A method and process for optimizing a warm drain gasification natural gas system for use with submerged combustion gasifiers

Abstract

The application discloses a kind of optimization method and process for reducing the gasification natural gas system of warm drainage used by submerged combustion gasifier, belong to liquefied natural gas gasification field, including: the warm drainage of power plant is directly supplied into open rack gasifier as heat source by special conveying system, set the temperature of warm drainage after heat exchange greater than 0 ℃ as only limiting condition;Based on the actual operation data of receiving station, a quantitative process model covering power plant warm drainage, low-temperature natural seawater and conventional natural seawater is constructed;According to the model, the minimum theoretical power consumption of open rack gasifier under different working conditions such as low-temperature seawater, normal temperature natural seawater and power plant warm drainage is calculated, and the operating parameters are optimized based on the calculation results.The application realizes the stable operation of open rack gasifier under low temperature condition in winter, significantly reduces the operation energy consumption and operation cost, and provides scientific and accurate operation optimization basis for liquefied natural gas receiving station.

Description

Technical Field

[0001] This invention belongs to the field of liquefied natural gas gasification technology, and particularly relates to an optimization method and process for reducing the use of submerged combustion gasifiers in a warm water gasification natural gas system. Background Technology

[0002] Liquefied Natural Gas (LNG) is clean and efficient. With the rapid development of the LNG industry, its value chain encompasses liquefaction, storage, transportation, and regasification. Due to the growth in global LNG demand and the urgent need for a low-carbon energy transition, the reliability and efficiency of LNG regasification technology have become core issues of concern in the industry. Therefore, LNG receiving terminals have become indispensable facilities in the value chain, occupying a crucial position in the energy supply network. The core function of an LNG receiving terminal is to regasify liquefied natural gas into gaseous natural gas (NG) and export it. The LNG vaporizer is the key equipment for achieving this function, directly determining the system's gas supply capacity, operating energy consumption, and economic efficiency.

[0003] Currently, the mainstream LNG vaporizers include open-rack vaporizers (ORVs) and submerged combustion vaporizers (SCVs). Open-rack vaporizers use seawater as a heat source; they are simple in structure, easy to operate and maintain, have low operating costs, and a wide load adjustment range, making them suitable for base load vaporization scenarios and the preferred vaporization equipment for LNG receiving terminals. Submerged combustion vaporizers are a type of water bath vaporizer that achieves LNG vaporization by heating a water bath through natural gas combustion. They are compact in structure, have a small footprint, fast start-up speed, high thermal efficiency, and are not limited by ambient temperature, allowing for rapid response to peak-shaving demands. They are often used as backup vaporization equipment in low-temperature winter conditions and emergency situations.

[0004] The vaporization performance of open-frame vaporizers is highly dependent on seawater temperature and quality. In the low-temperature environment of northern coastal areas during winter, the seawater temperature drops significantly, leading to a significant decrease in ORV heat exchange efficiency and even equipment freezing and inability to operate normally, making it difficult to meet the full-load vaporization demand in winter. To ensure a continuous and stable gas supply, LNG receiving terminals need to use submerged combustion vaporizers to vaporize LNG. However, SCV operation requires natural gas as fuel, and the supporting equipment such as blowers and circulating water pumps consume electricity, resulting in high operating costs. Moreover, the operation process generates a large amount of carbon dioxide flue gas, resulting in high carbon emission intensity, which does not meet the requirements of green and low-carbon development. The existing method of increasing the ORV seawater flow rate and reducing the LNG handling capacity to maintain ORV operation in low-temperature environments leads to a significant decrease in ORV vaporization efficiency, making it impossible to stably meet the external gas supply standards. This method fails to fundamentally solve the contradiction between ORV operation failure in winter and the high consumption and high emissions of SCVs, thus restricting the economic and environmental improvement of LNG receiving terminals. Therefore, how to ensure the stable operation of ORVs under low-temperature conditions and reduce the use of SCVs has become an urgent technical problem to be solved by LNG receiving terminals.

[0005] Based on the Tangshan Xintian LNG receiving terminal project, the technical solution to reduce the use of SCV (Supervised Water Treatment) is to incorporate warm wastewater from power plants into the ORV (Organic Container Receiving Unit) to replace SCV technology. Specifically, the ORV uses warm wastewater from power plants instead of natural seawater to gasify LNG. Warm wastewater from power plants is hot wastewater generated during power generation; its temperature is higher than that of natural seawater, and it contains more heat energy. Therefore, the amount of warm wastewater required for LNG gasification is less than that of natural seawater, significantly reducing pump station energy consumption, reducing carbon dioxide emissions, and better meeting environmental protection requirements. Furthermore, the average temperature of the warm wastewater from power plants is 16 degrees Celsius or higher in winter, ensuring the ORV's normal operation during winter. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes an optimized method and process for reducing the use of submerged combustion gasifiers in natural gas gasification systems, thereby resolving the issues present in the prior art.

