A method for stabilizing waste incineration fly ash based on biological agents

Abstract

This invention discloses a method for stabilizing waste incineration fly ash based on biological agents. The method includes grinding and sieving black soybean seeds to obtain black soybean powder; adding water to the black soybean powder to obtain a soybean powder solution; stirring the soybean powder solution, allowing it to stand, filtering to obtain a suspension; centrifuging the suspension using a centrifuge; using the supernatant of the centrifuged liquid as a soybean urease solution; adding urea to the qualified soybean urease solution to prepare a soybean urea mixed solution; uniformly mixing the soybean urea mixed solution and waste incineration fly ash using a mixer; covering the resulting mixed fly ash with a film and curing it in a room temperature and humid environment for a certain period of time to finally obtain stable waste incineration fly ash. This invention's method has good stabilizing effects on multiple heavy metals in fly ash, and has advantages such as high efficiency, simple process, low cost, and environmental friendliness, which is of significant importance for the resource utilization of municipal solid waste incineration fly ash.

Description

Technical Field

[0001] This invention belongs to the field of waste incineration fly ash treatment technology, and particularly relates to a method for treating stable waste incineration fly ash based on biological agents. Background Technology

[0002] In recent years, the proportion of municipal solid waste incineration in my country has increased significantly. Fly ash, a byproduct collected in the flue gas purification system of incineration, contains relatively high levels of heavy metals such as Pb, Cr, and Cd, as well as organic pollutants such as dioxins. Therefore, it is classified as hazardous waste and must be disposed of in hazardous waste landfills or stabilized before being sent to sanitary landfills. Thus, the solidification and stabilization treatment of heavy metals in waste incineration fly ash is the practical basis for its safe disposal and resource utilization.

[0003] Currently, the most commonly used methods for stabilizing heavy metals in waste incineration fly ash have the following limitations: 1. Cement solidification method. Cement solidification technology is currently the most commonly used solidification / stabilization technology for fly ash both domestically and internationally. The solidification process is simple, but its disadvantages include high cement content, large volume increase ratio, easy cracking of the solidified body, and difficulty in ensuring the stabilization effect of pollutants; 2. High-temperature melting stabilization method. Under high-temperature conditions, toxic components of fly ash are fixed in the generated silicates, thereby achieving fly ash stabilization. The advantages are a large volume reduction rate and effective removal of heavy metals and other harmful substances from fly ash. The disadvantages are high energy consumption and high cost; 3. Chemical stabilization method. Chemical agents are used to transform toxic substances into substances with low solubility, low migration, and low toxicity. It has the advantages of low dosage and minimal volume increase of fly ash after treatment, but the treatment effect is limited, and it is difficult to find universally applicable chemical agents; 4. Microbial induced carbonate precipitation (MICP) technology. This involves the microbial metabolism of urea to produce carbon dioxide and then hydrolyzing it to generate CO3. 2- The fly ash reacts with cations such as calcium and heavy metals to form carbonates, which then encapsulate the fly ash particles, achieving solidification and stabilization. This technology effectively utilizes the calcium-rich nature of fly ash while avoiding the disadvantages of cement solidification and chemical stabilization. It has advantages such as low volumetric efficiency, low cost, and low pollution. However, because the biological activity of microorganisms is greatly affected by the chemical composition of fly ash and environmental conditions, the treatment effect is susceptible to many interfering factors, resulting in poor feasibility for engineering applications. The aforementioned methods for stabilizing heavy metal-affected soils all have certain shortcomings due to complex processes or significant influence from environmental conditions. A novel, environmentally friendly treatment method is currently lacking. Summary of the Invention

[0004] To address the problems existing in the background art, the present invention aims to provide a method for stabilizing waste incineration fly ash based on biological agents. The biological agent used in this method can efficiently stabilize various heavy metals in waste incineration fly ash through EICP action. After stabilization, the waste incineration fly ash can be disposed of in sanitary landfills or utilized as a resource.

