Method for dechlorinating waste incineration fly ash and mineralizing carbon dioxide

Abstract

The invention provides a method for dechlorinating waste incineration fly ash and mineralizing carbon dioxide. The method provided by the invention comprises the following steps: S1, mixing the waste incineration fly ash with water, and carrying out first water washing treatment to obtain first water-washed fly ash; and S2, under the condition that gas containing carbon dioxide is introduced, mixing the first water washing fly ash obtained in the step S1 with water, and carrying out second water washing synergistic carbonization treatment to obtain a dechlorinated carbonization product. According to the method, the waste incineration fly ash serves as a mineralization material, CO2 in the industrial flue gas is absorbed and converted into stable carbonate minerals, meanwhile, deep removal of chlorine salt is achieved, and a new technical direction is provided for recycling of the waste incineration fly ash and carbon reduction of the industrial flue gas.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization, and in particular to a method for dechlorination and synergistic carbon dioxide mineralization of fly ash from waste incineration. Background Technology

[0002] Fly ash typically contains both soluble and insoluble chlorides. Soluble chlorides include NaCl, KCl, and CaClOH. During storage, fly ash can generate Friedel's salt (3CaO·Al₂O₃·CaCl₂·10H₂O), an insoluble chloride. The harmfulness of soluble chloride lies in the severe corrosion of reinforcing steel caused directly by chloride ions in the pore solution. The danger of insoluble Friedel's salt lies in its potential interconversion with ettringite, a characteristic product of cement hydration, under certain conditions when fly ash is used in cement-based materials. When calcium and sulfate ions are present simultaneously, Friedel's salt decomposes into ettringite, releasing chloride ions into the pore solution, which can easily lead to steel corrosion in the later stages of strength development. Therefore, the removal of both soluble and insoluble chlorides during the harmless treatment of fly ash from waste incineration is one of the significant obstacles to the resource utilization of fly ash in building materials.

[0003] Current research proposes two methods for dechlorination of waste incineration fly ash: water washing and acid washing. Water washing can remove most soluble chloride salts. The removal rate of soluble chloride salts typically depends on the chloride content in the fly ash and the operating parameters during the washing process (such as liquid-to-solid ratio, washing frequency, washing time, and agitation speed). Water washing achieves a soluble chloride removal rate between 40% and 90%. The presence of Friedel's salts is a key factor preventing the complete removal of chloride from waste incineration fly ash. A weakly acidic environment may promote the decomposition of insoluble chloride salts, causing insoluble chloride bound by strong covalent bonds to convert into soluble chloride and release it into the liquid phase. Acid washing requires the use of acidic agents, increasing the desalination pressure of the washing solution. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this application provides a method for dechlorination and synergistic carbon dioxide mineralization of waste incineration fly ash. The method provided in this application can effectively improve the resource utilization rate of waste incineration fly ash and solve the problem of removing insoluble chlorine from waste incineration fly ash.

[0005] In a first aspect, this application provides a method for dechlorination and synergistic carbon dioxide mineralization of waste incineration fly ash, which includes the following steps:

[0006] S1: Mix the fly ash from waste incineration with water and perform a first water washing treatment to obtain the first water-washed fly ash;

[0007] S2: Under the condition of introducing a gas containing carbon dioxide, the first water-washed fly ash from step S1 is mixed with water and subjected to a second water-washed synergistic carbonization treatment to obtain dechlorination carbonization products.

[0008] Waste incineration fly ash contains approximately 40% calcium oxide, making it a solid waste with excellent carbon mineralization potential. The method provided in this application uses waste incineration fly ash as raw material. First, the fly ash is washed with water to remove soluble chloride salts. After dehydration, a second water wash is performed while simultaneously introducing carbon dioxide gas (preferably industrial flue gas). During the fly ash washing process, the introduction of industrial flue gas allows the calcium-containing components in the fly ash to absorb CO2 from the flue gas and convert it into stable carbonate minerals in the liquid phase. Simultaneously, CO2 reduces the alkalinity of the fly ash washing solution, enabling the dissolution of the sparingly soluble mineral phase Friedel salt without the addition of additional reagents, thus achieving the carbonization and dechlorination of Friedel salt. The method provided in this application releases sparingly soluble chlorine into the solution, improving the chlorine removal efficiency of the fly ash solid phase and reducing the number of water washes. This provides a new technical direction for fly ash pretreatment and resource utilization, as well as for carbon reduction in industrial flue gas.

