A combined switching dust collector purification system for coal tar flue gas

Abstract

The utility model relates to a kind of for coal tar flue gas's combined switching type dust collector purification system, including tar flue gas into collection header and multiple independent purification dust removal units in parallel, tar flue gas into collection header is branched into multiple branch pipes by switching valve, and each branch pipe is connected with corresponding purification dust removal unit;Purification dust removal unit includes pre-spraying system, air compensation channel, detection and execution mechanism and bag filter, and branch pipe is connected with the air inlet of corresponding bag filter by flue gas valve;Lime powder bin is connected with air-solid injector by feeding valve, and compressed air drives air-solid injector by gas sending valve;Atmosphere is directly connected with the air inlet of bag filter by air valve;The import and export of bag filter are equipped with differential pressure detection mechanism.The utility model system uses multiple dust removal units parallel structure and air-solid injection pre-spraying design, completely solve filter bag paste bag, ash cleaning not completely and maintenance production stop problem, improve lime powder utilization.

Description

Technical Field

[0001] This utility model relates to the field of industrial flue gas purification technology, and in particular to a combined switching dust collector purification system for coal tar flue gas. Background Technology

[0002] Coke oven equipment or equipment that generates coal tar flue gas requires protection of filter bags when treating coal tar flue gas; otherwise, the coal tar will cause the filter bags to become clogged. Traditional dust collectors sometimes treat coal tar flue gas by continuously injecting lime powder into the flue gas duct. This method has the following technical drawbacks:

[0003] (1) Filter bag failure due to tar sticking to the filter bag: Tar adheres to the filter bag, causing a sharp drop in air permeability. Traditional continuous spraying of lime powder is less efficient.

[0004] (2) Losses due to maintenance downtime: The structure of a single dust collector requires the entire machine to be shut down for maintenance, which affects the continuity of production;

[0005] (3) Incomplete dust removal: Online dust removal is affected by airflow, and the residual tar layer accelerates the caking of filter bags.

[0006] Therefore, this utility model provides a combined switching dust collector purification system for coal tar flue gas, solving the above-mentioned problems. Utility Model Content

[0007] The purpose of this utility model is to overcome the above-mentioned shortcomings and provide a combined switching dust collector purification system for coal tar flue gas, so as to achieve efficient anti-clogging and non-stop operation and maintenance.

[0008] The purpose of this utility model is achieved as follows:

[0009] A combined switching dust collector purification system for coal tar flue gas includes a tar flue gas inlet manifold and multiple independent purification and dust removal units connected in parallel. The tar flue gas inlet manifold is connected to a coal tar flue gas source and branches into multiple branch pipes through a switching valve. Each branch pipe is connected to a corresponding purification and dust removal unit.

[0010] The purification and dust removal unit includes a pre-coating system, an air compensation channel, a detection and execution mechanism, and a bag filter. The pre-coating system includes a lime powder silo and a gas-solid injector. The air compensation channel includes an air valve. The detection and execution mechanism includes a differential pressure detection mechanism and a dust removal system.

[0011] The branch pipe is connected to the air inlet of the corresponding bag filter through a flue gas valve; the lime powder silo is connected to the gas-solid injector through a feeding valve, and compressed air drives the gas-solid injector through an air supply valve; atmospheric air is directly connected to the air inlet of the bag filter through an air valve; the bag filter is equipped with a differential pressure detection mechanism at the inlet and outlet; and a dust removal system is installed at the top inner part of the bag filter.

[0012] Furthermore, the air inlet of the bag filter is connected to a lime powder feeding pipe, and a gas-solid ejector is provided on the lime powder feeding pipe. The gas-solid ejector is connected to an active lime powder silo via a feeding valve. An air supply valve is also provided on the lime powder feeding pipe, and the air supply valve is connected to compressed air. The air supply valve is located on the outside of the gas-solid ejector away from the bag filter.

[0013] Furthermore, the bag filter is provided with an exhaust port on the upper side, and the exhaust port is connected to a fan to achieve the discharge of clean air.

[0014] Furthermore, the dust removal system employs a pulse jet cleaning device.

