Method for optimized operation of multiple open rack vaporizers for a liquefied natural gas station

Abstract

The application discloses a kind of for liquefied natural gas station The optimization operation method of multiple open rack gasifiers, comprising: obtaining the seawater heat required for each open rack gasifier operation, and the total seawater heat of the preset number of open rack gasifiers is obtained by addition;Based on the total seawater heat, the seawater flow of each open rack gasifier is obtained, and the total seawater flow of the preset number of open rack gasifiers is obtained by addition;When the total seawater flow of the preset number of open rack gasifiers is less than the total seawater flow of the open rack gasifier less than the preset number by 1, and also less than the total seawater flow of the open rack gasifier more than the preset number by 1, the preset number of open rack gasifiers is the optimal number of operation, and then the best liquefied natural gas flow allocated to each open rack gasifier is obtained.The application can optimize the energy efficiency of multiple gasifiers, give the energy efficiency optimization operation number and load distribution method, the measures taken have clear execution path, and it is realizable.

Description

Technical Field

[0001] This invention belongs to the field of operation optimization technology for liquefied natural gas (LNG) stations, and particularly relates to an optimized operation method for multiple open-frame gasifiers in an LNG station. Background Technology

[0002] Liquefied natural gas (LNG) terminals commonly use three types of vaporizers: open-frame vaporizers (ORVs), intermediate medium vaporizers (IFVs), and submerged combustion vaporizers (SCVs). LNG terminals use these three types of vaporizers to vaporize LNG and then convert it into natural gas (NG) for export. SCVs use natural gas combustion as the heat input for LNG vaporization, which is very costly. ORVs and IFVs use seawater and warm seawater discharged from power plants as heat inputs for LNG vaporization. Because seawater heat is a free natural energy source, and warm seawater discharged from power plants is a free waste containing heat energy, it is only necessary to ensure that the seawater discharged by the ORV meets environmental protection requirements. Many large LNG terminals are built along the coast, utilizing free heat energy from seawater, warm seawater discharged from power plants, and geothermal energy to provide heat for the ORV and IFV vaporizers, which can significantly reduce the operating costs of LNG terminals.

[0003] The LNG vaporization process is a comprehensive system utilizing thermal, cold, and electrical energy. LNG vaporization requires thermal energy, while the transportation of the thermal and cold energy media requires electrical energy. LNG itself also contains a significant amount of cold energy. Optimizing and balancing the relationship between these three elements, and rationally utilizing seawater, warm seawater from power plants, geothermal energy, or other resources to achieve both efficient use of thermal energy and full utilization of cold energy, while ensuring efficient transportation of the thermal and cold energy media, thereby minimizing total system energy consumption, CO2 emissions, and pollutants, has become an increasingly important research topic in the context of a "dual-carbon" environment.

[0004] Using seawater pumping stations to supply water to multiple ORV vaporizers is currently the most common method for LNG vaporization. Since seawater heat is free, research has primarily focused on how to optimize pump sets to reduce the power consumption of the pumping station. These studies have combined the optimization of multiple vaporizers with the optimization of seawater pumping stations composed of multiple pump sets, tentatively summarizing various optimal pump combinations, resulting in differing conclusions. In reality, these are two separate issues: first, determining the minimum seawater heat input required for LNG vaporization by optimizing the number of operating vaporizers and load distribution; and second, for this minimum heat input, how to optimize the number of operating pump sets and the load distribution of each pump set to minimize the overall power consumption of the seawater pumping station. Theoretical research and technological inventions on optimizing the energy efficiency of pump station operation have yielded definitive conclusions. For example, Springer's book "Efficient Energy-Saving Control and Optimization for Multi-unit Systems-A Guide for Electrical Engineers" and the US patent "POWER-SAVING OPTIMIZATION OPERATIONMETHOD AND SWITCHING POINT DETERMINING METHOD FOR WATER PUMP UNIT, 17 / 339,381".

