Cracking tail gas treatment system

Abstract

The utility model discloses a cracking tail gas treatment system, 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] This application belongs to the field of cracking tail gas treatment technology, specifically relating to a cracking tail gas treatment system. Background Technology

[0002] Cracking tail gas is an industrial waste gas produced during petroleum refining, containing a certain proportion of methane hydrogen. In the petrochemical industry, this tail gas is often used as boiler fuel to recover its heat energy. However, this method does not yield significant value.

[0003] However, simply using cracked tail gas as fuel to recover its heat energy cannot fully and effectively utilize and recover the components in the cracked tail gas, resulting in a low utilization rate of cracked tail gas.

[0004] Therefore, existing technologies suffer from low utilization rates of cracking exhaust gas. Utility Model Content

[0005] The purpose of this application is to provide a cracking tail gas treatment system that can solve the problem of low utilization rate of cracking tail gas in related technologies.

[0006] This application provides a cracking exhaust gas treatment system, including:

[0007] A dehydrocarbon removal unit is used to remove hydrocarbon components from cracking tail gas and generate product gas;

[0008] A dehydration device, wherein the air inlet of the dehydration device is connected to the air outlet of the dehydrocarbonization device, and the dehydration device is used to adsorb moisture in the product gas, so that the product gas becomes dry gas;

[0009] A liquefaction device, wherein the air inlet of the liquefaction device is connected to the air outlet of the dehydration device, and the liquefaction device is used to convert the dried gas into liquefied natural gas and hydrogen-rich gas.

[0010] In this embodiment, hydrocarbon components are removed from the cracking tail gas using a dehydrocarbonization unit, such as heavy hydrocarbons and unsaturated hydrocarbons, thereby generating product gas. The product gas is then dehydrated to remove moisture, forming dry gas, which is then liquefied in a liquefaction unit to produce liquefied natural gas (LNG) and hydrogen-rich gas. This allows for the production of natural gas and hydrogen-rich gas from the cracking tail gas, effectively improving its utilization rate. Furthermore, because the dehydrocarbonization unit removes hydrocarbon components, the product gas is less prone to polymerization during subsequent drying and liquefaction processes. This reduces the lifespan of catalysts in the dehydration unit and prevents freezing and blockage in the liquefaction unit's pipelines, thus extending the service life of both the dehydration and liquefaction units. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of the cracking tail gas treatment system disclosed in the embodiments of this application;

[0012] Figure 2 This is a schematic diagram of the structure of the dehydrocarbonization device disclosed in the embodiments of this application;

[0013] Figure 3 This is a schematic diagram of the dehydration device disclosed in the embodiments of this application;

[0014] Figure 4 This is a schematic diagram of the liquefaction device disclosed in the embodiments of this application;

[0015] Figure 5 This is a schematic diagram of the refrigeration mechanism disclosed in the embodiments of this application.

[0016] Explanation of reference numerals in the attached figures:

[0017] 100 - Dehydrocarbonization unit; 200 - Dehydration unit; 300 - Liquefaction unit; 400 - Pressurization unit;

[0018] 500 - Dust filter; 110 - Adsorption tower; 120 - Material conveying pipeline; 121 - First control valve;

[0019] 130 - Desorption gas discharge pipe; 131 - Second control valve; 140 - Vacuum pump pipe; 141 - Vacuum pump;

[0020] 142 - Third control valve; 150 - Pressure regulating pipeline; 151 - First pressure regulating pipeline; 152 - Second pressure regulating pipeline;

[0021] 153 - Fourth control valve; 1531 - First pressure regulating control valve; 1532 - Second pressure regulating control valve;

[0022] 160 - Product gas delivery pipeline; 161 - Ninth control valve; 170 - Product gas circuit;

[0023] 171 - Tenth control valve; 180 - First separator; 190 - Desorption gas buffer tank; 1010 - Desorption gas blower;

[0024] 1020 - Desorption gas cooler; 1030 - Product gas buffer tank; 210 - Drying tower; 211 - First drying tower;

