A method and system for treating dioxins in municipal solid waste incineration fly ash

Abstract

The present invention provides a method and a system for treating dioxins in municipal solid waste incineration fly ash, belonging to the technical field of environmental engineering. The method includes: adding the municipal solid waste incineration fly ash into a reactor and adding hydrogen peroxide with a volume fraction of 30% to obtain wet fly ash; wherein, the volume ratio of the fly ash to the hydrogen peroxide is 1:1 - 10:1; performing a first irradiation treatment on the wet fly ash to cause a dechlorination reaction of the dioxins; subjecting the wet fly ash after the first irradiation treatment to flotation separation to separate a solid pretreatment product and a liquid pretreatment product; respectively performing a second irradiation treatment on the solid pretreatment product and the liquid pretreatment product to obtain a solid treatment product and a liquid treatment product with a dioxin concentration less than 0.1 ng-TEQ / Nm<supgt;3< / supgt>; thereby, the present invention pre-dechlorinates the dioxins by first irradiation, and removes the dioxins after eluting the chloride ions, improving the treatment effect of electron beam irradiation on dioxins in fly ash.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental engineering, and particularly relates to a method and a system for treating dioxins in fly ash from waste incineration. Background Art

[0002] During the waste incineration process, flue gas and fly ash containing dioxin toxic substances are generated. Dioxins are the general term for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans. Currently, 210 congeners of dioxins have been identified, and 17 substances with chlorine substitution at the 2, 3, 7, and 8 positions are toxic. 2,3,7,8-Tetrachlorodioxin is one of the most toxic pollutants known to humans. How to effectively remove dioxins from fly ash is the primary problem currently faced by waste incineration technology.

[0003] Currently, the treatment methods for dioxins in fly ash can be mainly divided into: physical and chemical methods, solidification methods, and heat treatment methods. Physical and chemical methods usually include washing methods, chemical precipitation methods, chemical extraction, etc.; among them, chemical precipitation methods and chemical extraction methods are not widely used due to high costs and other reasons. Solidification methods mainly include cement solidification and chemical agent solidification; cement solidification is simple to operate, but soluble salts in fly ash are likely to cause the solidified body to crack; while using chemical agent solidification has the problem of high cost. Heat treatment methods mainly include hydrothermal methods and high-temperature sintering, etc., but this method has high energy consumption, and secondary fly ash is easily generated during the sintering process. Therefore, there is an urgent need to develop a treatment method for dioxins in fly ash with low cost and good treatment effect. Summary of the Invention

[0004] In view of this, the present invention aims to provide a method and a system for treating dioxins in fly ash from waste incineration to solve the problems of high cost or unsatisfactory treatment effect of the current treatment methods for dioxins in fly ash.

[0005] In the first aspect of the present invention, a method for treating dioxins in fly ash from waste incineration is provided, and the method includes:

[0006] Adding fly ash from waste incineration into a reactor, and adding hydrogen peroxide with a volume fraction of 30% to obtain wet fly ash; wherein, the volume ratio of the fly ash to the hydrogen peroxide is 1:1 - 10:1;

[0007] Performing a first-step irradiation treatment on the wet fly ash to cause the dioxins to undergo a dechlorination reaction;

[0008] Performing flotation separation on the wet fly ash after the first-step irradiation treatment to separate and obtain a solid pretreatment product and a liquid pretreatment product;

[0009] Performing a second-step irradiation treatment on the solid pretreatment product and the liquid pretreatment product respectively to obtain a dioxin concentration of less than 0.1 ng-TEQ / Nm3 Solid treatment product and liquid treatment product; wherein, the irradiation dose of the first-step irradiation treatment is less than that of the second-step irradiation treatment.

[0010] Furthermore, the irradiation treatment is carried out by using an electron accelerator; the irradiation dose of the first-step irradiation treatment is 1 - 6 kGy.

[0011] Furthermore, the steps of the flotation separation include:

[0012] Adding deionized water to the wet fly ash after the first-step irradiation treatment to obtain a mixed liquid;

[0013] Washing the mixed liquid with water in a flotation machine at a preset rotation speed for 20 - 60 min;

[0014] Separating the mixed liquid by centrifugation to obtain the solid pretreatment product and the liquid pretreatment product.

[0015] Furthermore, the volume ratio of the deionized water to the wet fly ash is 20% - 30%, and the preset rotation speed is 500 - 2000 rpm.

[0016] Furthermore, the second-step irradiation treatment is respectively carried out on the solid pretreatment product and the liquid pretreatment product:

[0017] Irradiating the solid pretreatment product with an irradiation dose of 15 - 50 kGy,

[0018] And irradiating the liquid pretreatment product with an irradiation dose of 7 - 40 kGy;

[0019] The solid treatment product and the liquid treatment product are respectively obtained.

[0020] Furthermore, the volume ratio of the fly ash to the hydrogen peroxide is 5:1 - 10:1.

[0021] Furthermore, the volume ratio of the fly ash to the hydrogen peroxide is 10:1.

[0022] Furthermore, the power of the electron accelerator is 100 kw and the energy is 2 MeV.

[0023] Furthermore, the wet fly ash and the solid pretreatment product are laid flat to make the treatment effect of the irradiation treatment uniform.

