Automatic control system and method for improving unloading rate of tank truck at gas station

Abstract

This invention discloses an automatic control system and method for improving the unloading rate of gas trucks at gas stations. It adds a fourth control valve and a pressure reducing device. The steps are as follows: S1: Determine whether the pressurization conditions are met; S2: When the pressure P inside the tank truck... 车 Gas input pressure below the compressor's lower limit P in‑low At that time, the gas in the low-pressure gas cylinder / well is reduced to the pressure P of the low-pressure gas cylinder group / well through the pressure reducing device. 低‑in It then enters the compressor as the second compression stage; S3: When the pressure P in the low-pressure gas storage cylinder group / well... 低 Pressure P inside the tanker 车 Compression ratio < compressor's limiting compression ratio ε limit At this time, the gas in the tanker is pressurized by the compressor and then injected into the low-pressure gas storage cylinder / well as the first compression stage; S4: according to steps S1, S2, and S3 until the gas pressure in the tanker is unloaded to the preset lower limit P of the tanker pressure at the gas station. in‑LL This invention increases the amount of gas unloaded per shipment, improves the gas unloading rate of tank trucks, and reduces the operating costs of gas stations.

Description

Technical Field

[0001] This invention relates to the field of gas stations, specifically to an automatic control system and method for improving the unloading rate of gas tank trucks at gas stations. Background Technology

[0002] Gas refueling stations include CNG refueling stations and hydrogen refueling stations. Taking a hydrogen refueling station as an example, in the actual use of hydrogen energy at a hydrogen refueling station, the hydrogen gas, which is below 20 MPa, is first transported from the hydrogen mother station to the refueling station. This gas is then pressurized to the target pressure (45 MPa or 90 MPa) by a compressor, and then distributed sequentially by a control panel into hydrogen storage cylinders or storage wells. When a vehicle needs to refuel, the refueling machine extracts high-pressure hydrogen from the storage cylinders or storage wells and dispenses it to the vehicle.

[0003] Currently, many hydrogen refueling stations suffer from insufficient unloading rates from tank trucks. On one hand, with the per-vehicle freight cost remaining constant, this directly increases the transportation cost per kilogram of natural hydrogen for the refueling station, reducing its operating profit. On the other hand, if the unloading volume from the tank truck is less than the loading volume from the hydrogen mother station, and the unloading rates of several refueling stations sharing the same tank truck are inconsistent, then the unloaded hydrogen will result in a direct loss for the refueling station. The root cause of this problem is that when the tank truck is unloaded to a lower pressure (below the designed unloading pressure requirement of the refueling station), the ratio of the compressor's output pressure to its input pressure increases, i.e., the compression ratio increases. This causes the temperature of the hydrogen output from the compressor to rise, thus failing to meet the compressor's operating requirements. Therefore, the tank truck cannot be unloaded further to the designed unloading pressure of the refueling station, which reduces the unloading rate, directly increasing the transportation cost per kilogram of natural hydrogen for the refueling station and potentially leading to direct losses, thus reducing the refueling station's operating profit.

[0004] The existing hydrogen refueling stations address this issue in roughly the following ways:

[0005] One approach is to replace or modify the compressor by adding hardware or replacing components to increase the number of compression stages, thereby reducing the compression ratio of each stage and lowering the output hydrogen temperature at each stage. This allows the hydrogen in the tanker to be unloaded to the designed unloading pressure, ultimately improving the hydrogen unloading rate. However, this method involves a large amount of engineering work, high costs, and a long time.

[0006] One approach involves changing the operation of the hydrogen refueling station. When the tanker pressure is low, causing the compressor's output hydrogen temperature to fall below the required operating temperature, the compressor is stopped. After the compressor's output hydrogen temperature cools down naturally (which takes a considerable amount of time), the compressor is manually restarted. When the compressor's output hydrogen temperature is about to reach the alarm shutdown temperature, the compressor is manually stopped again. The compressor is restarted once the output hydrogen temperature drops again, and this cycle is repeated until the hydrogen pressure in the tanker is reduced to the designed unloading pressure. However, this method still has the following drawbacks: 1. It is cumbersome to operate, requiring dedicated personnel to operate the compressor, increasing the station's operating costs and the operator's workload; 2. Because the compressor is manually operated, the operator needs to be very familiar with the operating procedures and cannot afford any carelessness, leading to potential safety hazards and reduced equipment lifespan; 3. The equipment is not intelligent, and the unloading time is significantly increased. Summary of the Invention

[0007] The purpose of this invention is to provide an automatic control system and method for improving the unloading rate of tank trucks at gas stations, thereby increasing the unloading volume per truck, shortening the unloading time, improving the unloading rate of tank trucks, reducing the operating costs of gas stations, and reducing the labor intensity of personnel.

