Flue gas purification process and system for synergistically removing multiple pollutants

Abstract

An existing sintering flue gas treatment process additionally provided with a CO removal device is improved, the flue gas purification process and system for synergistically removing multiple pollutants are provided, SO2, NOx, dust and CO are efficiently removed, pollutants such as SO3, HCl, HF and heavy metal can be efficiently and synergistically removed, long-term stable operation of a CO catalyst can be ensured, and the service life of the flue gas purification system is prolonged. And meanwhile, the system stability under different CO concentration fluctuations can be adapted, the CO device can be ensured to operate in a high-efficiency state for a long time, and meanwhile, the effects of saving energy and reducing carbon are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas purification, environmental protection technology and environmental protection equipment, and specifically relates to a flue gas purification technology and system for the coordinated removal of multiple pollutants. Background Art

[0002] Sintering is the largest air pollutant emission process in steel enterprises. In addition to containing a large amount of dust, SO 2 In addition to NOx, it also contains SO 3 , HCl, HF, heavy metals, dioxins, CO and many other pollutants. At present, the treatment of sintering flue gas mainly focuses on dust, SO 2 , NOx, dust in sintering exhaust gas, SO 2 , NOx has been significantly reduced, but other pollutants have not been effectively controlled, especially CO, which is still very high, with its original concentration generally reaching 5000-12000 mg / Nm 3 , CO not only directly harms human health, but also reacts photochemically with non-methane hydrocarbons and NOx in the atmosphere to form chemical smog, which is very unfavorable to the improvement of air quality. Since 2018, many places in China have successively issued relevant policy documents, requiring the implementation of CO governance work in the steel industry. In recent years, the relevant CO control indicators have become increasingly stringent.

[0003] At present, the most feasible technology for efficient removal of CO from sintering flue gas is CO catalytic oxidation technology. CO catalytic oxidation can achieve high-efficiency CO removal. At the same time, CO oxidation can release heat and increase the flue gas temperature, which is conducive to reducing the heating energy consumption of sintering flue gas denitrification, thereby achieving energy saving and carbon reduction. However, CO catalysts are mainly precious metal catalysts, which are expensive and relatively active, and are easily affected by SO in the flue gas. 2 、SO 3 The CO catalyst is deactivated due to the influence of HCl, HF, heavy metals and fine dust. Frequent replacement of expensive CO catalyst during process operation will greatly increase operating costs.

[0004] At present, the typical process flow of adding CO removal device to the more mature sintering flue gas treatment process is to simply embed CO removal into the flue gas desulfurization, denitrification and dust removal device. Figure 1, is a typical sintering flue gas process flow chart with a CO removal device. The sintering flue gas first passes through the front-end desulfurization and dust removal, and then enters the post-sintering SCR denitrification embedded with a CO removal device. After the flue gas is heated by GGH heat exchange, it passes through the CO removal device for CO removal. At the same time, the flue gas is heated and then enters the SCR denitrification reactor for denitrification reaction. The flue gas after NOx removal is recovered by GGH heat and then discharged into the chimney through the induced draft fan. Before the CO removal device, a heating device for burning coal gas is set to adjust the SCR reaction temperature and the temperature rise during the startup period.

[0005] The desulfurization process in the existing sintering flue gas treatment process has a significant impact on SO 2 It has high removal capacity, although it can also remove SO to a certain extent. 3 , HCl, HF and other acidic gases, but the reactions between the acidic gases and the alkaline absorbents are in a competitive relationship. 2 The concentration is generally much higher than other acid gases, which can easily lead to SO 3 The removal of acidic gases such as SO is not complete. It is difficult to efficiently and synergistically remove SO in the existing sintering flue gas treatment process. 3 , HCl, HF, heavy metals and other pollutants, the remaining SO 3 and heavy metals will affect the stability of subsequent CO catalysts. Summary of the invention

[0006] Based on the above technical status, the present invention improves the existing sintering flue gas treatment process with an additional CO removal device, and provides a flue gas purification process and system for the coordinated removal of multiple pollutants. 2 , NOx, dust, CO, and SO 3 , HCl, HF, heavy metals and other pollutants, which can ensure the long-term stable operation of the CO catalyst, and at the same time can adapt to the stability of the system under different CO concentration fluctuations, ensuring that the CO device can operate in a high-efficiency state for a long time, while playing a role in energy saving and carbon reduction.

