CN105032142B - Flue gas integrated removal system and method combined with gas-phase pre-oxidation and absorption - Google Patents

Abstract

The invention belongs to flue gases purification field is and in particular to gas-like phase pre-oxidation combines the flue gas integration removing system and method absorbing.Described system includes gas-like phase reagent generating meanss, pre-oxidation device and absorption tower.Described removal methods comprise the following steps：(1) prepare gas-like phase composite oxidant；(2) pre-oxidation：Realized in the gas phase to NO and Hg using gas-like phase composite oxidant⁰Efficient oxidation；(3) absorbing reaction：With the mixed liquor of sodium humate and ammonia as absorbing serosity, to the SO in oxidation product_x、NO_xAnd Hg²⁺Carry out absorbing and removing.The present invention combines two grades of arrangements of absorption using pre-oxidation and coal-fired flue-gas multi-pollutant is carried out with integration removing, solve the problems, such as the system complex of existing hierarchical arrangement form presence, floor space is big and operating cost is higher, desulfurization denitration demercuration efficiency can meet current pollutant emission standard, removing product is that a kind of sulfur-bearing contains nitrogen composite fertilizer, has higher economy and environmental benefit.

Description

Flue gas integrated removal system and method combined with gas-phase pre-oxidation and absorption

technical field

The invention belongs to the technical field of flue gas purification, and in particular relates to an integrated flue gas removal system and method combined with gas-phase pre-oxidation combined with absorption.

Background technique

Particulate matter, SO ₂ , NO _x and trace heavy metals (Hg ⁰ ) emitted from coal combustion are one of the causes of frequent smog in China, which pose a serious threat to human life, health and sustainable ecological development. Therefore, , the control of coal-fired flue gas pollutants is imminent. The existing desulfurization, denitrification and mercury removal systems in thermal power plants are wet limestone-gypsum system (WFGD), selective catalytic reduction system (SCR) and activated carbon injection system (ACI). , System complexity and high operating costs. Therefore, research and development of a new process for simultaneous desulfurization, denitrification and mercury removal of flue gas with low equipment investment, low operating cost and no secondary pollution has become an important direction in the field of coal-fired flue gas pollutant control technology at home and abroad.

At present, there are three technologies for desulfurization, denitrification and mercury removal: absorption method, adsorption method, and oxidation method, among which oxidation method has more advantages in denitrification and mercury removal. As we all know, in the process of power production, 90-95% of NO _x in coal-fired flue gas is NO, which has poor water solubility and cannot be absorbed by absorbents, resulting in low denitrification efficiency, while water-soluble NO ₂ , NO ₃ and N ₂ O ₅ Therefore, realizing the rapid oxidation of NO in the gas phase is the key to denitrification. For mercury, particulate mercury and oxidized mercury can be removed synergistically by existing pollutant control equipment such as electrostatic precipitators and wet desulfurization, and the removal of Hg ⁰ is the key. Therefore, rapid oxidation of Hg ⁰ in the gas phase Hg ^{2 +} is the focus of realizing mercury removal. In summary, the oxidation method is more conducive to the integrated removal of SO ₂ , NO and Hg ⁰ in coal-fired flue gas.

Coal-fired flue gas multi-pollutant purification technology is mainly divided into wet technology and dry technology. Wet technology is mainly divided into wet oxidation method and wet complexation absorption method. Wet technology has the advantages of high removal efficiency, strong adaptability to coal types and stable operation, but there are also problems of chloride ion corrosion, wastewater treatment, energy consumption and operation relatively high cost. Dry technology has the advantages of no wastewater treatment, but has disadvantages such as poor system operation stability, low removal efficiency, and inability to meet existing discharge standards.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides an integrated flue gas removal system and method similar to gas-phase pre-oxidation combined with absorption.

The technical scheme that the present invention takes is:

An integrated flue gas removal system with gas-phase pre-oxidation combined with absorption, which includes a gas-phase reagent generator, a pre-oxidizer and a wet absorption tower in sequence according to the process flow;

The gas-phase reagent generating device includes a process water inlet 1, a condenser 2, a high-temperature steam outlet 5 and a mixer 8;

Described pre-oxidizer is placed in the downstream of the gas-phase reagent generating device, including the gas-phase composite oxidant injection port 10, the flue gas inlet 11 and the flue gas outlet 12 after the mixed oxidation of the gas-phase composite oxidant 9 with the gas-like composite oxidant, the flue gas Outlet 12 is connected with wet absorption tower;

The wet absorption tower is placed downstream of the pre-oxidizer, and is used for absorbing the slurry to absorb and remove SO _x , NO _x and Hg ²⁺ in the oxidation product.