[0024] In the second aspect of the present invention, a treatment system for dioxins in waste incineration fly ash is provided, and the system includes:

[0025] A reaction device is used for mixing incineration fly ash of garbage and hydrogen peroxide. Among them, the volume ratio of the fly ash to the hydrogen peroxide is 1:1 - 10:1;

[0026] A first irradiation device is used for performing a first-step irradiation treatment on the incineration fly ash of garbage and hydrogen peroxide, so that the dioxin undergoes a dechlorination reaction;

[0027] A flotation device is used for performing flotation separation on the product obtained from the dechlorination reaction to separate and obtain a solid pretreatment product and a liquid pretreatment product;

[0028] A second irradiation device is used for performing a second-step irradiation treatment on the solid pretreatment product and the liquid pretreatment product respectively to obtain a solid treatment product and a liquid treatment product with a dioxin concentration less than 0.1 ng-TEQ / Nm 3 of the solid treatment product and the liquid treatment product.

[0029] Compared with the prior art, the method for treating dioxin in the incineration fly ash of garbage according to the present invention has the following advantages:

[0030] The method for treating dioxin in the incineration fly ash of garbage provided by the present invention includes: adding the incineration fly ash of garbage into a reactor, and adding hydrogen peroxide with a volume fraction of 30%, and stirring to obtain wet fly ash; among them, the volume ratio of the fly ash to the hydrogen peroxide is 1:1 - 10:1; performing a first-step irradiation treatment on the wet fly ash so that the dioxin undergoes a dechlorination reaction; performing flotation separation on the irradiated wet fly ash to separate and obtain a solid pretreatment product and a liquid pretreatment product; respectively performing a second-step irradiation treatment on the solid pretreatment product and the liquid pretreatment product to obtain a solid treatment product and a liquid treatment product with a dioxin concentration less than 0.1 ng-TEQ / Nm 3 of the solid treatment product and the liquid treatment product; among them, the irradiation dose of the first-step irradiation treatment is less than the irradiation dose of the second-step irradiation treatment; thus, through two-step electron beam irradiation treatment in the present invention, in the first-step irradiation, a reaction system mainly based on reduction is constructed by the synergistic action of electron beam irradiation with a lower irradiation dose and hydrogen peroxide, and the dioxin is dechlorinated by the generated hydroperoxyl radicals; then, electron beam irradiation with a higher irradiation dose is used to construct an oxidation-based reaction system to degrade the dechlorinated dioxin. By separating the dechlorination process from the oxidation process, the reversible process of dechlorination is avoided, and the removal effect of electron beam irradiation on dioxin is improved, so that the dioxin concentration of the irradiated fly ash can be reduced to 0.1 ng-TEQ / Nm 3 The following meets the emission standards. Description of the Drawings

[0031] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0032] Figure 1 The flowchart shows the steps of a method for treating dioxins in fly ash from municipal solid waste incineration provided by an embodiment of the present invention;

[0033] Figure 2 The schematic structural diagram shows a system for treating dioxins in fly ash from municipal solid waste incineration provided by an embodiment of the present invention;

[0034] Figure 3 The schematic structural diagram shows a system for treating dioxins in fly ash from municipal solid waste incineration that uses the same second irradiation device for solid and liquid treatment in an embodiment of the present invention;

[0035] Figure 4 The schematic structural diagram shows a system for treating dioxins in fly ash from municipal solid waste incineration that uses different second irradiation devices for solid and liquid treatment in an embodiment of the present invention. Detailed implementation manners

[0036] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0037] Currently, incineration is a commonly used method for treating municipal solid waste in China. However, fly ash and flue gas containing dioxin toxic substances are generated during the incineration process. Dioxins are a group of 210 congeners, and 17 of them with chlorine substitutions at positions 2, 3, 7, and 8 are toxic. 2,3,7,8-Tetrachlorodibenzo-p-dioxin is one of the most toxic pollutants known to humans. How to effectively remove dioxins from flue gas and fly ash is the primary problem currently faced by the waste incineration technology. Among them, since most dioxins in flue gas decompose at high temperatures, less dioxin is actually generated in the flue gas. Compared with flue gas, the composition of fly ash is more complex, and it is more difficult to remove dioxins from fly ash.

[0038] In related technologies, the treatment methods for treating dioxins in fly ash mainly include: physical and chemical methods, solidification methods, and heat treatment methods. Among them, physical and chemical methods include hydrothermal methods, chemical precipitation methods, and chemical extraction methods, etc.; while chemical precipitation methods and chemical extraction methods are not widely used due to high costs. Solidification methods include cement solidification and chemical agent solidification; among them, cement solidification is simple to operate, but soluble salts in fly ash are likely to cause the solidified body to crack; while chemical agent solidification has a high cost. Heat treatment methods mainly include hydrothermal methods and sintering, etc.; but heat treatment methods require high temperatures, resulting in high energy consumption for this method and high requirements for the reactor.

[0039] At present, there is already a method of using electron beam irradiation to degrade dioxins, which is applied to the removal of dioxins in flue gas. However, due to the more complex composition of fly ash than flue gas, the direct application of electron beam irradiation technology to the removal of dioxins in fly ash has limited removal effect.

[0040] In view of this, the present invention provides a method and system for treating dioxins in municipal solid waste incineration fly ash. First, low-dose irradiation is used in combination with hydrogen peroxide to perform dechlorination treatment on dioxins in fly ash. A reduction system is constructed by the hydroperoxyl radicals generated by electron beam irradiation, and the reducibility of the hydroperoxyl radicals is used to dechlorinate dioxins. After eluting the chloride ions, higher-dose electron beam irradiation is performed on the fly ash again to construct an oxidation system mainly composed of hydroxyl radicals, and then the dioxins are oxidized and decomposed. Thus, the concentration of dioxins in the fly ash can be reduced to 0.1 ng-TEQ / Nm 3 or less.

