Method and system for degrading dioxin in high-salt-content solid waste and deeply dechlorinating

Abstract

The invention discloses a method and a system for degrading dioxin in high-salt-content solid waste and deeply dechlorinating. The system comprises a retardant adding unit, a vacuum low-temperature detoxification unit, a flue gas treatment unit, a continuous three-stage washing unit, an evaporative crystallization unit, a mineralizer adding unit and a sodium hypochlorite generating unit. According to the method, the heavy metal oxide contained in the high-salt-content solid waste is used as the catalyst, so that the dioxin is thoroughly degraded under the vacuum low-temperature condition, and meanwhile, the retardant is added to prevent the resynthesis of the dioxin. Moreover, acidic substances in the flue gas are absorbed by the process water tank and are used for treating insoluble chlorides, so that deep dechlorination is realized while recycling of the acidic substances is realized. Besides, after heavy metals are removed from the water washing liquid, a small part of saline water is used for producing sodium hypochlorite for flue gas deamination, so that resource utilization is realized while harmless treatment of wastes is realized, and the treatment energy consumption is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of harmless treatment and resource utilization of high-salt solid waste, and in particular relates to a method and system for degrading dioxins in high-salt solid waste and deep dechlorination. Background Art

[0002] Waste incineration will produce a large amount of high-salt solid waste, such as fly ash, which contains high concentrations of dioxins, heavy metals and soluble chloride salts, and is classified as Class HW18 hazardous waste in the "National List of Hazardous Wastes".

[0003] Dioxins are highly toxic and can accumulate in the body for a long time after being absorbed by the human body, damaging multiple organs and systems, causing reproductive toxicity, genetic toxicity and carcinogenicity. The high chlorine content in high-salt solid waste not only increases the leaching toxicity of heavy metals, but also seriously limits the harmlessness and resource utilization of high-salt solid waste. Therefore, it is necessary to dechlorinate and remove heavy metals from high-salt solid waste.

[0004] There are many methods for degrading dioxins, each with its own advantages and disadvantages. Generally, photodegradation has the disadvantages of incomplete degradation and low degradation rate; although biodegradation does not cause secondary pollution, it has the disadvantage of a long degradation cycle; although high-temperature thermal degradation is thorough, it has high requirements for equipment and operation, high energy consumption, and is prone to secondary pollution; metal / metal oxide catalytic degradation technology has fast reaction, relatively mild temperature conditions, low energy consumption, but dioxins will be re-synthesized, and chlorine and heavy metals in the high-salt solid waste after degradation cannot be treated.

[0005] Chinese patent application CN202211165974.6 discloses a "waste incineration plant flue gas purification coupled fly ash water washing liquid heavy metal removal system and method". This method directly washes the fly ash after low-temperature degradation treatment, and the water washing liquid is crystallized and salted after removing heavy metals and decalcification. Although the fly ash water washing process can effectively remove soluble chlorine in fly ash, it is difficult to remove insoluble chlorine. In addition, most of the existing water washing equipment is batch processing and cannot achieve continuous production.

[0006] Therefore, there is still a need for a continuous production system and method for degrading dioxins in high-salt solid waste and inhibiting their resynthesis while achieving dechlorination and removal of heavy metals. Summary of the invention

[0007] In order to solve at least some of the technical problems in the above-mentioned prior art, the present invention realizes the continuous treatment of high-salt solid waste and greatly reduces energy consumption by setting a retarder addition unit, a vacuum low-temperature detoxification unit, a flue gas treatment unit, a continuous three-stage water washing unit, an evaporation crystallization unit, a mineralizer addition unit and a sodium hypochlorite generation unit. Specifically, the present invention includes the following contents.

[0008] In a first aspect of the present invention, a system for degrading dioxins in high-salt solid waste and deep dechlorination is provided, which comprises: A blocker adding unit, which is used to provide a thiamine blocker; A vacuum low-temperature detoxification unit, which is connected to the retarder adding unit, and the vacuum low-temperature detoxification unit comprises a preheating spiral, a first metering spiral, an electromagnetic heating reactor and a heat recovery spiral connected in sequence; A flue gas treatment unit, which is connected to the vacuum low-temperature detoxification unit for conveying and treating gas logistics, and the flue gas treatment unit includes a dust collector, a pipeline mixer, a water ring vacuum pump, a first process water tank and an activated carbon tank; A continuous three-stage water washing unit, which is connected to the vacuum low-temperature detoxification unit for conveying and washing the solid flow, and the continuous three-stage water washing unit comprises a first-stage horizontal double-screw continuous cleaning machine, a first-stage horizontal screw centrifuge, a first-stage buffer tank, a second-stage horizontal double-screw continuous cleaning machine, a second-stage horizontal screw centrifuge, a second-stage buffer tank, a third-stage horizontal double-screw continuous cleaning machine, a third-stage horizontal screw centrifuge, a third-stage buffer tank and a second process water tank; an evaporation crystallization unit connected to the continuous three-stage water washing unit, the evaporation crystallization unit being used to convert a liquid stream originating from the continuous three-stage water washing unit; A mineralizer adding unit, which is connected to the continuous three-stage water washing unit to provide a heavy metal mineralizer; The sodium hypochlorite generating unit is arranged between the flue gas treatment unit and the continuous three-stage water washing unit to convert the liquid flow after passing through the mineralizer adding unit into sodium hypochlorite, and at the same time transport the sodium hypochlorite to the flue gas treatment unit.

