Method for judging leakage during gas replacement in a gas pipeline

Abstract

The present application relates to a kind of coal gas pipeline in the judgment method of leakage when coal gas replacement, belong to the technical field of leakage inspection.This method first reads the carbon monoxide concentration in coal gas pipeline before coal gas replacement and is recorded as initial concentration;Then set the carbon monoxide concentration reading interval when coal gas replacement;When coal gas replacement to the set interval time, read the carbon monoxide concentration in coal gas pipeline and is recorded as actual concentration, and read the actual flow of purge gas, then calculate the total amount of gas required for coal gas replacement purge;Finally, according to the judgment formula of set actual flow and gas total amount, to determine whether there is leakage in coal gas pipeline.This method integrates the complex working condition environment when coal gas replacement in coal gas pipeline, through real-time detection and judgment, can be found immediately once leakage occurs.

Description

Technical Field

[0001] This invention relates to a method for determining leakage during gas replacement in a gas pipeline, belonging to the technical field of leakage inspection (F17D5 / 02). Background Technology

[0002] In the steelmaking process, blast furnace shutdown and maintenance is a crucial step in ensuring the safe operation of equipment. During the shutdown, the gas pipeline system needs to be replaced with other gases through gas replacement to prevent poisoning or explosion accidents during the maintenance process.

[0003] The "direct purging method" is commonly used for replacing gas in gas pipelines. This involves continuously purging gas into the pipeline, and the replacement is considered complete when the carbon monoxide concentration at the end of the pipeline is below a threshold. However, it was later discovered that while the carbon monoxide concentration in the pipeline remained below the threshold after each replacement, the time taken for the replacement varied, indicating a gas pipeline leak. Although methods for detecting pipeline leaks exist, in the complex environment of gas pipeline replacement, leaks are not only difficult to detect in a timely manner but also carry the risk of false alarms. Summary of the Invention

[0004] The technical problem to be solved by this invention is: how to detect leaks in a timely and accurate manner when gas replacement is carried out in a gas pipeline.

[0005] The technical solution proposed by this invention to solve the above-mentioned technical problems is: a method for judging leakage during gas replacement in a gas pipeline, comprising the following steps:

[0006] Step 1: Before gas replacement, read the carbon monoxide concentration in the gas pipeline and record it as the initial concentration C0;

[0007] Step 2: Set the interval M for reading the carbon monoxide concentration in the gas pipeline during gas replacement; take the moment of the first reading of the carbon monoxide concentration as time t1, take the moment of the second reading of the carbon monoxide concentration after one interval M as time t2, and so on up to time tn.

[0008] Step 3: Purge gas into the gas pipeline to start gas replacement. When the gas replacement reaches time t1, read the carbon monoxide concentration in the gas pipeline and record it as the actual concentration C1, and read the actual flow rate Q1 of the purging gas.

[0009] Calculate the total amount of gas required for purging, Q2, using the following formula (1).

[0010] (1);

[0011] In equation (1), P1 is the standard pressure of the gas pipeline, P1 = 101.325 kPa; P2 is the pressure inside the gas pipeline; P3 is the saturated water vapor pressure inside the gas pipeline; T1 is the temperature inside the gas pipeline; T2 is the standard temperature of the gas pipeline, T2 = 273.15 K; V is the volume of the gas pipeline; φ is the relative humidity inside the gas pipeline.

[0012] If Q1 > Q2 / t1, it is determined that there is a leak in the gas pipeline;

[0013] If Q1≤Q2 / t1, it is determined that there is no leak in the gas pipeline;

[0014] Step 4: When the gas replacement reaches time t2, repeat step 3;

[0015] This process continues until the gas replacement is completed.

[0016] Furthermore, the purging gas is nitrogen.

[0017] The beneficial effects of this invention are as follows: By fully integrating the gas compressibility, humidity, and temperature of the gas in the pipeline during the gas replacement process into a formula for the total gas demand, environmental interference is effectively eliminated, the accuracy of the total gas demand is improved, and the risk of misjudgment is significantly reduced. Furthermore, by dynamically monitoring the carbon monoxide concentration and purge gas flow rate in the gas pipeline at set intervals M, and combining this with continuous time-segmented judgment based on judgment conditions, leaks can be detected immediately, avoiding the lag problem of traditional methods and significantly improving the timeliness of leak detection. Detailed Implementation

[0018] Example

[0019] The method for determining leakage during gas replacement in a gas pipeline according to this embodiment includes the following steps:

[0020] Step 1: Before gas replacement, read the carbon monoxide concentration in the gas pipeline and record it as the initial concentration C0=23%.

