Flue gas denitration method for phthalic anhydride heat storage oxidation furnace

Abstract

The invention discloses a phthalic anhydride heat storage oxidation furnace flue gas denitration method which is characterized by comprising the following steps: introducing strong oxygen into a pipeline from an outlet of a heat storage oxidation furnace to flue gas before desulfurization to obtain oxidized flue gas, feeding the oxidized flue gas into a desulfurization tower, and spraying soluble alkali liquor to realize simultaneous desulfurization and denitration, the desulfurized and denitrated flue gas is obtained. According to the flue gas denitration method for the phthalic anhydride heat storage oxidation furnace, strong oxygen is introduced into the pipeline from the outlet of the heat storage oxidation furnace to the flue gas before desulfurization, NO in tail gas is quickly and effectively oxidized into high-valence NOx which is easy to absorb by utilizing the strong oxidizing property of the strong oxygen, and then simultaneous desulfurization and denitration are realized in a desulfurization tower.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to a method for denitrifying flue gas from a phthalic anhydride thermal storage oxidizer, and specifically relates to a method for denitrifying flue gas from a low-temperature phthalic anhydride thermal storage oxidizer by using strong oxygen. Background Art

[0002] Phthalic anhydride is an important basic chemical raw material and organic synthesis intermediate. It is widely used in dyes, resins, pharmaceuticals, plasticizers, new energy vehicles and other fields. It has a broad application space and is of great strategic significance in the production and development of the national economy.

[0003] The application of thermal storage oxidation furnace in the production of phthalic anhydride, especially in the production of phthalic anhydride by the naphthalene process, has been gradually promoted. The process of using thermal storage oxidation furnace to treat phthalic anhydride tail gas is usually as follows: first preheating is carried out to make the thermal storage ceramic reach the specified temperature, and then the phthalic anhydride tail gas is introduced into the furnace body, and the tail gas is distributed according to the program through the gas distribution chamber, and then the tail gas enters the thermal storage chamber, and the thermal storage ceramic preheats the tail gas to a certain temperature, and the tail gas enters the oxidation chamber, and the organic matter contained in the tail gas is fully oxidized in the oxidation chamber, and then discharged through the outlet valve.

[0004] In recent years, the national environmental protection policies and standards have become increasingly stringent. The "Key Enterprise Air Pollutant Emissions Total Control Index" issued by a certain city clearly stipulates strict control requirements for the total monthly, daily, and hourly emissions of tail gas pollutants from phthalic anhydride units, requiring the daily total emissions to be no more than 155kg, and strengthening the control period to be more stringent. At present, during normal control, the SO2 concentration (10mg / Nm 3 Below), dust concentration (1mg / Nm 3 The following) governance has reached its limit and there is no room for further reduction.

[0005] Therefore, it is urgent to find a further denitrification method for the flue gas of the phthalic anhydride thermal oxidation furnace in order to meet the government's environmental protection requirements and maintain normal production of the enterprise.

[0006] Among the existing methods for treating the tail gas of the phthalic anhydride thermal storage oxidizer, the selective catalytic reduction technology (SCR) process has the disadvantages of large investment, high operating cost, high catalyst activation temperature (180°C-220°C), easy ammonia escape in the production process, and sulfate easily causing catalyst blockage, poisoning and deactivation; the selective non-catalytic reduction method (SNCR) has the disadvantages of high cost, high energy consumption, large consumption of reducing agent in the production process, and low denitration efficiency (about 40%), and is not suitable for the treatment of the tail gas of the phthalic anhydride thermal storage oxidizer; and the medium and low temperature ammonia-free catalytic denitration process, the ammonia spraying denitration process in the thermal storage furnace, the liquid denitrifier, the tail gas desulfurization and denitration before the thermal storage oxidation and other technologies have high operating costs and investment in practice, and cannot meet industrial requirements. Summary of the invention