[0005] There is currently no clear path for optimizing the energy efficiency of multiple gasifiers, providing a method for determining the number of operating units and load allocation for energy efficiency optimization, and ultimately determining the minimum seawater thermal energy input and minimum seawater flow rate required for LNG gasification to meet the constraints.

[0006] Therefore, there is an urgent need to propose an optimized operation method for multiple open-frame gasifiers in liquefied natural gas stations. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes an optimized operation method for multiple open-frame gasifiers in liquefied natural gas (LNG) stations, thereby resolving the issues present in the prior art.

[0008] To achieve the above objectives, the present invention provides an optimized operation method for multiple open-frame gasifiers in a liquefied natural gas (LNG) station, comprising the following steps:

[0009] The number of open-frame gasifiers in the liquefied natural gas station is pre-set;

[0010] Obtain the seawater heat required for the operation of each open-rack gasifier, and add up the seawater heat required for the operation of each open-rack gasifier to obtain the total seawater heat of a preset number of open-rack gasifiers.

[0011] Based on the total heat of seawater in the preset number of open-rack gasifiers, the seawater flow rate of each open-rack gasifier is obtained, and the seawater flow rates of each open-rack gasifier are added together to obtain the total seawater flow rate of the preset number of open-rack gasifiers.

[0012] When the total seawater flow of the preset number of open-rack gasifiers is less than the total seawater flow of open-rack gasifiers that are one less than the preset number, and also less than the total seawater flow of open-rack gasifiers that are one more than the preset number, then the preset number of open-rack gasifiers is the optimal number of operating units.

[0013] Based on the optimal number of operating units and the total seawater flow rate of the open-rack gasifiers at the optimal number of operating units, the optimal liquefied natural gas flow rate allocated to each open-rack gasifier is obtained.

[0014] Optionally, the liquefied natural gas station consists of several identical open-frame gasifiers connected in parallel, with the liquefied natural gas inlets flowing through all the open-frame gasifiers connected together, and the liquefied natural gas outlets flowing through all the open-frame gasifiers connected together.

[0015] Optionally, the minimum seawater film formation flow rate, maximum seawater flow rate, and maximum liquefied natural gas flow rate are all equal for each open-frame gasifier.

[0016] Optionally, the formula for obtaining the seawater heat required for the operation of each open-rack gasifier is:

[0017] W SW-ORVi =xQ LNG-ORVi ΔT LNG-ORVi / (a-bQ LNG-ORVi )

[0018] Among them, W SW-ORVi Q is the amount of seawater heat required for the i-th open-rack gasifier, x is the density of liquefied natural gas, and Q is the amount of heat required. LNG-ORVi ΔT is the liquefied natural gas flow rate of the i-th open-frame gasifier. LNG-ORVi Q is the difference between the liquefied natural gas outlet temperature and the liquefied natural gas inlet temperature of the i-th open-frame gasifier, where a and b are constants. LNG-ORVi It is the liquefied natural gas flow rate of the i-th open-frame gasifier.

[0019] Optionally, the formula for calculating the total heat of seawater in a preset number of open-rack gasifiers is:

[0020] W LNG-ORV-k =W LNG-ORV1 +W LNG-ORV2 +…+W LNG-ORVk

[0021] Among them, W LNG-ORV-k W represents the total heat capacity of the seawater in all open-rack gasifiers.LNG-ORV1 W LNG-ORV2 …W LNG-ORVk The respective amounts are the seawater heat for each open-frame gasifier.

[0022] Optionally, based on the total heat of seawater in the preset number of open-rack gasifiers, the formula for obtaining the seawater flow rate of each open-rack gasifier is as follows:

[0023] Q SW-ORV1 =W LNG-ORV-k / (k*c*d*ΔT SW-ORV1 )

[0024] Among them, W LNG-ORV This is the total heat of seawater required for all open-rack gasifiers, ΔT SW-ORV1 is the temperature difference between seawater entering and exiting the open-rack gasifier, k is the number of open-rack gasifiers, and c and d are constants.

