Gas leakage monitoring system, FLNG system and gas leakage monitoring method thereof

Abstract

The present invention relates to a gas leakage monitoring system, an FLNG system and a gas leakage monitoring method thereof, and belongs to the fields of health, environmental protection and safety. The monitoring system includes a sensing unit, a control unit and an optical communication unit. The sensing unit collects information such as gas concentration, ambient temperature, wind speed, etc.; the control unit obtains the data collected by the sensor, performs signal conditioning, generates control instructions and sends them to the purification device; the optical communication unit uses optical fiber to communicate data with the FLNG main control system. The present invention adopts a distributed control method to design an automatic monitoring system to realize online monitoring of hydrogen sulfide. Once hydrogen sulfide leaks, emergency purification treatment is immediately carried out, thereby improving the safety and reliability of the system. The monitoring device of the present invention has a time-sensitive network, which can perform deterministic communication and synchronous measurement on various standard Ethernet networks, and can operate independently from the host computer, thereby improving the monitoring efficiency.

Description

Technical Field

[0001] The present invention belongs to the fields of health, environmental protection and safety, and in particular relates to a gas leakage monitoring system, a floating liquefied natural gas system (FLNG) and a gas leakage monitoring method thereof. Background Art

[0002] Gas leakage is an important problem in pipeline transportation. When leakage occurs, it may endanger personal safety and damage the surrounding environment and ecological balance, causing loss of life and property. The monitoring methods and technologies of pipeline leakage are becoming more and more perfect with the development of pipeline transportation, and have become an important research content in industrial, agricultural, environmental and ecological development and scientific research.

[0003] Taking the floating liquefied natural gas system (FLNG) as an example, at present, the floating liquefied natural gas production storage and offloading device (FPSO) is a floating production device used for the development of offshore natural gas fields. It is positioned at sea through a mooring system and has the functions of mining, processing, liquefaction, storage and loading and unloading natural gas. It is used in conjunction with liquefied natural gas (LNG) ships to achieve the mining and transportation of offshore natural gas fields. FLNG may produce a large amount of harmful gas leakage during operation, causing great corrosion to metal pipelines and equipment, and in severe cases, it may lead to catastrophic accidents. Taking hydrogen sulfide gas leakage as an example, in the production, processing, storage and transportation of natural gas, accidents caused by hydrogen sulfide gas are endless, so it is very important to monitor it in real time online.

[0004] Floating liquefied natural gas systems require high detection accuracy, short response time, and high reliability. At present, for the online monitoring of gas leakage in offshore FLNG systems, online monitoring and analysis technologies such as detection tube method and chromatography are generally used. The detection tube method has the advantages of easy portability, simple structure and operation, low price, and rapid gas analysis; however, its detection accuracy is poor, its life is short, and it needs to be replaced frequently. The advantages of chromatography are simple operation, sampling and analysis, and fast analysis speed, but the accuracy of trace gas analysis is not high, the response time is long, and the requirements for analytical instruments are high. At the same time, the current online monitoring technology is not suitable for long-term work in floating and corrosive environments at sea. Therefore, it is very necessary to provide an automatic online monitoring system based on the characteristics of FLNG to monitor the leakage of harmful gases in FLNG devices in real time. Summary of the invention

[0005] On the basis of the above-mentioned deficiencies, the present invention provides a gas leakage monitoring system, a floating liquefied natural gas system (FLNG) and a gas leakage monitoring method thereof for the sulfur recovery device of FLNG. The monitoring system can realize high-precision online monitoring. When leakage occurs, emergency purification treatment can be carried out immediately, thereby improving the safety and reliability of the monitoring system.

