Safe blocking distance calculation and automatic blocking control method for carbon dioxide transportation pipeline

Abstract

The invention discloses a safe blocking distance calculation and automatic blocking control method for a carbon dioxide transportation pipeline. The method comprises the steps that S1, the leakage rate is divided into four grades, and the wind speed of a mine working face roadway is calculated; s2, according to the leakage rate and the wind speed, the relation between the carbon dioxide diffusion concentration and the diffusion distance is obtained; s3, determining an expression of a pipeline safety cut-off distance L; s4, performing concentration constraint on the expression of the L, and calculating a pipeline safety cut-off distance; s5, performing field experiment verification; and S6, confirming the calculated safe cut-off distance L as the final cut-off distance, and triggering the automatic closing action of the pipeline cut-off valve in the L range corresponding to the leakage point. Through scientific and systematic quantitative analysis and accurate matching of leakage point positions and protection requirements, the relation between the set distance of the block valve and the leakage rate of the volume of carbon dioxide in the roadway after leakage is determined, the block valve is directly triggered to be automatically closed on the basis of the safety block distance L obtained through calculation, and delay of manual implementation is avoided.

Description

Technical Field

[0001] This invention belongs to the field of coal mine safety protection technology, specifically relating to a method for calculating the safe blocking distance of carbon dioxide transport pipelines and an automatic blocking control method. Background Technology

[0002] With the increasing depth of coal mining and the development of fully mechanized mining technology, the risk of spontaneous combustion fires in goaf areas has significantly increased. Under the "dual carbon" target (fire prevention and carbon sequestration), carbon dioxide fire suppression technology possesses dual value in both fire prevention and carbon management. This technology, through the laying of dedicated pipelines, transports liquid or high-pressure gaseous carbon dioxide to the goaf area for inerting and fire suppression. This not only suppresses fires through inerting but also sequesters carbon dioxide within the goaf, creating a synergistic effect of "fire suppression + carbon sequestration," providing a new path for carbon emission reduction in the coal mining sector. However, areas prone to breakage and bending in pipelines become high-risk areas for leakage due to external impacts and structural stress concentration. If cracks occur in these areas, carbon dioxide will leak into the roadway and spread to the coal face with the airflow. If its concentration exceeds the limit of 0.5% stipulated in Article 135 of the "Coal Mine Safety Regulations" for carbon dioxide concentration in the intake airflow of the mining face, it will lead to dangerous situations such as difficulty breathing, confusion, or even suffocation among personnel. Therefore, after a leak occurs, the analysis of the deployment strategy of the shut-off valves on which the safety shut-off settings of carbon dioxide transportation pipelines depend, as well as the rapid automatic shut-off control after the leak, has become an urgent problem to be solved.

[0003] Installing shut-off valves in carbon dioxide transport pipelines is a common measure to address leaks. The aim is to close nearby shut-off valves as quickly as possible when a leak occurs in the pipeline (especially at easily broken bends), reducing the amount of carbon dioxide leaked. However, existing technologies have two major drawbacks. First, valve spacing is mostly calculated and set based on field engineering experience (usually 200-500 meters), without considering the differences in carbon dioxide leakage rates under different leakage orifice diameters (especially the differentiated orifice diameters formed by varying degrees of fracture at easily broken bends). The design of shut-off distances at easily broken bends suffers from the problem of "over-shutting down for small leaks and under-shutting down for large leaks." Second, there is a lack of automatic shut-off mechanisms connected to precise shut-off distances. Most shut-off valves require manual shut-off or rely on fixed values, making it impossible to adjust the shut-off timing based on dynamic parameters such as real-time leakage rate and roadway wind speed. This leads to problems such as "delayed shut-off" or "deviation in shut-off range" after a leak occurs, further increasing safety risks and making it difficult to fully guarantee safe production in coal mines. Summary of the Invention

[0004] The purpose of this invention is to provide a method for calculating the safe shut-off distance and automatically shutting off carbon dioxide transport pipelines. Through scientific and systematic quantitative analysis, a leakage source location coefficient is introduced to accurately match the location of the leakage point with the protection requirements. The relationship between the setting distance of the shut-off valve and the leakage rate of carbon dioxide volume in the roadway after leakage is clarified. A control process of "monitoring real-time parameters - calculating safe distance - automatic shut-off" is constructed. Based on the calculated safe shut-off distance L, the shut-off valve is directly triggered to automatically close, avoiding the delay of manual implementation and ensuring that leakage can be quickly and accurately shut off after it occurs.

