Ship fuel gas supply and emergency cut-off control method based on automatic sequence control and causal matrix

Abstract

The invention belongs to the technical field of LNG (liquefied natural gas) utilization, and particularly relates to a ship fuel gas supply and emergency cut-off control method based on automatic sequential control and a causal matrix, and the ship fuel gas supply control method based on automatic sequential control utilizes a low-pressure system to automatically and sequentially control processes. A ship gas emergency cut-off control method based on a causal matrix comprises the steps that S1, related logic documents of a ship gas supply system are acquired, and a causal relationship is found; s2, according to the logic document in the S1, in addition to one event result caused by one trigger condition, a multi-cause-one-fruit relationship and a one-cause-multi-fruit relationship exist; s3, establishing a directed causal model according to the causal relationship extracted in S2; and S4, forming a matrix form in combination with the causal relationship. Automatic operation of the gas supply system can be achieved through the preset automatic sequence control process, and meanwhile rapid and accurate response to early warning signals and automatic execution of emergency cut-off measures are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of LNG utilization, and in particular relates to a control method for ship gas supply and emergency cutoff based on automatic sequential control and a cause-effect matrix. Background Art

[0002] With the increasing global awareness of environmental protection and increasing attention to energy consumption, the shipping industry is facing unprecedented pressure to save energy and reduce emissions. As an important part of the shipping industry, fuel consumption and carbon dioxide emissions of ships have become the focus of international attention. In order to meet this challenge, dual-fuel ships have gradually emerged as an innovative solution that can flexibly switch between traditional fuels and clean energy (such as liquefied natural gas LNG), thereby significantly reducing carbon emissions during ship operations;

[0003] However, in the gas supply system of dual-fuel ships, the gas control system (FGSS) is a core component, and its performance and safety are directly related to the overall operating efficiency and safety of the ship. Most existing gas control systems rely on manual operation and real-time monitoring by the crew to judge and perform corresponding operations based on changes in parameters such as temperature and pressure. This manual-dependent method is not only inefficient, but also prone to safety risks due to human error, such as gas leakage, fire, and even explosion.

[0004] In addition, due to the flammable and explosive characteristics of gas, the gas supply system faces many safety hazards during operation. Once the monitoring equipment detects an abnormal situation and sends out an early warning signal, the crew is often required to take emergency shut-off measures quickly and accurately to prevent the situation from escalating;

[0005] However, in actual operation, due to the limitations of human factors (such as reaction speed, judgment accuracy, etc.), it is often difficult to achieve timely and effective emergency response, which increases the possibility of accidents and the severity of consequences;

[0006] In order to solve the above problems and improve the safety and automation level of the ship gas supply system, the present invention proposes a ship gas supply system and an emergency cut-off control method based on automatic sequence control and cause-effect matrix. Summary of the invention

[0007] The purpose of the present invention is to provide a control method for ship gas supply and emergency shut-off based on automatic sequential control and cause-and-effect matrix, which can realize the automatic operation of the gas supply system through a preset automatic sequential control process, reduce the dependence on manual operation of the crew, and at the same time, use the cause-and-effect matrix to perform causal relationship analysis on the data source, so as to realize rapid and accurate response to early warning signals and automatic execution of emergency shut-off measures.

[0008] The technical solution adopted by the present invention is as follows:

[0009] A ship gas supply control method based on automatic sequential control, which uses a low-pressure system to automatically control the process in sequence;

[0010] The operation of the LNG low-pressure pump in the low-pressure system is controlled by a controller in the ship's gas supply system, which sends a frequency input to a variable frequency drive, and controls the frequency input of the LNG low-pressure pump through the variable frequency drive, and controls the speed of the LNG low-pressure pump based on the pressure required by the main engine, auxiliary engine and boiler load.

[0011] A ship gas emergency cut-off control method based on a cause-effect matrix comprises the following steps:

[0012] S1: Obtain relevant logical documents about emergency safety system events of ship gas supply system, find causal relationships from logical documents, and extract causes and results in the relationships from expression sentences;

[0013] S2: According to the logic document in S1, in addition to one trigger condition causing one event result, there are also multiple causes and one result relationship and one cause and multiple results relationship;

[0014] S3: Based on the causal relationship extracted in S2, a directed causal model is established to vividly describe the causal relationship;

[0015] S4: Based on the linear non-Gaussian acyclic model, combined with the causal relationship, a matrix form is formed.