[0041] Hereinafter, a method and system for treating dioxins in municipal solid waste incineration fly ash provided by the present invention will be described in detail with reference to the drawings and in conjunction with embodiments.

[0042] In the first aspect of the embodiments of the present invention, referring to Figure 1 , Figure 1 which shows a flowchart of the steps of a method for treating dioxins in municipal solid waste incineration fly ash provided by the embodiments of the present invention. As Figure 1 shown, the method includes:

[0043] S101, adding municipal solid waste incineration fly ash into a reactor, and adding hydrogen peroxide with a volume fraction of 30% to obtain wet fly ash.

[0044] Specifically, to uniformly moisten the municipal solid waste incineration fly ash with hydrogen peroxide, after adding the municipal solid waste incineration fly ash and hydrogen peroxide into the reactor, the mixture of the two is stirred to achieve the effect of uniform mixing.

[0045] Among them, the volume ratio of the fly ash to the hydrogen peroxide is 1:1 - 10:1.

[0046] Exemplarily, the volume ratio of the fly ash to the hydrogen peroxide is 1:1;

[0047] the volume ratio of the fly ash to the hydrogen peroxide is 3:1;

[0048] the volume ratio of the fly ash to the hydrogen peroxide is 5:1;

[0049] the volume ratio of the fly ash to the hydrogen peroxide is 7:1;

[0050] the volume ratio of the fly ash to the hydrogen peroxide is 9:1.

[0051] In the embodiments of the present invention, in combination with the concentration of dioxins in fly ash and in order to reduce the absorbed dose required for the second-step irradiation to decompose hydrogen peroxide, the dosage of hydrogen peroxide before the first-step irradiation only needs to wet the fly ash. Among them, hydrogen peroxide is evenly distributed on the surface of the wet fly ash obtained by stirring.

[0052] Preferably, in the embodiments of the present invention, the volume ratio of fly ash to hydrogen peroxide is 5:1 - 10:1; the main function of hydrogen peroxide is to generate hydroperoxyl radicals to dechlorinate dioxins through hydroperoxyl radicals. Therefore, there is no excessive requirement for the amount of hydrogen peroxide. At the same time, considering the cost issue of industrial treatment, when the volume of hydrogen peroxide is small, the cost is low. Therefore, it is preferred to use a volume ratio of fly ash to hydrogen peroxide of 5:1 - 10:1 for dioxin treatment, and the optimal is a volume ratio of fly ash to hydrogen peroxide of 10:1.

[0053] S102, perform a first-step irradiation treatment on the wet fly ash to cause a dechlorination reaction of dioxins.

[0054] In the embodiments of the present invention, the wet fly ash obtained by stirring is treated by electron beam irradiation. Through electron beam irradiation, hydrogen peroxide on the surface of the fly ash generates hydroperoxyl radicals to dechlorinate dioxins through hydroperoxyl radicals.

[0055] Among them, since the wet fly ash is solid, in order to ensure that the fly ash can be completely irradiated, before the irradiation treatment, the fly ash is laid flat to avoid the problem that during the irradiation process, due to the stacking of fly ash, part of the fly ash cannot be irradiated by the electron beam, resulting in the problem that part of the dioxins cannot undergo dechlorination reactions.

[0056] Among them, the irradiation dose of the first-step irradiation treatment is 1 - 6 kGy.

[0057] Exemplarily, the irradiation dose of the first-step irradiation treatment is 1 kGy;

[0058] The irradiation dose of the first-step irradiation treatment is 3 kGy;

[0059] The irradiation dose of the first-step irradiation treatment is 5 kGy;

[0060] The irradiation dose of the first-step irradiation treatment is 6 kGy.

[0061] In the embodiments of the present invention, since the first-step irradiation treatment is to cooperate with hydrogen peroxide to construct a reduction system, the irradiation dose of the first-step irradiation treatment should not be too high, and it is required that the concentration of active particles generated theoretically is much smaller than the dosage of hydrogen peroxide to prevent the formation of an oxidation system mainly composed of hydroxyl radicals in the system, resulting in the problem that the dechlorination reaction is reversible and dioxins are regenerated.

[0062] S103, perform flotation separation on the wet fly ash after the first-step irradiation treatment to separate a solid pretreatment product and a liquid pretreatment product.

[0063] In the embodiment of the present invention, free chloride ions are generated after the treatment of dioxins, and the fly ash itself contains a relatively large amount of soluble salt substances. Therefore, after the first-step irradiation treatment, the wet fly ash is subjected to flotation separation, and the soluble substances in the wet fly ash are separated from the insoluble fly ash by adding deionized water to obtain a solid pretreatment product and a liquid pretreatment product. Among them, the solid pretreatment product mainly includes insoluble heavy metals in the fly ash, the products of dioxin dechlorination, and some insoluble salt substances, etc.; the main components of the liquid pretreatment product include chloride ions, some soluble salts, and trace dioxin dechlorination products.

[0064] Among them, the specific steps of the flotation separation include:

[0065] S1031, adding deionized water to the wet fly ash after the first-step irradiation treatment to obtain a mixed liquid.