[0005] The technical solution adopted in this invention includes the following steps:

[0006] Step S1: Dry the black beans at 20-40℃ for 6-8 hours, then grind them into powder using a universal grinder and pass them through a 100-150 mesh sieve to obtain black bean powder.

[0007] Step S2: Take an appropriate amount of black bean powder and add deionized water to the black bean powder according to the preset liquid-solid ratio to obtain a bean powder solution.

[0008] Step S3: Place the soybean powder solution obtained in step S2 into an electromagnetic stirrer and stir for 30-40 minutes. Then, let the soybean powder solution stand for 2-3 hours and filter the residue with gauze to obtain a suspension.

[0009] Step S4: Centrifuge the suspension obtained in step S3 for 15-20 minutes to obtain the centrifuged liquid;

[0010] Step S5: Take the supernatant of the centrifuged liquid as the soybean urease solution, and store the soybean urease solution in a refrigerator at 4-5℃ for later use.

[0011] Step S6: Use conductivity and pH meter to determine if the soybean urease solution is up to standard.

[0012] If the test result is qualified, proceed to step S7; if the test result is unqualified, repeat steps S1 to S6 until a qualified soybean urease solution is obtained, and then proceed to step S7.

[0013] Step S7: Add urea to the qualified soybean urease solution to obtain a soybean urea mixed solution;

[0014] Step S8: Use a mixer to evenly mix the soybean enzyme-urea mixed solution obtained in step S7 with the waste incineration fly ash raw material to obtain mixed fly ash;

[0015] Step S9: Cover the mixed fly ash from step S8 with a film and cure it in a normal temperature and humid environment for 5-7 days to finally obtain stable waste incineration fly ash.

[0016] In step S2, the liquid-to-solid ratio between deionized water and black bean powder is 5-10:1, and the concentration of the bean powder solution is 100g / L-200g / L.

[0017] In step S4, the temperature of the centrifuge is controlled at 4-5℃ and the rotation speed is 3000 r / min.

[0018] In step S6, the specific method for detecting whether the soybean urease solution is qualified is as follows:

[0019] The urease activity and pH value of the soybean urease solution were determined by conductivity method and pH meter, respectively. If the urease activity of the soybean urease solution was 12-23 mM urea / min and the pH value was 7.5-8.5, it indicated that the soybean urease solution was qualified and could proceed to step S7 to prepare the soybean enzyme-urea mixed solution.

[0020] Otherwise, it indicates that the soybean urease solution is unqualified. Then repeat steps S1 to S6 until a qualified soybean urease solution is obtained, which can be used to prepare a soybean enzyme-urea mixed solution.

[0021] In step S7, the concentration of urea is 0.8–1.3 mol / L.

[0022] In step S8, the liquid-solid ratio between the soybean enzyme-urea mixed solution and the waste incineration fly ash raw material is 0.2-0.3:1.

[0023] During the curing process in step S9, the EICP (Enzyme-Induced Calcium Carbonate Precipitation) technique is used to stabilize various heavy metals in the fly ash raw material from waste incineration.

[0024] The heavy metals in the fly ash raw material from waste incineration include, but are not limited to, Cd, Cr, Pb, Zn, Ni, and Cu.

[0025] During the EICP process, the source of calcium ions is endogenous calcium leached from fly ash from waste incineration.

[0026] This invention uses black bean urease solution as a biological agent. This biological agent can efficiently stabilize various heavy metals in waste incineration fly ash through EICP. The black bean urease solution is extracted from black bean seeds and has high plant urease activity. The urease contained in black bean seeds is separated and purified to obtain the bean enzyme solution. The bean enzyme solution and urea are added to the waste incineration fly ash, stirred evenly, and cured under normal temperature and humidity conditions for a certain period of time, thus stabilizing the various heavy metals in the fly ash.