[0007] To achieve the above objectives, the present invention provides an optimization method and process for reducing the use of submerged combustion gasifiers in liquefied natural gas (LNG) gasification systems, applicable to LNG receiving stations including open-frame gasifiers and submerged combustion gasifiers, comprising the following steps: Based on actual operating data from the receiving station, a quantitative process model for the gasification of liquefied natural gas by an open-frame gasifier covering different heat source types is constructed. The heat source types include at least low-temperature natural seawater, normal-temperature natural seawater, and power plant wastewater. The power plant's wastewater is directly supplied to the open-frame gasifier via a dedicated conveying system as a heat source, and the only limiting condition is that the wastewater temperature after heat exchange is greater than 0°C. The minimum theoretical power consumption of the open-rack gasifier under different operating conditions is calculated based on the quantitative process model. Operating parameters are then optimized based on the calculation results to enable the open-rack gasifier to operate at rated or partial load under low-temperature conditions, thereby reducing the use of submerged combustion gasifiers. In summer, when the natural seawater temperature is sufficient for the open-rack gasifier to operate at full load, it achieves full-load operation with lower energy consumption, sharing the entire load of the SCV.

[0008] Preferably, the dedicated delivery system includes: a power plant warm wastewater open channel, a connecting pipeline, a warm wastewater pumping station forebay, a water delivery pipeline, a warm wastewater pump, and an electromagnetic valve installed on the water inlet side of the open-frame gasifier; the power plant warm wastewater is sequentially transported through the power plant warm wastewater open channel, connecting pipeline, warm wastewater pumping station forebay, warm wastewater pump, and water delivery pipeline to the seawater pumping station forebay of the liquefied natural gas receiving station, and the electromagnetic valve enables independent switching control between the supply of warm wastewater and natural seawater to the open-frame gasifier.

[0009] Preferably, the quantitative process model is constructed based on the measured seasonal temperature characteristics of natural seawater and power plant thermal discharge in the geographical area where the liquefied natural gas receiving station is located. The model input parameters include the inlet and outlet temperatures of the heat source, the heat source flow rate, the inlet and outlet temperatures of the liquefied natural gas, the liquefied natural gas flow rate, and the pressure.

[0010] Preferably, the minimum theoretical power consumption is calculated according to the following formula: ; ; Where, m water-cal Let p be the natural seawater mass flow rate, and m be the LNG pressure. LNG For LNG mass flow rate, t LNG-out t is the LNG outlet temperature. LNG-in t is the LNG inlet temperature. water-in The natural seawater inlet temperature, t water-out P represents the natural seawater outlet temperature. min-cal This represents the minimum theoretical power consumption when using natural seawater. water-cal2 Natural seawater mass flow rate after adding warm water discharge, m ww For the mass flow rate of the warm water discharge, t ww-in The inlet temperature of the power plant's thermal wastewater is t. ww-out P represents the outlet temperature of the power plant's thermal wastewater. min-cal2 This represents the minimum theoretical power consumption when the power plant's thermal discharge is included.

[0011] Preferably, the different operating conditions include the condition that the natural seawater temperature is lower than the normal operating threshold in winter and the condition that the natural seawater temperature is higher than the normal operating threshold in summer, and different replacement strategies for the submerged combustion gasifier are formulated for each type of operating condition.

[0012] Preferably, the optimized operating parameters include the calculation results based on the quantitative process model, adjusting the heat source type, heat source flow rate and liquefied natural gas flow rate of the open-frame gasifier, so as to minimize the total power consumption of the system while meeting the gasification requirements.

[0013] Preferably, the method also includes a comprehensive comparative analysis of operating costs based on the calculation results of the minimum theoretical power consumption of the open-frame gasifier, using low-temperature seawater, natural seawater, power plant warm water discharge, and submerged combustion gasifier, to obtain hourly, daily, monthly, and annual energy consumption and cost savings data.

[0014] Preferably, the seasonal temperature characteristics of the power plant's thermal wastewater serve as the core basis for constructing the quantitative process model, wherein the temperature of the power plant's thermal wastewater in winter is higher than that of natural seawater and remains stable above the threshold that ensures the normal operation of the open-frame gasifier.