[0005] The technical solution adopted in this invention is: a method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines, the specific steps of which are as follows: S1. Based on the size of the leak hole in the pipeline, the leakage rate is divided into four levels, and the wind speed in the mine working face roadway is calculated. S2. Based on the leakage rate and wind speed, the relationship between carbon dioxide diffusion concentration and diffusion distance is obtained through analysis. S3. Determine the safe cut-off distance for pipelines based on the provisions of coal mine safety regulations and design safety protection requirements. L The expression; S4, will L The expression is used to constrain concentration and ensure the actual carbon dioxide leakage time. t Less than the time required for complete carbon dioxide leakage T Based on this, the safe cut-off distance of the pipeline is calculated. L ; S5. Conduct on-site experimental verification and further optimization; S6. Based on the real-time leakage rate and wind speed, confirm the safe cutoff distance calculated in S4. L The final cutoff distance corresponds to the leak point. L The pipeline shut-off valve automatically closes within the specified range.

[0006] The invention is further characterized by: The leakage rate classification in S1 is as follows: Micro-leakage, diameter of pipe leak hole D ≤2mm, then the carbon dioxide leakage rate v The range is 0.001~0.005 m. 3 / s; Small leak, the diameter of the leak hole in the pipe is < 2 D≤ 5mm, then the carbon dioxide leakage rate v The value is 0.005~0.02 m. 3 / s; Leakage in the pipeline, diameter of the leak hole D 5 < D≤ 10mm, then the carbon dioxide leakage ratev The range is 0.02~0.08 m. 3 / s; Large leak, diameter of pipe leak hole D ≥10mm, then the carbon dioxide leakage rate v The range is 0.08~0.3 m. 3 / s; Based on the diameter of the leak D The carbon dioxide leakage rate is determined by the leakage rate classification standard. v .

[0007] S1 Coal Mine Working Face Roadway Vent Speed u The calculation formula is as follows: (1) in, A This represents the cross-sectional area of ​​the tunnel, expressed in m². Qw Air volume, in m³ / min. u The wind speed in the tunnel is expressed in m / s.

[0008] The concentration of CO2 during CO2 diffusion in the mine working face roadway when carbon dioxide diffuses in S2 c Distance from the leak point x The relationship is as follows: (2) The diffusion distance can be further calculated. x and c The relationship between them is as follows: (3) In the formula: u The wind speed inside the tunnel is expressed in m / s. A The cross-sectional area within the tunnel, in meters. 2 ; D The diffusion coefficient of CO2 in air. D =0.16×10 -4 m 2 / s; t The actual carbon dioxide leakage time is expressed in seconds. v The leakage rate of CO2 is expressed in meters per second (m³). 3 / s.

[0009] The specific method for S3 is as follows: Assuming the maximum setting distance of the shut-off valve is L The actual leakage time must be met. tThe CO2 concentration inside the mine is less than or equal to the carbon dioxide exposure threshold required by the coal mine safety regulations. c max ,in c max =0.5%, that is (4) According to formulas (3) and (7), we can obtain: (5) The specific method for S4 is as follows: When in formula (5) At that time, convection term Playing a dominant role, the concentration decreases rapidly with distance. According to the carbon dioxide leakage rate classification standards in S1, the safe cutoff distance... L Calculate and determine according to formula (5); When in formula (5) At that time, the actual carbon dioxide leakage time must be met. t Less than the time to complete leakage T ,Right now: (6) At this point, the safe cutoff distance L Calculate and determine using the following formula: (7).

[0010] Actual carbon dioxide leakage time t Including sensor detection time t 1. Signal transmission time t 2 and valve closing time t 3. The calculation is as follows: t = t 1+ t 2+ t 3 (8) Determine the sensor detection time based on the on-site equipment and facilities. t 1. Signal transmission time t 2 and valve closing time t 3: Time required for complete carbon dioxide leakage T The calculation is as follows: First, calculate the volume of CO2 leakage within the tunnel: (9) In the formula, d This refers to the inner diameter of the carbon dioxide transport pipeline. The time required for complete carbon dioxide leakage within the tunnel T as follows: (10) in, The volume of CO2 inside the leaking section of the pipeline, in cubic meters (m³). 3 , v The leakage rate of carbon dioxide, in meters per second (m). 3 / s.