[0006] In order to achieve the above object, the present invention provides a gas leakage monitoring system for monitoring the content of leaked gas, comprising a sensing unit, a control unit and an optical communication unit;

[0007] The sensing unit includes a gas sensor for detecting the concentration of leaked gas, a temperature sensor for detecting the ambient temperature, and a wind speed sensor for detecting the wind speed;

[0008] The control unit includes a controller, which is connected to the sensing unit, obtains data collected by the sensor of the sensing unit, performs signal conditioning and control algorithm processing, generates control instructions and sends them to the purification device and the sound and light alarm device;

[0009] The optical communication unit includes a photoelectric conversion module, which is connected to the control unit and is used to transmit the control unit information to the host computer in the main control room after modulation and demodulation by the photoelectric conversion module, and uses optical fiber to communicate data with the main control system.

[0010] Preferably, the control unit includes a signal conversion module, which is connected to the gas sensor and the wind speed sensor, obtains the gas concentration analog signal collected by the gas sensor and the wind speed analog signal collected by the wind speed sensor, converts them into current signals, and performs data storage and processing.

[0011] Preferably, the control unit further includes a temperature acquisition module, which is connected to the temperature sensor, obtains the working environment temperature information collected by the temperature sensor, converts the thermoelectromotive force collected by the temperature sensor into a voltage signal, and stores and processes the data.

[0012] Preferably, the control unit further comprises a relay control module, which is connected to the purification device and the sound and light alarm device and is used to control the purification device and the sound and light alarm device according to the detected leakage gas concentration.

[0013] Preferably, the optical communication unit further includes a pair of photoelectric converters between the host computer and the controller, one for modulation and the other for demodulation, and optical fiber is used for communication between the photoelectric converters; when the lower computer detects a gas leakage signal, the actuator immediately performs an emergency response and sends an instruction to the host computer, and after receiving the instruction, the host computer determines whether to close the valve of the upstream equipment of the sulfur recovery device.

[0014] The present invention also provides a floating liquefied natural gas system, comprising the above-mentioned gas leakage monitoring system.

[0015] Preferably, the controller adopts a CompactRIO controller, the signal conversion module adopts a multi-channel analog input board, the temperature control module adopts a multi-channel temperature acquisition board, and the relay control module adopts a multi-channel relay output board, and each board is integrated in the controller; the gas sensor adopts a linear 4-20mA output gas sensor, and the wind speed sensor adopts a 4-20mA output wind speed sensor, which are connected to the multi-channel analog input board; the temperature sensor adopts a thermocouple, which is connected to the multi-channel temperature acquisition card.

[0016] A method for monitoring gas leakage in a floating liquefied natural gas system, using the floating liquefied natural gas system, comprises the following steps:

[0017] (S1) Simulate the leakage scenario of sulfur recovery unit in FLNG system;

[0018] (S2) according to the simulated gas leakage scenario, simulate and obtain gas leakage and diffusion data, and place gas sensors according to the gas leakage and diffusion data;

[0019] (S3) starting the monitoring system to monitor the concentration of leaked gas, wind speed, wind direction, and temperature of the environment in real time: the controller collects the leakage gas concentration information detected by the gas sensor, the temperature information detected by the temperature sensor, and the wind speed information monitored by the wind speed sensor in real time;

[0020] (S4) According to the concentration information of the leaked gas, the sound and light alarm device and the purification device are activated to perform emergency purification treatment on the leaked gas.

[0021] Preferably, in step (S1), the gas leakage scenario includes factors of the leakage device itself and environmental factors of the leakage field, the leakage device itself factors include the location of the leakage point and the leakage source strength, and the leakage field environmental factors include wind speed, wind direction, and temperature; find out the device with leaking gas and determine the simulated leakage point; calculate the leakage source strength based on the process parameters of the leakage device; determine the simulated wind speed and wind direction in combination with the specific environmental conditions of the location of the leakage point; and establish a final simulation scenario set.

