WO2020082402A1

WO2020082402A1 - Denitration system and method employing ozone to perform cascade oxidation and absorption on sintering flue gas

Info

Publication number: WO2020082402A1
Application number: PCT/CN2018/112613
Authority: WO
Inventors: 朱廷钰; 刘霄龙; 邹洋; 蔡茂宇; 李二伟; 徐文青
Original assignee: 中国科学院过程工程研究所
Priority date: 2018-10-26
Filing date: 2018-10-30
Publication date: 2020-04-30
Also published as: JP2021502884A; JP6970470B2; CN109289471A

Abstract

A denitration system and method employing ozone to perform cascade oxidation and absorption on a sintering flue gas. The system comprises an ozone generation device, an ozone distribution device, a flue gas cooling device and a flue gas absorption device. The ozone distribution device comprises an ozone distribution module (2), and a primary ozone distribution unit (3), a secondary ozone distribution unit (6) and a tertiary ozone distribution unit (8), respectively connected to the ozone distribution module (2).

Description

Sintering flue gas ozone cascade oxidation-absorption denitration system and method

Technical field

The present application belongs to the technical field of pollutant control, for example, it relates to a sintered flue gas ozone cascade oxidation-absorption denitration system and method.

Background technique

With the increasing emphasis on environmental protection, the emission standards of flue gas pollutants in many industries in China are becoming stricter, and desulfurization and dust removal facilities have been basically popularized. In comparison, the treatment of nitrogen oxides NO _x has become the key to restricting environmental protection upgrades. NO _x emissions from the iron and steel industry, second only power station boilers and cement kilns, ranking third in the industry. In the NO _x emissions in the steel industry, more than 50% from the sintering process. Sintered flue gas has the characteristics of large flow rate (> 1 million m ³ / h), low flue gas temperature (120-180 ℃), and large fluctuations of NO _x concentration (180-600 mg / m ³ ), which makes it difficult for environmental governance. In recent years, NO _x emission limits already mentioned particularly from 300mg / m ³ of 100mg / m ^3, but some of the companies is made of ultra-low emissions standards 50mg / m ³ of. So since a large amount of sintering machine NO _x non-compliance. Therefore, it is urgent to develop low-temperature denitration technology for sintered flue gas.

The current sintering flue gas denitrification technology mainly includes activated carbon technology, selective catalytic reduction (SCR) technology, and oxidative denitration technology. Although activated carbon technology can achieve integrated control of sulphur and nitrate, related sintered flue gas activated carbon engineering cases show that a low space velocity is required during operation, which makes the activated carbon used very large, and requires the activated carbon to be heated and regenerated, which makes the operation cost very high. SCR denitration technology is to inject reducing agent into the flue gas to reduce NO _x to N ₂ in the presence of catalyst. The operating temperature of medium and high temperature SCR is generally 280-320 ℃, and the operating temperature of medium and low temperature SCR is generally 220-280 ℃ Both types of denitration technologies need to reheat the sintered flue gas, which makes the related SCR technology have higher operating costs, and the related catalysts are basically vanadium-based catalysts. The waste catalysts are hazardous wastes and are difficult to handle. Oxidative denitration technology is to spray ozone or other kinds of oxidants before entering the desulfurization tower in the flue gas to oxidize NO in the flue gas into high-valent nitrogen oxides such as NO ₂ or N ₂ O _{5 to} achieve simultaneous desulfurization in the desulfurization tower Denitration.

CN103977679A discloses a method and system for simultaneous desulfurization and denitrification of staged oxidation absorption sintering flue gas, using sodium hypochlorite and potassium permanganate solution to spray oxidize sintering flue gas in a first-level oxidation tower to oxidize NO _x and SO ₂ Into NO ₂ and SO ₃ ; use an absorbent solution in the secondary absorption tower to spray and absorb the sintered flue gas after spray oxidation, and absorb NO ₂ and SO ₃ ; finally, after spray oxidation and spray absorption The sintering flue gas is discharged. This method requires the use of sodium hypochlorite and potassium permanganate chemicals as the oxidant, which can only oxidize NO in the flue gas to NO ₂ , and the absorption capacity of NO ₂ itself is limited, and yellow smoke is likely to occur when the initial NO _x concentration is high. In addition, the oxidation of SO ₂ to SO ₃ also requires additional consumption of a large amount of oxidant.