[0015] Preferably, the method is applied to a liquefied natural gas receiving station with a preset natural gas turnover capacity, which is equipped with an open-frame gasifier and a submerged combustion gasifier, and has known equipment parameters and energy prices as the basis for calculating operating costs.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: This invention utilizes the technical feature of "directly supplying power plant wastewater to an open-frame gasifier as a heat source via a dedicated conveying system." Taking advantage of the stable temperature of the power plant wastewater, which is significantly higher than that of natural seawater, it replaces natural seawater as the heat source for the open-frame gasifier. This allows the open-frame gasifier to operate normally even when the natural seawater temperature is too low in winter, solving the problems of equipment icing and shutdown caused by low seawater temperatures and ensuring a stable gas supply capacity for LNG receiving stations during winter. In summer, when the natural seawater temperature is sufficient for the ORV to operate at full load, the use of the even warmer power plant wastewater and natural seawater together as the heat source for ORV operation enables the ORV to operate at full load with lower energy consumption.

[0017] This invention establishes a multi-heat-source quantitative process model that closely aligns with actual engineering practices by "constructing a quantitative process model for the gasification of liquefied natural gas using open-frame gasifiers covering different heat source types based on actual operating data from receiving stations." This model accurately reflects the heat exchange characteristics of open-frame gasifiers under different heat source temperatures and flow rates, providing a scientific basis for optimizing operating parameters. It changes the existing technology's reliance on extensive experience-based operations, making operational decisions more precise and reliable.

[0018] This invention, through its technical feature of "calculating the minimum theoretical power consumption of an open-rack gasifier under different operating conditions based on a process model, and optimizing operating parameters based on the calculation results," can calculate the minimum theoretical power consumption to meet gasification requirements for different heat source conditions and load demands, and optimize key operating parameters such as heat source type selection and heat source flow matching accordingly. This technical feature ensures that the system always operates in an energy-optimal state, minimizing the operating cost of the open-rack gasifier.

[0019] This invention, through its technical feature of "reducing the use of submerged combustion gasifiers under low-temperature conditions," integrates the synergistic effects of the aforementioned heat source substitution, process breakthroughs, model building, and parameter optimization. This enables open-frame gasifiers to effectively replace submerged combustion gasifiers in gasification tasks under low-temperature winter conditions. This technical feature directly reduces the frequency of submerged combustion gasifier use, thereby significantly reducing power consumption and operating costs, achieving the goals of saving electricity and reducing operating costs while ensuring gas supply security.

[0020] This invention constructs a complete technology chain, from heat source extraction and process breakthroughs to model building and parameter optimization, through the overall combination of all technical features. The technical solution is customized based on the actual engineering parameters of a specific liquefied natural gas receiving station. The various technical features support and synergize with each other, forming a practical and targeted complete solution that can be directly promoted and applied in similar projects. Attached Figure Description

[0021] 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: Figure 1 This is a process flow diagram of the heated water vaporization natural gas system of the present invention; Figure 2 This is the SCV gasification LNG process model of the present invention; Figure 3 This is the ORV gasification LNG process model of the present invention; Figure 4 The operating cost of SCV gasification of LNG according to the present invention; Figure 5 This is a schematic diagram illustrating the minimum theoretical power consumption of the ORV for gasifying LNG using low-temperature natural seawater, as per the present invention. Figure 6 This is a schematic diagram illustrating the operating costs of the ORV (Oriented Vehicle) of this invention, which uses cryogenic natural seawater to vaporize LNG. Figure 7 This is a schematic diagram illustrating the minimum theoretical power consumption of the ORV for gasifying LNG using ambient temperature natural seawater according to the present invention. Figure 8This is a schematic diagram illustrating the operating costs of the ORV (Oriented Vehicle) of this invention, which uses ambient temperature natural seawater to vaporize LNG. Figure 9 This is a schematic diagram illustrating the minimum theoretical power consumption of the ORV of the present invention for gasifying LNG using thermal wastewater from a power plant. Figure 10 This is a schematic diagram illustrating the operating costs of the ORV (Oriented Vehicle) of the present invention, which uses thermal wastewater from a power plant to vaporize LNG. Among them, 1. Power plant warm water drainage open channel; 2. Connecting pipeline; 3. Warm water drainage pump station forebay; 4. Water transmission pipeline; 5. Warm water drainage pump; 6. Seawater pump; 7. Seawater pump station forebay of LNG receiving terminal; 8. Seawater pipeline; 9. Seawater; 10. Solenoid valve; 11. Open frame vaporizer; 12. Vaporizer water transmission pipeline; 13. Solenoid valve; 14. Intermediate medium vaporizer; 15. Liquefied natural gas; 16. Cold water; 17. First burner; 18. Second burner; 19. Natural gas; 20. Hot water; 21. Seawater after heat exchange. Detailed Implementation

[0022] 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.

[0023] 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.

