Flue gas purification process and system for synergistically removing multiple pollutants

Abstract

The present invention belongs to the technical fields of flue gas purification treatments, environmental protection processes, and environmental protection equipment. The present invention improves the existing sintering flue gas treatment process in which a CO removal device is additionally provided, and provides a flue gas purification process and system for synergistically removing multiple pollutants. The flue gas purification process and system for synergistically removing multiple pollutants provided in the present invention not only efficiently remove SO2, NOx, dust and CO, but can also efficiently and synergistically remove pollutants such as SO3, HCl, HF and heavy metals, and can ensure long-term stable operation of a CO catalyst. Moreover, the present invention can adapt to fluctuations in different CO concentrations, thereby achieving a stable system, can keep the CO removal device operating in a long-time and high-efficiency operating state, and also has the functions of saving energy and carbon reduction.

Description

A flue gas purification process and system for synergistic removal of multiple pollutants

[0001] Cross-reference of related applications

[0002] This invention claims priority to Chinese Patent Application No. 2024119524712, filed with the Chinese Patent Office on December 27, 2024, entitled "A Flue Gas Purification Process and System for Synergistic Removal of Multiple Pollutants", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention belongs to the technical fields of flue gas purification treatment, environmental protection technology, and environmental protection equipment, and specifically relates to a flue gas purification process and system for the synergistic removal of multiple pollutants. Background Technology

[0004] Sintering is the largest air pollutant emission process in steel enterprises. Besides large amounts of dust, SO2, and NOx, it also contains numerous other pollutants such as SO3, HCl, HF, heavy metals, dioxins, and CO. Currently, the treatment of sintering flue gas mainly focuses on the three major pollutants: dust, SO2, and NOx. While dust, SO2, and NOx emissions from sintering have been significantly reduced, other pollutants have not been effectively controlled, especially CO, whose concentration remains very high, typically reaching 5000–12000 mg / Nm³. 3 CO not only directly harms human health, but also undergoes photochemical reactions with non-methane hydrocarbons and NOx in the atmosphere to form chemical smog, which is extremely detrimental to improving air quality. Since 2018, many regions in China have successively issued relevant policy documents requiring the implementation of CO control measures in the steel industry, and in recent years, relevant CO control indicators have become increasingly stringent.

[0005] Currently, the most feasible technology for efficient CO removal from sintering flue gas is CO catalytic oxidation. CO catalytic oxidation achieves high-efficiency CO removal, and simultaneously releases heat, increasing the flue gas temperature, which helps reduce the energy consumption for denitrification heating in sintering flue gas, thus achieving energy saving and carbon reduction. However, CO catalysts are mainly precious metal catalysts, which are expensive and highly reactive, easily deactivated by SO2, SO3, HCl, HF, heavy metals, and fine dust in the flue gas. Frequent replacement of expensive CO catalysts during process operation significantly increases operating costs.

[0006] Currently, a typical process flow for adding a CO removal device to a relatively mature sintering flue gas treatment process involves simply embedding the CO removal device into the flue gas desulfurization, denitrification, and dust removal unit. Figure 1 shows a typical process flow diagram for adding a CO removal device to sintering flue gas. The sintering flue gas first passes through the front-end desulfurization and dust removal system, then enters the post-sintering SCR denitrification reactor with the embedded CO removal device. After the flue gas is heated by the gas-fired heat exchanger (GGH), it passes through the CO removal device for CO removal. Simultaneously, the flue gas is heated again before entering the SCR denitrification reactor for the denitrification reaction. The flue gas after NOx removal is discharged through the chimney via an induced draft fan after heat recovery by the GGH. A gas-fired heating device is installed before the CO removal device to adjust the SCR reaction temperature and meet the temperature rise requirements during start-up.