[0016] The technical effects achieved by the present invention are:

[0017] The present invention can realize the automatic operation of the gas supply system through a preset automatic sequential control process, reducing the reliance on manual operation of the crew. At the same time, the cause-effect matrix is ​​used to perform causal relationship analysis on the data source, thereby realizing a rapid and accurate response to the early warning signal and the automatic execution of the emergency shut-off measures. It not only improves the operating efficiency and safety of the gas supply system, but also effectively reduces the risk of human error and the possibility of accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of automatic sequential control of the low-voltage system of the present invention;

[0019] Figure 2 This is a flow chart of automatic sequential control of the BOG air compressor in the present invention;

[0020] Figure 3 It is a one-cause-multiple-effects relationship diagram in the present invention;

[0021] Figure 4It is a cause-effect relationship diagram in the present invention;

[0022] Figure 5 It is a multi-cause-one-effect relationship diagram in the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention.

[0024] A control method for ship gas supply and emergency cut-off based on automatic sequential control and cause-effect matrix. This embodiment will explain the present invention in two parts: automatic sequential control of gas supply and emergency cut-off of cause-effect matrix.

[0025] The following is a further description of the automatic sequence control invention in conjunction with the accompanying drawings and specific embodiments;

[0026] Example 1: A ship gas supply control method based on automatic sequential control, which uses a low-pressure system to automatically control the process in sequence;

[0027] See attached Figure 1 As shown in the figure, the automatic sequence control process of the low-pressure system specifically refers to starting the valves, low-pressure pumps and other equipment associated with the low-pressure system. The liquefied natural gas low-pressure pumps are controlled by separate variable frequency drives, which receive their required frequency inputs from the gas supply system. The controller in the gas supply system controls the operation of the liquefied natural gas low-pressure pumps.

[0028] The speed of the liquefied natural gas low-pressure pump is controlled based on the pressure required by the main engine, auxiliary engine, boiler and other loads. The required pressure setting value changes according to the gas load requirements of the main engine and auxiliary engine using a high-performance sensor. The low-pressure system automatically adjusts the pump speed based on the pump outlet pressure to maintain the needs of low-pressure gas equipment, thereby providing a more stable gas supply.

[0029] The starting and control of the liquefied natural gas low-pressure pump includes the following steps:

[0030] Step 1: Before starting the system, first determine the system startup conditions, including tank pressure, liquid level, temperature, emergency stop, fan system, low-pressure pump, etc.;

[0031] Step 2: Open the discharge valve XV-114;

[0032] Step 3: Confirm the feedback signal of the discharge valve XV-114 opening. If the feedback fails to open, the sequence controller will automatically exit and an alarm will be sounded to alert the crew;

[0033] Step 4: Open the circulation valve XV-116;

[0034] Step 5: Confirm the feedback signal of the circulation valve XV-116. If the feedback fails to open, the sequence controller will automatically exit and an alarm will be sounded to remind the crew;

[0035] Step 6: Start the low-pressure pump PUMP1, and the low-pressure pump runs at the lowest frequency;

[0036] Step 7: Wait for the pipe to cool down according to the preset time;

[0037] Step 8: After the timer is up, open the inlet valve XV-411 of the low-pressure vaporizer

[0038] Step 9: Confirm the opening feedback signal of the inlet valve XV-411 of the low-pressure vaporizer. If the opening feedback fails, the sequence controller will automatically exit and an alarm will be sounded to remind the crew;

[0039] Step 10: The low-pressure pump automatically accelerates, and the acceleration rate can be set, such as 200RPM / Min;

[0040] Step 11: When the speed of the low-pressure pump reaches the preset value, activate the PID automatic adjustment control of the pump;

[0041] Step 12: The low-pressure pump starts running and the sequential control ends.

[0042] like Figure 2 As shown in the figure: the automatic sequential control process of BOG air compressor, specifically means: when the ambient temperature of the LNG storage tank rises, BOG evaporation gas will be automatically formed. When the amount of BOG evaporation gas reaches a certain level, the pressure of the storage tank will gradually increase. If it is not handled in time, when the pressure reaches a certain limit, the safety valve protection will be triggered. In this way, a large amount of BOG gas will be discharged into the air, causing economic losses and harm, and it is easy to cause fires, explosions and other incidents.