[0011] The specific method for S5 is as follows: After determining the safety distance S5, substitute the calculated safety distance L into formula (2) to calculate the diffusion distance. Concentration of carbon dioxide at time c And determine the concentration c If the value is less than 0.05, then the selected safe cutoff distance is reasonable.

[0012] The specific method for S6 is as follows: Based on real-time monitoring of leakage rate v Wind speed in alleyways u There is no need to calculate the length of the dynamic hazardous area; the safe cutoff distance calculated by S4 can be directly confirmed. L This is the final cutoff distance; the system uses this final cutoff distance as a basis. L The corresponding trigger point for the leak L The pipeline shut-off valve automatically closes within the specified range.

[0013] The beneficial effects of this invention are: (1) The present invention provides a method for calculating the safe shut-off distance and automatically shutting off carbon dioxide transport pipelines. Based on the size of the leak hole, the leakage rate is divided into four levels: micro, small, medium, and large. Parameters such as pipeline inner diameter and roadway wind speed are measured to calculate the actual leakage time and the complete leakage time of carbon dioxide. Concentration constraint verification is performed, and the diffusion effect of residual gas after the leak is closed is fully considered. The safe distance is calculated and verified based on the constraint results. Finally, the model is optimized through field experiments. Its features include combining leakage rate classification and fluid diffusion model, introducing a dual verification mechanism of concentration and time, dynamically optimizing the shut-off valve spacing to ensure the reliability of safe shut-off, and dynamically optimizing the shut-off valve spacing according to different leakage scenarios, thereby achieving accurate calculation and scientific setting of the safe shut-off distance for carbon dioxide transport pipelines. (2) The method for calculating the safe blocking distance and automatically blocking control of carbon dioxide transportation pipelines in this invention solves the problems of "delay in manual operation" and "mismatch of fixed threshold" in traditional shut-off valves. It calculates the distance based on accurate real-time data, so that the shut-off valve closing range matches the actual leakage risk range. This not only avoids leakage spread caused by "insufficient shut-off" but also avoids "excessive shut-off" affecting normal transportation, effectively improving the safety production level of coal mines. At the same time, it strongly promotes the synergistic application of carbon dioxide fire prevention and extinguishing technology and carbon sequestration, providing a guarantee for the safe and efficient development of the coal mining industry under the "dual carbon" goal.

[0014] (3) The final cutoff distance linkage automatic cutoff mechanism of the present invention can provide timely and accurate danger zone range after an accident occurs, by directly calculating... L To achieve the final distance, the response steps are reduced, the truncation delay is further shortened, and there is no need to calculate the dynamic danger zone, which reduces system complexity and improves the reliability of automatic truncation. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines according to the present invention. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] This invention relates to a method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines, such as... Figure 1 As shown, the details are as follows: S1. Based on the size of the leak hole in the pipeline, the leakage rate is divided into four levels to suit different leakage scenarios. The wind speed in the mine working face roadway is also calculated. The leakage rate is classified into the following levels: Leakage rate v The leaks are classified according to their different diameters. The specific classification criteria are shown in Table 1.

[0018] Table 1 Leakage Rate v Classification standards based on different leakage diameters

[0019] Micro-leakage, diameter of pipe leak hole D ≤2mm, then the carbon dioxide leakage rate v The range is 0.001~0.005 m. 3 / s; Small leak, the diameter of the leak hole in the pipe is < 2 D≤ 5mm, then the carbon dioxide leakage rate vThe value is 0.005~0.02 m. 3 / s; Leakage in the pipeline, diameter of the leak hole D 5 < D≤ 10mm, then the carbon dioxide leakage rate v The range is 0.02~0.08 m. 3 / s; Large leak, diameter of pipe leak hole D ≥10mm, then the carbon dioxide leakage rate v The range is 0.08~0.3 m. 3 / s; Leakage port diameter D The carbon dioxide leakage rate is determined by the leakage rate classification standard. v .

