LNG (Liquefied Natural Gas) integrated unloading pry and implementation method thereof

Abstract

The invention discloses an LNG (Liquefied Natural Gas) integrated unloading pry and an implementation method thereof, relates to the technical field of LNG unloading equipment, and aims to solve the problems that the pressurizing unloading speed is low, the time is generally 3-4 hours, and the increasing unloading and gasification requirements of an LNG storage peak regulation station cannot be met. According to the low-temperature centrifugal pump control device, the precise speed increasing and reducing control function of the low-temperature centrifugal pump is achieved, the safety of LNG unloading is improved to a certain degree, the safety consciousness of operators is enhanced, the safety of the LNG unloading process is ensured, guarantee is provided for meeting the requirement for the gasification capacity of an internal liquefaction reserve station and improving the unloading efficiency of the reserve station, and the device is simple and practical in design and easy to popularize. And the related requirements of explosion-proof safety performance are met.

Description

Technical Field

[0001] The present invention relates to the technical field of LNG unloading equipment, and in particular to an LNG integrated unloading skid and an implementation method thereof. Background Art

[0002] Natural gas is a clean, efficient, high-quality fuel, and an important chemical raw material. It has obvious social, environmental and economic benefits. The rapid development of the natural gas industry and the rapid promotion of LNG (liquid natural gas) applications require LNG storage stations to have a higher gasification level and supply guarantee capabilities. Therefore, LNG storage stations need to have the function of loading and selling LNG in the off-season and unloading purchased LNG in the peak season.

[0003] LNG unloading skid is an integrated device to complete the unloading of LNG tank trucks from LNG storage tanks. Its unloading function can meet the needs of LNG reserve peak-shaving stations for rapid unloading of LNG. At present, most LNG reserve peak-shaving stations use self-pressurization unloading. The basic idea is to use the unloading booster gasifier device to achieve gravity-flow pressurization of LNG tank trucks. However, the self-pressurization unloading speed is slow, and the time is generally 3 to 4 hours, which is not enough to meet the growing unloading and gasification needs of LNG reserve peak-shaving stations.

[0004] Therefore, there is a need for an integrated LNG unloading skid and an implementation method thereof. Summary of the invention

[0005] In order to solve all or part of the above problems, the purpose of the present invention is to provide an integrated LNG unloading skid and its implementation method, so as to solve the problem that the speed of pressurized unloading is slow, the time is generally 3 to 4 hours, which is insufficient to meet the growing unloading and gasification needs of LNG reserve peak-shaving stations.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: an integrated LNG unloading skid, comprising an emptying flare pipeline, a liquid phase pipeline, a nitrogen pipeline, a booster arm, a gas phase arm, a liquid phase arm, an anti-static controller, a PLC control box, a cryogenic pump, a vaporizer, a cold-insulating pipe support and a steel structure base, wherein the emptying flare pipeline, the liquid phase pipeline, the nitrogen pipeline, the booster arm, the gas phase arm, the liquid phase arm, the anti-static controller, the PLC control box, the cryogenic pump and the cold-insulating pipe support are all installed on the steel structure base, the vaporizer is installed on one side of the steel structure base, and the emptying flare pipeline and the liquid phase pipeline are both fixed to the steel structure base by using a cold-insulating pipe support;

[0007] The exhaust flare pipeline is interconnected with the liquid phase pipeline, the booster arm, the gas phase arm and the liquid phase arm;

[0008] The nitrogen pipeline is interconnected with the liquid phase pipeline, the booster arm, the gas phase arm and the liquid phase arm.

[0009] Furthermore, the liquid phase pipeline is installed on a steel structure base, and a low-temperature regulating valve, a low-temperature valve one, a low-temperature valve two, a low-temperature valve three, a low-temperature valve four, a low-temperature valve five, a low-temperature valve six, a low-temperature valve seven, a low-temperature valve eight, a low-temperature valve nine, a low-temperature valve ten, a low-temperature valve eleven and a safety valve are respectively installed on the liquid phase pipeline.

[0010] Furthermore, a boost arm manual valve, a boost vent valve and a boost arm nitrogen purge valve are installed on the boost arm, and the boost arm manual valve, the boost vent valve and the boost arm nitrogen purge valve are interconnected through the boost arm.

[0011] Furthermore, a gas phase arm hand valve, a gas phase vent valve and a gas phase arm nitrogen purge valve are installed on the gas phase arm, and the gas phase arm hand valve, the gas phase vent valve and the gas phase arm nitrogen purge valve are interconnected through the gas phase arm.

[0012] Furthermore, a liquid phase arm hand valve, a liquid phase vent valve and a liquid phase arm nitrogen purge valve are installed on the liquid phase arm, and the liquid phase arm hand valve, the liquid phase vent valve and the liquid phase arm nitrogen purge valve are interconnected through the liquid phase arm.

[0013] Furthermore, a method for implementing an integrated LNG unloading skid comprises the following steps:

[0014] S1: Liquid phase purge and pressure;

[0015] S2: gas phase purge and pressure;

[0016] S3: Boost phase purge and pressure reduction;

[0017] S4: carburetor boost;

[0018] S5: precooling;

[0019] S6: Unloading;

[0020] S7: Post-pump pressurization;

[0021] S8: Tank truck flat pressing;

[0022] S9: Nitrogen purge of liquid phase arm, gas phase arm and booster arm.

