Ashed coal gas full recovery system and control method thereof

Abstract

The present application relates to a kind of ash coal gas full recovery system and its control method, belong to blast furnace ironmaking technical field.The system includes ash tank, bag filter and gas storage tank, ash tank receives gravity / cyclone dust collector ash through ash valve, and is connected to gas storage tank through bag filter by first recovery pipeline;Gas storage tank is connected to clean gas pipe network by third recovery pipeline.System uses pressure balance as start-stop criterion, and executes " ash - pressure relief - cycle - recovery " closed-loop control: repeat ash and pressure relief operation, and batch transfer ash coal gas to gas storage tank;After the pressure of gas storage tank rises to set value, it is recovered to low pressure state after being discharged into clean gas pipe network once, and enters next cycle.The present application resolves the contradiction between recovery back pressure and ash pressure difference by time sequence decoupling, relies on natural pressure difference throughout the journey, does not need additional power, realizes ash coal gas full recovery and zero emission, with the advantages of low operating cost, safe and reliable, system simple.

Description

Technical Field

[0001] This invention belongs to the field of blast furnace ironmaking technology, specifically relating to a full recovery system for ash discharge gas and its control method. Background Technology

[0002] In the blast furnace ironmaking process, gravity dust collectors or cyclone dust collectors serve as primary dust removal equipment for blast furnace gas. A large amount of dust accumulates at the bottom of these collectors, requiring periodic ash removal via an ash discharge hopper. During ash discharge, the gravity dust collector or cyclone dust collector is connected to the ash discharge hopper, and the dust-laden gas enters the ash discharge hopper. In traditional processes, the gas in the ash discharge hopper is directly vented into the air. This practice has the following prominent problems: First, it will cause serious energy waste and environmental pollution. The ash discharge gas contains a large amount of combustible and toxic components such as CO. Directly discharging it into the atmosphere not only causes a huge waste of gas resources, but also leads to the release of dust and toxic gases into the atmosphere, seriously polluting the working environment and failing to meet increasingly stringent environmental protection requirements.

[0003] Secondly, existing recovery methods face technical bottlenecks. Some attempts to connect the ash discharge tank gas to the recovery system encounter an inherent contradiction: when the recovered gas enters the gas storage device, the pressure inside the storage device gradually increases, creating back pressure. Once the back pressure rises to near the internal pressure of the dust collector, the ash discharge tank cannot establish a sufficient pressure difference with the dust collector, making it difficult for the ash flow to fall smoothly, causing problems such as "material bridging" and "suspended ash" that hinder ash discharge. Forcibly recovering the ash would actually interfere with normal ash discharge operations and affect the continuity of blast furnace production.

[0004] Finally, there is a lack of systematic safety control logic. The ash unloading process involves high-temperature dust-laden gas. If the recovery path is not properly designed or the control logic is lacking, gas backflow can easily occur due to pressure imbalance, leading to safety accidents such as poisoning, fire, or even explosion.

[0005] In response to the above problems, some patents have proposed gas recovery solutions, but most of them focus on the equalization or venting gas recovery of the weighing tank at the top of the blast furnace, which is different from the dust removal and ash unloading scenario involved in this solution. Moreover, they have not provided effective solutions for the timing coordination between ash unloading operation and gas recovery and the back pressure control problem.

[0006] Designing a system that can fully recover and prevent the release of ash-discharging gas, eliminate the interference of back pressure on the ash-discharging operation through reasonable system settings and pressure control logic, and ensure safety and reliability throughout the entire process is a technical challenge that urgently needs to be solved in the industry. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a complete recovery system for ash unloading gas and its control method, so as to achieve complete recovery of ash unloading gas and eliminate the interference of back pressure on the ash unloading operation.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A coal gas recovery system for ash discharge includes an ash discharge tank 1, a bag filter 2, and a gas storage tank 3; the ash inlet of the ash discharge tank 1 is connected to the ash discharge outlet of the gravity / cyclone dust collector 13 through an ash discharge pipeline, and an ash discharge valve 14 is provided on the ash discharge pipeline. The vent of the ash discharge tank 1 is connected to the air inlet of the bag filter 2 through the first recovery pipe 4, and the first recovery pipe 4 is equipped with a first recovery shut-off valve 5. The outlet of the bag filter 2 is connected to the inlet of the air storage tank 3 through the second recovery pipe 6, and the second recovery pipe 6 is equipped with a second recovery shut-off valve 7. The outlet of the gas storage tank 3 is connected to the clean coal gas pipeline network 9 through the third recovery pipeline 8, and the third recovery pipeline 8 is equipped with a third recovery shut-off valve 10. The ash unloading tank 1 is equipped with a first pressure monitoring device 11, and the gas storage tank 3 is equipped with a second pressure monitoring device 12.

