Artificial aggregate prepared from desulfurized solid waste as well as preparation method and application of artificial aggregate

Abstract

The invention discloses an artificial aggregate prepared from desulfurized solid waste as well as a preparation method and application of the artificial aggregate, and belongs to the technical field of solid waste resource utilization. The preparation method comprises the following steps: carrying out ball milling treatment on the desulfurization slag to obtain desulfurization slag powder; the waste incineration fly ash is subjected to low-temperature pyrolysis treatment, and pretreated waste incineration fly ash is obtained; mixing the desulfurized fly ash, the desulfurized slag powder and the pretreated waste incineration fly ash to obtain a raw material mixture; adding water into the raw material mixture, and pelletizing to obtain aggregate particles; the aggregate particles are subjected to air curing and mineralization curing in sequence, and the composite material is obtained. The invention further discloses the artificial aggregate prepared by the method and application of the artificial aggregate. The artificial aggregate prepared from the desulfurized solid waste is high in compressive strength and stable in ion sealing, can solve the problems that existing coal ash-based aggregate is low in strength and high in dependency on additives, and is wide in application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization, and specifically relates to an artificial aggregate prepared by utilizing desulfurized solid waste, and a preparation method and application thereof. Background Art

[0002] As my country pays more and more attention to the management of industrial solid waste, power plants, which are large solid waste emitters, produce a large amount of solid waste such as coal ash and coal slag during the combustion and power generation process. Directly using the method of stacking and landfilling will cause serious damage to the surrounding ecological environment.

[0003] According to the differences in combustion process and combustion object, fly ash, coal slag, desulfurized coal ash, desulfurized coal slag and waste incineration fly ash will be produced during the combustion process. Since the fly ash and coal slag produced by conventional coal-fired power plants are a kind of sintered volcanic ash material, the main component is aluminosilicate glass, which has been used in building materials industries such as concrete and cement. However, desulfurized coal ash / coal slag is a by-product obtained from the flue gas desulfurization process of circulating fluidized bed, which usually contains a high calcium content. Direct application in concrete and cement will cause the material to expand, crack or alkali return, which will lead to its stability and durability. At the same time, waste incineration fly ash not only has a higher calcium content, but also contains a large amount of components such as chlorides and sulfates, which are more harmful to concrete. Therefore, no research has reported 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 curing them with flue gas CO2, it is not only possible to realize the resource utilization of industrial solid wastes and solve the problem of aggregate cracking caused by high calcium content in solid wastes, but also to achieve the mineralization and storage of CO2 in flue gas and solve the problem of CO2 emissions from power plants. However, the existing technology for preparing artificial aggregates is generally low in strength, and often requires the addition of cement or quicklime to increase the strength of the aggregates, which increases the production cost of artificial aggregates and makes the economic benefits of this technology low.

[0005] Therefore, it is particularly important to develop a low-cost artificial aggregate without cement / quicklime and other additives for solid wastes such as desulfurized coal ash, desulfurized coal cinder and waste incineration fly ash, and make full use of the high calcium content in this type of solid waste, which is particularly important for solid waste management in circulating fluidized bed coal-fired power plants and waste power plants. Summary of the invention

[0006] The problem to be solved by the present invention is to provide an artificial aggregate prepared by using desulfurized solid waste and a preparation method and application thereof, so as to solve the problems of low strength and high dependence on external additives of existing coal ash-based aggregates.

