Cracking tail gas treatment system and treatment method

Abstract

The invention discloses a cracking tail gas treatment system and method, and belongs to the technical field of cracking tail gas treatment. The cracking tail gas treatment system comprises a dealkylation device, a dehydration device and a liquefaction device, and the dealkylation device is used for removing hydrocarbon components in cracking tail gas and generating product gas; a gas inlet of the dehydration device is communicated with a gas outlet of the dealkylation device, and the dehydration device is used for adsorbing moisture in the product gas, so that the product gas forms dry gas; a gas inlet of the liquefying device is communicated with a gas outlet of the dehydrating device, and the liquefying device is used for enabling the dry gas to form liquefied natural gas and hydrogen-rich gas. According to the scheme, the natural gas and the hydrogen-rich gas in the cracking tail gas can be prepared, so that the utilization rate of the cracking tail gas can be effectively improved.

Description

Technical Field

[0001] The present application belongs to the technical field of cracking tail gas treatment, and specifically relates to a cracking tail gas treatment system and treatment method. Background Art

[0002] Cracking tail gas is an industrial waste gas produced during the petroleum refining process, which contains a certain proportion of methane and hydrogen. In the petrochemical industry, this tail gas is usually used as boiler fuel to recover its heat energy. However, the value that can be achieved in this way is not high.

[0003] However, the method of recovering the heat energy of the cracking tail gas only by using the cracking tail gas as fuel cannot fully and effectively utilize and recover the components in the cracking tail gas, thereby resulting in a low utilization rate of the cracking tail gas.

[0004] Therefore, the prior art has the problem of low utilization rate of cracking tail gas. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide a system and method for processing cracking tail gas, which can solve the problem of low utilization rate of cracking tail gas in related technologies.

[0006] In a first aspect, an embodiment of the present application provides a system for processing cracking tail gas, comprising: A dehydrocarbon removal device is used to remove hydrocarbon components from the cracking tail gas and generate product gas; A dehydration device, wherein the air inlet of the dehydration device is connected to the air outlet of the dehydrogenation device, and the dehydration device is used to absorb moisture in the product gas to form dry gas from the product gas; A liquefaction device, wherein the gas inlet of the liquefaction device is connected to the gas outlet of the dehydration device, and the liquefaction device is used to convert the dry gas into liquefied natural gas and hydrogen-rich gas.

[0007] In a second aspect, the present application also provides a method for treating cracking tail gas, which is applied to the above-mentioned cracking tail gas treatment system, comprising: Dehydrocarbonizing the cracked tail gas to remove hydrocarbon components in the cracked tail gas and generate product gas; Dehydrating the product gas to form dry gas; The dry gas is liquefied to generate liquefied natural gas and hydrogen-rich gas.

[0008] In the embodiment of the present application, the hydrocarbon components in the cracking tail gas are removed by a dehydrogenation device, such as removing heavy hydrocarbons and unsaturated hydrocarbons in the cracking tail gas, so that the cracking tail gas generates product gas, and then the water in the product gas is removed by a dehydration device to form dry gas, and finally enters the liquefaction device for liquefaction, thereby generating liquefied natural gas and hydrogen-rich gas. In this way, natural gas and hydrogen-rich gas can be prepared from the cracking tail gas, thereby effectively improving the utilization rate of the cracking tail gas, and because the dehydrogenation device removes the hydrocarbon components in the cracking tail gas, the product gas is not easy to polymerize during the subsequent drying and liquefaction process, and is not easy to shorten the life of the catalyst in the dehydration device, and is not easy to cause freezing and blocking of the pipeline in the liquefaction device, thereby extending the service life of the dehydration device and the liquefaction device. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a structural schematic diagram of a cracking tail gas processing system disclosed in an embodiment of the present application; Figure 2 It is a schematic diagram of the structure of the dehydrogenation device disclosed in the embodiment of the present application; Figure 3 It is a schematic diagram of the structure of the dehydration device disclosed in the embodiment of the present application; Figure 4 It is a schematic diagram of the structure of the liquefaction device disclosed in the embodiment of the present application; Figure 5 It is a structural schematic diagram of the refrigeration mechanism disclosed in the embodiment of the present application; Figure 6 It is a schematic flow chart of the method for treating cracking tail gas disclosed in the embodiment of the present application.

[0010] Description of reference numerals: 100-dehydrogenation unit; 200-dehydration unit; 300-liquefaction unit; 400-pressurization unit; 500-dust filter; 110-adsorption tower; 120-feeding pipeline; 121-first control valve; 130 - desorbed gas discharge pipeline; 131 - second control valve; 140 - vacuum pipeline; 141 - vacuum pump; 142 - third control valve; 150 - pressure regulating pipeline; 151 - first pressure regulating pipeline; 152 - second pressure regulating pipeline; 153-fourth control valve; 1531-first pressure regulating control valve; 1532-second pressure regulating control valve; 160-product gas delivery pipeline; 161-ninth control valve; 170-product gas circuit; 171-the tenth control valve; 180-the first separator; 190-the desorption gas buffer tank; 1010-the desorption gas fan; 1020-desorption gas cooler; 1030-product gas buffer tank; 210-drying tower; 211-first drying tower; 212-second drying tower; 213-third drying tower; 220-regeneration heater; 230-regeneration air intake pipe; 231 - fifth control valve; 240 - regeneration gas outlet pipe; 241 - sixth control valve; 250-product gas inlet pipeline; 251-first gas inlet pipeline; 252-second gas inlet pipeline; 253-seventh control valve; 2531-first air intake control valve; 2532-second air intake control valve; 260-drying gas exhaust pipe; 261-eleventh control valve; 270-regeneration cooler; 280-regeneration exhaust pipe; 281-eighth control valve; 290-regeneration separator; 2010-regeneration recovery pipeline; 2020-filter separator; 310-liquefied cold box; 311-natural gas flow channel; 3111-first natural gas flow channel; 3112-second natural gas flow channel; 312-first heat exchange flow channel; 3121-first throttle valve; 313-second heat exchange flow channel; 314-first heat recovery flow channel; 315 - second heat recovery channel; 316 - third heat exchange channel; 317 - fourth heat exchange channel; 318-first pipeline; 3181-fifth throttle valve; 319-second pipeline; 3191-sixth throttle valve; 320 - second separator; 330 - refrigeration mechanism; 331 - first compressor; 332 - first cooler; 333-third separator; 334-second compressor; 335-second cooler; 336-fourth separator; 340- flash mechanism; 341- high-pressure flash tank; 342- low-pressure flash tank; 343- second throttle valve; 344-third throttle valve; 345-fourth throttle valve. DETAILED DESCRIPTION

[0011] The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0012] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0013] The following is a detailed description of the cracking tail gas treatment system and treatment method provided in the embodiments of the present application through specific embodiments and their application scenarios in conjunction with the accompanying drawings.

[0014] refer to Figure 1-Figure 5 A cracking tail gas processing system provided in an embodiment of the present application may include a dehydrogenation device 100, a dehydration device 200 and a liquefaction device 300.

[0015] Among them, the dehydrogenation device 100 can be used to remove the hydrocarbon components in the cracking tail gas and generate product gas; the air inlet of the dehydration device 200 can be connected to the air outlet of the dehydrogenation device 100, and the dehydration device 200 can be used to absorb moisture in the product gas to form dry gas from the product gas; the air inlet of the liquefaction device 300 can be connected to the air outlet of the dehydration device 200, and the liquefaction device 300 can be used to form liquefied natural gas and hydrogen-rich gas from the dry gas.

[0016] The hydrocarbon components in the cracking tail gas are removed by the dehydrogenation device 100, such as heavy hydrocarbons and unsaturated hydrocarbons in the cracking tail gas, so that the cracking tail gas generates product gas, and then the water in the product gas is removed by the dehydration device 200 to form dry gas, and finally enter the liquefaction device 300 for liquefaction, so as to generate liquefied natural gas and hydrogen-rich gas. In this way, natural gas and hydrogen-rich gas can be prepared from the cracking tail gas, so as to effectively improve the utilization rate of the cracking tail gas, and avoid direct discharge of the cracking tail gas, so as to reduce the pollution of the cracking tail gas to the environment.

[0017] Furthermore, since the dehydrogenation device 100 removes hydrocarbon components from the cracking tail gas, the product gas is less likely to polymerize during the subsequent drying and liquefaction steps, thereby less likely to shorten the life of the catalyst in the dehydration device 200 and less likely to freeze the pipelines in the liquefaction device 300, thereby extending the service life of the dehydration device 200 and the liquefaction device 300.

[0018] In an optional embodiment of the present application, the dehydrogenation device 100 may include at least five adsorption towers 110, which may be used to adsorb hydrocarbon components in the cracking tail gas. Each adsorption tower 110 may be provided with a top opening and a bottom opening. The bottom opening of each adsorption tower 110 may be used to allow the cracking tail gas to enter, and the top opening of each adsorption tower 110 may be used to communicate with the dehydration device 200. Here, the gas outlet of the dehydrogenation device 100 may include a top opening.

[0019] Each adsorption tower 110 has a first operation cycle, and the first operation cycle may include multiple first operation stages, including an adsorption stage, an inversion stage, a vacuum stage, a pressure reduction stage, and a pressure increase stage. Optionally, the first operation stages of at least five adsorption towers 110 are different from each other. In this way, each adsorption tower 110 can work alternately between different first operation stages, and the first operation stages of at least five adsorption towers 110 are different from each other at the same time, which can ensure that at least one adsorption tower 110 is in the adsorption stage, thereby realizing continuous dehydrogenation treatment of cracking tail gas.

