A fire prevention and extinguishing system and method for injecting liquid CO2 into goaf

Abstract

The present invention discloses a goaf-injected liquid CO2 fire prevention and extinguishing system and method, belonging to the technical field of goaf-injected fire prevention and extinguishing. The system includes an injection unit, a goaf and drainage unit, and a gas storage and separation unit connected in sequence. The method includes: inputting gaseous CO2 to test whether the injection unit, the goaf and drainage unit, and the gas storage and separation unit can operate normally; converting CO2 into liquid and injecting it into the goaf and drainage unit; injecting a coating material into the goaf and drainage unit; injecting gaseous CO2 into the goaf, and displacing the original gas in the goaf into the gas storage and separation unit. The present invention uses liquid CO2 to inject into the goaf for fire prevention and extinguishing, increasing the contact area with the coal residue in the goaf, so that the coal residue can more effectively absorb CO2, reducing the concentration of O2 in the goaf while lowering the ignition point of the coal, thereby better performing fire prevention and extinguishing work.

Description

Technical Field

[0001] The present invention belongs to the technical field of goaf fire prevention and extinguishing, and more specifically, relates to a goaf fire prevention and extinguishing system and a fire prevention and extinguishing method for injecting liquid CO2. Background Art

[0002] Coal is my country's primary energy source, and coal-fired power plants are the foundation of the country's electricity supply. Coal and electricity are two highly interrelated pillars of the national economy. Transporting coal from coal yards to coal-fired power plants accelerates internal circulation. Coal-fired power plants are one of the largest sources of CO2. The CO2 they produce can then be transported via pipelines to planned mines for underground goaf fire prevention and carbon sequestration.

[0003] With the continuous development of coal mining, a large number of goafs are left behind after coal mining. These goafs contain a large amount of residual coal. When coal and oxygen continuously combine, they can easily cause spontaneous combustion, which can lead to accidents such as coal mine explosions. Therefore, the threat of spontaneous combustion in goafs has become a major problem restricting the development of the coal mining industry. Due to the special underground environment, the initial signs of spontaneous combustion are not obvious, and if they are not promptly addressed, the generated combustible gases such as CH4 can lead to dangerous phenomena such as combustion and explosions, seriously affecting the safety of life and property. Therefore, solving the problem of spontaneous combustion in goafs has become a top priority.

[0004] Injecting inert media into goafs to isolate oxygen is currently the primary fire prevention and extinguishing technology in goafs. However, inert gases such as CO2 and N2 do not adequately encapsulate the coal and can cause gas diffusion and escape. Gas escape to the surface can impact the surrounding ecological environment.

[0005] Specifically, the traditional gas injection process for underground fire prevention and extinguishing in goafs has the following drawbacks: 1. Gas flows through cracks and fissures, preventing it from remaining in the fire-prevention zone for extended periods, making it ineffective and unable to quickly and effectively extinguish the fire, resulting in low efficiency. 2. The injected gas is mostly inert, and high concentrations pose a threat to personnel safety and hinder subsequent underground monitoring and inspection of the fire-prevention zone. 3. The coal mass is unable to fully absorb the gas, causing it to adhere to the coal surface, effectively treating the symptoms rather than the root cause.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a goaf-injected liquid CO2 fire prevention and extinguishing system and fire prevention and extinguishing method. By setting an injection unit, a goaf and drainage unit and a gas storage and separation unit, liquid CO2 is injected into the goaf for fire prevention and extinguishing, and the contact area with the residual coal in the goaf is increased, so that the residual coal can more effectively adsorb CO2, and the concentration of O2 in the goaf is reduced while lowering the ignition point of the coal, thereby better performing fire prevention and extinguishing work; a gas storage and separation unit is set at the ground port to absorb CO2, CH4 and other gases escaping from the goaf and separate and utilize them.

[0008] The technical solutions of the present invention are as follows:

[0009] The present invention provides a goaf area liquid CO2 injection fire prevention and extinguishing system, comprising an injection unit, a goaf area and a drainage unit and a gas storage and separation unit connected in sequence.

