A method for harmless treatment of wastewater from waste incineration fly ash process

Abstract

The present invention relates to the field of environmental protection technology, and specifically to a method for harmless treatment of wastewater from fly ash process of garbage incineration. The present invention adds sodium sulfate to fly ash process wastewater to perform primary decalcification to obtain calcium sulfate precipitation and primary treatment waste liquid; adds sodium carbonate to the primary treatment waste liquid to perform secondary decalcification to obtain calcium carbonate precipitation and secondary treatment waste liquid; adds heavy metal remover to the secondary treatment waste liquid to remove heavy metals to obtain heavy metal sludge and tertiary treatment waste liquid; adds hydrochloric acid to the tertiary treatment waste liquid to perform neutralization reaction, and then adopts high temperature evaporation crystallization technology to obtain sodium chloride and mother liquor, and the mother liquor is cooled and crystallized to separate potassium chloride. It can not only effectively remove heavy metal ions and other harmful substances in wastewater and reduce the toxicity level of wastewater, but also recover part of water and crystallized salt, which is conducive to the recycling of water resources and reduces resource waste.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection, and in particular to a method for harmlessly treating wastewater from a garbage incineration fly ash process. Background Art

[0002] With the acceleration of urbanization and the improvement of living standards, waste incineration has been widely used as an effective method of waste disposal. Waste incineration can not only effectively reduce the volume of waste and reduce landfill pressure, but also convert waste into heat and electricity to achieve resource recycling. However, fly ash produced during waste incineration has become an environmental problem that needs to be solved urgently. Fly ash contains chloride salts, heavy metals, dioxins and other pollutants. If not treated, it may cause serious pollution to soil and water bodies. Fly ash can be dechlorinated by acid treatment, alkali treatment, heat treatment and water washing. Compared with other methods, water washing is an effective, simple, low-cost and relatively mature process; in addition, some usable resources such as sodium chloride and potassium chloride can be extracted from fly ash by water washing process.

[0003] The fly ash washing process is to mix the fly ash and water in a certain solid-liquid ratio and stir them evenly, fully react for a period of time, and then perform solid-liquid separation on the fly ash washing slurry after the reaction is complete. However, during the washing pretreatment process, washing liquid containing calcium, sodium, chloride salts and high concentrations of heavy metal ions will be produced. The main components of heavy metals include Cu, Zn, Cr, Cd, Pb, etc.

[0004] Therefore, we propose a method for harmless treatment of wastewater from waste incineration fly ash process. Summary of the invention

[0005] The purpose of the present invention is to provide a method for harmlessly treating wastewater from fly ash process of garbage incineration to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for harmless treatment of wastewater from waste incineration fly ash process, comprising the following steps:

[0008] Step S1: adding sodium sulfate to the fly ash process wastewater to perform primary decalcification to obtain calcium sulfate precipitate and primary treatment waste liquid;

[0009] Step S2: adding sodium carbonate to the primary treated waste liquid to perform secondary decalcification to obtain calcium carbonate precipitate and secondary treated waste liquid;

[0010] Step S3: adding a heavy metal remover to the secondary treatment waste liquid to remove heavy metals, thereby obtaining heavy metal sludge and tertiary treatment waste liquid;

[0011] Step S4: adding hydrochloric acid to the waste liquid from the tertiary treatment to carry out a neutralization reaction, and then adopting a high-temperature evaporation crystallization technique to obtain sodium chloride and a mother liquor, and separating potassium chloride from the mother liquor by cooling and crystallizing.

[0012] Furthermore, in step S1, the molar ratio of the amount of sodium sulfate added to the calcium content in the primary water washing liquid is (0.8-0.9):1.

[0013] Furthermore, in step S2, the molar ratio of the amount of sodium carbonate added to the calcium content in the primary treated waste liquid is (1.0-1.2):1.

[0014] Furthermore, in step S3, the amount of heavy metal remover used is 1-10% of the mass of the secondary treatment waste liquid.

