CN110787606B

CN110787606B - Denitration and demercuration integrated device and method for sintering flue gas circulating fluidized bed desulfurization

Info

Publication number: CN110787606B
Application number: CN201911104675.XA
Authority: CN
Inventors: 潘梦雅; 张千峰; 李玉娇; 陆伟星
Original assignee: Anhui University of Technology AHUT
Current assignee: Anhui University of Technology AHUT
Priority date: 2019-11-13
Filing date: 2019-11-13
Publication date: 2021-12-10
Anticipated expiration: 2039-11-13
Also published as: CN110787606A

Abstract

The invention discloses a denitration and demercuration integrated device and method in sintering flue gas circulating fluidized bed desulfurization, and belongs to the technical field of sintering flue gas desulfurization and denitration. The device comprises a CFB reactor, an industrial water tank, a digestion tank, a denitration reduction absorbent tank, a cloth bag dust removal system, a flue gas monitoring system and an electrostatic dust removal system. Firstly, spraying a denitration oxidant A component into a flue between an electrostatic dust collector and a CFB reactor, wherein the denitration oxidant A component can quickly oxidize part of NO in flue gas into a high-valence multi-nitrogen oxide mixture which is easily absorbed by water vapor, and then the high-valence multi-nitrogen oxide mixture enters the CFB reactor; and spraying the denitration reduction absorbent B component into the CFB reactor, spraying lime into the CFB reactor, and discharging the desulfurized and denitrated flue gas after dedusting and detecting by a flue gas monitoring system. The method is simple, green, cyclic and pollution-free, has low operation cost and has obvious economic and environmental benefits.

Description

Denitration and demercuration integrated device and method for sintering flue gas circulating fluidized bed desulfurization

The technical field is as follows:

the invention belongs to the technical field of desulfurization and denitration of sintering flue gas, and particularly relates to a denitration and demercuration integrated device and method for desulfurization of a sintering flue gas circulating fluidized bed.

Background art:

the sintering flue gas is a main source for atmospheric pollutant emission of iron and steel enterprises, and mainly comprises various pollutants such as sulfur dioxide, nitrogen oxide, particulate matters, dioxin, heavy metals and the like, wherein the problems of pollution control and emission reduction of sulfur dioxide, nitrogen oxide and trace toxic metal element mercury which are more important in China at present are solved. With the proposal of the national thirteen-middle five-meeting ecological civilization construction and green development policy, the single pollutant treatment which is mainly used for desulfurization originally in the steel industry is changed into the multi-pollutant cooperative treatment, thereby realizing the standard emission of all pollution factors.

In China, relatively mature desulfurization process technologies such as a limestone-gypsum method and a circulating fluidized bed method are mainly adopted for sintering flue gas desulfurization, wherein the circulating fluidized bed is a clean combustion technology suitable for low-cost pollution control of low-quality coal, can realize the advantages of direct desulfurization, wide fuel adaptability, high combustion efficiency, wide load regulation range and the like in the combustion process, and has become the first choice for clean combustion of domestic coal. However, denitration of sintering flue gas is still in a starting stage, and a corresponding matched control technology is not available at present. Because the existing circulating fluidized bed desulfurization device has higher equipment and operation cost, and a denitration engineering device with a complicated building system and larger occupied area cannot be added again, the invention adopts the denitration modification process in the original circulating fluidized bed desulfurization system without changing the original desulfurization process, thereby achieving the integration of desulfurization, denitration and demercuration. The addition of a denitration process to the circulating fluidized bed, however, causes many problems, such as an increase in capital investment, an increase in industrial sites of plants, and a specific denitration control process. At present, because the low-quality coal is often used for a circulating fluidized bed boiler, an SCR method is suggested to be adopted, although the denitration efficiency of the SCR technology is high, the dust content in the general flue gas is also high, the SCR catalyst is easy to block, and the catalyst is greatly lost, so that the operation cost is overhigh; if the SNCR method is adopted, although the cost is relatively low, the denitration efficiency of the technology is also low, so that the treated flue gas can hardly reach the emission standard; the pure ozone method has relatively low investment, but has the problem that the oxidation degree of NO is difficult to effectively control due to the instability of ozone.