[0020] In other embodiments, the dehydrogenation device 100 may include only one adsorption tower 110 , or the dehydrogenation device 100 may include at least five adsorption towers 110 , and the operation phases of the adsorption towers 110 are the same.

[0021] In an optional embodiment, the dehydrogenation device 100 may further include a feed pipeline 120, which may be used to transport cracked tail gas, and the bottom opening of each adsorption tower 110 may be connected to the feed pipeline 120, and a first control valve 121 may be provided between the bottom opening of each adsorption tower 110 and the feed pipeline 120, and the first control valve 121 may be used to control the connection and disconnection between the bottom opening and the feed pipeline 120. In this way, the feed conditions of each adsorption tower 110 may be controlled respectively by each first control valve 121, so as to control each adsorption tower 110 to perform the adsorption process alternately.

[0022] Of course, the first control valve 121 may not be provided between the bottom opening of each adsorption tower 110 and the feed pipeline 120 .

[0023] The dehydrocarbon removal device 100 may further include a desorbed gas discharge pipeline 130, the bottom opening of each adsorption tower 110 may be connected to the inlet of the desorbed gas discharge pipeline 130, the outlet of the desorbed gas discharge pipeline 130 may be used to communicate with an external desorbed gas delivery pipeline, and a second control valve 131 may be provided between the bottom opening of each adsorption tower 110 and the desorbed gas discharge pipeline 130, and the second control valve 131 may be used to control the on-off between the bottom opening and the desorbed gas discharge pipeline 130. In this way, the discharge of the desorbed gas of each adsorption tower 110 may be controlled separately by the second control valve 131, so as to control each adsorption tower 110 to perform the reverse placement process alternately.

[0024] Of course, the second control valve 131 may not be provided between the bottom opening of each adsorption tower 110 and the desorption gas discharge pipeline 130 .

[0025] The dehydrocarbon removal device 100 may further include a vacuum pipe 140, the bottom opening of each adsorption tower 110 may be connected to the inlet of the vacuum pipe 140, the outlet of the vacuum pipe 140 may be used to communicate with the external desorption gas delivery pipeline, and a third control valve 142 may be provided between the bottom opening of each adsorption tower 110 and the vacuum pipe 140, and the third control valve 142 may be used to control the connection and disconnection between the bottom opening and the vacuum pipe 140. In this way, the vacuuming conditions of each adsorption tower 110 may be controlled separately by the third control valve 142, so as to control each adsorption tower 110 to alternately perform the vacuuming process.

[0026] Here, a vacuum pump 141 may be provided on the vacuum pipe 140 to evacuate the adsorption tower 110 .

[0027] Of course, the third control valve 142 may not be provided between the bottom opening of each adsorption tower 110 and the vacuum pipe 140 .

[0028] The dehydrocarbon removal device 100 may also include a pressure regulating pipeline 150, and the top openings of each adsorption tower 110 are connected through the pressure regulating pipeline 150, and a fourth control valve 153 may be provided between the top opening of each adsorption tower 110 and the pressure regulating pipeline 150, and the fourth control valve 153 may be used to control the connection and disconnection between the top opening and the pressure regulating pipeline 150. In this way, the air intake and air outlet of each adsorption tower 110 can be controlled separately by the fourth control valve 153, so as to control each adsorption tower 110 to alternately perform the pressure reduction and pressure increase process. It should be noted that the pressure reduction here refers to the pressure equalization and the pressure increase refers to the pressure equalization and pressure increase, that is, the pressure of the two connected adsorption towers 110 is balanced by increasing and reducing the pressure.

[0029] Of course, the dehydrogenation device 100 may not include the pressure regulating pipeline 150 .

[0030] Optionally, the pressure regulating pipeline 150 may include a first pressure regulating pipeline 151 and a second pressure regulating pipeline 152. The top openings of each adsorption tower 110 may be connected through the first pressure regulating pipeline 151, and the top openings of each adsorption tower 110 may also be connected through the second pressure regulating pipeline 152. A first pressure regulating control valve 1531 may be arranged between the top opening of each adsorption tower 110 and the first pressure regulating pipeline 151. The first pressure regulating control valve 1531 may be used to control the connection and disconnection between the top opening and the first pressure regulating pipeline 151. A second pressure regulating control valve 1532 may be arranged between the top opening of each adsorption tower 110 and the second pressure regulating pipeline 152. The second pressure regulating control valve 1532 may be used to control the connection and disconnection between the top opening and the second pressure regulating pipeline 152. Here, the fourth control valve 153 may include the first pressure regulating control valve 1531 and the second pressure regulating control valve 1532. Among them, when the adsorption tower 110 is subjected to one pressure reduction and one pressure increase, the first pressure regulating control valve 1531 connected to the adsorption tower 110 that needs to be subjected to one pressure reduction and one pressure increase can be opened, so that the gas in the adsorption tower 110 that is subjected to one pressure reduction enters the adsorption tower 110 that is subjected to one pressure increase through the first pressure regulating pipeline 151; when the adsorption tower 110 is subjected to two or three pressure reductions or two or three pressure increases, the second pressure regulating control valve 1532 connected to the adsorption tower 110 that needs to be subjected to two or three pressure reductions or two or three pressure increases can be opened, so that the gas in the adsorption tower 110 that is subjected to two or three pressure reductions enters the adsorption tower 110 that is subjected to two or three pressure increases through the second pressure regulating pipeline 152. In this way, the first pressure regulating pipeline 151 and the second pressure regulating pipeline 152 can be used at the same time, so that the adsorption towers 110 can be operated in parallel during the pressure equalization process, which can reduce the waiting time when a single pipeline is operated, thereby improving the operating efficiency of the entire system. It should be noted that the adsorption tower 110 can perform secondary pressure regulation (ie, pressure reduction or pressure increase) and tertiary pressure regulation through the second pressure regulation pipeline 152. Here, the secondary pressure regulation and the tertiary pressure regulation can be performed in different time periods.

[0031] Of course, the pressure regulating pipeline 150 may also include only one pipeline, and the fourth control valve 153 may also include only one pressure regulating control valve.

[0032] Alternatively, the pressure regulating pipeline 150 may include a first pressure regulating pipeline 151, a second pressure regulating pipeline 152 and a third pressure regulating pipeline, and the top opening of each adsorption tower 110 may also be connected through the third pressure regulating pipeline, and a third pressure regulating control valve may be provided between the top opening of each adsorption tower 110 and the third pressure regulating pipeline, and the third pressure regulating control valve may be used to control the connection and disconnection between the top opening and the third pressure regulating pipeline. Here, the fourth control valve 153 may include a first pressure regulating control valve 1531, a second pressure regulating control valve 1532 and a third pressure regulating control valve. When the adsorption tower 110 performs one pressure reduction and one pressure increase, the first pressure regulating control valve 1531 connected to the adsorption tower 110 that needs to perform one pressure reduction and one pressure increase can be opened, so that the gas in the adsorption tower 110 that performs one pressure reduction enters the adsorption tower 110 that performs one pressure increase through the first pressure regulating pipeline 151; when the adsorption tower 110 performs two pressure reductions and two pressure increases, the second pressure regulating control valve 1532 connected to the adsorption tower 110 that needs to perform two pressure reductions and two pressure increases can be opened, so that the gas in the adsorption tower 110 that performs two pressure reductions can enter the adsorption tower 110 that performs two pressure increases through the second pressure regulating pipeline 152; when the adsorption tower 110 performs three pressure reductions and three pressure increases, the third pressure regulating control valve connected to the adsorption tower 110 that needs to perform three pressure reductions and three pressure increases can be opened, so that the gas in the adsorption tower 110 that performs three pressure reductions can enter the adsorption tower 110 that performs three pressure increases through the third pressure regulating pipeline.

[0033] Further optionally, the dehydrogenation device 100 may also include a product gas delivery pipeline 160 and a product gas loop 170, the top outlet of each adsorption tower 110 is connected to the dehydration device 200 through the product gas delivery pipeline 160, and a ninth control valve 161 is arranged between the top opening of each adsorption tower 110 and the product gas delivery pipeline 160, the two ends of the product gas loop 170 can be respectively connected to the product gas delivery pipeline 160 and the pressure regulating pipeline 150, and the product gas loop 170 is provided with a tenth control valve 171 for controlling the on-off of the product gas loop 170, part of the product gas can enter the adsorption tower 110 through the product gas loop 170 and the pressure regulating pipeline 150, thereby adjusting the pressure of the adsorption tower 110.

[0034] In some embodiments, the dehydrogenation device 100 may include ten adsorption towers 110, and all of the ten adsorption towers 110 have a first operation cycle, wherein when the adsorption tower 110A is in the first adsorption stage, the adsorption tower 110B is in the second adsorption stage, the adsorption tower 110C is in the third adsorption stage, the adsorption tower 110D is in the adsorption completion stage, the adsorption tower 110E is in the inversion stage, the adsorption tower 110F is in the vacuum stage, the adsorption tower 110G is in the first depressurization stage, the adsorption tower 110H is in the first pressure increase stage, the adsorption tower 110I is in the second pressure increase stage, and the adsorption tower 110J is in the third pressure increase stage. Here, the degree of adsorption in the first adsorption stage is less than the degree of adsorption in the second adsorption stage, and the degree of adsorption in the second adsorption stage is less than the degree of adsorption in the third adsorption stage. Here, each adsorption tower 110 can be depressurized three times and pressurized three times.

