Fly ash segmented desorption dioxin flue gas cooperative treatment method and system

Abstract

The invention discloses a fly ash segmented desorption dioxin flue gas cooperative treatment method and system in the technical field of solid waste treatment, and the method comprises the following steps: collecting fly ash generated by flue gas treatment from a fly ash bin, and carrying out dechlorination and / or catalyst passivation treatment on the fly ash to obtain pre-treated fly ash; preheating the pretreated fly ash to obtain preheated fly ash; and carrying out thermal desorption treatment on the preheated fly ash based on an air atmosphere. The fly ash is subjected to dechlorination and / or catalyst passivation treatment, so that a chlorine source and a passivation catalyst can be reduced, waste heat preheating is realized by adopting an indirect heat exchange mode, readsorption of dioxin is avoided, de novo synthesis of dioxin is effectively inhibited, high-efficiency desorption in an air atmosphere is realized, use of inert gas is avoided, and the service life of the device is prolonged. The operation cost of flue gas treatment can be greatly reduced, and reduction, harmlessness and resourceful treatment of the fly ash are practically realized.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, specifically a method and system for the staged desorption of dioxins from fly ash and the synergistic treatment of flue gas. Background Technology

[0002] Municipal solid waste incineration is currently one of the main methods of urban solid waste disposal. The fly ash produced during the incineration process contains high concentrations of dioxins (usually 1~1000 ng TEQ / kg). According to the National Hazardous Waste List, fly ash is classified as hazardous waste (HW18) and must be treated to render it harmless.

[0003] Currently, the main methods for treating fly ash include: landfill after cement solidification or chelation stabilization, co-processing in cement kilns, and manufacturing building materials. However, the high concentration of dioxins in fly ash severely limits its resource utilization. In recent years, thermal desorption technology has attracted attention due to its ability to effectively remove dioxins.

[0004] Existing thermal desorption technologies mainly include inert atmosphere desorption and high-temperature air atmosphere desorption. To avoid de novo dioxin synthesis, inert atmospheres such as N2 or CO2 are used for desorption. While this effectively avoids de novo synthesis, inert gases are expensive (approximately 30-50 RMB / ton of fly ash) and require a supporting gas supply and recovery system, demanding high system airtightness, resulting in high engineering complexity and large investment. At temperatures of 600-800℃, de novo dioxin synthesis is inhibited, allowing for high-temperature air atmosphere desorption within this temperature range. However, high-temperature operation leads to high energy consumption, severe equipment wear, and significant volatilization of heavy metals (such as Pb, Cd, and Zn), increasing the burden on downstream flue gas treatment. Some technologies perform desorption at medium temperatures (400~500℃) in an air atmosphere, but they do not take into account that fly ash contains a large amount of chlorine sources (10%~30%) and catalysts (heavy metals such as Cu and Fe). Dioxins are prone to de novo synthesis within this temperature range, which greatly reduces the desorption effect and may even lead to an increase in dioxin content instead of a decrease.

[0005] Meanwhile, the dioxin-containing flue gas generated by desorption requires a specialized flue gas purification system, including quenching, activated carbon adsorption, and bag filter dust collection. This system suffers from drawbacks such as high investment, high operating costs, and severe de novo synthesis, making it difficult to improve the removal efficiency of dioxins in fly ash. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for the staged desorption of dioxins from fly ash and the synergistic treatment of flue gas. By inhibiting the de novo synthesis of dioxins through pretreatment, optimizing energy consumption through staged desorption, and reducing investment through synergistic treatment of flue gas in the plant, this invention solves the problems of high energy consumption, high cost, and serious de novo synthesis in existing technologies, and achieves efficient removal of dioxins from fly ash and resource utilization of fly ash.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for the synergistic treatment of dioxin-containing flue gas by staged desorption of fly ash, comprising: Fly ash generated from flue gas treatment is collected from the fly ash bin, and then subjected to dechlorination and / or catalyst passivation treatment to obtain pretreated fly ash; The pretreated fly ash is preheated to obtain preheated fly ash; The preheated fly ash is subjected to thermal desorption treatment based on an air atmosphere.

[0008] As a further aspect of the present invention, the preheating temperature of the fly ash in the pretreatment process is 150~200℃.