[0009] Furthermore, the dust collector 2 is equipped with a high level switch 17 and a low level switch 18 at the ash hopper. The ash hopper of the dust collector 2 is connected to the ash discharge tank 1 through the ash discharge pipe 15. The ash discharge pipe 15 is equipped with an ash discharge shut-off valve 16.

[0010] Furthermore, the system is a fully enclosed structure, and the gas inside the ash unloading tank 1 is not discharged into the atmosphere.

[0011] The control method for the above-mentioned ash unloading gas full recovery system includes the following steps: S1. Ash discharge: Open the ash discharge valve 14 to allow the dust collected in the gravity / cyclone dust collector 13 to enter the ash discharge tank 1; when the pressure P1 in the ash discharge tank 1 is balanced with the pressure P0 in the gravity / cyclone dust collector 13, close the ash discharge valve 14 to stop ash discharge. S2, pressure relief: Open the first recovery shut-off valve 5 and the second recovery shut-off valve 7, and drive the gas in the ash unloading tank 1 through the first recovery pipe 4, the bag filter 2 and the second recovery pipe 6 in sequence and enter the gas storage tank 3 by natural pressure difference; until the pressure P1 in the ash unloading tank 1 is balanced with the pressure P2 in the gas storage tank 3, close the first recovery shut-off valve 5 and the second recovery shut-off valve 7. S3, Circulating ash unloading and pressure relief: Repeat S1 and S2 multiple times to gradually increase the pressure P2 in the air storage tank 3 until the pressure P2 in the air storage tank 3 is balanced with the pressure in the gravity / cyclone dust collector 13. S4. Recovery: Close the ash discharge valve 14, the first recovery shut-off valve 5, and the second recovery shut-off valve 7, and open the third recovery shut-off valve 10. Drive the gas in the gas storage tank 3 through the third recovery pipeline 8 into the clean gas pipeline network 9 by natural pressure difference; until the pressure P2 in the gas storage tank 3 is balanced with the pressure P3 in the clean gas pipeline network 9, close the third recovery shut-off valve 10.

[0012] Furthermore, when the high level switch 17 of the dust collector 2 hopper is triggered, the ash discharge shut-off valve 16 is opened, allowing the dust in the dust collector 2 hopper to enter the ash discharge tank 1 through the ash discharge pipe 15; when the low level switch 18 is triggered, the ash discharge shut-off valve 16 is closed.

[0013] The beneficial effects of this invention are as follows: (1) Through the complete closed-loop control of “ash unloading → pressure relief → circulation → recovery”, the coal gas in the ash unloading tank is not discharged into the atmosphere during the entire operation cycle; the recovered clean coal gas is directly connected to the clean coal gas pipeline network, which completely eliminates the environmental pollution and energy waste caused by venting into the air, and realizes the full recovery and zero emission of ash unloading coal gas.

[0014] (2) By using a timing control mechanism that "gas recovery is not performed during ash unloading, and ash unloading is paused during gas recovery," the "gas recovery" and "ash unloading operation" are separated in time: during ash unloading, the gas storage tank is in a low-pressure state (≈P3), maintaining a large pressure difference with the gravity / cyclone dust collector, ensuring smooth ash unloading; during recovery, the gas storage tank is in a high-pressure state (≈P0), ash unloading is paused, and the operation is not affected. Through this mode of "accumulating potential energy through multiple small cycles and releasing potential energy through one large cycle," it is ensured that the pressure in the gas storage tank will not continuously accumulate and interfere with ash unloading, guaranteeing the continuity and stability of the ash unloading operation and resolving the contradiction between "recovery back pressure and ash unloading pressure difference."