[0009] In certain embodiments, according to the system for degrading dioxins in high-salt solid waste and deep dechlorination of the present invention, a hot water-cold water cycle is formed between the preheating spiral and the heat recovery spiral.

[0010] In certain embodiments, according to the system for degrading dioxins in high-salt solid waste and deep dechlorination of the present invention, the electromagnetic heating reactor in the vacuum low-temperature detoxification unit is connected to the dust collector of the flue gas treatment unit.

[0011] In certain embodiments, according to the system for degrading dioxins in high-salt solid waste and deep dechlorination of the present invention, the heat recovery spiral of the vacuum low-temperature detoxification unit is connected to the first-stage horizontal double-screw continuous cleaning machine of the continuous three-stage water washing unit, and a detoxification ash temporary storage bin and a second metering spiral are further arranged between the heat recovery spiral and the first-stage horizontal double-screw continuous cleaning machine.

[0012] In certain embodiments, according to the system for degrading dioxins in high-salt solid waste and deep dechlorination of the present invention, the continuous three-stage water washing unit further includes a filter press device, and the mineralizer addition unit is arranged between the primary buffer tank of the continuous three-stage water washing unit and the filter press device.

[0013] In certain embodiments, according to the system for degrading dioxins in high-salt solid waste and deep dechlorination of the present invention, a brine tank is provided between the evaporation crystallization unit and the filter press device of the continuous three-stage water washing unit.

[0014] The second aspect of the present invention provides a method for degrading dioxins in high-salt solid waste and deep dechlorination, wherein the method comprises the steps of using the system of the present invention to treat high-salt solid waste, including: (1) adding a thioamine retarder to the high-salt solid waste through the retarder adding unit, and conveying the high-salt solid waste to the electromagnetic heating reactor through the preheating screw and the metering screw of the vacuum low-temperature detoxification unit, so that the high-salt solid waste undergoes a degradation reaction to obtain detoxified ash, and the cooled solid flow is obtained by using the heat recovery screw; (2) After the gas flow in the electromagnetic heating reactor is dedusted by the dust collector, it enters the pipeline mixer and reacts with the solution from the sodium hypochlorite generation unit. The deaminated gas flow is pumped to the first process water tank by a water ring vacuum pump, so that the acidic gas is absorbed by the process water to obtain acidic process water. The deaminated and deacidified gas flow enters the activated carbon tank, and the acidic process water in the first process water tank enters the first-stage horizontal double-screw continuous cleaning machine of the continuous three-stage water washing unit; (3) allowing the cooled solid flow to enter the first-stage horizontal double-screw continuous cleaning machine of the continuous three-stage water washing unit through a second metering screw, wherein the water-soluble chloride in the solid flow is dissolved in the acidic process water during the water washing process, and the water-insoluble chloride reacts with the acid in the process water to obtain a first-stage water washing liquid, a heavy metal mineralizer is added to the first-stage water washing liquid, the pH of the solution is adjusted and the heavy metals are precipitated, and then the first-stage water washing liquid is passed into a filter press to obtain a filtrate, and the filtrate is allowed to enter a brine tank; the third-stage water washing slag after the solid flow is treated by the continuous three-stage water washing unit is utilized as a raw material for unfired bricks; (4) The filtrate entering the brine tank enters the evaporation crystallization unit through the main outlet for conversion, and at the same time, the filtrate enters the sodium hypochlorite generation unit through the bypass outlet for reaction to obtain sodium hypochlorite that can be provided to the pipeline mixer.

[0015] In certain embodiments, according to the method for degrading dioxins and deep dechlorination in high-salt solid wastes of the present invention, the sulfur amino retarder includes at least one of urea, melamine, acetohydrazide, formic hydrazide, semicarbazide, thiosemicarbazide, thiomethylhydrazine, ammonium thiosulfate and ammonium sulfate, and the addition amount thereof is 3-10% of the mass of the high-salt solid waste.

[0016] In certain embodiments, according to the method for degrading dioxins in high-salt solid waste and deep dechlorination of the present invention, the temperature of the electromagnetic heating reactor is controlled at 350-450° C., and the reaction time is 1.5-2 h.

[0017] In certain embodiments, according to the method for degrading dioxins and deep dechlorination in high-salt solid wastes described in the present invention, the detoxification ash temporary storage bin is provided with a control device, and the control device is configured to automatically open the ash bin unloading valve when the ash volume reaches 2 / 3 of the bin capacity, and when the system is running, the ash intake in the bin is greater than the ash output every 2 hours.

[0018] In certain embodiments, according to the method for degrading dioxins in high-salt solid waste and deep dechlorination of the present invention, the water-to-solid mass ratio of the continuous three-stage water washing unit is (0.8-3):1.

[0019] In certain embodiments, according to the method for degrading dioxins in high-salt solid waste and deep dechlorination of the present invention, the amount of the heavy metal mineralizer added is 1-5% of the mass of the primary water wash liquid.

[0020] In certain embodiments, according to the method for degrading dioxins in high-salt solid waste and deep dechlorination of the present invention, the bypass outlet flow rate of the brine tank is 0.1-0.3% of the main outlet flow rate.