[0027] The obtained soybean enzyme solution was tested. Urease activity: An equal amount of urea (1.11 mol / L) was added to an equal amount of black soybean urease with an equal concentration of urease. Since soybean enzyme can decompose urea to produce ammonium and carbonate ions, the conductivity of the solution changes. Therefore, the conductivity of the mixture was monitored in real time over two hours. The faster the rate of increase in conductivity and the greater the increase, the stronger the urease activity. The urease activity should be between 12-23 mM urea / min.

[0028] The heavy metal stability of waste incineration fly ash was tested using a heavy metal stabilization test: black bean urease solution and urea were added to the waste incineration fly ash raw material, stirred evenly, and cured at room temperature and with moisture for 7 days. The leaching toxicity of heavy metals was then tested.

[0029] Heavy metal tolerance test: In the heavy metal stabilization test, the EICP test results showed that the soybean enzyme could carry out EICP normally in the fly ash environment, producing carbonate precipitation and stabilizing heavy metals. The activity of soybean enzyme was not significantly limited by the toxicity of heavy metals and it could still carry out EICP activities effectively. Therefore, it was determined that soybean enzyme is tolerant to the environment of multiple metals in fly ash.

[0030] This invention involves extracting soybean enzyme from black beans, adding soybean enzyme solution and urea to incineration fly ash, and inducing urea decomposition through black bean urease, adsorbing calcium ions and heavy metal ions in the fly ash to form carbonate precipitates (EICP). Heavy metal stabilization is achieved through the carbonation of heavy metals and the encapsulation and cementation effect of calcium carbonate, thus achieving the effect of harmless treatment of fly ash. The leaching toxicity of the treated fly ash meets the requirements of the "Technical Specification for Pollution Control of Municipal Solid Waste Incineration Fly Ash (Trial)" (HJ1134-2022). This invention's method has good stabilization effects on multiple heavy metals in fly ash, and has advantages such as high efficiency, simple process, low cost, and environmental friendliness. Compared with microbial-induced carbonate precipitation, the EICP technology used in this invention has higher urease activity, better alkali resistance and heavy metal toxicity, requires no nutrient solution, is less affected by environmental factors, easily penetrates fine soil pores, has a more uniform stabilization effect, and avoids potential biological hazards from bacteria. It has significant implications for the resource utilization of municipal solid waste incineration fly ash.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. The present invention proposes a method and biological agent for stabilizing fly ash from waste incineration, which can effectively reduce the leaching concentration of heavy metals in fly ash and has a good stabilizing effect on multiple heavy metals in fly ash.

[0033] 2. Compared with existing cement solidification and chemical stabilization methods, the method of this invention has the advantages of being low-carbon and environmentally friendly; compared with microbial-induced calcium carbonate precipitation technology, it has higher urease activity; it has good alkali resistance and heavy metal toxicity resistance; it does not require the provision of nutrient solution; urease can easily penetrate the pores of fine-grained soil, resulting in a more uniform stabilization effect; the stabilization process is less affected by natural environmental factors; and it can avoid potential biological hazards caused by bacteria. Attached Figure Description

[0034] Figure 1 This is a comparison chart showing the concentration of heavy metal leaching in fly ash from waste incineration before and after treatment, obtained through the implementation of this invention.

[0035] Figure 2 This is a graph showing the fixation rate of heavy metals by EICP obtained in the implementation of this invention. Detailed Implementation

[0036] The present invention will be described in detail below with reference to specific implementation examples. These examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way.

[0037] Implementation Case 1:

[0038] 1. Heavy metal testing of fly ash from waste incineration

[0039] The fly ash used in the experiment was taken from a municipal solid waste incineration plant in Hangzhou, Zhejiang Province. The incineration process used a mechanical grate furnace, and the fly ash was a grayish-white powder. Through relevant experiments, the leaching concentrations of various metals in the fly ash were measured as follows: Cd 0.065 mg / L, Cr 0.318 mg / L, Cu 0.199 mg / L, Ni 0.124 mg / L, Pb 9.104 mg / L, and Zn 1.981 mg / L. The heavy metal leaching concentrations far exceeded the standards specified in the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial) HJ 1134-2022," indicating that direct resource utilization would cause secondary pollution.

