LNG vaporization system and method based on dual cold storage cycle

Abstract

The application provides a LNG gasification system and method based on double cold storage cycle, belonging to the technical field of marine engineering, comprising a first gasification cold storage unit, a second gasification cold storage unit and a third open gasification unit, and a controller of a cold storage distribution control system is connected with each instrument on the first and second gasification cold storage units. The LNG heating carrier of the first and second gasification cold storage units is liquid cold storage carrier from a cold storage cabin, and the LNG heating carrier of the third open gasification unit is environmental seawater. According to the different functional needs of LNG gasification cold storage and the fluctuation needs of LNG gasification flow, the application adjusts the cold storage carrier flow and controls the series-parallel mode of the first and second gasification cold storage units, solves the problem of matching of cold storage and gasification functions, and stabilizes the cold storage carrier in a specified temperature range after cold storage, and realizes the efficiency and safety of cold storage and cold storage.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology, and in particular relates to an LNG gasification system and method based on a dual cold storage cycle. Background Technology

[0002] LNG, as a highly efficient energy source, contains a large amount of cold energy. Developing efficient cold storage and transportation functions during LNG gasification is particularly important for cold storage in other locations.

[0003] Currently, the technology based on LNG vaporization cold storage involves storing the cold energy generated during LNG vaporization using a cold storage carrier. The cold storage carrier is then stored in a cold storage chamber according to different temperature qualities to supply cold energy to users in other locations who need it, providing them with cold energy of different temperatures and qualities.

[0004] Fluctuations in the LNG vaporization process often result in fluctuations in the generated cold energy. In LNG vaporization cold storage operations, the passive influence of these fluctuations in LNG flow rates leads to low efficiency in cold energy extraction and storage. Inadequate temperature control of the cooled medium can also pose safety hazards to the cold storage system and storage chamber.

[0005] To meet the operational requirements of LNG vaporization cold storage, it is necessary not only to ensure the high efficiency of cold storage carriers in large-scale operations, but also to adapt to the fluctuations in LNG vaporization and to precisely control the low temperature of the cold storage carriers entering the cold storage chamber. However, simply controlling the flow rate of the cold storage carriers through the LNG vaporization cold storage unit is insufficient to adapt to the fluctuations in LNG vaporization, and it is also impossible to precisely control the output temperature of the cold storage carriers and ensure the safety of system operation.

[0006] Therefore, a rapid and efficient cold storage system and method are needed to adapt to fluctuations in LNG input. This system and method should ensure the stable extraction and precise control of LNG cold energy during LNG vaporization, even when the LNG inlet volume fluctuates, to achieve rapid and efficient recovery of LNG cold energy. Furthermore, the system should consider the efficiency, safety, and functional flexibility required for LNG energy utilization. Summary of the Invention

[0007] The problem to be solved by the present invention is to provide an LNG gasification system and method based on a dual cold storage cycle.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an LNG gasification system based on a dual-cold storage cycle, comprising an LNG gasification module, a cold storage chamber, and a cold storage distribution control system. The LNG gasification module includes a first gasification cold storage unit, a second gasification cold storage unit, and a third open gasification unit. The inlets of the first and second gasification cold storage units are connected to an LNG input port, and the outlets of the first and second gasification cold storage units are connected to the inlet of the third open gasification unit. The outlet of the third open gasification unit is connected to a natural gas output port. The first and second gasification cold storage units are functionally connected... The switching valve group performs series-parallel switching; the first and second gasification cold storage units are respectively connected to several cold storage chambers through pipelines, and the cold storage carrier is transferred to adjacent cold storage chambers or gasification cold storage units by the cold storage chamber pumps of each cold storage chamber, forming independent first and second cold storage carrier circulation loops respectively; the cold storage distribution control system adjusts the flow rate of the cold storage carrier entering the first or second gasification cold storage unit and controls the series-parallel switching of the first and second gasification cold storage units according to the monitored flow rate and temperature signals of the cold storage carrier and the LNG flow rate and temperature signals, thereby realizing the control of the temperature of the cold storage carrier entering the cold storage chamber.

[0009] Furthermore, the first and second gasification cold storage units are LNG closed-loop gasifiers, and the LNG gasification heat medium is a cold storage carrier from the cold storage chamber; the third open-loop gasification unit is an open-loop gasifier, and the heating medium is ambient seawater.

[0010] Furthermore, the cold storage carrier circulation loop between the first and second cold storage carrier circulation loops is achieved through the cold storage tank pump and overflow pipeline, transferring the cold storage carrier until it is stored in the first or second gasification cold storage unit before being output to the cold storage tank, thus completing the cold storage carrier circulation loop. The cold storage tank pump draws the cold storage carrier from the top of the cold storage tank and injects it into the bottom of the adjacent cold storage tank or the gasification cold storage unit. The advantage of the overflow cold storage method is that it utilizes the difference in density between the hot and cold states of the cold storage carrier in the cold storage tank, and the stratification of the cold storage carrier within the tank. By transporting the cold storage carrier tank by tank, the high and low temperature cold storage carriers are quickly displaced, achieving effective cold storage. The cold storage replacement of all cold storage tanks is completed in a short time, without changing the stability and draft difference of the ship, with minimal impact on the local strength of the ship, and it is easy to operate.

[0011] Furthermore, the cold storage distribution control system completes the series-parallel conversion by controlling the functional switching valve group between the first gasification cold storage unit and the second gasification cold storage unit. The functional switching valve group includes a first functional switching valve, a second functional switching valve, and a third functional switching valve. The first functional switching valve is installed on the pipeline between the LNG inlet and the inlet of the second gasification cold storage unit. The second functional switching valve is installed on the pipeline between the outlet of the first gasification cold storage unit and the outlet of the second gasification cold storage unit. The third functional switching valve is installed on the pipeline between the outlet of the first gasification cold storage unit and the inlet of the second gasification cold storage unit.