[0025] Optionally, when the seawater flow rate of the preset number of open-frame gasifiers is less than the minimum film-forming flow rate, the seawater flow rate of the preset number of open-frame gasifiers is set to the minimum film-forming flow rate.

[0026] When the seawater flow rate of the preset number of open-frame gasifiers is greater than the maximum seawater flow rate, the seawater flow rate of the preset number of open-frame gasifiers is set to the maximum seawater flow rate.

[0027] Optionally, the formula for calculating the total seawater flow rate of the preset number of open-rack gasifiers is:

[0028] Q SW-ORV-k =Q LNG-ORV1 +Q LNG-ORV2 +…+Q LNG-ORVk

[0029] Among them, Q SW-ORV-k Q is the total seawater flow rate of all open-rack gasifiers, k is the number of open-rack gasifiers, and Q is the total seawater flow rate of all open-rack gasifiers. LNG-ORV1 Q LNG-ORV2 …Q LNG-ORVk These represent the seawater flow rate for each open-frame gasifier.

[0030] Optionally, the formula for calculating the optimal liquefied natural gas flow rate allocated to each open-rack gasifier is as follows:

[0031] Q LNG-ORVi =Q SW-ORV-k / k

[0032] Among them, Q LNG-ORVi It is the optimal liquefied natural gas flow rate allocated to each open-rack gasifier.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] This invention provides an optimized operation method for multiple open-frame gasifiers in a liquefied natural gas station. This method can optimize the energy efficiency of multiple gasifiers, provides the number of operating gasifiers and load allocation method for energy efficiency optimization, and the measures taken have a clear execution path and are achievable. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0036] Figure 1 This is a schematic diagram of the structure of a liquefied natural gas station according to an embodiment of the present invention;

[0037] Among them, 1. First ORV vaporizer, 2. Second ORV vaporizer, 3. Third ORV vaporizer, 4. ORV vaporizer, 5. Seawater inlet pipe, 6. Seawater return channel, 7. LNG inlet pipe, 8. LNG outlet pipe. Detailed Implementation

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0040] This embodiment provides an optimized operation method for multiple open-frame vaporizers in a liquefied natural gas (LNG) station, supporting energy-saving operation of LNG station vaporizers.

[0041] A liquefied natural gas (LNG) station consists of n identical open-frame gasifiers connected in parallel, with each open-frame gasifier having the same minimum seawater film formation flow rate of Q. SW-ORV1-MIN (m 3 / h), the maximum seawater flow rate of each open-frame gasifier is equal to Q. SW-ORV1-MAX (m 3 / h), the maximum liquefied natural gas flow rate of each open-frame gasifier is equal to Q. LNG-ORV1-MAX (m 3 / h).

[0042] The liquefied natural gas inlets flowing through all the open-rack gasifiers are connected together, and the liquefied natural gas outlets flowing through all the open-rack gasifiers are connected together. k open-rack gasifiers are in operation. The seawater heat required for the i-th open-rack gasifier to operate is W.SW-ORVi =xQ LNG-ORVi ΔT LNG-ORVi / (a-bQ LNG-ORVi ), W SW-ORVi Let x be the heat of seawater required for the i-th open-rack gasifier, and x be the density of liquefied natural gas (t / m³). 3 ), Q LNG-ORVi ΔT is the liquefied natural gas flow rate of the i-th open-frame gasifier. LNG-ORVi Let Q be the temperature difference (°C) between the LNG outlet and inlet temperatures of the i-th open-rack gasifier. All operating open-rack gasifiers have the same LNG inlet and outlet temperature difference. Let a and b be constants. LNG-ORVi It is the liquefied natural gas flow rate of the i-th open-frame gasifier.