[0040] 2. Preparation of stable waste incineration fly ash

[0041] Step S1: Dry the black beans at 40℃ for 6 hours, then grind them into powder using a universal grinder and pass them through a 100-mesh sieve to obtain black bean powder.

[0042] Step S2: Take an appropriate amount of black bean powder and add deionized water to the black bean powder at a liquid-to-solid ratio of 5:1 to obtain a bean powder solution; wherein, the concentration of the bean powder solution is 200g / L.

[0043] Step S3: Place the soybean powder solution obtained in step S2 into an electromagnetic stirrer and stir for 30 minutes. Then, let the soybean powder solution stand for 2 hours and filter the residue with gauze to obtain a suspension.

[0044] Step S4: Using a centrifuge, control the centrifuge temperature at 4℃ and centrifuge the suspension obtained in step S3 at a speed of 3000r / min for 15min to obtain centrifuged liquid;

[0045] Step S5: Take the supernatant of the centrifuged liquid in step S4 as the soybean urease solution, and store the soybean urease solution in a refrigerator at 4°C for later use; wherein, the concentration of the soybean urease solution is 200g / L;

[0046] Step S6: The urease concentration and pH value of the soybean urease solution were determined by conductivity method and pH meter respectively: the soybean urease activity was 22.53 mM urea / min and the pH value was 7.9, indicating that the prepared soybean urease solution was qualified.

[0047] Step S7: Add urea to the soybean urease solution to obtain a soybean urea-urea mixed solution; wherein the concentration of urea is 1 mol / L;

[0048] Step S8: Use a mixer to evenly mix the soybean enzyme-urea mixed solution from step S7 with the waste incineration fly ash to obtain mixed fly ash; wherein, the liquid-solid ratio between the soybean enzyme-urea mixed solution and the waste incineration fly ash is 0.2:1;

[0049] Step S9: Cover the mixed fly ash obtained in step S8 with a film and cure it in a normal temperature and humid environment for 7 days to finally obtain stable waste incineration fly ash.

[0050] 3. Heavy metal leaching concentration test

[0051] Heavy metal leachate was prepared according to the "Horizontal Oscillation Method for Leaching Toxicity of Solid Waste" (HJ557-2010), and the heavy metals in the leachate were quantitatively analyzed using an inductively coupled plasma atomic emission spectrometer (Avio 300). The final measured heavy metal concentrations in the EICP-treated waste incineration fly ash leachate were: Cd 0 mg / L, Cr 0.051 mg / L, Cu 0.391 mg / L, Ni 0 mg / L, Pb 0.237 mg / L, and Zn 0.231 mg / L. A comparison chart of heavy metal leaching concentrations before and after treatment is shown below. Figure 1 As shown.

[0052] The leaching concentrations of heavy metals after treatment all meet the standards of the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial) HJ1134-2022", and the solidified fly ash can be considered for resource utilization.

[0053] Example 2:

[0054] 1. Heavy metal testing of fly ash from waste incineration

[0055] The fly ash used in the experiment was taken from a municipal solid waste incineration plant in Hangzhou, Zhejiang Province. The incineration process used a mechanical grate furnace, and the fly ash was a grayish-white powder. Through relevant experiments, the leaching concentrations of various metals in the fly ash were measured as follows: Cd 0.065 mg / L, Cr 0.318 mg / L, Cu 0.199 mg / L, Ni 0.124 mg / L, Pb 9.104 mg / L, and Zn 1.981 mg / L. The heavy metal leaching concentrations far exceeded the standards specified in the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial) HJ 1134-2022," indicating that direct resource utilization would cause secondary pollution.

[0056] 2. Preparation of stable waste incineration fly ash

[0057] Step S1: Dry the black beans at 40℃ for 6 hours, then grind them into powder using a universal grinder and pass them through a 100-mesh sieve to obtain black bean powder.