[0007] The inventors studied the composition of the tail gas from the phthalic anhydride thermal oxidation furnace and found that it has the following characteristics: (1) NO X Low content, less than 110mg / Nm 3 , and the NO content is high, making it difficult and costly to further reduce nitrogen oxides; (2) the dust in the exhaust gas is sticky and the sulfur dioxide concentration is high (greater than 600 mg / Nm 3 ); (3) The flue gas temperature of the thermal regenerative oxidizer is low, generally stable at 130-180°C. 3 ), high sulfur (greater than 600mg / Nm 3 ) is unique. After experimental verification, the present invention provides a method for strong oxygen denitrification of tail gas from a phthalic anhydride thermal storage oxidizer. With ozone as a strong oxidant, NO in the flue gas, which is difficult to dissolve in water and has poor reaction activity, is quickly and effectively oxidized into high-valent NOx that is easily soluble in water, so that it can be subsequently absorbed by the liquid phase at the same time as SO2, achieving the purpose of simultaneous desulfurization and denitrification. Moreover, the inventors have also found that under a specific strong oxygen concentration, the conversion of NO to high-valent NOx that is easily soluble in water can be completed at a normal flue gas temperature in a short time of a normal process, so that it can be smoothly carried out under the low temperature condition of the flue gas of the thermal storage oxidizer without having to significantly change the reaction equipment, and the tail gas of the phthalic anhydride device process can be effectively and economically desulfurized and denitrified.

[0008] In view of the particularity of the tail gas of the phthalic anhydride thermal storage oxidation furnace, there are currently no successful denitrification cases and industrial application performance in the phthalic anhydride industry nationwide. The present invention is the first denitrification technology in the phthalic anhydride industry that has been successfully tested, which can effectively solve the problem of substandard flue gas from the tail gas of the thermal storage furnace, effectively control the total amount of nitrogen oxide emissions, enable the phthalic anhydride device to produce at full load, and improve the efficiency of the enterprise. The present invention provides a solution for the denitrification of phthalic anhydride tail gas and low-temperature and low-density flue gas, and has good economic benefits and application prospects. In addition, the present invention effectively controls pollutants from the phthalic anhydride thermal storage oxidation furnace, enables the phthalic anhydride device to produce at full load, and improves efficiency. It can provide reference significance for the denitrification control of the phthalic anhydride industry, and at the same time has significant economic value.

[0009] According to one embodiment of the present invention, a method for denitrification of flue gas from a phthalic anhydride thermal regenerative oxidation furnace is provided, comprising the following steps:

[0010] (2) Strong oxygen is introduced into the pipeline from the outlet of the thermal oxidation furnace to the flue gas before desulfurization to obtain oxidized flue gas.

[0011] (3) The oxidized flue gas is sent to a desulfurization tower, and desulfurization and denitrification are achieved simultaneously by spraying a soluble alkali solution to obtain desulfurized and denitrified flue gas.

[0012] According to one embodiment of the present invention,

[0013] The strong oxygen described in step (2) is prepared by the following method:

[0014] (1) Oxygen at a certain pressure is transported to the discharge chamber of the strong oxygen generator through a pipeline. In the strong oxygen discharge chamber, the oxygen passes through a high-voltage electric field and uses dielectric barrier discharge technology to convert part of the oxygen into strong oxygen.

[0015] According to an embodiment of the present invention, the concentration of strong oxygen in step (2) is 140-150 mg / Nm 3 .

[0016] By controlling the concentration of strong oxygen, the operating efficiency of the equipment can be improved, the NOx concentration can be accurately controlled, the environmental protection standards for flue gas emissions can be met, and the amount of manual labor can be reduced.

[0017] According to an embodiment of the present invention, preferably, the concentration of strong oxygen in step (2) is adjusted to 140-150 mg / Nm by controlling the generator with a DCS unit in step (1). 3 .

[0018] According to the technical method of the present invention, preferably, in step (2), an air distribution device is provided in the flue.

[0019] The gas distribution device in the flue can evenly distribute the strong oxygen gas and the nitrogen oxides in the flue gas, so that they can fully contact and react, thereby improving the oxidation efficiency of nitrogen oxides.

[0020] According to the technical method of the present invention, preferably, in step (2), in order to ensure that the strong oxygen and nitrogen oxides react to reach a state of equilibrium, the reaction time is 0.5-2 seconds and the strong oxygen residence time is 0.5-2 seconds.

[0021] According to the technical method of the present invention, preferably, in step (2), in order to ensure that the reaction between strong oxygen and nitrogen oxides reaches a state of equilibrium, the current flue gas linear velocity is 10-12 m / s and the flue length is designed to be greater than 11 meters.

[0022] According to the technical method of the present invention, preferably, in step (2), under low temperature conditions (below 200° C.), the key reaction between strong oxygen and NO is as follows:

[0023] NO+O3→NO2+O2 (1)

[0024] NO2+O3→NO3+O2 (2)

[0025] NO3+NO2→N2O5 (3)

[0026] According to the technical method of the present invention, preferably, before step (2) or after step (2), it may further include:

[0027] (2') performing dust removal treatment on the flue gas after desulfurization and denitrification.