[0024] Example 1 This embodiment provides an optimization method and process for a warm water vaporization natural gas system that reduces the use of submerged combustion gasifiers. Applied to liquefied natural gas receiving stations including open-frame gasifiers and submerged combustion gasifiers, it enables open-frame gasifiers to operate at rated or partial load under low-temperature conditions, thereby reducing or eliminating the use of submerged combustion gasifiers. In summer, when natural seawater temperatures are sufficient for full-load operation of open-frame gasifiers, it enables them to operate at full load with lower energy consumption, sharing the full load of the submerged combustion gasifiers. The process includes the following steps: Step 1: The power plant's wastewater is directly supplied to the open-frame gasifier via a dedicated conveying system as a heat source, and the only limiting condition is that the temperature of the wastewater after heat exchange is greater than 0℃. Furthermore, the dedicated delivery system includes: a power plant warm wastewater open channel, a connecting pipeline, a warm wastewater pumping station forebay, a water delivery pipeline, a warm wastewater pump, and an electromagnetic valve installed on the water inlet side of the open-frame gasifier; the power plant warm wastewater is sequentially transported through the power plant warm wastewater open channel, connecting pipeline, warm wastewater pumping station forebay, warm wastewater pump, and water delivery pipeline to the seawater pumping station forebay of the liquefied natural gas receiving station, and the electromagnetic valve enables independent switching control of the supply of warm wastewater and natural seawater to the open-frame gasifier.

[0025] Furthermore, the power plant's wastewater undergoes heat exchange in an open-frame gasifier before being discharged into the power plant's circulating water pump house forebay via the gasifier's water delivery pipeline.

[0026] Step 2: Based on the actual operating data of the receiving station, construct a quantitative process model for the gasification of liquefied natural gas by open-frame gasifiers covering different heat source types, wherein the heat source types include at least power plant wastewater. Furthermore, the quantitative process model is constructed based on the measured seasonal temperature characteristics of natural seawater and power plant thermal discharge in the geographical area where the liquefied natural gas receiving station is located. The model input parameters include heat source temperature, heat source flow rate, liquefied natural gas temperature, liquefied natural gas flow rate, and pressure.

[0027] Furthermore, the seasonal temperature characteristics of the power plant's thermal discharge and its calorific value exceeding that of natural seawater serve as the core basis for constructing a quantitative process model. In winter, the temperature of the power plant's thermal discharge is higher than that of natural seawater and remains stable above the threshold that ensures the normal operation of the open-frame gasifier.

[0028] Step 3: Calculate the minimum theoretical power consumption of the open-frame gasifier under different operating conditions based on the quantitative process model, and optimize the operating parameters based on the calculation results to reduce the use of submerged combustion gasifiers under low temperature conditions.

[0029] Furthermore, the different operating conditions include the condition that the natural seawater temperature is lower than the normal operating threshold in winter and the condition that the natural seawater temperature is higher than the normal operating threshold in summer, and different replacement strategies for the submerged combustion gasifier are formulated for each type of operating condition.

[0030] Furthermore, the optimized operating parameters include the calculation results based on the quantitative process model, adjusting the heat source type, heat source flow rate and liquefied natural gas flow rate of the open-frame gasifier, so as to minimize the total power consumption of the system while meeting the gasification requirements.

[0031] Furthermore, the method also includes a comprehensive comparative analysis of the operating costs of power plant thermal discharge, natural seawater, and submerged combustion gasifier based on the calculation results of the minimum theoretical power consumption, to obtain hourly, daily, monthly, and yearly energy consumption and cost savings data.

[0032] Furthermore, the method is applied to a liquefied natural gas receiving station with a preset natural gas turnover capacity, which is equipped with open-frame gasifiers and submerged combustion gasifiers, and has known equipment parameters and energy prices as the basis for calculating operating costs.

[0033] Furthermore, the power range of the LNG low-pressure pump in the pump set is 150-400 kW; The power range of the LNG high-pressure pump in the pump set is 1500-4000 kW; The power range of the natural seawater pumps in the pump set is 600-2000 kW; The number of SCV gasification systems ranges from 1 to 20. The number of ORVs in the gasification system ranges from 1 to 20. The rated load for the SCV gasification system to gasify LNG is 180-220 t / h; The rated load for the ORV gasification system to gasify LNG is 180-220 t / h; The lower load for the ORV gasification system to gasify LNG is 20-150 t / h; The ORV cryogenic seawater inlet temperature is 0.5-6.5 ℃; The inlet temperature of the ORV (Oriented Oriented Vacuum) seawater is 7.5-30℃. The inlet temperature of the power plant's thermal wastewater is 10-50℃; The LNG inlet temperature in the ORV is -175 to -100 ℃; The LNG inlet temperature in the SCV is -175 to -100 ℃; The LNG outlet temperature in the ORV is 0-10 ℃; The LNG outlet temperature in the SCV is 0-10 ℃; The natural seawater inlet flow rate in the ORV is 3000-20000 t / h; The inlet flow rate of the power plant's thermal drainage in the ORV is 3000-20000 t / h.

