CN113237605B - Online analysis integrated cabinet and method for natural gas micro-leakage detection - Google Patents
Online analysis integrated cabinet and method for natural gas micro-leakage detection Download PDFInfo
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- CN113237605B CN113237605B CN202110570558.3A CN202110570558A CN113237605B CN 113237605 B CN113237605 B CN 113237605B CN 202110570558 A CN202110570558 A CN 202110570558A CN 113237605 B CN113237605 B CN 113237605B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M3/00—Investigating fluid-tightness of structures
- G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
- G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D5/00—Protection or supervision of installations
- F17D5/005—Protection or supervision of installations of gas pipelines, e.g. alarm
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D5/00—Protection or supervision of installations
- F17D5/02—Preventing, monitoring, or locating loss
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D5/00—Protection or supervision of installations
- F17D5/02—Preventing, monitoring, or locating loss
- F17D5/06—Preventing, monitoring, or locating loss using electric or acoustic means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M3/00—Investigating fluid-tightness of structures
- G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
- G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
- G01M3/16—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using electric detection means
- G01M3/18—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using electric detection means for pipes, cables or tubes; for pipe joints or seals; for valves; for welds; for containers, e.g. radiators
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- General Physics & Mathematics (AREA)
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- Examining Or Testing Airtightness (AREA)
Abstract
The invention relates to an online analysis integrated cabinet and method for detecting natural gas micro-leakage, which are characterized by comprising the following steps: 1) According to the detection requirement, connecting a pipeline to be detected with a marker gas interface and a sample gas interface of an online analysis integrated cabinet for natural gas micro leakage detection; 2) Determining the working mode of the cabinet, and controlling the sampling unit and the marking gas generating unit to convey the sample gas in the pipeline to be detected to the online analyzer combination unit; 3) The on-line analyzer combination unit detects the sample gas conveyed by the sampling unit, the detection result is sent to the industrial computer through the control unit, the industrial computer detects and locates and analyzes the trace natural gas leakage based on the detection result, and early warning is carried out according to the analysis result. The invention can be widely applied to the technical field of pipe transportation natural gas leakage detection.
Description
Technical Field
The invention belongs to the technical field of pipeline natural gas leakage detection, and particularly relates to an online analysis integrated cabinet and an online analysis integrated method for natural gas micro-leakage detection based on combination of a plurality of different gas detection probes, which are mainly suitable for online monitoring of micro-leakage of long-distance natural gas pipelines.
Background
The natural gas long-distance pipeline leakage accident has serious consequences and large influence range, and is the focus of safety production. Because natural gas pipelines are usually laid underground, the space span is large, and how to timely and effectively discover natural gas leakage is a hot spot and a difficult point of research in the industry.
The existing leakage detection technology, such as a infrasonic wave detection technology, a vibration optical fiber detection technology and the like, utilizes the fact that the vibration of a pipeline after gas leakage is converted into acoustic and optical signals to detect, and the leakage is obvious when the detection technology is found, the detection capability of the leakage detection technology does not exist for tiny leakage generated by tiny cracks and the like, and the gas leakage cannot be found in the very early stage.
In recent years, a leak detection technique based on a detection tube has also appeared. According to the technology, the detection pipe made of special materials is laid in the same ditch as the natural gas pipeline to capture natural gas in the environment, and then the supplementary natural gas is conveyed to the gas detector for analysis in a positive pressure or negative pressure driving mode, so that trace leakage natural gas can be detected, and accurate positioning is performed. However, in the detection technology, a set of online analysis device and a set of marking gas generation device are respectively arranged at two ends of a detection tube, the device is complex, and the application is limited by the space of a distribution station or a valve chamber. Moreover, the coverage distance of a single unit is typically within 40km due to the limited ability to drive the power source. Meanwhile, the current equal-mass positioning algorithm assumes that the gas in the detection tube is uniform in density, and the water content in the air is unevenly distributed, so that the positioning algorithm is possibly influenced to a certain extent, and positioning errors are generated. In addition, gas such as methane exists in the nature, and the gas possibly permeates into the detection tube to be extracted for analysis, so that false alarm is easily caused, and interference is generated on natural gas leakage detection.
Disclosure of Invention
Aiming at the problems, the invention aims to provide an online analysis integrated cabinet and an online analysis integrated method for detecting the micro leakage of natural gas, which can be used for effectively detecting the micro leakage of the natural gas of a long-distance pipeline online.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
In a first aspect of the present invention, there is provided an on-line analysis integrated cabinet for natural gas micro-leak detection, comprising: the device comprises a cabinet body, a control unit, a sampling unit, an industrial computer, an online analyzer combination unit, a marking gas generation unit, and a marking gas interface and a sample gas interface which are arranged on the side part of the cabinet body; the industrial computer is provided with a touch screen for realizing the functions of parameter setting, system control and analysis result display, and sending the received parameter setting and system control signals to the control unit; the control unit is used for controlling the sampling unit, the online analyzer combination unit and the marking gas generation unit according to the received parameter setting and system control signals; the sampling unit is communicated with one end of the pipeline to be detected through the sample gas interface, and is used for extracting the sample gas in the pipeline to be detected and conveying the sample gas to the online analyzer combination unit; the online analyzer combination unit is used for detecting the sample gas conveyed by the sampling unit and sending the detection result to the control unit; the marking gas generating unit is communicated with the other end of the pipeline to be detected through the marking gas interface and is used for conveying marking gas into the pipeline to be detected; and the control unit sends all the received detection data to the industrial computer, the industrial computer detects and locates and analyzes the trace natural gas leakage according to the detection result, and performs early warning according to the analysis result, and simultaneously stores all the detection data.