[0015] Furthermore, the preparation method of the heavy metal remover is as follows:

[0016] Step (1): β-cyclodextrin, N-hydroxymethyl acrylamide and dilute hydrochloric acid are uniformly mixed, reacted at 70-80° C. for 15-30 min, and precipitated, filtered, washed and dried to obtain double-bond β-cyclodextrin;

[0017] Step (2): 2,6-diaminopyridine, allyl glycidyl ether and N,N-dimethylformamide are mixed evenly, reacted at 30-40°C for 3-5h, filtered, washed and dried to obtain a double bond-containing amino compound; sodium hydroxide solution, double bond-containing amino compound and carbon disulfide are mixed evenly, reacted at room temperature for 30-60min, heated to 60-70°C, continued to react for 2-3h, filtered, washed and dried to obtain a dithiocarboxyl compound;

[0018] Step (3): 2-acrylamido-2-methylpropanesulfonic acid and deionized water are mixed evenly, methacrylic acid, butyl acrylate, a disulfide carboxyl compound, vinyl triethoxysilane, double-bond β-cyclodextrin and an aqueous solution of ammonium persulfate are added, and the mixture is reacted at 70-80° C. for 6-8 hours to obtain a modified silicone emulsion;

[0019] Step (4): Mix sodium alginate and deionized water evenly to obtain a sodium alginate solution, add the modified silicone emulsion dropwise for 1-2 hours, stir evenly, add to the calcium chloride solution, react for 2-3 hours, let stand for 24 hours, filter, wash and dry to obtain a heavy metal remover.

[0020] In the above technical scheme, N-hydroxymethyl acrylamide is used as a coupling agent to graft a double bond onto β-cyclodextrin to obtain β-cyclodextrin containing a double bond; by controlling the ratio of 2,6-diaminopyridine and allyl glycidyl ether, the amino group at one end of 2,6-diaminopyridine and the epoxy group of allyl glycidyl ether undergo a ring-opening reaction to generate a hydroxyl group and introduce a double bond to obtain an amino compound containing a double bond; then carbon disulfide reacts with sodium hydroxide to generate a dithiocarbonate, which then reacts with the hydroxyl group and the amino group on the amino compound containing a double bond to introduce a dithiocarboxyl group (—C=S—S - ) to obtain a dithiocarboxyl compound; using 2-acrylamido-2-methylpropanesulfonic acid, methacrylic acid, butyl acrylate, a dithiocarboxyl compound, vinyltriethoxysilane and double-bond β-cyclodextrin as raw materials and ammonium persulfate as initiator, a simple and environmentally friendly soap-free emulsion polymerization method was used to prepare a functionalized silicone emulsion containing amide, sulfonic acid, carboxyl and dithiocarboxyl groups, namely, a modified silicone emulsion, which not only increases its adsorption capacity for heavy metal ions by introducing a large number of multifunctional groups, but also forms a dense cross-linked structure by forming Si-O-Si and molecular interactions; finally, the modified silicone emulsion was mixed with sodium alginate and cross-linked with calcium chloride to prepare a heavy metal remover with rich functional groups.

[0021] Furthermore, in the step (1), the mass ratio of β-cyclodextrin, N-hydroxymethyl acrylamide and dilute hydrochloric acid is 1:(1.0-1.2):(2-3).

[0022] Furthermore, in step (1), the concentration of dilute hydrochloric acid is 1-3 wt %.

[0023] Furthermore, in the step (2), the mass ratio of 2,6-diaminopyridine, allyl glycidyl ether and N,N-dimethylformamide is 1:(0.9-1.0):(3-5).

[0024] Furthermore, in step (2), the mass ratio of the sodium hydroxide solution, the double-bond amino compound and carbon disulfide is 1: (0.1-0.2): (0.15-0.20).

[0025] Furthermore, in step (2), the concentration of the sodium hydroxide solution is 10-12 wt %.

[0026] Furthermore, in step (3), the modified silicone emulsion comprises the following components by weight: 3-5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2-3 parts of methacrylic acid, 1.5-2.5 parts of butyl acrylate, 4-6 parts of dithiocarboxyl compounds, 1-3 parts of vinyl triethoxysilane, 2-4 parts of double-bond β-cyclodextrin, 8-10 parts of ammonium persulfate aqueous solution, and 70-80 parts of deionized water.