[0021] The present invention has the following beneficial effects: (1) The present invention uses a water ring vacuum pump to achieve and maintain the vacuum environment in the electromagnetic heating reactor, and utilizes the heavy metal oxides (such as MnO x , CuO x CrO x etc.) as catalysts to completely degrade dioxins into CO2, H2O and HCl at low temperatures (350-450°C). At the same time, adding sulfur amino retarder to high-salt solid waste can prevent the re-synthesis of dioxins during the low-temperature degradation process. This process does not require nitrogen production or nitrogen filling, which can reduce equipment investment and processing energy consumption.

[0022] (2) The small amount of flue gas produced by the present invention contains SO2, NO xAcidic substances such as CO2 and HCl are absorbed in the process water tank and then passed into a first-stage horizontal double-screw continuous cleaning machine, which can convert the insoluble chlorine in the detoxification ash into soluble chlorine. This process not only purifies the flue gas, but also realizes the recycling of acidic substances, and further improves the water-washing dechlorination rate of the detoxification ash, achieving deep dechlorination, achieving three goals at one stroke.

[0023] (3) The slurry outflow in the horizontal double-screw continuous cleaning machine in the system of the present invention is set to overflow type, combined with the supporting connection mode of the three-stage water washing equipment, it can realize continuous water washing of high-salt solid waste.

[0024] (4) Since the flue gas produced by the low-temperature degradation of high-salt solid waste contains high-concentration ammonia, the present invention removes heavy metals from the water washing liquid of the detoxification ash, and then electrolyzes a small portion of the salt water to produce sodium hypochlorite, which reacts with the ammonia in the flue gas to produce N2 to achieve flue gas deammoniation, thereby treating waste with waste.

[0025] (5) In the present invention, the brine produced by washing high-salt solid waste enters the evaporation crystallization unit to recover sodium chloride and potassium chloride respectively, and the washed residue can be used as a raw material for building materials, thereby fully realizing the harmless continuous treatment and resource utilization of waste.

[0026] The system and method of the present invention are used to treat high-salt solid waste, the degradation rate of dioxins reaches more than 99%, and the overall process dechlorination rate reaches more than 99%. At the same time, waste heat utilization, flue gas acid recovery and chloride salt recovery can be carried out, and the washed slag can be used as a raw material for building materials, fully realizing the recycling of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a process flow chart for degradation of dioxins and deep dechlorination in high-salt solid waste.

[0028] Figure 2 It is a schematic diagram of the structure of the preheating spiral and the heat recovery spiral; among them, 1 is the solid waste feed port, 2 is the solid waste discharge port, 3 is the cold / hot water inlet, and 4 is the cold / hot water outlet.

[0029] Figure 3 It is a schematic diagram of the structure of the electromagnetic heating reactor; wherein 5 is a solid flow feed port, 6 is a solid flow discharge port, 7 is a flue gas outlet, 8 is a stirring paddle, and 9 is an electromagnetic heating jacket.