[0015] Furthermore, the bottom of the bag filter is equipped with an ash discharge valve.

[0016] Furthermore, the bag filter of the purification and dust removal unit is expanded into a multi-compartment structure, with each compartment independently equipped with valve groups and differential pressure detection; the branch pipe A is divided into multiple sub-channels, each sub-channel is equipped with corresponding flue gas valves, air valves and pre-coating systems, and the bag filter of the purification and dust removal unit is equipped with multiple independent compartments.

[0017] Furthermore, the bag filter includes an outer shell. On the lower part of one side of the outer shell, from bottom to top, are sequentially arranged in the following order: inlet valve for the first compartment, inlet valve for the second compartment, inlet valve for the third compartment, and so on. On the upper part of the other side of the outer shell, from bottom to top, are sequentially arranged in the following order: exhaust port for the first compartment, exhaust port for the second compartment, exhaust port for the third compartment, and so on. The inlet valve of each compartment is connected to a corresponding sub-channel, and the exhaust port of each compartment is connected to a fan. A differential pressure detection mechanism is provided between the inlet and outlet of each compartment to detect the inlet-outlet pressure difference.

[0018] Furthermore, each compartment is arranged from bottom to top as follows: a dust hopper, a dust settling area, a filter bag filtration area, and a clean air chamber. The clean air chamber is connected to the exhaust port through a lifting valve plate to form an air outlet channel. The sub-channel is connected to the dust hopper, the dust hopper is connected to the dust settling area, the dust settling area is connected to the filter bag filtration area, the filter bag filtration area is connected to the clean air chamber, and the clean air chamber is connected to the air outlet channel.

[0019] Furthermore, an L-shaped partition is provided between the air inlet valves of two adjacent compartments. One end of the L-shaped partition is connected between the corresponding two adjacent air inlet valves on the inner wall of the outer shell, and the other end reaches the connection point of the ash hoppers of the corresponding two adjacent compartments. A horizontal partition is provided above the air inlet valve of the last compartment. One end of the horizontal partition is connected above the air inlet valve of the corresponding compartment on the inner wall of the outer shell, and the other end is connected below the air inlet of the corresponding compartment on the inner wall of the outer shell.

[0020] Furthermore, a partition is provided between the clean air chambers of two adjacent compartments. The partition is L-shaped, with one end of the partition located in the middle between two adjacent clean air chambers on the top surface of the outer shell, and the other end connected to the air inlets of two adjacent compartments on the inner wall of the outer shell.

[0021] Compared with the prior art, the beneficial effects of this utility model are:

[0022] This utility model provides a combined switching dust collector purification system for coal tar flue gas. It adopts combined switching dust collector purification technology to ensure high-efficiency use of lime powder, realize offline high-intensity dust removal operation, and at the same time, enable maintenance and other operations on the bag filter dust collector that has stopped running without affecting the overall process operation. If the flue gas volume is relatively large, multiple purification and dust removal units can be flexibly designed.

[0023] This utility model's combined switching dust collector purification system adopts a gas-solid ejector and a differential pressure triggering mechanism, which greatly improves the utilization rate of lime powder; the air valve of the purification dust removal unit introduces clean air to avoid residual flue gas causing tar solidification; the purification dust removal unit supports parallel connection of multiple compartments, which can increase the processing capacity without adding new equipment.

[0024] This utility model's combined switching dust collector purification system allows for maintenance of individual dust removal units without affecting system operation, greatly increasing output and improving purification efficiency; the dust removal intensity is greatly enhanced, and the residual dust in the filter bags is greatly reduced; the purification process of this utility model achieves fully automatic control, realizing closed-loop control of differential pressure signal → valve action → fan start and stop, greatly reducing the error rate. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the purification system of Embodiment 1 of this utility model.

[0026] Figure 2 This is an airflow path diagram of the pre-coating stage of Embodiment 1 of this utility model.

[0027] Figure 3 This is a flow chart of the filtration-switching-dust removal process of Embodiment 1 of this utility model.