[0010] Furthermore, the injection unit includes a parallel upstream CO2 injection branch and a coating material injection branch, and a downstream pipeline-connected check valve, a reciprocating injection pump, a flow meter, an outlet safety valve, and an outlet pressure gauge. The upstream and downstream pipelines are connected, and the downstream is connected to the goaf and drainage unit via a pipeline.

[0011] Furthermore, the CO2 injection branch includes a CO2 storage tank, a stop valve, a pressurization and cooling device, and a centrifugal pump with an inducer, which are connected in sequence.

[0012] Furthermore, the gas storage and separation unit comprises a gas displacement pipeline, a mixed gas separation device and a gas storage tank connected in sequence. The upstream of the gas displacement pipeline is connected to the goaf and the drainage unit.

[0013] Furthermore, the goaf and drainage unit includes a goaf and a drainage pipe arranged in the goaf, and the drainage pipe is also provided with a plurality of CO2 monitors.

[0014] The present invention also provides a fire prevention and extinguishing method based on the goaf area liquid CO2 fire prevention and extinguishing system, comprising the following steps:

[0015] S1: Input gaseous CO2 to test whether the injection unit, goaf, drainage unit and gas storage and separation unit can operate normally;

[0016] S2: converting CO2 into liquid and injecting it into the goaf and drainage unit;

[0017] S3: injecting the covering material into the goaf and the drainage unit;

[0018] S3: Injecting gaseous CO2 into the goaf and displacing the original gas in the goaf to the gas storage and separation unit.

[0019] Furthermore, the method further includes S4: detecting the CO2 concentration of the gas storage and separation unit, and stopping the injection operation after the concentration reaches a set value.

[0020] Furthermore, it also includes S21 between S2 and S3: using a reciprocating injection pump and a flow meter to measure the CO2 pumping amount to prevent excessive pressure in the goaf.

[0021] Furthermore, it also includes S22 between S21 and S3: monitoring the CO2 injection amount and the remaining amount on the coal surface through a CO2 monitor installed along the drainage pipeline to judge the CO2 adsorption situation of the coal body in order to adjust the injection frequency; the CO2 injection work process moves with the mining working face and works in different areas.

[0022] Preferably, the plurality of CO2 monitors are used for subsequent CO2 gas leakage monitoring indicators.

[0023] The technical content disclosed in the present invention has the following beneficial effects:

[0024] The present invention sets an injection unit, a goaf and drainage unit and a gas storage and separation unit, and uses liquid CO2 to inject into the goaf for fire prevention and extinguishing, thereby increasing the contact area with the residual coal in the goaf, so that the residual coal can more effectively adsorb CO2, and reduce the concentration of O2 in the goaf while lowering the ignition point of the coal, thereby better performing fire prevention and extinguishing work; a gas storage and separation unit is set at the ground port to absorb CO2, CH4 and other gases escaping from the goaf and separate and utilize them.

[0025] The present invention solves the problem that the gas injected into the goaf will flow and diffuse within the area, making it impossible to effectively suppress the spontaneous combustion of coal, and the problem that the gas in the goaf will escape to the surface and affect the surrounding environment. The gas in the goaf will escape to the surface through faults, cracks, channels and the like, causing damage to the surrounding environment. In particular, the toxic and harmful gases flowing out of the well with the injected gas will spread into the atmosphere and endanger human safety. Grouting is performed to seal the pipes and cracks to seal the CO2 underground. At the same time, a mixed gas separation device is set up at a suitable point to collect the tail gas during the large-flow gas injection stage. It can also be used for the extraction of CO2 stored in underground spaces in the future.

[0026] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0028] Figure 1This is a schematic structural diagram of the goaf area liquid CO2 fire prevention and extinguishing system of the present invention;

[0029] Figure 2 This is a schematic diagram of the underground structure of the liquid CO2 fire prevention and extinguishing system for goaf areas of the present invention.