[0023] Furthermore, the specific steps of S5 are as follows:

[0024] S51: The operator opens cryogenic valve ten, connects the exhaust flare pipeline with the cryogenic pump, opens cryogenic valve four and cryogenic valve five, connects the exhaust flare pipeline with the cryogenic pump, the cryogenic pump is opened 10-15%, then fully opened within the first 5 seconds of startup, and then fully closed;

[0025] S52: Precooling starts, and cooling is completed when the temperature reaches below -148°C. After cooling for 20 minutes, the pump is considered to have cooled down;

[0026] S53: The operator confirms that cryogenic valve one and cryogenic valve ten are closed, and opens cryogenic valve six.

[0027] Further, the specific steps of S6 are as follows:

[0028] S61: The driver fully opens the valve connected to the liquid phase arm under the tank truck, the operator closes the cryogenic valve seven, disconnects the booster arm, activates the cryogenic pump to boost pressure, and prepares to unload the truck;

[0029] S62: Observe the filling condition of the cryogenic pump. When it is fully filled, press the "start button" of the PLC control box to start the cryogenic pump for unloading.

[0030] S63: Increase pump speed: According to the pressure before the pump, the temperature before the pump, the pressure after the pump, the temperature after the pump, and the gas phase pressure, the frequency of the cryogenic pump is increased through the PLC control box until it runs normally;

[0031] S64: Reduce pump speed: According to the pressure before the pump, the temperature before the pump, the pressure after the pump, the temperature after the pump, and the gas phase pressure, the frequency of the cryogenic pump is reduced through the PLC control box, and the pump is automatically stopped when it is higher than -148℃;

[0032] S65: Observe the temperature before and after the pump or refer to the level gauge reading on the tank truck, press the "stop button" on the PLC control box to stop the pump.

[0033] Furthermore, the PLC control box in S63 includes an analog input module, a digital output module and a central processing unit module;

[0034] Analog input module: used to collect analog signals of pressure before pump, temperature before pump, pressure after pump, temperature after pump and gas phase pressure;

[0035] Digital output module: According to the control logic of PLC, it outputs control signals to adjust the frequency of the pump, thereby achieving the operation of reducing the pump speed;

[0036] Central processing unit module: responsible for executing PLC programs, processing input analog signals, and continuously reading the pump front pressure, pump front temperature, pump back pressure, pump back temperature and gas phase pressure values ​​collected by the analog input module through PLC;

[0037] When the following conditions are met, the pump speed increase program is started: the pressure before the pump is > 0.09MPa, the temperature after the pump is <-150℃, the pressure after the pump is <0.7MPa, and the gas phase pressure is > 0.2MPa;

[0038] The PLC calculates the frequency value that needs to be increased according to the preset pump speed increase algorithm, and outputs a control signal to the frequency converter through the digital output module, so that the pump frequency gradually increases until it reaches the frequency range required for normal operation or meets other conditions for stopping the pump speed increase.

[0039] Furthermore, the specific calculation method of the PLC is as follows:

[0040] Define a basic frequency increment step Δf and calculate the current pump operating frequency f(t), where t represents the current moment;

[0041] When the pump speed increase condition is met, the new pump frequency f(t+1) is calculated according to the following formula: f(t+1)=f(t)+Δf×K, where K is the correction coefficient, which is used to make fine adjustments according to different working conditions. The value of K is adjusted according to the deviation of pressure and temperature from the set value. If the pressure and temperature are within the ideal range and close to the lower limit, K takes a larger value K=1.2 to speed up the increase of pump speed.

[0042] If the pressure and temperature are close to the upper limit but still within the allowable range, K takes a smaller value K=0.8 to increase the pump speed more slowly;

[0043] The correction coefficient is adjusted dynamically as follows:

[0044] Calculate the pressure change rate ( ) and the temperature change rate ( ),in and Respectively for a period of time Changes in internal pressure and temperature;

[0045] When the pressure and temperature are within the ideal range and close to the lower limit, and the pressure change rate and temperature change rate are also small, it means that the system condition is stable and there is a lot of room for improvement. The correction coefficient can be further increased. The specific formula is: ;

[0046] When the pressure and temperature are close to the upper limit but still within the allowable range, if the pressure change rate or temperature change rate is large, it means that the working condition has a tendency to deteriorate, and the correction coefficient K should be further reduced. The specific formula is: .

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The present invention proposes an integrated LNG unloading skid and an implementation method thereof. Based on the application of LNG skid-mounted engineering, the LNG unloading device is developed and designed by adopting main equipment such as a cryogenic centrifugal pump and a pressurized gasifier in the skid-mounted module. The control technology and detection technology of the PLC control system are used to realize the precise speed-up and speed-down control functions of the cryogenic centrifugal pump, which improves the safety of LNG unloading to a certain extent, enhances the safety awareness of operators, ensures the safety of the LNG unloading process, and provides a guarantee for meeting the gasification capacity of inland liquefied storage stations and improving the unloading efficiency of storage stations. The equipment is simple and practical in design and meets the relevant requirements of explosion-proof safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a process flow chart of an LNG integrated unloading skid of the present invention;

[0050] Figure 2 It is a schematic diagram of the side plan structure of an integrated LNG unloading skid of the present invention.