Further, the control unit adopts a PLC controller, and a data acquisition unit and an automatic control unit are arranged in the PLC controller; the data acquisition unit is used for receiving all detection signals sent by the online analyzer combination unit; the automatic control unit is used for realizing automatic control of the whole analysis flow according to the received sampling flow and the time interval parameter setting signal.
Further, the sampling unit comprises a first electromagnetic valve group, a first mass flow controller and a sampling pump; the first electromagnetic valve group comprises two connecting ports, the two connecting ports are respectively connected with a first pipeline to be detected and/or a second pipeline to be detected through the sample gas interface, the output end of the first electromagnetic valve group is connected with the input end of the sampling pump, and the output end of the sampling pump is connected with the first mass flow controller; the electromagnetic valve group, the sampling pump and the first mass flow controller are all connected with the control unit, and the electromagnetic valve group is used for switching pipelines according to control signals sent by the control unit; the sampling pump is used for extracting the sample gas in the pipeline to be detected according to the control signal sent by the control unit; the output end of the first mass flow controller is used as the output end of the sampling unit to be connected with the online analyzer combination unit and is used for carrying out flow measurement and control on the gas of the pipeline to be detected according to the control signal sent by the control unit, so that the gas in the pipeline to be detected is extracted according to uniform and stable flow rate and is output to the online analyzer combination unit for analysis.
Further, the online analyzer combination unit comprises a methane gas analyzer, a C3+ gas detector, a hydrogen gas detector and a water dew point detector; the input end of the methane gas analyzer is connected with the output end of the sampling unit, the output end of the methane gas analyzer is sequentially connected with the C3+ gas detector, the hydrogen gas detector and the water dew point detector, and the output end of the water dew point detector directly discharges the amplified gas through a pipeline; the methane gas analyzer, the C3+ gas detector, the hydrogen detector and the water dew point detector are all connected with the control unit, and are respectively used for detecting the contents of methane, C2, C3, hydrogen and water in the gas in the pipeline to be detected and sending the contents to the control unit.
Further, the marking gas generation unit comprises a second mass flow controller, a second electromagnetic valve group, a first filtering unit, a second filtering unit, an air compressor and a C3+ standard gas cylinder; the second electromagnetic valve group comprises two input ends and two output ends; the first input end is connected with the output end of the second mass flow controller, the input end of the second mass flow controller is connected with the air compressor arranged outside the cabinet through the first filtering unit to form a purging branch, the second mass flow controller is connected with the control unit, and the flow of the gas in the purging branch is measured and controlled under the control of the control unit; the second input end is connected with the C3+ standard gas cylinder arranged outside the cabinet through the second filtering unit to form a marking gas branch; and two output ends of the second electromagnetic valve group are connected with the pipeline to be detected and are used for switching the gas circuit under the control of the control unit, so that air or marking gas provided by the purging branch or marking gas branch is input into the pipeline to be detected.
The second aspect of the invention provides a detection method for an online analysis integrated cabinet for detecting micro leakage of natural gas, which comprises the following steps: 1) According to the detection requirement, connecting a pipeline to be detected with a marker gas interface and a sample gas interface of an online analysis integrated cabinet for natural gas micro leakage detection; 2) Determining the working mode of the cabinet, and controlling the sampling unit and the marking gas generating unit to convey the sample gas in the pipeline to be detected to the online analyzer combination unit; 3) The on-line analyzer combination unit detects the sample gas conveyed by the sampling unit, the detection result is sent to the industrial computer through the control unit, the industrial computer detects and locates and analyzes the trace natural gas leakage based on the detection result, and early warning is carried out according to the analysis result.
Further, in the step 1), the connection mode of the pipeline to be detected and the online analysis integrated cabinet for the micro leakage detection of the natural gas is two: annular detection mode: the sample gas interface and the mark gas interface at the side part of the integrated cabinet are respectively connected with two ends of a pipeline to be detected to form a detection passage; open circuit detection mode: the method comprises the steps of connecting a mark gas interface of a first integrated cabinet with one end of a first section of pipeline to be detected, connecting the other end of the first section of pipeline to be detected with a sampling interface of a second integrated cabinet, connecting one end of the second section of pipeline to be detected with the mark gas interface of the second integrated cabinet, connecting the other end of the second section of pipeline to be detected with the sampling interface of a third integrated cabinet, and sequentially connecting the two ends of the second section of pipeline to be detected in series to form open circuit detection.