[0012] Furthermore, when the first and second gasification cold storage units are operated in series, the cold storage distribution control system controls the closure of the first and second function switching valves and the opening of the third function switching valve. The cold storage carrier passes through the first and second cold storage carrier circulation loops respectively. The first gasification cold storage unit is set to a relatively low-temperature first gasification cold storage cycle, and the second gasification cold storage unit is set to a relatively high-temperature second gasification cold storage cycle. In the series mode, the cold storage carrier flow rate is relatively low, maximizing the utilization efficiency of LNG gasification heat. When the first and second gasification cold storage units are operated in parallel, the cold storage distribution control system controls the opening of the first and second function switching valves and the closing of the third function switching valve. The inlets of the first and second gasification cold storage units are simultaneously connected to liquid LNG. The natural gas vaporized by the first and second gasification cold storage units enters the third open gasification unit through the gas phase manifold outlet. After passing through the third open gasification unit, the natural gas reaches normal temperature and is connected to the shore-end user. In parallel mode, it meets the demand for larger LNG vaporization volume and realizes the cold storage operation of a relatively large flow of cold storage carrier, thereby maximizing the LNG vaporization and cold storage speed. Parallel operation is generally used during peak LNG vaporization periods or when there is a high demand for cold storage speed.

[0013] Furthermore, after passing through the first gasification cold storage unit and the second gasification cold storage unit, the cold storage carrier is distributed to its respective cold storage chamber through an independent closed-loop circulation. In the combination mode of the dual gasification cold storage unit with the first gasification cold storage unit and the second gasification cold storage unit, the output temperature of the cold storage carrier can be controlled according to the cold storage needs, and stored in different cold storage chambers. The combination modes include three modes: single gasification cold storage unit operation (either the first gasification cold storage unit or the second gasification cold storage unit), series operation of the first gasification cold storage unit and the second gasification cold storage unit, and parallel operation of the first gasification cold storage unit and the second gasification cold storage unit.

[0014] Due to the use of the above three combination modes and the cold storage distribution control system, single, series and parallel conversion can be performed to respond to changes in LNG flow in real time. The cold energy storage of the cold storage carrier is not limited by the fluctuation of LNG gasification flow or by passivity, which improves the efficiency of cold energy utilization, increases the flexibility of cold storage carrier temperature regulation, increases the amount of gasification operation and the efficiency of cold storage carrier operation time, enables precise control of cold storage carrier temperature, and improves the cold storage speed. It can cope with the fluctuation of LNG gasification volume and makes the selection of cold storage gasification more convenient.

[0015] Furthermore, each cold storage chamber has an isolation valve in front of it. When the overflow cold storage cycle is implemented, once the cold storage chamber reaches the set cold storage temperature, the cold storage distribution control system opens the isolation valve to isolate and bypass the cold storage chamber from the circulation loop and close the cold storage chamber to improve the overall operating efficiency.

[0016] Furthermore, the cold storage distribution control system of the present invention is also equipped with a remote data monitoring and operation platform to realize real-time monitoring and remote control of the cold storage capacity and effect of the cold storage chamber. The remote data monitoring and operation platform is equipped with a manual mode and an automatic mode conversion switch for cold storage operation to realize the conversion between manual mode and automatic mode for cold storage operation.

[0017] This invention also provides an LNG gasification method based on a dual cold storage cycle, comprising the following steps: S1. Determine whether all cold storage chambers are in a full state of cold storage carrier through the cold storage distribution control system. S2. After determining the full capacity status, implement the overflow circulation of the cold storage carrier; For the first and second cold storage carrier circulation loops, open the pipelines connecting each cold storage chamber, start the cold storage chamber pumps of each cold storage chamber in the same cold storage carrier circulation loop, and transfer the cold storage carrier to the next adjacent cold storage chamber in the same loop. S3. When LNG vaporization begins, the cold storage operation of the cold storage carrier is initially operated in parallel with the first vaporization cold storage unit and the second vaporization cold storage unit. LNG is injected from the inlet of the first vaporization cold storage unit and the second vaporization cold storage unit to carry out parallel vaporization cold storage operation. When the cold storage distribution control system determines that the LNG injection volume is continuously stable, it controls the temperature of the cold storage carrier passing through the first vaporization cold storage unit and the second vaporization cold storage unit by controlling the flow rate of the cold storage tank pumps in each cold storage tank. S4. During the cold storage operation, the cold storage distribution control system monitors the liquid level, flow rate, and temperature of each cold storage tank in real time, as well as the changes in LNG injection flow rate. Based on the changes in LNG injection flow rate, the system adjusts the optimal flow control rate of the cold storage tank pumps in each cold storage tank through manual or automatic mode to carry out the cold storage operation until the average temperature of the cold storage carrier in the farthest cold storage tank reaches a certain low temperature set value. The cold storage distribution control system then determines that the cold storage tank has completed cold storage, opens its isolation valve, and seals the farthest cold storage tank to carry out the cold storage operation in the next tank. S5. When all cold storage chambers reach the set low temperature value, all chambers are sealed, and the cold storage operation is completed.

[0018] Furthermore, in step S3, when the outlet temperature of the cold storage medium is too low, the flow rate of the cold storage medium increases to a certain value, and the cold storage medium still remains below the set temperature value, the cold storage distribution control system will change the parallel mode of the first gasification cold storage unit and the second gasification cold storage unit to the series mode.