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

[0008] (1) ball milling the desulfurized slag to obtain desulfurized slag powder;

[0009] (2) performing low-temperature pyrolysis treatment on the waste incineration fly ash to obtain pretreated waste incineration fly ash;

[0010] (3) mixing desulfurized ash, desulfurized slag powder and pre-treated waste incineration fly ash to obtain a raw material mixture;

[0011] (4) adding water to the raw material mixture and pelletizing to obtain aggregate particles;

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

[0013] The beneficial effects of the technical scheme adopted in the present invention are as follows: in the present invention, desulfurization ash, desulfurization slag and waste incineration fly ash are used to prepare artificial aggregates, wherein the introduction of desulfurization slag and waste incineration fly ash can significantly increase the calcium content in the system, and they react with CO2 in the flue gas during air curing and mineralization curing to generate hydrated calcium silicate and calcium carbonate, and calcium carbonate can fill the voids in the hydrated calcium silicate to form a denser microstructure. At the same time, the waste incineration fly ash added in the present invention has a certain content of chloride and sulfate. The introduction of chloride ions can react chemically with solid waste under alkaline excitation conditions, and part of them are adsorbed on the hydration product or pore wall. At the same time, chloride salt combinations with very small ion solubility product can be generated, which can promote the hydration process of the system; by controlling its content, sulfate is reacted with a part of calcium hydroxide generated by air curing and mineralization curing to generate calcium sulfate, and calcium sulfate further fills the micropores and capillaries in the aggregate particles to enhance the density of the aggregate; the chloride salt has a coagulant effect on the system and can improve the early strength of the material; in addition, the present invention can make the chloride salt structure more compact through the form of mineralization curing aggregate, which has a better effect on the stable sealing of chloride ions.

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

[0015] The beneficial effects of the above technical solution adopted in the present invention are as follows: the circulating fluidized bed adopts in-furnace desulfurization, that is, limestone is added into the belt combustion furnace in the form of raw material, first the limestone is decomposed into calcium oxide at high temperature in the furnace, and then the calcium oxide reacts with sulfur oxide to generate calcium sulfate. In order to ensure sufficient desulfurization, the limestone input is excessive, so the desulfurized solid waste obtained 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 the present invention are greatly different from the coal ash and coal 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 the present invention, thereby making the aggregate have a denser structure.

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

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

[0018] Preferably, in step (3), the mass ratio of desulfurized ash, desulfurized 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 to 35% of the total mass of the raw material mixture.

[0020] More preferably, the mass of water in step (4) 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°C, relative humidity of 70-90% RH, carbon dioxide volume concentration of 10-20% and curing time of 4-12 hours.

[0022] The invention also provides artificial aggregate prepared by the method.

[0023] The invention also provides application of the artificial aggregate in preparing building concrete.

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

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

[0026] (2) By adding a small amount of waste incineration fly ash, the artificial aggregate of the present invention 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 to achieve 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 of ≥4.0 MPa, a water absorption rate of ≤15.0% and is not easy to crack. It is suitable for road construction concrete materials and industrial building concrete materials, has a wide range of applications and huge application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Flow chart for preparing artificial aggregate using desulfurized solid waste. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments.

[0030] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0031] The features and performance of the present invention are further described in detail below in conjunction with embodiments.

[0032] Example 1

[0033] A method for preparing artificial aggregate using desulfurized solid waste comprises the following steps:

[0034] (1) ball milling the desulfurized slag until the particle size is less than 300 μm to obtain desulfurized slag powder;

[0035] (2) subjecting the waste incineration fly ash to low-temperature pyrolysis treatment at 300° C. for 15 minutes to obtain pretreated waste incineration fly ash;

[0036] (3) Weighing 760 g of desulfurized ash, 200 g of desulfurized slag powder and 40 g of pre-treated waste incineration fly ash, and sequentially putting them into a mixer and mixing for 30 min to obtain a raw material mixture;

[0037] (4) transferring the raw material mixture to a granulator, and preparing 300 g of water into a water mist and spraying it onto the surface of the raw material mixture to form a ball, thereby obtaining aggregate particles;