[0007] Existing sintering flue gas treatment processes have a high SO2 removal capacity during desulfurization. While they can also remove acidic gases such as SO3, HCl, and HF to some extent, the reactions between these acidic gases and the alkaline absorbent are competitive. The SO2 concentration in sintering flue gas is generally much higher than that of other acidic gases, and this competition can easily lead to incomplete removal of SO3 and other acidic gases. Furthermore, existing sintering flue gas treatment processes struggle to efficiently and synergistically remove pollutants such as SO3, HCl, HF, and heavy metals. The remaining SO3 and heavy metals can affect the stability of subsequent CO catalysts. Summary of the Invention

[0008] Based on the above-mentioned technological status, this invention improves the existing sintering flue gas treatment process that adds a CO removal device, and provides a flue gas purification process and system for the synergistic removal of multiple pollutants. In addition to the efficient removal of SO2, NOx, dust and CO, it can also efficiently remove pollutants such as SO3, HCl, HF and heavy metals. It can ensure the long-term stable operation of the CO catalyst, and can adapt to the stability of the system under different CO concentration fluctuations, ensuring that the CO device can operate at high efficiency for a long time, while also playing a role in energy saving and carbon reduction.

[0009] The technical solution adopted in this invention is as follows: a flue gas purification process for synergistic removal of multiple pollutants, comprising the following steps:

[0010] S1: Control the temperature of sintering flue gas to be no lower than 120℃, and inject absorbent 1 to mix with the sintering flue gas for deacidification;

[0011] S2: Water is sprayed into the flue gas after the treatment in step S1 to control the flue gas temperature to drop to 70℃~100℃. At the same time, absorbent II is sprayed in and mixed with the flue gas to remove acid and heavy metals again.

[0012] S3: The flue gas after step S2 is subjected to dust removal treatment to remove dust from the flue gas.

[0013] S4: The separated flue gas is heated to a higher temperature. After the flue gas temperature rises to meet the requirements of the carbon monoxide catalytic oxidation treatment process, CO is removed by catalytic oxidation.

[0014] S5: Use SCR denitrification equipment to treat the flue gas after CO removal.

[0015] In a preferred embodiment, in step S1 above, the absorbent is a calcium-based absorbent with a Ca(OH)₂ content ≥ 85%, and the specific surface area of ​​the Ca(OH)₂ particles is ≥ 30 m². 2 / g, particle size (D50) ≤10mm; control the calcium-sulfur ratio between 2 and 6, and the flue gas residence time is 1 to 3 seconds.

[0016] In a preferred embodiment, in step S2 above, the absorbent two is a calcium-based absorbent with a Ca(OH)2 content ≥75%, and the specific surface area of ​​the Ca(OH)2 particles is ≥18m². 2 / g, particle size (D50) ≤ 50mm; control the calcium-sulfur ratio between 1.4 and 2.2.

[0017] In a preferred embodiment, in step S2, activated carbon is used to further remove heavy metals from the flue gas after it has been purified by absorbent II.

[0018] By employing the above-described process of the present invention, the absorbent is refined and selected, and the temperature and timing of adding different absorbents to the process are controlled. This effectively avoids the competitive relationship between SO2 and SO3 contained in the flue gas and the absorbent. By utilizing the influence of temperature on the properties of acidic gases and in conjunction with the selection of absorbents, SO3 and SO2 are removed sequentially, thus solving the problem of the impact of SO3 residue on the subsequent CO catalyst activity.

[0019] In a preferred embodiment, in step S4, the heat energy of the flue gas after denitrification treatment in step S5 is used to exchange heat with the flue gas after dust removal treatment in step S3 to raise its temperature. Then, a heating device is selectively used to supplement the flue gas temperature rise, so that the flue gas temperature rises to meet the requirements.

[0020] In a preferred embodiment, before the flue gas after denitrification treatment in step S5 and the flue gas after dust removal treatment in step S3 exchange heat, if the flue gas temperature is too high, outside air can be introduced into the flue to pre-cool the flue gas after denitrification treatment.