[0007] The technical solution adopted by the present invention is as follows: a flue gas purification process for collaborative removal of multiple pollutants, comprising the following steps:

[0008] S1: Control the sintering flue gas temperature to not less than 120℃, first spray absorbent 1 to mix with the sintering flue gas for deacidification. This step focuses on removing SO 3 , HCl, HF and other acidic gases;

[0009] S2: After step S1, water is sprayed into the flue gas to control the flue gas temperature to 70℃~100℃, and absorbent 2 is sprayed into the flue gas to mix with the flue gas, and deacidification and heavy metal removal are performed again. This step can effectively remove SO in the flue gas. 2gas;

[0010] S3: performing dust removal treatment on the flue gas after the reaction and adsorption in step S2, separating the dust and the remaining absorbent 2 and / or absorbent 1 in the flue gas, and the ash containing the remaining absorbent can be further circulated and reacted in the circulating fluidized bed absorber through material circulation, so as to fully utilize the absorbent, and then discharged;

[0011] S4: heating the separated flue gas to raise its temperature, and after the flue gas temperature rises to meet the requirements of the carbon monoxide catalytic oxidation treatment process, catalytic oxidation removal of CO is performed;

[0012] S5: Use SCR denitrification equipment to denitrify flue gas.

[0013] In the above step S1, the absorbent is Ca(OH) 2 Calcium-based absorbents with a content of ≥85%, and Ca(OH) 2 The specific surface area of ​​the particles is ≥30m 2 / g, particle size (D50) ≤ 10mm; control the calcium-sulfur ratio between 2 and 6, and the flue gas residence time between 1 and 3 seconds.

[0014] In the above step S2, the absorbent 2 is Ca(OH) 2 Calcium-based absorbents with a content of ≥75%, and Ca(OH) 2 The specific surface area of ​​the particles is ≥18m 2 / g, particle size (D50) ≤ 50mm; control the calcium-sulfur ratio between 1.4 and 2.2. In step S2, the SO 2 In order to improve the removal effect of heavy metals, activated carbon is used to adsorb the flue gas after the second purification by the absorbent.

[0015] By adopting the above process of the present invention, the absorbent is carefully selected, and the temperature and timing of adding different absorbents to the process are controlled, so that SO contained in the flue gas can be effectively avoided. 2 and SO 3 The competitive relationship between the reaction with the absorbent, the influence of temperature on the properties of acidic gases, and the choice of absorbent are used to remove SO 3 and SO 2 , solved on SO 3 Effect of residue on subsequent CO catalyst activity.

[0016] In the above step S4, the heat energy of the flue gas after the denitration treatment in step S5 is used to exchange heat with the flue gas separated in step S3 to increase the temperature, and then a heating device is selectively used to supplement the flue gas temperature increase, so that the flue gas temperature is increased to meet the requirements.

[0017] Before the flue gas after denitration treatment in step S5 is heat exchanged with the flue gas separated in step S3, it is possible to introduce outside air into the flue to pre-cool the flue gas after denitration treatment according to the temperature requirements of the heat exchanger used and the actual temperature of the flue gas.

[0018] The present invention also claims protection for a flue gas purification system for collaborative removal of multiple pollutants, which is used to operate the above-mentioned flue gas purification process for collaborative removal of multiple pollutants, and is characterized in that:

[0019] It includes a high-temperature conveying bed deacidification reactor, a circulating fluidized bed absorption tower, a bag filter, a heating section of a GGH heat exchanger, a flue gas heating device, a carbon monoxide reactor, an SCR reactor, a cooling section of a GGH heat exchanger, an induced draft fan and a chimney which are sequentially connected through a flue.