[0051] In the figure:

[0052] 1. Drain the flare pipeline; 2. Liquid phase pipeline; 21. Cryogenic regulating valve; 22. Cryogenic valve 1; 23. Cryogenic valve 2; 24. Cryogenic valve 3; 25. Cryogenic valve 4; 26. Cryogenic valve 5; 27. Cryogenic valve 6; 28. Cryogenic valve 7; 29. ​​Cryogenic valve 8; 210. Cryogenic valve 9; 211. Cryogenic valve 10; 212. Cryogenic valve 11; 213. Safety valve; 3. Nitrogen pipeline; 4. Booster arm; 41. Booster arm hand valve; 4 2. Booster vent valve; 43. Booster arm nitrogen purge valve; 5. Gas phase arm; 51. Gas phase arm hand valve; 52. Gas phase vent valve; 53. Gas phase arm nitrogen purge valve; 6. Liquid phase arm; 61. Liquid phase arm hand valve; 62. Liquid phase vent valve; 63. Liquid phase arm nitrogen purge valve; 7. Anti-static controller; 71. Static electricity grounding clamp; 8. PLC control box; 9. Cryogenic pump; 10. Vaporizer; 11. Cold preservation pipe support; 12. Steel structure base. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] like Figure 1-Figure 2 As shown, an integrated LNG unloading skid includes an emptying flare pipeline 1, a liquid phase pipeline 2, a nitrogen pipeline 3, a booster arm 4, a gas phase arm 5, a liquid phase arm 6, an anti-static controller 7, a PLC control box 8, a cryogenic pump 9, a vaporizer 10, a cold-insulating pipe support 11 and a steel structure base 12.

[0055] The exhaust flare pipeline 1, liquid phase pipeline 2, nitrogen pipeline 3, booster arm 4, gas phase arm 5, liquid phase arm 6, anti-static controller 7, PLC control box 8, cryogenic pump 9 and cold-insulating pipe support 11 are all installed on the steel structure base 12, the vaporizer 10 is installed on one side of the steel structure base 12, and the exhaust flare pipeline 1 and the liquid phase pipeline 2 are fixed to the steel structure base 12 by the cold-insulating pipe support 11.

[0056] The flare exhaust pipeline 1 is interconnected with the liquid phase pipeline 2, the booster arm 4, the gas phase arm 5 and the liquid phase arm 6 for discharging the safety valve, the pressure relief pipeline medium and the unloading arm purge medium.

[0057] The nitrogen pipeline 3 is interconnected with the liquid phase pipeline 2, the booster arm 4, the gas phase arm 5 and the liquid phase arm 6, and is mainly used for purging the unloading arm pipeline and the unloading arm rotary joint to prevent residual medium from overflowing.

[0058] The liquid phase pipeline 2 is installed on the steel structure base 12, and the inlet diameter is confirmed according to the design flow rate. The liquid phase pipeline 2 is respectively installed with a low temperature regulating valve 21, a low temperature valve one 22, a low temperature valve two 23, a low temperature valve three 24, a low temperature valve four 25, a low temperature valve five 26, a low temperature valve six 27, a low temperature valve seven 28, a low temperature valve eight 29, a low temperature valve nine 210, a low temperature valve ten 211, a low temperature valve eleven 212 and a safety valve 213. The liquid phase pipeline 2 is also installed with a plurality of temperature sensors and pressure sensors for monitoring the pressure and temperature of the liquid phase pipeline 2.

[0059] The cryogenic valve 1 22 is used to block the pipelines on both sides, one of which is the pipeline between the cryogenic valve 9 210 and the gas phase arm manual valve 51, and the other is the pipeline between the liquid phase arm manual valve 61 and the cryogenic valve 6 27.

[0060] The low temperature regulating valve 21 is used to adjust the flow. When the system is abnormal (temperature exceeds the limit, pressure exceeds the limit), it plays a role in adjusting the flow and cutting off the pipeline flow to ensure the safety of on-site operation.

[0061] Safety valve 213 is a thermal expansion safety valve. When the LNG in the pipeline is vaporized due to excessive temperature, resulting in increased pressure in the pipeline, the safety valve will automatically release pressure to the flare pipeline 1 to ensure that the pressure in the pipeline is within a safe range.

[0062] The cryogenic valve 829 is connected to the vaporizer 10. When unloading, the BOG gas vaporized by the vaporizer 10 is controlled to enter the pipeline through the cryogenic valve 829 and the booster arm hand valve 41, thereby controlling the flow rate of unloading in the early stage. The vaporizer 10 is mainly used to vaporize LNG to generate LNG gas with a certain pressure, pressurize the tank truck, and lead out the LNG.

[0063] The vaporizer 10 is installed and designed at a low position, which facilitates the LNG to flow into the vaporizer 10 by gravity for vaporization.

[0064] A boost arm hand valve 41 , a boost vent valve 42 and a boost arm nitrogen purge valve 43 are installed on the boost arm 4 , and the boost arm hand valve 41 , the boost vent valve 42 and the boost arm nitrogen purge valve 43 are interconnected through the boost arm 4 .