[0035] Specifically, the process of the dehydrogenation device 100 is described by taking the operating conditions experienced by the adsorption tower 110A in the first operation cycle as an example.

[0036] Adsorption stage: the first control valve 121 between the adsorption tower 110A and the feed pipeline 120 and the ninth control valve 161 between the adsorption tower 110A and the product gas delivery pipeline 160 are opened, the cracked tail gas enters the adsorption tower 110A through the feed pipeline 120, the hydrocarbon components in the cracked tail gas are adsorbed by the adsorption bed in the adsorption tower 110A under the adsorption pressure, and then the cracked tail gas generates product gas, which is output to the dehydration device 200 through the product gas delivery pipeline 160 through the ninth control valve 161. When the front edge of the adsorption bed reaches the preset position, the first control valve 121 between the adsorption tower 110A and the feed pipeline 120 and the ninth control valve 161 between the adsorption tower 110A and the product gas delivery pipeline 160 are closed, so that the cracked tail gas stops entering the adsorption tower 110A, and the product gas in the adsorption tower 110A stops being discharged.

[0037] After the adsorption tower 110A stops adsorption, the fourth control valve 153 between the adsorption tower 110A and the pressure regulating pipe 150 and the fourth control valve 153 between the adsorption tower 110H and the pressure regulating pipe 150 are opened to connect the top opening of the adsorption tower 110A with the top opening of the adsorption tower 110H which has just finished the second pressurization. The gas in the adsorption tower 110A can enter the adsorption tower 110H, so that the adsorption tower 110A realizes the first pressure reduction and the adsorption tower 110H realizes the third pressure increase. At the end of this step, the pressures of the adsorption tower 110A and the adsorption tower 110H are basically balanced, thereby achieving the effect of pressure equalization.

[0038] After the adsorption tower 110A completes the first pressure reduction, the fourth control valve 153 between the adsorption tower 110A and the pressure regulating pipeline 150 and the fourth control valve 153 between the adsorption tower 110H and the pressure regulating pipeline 150 are closed, and the fourth control valve 153 between the adsorption tower 110I and the pressure regulating pipeline 150 is opened. The gas in the adsorption tower 110A can enter the adsorption tower 110I that has just completed the first pressure increase step, so that the adsorption tower 110A can achieve the second pressure reduction and the adsorption tower 110I can achieve the second pressure increase. At the end of this step, the pressures of the adsorption tower 110A and the adsorption tower 110I are basically balanced, thereby achieving the effect of pressure equalization.

[0039] After the adsorption tower 110A completes the second pressure reduction, the fourth control valve 153 between the adsorption tower 110I and the pressure regulating pipeline 150 is closed, and the fourth control valve 153 between the adsorption tower 110J and the pressure regulating pipeline 150 is opened. The gas in the adsorption tower 110A can enter the adsorption tower 110J that has just completed vacuuming, so that the adsorption tower 110A achieves the third pressure reduction and the adsorption tower 110J achieves the first pressure increase. At the end of this step, the pressures of the adsorption tower 110A and the adsorption tower 110J are basically balanced, thereby achieving the effect of pressure equalization.

[0040] After the adsorption tower 110A completes the third pressure reduction, the fourth control valve 153 between the adsorption tower 110A and the pressure regulating pipeline 150 and the fourth control valve 153 between the adsorption tower 110I and the pressure regulating pipeline 150 are closed, and the second control valve 131 between the adsorption tower 110A and the desorption gas discharge pipeline 130 is opened, so that the gas in the adsorption tower 110A is reversely discharged with the hydrocarbon components in the adsorption tower 110A to the desorption gas discharge pipeline 130, and is discharged from the desorption gas transport pipeline through the desorption gas discharge pipeline 130.

[0041] After the inversion is completed, close the second control valve 131 between the adsorption tower 110A and the desorption gas exhaust pipe 130, open the third control valve 142 between the adsorption tower 110A and the vacuum pipe 140, and turn on the vacuum pump 141 to desorb the gas adsorbed on the adsorption bed in the adsorption tower 110A by vacuuming and discharge it.

[0042] After the vacuuming is completed, the adsorption tower 110A enters the first pressurization process, and the fourth control valve 153 between the adsorption tower 110A and the pressure regulating pipe 150 and the fourth control valve 153 between the adsorption tower 110D and the pressure regulating pipe 150 are opened to connect the top opening of the adsorption tower 110A with the top opening of the adsorption tower 110D which has just finished the second pressure reduction. The gas in the adsorption tower 110A can enter the adsorption tower 110D, so that the adsorption tower 110A realizes the first pressure increase and the adsorption tower 110D realizes the third pressure reduction. At the end of this step, the pressures of the adsorption tower 110A and the adsorption tower 110D are basically balanced, thereby achieving the effect of pressure equalization.

[0043] After the adsorption tower 110A completes the first pressure increase, the fourth control valve 153 between the adsorption tower 110D and the pressure regulating pipeline 150 is closed, and the fourth control valve 153 between the adsorption tower 110F and the pressure regulating pipeline 150 is opened. The gas in the adsorption tower 110A can enter the adsorption tower 110F that has just completed the first pressure reduction, so that the adsorption tower 110A achieves the second pressure increase and the adsorption tower 110J achieves the second pressure reduction. At the end of this step, the pressures of the adsorption tower 110A and the adsorption tower 110F are basically balanced, thereby achieving the effect of pressure equalization.

[0044] After the adsorption tower 110A completes the second pressurization, the fourth control valve 153 between the adsorption tower 110F and the pressure regulating pipeline 150 is closed, and the fourth control valve 153 between the adsorption tower 110H and the pressure regulating pipeline 150 is opened. The gas in the adsorption tower 110A can enter the adsorption tower 110H that has just completed the adsorption, so that the adsorption tower 110A achieves the third pressurization and the adsorption tower 110H achieves the first pressure reduction. At the end of this step, the pressures of the adsorption tower 110A and the adsorption tower 110H are basically balanced, thereby achieving the effect of pressure equalization.

[0045] Finally, by opening the tenth control valve 171 and the fourth control valve 153 between the adsorption tower 110A and the pressure regulating pipeline 150, part of the product gas enters the adsorption tower 110A, and at the same time, the first control valve 121 between the adsorption tower 110A and the feed pipeline 120 is opened to allow part of the cracking tail gas to enter the adsorption tower 110A, so that the pressure of the adsorption tower 110A rises to the adsorption pressure, and then the adsorption tower 110A can carry out the adsorption step of the next cycle.

[0046] In an optional embodiment, the dehydrogenation device 100 may further include a first separator 180, which may be disposed upstream of the adsorption tower 110, and the first separator 180 may be used to separate liquid and gas in the cracking tail gas, and the feed pipeline 120 may be connected to the gas outlet of the first separator 180. In this way, the first separator 180 may separate the liquid and gas in the cracking tail gas, and remove the liquid and some impurities in the cracking tail gas, thereby helping to improve the purity of the raw gas entering the adsorption tower 110, thereby providing a higher quality raw material for the subsequent pressure swing adsorption process, thereby improving the purity and yield of the product gas, and by removing impurities in the cracking tail gas, the first separator 180 may also extend the service life of the adsorption tower 110 and the adsorbent in the adsorption tower 110, and reduce the maintenance cost and replacement frequency of the equipment; at the same time, the first separator 180 may also play a buffering role for the cracking tail gas, and prevent the cracking tail gas from impacting the adsorption tower 110. Here, the -0.3 MPa cracking tail gas from outside the boundary can enter the first separator 180 for separation, and the separated gas enters the adsorption tower 110.

[0047] In other embodiments, the dehydrogenation device 100 may not include the first separator 180 .

[0048] In an optional embodiment, the dehydrogenation device 100 may further include a desorbed gas buffer tank 190 and a desorbed gas blower 1010. The inlet of the desorbed gas buffer tank 190 may be connected to the outlet of the desorbed gas discharge pipeline 130 and the outlet of the vacuum pipeline 140, respectively. The outlet of the desorbed gas buffer tank 190 may be connected to the inlet of the desorbed gas blower 1010, and the outlet of the desorbed gas blower 1010 may be used to connect to an external desorbed gas delivery pipeline. The desorbed gas blower 1010 may be responsible for providing the necessary power for the desorption process during the pressure swing adsorption process of the adsorption tower 110. Specifically, when the adsorption tower 110 is in the inversion stage and the vacuum stage, the desorbed gas blower 1010 accelerates the desorption process of the adsorbed component by generating negative pressure or positive pressure, so that the adsorbent can be regenerated. Moreover, the desorbed gas may be pressurized to 60KPaG by the desorbed gas blower 1010 and then delivered to the subsequent processing equipment through the desorbed gas delivery pipeline. The desorbed gas buffer tank 190 can stabilize the pressure of the desorbed gas generated during the desorption process. Specifically, during the pressure swing adsorption process, as the adsorption bed of the adsorption tower 110 is depressurized, the components adsorbed by the adsorption bed are desorbed to form desorbed gas. Here, the desorbed gas generated by the inversion and the desorbed gas generated after vacuuming and pressurizing to 20 KPaG can be discharged into the desorbed gas buffer tank 190 through the desorbed gas discharge pipe 130 and the vacuum pipe 140, respectively. Since the desorption process (i.e., the inversion stage and the vacuuming stage) may be accompanied by pressure fluctuations, the desorbed gas buffer tank 190 can provide a stable pressure environment to ensure that the desorbed gas flows out smoothly, thereby avoiding impact on the desorbed gas fan 1010.