Further, the pre-oxidizer is a cyclone pre-oxidizer or an inverted U-shaped pre-oxidizer.

Further, a process water vaporization pipe 4 is arranged in the condenser 2 , in which the process water is vaporized, and the obtained high-temperature steam enters the mixer 8 through the high-temperature steam outlet 5 .

Further, the condenser 2 is also provided with an inlet of the hot flue gas 3 after the economizer, so as to thermally vaporize the process water in the process water vaporization pipe 4 .

Further, the mixer 8 includes an inlet where the liquid-phase composite oxidizer mother liquor 6 is carried by the impact of the compressed air 7 ; it also includes an outlet where the liquid-phase composite oxidizer mother liquor 6 and high-temperature steam are fully mixed to form a gas-phase composite oxidizer 9 .

The method for integrated flue gas removal by the system described above comprises the following steps:

a. The process water enters the condenser 2 through the process water inlet 1, and the process water vaporizes in the process water vaporization pipe 4 in the condenser 2 to obtain high-temperature steam; the high-temperature steam enters the mixer 8 through the high-temperature steam outlet 5;

b. The liquid-phase composite oxidant mother liquor 6 enters the mixer 8 under the impact of the compressed air 7; in the mixer 8, the mist-like liquid-phase composite oxidant mother liquor 6 and high-temperature steam are fully mixed to generate a gas-like composite oxidizer 9;

c. The gas-phase composite oxidant 9 enters the pre-oxidizer through the gas-phase composite oxidant injection port 10, and the original flue gas enters the pre-oxidizer through the flue gas inlet 11 and mixes with the gas-phase composite oxidant 9 to undergo an oxidation reaction to achieve NO and Hg ⁰ Oxidation;

d. The oxidation product is discharged from the pre-oxidizer through the flue gas outlet 12, and enters the wet absorption tower, and the SO _x , NO _x and Hg ²⁺ in the oxidation product are absorbed and removed with the absorption slurry.

Preferably, the liquid-phase composite oxidant consists of oxidant and additives.

Preferably, the oxidant is one or more of hydrogen peroxide, sodium persulfate and sodium chlorite; the additive is one or more of sodium bromide, nickel nitrate and glacial acetic acid; In the oxidant, the concentration of hydrogen peroxide is 15-30%wt, the concentration of sodium persulfate is 1-10%wt, and the concentration of sodium chlorite is 0.5-10%wt. Among the additives, sodium bromide, nitric acid The concentrations of nickel and glacial acetic acid are both 0.1-2%wt.

Preferably, the temperature of the gas-like reagent generating device is 130-170°C.

Preferably, the residence time of the original flue gas in the pre-oxidation reactor is 1-3s.

Preferably, the gas-liquid ratio of the raw flue gas to the liquid-phase composite oxidizer is 10 ⁴ m ³ : (13-40) L, and the gas-liquid ratio to the absorption slurry is 1 m ³ : (5-10) L.

Preferably, the absorption slurry is a mixture of sodium humate and ammonia water, with a pH of 9-12; the concentration of sodium humate is 0.1-1.0%wt, and the concentration of ammonia water is 10-20%wt.

Preferred liquid-phase composite oxidant combination forms include:

(1) hydrogen peroxide/sodium chlorite: the concentration ratio of the two is 25-30%wt: 0.5-1%wt, and the pH range is 4-6;

(2) Sodium chlorite/sodium persulfate: the concentration ratio of the two is 2-4%wt: 1-5%wt, and the pH range is 10-12;

(3) Sodium chlorite/sodium bromide: the concentration ratio of the two is 4-10%wt: 0.1-0.3%wt, and the pH range is 6-11;

(4) hydrogen peroxide/glacial acetic acid/sodium bromide: the concentration ratio of the three is 15-25%wt: 1-2%wt: 1-1.5%wt, and the pH range is 1-3;

(5) Sodium persulfate/sodium bromide/nickel nitrate: the concentration ratio of the three is 8-10%wt: 0.1-0.3%wt: 0.1-0.5%wt, and the pH range is 7-10.

The preparation process of the liquid-phase composite oxidant mother liquor is as follows: after mixing the oxidizer and the additive in proportion, dilute it to the concentration of the mother liquor with process water. The above multiple composite oxidants have strong stability, and there is no significant gas release phenomenon within 12 hours, which is beneficial to the preparation of liquid-phase composite oxidants and the safe operation of their storage systems.

The pre-oxidizer is a cyclone pre-oxidizer or an inverted U-shaped pre-oxidizer. The operation of the cyclone pre-oxidizer is as follows: the gas-like compound oxidant 9 and the original flue gas carry out the opposite shear flow movement, and the top-down rotary motion is carried out on the side of the barrel wall of the cyclone pre-oxidizer. During this process, the gas-like compound oxidizer The oxidizer 9 is turbulently mixed with the raw flue gas and undergoes an oxidation reaction. When the raw flue gas touches the bottom, it rotates from bottom to top in the sleeve until it is discharged from the pre-oxidation reactor.