[0020] The absorbent is sprayed into the high-temperature transport bed deacidification reactor for the first stage of deacidification treatment to mainly remove SO in the flue gas. 3 , HCl, HF and other acidic gases; water and absorbent are sprayed into the circulating fluidized bed absorber for the second stage of deacidification treatment to further remove SO in the flue gas 2 The circulating fluidized bed absorption tower is equipped with an independently detachable activated carbon adding device. According to the removal effect of heavy metals in the flue gas, it is selected to use or not to use activated carbon to re-adsorb the flue gas after the second purification by the absorbent.

[0021] The flue gas heating device is a multi-stage wide load flue gas heating device, which includes at least one high load burner and at least one low load burner, and the maximum heating power ratio of the high load burner and the low load burner is not less than 2; the high load burner and the low load burner are both equipped with flow regulating valves to achieve adjustable power.

[0022] Furthermore, an air mixing and cooling device is installed between the SCR reactor and the GGH heat exchanger, and the air mixing and cooling device includes an air mixing and regulating damper and a smoke temperature mixer. The smoke temperature mixer is a grid structure in which a plurality of horizontal tubes and a plurality of vertical tubes are arranged at intervals, and small holes are evenly distributed on the horizontal tubes and the vertical tubes; the smoke temperature mixer is arranged inside the flue and is connected to the outside of the flue through a pipeline, and the air mixing and regulating damper controls the opening size of the pipeline.

[0023] The advantages of the technical solution of the present invention are:

[0024] 1. Differentiate the deacidification space with high-quality calcium-based composite absorbent and the deacidification space with conventional calcium-based absorbent, and control the flue gas temperature entering the two deacidification spaces. Through the different settings of temperature and removal environment, SO is removed in a targeted manner. 2 and SO 3 , avoiding SO 3The retention of CO affects the stability of the CO catalyst. 2 , NOx, dust, CO removal, SO 3 , HCl, HF and heavy metal multi-pollutant removal device, especially SO 2 and SO 3 The synergistic removal of CO can protect the CO catalyst from the remaining SO 3 Influence and inactivation.

[0025] 2. Another outstanding advantage of the process method provided by the patent of the present invention is that its energy consumption has been significantly reduced compared with the prior art. A multi-stage wide-load flue gas heating device is set in the process, and at least one large and one small two-stage heating device is designed to consider that during the low flue gas temperature heating stage at startup, all heating furnaces are turned on at the same time to quickly heat up; when the CO concentration is high during normal operation, only the small heating device is turned on. At the same time, in order to further expand the adjustability, the regulating valve of the small heating device is matched with one large and one small two-stage; the heating load can be flexibly adjusted to a large extent according to the changes in CO concentration and flue gas temperature, which can meet the heating needs of flue gas temperature adjustment. The adjustable range of the heating load is 5% to 100%, while the adjustable range of the heating load in the prior art is generally 15 to 100%. When the CO concentration is high, the load is operated as low as possible, which can save more than 10% of the heating gas energy consumption compared with the prior art.

[0026] 3. When the CO concentration is too high, the oxidation heat release is too large, resulting in too high smoke temperature, which may cause the GGH heat exchanger to expand too much due to heat and get stuck, affecting the stable operation of the system. In the present invention, an air mixing and cooling device is arranged at the denitrification outlet and the GGH cooling side inlet. The air mixing and cooling device mainly includes an adjusting damper outside the flue and a high-efficiency smoke temperature mixer in the flue. The system negative pressure is used to appropriately mix cold air according to requirements. At the same time, the high-efficiency smoke temperature mixer is used to ensure uniform smoke temperature mixing and ensure that the GGH will not get stuck at high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a typical process flow chart of adding a CO removal device to sintering flue gas in the prior art;

[0028] Figure 2 This is a process flow chart of the synergistic removal of multiple pollutants and energy saving and carbon reduction of the present invention;

[0029] Figure 3 It is a structural schematic diagram of a specific embodiment of the air mixing and cooling device in the present invention;