[0043] BOG air compressors are mainly used to control the pressure of LNG tanks. BOG air compressors cannot meet the total consumption of auxiliary engines and boilers. They work with LNG forced evaporators to maintain the fuel gas pressure required by the low-pressure buffer tank, which is mainly met by the LNG low-pressure pump. BOG air compressors must be started under no-load conditions. When the pressure of the LNG tank reaches more than 1 bar, a prompt will appear on the operator station to remind the operator to start the BOG compressor. After the BOG air compressor is running, it will automatically run in 50% load mode or 100% load mode based on the external load. When the air compressor runs at 50% load, only the upper cylinder of the air compressor is compressed, and the lower cylinder is in a non-compressed state, otherwise the air compressor may be damaged. When the air compressor runs at 100% load, the upper and lower cylinders of the air compressor are in a compressed state at the same time to compress air.

[0044] The starting and control of the BOG air compressor includes the following steps:

[0045] Step 1: Before starting the system, first determine the system startup conditions, including tank pressure, liquid level, temperature, emergency stop, fan system, air compressor, etc.;

[0046] Step 2: Open the suction valve XV-228;

[0047] Step 3: Confirm the feedback signal of the suction valve XV-228 opening. If the feedback fails to open, the sequence controller will automatically exit and an alarm will be sounded to alert the crew;

[0048] Step 4: Open the discharge valve XV-229;

[0049] Step 5: Confirm the feedback signal of the discharge valve XV-229 opening. If the feedback fails to open, the sequence controller will automatically exit and an alarm will be sounded to alert the crew;

[0050] Step 6: Start the BOG air compressor;

[0051] Step 7:

[0052] Preset long delay waiting time;

[0053] Preset short delay waiting time;

[0054] After the short delay timing ends, determine the lubricating oil pressure of the air compressor;

[0055] Step 8: Short delay timing ends & lubricating oil pressure is normal, and the air compressor runs;

[0056] Step 9: Dynamically adjust 50% load mode;

[0057] Step 10: Preset the delay waiting time;

[0058] Step 11: After the timer is finished, open the 50% load valve XV-230;

[0059] Step 12: Dynamically Adjust 100% Load Mode

[0060] Step 13: Preset the delay waiting time;

[0061] Step 14: After the timer is up, open the 100% load valve XV-231.

[0062] Embodiment 2: A ship gas emergency cut-off control method based on a cause-effect matrix. The following will further illustrate the control method of the emergency safety system based on the cause-effect matrix in combination with the accompanying drawings and specific embodiments, which includes the following steps:

[0063] S1: Obtain relevant logical documents about emergency safety system events of ship gas supply system, find causal relationships from logical documents, and extract causes and results in the relationships from expression sentences;

[0064] For example: "When the SB BUNKER STATION VAPOUR LINE SDV-122CLOSE will cause the BUNKER STATION VAPOUR LINE SDV XV-112OPEN";

[0065] From this sentence, we can clearly get the causal relationship formula, where "cause" is the conjunction that identifies the causal relationship, and "SB BUNKER STATION VAPOUR LINE SDV-122 CLOSE" and "BUNKER STATION VAPOUR LINESDV XV-112 OPEN" have an obvious causal relationship because of the conjunction, so we can extract "B BUNKER STATION VAPOURLINE SDV-122 CLOSE" as the cause C1[t1] in the causal relationship;

[0066] Where [t1] is used to represent the time impact of the cause condition on the result event, and "BUNKER STATION VAPOURLINE SDV XV-112 OPEN" is the result event E1.