Further, in the step 2), the working modes of the integrated cabinet include a negative pressure extraction mode and a positive pressure conveying mode; the negative pressure extraction mode refers to: when the detection cycle starts, the second electromagnetic valve group is controlled, and the sampling pump is controlled to start at the same time, so that C3+ gas enters a pipeline to be detected, and the C3+ gas is extracted to a C3+ detector in the cabinet along with the sample gas for detection; identifying the moment when the peak value of the concentration of the C3+ gas appears according to data analysis, and taking the moment as the ending point of the detection cycle; the positive pressure delivery mode refers to: before the detection cycle starts, firstly opening the air compressor to purge, and closing the air compressor after purging is finished; when the detection cycle starts, the second electromagnetic valve group is controlled to enable the pipeline to be detected to be communicated with the marking gas steel cylinder, and C3+ mark ambition is injected into the cabinet; then, the air compressor is controlled to work, so that air in the air compressor enters a pipeline to be detected, and is detected along with the sample gas entering an online analyzer combination unit in the cabinet, the system analyzes and identifies the moment when the concentration peak value of the C3+ gas appears according to data, and the moment is taken as the end point of a detection cycle.
Further, in the step 3), the online analyzer combination unit detects the sample gas, detects and locates and analyzes the trace natural gas leakage based on the detection result, and performs the early warning method according to the analysis result, including the following steps: 3.1 A methane gas analyzer, a C3+ gas detector, a hydrogen gas detector and a water dew point detector respectively detect the concentration of methane and ethane, the concentration of C3 gas, the concentration of hydrogen and the water content in the sample gas, and send the detection results to a control unit; 3.2 The control unit sends all detection results to the industrial computer, and the industrial computer detects and performs positioning analysis on trace natural gas leakage based on the detection results and performs early warning according to the analysis results.
Further, in the step 3.2), when the trace natural gas leakage is detected and positioned based on the detection result, the analysis method is as follows:
Firstly, judging whether the methane in the detection tube is leaked or not according to the content of the hydrogen detected by the hydrogen detector, and if the methane concentration is detected and a hydrogen concentration signal is detected at the same time, judging that the methane in the detection tube is leaked instead of the natural gas; otherwise, natural gas leakage is considered;
Secondly, correcting errors caused by system positioning calculation due to uneven gas density distribution caused by water content according to the water content detected by the water dew point detector, so as to obtain leakage points;
The moisture content is corrected according to the density correction coefficient, and the calculation formula is as follows:
Wherein h is the water content in the air, T is the temperature, and the unit is the temperature;
Determining a positioning correction coefficient of the leakage point according to the density correction coefficient:
C1＝1/C0。
due to the adoption of the technical scheme, the invention has the following advantages:
(1) The integrated on-line analysis cabinet integrates a sampling unit (sampling pump, sampling pipeline, on-line analyzer, emptying pipeline, etc.), a marking gas generating unit (electromagnetic valve, marking gas bottle interface, etc.), a PLC control system and an industrial computer in a set of standard cabinet, thereby realizing the integration, miniaturization and automation of the device, saving the occupied area and being capable of being plugged and used.
(2) The integrated cabinet and the detection tube can be connected in a loop or an open circuit. The loop connection can be used for arranging the system in a single station yard, avoiding that the receiving and transmitting devices are respectively arranged at the two upstream and downstream station yards, and avoiding the problem of arranging independent control systems and communication between the upstream and downstream stations. The open circuit connection can realize the series connection of a plurality of cabinets, expands the detection range, and is suitable for natural gas long-distance pipelines of hundreds and thousands of kilometers.
(3) A combination of multiple gas on-line analyzers is employed. The laser analyzer adopted by the invention is a double-channel gas analyzer, and can detect the concentration of methane and ethane simultaneously. Because the natural gas generally contains ethane components, and the ethane content in the natural interference gas such as methane is zero, the ethane concentration detection can be used as a supplementary criterion for natural gas detection. In addition, the invention is provided with a hydrogen detector, which can detect the concentration of hydrogen contained in the gas. Biogas typically contains a certain amount of hydrogen, and if hydrogen is detected at the same time as methane, the hydrogen can be used as a criterion for biogas, so that false alarms are reduced.
(4) A laser type methane gas analyzer is used. In terms of detection principle, the laser type analyzer has the advantages of higher sensitivity and high response speed compared with an electrochemical type analyzer and an infrared type analyzer, and can detect methane gas with lower concentration.
(5) The water content analyzer can be used for detecting the water content in the sampled gas on line and correcting the density distribution non-uniformity caused by the water content in the air, so that errors occur in system positioning calculation.
Therefore, the invention can be widely applied to the technical field of pipeline natural gas leakage detection.
Drawings
Fig. 1 (a) and fig. 1 (b) are schematic structural diagrams of an on-line analysis integrated cabinet for detecting micro leakage of natural gas, wherein fig. 1 (a) is a schematic structural diagram of a back side of the on-line analysis integrated cabinet, and fig. 1 (b) is a schematic structural diagram of a front side of the on-line analysis integrated cabinet;
FIG. 2 is a piping diagram of an on-line analysis integrated cabinet for natural gas trace leak detection according to the present invention;
FIG. 3 is a schematic diagram of a method for loop connection of an on-line analysis integrated cabinet for natural gas trace leak detection according to the present invention;
FIG. 4 is a schematic diagram of an open circuit connection method for an on-line analysis integrated cabinet for natural gas trace leak detection according to the present invention;
The figures are marked as follows:
1. A control unit; 2. a sampling unit; 21. a first solenoid valve block; 22. a first mass flow controller; 23. a sampling pump; 3. an industrial computer; 31. a touch screen; 32. an upper computer; 4. an online analyzer combining unit; 41. a methane gas analyzer; 42. c3+ gas detector; 43. a hydrogen detector; 44. a water dew point detector; 5. a flag gas generation unit; 51. a second mass flow controller; 52. the second electromagnetic valve group; 53. a first filtering unit; 54. a second filtering unit; 55. an air compressor; 56. c3+ standard gas cylinder; 6. a flag gas interface; 7. a sample gas interface; 8. a first pipeline to be detected; 9. and a second pipeline to be detected.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings and examples.