[0049] Optionally, the dehydrogenation device 100 may further include a desorbed gas cooler 1020, which may cool the desorbed gas so as to make the desorbed gas meet the emission requirements.

[0050] In other embodiments, the dehydrogenation device 100 may also include only the desorbed gas blower 1010, but not the desorbed gas buffer tank 190. Specifically, the inlet of the desorbed gas blower 1010 may be respectively connected to the outlet of the desorbed gas discharge pipeline 130 and the outlet of the vacuum pipeline 140. Alternatively, the dehydrogenation device 100 may also not include the desorbed gas buffer tank 190 and the desorbed gas blower 1010.

[0051] In some embodiments, a product gas buffer tank 1030 may be further provided between the gas outlet of the dehydrogenation device 100 and the gas inlet of the dehydration device 200. In this way, the product gas buffer tank 1030 can effectively balance the fluctuations of the product gas pressure and flow rate at the outlet of the adsorption tower 110, ensure the stable output of the product gas, and make the flow rate of the product gas more stable, so as to meet the requirements of the subsequent process or equipment for the stability of the gas flow rate. At the same time, due to the buffering effect of the product gas buffer tank 1030, the impact of the product gas on the subsequent pipelines and equipment can also be reduced, the wear and failure rate of the dehydration device 200 can be reduced, and the service life of the dehydration device 200 can be extended.

[0052] Of course, the product gas buffer tank 1030 may not be provided between the gas outlet of the dehydrogenation device 100 and the gas inlet of the dehydration device 200 .

[0053] In an optional embodiment of the present application, the dehydration device 200 may include a first drying tower 211, a second drying tower 212 and a third drying tower 213. The first drying tower 211, the second drying tower 212 and the third drying tower 213 may be provided with a drying inlet and a drying outlet. The air inlet of the dehydration device 200 may include a drying inlet, and each drying outlet may be connected to the air inlet of the liquefaction device 300.

[0054] Among them, the first drying tower 211, the second drying tower 212 and the third drying tower 213 can all have a second operation cycle, and the second operation cycle can include multiple second operation stages, which can include a drying stage, a cooling stage and a regeneration stage, and the second operation stages of the first drying tower 211, the second drying tower 212 and the third drying tower 213 can be different from each other. In this way, the first drying tower 211, the second drying tower 212 and the third drying tower 213 can work alternately between different second operation stages, and the second operation stages of the first drying tower 211, the second drying tower 212 and the third drying tower 213 at the same time are different from each other to ensure the continuity of the dehydration process. Specifically, when one drying tower 210 is performing a drying operation, one of the remaining drying towers 210 can be regenerated, and the other can be cooled to meet the conditions for drying again, thereby achieving uninterrupted dehydration of the product gas. And through reasonable switching between towers, the adsorption capacity of the desiccant can be maximized, and the downtime caused by waiting for regeneration can be shortened, thereby improving the dehydration efficiency. At the same time, alternating operation can shorten the continuous working time of a single drying tower 210, reduce equipment wear and failure rate caused by long-term operation, and help each drying tower 210 to be heated evenly to avoid equipment damage caused by local overheating.

[0055] In other embodiments, the dehydration device 200 may include only one drying tower 210 , or the dehydration device 200 may include a plurality of drying towers 210 , and the second operation phase of each drying tower 210 may be the same.

[0056] Optionally, the dehydration device 200 may include a plurality of drying towers 210, including a first drying tower 211, a second drying tower 212 and a third drying tower 213, and the remaining drying towers 210 may be in at least one of a drying stage, a cooling stage and a regeneration stage, respectively.

[0057] In an optional embodiment, the dehydration device 200 may further include a regeneration heater 220 , a regeneration air inlet pipeline 230 , a regeneration air outlet pipeline 240 , and a product gas inlet pipeline 250 .

[0058] Among them, each drying outlet can be connected to the inlet of the regeneration heater 220 through the regeneration air inlet pipe 230, and a fifth control valve 231 can be provided between each drying outlet and the regeneration air inlet pipe 230, and the fifth control valve 231 can be used to control the connection and disconnection between the drying outlet and the regeneration air inlet pipe 230. The outlet of the regeneration heater 220 can be connected to each drying outlet through the regeneration air outlet pipe 240, and a sixth control valve 241 can be provided between the regeneration air outlet pipe 240 and each drying outlet, and the sixth control valve 241 can be used to control the connection and disconnection between the regeneration air outlet pipe 240 and the drying outlet. In this way, the regeneration of each drying tower 210 can be controlled by the fifth control valve 231 and the sixth control valve 241, so as to control each drying tower 210 to perform the regeneration process alternately. Here, the regeneration heater 220 can heat the regeneration gas to 260°C.

[0059] Of course, the fifth control valve 231 may not be provided between each drying outlet and the regeneration air inlet pipe 230 , and the sixth control valve 241 may not be provided between each regeneration air outlet pipe 240 and each drying outlet.

[0060] Each drying inlet can be connected to the gas outlet of the dehydrogenation device 100 through the product gas inlet pipeline 250, and a seventh control valve 253 can be provided between each drying inlet and the product gas inlet pipeline 250, and the seventh control valve 253 can be used to control the connection and disconnection between the drying inlet and the product gas inlet pipeline 250. In this way, the feeding conditions of each drying tower 210 can be controlled by the seventh control valve 253, so as to control each drying tower 210 to perform the drying process alternately.

[0061] Of course, the seventh control valve 253 may not be provided between each drying inlet and the product gas inlet pipeline 250 .

[0062] Optionally, the product gas inlet pipeline 250 may include a first inlet pipeline 251 and a second inlet pipeline 252. Each dry inlet can be connected to the outlet of the dehydrogenation device 100 through the first inlet pipeline 251, and each dry inlet can also be connected to the outlet of the dehydrogenation device 100 through the second inlet pipeline 252. A first inlet control valve 2531 may be arranged between each dry inlet and the first inlet pipeline 251, and the first inlet control valve 2531 can be used to control the connection between the dry inlet and the first inlet pipeline 251. A second inlet control valve 2532 may be arranged between each dry inlet and the second product inlet pipeline, and the second inlet control valve 2532 can be used to control the connection between the dry inlet and the second inlet pipeline 252. Here, the seventh control valve 253 may include the first inlet control valve 2531 and the second inlet control valve 2532.

[0063] Among them, the first component of product gas can enter the first drying tower 211 through the first air inlet pipe 251, and the first drying tower 211 can dry the first component of product gas to make the first component of product gas form dry gas; the second component of product gas can be used as regeneration gas and enter the second drying tower 212 through the second air inlet pipe 252, and the second component of product gas can be cold-blown to the second drying tower 212. Here, the second component of product gas can be cold-blown to cool the second drying tower 212 to 40°C. After the cold blowing is completed, the second component of product gas can enter the regeneration heater 220 through the regeneration air inlet pipe 230, and after being heated by the regeneration heater 220, enter the third drying tower 213 through the regeneration air outlet pipe 240 to regenerate the desiccant in the third drying tower 213. In this way, the product gas not only enters the drying tower 210 as the raw gas to be dehydrated, but can also be used as regeneration gas in the regeneration process. This dual function can improve the utilization efficiency of the product gas and reduce the demand for additional energy or gas. In addition, the direct use of the product gas as regeneration gas can avoid additional heating or compression processes, which is beneficial to reducing energy consumption. At the same time, there is no need to set up an additional generation, storage and transportation system for the regeneration gas, which simplifies the overall process flow and equipment configuration.

[0064] It should be noted that after the regeneration of the third drying tower 213 is completed, the regenerated gas can enter the third drying tower 213 from the drying inlet of the third drying tower 213, and the third drying tower 213 is cold-blown to cool it down to 40°C. The gas is then heated to 260°C by the regeneration heater 220, and then enters the first drying tower 211 to heat and regenerate the desiccant in the first drying tower 211.

[0065] In this embodiment, the first component may be 85%-90%, and the second component may be 10%-15%.

[0066] Optionally, the dehydration device 200 may further include a dry gas exhaust pipeline 260, each dry outlet may be connected to the air inlet of the liquefaction device 300 through the dry gas exhaust pipeline 260, and an eleventh control valve 261 may be provided between each dry outlet and the dry gas exhaust pipeline 260, and the eleventh control valve 261 may be used to control the connection and disconnection between the dry outlet and the dry gas exhaust pipeline 260. In this way, the exhaust of the dry gas of each drying tower 210 may be controlled by the eleventh control valve 261, so as to control each drying tower 210 to perform the drying process alternately.

[0067] In an optional embodiment, the dehydration device 200 may further include a regeneration cooler 270 , a regeneration exhaust pipe 280 , a regeneration separator 290 and a regeneration recovery pipe 2010 .

