Method for simultaneously desulfurizing and denitrifying flue gas

Abstract

The invention provides a method for simultaneously desulfurizing and denitrifying flue gas, and belongs to the technical field of air pollution control. According to the invention, NOx in flue gas is oxidized into NO2 and N2O5 by using ozone-containing gas, and the NO2 and N2O5 are easily absorbed by an alkaline solution, so that denitration is realized; meanwhile, SO2 does not react with O3 at the temperature of 50-80 DEG C, so that corrosion of SO3 to equipment is avoided, oxygen competition of SO2 and NOx is also avoided, and ozone consumption is reduced; by limiting the pH value of the alkaline solution, SO2, NO2 and N2O5 are enabled to be absorbed by the alkaline solution together and converted into harmless salt; by controlling the molar ratio of O3 to NOx, the NOx is guaranteed to be completely oxidized, and meanwhile waste caused by excessive O3 is avoided; sO2, NO2 and N2O5 can be completely absorbed by controlling the proportion of the flue gas to the absorption liquid, escape of harmful gas is avoided, and sulfite can be oxidized into sulfate by using oxygen in air.

Description

Technical Field

[0001] The present invention belongs to the technical field of air pollution control, and particularly relates to a method for simultaneously desulfurizing and denitrifying flue gas. Background Art

[0002] With the gradual improvement of environmental protection requirements, the emission standards for sulfur dioxide (SO 2 ) and nitrogen oxides (NO x ) in flue gas are becoming increasingly strict. Existing flue gas desulfurization and denitrification technologies include dry method, wet method, selective catalytic reduction (SCR), etc. Although existing desulfurization and denitrification technologies can remove SO 2 and NO x respectively, the synergistic effect is poor. For example, in the existing technology, the synchronous treatment of desulfurization and denitrification is achieved by combining wet desulfurization and SCR denitrification technologies; in this technology, desulfurization and denitrification are independent and carried out separately one after another, and desulfurization and denitrification cannot be carried out simultaneously in the same equipment, resulting in low treatment efficiency and high equipment and operation costs.

[0003] Existing technologies have reported a method for simultaneously desulfurizing and denitrifying flue gas by ozone oxidation and absorption. However, this method oxidizes SO 2 to SO 3 , and NO x to NO 2 , N 2 O 5 at 100 - 200°C, and then uses an alkaline solution for absorption; this method requires a relatively high temperature, and SO 3 has strong corrosiveness, which requires high requirements for equipment. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for simultaneously desulfurizing and denitrifying flue gas. The method provided by the present invention can achieve simultaneous desulfurization and denitrification with low energy consumption and high treatment efficiency.

[0005] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a method for simultaneously desulfurizing and denitrifying flue gas, comprising:

[0007] Mixing flue gas with an ozone-containing gas for an oxidation reaction to obtain oxidized flue gas; the molar ratio of ozone to NO x in the flue gas is (1 - 1.5):1; the temperature of the oxidation reaction is 50 - 80°C;

[0008] Contacting the oxidized flue gas with an alkaline solution for absorption to obtain desulfurized and denitrified flue gas;

[0009] The volume ratio of the oxidized flue gas to the alkaline solution is (1200 - 1500) Nm 3 / m 3 ;

[0010] The pH value of the alkaline solution is 8.5 - 10.

[0011] Preferably, the base in the alkaline solution includes one or more of inorganic bases and organic bases; the inorganic bases include calcium hydroxide, ammonia water, sodium carbonate or sodium hydroxide; the organic bases include methylamine, ethylamine or urea.

[0012] Preferably, the total mass concentration of the base in the alkaline solution is 1 - 5%.

[0013] Preferably, the concentration of ozone in the ozone-containing gas is 5 - 20 g / Nm 3 .

[0014] Preferably, the ozone is prepared by a plate-type ozone generator.

[0015] Preferably, the content of SO 2 in the flue gas is 500 - 3000 mg / Nm 3 ; the content of NO x is 200 - 1000 mg / Nm 3 .

[0016] Preferably, the absorption time is 5 - 10 min.

[0017] Preferably, the oxidized flue gas and the alkaline solution are in contact by spraying.

[0018] Preferably, the flow rate of the alkaline solution is 0.5 - 1 m / s.

[0019] Preferably, the alkaline solution is recycled through a recycling and regeneration system.