[0066] Among them, the volume ratio of deionized water to wet fly ash is 20% - 30%;

[0067] Exemplarily, the volume ratio of deionized water to wet fly ash is 20%;

[0068] The volume ratio of deionized water to wet fly ash is 25%;

[0069] The volume ratio of deionized water to wet fly ash is 30%.

[0070] Specifically, the wet fly ash after the first-step irradiation treatment is added to a flotation machine, and deionized water is added to obtain a mixed liquid. Thus, the soluble substances in the fly ash are dissolved in water and the two are separated.

[0071] S1032, washing the mixed liquid with water through the flotation machine at a preset speed for 20 - 60 min.

[0072] Among them, the preset speed is 500 - 2000 rpm;

[0073] Exemplarily, the mixed liquid is washed with water through the flotation machine at 500 rpm for 60 min;

[0074] The mixed liquid is washed with water through the flotation machine at 1000 rpm for 40 min;

[0075] The mixed liquid is washed with water through the flotation machine at 2000 rpm for 20 min.

[0076] S1033, separating the mixed liquid by centrifugation to obtain the solid pretreatment product and the liquid pretreatment product.

[0077] S104, perform a second irradiation treatment on the solid pretreatment product and the liquid pretreatment product respectively to obtain a solid treatment product and a liquid treatment product with a dioxin concentration less than 0.1 ng-TEQ / Nm 3 .

[0078] Among them, the irradiation dose of the first irradiation treatment is less than that of the second irradiation treatment.

[0079] Specifically, irradiate the solid pretreatment product with an irradiation dose of 15 - 50 kGy to obtain a solid treatment product; and irradiate the liquid pretreatment product with an irradiation dose of 7 - 40 kGy to obtain a liquid treatment product.

[0080] Considering that the dose of dioxin in the solid pretreatment product is more than that in the liquid pretreatment product, a higher irradiation dose is used for the second irradiation treatment of the solid pretreatment product, while a lower irradiation dose is used for the second irradiation treatment of the liquid pretreatment product. Among them, since the second irradiation treatment is mainly to generate hydroxyl radicals to oxidize the product after dioxin dechlorination, that is, the second irradiation treatment mainly constructs an oxidation system, the irradiation dose of the second irradiation treatment should be higher than that of the first irradiation treatment.

[0081] In the embodiments of the present invention, both the two-step irradiation treatments use an electron accelerator to irradiate fly ash with an electron beam; among them, the power of the electron accelerator is 100 kw and the energy is 2 MeV to meet the required irradiation dose.

[0082] A method for treating dioxin in waste incineration fly ash provided by the embodiments of the present invention mixes hydrogen peroxide in the fly ash to generate hydroperoxyl radicals at a lower irradiation dose, dechlorinate the dioxin in the fly ash, then perform flotation on the fly ash to remove soluble salt ions such as chloride ions from the fly ash, and then perform irradiation treatment on both the flotation liquid and solid by the second irradiation to remove the dioxin dechlorination product. Thus, through the first irradiation synergistic with hydrogen peroxide to construct a reduction system to achieve the effect of dioxin dechlorination, and separate the chloride ions from the fly ash and then perform electron beam irradiation treatment to construct an oxidation system with hydroxyl radicals to remove the dioxin dechlorination product. Since the chloride ions are removed in advance to avoid the reversible process of the chloride ions recombining with the dioxin dechlorination product during the electron beam irradiation process, and also avoid the problem that the quenching effect of the chloride ions on the free radicals leads to a reduction in the removal effect, and the method of using electron beam irradiation has a simple process and good treatment effect. After irradiation, the dioxin concentration in the flotation liquid and solid can be reduced to 0.1 ng-TEQ / Nm 3 The following meets the emission standards.

[0083] In the second aspect of the embodiments of the present invention, refer to Figure 2 ,Figure 2 shows a treatment system for dioxins in fly ash from waste incineration provided by an embodiment of the present invention. As Figure 2 shown, the system includes:

[0084] a reaction device 201 for mixing fly ash from waste incineration and hydrogen peroxide, wherein the volume ratio of the fly ash to the hydrogen peroxide is 1:1 - 10:1;

[0085] a first irradiation device 202 for performing a first-step irradiation treatment on the fly ash from waste incineration and hydrogen peroxide to cause a dechlorination reaction of dioxins;

[0086] a flotation device 203 for performing flotation separation on the product obtained from the dechlorination reaction to separate a solid pretreatment product and a liquid pretreatment product;

[0087] a second irradiation device 204 for performing a second-step irradiation treatment on the solid pretreatment product and the liquid pretreatment product respectively to obtain a solid treatment product and a liquid treatment product with a dioxin concentration less than 0.1 ng-TEQ / Nm 3 of the solid treatment product and the liquid treatment product.

[0088] Among them, the reaction device 201, the first irradiation device 202, the flotation device 203, and the second irradiation device 204 are arranged in sequence to sequentially process the fly ash to achieve the effect of removing dioxins.

[0089] In specific implementation, fly ash from waste incineration and hydrogen peroxide are added to the reaction device 201 and the volume ratio of the fly ash to the hydrogen peroxide is 1:1 - 10:1 to mix the two in the reaction device 201; the mixed fly ash is added to the first irradiation device 202 for the first-step irradiation treatment with an irradiation dose of 1 - 6 kGy; the irradiated fly ash is added to the flotation device 203 to separate a solid pretreatment product and a liquid pretreatment product by flotation; then, the solid pretreatment product and the liquid pretreatment product are respectively added to the second irradiation device 204, and the solid pretreatment product is subjected to electron beam irradiation treatment with an irradiation dose of 15 - 50 kGy, and the liquid pretreatment product is subjected to electron beam irradiation treatment with an irradiation dose of 7 - 40 kGy. Thus, a solid treatment product and a liquid treatment product with a dioxin concentration less than 0.1 ng-TEQ / Nm 3 of the solid treatment product and the liquid treatment product are obtained.

