A coke oven flue gas ozone oxidation and wet desulfurization treatment method and system

Abstract

This invention discloses a method and system for treating coke oven flue gas using ozone oxidation in conjunction with wet desulfurization, belonging to the field of flue gas purification technology in the coking industry. The method includes: S1, flue gas pretreatment: passing the raw coke oven flue gas sequentially through a waste heat boiler and a dust removal device; S2, precise ozone dosing and oxidation: real-time monitoring of the flow rate, temperature, and NOx concentration of the pretreated flue gas, calculating the ozone demand using an intelligent control system, and injecting ozone into the flue gas duct through a multi-stage vortex jet mixing device; S3, synergistic absorption: passing the flue gas containing SO2 and oxidized NOx into a wet desulfurization absorption tower, where it comes into countercurrent contact with limestone slurry to simultaneously remove SO2 and NOx; S4, byproduct control: controlling the pH value of the absorption tower slurry pool to 5.0–5.5, and introducing oxidizing air; S5, purified flue gas treatment: the desulfurized and denitrified flue gas sequentially passes through a demister, a wet electrostatic precipitator, and a flue gas heat exchanger for heating before being discharged.

Description

Technical Field

[0001] This invention belongs to the field of flue gas purification technology in the coking industry, and particularly relates to a method and system for treating coke oven flue gas by ozone oxidation combined with wet desulfurization. Background Technology

[0002] As a core piece of equipment in the metallurgical coking industry, coke ovens generate a large amount of flue gas during the coking process. This flue gas has an extremely complex composition, containing not only sulfur dioxide, nitrogen oxides, dust, and tar, but also potentially various harmful substances such as carbon monoxide, benzo[a]pyrene, heavy metals, and volatile organic compounds, posing a serious threat to the environment and human health. With increasing global environmental awareness and increasingly stringent emission regulations in various countries, more demanding requirements are being placed on the purification efficiency and treatment effect of coke oven flue gas, driving the industry towards ultra-low emission goals.

[0003] Currently, the industry commonly uses a combined approach of selective catalytic reduction (SCR) for denitrification and wet desulfurization to treat coke oven flue gas. This combined process uses ammonia as a reducing agent to remove nitrogen oxides and an alkaline absorbent to remove sulfur dioxide, thus reducing pollutant emissions to some extent. However, SCR technology has significant drawbacks: First, it requires a high temperature window; the optimal activity temperature of the catalyst is typically 300-400℃, while the temperature of coke oven flue gas often drops to around 200℃ after waste heat recovery. This necessitates significant additional energy consumption (such as natural gas or electricity) to raise the temperature, increasing operating costs and potentially leading to energy waste and secondary pollution. Second, there is a high risk of catalyst poisoning. Impurities such as arsenic, alkali metals, and phosphorus, which may be present in coke oven flue gas and originate from trace elements in the raw coal, can deactivate the active sites on the SCR catalyst surface, shortening its lifespan to only 1-2 years and significantly increasing the costs of maintenance, replacement, and waste disposal. Third, desulfurization and denitrification systems are complex. SCR systems include large reactors, ammonia injection devices, catalyst modules, and control systems, occupying a large area. Retrofitting existing coke ovens involves a significant amount of engineering work, requiring production shutdowns for construction, and incurring high investment costs, limiting their application to small and medium-sized enterprises. Fourth, the systems have poor synergy. Denitrification and desulfurization units are usually designed and operated independently, failing to achieve optimal integration of energy and material flow. For example, wastewater generated during desulfurization or waste heat from denitrification is not effectively recovered and utilized, resulting in low overall energy efficiency and resource waste.

[0004] Therefore, developing a synergistic removal technology that can adapt to the low-temperature, high-dust, and multi-component characteristics of coke oven flue gas, achieving integrated desulfurization, denitrification, dust removal, and organic matter removal, while optimizing energy and material cycles and reducing operating and maintenance costs, has become an urgent need for environmental upgrading in the coking industry. This technology should possess the characteristics of efficient removal of multiple pollutants, strong adaptability, stable operation, and economic feasibility to address increasingly stringent environmental challenges and promote the transformation of the metallurgical coking industry towards green and sustainable development. Summary of the Invention

[0005] This invention provides a method and system for treating coke oven flue gas by ozone oxidation in conjunction with wet desulfurization. It utilizes the strong oxidizing properties of ozone to oxidize insoluble NO into easily soluble high-valence nitrogen oxides at low temperatures, and achieves integrated removal using an existing wet desulfurization system, thereby overcoming the shortcomings of existing SCR technology.