[0020] The present invention provides a method for simultaneous desulfurization and denitrification in flue gas, including: mixing the flue gas with an ozone-containing gas to carry out an oxidation reaction to obtain oxidized flue gas; the molar ratio of the ozone to NO x in the flue gas is (1 - 1.5):1; the temperature of the oxidation reaction is 50 - 80 °C; contacting the oxidized flue gas with an alkaline solution for absorption to obtain desulfurized and denitrified flue gas; the volume ratio of the oxidized flue gas to the alkaline solution is (1200 - 1500) Nm 3 / m 3 ; the pH value of the alkaline solution is 8.5 - 10. The present invention uses the ozone-containing gas to oxidize NO x in the flue gas into NO 2 , N 2 O 5, it is easily absorbed by the alkaline solution to achieve denitrification; meanwhile, at 50 - 80 °C, SO 2 will not react with O 3 , avoiding the corrosion of the equipment caused by SO 3 , and also avoiding the oxygen competition between SO 2 and NO x , reducing ozone consumption; by limiting the pH value of the alkaline solution, it is ensured that SO 2 and NO 2 , N 2 O 5 are absorbed together by the alkaline solution and converted into harmless salts; by controlling the molar ratio of O 3 to NO x , it is ensured that NO x is completely oxidized while avoiding waste caused by excessive O 3 ; by controlling the ratio of flue gas to the absorption liquid, SO 2 and NO 2 , N 2 O 5 can be completely absorbed, avoiding the escape of harmful gases, and the oxygen in the air can also be used to oxidize sulfite to sulfate. The results of the examples show that by using the method provided by the present invention, the removal rate of SO 2 is higher than 96%, and the removal rate of NO x is higher than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic flow chart of Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] For all raw materials of the present invention, there is no special limitation on their sources, and they can be purchased on the market or prepared according to the conventional methods well-known to those skilled in the art.

[0023] For all raw materials of the present invention, there is no special limitation on their purity, and the present invention preferably uses industrial pure raw materials.

[0024] The present invention provides a method for simultaneously desulfurizing and denitrifying flue gas, including:[[]]

[0025] Mixing the flue gas with the ozone-containing gas for an oxidation reaction to obtain oxidized flue gas; the molar ratio of the ozone to NO x in the flue gas is (1 - 1.5):1; the temperature of the oxidation reaction is 50 - 80 °C;

[0026] Bringing the oxidized flue gas into contact with the alkaline solution for absorption to obtain desulfurized and denitrified flue gas;

[0027] The volume ratio of the oxidized flue gas to the alkaline solution is (1200 - 1500) Nm3 / m 3 ;

[0028] The pH value of the alkaline solution is 8.5 - 10.

[0029] In the present invention, flue gas is mixed with ozone-containing gas for an oxidation reaction to obtain oxidized flue gas.

[0030] The present invention has no special requirements for the source of the flue gas, and the conventional flue gas that needs desulfurization and denitrification in the art can all use the method of the present invention. As an embodiment of the present invention, the flue gas can be pretreated before the oxidation reaction, and the pretreatment can be dust removal by a high-efficiency bag filter. In the examples of the present invention, the flue gas is coal-fired power plant flue gas, steel plant sintering flue gas or cement plant waste gas.

[0031] In the present invention, the content of SO 2 in the flue gas is preferably 500 - 3000 mg / Nm 3 , more preferably 1000 - 2000 mg / Nm 3 ; As an embodiment of the present invention, the content of SO 2 in the flue gas can be 800 mg / Nm 3 , 1200 mg / Nm 3 , 1500 mg / Nm 3 , 1800 mg / Nm 3 , 2100 mg / Nm 3 , 2400 mg / Nm 3 or 2700 mg / Nm 3 ; The content of NO x is preferably 200 - 1000 mg / Nm 3 , more preferably 500 - 800 mg / Nm 3 ; As an embodiment of the present invention, the content of NO x in the flue gas can be 300 mg / Nm 3 , 400 mg / Nm 3 , 500 mg / Nm 3 , 600 mg / Nm 3 , 700 mg / Nm 3 , 800 mg / Nm 3 or 900 mg / Nm 3 . When the contents of SO 2 and NO x in the flue gas are within the above ranges, it is beneficial to the oxidation of NO x with ozone, and further improves the efficiency of desulfurization and denitrification.

