Gas metering and analyzing system of coal mine gas power station

Abstract

The invention relates to the field of coal mine gas treatment and utilization, and discloses a coal mine gas power station gas metering analysis system. The system comprises a flow metering unit based on a large-pipe-diameter V-cone flowmeter and differential pressure / pressure / temperature three parameters, a multi-point gas sampling and analyzing unit for cyclic sampling and parallel preprocessing, a methane concentration analyzing unit based on TDLAS and a redundant channel, a PLC metering and data integrity unit with an ms-level time reference and 64-bit high-precision calculation, and a data processing unit based on a redundant channel. A positive pressure purging explosion-proof control and alarm interlocking unit; and a local / cloud data issuing unit. The system solves the comprehensive problems of short straight pipe section, ultra-low concentration real-time analysis, continuous and reliable data and on-site explosion prevention, and the metering and safety management and control level of a gas power station is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of coal mine gas control and utilization, specifically a coal mine gas power plant gas metering and analysis system. Background Technology

[0002] Coal mine gas power plants require continuous, accurate, and reliable parameters such as methane concentration and flow rate in both intake and exhaust. These parameters must meet both the safety control requirements of power generation and oxidation units and the data continuity and verifiability requirements of carbon reduction projects (CDM). Limited on-site space, insufficient straight pipe sections, and the coexistence of high dust, high humidity, and explosion-proof requirements make it difficult for traditional metering and analysis methods to simultaneously address installation adaptability, response speed, measurement accuracy, and data integrity.

[0003] Differential pressure flow meters are widely used in industrial metering, but standard orifice plates typically require long straight pipe sections to ensure flow patterns, leading to installation difficulties and high retrofit costs due to space constraints. V-cone flow meters, as a new type of differential pressure throttling device, significantly reduce the requirements for upstream and downstream straight pipe sections, maintaining high system accuracy even with short straight pipe sections, making them suitable for large-diameter pipes and retrofit scenarios. On the other hand, online measurement of low-concentration methane often uses methods such as NDIR and catalytic combustion, which are significantly affected by cross-interference and hysteresis. TDLAS technology, through narrow-band scanning at the characteristic absorption lines of methane, features high selectivity, fast response, and strong anti-interference capabilities, making it suitable for online monitoring and rapid control of low concentrations.

[0004] The existing system still has problems such as: response lag caused by multiple analysis points and long sampling cables; impact of host computer failure on accumulation and report continuity; imperfect interlocking between on-site explosion-proof purging and analyzer; weak sensor self-diagnosis capability and insufficient identification of abnormal working conditions. There is an urgent need for a metering and analysis system that is comprehensively optimized in terms of short straight pipe sections, real-time analysis of ultra-low concentrations, data continuity and explosion-proof interlocking. Summary of the Invention

[0005] (a) Technical problems to be solved This invention, through the collaborative design of structure and algorithm, takes into account the stringent installation conditions, strict measurement indicators, and data compliance requirements, and is applicable to the renovation and new construction projects of coal mine gas power plants and oxidation units.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a gas metering and analysis system for a coal mine gas power plant, comprising a pipeline assembly for transporting gas; a large-diameter V-cone flow meter arranged on the intake pipe section and its matching differential pressure transmitter, pressure transmitter, and temperature transmitter; a multi-point sampling valve group and a sampling pretreatment system, wherein the sampling pretreatment system includes a sampling probe, a condensation / precooling unit, a filtration unit, a dehumidification unit, heat tracing and insulation, and an exhaust bypass; a methane concentration analysis module, including a laser methane analyzer and a redundant concentration analyzer; a PLC controller, which has a built-in time reference module, a data storage unit, and a communication module, and runs a metering program for standard condition conversion, methane mass flow rate calculation, and generation of various cumulative quantities; and a positive pressure purging explosion-proof control system, including a purging... The system includes a sweep valve and pressure monitoring to maintain positive pressure and safety interlocks in the analysis cabinet; an alarm interlock module; and a host computer / cloud platform. The multi-point sampling valve group and the sampling preprocessing system form a cyclic polling-parallel preprocessing structure. During periods when the analysis point is not currently active, samples are continuously extracted and preprocessed before being discharged through a venting bypass. When switching to an analysis point, analysis can proceed without waiting for preprocessing. The V-cone flowmeter is adapted to short straight pipe sections and performs standard condition conversions based on differential pressure, pressure, and temperature parameters. The laser methane analyzer is positioned close to the sampling point and directly connected to the sampling preprocessing system to reduce lag. The PLC controller performs integration and accumulation using millisecond-level time references. The data storage unit employs untamperable and tamper-proof storage to ensure the continuity and reliability of CDM data.