[0025] 212 - Second drying tower; 213 - Third drying tower; 220 - Regeneration heater; 230 - Regeneration inlet pipe;

[0026] 231 - Fifth control valve; 240 - Regeneration outlet gas pipeline; 241 - Sixth control valve;

[0027] 250 - Product air inlet pipe; 251 - First air inlet pipe; 252 - Second air inlet pipe;

[0028] 253-Seventh control valve; 2531-First intake control valve; 2532-Second intake control valve;

[0029] 260 - Dry gas exhaust pipe; 261 - Eleventh control valve; 270 - Regenerative cooler;

[0030] 280 - Regeneration exhaust pipe; 281 - Eighth control valve; 290 - Regeneration separator;

[0031] 2010 - Recycling pipeline; 2020 - Filter separator; 310 - Liquefied gas cold box; 311 - Natural gas flow channel;

[0032] 3111 - First natural gas flow channel; 3112 - Second natural gas flow channel; 312 - First heat exchange flow channel;

[0033] 3121 - First throttling valve; 313 - Second heat exchange channel; 314 - First reheating channel;

[0034] 315 - Second reheating flow channel; 316 - Third heat exchange flow channel; 317 - Fourth heat exchange flow channel;

[0035] 318 - First pipe; 3181 - Fifth throttle valve; 319 - Second pipe; 3191 - Sixth throttle valve;

[0036] 320 - Second separator; 330 - Refrigeration mechanism; 331 - First compressor; 332 - First cooler;

[0037] 333 - Third separator; 334 - Second compressor; 335 - Second cooler; 336 - Fourth separator;

[0038] 340 - Flash evaporation mechanism; 341 - High-pressure flash evaporator; 342 - Low-pressure flash evaporator; 343 - Second throttle valve;

[0039] 344 - Third throttle valve; 345 - Fourth throttle valve. Detailed Implementation

[0040] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0041] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0042] The cracking exhaust gas treatment system provided in this application will be described in detail below with reference to the accompanying drawings, through specific embodiments and application scenarios.

[0043] refer to Figures 1-5 The present application provides a cracking tail gas treatment system, which may include a dehydrocarbonization unit 100, a dehydration unit 200, and a liquefaction unit 300.

[0044] The dehydrogenation unit 100 can be used to remove hydrocarbon components from the cracking tail gas and generate product gas; the inlet of the dehydration unit 200 can be connected to the outlet of the dehydrogenation unit 100, and the dehydration unit 200 can be used to adsorb moisture in the product gas to form dry gas; the inlet of the liquefaction unit 300 can be connected to the outlet of the dehydration unit 200, and the liquefaction unit 300 can be used to form liquefied natural gas and hydrogen-rich gas from the dry gas.

[0045] The hydrocarbon components in the cracking tail gas are removed by the dehydrocarbonization unit 100, such as heavy hydrocarbons and unsaturated hydrocarbons, thus generating product gas. The product gas then passes through a dehydration unit 200 to remove moisture, forming dry gas. Finally, it enters the liquefaction unit 300 for liquefaction, producing liquefied natural gas (LNG) and hydrogen-rich gas. This process allows for the production of natural gas and hydrogen-rich gas from the cracking tail gas, effectively improving its utilization rate and preventing direct emissions, thereby reducing environmental pollution.

[0046] Furthermore, since the dehydrocarbon removal unit 100 removes hydrocarbon components from the cracking tail gas, the product gas is less likely to polymerize during the subsequent drying and liquefaction processes. This reduces the lifespan of catalysts in the dehydration unit 200 and the freezing blockage of pipelines in the liquefaction unit 300, thereby extending the service life of the dehydration unit 200 and the liquefaction unit 300.

[0047] In an optional embodiment of this application, the dehydrocarbon removal device 100 may include at least five adsorption towers 110. The adsorption towers 110 can 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 can be used to allow the cracking tail gas to enter. The top opening of each adsorption tower 110 can be used to communicate with the dehydration device 200. Here, the gas outlet of the dehydrocarbon removal device 100 may include a top opening.