[0058] Step S2: Take an appropriate amount of black bean powder and add deionized water to the black bean powder at a liquid-to-solid ratio of 5:1 to obtain a bean powder solution; wherein, the concentration of the bean powder solution is 200g / L.

[0059] Step S3: Place the soybean powder solution obtained in step S2 into an electromagnetic stirrer and stir for 30 minutes. Then, let the soybean powder solution stand for 2 hours and filter the residue with gauze to obtain a suspension.

[0060] Step S4: Using a centrifuge, control the centrifuge temperature at 4℃ and centrifuge the suspension obtained in step S3 at a speed of 3000r / min for 15min to obtain centrifuged liquid;

[0061] Step S5: Take the supernatant of the centrifuged liquid in step S4 as the soybean urease solution, and store the soybean urease solution in a refrigerator at 4°C for later use; wherein, the concentration of the soybean urease solution is 200g / L;

[0062] Step S6: The urease concentration and pH value of the soybean urease solution were determined by conductivity method and pH meter respectively: the soybean urease activity was 22.53 mM urea / min and the pH value was 7.9, indicating that the prepared soybean urease solution was qualified.

[0063] Step S7: Add urea to the soybean urease solution to obtain a soybean urea-urea mixed solution; wherein the concentration of urea is 1 mol / L;

[0064] Step S8: Use a mixer to evenly mix the soybean enzyme-urea mixed solution from step S7 with the waste incineration fly ash to obtain mixed fly ash; wherein, the liquid-solid ratio between the soybean enzyme-urea mixed solution and the waste incineration fly ash is 0.25:1;

[0065] Step S9: Cover the mixed fly ash obtained in step S8 with a film and cure it in a normal temperature and humid environment for 7 days to finally obtain stable waste incineration fly ash.

[0066] 3. Heavy metal leaching concentration test

[0067] Heavy metal leachate was prepared according to the "Horizontal Oscillation Method for Leaching Toxicity of Solid Waste" (HJ557-2010), and the heavy metals in the leachate were quantitatively analyzed using an inductively coupled plasma atomic emission spectrometer (Avio 300). The final measured heavy metal concentrations in the EICP-treated waste incineration fly ash leachate were: Cd 0 mg / L, Cr 0.054 mg / L, Cu 0.725 mg / L, Ni 0 mg / L, Pb 0.251 mg / L, and Zn 0.276 mg / L. A comparison chart of heavy metal leaching concentrations before and after treatment is shown below. Figure 1 As shown.

[0068] The leaching concentrations of heavy metals after treatment all meet the standards of the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial) HJ1134-2022", and the solidified fly ash can be considered for resource utilization.

[0069] Example 3:

[0070] 1. Heavy metal testing of fly ash from waste incineration

[0071] The fly ash used in the experiment was taken from a municipal solid waste incineration plant in Hangzhou, Zhejiang Province. The incineration process used a mechanical grate furnace, and the fly ash was a grayish-white powder. Through relevant experiments, the leaching concentrations of various metals in the fly ash were measured as follows: Cd 0.065 mg / L, Cr 0.318 mg / L, Cu 0.199 mg / L, Ni 0.124 mg / L, Pb 9.104 mg / L, and Zn 1.981 mg / L. The heavy metal leaching concentrations far exceeded the standards specified in the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial) HJ 1134-2022," indicating that direct resource utilization would cause secondary pollution.

[0072] 2. Preparation of stable waste incineration fly ash

[0073] Step S1: Dry the black beans at 40℃ for 6 hours, then grind them into powder using a universal grinder and pass them through a 100-mesh sieve to obtain black bean powder.

[0074] Step S2: Take an appropriate amount of black bean powder and add deionized water to the black bean powder at a liquid-to-solid ratio of 5:1 to obtain a bean powder solution; wherein, the concentration of the bean powder solution is 200g / L.

[0075] Step S3: Place the soybean powder solution obtained in step S2 into an electromagnetic stirrer and stir for 30 minutes. Then, let the soybean powder solution stand for 2 hours and filter the residue with gauze to obtain a suspension.