[0009] In some embodiments, the method further includes the following steps:

[0010] S3: The dechlorination and carbonization products of step S2 are subjected to pyrolysis to obtain dechlorination and carbon-fixed fly ash.

[0011] In some embodiments, the chlorine content in the waste incineration fly ash is 15wt%-30wt%, for example, 17wt%, 19wt%, 20wt%, 23wt%, 25wt%, 27wt%, 29wt%, or any value between them.

[0012] In some embodiments, the chlorine content in the first water-washed fly ash is 3 wt% to 15 wt%, for example, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or any value between them. In some embodiments, the chlorine content in the first water-washed fly ash is 3.5 wt% to 10 wt%.

[0013] In some embodiments, the first water washing treatment is performed 1-3 times, preferably once. This application prioritizes removing most of the soluble chloride salts through a first-stage water washing, and then synchronizes the carbonization process with the second-stage water washing to improve the solubility of the sparingly soluble chloride salts. This can reduce the number of water washings, save water consumption, and reduce carbon emissions while improving the chloride removal efficiency of the fly ash solid phase.

[0014] In some embodiments, the chlorine content in the dechlorination carbonization product is less than or equal to 1 wt%, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, or 0.9 wt%. In some embodiments, the chlorine content in the dechlorination carbonization product is less than or equal to 0.5 wt%.

[0015] In some embodiments, in step S1, the liquid-to-solid ratio of the first water washing treatment is 1:1 to 20:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, or any value between them. In some embodiments, the liquid-to-solid ratio of the first water washing treatment is 2:1 to 10:1. In some embodiments, the liquid-to-solid ratio of the first water washing treatment is 3:1 to 5:1.

[0016] In some embodiments, the temperature of the first water washing treatment in step S1 is 10°C-50°C, for example, 20°C, 25°C, 30°C, 35°C, 40°C, or 45°C. In some embodiments, the temperature of the first water washing treatment is 20°C-30°C. In some embodiments, the temperature of the first water washing treatment is room temperature.

[0017] In some embodiments, in step S1, the first water washing process is carried out under stirring conditions, wherein the stirring speed is 100r / min-500r / min, for example, 150r / min, 200r / min, 250r / min, 300r / min, 330r / min, 350r / min, 370r / min, 400r / min, 430r / min, 450r / min or 470r / min.

[0018] In some embodiments, in step S2, the liquid-to-solid ratio of the second water-washing synergistic carbonization treatment is 1:1-20:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, or any value between them. In some embodiments, the liquid-to-solid ratio of the second water-washing synergistic carbonization treatment is 2:1-10:1. In some embodiments, the liquid-to-solid ratio of the second water-washing synergistic carbonization treatment is 3:1-5:11.

[0019] In some embodiments, in step S2, the temperature of the second water washing co-carbonization treatment is 10°C-70°C, for example, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, or 65°C. In some embodiments, the temperature of the second water washing co-carbonization treatment is 20°C-30°C. In some embodiments, the temperature of the second water washing co-carbonization treatment is room temperature.

[0020] In some embodiments, the time for the second water washing and co-carbonization treatment in step S2 is 10 min to 150 min, for example, 15 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 100 min, 120 min, 130 min, 140 min, or any value between them. In some embodiments, the time for the second water washing and co-carbonization treatment is 40 min to 80 min.

[0021] In some embodiments, in step S2, the second water washing and co-carbonization treatment is carried out under stirring conditions, with the stirring speed being 100 r / min-500 r / min, for example, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 330 r / min, 350 r / min, 370 r / min, 400 r / min, 430 r / min, 450 r / min, or 470 r / min. In some embodiments, the stirring speed is 350 r / min-450 r / min.

[0022] In some embodiments, in step S2, the volume content of carbon dioxide gas in the carbon dioxide-containing gas is 10%-100%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 80%, 90%, or any value between them. In some embodiments, the volume content of carbon dioxide gas is 15%-50%.