[0021] This invention also claims protection for a flue gas purification system for the synergistic removal of multiple pollutants, used to operate the above-mentioned flue gas purification process for the synergistic removal of multiple pollutants, comprising a high-temperature conveying bed deacidification reactor, a circulating fluidized bed absorption tower, a dust collector, a heating section of a GGH heat exchanger, a flue gas heating device, a carbon monoxide reactor, an SCR reactor, and a cooling section of a GGH heat exchanger, which are connected sequentially through a flue.

[0022] In a preferred embodiment, absorbent one is sprayed into the interior of the high-temperature conveying bed deacidification reactor; water and absorbent two are sprayed into the circulating fluidized bed absorption tower, and the circulating fluidized bed absorption tower is equipped with an independently detachable activated carbon addition device.

[0023] In a preferred embodiment, 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, wherein the maximum heating power ratio of the high-load burner and the low-load burner is not less than 2; both the high-load burner and the low-load burner are equipped with flow regulating valves to achieve power adjustment.

[0024] In a preferred embodiment, an air mixing and cooling device is also installed between the SCR reactor and the GGH heat exchanger. The air mixing and cooling device includes an air mixing regulating damper and a flue gas temperature mixer. The flue gas temperature mixer has a grid structure with multiple horizontal pipes and multiple vertical pipes arranged at intervals, and small holes are evenly distributed on the horizontal pipes and vertical pipes. The flue gas temperature mixer is located inside the flue and is connected to the outside of the flue through a pipeline. The air mixing regulating damper controls the opening of the pipeline.

[0025] The advantages of the technical solution of this invention are:

[0026] 1. This invention distinguishes between a deacidification space equipped with a high-quality calcium-based composite absorbent and a deacidification space equipped with a conventional calcium-based absorbent, and controls the temperature of the flue gas entering the two spaces. By differentiating the temperature and removal environment, SO2 and SO3 are specifically removed, avoiding the impact of SO3 residue on the stability of the CO catalyst. This invention can remove SO2, NOx, dust, and CO, and can simultaneously achieve the synergistic removal of multiple pollutants including SO3, HCl, HF, and heavy metals. In particular, the synergistic removal of SO2 and SO3 protects the CO catalyst from deactivation due to residual SO3.

[0027] 2. Another outstanding advantage of the process method provided by this invention is that its energy consumption is significantly reduced compared with the prior art. The process is equipped with a multi-stage wide-load flue gas heating device, with at least one large and one small stage of heating device design. During the low temperature rise stage of start-up, all heating furnaces are turned on simultaneously for rapid temperature rise. During normal operation when the CO concentration is high, only the small heating device is turned on. At the same time, to further expand the adjustability, the regulating valve of the small heating device is matched with one large and one small stage. The heating load can be flexibly adjusted 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 heating load is 5% to 100%, while the adjustable range of heating load in the prior art is generally 15% to 100%. When the CO concentration is high, the low load operation can save more than 10% of heating gas energy consumption compared with the prior art.

[0028] 3. To address the issue that excessive CO concentration leads to excessive heat release during oxidation, resulting in excessively high flue gas temperature, which may cause the GGH heat exchanger to overheat and seize, affecting the stable operation of the system, this invention installs an air mixing and cooling device at the denitrification outlet and the GGH cooling side inlet. The air mixing and cooling device mainly includes an air mixing regulating damper outside the flue and a high-efficiency flue gas temperature mixer inside the flue. It utilizes the negative pressure of the system to appropriately mix in cold air as required, while using the high-efficiency flue gas temperature mixer to ensure uniform mixing of flue gas temperature and prevent the GGH from seizing up due to high temperature. Attached Figure Description

[0029] Figure 1 is a typical process flow diagram of adding a CO removal device to sintering flue gas in the prior art;

[0030] Figure 2 is a process flow diagram of the multi-pollutant synergistic removal and energy-saving carbon reduction process of the present invention;

[0031] Figure 3 is a schematic diagram of a specific embodiment of the air-mixing cooling device in this invention;

[0032] In the diagram: 1-High-temperature conveying bed deacidification reactor; 2-Circulating fluidized bed absorption tower; 3-Dust collector; 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 regulating damper; 802-Flue gas temperature mixer. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. It should be understood that the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar with the art.

