Method for recovering cold energy carried by LPG unloaded at the terminal and using it in DMC process

Abstract

The present invention provides a method for recovering the cold carried by LPG unloaded at the wharf for use in the DMC process. Based on this method, the volume of the cold recovery system can be greatly compressed, and the system investment, land occupation and construction difficulty can be greatly reduced. The method steps of a single cold recovery cycle include: during the unloading of LPG at the wharf, the LPG unloaded at the wharf is continuously sent to the cold taking heat exchanger through the wharf output pipeline, and the heat exchange medium in the cold storage tank can circulate between the two; during the unloading of LPG at the wharf, the carbon dioxide stream to be precooled in the DMC process is simultaneously sent to the cold using heat exchanger, and the heat exchange medium in the cold storage tank can circulate between the two; when the unloading of LPG at the wharf is completed, the valve on the first circulation pipeline for controlling the on-off of the first circulation pipeline is closed; when the time from the start of unloading of LPG at the wharf lasts to the predetermined cold using time, the heat exchange medium is circulated in a closed loop between the cold storage tank and the bypass circulation pipeline.

Description

Technical Field

[0001] The invention belongs to the technical field of energy utilization, and in particular relates to a method for recovering intermittent low-quality cold carried by LPG unloaded at a wharf for use in a DMC process. Background Art

[0002] Shipping chemical bulk commodities such as LPG requires a large amount of cold energy to maintain system stability. However, when unloading at the dock, the low-temperature LPG needs to be reheated, which means that the cold energy in the unloading system is consumed through certain public works. The cold energy of this type of dock is characterized by intermittent non-periodic cold energy, and it is currently difficult to directly recycle this part of the cold energy for industrial use.

[0003] Due to the differences in the quality of cold water at the terminal, irregular unloading cycles, unstable unloading cold water, matching problems between the continuity of industrial cold and intermittent cold water, and the evaluation of the land occupation of cold storage and the economic efficiency of the system, a large amount of cold water in the conventional unloading process is often abandoned for recycling, and the cold water is consumed by public works such as circulating water, air and even steam, or by generating electricity with high-quality ultra-low temperature cold water, thus avoiding the technical difficulties and economic dilemma of storing and using such low-quality intermittent cold water.

[0004] Patent CN200710068060.7 is an integrated air separation and liquefied natural gas cold recovery system, which makes full use of the high-quality cold of liquefied natural gas, significantly reduces the energy consumption of the air separation unit, ensures the safe operation of the air separation unit, and obtains great social and economic benefits. Although the system realizes the cold recovery of natural gas, it is limited to the recovery of high-quality and stable and continuous cold, and is not suitable for low-quality (i.e., high-temperature cold streams) and intermittent cold recovery.

[0005] Patent CN201811035975.2 is an oil and gas combined station energy storage type oil and gas recovery device and method. After the pressurized cold storage gas absorbs the LNG gasification cold energy efficiently in two stages, it is liquefied and settled in the forked comb-tooth phase change cold storage device. The low-temperature CNG produced is further stored in the cold storage type oil and gas precooler, and the cold is also released in two stages. Although this system realizes the recovery of natural gas cold for oil and gas recovery and is applicable to a wide range of cold temperature, the system is multi-stage cold storage and cold use, the system is complex, the cold storage form is phase change cold storage, and the operability is poor. It cannot be used for intermittent cold recovery for industrial continuous cold users.

[0006] Patent CN202010307813.0 is a cross-seasonal underground cold and heat storage system. In response to the temperature changes of the external environment, the cold and heat energy collected by the superconducting energy plates are stored separately. The system theoretically realizes seasonal energy storage, but its energy storage type is phase change energy storage. The key to energy storage is that the insulation layer isolates heat loss, and it is impossible to achieve continuous and stable energy output. It is even less suitable for the storage of high-frequency intermittent cooling (especially dock cooling) and recovery for industrial continuous cooling conditions. Summary of the invention

[0007] The present invention provides a method for recovering the cold carried by LPG unloaded at the dock for use in a DMC process. Based on this method, only a single cold storage tank needs to be configured to use the cold carried by the LPG unloaded at the dock for precooling the carbon dioxide stream in the DMC process. Compared with the existing technology, the volume of the cold recovery system can be greatly compressed, and the system investment, land occupation and construction difficulty are greatly reduced.

[0008] To achieve the purpose, the present invention provides the following technical solutions:

[0009] The present invention provides a method for recovering the cold energy carried by LPG unloaded at a terminal for use in a DMC process, wherein each time LPG is unloaded at a terminal corresponds to a cold energy recovery cycle; the method steps for a single cold energy recovery cycle include:

[0010] During the unloading of LPG at the wharf, the LPG unloaded at the wharf is continuously sent to the cold heat exchanger through the wharf output pipeline. The cold heat exchanger and the cold storage tank are connected through a first circulation pipeline so that the heat exchange medium in the cold storage tank can circulate between the two. The heat exchange medium from the cold storage tank exchanges heat with the LPG sent to the cold heat exchanger, so that the LPG unloaded at the wharf is first-stage reheated, and at the same time, the cold carried by the LPG unloaded at the wharf is stored in the heat exchange medium;

[0011] During the unloading of LPG at the terminal, the carbon dioxide stream to be precooled in the DMC process is simultaneously fed into the cold heat exchanger, the cold storage tank and the cold heat exchanger are connected via a second circulation pipeline so that the heat exchange medium in the cold storage tank can circulate between the two, and the heat exchange medium from the cold storage tank exchanges heat with the carbon dioxide stream fed into the cold heat exchanger, so that the carbon dioxide stream is precooled in the first stage;

[0012] When the terminal has completed unloading of LPG, closing the valve on the first circulation pipeline for controlling the on-off of the first circulation pipeline;

[0013] When the time from unloading LPG at the terminal starts to reach the predetermined cold usage time, the valve on the second circulation pipeline used to control the on-off of the second circulation pipeline is closed; at the same time, the valve on the bypass circulation pipeline connected to the cold storage tank is opened, so that the heat exchange medium circulates in a closed loop between the cold storage tank and the bypass circulation pipeline.

[0014] Preferably, within the predetermined cooling time, the heat exchange medium flow rates of the first circulation pipeline and the second circulation pipeline are controlled so that the cooling heat exchanger can receive a stable cooling load from the cold storage tank.