[0028] Figure 4 This is a schematic diagram of the purification system of Embodiment 2 of this utility model.

[0029] Figure 5 This is a schematic diagram of the structure of the bag filter dust collector in the purification system of Embodiment 2 of this utility model.

[0030] Figure 6 This is a side view of the bag filter of the purification system in Embodiment 2 of this utility model.

[0031] in:

[0032] Tar-laden flue gas enters the main manifold 1, three-way switching valve 2, branch pipe A3, branch pipe B4, bag filter A5, flue gas valve A6, air valve A7, gas-solid ejector A8, active lime powder silo A9, feeding valve A10, air supply valve A11, dust removal system A12, ash discharge valve A13, fan A14, bag filter B15, flue gas valve B16, air valve B17, gas-solid ejector B18, active lime powder silo B19, feeding valve B20, air supply valve B21, dust removal system B22, ash discharge valve B23, fan B24, air inlet valve 25, ash hopper 26, clean air chamber 27, lifting valve plate 28, L-shaped partition 29, horizontal partition 30, and zone partition 31. Detailed Implementation

[0033] To better understand the technical solution of this utility model, a detailed description will be provided below in conjunction with relevant illustrations. It should be understood that the specific embodiments described below are not intended to limit the specific implementation of the technical solution of this utility model, but are merely possible implementations of the technical solution of this utility model. It should be noted that the descriptions of the positional relationships of the components herein, such as component A being located above component B, are based on the relative positions of the components in the illustrations and are not intended to limit the actual positional relationships of the components. Example 1

[0034] See Figure 1-3 , Figure 1 A schematic diagram of a combined switching dust collector purification system for coal tar flue gas according to Embodiment 1 is shown. As shown in the figure, the combined switching dust collector purification system for coal tar flue gas according to Embodiment 1 includes a tar flue gas inlet manifold 1 and multiple independent purification and dust removal units connected in parallel. The tar flue gas inlet manifold 1 is connected to the coal tar flue gas source and branches into multiple branch pipes through a switching valve. The branch pipes are connected to the corresponding purification and dust removal units.

[0035] Tar-filled flue gas enters the main collection pipe 1 and connects to the coal tar-filled flue gas source. The tar-filled flue gas enters the main collection pipe 1 and connects to multiple independent purification and dust removal units through switching valves. The purification and dust removal unit includes a pre-coating system, an air compensation channel, a detection and execution mechanism, and a bag filter.

[0036] The branch pipe is connected to the air inlet of the corresponding bag filter through a flue gas valve;

[0037] Pre-coating system:

[0038] The lime powder silo is connected to a gas-solid injector via a feeding valve;

[0039] Compressed air drives the gas-solid ejector via an air supply valve;

[0040] Air compensation channel: Atmosphere is directly connected to the dust collector inlet via an air valve;

[0041] Testing and execution agencies:

[0042] The bag filter dust collector is equipped with differential pressure detection mechanisms at the inlet and outlet.

[0043] The top of the bag filter is equipped with a dust removal system, which can be a pulse jet cleaning device; the bottom of the dust collector is equipped with a dust discharge valve.

[0044] In this embodiment, the tar flue gas enters the main collection pipe 1 and is connected to branch pipe A3 and branch pipe B4 respectively through a three-way switching valve 2. Branch pipe A3 is connected to purification and dust removal unit A, and branch pipe B4 is connected to purification and dust removal unit B. Purification and dust removal unit A and purification and dust removal unit B have the same structure.

[0045] The branch pipe A3 is connected to the air inlet of the bag filter A5 via the flue gas valve A6. The air inlet of the bag filter A5 is also connected to the atmospheric inlet channel via the air valve A7. The air inlet of the bag filter A5 is also connected to the lime powder feeding pipe. The lime powder feeding pipe is equipped with a gas-solid ejector A8. The gas-solid ejector A8 is connected to the active lime powder silo A9 via the feeding valve A10. The lime powder feeding pipe is also equipped with an air supply valve A11. The air supply valve A11 is connected to compressed air and is located on the outside of the gas-solid ejector A8 away from the bag filter A5. The bag filter A5 is equipped with a dust removal system A12 at the top. The bag filter A5 is equipped with an exhaust port on the upper side, which is connected to a fan A14 to achieve clean air discharge. The bag filter A5 is equipped with an ash discharge valve A13 at the bottom outlet.