[0090] Among them, the fly ash can be collected during the waste incineration process and uniformly treated after collection. During the treatment process, a batch treatment method can be adopted to treat a certain amount of fly ash each time, or a continuous treatment method can be adopted to continuously treat the fly ash. Among them, adding the fly ash to the reaction device 201 can be in a manual addition manner or an automatic addition manner, and the present invention does not make specific limitations.

[0091] In some embodiments, a stirring device (not shown in the figure) is provided in the reaction device 201. The stirring device is used to stir the fly ash and the hydrogen peroxide in the reaction device to obtain wet fly ash;

[0092] The reaction device is connected to the first irradiation device 202 and the flotation device 203 through a first solid conveyor belt; wherein, the first solid conveyor belt is used to convey the wet fly ash;

[0093] The flotation device 203 is connected to the second irradiation device 204 through a second solid conveyor belt; wherein, the second solid conveyor belt is used to convey the solid pretreatment product.

[0094] Among them, hydrogen peroxide is added to generate hydroperoxyl radicals during the first-step irradiation process to perform dechlorination treatment on dioxins in the fly ash. Therefore, to ensure the dechlorination effect on dioxins, hydrogen peroxide and fly ash need to be evenly mixed. Thus, a stirring device is provided in the reaction device 201. The structure of the stirring device in the embodiments of the present invention is not specifically limited, as long as the effect of uniform mixing can be achieved.

[0095] Specifically in implementation, the mixed fly ash is sequentially transported from the reaction device 201 to the first irradiation device 202 and the flotation device 203 through a solid conveyor belt; the first irradiation device 202 is a reaction chamber equipped with an electron accelerator, and an entrance and exit through which the solid conveyor belt can enter and exit are provided in the reaction chamber. Then, after the wet fly ash is sent into the reaction chamber of the first irradiation device by the solid conveyor belt, wait for a certain time to make the irradiation dose 1 - 6 kGy, and then, transport the irradiated fly ash to the flotation device 203. In the first irradiation device 202, the role of irradiation is to generate hydroperoxyl radicals from hydrogen peroxide. Therefore, the irradiation dose cannot be too high. An overly high irradiation dose mainly generates hydroxyl radicals and undergoes oxidation reactions, making it difficult to perform dechlorination on dioxins. Therefore, the irradiation dose is controlled to be 1 - 6 kGy.

[0096] Among them, the flotation device 203 is provided with a flotation cell. To transport the fly ash into the flotation cell, the end of the solid conveyor belt can be set above the flotation cell. Thus, when the fly ash reaches the end of the solid conveyor belt, it directly enters the flotation cell through the opening above the flotation cell for flotation separation. The role of the flotation device is to separate the soluble substances and insoluble substances in the fly ash, that is, to separate the insoluble solids in the fly ash, the dechlorination products of dioxins, etc. and soluble salts, chloride ions generated by dechlorination, etc. Thus, in the subsequent irradiation process, the re-generation of dioxins is avoided and the removal effect cannot be achieved, and at the same time, the quenching effect of chloride ions on hydroxyl radicals is also avoided.

[0097] In some embodiments, the device further includes a water tank 205, and an inlet of the water tank 205 is connected to the flotation device 203 to receive the liquid pre-treatment product after flotation separation;

[0098] An outlet of the water tank 205 is connected to the second irradiation device 204. A water pump is provided in the water tank 205, and the water tank 205 is used to pump the liquid pre-treatment product into the second irradiation device 204 for irradiation treatment.

[0099] Specifically, since the second irradiation device 204 not only treats the solid pre-treatment product but also treats the liquid pre-treatment product, and due to different irradiation doses, the solid pre-treatment product and the liquid pre-treatment product are irradiated separately. Therefore, the liquid pre-treatment product in the flotation tank cannot be directly introduced into the reaction chamber of the second irradiation device 204. Thus, a water tank 205 is provided between the flotation device 203 and the second irradiation device 204. The liquid after flotation is sent into the water tank 205, and then pumped into the reaction chamber by the water tank 205 for irradiation treatment.

[0100] In some embodiments, a first extrusion device (not shown in the figure) is provided at the connection between the reaction device 201 and the first solid conveyor belt. The first extrusion device is used to extrude the wet fly ash so that the wet fly ash is laid flat on the first solid conveyor belt.

[0101] A second extrusion device (not shown in the figure) is provided at the connection between the flotation device 203 and the second solid conveyor belt. The second extrusion device is used to extrude the solid pre-treatment product so that the solid pre-treatment product is laid flat on the second solid conveyor belt.

[0102] Specifically, to ensure that the fly ash can be uniformly irradiated by the first irradiation device 202 and the second irradiation device 204, extrusion devices are provided at the connection between the reaction device 201 and the first solid conveyor belt and at the connection between the flotation device 203 and the second solid conveyor belt. The fly ash is laid flat on the conveyor belt by extrusion, thereby avoiding the problem that partial stacking of fly ash affects the effect of irradiation treatment.