[0030] Figure 4 It is a structural schematic diagram of a horizontal double-screw continuous cleaning machine; wherein 10 is a feed inlet, 11 is a discharge port, 12 is a filtrate inlet, and 13 is a process water inlet. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that the upper and lower limits of the scope and each intermediate value therebetween are specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0033] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the invention belongs. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0034] system In one aspect of the present invention, a system for degrading dioxins in high-salt solid waste and deep dechlorination is provided, which comprises: A blocker adding unit, which is used to provide a thiamine blocker. The blocker adding unit is not particularly limited, and can use a dosing device known in the art, examples of which include but are not limited to a manual dosing device, an automatic dosing device, etc.; A vacuum low-temperature detoxification unit is connected to the blocker adding unit. The vacuum low-temperature detoxification unit includes a preheating spiral, a first metering spiral, an electromagnetic heating reactor and a heat recovery spiral connected in sequence. The structures of the preheating spiral and the heat recovery spiral are as follows: Figure 2 As shown, 1 solid waste feed port and 2 solid waste discharge ports are respectively provided on both sides of the spiral device structure, and 3 cold / hot water inlets are provided on the side close to the solid waste discharge port, so as to provide the required hot water or cold water for the material flow in the device to achieve preheating and cooling operations, and 4 cold / hot water outlets are provided on the side close to the solid waste feed port to facilitate the outflow and circulation of the corresponding cold water or hot water. The first metering spiral is not particularly limited, and spiral metering equipment known in the art can be used, examples of which include but are not limited to spiral metering scales, etc. The structure of the electromagnetic heating reactor is as shown in FIG. Figure 3As shown, the reactor structure includes a cylindrical chamber at the top and an inverted cone structure at the bottom. The solid flow feed port and the smoke outlet of the electromagnetic heating reactor are arranged on both sides of the upper part of the reactor, and the solid flow discharge port is at the lower part of the reactor. A stirring paddle is arranged inside the reactor, and an electromagnetic heating jacket is arranged outside. Among them, 5 is a solid flow feed port, 6 is a solid flow discharge port, 7 is a smoke outlet, 8 is a stirring paddle, and 9 is an electromagnetic heating jacket. The system of the present invention can greatly reduce energy consumption by arranging an electromagnetic heating reactor compared with the system or treatment method in the prior art; A flue gas treatment unit, which is connected to the vacuum low-temperature detoxification unit for conveying and treating gas flow, and the flue gas treatment unit includes a dust collector, a pipeline mixer, a water ring vacuum pump, a first process water tank and an activated carbon box. The dust collector is not particularly limited, and a dust collector known in the art can be used, and examples thereof include but are not limited to precision bag dust collectors, cartridge dust collectors, cyclone dust collectors, wet dust collectors, electrostatic dust collectors, etc. The pipeline mixer is not particularly limited, and a pipeline mixing device known in the art can be used, and examples thereof include but are not limited to static baffle mixers, orifice plate mixers, spiral blade mixers, etc. The water ring vacuum pump is not particularly limited, and vacuum pump equipment known in the art can be used, and examples thereof include but are not limited to single-acting water ring vacuum pumps, double-acting water ring vacuum pumps, etc. The structure of the process water tank is not particularly limited, and a box-type device known in the art can be used, as long as it can accommodate the required fluid. The structure of the activated carbon box is not particularly limited, and a box-type device known in the art can be used, as long as it can accommodate the required solid support (i.e., activated carbon); a continuous three-stage water washing unit, which is connected to the vacuum low-temperature detoxification unit for conveying and washing solid flow, and the continuous three-stage water washing unit comprises a first-stage horizontal double-screw continuous cleaning machine (also called "horizontal double-screw continuous cleaning machine 1"), a first-stage horizontal screw centrifuge (also called "horizontal screw centrifuge 1"), a first-stage buffer tank (also called "buffer tank 1"), a second-stage horizontal double-screw continuous cleaning machine (also called "horizontal double-screw continuous cleaning machine 2"), a second-stage horizontal screw centrifuge (also called "horizontal screw centrifuge 2"), a second-stage buffer tank (also called "buffer tank 2"), a third-stage horizontal double-screw continuous cleaning machine (also called "horizontal double-screw continuous cleaning machine 3"), a third-stage horizontal screw centrifuge (also called "horizontal screw centrifuge 3"), a third-stage buffer tank (also called "buffer tank 3") and a second process water tank, and the second process water tank may be the same as or different from the first process water tank; An evaporation crystallization unit connected to the continuous three-stage water washing unit, the evaporation crystallization unit is used to convert the liquid stream from the continuous three-stage water washing unit and recover sodium chloride and potassium chloride respectively. The evaporation crystallization unit is not particularly limited, and evaporation crystallization equipment known in the art can be used, examples of which include but are not limited to MVR evaporators, multiple-effect evaporators, forced circulation evaporation crystallizers, HC series evaporation crystallizers, DTB type evaporation crystallizers, etc.; A mineralizer adding unit connected to the continuous three-stage water washing unit to provide a heavy metal mineralizer. The mineralizer adding unit is not particularly limited and can adopt a dosing device known in the art, examples of which include but are not limited to a manual dosing device, an automatic dosing device, etc.; The sodium hypochlorite generating unit is arranged between the flue gas treatment unit and the continuous three-stage water washing unit to convert the liquid flow after passing through the mineralizer adding unit into sodium hypochlorite, and at the same time transport the sodium hypochlorite to the flue gas treatment unit. The sodium hypochlorite generating unit is not particularly limited, and a sodium hypochlorite generating device known in the art can be used, examples of which include but are not limited to a sodium hypochlorite generator.

[0035] In the present invention, "high-salt solid waste" refers in particular to solid waste with a soluble salt content of not less than 5%. The high-salt solid waste includes waste incineration fly ash, preferably, includes domestic waste incineration fly ash.

[0036] In a preferred embodiment, a hot water-cold water circulation is formed between the preheating spiral and the heat recovery spiral through a pipeline, so that the heat recovered by the heat recovery spiral is transported to the preheating spiral to preheat the high-salt solid waste, thereby realizing waste heat utilization and avoiding the re-synthesis of dioxins.

[0037] In a preferred embodiment, the electromagnetic heating reactor in the vacuum low-temperature detoxification unit is connected to the dust collector of the flue gas treatment unit.

[0038] In a preferred embodiment, the heat recovery spiral of the vacuum low-temperature detoxification unit is connected to the first-stage horizontal double-screw continuous cleaning machine of the continuous three-stage water washing unit, and a detoxification ash temporary storage bin and a second metering spiral are further provided between the heat recovery spiral and the first-stage horizontal double-screw continuous cleaning machine. The structure of the detoxification ash temporary storage bin is not particularly limited, as long as it can temporarily store the detoxification ash from the heat recovery spiral. The second metering spiral is the same as or different from the first metering spiral.

[0039] In a preferred embodiment, the continuous three-stage water washing unit further includes a filter press device, and the mineralizer addition unit is arranged between the primary buffer tank of the continuous three-stage water washing unit and the filter press device. A brine tank is arranged between the evaporation crystallization unit and the filter press device of the continuous three-stage water washing unit. The filter press device is not particularly limited, and a filter press device known in the art can be used, examples of which include but are not limited to plate and frame precision filters, chamber filter presses, vertical filter presses, belt filter presses, diaphragm filter presses, etc. The structure of the brine tank and the buffer tank is not particularly limited, and a tank structure known in the art can be used.