[0034] In this embodiment, warm wastewater from the power plant is used instead of the natural seawater used in the open-frame gasifier. The heat from the warm wastewater is extracted, turning waste into treasure and enabling the open-frame gasifier to operate normally under low-temperature seawater conditions, thereby reducing the use of submerged combustion gasifiers. Furthermore, the high temperature of the warm wastewater reduces the water consumption of the open-frame gasifier, saving the electrical energy consumed by the seawater pump during LNG gasification.

[0035] Table 1 shows the seasonal temperatures of the Caofeidian sea area and the hydroelectric power plant's thermal discharge. The average annual seawater temperature is 14℃, with a maximum summer temperature of 26.0℃ and a minimum winter temperature of -1.7℃. The average seawater temperature is below 7℃ for three months, and the maximum seasonal temperature variation is 27.7℃ (-1.7℃ to 26℃). The hydroelectric power plant's thermal discharge has the highest temperature in August (37.2℃) and the lowest temperature in March (16.8℃).

[0036] Table 1 SCV operation is unaffected by ambient temperature; it only requires NG fuel gas to vaporize LNG, allowing for year-round operation and rapid stable operation after startup. The only power-consuming equipment is the LNG pump, combustion blower, and cooling water pump in the supporting facilities, resulting in stable power consumption. Table 2 shows the SCV power-consuming equipment, and Table 3 shows the SCV operating costs. Operating costs are based on the local electricity price of RMB 0.6 / kW·h and the fuel gas price of RMB 3.36 / kg. The total power consumption of the SCV is 2880kW, with a daily power consumption of 69120kW·h, a monthly power consumption of 2073600kW·h, and an annual power consumption of 24883200kW·h.

[0037] Table 2 Table 3 The following is a scenario-based discussion of adding ORV to power plant thermal drainage to replace SCV: ① Under the most extreme conditions, natural seawater cannot be drawn during winter, and ORV and IFV cannot operate. Almost all LNG vaporization is provided by SCV. In this case, adding warm water can minimize the vaporization volume and cost of SCV.

[0038] ② In winter, when the natural seawater temperature is around 5℃, without a warm drainage supply, the natural seawater cannot guarantee the full-load operation of the ORV and IFV combined transport system within the flow range that the pump set can handle. Therefore, the natural gas supply will be insufficient to meet demand in winter. According to preliminary calculations, the available load of ORV and IFV is only 55% of the rated gasification capacity. At this time, the addition of warm drainage can significantly reduce the gasification volume and cost of SCV.

[0039] ③ In summer, when the natural seawater temperature is around 20℃ and there is no supply of warm drainage, the natural seawater can ensure the full-load operation of the ORV within the flow range that the pump set can handle. At this time, the addition of warm drainage can further reduce system energy consumption and carbon emissions.

[0040] Based on the ORV operation data of the Caofeidian LNG receiving terminal, a gasifier process model and mathematical model that fit the actual site conditions were established. The minimum seawater flow rate required for LNG gasification can be obtained under different operating conditions, and then the minimum theoretical power consumption of each gasifier in the LNG receiving terminal under different operating conditions can be obtained.

[0041] The specific parameters of the ORV energy-consuming equipment are shown in Table 4. The total power of the LNG pumps is 2390kW (one high-pressure pump and one low-pressure pump), with each high-pressure pump having a power of 2140kW and each low-pressure pump having a power of 250kW. Each ORV requires one seawater pump to operate, with a single seawater pump having a power of 880kW. Actual operating costs of the vaporizer also include the energy consumption of the seawater cleaning machine, rotary filter, and alkali solution, but these are relatively small compared to the energy consumption of the seawater pump and fuel gas, so they are ignored in the cost comparison analysis.

[0042] Table 4 The ORV mathematical model is shown below: ; ; Among them, c water For the specific heat capacity of seawater, m water For seawater mass flow rate, t water-in The seawater inlet temperature, t water-out c is the seawater outlet temperature. LNG For the specific heat capacity of LNG, m LNG Let t be the LNG mass flow rate, t be the seawater temperature, and p be the LNG pressure. LNG-in t is the LNG inlet temperature. LNG-out P is the LNG outlet temperature. min-cal The minimum theoretical power consumption is given by k, where ΔH is the latent heat of vaporization. p is the proportionality coefficient, and A, B, and C are correction coefficients.