[0046] The bag filter A5 is equipped with a differential pressure detection mechanism between its air inlet and exhaust outlet, which detects the inlet-outlet pressure difference A.

[0047] The branch pipe B4 is connected to the air inlet of the bag filter B15 via the flue gas valve B16. The air inlet of the bag filter B15 is also connected to the atmospheric inlet channel via the air valve B17. The air inlet of the bag filter B15 is also connected to the lime powder feeding pipe. The lime powder feeding pipe is equipped with a gas-solid ejector B18. The gas-solid ejector B18 is connected to the active lime powder silo B19 via the feeding valve B20. The lime powder feeding pipe is also equipped with an air supply valve B21, which is connected to compressed air. The air supply valve B21 is located on the outside of the gas-solid ejector B18 away from the bag filter B15. The bag filter B15 is equipped with a dust removal system B22 at the top. The bag filter B15 is equipped with an exhaust port on the upper side, which is connected to a fan B24 to achieve clean air discharge. The bag filter B15 is equipped with an ash discharge valve B23 at the bottom outlet.

[0048] The bag filter B15 is equipped with a differential pressure detection mechanism between its air inlet and exhaust outlet, which detects the inlet-outlet pressure difference B.

[0049] See Figure 2-3 , Figure 2 An airflow path diagram for the pre-coating stage of a combined switching dust collector purification process for coal tar flue gas in Embodiment 1 has been drawn. Figure 2 A flow chart of the filtration-switching-cleaning process for a combined switching dust collector used in the purification of coal tar flue gas according to Embodiment 1 is shown. As shown in the figure, the combined switching dust collector purification process for coal tar flue gas involved in Embodiment 1 includes three stages: pre-coating, filtration, and switching cleaning.

[0050] (1) Pre-coating stage

[0051] Open air valve A7 → Start fan A14 after 5 seconds;

[0052] Open the air supply valve A11 → open the material supply valve A10 after 5 seconds;

[0053] When the pressure difference reaches 800Pa, stop spraying and close the air supply valve A11, the material supply valve A10 and the air valve A7.

[0054] (2) Dual-unit alternating filtration

[0055] Phase 1: Switch the three-way valve to position A, and open the flue gas valve A6 and the fan A14;

[0056] Differential pressure trigger switching: When the differential pressure of unit A is ≥1500Pa:

[0057] a) Switch the three-way valve to the neutral position O → open the flue gas valve B16 and the fan B24;

[0058] b) Switch the three-way valve to position B → open the air valve A7;

[0059] c) After 1 minute, turn off fan A14 and air valve A7;

[0060] Phase 2: The purification and dust removal unit B enters the filter, repeating the above differential pressure monitoring and switching logic.

[0061] (3) Offline dust removal and preparation

[0062] After shutting down the purification and dust removal unit A, start the dust removal system A12 with powerful jet cleaning.

[0063] After the ash removal is completed, the ash is discharged through the ash discharge valve A13;

[0064] Re-execute the pre-coating and enter standby mode. Example 2

[0065] See Figure 4-6 , Figure 4 A schematic diagram of a combined switching dust collector purification system for coal tar flue gas in Embodiment 2 is shown. As shown in the figure, the combined switching dust collector purification system for coal tar flue gas involved in Embodiment 2 differs from Embodiment 1 in that the bag filter of the purification dust removal unit can be expanded into a multi-compartment structure, with each compartment independently equipped with valve groups and differential pressure detection.