[0034] Figure 2 is a process flow diagram of the multi-pollutant synergistic removal and energy-saving carbon reduction process of the present invention. Referring to Figure 2, the multi-pollutant synergistic removal and energy-saving carbon reduction process of the present invention includes a high-temperature conveying bed deacidification reactor 1, a circulating fluidized bed absorption tower 2, a dust collector 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 and cooling device 8, a GGH heat exchanger 4, and an induced draft fan 9, which guide the cooled flue gas to the chimney for discharge.

[0035] Absorbent-101 is arranged inside the high-temperature conveying bed deacidification reactor 1, or absorbent-101 powder is sprayed in as the flue gas flows through the high-temperature conveying bed deacidification reactor 1. The incoming sintering flue gas is deacidified and purified using a dry absorption method, removing acidic gases such as SO3, HCl, and HF from the flue gas. Absorbent-101 is a high-quality calcium-based composite absorbent. To achieve the synergistic and efficient removal of SO2 and SO3 required by the process of this invention, absorbent-101 requires a Ca(OH)2 content ≥ 85% and a specific surface area ≥ 30 m². 2 The absorbent has a particle size (D50) ≤ 10 mm and a calcium-to-sulfur ratio of absorbent 101 in the high-temperature conveying bed desulfurization reactor controlled between 2 and 6, with a flue gas residence time of 1 to 3 seconds. Absorbent 201 is added to the front end of the circulating fluidized bed absorption tower 2, while water 202 is sprayed in simultaneously to cool the flue gas and perform secondary purification, removing acid (SO2) and heavy metals. Absorbent 201 is a conventional calcium-based absorbent, for example, with a Ca(OH)2 content ≥ 75% and a specific surface area ≥ 18 m². 2 / g, particle size (D50) ≤ 50mm, and the preferred calcium-to-sulfur ratio in this process is between 1.4 and 2.2. Based on the removal effect and requirements of heavy metals in the flue gas, activated carbon 203 can be selectively installed at the rear end of the circulating fluidized bed absorber 2 to ensure that the comprehensive removal capacity of heavy metals in the flue gas is above 95%. That is, absorbent 101 is injected into the high-temperature conveying bed desulfurization reactor 1 for the first-stage desulfurization treatment, mainly removing acidic gases such as SO3, HCl, and HF from the flue gas; water and absorbent 201 are injected into the circulating fluidized bed absorber 2 for the second-stage desulfurization treatment to further remove SO2 from the flue gas. The circulating fluidized bed absorber 2 is equipped with an independently detachable activated carbon addition device. Depending on the removal effect of heavy metals in the flue gas, activated carbon may or may not be used for re-adsorption treatment of the flue gas purified by absorbent 2.

[0036] Dust collector 3 is used to remove dust from flue gas. The dust includes ash from the flue gas and residual absorbent one and absorbent two. The ash containing residual absorbent can be further circulated and reacted within a circulating fluidized bed absorption tower through material recycling, fully utilizing the absorbent before being discharged. Furthermore, dust collector 3 is preferably a baghouse dust collector.

[0037] The multi-stage wide-load flue gas heating device 5 is used to further heat the flue gas after it has been heated by the GGH heat exchanger 4, so that it meets the temperature requirements of the carbon monoxide reactor 6. The air mixing cooling device 8 introduces cold air from the outside by adjusting the valve opening size, which mixes with the flue gas to achieve rapid and uniform cooling.