[0103] In some embodiments, the number of the second irradiation devices 204 is one or two;

[0104] When the number of the second irradiation devices 204 is one, the second irradiation device 204 is respectively connected to the second solid conveyor belt and the water tank 205;

[0105] When the number of the second irradiation devices 204 is two, one of the two second irradiation devices 204 is connected to the water tank 205, and the other is connected to the solid conveyor belt.

[0106] Since the second irradiation device processes both the liquid pre-treatment product and the solid pre-treatment product, the number of second irradiation devices can be set according to the actual situation. For example, when giving priority to the treatment cost of fly ash, one second irradiation device 204 is set, and the solid pre-treatment product and the liquid pre-treatment product are successively fed into the second irradiation device 204 for the second-step irradiation treatment. When giving priority to the treatment efficiency of fly ash, two second irradiation devices 204 are set, one for irradiating the solid pre-treatment product and the other for irradiating the liquid pre-treatment product.

[0107] In some embodiments, although the irradiation doses of the solid pre-treatment product and the liquid pre-treatment product are different, the irradiation dose can be changed by controlling the irradiation time, that is, the energy and power of the electron accelerator of the second irradiation device 204 can remain unchanged. Thus, referring to Figure 3 , in the system, both the solid pre-treatment product and the liquid pre-treatment product can be processed through the same second irradiation device 204, that is, the solid after flotation is sent into the second irradiation device 204 by the second solid conveyor belt for electron beam irradiation; the liquid pre-treatment product flows into the water tank 205 through the flotation device and is pumped into the second irradiation device 204 by the water pump in the water tank 205 for electron beam irradiation.

[0108] Among them, to avoid interference between the solid pre-treatment product and the liquid pre-treatment product, the reaction chamber of the second irradiation device 204 can be separated by a partition, and the solid pre-treatment product and the liquid pre-treatment product are irradiated simultaneously, and the residence time of the solid pre-treatment product and the liquid pre-treatment product in the chamber is changed to achieve the purpose of irradiating the solid pre-treatment product and the liquid pre-treatment product with different irradiation doses.

[0109] Thus, when the number of the second irradiation devices 204 is one, the second irradiation device 204 is provided with a reaction chamber, the reaction chamber is arranged in parallel with the second solid conveyor belt, and the water inlet of the reaction chamber is connected to the water outlet of the water tank 205. In the embodiment of the present invention, to avoid interference between the solid pre-treatment product and the liquid pre-treatment product, a partition is arranged in the reaction chamber, and two sub-chambers are formed in the reaction chamber by the partition, one sub-chamber is connected to the solid conveyor belt, and the other sub-chamber is connected to the water tank 205, and then the solid pre-treatment product and the liquid pre-treatment product are processed in the two sub-chambers respectively.

[0110] Among them, the material of the partition is preferably 306 steel plate, and its excellent corrosion resistance makes its service life longer, avoiding frequent replacement and increasing the treatment cost. In the case of simultaneous irradiation, the scanning window of the second irradiation device is 1-2m, so as to be able to form two sub-chambers to irradiate the solid pre-treatment product and the liquid pre-treatment simultaneously.

[0111] When the number of the second irradiation devices 204 is two, referring to Figure 4 , two second irradiation devices 204 are arranged in the system, one of which is set as an irradiation device applicable to solids, and the other is set as an irradiation device applicable to liquids. That is, the solid treatment object is sent into one of the two second irradiation devices 204 by the second solid conveyor belt, and the other second irradiation device 204 is connected to the flotation device 203 through the water tank 205. Thus, the liquid pretreatment object is loaded into the water tank 205, and the liquid pretreatment object is pumped into the other second irradiation device 204 through a water pump for irradiation treatment.

[0112] In some embodiments, the feed port of the reaction device 201 is connected to the discharge port of the hydrogen peroxide storage device, and the hydrogen peroxide storage device pumps hydrogen peroxide from the discharge port into the reaction device through a water pump.

[0113] Among them, since the volume ratio of fly ash to hydrogen peroxide needs to be controlled, a hydrogen peroxide storage device equipped with an electronic pump can be set. When treating fly ash, the amount of hydrogen peroxide added to the reaction device 201 is controlled by controlling the rotation speed of the electronic pump. Thus, the volume ratio of fly ash to hydrogen peroxide is controlled between 1:1 and 10:1.

[0114] In some embodiments, the second solid conveyor belt is connected to a motor, and the motor is configured to drive the second solid conveyor belt to operate at intervals of a first preset time;

[0115] The water tank 205 is connected to an electronic pump, and the electronic pump is configured to pump the liquid pretreatment object into the reaction chamber at intervals of a second preset time; wherein, the first preset time and the second preset time are determined according to the irradiation dose.

[0116] Among them, when there is one second irradiation device 201, since the power of the electron accelerator is fixed, that is, the irradiation dose received per second in the second irradiation device 204 is constant. Thus, it can be set to control the running time of the second conveyor belt and the running time of the water pump, so that the irradiation dose of the solid treatment object reaches 15 - 50 kGy, and the irradiation dose of the liquid pretreatment object reaches 7 - 40 kGy. That is, the irradiation dose per second of the second irradiation device is determined according to the power and energy of the electron accelerator, and the residence time of the solid treatment object and the liquid treatment object in the second irradiation device is determined based on the required irradiation dose.

[0117] In some embodiments, to avoid the mutual interference between the solid pretreatment object and the liquid pretreatment object, the two are respectively introduced into the second irradiation device 204 for irradiation treatment. At this time, the time interval is determined as the time interval when both the solid pretreatment object and the liquid pretreatment object are processed. That is, after the solid treatment object is processed, the liquid pretreatment object is processed, and then the next batch of solid pretreatment objects is processed.