With the gradual maturity of ozone generators, ozone has become the most widely used oxidant in oxidative denitration technology. For example, CN105854554A discloses an ozone low-temperature oxidative denitration system, including a flue, an ozone generator, and a scrubber. An ozone distributor is installed in the flue. The outlet of the ozone generator supplies ozone to the ozone distribution through a pipeline. In the ozone channel of the device, ozone is sprayed into the flue through an ozone distributor, and the outlet of the flue is connected to the scrubber, so that the mixed gas of ozone and flue gas in the flue enters the scrubber. CN205461724U discloses a high-efficiency reaction device for ozone denitration process, which includes a flue gas pipeline and an ozone injection mechanism. The flue gas pipeline is provided with an ozone reaction platform. The ozone reaction platform is provided with multiple spoilers and ozone injection The mechanism is arranged at the flue gas inlet end of the flue gas pipe. CN201832548U discloses a denitration treatment device for purifying flue gas, which includes a denitration absorber. The denitration absorber includes a housing with a flue gas inlet and a flue gas outlet at both ends, and the bottom in the housing includes alkali A liquid containing area, a multi-layer spray nozzle is provided above the alkaline liquid containing area, and further includes a flue mixer and an ozone generator, the flue mixer is connected to the flue gas inlet of the off-line absorber, The flue mixer includes an ozone inlet and outlet, and a mixing reaction chamber communicating with the ozone inlet and outlet, and the ozone inlet and outlet are connected to the ozone generator pipe.

Denitration ozonation engineering applications, typically NO ₂ absorption, oxidation to NO ₂ as a main product, tobacco chimney prone. In order to achieve efficient and coordinated absorption of sulfur and nitric acid, especially when the inlet NO _x concentration is high, it is generally necessary to oxidize NO _x to N ₂ O ₅ . However, very large ozone gas temperature and / NO molar ratio generation Effect of N ₂ O _5, N ₂ O ₅ generated in the optimum temperature range is 60-90 ℃. When the flue gas temperature is higher than 130 ° C, even with a higher ozone / NO molar ratio (> 1.5), the yield of N ₂ O ₅ is still low. The sintering flue gas is generally at 130-200 ℃ before desulfurization, further increasing the amount of ozone, which not only increases the operating cost and the risk of ozone escape, but also makes it difficult to ensure that N ₂ O ₅ is produced at a higher yield. Therefore, how to efficiently generate N ₂ O ₅ and effectively absorb it in the absorption tower, and even further reduce the ozone consumption and operating cost, is the key to the application of ozone oxidation-absorption denitration technology in sintering flue gas.

Summary of the invention

The following is an overview of the topics detailed in this article. This summary is not intended to limit the scope of protection of the claims.

This application provides a sintered flue gas ozone cascade oxidation-absorption denitration system and method, which uses ozone as an oxidant and adopts a step oxidation-absorption method to make full use of the absorption of NO ₂ and the rapid generation and absorption of N ₂ O ₅ in the desulfurization tower In order to achieve high-efficiency denitration at low ozone usage, it has good economic benefits and application prospects.

To achieve this goal, this application uses the following technical solutions:

In the first aspect, the present application provides a sintered flue gas ozone cascade oxidation-absorption denitration system, the system comprising: an ozone generating device, an ozone distributing device, a flue gas cooling device and a flue gas absorbing device, wherein the ozone generating device The device includes an ozone generator 1, the flue gas absorption device includes an absorption tower 7, the ozone distribution device includes an ozone distribution module 2 and a first-level ozone distributor 3, a second-level ozone distributor 6 and a third-level An ozone distributor 8, the first-level ozone distributor 3 and the second-level ozone distributor 6 are sequentially arranged on the sintered flue gas conveying pipeline connected to the absorption tower 7, and the flue gas cooling device is arranged on the first-level ozone distributor 3 and On the flue gas delivery pipeline between the second-level ozone distributor 6, the third-level ozone distributor 8 is provided in the absorption tower 7, and the ozone generator 1 is connected to the ozone distribution module 2.