The operation of the inverted U-shaped preoxidizer is as follows: the original flue gas is accelerated in the Venturi tube of the inverted U-shaped preoxidizer, and the gas-phase compound oxidant 9 is injected into the constriction of the Venturi tube, and the accelerated original flue gas impacts and carries The gas-phase composite oxidant enters the main part of the pre-oxidizer; the porous baffle is arranged at the outlet of the Venturi tube to enhance the turbulent effect of the flue gas, improve the dispersion of the oxidant and the pollutants in the flue gas, and accelerate the oxidation efficiency; the mixed raw The flue gas flows inside the inverted U-shaped pre-oxidizer and undergoes an oxidation reaction until it is discharged from the pre-oxidizer.

The operating conditions of the gas-phase reagent generator, pre-oxidizer and wet scrubber are as follows:

(1) The hot flue gas temperature of the gas-phase reagent generating device is 130-170°C;

(2) In the gas-phase reagent generating device, the gas-liquid ratio of the original flue gas to the liquid-phase composite oxidant is 10 ⁴ m ³ : (13-40) L (the amount of flue gas under working conditions);

(3) The reaction temperature range in the preoxidizer is 70-120°C;

(4) The original flue gas residence time in the preoxidizer is 1-3s;

(5) The absorption slurry in the wet scrubber is a mixture of sodium humate and ammonia, with a pH of 9-12; the concentration of sodium humate is 0.1-1.0%wt, and the concentration of ammonia is 10-20%wt;

(6) The pH range of sodium humate and ammonia water mixture is 9-12;

(7) The gas-liquid ratio of the raw flue gas to the absorption slurry is 1m ³ : (5-10)L.

The optimal desulfurization, denitrification and mercury removal efficiencies of the above-mentioned gas-phase pre-oxidation combined with absorption of coal-fired flue gas multi-pollutant integrated removal technology can reach 99-100%, 88-92% and 90-95%, respectively. Under the typical operating conditions of thermal power plants in my country, it can meet the current air pollutant emission standards for thermal power plants. Compared with the series-type hierarchical treatment system, this integrated oxidation-absorption secondary treatment system has lower infrastructure and operating costs, easier operation, and the removal of products is conducive to resource utilization, so it has better economic efficiency. and environmental benefits.

The process of the present invention is a two-stage treatment technology—gas-like pre-oxidation combined with absorption technology, that is, the liquid-phase composite oxidant is vaporized by using the waste heat of the flue gas in a thermal power plant, and then the generated gas-like composite oxidant is realized in the pre-oxidizer. The rapid oxidation of NO and Hg ⁰ , the oxidation products and residual gas-phase composite oxidants were absorbed by the subsequent sodium humate/ammonia water absorption solution. The invention is applicable to various types of boilers, and can simultaneously remove various flue gas pollutants, so the invention has good environmental and economic benefits, and has broad application prospects.

Reaction mechanism of the present invention is as follows:

Hydrogen peroxide, persulfate, and sodium chlorite are primary oxidants of the liquid-phase composite oxidant, peroxide, sulfate radical, hydroxyl radical, chlorine dioxide, chlorine free radical, peracetic acid, bromine simple substance, Bromine radicals are secondary oxidants, and these oxidants oxidize NO and Hg ⁰ in flue gas to divalent mercury, and oxidize NO to NO _x . The synergistic mechanism between oxidants is as follows:

H ₂ O ₂ +NaClO ₂ →HO ₂ ^- +HClO ₂ →ClO ₂ +M→Cl ^· +Cl ₂

H ₂ O+Na ₂ S ₂ O ₈ +H ₂ O ₂ →SO ₄ ^·- +HO ^· →HSO ₅ ^-

H ₂ O+Na ₂ S ₂ O ₈ +NaClO ₂ →SO ₄ ^·- +ClO ₂ +M→HSO ₅ ^- +Cl ^· +Cl ₂

The synergistic mechanism between oxidants and additives is as follows:

H ₂ O ₂ +CH ₃ COOH→CH ₃ COOOH

Ni ³⁺ +Na ₂ S ₂ O ₈ +H ₂ O→SO ₄ ^·- +HO ^· →HSO ₅ ^-

Br ^- + oxidizing agent/radical → Br ^- +Br ₂

The reaction mechanism between primary and secondary oxidants and pollutants is as follows:

H ₂ O ₂ +N(II)+Hg ⁰ +S(IV)→N(V)+Hg(II)+S(VI)+H ₂ O

Na ₂ S ₂ O ₈ +N(II)+Hg ⁰ +S(IV)→N(V)+Hg(II)+S(VI)+SO ₄ ^2-

NaClO ₂ +N(II)+Hg ⁰ +S(IV)→N(V)+Hg(II)+S(VI)+Cl ^-

ClO ₂ +Cl +Cl ² ₊ N(II)+Hg ⁰ +S(IV)→N(V)+Hg(II)+S(VI)+Cl ^-

SO ₄ ^·- +HO ^· +HSO ₅ ^- +N(II)+Hg ⁰ +S(IV)→N(V)+Hg(II)+S(VI)

SO ₄ ^·- +N(II)+Hg ⁰ +S(IV)→N(V)+Hg(II)+S(VI)+SO ₄ ^2-

CH3COOOH+N(II)+ ^Hg0 +S(IV)→N(V)+Hg(II)+ _S (VI)+ _CH3COOH

Br ^- +Br ₂ +N(II)+Hg ⁰ +S(IV)→N(V)+Hg(II)+S(VI)+Br ^-

H ₂ O ₂ +N(II)+Hg ⁰ +S(IV)→N(V)+Hg(II)+S(VI)

The reaction mechanism between the oxidation product and the absorbent is as follows:

H ₂ O+NH ₃ +N(V)+S(VI)→(NH ₄ ) ₂ SO ₄ +NH ₄ NO ₃

A ^- (humate)+NO ₂ →HA+NO ₃ ^-

A ^- +SO ₃ +SO ₂ →HA+SO ₃ ^2- +SO ₄ ^2-

Using multiple composite oxidants of the present invention to carry out desulfurization, denitrification and demercuration treatment to flue gas, the treatment effect is as shown in Table 1:

Table 1 Desulfurization, denitrification and mercury removal effects

project before processing after treatment Removal efficiency Hg ⁰ concentration 30μg/ ^m3 1.5-3μg/ ^m3 90-95% NO concentration 500mg/ ^m3 40-60mg/ ^m3 88-92% _SO2 concentration 4000mg/ ^m3 0-40mg/ ^m3 99-100%

The beneficial effects of the present invention are:

1. The method of the present invention is unique. The gas-like composite oxidant is used to first oxidize NO and Hg ⁰ in the flue gas, and then realize the simultaneous removal of SO ₂ , NO and Hg ⁰ , thereby realizing the integration of desulfurization, denitrification and mercury removal, which greatly reduces the The infrastructure and operating costs of hierarchical desulfurization, denitrification and mercury removal improve the integrated removal efficiency, and the obtained removal product is an excellent compound fertilizer containing sulfur and nitrogen, which has high economic and environmental benefits.

2. The present invention effectively utilizes the residual heat of hot flue gas and improves thermal efficiency.

3. The gas-phase pre-oxidation combined with absorption technology is applicable to a variety of industrial boilers, and it is one of the feasible solutions to solve the soot-type smog in the north.

Description of drawings

Figure 1 is a schematic diagram of the process flow of the gas-phase pre-oxidation combined with absorption of coal-fired flue gas multi-pollutants integrated removal process of the present invention.

Fig. 2 is a schematic diagram of a gas-like reagent generating device.

Figure 3 is a schematic diagram of a cyclone pre-oxidizer device.

Figure 4 is a schematic diagram of an inverted U-shaped pre-oxidizer.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The flue gas integrated removal system with gas-phase preoxidation combined with absorption includes a gas-phase reagent generator, a pre-oxidizer and a wet absorption tower; its structures are shown in Figures 2, 3 and 4, respectively. The specific meaning of each label in the figure is as follows: 1- process water inlet, 2- condenser, 3- hot flue gas after economizer, 4- process water vaporization pipe, 5- high temperature steam outlet, 6- liquid phase composite oxidant Mother liquor, 7-compressed air, 8-mixer, 9-type gas-phase composite oxidizer, 10-type gas-phase composite oxidant injection inlet, 11-flue gas inlet, 12-flue gas outlet, 13-water chamber, 14-shell, 15-support plate, 16-flue gas after cooling, 17-pipe shell, 18-left-handed unit piece, 19-right-handed unit piece.

The gas-phase reagent generating device includes a process water inlet 1, a condenser 2, a high-temperature steam outlet 5 and a mixer 8;

The pre-oxidizer is placed downstream of the gas-like reagent generating device, and includes a gas-like composite oxidant injection port 10 , a flue gas inlet 11 and a flue gas outlet 12 .

The pre-oxidizer is a cyclone pre-oxidizer or an inverted U-shaped pre-oxidizer.

