angle between the turntable and the horizontal plane and the rotation speed can increase the proportion of target particle size aggregate, improve the aggregate preparation efficiency, and reduce material waste. After reaching the target particle size, the turntable continues to rotate for a certain period of time, which can improve the density and strength of the aggregate.

[0040] (5) The aggregate prepared by the disc granulator has good particle shape and does not contain stone powder. The alkali-aggregate reaction is avoided by carbonization, thereby improving the aggregate quality. At the same time, the pressure steamer is used to quickly increase the aggregate strength, making the preparation process of low-carbon aggregate simple and fast.

[0041] In summary, the present invention utilizes a variety of bulk solid wastes to prepare low-carbon aggregates, and utilizes low-carbon cementitious materials with higher density to seal the waste residue inside the aggregate in the form of a package, thereby realizing the disposal of industrial waste. At the same time, due to the high strength and good durability of the low-carbon cementitious materials, the quality of the aggregate can be greatly improved, achieving the purpose of treating waste with waste, which is in line with the low-carbon development concept; the method of treating waste with waste is used to achieve the harmless treatment of industrial solid waste, and at the same time fills the problem of shortage of high-quality aggregates in the current market. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A flow chart of a process for preparing low-carbon aggregate based on solid waste provided in an embodiment of the present invention;

[0043] Figure 2 A schematic structural diagram of a low-carbon aggregate provided in an embodiment of the present invention having a particle size range of 5.0 mm to 10.0 mm;

[0044] Figure 3 A schematic structural diagram of a low-carbon aggregate provided in an embodiment of the present invention having a particle size range of 10.0 mm to 20.0 mm;

[0045] Figure 4 A schematic structural diagram of a low-carbon aggregate provided in an embodiment of the present invention having a particle size range of 20.0 mm to 40.0 mm;

[0046] Description of reference numerals:

[0047] 1. Solid waste layer; 2. Stabilization layer; 3. Pressure-bearing layer. DETAILED DESCRIPTION

[0048] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0049] The low-carbon aggregate based on solid waste and the preparation method provided by the present invention are now described.

[0050] For example 1, please refer to Figure 1 and Figure 2 :

[0051] A low-carbon aggregate based on solid waste, wherein the solid waste layer 1 comprises, by mass percentage, 16% of fly ash from waste incineration, 22% of slag, 35% of red mud, 12% of carbide slag, and 15% of other components, wherein the other components are composed of 25% of tailings fine powder, 20% of stone powder, 10% of boron slag, and 45% of lithium slag; the stabilizing layer 2 comprises, by mass percentage, 25% of steel slag, 46% of slag, 11.3% of desulfurized gypsum, 17% of fly ash, and 0.7% of Na2CO3; the pressure-bearing layer 3 comprises, by mass percentage, 16% of silica fume, 19% of steel slag, 45% of slag, 8% of desulfurized gypsum, and 12% of cement.

[0052] The particle size of the low-carbon aggregate prepared in this embodiment is 5.0 mm to 10.0 mm, the diameter of the solid waste layer 1 is 0.3 mm to 2.36 mm, the thickness of the stabilization layer 2 is 0.3 mm to 2.36 mm, and the thickness of the pressure-bearing layer 3 is 1.18 mm to 3.3 mm.

[0053] The preparation method comprises the following steps:

[0054] Step 1, Preparation of Solid Waste Layer 1: Set the angle θ between the turntable and the horizontal plane to 45°. Measure the turntable diameter to be 2.5m. Calculate the disc granulator speed range to be 10-14 rpm. Select a speed of 12 rpm for granulation. Weigh 20 kg of solid waste layer powder and evenly distribute it in the disc granulator. Turn on the turntable and spray the powder with a sprayer using 5.6 kg of water.

[0055] After the specified amount of water is sprayed and the particle size of more than 80% of the particles reaches 0.3mm to 2.36mm, the disc is kept rotating for 3 minutes, the disc granulator is turned off, and the particles that do not meet the target particle size are sieved out to obtain the low-carbon aggregate primary product a. The mass of the low-carbon aggregate primary product a is weighed to be 24.7kg.

[0056] Step 2, Coating with Stabilizing Layer 2: Excess stabilizing layer powder is mixed and stirred uniformly according to the appropriate proportions, then placed in the first hopper for later use. The low-carbon aggregate (a) is placed on the turntable of the disc granulator. The angle θ between the turntable and the horizontal plane is adjusted to 40°. The turntable diameter is 2.5m. The calculated speed range of the disc granulator is 8 to 13 rpm. A speed of 9 rpm is selected for granulation.