The relevant ozone oxidative denitration technology is mostly single-stage oxidation-absorption. Before entering the desulfurization absorption tower in the flue gas, all ozone is injected at once to oxidize the NO in the flue gas into high-valent nitrogen oxides such as NO ₂ or N ₂ O ₅ , To achieve simultaneous desulfurization and denitrification in the desulfurization tower. However, the original flue gas temperature of the sintered flue gas is usually higher (130-180 ℃), and above 130 ℃, even if the amount of ozone is increased, the yield of N ₂ O ₅ is still very low, and the NO ₂ absorption efficiency is limited, and there is operation High cost, risk of ozone escape and yellow smoke.

This application adopts a cascade oxidation-absorption structure. Ozone is mixed with the flue gas in three stages for oxidation. The first stage oxidation fully utilizes ozone to generate NO ₂ , and the second stage oxidation is realized in the absorption tower by cooling the flue gas. In order to generate higher yields of N ₂ O ₅ with a lower ozone amount and efficiently absorb it, the third-stage oxidation oxidizes the escaped NO or NO ₂ to NO ₂ or N ₂ O ₅ through a small amount of ozone and efficiently absorbs it. Under the same denitrification efficiency, the ozone consumption of this system is significantly lower than that of the single-stage oxidation absorption denitration system. Therefore, the sintered flue gas ozone cascade oxidation-absorption system can realize high-efficiency, low-cost and stable operation, and has strong applicability to sintered flue gas.

Optionally, the flue gas cooling device includes a cooling water tank 4 and a cooling nozzle 5. The outlet of the cooling water tank 4 is connected to the inlet of the cooling nozzle 5. The cooling nozzle 5 is provided in the primary ozone distributor 3 and secondary On the flue gas pipeline between the ozone distributor 6.

Optionally, the first-level ozone distributor 3 and the second-level ozone distributor 6 are sequentially arranged on the sintered flue gas conveying pipeline along the flue gas conveying direction.

Optionally, the second-level ozone distributor 6 is located on the flue gas transmission line at the entrance of the absorption tower 7 to achieve the simultaneous oxidation and absorption of the second-level ozone and the flue gas into the absorption tower after being mixed.

Optionally, the system is provided with a dust collector 10, and the flue gas inlet of the dust collector 10 is connected to the gas outlet of the absorption tower 7.

Optionally, a feed layer is provided in the absorption tower 7, and an absorbent is distributed on the feed layer for absorbing nitrogen oxides.

Optionally, the system is provided with an absorbent storage bin 9 whose outlet is connected to the inlet of the feed layer in the absorption tower 7.

Optionally, the absorbent storage silo 9 is provided with a circulating material inlet, which is connected to the circulating material outlet provided at the lower part of the absorption tower 7.

In a second aspect, the present application provides a sintered flue gas ozone cascade oxidation-absorption denitration method, which includes the following steps:

(1) Inject sintered flue gas into the sintered flue gas transmission pipeline, and at the same time send first-level ozone into the sintered flue gas transmission pipeline to obtain the mixed flue gas after first-level oxidation;

(2) The first-stage oxidized mixed flue gas obtained in step (1) is cooled, and then the second-stage ozone is mixed with the cooled flue gas, and the obtained mixed flue gas is passed into an absorption tower for oxidation and absorption, Get flue gas after secondary oxidation;

(3) The third-stage ozone is passed into the second-stage oxidized flue gas in the absorption tower to further oxidize and absorb the flue gas, and the absorbed flue gas is discharged out of the tower.

In this application, first-level ozone is introduced into the sintered flue gas to oxidize the NO in the flue gas to NO ₂ ; after the temperature is lowered, the generated NO ₂ and unreacted NO are mixed with the secondary ozone, unreacted NO And a part of NO ₂ will further react with secondary ozone to form NO ₂ and N ₂ O _{5 respectively} ; after entering the absorption tower, NO ₂ and N ₂ O ₅ in the flue gas will react with the alkaline absorbent in the absorption tower to form sub Nitrate and nitrate; the residual NO _{x in the} flue gas reacts with tertiary ozone to form high-valent nitrogen oxides and is further absorbed by the absorbent, thereby achieving deep denitration of sintered flue gas.

Alternatively, step (1) the molar ratio of an ozone and NO _x in the sintering gas is (0.4 to 1.8) to 1, optionally (0.6-1.0) to 1; 0.4, for example, may be , 0.5: 1, 0.8: 1, 1: 1, 1.2: 1, 1.5: 1, 1.6: 1, or 1.8: 1, and the specific points between the above values, due to space limitations and for simplicity, this application No more exhaustive enumeration.