[0030] Explanation of the accompanying symbols: 1. CO2 storage tank; 2. Shut-off valve; 3. Pressurization and cooling device; 4. Centrifugal pump with inducer; 5. Coating material storage tank; 6. Check valve; 7. Reciprocating injection pump; 8. Flow meter; 9. Outlet safety valve; 10. Outlet pressure gauge; 11. Above-ground pipeline; 12. Underground pipeline; 13. CO2 monitor; 14. Mixed gas separation device; 15. Storage gas tank; 16. Goaf; 17. Gas displacement pipeline; 18. Coal-fired power plant; 19. Coal-fired power plant CO2 transportation pipeline. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0032] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0033] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0034] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0035] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0036] See also Figure 1 and Figure 2 The present invention discloses a liquid CO2 fire prevention and extinguishing system for goaf, comprising an injection unit, a goaf and drainage unit and a gas storage and separation unit connected in sequence.

[0037] In this embodiment, the injection unit includes a CO2 injection branch and a coating material injection branch arranged in parallel at the upstream, and the injection unit also includes a check valve 6, a reciprocating injection pump 7, a flow meter 8, an outlet safety valve 9 and an outlet pressure gauge 10 connected to the pipeline at the downstream. The upstream and downstream pipelines are connected, and the downstream is connected to the goaf and the drainage unit through a pipeline. The pipeline includes an above-ground pipeline 11 and an underground pipeline 12. The reciprocating injection pump 7 can provide a stable CO2 injection amount due to its strong self-priming ability and high efficiency. At the same time, the CO2 injection amount can be calculated by the number of strokes, which can prevent the underground goaf from being over-pressured and the media can be fractured to adsorb CO2.

[0038] In this embodiment, the CO2 injection branch includes a CO2 storage tank 1, a stop valve 2, a pressurizing and cooling device 3, and a centrifugal pump with an inducer 4, which are connected in sequence. The coating material injection branch includes a coating material storage tank 5, which is used to store solid-liquid gel materials and subsequent gangue materials for filling. The solid-liquid gel material can form a solid film on the surface of liquid CO2, which can slow down the volatilization of liquid CO2, thereby prolonging the fire prevention and extinguishing effect of liquid CO2. Among them, the pressurizing and cooling device 3 is used to adjust CO2 to become liquid; the centrifugal pump with an inducer 4 can reduce the flow resistance caused by the high stroke frequency of the reciprocating injection pump 7 and increase the injection amount of CO2; at the same time, the centrifugal pump with an inducer 4 has a large head, which can ensure that CO2 enters the reciprocating injection pump 7 in liquid form, while reducing the physical strength and weight of the pump to ensure operational safety.

[0039] In this embodiment, the gas storage and separation unit includes a sequentially connected gas displacement pipeline 17, a mixed gas separation device 14, and a gas storage tank 15. The upstream portion of the gas displacement pipeline 17 is connected to the goaf and the drainage unit. The mixed gas separation device 14 can separate and utilize the gasified, displaced, and escaped mixed gases in the goaf environment. CH4, CO, and other gases can be used as fuel pathways, while N2, CO2, and other gases can be used for fracturing and displacement. The device can also function as a pump to extract stored CO2 for use.

[0040] In this embodiment, the goaf and drainage unit include a goaf 16 and a drainage pipe arranged in the goaf 16, and the drainage pipe is also provided with a number of CO2 monitors 13 and CO2 volume fraction sensors. The CO2 monitor 13 monitors the CO2 injection amount and CO2 concentration, and can also be used for subsequent monitoring of CO2 overflow. The CO2 volume fraction sensor is used to detect the CO2 volume fraction and can also be provided in the gas storage and separation unit. The CO2 volume fraction sensor is used to record the percentage of CO2 in the mixed gas escaping from the underground during CO2 injection, so as to determine the working time and working environment. When the CO2 concentration is low, CO2 injection can continue to work; when the CO2 concentration is half, the sensor sends a signal, and the mixed gas separation device 14 gives the gas displacement pipeline 17 a reverse pressure to seal the CO2 together with the underground gas in the goaf 16, and the CO2 injection work continues. After working for a period of time, the reverse pressure is cancelled and the CO2 concentration in the mixed gas continues to be monitored; when the CO2 concentration reaches 80%, the underground goaf is filled with CO2, the reverse pressure is increased and the pipeline mouth is sealed with grouting, and the injection work is completed at this time.