[0019] By adopting the above technical solution, the present invention has the following beneficial effects: (1) This invention implements an intelligent control strategy. Based on data analysis results, the cold storage distribution control system automatically adjusts the flow rate of the cold storage carrier to adapt to fluctuations in the LNG inflow. When the LNG inflow increases, the cold storage distribution control system automatically increases the flow rate of the cold storage carrier to maintain temperature stability in the first and second gasification cold storage units, ensuring that the gasification effect is not affected. When the LNG inflow decreases, the cold storage distribution control system automatically reduces the flow rate of the cold storage carrier to avoid energy waste, while maintaining temperature stability in the first and second gasification cold storage units. Therefore, the cold energy storage of this invention is not passively limited by fluctuations in LNG gasification operations, thus improving the efficiency of LNG cold storage utilization.

[0020] (2) This invention integrates multiple combination control methods and priority control strategies for gasification cold storage units. The cold storage distribution control system makes feedback adjustments based on the real-time cold storage effect and continuously optimizes the control strategies of the three combinations of the first gasification cold storage unit and the second gasification cold storage unit to ensure that the cold storage effect can still be maintained when the LNG inlet volume fluctuates greatly.

[0021] (3) The temperature of the cold storage carrier of the present invention can be precisely controlled. The inlet and outlet flow and temperature of the first gasification cold storage unit and the second gasification cold storage unit are monitored in real time. Flow meters and temperature meters (or flow sensors and temperature sensors) are set at the inlet and outlet of the cold storage carrier at the first gasification cold storage unit and the second gasification cold storage unit. The flow and temperature data of the cold storage carrier are collected in real time and transmitted to the cold storage distribution control system for system judgment, data processing and analysis.

[0022] (4) This invention not only makes LNG vaporization cold storage operable, but also controls the coordinated flow balance of each cold storage chamber and balances the coordination between each cold storage chamber.

[0023] (5) The present invention improves the matching degree and synergy between LNG gasification and cold energy storage, and the cold energy storage distribution control system monitors and receives the flow and temperature data of the cold energy storage carrier in real time.

[0024] (6) The present invention effectively enhances the stability and flexibility of the LNG gasification cold storage carrier cold storage control process and significantly improves the cold storage efficiency.

[0025] (7) The use of the cold storage distribution control system of the present invention can flexibly and accurately control the temperature of the cold storage carrier. The first gasification cold storage unit and the second gasification cold storage unit can be quickly switched between series and parallel, and can realize timely adaptive conversion of cold storage temperature priority and large flow cold storage priority according to the gasification requirements.

[0026] (8) The cold storage distribution control system of the present invention improves the cold storage efficiency of the first gasification cold storage unit and the second gasification cold storage unit, so that the LNG cold energy can be used efficiently, fundamentally solving the problem of the impact of traditional LNG gasification on seawater resources.

[0027] (9) This invention achieves efficient coordination between LNG gasification and cold storage, and is environmentally friendly, enabling sustainable utilization of LNG cold energy.

[0028] In summary, this invention adjusts the flow rate and temperature of the cold storage carrier in the first and second gasification cold storage units, and controls their series-parallel connection mode, based on the different functional requirements of LNG gasification cold storage and the need to cope with fluctuations in LNG gasification flow. Intelligent adjustment of the cold storage carrier flow rate adapts to the requirements of efficient, rapid, and flexible floating cold energy storage and transportation, ensuring stable extraction and precise control of LNG cold energy even when the LNG inflow fluctuates during LNG gasification. This allows the cold storage carrier to reach the specified temperature after storage, achieving rapid and efficient recovery of LNG cold energy. This invention solves the problem of matching cold storage carrier control with LNG gasification control, ensuring the cold storage carrier remains stable within the specified temperature range after storage, achieving both high efficiency and safety in cold storage, guaranteeing the cold storage effect, and ensuring the safety of the overall system. Attached Figure Description

[0029] The present invention will be described in detail below with reference to the accompanying drawings and examples. The advantages and implementation methods of the present invention will become more apparent from this description. The accompanying drawings are for illustrative purposes only and do not constitute any limitation on the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of the LNG gasification system based on a dual cold storage cycle according to the present invention.

[0030] In the picture: 1. First gasification cold storage unit; 2. Second gasification cold storage unit; 3. Third open gasification unit; 4. First cold storage chamber; 5. Second cold storage chamber; 6. Third cold storage chamber; 7. First cold storage chamber pump; 8. Second cold storage chamber pump; 9. Third cold storage chamber pump; 10. Fourth cold storage chamber; 11. Fifth cold storage chamber; 12. Sixth cold storage chamber; 13. Fourth cold storage chamber pump; 14. Fifth cold storage chamber pump; 15. Sixth cold storage chamber pump; 16. Overflow pipeline; 17. First function switching valve; 18. Second function switching valve; 19. Third function switching valve; 20. Isolation valve. Detailed Implementation

[0031] like Figure 1 As shown, the present invention discloses an LNG vaporization system based on a dual cold storage cycle, comprising an LNG vaporization module, a cold storage chamber, and a cold storage distribution and control system.

[0032] The LNG vaporization module includes a first vaporization cold storage unit 1, a second vaporization cold storage unit 2, and a third open vaporization unit 3. The first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 are closed-loop LNG vaporizers, and the LNG vaporization heat medium is a cold storage carrier from the cold storage chamber. The third open vaporization unit 3 is an open vaporizer, and the heating medium is ambient seawater.

[0033] The first gasification cold storage unit 1 and the second gasification cold storage unit 2 are arranged in parallel and can be switched between series and parallel by a functional conversion valve group.

