Preparation method and application of artificial aggregate prepared from desulfurization solid waste

Abstract

This invention discloses an artificial aggregate prepared using desulfurization solid waste, its preparation method, and its application, belonging to the field of solid waste resource utilization technology. The preparation method includes the following steps: ball milling desulfurization slag to obtain desulfurization slag powder; low-temperature pyrolysis treatment of waste incineration fly ash to obtain pretreated waste incineration fly ash; mixing desulfurization ash, desulfurization slag powder, and pretreated waste incineration fly ash to obtain a raw material mixture; adding water to the raw material mixture and pelletizing to obtain aggregate particles; subjecting the aggregate particles to air curing and mineralization curing sequentially to obtain the final product. This invention also discloses the artificial aggregate prepared by the above method and its application. The artificial aggregate prepared using desulfurization solid waste of this invention has high compressive strength and stable ion storage, which can solve the problems of low strength and high dependence on admixtures in existing coal ash-based aggregates, and has broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically relating to an artificial aggregate prepared from desulfurization solid waste, its preparation method, and its application. Background Technology

[0002] With my country placing increasing emphasis on the management of industrial solid waste, power plants, which are major emitters of solid waste, produce large quantities of coal ash and slag during the combustion and power generation process. Directly dumping and landfilling these solid wastes would cause serious damage to the surrounding ecological environment.

[0003] Depending on the combustion process and the object being burned, combustion produces various materials such as fly ash, slag, desulfurized fly ash, desulfurized slag, and waste incineration fly ash. Since fly ash and slag produced by conventional coal-fired power plants are sintered pozzolanic materials, primarily composed of aluminosilicate glass, they are already used in the concrete and cement industries. However, desulfurized fly ash / slag is a byproduct of circulating fluidized bed flue gas desulfurization and typically contains high levels of calcium. Direct application to concrete and cement can lead to problems such as expansion, cracking, or efflorescence, resulting in decreased stability and durability. Furthermore, waste incineration fly ash not only has an even higher calcium content but also contains significant amounts of chlorides and sulfates, which can severely damage concrete. Therefore, no research reports have yet documented the application of waste incineration fly ash in building materials.

[0004] Research has found that by preparing artificial aggregates from solid wastes such as coal ash, steel slag, mineral powder, red mud, and waste concrete powder, and then using flue gas CO2 for curing, it is possible not only to achieve resource utilization of industrial solid waste and solve the problem of aggregate cracking caused by high calcium content in solid waste, but also to achieve the mineralization and sequestration of CO2 in flue gas, thus addressing the CO2 emission problem from power plants. However, existing technologies for preparing artificial aggregates generally have low strength, often requiring the addition of components such as cement or quicklime to improve aggregate strength. This increases the production cost of artificial aggregates, resulting in low economic efficiency.

[0005] Therefore, it is crucial to develop a low-cost, additive-free artificial aggregate for solid wastes such as desulfurized coal ash, desulfurized coal slag, and waste incineration fly ash, which fully utilizes the high calcium content of these solid wastes. This is particularly important for the treatment of solid wastes in circulating fluidized bed coal-fired power plants and waste-to-energy plants. Summary of the Invention

[0006] The problem this invention aims to solve is to provide an artificial aggregate prepared using desulfurization solid waste, its preparation method, and its application, in order to address the issues of low strength and high dependence on admixtures in existing coal ash-based aggregates.

[0007] The technical solution adopted to solve the technical problem is to provide a method for preparing artificial aggregates using desulfurization solid waste, including the following steps:

[0008] (1) The desulfurization residue is ball-milled to obtain desulfurization residue powder;

[0009] (2) Low-temperature pyrolysis treatment of waste incineration fly ash to obtain pretreated waste incineration fly ash;

[0010] (3) Mix the desulfurization ash, desulfurization slag powder and pretreated waste incineration fly ash to obtain a raw material mixture;

[0011] (4) Add water to the raw material mixture and granulate it to obtain aggregate particles;

[0012] (5) The aggregate particles are subjected to air curing and mineralization curing in sequence to obtain the final product.