[0048] Each adsorption tower 110 has a first operating cycle, which may include multiple first operating stages, including an adsorption stage, a reverse release stage, a vacuum stage, a depressurization stage, and a pressurization stage. Optionally, at least five adsorption towers 110 may have different first operating stages. In this way, each adsorption tower 110 can operate alternately between different first operating stages, and at least five adsorption towers 110 may have different first operating stages at any given time, ensuring that at least one adsorption tower 110 is in the adsorption stage, thereby enabling continuous dehydrocarbonization treatment of cracking tail gas.

[0049] In other embodiments, the dehydrocarbon removal device 100 may include only one adsorption tower 110, or the dehydrocarbon removal device 100 may include at least five adsorption towers 110, and each adsorption tower 110 may be in the same operating phase.

[0050] In an optional embodiment, the dehydrocarbonization unit 100 may further include a feed pipeline 120 for conveying cracking tail gas. The bottom openings of each adsorption tower 110 are connected to the feed pipeline 120, and a first control valve 121 may be installed between the bottom opening of each adsorption tower 110 and the feed pipeline 120. The first control valve 121 is used to control the opening and closing of the connection between the bottom opening and the feed pipeline 120. Thus, the feed status of each adsorption tower 110 can be controlled by each first control valve 121, facilitating the alternating adsorption process of each adsorption tower 110.

[0051] Of course, the first control valve 121 may not be installed between the bottom opening of each adsorption tower 110 and the conveying pipe 120.

[0052] The dehydrocarbon removal unit 100 may further include a desorbed gas discharge pipe 130. The bottom opening of each adsorption tower 110 can be connected to the inlet of the desorbed gas discharge pipe 130, and the outlet of the desorbed gas discharge pipe 130 can be connected to an external desorbed gas delivery pipeline. A second control valve 131 can be installed between the bottom opening of each adsorption tower 110 and the desorbed gas discharge pipe 130. The second control valve 131 can be used to control the opening and closing of the connection between the bottom opening and the desorbed gas discharge pipe 130. In this way, the discharge of desorbed gas from each adsorption tower 110 can be controlled separately by the second control valve 131, so as to control the alternating reverse discharge process of each adsorption tower 110.

[0053] Of course, a second control valve 131 may not be installed between the bottom opening of each adsorption tower 110 and the desorption gas discharge pipe 130.

[0054] The dehydrocarbon removal unit 100 may further include a vacuum pipeline 140. The bottom opening of each adsorption tower 110 can be connected to the inlet of the vacuum pipeline 140, and the outlet of the vacuum pipeline 140 can be connected to an external desorption gas delivery pipeline. A third control valve 142 can be installed between the bottom opening of each adsorption tower 110 and the vacuum pipeline 140. The third control valve 142 can be used to control the opening and closing of the connection between the bottom opening and the vacuum pipeline 140. Thus, the vacuum status of each adsorption tower 110 can be controlled separately by the third control valve 142, facilitating the alternating vacuuming process of each adsorption tower 110.

[0055] Here, a vacuum pump 141 can be installed on the vacuum pipe 140 for evacuating the adsorption tower 110.

[0056] Of course, the third control valve 142 may not be installed between the bottom opening of each adsorption tower 110 and the vacuum pipe 140.

[0057] The dehydrocarbon removal unit 100 may further include a pressure regulating pipeline 150, through which the top openings of each adsorption tower 110 are connected. A fourth control valve 153 may be installed between the top opening of each adsorption tower 110 and the pressure regulating pipeline 150. The fourth control valve 153 can be used to control the on / off connection between the top opening and the pressure regulating pipeline 150. Thus, the gas inlet and outlet of each adsorption tower 110 can be controlled separately by the fourth control valve 153, facilitating the alternating pressure reduction and pressure increase processes of each adsorption tower 110. It should be noted that here, pressure reduction refers to pressure equalization reduction, and pressure increase refers to pressure equalization increase, that is, achieving pressure equilibrium between the two connected adsorption towers 110 by increasing and decreasing pressure.