[0007] Preferably, the V-cone flow meter is selected for large-diameter pipe conditions, has the requirement of straight pipe sections ~D upstream and ~D downstream, and the system metering accuracy reaches ±.% depending on calibration and installation conditions, in order to solve the constraint of insufficient straight pipe sections on site.

[0008] Preferably, the laser methane analyzer adopts the principle of tunable semiconductor laser absorption spectroscopy (TDLAS), which has high selectivity, fast response and online measurement capabilities, with a response time in the order of seconds, and strong suppression capability against interference such as water vapor.

[0009] Preferably, the metering program run by the PLC controller includes: calculating the working condition volumetric flow rate based on the three parameters of differential pressure / pressure / temperature, converting to standard condition and correcting with a configurable compressibility factor Z, calculating the standard condition volumetric flow rate and methane mass flow rate based on the methane volume fraction, and performing bit-double precision accumulation with a millisecond-level time base and storing it in the data storage unit.

[0010] Preferably, the sampling preprocessing system is equipped with an automatic calibration module for zero gas and standard gas, the PLC controller triggers a periodic zero point / range calibration process, and triggers an alarm interlock module when calibration fails or drift exceeds the limit.

[0011] Preferably, the multi-point sampling valve group works in conjunction with the circulating sampling pump to continuously extract and preprocess samples at non-analysis points at a bypass flow rate of not less than twice the analysis flow rate, and discharges them through the emptied bypass to reduce the lag during analysis switching to below a predetermined threshold.

[0012] Preferably, the PLC controller implements a sensor self-diagnostic algorithm, including: open circuit / short circuit detection, range out-of-range detection, rate change detection, flat-top stagnation detection, and noise variance anomaly detection. When any detection is triggered, the corresponding quantity is backed up to maintain the previous valid value or derating the calculation and the event is recorded to the data storage unit.

[0013] Preferably, the positive pressure purging explosion-proof control system forms an interlocking logic with the PLC controller. When the positive pressure in the analysis cabinet is not up to standard or the purging is not completed, the analyzer is prohibited from being powered on and the valve group is prohibited from switching to the analysis state. If the positive pressure is lost during operation, an orderly shutdown is executed and an audible and visual alarm is triggered.

[0014] Preferably, the data storage unit uses a tamper-proof medium with irreversible writing order, and uses timestamps and cyclic redundancy check (CRC) to segment and solidify instantaneous and cumulative quantities. The continuity of the PLC's metering calculation and storage is not affected by the computer host computer's failure or power failure.

[0015] Preferably, the host computer / cloud platform realizes the functions of historical / real-time curve generation, automatic CDM report generation, system management, data backup and query, and publishes real-time data and alarms through multiple channels, including on-site monitoring terminals and remote cloud; The redundant concentration analyzer is a non-dispersive infrared (NDIR) or catalytic combustion analyzer, used to participate in voting or switching when TDLAS self-test fails or its availability is insufficient, thereby improving overall availability.

[0016] A gas metering method, applied to the aforementioned coal mine gas power plant gas metering and analysis system, includes the following steps: Sampling point polling and parallel preprocessing; Obtain differential pressure / pressure / temperature at the V-cone flow meter and calculate the volumetric flow rate under operating and standard conditions; obtain the methane volume fraction and calculate the standard methane volumetric flow rate and methane mass flow rate; Integrating and permanently storing the instantaneous to cumulative amounts in millisecond-level time steps; Perform self-diagnosis and interlock control; Publish real-time and report data to the host computer / cloud.

[0017] (III) Beneficial Effects Compared with the prior art, the present invention provides a gas metering and analysis system for coal mine gas power plants, which has the following beneficial effects: 1. High-precision metering in short straight pipe sections: V-cone differential pressure metering can achieve high system accuracy in straight pipe sections of 0~3D / 0~1D, adapting to limited space on site and reducing modification costs and uncertainties.

[0018] 2. Rapid low-concentration measurement: TDLAS has high selectivity and second-level response. Combined with near-sampling point installation and parallel preprocessing, it greatly reduces analysis lag and cross-interference.

[0019] 3. Data continuity and tamper-proof: The metering logic operates independently on the PLC side, with millisecond-level integration and WORM data fixed, unaffected by upper computer failures, meeting the CDM requirements for continuity and traceability.

[0020] 4. Explosion-proof interlocking enhances safety: The entire positive pressure purging process is interlocked, prohibiting power-on and switching if the standard is not met, and orderly shutdown in case of loss of positive pressure during operation, thus improving inherent safety.