[0006] To achieve the above-mentioned technical objectives, the first objective of this invention is to provide a method for treating coke oven flue gas using ozone oxidation in conjunction with wet desulfurization, comprising:

[0007] S1. Flue gas pretreatment: The raw flue gas from the coke oven is passed through a waste heat boiler and a dust removal device in sequence to reduce the flue gas temperature to 180℃~220℃ and the dust concentration to below 30mg / Nm³. S2. Precise Ozone Dosing and Oxidation: Real-time monitoring of the flow rate, temperature and NOx concentration of the pretreated flue gas; calculation of ozone demand using an intelligent control system; injection of ozone into the flue gas through a multi-stage vortex jet mixing device to oxidize NO into NO2 and N2O5. S3, Synergistic Absorption: Flue gas containing SO2 and oxidized NOx is passed into a wet desulfurization absorption tower and comes into countercurrent contact with limestone slurry to remove SO2 and NOx simultaneously; S4. Byproduct control: Control the pH value of the slurry tank of the absorption tower to 5.0-5.5, and introduce oxidizing air to promote the conversion of nitrous acid to nitric acid and prevent NOx from escaping again. S5. Clean flue gas treatment: The flue gas after desulfurization and denitrification is successively heated by a demister, a wet electrostatic precipitator and a flue gas heat exchanger before being discharged.

[0008] Furthermore, the intelligent control system employs a feedforward-feedback composite control algorithm: Feedforward control: Based on the monitored flue gas flow rate Q and initial NO concentration C NO The baseline ozone dosage M is calculated based on the preset O3 / NO molar ratio R. base ; K is the conversion factor; Feedback control: The NO concentration and ozone escape at the outlet of the oxidation reactor are monitored in real time. If the NO concentration at the outlet is higher than the set threshold, the dosage is increased. If ozone escape is detected, the dosage is reduced, so that the actual O3 / NO molar ratio R is dynamically maintained between 1.1 and 1.3.

[0009] Furthermore, the multi-stage vortex jet mixing device includes: Primary mixing: High-speed nozzles arranged in a ring along the cross-section of the flue are used to achieve uniform distribution of ozone on a macroscopic scale; Secondary mixing: A static vortex generator located downstream of the nozzle is used to induce the flue gas to generate rotational motion, thereby achieving rapid mixing of ozone and NO molecules at the microscale.

[0010] Furthermore, the ozone used in S2 is generated by a high-frequency, high-efficiency ozone generator, with oxygen of greater than 90% purity as the gas source, and the generated ozone concentration is 100g / Nm³~150g / Nm³.

[0011] Furthermore, the wet desulfurization absorption tower uses the limestone-gypsum process, and the chemical reactions that occur include: SO2 reacts with CaCO3 to produce CaSO4·2H2O; NO2 and N2O5 react with water to produce HNO3 and HNO2, which in turn react with CaCO3 to produce Ca(NO3)2.

[0012] Furthermore, in S4, by adjusting the supply of limestone slurry and the air volume of the oxidation blower, the dissolved oxygen content in the slurry tank is maintained to ensure that HNO2 is completely oxidized to HNO3.

[0013] Furthermore, the flue gas heat exchanger utilizes clean flue gas to exchange heat with a high-temperature medium, raising the exhaust gas temperature above the dew point to eliminate white plumes.

[0014] Furthermore, it is applicable to denitrification treatment of coke oven flue gas with a temperature range of 80℃ to 220℃.

[0015] The second objective of this invention is to provide a coke oven flue gas treatment system that combines ozone oxidation with wet desulfurization, comprising: Flue gas pretreatment unit: includes waste heat boiler and bag filter or electrostatic precipitator; Ozone oxidation denitrification unit: includes an oxygen generator, an ozone generator, an intelligent ozone dosing control system and a multi-stage vortex jet mixing device; Wet desulfurization absorption unit: includes absorption tower, slurry circulation pump, oxidation fan and gypsum dewatering system; Clean flue gas treatment unit: includes demister, wet electrostatic precipitator, flue gas heat exchanger and induced draft fan.