[0027] Furthermore, the concentration of the ammonium persulfate aqueous solution is 10 wt %.

[0028] Furthermore, in step (4), the mass ratio of sodium alginate to deionized water is 1:(50-55).

[0029] Furthermore, in step (4), the mass of the modified silicone emulsion is 5-15wt% of the sodium alginate solution.

[0030] Furthermore, in step (4), the concentration of the calcium chloride solution is 2 wt %, and its amount is 1-2 times that of the sodium alginate solution.

[0031] Furthermore, in step S4, the concentration of hydrochloric acid is 36-38wt%.

[0032] Furthermore, in step S4, the temperature of the high temperature evaporation crystallization technology is 105-115°C.

[0033] Furthermore, in step S4, the temperature of the mother liquor after cooling and crystallization is 20-30°C.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. A method for harmlessly treating wastewater from fly ash process of garbage incineration of the present invention, wherein β-cyclodextrin has a hydrophilic outer edge and a hydrophobic inner cavity, and can form inclusion complexes with pollutants, thereby preventing secondary pollution while adsorbing pollutants, and using N-hydroxymethyl acrylamide as a coupling agent to graft double bonds onto β-cyclodextrin to obtain β-cyclodextrin containing double bonds;

[0036] By controlling the ratio of 2,6-diaminopyridine and allyl glycidyl ether, the amino group at one end of 2,6-diaminopyridine reacts with the epoxy group of allyl glycidyl ether to generate a hydroxyl group and introduce a double bond to obtain a double-bond amino compound; then carbon disulfide reacts with sodium hydroxide to generate dithiocarbonate, which then reacts with the hydroxyl and amino groups on the double-bond amino compound to introduce a dithiocarboxyl group (—C=S—S - ), a dithiocarboxyl-containing compound is obtained, and its functional group dithiocarboxyl reacts with heavy metal ions to undergo a chelate precipitation reaction, converting dissolved ions into insoluble ions, i.e., generating a chelate precipitate, and finally removing the heavy metal ions in the water by gravity sedimentation;

[0037] Functionalized silicone emulsions containing amide, sulfonic acid, carboxyl and disulfide carboxyl groups, i.e. modified silicone emulsions, were prepared by a simple and environmentally friendly soap-free emulsion polymerization method using 2-acrylamido-2-methylpropanesulfonic acid, methacrylic acid, butyl acrylate, disulfide carboxyl compounds, vinyl triethoxysilane and double-bond β-cyclodextrin as raw materials and ammonium persulfate as initiator. The modified silicone emulsions not only increase the adsorption capacity of heavy metal ions by introducing a large number of multifunctional groups, but also form a dense cross-linked structure by forming Si-O-Si and molecular interactions.

[0038] Sodium alginate is a natural polysaccharide with abundant hydroxyl and carboxyl groups on its molecular skeleton. These functional groups can lead to coordination chelation and ion exchange reaction with metal ions, thereby achieving the adsorption of heavy metals. Sodium alginate is selected as the matrix material, compounded with modified silicone emulsion, and cross-linked with calcium chloride to prepare a heavy metal remover with abundant functional groups, which not only improves the removal effect of heavy metals, but also has environmental advantages.

[0039] 2. The present invention provides a harmless treatment method for waste incineration fly ash process wastewater. The fly ash process wastewater undergoes a multi-step treatment of "softening + heavy metal removal + neutralization + evaporation and crystallization", which can effectively remove heavy metal ions and other harmful substances in the wastewater, reduce the toxicity level of the wastewater, and ensure that the treated water quality meets environmental protection standards. In the process of evaporation and crystallization, part of the water and crystallized salt can be recovered, which is beneficial to the recycling of water resources, reduces resource waste, and is environmentally friendly. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] In this example, the fly ash process wastewater comes from a waste incineration power plant in Nanjing. Its main components and contents are: ρ(Pb 2+ ) = 375.86 mg / L; ρ(Cd 2+ ) = 3.34 mg / L; ρ(Zn 2+ ) = 6.9 mg / L; ρ(Cu 2+ ) = 1.18 mg / L; ρ(Mn 2+ ) = 0.72 mg / L; w (K + ) = 5.22%; w (Ca 2+ ) = 3.44%; w (Na + ) = 4.87%; w (Cl - )=18.37%.