[0068] The regeneration cooler 270 can be used to cool the regeneration waste gas discharged from the drying inlet, and each drying inlet can be connected to the inlet of the regeneration cooler 270 through the regeneration exhaust pipe 280, and an eighth control valve 281 can be provided between each drying inlet and the regeneration exhaust pipe 280, and the eighth control valve 281 can be used to control the connection and disconnection between the drying inlet and the regeneration exhaust pipe 280. In this way, the discharge of the regeneration waste gas of each drying tower 210 can be controlled by the eighth control valve 281, so as to further control each drying tower 210 to alternately perform the regeneration process. Here, the regeneration cooler 270 can reduce the temperature of the regeneration waste gas to 40°C.

[0069] Of course, the eighth control valve 281 may not be provided between each drying inlet and the regeneration exhaust pipe 280 .

[0070] The regeneration separator 290 can be used to separate the moisture in the regeneration waste gas, the inlet of the regeneration separator 290 can be connected to the outlet of the regeneration exhaust pipe 280, the inlet of the regeneration recovery pipe 2010 can be connected to the gas outlet of the regeneration separator 290, and the outlet of the regeneration recovery pipe 2010 can be connected to the drying inlet. In this way, the regeneration waste gas can be recycled, which is conducive to improving the utilization rate and sustainability of resources.

[0071] Of course, the dehydration device 200 may also not be included in the regeneration separator 290 and the regeneration recovery pipeline 2010.

[0072] In an optional embodiment, the processing system may further include a dust filter 500, the inlet of the dust filter 500 may be connected to the air outlet of the dehydration device 200, and the outlet of the dust filter 500 may be connected to the air inlet of the liquefaction device 300. In this way, the dust filter 500 may filter the tiny dust particles in the dry gas to prevent the dust particles from entering the subsequent equipment or pipelines and causing wear to the equipment, or even clogging the pipelines, thereby affecting the normal operation and life of the equipment; at the same time, through the filtration of the dust filter 500, the dry gas can be further purified and the impurities therein can be removed, thereby improving the purity and quality of the liquefied natural gas and hydrogen-rich gas prepared subsequently.

[0073] Of course, the processing system may not include the dust filter 500 . Specifically, the air outlet of the dehydration device 200 may be directly connected to the air inlet of the liquefaction device 300 .

[0074] Optionally, the processing system may further include a booster device 400, the inlet of which may be connected to the gas outlet of the dehydrogenation device 100, and the outlet of which may be connected to the gas inlet of the dehydration device 200. In this way, the flow rate and pressure of the product gas may be increased by the boosting of the booster device 400, which in turn helps to increase the flow rate and diffusion capacity of the product gas in the drying tower 210, thereby facilitating the improvement of the drying efficiency, and the pressurized product gas may be more fully in contact with the desiccant in the drying tower 210, making the drying effect more uniform and thorough, thereby helping to reduce the residual moisture and impurity content in the dried gas after drying, thereby improving the purity and quality of the dried gas. Here, the booster device 400 may pressurize the product gas to 5MPaG.

[0075] Of course, the processing system may not include the boost device 400 .

[0076] In some embodiments, the dehydration device 200 may further include a filter separator 2020, which may be disposed downstream of the boosting device 400. Specifically, the inlet of the filter separator 2020 may be connected to the outlet of the boosting device 400, and the outlet of the filter separator 2020 may be respectively connected to each drying inlet. In this way, the filter separator 2020 may filter the product gas to filter out some impurities or some moisture in the product gas, thereby facilitating improving the subsequent dehydration efficiency and the purity and quality of the dry gas.

[0077] In an optional embodiment of the present application, the liquefaction device 300 may include a liquefaction cold box 310, and the liquefaction cold box 310 may include a natural gas flow channel 311 and a first heat exchange flow channel 312. Here, the inlet of the natural gas flow channel 311 may be an air inlet of the liquefaction device 300, and the natural gas flow channel 311 may exchange heat with the first heat exchange flow channel 312 so that the dry gas can form a cooled gas-phase natural gas.

[0078] The liquefaction device 300 may further include a refrigeration mechanism 330, which may be used to provide a mixed refrigerant to the first heat exchange channel 312, so that the mixed refrigerant may exchange heat with the dry gas in the natural gas channel 311 in the first heat exchange channel 312, thereby forming a cooled gas-phase natural gas through the dry gas.

[0079] The liquefaction device 300 may further include a flash mechanism 340 , which may be in communication with the outlet of the natural gas flow channel 311 . The flash mechanism 340 may be used to liquefy the gas-phase natural gas so as to convert the gas-phase natural gas into liquefied natural gas and hydrogen-rich gas.

[0080] With such arrangement, the dry gas is cooled to a temperature close to the liquefaction temperature in the liquefied cold box 310 and then enters the flash evaporation mechanism 340. The flash evaporation mechanism 340 can separate the residual unliquefied gas from the liquefied natural gas (LNG), and can effectively extract the natural gas and hydrogen components in the cracking tail gas, thereby improving the utilization rate of the cracking tail gas, and improving the purity of the liquefied natural gas, and can reduce the energy consumption and primary investment of the processing system, thereby maximizing the economic benefits of the cracking tail gas.

[0081] In other embodiments, the liquefaction device 300 may also include only the liquefaction cold box 310 and the refrigeration mechanism 330, and the natural gas flow channel 311 of the liquefaction cold box 310 may directly convert the dry gas into liquefied natural gas. Furthermore, the liquefaction device 300 may also include a cryogenic distillation device, which is connected to the outlet of the natural gas flow channel 311, and the cryogenic distillation device is used to liquefy the gas-phase natural gas to convert the gas-phase natural gas into liquefied natural gas and hydrogen-rich gas.

[0082] In an optional embodiment, the liquefaction device 300 may further include a second separator 320, which may be used to separate the heavy components in the dry gas so that the dry gas generates gas-phase natural gas. In this way, the second separator 320 may effectively remove the heavy components in the dry gas to prevent these components from condensing or clogging the equipment during the liquefaction process, thereby ensuring the efficient liquefaction process and significantly improving the purity and quality of the natural gas.

[0083] Here, the second separator 320 may be a low-temperature separator.

[0084] Optionally, the natural gas flow channel 311 may include a first natural gas flow channel 3111, where the inlet of the first natural gas flow channel 3111 may be the air inlet of the liquefaction device 300, that is, the inlet of the first natural gas flow channel 3111 is connected to the air outlet of the dehydration device 200, and the outlet of the first natural gas flow channel 3111 is connected to the inlet of the second separator 320, and the first natural gas flow channel 3111 may exchange heat with the first heat exchange flow channel 312 to achieve pre-cooling of the dry gas. In this way, by pre-cooling the dry gas, the temperature of the dryer can be initially reduced, thereby preparing for the subsequent supercooling process, and by pre-cooling the dry gas, the heat load of the dry gas in the subsequent supercooling process can also be reduced, thereby improving the supercooling efficiency; at the same time, during the pre-cooling process, some impurities in the dry gas will liquefy or solidify as the temperature decreases, thereby facilitating subsequent removal through the second separator 320, thereby facilitating improvement of the purity of the gas-phase natural gas.

[0085] The natural gas flow channel 311 may also include a second natural gas flow channel 3112, the inlet of the second natural gas flow channel 3112 may be communicated with the gas outlet of the second separator 320, the outlet of the second natural gas flow channel 3112 may be communicated with the inlet of the flash mechanism 340, and the second natural gas flow channel 3112 may exchange heat with the first heat exchange flow channel 312 to achieve supercooling of the gas phase natural gas. In this way, by supercooling the gas phase natural gas, the temperature of the gas phase natural gas may be further reduced to reach the liquefaction point or below the liquefaction point, thereby achieving the transition from gaseous state to liquid state.

[0086] In other embodiments, the liquefaction device 300 may not include the second separator 320, and the natural gas flow channel 311 may be a whole flow channel. The natural gas flow channel 311 exchanges heat with the first heat exchange flow channel 312, and can directly supercool the dry gas to form supercooled gas-phase natural gas.

[0087] In an optional embodiment, the flash mechanism 340 may include a high-pressure flash tank 341 and a low-pressure flash tank 342, the inlet of the high-pressure flash tank 341 may be connected to the outlet of the natural gas flow channel 311, the high-pressure flash tank 341 may be used to flash the supercooled gaseous natural gas into hydrogen-rich gas and primary liquefied natural gas, the inlet of the low-pressure flash tank 342 may be connected to the liquid outlet of the high-pressure flash tank 341, the low-pressure flash tank 342 may be used to flash the primary liquefied natural gas into mixed gas and liquefied natural gas. The high-pressure flash tank 341 may flash the gaseous natural gas at high pressure, and may use a high pressure difference to separate more high-boiling point components from the gas phase, thereby improving the separation efficiency, and further improving the purity and quality of the hydrogen-rich gas, and because the gaseous natural gas has a high pressure when entering the high-pressure flash tank 341, the high-pressure flash tank 341 may more effectively utilize this part of the pressure energy, thereby reducing the energy consumption in the subsequent process. The low-pressure flash tank 342 operates at a relatively low pressure, which can significantly reduce the boiling point of compounds in the primary liquefied natural gas, allowing high-boiling point components to be converted into a vapor state at a relatively low temperature, thereby achieving more effective separation, further removing impurities and non-condensable gases in the primary liquefied natural gas, and improving the purity and quality of the liquefied natural gas.