[0022] Preferably, the specific steps of simulating the leakage scenario of the sulfur recovery unit in the FLNG system include:

[0023] (ss1) Establish a sulfur recovery unit model and divide the grid;

[0024] (ss2) Determination of the leak point location: The leak point location is set at the top of the device where the leaked gas accumulates or where the pipeline passes through the device;

[0025] (ss3) Calculate the leakage source strength Q: Based on:

[0026]

[0027] Among them, P a is the atmospheric pressure, P c is the pressure inside the pressure vessel; C D is the leakage coefficient, K is the gas adiabatic coefficient, Z is the compressibility factor, R is the ideal gas constant; T is the temperature inside the pressure vessel, M is the molar mass of the leaking gas, A or is the leakage hole area;

[0028] Substitute the relevant parameters of the FLNG sulfur recovery unit into the above formula to obtain the leakage source strength of the unit;

[0029] (ss4) Boundary condition definition: The wind speed inlet boundary is set as the inlet boundary condition, the leakage port is set as the mass flow inlet boundary condition, the upper part and both sides of the simulation area are symmetrical boundary conditions, the outlet is set as the free outflow boundary condition, the bottom surface and the device wall surface use the wall boundary condition, the turbulence model uses the standard k-ε model, and the velocity inlet boundary layer wind speed condition and turbulence parameters are calculated according to the following formula:

[0030]

[0031]

[0032]

[0033] Where v is the wind speed at a height of z from the ground, τ is the von Karman coefficient, δ is the friction velocity, z0 is the ground roughness, C u is the model constant, k is the turbulence kinetic energy, and ε is the turbulence coefficient;

[0034] (ss5) According to the boundary conditions, solve the gas leakage and diffusion data, including the farthest distance of gas diffusion and the highest point of leakage concentration, and arrange the gas sensors according to the farthest distance and the highest point of leakage concentration.

[0035] Preferably, the step (ss5) includes a method for specifically arranging gas sensors according to the parameters of boundary conditions, the farthest gas diffusion distance and the highest leakage concentration point, sparsely arranging gas sensors within 0.5 m from the farthest distance of the diffusion concentration, and redundantly arranging gas sensors within 1.0 m from the highest leakage concentration point.

[0036] Preferably, the step (S4) includes starting the monitoring system, setting high and low alarm values ​​for the concentration of the gas to be tested, respectively, the system monitoring and collecting leakage gas concentration information; judging whether the gas concentration has reached the alarm value, starting the sound and light alarm and purification device, the purification device including a fan and a spray system; when the gas concentration reaches the low alarm value, starting the fan and the sound and light alarm device; when the leakage gas concentration reaches the high alarm value, starting the spray system at the same time; after purification treatment, detecting whether the leakage gas concentration has dropped to a safe value, and purifying until the concentration drops to a safe range.

[0037] Preferably, the setting range of the high alarm value of the measured gas concentration is 10-100 ppm, and the setting range of the low alarm value is 2-10 ppm.

[0038] Compared with the prior art, the advantages and positive effects of the present invention are:

[0039] Aiming at the requirements of the South China Sea deep-sea FLNG equipment for the hydrogen sulfide online monitoring system under floating conditions in terms of stability, modularization, corrosion resistance, explosion-proof and long-term safe operation, the present invention proposes a gas leakage monitoring system, a floating liquefied natural gas system and a gas leakage monitoring method thereof. By adopting this monitoring system and device, online monitoring and control are realized. When leakage occurs, the purification device immediately performs emergency treatment, thereby improving the safety and reliability of the system.

[0040] (1) The system of the present invention is an online automatic monitoring system integrating monitoring, early warning, safety control and emergency response. Based on the diffusion model and diffusion field numerical calculation results of the FLNG sulfur recovery device, combined with meteorological information such as leakage gas concentration, working environment temperature, wind direction, wind speed, etc., gas sensors are sparsely arranged within 0.5m from the farthest distance of the diffusion concentration, and gas sensors are redundantly arranged within 1.0m from the highest point of leakage concentration, so as to facilitate real-time collection and monitoring of hydrogen sulfide concentration at different locations, thereby improving the accuracy of monitoring. At the same time, remote sound and light alarms are performed on the online monitoring data in different levels, realizing safety interlock control, and timely and effectively starting the emergency response plan, providing safety guarantee for the exploitation of deep-sea gas fields.