[0040] In the present invention, the structure of the horizontal double-screw continuous cleaning machine is as follows: Figure 4 As shown; a filtrate inlet, a process water inlet and a feed inlet are sequentially arranged at the upper left side of the mixing chamber of the roughly rectangular structure of the cleaning machine, a discharge port is arranged at the upper right side of the mixing chamber, a spiral belt and a transmission shaft are arranged inside the mixing chamber, and a driving device is arranged outside, wherein 10 is the feed inlet, 11 is the discharge port, 12 is the filtrate inlet, and 13 is the process water inlet. The horizontal double-spiral continuous cleaning machine of the present invention is arranged in an overflow type, that is, the slurry flowing out of it enters the horizontal screw centrifuge by overflow, so that multi-stage continuous water washing of high-salt solid waste can be achieved.

[0041] Unless otherwise specified, the units in the system of the present invention are connected by pipelines.

[0042] method One aspect of the present invention provides a method for degrading dioxins in high-salt solid waste and deep dechlorination, which includes the step of treating high-salt solid waste with the system described in the present invention.

[0043] In a preferred embodiment, a thioamine retarder is added to the high-salt solid waste through the retarder adding unit, and the high-salt solid waste is transported to the electromagnetic heating reactor through the preheating screw and the metering screw of the vacuum low-temperature detoxification unit, so that the high-salt solid waste undergoes degradation reaction to obtain detoxified ash, and the cooled solid flow is obtained by using the heat recovery screw. Preferably, the solid flow is cooled to below 200°C, and the cooled solid flow enters the first-stage horizontal double-screw continuous cleaning machine of the continuous three-stage water washing unit through the second metering screw. The solid flow contacts the process water from the first process water tank in the cleaning machine, and the water-soluble chloride in the solid flow dissolves in the acidic process water during the water washing process, and the water-insoluble chloride reacts with the acid in the process water and is treated by the first-stage horizontal screw centrifuge to obtain the first-stage water washing liquid. In addition, the solid flow is cooled in the first-stage horizontal double-screw continuous cleaning machine. In addition to contact with process water from the first process water tank, the continuous cleaning machine also contacts with the secondary water washing liquid obtained by the secondary horizontal double-screw continuous cleaning machine and the secondary horizontal screw centrifuge, and the tertiary water washing liquid obtained by the tertiary horizontal double-screw continuous cleaning machine and the tertiary horizontal screw centrifuge. The supernatant after the above treatment flows through the primary buffer tank, and then a heavy metal mineralizer is added and the pH is adjusted to alkaline (preferably pH 7-8). After the heavy metals are precipitated, it is passed into the filter press device, and the filtrate obtained by the filter press device enters the brine tank.

[0044] In a preferred embodiment, the slurry overflows from the first-stage horizontal double-screw continuous cleaning machine of the continuous three-stage water washing unit into the first-stage horizontal screw centrifuge, and the liquid flow generated by the first-stage horizontal screw centrifuge enters the filter press device through the first-stage buffer tank, and the solid flow generated by the first-stage horizontal screw centrifuge and the filter press device of the continuous three-stage water washing unit enters the second-stage horizontal double-screw continuous cleaning machine, and the slurry overflows from the second-stage horizontal double-screw continuous cleaning machine into the second-stage horizontal screw centrifuge, and the liquid flow generated by the second-stage horizontal screw centrifuge enters the first-stage horizontal double-screw continuous cleaning machine through the second-stage buffer tank. Continuous cleaning machine, the solid flow generated by the secondary horizontal screw centrifuge enters the tertiary horizontal double-screw continuous cleaning machine, the liquid flow generated by the tertiary horizontal double-screw continuous cleaning machine overflows and enters the tertiary horizontal screw centrifuge, the liquid flow generated by the tertiary horizontal screw centrifuge enters the secondary horizontal double-screw continuous cleaning machine through the tertiary buffer tank, the solid flow generated by the tertiary horizontal screw centrifuge enters the unburned brick unit as the raw material for unburned bricks, and is disposed of together with solid wastes such as construction waste and slag for resource utilization, wherein the second process water tank provides liquid phase for the tertiary horizontal double-screw continuous cleaning machine.

[0045] In a preferred embodiment, the detoxified ash after cooling by the heat recovery spiral enters the continuous three-stage water washing unit through the detoxified ash temporary storage bin and the second metering spiral, and the water-soluble chlorides in the detoxified ash enter the liquid phase during the water washing process, and the water-insoluble chlorides (such as Friedel's salt, Ca4OCl6, AlOCl, Ca 10 (Si2O7)2(SiO4)Cl2(OH)2, Ca4OCl6, etc.) react with the acid in the process water to convert into water-soluble chlorine and enter the liquid phase. 3CaO·Al2O3·CaCl2·10H2O+3CO2→3CaCO3+Al2O3·xH2O+CaCl2+(10-x)H2O; AlOCl+2H + →Al 3+ +Cl - +H2O; Ca 10 (Si2O7)2(SiO4)Cl2(OH)2+2H + →2Ca3Si2O7+Ca2SiO4+2Ca 2+ +2Cl - +2H2O; Ca4OCl6+2H + →4Ca 2+ +6Cl - +H2O.

[0046] In a preferred embodiment, the gas flow generated in the electromagnetic heating reactor enters the dust collector through a pipeline for dust removal, and then enters the pipeline mixer to react with the sodium hypochlorite solution from the sodium hypochlorite generation unit. The ammonia in the flue gas is oxidized to N2 by sodium hypochlorite to achieve deammoniation. The deaminated flue gas is pumped to the first process water tank by a water ring vacuum pump, and the acidic gas is absorbed by the process water. The deaminated and deacidified flue gas enters the activated carbon box for adsorption and purification and then meets the emission standards. The acidic process water enters the first-stage horizontal double-screw continuous cleaning machine of the continuous three-stage water washing unit.