[0015] Furthermore, the control step of controlling the flow rate of the heat exchange medium in the first circulation pipeline and the second circulation pipeline includes:

[0016] S100, obtaining primary parameters, wherein the primary parameters include the total mass of LPG unloaded during the unloading of LPG at the terminal, the initial temperature of the LPG unloaded at the terminal, the preset primary rewarming temperature of the LPG after the primary rewarming, the specific heat (i.e., specific heat capacity) of the LPG unloaded at the terminal, the LPG flow rate of the terminal output pipeline, the total mass of the heat exchange medium, the initial temperature of the heat exchange medium in the cold storage tank when the unloading of LPG at the terminal starts, and the predetermined cold use time;

[0017] S200, calculating and obtaining secondary parameters according to the primary parameters, wherein the secondary parameters include the unloading time required for the terminal to unload the LPG, the total cold released by the terminal when unloading the LPG, the cold load received by the cold heat exchanger during the unloading time, the cold load received by the cold heat exchanger during the predetermined cold use time, and the net cold storage load of the cold storage tank during the unloading time;

[0018] S300, establishing a first relational expression, a second relational expression, and a third relational expression between flow and time according to the primary parameter and the secondary parameter; the first relational expression is a relational expression between the flow of heat exchange medium on the first circulation pipeline and time during the period when the terminal unloads LPG; the second relational expression is a relational expression between the flow of heat exchange medium on the second circulation pipeline and time during the period when the terminal unloads LPG; the third relational expression is a relational expression between the flow of heat exchange medium on the second circulation pipeline and time after the terminal has completed unloading LPG and within the predetermined cooling time;

[0019] S400. During the unloading of LPG at the terminal, the flow rate of heat exchange medium on the first circulation pipeline is controlled according to the first relationship, and the flow rate of heat exchange medium on the second circulation pipeline is controlled according to the second relationship; after the unloading of LPG at the terminal is completed and within the predetermined cooling time, the flow rate of heat exchange medium on the second circulation pipeline is controlled according to the third relationship.

[0020] Furthermore, the step S300 further includes: establishing a fourth relationship and a fifth relationship between temperature and time;

[0021] Establishing the fourth relational expression according to the primary parameter and the secondary parameter, wherein the fourth relational expression is a relational expression between the temperature of the heat exchange medium in the cold storage tank and time during the unloading of LPG at the terminal;

[0022] The primary parameters also include the temperature of the heat exchange medium in the cold storage tank when the terminal completes unloading of LPG. The fifth relationship is established based on the primary parameters and the secondary parameters. The fifth relationship is the relationship between the temperature of the heat exchange medium in the cold storage tank and time after the terminal completes unloading of LPG and within the predetermined cooling time. Alternatively, the temperature of the heat exchange medium in the cold storage tank when the terminal completes unloading of LPG is obtained based on the fourth relationship, and the fifth relationship is established based on the primary parameters, the secondary parameters and the temperature of the heat exchange medium in the cold storage tank when the terminal completes unloading of LPG.

[0023] Further, the temperature of the heat exchange medium in the cold storage tank during the unloading of LPG at the terminal is obtained in real time according to the fourth relationship;

[0024] According to the fifth relationship, the temperature of the heat exchange medium in the cold storage tank is obtained in real time after the unloading of LPG at the terminal is completed and within the predetermined cold use time.

[0025] Furthermore, in step S300:

[0026] Establishing the first relational expression according to the fourth relational expression and the cooling load received by the cooling heat exchanger within the predetermined cooling time;

[0027] The second relational expression is established according to the fourth relational expression and the cold load received by the cold extraction heat exchanger during the unloading time;

[0028] The third relational expression is established based on the fifth relational expression and the cold load received by the cold extraction heat exchanger during the unloading time.

[0029] Furthermore, the LPG after the primary rewarming is sent to a secondary rewarming heat exchanger for secondary rewarming to a secondary rewarming temperature;

[0030] The carbon dioxide stream after the primary precooling is sent to a cryogenic heat exchanger to be cooled to a preset secondary cryogenic temperature; the cryogenic heat exchanger is connected to a variable frequency electric drive refrigerator;

[0031] Preferably, according to the cooling load required for cooling the carbon dioxide stream to be pre-cooled to the secondary cryogenic temperature in the DMC process and the cooling load received by the cold heat exchanger, the refrigeration power of the variable frequency electric driven refrigerator is regulated so that the variable frequency electric driven refrigerator can provide the cryogenic heat exchanger with a cooling load that meets the demand.

[0032] Furthermore, when the previous terminal unloads LPG and the next terminal unloads LPG, the next terminal unloads LPG in the cold energy recovery cycle, regardless of whether the method steps of the cold energy recovery cycle corresponding to the previous terminal unloads LPG are completed, directly enters the cold energy recovery cycle of the next terminal unloads LPG.

[0033] In some specific embodiments, the temperature of the LPG unloaded from the terminal before and after the first-level rewarming ranges from -40°C to 0°C;

[0034] And / or, the temperature of the heat exchange medium varies in the range of -20°C to 10°C.

[0035] The present invention also provides an electronic device, comprising at least one processor; and

[0036] a memory communicatively connected to the at least one processor; wherein,

[0037] The memory stores instructions that can be executed by the at least one processor. The instructions are executed by the at least one processor to enable the at least one processor to perform the control steps described above.

[0038] The technical solution provided by the present invention has the following beneficial effects:

[0039] The method provided by the present invention for recovering the cold energy carried by LPG unloaded at the terminal for use in the DMC process optimizes the conventional two-tank or more cold storage / use configuration of the cold storage system to a single-tank cold storage / use, which not only compresses the volume of the mainstream cold energy recovery system to 50%, greatly reducing the system investment, land occupation and construction difficulty, but also helps to effectively reduce the cold energy loss in the operation of the cold storage system. In the preferred embodiment, within the predetermined cold use time, the heat exchange medium flow of the first circulation pipeline and the second circulation pipeline is dynamically regulated according to the working conditions, so that the intermittent, low-quality cold energy provided by the LPG unloaded at the terminal can be continuously and stably output to the cold use process. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of a process system in one embodiment;

[0041] Figure 2 A simplified timeline diagram of a cold recovery cycle in one embodiment;

[0042] Figure 3A schematic diagram of a method flow control method in an implementation manner;