[0041] (2) The host computer of the present invention is remotely deployed in the central control room of FLNG, and the slave computer is deployed at the hydrogen sulfide online monitoring site. According to the possible leakage location of the on-site sulfur recovery device, multiple slave CompactRIO controllers can be arranged. The slave CompactRIO controllers are connected in a star-shaped manner by using network cables. The master CompactRIO and the host computer communicate using optical fibers. Each CompactRIO controller is arranged in an explosion-proof box. The explosion-proof box controls external marine atmospheric corrosion and internal medium corrosion. Each explosion-proof box is arranged on the same side of the FLNG device to fully ensure the safety and reliability of the system.

[0042] (3) The controller of the present invention adopts a CompactRIO controller, which is small in size, high in protection level, easy to install, and can work stably in harsh environments and small areas. It has a time-sensitive network and can perform deterministic communication and synchronous measurement. It has high measurement accuracy and fast response speed and can perform high-speed dynamic measurement. It is highly flexible and can realize monitoring and control of different gases by replacing different gas sensors.

[0043] (4) The present invention can realize long-term high-precision real-time monitoring of hydrogen sulfide gas in a marine environment and obtain real-time information on the concentration. Specifically, the low alarm threshold of hydrogen sulfide concentration is set to 10ppm. When the monitored concentration of hydrogen sulfide is higher than 10ppm, the sound and light alarm will sound an alarm and the fan will start working; the low alarm threshold of hydrogen sulfide concentration is set to 50ppm. When the concentration of hydrogen sulfide exceeds 50ppm, the spray device will start to spray alkali solution until the concentration is reduced to a safe standard.

[0044] (5) The CompactRIO of the present invention has its own FPGA. The program is downloaded into the FPGA and can run independently from the host computer. The data can be automatically stored in the SD card on the CompactRIO controller. The staff can retrieve the data regularly, which reduces the dependence on the staff.

[0045] (6) The present invention uses optical communication for data transmission between the host computer and the slave CompactRIO controller. A photoelectric converter is placed between the host computer and the CompactRIO controller, one for modulation and the other for demodulation. Optical fiber is used for communication between the photoelectric converters. This is to cope with the large number of interference signals on the FLNG site and play an anti-interference role. At the same time, optical communication has a long transmission distance and a fast transmission speed. Once hydrogen sulfide leaks, the slave computer detects the leakage signal and immediately performs emergency purification processing, and sends instructions to the host computer. After receiving the instructions, the host computer determines whether to close the valve of the upstream equipment of the sulfur recovery device to fully ensure the safety of personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is the overall structural block diagram of the monitoring system of the present invention;

[0047] Figure 2 It is the layout diagram of the online monitoring system of the present invention;

[0048] Figure 3 It is a schematic diagram of the optical communication design of the upper and lower computers of the present invention;

[0049] Figure 4 It is the main program flow chart of the host computer of the present invention;

[0050] Figure 5The closed-loop execution flow chart of the lower computer of the present invention. DETAILED DESCRIPTION

[0051] The specific implementation modes of the present invention are further described below in conjunction with the accompanying drawings.

[0052] The present invention provides a gas leakage monitoring system for FLNG, which is used to monitor the gas leakage in the floating natural gas liquefaction system. The gas leakage of FLNG is mainly caused by the leakage of hydrogen sulfide gas in the source gas transmission pipeline of the sulfur recovery device. Figure 1 , Figure 2 , This embodiment takes the online monitoring of hydrogen sulfide gas as an example and proposes an online monitoring system for hydrogen sulfide, including a sensing unit, a control unit and an optical communication unit;

[0053] The sensing unit includes a hydrogen sulfide sensor for detecting the concentration of hydrogen sulfide, a temperature sensor for detecting the ambient temperature, and a wind speed sensor for detecting the wind speed;

[0054] The control unit obtains the data collected by the sensor of the sensing unit, performs signal conditioning and control algorithm processing, generates control instructions and sends them to the purification device and the sound and light alarm device. It includes a signal conversion module, a temperature acquisition module and a relay control module. The signal conversion module is connected to the hydrogen sulfide sensor and the wind speed sensor, obtains the hydrogen sulfide concentration analog signal collected by the hydrogen sulfide sensor and the wind speed analog signal collected by the wind speed sensor, converts them into current signals, and performs data storage and processing; the temperature acquisition module is connected to the temperature sensor, obtains the working environment temperature information collected by the temperature sensor, performs filtering sampling and other processing, converts the thermoelectric potential collected by the temperature sensor into a voltage signal, and performs data storage and processing; the relay control module is connected to the purification device and the sound and light alarm device, and controls the purification device and the sound and light alarm device according to the detected hydrogen sulfide concentration information.