[0020] Wind speed in mine working face roadways u The calculation formula is as follows: (1) in, A This represents the cross-sectional area of ​​the tunnel, expressed in m². Qw Air volume, in m³ / min. u The wind speed in the tunnel is expressed in m / s.

[0021] S2. Based on the leakage rate and wind speed, the relationship between carbon dioxide diffusion concentration and diffusion distance is obtained through analysis. The concentration of CO2 during the diffusion of carbon dioxide in the mine working face roadway c Distance from the leak point x The relationship is as follows: (2) Further calculations yielded the diffusion distance. x and c The relationship between them is as follows: (3) In the formula: u The wind speed inside the tunnel is expressed in m / s. A The cross-sectional area within the tunnel, in meters. 2 ; D The diffusion coefficient of CO2 in air. D =0.16×10 -4 m 2 / s; t The actual carbon dioxide leakage time is expressed in seconds. vThe leakage rate of CO2 is expressed in meters per second (m³). 3 / s.

[0022] S3. Determine the safe cut-off distance for pipelines based on the provisions of coal mine safety regulations and design safety cut-off requirements. L The expression, specifically the method, is as follows: Assuming the maximum setting distance of the shut-off valve is L The actual leakage time must be met. t The CO2 concentration inside the mine is less than or equal to the carbon dioxide exposure threshold required by the coal mine safety regulations. c max ,in c max =0.5%, that is (4) According to formulas (3) and (7), we can obtain: (5) S4, will L The expression is used to constrain concentration and ensure the actual carbon dioxide leakage time. t Less than the time required for complete carbon dioxide leakage T Based on this, the safe cut-off distance of the pipeline is calculated. L The specific method is as follows: In formula (5) ut For convection, the dominant safety distance is... As this is a diffusion term, it has little impact on the calculation of the safety distance. However, the residual gas in the pipeline after the valve is closed needs to be considered. When in formula (5) At that time, convection term Playing a dominant role, the concentration decreases rapidly with distance. According to the carbon dioxide leakage rate classification standards in S1, the safe cutoff distance... L Calculate and determine the value of the safe cut-off distance L according to formula (5), and take the maximum value in the calculation results as the safe cut-off distance for the final cut-off setting to ensure a more comprehensive consideration of all leakage scenarios.

[0023] When in formula (5) At this time, the diffusion term has a significant impact on the concentration, and concentration constraint verification is performed (which needs to meet the actual carbon dioxide leakage time). t Less than the time to complete leakage T ),Right now: (6) At this point, the safe cutoff distance L Calculate and determine using the following formula: (7).

[0024] Furthermore, the actual time of carbon dioxide leakage t Including sensor detection time t 1 (Sensor detection time, ≤0.5s) t 2 (Signal transmission time, ≤0.5s) t 3 (Valve closing time, 2-4s), calculated as follows: t = t 1+ t 2+ t 3 (8) Determine the sensor detection time based on the on-site equipment and facilities. t 1. Signal transmission time t 2 and valve closing time t 3: Time required for complete carbon dioxide leakage T The calculation is as follows: First, calculate the volume of CO2 leakage within the tunnel: (9) In the formula, d This refers to the inner diameter of the carbon dioxide transport pipeline. The time required for complete carbon dioxide leakage within the tunnel T as follows: (10) in, The volume of CO2 inside the leaking section of the pipeline, in cubic meters (m³). 3 , v The leakage rate of carbon dioxide, in meters per second (m). 3 / s.

[0025] S5. Conduct on-site experimental verification; After obtaining the safe cut-off distance value for the pipeline, this invention can be verified through field experiments and further optimized, as detailed below: CO2 pipelines were installed within a closed tunnel to artificially create four different levels of leakage scenarios (corresponding to different leakage diameters as defined in Table 1). These simulated real-world leakage scenarios, and the carbon dioxide concentration beyond the safe cutoff distance L was measured. 0.5%.

[0026] Adjust the wind speed based on the experimental results. u diffusion coefficient D or leakage rate v The value of .

[0027] S6. Based on the real-time leakage rate and wind speed, confirm the safe cutoff distance calculated in S4. L The final cutoff distance corresponds to the leak point. LThe pipeline shut-off valve automatically closes within the specified range. Details are as follows: Based on real-time leakage rate v Wind speed in alleyways u Confirm S4 calculation L To achieve the final safe cutoff distance, the system directly triggers the corresponding leak point. L The pipeline shut-off valves within the specified range are closed in conjunction with each other, completing the automatic shut-off control.

