A centralized purification system and method for flue gas from multiple kilns

Abstract

This invention discloses a centralized flue gas purification system and method for multiple kilns, belonging to the field of industrial flue gas purification. The system includes a flue gas collection unit, a switchable centralized induced draft unit, a desulfurization absorption unit, an oxidation and dehydration unit, a wet electrostatic precipitator for deep purification, an exhaust unit, a flushing unit, and a process water supply main. In the switchable centralized induced draft unit, the inlet flues of two centralized induced draft fans are connected by a connecting branch pipe equipped with an electric switching valve, enabling flexible distribution of flue gas between one or two desulfurization systems. The desulfurization absorption tower adopts a tower-trough separation structure and an external annular spray pipe. The slurry at the bottom of the tower flows into an independent desulfurization circulation tank via a return pipe. A hydrocyclone is installed on the liquid-concentrating pipeline to pre-concentrate the circulating slurry before forced oxidation outside the tower. The flushing unit periodically flushes the demister and wet electrostatic precipitator. This invention achieves ultra-low emissions, allows for online inspection and maintenance, and features flexible and reliable system operation with low water and material consumption.

Description

Technical Field

[0001] This invention belongs to the field of industrial flue gas purification technology, specifically relating to a centralized purification system and method for flue gas from multiple kilns. Background Technology

[0002] In non-ferrous metal smelting industrial parks, multiple furnaces, such as side-blown furnaces and anode furnaces, typically operate simultaneously. The total flue gas volume is large and fluctuates frequently, with high sulfur dioxide concentrations, and often contains highly corrosive components such as hydrogen fluoride and hydrogen chloride. Traditional lime-gypsum wet desulfurization units suffer from severe corrosion of the tower and pipelines, easy clogging of the spray system, slurry deposition and scaling within the tower, and insufficient oxidation of byproducts when treating this type of flue gas. More importantly, if a single unit in the existing centralized treatment system fails, the entire smelting production in the park must be forced to stop, resulting in extremely poor system availability and flexibility. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a centralized purification system and method for multi-furnace flue gas, which solves the problems of poor system flexibility, high corrosion risk, and inability to perform online maintenance when dealing with complex flue gas in existing technologies.

[0004] To achieve the above-mentioned technical objectives, the present invention is implemented through the following technical solution:

[0005] In a first aspect, the present invention provides a centralized purification system for flue gas from multiple kilns, comprising:

[0006] The flue gas collection unit includes a first gas collection pipe and a second gas collection pipe, and both the first gas collection pipe and the second gas collection pipe are equipped with gas collection pressure transmitters.

[0007] The switchable centralized exhaust unit includes a first centralized exhaust fan, a second centralized exhaust fan, and three electrically operated switching valves; the inlet of the first centralized exhaust fan is connected to a first gas collection pipe, and the inlet of the second centralized exhaust fan is connected to a second gas collection pipe; the inlet flue of the first centralized exhaust fan and the inlet flue of the second centralized exhaust fan are connected by a connecting branch pipe with an electrically operated switching valve.

[0008] The desulfurization absorption unit includes a first desulfurization absorption tower and a second desulfurization absorption tower arranged in parallel. Each desulfurization absorption tower is equipped with an independent desulfurization circulation tank, a desulfurization circulation pump, an annular spray pipe, and an absorbent supply system. The flue gas inlet of the first desulfurization absorption tower is connected to the outlet of the first centralized induced draft fan, and the flue gas inlet of the second desulfurization absorption tower is connected to the outlet of the second centralized induced draft fan.

[0009] The oxidation dehydration unit includes a hydrocyclone, an oxidation tank, an aeration oxidation blower, a filter press pump, and a filter press connected in sequence; the feed inlet of the hydrocyclone is connected to the first desulfurization circulation tank and the second desulfurization circulation tank through a liquid-serial pipeline.

[0010] The wet electrostatic precipitator deep purification unit includes two wet electrostatic precipitators. The outlet of the first desulfurization absorption tower is connected to one wet electrostatic precipitator through a first flue gas outlet, and the outlet of the second desulfurization absorption tower is connected to another wet electrostatic precipitator through a second flue gas outlet.

[0011] The smoke exhaust unit includes a chimney mounted on top of two wet electrostatic precipitators.