[0043] Figure 4 A flow rate variation trend diagram of heat exchange medium in the first circulation pipeline in one embodiment;

[0044] Figure 5 A flow rate variation trend diagram of heat exchange medium in the second circulation pipeline in one embodiment;

[0045] Figure 6 A graph showing a change trend of the temperature of the heat exchange medium in the cold storage tank in one embodiment;

[0046] Figure 7 A cold load variation trend diagram of a cold heat exchanger in one embodiment;

[0047] Figure 8 FIG. 4 is a schematic diagram of the hardware structure of an electronic device in one implementation manner. DETAILED DESCRIPTION

[0048] In order to better understand the technical solution of the present invention, the content of the present invention is further described below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0049] It is easy to understand that according to the technical solution of the present application, without changing the essential spirit of the present application, a variety of structural modes and implementation modes that can be replaced by those skilled in the art can be replaced with each other. Therefore, the following specific implementation modes and drawings are only exemplary descriptions of the technical solution of the present application, and should not be regarded as the entirety of the present application or as a limitation or restriction on the technical solution of the application.

[0050] The directional terms such as up, down, left, right, front, back, front, back, top, bottom, etc. mentioned or may be mentioned in this specification are defined relative to the structures shown in the drawings. They are relative concepts and may change accordingly according to their different positions and different usage states. Therefore, these or other directional terms should not be interpreted as restrictive terms. In addition, the terms "first", "second", "third", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0051] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above-mentioned in this application can be understood according to the specific circumstances.

[0052] See also Figure 1 The present invention provides a method for recovering the cold energy carried by LPG unloaded at the dock for use in a DMC (dimethyl carbonate) process, wherein the process device involved includes: a cold heat exchanger 2, a cold heat exchanger 3 and a cold storage tank 1, wherein the cold heat exchanger 2 is connected to a dock output pipeline 6, and the dock output pipeline 6 is used to continuously input the LPG unloaded at the dock into the cold heat exchanger 2 for heat exchange; the cold heat exchanger 2 and the cold storage tank 1 are connected through a first circulation pipeline 7, and the heat exchange medium in the cold storage tank 1 can circulate between the cold heat exchanger 2 and the cold storage tank 1; the cold heat exchanger 3 is connected to a carbon dioxide delivery pipeline 9, and the carbon dioxide delivery pipeline 9 is used to input the carbon dioxide material flow (gaseous state) to be pre-cooled from the DMC process into the cold heat exchanger 3 for heat exchange; the cold heat exchanger 3 and the cold storage tank 1 are connected through a second circulation pipeline 8, and the heat exchange medium in the cold storage tank 1 can circulate between the cold heat exchanger 3 and the cold storage tank 1. The cold storage tank 1 is also connected to the bypass circulation pipeline 10, and the heat exchange medium in the cold storage tank 1 can circulate between the cold storage tank 1 and the bypass circulation pipeline 10, that is, a closed loop. Valves (not shown in the figure) for controlling the on-off of the pipelines are provided on the first circulation pipeline 7, the second circulation pipeline 8, and the bypass circulation pipeline 10; flow regulating valves (not shown in the figure) are also provided on the first circulation pipeline 7 and the second circulation pipeline 8. The cold storage tank can be a jacketed storage tank.

[0053] Furthermore, a secondary rewarming heat exchanger 4 is provided, and the secondary rewarming heat exchanger 4 is connected to the cold heat exchanger 2 through a pipeline, and is used to perform secondary rewarming on the LPG after the primary rewarming by the cold heat exchanger 2, for example, secondary rewarming to 16°C; the secondary rewarming heat exchanger 4 can be, for example, a water cooler. A deep cold heat exchanger 5 and a variable frequency electric drive chiller 6 connected to the deep cold heat exchanger 5 through a pipeline 11 are also provided. The deep cold heat exchanger 5 is used to perform secondary deep cooling on the carbon dioxide stream after the primary precooling by the cold heat exchanger 3, and the working fluid flowing in the pipeline 11 is liquid Freon working fluid. The heat exchange medium used by the secondary rewarming heat exchanger can be liquid circulating water from a public utility, which can be returned to the public utility system after absorbing cold and cooling.

[0054] The present invention provides a method for recovering the cold energy carried by LPG unloaded at a terminal for use in a DMC process, wherein each time LPG is unloaded at the terminal corresponds to a cold energy recovery cycle; the method steps for a single cold energy recovery cycle include:

[0055] During the unloading of LPG at the terminal, the LPG unloaded at the terminal is continuously sent to the cold heat exchanger 2 through the terminal output pipeline 6; the cold heat exchanger 2 and the cold storage tank 1 are connected through the first circulation pipeline 7, so that the heat exchange medium in the cold storage tank 1 can circulate between the cold heat exchanger 2 and the cold storage tank 1; the heat exchange medium from the cold storage tank 1 exchanges heat with the LPG sent to the cold heat exchanger 2, so that the LPG unloaded at the terminal is reheated in the first stage; the heat exchange medium carrying cold energy due to heat exchange with the LPG continuously enters the cold storage tank, continuously accumulates cold energy, so that the cold energy carried by the LPG unloaded at the terminal can be stored in the heat exchange medium, and the heat exchange medium is cooled;

[0056] During the unloading of LPG at the wharf, the carbon dioxide stream (gaseous state) to be precooled in the DMC process is simultaneously fed into the cold heat exchanger 3; the cold storage tank 1 and the cold heat exchanger 3 are connected via the second circulation pipeline 8, so that the heat exchange medium in the cold storage tank 1 can circulate between the cold storage tank 1 and the cold heat exchanger 3; the heat exchange medium from the cold storage tank 1 is heat-exchanged with the carbon dioxide stream fed into the cold heat exchanger 3, so that the carbon dioxide stream is precooled in the first stage (condensation phase change occurs);

[0057] When the terminal has finished unloading LPG, the valve (not shown in the figure) on the first circulation pipeline 7 is closed. The valve is used to control the on-off of the first circulation pipeline 7. After closing the valve, the heat exchange medium will no longer circulate between the cold heat exchanger 2 and the cold storage tank 1.