[0066] In this embodiment, branch pipe A3 is divided into A 1 A 2 and A 3 Three sub-channels, each equipped with corresponding flue gas valves, air valves, and pre-coating systems. The bag filter A5 of the purification and dust removal unit A is equipped with A... 1 A 2 and A 3 The bag filter A5 comprises three independent compartments, including an outer shell, with the first compartment A arranged sequentially from bottom to top on the lower part of one side of the outer shell. 1 25. Air inlet valve, second compartment A 2 Air inlet valve 25, third compartment A 3 The air inlet valve 25, and the first compartment A is arranged sequentially from bottom to top on the upper part of the other side of the outer shell. 1 The exhaust vent, the second compartment A 2 The exhaust vent, the third compartment A 3 The exhaust port of each compartment is connected to the corresponding sub-channel by the air inlet valve 25, and the exhaust port of each compartment is connected to the fan A14; a differential pressure detection mechanism is provided between the air inlet and exhaust port of each compartment to detect the inlet and outlet pressure difference.

[0067] Each compartment is arranged from bottom to top as follows: ash hopper 26, dust settling area, filter bag filtration area, and clean air chamber 27. The clean air chamber 27 is connected to the exhaust port through the lifting valve plate 28, forming an air outlet channel. The sub-channel is connected to the ash hopper 26, the ash hopper 26 is connected to the dust settling area, the dust settling area is connected to the filter bag filtration area, the filter bag filtration area is connected to the clean air chamber 27, and the clean air chamber 27 is connected to the air outlet channel. Therefore, the path of the flue gas entering the compartment is: sub-channel → air inlet valve 25 → ash hopper 26 → dust settling area → filter bag filtration area → clean air chamber 27 → open lifting valve plate 28 → air outlet channel → exhaust port → fan.

[0068] An L-shaped partition 29 is provided between the air inlet valves 25 of two adjacent compartments. One end of the L-shaped partition 29 is connected between the corresponding two adjacent air inlet valves 25 on the inner wall of the outer shell, and the other end reaches the connection point of the ash hoppers 26 of the corresponding two adjacent compartments. A horizontal partition 30 is provided above the air inlet valve 25 of the last compartment. One end of the horizontal partition 30 is connected above the air inlet valve 25 of the corresponding compartment on the inner wall of the outer shell, and the other end is connected below the air inlet of the corresponding compartment on the inner wall of the outer shell.

[0069] A partition 31 is provided between the clean air chambers 27 of two adjacent compartments. The partition 31 is L-shaped. One end of the partition 31 is located in the middle between two adjacent clean air chambers 27 on the top surface of the outer shell, and the other end is connected to the air inlets of two adjacent compartments on the inner wall of the outer shell.

[0070] Working principle:

[0071] This utility model provides a combined switching dust collector purification system for coal tar flue gas.

[0072] The purification process is as follows:

[0073] 1. Before operation, all valves must be closed.

[0074] 2. All valves and three-way switching valves are automatic valves, which can be opened, closed and switch the airflow direction according to process requirements.

[0075] 3. Pre-coating is performed on baghouse dust collector A5 as follows: Open air valve A7. After 5 seconds, turn on fan A14, and baghouse dust collector A5 will begin operation (non-filtration). At this time, open air supply valve A11. After 5 seconds, open feed valve A10. Lime powder, under the action of compressed air and negative pressure in the branch pipes, is injected into the corresponding branch pipes and dust collector. The powdered lime powder is adsorbed on the outer surface of the filter bags, and clean airflow is drawn out by their respective fans. As time progresses, a certain thickness of lime powder is adsorbed on the outer surface of the filter bags, causing the dust collector resistance to increase. When the dust collector resistance rises to 800Pa, it indicates that pre-coating is complete, and filtration of coal tar flue gas can begin. At this time, stop the fan operation, close the gas-solid injector and air supply valve A11, close air valve A7, and wait for the next instruction.

[0076] 4. The pre-coating of bag filter B15 should also be carried out according to the above steps.

[0077] 5. Both dust collectors have been pre-coated. Preparations are complete.

[0078] 6. First, switch the three-way switching valve 2 to position A, open the flue gas valve A6, and start the fan A14. The flue gas containing coal tar enters the bag filter A5 through branch pipe A3 for filtration and purification. As filtration proceeds, the coal tar dust deposited on the outer surface of the filter bags thickens, increasing the dust collection resistance. When the differential pressure A between the inlet and outlet of dust collector A reaches 1500 Pa, it indicates that bag filter A5 needs a break. At this time, dust collector A is still running.