[0034] The first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 are connected to several cold storage chambers via pipelines. The cold storage carrier is transported to adjacent cold storage chambers or vaporization cold storage units by the cold storage chamber pumps of each cold storage chamber, forming independent first and second cold storage carrier circulation loops respectively. After the cold storage carrier from each cold storage chamber is vaporized into LNG in the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2, it undergoes a closed-loop cold storage cycle according to the overflow cold storage method.

[0035] In this embodiment, the first gasification cold storage unit 1 is connected to the first cold storage chamber 4, the second cold storage chamber 5, and the third cold storage chamber 6 via pipelines. The cold storage carrier is transported via the first cold storage chamber pump 7, the second cold storage chamber pump 8, and the third cold storage chamber pump 9. The first gasification cold storage unit 1, the first cold storage chamber 4, the second cold storage chamber 5, and the third cold storage chamber 6 form an independent first cold storage carrier circulation loop. The second gasification cold storage unit 2 is connected to the fourth cold storage chamber 10, the fifth cold storage chamber 11, and the sixth cold storage chamber 12 via pipelines. The cold storage carrier is transported via the fourth cold storage chamber pump 13, the fifth cold storage chamber pump 14, and the sixth cold storage chamber pump 15. The second gasification cold storage unit 2, the fourth cold storage chamber 10, the fifth cold storage chamber 11, and the sixth cold storage chamber 12 form an independent second cold storage carrier circulation loop. The overflow cold storage method of the cold storage carrier is as follows: In the independent first and second cold storage carrier circulation loops, when the cold storage tank is full, the cold storage carrier in the adjacent cold storage tank is transferred through the cold storage tank pump and the overflow pipeline 16 until it is transferred to the first gasification cold storage unit 1 or the second gasification cold storage unit 2 for cold storage, and then output to the cold storage tank, realizing a closed overflow circulation of the cold storage carrier and completing the cold storage carrier circulation loop. The cold storage tank pumps of each cold storage tank are turned on and the overflow pipeline 16 is opened. The cold storage tank pumps draw cold storage carrier from the top of the cold storage tank and inject it into the bottom of the adjacent cold storage tank or the gasification cold storage unit.

[0036] The corresponding cold storage chambers are connected by an overflow pipeline 16. The return carrier liquid is injected from the bottom of the chamber. In this embodiment, in the first cold storage carrier circulation loop, the first cold storage chamber 4 is the closest and adjacent to the first gasification cold storage unit 1. After startup, the third cold storage chamber pump 9 of the farthest third cold storage chamber 6 transports the cold storage carrier to the second cold storage chamber 5 through the overflow pipeline 16 between the third cold storage chamber 6 and the second cold storage chamber 5. Similarly, the second cold storage chamber pump 8 of the second cold storage chamber 5 transports the cold storage carrier to the first cold storage chamber 4. The first cold storage chamber pump 7 of the first cold storage chamber 4 transports the cold storage carrier to the first gasification cold storage unit 1. The cold storage carrier, after being stored in the first gasification cold storage unit 1, returns to the third cold storage chamber 6, realizing a closed-loop cold storage carrier overflow circulation and completing the first cold storage carrier circulation loop. The circulation mode of the second cold storage carrier circulation loop is the same as above.

[0037] The advantage of overflow cold storage method is that it utilizes the different densities of hot and cold cold storage carriers in the cold storage tank and the stratification of the cold storage carriers in the tank. By transporting the cold storage carriers in one tank at a time, the high and low temperature cold storage carriers are quickly displaced and replaced, achieving effective cold storage. The cold storage replacement of all cold storage tanks is completed in a short time, without changing the stability and draft difference of the ship, and has little impact on the local strength of the ship. It is also easy to operate.

[0038] The inlets of the first gasification cold storage unit 1 and the second gasification cold storage unit 2 are connected to the LNG input port. The outlets of the first gasification cold storage unit 1 and the second gasification cold storage unit 2 are connected to the inlet of the third open gasification unit 3. The outlet of the third open gasification unit 3 is connected to the natural gas output port.

[0039] The final process of LNG gasification is completed by the third open gasification unit 3, and the heating carrier is provided by the seawater system. Since the LNG has passed through the first gasification and cold storage unit 1 and the second gasification and cold storage unit 2, the temperature of the natural gas is increased only in the third open gasification unit 3. Therefore, the amount of seawater used in the third open gasification unit 3 will be greatly reduced, thus reducing the dependence on the environment and the adverse impact.

[0040] The cold storage distribution control system, based on the monitored flow and temperature signals of the cold storage carrier and the LNG flow and temperature signals, adjusts the flow of the cold storage carrier entering the first gasification cold storage unit 1 or the second gasification cold storage unit 2 and controls the series-parallel mode switching of the first gasification cold storage unit 1 or the second gasification cold storage unit 2 according to the control strategy of the gasification cold storage model. This achieves the control of the temperature of the cold storage carrier entering the cold storage chamber and solves the problem of coordinating and matching the cold storage carrier's cold storage and LNG gasification functions.

[0041] The cold storage distribution control system completes the series-parallel conversion by controlling the functional switching valve group between the first gasification cold storage unit 1 and the second gasification cold storage unit 2. The functional switching valve group consists of several control valves on the LNG pipeline, including a first functional switching valve 17, a second functional switching valve 18, and a third functional switching valve 19. The first functional switching valve 17 is installed on the pipeline between the LNG inlet and the inlet of the second gasification cold storage unit 2, the second functional switching valve 18 is installed on the pipeline between the outlet of the first gasification cold storage unit 1 and the outlet of the second gasification cold storage unit 2, and the third functional switching valve 19 is installed on the pipeline between the outlet of the first gasification cold storage unit 1 and the inlet of the second gasification cold storage unit 2.