[0009] As a further aspect of the present invention, the pretreated fly ash meets the requirements of the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial)" (HJ 1134-2020) regarding the chlorine content and heavy metal leaching concentration of the fly ash treatment products, and can be used for resource utilization.

[0010] As a further aspect of the present invention: preheating the pretreated fly ash, including: The pre-treated fly ash is preheated using indirect heat exchange, microwave, or infrared radiation.

[0011] As a further aspect of the present invention: preheating the pretreated fly ash using an indirect heat exchange method, including: Based on a heat exchanger, the waste heat from the high-temperature desorption section is used to heat the clean gas to obtain hot clean gas, wherein the clean gas includes air, and the heat exchanger includes at least one of plate heat exchanger, tubular heat exchanger, or heat pipe heat exchanger; Hot clean gas at temperatures above 500℃ is used to form a hot airflow to heat the fly ash, preventing dioxins in the desorbed flue gas from being re-adsorbed onto the fly ash.

[0012] As a further aspect of the present invention: thermal desorption treatment of the preheated fly ash based on an air atmosphere, comprising: The prerequisite for setting the staged desorption of preheated fly ash is that the residence time of preheated fly ash in the de novo synthesis sensitive temperature zone is less than 5 minutes. Collect chlorine content data of preheated fly ash, and set the desorption temperature and residence time of preheated fly ash based on the chlorine content data; Drive the preheated fly ash through the de novo synthesis sensitive temperature zone of 250℃~400℃ to obtain desorbed fly ash; The desorbed fly ash is cooled to below 200°C using a cooler to obtain cooled fly ash and desorbed flue gas. The temperature inside the furnace of the municipal solid waste incinerator is raised to above 850°C, and the desorbed flue gas is transported to the furnace through an insulated pipe. The residence time of the desorbed flue gas in the incinerator furnace shall be no less than 2 seconds, wherein the temperature of the insulation pipe shall be above 250°C.

[0013] As a further aspect of the present invention: by maintaining the residence time of the desorbed flue gas in the incinerator furnace for no less than 2 seconds, dioxins can be completely decomposed. After being treated by an existing external flue gas purification system, the flue gas can be discharged in compliance with standards.

[0014] As a further aspect of the present invention: setting the desorption temperature and residence time of preheated fly ash based on the chlorine content data, including: When the chlorine content is less than 0.5 wt%, the desorption temperature of the preheated fly ash is set to 380℃~410℃ and the residence time is set to 30 minutes~50 minutes; When the chlorine content is 0.5wt%~2wt%, the desorption temperature of the preheated fly ash is set to 470℃~510℃ and the residence time is 50 minutes~70 minutes.

[0015] As a further aspect of the present invention, the cooling rate for cooling the desorbed fly ash to below 200°C is not less than 50°C / min.

[0016] As a further aspect of the present invention: the fly ash undergoes dechlorination and / or catalyst passivation treatment, including: One or more of the following methods can be used to remove chlorine from fly ash: water washing, acid washing, thermochemical methods, or dry methods.

[0017] As a further aspect of the present invention: the fly ash is subjected to dechlorination and / or catalyst passivation treatment, which further includes: After dechlorinating the fly ash, phosphates are added, or adsorbents are added to passivate the fly ash.

[0018] As a further aspect of the present invention: the amount of phosphate added is 1% to 8% of the weight of fly ash, and the amount of adsorbent added is 3% to 15% of the weight of fly ash. The adsorbent includes kaolin, bentonite and activated carbon.

[0019] As a further aspect of the present invention: when fly ash is passivated by a catalyst, the desorption temperature can be reduced by 20-50°C under the same chlorine content.

[0020] Secondly, the present invention provides a fly ash staged desorption dioxin flue gas co-treatment system, comprising: The pretreatment unit is configured to collect fly ash from the flue gas, and to perform dechlorination and / or catalyst passivation treatment on the fly ash to obtain pretreated fly ash; A preheating unit is configured to preheat the pre-treated fly ash to obtain preheated fly ash, wherein the inlet of the preheating unit is connected to the outlet of the pre-treatment unit; The segmented desorption unit is configured to perform thermal desorption treatment on the preheated fly ash based on an air atmosphere, and the inlet of the segmented desorption unit is connected to the outlet of the preheating unit.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention reduces the chlorine source and passivation catalyst by dechlorinating and / or passivating fly ash, effectively inhibiting the de novo synthesis of dioxins, thereby achieving efficient desorption in an air atmosphere, avoiding the use of inert gases, and significantly reducing the operating cost of flue gas treatment.