[0118] The dioxin treatment system for municipal solid waste incineration fly ash provided by the embodiments of the present invention mixes hydrogen peroxide in the fly ash to generate hydroperoxyl radicals at a relatively low irradiation dose, dechlorinate the dioxin in the fly ash, then float the fly ash to remove soluble salt ions such as chloride ions from the fly ash, and then perform irradiation treatment on both the liquid and solid after flotation by the second-step irradiation to remove the dioxin dechlorination products. Thus, by constructing a reduction system through the first-step irradiation in cooperation with hydrogen peroxide, the effect of dioxin dechlorination is achieved, and after separating the chloride ions from the fly ash, electron beam irradiation treatment is carried out to construct an oxidation system with hydroxyl radicals to remove the dioxin dechlorination products. Since the chloride ions are removed in advance, the reversible process of the chloride ions recombining with the dioxin dechlorination products during the electron beam irradiation process is avoided, and the problem of the quenching effect of chloride ions on free radicals leading to a reduction in the removal effect is also avoided. Moreover, the method of using electron beam irradiation has a simple treatment process and good treatment effect. After the liquid and solid after flotation are irradiated, the dioxin concentration therein can be reduced to 0.1 ng-TEQ / Nm 3 The following meets the emission standards.

[0119] To enable those skilled in the art to better understand the present invention, the following uses multiple specific embodiments to illustrate a method and system for treating dioxin in municipal solid waste incineration fly ash of the present invention.

[0120] Example 1

[0121] Put 5 g of municipal solid waste incineration fly ash from a certain waste treatment plant into a flat-bottom quartz reactor (diameter 10 cm); add 20 ml of 30% hydrogen peroxide to the flat-bottom quartz reactor and stir evenly to obtain wet fly ash.

[0122] Perform the first-step irradiation treatment on the wet fly ash to cause the dioxin to undergo a dechlorination reaction; wherein, the irradiation dose is 5 kGy.

[0123] Transfer the fly ash after the first-step irradiation treatment to a flotation machine and add 1 L of deionized water to obtain a mixed liquid.

[0124] Float the mixed liquid at a rotation speed of 1000 rpm for 30 min;

[0125] Separate the mixed liquid by centrifugation to obtain a solid pretreatment product and a liquid pretreatment product.

[0126] Perform the second-step irradiation treatment on the liquid pretreatment product with an irradiation dose of 40 kGy, and perform the second-step irradiation treatment on the solid pretreatment product with an irradiation dose of 30 kGy.

[0127] It is measured that the dioxin concentration in the municipal solid waste incineration fly ash before treatment is between 40 and 110 ng TEQ / Nm3 No dioxins were detected in the liquid and solid after irradiation treatment, meeting the current national emission standards.

[0128] Example 2

[0129] Place 5 g of fly ash from a waste incineration plant in a flat-bottom quartz reactor (diameter 10 cm); add 20 ml of 30% hydrogen peroxide to the flat-bottom quartz reactor and stir evenly to obtain wet fly ash.

[0130] Perform the first-step irradiation treatment on the wet fly ash to cause the dechlorination reaction of dioxins; among them, the irradiation dose is 5 kGy.

[0131] Transfer the fly ash after the first-step irradiation treatment to a flotation machine and add 1.5 L of deionized water to obtain a mixed liquid.

[0132] Float the mixed liquid at a rotational speed of 1000 rpm for 30 min;

[0133] Separate the mixed liquid by centrifugation to obtain a solid pre-treatment product and a liquid pre-treatment product.

[0134] Perform the second-step irradiation treatment on the liquid pre-treatment product with an irradiation dose of 30 kGy, and perform the second-step irradiation treatment on the solid pre-treatment product with an irradiation dose of 40 kGy.

[0135] The concentration of dioxins in the fly ash was measured to be between 40 and 110 ng TEQ / Nm 3 ; No dioxins were detected in the liquid and solid after irradiation treatment, meeting the current national emission standards.

[0136] Example 3

[0137] Place 5 g of fly ash from a waste incineration plant in a flat-bottom quartz reactor (diameter 10 cm); add 20 ml of 30% hydrogen peroxide to the flat-bottom quartz reactor and stir evenly to obtain wet fly ash.

[0138] Perform the first-step irradiation treatment on the wet fly ash to cause the dechlorination reaction of dioxins; among them, the irradiation dose is 6 kGy.

[0139] Transfer the fly ash after the first-step irradiation treatment to a flotation machine and add 1 L of deionized water to obtain a mixed liquid.

[0140] Float the mixed liquid at a rotational speed of 1600 rpm for 20 min;

[0141] Separate the mixed liquid by centrifugation to obtain a solid pre-treatment product and a liquid pre-treatment product.

[0142] The second irradiation treatment was performed on the liquid pre-treatment material at a irradiation dose of 30 kGy, and the second irradiation treatment was performed on the solid pre-treatment material at a irradiation dose of 45 kGy.

[0143] The dioxin concentration in the fly ash was determined to be between 40 and 110 ng TEQ / Nm 3 No dioxins were detected in the liquid and solid after irradiation treatment, meeting the current national emission standards.

[0144] Comparative Example 1

[0145] 5 g of fly ash from the incineration of a waste treatment plant was placed in a flat-bottomed quartz reactor (10 cm in diameter); 20 ml of 30% hydrogen peroxide was added to the flat-bottomed quartz reactor and stirred evenly to obtain wet fly ash.