[0015] (3) The entire system does not require any external power equipment; the gas flow is entirely driven by the natural pressure difference within the system. During the depressurization phase: the gas flows automatically when P1 > P2 and automatically stops when P1 = P2; during the recovery phase: the gas flows automatically into the pipeline when P2 > P3 and automatically stops when P2 = P3. All valves are opened and closed based on the criterion of "pressure balance," achieving automatic balance based on physical laws. No manual intervention is required, resulting in extremely low energy consumption and significantly reducing operating costs.

[0016] (4) The system achieves full-process automatic control based on pressure monitoring (pressure of ash unloading tank and gas storage tank) and material level switch (high / low material level of ash hopper of bag dust collector). It uses "pressure balance" as the start and stop condition and "material level signal" as the trigger condition for automatic ash unloading, which greatly reduces the labor intensity of operators and improves the precision level of process control.

[0017] (5) The bag filter serves two functions: "gas purifier" and "dust transfer bin". It can perform fine dust removal on the dust-containing gas discharged from the ash unloading tank during the pressure relief operation, and can automatically monitor the ash level through the high / low material level switch and automatically discharge ash during the ash unloading tank operation window. This design eliminates the need for a separate ash storage tank and ash conveying equipment, reduces equipment footprint and investment costs, and simplifies the process flow.

[0018] (6) The fully enclosed recovery system eliminates safety hazards such as poisoning and fire caused by gas leakage. At the same time, the pressure control logic can effectively prevent gas backflow, which fundamentally improves the safety of blast furnace operation and improves the working environment.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the system of the present invention.

[0021] Figure label: 1. Ash discharge hopper; 2. Baghouse dust collector; 3. Gas storage tank; 4. First recovery pipeline; 5. First recovery shut-off valve; 6. Second recovery pipeline; 7. Second recovery shut-off valve; 8. Third recovery pipeline; 9. Clean gas pipeline; 10. Third recovery shut-off valve; 11. First pressure monitoring device; 12. Second pressure monitoring device; 13. Gravity / cyclone dust collector; 14. Ash discharge valve; 15. Ash discharge pipeline; 16. Ash discharge shut-off valve; 17. High level switch; 18. Low level switch. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0024] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0025] Please see Figure 1 This embodiment describes a complete recovery system for ash-discharging gas. The recovery system includes: The ash discharge tank 1 is used to receive dust from the gravity / cyclone dust collector 13 (i.e., gravity dust collector or cyclone dust collector). The ash inlet of the ash discharge tank 1 is connected to the ash outlet of the gravity / cyclone dust collector 13 through the ash discharge pipeline. The ash discharge pipeline is equipped with an ash discharge valve 14.

[0026] The bag filter 2 has its air inlet connected to the vent of the ash discharge tank 1 through the first recovery pipe 4, and the first recovery pipe 4 is equipped with a first recovery shut-off valve 5.

[0027] The gas storage tank 3 has its inlet connected to the outlet of the bag filter 2 via a second recovery pipe 6, and a second recovery shut-off valve 7 is installed on the second recovery pipe 6. The outlet of the gas storage tank 3 is connected to the clean coal gas pipeline network 9 via a third recovery pipe 8, and a third recovery shut-off valve 10 is installed on the third recovery pipe 8.

[0028] The ash unloading tank 1 is equipped with a first pressure monitoring device 11, which is used to monitor the internal pressure P1 of the ash unloading tank 1.

[0029] The gas storage tank 3 is equipped with a second pressure monitoring device 12, which is used to monitor the internal pressure P2 of the gas storage tank 3.