[0022] 2. By inhibiting the de novo synthesis of dioxins, this invention can reduce the desorption temperature by 60-100°C through the pretreatment process of fly ash, while reducing energy consumption by 20%-40%, and reducing the volatilization of heavy metals during low-temperature operation, thus extending the equipment life.

[0023] 3. This invention reduces investment through closed-loop collaborative processing within the plant. It utilizes the incinerator and existing flue gas purification system to treat desorbed flue gas, eliminating the need for separate flue gas treatment facilities. This achieves in-plant treatment of fly ash and avoids environmental risks and transportation costs during external transportation.

[0024] 4. This invention utilizes waste heat by preheating fly ash through indirect heat exchange, thus preventing dioxins in the desorbed flue gas from being re-adsorbed onto the fly ash and ensuring efficient removal of dioxins from the fly ash.

[0025] 5. This invention is applicable to fly ash that has undergone various pretreatments and has good flexibility. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the process flow of the system for staged desorption of dioxins from waste incineration fly ash according to the present invention. Figure 2 This is a flowchart of the method steps of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1: Please see Figure 2In this embodiment of the invention, a method for the synergistic treatment of dioxin-containing flue gas by staged desorption of fly ash includes the following steps: S1: Collect fly ash from flue gas, and treat the fly ash by dechlorination and / or catalyst passivation to obtain pretreated fly ash.

[0029] Preferably, the preheating temperature of the pretreatment fly ash is 180°C. The preheating of the pretreatment fly ash is carried out by indirect heat exchange: based on the use of plate heat exchangers, the waste heat of the high-temperature desorption section is used to heat the clean air to obtain hot clean air; hot clean gas above 500°C is used to form a hot airflow to heat the fly ash, so as to avoid the dioxins in the desorbed flue gas from being re-adsorbed onto the fly ash.

[0030] Dechlorination and / or catalyst passivation treatment of fly ash includes: dechlorinating fly ash using one or more methods such as water washing, acid washing, thermochemical methods, or dry dechlorination; after dechlorination, adding phosphate or adding adsorbent to passivate fly ash; the amount of phosphate added is 1% to 8% of the weight of fly ash, and the amount of adsorbent added is 3% to 15% of the weight of fly ash; the adsorbent includes kaolin, bentonite, and activated carbon; when fly ash is passedivated by catalyst, the desorption temperature can be reduced by 20 to 50°C under the same chlorine content.

[0031] S2: Preheat the pre-treated fly ash to obtain preheated fly ash.

[0032] S3: Thermal desorption treatment of preheated fly ash based on air atmosphere.

[0033] The process of thermal desorption treatment of preheated fly ash based on air atmosphere includes: setting preconditions for staged desorption of preheated fly ash, wherein the precondition is to keep the residence time of preheated fly ash in the de novo synthesis sensitive temperature zone less than 5 minutes; collecting chlorine content data of preheated fly ash, and setting the desorption temperature and residence time of preheated fly ash based on the chlorine content data; driving the preheated fly ash through the de novo synthesis sensitive temperature zone of 250℃~400℃ to obtain desorbed fly ash; using a cooler to cool the desorbed fly ash to below 200℃ to obtain cooled fly ash and desorbed flue gas; and raising the temperature inside the furnace of the municipal solid waste incinerator to above 850℃. Figure 1 As shown, ① represents the process of transporting flue gas to the incinerator for co-treatment through an insulated pipe. The insulated pipe transports the desorbed flue gas to the incinerator furnace. The residence time of the desorbed flue gas in the incinerator furnace is maintained for no less than 2 seconds. The temperature of the insulated pipe is above 250℃. By maintaining the residence time of the desorbed flue gas in the incinerator furnace for no less than 2 seconds, dioxins can be completely decomposed. After treatment with the existing external flue gas purification system, the flue gas can achieve the standard emission.

[0034] In this embodiment, the desorption temperature and residence time of the preheated fly ash are set based on the chlorine content data, including: when the chlorine content is less than 0.5 wt%, the desorption temperature of the preheated fly ash is set to 380℃~410℃ and the residence time is set to 30 minutes~50 minutes; when the chlorine content is 0.5wt%~2wt%, the desorption temperature of the preheated fly ash is set to 470℃~510℃ and the residence time is set to 50 minutes~70 minutes.