The invention provides an online analysis integrated cabinet for natural gas micro-leakage detection, which aims to solve the problems of online detection and analysis of micro-natural gas leakage. The invention solves the problems of integration, miniaturization and automation of an online analysis system; the problem that the monitoring distance of a single system is limited and long-distance pipeline leakage monitoring cannot be met is solved; the sensitivity and the response speed of the on-line analysis of the natural gas are improved through the combination of a plurality of gas analyzers, and meanwhile, the possible influence of the interference gas such as methane on the natural gas detection is solved; and correcting the positioning error caused by the water content in the air by a moisture analyzer.
As shown in fig. 1 (a) and fig. 1 (b), the online analysis integrated cabinet for detecting micro leakage of natural gas provided by the invention comprises: the device comprises a control unit 1 arranged at the upper part of the back of the cabinet, a sampling unit 2 arranged at the lower part of the back of the cabinet, an industrial computer 3 arranged at the upper part of the front of the cabinet, an on-line analyzer combination unit 4 arranged at the middle part of the front of the cabinet, a marking gas generation unit 5 arranged at the lower part of the front of the cabinet, a marking gas interface 6 and a sample gas interface 7 arranged at the side part of the cabinet. The industrial computer 3 is provided with a touch screen 31 for realizing functions of parameter setting, system control, analysis result display and the like, and sending received parameter setting and system control signals to the control unit 1; the control unit 1 is used for controlling the sampling unit 2, the online analyzer combination unit 4 and the marking gas generation unit 5 according to the received parameter setting and system control signals; the sampling unit 2 is communicated with one end of a pipeline to be detected through a sample gas interface 7, and is used for extracting sample gas in the pipeline to be detected and conveying the sample gas to the online analyzer combination unit 4; the online analyzer combination unit 4 is used for detecting the sample gas conveyed by the sampling unit 2 and sending the detection result to the control unit 1; the marking gas generating unit 5 is communicated with the other end of the pipeline to be detected through a marking gas interface 6 and is used for conveying marking gas into the pipeline to be detected; the control unit 1 sends all the received detection data to the industrial computer 3, the industrial computer 3 realizes detection and positioning analysis of trace natural gas leakage according to the detection result, and performs early warning according to the analysis result, and all the detection data are stored at the same time.
Further, the control unit 1 employs a PLC controller in which a data acquisition unit and an automatic control unit are provided. The data acquisition unit is used for receiving all detection signals sent by the online analyzer combination unit; the automatic control unit is used for realizing automatic control of the whole analysis flow according to the received parameter setting signals such as sampling flow, time interval and the like, and comprises the following steps: pipeline purging, standing (detection tube permeation trapping), sample extraction, online analysis, venting and the like.
Further, an upper computer 32 is provided in the industrial computer 3, and a database, a pre-loaded carrier gas real-time analysis system and a leakage positioning system are provided in the upper computer 22. The system comprises a control unit, a pre-loaded gas real-time analysis system, a leakage positioning system, a database and a monitoring system, wherein the pre-loaded gas real-time analysis system and the leakage positioning system are respectively used for completing the leakage alarming and leakage point positioning functions of the system according to monitoring data sent by the control unit, and the database is used for storing all detection data sent by the control unit and leakage alarming and leakage point fixed-point analysis results obtained by the pre-loaded gas real-time analysis system and the leakage positioning system.
Further, as shown in fig. 2, the sampling unit 2 includes a first solenoid valve block 21, a first mass flow controller 22, and a sampling pump 23. The first electromagnetic valve group 21 comprises two connection ports, the two connection ports are respectively connected with the first pipeline to be detected 8 and/or the second pipeline to be detected 9 through the sample gas interface 7, the output end of the first electromagnetic valve group 21 is connected with the input end of the sampling pump 23, and the output end of the sampling pump 23 is connected with the first mass flow controller 22. The electromagnetic valve group 21, the sampling pump 23 and the first mass flow controller 22 are all connected with the control unit 1, and the electromagnetic valve group 21 is used for switching pipelines according to control signals sent by the control unit 1, including selecting to extract gas in the first pipeline 8 or the second pipeline 9 to be detected for analysis or switching to purge the first pipeline 8 and the second pipeline 9 to be detected; the sampling pump 23 is used for pumping the sample gas in the pipeline 8 or 9 to be detected according to the control signal sent by the control unit 1; the output end of the first mass flow controller 22 is connected with the online gas analyzer combination unit 4 as the output end of the sampling unit 2, and is used for measuring and controlling the flow of the gas in the pipeline 8 or 9 to be detected according to the control signal sent by the control unit 1, so that the gas in the pipeline 8 or 9 to be detected is extracted according to the uniform and stable flow rate and is output to the online gas analyzer combination unit 4 for analysis.