[0013] The beneficial effects of the above technical solution adopted in this invention are as follows: In this invention, desulfurization ash, desulfurization slag and waste incineration fly ash are used to prepare artificial aggregates. The introduction of desulfurization slag and waste incineration fly ash can significantly increase the calcium content in the system. During the air curing and mineralization curing process, it reacts with CO2 in the flue gas to generate hydrated calcium silicate and calcium carbonate. Calcium carbonate can fill the voids in hydrated calcium silicate, making it form a denser microstructure. Meanwhile, the waste incineration fly ash added in this invention contains a certain amount of chloride and sulfate. The introduction of chloride ions can chemically react with solid waste under alkaline activation conditions, and some of it is adsorbed on the hydration products or pore walls. At the same time, it can also generate chloride salt complexes with very small ion solubility products, which can promote the hydration process of the system. By controlling its content, the sulfate reacts with some of the calcium hydroxide generated by air curing and mineralization curing to generate calcium sulfate. Calcium sulfate further fills the micropores and capillaries in the aggregate particles, enhancing the density of the aggregate. The chloride in it has a coagulation-promoting effect on the system, which can improve the early strength of the material. In addition, the form of mineralization curing of aggregates in this invention can make the chloride structure more compact, which has a good effect on the stable sequestration of chloride ions.

[0014] Preferably, the desulfurization ash and desulfurization slag are derived from the circulating fluidized bed process.

[0015] The beneficial effects of the above-mentioned technical solution in this invention are as follows: The circulating fluidized bed adopts in-furnace desulfurization, that is, limestone is added to the combustion furnace in the form of raw materials. First, the limestone decomposes into calcium oxide at high temperature in the furnace. Then, the calcium oxide reacts with sulfur oxides to generate calcium sulfate. Since the limestone added is excessive to ensure sufficient desulfurization, the desulfurization solid waste contains more calcium oxide, which can be used as a high-quality raw material for the mineralization process. The desulfurization ash and desulfurization slag of this invention are significantly different from the coal ash and slag obtained from ordinary coal-fired power plants. Compared with fly ash (usually less than 10%), the desulfurization ash has a higher calcium content (20% to 30%), which is more conducive to carbon fixation in the system of this invention, thereby making the aggregate have a denser structure.

[0016] Preferably, the particle size of the desulfurization ash powder in step (1) is less than 300 μm.

[0017] Preferably, the low-temperature pyrolysis temperature in step (2) is 300-400℃ and the time is 15-25 min.

[0018] Preferably, in step (3), the mass ratio of desulfurization ash, desulfurization slag powder and pretreated waste incineration fly ash is (5-95):(5-95):(1-10); and the mixing time is 20-60 min.

[0019] Preferably, the mass of water in step (4) is 20-35% of the total mass of the raw material mixture.

[0020] More preferably, in step (4), the mass of water is 25-30% of the total mass of the raw material mixture.

[0021] Preferably, the air curing conditions in step (5) are: normal temperature and pressure, relative humidity of 50-70%RH and curing time of 3-7 days; the mineralization curing conditions are: normal pressure, temperature of 45-65℃, relative humidity of 70-90%RH, carbon dioxide volume concentration of 10-20% and curing time of 4-12 hours.

[0022] The present invention also provides an artificial aggregate obtained by the above method.

[0023] The present invention also provides the application of the above-mentioned artificial aggregate in the preparation of building concrete.

[0024] The present invention has the following beneficial effects:

[0025] (1) The method of preparing artificial aggregate using desulfurization solid waste of the present invention is simple. At the same time, the artificial aggregate prepared by this method can significantly reduce the dependence of existing aggregates on admixtures (such as cement, quicklime, etc.). It has the advantages of low cost, excellent aggregate performance and strong environmental friendliness, and provides a feasible technical path for the resource utilization of desulfurization solid waste and solid waste such as fly ash.