[0047] In a preferred embodiment, the filtrate branch enters the sodium hypochlorite generating unit through a bypass outlet to generate a sodium hypochlorite solution, and the filtrate trunk enters the evaporation crystallization unit through a trunk outlet to recover sodium chloride and potassium chloride respectively, and the flow rate of the filtrate branch is 0.1-0.3% of the flow rate of the filtrate trunk.

[0048] In order to prevent the resynthesis of dioxins during the low-temperature degradation process, it is necessary to select a suitable retarder, and the amount of the retarder added should not be too high or too low. In the present invention, the sulfur amino retarder includes at least one of urea, melamine, acetic hydrazide, formic hydrazide, semicarbazide, thiosemicarbazide, thiomethylhydrazine, ammonium thiosulfate and ammonium sulfate, and the amount of the retarder added is 3-10% of the mass of the high-salt solid waste, preferably 3-9%, such as 3%, 4%, 5%, 6%, 7%, 8%, 9%.

[0049] In order to achieve efficient degradation of dioxins, the temperature and reaction time of the electromagnetic heating reactor need to be controlled within an appropriate range. In the present invention, the temperature of the electromagnetic heating reactor is controlled at 350-450°C, preferably 360-440°C, preferably 370-430°C, more preferably 380-420°C, such as 380, 390, 400, 410, 420, 430, 440°C, and the reaction time is 1.5-2h, such as 1.5, 1.6, 1.7, 1.8, 1.9, 2 h.

[0050] In order to ensure the continuous operation of the system, it is necessary to control the ash amount in the temporary storage bin of detoxification ash. In the present invention, the temporary storage bin of detoxification ash is provided with a control device, and the control device is configured to automatically open the ash bin discharge valve when the ash amount reaches 2 / 3 of the bin capacity, and when the system is running, the ash intake in the bin is greater than the ash output every 2 hours. The temporary storage bin of detoxification ash is provided with a control device to achieve the above purpose, and the control device can adopt devices such as control valves and ash amount detection systems known in the art.

[0051] In order to improve the dechlorination efficiency, the water-to-solid mass ratio of the continuous three-stage water washing unit should not be too high or too low. In the present invention, the water-to-solid mass ratio of the continuous three-stage water washing unit is (0.8-3):1, preferably (0.9-2.9):1, and further preferably (1-2.8):1, for example 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.6, 1:2.8.

[0052] In order to effectively remove heavy metals, the addition amount of the heavy metal mineralizer should not be too high or too low. In the present invention, the addition amount of the heavy metal mineralizer is 1-5% of the mass of the primary water wash liquid, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, and the addition amount of the heavy metal mineralizer is preferably controlled by PLC.

[0053] Example 1 The following uses fly ash as an example to illustrate the method of degrading dioxins and deep dechlorination in high-salt solid waste.

[0054] The composition of fly ash from the incineration of domestic waste will have a certain impact on the vacuum low-temperature degradation and water washing dechlorination treatment. The range of fly ash composition used in this embodiment is shown in Table 1 below. The following detailed description is only for exemplary purposes and does not mean that the present invention can only treat high-salt solid wastes with the following components.

[0055] Table 1 Composition of fly ash from incineration of domestic waste After unloading the fly ash from the incineration of domestic waste from the original ash bin, 10% ammonium sulfate is added to the fly ash, the fly ash is preheated by the preheating screw, and then weighed by the metering screw and transported to the electromagnetic heating reactor. The vacuum environment in the reactor is achieved and maintained by a water ring vacuum pump. At the same time, the reactor is heated and maintained at 400°C to make the fly ash undergo a low-temperature degradation reaction. The reaction time is 1.5 h. During the reaction, the stirring paddle in the reactor rotates at a uniform speed to make the fly ash evenly heated to ensure sufficient reaction. The dioxin degradation rate reaches 99.67%, and the residual amount is 8.23 ​​ng-TEQ / kg, which meets the standard requirements of "Technical Specifications for Pollution Control of Fly Ash from Incineration of Domestic Waste" (HJ 1134-2020).

[0056] The flue gas generated in the reactor is dedusted by a precision bag filter and then enters the pipeline mixer to react with the sodium hypochlorite solution. The ammonia in the flue gas is oxidized to N2 by sodium hypochlorite to achieve deammoniation. The deammonified flue gas is pumped to the process water tank by a water ring vacuum pump, and the acid gases (SO2, NO x , CO2 and HCl, etc.) are absorbed by the process water, and the flue gas after deamination and deacidification enters the activated carbon box for adsorption purification and meets the limit requirements of the "Hazardous Waste Incineration Pollution Control Standard" (GB18484-2020) before being discharged; the acidic process water enters the first-stage horizontal double-screw continuous cleaning machine 1 in the water washing unit.

[0057] After the fly ash in the electromagnetic heating reactor is detoxified, the valve is opened to unload. The detoxified ash enters the heat recovery spiral and indirectly contacts the cold water outside the spiral for heat exchange. The temperature of the detoxified ash drops below 200°C to prevent dioxins from being synthesized again. The cold water recovers the heat and is transported to the preheating spiral for waste heat utilization.