[0032] In the present invention, the concentration of ozone in the ozone-containing gas is preferably 5-20 g / Nm 3 , more preferably 10-15 g / Nm 3 ; as an embodiment of the present invention, the concentration of ozone in the ozone-containing gas can be 6 g / Nm 3 , 8 g / Nm 3 , 10 g / Nm 3 , 12 g / Nm 3 , 14 g / Nm 3 , 16 g / Nm 3 or 18 g / Nm 3 . When the concentration of ozone in the ozone-containing gas is within the above range, the oxidation requirements of flue gas with different NO x contents can be met, and the denitrification efficiency can be further improved.

[0033] In the present invention, the ozone is preferably prepared by a plate-type ozone generator. The plate-type ozone generator has the characteristics of low energy consumption and strong ozone preparation ability, which is beneficial to reducing the cost of flue gas treatment.

[0034] In the present invention, the molar ratio of ozone to NO x in the flue gas is (1-1.5):1, preferably (1.2-1.4):1; as an embodiment of the present invention, the molar ratio of ozone to NO x in the flue gas can be 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1. In the present invention, ozone is used to carry out an oxidation reaction with NO x in the flue gas to generate easily absorbable NO 2 , N 2 O 5 ; when the molar ratio of ozone to NO x in the flue gas is within the above range, it is beneficial to the oxidation of NO x in the flue gas, and the denitrification efficiency can be further improved.

[0035] As an embodiment of the present invention, a blower can be added to the flue gas pipeline before the flue gas is mixed with ozone to increase the oxygen content in the flue gas, which is beneficial to the oxidation of NO x in the flue gas; increasing the oxygen content in the flue gas is also beneficial to oxidizing the sulfite generated after absorbing SO 2 into sulfate, thereby improving the economic value of by-products.

[0036] The present invention has no special requirements for the mixing method of the flue gas and other ozone-containing gases, and the conventional mixing methods in the art can be used; in the examples of the present invention, the mixing is carried out by introducing the ozone-containing gas into the flue gas pipeline through a dosing mixer in the flue gas pipeline.

[0037] In the present invention, the temperature of the oxidation reaction is 50 to 80 °C, preferably 60 to 70 °C; as an embodiment of the present invention, the temperature of the oxidation reaction can be 55 °C, 58 °C, 65 °C, 67 °C, 72 °C or 75 °C. When the temperature of the oxidation reaction is within the above range, NO x can be oxidized to NO 2 , N 2 O 5 , which is easily absorbed by the alkaline solution to achieve denitrification; at the same time, when the temperature of the oxidation reaction is within the above range, SO 2 will not react with O 3 , avoiding the corrosion of the equipment caused by SO 3 , and also avoiding the oxygen competition between SO 2 and NO x , reducing ozone consumption; moreover, when the temperature of the oxidation reaction is within the above range, the heat in the flue gas can be further recovered to improve economic benefits.

[0038] After obtaining the oxidized flue gas, the present application contacts the oxidized flue gas with an alkaline solution for absorption to obtain a desulfurized and denitrified flue gas.

[0039] In the present invention, the pH value of the alkaline solution is 8.5 to 10, preferably 9 to 9.5; as an embodiment of the present invention, the pH value of the alkaline solution can be 8.6, 8.7, 8.8, 8.9, 9.1, 9.2, 9.3, 9.4, 9.6, 9.7, 9.8 or 9.9. The present invention uses the alkaline solution to carry out a neutralization reaction with SO 2 , NO 2 , N 2 O 5 in the oxidized flue gas to convert them into harmless salts; when the pH value of the alkaline solution is within the above range, while ensuring the absorption efficiency of the alkaline solution for SO 2 , NO 2 , N 2 O 5 in the oxidized flue gas, it also avoids corrosion of the equipment caused by excessive alkalinity.

[0040] In the present invention, the alkali in the alkaline solution preferably includes one or more of inorganic alkalis and organic alkalis. The inorganic alkali preferably includes calcium hydroxide, ammonia water, sodium carbonate or sodium hydroxide; the organic alkali preferably includes methylamine, ethylamine or urea. The above-mentioned alkalis are all common and inexpensive alkalis. Using the above-mentioned alkalis is beneficial to reducing the cost of flue gas treatment.

[0041] In the present invention, the total mass concentration of the alkali in the alkaline solution is preferably 1-5%, more preferably 2-4%; as an embodiment of the present invention, the total mass concentration of the alkali in the alkaline solution can be 1%, 2%, 3%, 4% or 5%. When the total mass concentration of the alkali in the alkaline solution is within the above range, it is beneficial to absorb SO 2 , NO 2 , N 2 O 5 in the flue gas, and will not cause excessive corrosion to the equipment.