[0058] Of course, the dehydrocarbonization unit 100 may also exclude the pressure regulating pipeline 150.

[0059] 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 can be connected through the first pressure regulating pipeline 151, and the top openings of each adsorption tower 110 can also be connected through the second pressure regulating pipeline 152. A first pressure regulating control valve 1531 may be provided between the top opening of each adsorption tower 110 and the first pressure regulating pipeline 151. The first pressure regulating control valve 1531 can be used to control the on / off connection between the top opening and the first pressure regulating pipeline 151. A second pressure regulating control valve 1532 may be provided between the top opening of each adsorption tower 110 and the second pressure regulating pipeline 152. The second pressure regulating control valve 1532 can be used to control the on / off connection 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. In this system, when adsorption tower 110 undergoes a first depressurization and a first pressurization, the first pressure regulating control valve 1531 connected to the adsorption tower 110 undergoing the first depressurization can be opened, allowing gas from the adsorption tower 110 undergoing the first depressurization to enter the adsorption tower 110 undergoing the first pressurization through the first pressure regulating pipe 151. When adsorption tower 110 undergoes a second or third depressurization or a second or third pressurization, the second pressure regulating control valve 1532 connected to the adsorption tower 110 undergoing the second or third depressurization or pressurization can be opened, allowing gas from the adsorption tower 110 undergoing the second or third depressurization to enter the adsorption tower 110 undergoing the second or third pressurization through the second pressure regulating pipe 152. In this way, the first pressure regulating pipe 151 and the second pressure regulating pipe 152 can be used simultaneously, allowing the adsorption towers 110 to operate in parallel during the pressure equalization process. This reduces the waiting time when operating a single pipe, thereby improving the overall system operating efficiency. It should be noted that the adsorption tower 110 can be subjected to secondary pressure regulation (i.e., pressure reduction or pressure increase) and tertiary pressure regulation through the second pressure regulating pipe 152. Here, the secondary and tertiary pressure regulation can be carried out at different time periods.

[0060] Of course, the pressure regulating pipeline 150 may also consist of only one pipeline, and the fourth control valve 153 may also consist of only one pressure regulating control valve.

[0061] 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. A third pressure regulating control valve may be provided between the top opening of each adsorption tower 110 and the third pressure regulating pipeline. The third pressure regulating control valve may be used to control the on / off connection 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 adsorption tower 110 undergoes a first depressurization and a first pressurization, the first pressure regulating control valve 1531 connected to the adsorption tower 110 undergoing the first depressurization and a first pressurization can be opened, allowing gas in the adsorption tower 110 undergoing the first depressurization to enter the adsorption tower 110 undergoing the first pressurization through the first pressure regulating pipe 151. When adsorption tower 110 undergoes a second depressurization and a second pressurization, the second pressure regulating control valve 1532 connected to the adsorption tower 110 undergoing the second depressurization can be opened, allowing gas in the adsorption tower 110 undergoing the second depressurization to enter the adsorption tower 110 undergoing the second pressurization through the second pressure regulating pipe 152. When adsorption tower 110 undergoes a third depressurization and a third pressurization, the third pressure regulating control valve connected to the adsorption tower 110 undergoing the third depressurization and a third pressurization can be opened, allowing gas in the adsorption tower 110 undergoing the third depressurization to enter the adsorption tower 110 undergoing the third pressurization through the third pressure regulating pipe.

[0062] Optionally, the dehydrocarbonization unit 100 may further include a product gas delivery pipeline 160 and a product gas circuit 170. The top outlet of each adsorption tower 110 is connected to the dehydration unit 200 through the product gas delivery pipeline 160. A ninth control valve 161 is provided between the top opening of each adsorption tower 110 and the product gas delivery pipeline 160. The two ends of the product gas circuit 170 can be connected to the product gas delivery pipeline 160 and the pressure regulating pipeline 150, respectively. A tenth control valve 171 is provided on the product gas circuit 170 to control the opening and closing of the product gas circuit 170. Part of the product gas can enter the adsorption tower 110 through the product gas circuit 170 and the pressure regulating pipeline 150, thereby regulating the pressure of the adsorption tower 110.