[0058] The detoxified ash after cooling is transported to the temporary storage bin. When the ash volume reaches 2 / 3 of the bin capacity, the ash bin unloading valve opens automatically. When the system is running, the ash input volume in the bin is greater than the ash output volume every 2 hours, ensuring continuous feeding of the water washing unit.

[0059] The washing unit adopts three-stage countercurrent continuous washing with a total water-ash mass ratio of 2:1. It has been determined that the removal rate of chloride salt is 99.19%. 3% heavy metal mineralizer is added to the first-stage washing liquid, and the solution pH is adjusted to 7-8 and the heavy metals are precipitated before entering the brine tank. The bypass outlet of the brine tank is connected to the sodium hypochlorite generator, and the main outlet is connected to the inlet of the evaporation crystallization unit. The bypass outlet flow is 0.2% of the main outlet flow. The brine recovers sodium chloride and potassium chloride respectively in the steam mechanical recompression (MVR) evaporator; the moisture content of the tertiary washing slag is 40%, which enters the unburned brick unit for resource recycling.

[0060] Example 2 The following uses fly ash as an example to illustrate the method of degrading dioxins and deep dechlorination in high-salt solid waste.

[0061] After unloading the fly ash from the incineration of domestic waste from the original ash bin, 5% urea is added to the fly ash, which is preheated by a preheating screw, and then weighed by a metering screw and transported to an electromagnetic heating reactor. A water ring vacuum pump is used to achieve and maintain the vacuum environment in the reactor. At the same time, the reactor is heated and maintained at a temperature of 350°C to cause the fly ash to undergo a low-temperature degradation reaction. The reaction time is 2 hours. During the reaction, the stirring paddle in the reactor rotates at a uniform speed to uniformly heat the fly ash to ensure sufficient reaction. It has been determined that the dioxin degradation rate is 99.31% and the residual amount is 17.15 ng-TEQ / kg, which meets the standard requirements of "Technical Specifications for Pollution Control of Fly Ash from Incineration of Domestic Waste" (HJ 1134-2020).

[0062] The flue gas generated in the reactor is dedusted by a precision bag filter and then enters the pipeline mixer to react with the sodium hypochlorite solution. The ammonia in the flue gas is oxidized to N2 by sodium hypochlorite to achieve deammoniation. The deammonified flue gas is pumped to the process water tank by a water ring vacuum pump, and the acid gases (SO2, NO x , CO2 and HCl, etc.) are absorbed by the process water, and the flue gas after deamination and deacidification enters the activated carbon box for adsorption purification and meets the limit requirements of the "Hazardous Waste Incineration Pollution Control Standard" (GB18484-2020) before being discharged; the acidic process water enters the first-stage horizontal double-screw continuous cleaning machine 1 in the water washing unit.

[0063] After the fly ash in the electromagnetic heating reactor is detoxified, the valve is opened to unload. The detoxified ash enters the heat recovery spiral and indirectly contacts the cold water outside the spiral for heat exchange. The temperature of the detoxified ash drops below 200°C to prevent dioxins from being synthesized again. The cold water recovers the heat and is transported to the preheating spiral for heat utilization.

[0064] The detoxified ash after cooling is transported to the temporary storage bin. When the ash volume reaches 2 / 3 of the bin capacity, the ash bin unloading valve opens automatically. When the system is running, the ash input volume in the bin is greater than the ash output volume every 2 hours, ensuring continuous feeding of the water washing unit.

[0065] The washing unit adopts three-stage countercurrent continuous washing with a total water-ash mass ratio of 3:1. It has been determined that the removal rate of chloride salt is 99.37%. 2% heavy metal mineralizer is added to the first-stage washing liquid, and the solution pH is adjusted to 7-8 and heavy metals are precipitated before entering the brine tank. The bypass outlet of the brine tank is connected to the sodium hypochlorite generator, and the main outlet is connected to the inlet of the evaporation crystallization unit. The bypass outlet flow is 0.1% of the main outlet flow. The brine recovers sodium chloride and potassium chloride in the MVR evaporator respectively; the moisture content of the tertiary washing slag is 44%, which enters the unburned brick unit for resource recycling.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for degrading dioxins in high-salt solid waste and deep dechlorination, characterized in that: include: A blocker adding unit, which is used to provide a thiamine blocker; A vacuum low-temperature detoxification unit, which is connected to the retarder adding unit, and the vacuum low-temperature detoxification unit comprises a preheating spiral, a first metering spiral, an electromagnetic heating reactor and a heat recovery spiral connected in sequence; A flue gas treatment unit, which is connected to the vacuum low-temperature detoxification unit for conveying and treating gas logistics, and the flue gas treatment unit includes a dust collector, a pipeline mixer, a water ring vacuum pump, a first process water tank and an activated carbon tank; A continuous three-stage water washing unit, which is connected to the vacuum low-temperature detoxification unit for conveying and washing the solid flow, and the continuous three-stage water washing unit comprises a first-stage horizontal double-screw continuous cleaning machine, a first-stage horizontal screw centrifuge, a first-stage buffer tank, a second-stage horizontal double-screw continuous cleaning machine, a second-stage horizontal screw centrifuge, a second-stage buffer tank, a third-stage horizontal double-screw continuous cleaning machine, a third-stage horizontal screw centrifuge, a third-stage buffer tank and a second process water tank; an evaporation crystallization unit connected to the continuous three-stage water washing unit, the evaporation crystallization unit being used to convert a liquid stream originating from the continuous three-stage water washing unit; A mineralizer adding unit, which is connected to the continuous three-stage water washing unit to provide a heavy metal mineralizer; The sodium hypochlorite generating unit is arranged between the flue gas treatment unit and the continuous three-stage water washing unit to convert the liquid flow after passing through the mineralizer adding unit into sodium hypochlorite, and at the same time transport the sodium hypochlorite to the flue gas treatment unit.