[0030] In the figure: 1-high temperature conveying bed deacidification reactor; 2-circulating fluidized bed absorber; 3-bag filter; 4-GGH heat exchanger; 5-multi-stage wide load flue gas heating device; 6-carbon monoxide reactor; 7-SCR reactor; 8-air mixing and cooling device; 9-induced draft fan; 101-absorbent 1; 201-absorbent 2; 202-water; 203-activated carbon; 801-air mixing and regulating damper; 802-smoke temperature mixer. DETAILED DESCRIPTION

[0031] The technical scheme of the present invention is clearly and completely described below with specific embodiments. It should be understood that the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention. Unless otherwise defined, all professional and scientific terms used in the text have the same meanings as those familiar to those skilled in the art.

[0032] Figure 2 This is a process flow chart of the synergistic removal of multiple pollutants and energy saving and carbon reduction of the present invention, see Figure 2 The multi-pollutant synergistic removal and energy-saving carbon reduction process of the present invention comprises a high-temperature conveying bed deacidification reactor 1, a circulating fluidized bed absorption tower 2, a bag filter 3, a GGH heat exchanger 4, a multi-stage wide-load flue gas heating device 5, a carbon monoxide reactor 6, an SCR reactor 7, an air mixing cooling device 8, a GGH heat exchanger 4, and an induced draft fan 9, which are connected in sequence. The induced draft fan 9 draws the cooled flue gas to the chimney for discharge.

[0033] The absorbent 101 is arranged inside the high-temperature conveyor bed deacidification reactor 1, or the absorbent 101 powder is sprayed into the flue gas when it flows through the high-temperature conveyor bed deacidification reactor 1, and the incoming sintering flue gas is deacidified and purified by dry absorption method to remove SO in the flue gas. 3 , HCl, HF and other acidic gases, absorbent 101 uses high-quality calcium-based composite absorbent to achieve the SO required by the process of the present invention. 2 and SO 3 The effect of synergistic and efficient removal, absorbent 101 requires Ca(OH) 2 Content ≥85%, specific surface area ≥30m 2 / g, particle size (D50) ≤ 10mm, and the calcium-sulfur ratio of the absorbent 101 in the high-temperature transport bed deacidification reactor is controlled between 2 and 6, and the flue gas residence time is 1 to 3 seconds. The absorbent 201 is added to the front end of the circulating fluidized bed absorber 2, and water 202 is sprayed in at the same time to cool the flue gas and perform secondary purification, and SO 2 and heavy metal removal, absorbent 201 is a conventional calcium-based absorbent, such as Ca(OH) 2Content ≥75%, specific surface area ≥18m 2 / g, particle size (D50) ≤ 50mm, the calcium sulfur ratio is preferably between 1.4 and 2.2. According to needs, the circulating fluidized bed absorber 2 is selectively provided with activated carbon 203 at the rear end to ensure that the comprehensive removal capacity of heavy metals in the flue gas is above 95%.

[0034] The multi-stage wide load flue gas heating device 5 is used to continue heating the flue gas after the temperature rises through the GGH heat exchanger 4, so that it meets the temperature requirement of the carbon monoxide reactor 6. The air mixing and cooling device 8 introduces external cold air by adjusting the valve opening size, and mixes with the flue gas to achieve rapid and uniform cooling.

[0035] The sintering flue gas is generally at 120-180℃. It is first introduced into the high-temperature conveyor bed deacidification reactor 1, and then the SO in the flue gas is removed by the absorbent 101. 3 , HCl, HF and other acidic gases are efficiently removed; then the flue gas continues to enter the circulating fluidized bed absorber 2, where water is sprayed inside the circulating fluidized bed absorber 2 to cool it down and the SO in the flue gas is removed by the absorbent 201 2 To remove heavy metals and adsorption, an independent detachable component containing activated carbon 203 can be installed inside the circulating fluidized bed absorber 2. According to the needs of sampling and testing, the flue gas can be selected to continue to pass through the activated carbon 203 for adsorption or directly discharged into the subsequent bag filter 3. The activated carbon 203 is used to ensure that the comprehensive removal effect of heavy metals in the flue gas reaches more than 95%. The flue gas after desulfurization is removed by the bag filter 3, and the dust in the flue gas at the outlet of the bag filter 3 is controlled to be less than 5mg / Nm 3 A material circulation path is provided between the bag filter 3 and the circulating fluidized bed absorber 2 to facilitate the separated dust containing absorbent 1 and / or absorbent 2 to return to the inside of the circulating fluidized bed absorber 2.