[0030] As a further optimization of the above scheme, in this system, the ash hopper of the bag filter 2 is equipped with a high level switch 17 and a low level switch 18. The ash hopper of the bag filter 2 is connected to the ash discharge tank 1 through the ash discharge pipe 15, and the ash discharge pipe 15 is equipped with an ash discharge shut-off valve 16. In addition to performing fine dust removal on the dust-laden gas discharged from the ash discharge tank 1 (so that the purified gas meets the grid connection standard), the bag filter 2 also serves as a "transfer silo". That is, it uses its own ash hopper to continuously accumulate ash during the purification process. When it accumulates to a certain level, it is discharged. This can prevent excessive ash discharge from causing gas leakage and eliminate the need for related equipment such as ash storage tanks, thereby simplifying the system structure.

[0031] The system is a fully enclosed structure, and the gas in the ash unloading tank 1 is not released into the atmosphere during the entire ash unloading and recycling process.

[0032] The control method for the above-mentioned ash unloading gas full recovery system includes the following steps: S1. Ash Discharge: Open the ash discharge valve 14 between the gravity / cyclone dust collector 13 and the ash discharge tank 1, allowing the dust collected in the gravity / cyclone dust collector 13 to enter the ash discharge tank 1 under gravity. Since the interior of the gravity / cyclone dust collector 13 is a high-pressure gas environment, a large amount of gas enters the ash discharge tank 1 during the ash discharge process, causing the pressure inside the ash discharge tank 1 to rise rapidly. When the pressure P1 inside the ash discharge tank 1 reaches equilibrium with the pressure P0 inside the gravity / cyclone dust collector 13, the ash flow loses its pressure differential driving force, and ash discharge automatically stops. At this point, close the ash discharge valve 14 to stop ash discharge and initiate a pressure relief operation.

[0033] S2. Pressure Relief: Open the first recovery shut-off valve 5 and the second recovery shut-off valve 7. The dust-laden gas in the ash discharge tank 1 enters the bag filter 2 through the first recovery pipe 4. The dust-laden gas undergoes fine dust removal in the bag filter 2, with dust trapped outside the filter bags. The purified gas then enters the gas storage tank 3 through the second recovery pipe 6. During this process, the gas flow is entirely driven by the natural pressure difference between the ash discharge tank 1 and the gas storage tank 3, without the need for external power equipment such as a compressor. When the pressure P1 in the ash discharge tank 1 and the pressure P2 in the gas storage tank 3 reach equality / balance, the pressure difference disappears, and the gas flow naturally stops. At this point, close the first and second recovery shut-off valves, and the pressure relief ends.

[0034] S3. Cyclic Ash Unloading and Pressure Relief: Repeat the "ash unloading → pressure relief" process multiple times. With each completed cycle, the pressure P2 in the air storage tank 3 increases. After multiple cycles, the pressure P2 in the air storage tank 3 gradually rises until it approaches or equals the pressure P0 level in the gravity / cyclone dust collector 13. When the pressure P2 in the air storage tank 3 approaches the pressure P0 in the gravity / cyclone dust collector 13, it will cause the pressure P1 in the ash unloading tank 1 to also approach P0 during subsequent ash unloading, resulting in poor ash unloading. At this point, the "recovery" operation can be performed; the trigger condition for recovery is "P2 approaches P0". S4. Recovery: When the pressure P2 in the gas storage tank 3 rises to the preset value (P2 is close to P0), close the ash discharge valve 14, the first recovery shut-off valve 5 and the second recovery shut-off valve 7, and open the third recovery shut-off valve 10. Driven by the natural pressure difference, the gas in the gas storage tank 3 enters the clean gas pipeline network 9 through the third recovery pipeline 8. When the pressure P2 in the gas storage tank 3 is balanced with the pressure P3 in the clean gas pipeline network 9, the gas stops flowing and the third recovery shut-off valve 10 is closed.

[0035] After the pressure in gas storage tank 3 decreases, the system returns to a "low-pressure state" and can then repeat the next round of "ash unloading → pressure relief → circulation → recovery" operation. This cycle repeats continuously, achieving full recovery and zero emissions of ash-unloaded coal gas.