[0063] In some embodiments, the dehydrocarbonization device 100 may include ten adsorption towers 110, each of which has a first operating cycle. When adsorption tower 110A is in the first adsorption stage, adsorption tower 110B is in the second adsorption stage, adsorption tower 110C is in the third adsorption stage, adsorption tower 110D is in the adsorption completion stage, adsorption tower 110E is in the reverse release stage, adsorption tower 110F is in the vacuum stage, adsorption tower 110G is in the first depressurization stage, adsorption tower 110H is in the first pressurization stage, adsorption tower 110I is in the second pressurization stage, and adsorption tower 110J is in the third pressurization stage. Here, the adsorption degree in the first adsorption stage is less than that in the second adsorption stage, and the adsorption degree in the second adsorption stage is less than that in the third adsorption stage. Each adsorption tower 110 can undergo three depressurizations and three pressurizations.

[0064] Specifically, the process of the dehydrocarbon removal unit 100 will be explained using the operating conditions experienced by the adsorption tower 110A in the first operating cycle as an example.

[0065] Adsorption Stage: The first control valve 121 between adsorption tower 110A and feed pipeline 120 and the ninth control valve 161 between adsorption tower 110A and product gas delivery pipeline 160 are opened. Cracking tail gas enters adsorption tower 110A through feed pipeline 120. Hydrocarbon components in the cracking tail gas are adsorbed by the adsorption bed within adsorption tower 110A under adsorption pressure, thereby generating product gas. The product gas is output to dehydration unit 200 through the product gas delivery pipeline 160 via the ninth control valve 161. When the leading edge of the adsorption bed reaches a preset position, the first control valve 121 between adsorption tower 110A and feed pipeline 120 and the ninth control valve 161 between adsorption tower 110A and product gas delivery pipeline 160 are closed, stopping the entry of cracking tail gas into adsorption tower 110A and stopping the discharge of product gas from adsorption tower 110A.

[0066] After adsorption tower 110A stops adsorption, the fourth control valve 153 between adsorption tower 110A and pressure regulating pipeline 150 and the fourth control valve 153 between adsorption tower 110H and pressure regulating pipeline 150 are opened, so that the top opening of adsorption tower 110A is connected to the top opening of adsorption tower 110H, which has just finished the second pressurization. The gas in adsorption tower 110A can enter adsorption tower 110H, so that adsorption tower 110A achieves the first pressure reduction and adsorption tower 110H achieves the third pressurization. When this step is completed, the pressure of adsorption tower 110A and adsorption tower 110H are basically balanced, thus achieving the effect of pressure equalization.

[0067] After the first pressure reduction of adsorption tower 110A, the fourth control valve 153 between adsorption tower 110A and pressure regulating pipeline 150 and the fourth control valve 153 between adsorption tower 110H and pressure regulating pipeline 150 are closed. The fourth control valve 153 between adsorption tower 110I and pressure regulating pipeline 150 is opened. The gas in adsorption tower 110A can enter adsorption tower 110I, which has just completed the first pressure increase step, so that adsorption tower 110A achieves a second pressure reduction and adsorption tower 110I achieves a second pressure increase. When this step is completed, the pressure of adsorption tower 110A and adsorption tower 110I are basically balanced, thus achieving the effect of pressure equalization.

[0068] 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, which has just completed the vacuuming, so that the adsorption tower 110A achieves the third pressure reduction and the adsorption tower 110J achieves the first pressure increase. When this step is completed, the pressure of the adsorption tower 110A and the adsorption tower 110J are basically balanced, thus achieving the effect of pressure equalization.

[0069] 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 110A and the pressure regulating pipeline 150 are closed. 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 carries the hydrocarbon components in the adsorption tower 110A and is discharged in reverse to the desorption gas discharge pipeline 130, and is discharged from the desorption gas conveying pipeline through the desorption gas discharge pipeline 130.