The process water enters the condenser 2 through the process water inlet 1, and vaporizes in the process water vaporization pipe 4 in the condenser 2 to obtain high-temperature steam; the high-temperature steam enters the mixer 8 through the high-temperature steam outlet 5;

The liquid-phase composite oxidizer mother liquor 6 enters the mixer 8 under the impact of the compressed air 7; in the mixer 8, the mist-like liquid-phase composite oxidant mother liquor 6 and high-temperature steam are fully mixed to generate a gas-like composite oxidizer 9;

The gas-phase composite oxidizer 9 enters the pre-oxidizer through the gas-phase composite oxidant injection port 10, and the original flue gas enters the pre-oxidizer through the flue gas inlet 11 to mix with the gas-phase composite oxidant 9, and an oxidation reaction occurs to realize the oxidation of NO and Hg ⁰ ;

The oxidation product exits the pre-oxidizer through the flue gas outlet 12 and enters the wet absorption tower, where SO _x , NO _x and Hg ²⁺ in the oxidation product are absorbed and removed with the absorption slurry.

The condenser 2 uses the hot flue gas 3 after the economizer to thermally vaporize the process water in the process water vaporization pipe 4 .

The liquid-phase composite oxidant consists of oxidant and additives.

The oxidizing agent is one or more of hydrogen peroxide, sodium persulfate and sodium chlorite; the additive is one or more of sodium bromide, nickel nitrate and glacial acetic acid; the oxidizing agent Among them, the concentration of hydrogen peroxide is 15-30%wt, the concentration of sodium persulfate is 1-10%wt, and the concentration of sodium chlorite is 0.5-10%wt. Among the additives, sodium bromide, nickel nitrate, ice The concentration of acetic acid is 0.1-2%wt.

Example 1

Preparation of liquid-phase composite oxidant mother liquor: wherein the concentration %wt ratio of hydrogen peroxide and sodium chlorite is 25:1, after mixing the two according to the above concentration ratio, dilute it to the mother liquor concentration with process water, and the pH is 4.5.

The above-mentioned liquid-phase composite oxidant is injected into the gas-phase reagent generating device, and after passing through the pre-oxidizer and the wet absorption tower, the integrated desulfurization, denitrification and demercuration are realized. The reaction conditions are shown in Table 2.

Table 2 Reaction Conditions

condition scope The internal temperature of the gas-phase composite oxidant generator 130°C The liquid-gas ratio of the amount of liquid-phase composite oxidant added to the amount of flue gas 13L: 10 ⁴ m ³ Reaction temperature in the preoxidizer 70°C Flue gas residence time in the preoxidizer 1.3s Concentration ratio of sodium humate to ammonia water 0.1:10%wt The pH of the mixture of sodium humate and ammonia water 9

According to the above conditions, the flue gas is desulfurized, demercurized and denitrified, and it is detected that the removal efficiency of _SO2 is 99%, the denitrification efficiency is 90.5%, and the mercury removal efficiency is above 92.7%.

Example 2

Preparation of composite oxidant: wherein the concentration %wt ratio of hydrogen peroxide and sodium chlorite is 30:0.5, after mixing the two according to the above concentration ratio, dilute it to the mother liquor concentration with process water, and the pH is 5.7.

The above-mentioned liquid-phase composite oxidant is injected into the gas-phase reagent generating device, and after passing through the pre-oxidizer and the wet absorption tower, the integrated desulfurization, denitrification and demercuration are realized. The reaction conditions are shown in Table 3.

Table 3 reaction conditions

condition scope The internal temperature of the gas-phase composite oxidant generator 150°C The liquid-gas ratio of the amount of liquid-phase composite oxidant added to the amount of flue gas 30L: 10 ⁴ m ³ Reaction temperature in the preoxidizer 100°C Flue gas residence time in the preoxidizer 1.0s Concentration ratio of sodium humate to ammonia water 0.5:15%wt The pH of the mixture of sodium humate and ammonia water 10

According to the above conditions, the flue gas is desulfurized, demercurized and denitrified. It is detected that the removal efficiency of _SO2 is 100%, the denitrification efficiency is 89.2%, and the mercury removal efficiency is above 93.3%.

Example 3

Prepare composite oxidant: the concentration %wt ratio of sodium chlorite and sodium persulfate is 2:4. After mixing the two according to the above concentration ratio, dilute it to the concentration of the mother liquor with process water, and the pH is 10.

The above-mentioned liquid-phase composite oxidant is injected into the gas-phase reagent generating device, and after passing through the pre-oxidizer and the wet absorption tower, the integrated desulfurization, denitrification and demercuration are realized. The reaction conditions are shown in Table 4.