[0036] The GGH heat exchanger 4 realizes heat exchange between the desulfurized low-temperature flue gas discharged from the bag filter 3 and the denitrified high-temperature flue gas discharged from the SCR reactor 7 , thereby increasing the flue gas temperature and reducing the heating energy consumption of the multi-stage wide-load flue gas heating device 5 .

[0037] After the flue gas temperature rises to meet the CO removal requirements, it enters the carbon monoxide reactor 6, where the CO is catalytically oxidized to CO by the catalyst. 2 , to remove CO, and the CO reaction releases heat to heat the flue gas, generally removing 1000mg / Nm 3CO can heat the flue gas to about 7.3°C. While achieving CO removal, it can reduce the heating gas required to meet the temperature requirements of the back-end SCR denitrification, which plays a role in energy saving and carbon reduction. In addition, detection nodes can be set at the inlet and outlet of the carbon monoxide reactor 6. Through the temperature fluctuation of the flue gas before and after passing through the carbon monoxide reactor 6, the CO catalyst activity can be monitored in real time and the CO concentration in the flue gas can be judged. In addition, the working load of the multi-stage wide load flue gas heating device 5 can be adjusted according to the temperature fluctuation to ensure that the flue gas temperature meets the subsequent denitrification temperature requirements. Preferably, the multi-stage wide load flue gas heating device 5 generally includes at least one high and one low burner with different loads, and the maximum heating power ratio of the high-load burner and the low-load burner is not less than 2; when the flue gas temperature is low at startup, the CO denitrification efficiency is low, and a large amount of reaction heat cannot be provided to meet the subsequent denitrification temperature requirements. All burners of the multi-stage wide load flue gas heating device 5 are turned on to meet the rapid heating requirements; when the flue gas temperature meets the design temperature requirements of CO denitrification, the high-load burner is turned off and only the low-load burner is turned on. Normal operation only needs to control the load of the small-load burner to adapt to the temperature control requirements of different CO concentration fluctuations. In order to further increase the adjustable range, the burner is configured with two sets of regulating valves, one large and one small, to adjust and control the total heating load in the adjustable range of 5% to 100%.

[0038] After CO is removed, the flue gas enters the SCR reactor 7, and NOx in the flue gas is removed by the injected ammonia under the action of the catalyst in the SCR reactor. The temperature of the SCR denitrification catalyst is preferably a medium-high temperature SCR denitrification catalyst, and the design temperature range is 280-400°C.

[0039] The high-temperature flue gas after denitration enters the GGH heat exchanger 4 to exchange heat with the low-temperature flue gas after dust removal in the previous process. At the same time, the high-temperature flue gas after denitration can selectively pass through the air mixing and cooling device 8 connected between the outlet of the SCR reactor 7 and the inlet of the GGH heat exchanger 4. Since the flue is a high negative pressure system, the valve opening of the air mixing and cooling device 8 can be adjusted to inhale external cold air, so as to achieve rapid mixing and uniform cooling of the flue gas and the cold air, and control the heat exchange effect of the GGH heat exchanger 4 within the range required by the working conditions to meet the stable operation of the system. The outlet flue gas of the GGH heat exchanger after flue gas purification is then discharged to the chimney through the induced draft fan 9. At the same time, a circulation loop is also set between the outlet of the induced draft fan 9 and the circulating fluidized bed absorber 2. When the load is low, the flue gas circulation loop can be used to supplement the flue gas to ensure that the flue gas entering the circulating fluidized bed absorber 2 meets the minimum flow rate for the stable operation of its bed layer, and adapt to the requirements of different working loads.