[0041] This embodiment also provides a fire prevention and extinguishing method based on the goaf liquid CO2 fire prevention and extinguishing system, comprising the following steps:

[0042] S1: Input gaseous CO2 to test whether the injection unit, goaf, drainage unit and gas storage and separation unit can operate normally;

[0043] S2: converting CO2 into liquid and injecting it into the goaf and drainage unit;

[0044] S3: injecting the covering material into the goaf and the drainage unit;

[0045] S3: Injecting gaseous CO2 into the goaf and displacing the original gas in the goaf to the gas storage and separation unit.

[0046] The method further includes S4: detecting the CO2 concentration of the gas storage and separation unit, and stopping the injection operation after the concentration reaches a set value.

[0047] It also includes S21 between S2 and S3: using a reciprocating injection pump and a flow meter to measure the amount of CO2 pumped in to prevent excessive pressure in the goaf.

[0048] It also includes S22 between S21 and S3: monitoring the CO2 injection amount and the remaining amount on the coal surface through a CO2 monitor installed along the drainage pipeline to judge the CO2 adsorption situation of the coal body in order to adjust the injection frequency; the CO2 injection work process moves with the mining working face and works in different areas.

[0049] The several CO2 monitors are used for subsequent CO2 gas leakage monitoring indicators.

[0050] In this embodiment, the specific process may be as follows:

[0051] The CO2 in the CO2 storage tank 1 is captured by a nearby coal-fired power plant 18 and directly transported in through the coal-fired power plant's CO2 transport pipeline 19.

[0052] Before operation begins, all units are in a static state. Gaseous CO2 is fed from CO2 storage tank 1 and injected into aboveground pipeline 11 and underground pipeline 12 via centrifugal pump 4 with an inducer to flush impurities from the pipes. CO2 monitor 13 provides real-time monitoring of gas impurities within the pipelines to prevent blockages and explosions. The overflowing mixed gas enters mixed gas separation device 14 through gas displacement pipeline 17 for separation and storage in corresponding gas storage tanks 15.

[0053] The CO2 in the CO2 storage tank 1 enters the pressurized cooling device 3 through the stop valve 2. This device is composed of a filter, a pressure gauge, a safety valve, a pressure regulating valve, a stop valve, and related pipelines, all of which are made of low-temperature and high-pressure resistant materials. After the CO2 is adjusted to the pressure of the underground pipeline in the goaf in the pressurized cooling device 3, the liquid CO2 is stabilized and regulated by the centrifugal pump 4 with an inducer and pumped into the reciprocating injection pump 7. A check valve 6 is provided to prevent the CO2 from flowing in the opposite direction. The centrifugal pump 4 with an inducer has a large head and can maintain the current state before the CO2 is pumped into the reciprocating injection pump 7. At the same time, it reduces the installation requirements of the injection pump, reduces the space occupied, and is convenient for mobile operation with the mining working face.

[0054] The reciprocating injection pump 7 pumps the liquid CO2 out through the flow meter 8, the outlet safety valve 9, and the outlet pressure gauge 10, and then injects it into the underground goaf 16 through the vertical pipeline. At the same time, the CO2 pumping amount is measured by recording the pumping times of the reciprocating injection pump 7 and the flow meter 8 to prevent excessive pressure in the underground goaf.

[0055] Drainage pipes in the goaf 16 can be laid in multiple, parallel lines, depending on practical circumstances. Liquid CO2 is drained through these underground pipes to fully cover the upper layers of the coal, completely enveloping the coal for optimal absorption. CO2 monitors 13, installed alongside the pipes, monitor the injected CO2 volume and remaining CO2 on the coal surface to assess CO2 absorption and adjust the injection frequency. The CO2 injection process progresses as the mining face moves, operating in separate zones.

[0056] After the liquid CO2 is covered, the coating material storage tank 5 is used as the input source, and the output solid-liquid gel material is directly pumped into the surface of the underground liquid CO2 by the reciprocating injection pump 7 to form a water-proof protective layer to prevent the volatilization of CO2, so that the liquid CO2 can fully play its role in fire prevention and extinguishing.