Preferably, the sampling pump 23 is a negative pressure type constant flow sampling pump.
Preferably, the first mass flow controller 22 employs an integrated mass flow meter and solenoid control valve.
Further, the online analyzer combination unit 4 includes a methane gas analyzer 41, a c3+ gas detector 42, a hydrogen gas detector 43, and a water dew point detector 44. The input end of the methane gas analyzer 41 is connected with the output end of the sampling unit, namely, the output end of the mass flow controller 22, the output end of the methane gas analyzer 41 is sequentially connected with the c3+ gas detector 42, the hydrogen detector 43 and the water dew point detector 44, and the output end of the water dew point detector 44 directly discharges the gas through a pipeline. The methane gas analyzer 41, the c3+ gas detector 42, the hydrogen gas detector 43 and the water dew point detector 44 are all connected to the control unit 1, and are respectively used for detecting the contents of methane, C2, C3, hydrogen and moisture in the gas in the pipeline 8 or 9 to be detected, and sending the contents to the control unit 1.
Preferably, the methane gas analyzer 41 adopts a high-precision dual-channel laser methane gas analyzer, and has the advantages of higher sensitivity and high response speed compared with electrochemical and infrared analyzers; the dual channel detection allows simultaneous analysis of methane and ethane concentrations. The concentration of methane is 0-100ppm, and the concentration of ethane is 0-1000ppm.
Preferably, the hydrogen gas detection range of the hydrogen gas detector 43 is 0-500ppm.
Further, the flag gas generation unit 5 includes a second mass flow controller 51, a second solenoid valve group 52, a first filter unit 53, a second filter unit 54, an air compressor 55, and a c3+ standard gas cylinder 56. The second electromagnetic valve group 52 includes two input ends and two output ends, the first input end is connected with the output end of the second mass flow controller 51, the input end of the second mass flow controller 51 is connected with an air compressor 55 arranged outside the cabinet through a first filtering unit 53 to form a purging branch, the second mass flow controller 51 is connected with the control unit 1, and the flow of the gas in the purging branch is measured and controlled under the control of the control unit 1; the second input end is connected with a C3+ standard gas bottle 56 arranged outside the cabinet through a second filtering unit 54 to form a marking gas branch; the two output ends of the second electromagnetic valve group 52 are respectively connected with the pipeline 8 to be detected and/or the pipeline 9 to be detected, and are used for switching the gas paths under the control of the control unit 1, so that the air or the marking gas provided by the purging branch or the marking gas branch is input into the pipeline 8 to be detected or the pipeline 9 to be detected.
Further, the second electromagnetic valve group 52 includes four three-way electromagnetic valves 521 to 524, and one of the through ports of the three-way electromagnetic valve 521 and the three-way electromagnetic valve 522 is connected in parallel and then is connected with the marking gas branch as a first input end; the bypass ports of the three-way electromagnetic valve 521 and the three-way electromagnetic valve 522 are connected in parallel and then used as a second input end to be connected with the marking gas branch; the other straight-through ports of the three-way electromagnetic valve 521 and the three-way electromagnetic valve 522 are respectively connected with one straight-through port of the three-way electromagnetic valve 523 and one straight-through port of the three-way electromagnetic valve 524; the bypass ports of the three-way electromagnetic valve 523 and the three-way electromagnetic valve 524 are connected in parallel and then connected with the atmosphere; the other through ports of the three-way electromagnetic valve 523 and the three-way electromagnetic valve 524 are used as two sign air interfaces of the cabinet and are respectively connected with a pipeline to be detected.
Further, the first filter unit 53 employs a molecular sieve air filter dryer.
The invention also provides a detection method of the online analysis integrated cabinet for detecting the micro-leakage of the natural gas, which comprises the following steps:
1) According to the detection requirement, the pipeline to be detected is connected with a marking gas interface 6 and a sample gas interface 7 of an online analysis integrated cabinet for the micro leakage detection of natural gas.
As shown in fig. 3, when the method is used for monitoring leakage in a small range, such as a station yard, a storage tank, etc., a ring detection mode is selected, and a specific connection method is as follows: and the sample gas interface 7 and the mark gas interface 6 at the side part of the integrated cabinet are respectively connected with two ends of a pipeline to be detected to form a detection passage. The other end of the sample gas interface 7 is connected to the sampling unit 2, and the sample gas is sampled by the sampling unit 2 and then is conveyed to the on-line analysis instrument combination unit 4 for analysis; the other end of the marking gas interface 6 is connected with the marking gas generating unit 5, and the marking gas generating unit 5 provides a marking ambition to a pipeline to be detected. At the beginning of each detection cycle, the control unit 1 controls the mark ambition generating unit 5 to inject a C3 gas with a certain concentration as a mark, and when the on-line analyzer combining unit 4 detects a peak value of the C3 gas concentration, it is determined that one detection cycle is ended.