[0088] Of course, the flash mechanism 340 may also include only the high-pressure flash tank 341 , or the flash mechanism 340 may also include only the low-pressure flash tank 342 . Specifically, the inlet of the low-pressure flash tank 342 may be connected to the outlet of the natural gas flow channel 311 .

[0089] Optionally, a second throttle valve 343 may be provided between the inlet of the high-pressure flash tank 341 and the outlet of the natural gas flow channel 311. The second throttle valve 343 may play a throttling role to reduce the pressure of the supercooled gas-phase natural gas, thereby facilitating the reduction of the temperature of the gas-phase natural gas, thereby facilitating the liquefaction of the gas-phase natural gas.

[0090] Further optionally, a third throttle valve 344 can be provided between the liquid outlet of the high-pressure flash tank 341 and the inlet of the low-pressure flash tank 342. The third throttle valve 344 can play a throttling role to reduce the pressure of the primary liquefied natural gas, and can accurately control the amount of primary liquefied natural gas entering the low-pressure flash tank 342 to avoid system instability caused by excessive or insufficient flow.

[0091] In some embodiments, the liquefied cold box 310 may further include a second heat exchange channel 313, the inlet of the first heat exchange channel 312 may be connected to the outlet of the first heat exchange channel 312 through a first throttle valve 3121, and the outlet of the second heat exchange channel 313 may be connected to the inlet of the refrigeration mechanism 330, so that the mixed refrigerant can flow back to the refrigeration mechanism 330.

[0092] The liquefaction cold box 310 may also include a first reheating channel 314, the inlet of the first reheating channel 314 may be connected to the outlet of the high-pressure flash tank 341, the outlet of the first reheating channel 314 may be used to connect to an external hydrogen delivery pipeline, and the first reheating channel 314 may exchange heat with the second heat exchange channel 313, so that the mixed refrigerant in the second heat exchange channel 313 may exchange heat with the hydrogen-rich gas in the first reheating channel 314 to reheat the hydrogen-rich gas, thereby allowing the hydrogen-rich gas to meet the delivery requirements and be delivered through an external hydrogen delivery pipeline, for example, it may be delivered to a hydrogenation unit in a petrochemical plant, so that the hydrogen-rich gas may be used as a raw material for the hydrogenation unit.

[0093] The liquefaction cold box 310 may also include a second reheating channel 315, the inlet of the second reheating channel 315 may be connected to the air outlet of the low-pressure flash tank 342, the outlet of the second reheating channel 315 may be connected to the air inlet of the dehydration device 200, and the second reheating channel 315 may exchange heat with the second heat exchange channel 313, so that the mixed refrigerant in the second heat exchange channel 313 may exchange heat with the mixed gas in the second reheating channel 315 to reheat the mixed gas, and the reheated mixed gas may enter the dehydration device 200 to continue to recover the hydrogen in the mixed gas.

[0094] In other embodiments, the liquefaction cold box 310 may not include the first recuperation channel 314 and the second recuperation channel 315 .

[0095] The liquefaction process of dry gas is as follows: The dry gas after adsorption and dehydration enters the liquefied cold box 310, and enters the second separator 320 after being pre-cooled by the mixed refrigerant. The gaseous natural gas after separation of the heavy components continues to be supercooled to -162°C, and is throttled and reduced in pressure to -3.3MPa by the second throttle valve 343 to enter the high-pressure flash tank 341 to flash out hydrogen-rich gas. The hydrogen-rich gas is reheated and measured by the liquefied cold box 310 and then transmitted to the outside. The primary liquefied natural gas is further reduced in pressure to -0.32MPa by the third throttle valve 344 and enters the low-pressure flash tank 342. The flashed mixed gas is reheated by the liquefied cold box 310 and sent to the inlet of the boosting device 400 to continue to recover hydrogen. The generated liquefied natural gas is throttled and reduced in pressure to 0.2MPa by the fourth throttle valve 345 and then sent to the outside.

[0096] Specifically, the dry gas enters the first natural gas flow channel 3111 for precooling and then enters the second separator 320. After the heavy components are separated in the second separator 320, the gaseous natural gas is formed. The gaseous natural gas enters the second natural gas flow channel 3112 and is supercooled to -162°C. After being throttled by the second throttle valve 343, it enters the high-pressure flash tank 341, and is flashed by the high-pressure flash tank 341 to produce hydrogen-rich gas and primary liquefied natural gas. The hydrogen-rich gas enters the first reheating flow channel of the liquefied cold box 310. After being reheated at 314, it is transported out through an external hydrogen transport pipeline; the primary liquefied natural gas is then reduced in pressure to -0.32MPa by the third throttle valve 344 and enters the low-pressure flash tank 342, where the mixed gas and liquefied natural gas are flashed out of the low-pressure flash tank 342, and the mixed gas enters the second reheating flow channel 315 of the liquefied cold box 310 for reheating and then enters the dehydration device 200, and the liquefied natural gas is throttled and reduced in pressure to 0.2MPa by the fourth throttle valve 345 and then transported outside the boundary.

[0097] Optionally, the refrigeration mechanism 330 can be a mixed refrigerant compressor unit, which adopts a closed cycle and is an independent closed system. The mixed refrigerant compressor unit uses methane, ethylene, propylene, nitrogen and isopentane as a mixed refrigerant. After being pressurized to 3.3MPaG by the mixed refrigerant compressor unit in two stages, it is cooled and separated and enters the cold box. The first stage is pre-cooled to -15°C and returns to the cold box after throttling and reducing pressure; the second stage pre-cooling refrigerant is cooled to -65°C and returns to the cold box after throttling and reducing pressure; the deep cooling refrigerant is deep cooled to -162°C, and returns to the cold box for reheating after throttling and reducing pressure. In the cold box, condensation, evaporation and throttling expansion are carried out step by step to obtain refrigeration capacity at different temperature levels. Here, in the mixed refrigerant, propylene is used instead of propane, which can reduce the purchase of external refrigerants, make full use of resources while meeting the existing process requirements, and generate greater economic value.

[0098] Specifically, the mixed refrigerant compressor unit may include a first compressor 331, a second compressor 334, a third separator 333, a fourth separator 336, a first cooler 332, and a second cooler 335. The inlet of the first compressor 331 may be connected to the outlet of the second heat exchange channel 313 of the liquefied cold box 310, and the outlet of the first compressor 331 may be connected to the inlet of the second compressor 334 and the third separator 333, respectively. Here, the outlet of the first compressor 331 may be connected to the third separator 333 through the first cooler 332; the outlet of the second compressor 334 may be connected to the fourth separator 336 through the second cooler 335, and the fourth separator 336 may be connected to the fourth separator 336. The gas phase outlet of 336 can be communicated with the inlet of the first heat exchange channel 312, and the liquefied cold box 310 can also include a third heat exchange channel 316 and a fourth heat exchange channel 317, the gas phase outlet of the first separator 180 can be communicated with the inlet of the second compressor 334, the liquid phase outlet of the first separator 180 can be communicated with the inlet of the third heat exchange channel 316, the outlet of the third heat exchange channel 316 can be communicated with the second heat exchange channel 313 through the first pipeline 318, the liquid phase outlet of the second separator 320 can be communicated with the inlet of the fourth heat exchange channel 317, and the outlet of the fourth heat exchange channel 317 can be communicated with the second heat exchange channel 313 through the second pipeline 319. Here, a fifth throttle valve 3181 can be provided on the first pipeline 318, and a sixth throttle valve 3191 can be provided on the second pipeline 319.

[0099] The gas-phase mixed refrigerant flowing out of the gas phase outlet of the fourth separator 336 enters the first heat exchange flow channel 312 of the liquefied cold box 310, and undergoes step-by-step condensation, evaporation, and throttling expansion in the liquefied cold box 310 to obtain refrigeration capacity at different temperature levels. Specifically, the gas-phase mixed refrigerant enters the first heat exchange flow channel 312 of the liquefied cold box 310 and is cooled to -162°C. Thereafter, it is throttled by the first throttle valve 3121 to become a low-temperature and low-pressure mixed refrigerant, and enters the second heat exchange flow channel 313 to provide liquefaction and supercooling cooling capacity for the gas-phase natural gas and the gas passing through the liquefied cold box 310, thereby obtaining a high-temperature and low-pressure mixed refrigerant. The high-temperature and low-pressure mixed refrigerant flows into the first compressor 331 for pressurization for the next cycle. The liquid mixed refrigerant flowing out of the liquid phase outlet of the fourth separator 336 enters the fourth heat exchange channel 317 for heat exchange and is cooled to -65°C, and then passes through the sixth throttle valve 3191 on the second pipeline 319 to reduce pressure and cool down before entering the second heat exchange channel 313. The liquid mixed refrigerant at the liquid phase outlet of the third separator 333 enters the third heat exchange channel 316 for heat exchange and is cooled to -15°C, and then passes through the fifth throttle valve 3181 on the first pipeline 318 to reduce pressure and cool down before entering the second heat exchange channel 313.

[0100] Based on the cracking tail gas processing system provided in the embodiment of the present application, the embodiment of the present application also provides a cracking tail gas processing method, which can be applied to the cracking tail gas processing system described in any of the above embodiments. The cracking tail gas processing method, such as Figure 6 Specifically, the steps may include: S1. Dehydrogenating the cracking tail gas to remove hydrocarbon components in the cracking tail gas and generate product gas; S2, dehydrating the product gas to form dry gas; S3. The dry gas is liquefied to generate liquefied natural gas and hydrogen-rich gas.