2. The system for degrading dioxins and deep dechlorination in high-salt solid waste according to claim 1, characterized in that: A hot water-cold water cycle is formed between the preheating spiral and the heat recovery spiral.

3. The system for degrading dioxins and deep dechlorination in high-salt solid waste according to claim 1, characterized in that: The electromagnetic heating reactor in the vacuum low-temperature detoxification unit is connected to the dust collector of the flue gas treatment unit.

4. The system for degrading dioxins and deep dechlorination in high-salt solid waste according to claim 1, characterized in that: The heat recovery spiral of the vacuum low-temperature detoxification unit is connected to the first-stage horizontal double-screw continuous cleaning machine of the continuous three-stage water washing unit, and a detoxification ash temporary storage bin and a second metering spiral are further arranged between the heat recovery spiral and the first-stage horizontal double-screw continuous cleaning machine.

5. The system for degrading dioxins and deep dechlorination in high-salt solid waste according to claim 1, characterized in that: The continuous three-stage water washing unit further comprises a filter press device, and the mineralizer adding unit is arranged between the primary buffer tank of the continuous three-stage water washing unit and the filter press device.

6. The system for degrading dioxins and deep dechlorination in high-salt solid waste according to claim 5, characterized in that: A brine tank is provided between the evaporation crystallization unit and the filter press device of the continuous three-stage water washing unit.

7. A method for degrading dioxins and deep dechlorination in high-salt solid waste, characterized in that: The method comprises the steps of treating high-salt solid waste using the system according to any one of claims 1 to 6, including: (1) adding a thioamine retarder to the high-salt solid waste through the retarder adding unit, and conveying the high-salt solid waste to the electromagnetic heating reactor through the preheating screw and the metering screw of the vacuum low-temperature detoxification unit, so that the high-salt solid waste undergoes a degradation reaction to obtain detoxified ash, and the cooled solid flow is obtained by using the heat recovery screw; (2) After the gas flow in the electromagnetic heating reactor is dedusted by the dust collector, it enters the pipeline mixer and reacts with the solution from the sodium hypochlorite generation unit. The deaminated gas flow is sent to the first process water tank by a water ring vacuum pump, so that the acidic gas is absorbed by the process water to obtain acidic process water. The deaminated and deacidified gas flow enters the activated carbon tank, and the acidic process water in the first process water tank enters the first-stage horizontal double-screw continuous cleaning machine of the continuous three-stage water washing unit; (3) allowing the cooled solid flow to enter the first-stage horizontal double-screw continuous cleaning machine of the continuous three-stage water washing unit through a second metering screw, wherein the water-soluble chloride in the solid flow is dissolved in the acidic process water during the water washing process, and the water-insoluble chloride reacts with the acid in the process water to obtain a first-stage water washing liquid, a heavy metal mineralizer is added to the first-stage water washing liquid, the pH of the solution is adjusted and the heavy metals are precipitated, and then the first-stage water washing liquid is passed into a filter press to obtain a filtrate, and the filtrate is allowed to enter a brine tank; the third-stage water washing slag after the solid flow is treated by the continuous three-stage water washing unit is utilized as a raw material for unfired bricks; (4) The filtrate entering the brine tank enters the evaporation crystallization unit through the main outlet for conversion, and at the same time, the filtrate enters the sodium hypochlorite generation unit through the bypass outlet for reaction to obtain sodium hypochlorite that can be provided to the pipeline mixer.

8. The method for degrading dioxins and deep dechlorination in high-salt solid waste according to claim 7, characterized in that: The sulfur amino retarder includes at least one of urea, melamine, acetohydrazide, formic hydrazide, semicarbazide, thiosemicarbazide, thiomethylhydrazine, ammonium thiosulfate and ammonium sulfate, and its addition amount is 3-10% of the mass of high-salt solid waste. The temperature of the electromagnetic heating reactor is controlled at 350-450°C, and the reaction time is 1.5-2 h.

9. The method for degrading dioxins and deep dechlorination in high-salt solid waste according to claim 7, characterized in that: The detoxification ash temporary storage bin is provided with a control device, and the control device is configured to automatically open the ash bin unloading valve when the ash volume reaches 2 / 3 of the bin capacity, and when the system is running, the ash intake in the bin is greater than the ash output every 2 hours.

10. The method for degrading dioxins and deep dechlorination in high-salt solid waste according to claim 7, characterized in that: The water-to-solid mass ratio of the continuous three-stage water washing unit is (0.8-3):1, the addition amount of the heavy metal mineralizer is 1-5% of the mass of the primary water washing liquid, and the bypass outlet flow of the brine tank is 0.1-0.3% of the main outlet flow.

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