Preferably, since the first electromagnetic valve group 21 and the second electromagnetic valve group 52 in the integrated cabinet are respectively provided with two connection ports, the integrated cabinet can be simultaneously connected with two pipelines to be detected, so that automatic alternate detection is realized. At the beginning of each detection cycle, the control unit 1 controls the mark ambition generating unit 5 to inject a C3 gas with a certain concentration as a mark, and when the on-line analyzer combining unit 4 detects a peak value of the C3 gas concentration, it is determined that one detection cycle is ended.
As shown in fig. 4, when a long natural gas pipeline of hundreds or thousands kilometers needs to be detected, an open circuit detection mode is selected, and at this time, a plurality of integrated cabinets need to be connected in series, and a specific connection method is as follows: one end of a first section of pipeline to be detected is connected with a marking gas generating unit of a first cabinet through a marking gas interface, and the other end of the first section of pipeline to be detected is connected with a sampling unit of a second cabinet through a sample gas interface; one end of the second section of pipeline to be detected is connected with the marking gas generating unit of the second cabinet, the other end of the second section of pipeline to be detected is connected with the sampling unit of the third cabinet, and other sections of pipelines to be detected are sequentially connected by adopting the same method to form a serial detection passage. And extracting the gas in the pipeline to be detected to a second cabinet for analysis, injecting C3 gas with a certain concentration into the pipeline to be detected by the first cabinet when the detection starts, and judging that one detection cycle is finished when the concentration of the C3 gas detected by the second cabinet reaches a peak value. Because the monitoring distance of a single cabinet can reach 40km, the detection range can be expanded by connecting a plurality of cabinets in series in an open circuit detection mode.
2) And determining the working mode of the cabinet, and controlling the marking gas generation unit and the sampling unit to convey the sample gas in the detection tube to the online analyzer combination unit through the control unit.
The working modes of the cabinet comprise a negative pressure extraction mode and a positive pressure conveying mode, and the sampling pump 23 is adopted as a power source for air extraction in the negative pressure extraction mode; in the positive pressure conveyance mode, the air compressor 55 is used as a power source for air supply.
The negative pressure extraction mode refers to:
In the invention, C3+ gas is used as a characteristic gas for judging the end of the detection cycle. When the detection cycle starts (the system records the detection starting time), the second electromagnetic valve group 52 is controlled, namely the electromagnetic valve 521 and the electromagnetic valve 523 are controlled to be conducted, and the sampling pump 23 is controlled to be started (at the moment, the air compressor 55 is not operated), so that the C3+ gas enters the pipeline 8 to be detected, and the C3+ gas is extracted to the C3+ detector 42 in the cabinet along with the sample gas for detection. The system identifies the moment when the peak of the concentration of the C3+ gas appears according to the data analysis, and takes the moment as the ending point of the detection cycle. For the line 9 to be tested, the solenoid valve 522 and the solenoid valve 524 are controlled in the same manner.
The positive pressure delivery mode refers to:
the air compressor 55 is used for replacing the vacuum pump 23 as a power source, and the air in the pipeline to be detected is conveyed into the cabinet for detection. In the mode, before the detection cycle starts, the air compressor 55 is opened for purging, and after purging is finished, the air compressor 55 is closed; when the detection cycle starts, the electromagnetic valve 521 and the electromagnetic valve 523 are controlled to be conducted, so that the pipeline 8 to be detected is communicated with the marking gas steel cylinder 56, and the C3+ mark ambition is injected into the cabinet; then, the air compressor 18 is controlled to operate (at this time, the sampling pump is not operated), so that air in the air compressor 55 enters the pipeline 8 to be detected, and the on-line analyzer combination unit in the cabinet is used for detecting the sample gas, and the system analyzes and identifies the moment when the peak value of the concentration of the C3+ gas appears according to the data, and takes the moment as the end point of the detection cycle. For the line 3 to be tested, the control solenoid 522 and the solenoid 524 are controlled in the same way.
3) The on-line analyzer combination unit detects the sample gas conveyed by the sampling unit, the detection result is sent to the industrial computer through the control unit, the industrial computer detects and locates and analyzes the trace natural gas leakage based on the detection result, and early warning is carried out according to the analysis result.
Specifically, the method comprises the following steps:
3.1 A methane gas analyzer 41, a c3+ gas detector 42, a hydrogen gas detector 43, and a water dew point detector 44 in the online analyzer combining unit 4 detect the methane and ethane concentrations, the C3 gas concentration, the hydrogen gas concentration, and the moisture content, respectively, in the sample gas, and send the detection results to the control unit 1.
3.2 The control unit 1 transmits all the detection results to the industrial computer 3, and the industrial computer 3 detects and performs positioning analysis on the trace natural gas leakage based on the detection results and performs early warning according to the analysis results.
Specifically, the analysis method comprises the following steps:
firstly, judging whether the methane in the detection pipe is leaked or not according to the hydrogen content detected by the hydrogen detector 43, and if the methane concentration is detected and the hydrogen concentration signal is detected, judging that the methane in the detection pipe is leaked instead of the natural gas; otherwise, natural gas leakage is considered;
Second, the gas density distribution unevenness due to the water content is corrected based on the water content detected by the water dew point detector 44, resulting in errors in the system positioning calculation.