[0055] The optical communication unit includes a photoelectric conversion module, which is connected to the control unit and is used to transmit the control unit information to the host computer in the main control room after modulation and demodulation by the photoelectric conversion module, and uses optical fiber to communicate data with the main control system.

[0056] The present invention takes into account the special working environment of the ocean. The hardware design part adopts the CompactRIO field embedded system based on NI. The hydrogen sulfide concentration information is collected through the hydrogen sulfide sensor to obtain the real-time concentration information of hydrogen sulfide, and then automatic control and early warning are performed. The CompactRIO controller and various modules can work at a temperature of -40℃-70℃ and a humidity of 10%RH-90%RH, and are equipped with a conformal protective coating, which is an ideal choice for long-term work and floating marine environment. In this embodiment, the controller adopts the cRIO-9035 controller, the relay module adopts the NI9482 board, the signal conversion module adopts the NI9203 board, and the temperature control module adopts the NI9217 board. Each board is integrated on the controller cRIO-9035. The hydrogen sulfide sensor uses the Searchpoint Optima Plus sensor, and the wind speed sensor uses the YGC-FS wind speed sensor. Each sensor is directly connected to the AI ​​terminal of the NI9203 acquisition card on the CompactRIO controller; the temperature sensor uses a thermocouple, and the temperature sensor is connected to the NI9217 board. The positive pole of the thermocouple is connected to the RTD+ terminal, and the negative end of the thermocouple is connected to the RTD- terminal.

[0057] refer to Figure 3 In this embodiment, the host computer main control room is remotely deployed in the central control room of FLNG, and the lower computer is deployed at the hydrogen sulfide online monitoring site. The lower computer can be equipped with multiple slave CompactRIO controllers according to the number of FLNG devices on site. The slave CompactRIO controllers are connected in a star-shaped manner by network cables. Each CompactRIO controller is arranged in an explosion-proof box, which controls external marine atmospheric corrosion and internal medium corrosion. The main CompactRIO controller and the host computer communicate with each other using optical fiber, and the optical interface module is used for high-speed data communication. The host computer and Com A photoelectric converter is placed between the pactRIO controllers, one for modulation and the other for demodulation. The CompactRIO controller is connected to the photoelectric converter through a network cable, the photoelectric converters are connected through optical fibers, and the photoelectric converter and the host computer are connected through a network cable to achieve data communication between the host computer and the slave computer. The controller output information is transmitted to the host computer after modulation and demodulation by the photoelectric converter. When the slave computer detects a leakage signal, the actuator can immediately perform emergency purification and send instructions to the host computer. After receiving the instructions, the host computer determines whether to close the valve of the upstream equipment of the sulfur recovery unit to fully ensure the safety of personnel.

[0058] The host computer of the present invention is responsible for functions such as terminal display, parameter setting, data storage and data transmission, and is divided into a real-time data display window and a historical data viewing window. The real-time data display window is used to realize the real-time display of hydrogen sulfide gas concentration, weather station data, on-site temperature and wind speed, real-time hydrogen sulfide concentration change curve display and real-time Fourier transform (FFT) display; the historical data viewing window is mainly used for reading and processing historical data, that is, Fourier transform (FFT) analysis and display of historical data.

[0059] refer to Figure 4 ,After the data is transmitted to the host computer, the system executes the ,program to perform Fourier transform to remove errors, data reorganization, data packet merging and other data ,processing, and display the results on the user interface and selects the ,save path according to the user’s instructions; then the buffer is ,cleared and the information collection button is pressed, and the user can select information ,collection or historical data viewing as needed.