[0038] The sintering flue gas, typically at 120–180°C, first enters the high-temperature conveying bed desulfurization reactor 1, where absorbent 101 efficiently removes acidic gases such as SO3, HCl, and HF. The flue gas then continues into the circulating fluidized bed absorption tower 2, where water is sprayed to cool it, and absorbent 201 adsorbs and removes SO2 and heavy metals. An independent, detachable assembly containing activated carbon 203 can be installed inside the circulating fluidized bed absorption tower 2. Depending on sampling and testing needs, the flue gas can either continue to pass through activated carbon 203 for adsorption or be directly discharged into the subsequent dust collector 3. Activated carbon 203 ensures a comprehensive heavy metal removal efficiency of over 95%. The desulfurized flue gas then passes through the dust collector 3 for dust removal, controlling the dust concentration at the outlet of the dust collector 3 to be less than 5 mg / Nm³. 3 A material circulation path is provided between the dust collector 3 and the circulating fluidized bed absorption tower 2 to facilitate the return of the separated dust containing absorbent one and / or absorbent two to the interior of the circulating fluidized bed absorption tower 2.

[0039] The GGH heat exchanger 4 facilitates heat exchange between the low-temperature desulfurized flue gas discharged from the dust collector 3 and the high-temperature denitrification 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. Before heat exchange, depending on the temperature requirements of the heat exchanger and the actual flue gas temperature, outside air can be introduced into the flue to pre-cool the denitrified flue gas.

[0040] After the flue gas temperature rises to meet the CO removal requirements, it enters the carbon monoxide reactor 6. Inside the reactor, CO is catalytically oxidized to CO2 by a catalyst, thus removing CO. Simultaneously, the exothermic CO reaction heats the flue gas. Generally, 1000 mg / Nm³ of CO is removed. 3 The CO can be heated to approximately 7.3°C in the flue gas, achieving CO removal while reducing the amount of heating gas needed to meet the downstream SCR denitrification temperature requirements, thus achieving energy saving and carbon reduction. Furthermore, detection nodes can be installed at both the inlet and outlet of the carbon monoxide reactor 6. By monitoring the temperature fluctuations of the flue gas before and after passing through the reactor 6, the activity of the CO catalyst and the CO concentration in the flue gas can be determined in real time. The operating load of the multi-stage wide-load flue gas heating device 5 can be adjusted according to the temperature fluctuations 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-load and one low-load burner, with a maximum heating power ratio of not less than 2 between the high-load and low-load burners. At startup, the flue gas temperature is low, and the CO denitrification efficiency is low, insufficient to provide sufficient reaction heat to meet the subsequent denitrification temperature requirements. Therefore, all burners in the multi-stage wide-load flue gas heating device 5 are activated to meet the rapid heating requirements. Once the flue gas temperature meets the design temperature requirements for CO denitrification, the high-load burner is shut down, and only the low-load burner is activated. Normal operation only requires controlling the load of the small-load burner to adapt to the temperature control requirements of different CO concentration fluctuations. To further increase the adjustable range, the burner is configured with two sets of regulating valves, one large and one small, to meet the total heating load adjustable range of 5% to 100%.

[0041] After CO removal, the flue gas enters the SCR reactor 7. NOx in the flue gas is removed by the injected ammonia under the action of the catalyst in the SCR reactor. The SCR denitrification catalyst is preferably a medium-high temperature SCR denitrification catalyst with a designed temperature range of 280 to 400℃.

[0042] After denitrification, the high-temperature flue gas enters the GGH heat exchanger 4 to exchange heat with the low-temperature flue gas from the previous dust removal process. Simultaneously, the high-temperature flue gas can selectively pass through the air-mixing 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, adjusting the valve opening of the air-mixing cooling device 8 allows for the intake of external cold air, achieving rapid and uniform mixing and cooling of the flue gas and cold air. This keeps the heat exchange effect of the GGH heat exchanger 4 within the required operating range, ensuring stable system operation. The purified flue gas from the GGH heat exchanger is then discharged to the chimney by the induced draft fan 9. A circulation loop is also provided between the outlet of the induced draft fan 9 and the circulating fluidized bed absorption tower 2. When the load is low, the flue gas circulation loop can be used to supplement the flue gas, ensuring that the flue gas entering the circulating fluidized bed absorption tower 2 meets the minimum flow rate required for stable bed operation, adapting to different load conditions.