[0057] Turn on the disc granulator and the first hopper at the same time, so that the stable layer powder in the first hopper falls into the turntable in batches. The mass of the stable layer powder falling each time is controlled at 4.5 kg. After each discharge, turn on the sprayer and spray water each time so that the mass of the powder falling into the turntable is 1.3 kg.

[0058] The first hopper was then opened again to discharge material, and the above steps were repeated until more than 80% of the stable layer reached a thickness of 0.3 mm to 2.36 mm. The turntable was kept rotating for another 6 minutes before the disc granulator was turned off. Particles that did not meet the target particle size were screened out to obtain the low-carbon aggregate primary product B, which was weighed and found to have a mass of 183.1 kg.

[0059] Step 3, wrapping the pressure-bearing layer 3: After mixing and stirring the excess pressure-bearing layer powder in proportion, place it in the second hopper for later use.

[0060] The low-carbon aggregate product b is placed on the turntable of the disc granulator; the angle θ between the turntable and the horizontal plane is adjusted to 35°, the turntable diameter is 2.5m, and the speed range of the disc granulator is calculated to be 7r / min to 11r / min. The speed of 8r / min is selected for granulation.

[0061] Turn on the disc granulator and the second hopper at the same time, so that the pressure-bearing layer powder in the second hopper falls into the disc in batches. The mass of the pressure-bearing layer powder falling each time is controlled at 42.1 kg. After each discharge, turn on the sprayer and the amount of water sprayed each time is 9.3 kg.

[0062] Then, the second hopper is opened again to discharge the material, and the above steps are repeated until more than 80% of the pressure-bearing layer reaches a thickness of 1.18mm to 3.3mm. The turntable is kept rotating for 8 minutes, and then the disc granulator is turned off. Particles that do not meet the target particle size are screened out to obtain the low-carbon aggregate product C.

[0063] Step 4: Place the low-carbon aggregate product c in a curing box and cure it at a temperature of 20°C ± 1°C and a humidity of ≥ 90% for 17 hours. Then place it in an autoclave and autoclave and cure it at 2.3 MPa and 175°C for 3 hours. After the autoclave curing is completed, open the exhaust valve, and after the pressure and temperature in the autoclave drop to normal pressure and room temperature, take out the aggregate to obtain the low-carbon aggregate product d.

[0064] Step 5: Place the low-carbon aggregate product d in a rapid carbonization box and carbonize it for 84 hours at 20°C ± 5°C, a carbon dioxide concentration of 0.95%, and a relative humidity of 68% to obtain a low-carbon aggregate finished product.

[0065] For example 2, please refer to Figure 1 and Figure 3 :

[0066] A low-carbon aggregate based on solid waste, wherein the solid waste layer 1 comprises, by mass percentage, 20% of waste incineration fly ash, 25% of slag, 26% of red mud, 17% of carbide slag, and 12% of other components, wherein the other components are composed of 15% of phosphogypsum, 15% of tailings fine powder, 25% of dust removal ash, 10% of chromium slag, and 35% of lithium slag; the stabilization layer 2 comprises, by mass percentage, 30% of steel slag, 43% of slag, 13.6% of desulfurized gypsum, 12.2% of fly ash, and 1.2% of Na2CO3; the pressure-bearing layer 3 comprises, by mass percentage, 21% of silica fume, 15% of steel slag, 47% of slag, 6% of desulfurized gypsum, and 11% of cement.

[0067] The aggregate prepared in this embodiment is 10.0 mm to 20.0 mm in diameter, the solid waste layer 1 has a diameter of 0.6 mm to 4.5 mm, the stabilization layer 2 has a thickness of 0.6 mm to 4.5 mm, and the pressure-bearing layer 3 has a thickness of 2.36 mm to 8.0 mm.

[0068] The preparation method comprises the following steps:

[0069] Step 1, preparation of solid waste layer 1: setting the angle θ between the turntable and the horizontal plane to 42°, measuring the turntable diameter to be 4.0 m, calculating the speed range of the disc granulator to be 7 r / min to 11 r / min, and selecting a speed of 8 r / min for granulation.