[0065] A gas phase arm hand valve 51 , a gas phase vent valve 52 and a gas phase arm nitrogen purge valve 53 are installed on the gas phase arm 5 , and the gas phase arm hand valve 51 , the gas phase vent valve 52 and the gas phase arm nitrogen purge valve 53 are interconnected through the gas phase arm 5 .

[0066] The liquid phase arm 6 is provided with a liquid phase arm hand valve 61 , a liquid phase vent valve 62 and a liquid phase arm nitrogen purge valve 63 . The liquid phase arm hand valve 61 , the liquid phase vent valve 62 and the liquid phase arm nitrogen purge valve 63 are interconnected through the liquid phase arm 6 .

[0067] like Figure 1-Figure 2 As shown, another technical solution proposed by the present invention is to provide an implementation method of an integrated LNG unloading skid, comprising the following steps:

[0068] Step 1: Preparation:

[0069] 1. The driver parks the tank truck at the unloading platform, checks whether the tank truck is parked in a suitable position, stops the tank truck engine, places the skid blocker under the wheel, and hands the key to the operator for safekeeping;

[0070] 2. Step 2: The driver connects the electrostatic grounding clamp 71 on the unloading platform to the tank truck, and the operator confirms that the grounding signal is received;

[0071] 3. Step 3: The operator closes the low temperature regulating valve 21, closes the low temperature valve 1 22, the low temperature valve 2 23, the low temperature valve 3 24, the low temperature valve 4 25, the low temperature valve 5 26 and closes the low temperature valve 6 27.

[0072] Step 2: Tank truck pipeline connection:

[0073] 1. The driver connects the corresponding liquid phase pipeline, gas phase pipeline and booster pipeline on the tank truck to the booster arm 4, gas phase arm 5 and liquid phase arm 6 on the unloading platform in sequence;

[0074] 2. The driver inspects the site and fills out the “Tank Truck Filling Inspection Record Form”.

[0075] Step 3: Liquid phase purge and pressure reduction:

[0076] 1. The operator confirms that the liquid phase arm hand valve 61 is closed;

[0077] 2. The driver slowly opens the liquid phase drain valve 62, and the liquid phase drain valve 62 is connected to the drain flare pipeline 1;

[0078] 3. The operator manually opens the liquid phase arm nitrogen purge valve 63 for 5 seconds, repeats two or three times, and then closes the liquid phase arm nitrogen purge valve 63 to replace the air with nitrogen. The air is discharged to the venting flare pipeline 1, and the operator closes the liquid phase vent valve 62;

[0079] 4. The operator opens the nitrogen purge valve 63 of the liquid phase arm to pressurize the liquid phase arm 6. The operator checks that there is no leakage at the connection flange of the liquid phase arm 6. If there is a leakage point at the connection flange, it needs to be reconnected and then re-checked for leakage until the requirements are met;

[0080] 5. The operator closes the liquid phase arm nitrogen purge valve 63 and opens the liquid phase vent valve 62 again. After the liquid phase arm 6 is depressurized, the operator closes the liquid phase vent valve 62.

[0081] Step 4: Gas phase purge and pressure reduction:

[0082] 1. The operator confirms that the gas phase arm hand valve 51 is closed;

[0083] 2. The driver slowly opens the gas phase vent valve 52;

[0084] 3. The operator manually opens the nitrogen purge valve 53 of the gas phase arm and opens it for 5 seconds, repeats it two or three times, and then closes the nitrogen purge valve 53 of the gas phase arm to replace the air with nitrogen. The air is discharged to the flare pipeline 1, and the operator closes the gas phase vent valve 52;

[0085] 4. The operator opens the nitrogen purge valve 53 of the gas phase arm to pressurize the gas phase arm 5. The operator checks that there is no leakage at the connection flange of the gas phase arm 5. If there is a leakage point at the connection flange, it needs to be reconnected and then re-checked for leakage until the requirements are met;

[0086] 5. The operator closes the nitrogen purge valve 53 of the gas phase arm and opens the gas phase vent valve 52 again. After the pressure of the gas phase arm 5 is released, the operator closes the gas phase vent valve 52.

[0087] Step 5: Pressurization phase purge and pressure reduction:

[0088] 1. The operator confirms that the booster arm hand valve 41 is closed;

[0089] 2. The driver slowly opens the boost vent valve 42;

[0090] 3. The operator manually opens the booster arm nitrogen purge valve 43 for 5 seconds, repeats two or three times, and then closes the booster arm nitrogen purge valve 43 to replace the air with nitrogen. The air is discharged to the flare pipeline 1, and the operator closes the booster vent valve 42;

[0091] 4. The operator opens the nitrogen purge valve 43 of the booster arm to pressurize the booster arm 4. The operator checks that there is no leakage at the connection flange of the booster arm 4. If there is a leakage point at the connection flange, it needs to be reconnected and then re-checked for leakage until the requirements are met;

[0092] 5. The operator closes the nitrogen purge valve 43 of the boost arm and opens the boost vent valve 42 again. After the boost arm 4 is depressurized, the operator closes the boost vent valve 42;

[0093] 6. Open the boost arm hand valve 41, the gas phase arm hand valve 51 and the liquid phase arm hand valve 61.