[0028] Example 1 The method of this invention is used to calculate the safe cut-off distance for leakage in a fully mechanized mining face of a coal mine, as detailed below: Step 1: Determine the values ​​of various parameters in a local ventilation system of a coal mine. The roadway cross-section is 17.75 m², and the actual air volume at the working face is 1246 m³ / h. 3 / min.

[0029] The actual air volume is calculated using the formula for wind speed: .

[0030] Step 2: Assuming the leak diameter is 6mm, according to the leakage standards in Table 1, this leak is classified as a medium leak, with a leakage rate of... v It is 0.05m 3 / s.

[0031] Step 3: Perform constraint verification; <1 At this point, concentration constraint verification is required.

[0032] Step 4, Inner diameter of the pipe d Given a depth of 0.1m, calculate the volume of carbon dioxide inside the pipe. , Time of complete carbon dioxide leakage T : ; Based on the reaction time data of commonly available electronic sensors and other equipment, this implementation case selects sensor detection time t1 = 0.5s, signal transmission time t2 = 0.2s, and valve closing time t3 = 3s. Therefore, the leakage time t = t1 + t2 + t3 = 0.5 + 0.2 + 3 = 3.7 s .

[0033] This embodiment ensures leakage time. t No more than the time required for complete CO2 leakage from the pipeline T Therefore, t < T Substituting, we get: 3.7

[0034] >23.75m Therefore, the safe cutoff distance can be calculated to be 24m.

[0035] Step 5: Verify concentration Total time of leakage ; Substitute x=24 into the formula achievable

[0036] Therefore, choosing 24m as the safe distance is reasonable.

[0037] Step 6: Based on real-time leakage rate v Wind speed in alleyways u Once it is confirmed that the 24m calculated in step S4 is the final safe cut-off distance, the system directly triggers the pipeline shut-off valve within a 24m range corresponding to the leak point to close automatically, thus completing the automatic cut-off control.

[0038] Example 2 The method of this invention is used to calculate the safe cut-off distance for leakage in a fully mechanized mining face of a coal mine, as detailed below: Step 1: Determine the values ​​of various parameters in a local ventilation system of a coal mine. The roadway cross-section is 21.84 m², and the actual air volume at the working face is 1740 m³ / h. 3 / min.

[0039] The actual air volume is calculated using the formula for wind speed: .

[0040] Step 2: Assuming the leak diameter is 8mm, according to the leakage standards in Table 1, this leak is classified as a medium leak, with a leakage rate of... v It is 0.04m 3 / s.

[0041] Step 3: Perform constraint verification: <1 Concentration constraint verification is required.

[0042] Step 4, Inner diameter of the pipe d Given a depth of 0.12m, calculate the volume of carbon dioxide inside the pipe. .

[0043] Time of complete carbon dioxide leakage ; According to the response time data of common electronic sensors and other devices on the market, in the first implementation case of this patent, the sensor detection time t1 = 0.4s, the signal transmission time t2 = 0.5s, and the valve closing time t3 = 3s are selected. Then the leakage time t = t1 + t2 + t3 = 0.4 + 0.5 + 3 = 3.9 s ; This embodiment ensures that the leakage time t does not exceed the time required for the complete leakage of CO2 in the pipeline T , so substituting t < T gives 3.9 <

[0044] > 13.80m The safety cut-off distance is 14m.

[0045] Step 5, Verify the concentration The total leakage time ; Substitute x = 14 into the formula to obtain

[0046] Then it is reasonable to select 14m as the safety distance.

[0047] Step 6, Based on the real-time leakage rate v , the air velocity in the roadway u , confirm that the 14m calculated in step S4 is the final safety cut-off distance, and the system directly triggers the linkage closing of the pipeline cut-off valve within the 14m range corresponding to the leakage point to complete the automatic cut-off control.

[0048] Example 3 Use the method of this invention to calculate the safety cut-off distance for the leakage situation of a certain coal mine, specifically as follows: Step 1, Determine the values of various parameters in the local ventilation system of a certain coal mine. The roadway cross-section is 20m², and the actual air volume of the working face is 650m 3 / min; Calculate the actual air volume according to the air velocity calculation formula: .