Optionally, the temperature of the flue gas in step (1) is 130-180 ° C, optionally 130-160 ° C; for example, 130 ° C, 135 ° C, 140 ° C, 145 ° C, 150 ° C, 155 ° C, 160 ℃, 165 ℃, 170 ℃, 175 ℃ or 180 ℃, and the specific point value between the above values, due to space limitations and for the sake of simplicity, this application will not be exhaustively listed.

Optionally, the cooling method in step (2) is spray water cooling.

Optionally, the temperature of the mixed flue gas after cooling in step (2) is 80-129 ° C, optionally 90-110 ° C; for example, it can be 80 ° C, 85 ° C, 90 ° C, 95 ° C, 100 ° C, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃ or 129 ℃, and the specific points between the above values, due to space limitations and for the sake of simplicity, this application will not be exhaustively listed.

Optionally, in step (2), the second-stage ozone flue gas pipeline at the entrance of the absorption tower is mixed with the flue gas after the temperature is lowered, and after mixing, it quickly enters the absorption tower, where it is simultaneously oxidized and absorbed in the absorption tower.

The molar ratio of NO _x Optionally, the step (2) with two ozone in step (1) into the sintering gas (raw flue gas) is (0.1-1.0) to 1, optionally ( 0.1-0.8): 1; for example, it can be 0.1: 1, 0.2: 1, 0.3: 1, 0.4: 1, 0.5: 1, 0.6: 1, 0.7: 1, 0.8: 1, 0.9: 1, or 1: 1, As well as the specific point values between the above values, due to space limitations and for simplicity, this application will not be exhaustively listed.

In step (1) of the present application, the sintered flue gas flowing into the sintered flue gas conveying pipeline is the original flue gas.

This application selects absorption towers commonly used in the art to absorb nitrogen oxides, such as circulating fluidized bed semi-dry absorption tower, rotary spray drying semi-dry absorption tower, dense phase dry tower semi-dry absorption tower, limestone-gypsum Method wet absorption tower, magnesium method wet absorption tower, ammonia method wet absorption tower or sodium alkali wet absorption tower, etc., but not limited to this, other absorption towers that can be used to absorb nitrogen oxides are also applicable to this application , Due to space limitations and for the sake of simplicity, this application is no longer exhaustive.

Optionally, the absorbent in step (3) of the present application may be a calcium-based absorbent, a magnesium-based absorbent, a sodium-based absorbent or an amino-based absorbent, etc., and may be a calcium-based absorbent, a magnesium-based absorbent or an amino-based absorbent Absorbent, but not limited to this, other suitable absorbents in the art are also suitable for this application, and should be specifically selected according to the actual situation.

Molar ratio Optionally, step (3) and the three ozone step (1) into the flue gas of the sintering of the NO _x (0.1-0.5) to 1, optionally (0.1-0.4) to 1; For example, it can be 0.1: 1, 0.15: 1, 0.2: 1, 0.25: 1, 0.3: 1, 0.35: 1, 0.4: 1, 0.45: 1, or 0.5: 1, and the specific point value between the above values is limited to For reasons of length and simplicity, this application is not exhaustive.

Optionally, the method further includes: using a dust collector to remove the flue gas absorbed in step (3) to obtain purified flue gas. When the absorption tower is a semi-dry absorption tower, the dust collector is a bag-type dust collector, and when the absorption tower is a wet absorption tower, the dust collector is a wet electric dust collector.

Alternatively, the flue gas purifying NO _x in _the content of less than 50mg / m ^3.

As an optional technical solution, this application uses the system described in the first aspect to perform ozone cascade oxidation and absorption denitrification of sintering flue gas. The method includes the following steps:

(1) The sintered flue gas is introduced into the sintered flue gas transmission pipeline, and at the same time, the ozone distribution module 2 is used to distribute the ozone generated in the ozone generator 1 to the first-level ozone distributor 3, and then the first-level ozone is sent to the sintered smoke In the gas transmission pipeline, the mixed flue gas after first-level oxidation is obtained;

(2) Use the flue gas cooling device to cool the first-level oxidized mixed flue gas obtained in step (1), and then use the ozone distribution module 2 to distribute ozone to the secondary ozone distributor 6 and pass the secondary ozone and The flue gas after cooling is mixed, and the resulting mixed flue gas is passed into the absorption tower 7 for oxidation and absorption to obtain the flue gas after secondary oxidation;

(3) Use the ozone distribution module 2 to distribute ozone to the second-level ozone distributor 8 and pass three-level ozone into the second-stage oxidized flue gas in the absorption tower 7 to further oxidize and absorb the flue gas. The gas is discharged outside the tower.