In order to solve the problems, the invention provides a process for simultaneously desulfurizing and denitrating in one system, namely, under the premise of not changing the original process, auxiliary devices and denitration catalyst components are added to achieve the effect of oxidation reduction, so that the oxidation reduction effect can be reducedLess complexity of an engineering system, improved operation performance and reduced operation cost, and is a new way to treat SO in flue gas₂、NO_XAnd heavy metal mercury, etc. in a set of equipment. Wherein the oxidant can be selected from stable chlorine dioxide, ozone or metal catalyst, etc. to oxidize NO into NO₂Introducing part of the SO₂Is also oxidized to SO₃。NO₂The circulating reaction is carried out in a circulating fluidized bed, and the further oxidation is carried out to high-valence nitrogen, such as N₂O₄、N₂O₅The absorption effect is more obvious and the reduction to zero-valent nitrogen is easier. And synchronously adding a reducing agent component into the circulating fluidized bed, reducing one part of the mixture into nitrogen gas through a circulating reaction, discharging the nitrogen gas, and generating nitrate on the other part of the mixture to reduce or inhibit the formation of nitrite. Form of mercury in flue gas: elemental mercury (Hg)⁰) Mercury (Hg) in monovalent form⁺) And gaseous mercury (Hg) in the divalent state²⁺) Mercury (Hg) in the form of particles in flue gas⁺) Can be partially removed by bag-type dust remover or classical dust remover, and bivalent mercury (Hg)²⁺) Is stable and easy to dissolve in water, can be adsorbed and removed by fly ash in flue gas or removed by a desulphurization device, and has simple substance mercury (Hg)⁰) The mercury in the gas phase is more difficult to control, and thus the mercury pollution on the whole sphere can be formed. Therefore, the elemental mercury can be oxidized into high-valence mercury compounds to be removed, so that the pollution of heavy metal ions is reduced.

The integrated process for desulfurization, denitrification and demercuration can ensure the original desulfurization effect, and solve the problem of denitrification and demercuration so as to achieve ultra-clean emission of sintering flue gas in the atmosphere. Meanwhile, the obtained desulfurization ash mainly comprises calcium sulfate or a small amount of calcium nitrate and part of calcium carbonate, so that the desulfurization and denitrification byproducts of the process can be used as coagulation auxiliary materials for producing products such as cement and the like after being modified so as to be comprehensively utilized, and secondary pollution of solid byproducts after desulfurization, denitrification and demercuration is not generated.

The invention content is as follows:

aiming at the problems in the prior art, the invention provides the denitration and demercuration integrated device and the method for the sintering flue gas circulating fluidized bed desulfurization, which have the advantages of low investment, low energy consumption and higher desulfurization, denitration and demercuration efficiency.

The invention provides a denitration and demercuration integrated device for sintering flue gas circulating fluidized bed desulfurization, which comprises an inlet flue gas monitoring system 1, an electrostatic dust collector 2, a denitration reduction absorbent tank 4, a CFB (circulating fluidized bed) reactor 6, an industrial water tank 7, a digestion tank 8, a first cloth bag dust removal system 10, a second cloth bag dust removal system 11 and an outlet flue gas monitoring system 12;

the flue gas inlet detection system 1 is connected to the inlet of a flue, the electrostatic dust collector 2 and the high-pressure spray gun 3 are sequentially connected behind the flue gas inlet detection system 1, and the flue is connected with the lower part of the CFB reactor 6; the denitration reduction absorbent tank 4 is connected to the lower part of the CFB reactor 6 through an external pipeline and the denitration pump 5; a desulfurization and denitrification byproduct discharge pipeline is arranged at the lower part of the CFB reactor 6 and is connected with the desulfurization and denitrification byproduct collecting tank 9; the industrial water tank 7 is connected with the middle section of the CFB reactor 6 through a pipeline and the digestion tank 8, the upper part of the CFB reactor 6 is connected with the first cloth bag dust removal system 10 and the second cloth bag dust removal system 11 through pipelines, the first cloth bag dust removal system 10 is connected with the second cloth bag dust removal system 11 in parallel, and the first cloth bag dust removal system 10 and the second cloth bag dust removal system 11 are connected with a flue gas discharge port through the outlet flue gas monitoring system 12.