[0012] Both the first and second desulfurization absorption towers adopt a tower-trough separation structure, with a sloping bottom and connected to the corresponding desulfurization circulation tank through a bottom return pipe; the top of the desulfurization circulation tank is equipped with an agitator.

[0013] The annular spray pipe is installed outside the desulfurization absorption tower and is connected to the outlet of the desulfurization circulating pump through a spray supply pipe. The annular spray pipe is provided with multiple branch pipes extending into the tower, and the ends of the branch pipes are equipped with vortex nozzles. Inside each desulfurization absorption tower, above the annular spray pipe, there are also plate demisters and demister backwashing layers in sequence.

[0014] The system also includes a flushing unit, which includes a demister backwash water tank and a backwash pump. The inlet of the backwash pump is connected to the demister backwash water tank, and the outlet is connected to the backwash layer of the demister in the two desulfurization absorption towers and the spray device of the two wet electrostatic precipitators through a flushing water supply pipe.

[0015] The absorbent supply system includes a lime powder storage silo, a spiral weighing scale, a lime slurry preparation tank, and a lime slurry addition pump connected in sequence; the outlet of the lime slurry addition pump is connected to the corresponding desulfurization circulation tank through a lime slurry supply pipe.

[0016] The system also includes a process water supply main pipe, which is connected to the inlet of the first desulfurization circulation tank, the inlet of the second desulfurization circulation tank, the inlet of the demister backwash water tank, and the inlet of the lime slurry tank.

[0017] The oxidation tank is provided in two units, which are connected to the underflow port of the hydrocyclone through underflow pipes. Each oxidation tank is equipped with a stirrer and connected to an aeration oxidation blower through an aeration pipeline. The top of each oxidation tank is connected to the flue gas inlet side of the corresponding desulfurization absorption tower through a waste gas recovery pipe, and an oxidation tank induced draft fan is provided on the waste gas recovery pipe.

[0018] The inlet of the filter press pump is connected to the oxidation tank, and the outlet is connected to the filter press through the filter press feed pipe; the filtrate outlet of the filter press is connected to the filter press storage tank through the filtrate recovery pipe; the outlet of the filter press storage tank is equipped with a filter press delivery pump, and the outlet of the pump is connected to the water inlet of the lime slurry tank.

[0019] The bottom of the wet electrostatic precipitator is connected to the corresponding desulfurization circulation tank through a drain return pipe; it also includes a water collection pit set below ground and a pit pump installed in the pit, the outlet of the pit pump being connected to the inlet of the lime slurry tank through a slurry water supply pipe.

[0020] Secondly, the present invention provides a flue gas purification method utilizing the above-described system, comprising the following steps:

[0021] S1. The flue gas from the furnace in the first zone is pretreated and then enters the first gas collection pipe; the flue gas from the furnace in the second zone is pretreated and then enters the second gas collection pipe.

[0022] S2. Based on the number of operating furnaces and the total flue gas volume, selectively operate the opening and closing status of the three electric switching valves to guide the flue gas into one or two desulfurization absorption towers for treatment; when all furnaces are running at full load, the three electric switching valves remain closed, and the flue gas enters the corresponding centralized induced draft fan and desulfurization absorption tower independently; when only some furnaces are running, open the electric switching valve on the connecting branch pipe and selectively close the electric switching valve on any inlet flue, so that all flue gas is concentrated and guided into a single desulfurization system, while the other system is shut down for maintenance;

[0023] S3. Flue gas enters from the bottom of the desulfurization absorption tower and comes into countercurrent contact with lime slurry sprayed through the annular spray pipe from bottom to top, thus completing the absorption and removal of sulfur dioxide; the sprayed slurry flows back to the corresponding desulfurization circulation tank through the bottom return pipe of the tower.

[0024] S4. The process water supply main pipe replenishes process water to the first desulfurization circulation tank, the second desulfurization circulation tank, the demister backwash water tank, and the lime slurry preparation tank; part of the slurry in the desulfurization circulation tank enters the hydrocyclone through the liquid transfer pipeline for graded concentration, and the underflow concentrated slurry enters the oxidation tank through the underflow pipe; the sump pump sends the slurry and flushing water collected in the water collection sump to the lime slurry preparation tank through the slurry supply pipe.