[0042] When the first gasification cold storage unit 1 and the second gasification cold storage unit 2 are connected in series, the cold storage distribution control system closes the first function switching valve 17 and the second function switching valve 18, and opens the third function switching valve 19, realizing the series mode of the first gasification cold storage unit 1 and the second gasification cold storage unit 2 for LNG gasification. The inlet (LNG pipe interface) of the first gasification cold storage unit 1 is connected to the LNG input port (liquid LNG interface). After the first gasification of LNG in the first gasification cold storage unit 1, the low-temperature natural gas enters the second gasification cold storage unit 2. After passing through the second gasification cold storage unit 2, the natural gas enters the third open gasification unit 3 through the gas phase pipe outlet for heating. After passing through the third open gasification unit 3, the natural gas reaches the normal temperature and is connected to the shore-end user. The corresponding cold storage carriers pass through the first cold storage carrier circulation loop and the second cold storage carrier circulation loop respectively. The first gasification cold storage unit 1 is set to a relatively low temperature first gasification cold storage cycle, and the second gasification cold storage unit 2 is set to a relatively high temperature second gasification cold storage cycle. In the series mode, the cold storage carrier flow rate is relatively low, which maximizes the utilization efficiency of LNG gasification heat.

[0043] When the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 operate in parallel, the cold storage distribution control system controls the opening of the first function switching valve 17 and the second function switching valve 18, and closes the third function switching valve 19, to achieve the parallel operation mode of the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 for LNG vaporization. The inlets of both the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 are simultaneously connected to liquid LNG. The natural gas produced after vaporization by the LNG in the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 enters the third open vaporization unit 3 through the gas phase manifold outlet. After passing through the third open vaporization unit 3, the natural gas reaches normal temperature and is connected to the shore-end user. The parallel operation mode meets the demand for larger LNG vaporization volumes while simultaneously achieving cold storage operations with a relatively large flow rate of cold storage carrier (the cold storage distribution control system will adjust the output flow rate of the cold storage tank pump to a relatively large flow rate), maximizing the LNG vaporization and cold storage speed. Parallel operation is generally used during peak LNG vaporization periods or when there is a high demand for cold storage speed.

[0044] The cold storage distribution control system includes a controller connected to flow meters and temperature meters at the inlets of the first gasification cold storage unit 1 and the second gasification cold storage unit 2, as well as temperature meters at the inlets and outlets of the cold storage carrier, and temperature and flow meters within each cold storage chamber pump and chamber. The temperature signals monitored by the cold storage distribution control system include: the temperature signals at the inlets and outlets of the cold storage carrier in the first gasification cold storage unit 1 and the second gasification cold storage unit 2, and the temperature signals within each cold storage chamber. The flow signals monitored by the cold storage distribution control system include: the LNG flow signals at the inlets of the first gasification cold storage unit 1 and the second gasification cold storage unit 2, and the flow signals of the cold storage carrier in each cold storage chamber. Through the above-mentioned temperature and flow data acquisition and control strategies, the cold storage distribution control system controls the flow rate and temperature of the cold storage carrier entering the first gasification cold storage unit 1 and the second gasification cold storage unit 2.

[0045] After passing through the first gasification cold storage unit 1 and the second gasification cold storage unit 2, the cold storage carrier is distributed to its respective cold storage chamber via independent closed-loop circulation. In the combined mode of the dual gasification cold storage units (first gasification cold storage unit 1 and second gasification cold storage unit 2), the output temperature of the cold storage carrier can be controlled according to the cold storage requirements, and the carrier is stored in different cold storage chambers. The combined modes include single gasification cold storage unit operation (either first gasification cold storage unit 1 or second gasification cold storage unit 2), series operation of first gasification cold storage unit 1 and second gasification cold storage unit 2, and parallel operation of first gasification cold storage unit 1 and second gasification cold storage unit 2. The characteristics of different combined modes are as follows: In single-gasification cold storage mode: To meet the demand for LNG gasification at relatively small flow rates, the temperature control accuracy of the cold storage carrier is high. For example, the cold storage carrier temperature output is controlled between -60°C and -35°C, and the cold storage rate is controlled at 400 cubic meters per hour. Based on the LNG flow rate and the set cold storage carrier temperature, the cold storage carrier flow rate is adjusted in real time. When the LNG inflow is stable, adaptive feedback adjustment is performed based on the outlet temperature of either the first gasification cold storage unit 1 or the second gasification cold storage unit 2. If the outlet temperature of the cold storage carrier pipeline is too high, the cold storage carrier flow rate is increased, and the flow rate is monitored.

[0046] In series operation mode: the cold storage medium has a wide storage temperature range, high cold storage efficiency, low cold energy loss, and precise temperature control. Through the first gasification cold storage unit 1 and the second gasification cold storage unit 2, cold storage is implemented at two temperature levels, for example, the temperature output of the cold storage medium in the first gasification cold storage unit 1 is controlled at -65°C to -30°C, and the output of the cold storage medium in the second gasification cold storage unit 2 is controlled at -35°C to -20°C. The cold storage rate can be controlled at 300~500 cubic meters per hour.

[0047] In parallel operation mode: it can meet the demand for high-flow LNG gasification, while the cold storage capacity of the cold storage carrier increases, thus improving the cold energy storage speed. For example, the temperature output of the cold storage carrier of the first gasification cold storage unit 1 and the second gasification cold storage unit 2 is controlled at -60°~-35° respectively, and the cold storage speed can be controlled at 800 cubic meters / hour.