[0035] In this embodiment, the cooling rate for cooling the desorbed fly ash to below 200°C is not less than 50°C / min.

[0036] In this embodiment, a waste incineration power plant processes 1,000 tons of municipal solid waste per day, producing approximately 30 tons of fly ash per day. The original fly ash contains 15 wt% chlorine, 800 mg / kg Cu, and 88 ng TEQ / kg dioxin.

[0037] The specific process parameters are as follows: (1) Pretreatment steps: A water washing dechlorination process is adopted with a liquid-to-solid ratio of 3:1 and a washing time of 30 minutes. After washing, the chlorine content of fly ash is reduced to 0.4wt%. At the same time, 5wt% of disodium hydrogen phosphate (Na2HPO4) is added for catalyst passivation, so that metals such as Cu form stable phosphates. The passivation rate is over 95%. The pretreated fly ash meets the requirements of HJ 1134-2020 and can be used for resource utilization.

[0038] (2) Preheating step: After pretreatment, the fly ash is shaped and its moisture content is adjusted to 20%, then it is sent to the preheating unit via a screw conveyor. The preheating unit uses a plate heat exchanger. The flue gas in the high-temperature desorption section is about 480°C. The heat exchanger heats the clean air to 380°C, forming hot air. This hot air comes into countercurrent contact with the fly ash in a closed pipe, preheating the fly ash to 180°C. The indirect heat exchange in the closed pipe avoids the re-adsorption of dioxins in the desorbed flue gas in the fly ash.

[0039] (3) Segmented desorption steps: Rapid heating section: The preheated fly ash enters the rotary kiln desorption furnace and is rapidly heated with 500°C hot air. Within 8 minutes, the temperature rises from 200°C to 395°C, quickly passing through the sensitive temperature zone of de novo synthesis (250~400°C).

[0040] High-temperature desorption section: Based on the detected chlorine content of 0.4wt%, the desorption temperature is set to 395℃, air atmosphere, residence time of 40 minutes, desorption furnace speed of 2rpm, and material filling rate of 30%.

[0041] (4) Rapid cooling step: The temperature of the fly ash after desorption is 395℃. The fly ash after desorption enters the water-cooled cooler and is cooled to 120℃ in 5 minutes by indirect water cooling. The cooling rate is about 55℃ / min. Then it is cooled to room temperature by air.

[0042] (5) Flue gas co-treatment steps: The flue gas flow rate generated by desorption is approximately 3000 Nm3 / h, and the temperature is approximately 395℃. The flue gas generated by desorption is transported to the secondary air inlet of the incinerator through a stainless steel insulated pipe. The insulation layer of the stainless steel insulated pipe is 100mm thick, and the pipe temperature is greater than 250℃. It is burned with domestic waste in the furnace of the incinerator. The temperature of the secondary combustion chamber in the furnace is maintained at 900~1000℃, and the flue gas residence time is approximately 2.5 seconds. Dioxins are completely decomposed at high temperature. The flue gas is then treated by existing flue gas purification systems such as SNCR denitrification, semi-dry deacidification, activated carbon injection, and bag filter dust collection. The dioxin content in the flue gas is <0.1ng TEQ / Nm3, meeting the emission standards.

[0043] The treatment results are as follows: the dioxin content in the fly ash after desorption is 1.7 ng TEQ / kg, the dioxin removal rate is 98.1%, and no obvious de novo synthesis phenomenon was detected; the chlorine content in the fly ash after desorption is 0.4wt%, which meets the requirement of less than 2% in HJ 1134-2020; the energy consumption is about 80 kWh / ton of fly ash (as a baseline).

[0044] Example 2: The original fly ash characteristics of this embodiment are the same as those of Embodiment 1, and the difference from the above embodiments is as follows: (1) Pretreatment steps: Water washing is used to remove chlorine, and the chlorine content of fly ash is reduced to 1.5wt% (0.5~2wt%). No catalyst passivation treatment is performed.

[0045] (2) Preheating steps: Same as in Example 1, preheat fly ash to 180°C.