[0067] After extracting the causal relationship, the following formula is used to simplify the causal relationship:

[0068]

[0069] Therefore, the causal relationship in the above example can be described by the following relationship:

[0070]

[0071] In addition, there are other conjunctions that mark causal relationships, such as: "because of", "effect", etc.;

[0072] S2: According to the logic document in S1, in addition to one trigger condition causing one event result (one cause one result relationship), there are also multiple causes one result relationship and one cause multiple results relationship;

[0073] For example, one cause and multiple effects relationship:

[0074] "When the pressure of PS LNG DISCHARGE DWP(TP-401)Higher than 0.5Barwill cause P-001A EMERGENCY COMMAND FROM FGSS(TRIP)and P-001B EMERGENCYCOMMAND FROM FGSS(TRIP),and also cause P-002A / 2B EMERGENCY COMMAND FROM FGSS(TRIP)";

[0075] Extract the causal relationship and get "the pressure of PS LNG DISCHARGE DWP (TP-401) Higher than 0.5 Bar" as the cause C2[t2];

[0076] Get the result events respectively:

[0077] E2: "P-001AEMERGENCY COMMAND FROM FGSS(TRIP)";

[0078] E3: "P-001B EMERGENCYCOMMAND FROM FGSS(TRIP)";

[0079] E4: "P-002AEMERGENCYCOMMAND FROM FGSS(TRIP)";

[0080] E5: "P-002B EMERGENCYCOMMAND FROM FGSS(TRIP)".

[0081] The causal relationship in the example can be described by the following relationship:

[0082]

[0083] And multiple causes and one effect relationship:

[0084] "The pressure of LNG STORAGE TANK1(PZIT-211)higher than 3.2 Bar willdelay 300 seconds open LNG STORAGE TANK 1 FILL LINE2 SDV(XV-212AA),and the temperature of SB BUNKER DRIP TRAY(TE-121)below 50Degc delay 10seconds alsoopen(XV-212AA)";

[0085] "The level of T-001(LZT-212)higher than 90%open the LNG STORAGE TANK1FILL LINE2SDV(XV-212AA)";

[0086] Similarly, the causes of the causal relationship can be extracted as follows:

[0087] C3[t3]: "The pressure of LNG STORAGE TANK1(PZIT-211)higher than3.2Bar";

[0088] C4[t4]: "The temperature of SB BUNKER DRIP TRAY(TE-121)below 50Degc";

[0089] C5[t5]: "The level of T-001(LZT-212)higher than 90%";

[0090] Result Event:

[0091] E6 "open LNG STORAGE TANK 1FILL LINE2SDV(XV-212AA)".

[0092] The causal relationship in the example can be described by the following relationship:

[0093]

[0094] From the logical document, the causal relationship we extracted is shown in Table 1 below:

[0095]

[0096] Table 1 is a table showing the relationship between cause conditions and result events;

[0097] S3: Based on the causal relationship extracted in S2, a directed causal model graph is established, such as Figure 3 , Figure 4 , Figure 5 To vividly describe the causal relationship, the causal model diagram is a directed graph;

[0098] By cause condition C i Point to the result event E j , and set f τ (C) Formal causal model, where:

[0099] C={C1[t1], C2[t2], C3[t3],…C i [t i ]}, i∈[1,n]

[0100] where t i Used to indicate path length;

[0101] When t i When >0, it indicates that the cause condition triggers the result event with a delay;

[0102] When t i When <0, it indicates that the cause condition is restored within the time and does not trigger the result event.

[0103] S4: Based on the linear non-Gaussian acyclic model (LINGAM), combined with the causal relationship, a matrix form is formed.

[0104] The matrix formation is expressed as:

[0105] E=MC

[0106] Among them, C is the n-dimensional cause condition vector, E is the m-dimensional vector of result event variables, and M is an n×m matrix storing connection paths.

[0107] According to the causal relationship extracted in the previous steps, we can get:

[0108] E1=f τ {C1[t1]}=C1

[0109] E2=f τ {C2[t2]}=C2

[0110] E3=f τ {C2[t2]}=C2

[0111] E4=f τ {C2[t2]}=C2

[0112] E5=f τ {C2[t2]}=C2

[0113] E6=f τ {C3[t3], C4[t4], C5[t5]}=300C3+10C4+C5

[0114] Its matrix form can be expressed as:

[0115]

[0116] According to the algorithm table 2, the causal matrix is:

[0117]

[0118]

[0119] Table 2 is the cause-effect matrix algorithm table;