[0042] In the following examples and comparative examples, 1 part is equal to 10 g.

[0043] Embodiment 1: A method for harmless treatment of wastewater from waste incineration fly ash process, comprising the following processes:

[0044] Step S1: adding sodium sulfate to the fly ash process wastewater to perform primary decalcification to obtain calcium sulfate precipitate and primary treatment waste liquid, wherein the molar ratio of the amount of sodium sulfate added to the calcium content in the primary water washing liquid is 0.8:1;

[0045] Step S2: adding sodium carbonate to the primary treated waste liquid to perform secondary decalcification to obtain calcium carbonate precipitate and secondary treated waste liquid, wherein the molar ratio of the amount of sodium carbonate added to the calcium content in the primary treated waste liquid is 1:1;

[0046] Step S3: adding 1 wt% of a heavy metal remover to the secondary treatment waste liquid to remove heavy metals, thereby obtaining heavy metal sludge and tertiary treatment waste liquid;

[0047] Step S4: adding 36 wt % hydrochloric acid to the waste liquid from the third treatment to carry out a neutralization reaction, and then adopting a high temperature evaporation crystallization technology (temperature is 105° C.) to obtain sodium chloride and a mother liquor, and separating potassium chloride from the mother liquor by cooling and crystallizing (temperature is 20° C.);

[0048] The preparation method of heavy metal remover is as follows:

[0049] Step (1): 2 parts of β-cyclodextrin, 2 parts of N-hydroxymethyl acrylamide and 1 wt% of dilute hydrochloric acid are mixed evenly, reacted at 70°C for 15 minutes, and precipitated, filtered, washed and dried to obtain double-bond β-cyclodextrin;

[0050] Step (2): 4 parts of 2,6-diaminopyridine, 3.6 parts of allyl glycidyl ether and 12 parts of N,N-dimethylformamide are mixed evenly, reacted at 30°C for 3 hours, filtered, washed and dried to obtain a double bond-containing amino compound; 40 parts of 10wt% sodium hydroxide solution, 4 parts of a double bond-containing amino compound and 6 parts of carbon disulfide are mixed evenly, reacted at room temperature for 30 minutes, heated to 60°C, continued to react for 2 hours, filtered, washed and dried to obtain a dithiocarboxyl compound;

[0051] Step (3): 3 parts of 2-acrylamido-2-methylpropanesulfonic acid and 70 parts of deionized water are mixed evenly, and 2 parts of methacrylic acid, 1.5 parts of butyl acrylate, 4 parts of dithiocarboxyl compounds, 1 part of vinyl triethoxysilane, 2 parts of double-bond β-cyclodextrin and 8 parts of 10 wt% ammonium persulfate aqueous solution are added, and the mixture is reacted at 70° C. for 6 hours to obtain a modified silicone emulsion;

[0052] Step (4): 5 parts of sodium alginate and 250 parts of deionized water are mixed evenly to obtain a sodium alginate solution, 5 wt% of modified silicone emulsion is added dropwise for 1 hour, the solution is stirred evenly, and 255 parts of 2 wt% calcium chloride solution are added to react for 2 hours. After standing for 24 hours, the heavy metal remover is obtained after filtering, washing and drying.