[0025] S5. The aeration oxidation blower supplies air into the oxidation tank through the aeration pipeline to oxidize calcium sulfite into gypsum; the waste gas from the oxidation tank is drawn back to the desulfurization absorption tower by the oxidation tank exhaust fan through the waste gas recovery pipe.

[0026] S6. The oxidized gypsum slurry is sent to the filter press by the filter press pump for solid-liquid separation. The filtrate is recovered to the filter press liquid storage tank and then sent back to the lime slurry tank by the filter press liquid transfer pump for recycling.

[0027] S7. The clean flue gas after desulfurization enters the corresponding wet electrostatic precipitator for deep purification through the first or second flue gas outlet. The condensate at the bottom of the wet electrostatic precipitator is recovered to the desulfurization circulation tank through the drain return pipe. Finally, the clean flue gas is discharged from the chimney in compliance with standards.

[0028] The beneficial effects of this invention are:

[0029] Compared with existing technologies, this invention improves system flexibility and availability by installing a connecting branch pipe with an electric switching valve between the inlet flue of the first and second centralized induced draft fans. This allows all flue gas to be centrally introduced into a single desulfurization system for treatment when only some kilns in the industrial park are operating, while the other system can be shut down for maintenance. The desulfurization absorption tower adopts a tower-trough separation structure and is equipped with a bottom return pipe, enabling the sprayed slurry to flow smoothly into an independent desulfurization circulation tank, preventing slurry deposition and scaling inside the tower. Simultaneously, the annular spray pipe is installed outside the tower, with the branch pipe sealed from the outside into the tower, facilitating maintenance and replacement of the spray pipeline without shutdown. Furthermore, a hydrocyclone is installed on the liquid-conducting pipeline to concentrate and classify the circulating slurry, sending only the high-concentration underflow slurry to the oxidation tank for forced oxidation, improving oxidation efficiency and gypsum quality while reducing the required oxidation tank volume. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments are briefly introduced below.

[0031] Figure 1 This is a schematic diagram of the process pipeline connection of the multi-furnace flue gas centralized purification system in an embodiment of the present invention.

[0032] Figure 2 A plan view of the centralized purification system for multi-furnace flue gas in an embodiment of the present invention.

[0033] Figure 3 A front view of the equipment layout of the multi-furnace flue gas centralized purification system in this embodiment of the invention.

[0034] In the attached diagram, the structural names represented by each number are as follows:

[0035] 1. First centralized induced draft fan; 2. Second centralized induced draft fan; 3. Electric switching valve; 4. Gas pressure transmitter; 5. First desulfurization absorption tower; 6. Second desulfurization absorption tower; 7. Annular spray pipe; 8. Plate demister; 9. Demister backwash layer; 10. First desulfurization circulation tank; 11. Second desulfurization circulation tank; 12. Desulfurization circulation pump; 13. Agitator; 14. Lime powder storage silo; 15. Screw weigher; 16. Lime slurry preparation tank; 17. Lime slurry addition pump; 18. Hydrocyclone; 19. Oxidation tank; 20. Aeration oxidation fan; 21. Oxidation tank induced draft fan; 22. Filter press pump; 23. Filter press; 24. Filter press liquid storage tank; 25. Wet electrostatic precipitator; 26. Chimney; 27. Demister backwash water tank; 28. Backwash pump; 29. ​​Sump; 30. Sump pump; 31. Filter press liquid transfer pump.

[0036] L1, First gas collection pipe; L2, Second gas collection pipe; L3, First flue gas outlet; L4, Second flue gas outlet; L5, Connecting branch pipe; L6, Bottom return pipe; L7, Spray supply pipe; L8, Liquid transfer pipe; L9, Lime slurry supply pipe; L10, Pulping water supply pipe; L11, Underflow pipe; L12, Aeration pipe; L13, Waste gas recovery pipe; L14, Filter press feed pipe; L15, Filtrate recovery pipe; L16, Washing water supply pipe; L17, Process water main supply pipe; L18, Drainage return pipe. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0038] Example 1

[0039] See Figures 1 to 3 As shown, this embodiment provides a centralized purification system for flue gas from multiple kilns, including a flue gas collection unit, a switchable centralized induced draft unit, a desulfurization absorption unit, an oxidation dehydration unit, a wet electrostatic precipitator for deep purification, a flue gas exhaust unit, a flushing unit, and a process water supply main pipe.