[0094] Step 6: Carburetor Boost:

[0095] 1. The operator confirms that the cryogenic valve 22 is closed and disconnects the connection between the gas phase arm 5 and the liquid phase arm 6;

[0096] 2. The operator opens the cryogenic valve 7 28 to connect the boosting arm 4 with the vaporizer 10, slightly opens the cryogenic valve 11 212 to connect the liquid phase arm 6 with the vaporizer 10, opens the safety valve 213 and slightly opens the valve under the tank car connected to the liquid phase arm 6, a small amount of LNG is drained into the vaporizer 10 through the liquid phase arm 6, the pressure in the pipeline increases, and vaporization and pressurization begin;

[0097] 3. The driver opens the valve connected to the gas phase arm 5 on the tank truck, and slowly opens the valve connected to the booster arm 4 on the tank truck;

[0098] It should be noted that: pay attention to the stability of the pressure in the tank of the tank truck; the pressure in the tank of the tank truck is greater than 0.3MPa and not greater than 0.4Mpa; if the pressure exceeds 0.4Mpa, the operator should appropriately close the cryogenic valve 728.

[0099] Step 7: Precooling:

[0100] 1. The operator opens the cryogenic valve ten 211 to connect the flare pipeline 1 with the cryogenic pump 9, opens the cryogenic valve four 25 and the cryogenic valve five 26 to connect the flare pipeline 1 with the cryogenic pump 9, and the cryogenic pump 9 is slightly opened by 10-15%, and then fully opened within the first 5 seconds of startup, and then fully closed, for preliminary low-temperature pre-cooling and unblocking of the pipeline;

[0101] 2. Precooling begins, pay attention to the pressure and temperature of liquid pipeline 2 and the frost on the unloading arm. When the temperature reaches below -148°C, cooling is completed. After cooling for 20 minutes, the pump is considered to have cooled down;

[0102] 3. The operator confirms that cryogenic valve 1 22 and cryogenic valve 10 211 are closed, and opens cryogenic valve 6 27 to connect liquid phase pipeline 2 with the pipeline to the cryogenic tank, with an opening degree of 20%.

[0103] Step 8: Unloading:

[0104] 1. The driver fully opens the valve connected to the liquid phase arm 6 under the tank truck, the operator closes the cryogenic valve 7 28, disconnects the booster arm 4, activates the cryogenic pump 9 for boosting, and prepares for unloading;

[0105] 2. Observe the filling condition of cryogenic pump 9. When it is fully filled, press the "start button" to start cryogenic pump 9 (set parameters 20%) for unloading (gas phase pressure>0.15MPa, temperature before the pump<-148℃, temperature after the pump is about 2 degrees higher than the pump inlet temperature, pressure after the pump<0.5MPa, cryogenic valve 627 open, slowly open to the required pressure after the pump after starting);

[0106] 3. Increase pump speed: According to the pressure before the pump, the temperature before the pump, the pressure after the pump, the temperature after the pump, and the gas phase pressure, slowly increase the frequency of the cryogenic pump 9 through the PLC control box 8 until it runs normally (pressure before the pump>0.09MPa, temperature before the pump<-148℃, temperature after the pump<-150℃, pressure after the pump<0.7MPa, gas phase pressure>0.2MPa);

[0107] The PLC control box 8 includes an analog input module, a digital output module and a central processing unit module:

[0108] Analog input module: used to collect analog signals of pressure before pump, temperature before pump, pressure after pump, temperature after pump and gas phase pressure;

[0109] Digital output module: According to the control logic of PLC, it outputs control signals to adjust the frequency of the pump, thereby realizing the operation of increasing the pump speed;

[0110] Central Processing Unit Module: Responsible for executing PLC programs, processing input analog signals, performing calculations based on preset logic and algorithms, and outputting control signals to the digital output module to achieve precise control of the pump speed;

[0111] Furthermore, the control logic of the PLC for increasing the pump speed is as follows:

[0112] The PLC continuously reads the pressure before the pump, the temperature before the pump, the pressure after the pump, the temperature after the pump, and the gas phase pressure values ​​collected by the analog input module;

[0113] When the following conditions are met, the pump speed increase program is started: the pressure before the pump is > 0.09MPa, the temperature before and after the pump is <-150℃, the pressure after the pump is <0.7MPa, and the gas phase pressure is > 0.2MPa;

[0114] The PLC calculates the frequency value that needs to be increased according to the preset pump speed increase algorithm, and outputs the control signal to the frequency converter through the digital output module, so that the pump frequency gradually increases until it reaches the frequency range required for normal operation or meets other conditions for stopping the pump speed increase;

[0115] Furthermore, the pump speed increase algorithm is as follows:

[0116] Define a basic frequency increment step Δf and calculate the current pump operating frequency f(t) (t represents the current moment);

[0117] When the pump speed increase condition is met, the new pump frequency f(t+1) is calculated according to the following formula: f(t+1)=f(t)+Δf×K, where K is the correction factor, which is used to make fine adjustments according to different working conditions. For example, the value of K can be adjusted according to the deviation of pressure and temperature from the set value. If the pressure and temperature are within the ideal range and close to the lower limit, K can take a larger value K=1.2 to speed up the increase of pump speed; if the pressure and temperature are close to the upper limit but still within the allowable range, K can take a smaller value K=0.8 to increase the pump speed more slowly to ensure safety;