[0040] Figure 3It is a structural schematic diagram of a specific embodiment of the air mixing and cooling device in the present invention. An air mixing and cooling damper 801 is arranged outside the flue between the outlet of the SCR reactor 7 and the inlet of the GGH heat exchanger 4. The air mixing and cooling damper 801 is connected to a plurality of branch pipes via a pipeline. The branch pipes are connected to a grid-type flue gas temperature mixer 802 installed inside the flue. The flue gas temperature mixer 802 is a grid-type structure in which a plurality of horizontal pipes and a plurality of vertical pipes are arranged at intervals. Small holes are evenly arranged on the flue gas temperature mixer 802 so that negative pressure is used to suck external cold air into the flue when the air mixing and cooling damper 801 is opened.

[0041] The following is an introduction to the process of this patent in combination with the actual engineering projects we have carried out based on this patent technology. 2 The sintering machine has successfully applied this patented technology (internal application, not disclosed to the public): the sintering flue gas volume is ~1300000Nm 3 / h (standard condition), flue gas temperature is about 150℃, SO 2 Concentration 2000mg / Nm 3 、NOx concentration is 350mg / Nm 3 、CO concentration is ~6000mg / Nm 3 , Dust: 50mg / Nm 3 、SO 3 Concentration about 90mg / Nm 3 、HCl about 8mg / Nm 3 , HF about 5mg / Nm 3 The patent is used for flue gas treatment. During normal operation, the sintering flue gas first enters the high-temperature conveyor bed deacidification reactor 1, and by adding absorbent 101, the calcium-sulfur ratio is 5, and the flue gas reaction shutdown time is 1.5S, the SO 3 , HCl, HF, and export SO 3 Concentration<2mg / Nm 3 、HCl<0.8mg / Nm 3 HF<0.5mg / Nm 3 The deacidified flue gas enters the circulating fluidized bed absorber 2, where water 202 and absorbent 201 are added. The calcium-sulfur ratio is 1.6, and the reaction temperature is controlled at 80-90°C. The SO in the flue gas 2 The newly added absorbent 201 and the remaining absorbent 2 in the bag circulation material react to achieve the export SO 2 Concentration<15mg / Nm 3 ; Adding activated carbon 203, the comprehensive removal efficiency of heavy metal mercury, lead and its compounds reaches 95%. After the flue gas after desulfurization is filtered by bag dust collector, the outlet dust concentration is less than 5mg / Nm 3The flue gas temperature after dust removal is 80-90℃, and it exchanges heat with GGH heat exchanger 4. At the same time, the low-load burner of the flue gas heating device operates at a low load of 5%. The flue gas temperature entering the carbon monoxide reactor is about 270℃. After passing through the carbon monoxide reactor, the outlet CO concentration is less than 1500mg / Nm 3 The flue gas temperature reaches about 300℃, and then enters the SCR reactor 7 to remove NOx in the flue gas to <30mg / Nm 3 The high-temperature flue gas after denitration enters the GGH heat exchanger and exchanges heat with the flue gas after dust removal, and the flue gas temperature is reduced to 130-140°C, and then discharged to the chimney through the induced draft fan 9. When the CO concentration in the flue gas decreases and the temperature entering the SCR reactor is lower than 280°C, the heating load of the flue gas heating device is increased to ensure that the denitration temperature is not lower than 280°C. At the same time, the CO concentration in the flue gas under certain working conditions reaches 10000mg / Nm 3 , the heat release of CO increases, and the flue gas temperature at the outlet of the carbon monoxide reactor reaches 330℃, which exceeds the maximum temperature of 320℃ allowed by the design of the GGH heat exchanger of this project. The air mixing and cooling regulating valve of the air mixing and cooling device is quickly opened to cool the flue gas entering the GGH heat exchanger after denitrification to below 320℃, ensuring the safe and stable operation of the system.