[0043] Figure 3 is a schematic diagram of a specific embodiment of the air mixing and cooling device in this invention. An air mixing regulating damper 801 is installed outside the flue between the outlet of the SCR reactor 7 and the inlet of the GGH heat exchanger 4. The air mixing regulating damper 801 is connected to multiple branch pipes via pipelines. The branch pipes are connected to a mesh flue gas temperature mixer 802 installed inside the flue. The flue gas temperature mixer 802 has a mesh structure with multiple horizontal pipes and multiple vertical pipes arranged at intervals. Small holes are evenly opened on the flue gas temperature mixer 802 so that external cold air is drawn into the flue using negative pressure when the air mixing regulating damper 801 is opened.

[0044] The process of this invention will be described below in conjunction with an actual engineering project, in a 360m... 2 This technology has been successfully applied in sintering machines: sintering flue gas volume is ~1,300,000 Nm³. 3 / h (standard conditions), flue gas temperature approximately 150℃, SO2 concentration in flue gas 2000 mg / Nm³ 3 NOx concentration was 350 mg / Nm³ 3 CO concentration is ~6000 mg / Nm³ 3 Dust concentration: 50 mg / Nm 3 SO3 concentration approximately 90 mg / Nm 3 HCl approximately 8 mg / Nm 3 HF approximately 5 mg / Nm 3 In this flue gas treatment process, during normal operation, the sintering flue gas first enters the high-temperature conveying bed deacidification reactor 1, where absorbent-101 (a calcium-based absorbent with a Ca(OH)2 content of 90% and a specific surface area of ​​32 m²) is added. 2 With a median particle size of 8 mm, a calcium-to-sulfur ratio of 5, and a flue gas reaction shutdown time of 1.5 s, the system achieved efficient removal of SO3, HCl, and HF, with an outlet SO3 concentration of <2 mg / Nm³. 3HCl < 0.8 mg / Nm 3 HF < 0.5 mg / Nm 3 The deacidified flue gas enters circulating fluidized bed absorption tower 2, where water 202 and absorbent 201 (a calcium-based absorbent with a Ca(OH)2 content of 80% and a specific surface area of ​​20 m²) are added. 2 / g, median particle size 33mm), calcium-sulfur ratio 1.6, reaction temperature controlled at 80-90℃, SO2 in flue gas reacts with newly added absorbent 201 and residual absorbent 2 in the recycled material from the filter bag, achieving an outlet SO2 concentration <15mg / Nm³. 3 With the addition of activated carbon 203, the comprehensive removal efficiency of heavy metals mercury, lead, and their compounds reaches 95%. After desulfurization, the flue gas outlet dust concentration after passing through a bag filter is <5mg / Nm³. 3 After dust removal, the flue gas temperature is 80-90℃, exchanging heat with the GGH heat exchanger 4. Simultaneously, the low-load burner of the flue gas heating device operates at a 5% lower load. The flue gas temperature entering the carbon monoxide reactor (filled with CO catalyst) is approximately 270℃. After passing through the carbon monoxide reactor, the outlet CO concentration is <1500mg / Nm³. 3 When the flue gas temperature reaches approximately 300℃, it enters SCR reactor 7 where ammonia is injected to remove NOx from the flue gas to <30mg / Nm³. 3 The high-temperature flue gas after denitrification enters the GGH heat exchanger and exchanges heat with the flue gas after dust removal, reducing the flue gas temperature to 130-140℃. It then passes through the induced draft fan (F9) and exits to the chimney. When the CO concentration in the flue gas decreases and the temperature entering the SCR reactor drops below 280℃, the heating load of the flue gas heating device is increased to ensure that the denitrification temperature does not fall below 280℃. Simultaneously, under certain operating conditions, the CO concentration in the flue gas reaches 10000 mg / Nm³. 3 When the heat release of CO increases and the flue gas temperature at the outlet of the carbon monoxide reactor reaches 330℃, exceeding the maximum allowable temperature of 320℃ for the GGH heat exchanger, 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.