[0118] Furthermore, the correction coefficient is dynamically adjusted as follows:

[0119] Calculate the pressure change rate ( ) and the temperature change rate ( ),in and Respectively for a period of time Changes in internal pressure and temperature;

[0120] When the pressure and temperature are within the ideal range and close to the lower limit, and the pressure change rate and temperature change rate are also small, it means that the system condition is stable and there is a large room for improvement. The correction coefficient can be further increased. The specific formula is: ; For example, when the rate of change of pressure is less than a certain threshold and the rate of change of temperature is less than, this allows the pump speed to be increased more quickly when the operating conditions are very stable;

[0121] When the pressure and temperature are close to the upper limit but still within the allowable range, if the pressure change rate or temperature change rate is large, it means that the working condition has a tendency to deteriorate, and the correction coefficient K should be further reduced; for example, when the pressure change rate is greater than a certain threshold Or the temperature change rate is greater than hour, , so that the pump speed increases more gradually to ensure safety;

[0122] 4. Reduce pump speed: according to the pressure before the pump, the temperature before the pump, the pressure after the pump, the temperature after the pump, and the gas phase pressure, the frequency of the cryogenic pump 9 is slowly reduced through the PLC control box 8, and the pump is automatically stopped when it is higher than -148℃;

[0123] The PLC control box 8 includes an analog input module, a digital output module and a central processing unit module.

[0124] Analog input module: used to collect analog signals of pressure before pump, temperature before pump, pressure after pump, temperature after pump and gas phase pressure;

[0125] Digital output module: According to the control logic of PLC, it outputs control signals to adjust the frequency of the pump, thereby achieving the operation of reducing the pump speed;

[0126] Central Processing Unit Module: Responsible for executing PLC programs, processing input analog signals, performing calculations based on preset logic and algorithms, and outputting control signals to the digital output module to achieve precise control of the pump speed;

[0127] Furthermore, the control logic of the PLC for reducing the pump speed is as follows:

[0128] The PLC also monitors the above-mentioned pressure and temperature values ​​in real time;

[0129] When one of the following situations occurs, the pump speed reduction operation is triggered: the pressure before the pump or after the pump is too high, the temperature before the pump or after the pump is too high and close to the critical value, and the gas phase pressure is abnormally low;

[0130] According to the pump speed reduction algorithm, the PLC calculates the frequency value that needs to be reduced and outputs the corresponding control signal to the frequency converter to gradually reduce the pump frequency to ensure the safe operation of the system; if the temperature continues to rise and reaches the set shutdown temperature (such as higher than -148°C), the PLC outputs a shutdown signal to stop the operation of the pump;

[0131] Furthermore, the pump speed reduction algorithm is as follows:

[0132] Define a basic frequency reduction step Δf'. When the pump speed reduction condition is met, the new pump frequency f(t+1) is calculated according to the following formula: f(t+1)=f(t)-Δf'×K'

[0133] Where K' is the pump speed reduction correction factor, and its value selection principle is similar to that of the pump speed increase correction factor, but in the opposite direction; for example, if the pressure is too high or the temperature is too high and close to the critical value, K' can take a larger value K'=1.5 to quickly reduce the pump speed; if it is a normal speed reduction near the end of unloading, K' can take a smaller value K'=1.0;

[0134] If the temperature continues to rise and reaches the shutdown temperature (such as -148°C) during the process of reducing the pump speed, the PLC will directly output a shutdown signal to stop the operation of the pump, that is, f(t+1)=0;

[0135] Through the above module, logic and algorithm design, the PLC control box 8 can accurately control the increase and decrease pump speed operations of the cryogenic pump 9 according to the actual working conditions during the unloading process, ensuring the safety, efficiency and stability of the unloading process;

[0136] 5. Observe the temperature before and after the pump or refer to the level gauge reading on the tank truck, press the "stop button" on the PLC control box 8 to stop the pump (the pump will stop automatically if the temperature before and after the pump is > -148°C, the gas pressure is <0.15MPa, and the pump speed is <20%).

[0137] Step 9: Pump and then pressurize:

[0138] 1. The operator confirms that the cryogenic valve 728 is closed;

[0139] 2. The operator should pay attention to adjusting the low-temperature regulating valve 21 to control the gas phase pressure delivered by the vaporizer 10 to be stable at about 0.3MPa. When the gas phase pressure is less than 0.3MPa, the low-temperature valve 6 27 should be closed. When the gas phase pressure is greater than 0.3MPa but not greater than 0.4Mpa, the low-temperature valve 6 27 should be opened. If the pressure exceeds 0.4Mpa, the operator should close the low-temperature valve 11 212.