[0053] Embodiment 2: A method for harmless treatment of wastewater from waste incineration fly ash process, comprising the following process:

[0054] Step S1: adding sodium sulfate to the fly ash process wastewater to perform primary decalcification to obtain calcium sulfate precipitate and primary treatment waste liquid, wherein the molar ratio of the amount of sodium sulfate added to the calcium content in the primary water washing liquid is 0.85:1;

[0055] Step S2: adding sodium carbonate to the primary treated waste liquid to perform secondary decalcification to obtain calcium carbonate precipitate and secondary treated waste liquid, wherein the molar ratio of the amount of sodium carbonate added to the calcium content in the primary treated waste liquid is 1.1:1;

[0056] Step S3: adding 5 wt % of a heavy metal remover to the secondary treatment waste liquid to remove heavy metals, thereby obtaining heavy metal sludge and tertiary treatment waste liquid;

[0057] Step S4: adding 37 wt % hydrochloric acid to the waste liquid from the third treatment to carry out a neutralization reaction, and then adopting a high temperature evaporation crystallization technology (temperature is 110° C.) to obtain sodium chloride and a mother liquor, and separating potassium chloride from the mother liquor by cooling and crystallizing (temperature is 25° C.);

[0058] The preparation method of heavy metal remover is as follows:

[0059] Step (1): 3 parts of β-cyclodextrin, 3.3 parts of N-hydroxymethyl acrylamide and 7.5 parts of 2 wt% dilute hydrochloric acid are mixed evenly, reacted at 75°C for 20 minutes, and precipitated, filtered, washed and dried to obtain double-bond β-cyclodextrin;

[0060] Step (2): 5 parts of 2,6-diaminopyridine, 4.8 parts of allyl glycidyl ether and 20 parts of N,N-dimethylformamide are mixed evenly, reacted at 35°C for 4 hours, filtered, washed and dried to obtain a double bond-containing amino compound; 30 parts of 11wt% sodium hydroxide solution, 5 parts of double bond-containing amino compound and 5.4 parts of carbon disulfide are mixed evenly, reacted at room temperature for 45 minutes, heated to 65°C, continued to react for 2.5 hours, filtered, washed and dried to obtain a dithiocarboxyl compound;

[0061] Step (3): 4 parts of 2-acrylamido-2-methylpropanesulfonic acid and 75 parts of deionized water are mixed evenly, and 2.5 parts of methacrylic acid, 2 parts of butyl acrylate, 5 parts of dithiocarboxyl compounds, 2 parts of vinyl triethoxysilane, 3 parts of double-bond β-cyclodextrin and 9 parts of 10 wt% ammonium persulfate aqueous solution are added, and the mixture is reacted at 75° C. for 7 hours to obtain a modified silicone emulsion;

[0062] Step (4): 5 parts of sodium alginate and 260 parts of deionized water are mixed evenly to obtain a sodium alginate solution, 10 wt % of modified silicone emulsion is added dropwise for 1.5 hours, the mixture is stirred evenly, and 400 parts of 2 wt % calcium chloride solution are added to react for 2.5 hours. After standing for 24 hours, the heavy metal remover is obtained after filtering, washing and drying.

[0063] Embodiment 3: A method for harmless treatment of wastewater from fly ash incineration process, comprising the following processes:

[0064] Step S1: adding sodium sulfate to the fly ash process wastewater to perform primary decalcification to obtain calcium sulfate precipitate and primary treatment waste liquid, wherein the molar ratio of the amount of sodium sulfate added to the calcium content in the primary water washing liquid is 0.9:1;

[0065] Step S2: adding sodium carbonate to the primary treated waste liquid to perform secondary decalcification to obtain calcium carbonate precipitate and secondary treated waste liquid, wherein the molar ratio of the amount of sodium carbonate added to the calcium content in the primary treated waste liquid is 1.2:1;

[0066] Step S3: adding 10 wt % of a heavy metal remover to the secondary treatment waste liquid to remove heavy metals, thereby obtaining heavy metal sludge and tertiary treatment waste liquid;

[0067] Step S4: adding 38 wt% hydrochloric acid to the waste liquid from the third treatment to carry out a neutralization reaction, and then adopting a high temperature evaporation crystallization technology (temperature is 115°C) to obtain sodium chloride and a mother liquor, and separating potassium chloride from the mother liquor by cooling and crystallizing (temperature is 30°C);

[0068] The preparation method of heavy metal remover is as follows:

[0069] Step (1): 4 parts of β-cyclodextrin, 4.8 parts of N-hydroxymethyl acrylamide and 12 parts of 3 wt% dilute hydrochloric acid are mixed evenly, reacted at 80°C for 30 minutes, and precipitated, filtered, washed and dried to obtain double-bond β-cyclodextrin;