[0049] Step 2, Assume that the leakage port diameter here is 10mm. According to the leakage standards divided in Table 1, this leakage is a large leakage, and the leakage rate v is 0.25m 3 / s.

[0050] Step 3, Conduct constraint verification: <1 Concentration constraint verification needs to be carried out.

[0051] Step 4: The inner diameter d of the pipeline is 0.2 m, calculate the volume of carbon dioxide in the pipeline, , The time for complete leakage of carbon dioxide ; According to the response time data of common electronic sensors and other devices on the market, in Embodiment 1 of this patent, the sensor detection time t1 = 0.4 s, the signal transmission time t2 = 0.4 s, and the valve closing time t3 = 3 s are selected. Then the leakage time t = t1 + t2 + t3 = 0.4 + 0.4 + 3 = 3.8 s ; This embodiment ensures that the leakage time t does not exceed the time required for complete leakage of CO2 in the pipeline T , so substituting t < T gives 3.8 <

[0052] > 30.25 m Then the concentration has no constraint on the distance calculation, and the safety cut-off distance is 31 m.

[0053] Step 5: Verify the concentration The total leakage time ; Substitute x = 31 into the formula to obtain

[0054] Then it is reasonable to select 31 m as the safety distance.

[0055] Step 6: Based on the real-time leakage rate v , the roadway wind speed u , confirm that 31 m calculated in Step S4 is the final safety cut-off distance, and the system directly triggers the linkage closing of the pipeline cut-off valve within the range of 31 m corresponding to the leakage point to complete the automatic cut-off control.

[0056] Embodiment 4 Use the method of this invention to calculate the safety cut-off distance for the leakage situation of a certain coal mine, specifically as follows: Step 1: Determine the values of various parameters in the local ventilation system of a certain coal mine. The roadway cross-section is 20 m², and the actual air volume of the working face is 2076 m 3 / min; Calculate the actual air volume according to the formula for wind speed: .

[0057] Step 2: Assume the diameter of the leakage port here is 9 mm. According to the leakage standards divided in Table 1, this leakage is a large leakage, and the leakage rate v is 0.07 m 3 / s.

[0058] Step 3: Conduct constraint verification: <1 Concentration constraint verification needs to be carried out.

[0059] Step 4: The inner diameter d of the pipeline is 0.15 m. Calculate the volume of carbon dioxide in the pipeline, , The time for complete leakage of carbon dioxide ; According to the reaction time data of common electronic sensors and other devices on the market, in Embodiment 1 of this patent, the sensor detection time t1 = 0.5 s, the signal transmission time t2 = 0.4 s, and the valve closing time t3 = 3.6 s are selected. Then the leakage time t = t1 + t2 + t3 = 0.5 + 0.4 + 3.6 = 4.5 s ; This embodiment ensures that the leakage time t does not exceed the time required for complete leakage of CO2 in the pipeline T , so substituting t < T gives 4.5 <

[0060] > 17.84 m Then the concentration has no constraint on the distance calculation, and the safety cut-off distance is 18 m.

[0061] Step 5: Verify the concentration The total leakage time ; Substitute x = 18 into the formula to obtain Then it is reasonable to select 18 m as the safety distance.

[0062] Step 6: Based on the real-time leakage rate v , the roadway wind speed u , confirm that the 18 m calculated in Step S4 is the final safety cut-off distance, and the system directly triggers the联动 closing of the pipeline cut-off valve within the 18 m range corresponding to the leakage point to complete the automatic cut-off control.

[0063] Embodiment 5 Use the method of this invention to calculate the safety cut-off distance for a coal mine leakage situation as follows: Step 1: Determine the values of various parameters in the local ventilation system of a certain coal mine. The roadway cross-section is 18 m², and the actual air volume of the working face is 3683 m 3 / min; Calculate the actual air volume according to the formula for wind speed: .

[0064] Step 2: Assume that the diameter of the leakage port here is 10 mm. According to the leakage standards divided in Table 1, this leakage is a large leakage, and the leakage rate v is 0.22 m 3 / s.

[0065] Step 3: Conduct constraint verification: <1 Concentration constraint verification needs to be carried out.