[0079] 7. Switch the three-way switching valve 2 to the neutral position (O), allowing flue gas to simultaneously enter branch pipes A3 and B4. Next, slowly open the flue gas valve B16, start the fan B24, and the flue gas containing coal tar enters the bag filter B15 through branch pipe B4 for filtration and purification. Some flue gas still enters branch pipe A3. At this time, open the air valve A7 and switch the three-way switching valve 2 to position B. The flue gas is completely drawn into the bag filter B, and the bag filter A no longer receives flue gas containing coal tar. The bag filter A continues to run for one minute, then the fan A14 is turned off, the air valve A7 is closed, and the cleaning system A12 begins a powerful jet cleaning operation to remove the accumulated ash from the outer surface of the filter bags in the bag filter A. The removed ash is discharged through the ash discharge valve A13.

[0080] 8. Dust collector A begins pre-coating to prepare for the next operation. The steps are the same as the pre-coating operation above.

[0081] 9. When the differential pressure between the inlet and outlet of dust collector B reaches 1500Pa, it indicates that dust collector B needs to be cleaned. The operation sequence is the same as that of bag dust collector A5.

[0082] This invention employs a combined purification technology, ensuring that while one dust collector is running, another dust collector has already completed cleaning and pre-coating, and is entering the waiting operation phase. The process of this invention guarantees thorough bag cleaning without interference from airflow. Simultaneously, it allows for maintenance and other operations on the stopped bag dust collector without affecting the overall process operation.

[0083] The purification system of this utility model also includes a dust collector with multiple individual compartments. The above steps are performed on each compartment, and each compartment has a three-way reversing valve and a valve configured as described above at its inlet and outlet.

[0084] Key points regarding the pre-coating stage in the purification process of this utility model:

[0085] 1. Prioritize establishing negative pressure: First, open the air valve to introduce atmospheric air, then start the fan to create a negative pressure environment;

[0086] 2. Prevent powder waste: The compressed air is turned on before the lime powder to ensure uniform gas-solid mixing;

[0087] 3. Precise pressure differential control: The thickness of lime powder adsorption is quantitatively determined by ΔP=800Pa, with an error of ±50Pa.

[0088] Key points regarding the filtration and dust removal stages in the purification process of this utility model:

[0089] 1. Three steps for seamless handover:

[0090] 1.1 Transition: Cutting the midpoint O enables parallel operation of two units (to prevent sudden pressure changes);

[0091] 1.2 Switching: Before switching to position B, open air valve A7 to prevent residual smoke tar from solidifying;

[0092] 1.3 Isolation: After shutting down fan A14, clean the dust to ensure zero airflow interference.

[0093] 2. Guaranteed cleaning strength: The pulse pressure is increased to 0.6MPa in offline mode (3 times that of online cleaning).

[0094] 3. Fully automatic closed loop: Differential pressure signal → valve action → fan start and stop are controlled in real time by PLC.

[0095] The switching steps mentioned above include: when the pressure difference of the active unit is ≥1500Pa, first switch the three-way valve to the neutral position (O), and then open the flue gas valve and fan of the standby unit.

[0096] The above are merely specific application examples of this utility model and do not constitute any limitation on the scope of protection of this utility model. All technical solutions formed by equivalent transformations or equivalent substitutions fall within the scope of protection of this utility model.

Claims

1. A combined switching dust collector purification system for coal tar flue gas, characterized in that: It includes a tar flue gas inlet manifold and multiple independent purification and dust removal units connected in parallel. The tar flue gas inlet manifold is connected to a coal tar flue gas source and branches into multiple branch pipes through a switching valve. Each branch pipe is connected to a corresponding purification and dust removal unit. The purification and dust removal unit includes a pre-coating system, an air compensation channel, a detection and execution mechanism, and a bag filter. The pre-coating system includes a lime powder silo and a gas-solid injector. The air compensation channel includes an air valve. The detection and execution mechanism includes a differential pressure detection mechanism and a dust removal system. The branch pipe is connected to the air inlet of the corresponding bag filter through a flue gas valve; the lime powder silo is connected to the gas-solid injector through a feeding valve, and compressed air drives the gas-solid injector through an air supply valve; atmospheric air is directly connected to the air inlet of the bag filter through an air valve; the bag filter is equipped with a differential pressure detection mechanism at the inlet and outlet; and a dust removal system is installed at the top inner part of the bag filter.