[0016] Furthermore, the intelligent ozone dosing control system is connected to the online analyzer at the flue gas inlet and the NOx online analyzer and ozone monitor at the oxidation reactor outlet, forming a closed-loop control circuit.

[0017] Compared with the prior art, the present invention has the following technical effects: The present invention has high denitrification efficiency: when the O3 / NO molar ratio is sufficient, the denitrification efficiency can reach more than 85%-90%.

[0018] The present invention has a wide reaction temperature window: it can work efficiently in a temperature range of 80℃~200℃ or even wider, and is particularly suitable for treating low-temperature coke oven flue gas that has undergone waste heat recovery, without the need for additional heating, and has obvious energy-saving advantages.

[0019] The system of this invention is simple and easy to modify: it only requires adding an ozone generation system and an injection device before the existing wet desulfurization system, with minimal changes to the existing process, making it particularly suitable for the retrofitting of older units. This approach is applicable to the retrofitting of existing coke ovens, especially in situations where space is limited or the flue gas temperature is too low to accommodate SCR.

[0020] This invention can achieve synergistic removal: ozone can also oxidize trace amounts of toxic substances such as mercury and dioxins in flue gas, thus having a certain synergistic purification effect.

[0021] Ozone dosage and control: Insufficient ozone dosage will lead to incomplete oxidation of NO, as NO2 dissolves in water more slowly than N2O5; excessive dosage will cause ozone to escape and cause secondary pollution, requiring precise online control. Attached Figure Description

[0022] Figure 1 The flowchart provided is for a preferred embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention, and not all of them. Generally, the embodiments of the present invention described and shown in the accompanying drawings are characteristic technologies and solutions. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0024] Please see Figure 1 A method for treating coke oven flue gas using ozone oxidation in conjunction with wet desulfurization mainly includes: S1. Flue gas pretreatment: The raw flue gas from the coke oven is passed through a waste heat boiler and a dust removal device in sequence to reduce the flue gas temperature to 180℃~220℃ and the dust concentration to below 30mg / Nm³. S2. Precise Ozone Dosing and Oxidation: Real-time monitoring of the flow rate, temperature and NOx concentration of the pretreated flue gas; calculation of ozone demand using an intelligent control system; injection of ozone into the flue gas through a multi-stage vortex jet mixing device to oxidize NO into NO2 and N2O5. S3, Synergistic Absorption: Flue gas containing SO2 and oxidized NOx is passed into a wet desulfurization absorption tower and comes into countercurrent contact with limestone slurry to remove SO2 and NOx simultaneously; S4. Byproduct control: Control the pH value of the slurry tank of the absorption tower to 5.0-5.5, and introduce oxidizing air to promote the conversion of nitrous acid to nitric acid and prevent NOx from escaping again. S5. Clean flue gas treatment: The flue gas after desulfurization and denitrification is successively heated by a demister, a wet electrostatic precipitator and a flue gas heat exchanger before being discharged.

[0025] In S2, the intelligent control system employs a feedforward-feedback composite control algorithm: Feedforward control: Based on the monitored flue gas flow rate Q and initial NO concentration C NO The baseline ozone dosage M is calculated based on the preset O3 / NO molar ratio R. base ; K is the conversion factor; Feedback control: The NO concentration and ozone escape at the outlet of the oxidation reactor are monitored in real time. If the NO concentration at the outlet is higher than the set threshold, the dosage is increased. If ozone escape is detected, the dosage is reduced, so that the actual O3 / NO molar ratio R is dynamically maintained between 1.1 and 1.3.

[0026] The multi-stage vortex jet mixing device includes: Primary mixing: High-speed nozzles arranged in a ring along the cross-section of the flue are used to achieve uniform distribution of ozone on a macroscopic scale; Secondary mixing: A static vortex generator located downstream of the nozzle is used to induce the flue gas to generate rotational motion, thereby achieving rapid mixing of ozone and NO molecules at the microscale.

[0027] The ozone used in S2 is generated by a high-frequency, high-efficiency ozone generator. The gas source is oxygen with a purity greater than 90%, and the generated ozone concentration is 100g / Nm³~150g / Nm³.