[0076] Step S4: Using a centrifuge, control the centrifuge temperature at 4℃ and centrifuge the suspension obtained in step S3 at a speed of 3000r / min for 15min to obtain centrifuged liquid;

[0077] Step S5: Take the supernatant of the centrifuged liquid in step S4 as the soybean urease solution, and store the soybean urease solution in a refrigerator at 4°C for later use; wherein, the concentration of the soybean urease solution is 200g / L;

[0078] Step S6: The urease concentration and pH value of the soybean urease solution were determined by conductivity method and pH meter respectively: the soybean urease activity was 22.53 mM urea / min and the pH value was 7.9, indicating that the prepared soybean urease solution was qualified.

[0079] Step S7: Add urea to the soybean urease solution to obtain a soybean urea-urea mixed solution; wherein the concentration of urea is 1 mol / L;

[0080] Step S8: Use a mixer to evenly mix the soybean enzyme-urea mixed solution from step S7 with the waste incineration fly ash to obtain mixed fly ash; wherein, the liquid-solid ratio between the soybean enzyme-urea mixed solution and the waste incineration fly ash is 0.3:1;

[0081] Step S9: Cover the mixed fly ash obtained in step S8 with a film and cure it in a normal temperature and humid environment for 7 days to finally obtain stable waste incineration fly ash.

[0082] 3. Heavy metal leaching concentration test

[0083] Heavy metal leachate was prepared according to the "Horizontal Oscillation Method for Leaching Toxicity of Solid Waste" (HJ557-2010), and the heavy metals in the leachate were quantitatively analyzed using an inductively coupled plasma atomic emission spectrometer (Avio 300). The final heavy metal concentrations in the EICP-treated waste incineration fly ash leachate were: Cd 0 mg / L, Cr 0.058 mg / L, Cu 0.911 mg / L, Ni 0 mg / L, Pb 0.266 mg / L, and Zn 0.25 mg / L. A comparison chart of heavy metal leaching concentrations before and after treatment was plotted, as shown below. Figure 1 As shown.

[0084] The leaching concentrations of heavy metals after treatment all meet the standards of the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial) HJ1134-2022", and the solidified fly ash can be considered for resource utilization.

[0085] Comparative Example 1:

[0086] A comparative case was set up in which water was used instead of black bean urease solution. In the step of solidifying and stabilizing waste incineration fly ash, the black bean urease solution was replaced with an equal amount of deionized water (i.e., in step S7, the soybean urease solution was replaced with deionized water) to form a blank control group. The remaining operation steps were the same as in Example 2.

[0087] The final measured heavy metal concentrations in the fly ash leachate of Comparative Example 1 were: Cd 0.049 mg / L, Cr 0.227 mg / L, Cu 0.154 mg / L, Ni 0.082 mg / L, Pb 6.85 mg / L, and Zn 1.405 mg / L. A comparison chart of heavy metal leaching concentrations before and after treatment, as well as a chart of EICP fixation rates for heavy metals, are shown below. Figure 1 and Figure 2 As shown.

[0088] Comparative Example 2:

[0089] A comparative case was set up in which water was used instead of black bean urease solution. In the step of solidifying and stabilizing waste incineration fly ash, the black bean urease solution was replaced with an equal amount of deionized water to form a blank control group. The remaining operation steps were the same as in Example 3.

[0090] The final measured heavy metal concentrations in the fly ash leachate of Comparative Example 2 were: Cd 0.04 mg / L, Cr 0.253 mg / L, Cu 0.158 mg / L, Ni 0.091 mg / L, Pb 6.552 mg / L, and Zn 1.392 mg / L. A comparison chart of heavy metal leaching concentrations before and after treatment, as well as a chart of EICP fixation rates for heavy metals, are shown below. Figure 1 and Figure 2 As shown.