The invention also provides a denitration and demercuration integrated method of the denitration and demercuration integrated device in the sintering flue gas circulating fluidized bed desulfurization, which comprises the following steps:

(1) spraying a pre-prepared denitration oxidant A component into a flue between the electrostatic dust collector 2 and the CFB reactor 6, and enabling the denitration oxidant A component to be in contact with the sintering flue gas subjected to electrostatic dust collection, wherein the denitration oxidant A component can quickly oxidize part of NO in the flue gas into a high-valence multi-nitrogen oxide mixture which is easily absorbed by water vapor, and the treated flue gas then enters the CFB reactor 6;

(2) spraying the component B of the denitration reduction absorbent in the denitration reduction absorbent tank 4 into the bottom of the CFB reactor 6 through the denitration pump 5, then allowing the component B of the denitration reduction absorbent to enter the CFB reactor 6 for reaction, and reducing part of high-valence nitrogen oxides obtained by oxidation into zero-valence nitrogen by using the component B of the denitration reduction absorbent;

(3) lime is sprayed into a connecting pipeline between the industrial water tank 7 and the CFB reactor 6 through the digestion tank 8, and then enters the CFB reactor 6, and gaseous pollutants SO which are not removed in time₂And NO_XThe CFB reactor 6 is further reacted with the denitration agent A component continuously, and in order to ensure that the CFB reactor 6 can achieve high-efficiency desulfurization and denitration effects, the temperature of the CFB reactor 6 is controlled to be 50-90 ℃ by controlling the water injection quantity through an industrial water tank;

(4) the flue gas after desulfurization and denitrification carries the removal product to enter a cloth bag dust removal system, the flue gas after dust removal is discharged along with a flue gas pipeline after passing through an outlet flue gas monitoring system 12, and the separated solid is discharged from an ash discharge port and mainly contains calcium sulfate or a small amount of calcium nitrate and part of calcium carbonate.

The main reaction principle of the denitration and demercuration technology based on the desulfurization of the sintering flue gas circulating fluidized bed is as follows:

firstly, NO and SO in the flue gas₂And oxidizing Hg simple substance, wherein the specific reaction is as follows:

NO+NO₂→N₂O₃

next, the formed partial oxidation product diffuses from the gas phase to the atomized liquid phase bulk from the two-phase interface by molecular diffusion, and the specific absorption reaction is as follows:

SO₂+Ca(OH)₂→CaSO₃+H₂O

SO₃+Ca(OH)₂→CaSO₄+H₂O

NO₂+H₂O→HNO₃+NO

N₂O₃+H₂O→2HNO₂

N₂O₅+H₂O→2HNO₃

HNO₃+Ca(OH)₂→Ca(NO₃)₂+H₂O

2HNO₂+Ca(OH)₂→Ca(NO₂)₂+2H₂O

2HNO₂+(NH₂)₂CO→2N₂+CO₂+3H₂O

Ca(NO₂)₂+SO₃+O₂→CaSO₄+NO₂

2HCl+Ca(OH)₂→CaCl₂+2H₂O

the specific redox reaction is shown below:

the denitration oxidant A component is an aqueous product prepared from 8-10 wt% of stable chlorine dioxide, 20-22 wt% of sodium chlorite or ozone in an alkaline system, 0.9-1.5 wt% of ferric sulfate and 0.3-0.6 wt% of sodium sulfate. The concrete preparation is according to SO in different inlet flue gas₂、NO_XIn accordance with the control of NO/NO₂The degree of oxidation of (a) is in the range of 0.5 to 0.9, and NO is selected and imported_XPreparing aqueous solution with the content of strong oxidant with equal molar ratio, and then adding Fe₂(SO₄)₃As a metal catalyst and sodium sulfate as a cocatalyst, and the obtained solution is a denitration oxidant aqueous solution. In addition, the oxidation of elemental mercury to monovalent or divalent mercury is accomplished by increasing the proportion of strong oxidizing agent and increasing the number of reaction cycles in the CFB as appropriate.

The component B of the denitration reduction absorbent is prepared by 30-40 wt% of urea or paraformaldehyde and 1.5-3.2 wt% of FeSO₄·7H₂O or Fe (EDTA)₂0.3 to 0.8 wt% of Na₂S₂O₃Or Na₂SO₃And 0.01 wt% of polyvinyl alcohol 200. Is prepared according to NO₂/NO_XDegree of oxidation of and NO in different inlet flue gases_XAnd SO₂Selecting 4-5 equivalent ratio of urea or paraformaldehyde content to prepare aqueous solution, and adding FeSO₄·7H₂O or Fe (EDTA)₂As a metal catalyst, and Na₂S₂O₃Or Na₂SO₃An aqueous solution is prepared by an auxiliary catalytic reducing agent, polyvinyl alcohol 200 is selectively added to increase the atomization effect, and the aqueous solution is atomized into the CFB reactor through an industrial water tank high-pressure spray gun.

The invention has the following technical characteristics:

(1) the denitration process engineering is modified on the basis of not changing the original circulating fluidized bed desulfurization process, so that the integrated effect of desulfurization, denitration and demercuration is achieved.