[0140] Step 10: Tank truck flattening:

[0141] 1. Liquid phase pressure equalization: After stopping the pump, observe the gas phase pressure and the pressure after the pump. When they are close, the operator closes the cryogenic valve six 27, closes the gas phase arm hand valve 51, opens the cryogenic valve seven 28, opens the cryogenic valve two 23 and the cryogenic valve three 24, and enters the exhaust flare pipeline 1 through the outlet of the vaporizer 10;

[0142] 2. After the liquid phase is completely discharged, the driver closes the liquid inlet under the tank truck;

[0143] 3. Keep the low-temperature regulating valve 21 behind the pump open, open the gas phase arm hand valve 51, and level the gas phase pressure in the tank truck;

[0144] 4. After the tank truck pressure is lower than 0.1 MPa, the driver closes the valve on the tank truck connected to the gas phase arm hand valve 51.

[0145] Step 11: Nitrogen purging of liquid phase arm, gas phase arm and booster arm:

[0146] 1. The operator closes the liquid phase arm hand valve 61; the driver opens the valve on the tank truck connected to the liquid phase arm hand valve 61; the operator opens and closes the liquid phase arm nitrogen purge valve 63, repeating two or three times to blow the LNG in the liquid phase arm 6 onto the tank truck;

[0147] 2. The driver closes the valve on the tank truck; the operator opens the liquid phase vent valve 62 and the liquid phase arm nitrogen purge valve 63;

[0148] 3. The operator closes the gas phase arm hand valve 51, and opens the gas phase vent valve 52 and the gas phase arm nitrogen purge valve 53;

[0149] 4. The operator closes the boost arm hand valve 41, and opens the boost vent valve 42 and the boost arm nitrogen purge valve 43;

[0150] 5. After the operator confirms that the unloading liquid phase arm, gas phase arm and booster arm are emptied, close the booster arm nitrogen purge valve 43, gas phase arm nitrogen purge valve 53 and liquid phase arm nitrogen purge valve 63, and then close the booster vent valve 42, gas phase vent valve 52 and liquid phase vent valve 62;

[0151] Step 12: Unloading arm removal:

[0152] 1. The driver closes the valve on the tank truck;

[0153] 2. The driver disconnects the booster arm 4, the gas phase arm 5, and the liquid phase arm 6, and returns the unloading arm to its original position;

[0154] 3. The driver removes the static grounding clamp 71 of the tank car and places the skid blockers neatly;

[0155] 4. After the driver has completed the unloading work, he will check the condition of the tank truck and fill in the "Tank Truck Unloading Record Form". After confirming that everything is normal, he can leave the unloading platform and go to the weighing area to weigh the empty truck.

[0156] It should be noted that, in the description of the present application, it should be understood that the terms "length", "thickness", "inside", "outside", "axial", "radial", etc., indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0157] In addition, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises", or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article, or apparatus.

[0158] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An integrated LNG unloading skid, characterized in that: The invention comprises an exhaust flare pipeline (1), a liquid phase pipeline (2), a nitrogen pipeline (3), a booster arm (4), a gas phase arm (5), a liquid phase arm (6), an antistatic controller (7), a PLC control box (8), a cryogenic pump (9), a vaporizer (10), a cold-insulating pipe support (11) and a steel structure base (12); the exhaust flare pipeline (1), the liquid phase pipeline (2), the nitrogen pipeline (3), the booster arm (4), the gas phase arm (5), the liquid phase arm (6), the antistatic controller (7), the PLC control box (8), the cryogenic pump (9) and the cold-insulating pipe support (11) are all installed on the steel structure base (12); the vaporizer (10) is installed on one side of the steel structure base (12); the exhaust flare pipeline (1) and the liquid phase pipeline (2) are both fixed to the steel structure base (12) by using the cold-insulating pipe support (11); The exhaust flare pipeline (1) is interconnected with the liquid phase pipeline (2), the booster arm (4), the gas phase arm (5) and the liquid phase arm (6); The nitrogen pipeline (3) is interconnected with the liquid phase pipeline (2), the booster arm (4), the gas phase arm (5) and the liquid phase arm (6).

2. The LNG integrated unloading skid according to claim 1, characterized in that: The liquid phase pipeline (2) is installed on the steel structure base (12), and the liquid phase pipeline (2) is respectively installed with a low temperature regulating valve (21), a low temperature valve one (22), a low temperature valve two (23), a low temperature valve three (24), a low temperature valve four (25), a low temperature valve five (26), a low temperature valve six (27), a low temperature valve seven (28), a low temperature valve eight (29), a low temperature valve nine (210), a low temperature valve ten (211), a low temperature valve eleven (212) and a safety valve (213).

3. The LNG integrated unloading skid according to claim 1, characterized in that: A boosting arm hand valve (41), a boosting vent valve (42) and a boosting arm nitrogen purge valve (43) are installed on the boosting arm (4); the boosting arm hand valve (41), the boosting vent valve (42) and the boosting arm nitrogen purge valve (43) are interconnected through the boosting arm (4).

4. The LNG integrated unloading skid according to claim 1, characterized in that: The gas phase arm (5) is provided with a gas phase arm hand valve (51), a gas phase vent valve (52) and a gas phase arm nitrogen purge valve (53); the gas phase arm hand valve (51), the gas phase vent valve (52) and the gas phase arm nitrogen purge valve (53) are interconnected via the gas phase arm (5).

5. The LNG integrated unloading skid according to claim 1, characterized in that: The liquid phase arm (6) is provided with a liquid phase arm hand valve (61), a liquid phase vent valve (62) and a liquid phase arm nitrogen purge valve (63); the liquid phase arm hand valve (61), the liquid phase vent valve (62) and the liquid phase arm nitrogen purge valve (63) are interconnected through the liquid phase arm (6).