[0042] As an embodiment of the present invention, by mass concentration, the alkaline solution can be a 2-5% calcium hydroxide solution, or a 1-3% ammonia water, or a 2-4% sodium carbonate solution, or a 1-2% sodium hydroxide solution; it can also be a mixed solution containing 3% calcium hydroxide and 1-2% urea. In the embodiments of the present invention, the alkaline solution is a mixed solution containing 3% calcium hydroxide and 1% urea; calcium hydroxide reacts with SO 2 in the flue gas to form calcium sulfite, and calcium sulfite will oxidize in the air to form calcium sulfate; the solubility of calcium sulfate in water is relatively low and will precipitate out, and calcium sulfate can be obtained through simple solid-liquid separation, which can be used as a setting retarder in cement plants to improve the economic value of by-products.

[0043] In another embodiment of the present invention, 0.1-0.5 wt% of hydrogen peroxide can also be added to the alkaline solution as an oxidation aid to accelerate the absorption of SO 2 , NO 2 , N 2 O 5 in the flue gas.

[0044] In the present invention, the volume ratio of the oxidation flue gas to the alkaline solution is (1200-1500) Nm 3 / m 3 , preferably (1300-1400) Nm 3 / m 3 ; as an embodiment of the present invention, the volume ratio of the oxidation flue gas to the alkaline solution can be 1200 Nm 3 / m 3 , 1300 Nm 3 / m 3 , 1400 Nm 3 / m 3 , 1400 Nm 3 / m 3 or 1500 Nm 3 / m 3 . When the volume ratio of the oxidation flue gas to the alkaline solution is within the above range, it is beneficial to further improve the SO 2, NO 2 , N 2 O 5 absorption efficiency.

[0045] In the present invention, the oxidized flue gas and the alkaline solution preferably come into contact by spraying; the present invention does not particularly limit the specific manner of the spraying, and the conventional spraying manner in the art can be adopted. In the embodiments of the present invention, the spraying is carried out in a liquid-phase absorption tower.

[0046] In the present invention, the flow rate of the alkaline solution is preferably 0.5 - 1 m / s, more preferably 0.6 - 0.8 m / s; as an embodiment of the present invention, the flow rate of the alkaline solution can be 0.5 m / s, 0.6 m / s, 0.7 m / s, 0.8 m / s, 0.9 m / s or 1 m / s. When the flow rate of the alkaline solution is within the above range, the absorption efficiency and the equipment energy consumption can be taken into account, which is beneficial to absorbing SO in the flue gas with low cost and high efficiency 2 , NO 2 , N 2 O 5 . In the embodiments of the present invention, the flow rate of the alkaline solution is 500 L / h.

[0047] In the present invention, the absorption time is preferably 5 - 10 min, more preferably 6 - 8 min; as an embodiment of the present invention, the absorption time can be 5 min, 6 min, 7 min, 8 min, 9 min or 10 min. When the absorption time is within the above range, the flue gas and the absorption liquid can be in full contact, which is beneficial to further improving the absorption efficiency of SO in the flue gas 2 , NO 2 , N 2 O 5 absorption efficiency.

[0048] In the present invention, the alkaline solution is preferably recycled through a recycling and regeneration system. The present invention does not have special requirements for the recycling and regeneration system, and the conventional recycling and regeneration system in the art can be adopted. As an embodiment of the present invention, the recycling and regeneration system can recover calcium sulfate and nitrate by setting a recycling washing device; as another embodiment of the present invention, the recycling can be 4 h / time.

[0049] The present invention uses the gas containing ozone to oxidize NO in the flue gas x to NO 2 , N 2 O 5 , which is easily absorbed by the alkaline solution to achieve denitrification; meanwhile, at 50 - 80 °C, SO 2 will not react with O 3 , avoiding SO 3The corrosion of the equipment is also avoided, and at the same time, the competition with oxygen of SO 2 and NO x is avoided, reducing ozone depletion; by limiting the pH value of the alkaline solution, it is ensured that SO 2 and NO 2 and N 2 O 5 are absorbed together by the alkaline solution and converted into harmless salts; by controlling the molar ratio of O 3 and NO x , it is ensured that while NO x is completely oxidized, the waste caused by excessive O 3 is avoided; by controlling the ratio of flue gas to absorbent solution, SO 2 , NO 2 , N 2 O 5 can be completely absorbed, the escape of harmful gases is avoided, and the oxygen in the air can be used to oxidize sulfite to sulfate.