Optionally, in step (2), the cooling water tank 4 and the cooling nozzle 5 are used to spray water to cool the mixed flue gas after the first-stage oxidation.

Optionally, the deduster 10 is used to remove the flue gas absorbed in step (3) to obtain purified flue gas.

Compared with related technical solutions, this application has at least the following beneficial effects:

(1) This application uses the principle of cascade oxidation-absorption to achieve full absorption of nitrogen oxides in the case of lower ozone consumption, and control the production and absorption of N ₂ O ₅ in the absorption tower, which can be ₂ O _{5 is} quickly absorbed after it is generated, accelerating the reversible reaction of N ₂ O ₅ to the right, achieving efficient denitration of ozone under the premise of low consumption, and the NO _x removal efficiency can reach more than 85%, while avoiding ozone escape The problem of yellow smoke has strong applicability to sintering flue gas denitration.

(2) This application overcomes the problems of excessive ozone consumption and high original temperature of sintered flue gas in the related art, and there is no suitable temperature range for N ₂ O ₅ generation. By cooling the flue gas and performing three successive ozone Oxidation, while transferring the formation of N ₂ O ₅ from the flue to the in-situ oxidation-absorption in the absorption tower, reduces the amount of ozone, provides guarantee for efficient denitration, and has good economic benefits and application prospects.

BRIEF DESCRIPTION

1 is a schematic structural diagram of a sintered flue gas ozone cascade oxidation-absorption denitration system provided in Example 1 of the present application;

Among them, 1-ozone generator, 2-ozone distribution module, 3-level ozone distributor, 4-cooling water tank, 5-cooling nozzle, 6-level ozone distributor, 7-absorbing tower, 8-level ozone Distributor, 9-absorbent storage, 10-dust collector.

After reading and understanding the detailed description and drawings, other aspects can be understood.

detailed description

In order to better explain this application and facilitate the understanding of the technical solutions of this application, the following describes this application in further detail. However, the following embodiments are only simple examples of this application, and do not represent or limit the scope of protection of the rights of this application. The scope of protection of this application is subject to the claims.

In the specific implementation part of the present application, a sintered flue gas ozone cascade oxidation-absorption denitration system is provided. The system includes: an ozone generating device, an ozone distribution device, a flue gas cooling device and a flue gas absorption device, wherein the ozone The generating device includes an ozone generator 1, the flue gas absorption device includes an absorption tower 7, the ozone distribution device includes an ozone distribution module 2 and a first-level ozone distributor 3, a second-level ozone distributor 6 and three respectively connected thereto -Level ozone distributor 8, the first-level ozone distributor 3 and the second-level ozone distributor 6 are sequentially arranged on the sintered flue gas conveying pipeline connected to the absorption tower 7, and the flue gas cooling device is arranged on the first-level ozone distributor 3 On the flue gas transportation pipeline between the second-level ozone distributor 6, the third-level ozone distributor 8 is provided in the absorption tower 7, and the ozone generator 1 is connected to the ozone distribution module 2.

This application also provides a sintered flue gas ozone cascade oxidation-absorption denitration method in the specific implementation section. The method includes the following steps:

Optionally, the method is performed using the above-mentioned sintered flue gas ozone cascade oxidation-absorption denitration system.

Typical but non-limiting examples of this application are as follows:

Example 1

This embodiment provides a sintered flue gas ozone cascade oxidation-absorption denitration system. As shown in FIG. 1, the system includes an ozone generator 1, an ozone distribution module 2, a primary ozone distributor 3, and a secondary ozone distributor 6. Three-stage ozone distributor 8, cooling nozzle 5, cooling water tank 4, absorption tower 7, absorbent storage bin 9 and dust collector 10;

Wherein, the ozone generator 1 is connected to an ozone distribution module 2, and the ozone distribution module 2 is respectively connected to a first-level ozone distributor 3, a second-level ozone distributor 6 and a third-level ozone distributor 8, the first-level ozone The distributor 3 and the second-level ozone distributor 6 are sequentially provided on the sintered flue gas pipeline connected to the absorption tower 7 along the flue gas transport direction, and the third-level ozone distributor 8 is provided in the absorption tower 7;

The cooling nozzle 5 is provided on the flue gas pipeline between the first-level ozone distributor 3 and the second-level ozone distributor 6, and its inlet is connected to the outlet of the cooling water tank 4;

There are three feed layers in the absorption tower 7, the feed layer is connected to the absorbent storage silo 9, and the absorbent storage silo 9 is provided with a circulating material inlet, which is connected to the circulating material outlet provided at the lower part of the absorption tower 7; The outlet of the absorption tower 7 is connected to the inlet of the dust collector 10.