[0120] According to Algorithm Table 2, we can easily obtain not only the causal relationship between the cause condition and the result event, but also the time impact of the cause condition on the result event. Therefore, when the cause condition is triggered, we can promptly and correctly find the relevant result event corresponding to the cause-effect matrix, so as to promptly and correctly activate the emergency safety protection system and protect the fuel supply system;

[0121] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A ship gas supply control method based on automatic sequential control, characterized in that: Automatic sequence control process using low-pressure system; The operation of the LNG low-pressure pump in the low-pressure system is controlled by a controller in the ship's gas supply system, which sends a frequency input to a variable frequency drive, and controls the frequency input of the LNG low-pressure pump through the variable frequency drive, and controls the speed of the LNG low-pressure pump based on the pressure required by the main engine, auxiliary engine and boiler load.

2. A ship gas supply control method based on automatic sequential control according to claim 1, characterized in that: The starting and control of the liquefied natural gas low-pressure pump includes the following steps: A1: Before starting the low-pressure system, first determine the system startup conditions, including LNG tank pressure, liquid level, temperature, emergency stop, fan system and LNG low-pressure pump; A2: Open the discharge valve; A3: Open the circulation valve; A4: Start the liquefied natural gas low-pressure pump and run it at the lowest frequency; A5: Wait for the pipe to cool down; A6: Open the inlet valve of the low-pressure vaporizer; A7: LNG low-pressure pump automatically accelerates; A8: When the speed of the LNG low-pressure pump reaches the preset value, the PID of the LNG low-pressure pump is activated and automatically adjusted and controlled; A9: The liquefied natural gas low-pressure pump is running and the sequence control ends.

3. A ship gas supply control method based on automatic sequential control according to claim 2, characterized in that: Use BOG air compressor to control automatic sequential process; The BOG air compressor is used to control the pressure of the LNG storage tank. The BOG air compressor and the liquefied natural gas forced evaporator simultaneously maintain the pressure of the LNG storage tank.

4. A ship gas supply control method based on automatic sequential control according to claim 3, characterized in that: The starting and control of the BOG air compressor includes the following steps: B1: Before starting the BOG air compressor, first determine the starting conditions, including LNG tank pressure, liquid level, temperature, emergency stop, fan system and BOG air compressor; B2: Open the suction valve; B3: Open the discharge valve; B4: Start the BOG air compressor; B5： Preset long delay waiting time; Preset short delay waiting time; After the short delay timing ends, determine the BOG air compressor lubricating oil pressure; B6: After the short delay timer ends and the lubricating oil pressure is normal, the BOG air compressor runs; B7: Dynamically adjust 50% load mode; B8: preset delay waiting time; B9: After the timer ends, open the 50% load valve; B10: Dynamically adjust 100% load mode; B11: preset delay waiting time; B12: After the timer is up, open the 100% load valve.

5. A ship gas emergency cut-off control method based on a cause-effect matrix, characterized in that: The following steps are involved: S1: Obtain relevant logical documents about emergency safety system events of ship gas supply system, find causal relationships from logical documents, and extract causes and results in the relationships from expression sentences; S2: According to the logic document in S1, in addition to one trigger condition causing one event result, there are also multiple causes and one result relationship and one cause and multiple results relationship; S3: Based on the causal relationship extracted in S2, a directed causal model is established to vividly describe the causal relationship; S4: Based on the linear non-Gaussian acyclic model, combined with the causal relationship, a matrix form is formed.

6. A ship gas emergency shut-off control method based on a cause-effect matrix according to claim 5, characterized in that: After the causal relationship is extracted in S1, the causal relationship is simplified using the following formula:

7. A ship gas emergency shut-off control method based on a cause-effect matrix according to claim 5, characterized in that: S3 is caused by condition C i Point to the result event E j , and set f τ (C) Formal causal model, where: C={C1[t1],C2[t2],C3[t3],…C i [t i ]},i∈[1,b] where t i Used to indicate path length; When t i When >0, it indicates that the cause condition triggers the result event with delay; When t i When <0, it indicates that the cause condition is restored within the time and does not trigger the result event.

8. A ship gas emergency shut-off control method based on a cause-effect matrix according to claim 5, characterized in that: The matrix formation in S4 is expressed as: E=MC Among them, C is the n-dimensional cause condition vector, E is the m-dimensional vector of result event variables, and M is an n×m matrix storing connection paths.

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