[0008] To achieve one of the above objectives, the present invention adopts the following technical solution:

[0009] An automatic control system for improving the unloading rate of tank trucks at gas filling stations includes a controller, an unloading column, a gas storage cylinder group / well, and a gas dispenser. The unloading column is connected to the gas storage cylinder group / well via a compressor. A sequence control panel is provided between the compressor and the gas storage cylinder group / well. The gas storage cylinder group / well includes a low-pressure gas storage cylinder / well, a medium-pressure gas storage cylinder / well, and a high-pressure gas storage cylinder / well. A first control valve is provided in the low-pressure gas storage cylinder / well pipeline, a second control valve is provided in the medium-pressure gas storage cylinder / well pipeline, and a third control valve is provided in the high-pressure gas storage cylinder / well pipeline. The controller is used to control each control valve of the gas storage cylinder group / well and the sequence control panel respectively. A pressure reducing pipeline is also provided between the low-pressure gas storage cylinder / well and the compressor inlet. A fourth control valve and a pressure reducing device are provided on the pressure reducing pipeline. The fourth control valve is located between the pressure reducing device and the low-pressure gas storage cylinder / well and is electrically connected to the controller.

[0010] Furthermore, the fourth control valve is located at the air inlet end of the pressure reducing device.

[0011] To achieve the second objective mentioned above, the present invention adopts the following technical solution:

[0012] An automatic control method for improving the gas unloading rate of tank trucks at gas stations, based on the aforementioned automatic control system.

[0013] S1: Determine if the pressurization conditions are met; if so, unload normally.

[0014] S2: When the pressure P inside the tanker truck 车 Gas input pressure below the compressor's lower limit P in-low At this time, the low-pressure gas cylinder / well is used as an intermediate stage. The fourth control valve from the low-pressure gas cylinder / well to the pressure reducing device, the third control valve of the high-pressure gas cylinder / well pipeline, the second control valve of the medium-pressure gas cylinder / well pipeline, and the first control valve of the low-pressure gas cylinder / well pipeline are opened. The gas in the low-pressure gas cylinder / well is reduced to the preset pressure by the pressure reducing device, and the pressure P of the low-pressure gas cylinder group / well is obtained. 低-in The gas then enters the compressor's gas inlet as the compressor's input pressure. The compressor then pressurizes the gas in the low-pressure storage cylinder / well and adds it to the medium-pressure and high-pressure storage cylinders / wells, serving as the second compression stage.

[0015] S3: When the pressure P in the low-pressure gas storage cylinder group / well 低 The pressure P inside the tanker 车 Compression ratio < compressor's limiting compression ratio ε limit At that time, close the third control valve of the high-pressure gas cylinder / well pipeline, the second control valve and the fourth control valve of the medium-pressure gas cylinder / well pipeline, and allow gas P in the tank truck to flow. 车 After being pressurized by a compressor, it is injected into the low-pressure gas storage cylinder / well P. 低 As the first compression level;

[0016] S4: Follow steps S1, S2, and S3 until the gas pressure in the tanker truck is unloaded to the preset lower limit P of the tanker truck pressure at the gas station. in-LL until.

[0017] Furthermore, it also includes a standby process. In step S1, if the boosting conditions are not met, the standby process is entered.

[0018] Furthermore, in step S2, the low-pressure gas cylinder / well pressure P 低 The pressure of the high-pressure gas cylinder / well and the medium-pressure gas cylinder / well gradually increases. When the following condition 1 is met, the controller will switch the control flow to step S3. When the following conditions 2 and 3 are met, the controller will switch the control flow to step S3. When the following conditions 2 are met and conditions 3 are not met, the controller will switch the control flow to standby mode and wait for the pressurization conditions of step S1 to be met before restarting.

[0019] Condition 1: Low-pressure gas cylinder / well pressure P 低 Less than the lower limit P of the low-pressure gas storage cylinder / well pressure 低-low hour;

[0020] Condition 2: Pressure P of the high-pressure gas cylinder / well 高and the pressure P of the medium-pressure gas storage cylinder / well 中 All reached the set shutdown pressure of the gas storage cylinder group / well, i.e., the target pressure P. 目标 ;

[0021] Condition 3: Low-pressure gas cylinder / well pressure P 低 Less than the upper limit P of the low-pressure gas storage cylinder / well pressure 低-high hour.

[0022] Furthermore, in step S3, as the pressure P of the gas inside the tanker increases... 车 Gradually reduce the pressure P of the low-pressure gas storage cylinder group / well. 低 The compression ratio of the first compression stage gradually increases, ε1. When ε1 = ε limit ; or the pressure P of the high-pressure gas storage cylinder group / well 高 Less than the minimum gas supply pressure requirement P of the gas dispenser 高-low At this time, the controller needs to switch the control flow;

[0023] When condition 4 is met, the control flow switches to step S2; when condition 5 or condition 6 is met, the controller switches the control flow to standby mode and waits for the boosting condition in step S1 to be met before restarting.