[0146] The wet fly ash is directly irradiated with an electron beam (power 100 kW, energy 2 MeV) with an irradiation dose of 50 kGy.

[0147] The dioxin concentration in the fly ash was determined to be between 40 and 110 ng TEQ / Nm3. The dioxin concentration in the solid after treatment was between 10 and 70 ng TEQ / Nm3, which did not meet the national emission standards.

[0148] The method for treating dioxins in fly ash from garbage incineration provided by the embodiment of the present invention comprises the following steps: in the first step of irradiation, hydrogen peroxide is used in combination with electron beam irradiation to treat fly ash, reducing active ions are generated to cause dioxins to undergo dechlorination reaction, and after washing away the generated chloride ions and other soluble salt ions, the second step of irradiation is used to treat fly ash and liquid after flotation to remove the dechlorination products of dioxins, and the problem of poor treatment effect caused by reversible reaction is avoided by dividing reduction and oxidation into two steps, as well as the quenching effect of chloride ions on hydroxyl radicals during electron beam irradiation. Compared with the single electron beam irradiation, the method provided by the embodiment of the present invention is used to treat dioxins in fly ash, and its treatment effect is better.

[0149] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0150] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily required by the present invention.

[0151] The above has introduced in detail a method and system for treating dioxins in municipal solid waste incineration fly ash. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for treating dioxins in municipal solid waste incineration fly ash, characterized in that, The method includes: Adding waste incineration fly ash into a reactor and adding hydrogen peroxide with a volume fraction of 30% to obtain wet fly ash; wherein, the volume ratio of the fly ash to the hydrogen peroxide is 1:1 - 10:1; Performing a first-step irradiation treatment on the wet fly ash. Under the synergistic action of the irradiation and hydrogen peroxide, a reaction system mainly based on reduction is constructed to cause the dechlorination reaction of dioxins; Performing flotation separation on the wet fly ash after the first-step irradiation treatment to separate a solid pretreatment product and a liquid pretreatment product; Perform a second irradiation treatment on the solid pretreatment product and the liquid pretreatment product respectively to construct an oxidation system mainly composed of hydroxyl radicals, and then oxidize and decompose dioxin to obtain a solid treatment product and a liquid treatment product with a dioxin concentration less than 0.1 ng-TEQ / Nm 3 ; wherein, the irradiation dose of the first irradiation treatment is less than the irradiation dose of the second irradiation treatment; Including: the irradiation dose of the first-step irradiation treatment is 1 - 6 kGy; The irradiation doses of the second-step irradiation treatment are respectively: Irradiating the solid pretreatment product with an irradiation dose of 15 - 50 kGy, And irradiating the liquid pretreatment product with an irradiation dose of 7 - 40 kGy; Respectively obtaining the solid treatment product and the liquid treatment product.

2. The method for treating dioxins in fly ash from waste incineration according to claim 1, characterized in that, The irradiation treatment is carried out using an electron accelerator.

3. The method for treating dioxins in fly ash from waste incineration according to claim 1, characterized in that, The steps of the flotation separation include: Adding deionized water to the wet fly ash after the first-step irradiation treatment to obtain a mixed liquid; Washing the mixed liquid with water in a flotation machine at a preset rotation speed for 20 - 60 min; Separating the mixed liquid by centrifugation to obtain the solid pretreatment product and the liquid pretreatment product.

4. The method for treating dioxins in municipal solid waste incineration fly ash according to claim 3, wherein The volume ratio of the deionized water to the wet fly ash is 20% - 30%, and the preset rotation speed is 500 - 2000 rpm.

5. The method for treating dioxins in fly ash from waste incineration according to claim 1, characterized in that, The volume ratio of the fly ash to the hydrogen peroxide is 5:1 - 10:

1.

6. The method for treating dioxins in waste incineration fly ash according to claim 5, characterized in that, The volume ratio of the fly ash to the hydrogen peroxide is 10:

1.

7. The method for treating dioxins in waste incineration fly ash according to claim 2, characterized in that, The power of the electron accelerator is 100 kw and the energy is 2 MeV.

8. The method for treating dioxins in municipal solid waste incineration fly ash according to claim 1, wherein, The wet fly ash and the solid pretreatment product are laid flat to make the treatment effect of the irradiation treatment uniform.

9. A treatment system for dioxins in municipal solid waste incineration fly ash, which is used to implement the treatment method described in any one of claims 1 to 8, and is characterized in that, The system includes: A reaction device for mixing waste incineration fly ash and hydrogen peroxide, wherein the volume ratio of the fly ash to the hydrogen peroxide is 1:1 - 10:1; A first irradiation device for performing a first-step irradiation treatment on waste incineration fly ash and hydrogen peroxide. Under the synergistic action of the irradiation and hydrogen peroxide, a reaction system mainly based on reduction is constructed to cause the dechlorination reaction of dioxins; A flotation device for performing flotation separation on the product obtained from the dechlorination reaction to separate a solid pretreatment product and a liquid pretreatment product; A second irradiation device is used to perform a second-step irradiation treatment on the solid pretreatment material and the liquid pretreatment material respectively, construct an oxidation system mainly composed of hydroxyl radicals, and then oxidize and decompose dioxins to obtain a solid treatment material and a liquid treatment material with a dioxin concentration less than 0.1 ng-TEQ / Nm 3 .

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