[0028] Beneficial Effects

[0029] The flue gas denitrification method of the phthalic anhydride thermal storage oxidation furnace provided by the present invention introduces strong oxygen into the pipeline from the outlet of the thermal storage oxidation furnace to the flue gas before desulfurization, and utilizes the strong oxidizing property of the strong oxygen to quickly and effectively oxidize NO in the tail gas into high-valent NOx that is easily absorbed, and then achieves simultaneous desulfurization and denitrification in the desulfurization tower. Compared with conventional SCR technology, the strong oxygen denitrification has low operating costs and investment, and a high NOx removal efficiency of more than 90%. The strong oxygen denitrification process is simple, the reaction temperature is low, and no catalyst is required, which avoids the shortcomings of the SCR method such as ammonia escape, easy poisoning and deactivation of the catalyst, and secondary pollution. In view of the particularity of the process tail gas of the phthalic anhydride device, namely, low temperature (130-180°C), low NOx concentration (less than 110 mg / Nm3), high sulfur (greater than 600 mg / Nm3) and high dust, the method of the present invention effectively solves the problem of substandard tail gas from the regenerative furnace, provides a solution for the denitrification of the flue gas from the phthalic anhydride regenerative oxidation furnace and the low-temperature and low-density flue gas, enables the phthalic anhydride device to produce at full load, improves the enterprise's benefits, and has good economic benefits and application prospects.

[0030] Instruction Manual

[0031] Figure 1 It is a structural schematic diagram of the strong oxygen generating device described in an embodiment of the present invention.

[0032] Figure 2 It is a data graph of total nitrogen oxide concentration before and after the long-term strong oxygen treatment described in the embodiment of the present invention.

[0033] Figure 3 It is a schematic diagram of the structure of the strong oxygen low temperature oxidation denitrification system described in an embodiment of the present invention.

[0034] Figure 4 It is a schematic diagram of the structure of the gas distribution device in the flue of the strong oxygen low temperature oxidation denitrification system described in an embodiment of the present invention.

[0035] Reference numerals

[0036] 1: Oxygen

[0037] 2: Strong oxygen generator

[0038] 3: Flow control valve

[0039] 4: Booster pump

[0040] 5: Thermal oxidation furnace for the production of phthalic anhydride

[0041] 6: Desulfurization tower

[0042] 7: Circulation pump

[0043] 8: Dust removal device

[0044] 9: Internal sprinkler

[0045] 10: Chimney

[0046] 11: Nozzle

[0047] 12: Booster pump

[0048] 13: Flow control valve Specific embodiments

[0049] In order to deepen the understanding of the present invention, the technical scheme of the present invention will be further described in detail below in combination with the embodiments and drawings. The described embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without making substantial creative work all belong to the protection scope of the present invention.

[0050] The total nitrogen oxides in the tail gas of the phthalic anhydride thermal storage oxidation furnace are mainly composed of NO with a volume concentration of more than 95%. NO is insoluble in water and has poor reaction activity. It is one of the gaseous pollutants that is difficult to treat, while high-valent NOx is easily removed by liquid phase washing. The present invention generates strong oxygen by a strong oxygen generating device, and transports it to the interface between the thermal storage oxidation outlet and the pre-desulfurization pipeline through a flue gas pipeline. The strong oxidizing property of the strong oxygen is used to quickly and effectively oxidize NO in the tail gas into high-valent NO2, NO3, N2O5, etc. that are easy to absorb, so that it can be absorbed by the liquid phase at the same time as the subsequent SO2, achieving the purpose of simultaneous desulfurization and denitrification.

[0051] The parameters of the initial flue gas of the phthalic anhydride regenerative thermal oxidizer are as follows: the outlet temperature of the flue gas of the regenerative thermal oxidizer is generally stable at 130-180℃, and the total NOx content is generally 70-110mg / Nm 3 , oxygen content is 10-15%, flue gas flow rate is 145000-16000Nm 3 / h; smoke linear velocity 10-11m / s, smoke duct length 18m.

[0052] The oxygen generating device produces 20kg / h of oxygen, one on and one on standby, and the oxygen concentration is 140-150mg / Nm 3 The concentration of strong oxygen can be adjusted by controlling the generator through the DCS unit, which can achieve precise control of NOx concentration.