[0058] When the time from unloading LPG at the terminal starts to last until the predetermined cold use time, the valve (not shown in the figure) on the second circulation pipeline 8 for controlling the on-off of the second circulation pipeline 8 is closed. At this time, the heat exchange medium will no longer circulate between the cold storage tank 1 and the cold use heat exchanger 3; at the same time, the valve (not shown in the figure) on the bypass circulation pipeline 10 connected to the cold storage tank 1 is opened, so that the heat exchange medium circulates in a closed loop between the cold storage tank 1 and the bypass circulation pipeline 10, that is, it no longer flows into the cold extraction heat exchanger 2 and the cold use heat exchanger 3.

[0059] Combination Figure 2 , a complete cold recovery cycle corresponding to each unloading of LPG at a terminal in an embodiment is introduced. Figure 2As shown, the time when each terminal unloads LPG is taken as time 0, and based on the time starting point t, time t0 is the end of the terminal unloading LPG, t1 is the time when the time continues to the predetermined cooling time; t1-t2 is the time interval when the predetermined cooling time ends and waits for the next terminal to unload LPG. In the following, the 0-t0 period is regarded as the first working condition, the t0-t1 period is regarded as the second working condition, and the t1-t2 period is regarded as the third working condition. In some embodiments, the 0-t0 period, i.e., the unloading time, is 12-36h, and the t0-t2 period, i.e., the non-unloading time, is 24-336h.

[0060] Furthermore, within a predetermined cooling time, the heat exchange medium flow rates of the first circulation pipeline 7 and the second circulation pipeline 8 are dynamically controlled so that the cooling heat exchanger 3 can receive a stable cooling load from the cold storage tank 1 .

[0061] In one embodiment, the control step of controlling the flow rate of the heat exchange medium in the first circulation pipeline 7 and the second circulation pipeline 8 includes:

[0062] S100, obtaining primary parameters, wherein the primary parameters include the total mass of LPG unloaded during the unloading of LPG at the terminal, the initial temperature of the LPG unloaded at the terminal, the preset primary rewarming temperature of the LPG after the primary rewarming, the specific heat of the LPG unloaded at the terminal, the LPG flow rate of the terminal output pipeline 6, the total mass of the heat exchange medium, the initial temperature of the heat exchange medium in the cold storage tank 1 when the unloading of LPG at the terminal starts, and the predetermined cold use time;

[0063] S200, determining secondary parameters according to the primary parameters, the secondary parameters including the unloading time required for the terminal to unload the LPG, the total cold released by the terminal to unload the LPG, the cold load received by the cold heat exchanger 2 during the unloading time, the cold load received by the cold heat exchanger 3 within the predetermined cold use time, and the net cold storage load of the cold storage tank 1 during the unloading time;

[0064] S300, establishing a first relational expression, a second relational expression, and a third relational expression between flow and time according to the primary parameters and the secondary parameters; the first relational expression is a relational expression between the flow of the heat exchange medium on the first circulation pipeline 7 and time during the period when the terminal unloads the LPG; the second relational expression is a relational expression between the flow of the heat exchange medium on the second circulation pipeline 8 and time during the period when the terminal unloads the LPG; the third relational expression is a relational expression between the flow of the heat exchange medium on the second circulation pipeline 8 and time after the terminal has completed the unloading of the LPG and within the predetermined cooling time;

[0065] S400. During the unloading of LPG at the terminal, the flow rate of heat exchange medium on the first circulation pipeline 7 is controlled according to the first relationship, and the flow rate of heat exchange medium on the second circulation pipeline 8 is controlled according to the second relationship; after the unloading of LPG at the terminal is completed and within the predetermined cooling time, the flow rate of heat exchange medium on the second circulation pipeline 8 is controlled according to the third relationship.

[0066] Furthermore, step S300 further includes: establishing a fourth relational expression and a fifth relational expression between temperature and time according to the primary parameter and the secondary parameter;

[0067] Among them, the fourth relational expression is the relational expression between the temperature of the heat exchange medium in the cold storage tank 1 and time during the unloading of LPG at the wharf; the fifth relational expression is the relational expression between the temperature of the heat exchange medium in the cold storage tank 1 and time after the unloading of LPG at the wharf is completed and within the predetermined cold use time. Specifically, the temperature of the heat exchange medium in the cold storage tank 1 during the unloading of LPG at the wharf can be obtained in real time according to the fourth relational expression; the temperature of the heat exchange medium in the cold storage tank 1 after the unloading of LPG at the wharf is completed and within the predetermined cold use time can be obtained in real time according to the fifth relational expression. Of course, when it is necessary to know the temperature of the heat exchange medium in the cold storage tank 1 at a certain point in time, the temperature can also be obtained by actual temperature measurement using a temperature measuring element.

[0068] Further, in step S300: the first relational expression is established according to the fourth relational expression and the cooling load received by the cooling heat exchanger 3 within the predetermined cooling time;

[0069] The second relational expression is established according to the fourth relational expression and the cold load received by the cold heat exchanger 2 during the unloading time;

[0070] The third relational expression is established by the fifth relational expression and the cold load received by the cold heat exchanger 2 during the unloading time.

[0071] The following is an example to illustrate the process of establishing the first to fifth relationship mentioned above:

[0072] 1.1. Obtain primary parameters, including: the scheduled cooling time t1 (in hours, or standard cycle cooling time) corresponding to the unloading of LPG at the terminal, the total mass ml of LPG unloaded during the unloading of LPG at the terminal pg (or called the amount from the terminal, in tons), the initial temperature of the LPG unloaded from the terminal is T lpg0 (or called cooling temperature, in °C, in the following calculation process, the temperature is -30 °C, which is only an example, and can be other temperature values ​​according to actual conditions), the preset first-stage reheating temperature T after the LPG is reheated lpg 1 (or the unit is ℃), the specific heat of LPG unloaded at the terminal is cplpg (unit: kWh / (℃*t)), LPG flow rate Vpipe of the terminal output pipeline (unit: ton / h), the total mass of the heat exchange medium provided by the cold storage tank is m1, and the initial temperature of the heat exchange medium in the cold storage tank when the terminal starts unloading LPG is T0 (or tank temperature).

[0073] like Figure 2 As indicated, the time t referred to in the following content refers to the time taken as the starting point (i.e., time 0) when the LPG is unloaded at the current terminal.