(2) The desulfurization and denitrification integrated process is simple, green, circulating, pollution-free and low in operation cost, and can be used for timely regulating and controlling the desulfurization and denitrification of the sintering flue gas, so that the state of higher removal efficiency is kept.

(3) The technology belongs to low-temperature desulfurization and denitrification, the temperature is controlled within the range of 50-120 ℃, and when the temperature is controlled within the range of 50-90 ℃, the desulfurization and denitrification effect is optimal.

(4) The preparation raw materials of the components of the denitration agent are wide in source and low in price, and the prepared denitration agent can be locally recycled until the denitration agent is gradually and completely consumed, and no waste liquid is produced.

(5) The solid product of desulfurization and denitrification can be used as an auxiliary material for preparing products such as cement and the like, so that the comprehensive utilization of the desulfurization and denitrification product is realized.

(6) The elemental mercury with higher toxicity is oxidized into the mercury compound with high valence state, and the pollution of heavy metal ions in the atmosphere is reduced.

(7) The process of desulfurization, denitrification and demercuration of the flue gas does not use a solid oxide catalyst, so that the investment on a large batch of solid catalysts and the cost of frequent replacement in the use process are not needed.

(8) The product after the denitration reaction is N₂、CO₂And H₂And O, no secondary pollutant is generated.

(9) The addition of the reducing absorbent can completely eliminate the formed NO₂Yellow smoke is not absorbed in time, and excessive reducing agent can suppress large amount of CaCO₃Forming; forced oxidation of the oxidant favors NO₂Is easily absorbed by the atomized water vapor and also promotes SO₃Thereby forming CaSO₄The product of (1).

(10) The reducing agent used in the desulfurization and denitrification reaction process is urea or paraformaldehyde and the like, is in a solid form, and is safer and more environment-friendly in storage, transportation and use compared with other chemicals such as liquid ammonia and the like required in the removal process.

(11) The reaction conditions in the desulfurization, denitrification and demercuration processes are mild, and the catalyst is in an alkaline system and has small corrosion to equipment.

(12) The operation process can be timely adjusted according to the environmental protection requirement and the content of nitrogen oxides in the waste gas, and the operation is simple, safe and reliable, and has high operation elasticity.

Description of the drawings:

FIG. 1 is a schematic structural diagram of an integrated denitration and demercuration device for desulfurization of a sintering flue gas circulating fluidized bed.

In the figure: 1: import flue gas monitoring system, 2: electrostatic precipitator, 3: high-pressure spray gun, 4: denitration reduction absorbent tank, 5: denitration pump, 6: CFB reactor, 7: industrial water tank, 8: digestion tank, 9: SOx/NOx control by-product collecting tank, 10: first bag house dust removal system, 11: second bag house dust removal system, 12: export flue gas monitoring system.

The specific implementation mode is as follows:

in order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following specific examples. The following specific examples are all the most preferable examples.

Example 1: the flue gas amount of the sintering flue gas is 100 ten thousand Nm³H, in which SO₂The content is 650-800 mg/Nm³，NO_XThe content is 200-280 mg/Nm³The oxygen content is 13-16%, and the water content is 5-7%. When the flue gas enters a pipeline through the electrostatic dust collector, the prepared denitration oxidant A component is sprayed into a flue by a high-pressure spray gun, the formed vaporific water vapor is fully contacted with the flue gas, and NO is rapidly oxidized into NO₂，SO₂In Fe³⁺Catalytic conversion of ions to SO₃About 276-387 Kg/h of the denitration oxidant A component is consumed. Meanwhile, lime is added into a pipeline where the industrial water tank is located through the slaking tank, the denitration reduction absorbent B component in the denitration reduction absorbent tank is sprayed into the bottom of the CFB reactor through the denitration pump, and then the denitration reduction absorbent B component enters the CFB reactor to participate in reaction, so that 642.6-1200 Kg/h of the denitration reduction absorbent B component is consumed approximately. Then, the incompletely reacted substances enter a CFB reactor for continuous circulation reaction, wherein sulfur dioxide in the flue gas can not only be directly reacted with lime to be removed, but also be catalyzed into NO together with oxygen and water vapor in the flue gas in the presence of the lime₂The latter is reacted with lime to reduce SO in the flue gas₂And NO_XThe purpose of (1). In order to ensure that the CFB reactor can achieve high desulfurization and denitrification efficiency, the reactor can pass throughThe water injection amount is controlled by the water tank, and the temperature of the CFB reactor is 80 +/-3 ℃. The flue gas after desulfurization and denitrification in the CFB reactor carries the removal product to enter a cloth bag dust removal system, the flue gas after dust removal is discharged along with a flue gas pipeline after passing through an outlet flue gas monitoring system, and the separated solid is discharged from an ash discharge port. After continuous operation for 60 days, the desulfurization efficiency can reach 97.9 percent averagely, and the denitration efficiency can reach 92 percent.