[0048] After LNG undergoes gasification and cold storage, it transforms from a liquid state into gaseous natural gas. The natural gas is then heated by the third open gasification unit 3. The cold storage distribution control system can adjust the seawater flow rate according to the natural gas outlet temperature. Furthermore, due to the high efficiency of cold energy utilization in the first and second gasification and cold storage units 1 and 2, the amount of seawater used in the third open gasification unit 3 is reduced. Compared to traditional receiving terminals that directly utilize seawater to gasify LNG, the amount of seawater used is smaller, reducing the dependence of LNG gasification on seawater and mitigating the adverse effects of low temperatures on the marine environment caused by LNG gasification.

[0049] Due to the use of the above three combination modes and the cold storage distribution control system, single, series and parallel conversion can be performed to respond to changes in LNG flow in real time. The cold energy storage of the cold storage carrier is not limited by the fluctuation of LNG gasification flow or by passivity, which improves the efficiency of cold energy utilization, increases the flexibility of cold storage carrier temperature regulation, increases the amount of gasification operation and the efficiency of cold storage carrier operation time, enables precise control of cold storage carrier temperature, and improves the cold storage speed. It can cope with the fluctuation of LNG gasification volume and makes the selection of cold storage gasification more convenient.

[0050] The cold storage carrier circulation system of this invention has low-temperature and flow balance protection functions. The cold storage distribution control system monitors the outlet temperature of the cold storage carrier in the first gasification cold storage unit 1 and the second gasification cold storage unit 2, as well as the flow balance of the pumps in each cold storage chamber. When the temperature is lower than the set temperature or the flow of the pumps in each cold storage chamber is unbalanced, an alarm will be triggered and adjustments will be made to protect the structure of the cold storage chamber. The cold storage distribution control system provides distributed monitoring of the flow of the cold storage carrier in each cold storage chamber, and monitors the flow balance of each cold storage chamber in real time. The cold storage distribution control system has a temperature monitoring function. If the temperature of the cold storage carrier is lower than the set value or the flow of the cold storage carrier is unbalanced, the cold storage distribution control system implements alarm protection measures such as low-temperature protection and flow protection to protect the performance of the cold storage carrier and the structure of the cold storage chamber.

[0051] Each cold storage chamber has an isolation valve 20. During overflow cold storage circulation, when the cold storage chamber reaches the set cold storage temperature, the cold storage distribution control system opens the isolation valve 20 to isolate and bypass the cold storage chamber from the circulation loop and close the cold storage chamber to improve overall operating efficiency. For example, when the temperature of the first cold storage chamber 4 reaches the set cold storage temperature, the isolation valve 20 on the first cold storage chamber 4 opens to isolate and bypass the first cold storage chamber 4, and at the same time closes the inlet and outlet valves of the first cold storage chamber 4 to achieve closure.

[0052] The cold storage distribution control system of this invention establishes a remote data monitoring and operation platform to realize real-time monitoring and remote control of the cold storage capacity and effect of the cold storage chamber. By collecting data on LNG vaporization and cold storage carrier temperature, the system can keep track of the operating status of cold storage and release. Through data collection and calculation, including the cumulative LNG vaporization, cumulative cold storage heat, and cold storage efficiency of the cold storage carrier, remote operation and adjustment are performed based on the above results.

[0053] The cold storage distribution control system calculates the cold storage capacity and efficiency of this invention during cold storage operations. This invention establishes a cold storage calculation model, which calculates the cold energy storage capacity and corresponding time efficiency based on the heat capacity of the cold storage carrier, the temperature change and flow rate of the cold storage carrier after gasification and cold storage collected per unit time. The calculation formula is as follows: Q1 = ΔT1 × R1 × M1 + ΔT2 × R1 × M2 Wherein, Q1 is the calorific value of cold storage per unit time; ΔT1 is the temperature change of the cold storage medium in the first gasification cold storage unit 1 per unit time; R1 is the heat capacity of the cold storage medium; M1 is the flow rate of the cold storage medium passing through the first gasification cold storage unit 1 per unit time; ΔT2 is the temperature change of the cold storage medium in the second gasification cold storage unit 2 per unit time; and M2 is the flow rate of the cold storage medium passing through the second gasification cold storage unit 2 per unit time.

[0054] Q2=M3×R2 Where Q2 is the calorific value of LNG vaporization per unit time; M3 is the sum of the LNG flow rates passing through the first vaporization cold storage unit 1 or the second vaporization cold storage unit 2 per unit time; and R2 is the calorific value of LNG vaporization.

[0055] N = Q1 / Q2 × 100% Where N is the system's thermal storage efficiency.

[0056] The remote data monitoring and operation platform of the present invention has a manual mode and an automatic mode switch for cold storage operation, so as to realize the switching between the manual mode and the automatic mode of cold storage operation of the present invention.

[0057] Manual mode control: When the LNG flow rate through the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2, as monitored by the cold storage distribution control system, is stable within the rated range, priority control of the cold storage carrier is implemented. This includes three combination options: First, the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 can be adjusted to a series cycle as needed, prioritizing maximum cold storage efficiency and maximizing the utilization of LNG vaporization potential, while simultaneously achieving cold storage in two temperature ranges (high and low). Alternatively, if the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 are selected in parallel, it can meet the needs of rapid cold storage with large flow rates, prioritizing rapid cold storage and achieving cold storage of the medium with a large flow rate. The first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 perform vaporization cold storage at the same level. Finally, if a single vaporization cold storage unit is selected, it can meet the cold storage needs of smaller LNG flow rates.