2. The combined switching dust collector purification system for coal tar flue gas according to claim 1, characterized in that: The air inlet of the bag filter is connected to a lime powder feeding pipe. A gas-solid ejector is installed on the lime powder feeding pipe. The gas-solid ejector is connected to an active lime powder silo via a feeding valve. An air supply valve is also installed on the lime powder feeding pipe. The air supply valve is connected to compressed air and is located on the outside of the gas-solid ejector away from the bag filter.

3. The combined switching dust collector purification system for coal tar flue gas according to claim 1, characterized in that: The bag filter is provided with an exhaust port on one side of its upper part, and the exhaust port is connected to a fan to achieve the discharge of clean air.

4. A combined switching dust collector purification system for coal tar flue gas according to claim 1, characterized in that: The dust removal system uses a pulse jet cleaning device.

5. A combined switching dust collector purification system for coal tar flue gas according to claim 1, characterized in that: The bottom of the bag filter is equipped with an ash discharge valve.

6. A combined switching dust collector purification system for coal tar flue gas according to claim 1, characterized in that: The bag filter of the purification and dust removal unit is expanded into a multi-compartment structure, with each compartment independently equipped with valve groups and differential pressure detection; the branch pipe A is divided into multiple sub-channels, each sub-channel is equipped with corresponding flue gas valves, air valves and pre-coating systems, and the bag filter of the purification and dust removal unit is equipped with multiple independent compartments.

7. A combined switching dust collector purification system for coal tar flue gas according to claim 6, characterized in that: The bag filter dust collector includes an outer shell. On the lower part of one side of the outer shell, from bottom to top, are arranged the air inlet valves for the first compartment, the second compartment, the third compartment, and so on. On the upper part of the other side of the outer shell, from bottom to top, are arranged the exhaust ports for the first compartment, the second compartment, the third compartment, and so on. The air inlet valve of each compartment is connected to a corresponding sub-channel, and the exhaust port of each compartment is connected to a fan. A differential pressure detection mechanism is provided between the air inlet and exhaust port of each compartment to detect the inlet and outlet pressure difference.

8. A combined switching dust collector purification system for coal tar flue gas according to claim 7, characterized in that: Each compartment is arranged from bottom to top as follows: a dust hopper, a dust settling area, a filter bag filtration area, and a clean air chamber. The clean air chamber is connected to the exhaust port through a lifting valve plate to form an air outlet channel. The sub-channel is connected to the dust hopper, the dust hopper is connected to the dust settling area, the dust settling area is connected to the filter bag filtration area, the filter bag filtration area is connected to the clean air chamber, and the clean air chamber is connected to the air outlet channel.

9. A combined switching dust collector purification system for coal tar flue gas according to claim 8, characterized in that: An L-shaped partition is provided between the air inlet valves of two adjacent compartments. One end of the L-shaped partition is connected between the corresponding two adjacent air inlet valves on the inner wall of the outer shell, and the other end reaches the connection point of the ash hoppers of the corresponding two adjacent compartments. A horizontal partition is provided above the air inlet valve of the last compartment. One end of the horizontal partition is connected above the air inlet valve of the corresponding compartment on the inner wall of the outer shell, and the other end is connected below the air inlet of the corresponding compartment on the inner wall of the outer shell.

10. A combined switching dust collector purification system for coal tar flue gas according to claim 8, characterized in that: A partition is provided between the clean air chambers of two adjacent compartments. The partition is L-shaped. One end of the partition is located in the middle between two adjacent clean air chambers on the top surface of the outer shell, and the other end is connected to the air inlet between two adjacent compartments on the inner wall of the outer shell.

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