Example 2: the flue gas amount of the sintering flue gas is about 130 ten thousand Nm³H, in which SO₂The content is 680-850 mg/Nm³， NO_XThe content is 210-250 mg/Nm³The oxygen content is about 14-16%, and the water content is about 8-10%. When the flue gas enters a pipeline through the electrostatic dust collector, the prepared denitration oxidant A component is sprayed into a flue by a high-pressure spray gun and is fully contacted with the flue gas, and NO is rapidly oxidized into NO₂，SO₂In Fe³⁺Catalytic conversion of ions to SO₃364.7-432.9 Kg/h of the denitration oxidant A is consumed. Meanwhile, lime is added into a pipeline where the industrial water tank is located through the digestion tank, the denitration reduction absorbent B component in the denitration reduction absorbent tank is sprayed into the bottom of the CFB reactor through the denitration pump, and then enters the CFB reactor to participate in reaction, so that 853.2-1344 Kg/h of the denitration reduction absorbent B component is consumed approximately. Then, the incompletely reacted substances enter a CFB reactor for continuous circulation reaction, wherein sulfur dioxide in the flue gas can not only be directly reacted with lime to be removed, but also be catalyzed into NO together with oxygen and water vapor in the flue gas in the presence of the lime₂The latter is reacted with lime to reduce SO in the flue gas₂And NO_XThe purpose of (1). In order to ensure that the CFB reactor can achieve high desulfurization and denitrification efficiency, the water spraying amount can be controlled by an industrial water tank, and the temperature of the CFB reactor is 80 +/-3 ℃. The flue gas after desulfurization and denitrification in the CFB reactor carries the removal product to enter a cloth bag dust removal system, the flue gas after dust removal is discharged along with a flue gas pipeline after passing through an outlet flue gas monitoring system, and the separated solid is discharged from an ash discharge port. After continuous operation for 48 days, the average desulfurization efficiency can reach 98.08 percent, and the denitration efficiency can reach 89 percent。

Example 3: the flue gas amount of the sintering flue gas is about 160 ten thousand Nm³H, in which SO₂The content is 800-1000 mg/Nm³， NO_XThe content is 250-280 mg/Nm³The oxygen content is about 15-16%, and the water content is about 10-11%. When the flue gas enters a pipeline through the electrostatic dust collector, the prepared denitration oxidant A component is sprayed into a flue by a high-pressure spray gun and is fully contacted with the flue gas, and NO is rapidly oxidized into NO₂，SO₂In Fe³⁺Catalytic conversion of ions to SO₃And approximately 523.2-583.2 Kg/h of the denitration oxidant A is consumed. Meanwhile, lime is added into a pipeline where the industrial water tank is located through the slaking tank, the denitration reduction absorbent B component in the denitration reduction absorbent tank is sprayed into the bottom of the CFB reactor through the denitration pump, and then the denitration reduction absorbent B component enters the CFB reactor to participate in reaction, so that 1218.6-1812 Kg/h of the denitration reduction absorbent B component is consumed approximately. Then, the incompletely reacted substances enter a CFB reactor for continuous circulation reaction, wherein sulfur dioxide in the flue gas can not only be directly reacted with lime to be removed, but also be catalyzed into NO together with oxygen and water vapor in the flue gas in the presence of the lime₂The latter is reacted with lime to reduce SO in the flue gas₂And NO_XThe purpose of (1). In order to ensure that the CFB reactor can achieve high desulfurization and denitrification efficiency, the water spraying amount can be controlled by an industrial water tank, and the temperature of the CFB reactor is 80 +/-3 ℃. The flue gas after desulfurization and denitrification in the CFB reactor carries the removal product to enter a cloth bag dust removal system, the flue gas after dust removal is discharged along with a flue gas pipeline after passing through an outlet flue gas monitoring system, and the separated solid is discharged from an ash discharge port. After continuous operation for 28 days, the desulfurization efficiency can reach 98.2 percent averagely, and the denitration efficiency can reach 87 percent. The desulfurization and denitrification conditions of the above examples are shown in Table 1.