[0026] (2) The artificial aggregate of the present invention, by adding a small amount of waste incineration fly ash, can not only directly utilize the solid waste (coal ash / coal slag) and waste gas (flue gas CO2) produced by the circulating fluidized bed combustion boiler, realize the fixed storage of CO2 and the resource utilization of desulfurized coal ash and desulfurized coal slag, but also realize the harmless treatment of waste incineration fly ash.

[0027] (3) The artificial aggregate prepared by the present invention has a compressive strength ≥4.0MPa, a water absorption rate ≤15.0%, and is not easy to crack. It is suitable for road construction concrete materials and industrial building concrete materials, with a wide range of applications and great application potential. Attached Figure Description

[0028] Figure 1 A flowchart for preparing artificial aggregates using desulfurization solid waste. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments.

[0030] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0031] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0032] Example 1

[0033] A method for preparing artificial aggregates using desulfurization solid waste includes the following steps:

[0034] (1) The desulfurization slag is ball-milled until the particle size is less than 300μm to obtain desulfurization slag powder;

[0035] (2) The fly ash from waste incineration is pyrolyzed at 300℃ for 15 minutes to obtain pretreated fly ash from waste incineration.

[0036] (3) Weigh 760g of desulfurization ash, 200g of desulfurization slag powder and 40g of pretreated waste incineration fly ash and put them into the mixer in sequence and mix for 30 minutes to obtain the raw material mixture;

[0037] (4) Transfer the raw material mixture to the granulator and spray 300g of water into a water mist onto the surface of the raw material mixture to form aggregate granules.

[0038] (5) Place the aggregate particles in a closed air curing chamber at normal temperature and pressure and relative humidity of 70%RH for 3 days. After taking them out, place them in a mineralization reactor and set the temperature of the mineralization reactor to 60℃ and the relative humidity to 80%RH. Then, introduce 15% CO2 flue gas into the mineralization reactor to mineralize and cure the aggregate particles for 8 hours.

[0039] Example 2

[0040] A method for preparing artificial aggregate using desulfurized solid waste, which differs from Example 1 in that: step (3) includes the following steps: weigh 570g of desulfurized ash, 400g of desulfurized slag powder and 30g of pretreated waste incineration fly ash and put them into a mixer in sequence and mix for 30min to obtain a raw material mixture; the remaining steps and parameters are the same as in Example 1.

[0041] Example 3

[0042] A method for preparing artificial aggregate using desulfurized solid waste, which differs from Example 1 in that: step (3) includes the following steps: weigh 380g of desulfurized ash, 600g of desulfurized slag powder and 20g of pretreated waste incineration fly ash and put them into a mixer in sequence and mix for 30min to obtain a raw material mixture; the remaining steps and parameters are the same as in Example 1.

[0043] Example 4

[0044] A method for preparing artificial aggregate using desulfurized solid waste, which differs from Example 1 in that: step (3) includes the following steps: weigh 200g of desulfurized ash, 790g of desulfurized slag powder and 10g of pretreated waste incineration fly ash and put them into a mixer in sequence and mix for 30min to obtain a raw material mixture; the remaining steps and parameters are the same as in Example 1.

[0045] Comparative Example 1

[0046] A method for preparing artificial aggregate using desulfurized solid waste, which differs from Example 1 in that step (1) is omitted and step (3) includes the following steps: weighing 900g of desulfurized ash and 100g of pretreated waste incineration fly ash and mixing them in a mixer for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as in Example 1.

[0047] Comparative Example 2

[0048] A method for preparing artificial aggregate using desulfurized solid waste differs from Example 1 in that step (1) is omitted, and step (3) includes the following steps: weighing 980g of desulfurized slag and 20g of pretreated waste incineration fly ash and mixing them in a mixer for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as in Example 1.

[0049] Comparative Example 3

[0050] A method for preparing artificial aggregate using desulfurization solid waste differs from Example 1 in that step (1) is omitted, and step (3) includes the following steps: weighing 400g of desulfurization ash and 600g of desulfurization slag and mixing them in a mixer for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as in Example 1.