[0024] Condition 4: Pressure P of the high-pressure gas storage cylinder group / well 高 Less than the minimum gas supply pressure requirement P of the gas dispenser 高-low ;

[0025] Condition 5: Pressure P of the high-pressure gas storage cylinder group / well 高 The pressure is greater than the minimum gas supply pressure required by the gas dispenser, P. 高-low And the pressure P of the low-pressure gas storage cylinder group / well 低 Pressure greater than the upper limit P of the low-pressure gas storage cylinder group / well 低-high ;

[0026] Condition 6: Pressure P of the high-pressure gas storage cylinder group / well 高 The pressure is greater than the minimum gas supply pressure required by the gas dispenser, P. 高-low Pressure P of low-pressure gas storage cylinder group / well 低 Pressure less than the upper limit P of the low-pressure gas storage cylinder group / well 低-high And the gas pressure P inside the tanker 车 That is, the compressor input pressure P in Compressor input pressure P in The pressure is less than the preset lower limit P of the tanker truck pressure at the gas station. in-LL .

[0027] Furthermore, the settings for each pressure parameter should satisfy the condition that its compression ratio ε < ε limit Requirements.

[0028] Furthermore, the minimum value P of the low-pressure gas cylinder / well pressure 低-low The setting should meet the compressor's limiting compression ratio ε limit The requirement, namely P 目标 / P 低-low <ε limit .

[0029] Furthermore, the maximum value P of the low-pressure gas cylinder / well pressure 低-high The setting should meet the compressor's limiting compression ratio ε limit The requirement, namely P 低-high / P in-LL <ε limit .

[0030] The beneficial effects of this invention are: by increasing the number of compression stages, the compression ratio of each stage is reduced, thereby lowering the output gas temperature of each stage, and achieving the unloading of gas from the tank truck to a pressure lower than the designed unloading pressure. Therefore, it has the following advantages:

[0031] 1. It improved the unloading rate of tank trucks, increased the unloading volume of tank trucks, shortened the unloading time, and reduced the transportation cost per kilogram of gas for gas stations and potential direct losses.

[0032] 2. Since the unloading process of the gas station tanker truck in this invention is automatically controlled by the controller, it makes the operation more convenient and simple, reduces the labor intensity, reduces the requirements for personnel, and reduces the frequency of manual operation of equipment. Therefore, it also reduces the risk of personnel misoperation of equipment and improves safety.

[0033] 3. Since the entire process only requires the addition of a small number of control devices, and the main process is automatically implemented by the controller, only programmers need to modify and optimize the control software program. Therefore, it has the advantages of small amount of modification work, low cost, and short impact on the operation of the gas station. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the control system of the present invention;

[0035] Figure 2 This is a schematic diagram of the controller of the present invention;

[0036] Figure 3 This is a flowchart of the control method of the present invention;

[0037] Figure 4 This invention relates to a hydrogen refueling station tanker unloading system.

[0038] Figure 5 for Figure 4 A schematic diagram of the controller principle. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0040] See Figure 1 and Figure 2 As shown, an automatic control system for improving the unloading rate of tank trucks at gas stations includes a controller, an unloading column, a gas storage cylinder group / storage well, and a gas dispenser. The unloading column is connected to the gas storage cylinder group / storage well via a compressor. A sequence control panel is provided between the compressor and the gas storage cylinder group / storage well. The gas storage cylinder group / storage well includes a low-pressure gas storage cylinder / well, a medium-pressure gas storage cylinder / well, and a high-pressure gas storage cylinder / well. The low-pressure gas storage cylinder / well pipeline is equipped with a first control valve 1, the medium-pressure gas storage cylinder / well pipeline is equipped with a second control valve 2, and the high-pressure gas storage cylinder / well pipeline is equipped with a third control valve 3. The first control valve 1, the second control valve 2, and the third control valve 3 are respectively connected to the sequence control panel. The controller is electrically connected to the first control valve 1, the second control valve 2, the third control valve 3, and the sequence control panel. The controller controls each control valve and the sequence control panel of the gas cylinder group / storage well. A pressure-reducing pipe is also provided between the low-pressure gas cylinder / well and the compressor inlet. A fourth control valve 4 and a pressure-reducing device are provided on the pressure-reducing pipe. The fourth control valve 4 is located between the pressure-reducing device and the low-pressure gas cylinder / well, at the inlet end of the pressure-reducing device, and is electrically connected to the controller. In this specific embodiment, the pressure-reducing device is a pressure-reducing valve. Pressure sensors are respectively installed at the output end of the tank truck, the low-pressure gas cylinder / well, the medium-pressure gas cylinder / well, the high-pressure gas cylinder / well, and the compressor. Each pressure sensor is electrically connected to the controller and collects the tank truck pressure P. 车 Low-pressure gas cylinder / well pressure P 低 Medium-pressure gas storage cylinder / well pressure P 中 High-pressure gas cylinder / well pressure P 高 Compressor input pressure P in Compressor output pressure P out The signal is sent to the controller. Temperature sensors are installed at both the input and output terminals of the compressor; these sensors are used to collect the compressor input temperature T. in Compressor output temperature T out The data is sent to the controller, which controls the opening and closing of the first control valve 1, the second control valve 2, the third control valve 3, the fourth control valve 4, and the sequence control panel based on the pressure information from each pressure sensor and the information from each temperature sensor, and preset control conditions.