[0058] Automatic mode control: When the LNG flow rate through the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2, as monitored by the cold storage distribution control system, fluctuates, or when the total LNG inlet flow rate is determined, the system automatically switches between series and parallel operation of the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2. The system adaptively adjusts the state of the switching valve group. Specifically, it uses flow meters installed at the inlets of the first and second vaporization cold storage units 1 and 2 to determine the flow rate. When the total LNG injection flow rate is less than 60% of the set rated flow rate, the system automatically starts the single vaporization cold storage mode; when the total LNG flow rate is between 60% and 80%, it switches to series operation mode; and when the flow rate is greater than 80% or the total LNG flow rate fluctuation exceeds 20%, it switches to parallel operation mode. This invention fully addresses the LNG vaporization requirements and the impact of LNG injection fluctuations, adopting intelligent control measures to improve the overall efficiency of cold energy utilization.

[0059] This invention also provides an LNG gasification method based on a dual cold storage cycle, comprising the following steps: S1. Determine whether all cold storage chambers are in a full state of cold storage carrier through the cold storage distribution control system.

[0060] S2. After determining the full capacity status, implement the overflow circulation of the cold storage carrier; For the first and second cold storage carrier circulation loops, open the pipelines connecting each cold storage chamber, start the cold storage chamber pumps of each cold storage chamber in the same cold storage carrier circulation loop, and transfer the cold storage carrier to the previous cold storage chamber in the same loop. In this embodiment, in the first cold storage carrier circulation loop, the first compartment closest to and adjacent to the first gasification cold storage unit 1 is the first cold storage compartment 4. After startup, the third cold storage compartment pump 9 of the farthest third cold storage compartment 6 transfers the cold storage carrier to the second cold storage compartment 5 through the overflow pipeline 16 between the third cold storage compartment 6 and the second cold storage compartment 5. Similarly, the second cold storage compartment pump 8 of the second cold storage compartment 5 transfers the cold storage carrier to the first cold storage compartment 4, and the first cold storage compartment pump 7 of the first cold storage compartment 4 transfers the cold storage carrier to the first gasification cold storage unit 1. The cold storage carrier, after being cooled by the first gasification cold storage unit 1, returns to the third cold storage compartment 6, realizing a closed-loop cold storage carrier overflow circulation and completing the first cold storage carrier circulation loop. The circulation mode of the second cold storage carrier circulation loop is the same as above.

[0061] S3. When LNG vaporization begins, the cold storage operation of the cold storage carrier is initially operated in parallel with the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2. LNG is injected from the inlet of the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 to carry out parallel vaporization cold storage operation. When the cold storage distribution control system determines that the LNG injection volume is continuously stable, it controls the temperature of the cold storage carrier passing through the first vaporization cold storage unit 1 and the second vaporization cold storage unit 2 by controlling the flow rate of the cold storage tank pumps in each cold storage tank. During implementation, the cold storage distribution control system monitors the temperature and flow rate of the cold storage carrier and automatically provides feedback based on the outlet temperatures of the cold storage carrier measured in the first gasification cold storage unit 1 and the second gasification cold storage unit 2. When the outlet temperature of the cold storage carrier is too low and below the design value, the cold storage distribution control system increases the flow rate of the cold storage carrier. When the outlet temperature of the cold storage carrier is too high and above the set value, the system decreases the flow rate of the cold storage carrier.

[0062] When the outlet temperature of the cold storage medium is too low, and the flow rate of the cold storage medium increases to a certain value, such as 85-90% of the rated flow rate, if the cold storage medium still remains below the set temperature value, the cold storage distribution control system will adaptively change the parallel mode of the first gasification cold storage unit 1 and the second gasification cold storage unit 2 to the series mode.

[0063] S4. During the cold storage operation, the cold storage distribution control system monitors the liquid level, flow rate, and temperature of each cold storage tank in real time, as well as the changes in LNG injection flow rate. Based on the changes in LNG injection flow rate, the system adjusts the optimal flow control rate of the cold storage tank pumps in each cold storage tank through manual or automatic mode to carry out the cold storage operation until the average temperature of the cold storage carrier in the farthest third cold storage tank 6 reaches a certain low temperature set value. The cold storage distribution control system then determines that the cold storage tank has completed cold storage, opens its isolation valve 20, and simultaneously seals the third cold storage tank 6, closing the cold storage tank and proceeding to the next tank for cold storage operation.

[0064] S5. When all cold storage chambers reach the set low temperature value, all chambers are sealed, and the cold storage operation is completed.

[0065] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. An LNG gasification system based on a dual-cold storage cycle, characterized in that: The system includes an LNG vaporization module, a cold storage chamber, and a cold storage distribution control system. The LNG vaporization module comprises a first vaporization cold storage unit, a second vaporization cold storage unit, and a third open vaporization unit. The inlets of the first and second vaporization cold storage units are connected to an LNG input port, and their outlets are connected to the inlet of the third open vaporization unit. The outlet of the third open vaporization unit is connected to a natural gas output port. The first and second vaporization cold storage units are connected in series and parallel via a functional switching valve group. The first vaporization cold storage unit... The first and second gasification cold storage units are connected to several cold storage chambers via pipelines. The cold storage carrier is transported to adjacent cold storage chambers or gasification cold storage units by the cold storage chamber pumps of each cold storage chamber, forming independent first and second cold storage carrier circulation loops respectively. The cold storage distribution control system is used to monitor the flow rate and temperature signals of the cold storage carrier and the flow rate and temperature signals of LNG, adjust the flow rate of the cold storage carrier entering the first or second gasification cold storage unit, and control the series-parallel mode switching of the first and second gasification cold storage units to achieve control of the temperature of the cold storage carrier entering the cold storage chamber. The cold storage distribution control system completes the series-parallel conversion by controlling the functional switching valve group between the first gasification cold storage unit and the second gasification cold storage unit. The functional switching valve group includes a first functional switching valve, a second functional switching valve and a third functional switching valve. The first functional switching valve is installed on the pipeline between the LNG inlet and the inlet of the second gasification cold storage unit. The second functional switching valve is installed on the pipeline between the outlet of the first gasification cold storage unit and the outlet of the second gasification cold storage unit. The third functional switching valve is installed on the pipeline between the outlet of the first gasification cold storage unit and the inlet of the second gasification cold storage unit. After passing through the first and second gasification cold storage units, the cold storage carrier is distributed to its respective cold storage chambers via independent closed-loop circulation. In the combination mode of the dual gasification cold storage units with the first and second gasification cold storage units, the output temperature of the cold storage carrier can be controlled according to the cold storage needs, and the carrier can be stored in different cold storage chambers. The combination modes include single gasification cold storage unit operation, series operation of the first and second gasification cold storage units, and parallel operation of the first and second gasification cold storage units.