[0074] 1.2. Perform basic calculation (or C0 calculation) based on the above primary parameters to obtain secondary parameters:

[0075] The unloading time required for unloading LPG at the terminal is calculated according to the following formula (1), which is denoted as t0 and the unit is h:

[0076]

[0077] The total cooling capacity released by unloading LPG at the terminal is calculated according to the following formula (2), which is recorded as E n , in kWh:

[0078] E n =m lpg ×cp lpg ×(-30-T lpg1 ) (2)

[0079] The "-30" in formula (2) refers to the initial temperature of LPG unloaded at the terminal -30℃ (T lpg0 ).

[0080] According to the following formula (3), the load of the cold storage tank receiving the cold capacity of the terminal steadily from the beginning of the unloading of LPG at the terminal (recorded as time 0) to the completion of the unloading at the terminal, that is, the time period 0-t0 (unloading period), that is, the cold load received by the cold heat exchanger during the unloading time (or called the cold taker load), recorded as e s , in kW:

[0081]

[0082] According to the following formula (4), the average external cold load stably released and delivered to the downstream by the cold storage tank from the beginning of LPG unloading at the terminal (recorded as time 0) to the predetermined cold use time t1, that is, in the period 0-t1 (i.e., within the predetermined cold use time), that is, the cold load stably received by the cold heat exchanger within the predetermined cold use time (or called the cold load received by the cold heat exchanger, or simply the cold heat exchanger load), is calculated as e a , in kW:

[0083]

[0084] According to the following formula (5), the stable net cold storage load of the cold storage tank (i.e., the net cold storage load of the cold storage tank) is calculated from the beginning of the unloading of LPG at the terminal to the completion of the unloading at the terminal, that is, during the period 0-t0 (i.e., the unloading time), recorded as e1, in kW:

[0085] e1=e s -e a (5)

[0086] 1.3. The process of establishing the first to fifth relationship equations based on the above primary parameters and secondary parameters is as follows:

[0087] 1.3.1. In the first operating condition, i.e. during the unloading of LPG at the terminal (i.e. the period from 0 to t0), the following C1 calculation is performed to establish the first, second and fourth relationship equations based on the primary and secondary parameters.

[0088] The specific heat cp1(T) of the heat exchange medium in the cold storage tube is a function of the temperature T. The unit of the specific heat cp1(T) is kWh / (℃*t). The functional relationship between the two is shown in the following formula (6). Therefore, the cold storage capacity at time t needs to be calculated based on the integral of the functional relationship:

[0089] cp1(T)=0.0011×T+0.8905 (6)

[0090]

[0091] E sp (t) is the net cold storage capacity of the cold storage tank at time t, in kWh; t is the time variable, in h; T is the tank temperature of the cold storage tank at time t, that is, the temperature of the heat exchange medium in the cold storage tank at that time, in °C;

[0092] By integrating and solving the above equation (7), we get the following equation (8), which is the fourth relation:

[0093]

[0094] In formula (8), T(t) is the temperature of the heat exchange medium in the cold storage tank at time t in the period 0-t0 (or tank temperature), and the unit is ° C. According to this relationship, the temperature of the heat exchange medium in the cold storage tank under the first working condition can be obtained in real time.

[0095]

[0096] Solving the above equation (9), we get the following equation (10), which is the first relation:

[0097]

[0098] In the above formulas (9) and (10), F1(t) is the heat exchange medium flow rate entering the cooling heat exchanger (or cooling device) at time t during the period 0-t0 (i.e., the heat exchange medium flow rate in the first circulation pipeline), and the unit is tons / h.

[0099]

[0100] Solving the above equation (11), we get the following equation (12), which is the second relation:

[0101]

[0102] In the above formulas (11) and (12), F2(t) is the heat exchange medium flow rate entering the cold heat exchanger (or cold heat exchanger) at time t during the period 0-t0 (i.e. the heat exchange medium flow rate in the second circulation pipeline), and the unit is tons / h.

[0103] In practical applications, during the period of 0-t0, the flow control valve set on the first circulation pipeline is integrally controlled according to the first relationship to achieve real-time integral control of the flow of the heat exchange medium entering the cold heat exchanger; at the same time, the flow control valve set on the second circulation pipeline is integrally controlled according to the second relationship to achieve real-time integral control of the flow of the heat exchange medium entering the cold heat exchanger. During the period of 0-t0, the temperature T of the heat exchange medium in the cold storage tank gradually decreases. At time 0, the temperature of the heat exchange medium in the cold storage tank is T0, and at time t0, the tank temperature is T1 (℃).

[0104] 1.3.2. In the second working condition, that is, after the unloading of LPG at the terminal is completed and within the predetermined cooling time (i.e., the period t0-t1), the following C2 calculation is performed, and the third and fifth relationship equations are established based on the first-level parameters and the second-level parameters.

[0105]

[0106] E2(t) is the cold storage tank (or cold storage system) delivered cold capacity at time t, in kWh; t is the time variable, in h; T is the tank temperature of the cold storage tank at time t, that is, the temperature of the heat exchange medium in the cold storage tank at that time, in °C; T1 is the temperature of the heat exchange medium in the cold storage tank at t=t0, that is, the initial temperature of the heat exchange medium in the cold storage tank in the second working condition, in °C;

[0107] By integrating and solving the above equation (13), we obtain the following equation (14), which is the fifth relation:

[0108]

[0109] In the above formula (14), T(t) is the temperature of the heat exchange medium in the cold storage tank at time t in the period t0-t1 (or tank temperature), and the unit is ° C. According to this relationship, the temperature of the heat exchange medium in the cold storage tank can be obtained in real time.

[0110]

[0111] Solve the above equation:

[0112] F1(t)=0

[0113] F1(t) is the heat exchange medium flow rate entering the cooling heat exchanger at time t during the period t0-t1, in tons / h. a is 0, and the heat exchange medium flow entering the cold heat exchanger is 0. That is, when the unloading of LPG at the terminal is completed, the valve on the first circulation pipeline is closed so that the heat exchange medium no longer enters the cold heat exchanger.

[0114]

[0115] Solving the above equation, we get equation (16), which is the third relation:

[0116]

[0117] In the above formulas (15) and (16), F2(t) is the heat exchange medium flow rate entering the cold heat exchanger at time t during the period t0-t1 (i.e., the heat exchange medium flow rate in the second circulation pipeline), and the unit is tons / h.

[0118] In practical applications, during the period t0-t1, the flow control valve provided on the second circulation pipeline is integrally controlled according to the third relationship to achieve real-time control of the flow of the heat exchange medium entering the cold heat exchanger.