TABLE 1 desulfurization and denitrification in examples 1 to 3 of the present invention

Claims

1. An integrated denitration and demercuration method in sintering flue gas circulating fluidized bed desulfurization is characterized in that a denitration and demercuration integrated device is adopted, and the integrated denitration and demercuration device comprises an inlet flue gas monitoring system (1), an electrostatic dust collector (2), a denitration reduction absorbent tank (4), a CFB reactor (6), an industrial water tank (7), a digestion tank (8), a first cloth bag dust removal system (10), a second cloth bag dust removal system (11) and an outlet flue gas monitoring system (12); the flue gas inlet detection system (1) is connected to the inlet of a flue, the electrostatic dust collector (2) and the high-pressure spray gun (3) are sequentially connected behind the flue gas inlet detection system (1), and the flue is connected with the lower part of the CFB reactor (6); spraying a pre-prepared denitration oxidant A component into a flue between the electrostatic dust collector (2) and the CFB reactor (6) through the high-pressure spray gun (3), enabling the denitration oxidant A component to be in contact with sintering flue gas subjected to electrostatic dust collection, enabling part of NO in the flue gas to be quickly oxidized into a high-valence multi-nitrogen oxide mixture which is easily absorbed by water vapor through the denitration oxidant A component, and enabling the treated flue gas to enter the CFB reactor (6); the denitration oxidant A component is an aqueous product prepared from 8-10 wt% of stable chlorine dioxide, 20-22 wt% of sodium chlorite or ozone in an alkaline system, 0.9-1.5 wt% of ferric sulfate and 0.3-0.6 wt% of sodium sulfate; the denitration reduction absorbent tank (4) is connected to the lower part of the CFB reactor (6) through an external pipeline and a denitration pump (5); a desulfurization and denitrification byproduct discharge pipeline is arranged at the lower part of the CFB reactor (6), and is connected with a desulfurization and denitrification byproduct collecting tank (9); the industrial water tank (7) is connected with the middle section of the CFB reactor (6) through a pipeline and the digestion tank (8), the upper part of the CFB reactor (6) is connected with the first cloth bag dust removal system (10) and the second cloth bag dust removal system (11) through pipelines, the first cloth bag dust removal system (10) is connected with the second cloth bag dust removal system (11) in parallel, and the first cloth bag dust removal system (10) and the second cloth bag dust removal system (11) are connected with a flue gas discharge port through the outlet flue gas monitoring system (12);

the denitration and demercuration integrated method in the sintering flue gas circulating fluidized bed desulfurization comprises the following specific steps:

firstly, spraying a pre-prepared denitration oxidant A component into a flue between the electrostatic dust collector (2) and the CFB reactor (6), enabling the denitration oxidant A component to be in contact with sintering flue gas subjected to electrostatic dust collection, enabling part of NO in the flue gas to be quickly oxidized into a high-valence multi-nitrogen oxide mixture which is easily absorbed by water vapor by the denitration oxidant A component, and enabling the treated flue gas to enter the CFB reactor (6);

secondly, spraying the component B of the denitration reduction absorbent in the denitration reduction absorbent tank (4) into the bottom of the CFB reactor (6) through the denitration pump (5), then entering the CFB reactor (6) for participating in reaction, and reducing part of high-valence nitrogen oxides obtained by oxidation into nitrogen with zero valence by using the component B of the denitration reduction absorbent; the component B of the denitration reduction absorbent is prepared by 30-40 wt% of urea or paraformaldehyde and 1.5-3.2 wt% of FeSO₄·7H₂O or Fe (EDTA)₂0.3 to 0.8 wt% of Na₂S₂O₃Or Na₂SO and 0.01 wt% polyvinyl alcohol 200;

thirdly, lime is sprayed into a connecting pipeline between the industrial water tank (7) and the CFB reactor (6) through the digestion tank (8) and enters the CFB reactor (6), and gaseous pollutants SO which are not removed in time are removed₂And NO_XThe reaction is further continued with the denitration oxidant A in the CFB reactor (6), and in order to ensure that the CFB reactor (6) can achieve high-efficiency desulfuration and denitration effects, the temperature of the CFB reactor (6) is controlled to be 50-90 ℃ by controlling the water injection quantity through an industrial water tank;

and fourthly, the desulfurized and denitrated flue gas carries the removal products to enter a cloth bag dust removal system, and the flue gas after dust removal passes through the outlet flue gas monitoring system (12) and then is discharged along with a flue gas pipeline.