The principle of correcting and positioning by adopting a water dew point detector is adopted: the integrated analysis cabinet is provided with a mass flow controller which can control the sample gas to be pumped into the on-line analysis instrument combination unit for detection at a constant mass flow. According to the monitored gas mass flow, the monitored gas temperature and pressure, converting the gas flow into a distance with a corresponding length, and then reversely calculating the position of the leakage point, and determining the leakage point by solving the first derivative zero position of the leakage signal curve.
However, in practical situations, because the air density in the detection tube is not uniformly distributed, especially when the distance between the pipelines is long, the density is affected by the different water contents of the air at different positions. In the invention, the water dew point detector is adopted to synchronously and online detect the water content in the sample gas, and meanwhile, the temperature measured value at the moment is combined to obtain the sample gas density correction coefficient, so that the positioning of the leakage point is corrected.
Specifically, since the molecular weight of air is 29 and the molecular weight of water is 18, the calculation formula of the density correction coefficient is:
Wherein h is the water content (volume ratio) in the air, T is the temperature, and the unit is the temperature.
Accordingly, the location of the leak should be multiplied by a correction factor:
C1＝1/C0
The foregoing embodiments are only for illustrating the present invention, wherein the structures, connection modes, manufacturing processes, etc. of the components may be changed, and all equivalent changes and modifications performed on the basis of the technical solutions of the present invention should not be excluded from the protection scope of the present invention.
Claims (7)
1. An integrated rack of online analysis of natural gas trace leak testing, characterized by comprising:
The device comprises a cabinet body, a control unit, a sampling unit, an industrial computer, an online analyzer combination unit, a marking gas generation unit, and a marking gas interface and a sample gas interface which are arranged on the side part of the cabinet body;
The industrial computer is provided with a touch screen for realizing the functions of parameter setting, system control and analysis result display, and sending the received parameter setting and system control signals to the control unit;
The control unit is used for controlling the sampling unit, the online analyzer combination unit and the marking gas generation unit according to the received parameter setting and system control signals;
The sampling unit is communicated with one end of the pipeline to be detected through the sample gas interface, and is used for extracting the sample gas in the pipeline to be detected and conveying the sample gas to the online analyzer combination unit;
The online analyzer combination unit is used for detecting the sample gas conveyed by the sampling unit and sending the detection result to the control unit;
The marking gas generating unit is communicated with the other end of the pipeline to be detected through the marking gas interface and is used for conveying marking gas into the pipeline to be detected;
The control unit sends all the received detection data to the industrial computer, the industrial computer detects and locates and analyzes the trace natural gas leakage according to the detection result, and performs early warning according to the analysis result, and simultaneously stores all the detection data;
The sampling unit comprises a first electromagnetic valve group, a first mass flow controller and a sampling pump; the first electromagnetic valve group comprises two connecting ports, the two connecting ports are respectively connected with a first pipeline to be detected and/or a second pipeline to be detected through the sample gas interface, the output end of the first electromagnetic valve group is connected with the input end of the sampling pump, and the output end of the sampling pump is connected with the first mass flow controller; the electromagnetic valve group, the sampling pump and the first mass flow controller are all connected with the control unit, and the electromagnetic valve group is used for switching pipelines according to control signals sent by the control unit; the sampling pump is used for extracting the sample gas in the pipeline to be detected according to the control signal sent by the control unit; the output end of the first mass flow controller is used as the output end of the sampling unit and is connected with the online analyzer combination unit and is used for measuring and controlling the flow of the gas in the pipeline to be detected according to the control signal sent by the control unit, so that the gas in the pipeline to be detected is extracted according to uniform and stable flow rate and is output to the online analyzer combination unit for analysis;
The online analyzer combination unit comprises a methane gas analyzer, a C3+ gas detector, a hydrogen gas detector and a water dew point detector; the input end of the methane gas analyzer is connected with the output end of the sampling unit, the output end of the methane gas analyzer is sequentially connected with the C3+ gas detector, the hydrogen gas detector and the water dew point detector, and the output end of the water dew point detector directly discharges the amplified gas through a pipeline; the methane gas analyzer, the C3+ gas detector, the hydrogen detector and the water dew point detector are all connected with the control unit, and are respectively used for detecting the contents of methane, C2, C3, hydrogen and water in the gas in the pipeline to be detected and sending the contents to the control unit;
The marking gas generation unit comprises a second mass flow controller, a second electromagnetic valve group, a first filtering unit, a second filtering unit, an air compressor and a C3+ standard gas cylinder; the second electromagnetic valve group comprises two input ends and two output ends; the first input end is connected with the output end of the second mass flow controller, the input end of the second mass flow controller is connected with the air compressor arranged outside the cabinet through the first filtering unit to form a purging branch, the second mass flow controller is connected with the control unit, and the flow of the gas in the purging branch is measured and controlled under the control of the control unit; the second input end is connected with the C3+ standard gas cylinder arranged outside the cabinet through the second filtering unit to form a marking gas branch; and two output ends of the second electromagnetic valve group are connected with the pipeline to be detected and are used for switching the gas circuit under the control of the control unit, so that air provided by the purging branch or marking gas provided by the marking gas branch is input into the pipeline to be detected.