6. The implementation method of an integrated LNG unloading skid according to any one of claims 1 to 5, characterized in that: The steps include: S1: Liquid phase purge and pressure; S2: gas phase purge and pressure; S3: Boost phase purge and pressure reduction; S4: carburetor boost; S5: precooling; S6: Unloading; S7: Post-pump pressurization; S8: Tank truck flat pressing; S9: Nitrogen purge of liquid phase arm, gas phase arm and booster arm.

7. The implementation method of the LNG integrated unloading skid according to claim 6, characterized in that: The specific steps of S5 are as follows: S51: The operator opens the cryogenic valve ten (211) to connect the exhaust flare pipeline (1) and the cryogenic pump (9), opens the cryogenic valve four (25) and the cryogenic valve five (26), connects the exhaust flare pipeline (1) and the cryogenic pump (9), the cryogenic pump (9) is opened by 10-15%, then fully opened within the first 5 seconds of startup, and then fully closed; S52: Precooling starts, and cooling is completed when the temperature reaches below -148°C. After cooling for 20 minutes, the pump is considered to have cooled down; S53: The operator confirms that cryogenic valve one (22) and cryogenic valve ten (211) are closed, and cryogenic valve six (27) is opened.

8. The implementation method of the LNG integrated unloading skid according to claim 6, characterized in that: The specific steps of S6 are as follows: S61: The driver fully opens the valve connected to the liquid phase arm (6) under the tank truck, the operator closes the cryogenic valve seven (28), disconnects the boosting arm (4), activates the cryogenic pump (9) to boost pressure, and prepares to unload the truck; S62: Observe the filling condition of the cryogenic pump (9). When the cryogenic pump (9) is fully filled, press the "start button" of the PLC control box (8) to start the cryogenic pump (9) to unload the vehicle; S63: Increase pump speed: according to the conditions of the pressure before the pump, the temperature before the pump, the pressure after the pump, the temperature after the pump, and the gas phase pressure, the frequency of the cryogenic pump (9) is increased through the PLC control box (8) until normal operation; S64: Reduce pump speed: according to the conditions of the pressure before the pump, the temperature before the pump, the pressure after the pump, the temperature after the pump, and the gas phase pressure, the frequency of the cryogenic pump (9) is reduced through the PLC control box (8), and the pump is automatically stopped when the temperature is higher than -148°C; S65: Observe the temperature before and after the pump or refer to the level gauge reading on the tank truck, and press the "stop button" on the PLC control box (8) to stop the pump.

9. The implementation method of the LNG integrated unloading skid as claimed in claim 8, characterized in that: The PLC control box (8) in S63 comprises an analog input module, a digital output module and a central processing unit module; Analog input module: used to collect analog signals of pressure before pump, temperature before pump, pressure after pump, temperature after pump and gas phase pressure; Digital output module: According to the control logic of PLC, it outputs control signals to adjust the frequency of the pump, thereby achieving the operation of reducing the pump speed; Central processing unit module: responsible for executing PLC programs, processing input analog signals, and continuously reading the pump front pressure, pump front temperature, pump back pressure, pump back temperature and gas phase pressure values ​​collected by the analog input module through PLC; When the following conditions are met, the pump speed increase program is started: the pressure before the pump is > 0.09MPa, the temperature after the pump is <-150℃, the pressure after the pump is <0.7MPa, and the gas phase pressure is > 0.2MPa; The PLC calculates the frequency value that needs to be increased according to the preset pump speed increase algorithm, and outputs a control signal to the frequency converter through the digital output module, so that the pump frequency gradually increases until it reaches the frequency range required for normal operation or meets other conditions for stopping the pump speed increase.

10. The implementation method of the LNG integrated unloading skid according to claim 9, characterized in that: The specific calculation method of the PLC is as follows: Define a basic frequency increment step Δf and calculate the current pump operating frequency f(t), where t represents the current moment; When the pump speed increase condition is met, the new pump frequency f(t+1) is calculated according to the following formula: f(t+1)=f(t)+Δf×K, where K is the correction coefficient, which is used to make fine adjustments according to different working conditions. The value of K is adjusted according to the deviation of pressure and temperature from the set value. If the pressure and temperature are within the ideal range and close to the lower limit, K takes a larger value K=1.2 to speed up the increase of pump speed. If the pressure and temperature are close to the upper limit but still within the allowable range, K takes a smaller value K=0.8 to increase the pump speed more slowly; The correction coefficient is adjusted dynamically as follows: Calculate the pressure change rate ( ) and the temperature change rate ( ),in and Respectively for a period of time Changes in internal pressure and temperature; When the pressure and temperature are within the ideal range and close to the lower limit, and the pressure change rate and temperature change rate are also small, it means that the system condition is stable and there is a lot of room for improvement. The correction coefficient can be further increased. The specific formula is: ; When the pressure and temperature are close to the upper limit but still within the allowable range, if the pressure change rate or temperature change rate is large, it means that the working condition has a tendency to deteriorate, and the correction coefficient K should be further reduced. The specific formula is: .

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