[0101] The beneficial effects achieved by the method for treating cracking tail gas provided in the embodiment of the present application are consistent with the beneficial effects achieved by the system for treating cracking tail gas provided in the embodiment of the present application, and will not be described in detail here.

[0102] In an optional embodiment of the present application, the product gas is dehydrated, which may include the following steps: S21, introducing a first amount of product gas into the first drying tower 211, and the molecular sieve of the first drying tower 211 adsorbs moisture in the product gas, so that the first amount of product gas forms dry gas; S22, the second quantity of product gas is passed into the second drying tower 212 as the regeneration gas, so as to cold-blow the second drying tower 212 and then enter the regeneration heater 220. After the regeneration heater 220 heats the regeneration gas, the regeneration gas enters the third drying tower 213 and regenerates the molecular sieve in the third drying tower 213.

[0103] In this way, when the first drying tower 211 is performing a drying process, the second drying tower 212 can perform a cooling process, and the third drying tower 213 can perform a regeneration process, so that the second drying tower 212 and the third drying tower 213 can meet the conditions for drying again, thereby achieving uninterrupted dehydration of the product gas. In addition, the product gas not only enters the drying tower 210 as the raw gas to be dehydrated, but can also be used as regeneration gas in the regeneration process. Such dual functions can improve the utilization efficiency of the product gas and reduce the demand for additional energy or gas. In addition, the direct use of the product gas as the regeneration gas can avoid additional heating or compression processes, which is beneficial to reducing energy consumption. At the same time, there is no need to set up an additional generation, storage and transportation system for the regeneration gas, which simplifies the overall process flow and equipment configuration.

[0104] In other embodiments, the dehydration treatment of the product gas may include the following steps: Product gas is introduced into all drying towers 210, and the molecular sieves of the drying towers 210 absorb moisture in the product gas to form dry gas from the product gas.

[0105] or, The product gas is passed into the first drying tower 211, and the molecular sieve of the first drying tower 211 absorbs moisture in the product gas to form dry gas; Other gases are used as regeneration gas and introduced into the second drying tower 212 to cold-blow the second drying tower 212 and then enter the regeneration heater 220. After the regeneration heater 220 heats the regeneration gas, the regeneration gas enters the third drying tower 213 and regenerates the molecular sieve in the third drying tower 213.

[0106] In an optional embodiment, the liquefaction treatment of the dry gas may include the steps of: S31, cooling the dry gas to form gas-phase natural gas; S32. Flashing the gaseous natural gas to generate liquefied natural gas and hydrogen-rich gas.

[0107] In this way, the dry gas is first cooled to a temperature close to the liquefaction temperature and then enters the flash evaporation mechanism 340. The flash evaporation mechanism 340 can separate the residual unliquefied gas from the liquefied natural gas, and can effectively extract the natural gas and hydrogen components in the cracking tail gas, thereby improving the utilization rate of the cracking tail gas and the purity of the liquefied natural gas.

[0108] In other embodiments, the liquefaction process of the dry gas may include the following steps: The dry gas is cooled to form liquefied natural gas.

[0109] In an optional embodiment, the drying gas is cooled, which may include the steps of: S311, precooling the dry gas; S312, performing separation treatment on the pre-cooled dry gas to separate heavy components in the dry gas, so that the dry gas generates gas-phase natural gas; S313, supercooling the gas phase natural gas.

[0110] In this way, the dryer is precooled to initially reduce the temperature of the dryer, thereby preparing for the subsequent supercooling process. By precooling the dry gas, the heat load of the dry gas in the subsequent supercooling process can also be reduced, thereby improving the supercooling efficiency. At the same time, during the precooling process, some impurities in the dry gas will liquefy or solidify as the temperature decreases, thereby facilitating subsequent removal by the second separator 320, thereby helping to improve the purity of the gaseous natural gas. By separating the precooled dry gas, the heavy components in the dry gas can be removed to prevent these components from condensing or clogging the equipment during the liquefaction process, thereby ensuring the efficient liquefaction process and significantly improving the purity and quality of the natural gas. Moreover, by supercooling the gaseous natural gas, the temperature of the gaseous natural gas can be further reduced to reach the liquefaction point or below the liquefaction point, thereby achieving a transition from gas to liquid.

[0111] Of course, in other embodiments, cooling the dry gas may also include the following steps: The dry gas is subjected to supercooling treatment so that the dry gas directly generates supercooled gas-phase natural gas.

[0112] In an optional embodiment, flash treatment of gas phase natural gas may include the steps of: S321, performing high-pressure flash treatment on the gas-phase natural gas to flash out hydrogen-rich gas and primary liquefied natural gas; S322, performing low-pressure flash treatment on the primary liquefied natural gas to flash the primary liquefied natural gas into mixed gas and liquefied natural gas.

[0113] In this way, by subjecting the gas phase natural gas to high-pressure flash treatment, a higher pressure difference can be used to separate more high-boiling point components from the gas phase, thereby improving the separation efficiency and further improving the purity and quality of the hydrogen-rich gas; by subjecting the primary liquefied natural gas to low-pressure flash treatment, the boiling point of the compounds in the primary liquefied natural gas can be significantly reduced, so that the high-boiling point components can be converted into a vapor state at a lower temperature, thereby achieving more effective separation, further removing impurities and non-condensable gases in the primary liquefied natural gas, and improving the purity and quality of the liquefied natural gas.

[0114] In other embodiments, flashing the gas phase natural gas may only include the following steps: Performing high-pressure flash treatment on gas-phase natural gas to flash hydrogen-rich gas and primary liquefied natural gas; or, The gas phase natural gas is subjected to low-pressure flash evaporation treatment to flash the gas phase natural gas into mixed gas and liquefied natural gas.

[0115] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A cracking tail gas processing system, characterized in that: include: A dehydrocarbon removal device (100), used to remove hydrocarbon components from the cracking tail gas and generate product gas; a dehydration device (200), wherein the air inlet of the dehydration device (200) is connected to the air outlet of the dehydrogenation device (100), and the dehydration device (200) is used to absorb moisture in the product gas to form dry gas from the product gas; A liquefaction device (300), wherein the gas inlet of the liquefaction device (300) is connected to the gas outlet of the dehydration device (200), and the liquefaction device (300) is used to convert the dry gas into liquefied natural gas and hydrogen-rich gas.

2. The cracking tail gas processing system according to claim 1, characterized in that: The dehydrogenation device (100) comprises at least five adsorption towers (110), the adsorption towers (110) being used to adsorb hydrocarbon components in the cracked tail gas, each of the adsorption towers (110) being provided with a top opening and a bottom opening, the bottom opening of each of the adsorption towers (110) being used to allow the cracked tail gas to enter, the top opening of each of the adsorption towers (110) being used to communicate with the dehydration device (200), and the gas outlet of the dehydrogenation device (100) comprising the top opening; Each of the adsorption towers (110) has a first operation cycle, the first operation cycle includes a plurality of first operation stages, including an adsorption stage, an inversion stage, a vacuum stage, a pressure reduction stage and a pressure increase stage, and the first operation stages of at least five of the adsorption towers (110) are different from each other.

3. The cracking tail gas processing system according to claim 2, characterized in that: The dehydrocarbon removal device (100) further comprises: A feed pipeline (120) is used to transport the cracked tail gas, the bottom opening of each adsorption tower (110) is in communication with the feed pipeline (120), and a first control valve (121) is provided between the bottom opening of each adsorption tower (110) and the feed pipeline (120), the first control valve (121) being used to control the connection and disconnection between the bottom opening and the feed pipeline (120); a desorbed gas discharge pipeline (130), wherein the bottom opening of each adsorption tower (110) is communicated with the inlet of the desorbed gas discharge pipeline (130), and the outlet of the desorbed gas discharge pipeline (130) is used to communicate with an external desorbed gas delivery pipeline, and a second control valve (131) is provided between the bottom opening of each adsorption tower (110) and the desorbed gas discharge pipeline (130), and the second control valve (131) is used to control the connection and disconnection between the bottom opening and the desorbed gas discharge pipeline (130); A vacuum pipe (140), wherein the bottom opening of each adsorption tower (110) is communicated with the inlet of the vacuum pipe (140), and the outlet of the vacuum pipe (140) is used to communicate with the external desorption gas delivery pipeline. A vacuum pump (141) is provided on the vacuum pipe (140), and a third control valve (142) is provided between the bottom opening of each adsorption tower (110) and the vacuum pipe (140), and the third control valve (142) is used to control the connection and disconnection between the bottom opening and the vacuum pipe (140); A pressure regulating pipeline (150), wherein the top openings of the adsorption towers (110) are connected to each other through the pressure regulating pipeline (150), and a fourth control valve (153) is provided between the top opening of each adsorption tower (110) and the pressure regulating pipeline (150), and the fourth control valve (153) is used to control the connection and disconnection between the top opening and the pressure regulating pipeline (150).

4. The cracking tail gas processing system according to claim 3, characterized in that: The dehydrocarbon removal device (100) further comprises a first separator (180) arranged upstream of the adsorption tower (110), the first separator (180) being used to separate liquid and gas in the cracking tail gas, and the feed pipeline (120) being in communication with a gas outlet of the first separator (180).