[0043] The total flow rate of liquefied natural gas is Q LNG-ORV (m 3 / h), Q LNG-ORV-k =Q LNG-ORV1 +Q LNG-ORV2 +…+Q LNG-ORVk The flow rate of each open-rack gasifier is equal to Q. LNG-ORV1 =Q LNG-ORV / k, each open-rack gasifier requires the same amount of seawater heat (W). SW-ORV1 The total heat of seawater required for k open-frame gasifiers (W) LNG-ORV-k =W LNG-ORV1 +W LNG-ORV2 +…+W LNG-ORVk The specific heat capacity of seawater is c(MW / (tk), and the total flow rate of seawater is Q. SW-ORV (m 3 / h), seawater density is d(t / m 3 The seawater flow rate for each operating open-frame gasifier is equal to Q. SW-ORV1 (m 3 / h), calculate Q SW-ORV1 =W LNG-ORV-k / (k*c*d*ΔT SW-ORV1 ), ΔT SW-ORV1 The temperature difference (°C) between seawater entering and exiting the open-frame gasifier is required by environmental regulations. SW-ORV1 The maximum temperature is 5℃.

[0044] If the calculated Q SW-ORV1 SW-ORV1-MIN Then Q SW-ORV1 =Q SW-ORV1-MIN If the calculated Q SW-ORV1 Q SW-ORV1-MAX Then Q SW-ORV1 =Q SW-ORV1-MAX Calculate the total seawater flow Q SW-ORV-k =Q LNG-ORV1 ​+Q LNG-ORV2 +…+Q LNG-ORVk If the total seawater flow rate Q is calculated from the operation of k open-frame gasifiers... SW-ORV-k The total seawater flow rate Q required to operate one open-frame gasifier compared to k-1 SW-ORV-(k-1) Smaller than the total seawater flow rate Q required to operate k+1 open-frame gasifiers. SW-ORV-(k+1) If k is also small, then k is the optimal number of operating units. The optimal LNG load allocation method for each operating open-frame gasifier is Q. LNG-ORVi =Q SW-ORV-k / k.

[0045] Furthermore, the value range of constant 'a' is 1440-1466, with a preferred value of 1453, and the value range of 'b' is 1-1.04, with a preferred value of 1.02. This method of selecting the number of pumps and the load allocation method requires the least total seawater flow and also minimizes the power consumption of the seawater pumping station.

[0046] As a specific example, such as Figure 1 As shown, this LNG vaporizer station has four ORV vaporizers: ORV vaporizer 1, ORV vaporizer 2, ORV vaporizer 3, and ORV vaporizer 4, n=4. Seawater enters the top of the four ORV vaporizers through seawater inlet pipe 5. The seawater temperature is 7℃. The minimum film-forming flow rate Q for each ORV vaporizer is... SW-ORV1-MIN =3660(m) 3 / h), maximum seawater flow rate Q SW-ORV1-MAX =8500(m) 3 / h), the low-temperature seawater return water flowing from the ORV vaporizer enters the seawater return water channel 6. According to environmental protection requirements, the seawater return water temperature must not be lower than 2℃. The maximum LNG flow rate Q of each ORV vaporizer is... LNG-ORV1-MAX =900(m) 3 LNG is fed into each operating ORV vaporizer via LNG inlet pipe 7. The LNG entering the ORV vaporizer has a temperature of -130℃ and a density of 0.444 (t / m³). 3 ), Total LNG flow rate Q LNG-ORV =900(m) 3 Natural gas is delivered via LNG outlet pipe 8 ( / h), and the temperature of NG is 5℃. Optimal values ​​are taken as a = 1453, b = 1.02, and seawater density d = 1.031 (t / m³). 3 The specific heat capacity of seawater, c = 0.0011083 (MW / (tk), is calculated as follows:

[0047] 1) When k = 4, Q LNG-ORV1 =Q LNG-ORV / k=225(m 3 If the total heat required from the seawater is W / h, then the total heat required is W / h.SW =k*W SW-ORV1 =k*xQ LNG-ORV1 ΔT LNG-ORVi / (a-bQ LNG-ORV1 = 44.092 (MW), the seawater flow rate Q required for each ORV gasifier SW-ORV1 =W LNG-ORV / (k*c*d*ΔT SW-ORV1 ), to get Q SW-ORV1 =1928(m) 3 / h), because it is less than the minimum film-forming flow rate Q. SW-ORV1-MIN Therefore, take Q. SW-ORV1 =3660(m) 3 / h), the final total seawater flow rate Q SW-ORV =k*3660=14640(m) 3 / h).