[0119] 1.3.3. Under the third working condition, that is, during the period t1-t2, the heat exchange medium circulates only in a closed loop between the cold storage tank and the bypass circulation pipeline and is in an idling state. C3 calculation can also be performed:

[0120] T(t)=T(t1)

[0121] F1(t)-0

[0122] F2(t)=0

[0123] F2 * (t)=100

[0124] T(t) is the temperature of the heat exchange medium in the cold storage tank at time t during the period t1-t2, in degrees Celsius.

[0125] F1(t) is the heat exchange medium flow rate entering the cold heat exchanger at time t during the period t1-t2, in tons / h. F2(t) is the heat exchange medium flow rate entering the cold heat exchanger at time t during the period t1-t2. Under the third working condition, both flow rates are 0 tons / h.

[0126] F2 * (t) is the flow rate of refrigerant water bypassing the chiller and entering the bypass circulation pipeline 10 at time t during the period t1-t2. In this embodiment, the flow rate is set to 100 tons / h. A flow regulating valve can also be set on the bypass circulation pipeline 10.

[0127] Under this working condition, the temperature of the heat exchange medium in the cold storage tank remains unchanged and is the same as the temperature at time t1. In one embodiment, under the third working condition, the heat exchange medium flow rate on the bypass circulation line is set to the minimum economic flow rate, for example, 100 t / h.

[0128] The present invention adopts a single tank for cold storage and use, and does not control the temperature of the cold storage tank. Therefore, the temperature of the cold storage tank changes dynamically with time. Since the cold capacity carried by the LPG unloading at the terminal is intermittent and irregular, in order to ensure the stability and continuity of the cold use of the downstream process, the present invention establishes a system heat balance model based on the temperature-flow-cold capacity output relationship without controlling the tank temperature of the cold storage tank, and dynamically integrates the flow of the first circulation pipeline and the second circulation pipeline. The cold capacity released by the unloading of LPG at the terminal can be stably transported to downstream users.

[0129] The above control process of controlling the heat exchange medium flow rates of the first circulation pipeline and the second circulation pipeline can be implemented by corresponding calculation and control through the controller. Figure 3 A schematic diagram of a specific control process in an embodiment is shown for reference.

[0130] In one embodiment, the change trend of the heat exchange medium flow rate of the first circulation pipeline is as follows: Figure 4 As shown, the change trend of the heat exchange medium flow rate in the second circulation pipeline is as follows Figure 5 As shown in the figure, the temperature change trend of the heat exchange medium in the cold storage tank is as follows Figure 6 As shown in the figure, the change trend of the cooling load of the cold heat exchanger (or the cooling load of the cold heat exchanger) is as follows Figure 7 shown.

[0131] Furthermore, when the previous terminal unloads LPG and the next terminal unloads LPG, the next terminal unloads LPG directly into the cold recovery cycle, regardless of whether the method steps of the cold recovery cycle corresponding to the previous terminal unloads LPG are completed.

[0132] In some embodiments, the cooling load required to be provided by the cryogenic heat exchanger 5 is determined based on the cooling load required to cool the carbon dioxide stream to be pre-cooled to a preset secondary cryogenic temperature in the DMC process and the cooling load of the cold heat exchanger 3 receiving the cooling capacity released by unloading LPG from the terminal, thereby adjusting the refrigeration power of the variable frequency electric drive refrigerator 6 so that the variable frequency electric drive refrigerator 6 provides the cryogenic heat exchanger 5 with a cooling load that meets the demand.

[0133] In some embodiments, the temperature of the LPG unloaded from the dock varies from -40°C to 0°C before and after the first-level rewarming, and the pressure of the LPG transported by the dock pipeline is, for example, 20 barg or less, and the pressure remains unchanged during the heat exchange process; in the system of the present invention, the temperature of the heat exchange medium in the cold storage tank varies from -20°C to 10°C. The heat exchange medium in the cold storage tank is, for example, a 40wt% ethylene glycol aqueous solution. During the operation of the entire method, the heat exchange medium does not undergo a phase change and is a liquid medium. In the method of the present invention, the temperature and liquid level of the cold storage tank are not additionally controlled.

[0134] The following is a specific application case to further illustrate:

[0135] In the cold recovery cycle corresponding to a certain terminal unloading of LPG, the total mass of the LPG unloaded at the terminal is 15,700 tons, the initial temperature of the LPG unloaded at the terminal is -30°C, the specific heat of the LPG unloaded at the terminal is 0.833kWh / (°C*t), the LPG flow rate of the terminal output pipeline 6 is 1200 tons / h, and the first-level rewarming is performed to the first-level rewarming temperature of 0°C through the cold heat exchanger 2, and the predetermined cold time is 72h. In this example, the cooling load required to cool the carbon dioxide stream to be pre-cooled in the DMC process to the preset secondary deep cooling temperature is 10MW, the total mass of the heat exchange medium in the cold storage tank 1 is 11,110 tons, and the initial temperature of the heat exchange medium in the cold storage tank 1 at the beginning of the terminal unloading of LPG is 10°C.

[0136] First, C0 calculation is performed. The system calculates that t0=13h in this cycle, that is, the unloading time is 13h, and the continuous cooling time after unloading is 72h-13h=59h. Within the predetermined cooling time of 72h, the cooling system continuously and stably delivers a cooling load of 5MW to the downstream process users (that is, to the cooling heat exchanger).

[0137] Determine time t. When t is within the time period 0-t0, first perform C1 calculation, that is, enter the first working condition, and control the heat exchange medium flow of the first circulation pipeline according to the generated first relationship (specifically, the flow regulating valve on the first circulation pipeline can be controlled to change dynamically according to the control signal of the first relationship). In the time period 0-t0, the cold load of the cold heat exchanger 2 is stabilized at 27.55MW. After the LPG first-stage rewarming is stabilized at 0℃, the first-stage rewarmed LPG is sent to the second-stage rewarming heat exchanger 4, and then sent to the freezer after the second-stage rewarming reaches the required second-stage rewarming temperature. Control the heat exchange medium flow of the second circulation pipeline 8 according to the generated second relationship (specifically, the flow regulating valve on the second circulation pipeline 8 can be controlled to change dynamically according to the control signal of the second relationship). In the time period 0-t0, use the cold heat exchanger to stably receive the cold load of 5MW, and at the same time adjust the refrigeration power of the corresponding variable frequency electric drive chiller 6, so that the cold load provided by the deep cold heat exchanger 5 is 5MW unchanged.