[0070] Weigh 10 kg of solid waste layer powder and evenly arrange it in the disc granulator, turn on the turntable, and use a sprayer to spray the powder at the same time, using 3.0 kg of water.

[0071] After the specified amount of water is sprayed and the particle size of more than 80% of the particles reaches 0.6mm-4.5mm, the turntable continues to rotate for 4 minutes, the disc granulator is turned off, and the particles that do not meet the target particle size are sieved out to obtain the low-carbon aggregate primary product a. The mass of the low-carbon aggregate primary product a is 12.2kg.

[0072] Step 2: Wrapping the stabilizing layer 2: Mix the excess stabilizing layer powder according to the proportion and stir evenly, then place it in the first hopper for later use.

[0073] The low-carbon aggregate product a is placed on the turntable of the disc granulator. The angle θ between the turntable and the horizontal plane is adjusted to 38°. The turntable diameter is 4.0m. The speed range of the disc granulator is calculated to be 6r / min to 10r / min. The speed of 7r / min is selected for granulation.

[0074] Turn on the disc granulator and the first hopper at the same time, so that the stabilization layer powder in the first hopper falls into the disc in batches. The mass of the stabilization layer powder falling each time is controlled at 2.1 kg. After each discharge, turn on the sprayer and spray water each time so that the mass of the powder falling into the disc is 0.55 kg.

[0075] Then open the first hopper again to discharge the material, repeat the above steps until more than 80% of the stable layer thickness reaches 0.6mm to 4.5mm, continue to keep the disc rotating for 5 minutes and then turn off the disc granulator.

[0076] Particles that do not meet the target particle size are sieved out to obtain the low-carbon aggregate preliminary product b, and the mass of the low-carbon aggregate preliminary product b is 97.6 kg.

[0077] Step 3, wrapping the pressure-bearing layer 3: After mixing and stirring the excess pressure-bearing layer powder in proportion, place it in the second hopper for later use.

[0078] The low-carbon aggregate product b was placed on the turntable of a disc pelletizer. The angle θ between the turntable and the horizontal plane was adjusted to 32°. The turntable diameter was 4.0 m. The calculated speed range of the disc pelletizer was 6 rpm to 9 rpm. A speed of 7 rpm was selected for pelletizing.

[0079] Turn on the disc granulator and the second hopper at the same time, so that the pressure-bearing layer powder in the second hopper falls into the turntable in batches. The mass of the pressure-bearing layer powder falling each time is controlled at 25.4 kg. After each discharge, turn on the sprayer and the amount of water sprayed each time is 5.3 kg.

[0080] Then, the second hopper is opened again to discharge the material, and the above steps are repeated until more than 80% of the pressure-bearing layer reaches a thickness of 2.36mm to 8.0mm. The turntable is kept rotating for 9 minutes, and then the disc granulator is turned off. Particles that do not meet the target particle size are screened out to obtain the low-carbon aggregate product C.

[0081] Step 4: Place the low-carbon aggregate product c in a curing box, cure it at a temperature of 20°C ± 1°C and a humidity of ≥ 90% for 20 hours, then place it in an autoclave and autoclave curing at 2.8 MPa and 186°C for 4 hours. After the autoclave curing is completed, open the exhaust valve, wait until the pressure in the autoclave drops to normal pressure and the temperature drops to room temperature, take out the aggregate to obtain the low-carbon aggregate product d.

[0082] Step 5: Place the low-carbon aggregate product d in a rapid carbonization chamber and carbonize for 96 hours at 20°C ± 5°C, a carbon dioxide concentration of 1.20%, and a relative humidity of 71% to obtain a finished low-carbon aggregate product.

[0083] For example three, please refer to Figure 1 and Figure 4 :

[0084] A low-carbon aggregate based on solid waste, wherein the solid waste layer 1 comprises, by mass percentage, 14% of waste incineration fly ash, 23% of slag, 29% of red mud, 13% of carbide slag, and 21% of other components, wherein the other components are composed of 27% of stone powder, 15% of dust removal ash, 11% of mercury slag, 27% of boron slag, and 20% of lithium slag; the stabilization layer 2 comprises, by mass percentage, 23% of steel slag, 52% of slag, 9.5% of desulfurized gypsum, 14.2% of fly ash, and 1.3% of Na2CO3; the pressure-bearing layer 3 comprises, by mass percentage, 25% of silica fume, 12% of steel slag, 44% of slag, 11% of desulfurized gypsum, and 8% of cement.