[0050] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0051] Embodiment 1

[0052] A method for simultaneously desulfurizing and denitrifying flue gas, the flow chart is as Figure 1 shown, and the specific steps are as follows:

[0053] The flue gas is transported through a pipeline by a fan, and the ozone prepared by the plate ozone generator is introduced into the flue gas pipeline through the dosing mixer, and after mixing and oxidation, it is introduced into the liquid-phase absorption tower to contact with the absorbent solution for absorption. The desulfurized and denitrified flue gas obtained enters the dust removal equipment for dust removal, and then is discharged through the chimney; the absorbent solution is recycled through the circulation regeneration device and the wastewater treatment unit.

[0054] The key equipment includes a plate ozone generator: generating high-concentration ozone; a dosing mixer: uniformly injecting ozone into the flue gas pipeline, mixing and oxidizing with the flue gas; a liquid-phase absorption tower: including a spraying system, a packing layer and a gas-liquid separation area, which can make the flue gas and the absorbent solution contact and absorb fully; a dust removal equipment: removing the fine particulate matter remaining in the flue gas after being treated by the absorption tower to ensure the cleanliness of the discharged flue gas; a wastewater treatment unit: performing harmless treatment on the wastewater discharged from the absorption tower and recycling the available resources at the same time.

[0055] The flue gas in this embodiment is the flue gas discharged from a certain coal-fired power plant, and the SO in the flue gas 2The content is 1200 mg / Nm 3 , NO x The content is 400 mg / Nm 3 ;

[0056] Install a blower to increase the oxygen content in the flue gas; use a plate-type ozone generator to prepare ozone to obtain air with an ozone concentration of 10 g / Nm 3 , mix the air containing ozone with the flue gas to obtain oxidized flue gas; the molar ratio of ozone to NO x is 1.2:1;

[0057] Prepare an alkaline solution containing 3 wt% calcium hydroxide and 1 wt% urea, with the pH value of the solution being 9, denoted as the absorbent; pass the oxidized flue gas into the absorption tower to contact with the absorbent for absorption, with the volume ratio of the oxidized flue gas to the absorbent being 1200 Nm 3 / m 3 , the flow rate of the absorbent is 0.5 m / s, the absorption temperature is 50 °C, and the absorption time is 5 min; the absorbent is recycled every 4 h.

[0058] The SO 2 content in the flue gas is reduced to 50 mg / Nm 3 , and the removal rate is 95.8%; NO x content is reduced to 40 mg / Nm 3 , and the removal rate is 90%; meeting the ultra-low emission standard.

[0059] Example 2

[0060] A method for simultaneously desulfurizing and denitrifying flue gas, the specific steps are as follows:

[0061] The flue gas in this example is the waste gas discharged from a sintering furnace of a steel plant, and the SO 2 content in the flue gas is 1500 mg / Nm 3 , NO x content is 600 mg / Nm 3 ;

[0062] Install a blower to increase the oxygen content in the flue gas; use a plate-type ozone generator to prepare ozone to obtain air with an ozone concentration of 15 g / Nm 3 , mix the air containing ozone with the flue gas to obtain oxidized flue gas; the molar ratio of ozone to NO x is 1.5:1;

[0063] Prepare an alkaline solution containing 3 wt% calcium hydroxide, 1 wt% urea and 0.3 wt% hydrogen peroxide, with the pH value of the solution being 9, denoted as the absorbent; pass the oxidized flue gas into the absorption tower to contact with the absorbent for absorption, with the volume ratio of the oxidized flue gas to the absorbent being 1500 Nm 3 / m3 The flow rate of the absorption liquid is 0.5 m / s, the absorption temperature is 50 °C, and the absorption time is 5 min; the absorption liquid is recycled every 4 h.

[0064] SO in the flue gas 2 content is reduced to 30 mg / Nm 3 , and the removal rate is 98%; NO x content is reduced to 50 mg / Nm 3 , and the removal rate is 91.7%; reaching the ultra-low emission standard.