[0028] The wet desulfurization absorption tower uses the limestone-gypsum process, and the chemical reactions that occur include: SO2 reacts with CaCO3 to produce CaSO4·2H2O; NO2 and N2O5 react with water to produce HNO3 and HNO2, which in turn react with CaCO3 to produce Ca(NO3)2.

[0029] In S4, the dissolved oxygen content in the slurry tank is maintained by adjusting the amount of limestone slurry replenished and the air volume of the oxidation blower, ensuring that HNO2 is completely oxidized to HNO3.

[0030] Flue gas heat exchangers utilize clean flue gas to exchange heat with a high-temperature medium, raising the exhaust gas temperature above the dew point to eliminate white plumes.

[0031] It is suitable for denitrification treatment of coke oven flue gas with a temperature range of 80℃~220℃.

[0032] In one specific embodiment, the method includes the following detailed steps: S1: Flue gas pretreatment and operating condition monitoring The raw coke oven flue gas first enters a waste heat boiler to recover heat, and the temperature drops to the optimal ozone oxidation window of 180-220℃. Subsequently, the flue gas enters a high-efficiency bag filter, reducing the dust concentration to below 30 mg / Nm³. The flow rate, temperature, SO2 concentration, NOx concentration, and NO / NO2 ratio of the flue gas after dust removal are monitored in real time.

[0033] S2: Precise preparation and dosing control of ozone Ozone preparation: Using an oxygen generator to prepare oxygen with a purity of >90% as the gas source, the gas is introduced into a high-frequency, high-efficiency ozone generator to produce ozone with a concentration of 100-150 g / Nm³.

[0034] Intelligent dosing control: The intelligent control system executes the following algorithm: Feedforward control: Based on the flue gas flow rate and initial NO concentration monitored in step S1, the basic ozone demand is calculated according to the preset O3 / NO molar ratio (1.0~1.5).

[0035] Feedback control: An online NOx analyzer is installed at the outlet of the ozone oxidation reactor to monitor the concentrations of unreacted NO and generated NO2 in real time. If the outlet NO concentration is higher than the set value, the O3 dosage is slightly increased; if O3 escape is detected by the ozone monitor, the dosage is rapidly reduced.

[0036] Ultimate goal: To dynamically control the O3 / NO molar ratio between 1.1 and 1.3, ensuring NO oxidation efficiency >90%, while essentially achieving zero O3 escape.

[0037] S3: High-efficiency mixing and low-temperature oxidation reaction Ozone is injected into the flue gas through a multi-stage vortex jet mixing device. First stage: Multiple high-speed nozzles arranged in a ring are used to ensure that ozone is evenly distributed across the flue cross-section.

[0038] Second stage: A static vortex generator is set up to make the flue gas rotate strongly, so as to achieve rapid micro-scale mixing of O3 and NO molecules in the flue gas.

[0039] Oxidation reaction: NO + O3 → NO2 + O2 NO2 + O3 → NO3 + O2 NO2 + NO3 → N2O5 N2O5, which is more soluble in water, is generated. S4: Co-absorption and byproduct control Flue gas containing SO2 and oxidized NOx (NO2, N2O5) enters from the bottom of the absorption tower.

[0040] Absorption process: The flue gas flows upward and comes into countercurrent contact with the limestone slurry sprayed down from the absorption spray layer.

[0041] SO2 is absorbed: SO2+CaCO3+1 / 2O2+2H2O→CaSO4·2H2O+CO2 Oxidized NOx is absorbed: 2NO2 + H2O → HNO3 + HNO2 N₂O₅ + H₂O → 2HNO₃ The generated nitric acid / nitrous acid reacts with limestone: 2HNO3+CaCO3→Ca(NO3)2+CO2+H2O Measures to prevent secondary precipitation: Maintain a pH of 5.0–5.5 in the slurry tank and keep a sufficient volume of oxidizing air to promote the conversion of HNO2 to HNO3 and effectively inhibit the secondary release of NOx caused by the decomposition of nitrite.

[0042] Byproduct treatment: The gypsum slurry in the slurry tank is pumped to a hydrocyclone and a vacuum belt dewatering machine to produce gypsum (CaSO4·2H2O), which has a wide range of uses and can be used as an industrial and building material. The desulfurization wastewater containing nitrates is sent to the original wastewater treatment system for further treatment.