[0048] 2) When k = 3, Q LNG-ORV1 =Q LNG-ORV / k=300(m 3 If the total heat required from the seawater is W / h, then the total heat required is W / h. SW =k*W SW-ORVi =k*xQ LNG-ORV1 ΔT LNG-ORVi / (a-bQ LNG-ORV1 = 47.032 (MW), the seawater flow rate Q required for each ORV gasifier SW-ORV1 =W LNG-ORV / (k*c*d*ΔT SW-ORV1 ), to get Q SW-ORV1 =2744(m) 3 / h), because it is less than the minimum film-forming flow rate Q. SW-ORV1-MIN Therefore, take Q. SW-ORV1 =3660(m) 3 / h), the final total seawater flow = k * 3660 = 10980 (m³ / h) 3 / h).

[0049] 3) When k = 2, Q LNG-ORV1 =Q LNG-ORV / k=450(m 3 If the total heat required from the seawater is W / h, then the total heat required is W / h. SW =k*W SW-ORVi =k*xQ LNG-ORV1 ΔT LNG-ORVi / (a-bQ LNG-ORV1 = 54.272 (MW), the seawater flow rate Q required for each ORV gasifier SW-ORV1 =W LNG-ORV / (k*c*d*ΔT SW-ORV1 ), to get Q SW-ORV1=4750(m) 3 / h), greater than the minimum film-forming flow rate Q SW-ORV1-MIN The final total seawater flow = k * 4750 = 9499 (m³) 3 / h).

[0050] 4) When k = 1, Q LNG-ORV1 =Q LNG-ORV / k=900(m 3 If the total heat required from the seawater is W / h, then the total heat required is W / h. SW =k*W SW-ORVi =k*xQ LNG-ORV1 ΔT LNG-ORVi / (a-bQ LNG-ORV1 = 100.83 (MW), the seawater flow rate Q required for each ORV gasifier SW-ORV1 =W LNG-ORV / (k*c*d*ΔT SW-ORV1 ), to get Q SW-ORV1 =17649(m) 3 / h), greater than the maximum seawater flow rate of a single ORV, 8500 (m³ / h). 3 / h), not feasible.

[0051] Final conclusion: k=2 is the optimal number of units to operate, with each ORV vaporizer handling 50% of the LNG vaporization load. This allocation method is the closest to the minimum film formation flow rate among all combinations, resulting in the lowest seawater flow rate and the lowest energy consumption for the seawater pumping station.

[0052] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An optimized operation method for multiple open-frame gasifiers in a liquefied natural gas (LNG) station, wherein the LNG station comprises several identical open-frame gasifiers connected in parallel, the LNG inlets flowing through all the open-frame gasifiers are connected together, and the LNG outlets flowing through all the open-frame gasifiers are connected together; the minimum seawater film formation flow rate, maximum seawater flow rate, and maximum LNG flow rate of each open-frame gasifier are all equal, characterized in that, Includes the following steps: The number of open-frame gasifiers in the liquefied natural gas station is pre-set; Obtain the seawater heat required for the operation of each open-rack gasifier, and add up the seawater heat required for the operation of each open-rack gasifier to obtain the total seawater heat of a preset number of open-rack gasifiers. Based on the total heat of seawater in the preset number of open-rack gasifiers, the seawater flow rate of each open-rack gasifier is obtained, and the seawater flow rates of each open-rack gasifier are added together to obtain the total seawater flow rate of the preset number of open-rack gasifiers. When the total seawater flow of the preset number of open-rack gasifiers is less than the total seawater flow of open-rack gasifiers that are one less than the preset number, and also less than the total seawater flow of open-rack gasifiers that are one more than the preset number, then the preset number of open-rack gasifiers is the optimal number of operating units. Based on the optimal number of operating units and the total seawater flow rate of the open-rack gasifiers at the optimal number of operating units, the optimal liquefied natural gas flow rate allocated to each open-rack gasifier is obtained.