[0060] The controller of the present invention adopts a CompactRIO controller, and users can select different controller models according to corresponding needs, and select different module models according to different needs. The present invention can realize monitoring and control for different gases by replacing different gas sensors.

[0061] The present invention also provides a method for monitoring gas leakage in an FLNG system, which is used for monitoring gas leakage in an FLNG. The FLNG leakage scenario includes the leakage device's own factors and the leakage field environmental factors, specifically the leakage point location, leakage source strength, wind speed, wind direction, and temperature. Based on the FLNG process analysis, the present invention finds out the device with hydrogen sulfide, thereby determining the simulated leakage point location; according to the process parameters of the leakage device, the leakage source strength is calculated; combined with the environmental conditions, the simulated wind speed, wind direction, and temperature are determined; and the final simulation scenario set is established. The specific steps are:

[0062] (1) Simulate the sulfur recovery unit leakage scenario in FLNG;

[0063] The specific steps of simulating the FLNG hydrogen sulfide leakage scenario in this embodiment include:

[0064] ①Use Comsol software to build the device model and divide the grid;

[0065] ② Determination of the leakage point location: The leakage point is set at the top of the device where hydrogen sulfide accumulates or where the hydrogen sulfide pipeline passes through the device;

[0066] ③ Calculation of leakage source strength Q: Based on:

[0067]

[0068] Among them, P ais the atmospheric pressure, P c is the pressure inside the pressure vessel; C D is the leakage coefficient, K is the gas adiabatic coefficient, Z is the compressibility factor, R is the ideal gas constant; T is the temperature inside the pressure vessel, M is the molar mass of the leaking gas, A or is the leakage hole area;

[0069] Substitute the relevant parameters of the FLNG sulfur recovery unit into the above formula to obtain the leakage source strength of the unit;

[0070] ④ Definition of boundary conditions: The wind speed inlet boundary is set as the inlet boundary condition, the leakage port is set as the mass flow inlet boundary condition, the upper part and both sides of the simulation area are symmetrical boundary conditions, the outlet is set as the free outflow boundary condition, the bottom surface and the device wall surface adopt the wall boundary condition, the turbulence model adopts the standard k-ε model, and the velocity inlet boundary layer wind speed condition and turbulence parameters are calculated according to the following formula:

[0071]

[0072]

[0073]

[0074] Where v is the wind speed at a height z from the ground, τ is the von Karman coefficient, which is taken as 0.4, δ is the friction velocity, and z0 is the ground roughness, which is taken as 0.01; C u is the model constant, which is taken as 0.09; k is the turbulent kinetic energy, and ε is the turbulence coefficient;

[0075] ⑤ According to the boundary conditions, calculate the maximum distance of hydrogen sulfide diffusion and the point with the highest hydrogen sulfide leakage concentration.

[0076] (2) Based on the simulated FLNG hydrogen sulfide leakage scenario data, the gas concentration sensors are distributedly placed according to the parameters such as the farthest distance and the highest concentration of the simulated scenario. That is, the gas sensors are sparsely arranged within 0.5 m from the farthest distance of the diffusion concentration, and the gas sensors are redundantly arranged within 1.0 m from the highest leakage concentration point.

[0077] (3) Start the hydrogen sulfide online monitoring system to monitor the hydrogen sulfide leakage concentration in real time: Start and initialize the sound and light alarm device and purification device. The CompactRIO controller collects the gas concentration information, environmental wind speed, wind direction, and temperature from the sensor in real time, and performs emergency purification treatment on the leaked gas.