[0051] Comparative Example 4

[0052] A method for preparing artificial aggregates using desulfurization solid waste includes the following steps:

[0053] (1) The desulfurization slag is ball-milled until the particle size is less than 300μm to obtain desulfurization slag powder;

[0054] (2) The fly ash from waste incineration is pyrolyzed at 300℃ for 15 minutes to obtain pretreated fly ash from waste incineration.

[0055] (3) Weigh 760g of desulfurization ash, 200g of desulfurization slag powder and 40g of pretreated waste incineration fly ash and put them into the mixer in sequence and mix for 30 minutes to obtain the raw material mixture;

[0056] (4) Transfer the raw material mixture to the granulator and spray 300g of water into a water mist onto the surface of the raw material mixture to form aggregate granules.

[0057] (5) Place the aggregate particles in a closed air curing room with normal temperature and pressure and a relative humidity of 70%RH for 3 days to cure them.

[0058] Comparative Example 5

[0059] A method for preparing artificial aggregate using desulfurized solid waste, which differs from Comparative Example 3 in that: step (3) includes the following steps: weigh 570g of desulfurized ash, 400g of desulfurized slag powder and 30g of pretreated waste incineration fly ash and put them into a mixer in sequence and mix for 30min to obtain a raw material mixture; the remaining steps and parameters are the same as those in Comparative Example 4.

[0060] Comparative Example 6

[0061] A method for preparing artificial aggregate using desulfurized solid waste, which differs from Comparative Example 3 in that: step (3) includes the following steps: weigh 380g of desulfurized ash, 600g of desulfurized slag powder and 20g of pretreated waste incineration fly ash and put them into a mixer in sequence and mix for 30min to obtain a raw material mixture; the remaining steps and parameters are the same as those in Comparative Example 4.

[0062] Comparative Example 7

[0063] A method for preparing artificial aggregate using desulfurized solid waste, which differs from Comparative Example 3 in that: step (3) includes the following steps: weigh 200g of desulfurized ash, 790g of desulfurized slag powder and 10g of pretreated waste incineration fly ash and put them into a mixer in sequence and mix for 30min to obtain a raw material mixture; the remaining steps and parameters are the same as those in Comparative Example 4.

[0064] Experimental Example

[0065] The compressive strength and water absorption of the circulating fluidized bed desulfurization solid waste artificial aggregates prepared in Examples 1-4 and Comparative Examples 1-7 were tested, and the results are shown in Table 1.

[0066] 1. Compressive strength test:

[0067] The mechanical properties of each aggregate were determined using a compressive strength tester, and the strength was calculated using the following formula (1), taking the average value of five experiments.

[0068]

[0069] Where σ is the compressive strength of a single aggregate particle, in MPa; P is the load applied when the aggregate breaks, in N; and d is the average particle size of the aggregate, in mm.

[0070] 2. Water absorption rate test:

[0071] According to ASTM C127 standard, the aggregate is soaked for 24 hours, weighed, and then dried; the water absorption rate is then calculated by the weight difference between the wet and dry aggregates.

[0072] The results of the compressive strength and water absorption tests are shown in Figure 1.

[0073] Table 1. Test results of compressive strength and water absorption of desulfurized ash-based artificial aggregate.

[0074]

[0075]

[0076] As shown in Table 1, the compressive strength and water absorption of the artificial aggregates in Examples 1-4 show that as the content of desulfurization slag increases and the content of desulfurization ash decreases, the compressive strength first increases and then decreases, while the water absorption first decreases and then increases. The compressive strength and water absorption reach their optimal values ​​under the conditions of 38% desulfurization ash content, 60% desulfurization slag content, and 2% waste incineration fly ash, with a compressive strength of 5.01 MPa and a water absorption of 9.98%.