[0038] (5) The aggregate particles are placed in a closed air curing room at room temperature, pressure and relative humidity of 70% RH for air curing for 3 days. After being taken out, they are placed in a mineralization reactor and the temperature of the mineralization reactor is set to 60°C and the relative humidity is set to 80% RH. Then, flue gas CO2 with a volume concentration of 15% is introduced 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: weighing 570g of desulfurized ash, 400g of desulfurized slag powder and 30g of pretreated waste incineration fly ash, sequentially putting them into a mixer and mixing for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as those 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: weighing 380g of desulfurized ash, 600g of desulfurized slag powder and 20g of pretreated waste incineration fly ash, sequentially putting them into a mixer and mixing for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as those 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: weighing 200g of desulfurized ash, 790g of desulfurized slag powder and 10g of pretreated waste incineration fly ash, and sequentially putting them into a mixer and mixing for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as those 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 not performed, and step (3) includes the following steps: 900 g of desulfurized ash and 100 g of pretreated waste incineration fly ash are weighed and put into a mixer in sequence and mixed for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as those in Example 1.

[0047] Comparative Example 2

[0048] A method for preparing artificial aggregate using desulfurized solid waste, which differs from Example 1 in that step (1) is not performed, and step (3) includes the following steps: 980 g of desulfurized slag and 20 g of pretreated waste incineration fly ash are weighed and put into a mixer in sequence and mixed for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as those in Example 1.

[0049] Comparative Example 3

[0050] A method for preparing artificial aggregate using desulfurized solid waste, which differs from Example 1 in that step (1) is not performed, and step (3) includes the following steps: 400 g of desulfurized ash and 600 g of desulfurized slag are weighed and put into a mixer in sequence and mixed for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as those in Example 1.

[0051] Comparative Example 4

[0052] A method for preparing artificial aggregate using desulfurized solid waste comprises the following steps:

[0053] (1) ball milling the desulfurized slag until the particle size is less than 300 μm to obtain desulfurized slag powder;

[0054] (2) subjecting the waste incineration fly ash to low-temperature pyrolysis treatment at 300° C. for 15 minutes to obtain pretreated waste incineration fly ash;

[0055] (3) Weighing 760 g of desulfurized ash, 200 g of desulfurized slag powder and 40 g of pre-treated waste incineration fly ash, and sequentially putting them into a mixer and mixing for 30 min to obtain a raw material mixture;

[0056] (4) transferring the raw material mixture to a granulator, and preparing 300 g of water into a water mist and spraying it onto the surface of the raw material mixture to form a ball, thereby obtaining aggregate particles;

[0057] (5) The aggregate particles are placed in a closed air curing room at normal temperature, pressure and relative humidity of 70% RH for air curing for 3 days.

[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) comprises the following steps: weighing 570 g of desulfurized ash, 400 g of desulfurized slag powder and 30 g of pretreated waste incineration fly ash, sequentially putting them into a mixer and mixing for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as those of 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) comprises the following steps: weighing 380 g of desulfurized ash, 600 g of desulfurized slag powder and 20 g of pretreated waste incineration fly ash, sequentially putting them into a mixer and mixing for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as those of 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) comprises the following steps: weighing 200 g of desulfurized ash, 790 g of desulfurized slag powder and 10 g of pretreated waste incineration fly ash, sequentially putting them into a mixer and mixing for 30 minutes to obtain a raw material mixture; the remaining steps and parameters are the same as those of Comparative Example 4.

[0064] Experimental example

[0065] The compressive strength and water absorption rate of the circulating fluidized bed desulfurization solid waste artificial aggregate prepared in Examples 1 to 4 and Comparative Examples 1 to 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 tests.

[0068]

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

[0070] 2. Water absorption test:

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

[0072] The compressive strength and water absorption test results 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, it can be seen from the compressive strength and water absorption of the artificial aggregates of Examples 1 to 4 that, with the increase of the desulfurization slag content and the decrease of the desulfurization ash content in the artificial aggregate, the compressive strength shows a trend of first increasing and then decreasing, and the water absorption shows a trend of first decreasing and then increasing. Under the conditions of a desulfurization ash content of 38%, a desulfurization slag content of 60%, and a waste incineration fly ash content of 2%, the compressive strength and water absorption reach the optimum, with a compressive strength of 5.01 MPa and a water absorption of 9.98%.