[0053] Embodiment 1:

[0054] The oxygen 1 of a certain pressure is dried and purified and then transported to the strong oxygen generating device 2. The generated strong oxygen is transported to the outlet of the thermal storage oxidation furnace 5 and the pipeline interface of the desulfurization tower 6 through the flow regulating valve 3 and the booster pump 4, and is evenly sprayed through the gas distribution device to make the strong oxygen and the flue gas fully mixed and reacted. The reaction time is 0.7s. Then the soluble alkali solution circulation pump 7 and the flow regulating valve 13 and the booster pump 12 are opened to make the alkali solution in the alkali solution tank 6 be sent to the internal sprayer 9 of the desulfurization tower through the pipeline and sprayed through the nozzle 11. The flow rate of the alkali solution is adjusted by the flow regulating valve 13, so as to achieve the purpose of simultaneous desulfurization and denitrification. After purification by the dust removal device 8, the flue gas is discharged through the chimney 10. The flue gas temperature of the phthalic anhydride thermal storage oxidation furnace before the reaction with strong oxygen is 150℃, and the total nitrogen oxide content is 108mg / Nm 3 , where NO is 105 mg / Nm 3 About, NO2 is 3mg / Nm 3 Around, oxygen content is 12%, flue gas flow is 145000Nm 3 / h; the flue gas linear velocity is 10.5m / s, the flue gas duct length is 18 meters, the strong oxygen production is 14.2kg / h, one is on and one is on standby, and the DCS unit is used to control the generator (not shown) to adjust the power of the strong oxygen concentration to 146mg / Nm 3 .

[0055] The exhaust gas outlet (10 chimneys) was tested continuously for 19 days using flue gas testing equipment. The total nitrogen oxide content at the outlet was detected as shown in Table 1 below. The total efficiency of NO conversion - NOx absorption was as high as over 80%, meeting the national environmental emission standards and enabling the normal production and operation of the phthalic anhydride unit.

[0056] Table 1

[0057]

[0058] Embodiment 2:

[0059] The oxygen 1 of a certain pressure is dried and purified and then transported to the strong oxygen generating device 2. The generated strong oxygen is transported to the outlet of the thermal storage oxidation furnace 5 and the pipeline interface of the desulfurization tower 6 through the flow regulating valve 3 and the booster pump 4, and is evenly sprayed through the gas distribution device to make the strong oxygen and the flue gas fully mixed and reacted. The reaction time is 0.9s. Then the soluble alkali solution circulation pump 7 and the flow regulating valve 13 and the booster pump 12 are opened to make the alkali solution in the alkali solution tank 6 be sent to the internal sprayer 9 of the desulfurization tower through the pipeline, and evenly sprayed through the nozzle 11. The flow rate of the alkali solution is adjusted by the flow regulating valve 13, so as to achieve the purpose of simultaneous desulfurization and denitrification. After purification by the dust removal device 8, the flue gas is discharged through the chimney 10. The flue gas temperature of the phthalic anhydride thermal storage oxidation furnace before the reaction with strong oxygen is 155℃, and the total nitrogen oxide content is 107mg / Nm 3, oxygen content is 10%, flue gas flow rate is 146000Nm 3 / h; the flue gas linear velocity is 11m / s, the flue gas duct length is 18m, the strong oxygen production is 14.8kg / h, one is on and one is on standby, and the DCS unit is used to control the generator power to adjust the strong oxygen concentration to 143mg / Nm 3 .

[0060] The exhaust gas outlet was tested for 19 consecutive days using flue gas testing equipment, and the results are shown in Table 2. The total nitrogen oxide content at the outlet was detected as shown in Table 2. The total efficiency of NO conversion - NOx absorption was as high as 80%, meeting the national environmental protection emission standards, and enabling the normal production and operation of the phthalic anhydride unit.

[0061] Table 2

[0062]

[0063] Embodiment 3:

[0064] The oxygen 1 of a certain pressure is dried and purified and then transported to the strong oxygen generating device 2. The generated strong oxygen is transported to the outlet of the thermal storage oxidation furnace 5 and the pipeline interface of the desulfurization tower 6 through the flow regulating valve 3 and the booster pump 4, and is evenly sprayed through the gas distribution device to make the strong oxygen and the flue gas fully mixed and reacted. The reaction time is 1.0s. Then the soluble alkali solution circulation pump 7 and the flow regulating valve 13 and the booster pump 12 are opened to make the alkali solution in the alkali solution tank 6 be sent to the internal sprayer 9 of the desulfurization tower through the pipeline, and evenly sprayed through the nozzle 11. The flow rate of the alkali solution is adjusted by the flow regulating valve 13, so as to achieve the purpose of simultaneous desulfurization and denitrification. After being purified by the dust removal device 8, the flue gas is discharged through the chimney 10. The flue gas temperature of the phthalic anhydride thermal storage oxidation furnace before the reaction with strong oxygen is 158°C, and the total nitrogen oxide content is 106mg / Nm 3 , oxygen content is 10%, flue gas flow rate is 148000Nm 3 / h; the flue gas linear velocity is 11.2m / s, the flue gas duct length is 18m, the strong oxygen production is 14.0kg / h, one is on and one is on standby, and the DCS unit is used to control the generator power to adjust the strong oxygen concentration to 141mg / Nm 3 .

[0065] The exhaust gas outlet was tested continuously for 19 days using flue gas testing equipment. The total nitrogen oxide content at the outlet was detected as shown in Table 3 below. The total efficiency of NO conversion - NOx absorption was as high as over 81%, meeting the national environmental emission standards and enabling the phthalic anhydride unit to operate normally.

[0066] Table 3

[0067]

[0068] Embodiment 4:

[0069] The oxygen 1 of a certain pressure is dried and purified and then transported to the strong oxygen generating device 2. The generated strong oxygen is transported to the outlet of the thermal storage oxidation furnace 5 and the pipeline interface of the desulfurization tower 6 through the flow regulating valve 3 and the booster pump 4, and is evenly sprayed through the gas distribution device to make the strong oxygen and the flue gas fully mixed and reacted. The reaction time is 0.9s. Then the soluble alkali solution circulation pump 7 and the flow regulating valve 13 and the booster pump 12 are opened to make the alkali solution in the alkali solution tank 6 be sent to the internal sprayer 9 of the desulfurization tower through the pipeline, and evenly sprayed through the nozzle 11. The flow rate of the alkali solution is adjusted by the flow regulating valve 13, so as to achieve the purpose of simultaneous desulfurization and denitrification. After purification by the dust removal device 8, the flue gas is discharged through the chimney 10. The flue gas temperature of the phthalic anhydride thermal storage oxidation furnace before the reaction with strong oxygen is 156°C, and the total nitrogen oxide content is 107mg / Nm 3 , oxygen content is 11.1%, flue gas flow rate is 147000Nm 3 / h; the flue gas linear velocity is 11.0m / s, the flue gas duct length is 18m, the strong oxygen production is 13.8kg / h, one is on and one is on standby, and the DCS unit is used to control the generator power and adjust the strong oxygen concentration to 144mg / Nm 3 .

[0070] The exhaust gas outlet was tested continuously for 21 days using flue gas testing equipment. The total nitrogen oxide content at the outlet was detected as shown in Table 4 below. The total efficiency of NO conversion - NOx absorption was as high as over 81%, meeting the national environmental emission standards and enabling the normal production and operation of the phthalic anhydride unit.

[0071] Table 4

[0072]

[0073] Embodiment 5:

[0074] The oxygen 1 of a certain pressure is dried and purified and then transported to the strong oxygen generating device 2. The generated strong oxygen is transported to the outlet of the thermal storage oxidation furnace 5 and the pipeline interface of the desulfurization tower 6 through the flow regulating valve 3 and the booster pump 4, and is evenly sprayed through the gas distribution device to make the strong oxygen and the flue gas fully mixed and reacted. The reaction time is 0.9s. Then the soluble alkali solution circulation pump 7 and the flow regulating valve 13 and the booster pump 12 are opened to make the alkali solution in the alkali solution tank 6 be sent to the internal sprayer 9 of the desulfurization tower through the pipeline, and evenly sprayed through the nozzle 11. The flow rate of the alkali solution is adjusted by the flow regulating valve 13, so as to achieve the purpose of simultaneous desulfurization and denitrification. After purification by the dust removal device 8, the flue gas is discharged through the chimney 10. The flue gas temperature of the phthalic anhydride thermal storage oxidation furnace before the reaction with strong oxygen is 159°C, and the total nitrogen oxide content is 106mg / Nm 3 , oxygen content is 12.0%, flue gas flow rate is 149000Nm 3 / h; the flue gas linear velocity is 11.5m / s, the flue gas duct length is 18m, the strong oxygen production is 5.3kg / h, one is on and one is on standby, and the DCS unit is used to control the generator power and adjust the strong oxygen concentration to 52mg / Nm 3 .