Table 4 reaction conditions

condition scope The internal temperature of the gas-phase composite oxidant generator 140°C The liquid-gas ratio of the amount of liquid-phase composite oxidant added to the amount of flue gas 20L: 10 ⁴ m ³ Reaction temperature in the preoxidizer 120°C Flue gas residence time in the preoxidizer 1.0s Concentration ratio of sodium humate to ammonia water 1.0:15%wt The pH of the mixture of sodium humate and ammonia water 10.5

According to the above conditions, the flue gas is desulfurized, demercurized and denitrified, and it is detected that the removal efficiency of _SO2 is 100%, the denitrification efficiency is 92.0%, and the mercury removal efficiency is above 94.8%.

Example 4

Prepare composite oxidant: the concentration %wt ratio of sodium chlorite and sodium persulfate is 4:4. After mixing the two according to the above concentration ratio, use process water to dilute it to the concentration of the mother liquor, and the pH is 11.

The above-mentioned liquid-phase composite oxidant is injected into the gas-phase reagent generating device, and after passing through the pre-oxidizer and the wet absorption tower, the integrated desulfurization, denitrification and demercuration are realized. The reaction conditions are shown in Table 5.

Table 5 Reaction Conditions

condition scope The internal temperature of the gas-phase composite oxidant generator 170°C The liquid-gas ratio of the amount of liquid-phase composite oxidant added to the amount of flue gas 25L: 10 ⁴ m ³ Reaction temperature in the preoxidizer 100°C Flue gas residence time in the preoxidizer 2.4s Concentration ratio of sodium humate to ammonia water 0.5:20%wt The pH of the mixture of sodium humate and ammonia water 12

According to the above conditions, the flue gas is desulfurized, demercurized and denitrified, and it is detected that the removal efficiency of _SO2 is 100%, the denitrification efficiency is 92.0%, and the mercury removal efficiency is above 95.0%.

Example 5

Preparation of composite oxidant: the concentration %wt ratio of sodium chlorite and sodium bromide is 4:0.1, after mixing the two according to the above concentration ratio, dilute it to the mother liquor concentration with process water, and the pH is 8.5.

The above-mentioned liquid-phase composite oxidant is injected into the gas-phase reagent generating device, and after passing through the pre-oxidizer and the wet absorption tower, the integrated desulfurization, denitrification and demercuration are realized. The reaction conditions are shown in Table 6.

Table 6 Reaction Conditions

condition scope The internal temperature of the gas-phase composite oxidant generator 160°C The liquid-gas ratio of the amount of liquid-phase composite oxidant added to the amount of flue gas 20L: 10 ⁴ m ³ Reaction temperature in the preoxidizer 130°C Flue gas residence time in the preoxidizer 2.7s Concentration ratio of sodium humate to ammonia water 0.3:20%wt The pH of the mixture of sodium humate and ammonia water 10.5

According to the above conditions, the flue gas is desulfurized, demercurized and denitrified. It is detected that the removal efficiency of SO2 is _99.3 %, the denitrification efficiency is 88.4%, and the mercury removal efficiency is above 94.3%.

Example 6

Preparation of composite oxidant: the concentration %wt ratio of sodium chlorite and sodium bromide is 10:0.3, after mixing the two according to the above concentration ratio, dilute it to the concentration of the mother liquor with process water, and the pH is 11.

The above-mentioned liquid-phase composite oxidant is injected into the gas-phase reagent generating device, and after passing through the pre-oxidizer and the wet absorption tower, the integrated desulfurization, denitrification and demercuration are realized. The reaction conditions are shown in Table 7.

Table 7 Reaction Conditions

condition scope The internal temperature of the gas-phase composite oxidant generator 170°C The liquid-gas ratio of the amount of liquid-phase composite oxidant added to the amount of flue gas 13L: 10 ⁴ m ³ Reaction temperature in the preoxidizer 120°C Flue gas residence time in the preoxidizer 1s Concentration ratio of sodium humate to ammonia water 1: 20%wt The pH of the mixture of sodium humate and ammonia water 12

According to the above conditions, the flue gas is desulfurized, demercurized and denitrified. It is detected that the removal efficiency of _SO2 is 100%, the denitrification efficiency is 91.8%, and the mercury removal efficiency is above 95.0%.

Example 7

Preparation of composite oxidant: the concentration %wt ratio of hydrogen peroxide, glacial acetic acid and sodium bromide is 15:2:1.5, after mixing the two according to the above concentration ratio, dilute it to the mother liquor concentration with process water, and the pH is 2.5 .

The above-mentioned liquid-phase composite oxidant is injected into the gas-phase reagent generating device, and after passing through the pre-oxidizer and the wet absorption tower, the integrated desulfurization, denitrification and demercuration are realized. The reaction conditions are shown in Table 8.