[0085] The aggregate prepared in this embodiment is 10.0 mm to 20.0 mm in diameter, the diameter of the solid waste layer 1 is 0.6 mm to 4.5 mm, the thickness of the stabilization layer 2 is 0.6 mm to 4.5 mm, and the thickness of the pressure-bearing layer 3 is 2.36 mm to 8.0 mm.

[0086] The preparation method comprises the following steps:

[0087] Step 1, preparation of solid waste layer 1: setting the angle θ between the turntable and the horizontal plane to 45°, measuring the turntable diameter to be 2.0 m, calculating the speed range of the disc granulator to be 11 r / min to 16 r / min, and selecting a speed of 15 r / min for granulation.

[0088] Weigh 15 kg of solid waste layer powder and evenly distribute it in a disc granulator. Turn on the turntable and spray the powder with 4.5 kg of water using a sprayer. Once the required amount of water has been sprayed and more than 80% of the particles have reached a particle size of 0.6 mm to 4.5 mm, continue rotating the turntable for 5 minutes, turn off the disc granulator, and sieve out particles that do not meet the target particle size to obtain a low-carbon aggregate product A. The mass of this low-carbon aggregate product A is 18.0 kg.

[0089] Step 2, Coating with Stabilizing Layer 2: Excess stabilizing layer powder is mixed and stirred uniformly according to the appropriate proportions, then placed in the first hopper for later use. The low-carbon aggregate (a) is placed on the turntable of the disc granulator. The angle θ between the turntable and the horizontal plane is adjusted to 39°. The turntable diameter is 2.0 m. The calculated speed range of the disc granulator is 9 to 14 rpm. A speed of 10 rpm is selected for granulation.

[0090] Turn on the disc granulator and the first hopper at the same time, so that the stable layer powder in the first hopper falls into the disc in batches. The mass of the stable layer powder falling each time is controlled at 3.1 kg. After each discharge, turn on the sprayer and spray water each time so that the mass of the powder falling into the turntable is 0.74 kg.

[0091] The discharge hopper was then reopened and the above steps were repeated until at least 80% of the stabilized layer reached a thickness of 0.6 mm to 4.5 mm. The turntable was then rotated for another 8 minutes before the disc granulator was closed. Particles that did not meet the target particle size were screened out to obtain the low-carbon aggregate primary product B, which was weighed to obtain a mass of 142.6 kg.

[0092] Step 3, wrapping the pressure-bearing layer 3: After mixing and stirring the excess pressure-bearing layer powder in proportion, place it in the second hopper for later use.

[0093] The low-carbon aggregate product b was placed on the turntable of a disc pelletizer. The angle θ between the turntable and the horizontal plane was adjusted to 30°. The turntable diameter was 2.0 m. The calculated speed range of the disc pelletizer was 7 rpm to 11 rpm. A speed of 8 rpm was selected for pelletizing.

[0094] Turn on the disc granulator and the second hopper at the same time, so that the pressure-bearing layer powder in the second hopper falls into the turntable in batches. The mass of the stable pressure-bearing layer powder falling each time is controlled at 41.4 kg. After each discharge, turn on the sprayer, and the amount of water sprayed each time is 8.7 kg.

[0095] Then, the hopper is opened again to discharge the material, and the above steps are repeated until more than 80% of the pressure-bearing layer reaches a thickness of 2.36mm to 8.0mm. The turntable is kept rotating for 10 minutes, and then the disc granulator is turned off. Particles that do not meet the target particle size are screened out to obtain the low-carbon aggregate product C.

[0096] Step 4: Place the low-carbon aggregate product c in a curing box, cure it at a temperature of 20°C ± 1°C and a humidity of ≥ 90% for 24 hours, then place it in an autoclave and autoclave curing at 3.3 MPa and 196°C for 5 hours. After the autoclave curing is completed, open the exhaust valve, wait until the pressure in the autoclave drops to normal pressure and the temperature drops to room temperature, take out the aggregate to obtain the low-carbon aggregate product d.

[0097] Step 5: Place the low-carbon aggregate product d in a rapid carbonization chamber and carbonize for 125 hours at 20°C ± 5°C, a carbon dioxide concentration of 1.30%, and a relative humidity of 73% to obtain a finished low-carbon aggregate product.