[0021] Step 2: Set the interval M for reading the carbon monoxide concentration in the gas pipeline during gas replacement to 1 min; take the first reading of the carbon monoxide concentration as time t1, take the second reading of the carbon monoxide concentration after one interval M as time t2, and so on up to time tn.

[0022] Step 3: Purge the gas pipeline with nitrogen to begin gas replacement. When the gas replacement reaches time t1 (1 minute), read the carbon monoxide concentration in the gas pipeline and record it as the actual concentration C1 = 22.25%, and read the actual flow rate of the purging nitrogen Q1 = 5050 m³ / h. 3 / h;

[0023] Calculate the total amount of nitrogen required for purging, Q2, using the following formula (1).

[0024] (1);

[0025] In equation (1), P1 is the standard state pressure of the gas pipeline, P1 = 101.325 kPa; the pressure inside the gas pipeline is P2 = 60 kPa; the saturated water vapor pressure inside the gas pipeline is P3 = 270 kPa; the temperature inside the gas pipeline is T1 = 403.15 K; T2 is the standard state temperature of the gas pipeline, T2 = 273.15 K; and the volume of the gas pipeline is V = 800 m³. 3 The relative humidity inside the gas pipeline is φ=5%.

[0026] In this embodiment, Q2 = 85.30m is calculated according to formula (1). 3 Q2 / t1=85.30m 3 / min=5118m 3 / h

[0027] If Q1 > Q2 / t1, it is determined that there is a leak in the gas pipeline;

[0028] If Q1≤Q2 / t1, it is determined that there is no leak in the gas pipeline.

[0029] Since Q1 ≤ Q2 / t1, it can be determined that there is no leak in the gas pipeline at time t1.

[0030] Step 4: When the gas replacement reaches time t2, repeat step 3;

[0031] This process continues until the gas replacement is completed.

[0032] In this embodiment, at time t4 (4 minutes), the actual carbon monoxide concentration C4 = 21.5%, and at time t4, P2 = 55 kPa, P3 = 247 kPa, T1 = 400.15 K, and φ = 4.9%. According to equation (1), Q2 = 186.69 m 3 Q2 / t4 = 186.69 / 4 = 46.67m 3 / min=2800m 3 / h, read the actual flow rate of the purging nitrogen Q4=5100m³ / h. 3 If / min > Q2 / t4, it is determined that there is a leak in the gas pipeline.

[0033] The above description is only a preferred embodiment of the present invention, but the present invention is not limited thereto. All equivalent substitutions or modifications made to the concepts and technical solutions of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for determining leakage during gas replacement in a gas pipeline, characterized in that... Includes the following steps: Step 1: Before gas replacement, read the carbon monoxide concentration in the gas pipeline and record it as the initial concentration C0; Step 2: Set the interval M for reading the carbon monoxide concentration in the gas pipeline during gas replacement; take the moment of the first reading of the carbon monoxide concentration as time t1, take the moment of the second reading of the carbon monoxide concentration after one interval M as time t2, and so on up to time tn. Step 3: Purge gas into the gas pipeline to start gas replacement. When the gas replacement reaches time t1, read the carbon monoxide concentration in the gas pipeline and record it as the actual concentration C1, and read the actual flow rate Q1 of the purging gas. Calculate the total amount of gas required for purging, Q2, using the following formula (1). （1）； In equation (1), P1 is the standard pressure of the gas pipeline, P1 = 101.325 kPa; P2 is the pressure inside the gas pipeline; P3 is the saturated water vapor pressure inside the gas pipeline; T1 is the temperature inside the gas pipeline; T2 is the standard temperature of the gas pipeline, T2 = 273.15 K; V is the volume of the gas pipeline; φ is the relative humidity inside the gas pipeline. If Q1 > Q2 / t1, it is determined that there is a leak in the gas pipeline; If Q1≤Q2 / t1, it is determined that there is no leak in the gas pipeline; Step 4: When the gas replacement reaches time t2, repeat step 3; This process continues until the gas replacement is completed.

2. The method for determining leakage during gas replacement in a gas pipeline according to claim 1, characterized in that: The purging gas is nitrogen.

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