[0091] according to Figure 1 It can be seen that the fly ash from waste incineration prepared in Examples 1-3 contains less than 0.03 mg / L of Cd, less than 0.2 mg / L of Cr, less than 1 mg / L of Cu, less than 0.2 mg / L of Ni, less than 0.3 mg / L of Pb, and less than 1 mg / L of Zn, meeting the specifications and allowing for resource utilization of the solidified fly ash. In contrast, the contents of each heavy metal in Comparative Examples 1-2 are relatively high. Figure 2 It can be seen that in Examples 1 to 3, the EICP fixation rate of various metals in waste incineration fly ash, except for Cu ions, reached more than 80%. This shows that the present invention can significantly reduce the concentration of heavy metals in waste incineration fly ash and achieve heavy metal stabilization.

[0092] The heavy metal detection results of Comparative Examples 1 and 2 verify that the method, process and biological agent - soybean enzyme used in this invention can effectively stabilize mobile heavy metal ions in the fly ash from waste incineration, meeting the requirements of the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial) HJ 1134-2022". It is possible to consider the resource utilization of the solidified fly ash.

Claims

1. A method for treating stabilized waste incineration fly ash based on biological agents, characterized in that, Includes the following steps: Step S1: Dry the black beans at 20~40℃ for 6~8 hours, grind the black beans into powder using a universal grinder, and pass them through a 100~150 mesh sieve to obtain black bean powder. Step S2: Take black bean powder and add deionized water to the black bean powder according to the preset liquid-solid ratio to obtain bean powder solution. Step S3: Place the soybean powder solution obtained in step S2 into an electromagnetic stirrer and stir for 30-40 minutes. Then, let the soybean powder solution stand for 2-3 hours and filter the residue with gauze to obtain a suspension. Step S4: Centrifuge the suspension obtained in step S3 for 15-20 minutes to obtain the centrifuged liquid; Step S5: Take the supernatant of the centrifuged liquid as the soybean urease solution, and store the soybean urease solution in a refrigerator at 4~5℃ for later use. Step S6: Measure the urease activity and pH value of the soybean urease solution using the conductivity method and pH meter, respectively. If the urease activity of the soybean urease solution is 12~23 mM urea / min and the pH value is 7.5~8.5, it indicates that the soybean urease solution is qualified; otherwise, it indicates that the soybean urease solution is unqualified. If the test result is qualified, proceed to step S7; if the test result is unqualified, repeat steps S1 to S6 until a qualified soybean urease solution is obtained. Step S7: Add urea to the soybean urease solution to obtain a soybean urea-urea mixed solution; Step S8: Use a mixer to evenly mix the soybean enzyme-urea mixed solution and the waste incineration fly ash raw material to obtain mixed fly ash; Step S9: Cover the mixed fly ash with a film and place it in a normal temperature and humid environment. Use soybean enzyme-induced calcium carbonate precipitation technology to stabilize and maintain the various heavy metals in the waste incineration fly ash raw material for 5-7 days, and finally obtain stable waste incineration fly ash.

2. The method for treating stabilized waste incineration fly ash based on biological agents according to claim 1, characterized in that: In step S2, the liquid-to-solid ratio between deionized water and black bean powder is 5-10:1, and the concentration of the bean powder solution is 100g / L-200g / L.

3. The method for treating stabilized waste incineration fly ash based on biological agents according to claim 1, characterized in that: In step S4, the temperature of the centrifuge is controlled at 4~5℃ and the rotation speed is 3000r / min.

4. The method for treating stabilized waste incineration fly ash based on biological agents according to claim 1, characterized in that: In step S7, the concentration of urea is 0.8~1.3 mol / L.

5. The method for treating stabilized waste incineration fly ash based on biological agents according to claim 1, characterized in that: In step S8, the liquid-solid ratio between the soybean enzyme-urea mixed solution and the waste incineration fly ash raw material is 0.2~0.3:

1.

6. The method for treating stabilized waste incineration fly ash based on biological agents according to claim 1, characterized in that: During the curing process in step S9, the heavy metals in the waste incineration fly ash raw material include Cd, Cr, Pb, Zn, Ni, and Cu.

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