[0041] See Figure 3As shown, an automatic control method for improving the unloading rate of tank trucks at gas stations is proposed, based on the aforementioned automatic control system for improving the unloading rate of tank trucks at gas stations.

[0042] Step S1: Determine if the pressurization conditions are met. If they are met, unload normally. If the pressurization conditions are not met, enter the standby process.

[0043] Step S2: When the pressure P inside the tanker truck... 车 Gas input pressure below the compressor's lower limit P in-low At this point, the gas in the tanker can no longer be unloaded in the original way. Therefore, the low-pressure gas cylinder / well is used as an intermediate stage. The fourth control valve from the low-pressure gas cylinder / well to the pressure reducing device, the third control valve of the high-pressure gas cylinder / well pipeline, the second control valve of the medium-pressure gas cylinder / well pipeline, and the first control valve of the low-pressure gas cylinder / well pipeline are opened. The gas in the low-pressure gas cylinder / well is then reduced to a preset pressure by the pressure reducing device, resulting in the pressure P of the low-pressure gas cylinder group / well. 低-in The gas then enters the compressor's gas inlet as the compressor's input pressure. The compressor then pressurizes the gas in the low-pressure storage cylinder / well and adds it to the medium-pressure and high-pressure storage cylinders / wells, serving as the second compression stage.

[0044] Its compression ratio is ε 2：

[0045] ε2=P 目标 / P 低-in

[0046] Where ε2 is the compression ratio of the second compression stage; P 目标 —Shutdown pressure of the gas storage cylinder group / well; P 低-in —The pressure of the gas in the low-pressure gas cylinder group / well after being reduced by the pressure reducing device;

[0047] Due to the initial low-pressure gas cylinder / well gas pressure P 低 Typically higher, the compressor input pressure P after pressure reduction by the pressure reducing device is... 低-in It can also maintain a relatively high pressure value, and the set shutdown pressure of the gas storage cylinder group / well is the target pressure P. 目标 If the compression ratio ε2 remains unchanged, it can be maintained at a low value, allowing the compressor to operate normally.

[0048] During the unloading process in step S2, the low-pressure gas cylinder / well pressure P 低The pressure of the high-pressure gas cylinder / well and the medium-pressure gas cylinder / well gradually increases. When the following condition 1 is met, the controller will switch the control flow to step S3. When the following conditions 2 and 3 are met, the controller will switch the control flow to step S3. When the following conditions 2 are met and conditions 3 are not met, the controller will switch the control flow to standby mode and wait for the pressurization conditions of step S1 to be met before restarting.

[0049] Condition 1: Low-pressure gas cylinder / well pressure P 低 Less than the lower limit P of the low-pressure gas storage cylinder / well pressure 低-low hour;

[0050] Condition 2: Pressure P of the high-pressure gas cylinder / well 高 and the pressure P of the medium-pressure gas storage cylinder / well 中 All reached the set shutdown pressure of the gas storage cylinder group / well, i.e., the target pressure P. 目标 ;

[0051] Condition 3: Low-pressure gas cylinder / well pressure P 低 Less than the upper limit P of the low-pressure gas storage cylinder / well pressure 低-high Time (P) 低-high The value setting should meet the compressor's limiting compression ratio ε. limit The requirement, namely P 低-high / P in-LL <ε limit P in-LL The preset lower limit of tanker truck pressure for gas stations to meet the operational requirements of gas stations.

[0052] Step S3: When the pressure P in the low-pressure gas storage cylinder group / well 低 The pressure P inside the tanker 车 Compression ratio < compressor's limiting compression ratio ε limit At that time, close the third control valve of the high-pressure gas cylinder / well pipeline, the second control valve and the fourth control valve of the medium-pressure gas cylinder / well pipeline, and allow gas P in the tank truck to flow. 车 After being pressurized by a compressor, it is injected into the low-pressure gas storage cylinder / well P. 低 As the first compression level;

[0053] Its compression ratio is ε 1：

[0054] ε1=P 低 / P 车

[0055] Where ε1 is the compression ratio of the first compression stage; P 低 —Pressure of the low-pressure gas storage cylinder group / well;

[0056] P 车 —The pressure of the gas inside the tanker;

[0057] As can be seen from the switching conditions in step S3 above, the pressure P in the low-pressure gas storage cylinder group / well at this time is... 低 Satisfy P 低 / P 车 <ε limit Under certain conditions, the gas inside the tank truck can be pressurized by a compressor and injected into a low-pressure gas storage cylinder group / well. Therefore, the gas inside the tank truck can continue to be unloaded to a lower pressure, which improves the unloading rate of the tank truck.