[0077] Based on the compressive strength and water absorption of the artificial aggregates in Comparative Examples 4-6, it can be seen that, without mineralization curing, as the content of desulfurization slag increases and the content of desulfurization ash decreases, the compressive strength also shows a trend of first increasing and then decreasing, while the water absorption shows a trend of first decreasing and then increasing. The compressive strength and water absorption reach their optimal values ​​under the conditions of 38% desulfurization ash content, 60% desulfurization slag content, and 2% waste incineration fly ash, with a compressive strength of 2.04 MPa and a water absorption of 12.34%. That is, the compressive strength of the artificial aggregate prepared without mineralization oxidation is significantly lower than that of the artificial aggregate prepared in this invention.

[0078] Based on the compressive strength and water absorption of the artificial aggregates in Examples 1-4 and Comparative Examples 1-3, it can be seen that in the two-component system with only desulfurization ash, desulfurization slag, or waste incineration fly ash added, the compressive strength of the prepared artificial aggregates is all below 3.0 MPa, and the water absorption is all above 15%. This indicates that the abundant silica and alumina in the desulfurization ash and the abundant calcium oxide in the desulfurization slag form a synergistic compound system in the artificial aggregates of the examples. Under the synergistic effect of air curing and mineralization curing, the system achieves better mechanical properties. Meanwhile, the presence of sulfate and chloride ions in waste incineration fly ash promotes the hydration reaction of desulfurized solid waste, generating more hydration products. When the hydrated system is mineralized, the generated calcium carbonate can fill the voids in the hydration products, making the aggregate structure denser. This promotes the improvement of system strength and the reduction of water absorption. Without the addition of waste incineration fly ash, there will be far fewer hydration products under the same conditions. Although calcium carbonate can fill the aggregate to some extent, there are still many voids, resulting in lower aggregate strength and relatively higher water absorption.

[0079] In summary, the artificial aggregate prepared from desulfurization solid waste disclosed in this invention, along with its preparation method and application, enables the preparation of high-performance artificial aggregate for concrete using a formula based entirely on solid waste, achieving low-cost utilization of desulfurization ash and slag.

[0080] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent transformation fall within the scope of the present invention.

Claims

1. A method for preparing artificial aggregates using desulfurization solid waste, characterized in that, Includes the following steps: (1) The desulfurization residue is ball-milled to obtain desulfurization residue powder; (2) Low-temperature pyrolysis treatment of waste incineration fly ash to obtain pretreated waste incineration fly ash; (3) Mix the desulfurization ash, desulfurization slag powder and pretreated waste incineration fly ash to obtain a raw material mixture; (4) Add water to the raw material mixture and granulate it to obtain aggregate particles; (5) The aggregate particles are subjected to air curing and mineralization curing in sequence to obtain the final product; In step (3), the mass ratio of desulfurization ash, desulfurization slag powder and pretreated waste incineration fly ash is (5~95):(5~95):(1~10).

2. The method for preparing artificial aggregates using desulfurization solid waste as described in claim 1, characterized in that, In step (1), the particle size of the desulfurization ash powder is less than 300 μm.

3. The method for preparing artificial aggregates using desulfurization solid waste as described in claim 1, characterized in that, In step (2), the low-temperature pyrolysis temperature is 300~400℃ and the time is 15~25min.

4. The method for preparing artificial aggregates using desulfurization solid waste as described in claim 1, characterized in that, The mixing time in step (3) is 20~60 min.

5. The method for preparing artificial aggregates using desulfurization solid waste as described in claim 1, characterized in that, In step (4), the mass of water is 20-35% of the total mass of the raw material mixture.

6. The method for preparing artificial aggregates using desulfurization solid waste as described in claim 1, characterized in that, The air curing conditions in step (5) are: normal temperature and pressure, relative humidity of 50~70%RH and curing time of 3~7 days; the mineralization curing conditions are: normal pressure, temperature of 45~65℃, relative humidity of 70~90%RH, carbon dioxide volume concentration of 10~20% and curing time of 4~12h.

7. Artificial aggregate prepared by the method according to any one of claims 1 to 6.

8. The application of the artificial aggregate according to claim 7 in the preparation of building concrete.

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