Example 2

This embodiment provides a sintering flue gas ozone cascade oxidation-absorption denitration method, which denitrates the flue gas of a 240m ² sintering machine, and the NO _x concentration in the flue gas is 350mg / m ^{3. The} method includes the following steps:

(1) fed to the flue gas duct into the sintering sintering flue gas, flue gas temperature of 155 deg.] C, while the sintering gas into an ozone feed line, a control ozone and NO _x in the flue gas sintering of The molar ratio is 0.5: 1, and the mixed flue gas after first-level oxidation is obtained;

(2) Step (1) mixing the flue gas after cooling to obtain an oxide 85 ℃, then mixed into the flue gas of ozone and secondary cooling, controlling the molar two ozone and NO _x in the original flue gas The ratio is 0.7: 1, and the resulting mixed flue gas is passed into the absorption tower for oxidation and absorption to obtain flue gas after secondary oxidation;

(3) Introduce tertiary ozone into the flue gas after secondary oxidation in the absorption tower, control the molar ratio of tertiary ozone to NO _x in the original flue gas to 0.2: 1, and further oxidize and absorb the flue gas, The absorbed flue gas is discharged outside the tower.

In this embodiment, the NO _x concentration in the purified flue gas is 36 mg / m ³ .

Example 3

This embodiment provides a sintering flue gas ozone cascade oxidation-absorption denitration method. The method uses the sintering flue gas ozone cascade oxidation-absorption denitration system provided in Example 1 to denitrate the 240 m ² sintering machine flue gas. The concentration of NO _x in the flue gas is 350 mg / m ³ .

It includes the following steps:

(1) The sintered flue gas is introduced into the sintered flue gas transportation pipeline at a temperature of 150 ° C. The ozone distribution module 2 is used to distribute the ozone generated in the ozone generator 1 to the primary ozone distributor 3, and then into the ozone stage sintering gas conveying pipe, a molar ratio of ozone to NO _x in the flue gas sintering is 0.9, to obtain a mixed oxide of the flue gas;

(2) Use the cooling water tank 4 and cooling nozzle 5 to spray water to cool the first-level oxidized mixed flue gas obtained in step (1), the flue gas temperature drops to 120 ℃, and then use the ozone distribution module 2 to distribute ozone to the second In the primary ozone distributor 6, the molar ratio of secondary ozone to NO _x in the original flue gas is controlled to be 0.2: 1. The secondary ozone and the temperature-reduced flue gas are mixed in the flue gas pipeline to pass the mixed flue gas into Oxidation and absorption in the circulating fluidized bed semi-dry absorption tower 7;

(3) Use the ozone distribution module 2 to distribute ozone to the second-level ozone distributor 8 and pass three-level ozone into the second-stage oxidized flue gas in the absorption tower 7 to control the third-level ozone and the original flue gas NO _x The molar ratio is 0.3: 1, the remaining NO _x in the absorption tower is further oxidized and absorbed, and the absorbed flue gas is discharged through the bag filter 10 and then discharged.

In this embodiment, the NO _x concentration in the purified flue gas is 35 mg / m ³ .

Example 4

This embodiment provides a sintered flue gas ozone cascade oxidation-absorption denitration method. The method is performed using the sintered flue gas ozone cascade oxidation-absorption denitration system provided in Example 1. The processing method is the same as that in Example 3. The difference is only that: the temperature of the sintered flue gas in step (1) is 160 ℃, the molar ratio of the first-level ozone to the NO _x in the original flue gas is 0.8: 1, and the temperature of the mixed flue gas in step (2) is reduced by water spray cooling It is 110 ℃, the molar ratio of second-level ozone to NO _x in the original flue gas is 0.3: 1, the absorption tower is a rotary spray drying semi-dry absorption tower, and the third-level ozone in step (3) and the NO _x in the original flue gas The molar ratio is 0.3: 1.