[0098] The apparent density, water absorption rate and cylinder compressive strength of the above three low-carbon aggregates were tested according to the test methods in GB / T 14685-2022 and GB / T 17431.2-2010, and the aggregates purchased on the market were used as a control example for comparison. The results are shown in Table 1.

[0099] Leaching toxicity tests were conducted on the three aggregates mentioned above in accordance with GB 5085.3-2007. The leaching concentration thresholds of several heavy metal elements specified in GB 5085.3-2007 and the surface water and groundwater quality standards in GB 3838-2002 and GB / T 14848-2017 were then compared. The results are shown in Table 2.

[0100] Table 1 Test results

[0101]

[0102]

[0103] Table 2 Leaching toxicity test results (mg / L)

[0104]

[0105] The low-carbon aggregate prepared by the present invention meets the performance requirements of the standard and outperforms similar products currently available on the market. The leaching concentrations of several heavy metal elements are far below the threshold for leaching toxicity assessment and also meet the Class I standards for surface water and groundwater.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A low-carbon aggregate based on solid waste, characterized in that: include: A solid waste layer (1) and a stabilizing layer (2) and a pressure-bearing layer (3) sequentially wrapped around the solid waste layer (1) from the inside out; according to the particle size range of the low-carbon aggregate, the thicknesses of the solid waste layer (1), the stabilizing layer (2) and the pressure-bearing layer (3) are determined in the following manner: When the particle size of the low-carbon aggregate is between 5.0 mm and 10.0 mm, the diameter of the solid waste layer (1) is between 0.3 mm and 2.36 mm, the thickness of the stabilizing layer (2) is between 0.3 mm and 2.36 mm, and the thickness of the pressure-bearing layer (3) is between 1.18 mm and 3.3 mm; When the particle size of the low-carbon aggregate is between 10.0 mm and 20.0 mm, the diameter of the solid waste layer (1) is between 0.6 mm and 4.5 mm, the thickness of the stabilizing layer (2) is between 0.6 mm and 4.5 mm, and the thickness of the pressure-bearing layer (3) is between 2.36 mm and 8.0 mm; When the particle size of the low-carbon aggregate is in the range of 20.0 mm to 40.0 mm, the diameter of the solid waste layer (1) is 1.18 mm to 9.5 mm, the thickness of the stabilizing layer (2) is 2.36 mm to 8.0 mm, and the thickness of the pressure-bearing layer (3) is 4.5 mm to 12.5 mm.

2. The low-carbon aggregate based on solid waste according to claim 1, characterized in that The solid waste layer (1) comprises, by mass percentage, 10% to 25% of fly ash from garbage incineration, 13% to 30% of slag, 22% to 37% of red mud, 10% to 20% of carbide slag, and 10% to 26% of other components; The other components are composed of one or more of phosphogypsum, tailings powder, stone powder, dust removal ash, phosphorus slag, mercury slag, chromium slag, boron slag, and lithium slag in any proportion; The stabilization layer (2) comprises, by mass percentage, 20% to 35% of steel slag, 30% to 55% of slag, 5% to 15% of desulfurized gypsum, 10% to 25% of fly ash, and 0.5% to 1.5% of Na2CO3; The pressure-bearing layer (3) comprises, by mass percentage, 15% to 25% silica fume, 10% to 25% steel slag, 30% to 50% slag, 5% to 15% desulfurized gypsum, and 5% to 15% cement.