[0070] Step (2): 6 parts of 2,6-diaminopyridine, 6 parts of allyl glycidyl ether and 30 parts of N,N-dimethylformamide are mixed evenly, reacted at 40°C for 5 hours, filtered, washed and dried to obtain a double bond-containing amino compound; 30 parts of 12wt% sodium hydroxide solution, 6 parts of double bond-containing amino compound and 6 parts of carbon disulfide are mixed evenly, reacted at room temperature for 60 minutes, heated to 70°C, continued to react for 3 hours, filtered, washed and dried to obtain a dithiocarboxyl compound;

[0071] Step (3): 5 parts of 2-acrylamido-2-methylpropanesulfonic acid and 80 parts of deionized water are uniformly mixed, 3 parts of methacrylic acid, 2.5 parts of butyl acrylate, 6 parts of dithiocarboxyl compounds, 3 parts of vinyl triethoxysilane, 4 parts of double-bond β-cyclodextrin and 10 parts of 10 wt% ammonium persulfate aqueous solution are added, and the mixture is reacted at 80° C. for 8 hours to obtain a modified silicone emulsion;

[0072] Step (4): 5 parts of sodium alginate and 275 parts of deionized water are mixed evenly to obtain a sodium alginate solution, 15 wt % of a modified silicone emulsion is added dropwise for 2 h, the solution is stirred evenly, and 560 parts of a 2 wt % calcium chloride solution are added to react for 3 h. After standing for 24 h, the heavy metal remover is obtained after filtering, washing and drying.

[0073] Comparative Example 1: A method for harmless treatment of wastewater from fly ash incineration process, comprising the following processes:

[0074] Compared with Example 2, in Comparative Example 2, the double-bond-containing β-cyclodextrin is replaced with β-cyclodextrin of the same mass, and the other steps are the same as those of Example 2.

[0075] Comparative Example 2: A method for harmless treatment of wastewater from fly ash incineration process, comprising the following processes:

[0076] Compared with Example 2, no dithiocarboxyl compound is added to the heavy metal remover of Comparative Example 2, and the other steps are the same as those of Example 2.

[0077] experiment:

[0078] Take the sodium chloride and potassium chloride obtained in Example 1-3, and measure their recovery rates respectively. 2+ The content was determined by ion selective electrode method; K + The content was determined by sodium tetraphenylborate gravimetric method.

[0079] The test results are as follows:

[0080]

[0081] According to the data in the above table, we can clearly draw the following conclusions:

[0082] The present application effectively separates potassium salt and sodium salt in fly ash through a multi-step treatment of "softening + heavy metal removal + neutralization + evaporation crystallization". The process has no wastewater discharge and realizes the separation and recovery of potassium salt and sodium salt in fly ash.

[0083] Take the three-times treated waste liquid obtained in Example 1-3 and Comparative Example 1-2 to prepare samples, and test the heavy metal removal rates and record the test results: Pb 2+ 、Cd 2+ , Cu 2+ 、Zn 2+ , Mn 2+ The content was determined by TAS-990 atomic absorption spectrophotometer;

[0084] The test results are as follows:

[0085]

[0086] According to the data in the above table, we can clearly draw the following conclusions:

[0087] Compared with Examples 1-3, the heavy metal removal rates of the products obtained in Comparative Examples 1 and 2 are both reduced, indicating that compared with β-cyclodextrin, the double-bond β-cyclodextrin prepared by the present invention can participate in the polymerization reaction under the action of the initiator to obtain a modified silicone emulsion, thereby exerting its effect; at the same time, the addition of the dithiocarboxyl compound prepared by the present invention can react with a variety of heavy metal ions to generate insoluble chelated precipitates, thereby removing heavy metals in the solution.