[0043] From this, a mathematical model for seawater mass flow rate and minimum theoretical power consumption can be derived: ; The mathematical model for ORV after adding warm water is as follows: ; Where, m water-cal The calculated natural seawater mass flow rate is given by p, where p is the LNG pressure and m is the LNG pressure. LNG For LNG mass flow rate, t LNG-out t is the LNG outlet temperature. LNG-in t is the LNG inlet temperature. water-in The natural seawater inlet temperature, twater-out P is the natural seawater outlet temperature. min-cal This represents the minimum theoretical power consumption when using natural seawater. water-cal2 Natural seawater mass flow rate after adding warm water discharge, m ww For the mass flow rate of the warm water discharge, t ww-in The inlet temperature of the power plant's thermal wastewater is t. ww-out P represents the outlet temperature of the power plant's thermal wastewater. min-cal2 This represents the minimum theoretical power consumption when the power plant's thermal discharge is included.

[0044] Based on the temperature data of seawater and warm wastewater, the following parameters were set: low-temperature natural seawater 2.5-6.5℃, natural seawater temperature 7.5-26℃, warm wastewater temperature 16.5-37.5℃, LNG input rate 150-400t / h, LNG pressure 10mpag, LNG inlet temperature -160℃, and LNG outlet temperature 3℃. The minimum theoretical power consumption of ORV under different loads was calculated and compared under different operating conditions. Table 5 shows the detailed parameters of each scheme.

[0045] Table 5 Table 6 shows the power consumption of ORV using low-temperature natural seawater, Table 7 shows the power consumption of ORV using natural seawater, and Table 8 shows the power consumption of ORV using warm water discharge. This data is based on the minimum theoretical power consumption under different operating conditions in natural seawater, obtained from the ORV process model and mathematical model.

[0046] Table 6 Table 7 Table 8 As shown in Tables 6, 7, and 8, the ORV gasification of LNG under the condition of adding power plant warm water discharge has the best efficiency. Compared with LNG gasification under the condition of low temperature natural seawater, it can save a maximum of 124,623 kWh of electricity per day, 3,738,708 kWh of electricity per month, and 44,864,496 kWh of electricity per year. Compared with LNG gasification under the condition of natural seawater, it can save a maximum of 4,693 kWh of electricity per day, 140,803 kWh of electricity per month, and 1,689,638 kWh of electricity per year.

[0047] As shown in the tables, the ORV achieves optimal LNG vaporization efficiency under the conditions of 1000 t / h warm wastewater and 10 mpag LNG pressure. Compared to LNG vaporization under natural seawater conditions, it saves a maximum of 4693 kWh of electricity per day, 140803 kWh per month, and 1689638 kWh per year. Table 9 shows the operating costs of the ORV using low-temperature natural seawater, Table 10 shows the operating costs of the ORV using natural seawater, and Table 11 shows the operating costs of the ORV using warm wastewater. These data are based on the ORV process model and mathematical model, representing the operating costs under different conditions for natural seawater and warm wastewater.

[0048] Table 9 Table 10 Table 11 Therefore, it is evident that adding ORV to LNG under power plant warm wastewater conditions yields the best cost savings. Compared to LNG gasification under low-temperature natural seawater conditions, it can save a maximum of 74,774 yuan per day, 2.24 million yuan per month, and 26.92 million yuan per year. Compared to operating costs under natural seawater conditions, it can save a maximum of 2,816 yuan per day, 84,484 yuan per month, and 1.01 million yuan per year.

[0049] Compared with the operating costs of SCV, the addition of ORV to gasify LNG under the condition of power plant warm wastewater can save up to RMB 264,000 per day, RMB 7.907 million per month, and RMB 94.88 million per year in operating costs.

[0050] In conclusion, using wastewater gasification systems can significantly reduce operating costs and can replace the use of SCVs, offering substantial economic and social benefits. Furthermore, this technology utilizes the waste heat from power plant wastewater to replace natural gas combustion, effectively reducing carbon dioxide emissions. It holds significant engineering application value and industry demonstration significance for promoting energy structure optimization and sustainable operation of receiving terminals.

[0051] The technical solution of this embodiment is as follows: the warm wastewater from the power plant is discharged from the open channel of the power plant into the forebay of the warm wastewater pumping station, and then from the forebay of the warm wastewater pumping station is discharged into the seawater pumping station forebay of the LNG receiving station through the water transmission pipeline. The seawater pump then pressurizes the warm wastewater and flows it into the ORV, where it exchanges heat with the LNG in the ORV, thereby vaporizing the LNG.

[0052] This embodiment provides an optimized method and process for reducing the use of submerged combustion gasifiers in a warm wastewater gasification natural gas system. It utilizes the waste heat from the power plant's warm wastewater to reduce pump station power consumption, while simultaneously reducing the use of submerged combustion gasifiers, lowering operating costs, and protecting the environment.