[0065] Example 3

[0066] A method for simultaneous desulfurization and denitrification of flue gas, the specific steps are as follows:

[0067] The flue gas in this example is the waste gas of a certain cement plant, and the SO in the flue gas 2 content is 800 mg / Nm 3 , NO x content is 300 mg / Nm 3 ;

[0068] Install a blower to increase the oxygen content in the flue gas; use a plate-type ozone generator to prepare ozone to obtain air with an ozone concentration of 10 g / Nm 3 ; Pretreat the flue gas with a high-efficiency bag filter and then mix it with the air containing ozone to obtain oxidized flue gas; the molar ratio of ozone to NO x is 1.0:1;

[0069] Prepare an alkaline solution containing 3 wt% calcium hydroxide and 1 wt% urea, with the pH value of the solution being 9, denoted as the absorption liquid; pass the oxidized flue gas into the absorption tower to contact with the absorption liquid for absorption, and the volume ratio of the oxidized flue gas to the absorption liquid is 1200 Nm 3 / m 3 , the flow rate of the absorption liquid is 0.5 m / s, the absorption temperature is 50 °C, and the absorption time is 5 min; the absorption liquid is recycled every 4 h.

[0070] SO in the flue gas 2 content is reduced to 30 mg / Nm 3 , and the removal rate is 96.3%; NO x content is reduced to 20 mg / Nm 3 , and the removal rate is 93.3%; reaching the ultra-low emission standard.

[0071] The removal situation of SO in Examples 1 to 3 2 is recorded in Table 1 (calculated according to the inlet flue gas flow rate of 100000 Nm 3 / h).

[0072] Table 1 SO in Examples 1 to 32 Removal Situation Record Table

[0073]

[0074] SO 2 Removal amount = flue gas flow × SO 2 content × SO 2 Removal rate

[0075] The addition situation of calcium hydroxide and the production situation of calcium sulfate in Examples 1 to 3 are recorded in Table 2.

[0076] Table 2 Record Table of the Addition of Calcium Hydroxide and the Production of Calcium Sulfate in Examples 1 to 3

[0077] Embodiment <![CDATA[SO 2 Removal amount (kg / h)]]> <![CDATA[Ca(OH) 2 Dosage (kg / h)]]> <![CDATA[CaSO 4 Output (kg / h)]]> 1 115 133 244 2 147 170 312 3 77 89 164

[0078] It can be seen from Table 2 that the production amount of calcium sulfate is basically the same as the theoretical production amount, indicating that the SO removed from the flue gas 2 is ultimately basically converted into calcium sulfate.

[0079] The addition situation of O in Examples 1 to 3 3 and the removal situation of NO X are recorded in Table 3.

[0080] Table 3 Record Table of the Addition of O and the Removal Situation of NO in Examples 1 to 3 3 and the removal situation of NO X are recorded in Table 3.

[0081]

[0082] NO X Removal amount = flue gas flow × NO X content × NO X Removal rate

[0083] It can be seen from the above examples that the method for simultaneously desulfurizing and denitrifying flue gas provided by the present invention can efficiently and low - energy - consumedly remove SO in the flue gas 2 and NO x , and the production amount of by - product calcium sulfate is high, with prominent economic benefits.

[0084] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for simultaneously desulfurizing and denitrifying flue gas, comprising: The flue gas is mixed with an ozone-containing gas for oxidation reaction to obtain oxidized flue gas; the ozone reacts with NO in the flue gas. x The molar ratio is (1-1.5):1; the temperature of the oxidation reaction is 50-80°C; The oxidized flue gas is contacted with an alkaline solution for absorption to obtain desulfurized and denitrified flue gas; The volume ratio of the oxidizing flue gas to the alkaline solution is (1200-1500) Nm 3 / m 3 ; The pH value of the alkaline solution is 8.5-10.

2. The method according to claim 1, characterized in that The alkali in the alkaline solution includes one or more of an inorganic alkali and an organic alkali; the inorganic alkali includes calcium hydroxide, ammonia water, sodium carbonate or sodium hydroxide; the organic alkali includes methylamine, ethylamine or urea.

3. The method according to claim 2, characterized in that The total mass concentration of alkali in the alkaline solution is 1-5%.

4. The method according to claim 1, characterized in that: The concentration of ozone in the ozone-containing gas is 5 to 20 g / Nm 3 .

5. The method according to claim 4, characterized in that The ozone-containing gas is prepared by a plate-type ozone generator.

6. The method according to claim 1, characterized in that The content of SO2 in the flue gas is 500-3000 mg / Nm 3 ; NO x The content is 200~1000mg / Nm 3 .

7. The method according to claim 1, characterized in that The absorption time is 5 to 10 minutes.

8. The method according to claim 1, characterized in that The oxidizing flue gas is contacted with the alkaline solution by spraying.

9. The method according to claim 8, characterized in that The flow rate of the alkaline solution is 0.5-1 m / s.

10. The method according to claim 1 or 9, characterized in that: The alkaline solution is recycled through a recycling system.

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