[0040] In this implementation, the multiple side-blown furnaces, anode furnaces and other smelting furnaces in the park are divided into the first area and the second area according to their geographical distribution.

[0041] The flue gas collection unit includes a first gas collection pipe L1 for collecting flue gas from the first zone and a second gas collection pipe L2 for collecting flue gas from the second zone; each gas collection pipe is equipped with a gas collection pressure transmitter 4 for real-time monitoring of the flue gas pressure in the gas collection pipe.

[0042] The switchable centralized exhaust fan unit includes a first centralized exhaust fan 1, a second centralized exhaust fan 2, and three electrically operated switching valves 3; a first gas collection pipe L1 is connected to the inlet of the first centralized exhaust fan 1. A second gas collection pipe L2 is connected to the inlet of the second centralized exhaust fan 2. A connecting branch pipe L5 equipped with an electrically operated switching valve 3 is provided between the inlet flue of the first centralized exhaust fan 1 and the inlet flue of the second centralized exhaust fan 2.

[0043] By operating the opening and closing of each electric switching valve 3, the following operating modes can be achieved: When all furnaces are running at full load, the three electric switching valves 3 remain closed, and the flue gas from the two areas enters the corresponding centralized induced draft fan and desulfurization absorption tower independently; when only some furnaces are running, the electric switching valve 3 on the connecting branch pipe L5 is opened, and the electric switching valve 3 on any inlet flue is selectively closed, so that all flue gas is concentrated and introduced into a single desulfurization system, while the other system is shut down for maintenance.

[0044] The desulfurization absorption unit includes a first desulfurization absorption tower 5 and a second desulfurization absorption tower 6 arranged in parallel. The outlet of the first centralized induced draft fan 1 is connected to the flue gas inlet of the first desulfurization absorption tower 5, and the outlet of the second centralized induced draft fan 2 is connected to the flue gas inlet of the second desulfurization absorption tower 6. Each desulfurization absorption tower is equipped with an independent desulfurization circulation tank, a desulfurization circulation pump 12, an annular spray pipe 7, and an absorbent supply system.

[0045] Taking the first desulfurization absorption tower 5 as an example (the second desulfurization absorption tower 6 has the same structure), the desulfurization absorption tower adopts a tower-trough separation structure. The bottom of the tower body is sloping and is connected to the first desulfurization circulation tank 10 through the tower bottom return pipe L6. An agitator 13 is installed on the top of the first desulfurization circulation tank 10. The slurry in the first desulfurization circulation tank 10 is drawn by the desulfurization circulation pump 12 and sent to the annular spray pipe 7 installed outside the tower body through the spray supply pipe L7. Each branch pipe on the annular spray pipe 7 is sealed from the outside of the tower and inserted into the tower, with vortex nozzles at the end. Above the annular spray pipe 7, a plate demister 8 and a demister backwashing layer 9 are installed in sequence inside the tower.

[0046] The absorbent supply system includes a lime powder storage silo 14, a screw weigher 15, a lime slurry preparation tank 16, and a lime slurry addition pump 17 connected in sequence. The outlet of the lime slurry addition pump 17 is connected to the first desulfurization circulation tank 10 and the second desulfurization circulation tank 11 through the lime slurry supply pipe L9.

[0047] The oxidation dehydration unit includes a hydrocyclone 18, an oxidation tank 19, an aeration oxidation blower 20, a filter press pump 22, and a filter press 23 connected in sequence.

[0048] The first desulfurization circulation tank 10 and the second desulfurization circulation tank 11 are interconnected by a liquid-connecting pipeline L8, on which a hydrocyclone 18 is installed. After the circulating slurry is classified by the hydrocyclone 18, the concentrated underflow slurry enters the oxidation tank 19 through the underflow pipe L11.

[0049] This embodiment features two oxidation tanks 19, each equipped with a stirrer 13 on its top. An aeration oxidation blower 20 forces air into the oxidation tank 19 via an aeration pipe L12. A waste gas recovery pipe L13 is connected to the top of the oxidation tank 19. Under the action of the oxidation tank induced draft fan 21, the acid mist waste gas generated during the oxidation process is returned to the flue gas inlet side of the desulfurization absorption tower for re-purification. The fully oxidized gypsum slurry is pumped by a filter press pump 22 through a filter press feed pipe L14 into a filter press 23 for solid-liquid separation. The filtrate produced by the filter press flows into a filter press storage tank 24 via a filtrate recovery pipe L15. A filter press transfer pump 31 is installed at the outlet of the filter press storage tank 24. This pump returns the filtrate to the inlet of the lime slurry preparation tank 16 for the preparation of lime slurry.