[0066] Step 4: The inner diameter d of the pipeline is 0.14 m. Calculate the volume of carbon dioxide in the pipeline, , The time for complete leakage of carbon dioxide ; According to the response time data of common electronic sensors and other devices on the market, in the first implementation case of this patent, the sensor detection time t1 = 0.4 s, the signal transmission time t2 = 0.3 s, and the valve closing time t3 = 3.7 s are selected. Then the leakage time t = t1 + t2 + t3 = 0.4 + 0.3 + 3.7 = 4.4 s ; This embodiment ensures that the leakage time t does not exceed the time required for complete leakage of CO2 in the pipeline T , so substituting t < T gives 4.4 <

[0067] > 62.9 m Then the concentration has no constraint on the distance calculation, and the safety cut-off distance is 63 m.

[0068] Step 5: Verify the concentration The total leakage time ; Substitute x = 63 into the formula It can be obtained that Then it is reasonable to select 31 m as the safety distance.

[0069] Step 6: Based on the real-time leakage rate v and the roadway wind speed u, confirm that the 31m calculated in step S4 is the final safe cut-off distance, and the system directly triggers the linkage closing of the pipeline cut-off valve within the 31m range corresponding to the leakage point to complete the automatic cut-off control.

[0070] Embodiment 6 Use the method of the present invention to calculate the safe cut-off distance for a coal mine leakage situation as follows: Step 1: Determine the values of various parameters in the local ventilation system of a coal mine. The roadway cross-section is 19 m², and the actual air volume of the working face is 2006 m 3 / min; Calculate the actual air volume according to the calculation formula of wind speed: .

[0071] Step 2: Assume that the diameter of the leakage port here is 9 mm. According to the leakage standards divided in Table 1, this leakage is a large leakage, and the leakage rate v is 0.075 m 3 / s.

[0072] Step 3: Conduct constraint verification: <1 It is necessary to conduct concentration constraint verification.

[0073] Step 4: The inner diameter d of the pipeline is 0.12 m. Calculate the volume of carbon dioxide in the pipeline, , The time for complete leakage of carbon dioxide ; According to the response time data of common electronic sensors and other devices on the market, in the first implementation case of this patent, the sensor detection time t1 = 0.5 s, the signal transmission time t2 = 0.4 s, and the valve closing time t3 = 3.5 s are selected. Then the leakage time t = t1 + t2 + t3 = 0.5 + 0.4 + 3.5 = 4.4 s ; This embodiment ensures that the leakage time t does not exceed the time required for complete leakage of CO2 in the pipeline T , so substituting t < T gives 4.4 <

[0074] > 29.18 m Then the concentration has no constraint on the distance calculation, and the safe cut-off distance is 30 m.

[0075] Step 5: Verify the concentration The total leakage time ; Substitute x = 31 into the formula achievable Therefore, choosing 30m as the safe distance is reasonable.

[0076] Step 6: Based on real-time leakage rate v Wind speed in alleyways u Once it is confirmed that the 30m calculated in step S4 is the final safe cut-off distance, the system directly triggers the pipeline shut-off valve within a 30m range corresponding to the leak point to close automatically, thus completing the automatic cut-off control.

Claims

1. A method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines, characterized in that, The specific steps are as follows: S1. Based on the size of the leak hole in the pipeline, the leakage rate is divided into four levels, and the wind speed in the mine working face roadway is calculated. S2. Based on the leakage rate and wind speed, the relationship between carbon dioxide diffusion concentration and diffusion distance is obtained through analysis. S3. Determine the safe cut-off distance for pipelines based on the provisions of coal mine safety regulations and design safety cut-off requirements. L The expression; S4, will L The expression is used to constrain concentration and ensure the actual carbon dioxide leakage time. t Less than the time required for complete carbon dioxide leakage T Based on this, the safe cut-off distance of the pipeline is calculated. L ; S5. Conduct on-site experimental verification and further optimization; S6. Based on the real-time leakage rate and wind speed, confirm the safe cutoff distance calculated in S4. L The final cutoff distance corresponds to the leak point. L The pipeline shut-off valve automatically closes within the specified range.