[0046] (3) Segmented desorption steps: Rapid heating phase: The temperature rises from 180℃ to 480℃ within 10 minutes.

[0047] High-temperature desorption section: Based on a chlorine content of 1.5wt% (range of 0.5~2wt%), the desorption temperature is set at 480℃ (range of 470~510℃), and the residence time is 60 minutes.

[0048] (4) Rapid cooling step: Same as in Example 1.

[0049] (5) Flue gas co-treatment steps: Same as in Example 1.

[0050] The treatment results are as follows: the dioxin content in the fly ash after desorption was 2.1 ng TEQ / kg, the dioxin removal rate was 97.6%, and no obvious de novo synthesis was detected; the chlorine content in the fly ash after desorption was 1.5 wt%, which meets the requirement of <2% in HJ 1134-2020; the energy consumption was about 107 kWh / ton of fly ash, which is 34% higher than that in Example 1.

[0051] Comparative Example 1: The original fly ash characteristics were the same as in Example 1. Air desorption was performed directly, without dechlorination or catalyst passivation.

[0052] Desorption conditions: After humidifying to a moisture content of 10%, desorb directly at 500℃ in air for 90 minutes.

[0053] The treatment results are as follows: the dioxin content in the fly ash after desorption was 25 ng TEQ / kg, and the dioxin removal rate was 71.6%. Through isotope tracing experiments, it was estimated that the de novo synthesized dioxin was about 10 ng TEQ / kg, equivalent to 11% of the initial amount; the energy consumption was about 125 kWh / ton of fly ash, which is 56% higher than that of Example 1. The Pb volatilization rate was 35%, and the Zn volatilization rate was 28%, which increased the burden of flue gas treatment.

[0054] Comparative Example 1 illustrates that even with high-temperature (500°C) air atmosphere desorption without pretreatment, severe de novo dioxin synthesis still occurs due to the high concentration of chlorine source (15%) and large amount of catalyst (Cu, Fe, etc.) in the fly ash, resulting in a significant reduction in desorption efficiency and even higher energy consumption. This fully demonstrates the necessity and superiority of the pretreatment-temperature coupling control strategy of this invention.

[0055] Comparative Example 2: The original fly ash characteristics were the same as in Example 1. No pretreatment was performed; desorption was carried out using a nitrogen atmosphere.

[0056] Desorption conditions: nitrogen atmosphere (O2<0.5%), 450℃, 60 minutes.

[0057] The treatment results are as follows: the dioxin content in the fly ash after desorption is 2.5 ng TEQ / kg, the dioxin removal rate is 97.2%, and no significant de novo synthesis phenomenon was found; the energy consumption is about 90 kWh / ton of fly ash, the N2 cost is about 40 yuan / ton of fly ash, and the desorbed flue gas needs to be equipped with a separate flue gas purification system, with an investment of about 8 million yuan.

[0058] While Comparative Example 2 avoids the de novo synthesis problem and achieves a high removal rate, it requires expensive inert gases, resulting in high operating costs and necessitates a separate flue gas purification system, leading to substantial investment. In contrast, this invention suppresses de novo synthesis through pretreatment, achieving a higher removal rate even in an air atmosphere. Furthermore, the flue gas co-treatment system significantly reduces investment and operating costs.

[0059] like Figure 2 As shown, this embodiment discloses a fly ash staged desorption and dioxin flue gas co-treatment system, comprising: The pretreatment unit is configured to collect fly ash from the flue gas, and to perform dechlorination and / or catalyst passivation treatment on the fly ash to obtain pretreated fly ash; The preheating unit is configured to preheat the pre-treated fly ash to obtain preheated fly ash, and the inlet of the preheating unit is connected to the outlet of the pre-treatment unit; The segmented desorption unit is configured to perform thermal desorption treatment on preheated fly ash based on air atmosphere, and the inlet of the segmented desorption unit is connected to the outlet of the preheating unit.

[0060] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for synergistically treating fly ash fractionated desorbed dioxin flue gas, characterized in that, The method comprises the following steps: Collecting fly ash generated by flue gas treatment from a fly ash bin, and performing chlorine removal and / or catalyst passivation on the fly ash to obtain pretreated fly ash; Preheating the pretreated fly ash to obtain preheated fly ash; Performing thermal desorption treatment on the preheated fly ash based on an air atmosphere.