[0058] During the unloading process in step S3, as the pressure P of the gas inside the tanker increases... 车 Gradually reduce the pressure P of the low-pressure gas storage cylinder group / well. 低 The compression ratio of the first compression stage gradually increases, ε1. When ε1 = ε limit ; or the pressure P of the high-pressure gas storage cylinder group / well 高 Less than the minimum gas supply pressure requirement P of the gas dispenser 高-low At this time, the controller needs to switch the control flow;

[0059] When condition 4 is met, the control flow switches to step S2; when condition 5 or condition 6 is met, the controller switches the control flow to standby mode and waits for the boosting condition in step S1 to be met before restarting.

[0060] Condition 4: Pressure P of the high-pressure gas storage cylinder group / well 高 Less than the minimum gas supply pressure requirement P of the gas dispenser 高-low ;

[0061] Condition 5: Pressure P of the high-pressure gas storage cylinder group / well 高 The pressure is greater than the minimum gas supply pressure required by the gas dispenser, P. 高-low And the pressure P of the low-pressure gas storage cylinder group / well 低 Pressure greater than the upper limit P of the low-pressure gas storage cylinder group / well 低-high ;

[0062] Condition 6: Pressure P of the high-pressure gas storage cylinder group / well 高 The pressure is greater than the minimum gas supply pressure required by the gas dispenser, P. 高-low Pressure P of low-pressure gas storage cylinder group / well 低 Pressure less than the upper limit P of the low-pressure gas storage cylinder group / well 低-high And the gas pressure P inside the tanker 车 That is, the compressor input pressure P in Compressor input pressure P in The pressure is less than the preset lower limit P of the tanker truck pressure at the gas station. in-LL The preset lower limit of tanker pressure at the gas station meets the operational requirements of the gas station.

[0063] Step S4: Follow steps S1, S2, and S3 until the gas pressure in the tanker truck is unloaded to the preset lower limit P of the tanker truck pressure at the gas station. in-LL Up to this point. After steps S1, S2, and S3, the total compression ratio ε from the tanker truck to the gas storage cylinder group / well is... 总 for:

[0064] ε 总 =ε1×ε2

[0065] Wherein, ε1—compression ratio of the first compression stage; ε2—compression ratio of the second compression stage; ε 总 —Overall compression ratio.

[0066] The settings for each pressure parameter should satisfy the condition that the compression ratio ε < ε limit The requirements. The minimum pressure P of the low-pressure gas cylinder / well. 低-low The setting should meet the compressor's limiting compression ratio ε limit The requirement, namely P 目标 / P 低-low <ε limit The maximum value P of the low-pressure gas storage cylinder / well pressure. 低-high The setting should meet the compressor's limiting compression ratio ε limit The requirement, namely P 低-high / P in-LL <ε limit .

[0067] Working principle of the invention:

[0068] The automatic control method for improving the unloading rate of gas tank trucks at gas stations, as described in this invention, achieves the following objective, which incorporates some calculation formulas from GB / T 31138-2022 "Gas Dispensers":

[0069] Gas unloading rate of tank trucks at gas filling stations:

[0070]

[0071] In Formula 1: η—Gas unloading rate of tank trucks at gas stations, (%);

[0072] m 余 — Remaining gas volume in the tanker truck, (kg);

[0073] m 总 —Total gas volume inside the tanker truck, (kg);

[0074] Conclusion 1: Because the total amount of gas that a tanker truck can transport each time is m 总 It is fixed. As can be seen from Equation 1, to increase the unloading rate η, the amount of gas remaining in the tanker truck must be reduced. 余 .

[0075] Gas density:

[0076] ρ=Mp / (ZRT)------Equation 2

[0077] Gas mass:

[0078] m=ρv------Equation 3

[0079] Gas compressibility factor:

[0080]

[0081] In Equations 2, 3, and 4:

[0082] ρ—Gas density, in kg / m³ 3 ;

[0083] M—molar mass of a gas molecule, with a value of 2.016 g / mol;

[0084] p — gas pressure, in MPa;

[0085] Z—Gas compressibility factor;

[0086] R—gas constant, with a value of 0.0083145 MPa·L / (mol·K);

[0087] T—Gas temperature, in Kelvin (K);

[0088] m—gas mass, in kg;

[0089] v — gas volume, in cubic meters (m³) 3 ;

[0090]

[0091] Conclusion 2: With the tanker volume v constant, it can be seen from equations 2, 3, and 4 that the remaining gas volume m inside the tanker is... 余 With the gas pressure P inside the tanker 车 Proportional, to reduce m 余 This means it is necessary to reduce the gas pressure P inside the tanker truck. 车 .