[0023] In some embodiments, in step S2, based on the first water-washed fly ash per gram, the flow rate of the carbon dioxide-containing gas is 0.005 L / min to 0.5 L / min, for example, 0.007 L / min, 0.01 L / min, 0.013 L / min, 0.015 L / min, 0.017 L / min, 0.02 L / min, 0.023 L / min, 0.025 L / min, 0.027 L / min, 0.03 L / min, 0.033 L / min, 0.035 L / min, 0.037 L / min, 0.04 L / min, 0.043 L / min, 0.045 L / min, 0.047 L / min, 0.05 L / min, 0.055 L / min, 0.057 L / min, 0.06 L / min, or 0.065 L / m³. The following speeds are specified: 0.07 L / min, 0.075 L / min, 0.08 L / min, 0.085 L / min, 0.09 L / min, 0.095 L / min, 0.1 L / min, 0.105 L / min, 0.11 L / min, 0.115 L / min, 0.12 L / min, 0.125 L / min, 0.13 L / min, 0.135 L / min, 0.14 L / min, 0.145 L / min, 0.15 L / min, 0.155 L / min, 0.15 L / min, 0.17 L / min, 0.2 L / min, 0.23 L / min, 0.25 L / min, 0.27 L / min, 0.3 L / min, 0.35 L / min, 0.4 L / min, 0.45 L / min, or any value between them. In some embodiments, in step S2, the flow rate of the carbon dioxide-containing gas is 10 L / min to 30 L / min based on the first water-washed fly ash per gram.

[0024] In some embodiments, in step S2, the carbon dioxide-containing gas is selected from one or more industrial flue gases, preferably from one or more of steel industry flue gases, waste incineration flue gases, and coal-fired power plant flue gases.

[0025] In some embodiments, the pyrolysis temperature in step S3 is 300°C-500°C, for example, 350°C, 400°C, or 450°C. In some embodiments, the pyrolysis temperature is 300°C-400°C.

[0026] In some embodiments, the pyrolysis treatment time in step S3 is 0.5h-10h, for example, 2h, 3h, 4h, 5h, 6h, 7h, 8h, or 9h. In some embodiments, the pyrolysis treatment time is 1h-5h.

[0027] In some embodiments, in step S3, the dioxin concentration in the dechlorinated and carbon-fixed fly ash is less than or equal to 20 ng-TEQ / Nm³. 3 .

[0028] In some embodiments, the dechlorination and carbon dioxide mineralization method for waste incineration fly ash provided in this application includes the following specific steps:

[0029] A1: Mix the fly ash from waste incineration with water to remove most of the soluble chloride salts, and then filter to obtain solid-phase primary water-washed fly ash.

[0030] A2: The primary water-washed fly ash is mixed with water and simultaneously introduced into industrial flue gas. After deep dechlorination and simultaneous carbonization, the solid phase obtained after filtration is the secondary water-washed fly ash.

[0031] A3: Heat treatment of secondary water-washed fly ash yields deeply dechlorinated, carbon-fixed, and detoxified fly ash, which can be used in the preparation of building materials.

[0032] Secondly, this application provides a dechlorinated and carbon-fixed fly ash prepared according to the method described in the first aspect.

[0033] In some embodiments, the chlorine content in the dechlorinated and carbon-fixed fly ash is less than or equal to 1%, preferably less than or equal to 0.5%.

[0034] Thirdly, this application provides the application of the dechlorinated and carbon-fixed fly ash described in the second aspect in building materials. It can be applied in [the context of the application].

[0035] In some embodiments, the building material is selected from one or more of the following: roadbed material, filling material, cement kiln co-processing material, and admixture.

[0036] Compared to existing technologies, the beneficial effects of this application are:

[0037] 1. This application uses fly ash from waste incineration as raw material. In the liquid phase, the calcium-containing components in the fly ash absorb CO2 from biomass flue gas and convert it into stable carbonate minerals. At the same time, it achieves the carbonization and dechlorination of Friedel salt, releasing sparingly soluble chlorine into the solution, thereby further reducing the chlorine content of the fly ash residue. This provides a new technical direction for the pretreatment and resource utilization of fly ash and the reduction of carbon in biomass flue gas.