[0077] Combined with the compressive strength and water absorption of the artificial aggregates of Comparative Examples 4 to 6, it can be seen that under the condition of no mineralization curing, with the increase of the desulfurization slag content and the decrease of the desulfurization ash content, the compressive strength also shows a trend of first increasing and then decreasing, and the water absorption rate shows a trend of first decreasing and then increasing. Under the conditions of desulfurization ash content of 38%, desulfurization slag content of 60%, and waste incineration fly ash of 2%, the compressive strength and water absorption rate reach the optimal level, with a compressive strength of 2.04 MPa and a water absorption rate 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 by the present invention.

[0078] Combining the compressive strength and water absorption of the artificial aggregates of Examples 1 to 4 and Comparative Examples 1 to 3, it can be seen that in the two-component system where only desulfurization ash or desulfurization slag or waste incineration fly ash is added, the compressive strength of the prepared artificial aggregates is lower than 3.0 MPa, and the water absorption rate is higher than 15%, indicating that the more silicon oxide and aluminum oxide in the desulfurization ash and the more calcium oxide in the desulfurization slag in the artificial aggregate of the embodiment form a synergistic compound system, and under the synergistic effect of air curing and mineralization curing, the system achieves better mechanical properties. At the same time, since waste incineration fly ash contains sulfate ions and chloride ions, it can promote the hydration reaction of desulfurized solid waste and generate 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, which will promote the improvement of system strength and reduce water absorption. When waste incineration fly ash is not added, the hydration products will be much less under the same conditions. Although calcium carbonate can fill aggregates to a certain extent, there are still many voids, resulting in lower strength of aggregates and relatively high water absorption.

[0079] In summary, the artificial aggregate prepared using desulfurized solid waste and its preparation method and application disclosed in the present invention can adopt a full solid waste formula to prepare artificial aggregate with excellent performance for the preparation of concrete, and can achieve low-cost utilization of desulfurized ash and desulfurized 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 form. Any technical solutions obtained by equivalent replacement or equivalent transformation shall fall within the scope of the present invention.

Claims

1. A method for preparing artificial aggregate using desulfurized solid waste, characterized in that: The following steps are involved: (1) ball milling the desulfurized slag to obtain desulfurized slag powder; (2) performing low-temperature pyrolysis treatment on the waste incineration fly ash to obtain pretreated waste incineration fly ash; (3) mixing desulfurized ash, desulfurized slag powder and pre-treated waste incineration fly ash to obtain a raw material mixture; (4) adding water to the raw material mixture and pelletizing to obtain aggregate particles; (5) The aggregate particles are subjected to air curing and mineralization curing in sequence to obtain the product.

2. The method for preparing artificial aggregate using desulfurized solid waste according to claim 1, characterized in that: In the step (1), the particle size of the desulfurized ash powder is less than 300 μm.

3. The method for preparing artificial aggregate using desulfurized solid waste according to claim 1, characterized in that: In the step (2), the low-temperature pyrolysis temperature is 300-400° C. and the time is 15-25 minutes.

4. The method for preparing artificial aggregate using desulfurized solid waste according to claim 1, characterized in that: In the step (3), the mass ratio of desulfurized ash, desulfurized slag powder and pre-treated waste incineration fly ash is (5-95):(5-95):(1-10); and the mixing time is 20-60 min.

5. The method for preparing artificial aggregate using desulfurized solid waste according to claim 1 or 4, characterized in that: The mass of water in step (4) is 20-35% of the total mass of the raw material mixture.

6. The method for preparing artificial aggregate using desulfurized solid waste according to 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°C, relative humidity of 70-90% RH, carbon dioxide volume concentration of 10-20% and curing time of 4-12 hours.

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

8. Use of the artificial aggregate according to claim 7 in preparing building concrete.

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