[0088] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for harmless treatment of wastewater from fly ash incineration process, characterized by: The steps include: Step S1: adding sodium sulfate to the fly ash process wastewater to perform primary decalcification to obtain calcium sulfate precipitate and primary treatment waste liquid; Step S2: adding sodium carbonate to the primary treated waste liquid to perform secondary decalcification to obtain calcium carbonate precipitate and secondary treated waste liquid; Step S3: adding a heavy metal remover to the secondary treatment waste liquid to remove heavy metals, thereby obtaining heavy metal sludge and tertiary treatment waste liquid; Step S4: adding hydrochloric acid to the waste liquid from the third treatment to carry out a neutralization reaction, and then using a high-temperature evaporation crystallization technique to obtain sodium chloride and a mother liquor, and separating potassium chloride from the mother liquor by cooling and crystallizing; The preparation method of the heavy metal remover is as follows: Step (1): β-cyclodextrin, N-hydroxymethyl acrylamide and dilute hydrochloric acid are uniformly mixed, reacted at 70-80° C. for 15-30 min, and precipitated, filtered, washed and dried to obtain double-bond β-cyclodextrin; Step (2): 2,6-diaminopyridine, allyl glycidyl ether and N,N-dimethylformamide are mixed evenly, reacted at 30-40°C for 3-5h, filtered, washed and dried to obtain a double bond-containing amino compound; sodium hydroxide solution, double bond-containing amino compound and carbon disulfide are mixed evenly, reacted at room temperature for 30-60min, heated to 60-70°C, continued to react for 2-3h, filtered, washed and dried to obtain a dithiocarboxyl compound; Step (3): 2-acrylamido-2-methylpropanesulfonic acid and deionized water are mixed evenly, methacrylic acid, butyl acrylate, a disulfide carboxyl compound, vinyl triethoxysilane, double-bond β-cyclodextrin and an aqueous solution of ammonium persulfate are added, and the mixture is reacted at 70-80° C. for 6-8 hours to obtain a modified silicone emulsion; Step (4): Mix sodium alginate and deionized water evenly to obtain a sodium alginate solution, add the modified silicone emulsion dropwise for 1-2 hours, stir evenly, add to the calcium chloride solution, react for 2-3 hours, let stand for 24 hours, filter, wash and dry to obtain a heavy metal remover.

2. The method for harmless treatment of wastewater from fly ash incineration process according to claim 1, characterized in that: In step S1, the molar ratio of the amount of sodium sulfate added to the calcium content in the primary water washing liquid is (0.8-0.9):

1.

3. The method for harmless treatment of wastewater from fly ash incineration process according to claim 1, characterized in that: In step S2, the molar ratio of the amount of sodium carbonate added to the calcium content in the primary treated waste liquid is (1.0-1.2):

1.

4. The method for harmless treatment of wastewater from waste incineration fly ash process according to claim 1, characterized in that: In step S3, the amount of heavy metal remover used is 1-10% of the mass of the secondary treatment waste liquid.

5. The method for harmless treatment of wastewater from waste incineration fly ash process according to claim 1, characterized in that: In the step (2), the mass ratio of 2,6-diaminopyridine, allyl glycidyl ether and N,N-dimethylformamide is 1:(0.9-1.0):(3-5).

6. The method for harmless treatment of wastewater from fly ash incineration process according to claim 1, characterized in that: In the step (3), the modified silicone emulsion comprises the following components by weight: 3-5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2-3 parts of methacrylic acid, 1.5-2.5 parts of butyl acrylate, 4-6 parts of dithiocarboxyl compounds, 1-3 parts of vinyltriethoxysilane, 2-4 parts of double-bond β-cyclodextrin, 8-10 parts of ammonium persulfate aqueous solution, and 70-80 parts of deionized water.

7. The method for harmless treatment of wastewater from fly ash incineration process according to claim 1, characterized in that: In the step (4), the mass of the modified silicone emulsion is 5-15wt% of the sodium alginate solution.

8. The method for harmless treatment of wastewater from fly ash incineration process according to claim 1, characterized in that: In step S4, the temperature of the high temperature evaporation crystallization technology is 105-115°C.

9. The method for harmless treatment of wastewater from waste incineration fly ash process according to claim 1, characterized in that: In step S4, the temperature of the mother liquor after cooling and crystallization is 20-30°C.

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