5. The cracking tail gas processing system according to claim 3, characterized in that: The dehydrocarbon removal device (100) further comprises a desorbed gas buffer tank (190) and a desorbed gas blower (1010), wherein the inlet of the desorbed gas buffer tank (190) is respectively connected to the outlet of the desorbed gas discharge pipeline (130) and the outlet of the vacuum pumping pipeline (140), the outlet of the desorbed gas buffer tank (190) is connected to the inlet of the desorbed gas blower (1010), and the outlet of the desorbed gas blower (1010) is used to be connected to the external desorbed gas delivery pipeline; and / or, A product gas buffer tank (1030) is also provided between the gas outlet of the dehydrogenation device (100) and the gas inlet of the dehydration device (200).

6. The cracking tail gas processing system according to claim 1, characterized in that: The dehydration device (200) comprises a first drying tower (211), a second drying tower (212) and a third drying tower (213); the first drying tower (211), the second drying tower (212) and the third drying tower (213) are all provided with a drying inlet and a drying outlet; an air inlet of the dehydration device (200) comprises the drying inlet, and each of the drying outlets is communicated with an air inlet of the liquefaction device (300); The first drying tower (211), the second drying tower (212) and the third drying tower (213) all have a second operating cycle, the second operating cycle includes a plurality of second operating stages, including a drying stage, a cooling stage and a regeneration stage, and the second operating stages of the first drying tower (211), the second drying tower (212) and the third drying tower (213) are different from each other.

7. The cracking tail gas processing system according to claim 6, characterized in that: The dehydration device (200) further comprises: Regeneration heater (220); a regeneration air intake pipe (230), each of the drying outlets being in communication with an inlet of the regeneration heater (220) via the regeneration air intake pipe (230), and a fifth control valve (231) being provided between each of the drying outlets and the regeneration air intake pipe (230), the fifth control valve (231) being used to control the connection and disconnection between the drying outlet and the regeneration air intake pipe (230); a regeneration gas outlet pipeline (240), wherein the outlet of the regeneration heater (220) is respectively connected to each of the drying outlets through the regeneration gas outlet pipeline (240), and a sixth control valve (241) is provided between the regeneration gas outlet pipeline (240) and each of the drying outlets, and the sixth control valve (241) is used to control the connection between the regeneration gas outlet pipeline (240) and the drying outlet; A product gas inlet pipeline (250), each of the drying inlets is connected to the gas outlet of the dehydrogenation device (100) through the product gas inlet pipeline (250), and a seventh control valve (253) is provided between each of the drying inlets and the product gas inlet pipeline (250), and the seventh control valve (253) is used to control the connection and disconnection between the drying inlet and the product gas inlet pipeline (250).

8. The cracking tail gas processing system according to claim 6, characterized in that: The dehydration device (200) further comprises: A regeneration cooler (270) for cooling the regeneration waste gas discharged from the drying inlet; a regeneration exhaust pipe (280), each of the dry inlets being in communication with an inlet of the regeneration cooler (270) through the regeneration exhaust pipe (280), and an eighth control valve (281) being provided between each of the dry inlets and the regeneration exhaust pipe (280), the eighth control valve (281) being used to control the connection and disconnection between the dry inlet and the regeneration exhaust pipe (280); A regeneration separator (290) is used to separate moisture from the regeneration exhaust gas, and an inlet of the regeneration separator (290) is connected to an outlet of the regeneration exhaust pipe (280); A regeneration recovery pipeline (2010), wherein the inlet of the regeneration recovery pipeline (2010) is connected to the gas outlet of the regeneration separator (290), and the outlet of the regeneration recovery pipeline (2010) is connected to the drying inlet.

9. The cracking tail gas processing system according to claim 1, characterized in that: The processing system further comprises a dust filter (500), wherein an inlet of the dust filter (500) is communicated with an air outlet of the dehydration device (200), and an outlet of the dust filter (500) is communicated with an air inlet of the liquefaction device (300); and / or, The processing system further comprises a pressure boosting device (400), the inlet of the pressure boosting device (400) being connected to the gas outlet of the dehydrogenation device (100), and the outlet of the pressure boosting device (400) being connected to the gas inlet of the dehydration device (200).

10. The cracking tail gas processing system according to claim 1, characterized in that: The liquefaction device (300) comprises: A liquefaction cold box (310), comprising a natural gas flow channel (311) and a first heat exchange flow channel (312), wherein the inlet of the natural gas flow channel (311) is the gas inlet of the liquefaction device (300), and the natural gas flow channel (311) can exchange heat with the first heat exchange flow channel (312) so that the dry gas forms cooled gas-phase natural gas; a refrigeration mechanism (330), the refrigeration mechanism (330) being used to provide a mixed refrigerant for the first heat exchange flow channel (312); The flash evaporation mechanism (340) is in communication with the outlet of the natural gas flow channel (311), and the flash evaporation mechanism (340) is used to liquefy the gas-phase natural gas so that the gas-phase natural gas forms liquefied natural gas and hydrogen-rich gas.

11. The cracking tail gas processing system according to claim 10, characterized in that: The liquefaction device (300) further comprises a second separator (320), wherein the second separator (320) is used to separate heavy components from the dry gas, so that the dry gas generates the gas-phase natural gas; The natural gas flow channel (311) comprises a first natural gas flow channel (3111) and a second natural gas flow channel (3112); the inlet of the first natural gas flow channel (3111) is the gas inlet of the liquefaction device (300); the outlet of the first natural gas flow channel (3111) is connected to the inlet of the second separator (320); the inlet of the second natural gas flow channel (3112) is connected to the gas outlet of the second separator (320); the outlet of the second natural gas flow channel (3112) is connected to the inlet of the flash mechanism (340); the first natural gas flow channel (3111) can exchange heat with the first heat exchange flow channel (312) to pre-cool the dry gas; and the second natural gas flow channel (3112) can exchange heat with the first heat exchange flow channel (312) to super-cool the gas-phase natural gas.

12. The cracking tail gas processing system according to claim 10, characterized in that: The flash evaporation mechanism (340) comprises: a high-pressure flash tank (341), wherein the inlet of the high-pressure flash tank (341) is connected to the outlet of the natural gas flow channel (311), and the high-pressure flash tank (341) is used to flash the supercooled gas-phase natural gas into hydrogen-rich gas and primary liquefied natural gas; A low-pressure flash tank (342), wherein the inlet of the low-pressure flash tank (342) is connected to the liquid outlet of the high-pressure flash tank (341), and the low-pressure flash tank (342) is used to flash the primary liquefied natural gas into a mixed gas and liquefied natural gas.

13. The cracking tail gas processing system according to claim 12, characterized in that: The liquefaction cold box (310) further includes: a second heat exchange flow channel (313), wherein the inlet of the second heat exchange flow channel (313) is connected to the outlet of the first heat exchange flow channel (312) via a first throttle valve (3121), and the outlet of the second heat exchange flow channel (313) is connected to the inlet of the refrigeration mechanism (330); a first reheating channel (314), wherein the inlet of the first reheating channel (314) is in communication with the gas outlet of the high-pressure flash tank (341), the outlet of the first reheating channel (314) is used to be in communication with an external hydrogen delivery pipeline, and the first reheating channel (314) can exchange heat with the second heat exchange channel (313); A second reheating channel (315), wherein the inlet of the second reheating channel (315) is connected to the air outlet of the low-pressure flash tank (342), the outlet of the second reheating channel (315) is connected to the air inlet of the dehydration device (200), and the second reheating channel (315) can exchange heat with the second heat exchange channel (313).

14. A method for treating cracking tail gas, characterized in that: A system for processing cracking tail gas according to any one of claims 1 to 13, comprising: Dehydrocarbonizing the cracked tail gas to remove hydrocarbon components in the cracked tail gas and generate product gas; Dehydrating the product gas to form dry gas; The dry gas is liquefied to generate liquefied natural gas and hydrogen-rich gas.

15. The method for treating cracking tail gas according to claim 14, characterized in that: The dehydration treatment of the product gas comprises: A first amount of the product gas is introduced into a first drying tower (211), and a molecular sieve in the first drying tower (211) adsorbs moisture in the product gas, so that the first amount of the product gas forms the dry gas; The second portion of the product gas is passed into the second drying tower (212) as the regeneration gas to cold-blow the second drying tower (212) and then enter the regeneration heater (220). After the regeneration heater (220) heats the regeneration gas, the regeneration gas enters the third drying tower (213) and regenerates the molecular sieve in the third drying tower (213).

16. The method for treating cracking tail gas according to claim 14, characterized in that: The dry gas is liquefied, comprising: Cooling the dry gas to form gas-phase natural gas; The gas phase natural gas is flashed to generate liquefied natural gas.

17. The method for treating cracking tail gas according to claim 16, characterized in that: The step of cooling the dry gas comprises: Precooling the dry gas; Performing separation treatment on the pre-cooled dry gas to separate heavy components in the dry gas, so that the dry gas generates the gas-phase natural gas; The gas-phase natural gas is subjected to a supercooling treatment.

18. The method for treating cracking tail gas according to claim 16, characterized in that: The flash treatment of the gas phase natural gas comprises: Performing high-pressure flash treatment on the gas-phase natural gas to flash hydrogen-rich gas and primary liquefied natural gas from the gas-phase natural gas; The primary liquefied natural gas is subjected to a low-pressure flash treatment so as to flash the primary liquefied natural gas into a mixed gas and liquefied natural gas.

Images