[0021] 5. Self-diagnosis and robust calculation: Multi-dimensional anomaly detection and backoff calculation ensure that the trend remains available and timely alarms are issued when sensors malfunction, improving system availability.

[0022] 6. Multi-point integration and footprint optimization: Cyclic polling-parallel preprocessing reduces the number of analyzers and public facilities, shortens sampling cabling, and reduces investment and maintenance difficulty. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall system structure; Figure 2 A schematic diagram of the sampling and valve group piping for cyclic polling-parallel preprocessing; Figure 3 This is a schematic diagram of the V-cone differential pressure measurement and the arrangement of three-parameter measuring points; Figure 4 This is a schematic diagram of TDLAS methane analysis and redundant channel connections; Figure 5 PLC metering and data integrity, interlocking logic block diagram; Figure 6 This is a schematic diagram of positive pressure purging explosion-proof control.

[0024] In the diagram: 100 Pipe assembly; 101 Intake pipe section; 102 Exhaust pipe section; 110 V-cone flow meter; 111 Differential pressure transmitter; 112 Pressure transmitter; 113 Temperature transmitter; 120 Sampling pretreatment system; 121 Sampling probe; 122 Condensation / precooling unit; 123 Filtration unit; 124 Dehumidification unit; 125 Heat tracing and insulation; 126 Exhaust bypass; 127 Automatic calibration module; 130 Multi-point sampling valve assembly; 131 Circulating sampling pump; 140 Methane concentration analysis module; 141 Laser methane analyzer; 142 Redundant concentration analyzer; 150 PLC controller; 151 Time reference module; 152 Data storage unit; 153 Communication module; 160 Positive pressure purging explosion-proof control system; 161 Purge valve; 162 Pressure monitoring; 170 Alarm interlock module; 180 Host computer / cloud platform; 181 Local monitoring terminal; 182 Remote cloud. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] As described in the background section, there are shortcomings in the existing technology. In order to solve the above-mentioned technical problems, this application proposes a gas metering and analysis system for coal mine gas power plants.

[0027] In one embodiment, such as Figure 1 As shown, the system installs a V-cone flow meter 110 on the inlet pipe section 101. To adapt to short straight pipe sections on site, a straight pipe section configuration that meets the requirements of ≥3D upstream and ≥1D downstream within the available space is preferred; when space is further limited, the measurement stability is improved by installing flow guiding and rectifying components and optimizing the pressure tapping at the measuring point. The V-cone differential pressure signal is acquired by the differential pressure transmitter 111, which, together with the pressure transmitter 112 and temperature transmitter 113 at the same or nearby locations, forms a three-parameter metering combination.

[0028] like Figure 2 As shown, the multi-point sampling valve group 130 adopts a ring-shaped polling structure composed of electric ball valves or diaphragm valves, and the circulating sampling pump 131 provides constant suction. Each sampling branch is equipped with a sampling probe 121 and a heat tracing pipeline 125, which enters the condensation / pre-cooling unit 122, filtration unit 123, and dehumidification unit 124 of the sampling pretreatment system 120. During the polling waiting period, non-current analysis points are continuously emptied through the emptying bypass 126 at a bypass flow rate of ≥2 times the analysis flow rate, so that when switching to that point, the pretreatment link is already in a steady state, which basically eliminates the response delay caused by condensation, filtration, and pipeline lag.

[0029] like Figure 4 As shown, the methane concentration analysis module 140 includes a laser methane analyzer 141 and a redundant concentration analyzer 142 housed within the analysis cabinet. The TDLAS analyzer 141 (TDLAS) is preferably a single-path model with temperature / pressure compensation and anti-vapor algorithms. The sampling chamber is made of corrosion-resistant material and equipped with temperature control. A short-distance heat tracing connection is used between the analysis unit and the pretreatment outlet to minimize hysteresis and condensation effects. The redundant analyzer 142 can be an NDIR or catalytic combustion type, used to participate in voting or take over in case of TDLAS self-test failure, absorbance saturation, or other anomalies, ensuring continuity.

[0030] In terms of calibration, such as Figure 2 As shown, the automatic calibration module 127 switches the zero gas and methane standard gas to the analysis channel through the valve group. The PLC controller 150 performs zero point and range calibration according to the plan: the process includes purging, steady state determination, data acquisition and deviation assessment; if the deviation exceeds the threshold, the system records the event and triggers the alarm interlock module 170, and if necessary, prohibits the relevant channel from participating in the measurement.