[0043] S5: Flue Gas Treatment and Emission After desulfurization and denitrification, the saturated wet flue gas passes sequentially through a demister to remove most of the droplets, a wet electrostatic precipitator to remove fine particulate matter and droplets, a flue gas heat exchanger to recover heat and heat up the clean flue gas to eliminate white plumes, and finally is discharged through a chimney by an induced draft fan, completely eliminating white plumes.

[0044] Implementation Case: A coke oven flue gas treatment project at a coking plant has a flue gas volume of 100,000 Nm³ / h, a raw flue gas temperature of 300℃, a NOx concentration of 400 mg / Nm³, and a SO2 concentration of 600 mg / Nm³.

[0045] Pretreatment: The flue gas is cooled to 200℃ by a waste heat boiler and then enters a bag filter dust collector, with an outlet dust concentration of <20mg / Nm³.

[0046] Ozone addition: Online monitoring showed that the NO concentration was 180 ppm.

[0047] The intelligent system sets the O3 / NO molar ratio to 1.2.

[0048] The oxygen generator provides 93% pure oxygen, and the ozone generator produces ozone at a concentration of 120g / Nm³.

[0049] Ozone is injected into the flue through a multi-stage vortex mixer, with a mixing time of less than 2 seconds.

[0050] Export monitoring showed that the NO concentration dropped to below 20 mg / Nm³, and no ozone escape was detected.

[0051] Absorption and removal: Flue gas enters the limestone-gypsum desulfurization tower.

[0052] Control the pH of the slurry to 5.2 and turn the oxidation blower on full blast.

[0053] Desulfurization efficiency >98%, outlet SO2 <35mg / Nm³.

[0054] Denitrification efficiency >92%, NOx at outlet <40mg / Nm³.

[0055] The by-product gypsum is of normal quality and contains a small amount of calcium nitrate. The desulfurization wastewater is sent to the plant's wastewater treatment station.

[0056] Emissions: The clean flue gas is heated to 80°C after passing through wet electrostatic precipitator and heat exchange before being emitted, with no visible plume.

[0057] A coke oven flue gas treatment system combining ozone oxidation and wet desulfurization comprises, in sequence along the flue gas flow direction: Flue gas pretreatment unit: includes waste heat boiler and bag filter or electrostatic precipitator; Ozone oxidation denitrification unit: includes an oxygen generator, an ozone generator, an intelligent ozone dosing control system and a multi-stage vortex jet mixing device; Wet desulfurization absorption unit: includes absorption tower, slurry circulation pump, oxidation fan and gypsum dewatering system; Clean flue gas treatment unit: includes demister, wet electrostatic precipitator, flue gas heat exchanger and induced draft fan.

[0058] The intelligent ozone dosing control system is connected to the online analyzer at the flue gas inlet and the NOx online analyzer and ozone monitor at the oxidation reactor outlet, forming a closed-loop control circuit.

[0059] In the embodiment described: The flue gas pretreatment unit mainly includes the main coke oven flue, waste heat boiler, and bag filter or electrostatic precipitator. The waste heat boiler is used to reduce the flue gas temperature from about 300℃ to a suitable oxidation temperature of 180-220℃; the bag filter or electrostatic precipitator is used to remove most of the dust, preventing it from consuming ozone and wearing down the equipment.

[0060] The ozone oxidation denitrification unit mainly includes an ozone generator, an oxygen generator, an intelligent ozone dosing control system, and a multi-stage vortex jet mixing device installed in the flue after the dust collector.

[0061] The wet desulfurization absorption unit mainly includes an absorption tower, inside which are arranged from bottom to top a slurry pool, a spray layer, a demister, etc. The slurry pool is connected to the gypsum discharge and dewatering system.

[0062] The flue gas reheat and emission unit mainly includes a wet electrostatic precipitator, a flue gas heat exchanger, an induced draft fan, and a chimney.