In this embodiment, the NO _x concentration in the purified flue gas is 38 mg / m ³ .

Example 5

This embodiment provides a sintered flue gas ozone cascade oxidation-absorption denitration method. The method is performed using the sintered flue gas ozone cascade oxidation-absorption denitration system provided in Example 1. The processing method is the same as that in Example 3. The difference is only that: the molar ratio of primary ozone in step (1) to NO _x in the original flue gas is 1: 1, and the temperature of the mixed flue gas after water cooling in step (2) is 90 ℃. original molar ratio of NO _x in the flue gas is 0.2, the wet method is a magnesium absorber tower, in step (3) the molar ratio of ozone in the three original NO _x in the flue gas is 0.1.

In this embodiment, the NO _x concentration in the purified flue gas is 32 mg / m ³ .

Example 6

This embodiment provides a sintered flue gas ozone cascade oxidation-absorption denitration method. The method is performed using the sintered flue gas ozone cascade oxidation-absorption denitration system provided in Example 1. The processing method is the same as that in Example 3. The difference is only that: the temperature of the sintered flue gas in step (1) is 130 ° C, the molar ratio of first-level ozone to NO _x in the original flue gas is 0.6: 1, and the temperature of the mixed flue gas in step (2) after water cooling is 80 ℃, molar ratio of the original two ozone NO _x in the flue gas is 0.8, the absorption column limestone - gYPSUM absorber, in step (3) with ozone in the three original NO _x in the flue gas The molar ratio is 0.1: 1.

In this embodiment, the NO _x concentration in the purified flue gas is 40 mg / m ³ .

Comparative Example 1

This comparative example provides a sintered flue gas ozone oxidation-absorption denitration system. The system is only provided with a single-stage ozone distributor, and the position is the same as that of the first-stage ozone distributor in Example 1. Other components The positions and positions are the same as in Example 1.

Ozone oxidation-absorption denitrification of sintered flue gas according to the following method:

(1) Pass sintered flue gas into the sintered flue gas pipeline, the temperature of the flue gas is 150 ℃, while using a single-stage ozone distributor to send ozone into the sintered flue gas pipeline, control ozone and NO in the sintered flue gas The molar ratio of _x is 1.2: 1, and the mixed flue gas after oxidation is obtained;

(2) The oxidized mixed flue gas obtained in step (1) is sprayed with water to lower the temperature, and the flue gas temperature is lowered to 120 ° C. The bag-type dust collector discharges the dust.

The total amount of ozone in this comparative example is the same as the total amount of ozone introduced in Example 4. The NO _x concentration in the purified flue gas is 120 mg / m ³ , of which the NO ₂ concentration is 75 mg / m ^{3. The} chimney has obvious yellow smoke. It can be seen that the single-stage ozone oxidation-absorption removal efficiency is obviously low, and yellow smoke cannot be effectively controlled.

The applicant declares that the present application describes the detailed structural features of the present application through the above-mentioned embodiments, but the present application is not limited to the detailed structural features described above, that does not mean that the present application must rely on the detailed structural features to implement.

The optional embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above embodiments.

In addition, it should be noted that the specific technical features described in the above specific embodiments can be combined in any suitable manner without contradictions. In order to avoid unnecessary repetition, this application The combination method will not be explained separately.

In addition, various combinations of various embodiments of the present application may also be performed.

Claims

A sintered flue gas ozone cascade oxidation-absorption denitration system, wherein the system includes: an ozone generating device, an ozone distribution device, a flue gas cooling device and a flue gas absorption device;

The ozone generating device includes an ozone generator (1), and the flue gas absorption device includes an absorption tower (7),

The ozone distribution device includes an ozone distribution module (2) and a first-level ozone distributor (3), a second-level ozone distributor (6) and a third-level ozone distributor (8) respectively connected to the first-level ozone The distributor (3) and the secondary ozone distributor (6) are sequentially arranged on the sintered flue gas conveying pipeline connected to the absorption tower (7), and the flue gas cooling device is disposed on the primary ozone distributor (3) and the secondary On the flue gas delivery pipeline between the ozone distributor (6), the three-stage ozone distributor (8) is provided in the absorption tower (7), and the ozone generator (1) is connected to the ozone distribution module (2) .
The system according to claim 1, wherein the flue gas cooling device includes a cooling water tank (4) and a cooling nozzle (5), and the outlet of the cooling water tank (4) is connected to the inlet of the cooling nozzle (5).
The system according to claim 1 or 2, wherein the system is further provided with a dust collector (10), the flue gas inlet of the dust collector (10) is connected to the gas outlet of the absorption tower (7).
The system according to any one of claims 1-3, wherein the system is further provided with an absorbent storage silo (9), the outlet of the absorbent storage silo (9) and the feed in the absorption tower (7) Entrance connection of the floor;