Table 8 Reaction Conditions

condition scope The internal temperature of the gas-phase composite oxidant generator 130°C The liquid-gas ratio of the amount of liquid-phase composite oxidant added to the amount of flue gas 40L: 10 ⁴ m ³ Reaction temperature in the preoxidizer 80°C Flue gas residence time in the preoxidizer 3s Concentration ratio of sodium humate to ammonia water 0.5:20%wt

The pH of the mixture of sodium humate and ammonia water 12

According to the above conditions, the flue gas is desulfurized, demercurized and denitrified. It is detected that the removal efficiency of _SO2 is 100%, the denitrification efficiency is 91.4%, and the mercury removal efficiency is above 93.2%.

Example 8

Preparation of composite oxidant: the concentration %wt ratio of hydrogen peroxide, glacial acetic acid and sodium bromide is 25:1:1, after mixing the two according to the above concentration ratio, dilute it to the mother liquor concentration with process water, and the pH is 1 .

The above-mentioned liquid-phase composite oxidant is injected into the gas-phase reagent generating device, and after passing through the pre-oxidizer and the wet absorption tower, the integrated desulfurization, denitrification and demercuration are realized. The reaction conditions are shown in Table 9.

Table 9 reaction conditions

condition scope The internal temperature of the gas-phase composite oxidant generator 130°C The liquid-gas ratio of the amount of liquid-phase composite oxidant added to the amount of flue gas 35L: 10 ⁴ m ³ Reaction temperature in the preoxidizer 110°C Flue gas residence time in the preoxidizer 2s Concentration ratio of sodium humate to ammonia water 0.3:20%wt The pH of the mixture of sodium humate and ammonia water 9

According to the above conditions, the flue gas is desulfurized, demercurized and denitrified. It is detected that the removal efficiency of _SO2 is 99%, the denitrification efficiency is 90.2%, and the mercury removal efficiency is above 91.4%.

Example 9

Preparation of composite oxidant: wherein the concentration %wt ratio of sodium persulfate, sodium bromide and nickel nitrate is 8:0.1:0.1, after mixing the two according to the above concentration ratio, dilute it to the mother liquor concentration with process water, and the pH is 7 .

The above-mentioned liquid-phase composite oxidant is injected into the gas-phase reagent generating device, and after passing through the pre-oxidizer and the wet absorption tower, the integrated desulfurization, denitrification and demercuration are realized. The reaction conditions are shown in Table 10.

Table 10 reaction conditions

condition scope The internal temperature of the gas-phase composite oxidant generator 150°C The liquid-gas ratio of the amount of liquid-phase composite oxidant added to the amount of flue gas 30L: 10 ⁴ m ³

Reaction temperature in the preoxidizer 120°C Flue gas residence time in the preoxidizer 2.7s Concentration ratio of sodium humate to ammonia water 1: 20%wt The pH of the mixture of sodium humate and ammonia water 10

According to the above conditions, the flue gas is desulfurized, demercurized and denitrified, and it is detected that the removal efficiency of _SO2 is 100%, the denitrification efficiency is 88.9%, and the mercury removal efficiency is above 89.5%.

Example 10

Preparation of composite oxidant: the concentration %wt ratio of sodium persulfate, sodium bromide and nickel nitrate is 10:0.3:0.5, after mixing the two according to the above concentration ratio, dilute it to the mother liquor concentration with process water, and the pH is 10 .

The above-mentioned liquid-phase composite oxidant is injected into the gas-phase reagent generating device, and after passing through the pre-oxidizer and the wet absorption tower, the integrated desulfurization, denitrification and demercuration are realized. The reaction conditions are shown in Table 11.

Table 11 Reaction Conditions

condition scope The internal temperature of the gas-phase composite oxidant generator 140°C The liquid-gas ratio of the amount of liquid-phase composite oxidant added to the amount of flue gas 25L: 10 ⁴ m ³ Reaction temperature in the preoxidizer 100°C Flue gas residence time in the preoxidizer 2s Concentration ratio of sodium humate to ammonia water 0.8:10%wt The pH of the mixture of sodium humate and ammonia water 10

According to the above conditions, the flue gas is desulfurized, demercurized and denitrified. It is detected that the removal efficiency of _SO2 is 100%, the denitrification efficiency is 89.4%, and the mercury removal efficiency is above 91.2%.

The present invention can have a variety of specific implementations without departing from its spirit and essential characteristics. It should be understood that the above-mentioned embodiments are not limited to any of the above-mentioned details, but should be widely used within the spirit and scope defined by the appended claims. Therefore, all changes and modifications that come within the metes and bounds of the claims or are equivalent to such metes and bounds are therefore intended to be embraced in the appended claims.