2. The fly ash staged desorption dioxin off-gas co-processing method according to claim 1, characterized in that, The preheating of the pretreated fly ash comprises: Preheating the pretreated fly ash by indirect heat exchange, or by microwaves, or by infrared radiation.

3. The fly ash staged desorption dioxin flue gas co-processing method according to claim 1, characterized in that, The preheating of the pretreated fly ash by indirect heat exchange comprises: Based on a heat exchanger, heating clean gas by waste heat of a high-temperature desorption section to obtain hot clean gas, wherein the clean gas comprises air, and the heat exchanger comprises at least one of a plate heat exchanger, a tube heat exchanger, or a heat pipe heat exchanger; Forming a hot gas flow by using the hot clean gas with a temperature of 500 DEG C or higher to heat the fly ash, so as to avoid re-adsorption of dioxins in the desorption flue gas onto the fly ash.

4. The fly ash staged desorption dioxin-containing flue gas co-treatment method according to claim 3, characterized in that, The thermal desorption treatment on the preheated fly ash based on an air atmosphere comprises: Setting a precondition for preheated fly ash staged desorption, wherein the precondition is to keep the residence time of the preheated fly ash in a de novo synthesis sensitive temperature zone less than 5 minutes; Collecting chlorine content data of the preheated fly ash, and setting the desorption temperature and residence time of the preheated fly ash based on the chlorine content data; Driving the preheated fly ash to pass through a de novo synthesis sensitive temperature zone of 250 DEG C to 400 DEG C to obtain desorbed fly ash; Cooling the desorbed fly ash to 200 DEG C or lower by using a cooler to obtain cooled fly ash and desorption flue gas; Raising the temperature in the hearth of a household waste incinerator to 850 DEG C or higher, and using a heat preservation pipeline to transport the desorption flue gas to the hearth of the incinerator; Keeping the residence time of the desorption flue gas in the hearth of the incinerator not less than 2 seconds, wherein the pipeline temperature of the heat preservation pipeline is 250 DEG C or higher.

5. The fly ash staged desorption dioxin flue gas co-processing method according to claim 4, characterized in that, The setting of the desorption temperature and residence time of the preheated fly ash based on the chlorine content data comprises: When the chlorine content is less than 0.5 wt%, the desorption temperature of the preheated fly ash is set to 380 DEG C to 410 DEG C, and the residence time is set to 30 minutes to 50 minutes; When the chlorine content is 0.5 wt% to 2 wt%, the desorption temperature of the preheated fly ash is set to 470 DEG C to 510 DEG C, and the residence time is set to 50 minutes to 70 minutes.

6. The fly ash staged desorption dioxin-containing flue gas co-treatment method according to claim 5, characterized in that, The cooling rate of the desorbed fly ash to 200 DEG C or lower is not less than 50 DEG C / min.

7. The fly ash staged desorption dioxin-containing flue gas co-treatment method according to claim 6, characterized in that, The chlorine removal and / or catalyst passivation of the fly ash comprises: Removing chlorine from the fly ash by using one or more of a water washing method, an acid washing method, a thermal chemical method, or a dry method.

8. The fly ash staged desorption dioxin-containing flue gas co-treatment method according to claim 7, characterized in that, The chlorine removal and / or catalyst passivation of the fly ash further comprises: After removing chlorine from the fly ash, adding phosphates, or passivating the fly ash by adding adsorbents.

9. The fly ash staged desorption dioxin-containing flue gas co-treatment method according to claim 8, characterized in that, The addition amount of the phosphates is 1% to 8% of the weight of the fly ash, and the addition amount of the adsorbents is 3% to 15% of the weight of the fly ash, and the adsorbents comprise kaolin, bentonite, and activated carbon.

10. A fly ash staged desorption dioxin flue gas co-processing system, characterized in that, The method comprises the following steps: A pretreatment unit is configured to collect fly ash in flue gas, and perform chlorine removal and / or catalyst passivation on the fly ash to obtain pretreated fly ash; A preheating unit is configured to preheat the pretreated fly ash to obtain preheated fly ash, and an inlet of the preheating unit is communicated with an outlet of the pretreatment unit. A staged desorption unit configured to perform thermal desorption treatment of the preheated fly ash based on an air atmosphere, an inlet of the staged desorption unit being in communication with the outlet of the preheating unit.

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