[0036] In step S2 above, the bag filter 2 performs fine dust removal on the coal gas discharged from the ash discharge tank 1. The purified coal gas enters the gas storage tank 3, and the separated dust is collected in the ash hopper of the bag filter 2. When the high level switch 17 of the ash hopper of the bag filter 2 is triggered, the ash discharge shut-off valve 16 is opened, allowing the dust in the ash hopper of the bag filter 2 to enter the ash discharge tank 1 through the ash discharge pipe 15 and be processed together with the next ash discharge operation; when the low level switch 18 is triggered, the ash discharge shut-off valve 16 is closed.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A coal gas recovery system for ash discharge, comprising an ash discharge tank (1), a bag filter (2), and a gas storage tank (3); the ash inlet of the ash discharge tank (1) is connected to the ash outlet of a gravity / cyclone dust collector (13) via an ash discharge pipeline, and an ash discharge valve (14) is provided on the ash discharge pipeline; characterized in that: The vent of the ash discharge tank (1) is connected to the air inlet of the bag filter (2) through the first recovery pipe (4), and the first recovery pipe (4) is equipped with a first recovery shut-off valve (5). The outlet of the bag filter (2) is connected to the inlet of the air storage tank (3) through the second recovery pipe (6), and the second recovery pipe (6) is equipped with a second recovery shut-off valve (7). The outlet of the gas storage tank (3) is connected to the clean coal gas pipeline (9) through the third recovery pipeline (8), and the third recovery pipeline (8) is equipped with a third recovery shut-off valve (10). The ash unloading tank (1) is equipped with a first pressure monitoring device (11), and the gas storage tank (3) is equipped with a second pressure monitoring device (12).

2. The ash-recovery gas recovery system according to claim 1, characterized in that: The dust collector (2) is equipped with a high level switch (17) and a low level switch (18) at the ash hopper. The ash hopper of the dust collector (2) is connected to the ash discharge tank (1) through the ash discharge pipe (15). The ash discharge pipe (15) is equipped with an ash discharge shut-off valve (16).

3. The ash-recovery gas recovery system according to claim 2, characterized in that: The system is a fully enclosed structure, and the gas in the ash unloading tank (1) is not discharged into the atmosphere.

4. The control method for the ash unloading gas full recovery system according to claim 2 or 3, characterized in that: Includes the following steps: S1. Ash discharge: Open the ash discharge valve (14) to allow the dust collected in the gravity / cyclone dust collector (13) to enter the ash discharge tank (1); when the pressure P1 in the ash discharge tank (1) is balanced with the pressure P0 in the gravity / cyclone dust collector (13), close the ash discharge valve (14) to stop ash discharge. S2, Pressure relief: Open the first recovery shut-off valve (5) and the second recovery shut-off valve (7), and drive the gas in the ash discharge tank (1) through the first recovery pipe (4), the bag filter (2) and the second recovery pipe (6) in sequence and enter the gas storage tank (3) by natural pressure difference; until the pressure P1 in the ash discharge tank (1) is balanced with the pressure P2 in the gas storage tank (3), close the first recovery shut-off valve (5) and the second recovery shut-off valve (7); S3, Circulating ash unloading and depressurization: Repeat S1 and S2 multiple times to gradually increase the pressure P2 in the gas storage tank (3) until the pressure P2 in the gas storage tank (3) is balanced with the pressure in the gravity / cyclone dust collector (13); S4. Recovery: Close the ash discharge valve (14), the first recovery shut-off valve (5), and the second recovery shut-off valve (7), and open the third recovery shut-off valve (10). Drive the gas in the gas storage tank (3) through the third recovery pipeline (8) into the clean gas pipeline network (9) by natural pressure difference; until the pressure P2 in the gas storage tank (3) is balanced with the pressure P3 in the clean gas pipeline network (9), close the third recovery shut-off valve (10).

5. The control method according to claim 4, characterized in that: When the high level switch (17) of the dust collector (2) is triggered, the ash discharge shut-off valve (16) is opened, so that the dust in the dust collector (2) dust hopper enters the ash discharge tank (1) through the ash discharge pipe (15); when the low level switch (18) is triggered, the ash discharge shut-off valve (16) is closed.

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