2. The method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines according to claim 1, characterized in that, The leakage rate classification in S1 is as follows: Micro-leakage, diameter of pipe leak hole D ≤2mm, then the carbon dioxide leakage rate v The range is 0.001~0.005 m. 3 / s; Small leak, the diameter of the leak hole in the pipe is < 2 D≤ 5mm, then the carbon dioxide leakage rate v The value is 0.005~0.02 m. 3 / s; Leakage in the pipeline, diameter of the leak hole D 5 < D≤ 10mm, then the carbon dioxide leakage rate v The range is 0.02~0.08 m. 3 / s; Large leak, diameter of pipe leak hole D ≥10mm, then the carbon dioxide leakage rate v The range is 0.08~0.3 m. 3 / s; Based on the diameter of the leak D The carbon dioxide leakage rate is determined by the leakage rate classification standard. v .

3. The method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines according to claim 1, characterized in that, The wind speed in the mine working face roadway of S1 u The calculation formula is as follows: （1） in, A This represents the cross-sectional area of ​​the tunnel, expressed in m². Qw Air volume, in m³ / min. u The wind speed in the tunnel is expressed in m / s.

4. The method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines according to claim 3, characterized in that, The concentration of CO2 during CO2 diffusion in the mine working face roadway during the diffusion of carbon dioxide in S2. c Distance from the leak point x The relationship is as follows: （2） The diffusion distance can be further calculated. x and c The relationship between them is as follows: （3） In the formula: u The wind speed inside the tunnel is expressed in m / s. A The cross-sectional area within the tunnel, in meters. 2 ; D The diffusion coefficient of CO2 in air. D =0.16×10 -4 m 2 / s; t The actual carbon dioxide leakage time is expressed in seconds. v The leakage rate of CO2 is expressed in meters per second (m³). 3 / s.

5. The method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines according to claim 4, characterized in that, The specific method of S3 is as follows: Assuming the maximum setting distance of the shut-off valve is L The actual leakage time must be met. t The CO2 concentration inside the mine is less than or equal to the carbon dioxide exposure threshold required by the coal mine safety regulations. c max ,in c max =0.5%, that is （4） According to formulas (3) and (7), we can obtain: （5）。 6. The method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines according to claim 5, characterized in that, The specific method of S4 is as follows: When in formula (5) At that time, convection term Playing a dominant role, the concentration decreases rapidly with distance. According to the carbon dioxide leakage rate classification standards in S1, the safe cutoff distance... L Calculate and determine according to formula (8); When in formula (5) At that time, the actual carbon dioxide leakage time must be met. t Less than the time to complete leakage T ,Right now: （6） At this point, the safe cutoff distance L Calculate and determine using the following formula: （7）。 7. The method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines according to claim 6, characterized in that, The actual time of carbon dioxide leakage t Including sensor detection time t 1. Signal transmission time t 2 and valve closing time t 3. The calculation is as follows: t = t 1+ t 2+ t 3（8） Determine the sensor detection time based on the on-site equipment and facilities. t 1. Signal transmission time t 2 and valve closing time t 3: The time required for complete carbon dioxide leakage T The calculation is as follows: First, calculate the volume of CO2 leakage within the tunnel: （9） In the formula, d This refers to the inner diameter of the carbon dioxide transport pipeline. The time required for complete carbon dioxide leakage within the tunnel T as follows: （10） in, The volume of CO2 inside the leaking section of the pipeline, in cubic meters (m³). 3 , v The leakage rate of carbon dioxide, in meters per second (m). 3 / s.

8. The method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines according to claim 7, characterized in that, The specific method of S5 is as follows: After determining the safety distance S5, substitute the calculated safety distance L into formula (2) to calculate the diffusion distance. Concentration of carbon dioxide at time c And determine the concentration c If the value is less than 0.05, then the selected safe cutoff distance is reasonable.

9. The method for calculating the safe blocking distance and automatically controlling the blocking of carbon dioxide transport pipelines according to claim 8, characterized in that, The specific method of S6 is as follows: Based on real-time monitoring of leakage rate v Wind speed in alleyways u There is no need to calculate the length of the dynamic hazardous area; the safe cutoff distance calculated by S4 can be directly confirmed. L This is the final cutoff distance; the system uses this final cutoff distance as a basis. L The corresponding trigger point for the leak L The pipeline shut-off valve automatically closes within the specified range.

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