2. The optimized operation method for multiple open-frame gasifiers in a liquefied natural gas station according to claim 1, characterized in that, The formula for obtaining the seawater heat required for the operation of each open-frame gasifier is as follows: W SW-ORVi =xQ LNG-ORVi ΔT LNG-ORVi / (a-bQ LNG-ORVi ) Among them, W SW-ORVi Q is the amount of seawater heat required for the i-th open-rack gasifier, x is the density of liquefied natural gas, and Q is the amount of heat required. LNG-ORVi ΔT is the liquefied natural gas flow rate of the i-th open-frame gasifier. LNG-ORVi It is the difference between the liquefied natural gas outlet temperature and the liquefied natural gas inlet temperature of the i-th open-frame gasifier. a and b are constants. The value of constant a ranges from 1440 to 1466, and the value of b ranges from 1 to 1.

04.

3. The optimized operation method for multiple open-frame vaporizers in a liquefied natural gas station according to claim 1, characterized in that, The formula for calculating the total heat of seawater in a preset number of open-rack gasifiers is: IN LNG-ORV-k =W LNG-ORV1 +W LNG-ORV2 +…+In LNG-ORVk Among them, W LNG-ORV-k W represents the total heat capacity of the seawater in all open-rack gasifiers. LNG-ORV1、 W LNG-ORV2 …W LNG-ORVk The respective amounts are the seawater heat for each open-frame gasifier.

4. The optimized operation method for multiple open-frame gasifiers in a liquefied natural gas station according to claim 1, characterized in that, Based on the total heat of seawater in the preset number of open-rack gasifiers, the formula for obtaining the seawater flow rate of each open-rack gasifier is as follows: Q SW-ORV1 =W LNG-ORV-k / (k*c*d*ΔT SW-ORV1 ) Among them, W LNG-ORV This is the total heat of seawater required for all open-rack gasifiers, ΔT SW-ORV1 is the temperature difference between seawater entering and exiting the open-frame gasifier, k is the number of open-frame gasifiers, c and d are constants, c is the specific heat capacity of seawater, and d is the density of seawater.

5. The optimized operation method for multiple open-frame gasifiers in a liquefied natural gas station according to claim 1, characterized in that, When the seawater flow rate of the preset number of open-frame gasifiers is less than the minimum film-forming flow rate, the seawater flow rate of the preset number of open-frame gasifiers is set to the minimum film-forming flow rate. When the seawater flow rate of the preset number of open-frame gasifiers is greater than the maximum seawater flow rate, the seawater flow rate of the preset number of open-frame gasifiers is set to the maximum seawater flow rate.

6. The optimized operation method for multiple open-frame gasifiers in a liquefied natural gas station according to claim 1, characterized in that, The formula for calculating the total seawater flow rate of the preset number of open-rack gasifiers is: Q SW-ORV-k =Q LNG-ORV1 +Q LNG-ORV2 +…+Q LNG-ORVk Among them, Q SW-ORV-k Q is the total seawater flow rate of all open-rack gasifiers, k is the number of open-rack gasifiers, and Q is the total seawater flow rate of all open-rack gasifiers. LNG-ORV1 Q LNG-ORV2 …Q LNG-ORVk These represent the seawater flow rate for each open-frame gasifier.

7. The optimized operation method for multiple open-frame gasifiers in a liquefied natural gas station according to claim 6, characterized in that, The formula for calculating the optimal liquefied natural gas flow rate allocated to each open-rack gasifier is as follows: Q LNG-ORVi =Q SW-ORV-k / k Among them, Q LNG-ORVi It is the optimal liquefied natural gas flow rate allocated to each open-rack gasifier.

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