Claims (8)

1. An integrated flue gas removal system with gas-phase pre-oxidation combined with absorption, which is characterized in that it includes a gas-phase reagent generator, a pre-oxidizer and a wet absorption tower in sequence according to the flow; The gas-phase reagent generator includes a process water inlet (1), a condenser (2), a high-temperature steam outlet (5) and a mixer (8); The pre-oxidizer is placed downstream of the gas-like reagent generating device, including a gas-like composite oxidant injection port (10), a flue gas inlet (11) and a flue gas outlet after the mixed oxidation of the flue gas and the gas-like composite oxidant (9) (12), the flue gas outlet (12) is connected to a wet absorption tower; The wet absorption tower is placed downstream of the pre-oxidizer, and is used to absorb and remove SO _x , NO _x and Hg ²⁺ in the oxidation product by absorbing the slurry; The gas-phase composite oxidant (9) is obtained by fully mixing the liquid-phase composite oxidant mother liquid (6) into the mixer (8) under the impact of compressed air (7) and high-temperature steam; The liquid-phase composite oxidizer mother liquor (6) is selected from combinations a to f: a: hydrogen peroxide/sodium chlorite: the concentration ratio of the two is 25-30%wt: 0.5-1%wt, and the pH is 4-6; b: sodium chlorite/sodium persulfate: the concentration ratio of the two is 2-4%wt: 1-5%wt, and the pH is 10-12; c: sodium chlorite/sodium bromide: the concentration ratio of the two is 4%wt: 0.1%wt, and the pH is 8.5; d: sodium chlorite/sodium bromide: the concentration ratio of the two is 10%wt: 0.3%wt, and the pH is 11; e: hydrogen peroxide/glacial acetic acid/sodium bromide: the concentration ratio of the three is 15-25%wt: 1-2%wt: 1-1.5%wt, and the pH is 1-3; f: sodium persulfate/sodium bromide/nickel nitrate: the concentration ratio of the three is 8-10%wt: 0.1-0.3%wt: 0.1-0.5%wt, and the pH is 7-10. 2. The removal system according to claim 1, wherein the pre-oxidizer is a cyclone pre-oxidizer or an inverted U-shaped pre-oxidizer. 3. The removal system according to claim 1, characterized in that a process water vaporization pipe (4) is arranged in the condenser (2), in which the process water is vaporized, and the obtained high-temperature steam passes through the high-temperature steam outlet (5) enters the mixer (8). 4. The removal system according to claim 1, characterized in that, the condenser (2) is also provided with an inlet of the hot flue gas (3) after the economizer, so that the process water vaporization pipe (4) The process water is thermally vaporized. 5. removal system according to claim 1, is characterized in that, described mixer (8) comprises the inlet port that liquid phase compound oxidizer mother liquid (6) is carried under the impact of compressed air (7); Also comprises liquid The composite oxidizer mother liquor (6) and the high-temperature steam are fully mixed to form an outlet similar to a gas-phase composite oxidizer (9). 6. The method for integrated flue gas removal by the system of claim 1, characterized in that it comprises the following steps: a. The process water enters the condenser (2) through the process water inlet (1), and vaporizes in the process water vaporization pipe (4) in the condenser (2) to obtain high-temperature steam; the high-temperature steam passes through the high-temperature steam outlet ( 5) enter mixer (8); B. liquid phase composite oxidizer mother liquor (6) enters mixer (8) under the impact of compressed air (7); Mix to generate gas-like composite oxidant (9); c. The gas-phase composite oxidant (9) enters the pre-oxidizer through the gas-phase composite oxidant injection port (10), and the original flue gas enters the pre-oxidizer through the flue gas inlet (11) and mixes with the gas-phase composite oxidant (9) to oxidize reaction to realize the oxidation of NO and Hg ⁰ ; d. The oxidation product is discharged from the pre-oxidizer through the flue gas outlet (12), and enters the wet absorption tower, and the SO _x , NO _x and Hg ²⁺ in the oxidation product are absorbed and removed by the absorption slurry. 7. The method according to claim 6, characterized in that, the temperature of the gas-like reagent generating device is 130-170°C; the residence time of the original flue gas in the pre-oxidation reactor is 1-3s; the The gas-liquid ratio of the raw flue gas to the liquid-phase composite oxidant is 10 ⁴ m ³ : (13-40) L, and the gas-liquid ratio to the absorption slurry is 1 m ³ : (5-10) L. 8. The method according to claim 6, characterized in that, the absorption slurry is a mixture of sodium humate and ammonia, pH is 9-12; the concentration of sodium humate is 0.1-1.0%wt, the Ammonia concentration is 10-20%wt.