[0092] For the compressor to operate normally, the temperature of the gas output from the compressor must be lower than the gas alarm temperature, which means the following condition (Equation 5) must be met:

[0093] T out <T err ------Formula 5

[0094] In Equation 5: T out —Compressor output gas temperature, (K);

[0095] T err—Compressor gas alarm temperature, (K);

[0096] Compressor output temperature:

[0097] To ut =T in ε (k-1) / k ------Form 6

[0098] In Equation 6: T out —Gas output temperature, (K);

[0099] T in —Gas input temperature, (K);

[0100] k—Adiabatic index, a constant;

[0101] ε—compression ratio;

[0102] Conclusion 3: Compressor input temperature T in Due to the influence of ambient temperature and the cooling system, the variation range is relatively small. As shown in Equation 6, the compressor output gas temperature T out It is related to the compression ratio ε, that is, the larger the compression ratio ε, the higher the T out The higher the value, the better. The definition is that T is just enough to prevent the compressor from malfunctioning. out =T err The compression ratio is the compressor's limiting compression ratio ε. limit .

[0103] The compression ratio ε of the compressor:

[0104] ε=P out / P in ------Form 7

[0105] In Equation 7: ε—compression ratio;

[0106] P out —Output pressure;

[0107] P in —Input pressure;

[0108] Conclusion 4: For gas stations, the set shutdown pressure for the gas storage cylinder group / well is the target pressure P. 目标 Its value rarely changes and can be considered a fixed value. In this case, the target pressure is the output pressure P. out From Equation 7, it can be seen that the input gas pressure P of the compressor is... in The smaller the value, the larger the compressor's compression ratio ε, and the higher the compressor's output gas temperature T. out The higher the compression ratio, the better, as the compressor's compression ratio increases to ε = ε limit At this time, according to conclusion 3, T out =T errThe compressor alarmed and shut down, unable to further reduce the compressor's input gas pressure P. in Unloading to a lower level, since the tank truck and compressor inlet are only connected by the unloading column and pipeline, the pressure loss is very small, and P can be considered as... 车 =P in According to conclusion 2 above, the mass of the remaining gas inside the tanker is m. 余 It cannot be reduced any lower; the unloading rate η of the tanker truck has reached its maximum value under this method. max Define parameter P in-low This is equal to the compressor's input gas pressure P at this time. in +1MPa, i.e., P in-low =P in +1MPa.

[0109] Conclusion 5: As can be seen from the above inferences, the compression ratio ε is closely related to the tank truck unloading rate. That is, the larger the compression ratio ε, the lower the tank truck unloading rate. Therefore, reducing the compression ratio ε is the key to solving the problem.

[0110] When the gas pressure P inside the tanker 车 Too low, the gas P in the tanker truck 车 After being pressurized by the compressor, it is injected directly into the gas storage cylinder group / well, when the target pressure P 目标 Unable to meet compression ratio ε 总 =P 目标 / P 车 When required, the compression ratio ε is used. 总 The compression is broken down into two stages to meet the compressor's operating requirements, allowing unloading to continue and reducing the gas pressure P inside the tanker truck. 车 By unloading to a lower level, the unloading volume of tank trucks is increased, ultimately achieving the goal of increasing the unloading rate of tank trucks, i.e., ε. 总 =ε1×ε2.

[0111] First-stage compression: The controller uses the low-pressure gas cylinder / well as an intermediate stage, and the first-stage compression is achieved by the gas P inside the tank truck. 车 After being pressurized by the compressor, it is added to the intermediate stage P. 低 Its compression ratio is ε1, and its calculated value is: ε1 = P 低 / P 车 .

[0112] Second-stage compression: The controller uses flexible control of gas station equipment and control valves to perform second-stage compression, that is, drawing gas P from the intermediate stage's low-pressure storage cylinder / well. 低 The gas is used as the input gas source for the compressor, and after being pressurized by the compressor, it is injected into the high-pressure gas cylinder / well and the medium-pressure gas cylinder / well. At this time, the gas pressure in the high-pressure gas cylinder / well and the medium-pressure gas cylinder / well is the target pressure P. 目标The target pressure is the shutdown pressure set at the gas station, and once set, it remains essentially constant. The compression ratio of the second stage is ε2, calculated as: ε2 = P 目标 / P 低 .

[0113] This invention improves the unloading rate of gas from tank trucks, increases the unloading volume of tank trucks, and reduces the transportation cost per kilogram of gas at gas stations, as well as potential direct losses. It is applicable to unloading gas from tank trucks at various gas stations. This method can be used to improve the unloading rate of gas from tank trucks when the compression ratio does not meet the design temperature requirements.