[0050] The wet electrostatic precipitator (ESP) deep purification unit includes two wet ESPs 25. The outlet of the first desulfurization absorption tower 5 is connected to one wet ESP 25 via the first flue gas outlet L3, and the outlet of the second desulfurization absorption tower 6 is connected to the other wet ESP 25 via the second flue gas outlet L4. Each wet ESP 25 has a drain port at its bottom, which is connected to the corresponding desulfurization circulation tank via a drain return pipe L18, recovering the condensate generated inside the wet ESP and the wastewater from the spray washing process to the slurry circulation system.

[0051] The exhaust unit includes a chimney 26 installed on top of each wet electrostatic precipitator 25, from which the purified clean flue gas is discharged at high altitude.

[0052] The flushing unit includes a demister backwash water tank 27 and a backwash pump 28. The inlet of the demister backwash water tank 27 is connected to the process water supply main L17, the inlet of the backwash pump 28 is connected to the demister backwash water tank 27, and the outlet is connected to the spray device of the demister backwash layer 9 in the two desulfurization absorption towers and the two wet electrostatic precipitators 25 through the flushing water supply pipe L16, for periodically flushing the dust and scale on the demisters and wet electrostatic electrodes.

[0053] The process water supply main pipe L17 is connected to the inlet of the first desulfurization circulation tank 10, the inlet of the second desulfurization circulation tank 11, the inlet of the demister backwash water tank 27, and the inlet of the lime slurry tank 16, respectively, for supplying process water to all water-using points. The lime slurry tank 16 also receives recovered filtrate from the filtrate storage tank 24 via the filtrate transfer pump 31, and receives recovered slurry from the collection pit 29 via the sump pump 30 and the slurry supply pipe L10.

[0054] This embodiment also includes a water collection pit 29 located underground and a pit pump 30 installed in the pit. Slurry and ground flushing water scattered throughout the system are collected in the water collection pit 29 through the drainage ditch. The outlet of the pit pump 30 is connected to the inlet of the lime slurry tank 16 through a slurry supply pipe L10, so that the collected slurry is returned to the slurry system for recycling.

[0055] Flue gas purification method using the above system:

[0056] Flue gas from the furnaces in the first zone is pretreated and then flows into the first gas collection pipe L1. Flue gas from the furnaces in the second zone is pretreated and then flows into the second gas collection pipe L2. Depending on the number of operating furnaces and the total flue gas volume, the opening and closing states of three electric switching valves 3 are selectively operated to guide the flue gas into one or two desulfurization absorption towers for treatment. The flue gas enters from the bottom of the desulfurization absorption tower and comes into countercurrent contact with the lime slurry sprayed through the annular spray pipe 7, completing the absorption and removal of sulfur dioxide. The sprayed slurry flows back to the corresponding desulfurization circulation tank through the bottom return pipe L6. The process water supply main pipe L17 replenishes process water to each water point. Part of the slurry in the desulfurization circulation tank enters the hydrocyclone 18 through the liquid transfer pipe L8 for classification. The concentrated underflow slurry enters the oxidation tank 19 through the underflow pipe L11; the aeration oxidation blower 20 forces air into the oxidation tank 19 through the aeration pipe L12 to oxidize calcium sulfite into gypsum. The waste gas from the oxidation tank is drawn back to the desulfurization absorption tower by the oxidation tank exhaust fan 21 through the waste gas recovery pipe L13; the oxidized gypsum slurry is sent to the filter press 23 by the filter press pump 22 for solid-liquid separation. The filtrate is recovered to the filter press liquid storage tank 24 and then sent back to the lime slurry tank 16 for recycling via the filter press liquid transfer pump 31; the clean flue gas after desulfurization enters the corresponding wet electrostatic precipitator 25 for deep purification through the tower outlet flue. The condensate at the bottom of the wet electrostatic precipitator 25 is recovered to the desulfurization circulation tank through the drain return pipe L18. Finally, the clean flue gas is discharged from the chimney 26 in compliance with standards.