[0038] 2. The method provided in this application can improve the chlorine removal efficiency of fly ash solid phase, reduce the number of water washing cycles, improve the resource utilization rate of fly ash, save water consumption and reduce carbon emissions.

[0039] 3. The method provided in this application introduces carbon dioxide gas under different conditions after removing most of the soluble chloride salts. This not only mineralizes the carbon dioxide in the flue gas but also reduces the alkalinity of the solution, allowing chloride salts existing in the form of sparingly soluble mineral phases to decompose without the need for additional reagents. This improves the chloride removal efficiency of the fly ash solid phase and reduces the number of water washing cycles. This is of great significance for improving the resource utilization rate of fly ash, conserving water resources, and reducing carbon emissions. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application in any way.

[0041] In the examples and comparative examples, the water used for washing was deionized water, the chlorine content was detected using XRF (X-ray fluorescence spectrometry), and the calcium carbonate content was detected using thermogravimetric analysis (TG); the simulated flue gas was a mixture of carbon dioxide and compressed air.

[0042] Example

[0043] The fly ash 1 is fly ash from a waste incineration power plant in Liaoning Province, with a total chlorine content of 28.86 wt%.

[0044] (1) First water washing treatment

[0045] Fly ash 1 was subjected to a first water washing treatment under stirring conditions to obtain first water-washed fly ash 1 and second water-washed fly ash 2. The liquid-solid ratio, number of water washings, water washing temperature, stirring speed, and total chlorine content in the water-washed fly ash after drying are detailed in Table 1.

[0046] Table 1

[0047]

[0048] (2) Second water washing and carbonization treatment

[0049] The first water-washed fly ash 1 after step (1) is mixed with water, and simulated flue gas is introduced at the same time. Under stirring conditions, deep water washing and dechlorination synergistic carbonization treatment is carried out to obtain dechlorinated carbonized fly ash.

[0050] The temperature, carbon dioxide volume content, gas flow rate, carbonization time, and stirring speed of the simulated flue gas carbonization are detailed in Table 2 below.

[0051] Table 2

[0052]

[0053]

[0054] Based on the comparison in Table 2 above, and considering the comprehensive water consumption and carbonization stirring time, the optimal conditions for simultaneous dechlorination carbonization reaction are: liquid-to-solid ratio of 3:1, room temperature, 30% carbon dioxide concentration, gas flow rate of 0.02 L / min / g, carbonization time of 60 min, and rotation speed of 400 r / min.

[0055] (3) Pyrolysis treatment

[0056] After centrifuging and dehydrating the dechlorinated carbonized fly ash obtained in Example 1 in step (2), it was kept at 300℃~400℃ for 5h, and the dioxin content and calcium carbonate loss were measured. As can be seen from the results in Table 3, pyrolysis has a relatively obvious effect on the removal of dioxins, and there is no significant loss of calcium carbonate at the temperature of 300℃-400℃.

[0057] Table 3

[0058]

[0059] Comparative Example 1

[0060] The fly ash 1 is fly ash from a waste incineration power plant in Liaoning Province, with a total chlorine content of 28.86 wt%.

[0061] Fly ash 1 was mixed with water under stirring conditions, and simulated flue gas was introduced at the same time to carry out the first water washing treatment for dechlorination and co-carbonization treatment, so as to obtain dechlorinated water-washed fly ash.

[0062] The parameters for water washing and carbonization, as well as the total chlorine content in the dechlorinated fly ash measured after drying, are detailed in Table 4.

[0063] Table 4

[0064]

[0065] As can be seen from the data in Table 4, during the first wash, due to the high concentration of calcium ions in the washing solution, carbon dioxide preferentially combines with calcium to form calcium carbonate, and its effect on removing sparingly soluble chlorine is not significant.

[0066] Comparative Example 2

[0067] The fly ash 1 is fly ash from a waste incineration power plant in Liaoning Province, with a total chlorine content of 28.86 wt%.

[0068] (1) First water washing treatment

[0069] Fly ash 1 was subjected to a first water washing treatment under stirring conditions to obtain first water-washed fly ash 1. The liquid-solid ratio, number of water washings, water washing temperature, stirring speed, and total chlorine content and calcium carbonate content of the water-washed fly ash after drying are detailed in Table 5.