2. The integrated on-line analysis cabinet for natural gas micro-leak detection of claim 1, wherein: the control unit adopts a PLC controller, and a data acquisition unit and an automatic control unit are arranged in the PLC controller; the data acquisition unit is used for receiving all detection signals sent by the online analyzer combination unit; the automatic control unit is used for realizing automatic control of the whole analysis flow according to the received sampling flow and the time interval parameter setting signal.
3. A method for detecting an on-line analysis integrated cabinet employing the natural gas micro-leakage detection according to any one of claims 1 to 2, characterized by comprising the steps of:
1) According to the detection requirement, connecting a pipeline to be detected with a marker gas interface and a sample gas interface of an online analysis integrated cabinet for natural gas micro leakage detection;
2) Determining the working mode of the cabinet, and controlling the sampling unit and the marking gas generating unit to convey the sample gas in the pipeline to be detected to the online analyzer combination unit;
3) The on-line analyzer combination unit detects the sample gas conveyed by the sampling unit, the detection result is sent to the industrial computer through the control unit, the industrial computer detects and locates and analyzes the trace natural gas leakage based on the detection result, and early warning is carried out according to the analysis result.
4. The method for detecting the natural gas micro-leakage detection on-line analysis integrated cabinet according to claim 3, wherein the method comprises the following steps: in the step 1), the connection mode of the pipeline to be detected and the online analysis integrated cabinet for the micro leakage detection of the natural gas is two:
annular detection mode: the sample gas interface and the mark gas interface at the side part of the integrated cabinet are respectively connected with two ends of a pipeline to be detected to form a detection passage;
Open circuit detection mode: the method comprises the steps of connecting a mark gas interface of a first integrated cabinet with one end of a first section of pipeline to be detected, connecting the other end of the first section of pipeline to be detected with a sampling interface of a second integrated cabinet, connecting one end of the second section of pipeline to be detected with the mark gas interface of the second integrated cabinet, connecting the other end of the second section of pipeline to be detected with the sampling interface of a third integrated cabinet, and sequentially connecting the two ends of the second section of pipeline to be detected in series to form open circuit detection.
5. The method for detecting the natural gas micro-leakage detection on-line analysis integrated cabinet according to claim 3, wherein the method comprises the following steps: in the step 2), the working modes of the integrated cabinet include a negative pressure extraction mode and a positive pressure conveying mode;
The negative pressure extraction mode refers to: when the detection cycle starts, the second electromagnetic valve group is controlled, and the sampling pump is controlled to start at the same time, so that C3+ gas enters a pipeline to be detected, and the C3+ gas is extracted to a C3+ detector in the cabinet along with the sample gas for detection; identifying the moment when the peak value of the concentration of the C3+ gas appears according to data analysis, and taking the moment as the ending point of the detection cycle;
The positive pressure delivery mode refers to: before the detection cycle starts, firstly opening the air compressor to purge, and closing the air compressor after purging is finished; when the detection cycle starts, the second electromagnetic valve group is controlled to enable the pipeline to be detected to be communicated with the marking gas steel cylinder, and C3+ mark ambition is injected into the cabinet; then, the air compressor is controlled to work, so that air in the air compressor enters a pipeline to be detected, and is detected along with the sample gas entering an online analyzer combination unit in the cabinet, the system analyzes and identifies the moment when the concentration peak value of the C3+ gas appears according to data, and the moment is taken as the end point of a detection cycle.
6. The method for detecting the natural gas micro-leakage detection on-line analysis integrated cabinet according to claim 3, wherein the method comprises the following steps: in the step 3), the on-line analyzer combination unit detects the sample gas, detects and locates and analyzes the trace natural gas leakage based on the detection result, and performs early warning according to the analysis result, comprising the following steps:
3.1 A methane gas analyzer, a C3+ gas detector, a hydrogen gas detector and a water dew point detector respectively detect the concentration of methane and ethane, the concentration of C3 gas, the concentration of hydrogen and the water content in the sample gas, and send the detection results to a control unit;
3.2 The control unit sends all detection results to the industrial computer, and the industrial computer detects and performs positioning analysis on trace natural gas leakage based on the detection results and performs early warning according to the analysis results.
7. The method for detecting the natural gas micro-leakage detection on-line analysis integrated cabinet according to claim 6, wherein the method comprises the following steps: in the step 3.2), when detecting and positioning analyzing the trace natural gas leakage based on the detection result, the analysis method comprises the following steps:
Firstly, judging whether the methane in the detection tube is leaked or not according to the content of the hydrogen detected by the hydrogen detector, and if the methane concentration is detected and a hydrogen concentration signal is detected at the same time, judging that the methane in the detection tube is leaked instead of the natural gas; otherwise, natural gas leakage is considered;
Secondly, correcting errors caused by system positioning calculation due to uneven gas density distribution caused by water content according to the water content detected by the water dew point detector, so as to obtain leakage points;
The moisture content is corrected according to the density correction coefficient, and the calculation formula is as follows:
In the method, in the process of the invention, Is the water content in the air, and the water content in the air,Temperature in degrees celsius;
Determining a positioning correction coefficient of the leakage point according to the density correction coefficient:
。
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