[0078] refer to Figure 5, the monitoring system is started, and the high and low alarm values ​​of hydrogen sulfide concentration are set respectively. The setting range of the high alarm value is 10-100ppm, and the setting range of the low alarm value is 2ppm-10ppm. Initialize the fan and sound and light alarm, set the running time of the fan and sound and light alarm, collect hydrogen sulfide concentration information, wind speed and temperature information; judge whether the detected hydrogen sulfide gas concentration reaches the low alarm value, and start the fan and sound and light alarm device when it reaches the alarm value. The fan continues to extract hydrogen sulfide gas and the alarm alarm sounds; judge whether the gas reaches the preset high alarm value, and start the spray system at the same time, the FLNG equipment stops working, and the leaked gas is purified; the spray counter and the fan timer are synchronized, and after purification, it is judged whether the fan has reached the preset running time, whether the spray system has reached the preset running time, and whether the hydrogen sulfide concentration has dropped to a safe value. Purification is performed until the hydrogen sulfide concentration drops to a safe range, and then the fan, alarm and spray system are turned off. The monitoring system continuously monitors online and performs closed-loop automatic control until the user stops the operation.

[0079] In this embodiment, the low alarm threshold of hydrogen sulfide concentration is set to 10ppm. When the monitored concentration of hydrogen sulfide is higher than 10ppm, the sound and light alarm will sound an alarm and the fan will start working; the low alarm threshold of hydrogen sulfide concentration is set to 50ppm. When the concentration of hydrogen sulfide exceeds 50ppm, the spray device will start to spray alkali solution until the concentration drops to a safety standard.

[0080] In this embodiment, hydrogen sulfide sensors are redundantly arranged in the downwind direction and in the direction of gas leakage points in the pipeline within 0.5m from the leakage points to monitor the diffusion range and diffusion concentration of hydrogen sulfide in real time; after the distance exceeds 1.0m, hydrogen sulfide sensors are sparsely arranged to detect the hydrogen sulfide concentration on the pedestrian walkway after the gas leakage and the residual hydrogen sulfide concentration in the pedestrian walkway after certain emergency treatments are taken, so as to judge whether the leaked hydrogen sulfide will have an impact on the human body and the surrounding environment.

[0081] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A gas leakage monitoring system for monitoring the content of leaked gas, characterized in that: comprising a sensing unit, a control unit and an optical communication unit; The sensing unit includes a gas sensor for detecting the concentration of leaked gas, a temperature sensor for detecting the working environment temperature, and a wind speed sensor for detecting the wind speed; the gas sensors are arranged according to the farthest gas diffusion distance and the highest point of leakage concentration; specifically: the gas sensors are sparsely arranged within 0.5m from the farthest distance of the diffusion concentration, and the gas sensors are redundantly arranged within 1.0m from the highest point of leakage concentration; The control unit includes a controller, which is connected to the sensing unit, obtains data collected by the sensor of the sensing unit, performs signal conditioning and control algorithm processing, generates control instructions and sends them to the purification device and the sound and light alarm device; The optical communication unit includes a photoelectric conversion module, which is connected to the control unit and is used to transmit the control unit information to the host computer in the main control room after being modulated and demodulated by the photoelectric conversion module, and uses optical fiber to communicate data with the main control system; The control unit includes a signal conversion module, which is connected to the gas sensor and the wind speed sensor, obtains the gas concentration analog signal collected by the gas sensor and the wind speed analog signal collected by the wind speed sensor, and converts them into current signals for data storage and processing; The control unit further includes a temperature acquisition module, which is connected to the temperature sensor to obtain the working environment temperature information collected by the temperature sensor, convert the thermoelectromotive force collected by the temperature sensor into a voltage signal, and perform data storage and processing; The control unit also includes a relay control module, which is connected to the purification device and the sound and light alarm device and is used to control the purification device and the sound and light alarm device according to the detected leakage gas concentration.

2. A floating liquefied natural gas system, characterized in that: It includes the gas leakage monitoring system as described in claim 1; the controller adopts a CompactRIO controller, the signal conversion module adopts a multi-channel analog input board, the temperature acquisition module adopts a multi-channel temperature acquisition card, and the relay control module adopts a multi-channel relay output board, and each board is integrated in the controller; the gas sensor adopts a linear 4-20 mA output gas sensor, and the wind speed sensor adopts a 4-20 mA output wind speed sensor, which are connected to the multi-channel analog input board; the temperature sensor adopts a thermocouple, which is connected to the multi-channel temperature acquisition card.