3. A method for preparing low-carbon aggregate based on solid waste according to claim 2, characterized in that: The preparation method comprises the following steps: Step 1, preparation of the solid waste layer (1): After the solid waste layer powder is mixed and stirred uniformly according to a certain proportion, X kg is weighed and evenly arranged in a disc granulator. The turntable is turned on and the mixed powder is sprayed at the same time with a water amount of 0.27X to 0.32X until the spraying is completed; particles that do not meet the target particle size are sieved out and the mass m1 of the low-carbon aggregate primary product a is obtained by weighing; Step 2: Wrapping the stabilizing layer (2) on the surface of the low-carbon aggregate primary product a: Mix the excess stabilization layer powder in proportion and stir evenly, then place it in the first hopper for later use; The low-carbon aggregate primary product a is placed in the turntable of the disc granulator, and the angle θ between the turntable and the horizontal plane is adjusted to 38° to 43°; the disc granulator is turned on, and the first hopper is turned on at the same time, so that the stabilized layer powder in the first hopper falls into the turntable in batches, and the mass of the stabilized layer powder falling each time is controlled to be 0.15ml to 0.25ml; after each discharge, the sprayer is turned on, and the amount of water sprayed each time is 0.23 to 0.28 of the mass of the powder falling into the disc; Then, the first hopper is opened again to discharge the material, and the above steps are repeated until more than 80% of the particles reach the diameter of the stable layer. The disc is kept rotating for 5 to 8 minutes, and then the disc granulator is closed; particles that do not meet the target particle size are screened out to obtain a low-carbon aggregate primary product b, which is weighed to obtain a mass m2 of the low-carbon aggregate primary product b; Step 3: Wrapping the pressure-bearing layer (3) on the surface of the low-carbon aggregate primary product b: Mix the excess pressure-bearing layer powder in proportion and stir evenly, then place it in the second hopper for later use; The low-carbon aggregate product b is placed on the turntable of the disc granulator; the angle θ between the turntable and the horizontal plane is adjusted to 30° to 36°; the disc granulator is turned on, and the second hopper is opened at the same time, so that the pressure layer powder in the second hopper falls into the turntable in batches. Then, the second hopper is opened again to discharge the material, and the above steps are repeated until more than 80% of the particles reach the diameter of the pressure-bearing layer. The turntable is kept rotating for 6 to 10 minutes, and then the disc granulator is closed. Particles that do not meet the target particle size are screened out to obtain the low-carbon aggregate product C; Step 4: After curing the low-carbon aggregate product c in a curing box, the product is placed in an autoclave for autoclave curing. After the pressure and temperature in the autoclave drop to normal pressure and room temperature, the product is taken out to obtain the low-carbon aggregate product d. Step 5: placing the low-carbon aggregate primary product d in a rapid carbonization box for carbonization to obtain a low-carbon aggregate finished product.

4. The method for preparing low-carbon aggregate based on solid waste according to claim 3, characterized in that: In step 1, the rotation speed of the disc granulator is controlled at between; Where n is the speed, unit is r / min; θ is the angle between the turntable and the horizontal plane, which is the inclination angle and is controlled to be between 40° and 45°; d is the diameter of the turntable, and its value is controlled to be 0.5m~8.5m.

5. The method for preparing low-carbon aggregate based on solid waste according to claim 3, characterized in that: In step 1, after spraying with water, the disc is kept rotating and observed. When more than 80% of the particles reach the diameter of the solid waste layer, the disc is kept rotating for 3 to 5 minutes and then the disc granulator is turned off.

6. The method for preparing low-carbon aggregate based on solid waste according to claim 4, characterized in that: In step 2, the angle θ between the turntable and the horizontal plane is adjusted to 38° to 43°, and the speed is calculated according to the speed control formula.

7. The method for preparing low-carbon aggregate based on solid waste according to claim 3, characterized in that: In step 2, the mass of the powder falling into the stabilization layer each time is controlled at 0.15ml~0.25ml. After each discharge, the sprayer is turned on and the amount of water sprayed each time is 0.23~0.28 of the mass of the powder falling into the disc.

8. The method for preparing low-carbon aggregate based on solid waste according to claim 4, characterized in that: In step three, the angle θ between the turntable and the horizontal plane is adjusted to 30°~36°, and the speed is calculated according to the speed control formula; the mass of the pressure-bearing layer powder falling into the turntable each time is controlled at 0.20m2~0.30m2, and after each discharge, the sprayer is turned on, and the amount of water sprayed each time is 0.19~0.24 of the mass of the pressure-bearing layer powder falling into the turntable.

9. The method for preparing low-carbon aggregate based on solid waste according to claim 3, characterized in that: In step 4, after curing in the curing box at a temperature of 20°C ± 1°C and a humidity of ≥90% for 16 to 24 hours, the product is placed in the autoclave at 2.0 MPa to 3.5 MPa and 170°C to 200°C for autoclave curing for 2 to 5 hours. After the autoclave curing is completed, the exhaust valve is opened to exhaust.

10. The method for preparing low-carbon aggregate based on solid waste according to claim 3, characterized in that: Step 5: carbonizing the low-carbon aggregate product d at 20° C.±5° C., a carbon dioxide concentration of 0.85% to 1.50%, and a relative humidity of 65% to 75% for 72 hours to 144 hours to obtain a low-carbon aggregate finished product.

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