[0031] In terms of measurement and algorithms, the PLC controller 150 has a built-in millisecond-level time base 151, with a sampling period of, for example, 100 ms. Differential pressure measurement uses a working condition volumetric flow rate model Qm, determined by differential pressure, β ratio, discharge coefficient, density, etc., and performs standard condition conversion by combining pressure Pt and temperature Tt. Qn = Qm × (Pt / Pn) × (Tn / Tt) × (Zt / Zn), Wherein, Pn and Tn are standard state pressure and temperature, Zt and Zn are compressibility factors, Zt can be configured according to gas composition or empirical model, and Zn can be 1 or based on standard gas. The standard condition volumetric flow rate of methane, Qn,CH4 = Qn × CCH4, where CCH4 is the volume fraction; the methane mass flow rate, mCH4 = ρn,CH4 × Qn,CH4, where ρn,CH4 is the density of methane under standard conditions (which can be corrected for temperature and pressure). Cumulative calculations use rectangular or trapezoidal integration, calculating minute / hour / day cumulatives for instantaneous mCH4, Qn, and Qn,CH4 respectively. In each sampling period, the integration result is written in 64-bit double-precision format to the sequential record area of ​​data storage unit 152, along with a timestamp and CRC check, and periodically solidified into an unrewritable segment to ensure traceability.

[0032] Anomaly and Backoff Logic: The PLC performs open / short circuit detection (4-20 mA loop), range out-of-range detection, rate jump (dX / dt) threshold, flat-top dwell (continuous sampling variance below the threshold), and noise anomaly (sliding window variance exceeding the threshold) on each channel. Upon triggering any anomaly, the system adopts a backoff strategy for the affected quantity, such as maintaining the previous valid value for no more than a set time or limiting updates based on physical constraints; simultaneously, an event is generated and pushed to the host computer / cloud.

[0033] In terms of interlocking and explosion protection, such as Figure 6 As shown, the positive pressure purging explosion-proof control system 160 connects to clean gas through the purging valve 161. The pressure monitoring 162 in the control cabinet, together with the flow / time dual criteria, jointly determines that the purging is complete before allowing the analyzers 141, 142 and valve group 130 to be powered on and switched. During operation, positive pressure is maintained continuously. If the positive pressure drops below the threshold, the PLC triggers an orderly shutdown, closes the valve group and stops the analyzer, and the alarm interlock module 170 drives the audible and visual alarm and uploads the event.

[0034] In terms of communication and reporting, the host computer / cloud platform 180 reads instantaneous and cumulative data and event logs from the PLC150 via Ethernet, realizing the automatic generation of real-time and historical curves, CDM daily / weekly / monthly reports. Data and alarms are published through multiple channels via the local monitoring terminal 181 and the remote cloud 182. The cumulative value on the PLC side serves as the sole metering master record, while the host computer side stores only a mirror image, ensuring that computer failures do not affect data continuity.

[0035] Installation Points: The V-cone differential pressure tap and temperature / pressure measuring points should be as close as possible to reduce errors caused by inconsistencies between static pressure and temperature; the sampling pipeline should be heated and insulated throughout 125 and properly equipped with condensation / filtration 122, 123 to prevent liquid water and dust from entering the analysis chamber; electrical and piping systems should meet mining explosion-proof standards and grounding requirements; each valve group 130 and pump 131 should have redundant bypasses for maintenance; standard gas and zero gas cylinders should be equipped with pressure reducing and check valves, and the venting 126 should be led to a safe area.

[0036] Through the synergy of the above structure and algorithm, this invention achieves high-precision metering under short straight pipe section conditions, enables rapid analysis of low hysteresis and low concentration under multi-point conditions, and pushes the metering logic down to the PLC side to ensure data continuity and verifiability. At the same time, it meets the requirements of explosion-proof and joint safety on site and is suitable for the long-term stable operation of gas power plants and oxidation units.