[0138] Determine time t. When t=t0, the temperature of the heat exchange medium in the cold storage tank drops to T1 (-20°C).

[0139] Start to execute C2 calculation and enter the second working condition. The valve on the first circulation pipeline 7 is closed, and the heat exchange medium flow on the pipeline is 0, that is, at this time, the terminal cold capacity has been unloaded, and the LPG has been reheated and has entered the freezer. The heat exchange medium flow of the second circulation pipeline 8 is controlled according to the generated third relationship (specifically, the flow regulating valve on the second circulation pipeline 8 can be controlled to change dynamically according to the control signal of the third relationship). Under this working condition, the cold heat exchanger is used to stably receive the cold load of 5MW, and at the same time, the refrigeration power of the corresponding variable frequency electric drive refrigerator 6 is adjusted to make the cold load provided by the deep cold heat exchanger 5 remain unchanged at 5MW.

[0140] Determine time t. When t=t1, the temperature of the heat exchange medium in the cold storage tank rises to T1 (10°C).

[0141] Enter the third working condition, under which the C3 calculation begins. The heat exchange medium flow rates of the first circulation pipeline 7 and the second circulation pipeline 8 are both 0, that is, the predetermined cooling time in a single cooling recovery cycle has ended, and the valves of the first circulation pipeline and the second circulation pipeline are both closed. The valve on the bypass circulation pipeline 10 is opened, and the heat exchange medium neither enters the cooling heat exchanger nor the cooling heat exchanger. The flow rate of the bypass circulation pipeline 10 maintains the minimum flow rate F2 * (t) = 100 tons / h. Until the next cooling recovery cycle. During this period, the downstream continues to stably receive 0MW of cooling capacity, and the refrigeration power of the corresponding variable frequency electric drive chiller 6 is adjusted so that the cooling load provided by the cryogenic heat exchanger 5 is 10MW until the next cooling recovery cycle.

[0142] Enter the next cooling recovery cycle, re-execute the above steps, and perform corresponding calculations and controls.

[0143] In summary, combined with the above calculations, a storage and utilization model is established for the cold capacity of the terminal, and each cold capacity recovery cycle is divided into three working conditions for separate control, so as to maximize the recovery of low-quality intermittent cold capacity at the terminal, and realize continuous and stable external cold capacity delivery. Based on the method of the present invention, the valves and equipment operating load adjustments involved can meet the feasible range of the current hardware equipment, avoiding the engineering infeasibility and system operation risks caused by long-term and drastic fluctuations. In the above case, the system can stably recover an average of 5MW of cold capacity, and the corresponding refrigeration machine can save 2500kW of electricity. According to the stable operating conditions of 8000h throughout the year, the electricity cost is 0.6 yuan / kWh, and the economic benefit of the cold capacity recovery system of this process reaches 12 million yuan / year. The electricity saving in the cold capacity recovery process is converted into 9091 tons of bituminous coal per year, and the economic and environmental benefits are relatively significant.

[0144] The method provided by the present invention can meet the high-frequency and low-quality cold recovery conditions of the dock, and has good economic and engineering feasibility for intermittent energy recovery. Based on this method, because the design of the cold storage system occupies half the area of ​​the conventional design, the corresponding investment and construction can be reduced by half, the operating cost is low, and the risks to the process and environment are controllable, easy to adjust, with a wide recovery temperature range and strong universality, it is especially suitable for intermittent energy recovery with an intermittent peak-to-valley ratio greater than 1<12.

[0145] In the method provided by the present invention for recovering the cold energy carried by LPG unloaded at the wharf for use in the DMC process, the control of each valve and each flow rate involved can be implemented by an automatic control system.

[0146] Figure 8 An electronic device is shown, comprising: at least one processor 401; and a memory 402 communicatively connected to the at least one processor 401; wherein the memory 402 stores instructions executable by the at least one processor 401, and the instructions are executed by the at least one processor 401 so that the at least one processor 401 can execute the corresponding control steps involved in the method of the present invention, and these control steps include but are not limited to the flow control of the heat exchange medium of the first circulation pipeline and the second circulation pipeline, and may also include the refrigeration power control of the variable frequency electric drive chiller, the flow control of the bypass circulation pipeline, the control of the opening and closing of the corresponding valves according to different working conditions, etc.

[0147] Figure 4 Take a processor 402 as an example:

[0148] The electronic device may further include: an input device 403 and an output device 404 .

[0149] The processor 401, the memory 402, the input device 403 and the output device 404 may be connected via a bus or other means, and the figure takes the connection via a bus as an example.

[0150] The memory 402 is a non-volatile computer-readable storage medium that can be used to store non-volatile software programs, non-volatile computer executable programs and modules, such as program instructions / modules corresponding to the control steps in the embodiments of the present application. The processor 401 executes various functional applications and data processing by running the non-volatile software programs, instructions and modules stored in the memory 402, that is, realizing the corresponding control in the above embodiments.

[0151] The memory 402 may include a program storage area and a data storage area, wherein the program storage area may store an operating system and an application required by at least one function; the data storage area may store data created by using the method of the present invention, etc. In addition, the memory 402 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage devices.

[0152] The input device 403 can receive input user clicks and generate signal inputs related to user settings and function control of the method of the present invention. The output device 404 can include display devices such as display screens.

[0153] The above description is only the principle and preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this field, the implementation methods obtained by appropriately combining the technical solutions disclosed in different embodiments are also included in the technical scope of the present invention. On the basis of the principle of the present application, several other variations can be made, which should also be regarded as the protection scope of the present application.