[0045] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to 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 temperature of sintering flue gas to be no lower than 120℃, and inject absorbent 1 to mix with the sintering flue gas for deacidification; S2: Water is sprayed into the flue gas after the treatment in step S1 to control the flue gas temperature to drop to 70℃~100℃. At the same time, absorbent II is sprayed in and mixed with the flue gas to remove acid and heavy metals again. S3: The flue gas after step S2 is subjected to dust removal treatment to remove dust from the flue gas. S4: Heat the flue gas after dust removal by heat exchange. 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 treat the flue gas after CO removal.

2. The process according to claim 1, further characterized in that: In step S1, the absorbent is a calcium-based absorbent with a Ca(OH)2 content ≥ 85%, and the specific surface area of ​​the Ca(OH)2 particles is ≥ 30 m². 2 / g, median particle size ≤10mm; control the calcium-sulfur ratio between 2 and 6, and the flue gas residence time is 1 to 3 seconds.

3. The process according to claim 1, further characterized in that: In step S2, the absorbent two is a calcium-based absorbent with a Ca(OH)2 content ≥75%, and the specific surface area of ​​the Ca(OH)2 particles is ≥18m². 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 further remove heavy metals from the flue gas after it has been purified by absorbent II.

5. The process according to claim 1, further characterized in that: In step S4, the heat energy of the flue gas after denitrification treatment in step S5 is used to exchange heat with the flue gas after dust removal treatment in step S3 to raise its temperature. Then, a heating device is selectively used to supplement the flue gas temperature rise, so that the flue gas temperature rises to meet the requirements.

6. The process according to claim 5, further characterized in that: Before exchanging heat between the flue gas after denitrification treatment in step S5 and the flue gas after dust removal treatment 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 denitrification treatment.

7. A flue gas purification system for synergistic removal of multiple pollutants, used to operate the flue gas purification process for synergistic removal of multiple pollutants as described in claim 1, characterized in that, It includes the heating section of the high-temperature conveying bed deacidification reactor (1), the circulating fluidized bed absorption tower (2), the dust collector (3), the GGH heat exchanger (4) connected in sequence, the flue gas heating device, the carbon monoxide reactor (6), the SCR reactor (7), and the cooling section of the GGH heat exchanger (4).

8. The system according to claim 7, further characterized in that: Absorbent 1 is sprayed into the high-temperature conveying bed deacidification reactor (1); water and absorbent 2 are sprayed into the circulating fluidized bed absorption tower (2), and the circulating fluidized bed absorption tower (2) is equipped with an independently detachable activated carbon addition 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). The multi-stage wide-load flue gas heating device (5) includes at least one high-load burner and at least one low-load burner. The maximum heating power ratio of the high-load burner and the low-load burner is not less than 2. Both the high-load burner and the low-load burner are equipped with flow regulating valves to achieve power adjustment.

10. The system according to claim 7, 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) includes an air mixing regulating damper (801) and a flue gas temperature mixer (802). The flue gas temperature mixer (802) has a grid structure with multiple horizontal pipes and multiple vertical pipes arranged at intervals. Small holes are evenly distributed on the horizontal pipes and vertical pipes. The flue gas temperature mixer (802) is set inside the flue and is connected to the outside of the flue through a pipeline. The air mixing regulating damper (801) controls the opening of the pipeline.

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