[0037] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A gas metering and analysis system for a coal mine gas power plant, comprising a pipeline assembly (100) for conveying gas; a large-diameter V-cone flow meter (110) arranged on the intake pipe section (101) and its matching differential pressure transmitter (111), pressure transmitter (112) and temperature transmitter (113); a multi-point sampling valve group (130) and a sampling pretreatment system (120), wherein the sampling pretreatment system (120) includes a sampling probe (121), a condensation / precooling unit (122), a filtration unit (123), a dehumidification unit (124), a heat tracing and insulation unit (125), and an exhaust bypass (126); The methane concentration analysis module (140) includes a laser methane analyzer (141) and a redundant concentration analyzer (142); a PLC controller (150) with a built-in time reference module (151), a data storage unit (152) and a communication module (153), and runs a metering program for standard condition conversion, methane mass flow rate calculation and generation of various cumulative quantities; a positive pressure purging explosion-proof control system (160) including a purging valve (161) and a pressure monitor (162) for maintaining positive pressure and safety interlock of the analysis cabinet; an alarm interlock module (170); and a host computer / cloud platform (180), characterized in that: The multi-point sampling valve group (130) and the sampling preprocessing system (120) form a cyclic polling-parallel preprocessing structure. During periods when the analysis point is not currently being analyzed, samples are continuously extracted and preprocessed before being discharged through the venting bypass (126). When switching to the analysis point, analysis can begin without waiting for preprocessing. The V-cone flowmeter (110) is adapted to short straight pipe sections and is combined with differential pressure / pressure / temperature parameters for standard condition conversion. The laser methane analyzer (141) is located near the sampling point and is directly connected to the sampling preprocessing system (120) to reduce lag. The PLC controller (150) performs integration and accumulation with a ms-level time base. The data storage unit (152) uses untamperable storage to ensure the continuity and reliability of CDM data.

2. The system according to claim 1, characterized in that: The V-cone flowmeter (110) is selected for large-diameter pipe conditions, with straight pipe sections required for 0-3D upstream and 0-1D downstream, and the system metering accuracy reaches ±0.5% (depending on calibration and installation conditions), to solve the constraint of insufficient straight pipe sections on site.

3. The system according to claim 1 or 2, characterized in that: The laser methane analyzer (141) adopts the principle of tunable semiconductor laser absorption spectroscopy (TDLAS), which has the ability to perform online measurement with high selectivity and fast response. The T90 response time is in the second range, and it has a strong ability to suppress interference such as water vapor.

4. The system according to claim 1, characterized in that: The metering program run by the PLC controller (150) includes: calculating the working condition volumetric flow rate based on the three parameters of differential pressure / pressure / temperature, converting to standard condition and correcting with configurable compressibility factor Z, calculating the standard condition volumetric flow rate and mass flow rate of methane based on the volume fraction of methane, and performing 64-bit double precision accumulation with a ms-level time base (151) and storing it in the data storage unit (152).

5. The system according to claim 1, characterized in that: The sampling preprocessing system (120) is equipped with an automatic calibration module (127) for zero gas and standard gas. The PLC controller (150) triggers a periodic zero point / range calibration process and triggers an alarm interlock module (170) when calibration fails or drift exceeds the limit.

6. The system according to claim 1, characterized in that: The multi-point sampling valve group (130) works in conjunction with the circulating sampling pump (131) to continuously extract and pre-process samples at non-analysis points at a bypass flow rate of not less than twice the analysis flow rate, and discharge them through the emptied bypass (126) to reduce the lag during analysis switching to below a predetermined threshold.

7. The system according to claim 1, characterized in that: The PLC controller (150) implements a sensor self-diagnosis algorithm, including: open circuit / short circuit detection, range overrun detection, rate change detection, flat top stagnation detection and noise variance abnormality detection, and performs backoff processing on the corresponding quantity when any detection is triggered (keeping the previous valid value or derating calculation) and records the event to the data storage unit (152).

8. The system according to claim 1, characterized in that: The positive pressure purging explosion-proof control system (160) and the PLC controller (150) form an interlocking logic. When the positive pressure in the analysis cabinet is not up to standard or the purging is not completed, the analyzer (141, 142) is prohibited from being powered on and the valve group (130) is prohibited from switching to the analysis state. If the positive pressure is lost during operation, an orderly shutdown will be performed and an audible and visual alarm will be triggered.

9. The system according to claim 1, characterized in that: The data storage unit (152) uses a tamper-proof medium with irreversible writing order. It uses timestamps and cyclic redundancy check (CRC) to segment and solidify instantaneous and cumulative quantities. The computer host computer (180) does not affect the continuity of PLC's metering calculation and storage regardless of faults or power outages.

10. The system according to claim 1, characterized in that: The host computer / cloud platform (180) realizes the functions of historical / real-time curve generation, automatic CDM report generation, system management, data backup and query, and publishes real-time data and alarms through multiple channels, including on-site monitoring terminal (181) and remote cloud (182). The redundant concentration analyzer (142) is a non-dispersive infrared (NDIR) or catalytic combustion analyzer, used to participate in voting or switching when TDLAS (141) fails to self-test or has insufficient availability, thereby improving overall availability.

Images