[0042] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A flue gas purification process for synergistic removal of multiple pollutants, comprising the following steps: S1: Control the sintering flue gas temperature to not less than 120℃, spray absorbent 1 to mix with the sintering flue gas for deacidification; S2: spraying water into the flue gas after step S1 to control the flue gas temperature to 70°C to 100°C, and spraying absorbent 2 to mix with the flue gas to perform deacidification and heavy metal removal again; S3: performing dust removal treatment on the flue gas after the reaction and adsorption in step S2 to remove dust in the flue gas; S4: The flue gas after dust removal is heated by heat exchange, and after the flue gas temperature rises to meet the requirements of the carbon monoxide catalytic oxidation treatment process, CO is removed by catalytic oxidation; S5: Use SCR denitrification equipment to denitrify flue gas.

2. The process according to claim 1, further characterized in that: In step S1, the absorbent 1 is a calcium-based absorbent with a Ca(OH)2 content of ≥85%, and the specific surface area of ​​the Ca(OH)2 particles is ≥30m 2 / g, median particle size ≤10mm; control the calcium-sulfur ratio between 2 and 6, and the flue gas residence time between 1 and 3 seconds.

3. The process according to claim 1 or 2, further characterized in that: In step S2, the absorbent 2 is a calcium-based absorbent with a Ca(OH)2 content of ≥75%, and the specific surface area of ​​the Ca(OH)2 particles is ≥18m 2 / g, median particle size ≤50mm; control the calcium-sulfur ratio between 1.4 and 2.

2.

4. The process according to claim 3, further characterized in that: In step S2, activated carbon is used to adsorb the flue gas purified by the second absorbent again to further remove heavy metals in the flue gas.

5. The process according to claim 1, further characterized in that: In step S4, the heat energy of the flue gas after the denitration treatment in step S5 is used to exchange heat with the flue gas separated in step S3 to increase the temperature, and then a heating device is selectively used to supplement the flue gas temperature increase, so that the flue gas temperature is increased to meet the requirements.

6. The process according to claim 5, further characterized in that: Before the flue gas after the denitration treatment in step S5 is heat exchanged with the flue gas separated in step S3, if the flue gas temperature is too high, outside air can be introduced into the flue to pre-cool the flue gas after the denitration treatment.

7. A flue gas purification system for collaborative removal of multiple pollutants, used for operating the flue gas purification process for collaborative removal of multiple pollutants according to any one of claims 1 to 6, characterized in that: The invention comprises a high-temperature conveying bed deacidification reactor (1), a circulating fluidized bed absorption tower (2), a bag filter (3), a temperature rising section of a GGH heat exchanger (4), a flue gas heating device, a carbon monoxide reactor (6), an SCR reactor (7), a temperature falling section of a GGH heat exchanger (4), an induced draft fan (9) and a chimney, which are sequentially connected through a flue.

8. The system according to claim 7, further characterized in that: The high-temperature transport bed deacidification reactor (1) is sprayed with absorbent 1; the circulating fluidized bed absorber (2) is sprayed with water and absorbent 2, and the circulating fluidized bed absorber (2) is equipped with an independently detachable activated carbon adding device.

9. The system according to claim 7, further characterized in that: The flue gas heating device is a multi-stage wide load flue gas heating device (5), which comprises at least one high load burner and at least one low load burner, wherein the maximum heating power ratio of the high load burner and the low load burner is not less than 2; the high load burner and the low load burner are both equipped with flow regulating valves to achieve power adjustability.

10. The system according to claim 7 or 9, further characterized in that: An air mixing and cooling device (8) is also installed between the SCR reactor (7) and the GGH heat exchanger (4), the air mixing and cooling device (8) comprising an air mixing and regulating damper (801) and a smoke temperature mixer (802), the smoke temperature mixer (802) being a grid structure in which a plurality of horizontal tubes and a plurality of vertical tubes are arranged at intervals, and small holes are evenly distributed on the horizontal tubes and the vertical tubes; the smoke temperature mixer (802) is arranged inside the flue and is connected to the outside of the flue through a pipeline, and the air mixing and regulating damper (801) controls the opening size of the pipeline.

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