[0070] (2) Second water washing treatment

[0071] The first water-washed fly ash 1 after step (1) is mixed with water, and a second water-washing treatment is carried out under stirring conditions to obtain dechlorinated fly ash.

[0072] The liquid-solid ratio, number of washes, washing temperature, stirring speed, and total chlorine content and calcium carbonate in the dechlorinated fly ash measured after drying in the second water washing treatment are detailed in Table 5.

[0073] Table 5

[0074]

[0075] The data in Table 5 show that if only two water washes are used, the chlorine content is difficult to be reduced to below 1 wt%, indicating that simple water washing is less effective at removing sparingly soluble chloride salts than carbonized water washing.

Claims

1. A method for dechlorination and synergistic carbon dioxide mineralization of waste incineration fly ash, comprising the following steps: S1: Mix the fly ash from waste incineration with water and perform a first water washing treatment to obtain the first water-washed fly ash; S2: Under the condition of introducing a gas containing carbon dioxide, the first water-washed fly ash from step S1 is mixed with water and subjected to a second water-washed synergistic carbonization treatment to obtain dechlorination carbonization products.

2. The method according to claim 1, characterized in that, It also includes the following steps: S3: The dechlorination and carbonization products of step S2 are subjected to pyrolysis to obtain dechlorination and carbon-fixed fly ash.

3. The method according to claim 1 or 2, characterized in that, The chlorine content in the fly ash from the waste incineration is 15wt%-30wt%; and / or The chlorine content in the first water-washed fly ash is 3wt%-15wt%, preferably 3.5wt%-10wt%; and / or The chlorine content in the dechlorination carbonization product is less than or equal to 1 wt%, preferably less than or equal to 0.5 wt%.

4. The method according to any one of claims 1-3, characterized in that, In step S1, the liquid-to-solid ratio of the first water washing treatment is 1:1-20:1, preferably 2:1-10:1, more preferably 3:1-5:1; and / or The temperature of the first water washing treatment is 10℃-50℃, preferably 20℃-30℃; and / or The first water washing treatment is carried out under stirring conditions, wherein the stirring speed is 100 r / min-500 r / min; and / or The first water washing process is performed 1-3 times, preferably 1 time.

5. The method according to any one of claims 1-4, characterized in that, In step S2, the liquid-solid ratio of the second water washing and co-carbonization treatment is 1:1-20:1, preferably 2:1-10:1, more preferably 3:1-5:11; and / or The temperature for the second water washing and co-carbonization treatment is 10℃-70℃, preferably 20℃-30℃; and / or The second water washing and co-carbonization treatment time is 10 min-150 min, preferably 40 min-80 min; and / or The second water washing and co-carbonization treatment is carried out under stirring conditions, with a stirring speed of 100 r / min-500 r / min, preferably 350 r / min-450 r / min.

6. The method according to any one of claims 1-5, characterized in that, In step S2, the volume content of carbon dioxide gas in the carbon dioxide-containing gas is 10%-100%, preferably 15%-50%; and / or Based on the first water-washed fly ash per gram, the flow rate of the carbon dioxide-containing gas is 0.005 L / min to 0.50 L / min, preferably 0.010 L / min to 0.3 L / min.

7. The method according to any one of claims 1-6, characterized in that, In step S2, the carbon dioxide-containing gas is selected from one or more industrial flue gases, preferably from one or more of the following: iron and steel industry flue gas, waste incineration flue gas, and coal-fired power plant flue gas.

8. The method according to any one of claims 2-7, characterized in that, In step S3, the pyrolysis temperature is 300℃-500℃, preferably 300℃-400℃; and / or The pyrolysis treatment time is 0.5h-10h, preferably 1h-5h; and / or The dioxin concentration in dechlorination and carbon fixation fly ash is less than or equal to 20 ng-TEQ / Nm³. 3 .

9. A dechlorinated and carbon-fixing fly ash prepared by the method according to any one of claims 1-8, preferably, the chlorine content in the dechlorinated and carbon-fixing fly ash is less than or equal to 1 wt%, more preferably less than or equal to 0.5 wt%.

10. The application of dechlorinated and carbon-fixed fly ash according to claim 9 in building materials.

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