[0057] This system enables efficient, stable, and flexible treatment of flue gas from multiple kilns, ensuring that the outlet sulfur dioxide concentration remains stable below 100 mg / Nm³ and the particulate matter concentration is below 10 mg / Nm³, meeting the requirements of ultra-low emission standards.

[0058] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A centralized purification system for flue gas from multiple kilns, characterized in that, include: The flue gas collection unit includes a first gas collection pipe (L1) and a second gas collection pipe (L2), and both the first gas collection pipe (L1) and the second gas collection pipe (L2) are equipped with gas collection pressure transmitters (4). The switchable centralized exhaust unit includes a first centralized exhaust fan (1), a second centralized exhaust fan (2), and three electrically operated switching valves (3); the inlet of the first centralized exhaust fan (1) is connected to the first gas collection pipe (L1), and the inlet of the second centralized exhaust fan (2) is connected to the second gas collection pipe (L2); the inlet flue of the first centralized exhaust fan (1) and the inlet flue of the second centralized exhaust fan (2) are connected by a connecting branch pipe (L5) with an electrically operated switching valve (3); The desulfurization absorption unit includes a first desulfurization absorption tower (5) and a second desulfurization absorption tower (6) arranged in parallel. Each desulfurization absorption tower is equipped with an independent desulfurization circulation tank, a desulfurization circulation pump (12), an annular spray pipe (7) and an absorbent supply system. The flue gas inlet of the first desulfurization absorption tower (5) is connected to the outlet of the first centralized induced draft fan (1), and the flue gas inlet of the second desulfurization absorption tower (6) is connected to the outlet of the second centralized induced draft fan (2). The oxidation dehydration unit includes a hydrocyclone (18), an oxidation tank (19), an aeration oxidation blower (20), a filter press pump (22), and a filter press (23) connected in sequence; the feed inlet of the hydrocyclone (18) is connected to the first desulfurization circulation tank (10) and the second desulfurization circulation tank (11) through a liquid-connecting pipeline (L8); The wet electrostatic precipitator deep purification unit includes two wet electrostatic precipitators (25). The outlet of the first desulfurization absorption tower (5) is connected to one wet electrostatic precipitator (25) through the first tower outlet flue (L3), and the outlet of the second desulfurization absorption tower (6) is connected to another wet electrostatic precipitator (25) through the second tower outlet flue (L4). The exhaust unit includes a chimney (26) mounted on top of two wet electrostatic precipitators (25).

2. The multi-furnace flue gas centralized purification system according to claim 1, characterized in that, The desulfurization absorption towers all adopt a tower-trough separation structure, with a sloping bottom and connected to the corresponding desulfurization circulation tank through a tower bottom return pipe (L6); the top of the desulfurization circulation tank is equipped with an agitator (13).

3. The multi-furnace flue gas centralized purification system according to claim 1, characterized in that, The annular spray pipe (7) is installed outside the desulfurization absorption tower and is connected to the outlet of the desulfurization circulation pump (12) through the spray supply pipe (L7). The annular spray pipe (7) is provided with multiple branch pipes extending into the tower, and the ends of the branch pipes are equipped with vortex nozzles. Inside each desulfurization absorption tower, above the annular spray pipe (7), there is also a plate demister (8) and a demister backwashing layer (9).

4. The multi-furnace flue gas centralized purification system according to claim 3, characterized in that, It also includes a flushing unit, which includes a demister backwash water tank (27) and a backwash pump (28); the inlet of the backwash pump (28) is connected to the demister backwash water tank (27), and the outlet is connected to the spraying devices of the demister backwash layer (9) in the two desulfurization absorption towers and the two wet electrostatic precipitators (25) through the flushing water supply pipe (L16).

5. The multi-furnace flue gas centralized purification system according to claim 1, characterized in that, The absorbent supply system includes a lime powder storage silo (14), a spiral weighing scale (15), a lime slurry tank (16), and a lime slurry addition pump (17) connected in sequence; the outlet of the lime slurry addition pump (17) is connected to the corresponding desulfurization circulation tank through a lime slurry supply pipe (L9).

6. The multi-furnace flue gas centralized purification system according to claim 5, characterized in that, It also includes a process water supply main pipe (L17), which is connected to the inlet of the first desulfurization circulation tank (10), the inlet of the second desulfurization circulation tank (11), the inlet of the demister backwash water tank (27), and the inlet of the lime slurry tank (16).