Optionally, the absorbent storage warehouse (9) is provided with a circulating material inlet, which is connected to the circulating material outlet provided at the lower part of the absorption tower (7);

Optionally, a feed layer is provided in the absorption tower (7).
A sintered flue gas ozone cascade oxidation-absorption denitration method, wherein the method includes the following steps:

(1) Inject sintered flue gas into the sintered flue gas transmission pipeline, and at the same time send first-level ozone into the sintered flue gas transmission pipeline to obtain the mixed flue gas after first-level oxidation;

(2) The first-stage oxidized mixed flue gas obtained in step (1) is cooled, and then the second-stage ozone is mixed with the cooled flue gas, and the obtained mixed flue gas is passed into an absorption tower for oxidation and absorption, Get flue gas after secondary oxidation;

(3) The third-stage ozone is passed into the second-stage oxidized flue gas in the absorption tower to further oxidize and absorb the flue gas, and the absorbed flue gas is discharged out of the tower.
The molar ratio of the method as claimed in claim 5, wherein, in step (1) an ozone and NO x in the sintering gas is (0.4 to 1.8) to 1.
The method according to claim 5 or 6, wherein the cooling method in step (2) is water spray cooling.
The method according to any one of claims 5-7, wherein step (1) a molar ratio of ozone to NO x in the flue gas sintering is (0.6-1.0) to 1;

Optionally, the temperature of the flue gas in step (1) is 130-180 ° C, optionally 130-160 ° C;

Optionally, the temperature of the mixed flue gas after the temperature reduction in step (2) is 80-129 ° C, optionally 90-110 ° C;

Optionally molar ratio, the step (2) with two ozone in step (1) into the flue gas of the sintering of the NO x (0.1-1.0) to 1, optionally (0.1-0.8): 1;

Molar ratio Optionally, step (3) and the three ozone step (1) into the flue gas of the sintering of the NO x (0.1-0.5) to 1, optionally (0.1-0.4) to 1;

Optionally, the method further includes: using a dust collector to remove the flue gas absorbed in the step (3) to obtain purified flue gas;

Optionally, when the absorption tower is a semi-dry absorption tower, the dust collector is a bag-type dust collector, and when the absorption tower is a wet absorption tower, the dust collector is a wet electric dust collector;

Alternatively, the flue gas purifying NO x in the content of less than 50mg / m 3.
The method according to any one of claims 5-8, wherein using the system according to any one of claims 1-4 to perform ozone cascade oxidation and absorption denitrification of sintering flue gas, the method includes the following steps:

(1) The sintered flue gas is introduced into the sintered flue gas transmission pipeline, and at the same time, the ozone distribution module (2) is used to distribute the ozone generated in the ozone generator (1) to the first-level ozone distributor (3). The first-level ozone is sent into the sintered flue gas pipeline to obtain the first-level oxidized mixed flue gas;

(2) Use the flue gas cooling device to cool the first-level oxidized mixed flue gas obtained in step (1), and then use the ozone distribution module (2) to distribute ozone to the second-level ozone distributor (6) and pass The second-level ozone is mixed with the flue gas after cooling, and the resulting mixed flue gas is passed into an absorption tower (7) for oxidation and absorption to obtain the second-level oxidized flue gas;

(3) Use the ozone distribution module (2) to distribute the ozone to the secondary ozone distributor (8), and pass the tertiary ozone into the flue gas after secondary oxidation in the absorption tower (7) to further promote the flue gas After oxidation and absorption, the flue gas will be discharged out of the tower.
The method according to claim 9, wherein in step (2), the cooling water tank (4) and the cooling nozzle (5) are used to spray water to cool the mixed flue gas after the first-stage oxidation;

Optionally, a dust remover (10) is used to remove the flue gas absorbed in step (3) to obtain purified flue gas.