2. The LNG gasification system based on a dual-cold storage cycle according to claim 1, characterized in that: The first and second gasification cold storage units are LNG closed-loop gasifiers, and the LNG gasification heat medium is a cold storage carrier from the cold storage chamber; the third open-loop gasification unit is an open-loop gasifier, and the heating medium is ambient seawater.

3. The LNG gasification system based on a dual-cold storage cycle according to claim 1, characterized in that: The cold storage carrier circulation loop of the first cold storage carrier circulation loop or the cold storage carrier circulation loop of the second cold storage carrier circulation loop realizes the transfer of cold storage carrier through the cold storage carrier pump and the overflow pipeline until it is transferred to the first gasification cold storage unit or the second gasification cold storage unit for cold storage and then output to the cold storage carrier to complete the cold storage carrier circulation loop. The cold storage carrier pump draws cold storage carrier from the top of the cold storage carrier and injects it into the bottom of the adjacent cold storage carrier or the gasification cold storage unit.

4. The LNG gasification system based on a dual-cold storage cycle according to claim 1, characterized in that: When the first and second gasification cold storage units are connected in series, the cold storage distribution control system controls the closure of the first and second function switching valves and the opening of the third function switching valve. The cold storage carrier passes through the first and second cold storage carrier circulation loops respectively. The first gasification cold storage unit is set to a relatively low-temperature first gasification cold storage cycle, and the second gasification cold storage unit is set to a relatively high-temperature second gasification cold storage cycle. When the first and second gasification cold storage units are connected in parallel, the cold storage distribution control system controls the opening of the first and second function switching valves and the closing of the third function switching valve. The inlets of the first and second gasification cold storage units are simultaneously connected to liquid LNG. The natural gas vaporized by the first and second gasification cold storage units enters the third open gasification unit through the gas phase manifold outlet. After passing through the third open gasification unit, the natural gas reaches normal temperature and is connected to the shore-end user.

5. The LNG vaporization system based on a dual-cold storage cycle according to claim 1, characterized in that: Each cold storage chamber has an isolation valve in front of it. When the overflow cold storage cycle is implemented, once the cold storage chamber reaches the set cold storage temperature, the cold storage distribution control system opens the isolation valve to isolate and bypass the cold storage chamber from the circulation loop and close the cold storage chamber.

6. The LNG vaporization system based on a dual-cold storage cycle according to claim 1, characterized in that: The cold storage distribution control system is also equipped with a remote data monitoring and operation platform to realize real-time monitoring and remote control of the cold storage capacity and effect of the cold storage chamber. The remote data monitoring and operation platform is equipped with a manual mode and an automatic mode switch for cold storage operation to realize the switching between manual mode and automatic mode for cold storage operation.

7. An LNG gasification method based on a dual-cold storage cycle, implemented by the LNG gasification system based on a dual-cold storage cycle as described in any one of claims 1 to 6, characterized in that: Includes the following steps: S1. Determine whether all cold storage chambers are in a full state of cold storage carrier through the cold storage distribution control system. S2. After determining the full capacity status, implement the overflow circulation of the cold storage carrier; For the first and second cold storage carrier circulation loops, open the pipelines connecting each cold storage chamber, start the cold storage chamber pumps of each cold storage chamber in the same cold storage carrier circulation loop, and transfer the cold storage carrier to the adjacent cold storage chamber in the same loop. S3. When LNG vaporization begins, the cold storage operation of the cold storage carrier is initially operated in parallel with the first vaporization cold storage unit and the second vaporization cold storage unit. LNG is injected from the inlet of the first vaporization cold storage unit and the second vaporization cold storage unit to carry out parallel vaporization cold storage operation. When the cold storage distribution control system determines that the LNG injection volume is continuously stable, it controls the temperature of the cold storage carrier passing through the first vaporization cold storage unit and the second vaporization cold storage unit by controlling the flow rate of the cold storage tank pumps in each cold storage tank. S4. During the cold storage operation, the cold storage distribution control system monitors the liquid level, flow rate, and temperature of each cold storage tank in real time, as well as the changes in LNG injection flow rate. Based on the changes in LNG injection flow rate, the system adjusts the optimal flow control rate of the cold storage tank pumps in each cold storage tank through manual or automatic mode to carry out the cold storage operation until the average temperature of the cold storage carrier in the farthest cold storage tank reaches a certain low temperature set value. The cold storage distribution control system then determines that the cold storage tank has completed cold storage, opens its isolation valve, and seals the farthest cold storage tank to carry out the cold storage operation in the next tank. S5. When all cold storage chambers reach the set low temperature value, all chambers are sealed, and the cold storage operation is completed.

8. The LNG gasification method based on a dual-cold storage cycle according to claim 7, characterized in that: In step S3, when the outlet temperature of the cold storage medium is too low, the flow rate of the cold storage medium increases to a certain value, and the cold storage medium still remains below the set temperature value, the cold storage distribution control system will change the parallel mode of the first gasification cold storage unit and the second gasification cold storage unit to the series mode.

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