[0057] After the liquid CO2 has completely covered the surface of the coal body, the heating and pressure reduction device 3 is closed to allow the gaseous CO2 in the CO2 storage tank 1 to be directly injected into the underground goaf at a large flow rate. While storing CO2, the mixed gas such as combustible gas in the goaf can be displaced into the mixed gas separation device 14 through the pipeline, thereby reducing the concentration of combustible gas and other gases in the goaf 16, and more effectively preventing goaf fires. At the same time, the displaced gas can be detected and classified and stored in the corresponding storage gas tank 15 for reuse. The CO2 volume fraction sensor in the mixed gas separation device 14 is used as the starting basis for the injection work. When the CO2 concentration is small, the CO2 injection can continue to work; when the CO2 concentration is half, the sensor sends a signal, and the mixed gas separation device 14 gives the gas displacement pipeline 17 a reverse pressure to seal the CO2 together with the underground gas in the goaf 16, and the CO2 injection work continues. After working for a period of time, the reverse pressure is cancelled and the CO2 concentration in the mixed gas continues to be monitored; when the CO2 concentration reaches 80%, the underground goaf 16 is filled with CO2, the reverse pressure is increased, and the pipeline mouth is sealed by grouting, and the injection work is completed at this time.

[0058] After filling is complete, the CO2 monitor 13 installed at the connection between the mixed gas separation device 14 and the gas displacement pipeline 17 can be used as a subsequent CO2 gas leakage monitoring indicator. Grouting is performed on the surface cracks in the goaf 16 to restore its original environmental integrity while enhancing the stability and carrying capacity of the surface, ensuring that the CO2 can be effectively sealed within the goaf. Appropriate points are selected and marked for later mining and extraction of CO2 stored in the goaf.

[0059] This device can be used for underground storage of CO2. The mixed gas separation device 14 and the gas storage tank 15 can be used to extract gas from the goaf.

[0060] Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It should be understood by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A method for preventing and extinguishing fire by injecting liquid CO2 into goaf, characterized in that: The method is based on a fire prevention and extinguishing system, which includes an injection unit, a goaf and drainage unit, and a gas storage and separation unit connected in sequence; The injection unit includes a CO2 injection branch and a coating material injection branch arranged in parallel upstream, and also includes a check valve, a reciprocating injection pump, a flow meter, an outlet safety valve and an outlet pressure gauge connected to the pipeline downstream; The upstream and downstream pipelines are connected, and the downstream is connected to the goaf and the drainage unit through a pipeline; The CO2 injection branch includes a CO2 storage tank, a stop valve, a pressurization and cooling device, and a centrifugal pump with an inducer connected in sequence; The gas storage and separation unit comprises a gas displacement pipeline, a mixed gas separation device and a gas storage tank connected in sequence; The upstream of the gas displacement pipeline is connected to the goaf and the drainage unit; The goaf and drainage unit includes a goaf and a drainage pipe arranged in the goaf, and the drainage pipe is also provided with a plurality of CO2 monitors; The fire prevention and extinguishing method comprises the following steps: S1: Input gaseous CO2 to test whether the injection unit, goaf, drainage unit and gas storage and separation unit can operate normally; S2: converting CO2 into liquid and injecting it into the goaf and drainage unit; S3: injecting the covering material into the goaf and the drainage unit; S4: Injecting gaseous CO2 into the goaf and displacing the original gas in the goaf into the gas storage and separation unit.

2. The fire prevention and extinguishing method according to claim 1, characterized in that: The process also includes S5: detecting the CO2 concentration of the gas storage and separation unit, and stopping the injection operation when the concentration reaches a set value.

3. The fire prevention and extinguishing method according to claim 1, characterized in that: It also includes S21 between S2 and S3: using a reciprocating injection pump and a flow meter to measure the amount of CO2 pumped in to prevent excessive pressure in the goaf.

4. The fire prevention and extinguishing method according to claim 1, characterized in that: It also includes S22 between S21 and S3: monitoring the CO2 injection amount and the remaining amount on the coal surface through a CO2 monitor installed along the drainage pipeline to judge the CO2 adsorption situation of the coal body in order to adjust the injection frequency; the CO2 injection work process moves with the mining working face and works in different areas.

5. The fire prevention and extinguishing method according to claim 1, characterized in that: The several CO2 monitors are used for subsequent CO2 gas leakage monitoring indicators.

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