[0075] The exhaust gas outlet was tested for 21 consecutive days using flue gas detection equipment. The total nitrogen oxide content at the outlet was found to be as shown in Table 5. The nitrogen oxide content at the outlet was reduced to 80 mg / Nm 3 about.

[0076] Table 5

[0077]

[0078] Comparative Example 1:

[0079] No strong oxygen is introduced into the pipe interface between the outlet of the thermal oxidation furnace 5 and the desulfurization tower 6. Then the soluble alkali solution circulation pump 7, flow regulating valve 13 and booster pump 12 are turned on, so that the alkali solution in the alkali solution tank 6 is sent to the internal sprayer 9 of the desulfurization tower through the pipeline, and is evenly sprayed through the nozzle 11. The flow rate of the alkali solution is adjusted by the flow regulating valve 13. The flue gas temperature of the phthalic anhydride thermal oxidation furnace before the reaction with strong oxygen is 161°C, and the total nitrogen oxide content is 108mg / Nm 3 , oxygen content is 11.6%, flue gas flow rate is 150000Nm 3 / h; smoke linear velocity 11.9m / s, smoke duct length 18m.

[0080] The exhaust gas outlet was tested for 19 consecutive days using flue gas detection equipment. The total nitrogen oxide content at the outlet was as high as 95 mg / Nm 3 The change is very small and cannot meet the national environmental protection emission standards. The phthalic anhydride unit cannot produce normally.

[0081] Table 6

[0082]

[0083] It can be seen from the records in Example 5 that the denitrification method of the method of the present invention has low operating costs and can effectively remove the total nitrogen oxide content; it can be seen from the records in Examples 1-4 that under a specific strong oxygen concentration, the total nitrogen oxide removal efficiency is high, which can effectively solve the problem of tail gas treatment in the process of the phthalic anhydride device and ensure the normal production of the phthalic anhydride device, and has significant economic benefits and application prospects.

[0084] It can be seen from the record of Comparative Example 1 that, when spraying directly, since NO cannot be absorbed, the total nitrogen oxide content at the outlet is high, which cannot meet the national environmental protection emission standards, and the phthalic anhydride device cannot produce normally.

Claims

1. A method for denitrification of flue gas from a phthalic anhydride thermal regenerative oxidation furnace, characterized in that: The following steps are involved: (2) Strong oxygen is introduced into the pipeline from the outlet of the thermal oxidation furnace to the flue gas before desulfurization to obtain oxidized flue gas. (3) The oxidized flue gas is sent to a desulfurization tower, and desulfurization and denitrification are achieved simultaneously by spraying a soluble alkali solution to obtain desulfurized and denitrified flue gas.

2. The method for denitrification of flue gas from a phthalic anhydride thermal oxidation furnace according to claim 1, characterized in that: The strong oxygen described in step (2) is prepared by the following method: (1) Oxygen at a certain pressure is transported to the discharge chamber of the strong oxygen generator through a pipeline. In the strong oxygen discharge chamber, the oxygen passes through a high-voltage electric field and uses dielectric barrier discharge technology to convert part of the oxygen into strong oxygen.

3. The flue gas denitration method of phthalic anhydride thermal storage oxidation furnace according to claim 1, characterized in that: The strong oxygen concentration in step (2) is 140-150 mg / Nm 3 .

4. The method for denitrification of flue gas from a phthalic anhydride thermal storage oxidation furnace according to claim 2, characterized in that By using the DCS unit to control the generator in step (1), the strong oxygen concentration in step (2) is adjusted to 140-150 mg / Nm 3 .

5. The method for denitrification of flue gas from a phthalic anhydride thermal storage oxidation furnace according to claim 1, characterized in that: In step (2), a gas distribution device is provided in the flue.

6. The method for denitrification of flue gas from a phthalic anhydride thermal storage oxidation furnace according to claim 1, characterized in that: In step (2), the reaction time is 0.5-2 seconds, and the strong oxygen residence time is 0.5-2 seconds.

7. The method for denitrification of flue gas from a phthalic anhydride thermal storage oxidation furnace according to claim 1, characterized in that: In step (2), the flue gas linear velocity of the phthalic anhydride thermal regenerative oxidation furnace is 10-12 m / s, and the flue length is designed to be greater than 11 meters.

8. The method for denitrification of flue gas from a phthalic anhydride thermal storage oxidation furnace according to claim 1, characterized in that: Before step (2) or after step (2), the method may further include: (2') performing dust removal treatment on the flue gas after desulfurization and denitrification.

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