[0053] Figure 1 This is a process flow diagram of a heated water vaporization natural gas system. Figure 1 In the process, warm wastewater first flows from the power plant's warm wastewater open channel 1 through connecting pipe 2 into the warm wastewater pumping station forebay 3. Warm wastewater pump 5 then pumps the warm wastewater through water pipeline 4 into the seawater pumping station forebay 7 of the LNG receiving terminal. Seawater 9 typically flows into the seawater pumping station forebay 7 of the LNG receiving terminal through seawater pipeline 8. When the open-frame vaporizer 11 and intermediate medium vaporizer 14 vaporize LNG, solenoid valves 10 and 13 open, and seawater pump 6 pumps warm wastewater through vaporizer water pipeline 12 into the vaporizer, where it exchanges heat with the LNG, thus vaporizing the LNG.

[0054] Figure 2 This is a model for the SCV-to-LNG gasification process. Figure 2 In the process, cold water 16 is heated into hot water 20 by the first burner 17 and then enters the second burner 18. Liquefied natural gas 15 also enters the second burner 18 and exchanges heat with the hot water 20, and is gasified into natural gas 19.

[0055] Figure 3 This is a model for the ORV (Organic Rotary Vehicle) gasification of LNG process. Figure 3 In the process, seawater 9 enters the open-frame gasifier 11, and liquefied natural gas 15 enters the open-frame gasifier 11 to exchange heat with seawater 9. The temperature of seawater 9 drops to seawater 21 after heat exchange, and liquefied natural gas 15 is gasified into natural gas 19.

[0056] Figure 4 The operating costs for SCV-gasified LNG.

[0057] Figure 5 This diagram illustrates the minimum theoretical power consumption for ORV (Organic Container Vehicle) to vaporize LNG using cryogenic natural seawater. Figure 6 A schematic diagram illustrating the operating costs of using cryogenic natural seawater to gasify LNG for ORV.

[0058] Figure 7 A schematic diagram illustrating the minimum theoretical power consumption for ORV (Organic Container Vehicle) to vaporize LNG using ambient temperature natural seawater. Figure 8 A schematic diagram illustrating the operating costs of using ambient temperature natural seawater to gasify LNG for ORV.

[0059] Figure 9 A schematic diagram illustrating the minimum theoretical power consumption for ORV (Organic Container Vehicle) to gasify LNG using wastewater from a power plant. Figure 10 A schematic diagram illustrating the operating costs of using power plant thermal wastewater to gasify LNG for ORV.

[0060] 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. A method and process for optimizing a natural gas gasification system that reduces the use of submerged combustion gasifiers, applied to a liquefied natural gas receiving station including open-frame gasifiers and submerged combustion gasifiers, characterized in that... Includes the following steps: An optimized method and process for an open-frame gasifier (ORV) that uses power plant wastewater or a combination of power plant wastewater and natural seawater to gasify natural gas, thereby reducing the use of submerged combustion gasifiers (SCVs); specifically, based on the principle of a circular economy, it uses power plant wastewater and natural seawater as a heat source for liquefied natural gas (LNG) regasification; in winter, when the natural seawater temperature is extremely low and cannot support ORV operation, the use of power plant wastewater to gasify LNG allows the ORV to operate at rated or higher loads, reducing or eliminating the use of SCVs; during the spring and autumn transition seasons, natural seawater... When seawater temperature is insufficient to fully support ORV operation at rated load, both power plant wastewater and natural seawater are used as heat sources for ORV operation, enabling ORV to operate at rated load or partial load and share some or all of the load of SCV. In summer, when natural seawater temperature can meet ORV's full-load operation, both higher-temperature power plant wastewater and natural seawater are used as heat sources for ORV operation, enabling ORV to operate at full load with lower energy consumption and share all of SCV's load. The flow load distribution of ORV and SCV is precisely matched to reduce SCV usage and lower energy costs.

2. The method and process according to claim 1, characterized in that, The power plant's warm wastewater is directly supplied to the open-frame gasifier as a heat source via a dedicated transmission system, and the only limiting condition is that the temperature of the warm wastewater after heat exchange is greater than 0°C. Based on the actual operating data of the receiving station, a quantitative process model for the gasification of liquefied natural gas by the open-frame gasifier, which covers different heat source types, is constructed. The heat source types are power plant warm wastewater or power plant warm wastewater-natural seawater combined. The minimum theoretical power consumption of the open-frame gasifier under different operating conditions is calculated based on the quantitative process model, and the operating parameters are optimized based on the calculation results to reduce the use of submerged combustion gasifiers under low temperature conditions.

3. The method and process according to claim 2, characterized in that, The dedicated delivery system includes: a power plant warm wastewater open channel, a connecting pipeline, a warm wastewater pump station forebay, a water delivery pipeline, a warm wastewater pump, and an electromagnetic valve installed on the water inlet side of the open-frame gasifier. The power plant warm wastewater is sequentially transported through the power plant warm wastewater open channel, connecting pipeline, warm wastewater pump station forebay, warm wastewater pump, and water delivery pipeline to the seawater pump station forebay of the liquefied natural gas receiving station. The electromagnetic valve enables independent switching control between the supply of warm wastewater and natural seawater to the open-frame gasifier.