Claims

1. A method for recovering the cold energy carried by LPG unloaded at the wharf for use in a DMC process, characterized in that: Each time the terminal unloads LPG, it corresponds to a cold recovery cycle; the method steps of a single cold recovery cycle include: During the unloading of LPG at the wharf, the LPG unloaded at the wharf is continuously sent to the cold heat exchanger through the wharf output pipeline. The cold heat exchanger and the cold storage tank are connected through a first circulation pipeline so that the heat exchange medium in the cold storage tank can circulate between the two. The heat exchange medium from the cold storage tank exchanges heat with the LPG sent to the cold heat exchanger, so that the LPG unloaded at the wharf is first-stage reheated, and at the same time, the cold carried by the LPG unloaded at the wharf is stored in the heat exchange medium; During the unloading of LPG at the terminal, the carbon dioxide stream to be precooled in the DMC process is simultaneously fed into the cold heat exchanger, the cold storage tank and the cold heat exchanger are connected via a second circulation pipeline so that the heat exchange medium in the cold storage tank can circulate between the two, and the heat exchange medium from the cold storage tank exchanges heat with the carbon dioxide stream fed into the cold heat exchanger, so that the carbon dioxide stream is precooled in the first stage; When the terminal has completed unloading of LPG, closing the valve on the first circulation pipeline for controlling the on-off of the first circulation pipeline; When the time from unloading LPG at the terminal starts to reach the predetermined cold usage time, the valve on the second circulation pipeline used to control the on-off of the second circulation pipeline is closed; at the same time, the valve on the bypass circulation pipeline connected to the cold storage tank is opened, so that the heat exchange medium circulates in a closed loop between the cold storage tank and the bypass circulation pipeline.

2. The method according to claim 1, characterized in that: During the predetermined cooling time, the heat exchange medium flow rates of the first circulation pipeline and the second circulation pipeline are controlled so that the cooling heat exchanger can receive a stable cooling load from the cold storage tank.

3. The method according to claim 2, characterized in that The control step of controlling the heat exchange medium flow of the first circulation pipeline and the second circulation pipeline includes: S100, obtaining primary parameters, wherein the primary parameters include the total mass of LPG unloaded during the unloading of LPG at the terminal, the initial temperature of the LPG unloaded at the terminal, the preset primary rewarming temperature of the LPG after the primary rewarming, the specific heat of the LPG unloaded at the terminal, the LPG flow rate of the terminal output pipeline, the total mass of the heat exchange medium, the initial temperature of the heat exchange medium in the cold storage tank when the unloading of LPG at the terminal starts, and the predetermined cold use time; S200, calculating and obtaining secondary parameters according to the primary parameters, wherein the secondary parameters include the unloading time required for the terminal to unload the LPG, the total cold released by the terminal when unloading the LPG, the cold load received by the cold heat exchanger during the unloading time, the cold load received by the cold heat exchanger during the predetermined cold use time, and the net cold storage load of the cold storage tank during the unloading time; S300, establishing a first relational expression, a second relational expression, and a third relational expression between flow and time according to the primary parameter and the secondary parameter; the first relational expression is a relational expression between the flow of heat exchange medium on the first circulation pipeline and time during the period when the terminal unloads LPG; the second relational expression is a relational expression between the flow of heat exchange medium on the second circulation pipeline and time during the period when the terminal unloads LPG; the third relational expression is a relational expression between the flow of heat exchange medium on the second circulation pipeline and time after the terminal has completed unloading LPG and within the predetermined cooling time; S400. During the unloading of LPG at the terminal, the flow rate of heat exchange medium on the first circulation pipeline is controlled according to the first relationship, and the flow rate of heat exchange medium on the second circulation pipeline is controlled according to the second relationship; after the unloading of LPG at the terminal is completed and within the predetermined cooling time, the flow rate of heat exchange medium on the second circulation pipeline is controlled according to the third relationship.

4. The method according to claim 3, characterized in that The step S300 further includes: establishing a fourth relationship and a fifth relationship between temperature and time; Establishing the fourth relational expression according to the primary parameter and the secondary parameter, wherein the fourth relational expression is a relational expression between the temperature of the heat exchange medium in the cold storage tank and time during the unloading of LPG at the terminal; The primary parameters also include the temperature of the heat exchange medium in the cold storage tank when the terminal completes unloading of LPG. The fifth relationship is established based on the primary parameters and the secondary parameters. The fifth relationship is the relationship between the temperature of the heat exchange medium in the cold storage tank and time after the terminal completes unloading of LPG and within the predetermined cooling time. Alternatively, the temperature of the heat exchange medium in the cold storage tank when the terminal completes unloading of LPG is obtained based on the fourth relationship, and the fifth relationship is established based on the primary parameters, the secondary parameters and the temperature of the heat exchange medium in the cold storage tank when the terminal completes unloading of LPG.

5. The method according to claim 4, characterized in that According to the fourth relationship, the temperature of the heat exchange medium in the cold storage tank is obtained in real time during the unloading of LPG at the terminal; According to the fifth relationship, the temperature of the heat exchange medium in the cold storage tank is obtained in real time after the unloading of LPG at the terminal is completed and within the predetermined cold use time.

6. The method according to claim 4, characterized in that In step S300: Establishing the first relational expression according to the fourth relational expression and the cooling load received by the cooling heat exchanger within the predetermined cooling time; The second relational expression is established according to the fourth relational expression and the cold load received by the cold extraction heat exchanger during the unloading time; The third relational expression is established based on the fifth relational expression and the cold load received by the cold extraction heat exchanger during the unloading time.

7. The method according to claim 3, characterized in that The LPG after the primary rewarming is sent to the secondary rewarming heat exchanger for secondary rewarming to the secondary rewarming temperature; The carbon dioxide stream after the primary precooling is sent to the cryogenic heat exchanger to be cooled to a preset secondary cryogenic temperature; the cryogenic heat exchanger is connected to a variable frequency electric drive refrigerator.

8. The method according to claim 7, characterized in that According to the cooling load required for cooling the carbon dioxide stream to be pre-cooled to the secondary cryogenic temperature in the DMC process and the cooling load received by the cold heat exchanger, the refrigeration power of the variable frequency electric driven refrigerator is regulated so that the variable frequency electric driven refrigerator can provide the cryogenic heat exchanger with a cooling load that meets the demand.

9. The method according to any one of claims 1 to 8, characterized in that: After the previous terminal unloading of LPG is completed, when the next terminal unloading of LPG is required, no matter whether the method steps of the cold energy recovery cycle corresponding to the previous terminal unloading of LPG are completed, the next terminal unloading of LPG cold energy recovery cycle is directly entered.

10. The method according to any one of claims 2 to 8, characterized in that: The temperature variation range of the LPG unloaded from the terminal before and after the first-level rewarming is -40°C to 0°C; And / or, the temperature of the heat exchange medium varies in the range of -20°C to 10°C.

11. An electronic device, characterized in that: comprising at least one processor; and, a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the control steps according to any one of claims 3 to 9.

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