3. A method for monitoring gas leakage in a floating liquefied natural gas system, using the floating liquefied natural gas system according to claim 2, characterized in that: The following steps are involved: (S1) Simulate the leakage scenario of the sulfur recovery unit in the FLNG system; including: simulate the leakage source intensity Q, simulate the velocity inlet boundary layer wind speed conditions and turbulence parameters; (S2) according to the simulated gas leakage scenario, simulate and obtain gas leakage and diffusion data, including the farthest distance of gas diffusion and the highest point of leakage concentration, and arrange gas sensors according to the farthest distance and the highest point of leakage concentration; (S3) starting the monitoring system to monitor the concentration of leaked gas, wind speed, wind direction, and temperature of the environment in real time: the controller collects the leakage gas concentration information detected by the gas sensor, the temperature information detected by the temperature sensor, and the wind speed information monitored by the wind speed sensor in real time; (S4) activating the sound and light alarm device and the purification device according to the concentration information of the leaked gas to perform emergency purification treatment on the leaked gas; In step (S1), the gas leakage scenario includes factors of the leakage device itself and environmental factors of the leakage field. The factors of the leakage device itself include the location of the leakage point and the leakage source strength. The environmental factors of the leakage field include wind speed, wind direction, and temperature. Find the device with gas leakage and determine the simulated leakage point. Calculate the leakage source strength according to the process parameters of the leakage device. Determine the simulated wind speed, wind direction, and temperature in combination with the specific environmental conditions of the location of the leakage point. Establish a final simulation scenario set. Step (S4) specifically includes starting the monitoring system, setting high and low alarm values ​​of the gas concentration to be measured, respectively, the system monitoring and collecting the leakage gas concentration, temperature, and wind speed information; judging whether the gas concentration has reached the alarm value, starting the sound and light alarm and purification device, the purification device including a fan and a spray system; when the gas concentration reaches the low alarm value, starting the fan and the sound and light alarm device; when the leakage gas concentration reaches the high alarm value, starting the spray system at the same time; after the purification treatment, detecting whether the leakage gas concentration has dropped to a safe value, and purifying until the concentration drops to a safe range.

4. The method for monitoring gas leakage in a floating liquefied natural gas system according to claim 3, characterized in that: The specific steps of simulating the leakage scenario of the sulfur recovery unit in the FLNG system include: (ss1) Establish a sulfur recovery unit model and divide the grid; (ss2) Determination of the leak point location: The leak point location is set at the top of the device where the leaked gas accumulates or where the pipeline passes through the device; (ss3) Calculate the leakage source strength Q: According to: in, is the atmospheric pressure, is the pressure inside the pressure vessel; C D is the leakage coefficient, K is the gas adiabatic coefficient, Z is the compressibility factor, R is the ideal gas constant; T is the temperature inside the pressure vessel, M is the molar mass of the leaking gas, is the leakage hole area; Substitute the relevant parameters of the sulfur recovery unit in FLNG into the above formula to obtain the leakage source strength of the unit; (ss4) Boundary condition definition: The wind speed inlet boundary is set as the inlet boundary condition, the leakage port is set as the mass flow inlet boundary condition, the upper part and both sides of the simulation area are symmetrical boundary conditions, the outlet is set as the free outflow boundary condition, the bottom surface and the device wall surface use the wall boundary condition, the turbulence model uses the standard k-ε model, and the velocity inlet boundary layer wind speed condition and turbulence parameters are calculated according to the following formula: Where v is the wind speed at a height of z from the ground, τ is the von Karman coefficient, δ is the friction velocity, z0 is the ground roughness, C u is the model constant, k is the turbulence kinetic energy, and ε is the turbulence coefficient; (ss5) According to the boundary conditions, solve the gas leakage and diffusion data, including the farthest distance of gas diffusion and the highest point of leakage concentration, and arrange the gas sensors according to the farthest distance and the highest point of leakage concentration.

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