4. The method and process according to claim 3, characterized in that: The specific process of directly supplying the power plant's wastewater to the open-frame gasifier as a heat source via a dedicated transmission system includes: the wastewater is discharged from the power plant's open channel into the wastewater pumping station forebay, and then from the wastewater pumping station forebay through a water pipeline into the seawater pumping station forebay of the liquefied natural gas receiving station. The seawater pump then pressurizes the wastewater and flows it into the open-frame gasifier, where it exchanges heat with the liquefied natural gas inside the gasifier, thereby gasifying the liquefied natural gas.

5. The method and process according to claim 2, characterized in that, The quantitative process model is constructed based on the measured seasonal temperature characteristics of natural seawater and power plant thermal discharge in the geographical area where the LNG receiving station is located. The model input parameters include heat source temperature, heat source flow rate, LNG temperature, LNG flow rate and pressure. It is applied to LNG receiving stations with preset natural gas turnover capacity, which are equipped with open-frame gasifiers and submerged combustion gasifiers, and have known equipment parameters and energy prices as the basis for calculating operating costs.

6. The method and process according to claim 2, characterized in that, The minimum theoretical power consumption is calculated according to the following formula: ； Where, m water-cal Let p be the natural seawater mass flow rate, and m be the LNG pressure. LNG For LNG mass flow rate, t LNG-out t is the LNG outlet temperature. LNG-in t is the LNG inlet temperature. water-in The natural seawater inlet temperature, t water-out P represents the natural seawater outlet temperature. min-cal To determine the minimum theoretical power consumption when using natural seawater, m water-cal2 Natural seawater mass flow rate after adding warm water discharge, m ww For the mass flow rate of thermal wastewater from the power plant, t ww-in The inlet temperature of the power plant's thermal wastewater is t. ww-out P represents the outlet temperature of the power plant's thermal wastewater. min-cal2 This represents the minimum theoretical power consumption when the power plant's thermal discharge is included.

7. The method and process according to claim 2, characterized in that, The different operating conditions include low-temperature natural seawater conditions, normal-temperature natural seawater conditions, and the use of power plant warm water discharge conditions. Different replacement strategies for submerged combustion gasifiers using warm water discharge are formulated for each type of operating condition. With minimizing the total energy consumption of the system as the primary goal, combined operating condition simulations are conducted for different seasons, different heat source conditions, and different liquefied natural gas load demands.

8. The method and process according to claim 1, characterized in that, By establishing a gasification process model and mathematical model for an open-frame gasifier, the minimum heat source flow rate and corresponding pump power consumption required to meet gasification requirements under different drainage temperatures, seawater temperatures, and liquefied natural gas flow rates are calculated. Based on the calculation results, heat source scheduling strategies for different seasons and operating conditions are formulated to achieve the lowest total system energy consumption.

9. The method and process according to claim 1, characterized in that, It also includes a comprehensive comparative analysis of operating costs based on the calculation results of minimum theoretical power consumption, comparing the operating costs of power plant thermal drainage, natural seawater, and submerged combustion gasifier, and obtaining hourly, daily, monthly, and yearly energy consumption and cost savings data.

10. The optimization method and process according to claim 1, characterized in that, The power range of the LNG low-pressure pump in the pump set is 150-400 kW; The power range of the LNG high-pressure pump in the pump set is 1500-4000 kW; The power range of the natural seawater pumps in the pump set is 600-2000 kW; The number of SCV gasification systems ranges from 1 to 20. The number of ORVs in the gasification system ranges from 1 to 20. The rated load for the SCV gasification system to gasify LNG is 180-220 t / h; The rated load for the ORV gasification system to gasify LNG is 180-220 t / h; The lower load for the ORV gasification system to gasify LNG is 20-150 t / h; The ORV cryogenic seawater inlet temperature is 0.5-6.5 ℃; The inlet temperature of the ORV (Oriented Oriented Vacuum) seawater is 7.5-30℃. The inlet temperature of the power plant's thermal wastewater is 10-50℃; The LNG inlet temperature in the ORV is -175 to -100 ℃; The LNG inlet temperature in the SCV is -175 to -100 ℃; The LNG outlet temperature in the ORV is 0-10 ℃; The LNG outlet temperature in the SCV is 0-10 ℃; The natural seawater inlet flow rate in the ORV is 3000-20000 t / h; The inlet flow rate of the power plant's thermal drainage in the ORV is 3000-20000 t / h.

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