[0063] To better understand the technical solution of the present invention, non-limiting examples are given below: A method for treating coke oven flue gas using ozone oxidation combined with wet desulfurization includes the following steps: Flue gas pretreatment: The raw flue gas from the coke oven first enters the waste heat boiler to recover heat and lower the temperature to a suitable oxidation window of 180℃~220℃. Then it enters a high-efficiency bag filter or electrostatic precipitator to remove most of the dust (concentration <30mg / Nm³), preventing dust from consuming ozone and abrading equipment.

[0064] Precise Ozone Dosing and Low-Temperature Oxidation: Intelligent Control: Real-time monitoring of flue gas flow rate, temperature, and NOx concentration. A feedforward-feedback composite control algorithm is employed: the feedforward part calculates the basic dosage based on the initial NO concentration and a preset molar ratio (1.0–1.5); the feedback part dynamically fine-tunes the O3 / NO molar ratio based on the outlet NO concentration and ozone escape, precisely controlling it between 1.1 and 1.3 to ensure NO oxidation efficiency >90% and no ozone escape.

[0065] High-efficiency mixing: Ozone is injected through a multi-stage vortex jet mixing device. The first stage uses a ring-shaped high-speed nozzle to achieve macroscopic uniform distribution; the second stage uses a static vortex generator to induce flue gas rotation to achieve microscopic rapid mixing.

[0066] Oxidation reaction: At low temperatures of 80–220°C, the following reaction occurs: NO + O3 → NO2 + O2 NO2 + O3 → NO3 + O2 NO2 + NO3 → N2O5 It generates N2O5, which is more soluble in water.

[0067] Synergistic absorption: Flue gas containing SO2 and oxidized NOx enters a wet desulfurization absorption tower (limestone-gypsum method).

[0068] SO2 is absorbed by the slurry to form gypsum (CaSO4·2H2O).

[0069] Oxidized NOx (NO2, N2O5) is highly soluble in water to form nitric acid (HNO3) and nitrous acid (HNO2), and reacts with limestone to form calcium nitrate (Ca(NO3)2) which enters the liquid phase.

[0070] Byproduct control and prevention of secondary escape: Strictly control the pH value of the slurry tank in the absorption tower within the range of 5.0 to 5.5, and maintain a sufficient oxidation air volume. These conditions can promote the rapid oxidation of unstable nitrite (HNO2) to stable nitrate (HNO3), effectively inhibiting the secondary release of NOx caused by the decomposition of nitrite.

[0071] Flue gas treatment: The purified flue gas passes through a demister and a wet electrostatic precipitator (to remove fine particles and droplets), and is finally heated and de-whitened by a flue gas heat exchanger before being discharged through a chimney.

[0072] This invention has the effect of high-efficiency low-temperature denitrification: by utilizing the ozone oxidation characteristics, it achieves a denitrification efficiency of >90% in a wide temperature range of 80℃~220℃, without the need for additional heating of flue gas, resulting in significant energy savings.

[0073] This invention only requires the addition of an ozone generation and injection system before the existing wet desulfurization process, with a small amount of modification work, making it particularly suitable for old coke ovens and projects with limited space.

[0074] The present invention has low operating costs: it avoids expensive catalyst replacement costs and heating energy consumption; the intelligent control algorithm avoids ozone waste.

[0075] This invention produces no secondary pollution: precise ozone control and an optimized pH strategy for the absorption tower completely solve the problems of ozone escape and secondary NOx precipitation.

[0076] This invention has a synergistic purification function: it has the potential to remove trace amounts of toxic substances such as mercury and dioxins.

[0077] The above description is only a preferred embodiment of the present invention. It should be noted that any improvements, modifications, substitutions or variations made by those skilled in the art without departing from the principle of the present invention should be considered as being included within the protection scope of the present invention.

Claims

1. A method for treating coke oven flue gas using ozone oxidation in conjunction with wet desulfurization, characterized in that, include: S1. Flue gas pretreatment: The raw flue gas from the coke oven is passed through a waste heat boiler and a dust removal device in sequence to reduce the flue gas temperature to 180℃~220℃ and the dust concentration to below 30mg / Nm³. S2. Precise Ozone Dosing and Oxidation: Real-time monitoring of the flow rate, temperature and NOx concentration of the pretreated flue gas; calculation of ozone demand using an intelligent control system; injection of ozone into the flue gas through a multi-stage vortex jet mixing device to oxidize NO into NO2 and N2O5. S3, Synergistic Absorption: Flue gas containing SO2 and oxidized NOx is passed into a wet desulfurization absorption tower and comes into countercurrent contact with limestone slurry to remove SO2 and NOx simultaneously; S4. Byproduct control: Control the pH value of the slurry tank of the absorption tower to 5.0-5.5, and introduce oxidizing air to promote the conversion of nitrous acid to nitric acid and prevent NOx from escaping again. S5. Clean flue gas treatment: The flue gas after desulfurization and denitrification is successively heated by a demister, a wet electrostatic precipitator and a flue gas heat exchanger before being discharged.