[0114] Taking a hydrogen refueling station as an example, see Figure 4 and Figure 5 As shown, the hydrogen pressure transported by the tank trucks from the hydrogen mother station each time is 20 MPa, and the tank truck water volume is 26 m³. 3 With the ambient temperature set at 25℃, when unloading using the existing method, the station can at least reduce the hydrogen pressure P inside the tanker truck. 车 The pressure was reduced to 7MPa due to the compressor's compression ratio ε. 总 The compression ratio limit ε has been reached. limit The target pressure P at this station 目标 The pressure was set at 43 MPa, and the compression ratio ε was calculated. limit =ε 实际 =6.1. The station and equipment supplier require that the hydrogen pressure P inside the tanker be increased. 车 Unload to 5MPa, target pressure P 目标 Given a pressure of 45 MPa, the required compression ratio is calculated to be ε. 设计 =9, which obviously does not meet the requirements.

[0115] The required residual hydrogen pressure P inside the tanker truck 车 =5MPa. Calculate the total amount of hydrogen that each tanker truck can transport from the hydrogen mother station. Based on Equations 2, 3, and 4, and in conjunction with the coefficient v provided in GB / T 31138-2022 "Hydrogen Refueling Machines". ij It can be calculated that:

[0116] Total amount of hydrogen in the tanker m 总 =376kg;

[0117] Tankers loading m tons from hydrogen mother station 装 =264kg;

[0118] Tanker truck unloading to P 车 At 7 MPa, the mass of the remaining hydrogen in the tanker is m. 余7 =142kg;

[0119] Tanker truck unloading to P 车 At 5 MPa, the mass m of the remaining hydrogen in the tanker truck 余5=102kg.

[0120] From Equation 1, we can calculate:

[0121] Tanker truck unloading to P 车 When = 7MPa, η 余7 =62%;

[0122] Tanker truck unloading to P 车 When = 5MPa, η 余5 =70%;

[0123] Therefore, if the station uses the original unloading method, compared with the requirements, each truck will have 40kg of hydrogen remaining that cannot be unloaded. Based on the above data, for every 6.5 transport trips by the tanker truck, an additional transport cost will be incurred. With the station refueling one truckload of hydrogen per day, this will result in approximately 5 additional transport costs per month. Since this station shares tankers with other stations, if another hydrogen refueling station can unload the tankers to 5MPa, this station will directly lose 40kg of hydrogen. Given the current high price of hydrogen, this loss will be substantial.

[0124] When using the solution of this invention, ε 总 =ε 设计 =ε1×ε2=9=3×3, that is, ε1=3<ε limit ε2=3<ε limit This will meet the requirement of unloading tank trucks to 5MPa, thereby reducing the transportation costs and potential direct losses of hydrogen refueling stations, while increasing the unloading rate of tank trucks from 62% to 70%.

[0125] When using the scheme of this invention, if the compression ratio of each stage is taken as the limiting compression ratio of the compressor at that station, that is, ε1=ε2=ε limit =6.1, then ε at this time 总 =ε1×ε2≥36, from Equation 7, the hydrogen pressure P inside the tanker can be calculated. 车 =P 目标 / ε 总 =45 / 36=1.25<2. Unload the tanker truck at P. 车 When the pressure is 2 MPa, the mass m of the remaining hydrogen gas in the tanker can be calculated using equations 1, 2, 3, and 4. 余2 =42kg; η 余2 =88%; Under this extreme condition, compared with the original unloading plan, 100 kg more can be unloaded, and at the same time, the unloading rate of the tank truck can be increased from 62% to 88%.

[0126] The technical solution provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. An automatic control method for improving the unloading rate of gas trucks at gas filling stations, characterized in that: The system includes a controller, a gas unloading column, a gas storage cylinder group / well, and a gas dispenser. The gas unloading column is connected to the gas storage cylinder group / well via a compressor. A sequence control panel is provided between the compressor and the gas storage cylinder group / well. The gas storage cylinder group / well includes low-pressure, medium-pressure, and high-pressure gas cylinders / wells. A first control valve is provided in the low-pressure gas cylinder / well pipeline, a second control valve in the medium-pressure gas cylinder / well pipeline, and a third control valve in the high-pressure gas cylinder / well pipeline. The controller is used to control each control valve and the sequence control panel of the gas storage cylinder group / well. A pressure-reducing pipeline is also provided between the low-pressure gas cylinder / well and the compressor inlet. A fourth control valve and a pressure-reducing device are provided on the pressure-reducing pipeline. The fourth control valve is located between the pressure-reducing device and the low-pressure gas cylinder / well and is electrically connected to the controller. The fourth control valve is located at the inlet of the pressure-reducing device in the automatic control system. S1: Determine if the pressurization conditions are met; if so, unload normally. S2: When the pressure P inside the tanker truck 车 Gas input pressure below the compressor's lower limit P in-low At this time, the low-pressure gas cylinder / well is used as an intermediate stage. The fourth control valve from the low-pressure gas cylinder / well to the pressure reducing device, the third control valve of the high-pressure gas cylinder / well pipeline, the second control valve of the medium-pressure gas cylinder / well pipeline, and the first control valve of the low-pressure gas cylinder / well pipeline are opened. The gas in the low-pressure gas cylinder / well is reduced to the preset pressure by the pressure reducing device, and the pressure P of the low-pressure gas cylinder group / well is obtained. 低-in The gas then enters the compressor's gas inlet as the compressor's input pressure. The compressor then pressurizes the gas in the low-pressure gas cylinder / well and injects it into the medium-pressure gas cylinder / well and the high-pressure gas cylinder / well as the second compression stage. S3: When the pressure P in the low-pressure gas storage cylinder group / well 低 Pressure P inside the tanker 车 Compression ratio < compressor's limiting compression ratio ε limit At that time, close the third control valve of the high-pressure gas cylinder / well pipeline, the second control valve and the fourth control valve of the medium-pressure gas cylinder / well pipeline, and allow gas P in the tank truck to flow. 车 After being pressurized by a compressor, it is injected into the low-pressure gas storage cylinder / well P. 低 As the first compression level; S4: Follow steps S1, S2, and S3 until the gas pressure in the tanker truck is unloaded to the preset lower limit P of the tanker truck pressure at the gas station. in-LL until.