7. The multi-furnace flue gas centralized purification system according to claim 1, characterized in that, Two oxidation tanks (19) are provided, which are connected to the underflow port of the hydrocyclone (18) through the underflow pipe (L11); each oxidation tank (19) is equipped with a stirrer (13) and is connected to the aeration oxidation blower (20) through the aeration pipe (L12); the top of each oxidation tank (19) is connected to the flue gas inlet side of the corresponding desulfurization absorption tower through the waste gas recovery pipe (L13), and the waste gas recovery pipe (L13) is equipped with an oxidation tank induced draft fan (21).

8. The multi-furnace flue gas centralized purification system according to claim 5, characterized in that, The inlet of the filter press pump (22) is connected to the oxidation tank (19), and the outlet is connected to the filter press (23) through the filter press feed pipe (L14); the filtrate outlet of the filter press (23) is connected to the filter press storage tank (24) through the filtrate recovery pipe (L15); the outlet of the filter press storage tank (24) is equipped with a filter press delivery pump (31), and the outlet of the pump is connected to the water inlet of the lime slurry tank (16).

9. The multi-furnace flue gas centralized purification system according to claim 5, characterized in that, The bottom of each wet electrostatic precipitator (25) is connected to the corresponding desulfurization circulation tank through a drain return pipe (L18); it also includes a water collection pit (29) set below ground and a pit pump (30) installed in the pit, the outlet of which is connected to the inlet of the lime slurry tank (16) through a slurry water supply pipe (L10).

10. A method for purifying flue gas using the system according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. The flue gas from the furnace in the first zone is pretreated and then enters the first gas collection pipe (L1). The flue gas from the furnace in the second zone is pretreated and then enters the second gas collection pipe (L2). S2. Based on the number of operating furnaces and the total flue gas volume, selectively operate the opening and closing states of the three electric switching valves (3) to introduce the flue gas into one or two desulfurization absorption towers for treatment; when all furnaces are running at full load, the three electric switching valves (3) remain closed, and the flue gas enters the corresponding centralized induced draft fan and desulfurization absorption tower independently; when only some furnaces are running, open the electric switching valve (3) on the connecting branch pipe (L5) and selectively close the electric switching valve (3) on any inlet flue, and concentrate all the flue gas into a single desulfurization system, while the other system is shut down for maintenance; S3. Flue gas enters from the bottom of the desulfurization absorption tower and comes into countercurrent contact with the lime slurry sprayed through the annular spray pipe (7) from bottom to top, thus completing the absorption and removal of sulfur dioxide; the sprayed slurry flows back to the corresponding desulfurization circulation tank through the bottom return pipe (L6). S4. The process water supply main pipe (L17) replenishes process water to the first desulfurization circulation tank (10), the second desulfurization circulation tank (11), the demister backwash water tank (27), and the lime slurry tank (16). Part of the slurry in the desulfurization circulation tank enters the hydrocyclone (18) through the liquid-connecting pipeline (L8) for graded concentration. The underflow concentrated slurry enters the oxidation tank (19) through the underflow pipe (L11). The sump pump (30) sends the slurry and flushing water collected in the water collection sump (29) to the lime slurry tank (16) through the slurry supply pipe (L10). S5. The aeration oxidation blower (20) supplies air to the oxidation tank (19) through the aeration pipeline (L12) to oxidize calcium sulfite into gypsum; the waste gas from the oxidation tank is drawn back to the desulfurization absorption tower by the oxidation tank exhaust fan (21) through the waste gas recovery pipe (L13); S6. The oxidized gypsum slurry is sent to the filter press (23) by the filter press pump (22) for solid-liquid separation. The filtrate is recovered to the filter press storage tank (24) and then sent back to the lime slurry tank (16) by the filter press transfer pump (31) for recycling. S7. The clean flue gas after desulfurization enters the corresponding wet electrostatic precipitator (25) through the first flue gas outlet (L3) or the second flue gas outlet (L4) for deep purification. The condensate at the bottom of the wet electrostatic precipitator (25) is recovered to the desulfurization circulation tank through the drain return pipe (L18). Finally, the clean flue gas is discharged from the chimney (26) in compliance with the standards.

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