2. The method for treating coke oven flue gas using ozone oxidation in conjunction with wet desulfurization according to claim 1, characterized in that, The intelligent control system adopts a feedforward-feedback composite control algorithm: Feedforward control: Based on the monitored flue gas flow rate Q and initial NO concentration C NO The baseline ozone dosage M is calculated based on the preset O3 / NO molar ratio R. base ; K is the conversion factor; Feedback control: The NO concentration and ozone escape at the outlet of the oxidation reactor are monitored in real time. If the NO concentration at the outlet is higher than the set threshold, the dosage is increased. If ozone escape is detected, the dosage is reduced, so that the actual O3 / NO molar ratio R is dynamically maintained between 1.1 and 1.

3.

3. The method for treating coke oven flue gas using ozone oxidation in conjunction with wet desulfurization according to claim 1, characterized in that, The multi-stage vortex jet mixing device includes: Primary mixing: High-speed nozzles arranged in a ring along the cross-section of the flue are used to achieve uniform distribution of ozone on a macroscopic scale; Secondary mixing: A static vortex generator located downstream of the nozzle is used to induce the flue gas to generate rotational motion, thereby achieving rapid mixing of ozone and NO molecules at the microscale.

4. The method for treating coke oven flue gas using ozone oxidation in conjunction with wet desulfurization according to claim 1, characterized in that, The ozone used in S2 is generated by a high-frequency, high-efficiency ozone generator. The gas source is oxygen with a purity greater than 90%, and the generated ozone concentration is 100g / Nm³~150g / Nm³.

5. The method for treating coke oven flue gas using ozone oxidation in conjunction with wet desulfurization according to claim 1, characterized in that, The wet desulfurization absorption tower uses the limestone-gypsum process, and the chemical reactions that occur include: SO2 reacts with CaCO3 to produce CaSO4·2H2O; NO2 and N2O5 react with water to produce HNO3 and HNO2, which in turn react with CaCO3 to produce Ca(NO3)2.

6. The method for treating coke oven flue gas using ozone oxidation in conjunction with wet desulfurization according to claim 1, characterized in that, In S4, the dissolved oxygen content in the slurry tank is maintained by adjusting the amount of limestone slurry replenished and the air volume of the oxidation blower, ensuring that HNO2 is completely oxidized to HNO3.

7. The method for treating coke oven flue gas by ozone oxidation combined with wet desulfurization according to claim 1, characterized in that, Flue gas heat exchangers utilize clean flue gas to exchange heat with a high-temperature medium, raising the exhaust gas temperature above the dew point to eliminate white plumes.

8. The method for treating coke oven flue gas by ozone oxidation combined with wet desulfurization according to claim 1, characterized in that, It is suitable for denitrification treatment of coke oven flue gas with a temperature range of 80℃~220℃.

9. A coke oven flue gas ozone oxidation combined with wet desulfurization treatment system, characterized in that, include: Flue gas pretreatment unit: includes waste heat boiler and bag filter or electrostatic precipitator; Ozone oxidation denitrification unit: includes an oxygen generator, an ozone generator, an intelligent ozone dosing control system and a multi-stage vortex jet mixing device; Wet desulfurization absorption unit: includes absorption tower, slurry circulation pump, oxidation fan and gypsum dewatering system; Clean flue gas treatment unit: includes demister, wet electrostatic precipitator, flue gas heat exchanger and induced draft fan.

10. The coke oven flue gas ozone oxidation synergistic wet desulfurization treatment system according to claim 9, characterized in that, The intelligent ozone dosing control system is connected to the online analyzer at the flue gas inlet and the NOx online analyzer and ozone monitor at the oxidation reactor outlet, forming a closed-loop control circuit.

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