2. The automatic control method for improving the unloading rate of gas trucks at gas stations according to claim 1, characterized in that: It also includes a standby process. In step S1, if the boosting conditions are not met, the standby process is entered.

3. The automatic control method for improving the unloading rate of gas trucks at gas stations according to claim 1, characterized in that: In step S2, the low-pressure gas cylinder / well pressure P 低 The pressure of the high-pressure gas cylinder / well and the medium-pressure gas cylinder / well gradually increases. When the following condition 1 is met, the controller will switch the control flow to step S3. When the following conditions 2 and 3 are met, the controller will switch the control flow to step S3. When the following conditions 2 are met and conditions 3 are not met, the controller will switch the control flow to standby mode and wait for the pressurization conditions of step S1 to be met before restarting. Condition 1: Low-pressure gas cylinder / well pressure P 低 Less than the lower limit P of the low-pressure gas storage cylinder / well pressure 低-low hour; Condition 2: Pressure P of the high-pressure gas cylinder / well 高 and the pressure P of the medium-pressure gas storage cylinder / well 中 All reached the set shutdown pressure of the gas storage cylinder group / well, i.e., the target pressure P. 目标 ; Condition 3: Low-pressure gas cylinder / well pressure P 低 Less than the upper limit P of the low-pressure gas storage cylinder / well pressure 低-high hour.

4. The automatic control method for improving the unloading rate of gas trucks at gas stations according to claim 1, characterized in that: In step S3, as the pressure P of the gas inside the tanker truck increases... 车 Gradually reduce the pressure P of the low-pressure gas storage cylinder group / well. 低 The compression ratio of the first compression stage gradually increases, ε1. When ε1 = ε limit ; or the pressure P of the high-pressure gas storage cylinder group / well 高 Less than the minimum gas supply pressure requirement P of the gas dispenser 高-low At this time, the controller switches the control flow; When condition 4 is met, the control flow switches to step S2; when condition 5 or condition 6 is met, the controller switches the control flow to standby mode and waits for the boosting condition in step S1 to be met before restarting. Condition 4: Pressure P of the high-pressure gas storage cylinder group / well 高 Less than the minimum gas supply pressure requirement P of the gas dispenser 高-low ; Condition 5: Pressure P of the high-pressure gas storage cylinder group / well 高 The pressure is greater than the minimum gas supply pressure required by the gas dispenser, P. 高-low And the pressure P of the low-pressure gas storage cylinder group / well 低 Pressure greater than the upper limit P of the low-pressure gas storage cylinder group / well 低-high ; Condition 6: Pressure P of the high-pressure gas storage cylinder group / well 高 The pressure is greater than the minimum gas supply pressure required by the gas dispenser, P. 高-low Pressure P of low-pressure gas storage cylinder group / well 低 Pressure less than the upper limit P of the low-pressure gas storage cylinder group / well 低-high And the gas pressure P inside the tanker 车 That is, the compressor input pressure P in Compressor input pressure P in The pressure is less than the preset lower limit P of the tanker truck pressure at the gas station. in-LL .

5. The automatic control method for improving the unloading rate of gas trucks at gas stations according to claim 1, characterized in that: The settings for each pressure parameter should satisfy the condition that the compression ratio ε < ε limit Requirements.

6. The automatic control method for improving the unloading rate of gas trucks at gas stations according to claim 3, characterized in that: The minimum value P of the low-pressure gas cylinder / well pressure 低-low The setting should meet the compressor's limiting compression ratio ε limit The requirement, namely P 目标 / P 低-low <ε limit .

7. The automatic control method for improving the unloading rate of gas trucks at gas stations according to claim 3, characterized in that: The maximum value P of the low-pressure gas cylinder / well pressure 低-high The setting should meet the compressor's limiting compression ratio ε limit The requirement, namely P 低-high / P in-LL <ε limit .

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