[0070] After the reverse release is completed, close the second control valve 131 between the adsorption tower 110A and the desorption gas discharge 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.

[0071] After the vacuuming is completed, adsorption tower 110A enters the first pressurization process. The fourth control valve 153 between adsorption tower 110A and pressure regulating pipeline 150 and adsorption tower 110D and pressure regulating pipeline 150 are opened, so that the top opening of adsorption tower 110A is connected to the top opening of adsorption tower 110D, which has just completed the second depressurization. The gas in adsorption tower 110A can enter adsorption tower 110D, so that adsorption tower 110A achieves the first pressurization and adsorption tower 110D achieves the third depressurization. When this step is completed, the pressure of adsorption tower 110A and adsorption tower 110D is basically balanced, thus achieving the effect of pressure equalization.

[0072] After the adsorption tower 110A completes the first pressurization, 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, which has just completed the first depressurization, so that the adsorption tower 110A achieves the second pressurization and the adsorption tower 110F achieves the second depressurization. When this step is completed, the pressure of the adsorption tower 110A and the adsorption tower 110F are basically balanced, thus achieving the effect of pressure equalization.

[0073] 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 adsorption, so that the adsorption tower 110A achieves the third pressurization and the adsorption tower 110H achieves the first depressurization. When this step is completed, the pressure of the adsorption tower 110A and the adsorption tower 110H are basically balanced, thus achieving the effect of pressure equalization.

[0074] 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, some product gas is allowed to enter the adsorption tower 110A. At the same time, the first control valve 121 between the adsorption tower 110A and the conveying pipeline 120 is opened, allowing some cracking tail gas to enter the adsorption tower 110A, raising the pressure of the adsorption tower 110A to the adsorption pressure, thereby enabling the adsorption tower 110A to carry out the next cycle of adsorption.

[0075] In an optional embodiment, the dehydrocarbonization unit 100 may further include a first separator 180, which may be located upstream of the adsorption tower 110. The first separator 180 is used to separate liquids and gases in the cracking tail gas, and the feed pipeline 120 may be connected to the outlet of the first separator 180. In this way, the first separator 180 can separate liquids and gases in the cracking tail gas and remove liquids and some impurities, thereby helping to improve the purity of the feed gas entering the adsorption tower 110, thus providing higher quality feedstock for the subsequent pressure swing adsorption process, thereby improving the purity and yield of the product gas. Furthermore, by removing impurities from the cracking tail gas, the first separator 180 can also extend the service life of the adsorption tower 110 and the adsorbent in the adsorption tower 110, reducing equipment maintenance costs and replacement frequency. Simultaneously, the first separator 180 can also buffer the cracking tail gas, preventing it from impacting the adsorption tower 110. Here, the -0.3MPa cracking tail gas from outside the boundary can enter the first separator 180 for separation, and the separated gas enters the adsorption tower 110.

[0076] In other embodiments, the dehydrocarbonization device 100 may also exclude the first separator 180.

[0077] In an optional embodiment, the dehydrocarbonization device 100 may further include a desorption gas buffer tank 190 and a desorption gas blower 1010. The inlet of the desorption gas buffer tank 190 can be connected to the outlet of the desorption gas discharge pipe 130 and the outlet of the vacuum pipe 140, respectively. The outlet of the desorption gas buffer tank 190 can be connected to the inlet of the desorption gas blower 1010, and the outlet of the desorption gas blower 1010 can be connected to an external desorption gas delivery pipeline. The desorption gas blower 1010 is 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 reverse release stage and the vacuum stage, the desorption gas blower 1010 accelerates the desorption process of the adsorbed components by generating negative or positive pressure, thereby regenerating the adsorbent. Furthermore, the desorption gas can be pressurized to 60 kPaG by the desorption gas blower 1010 and then delivered to subsequent processing equipment via the desorption gas delivery pipeline. The desorption gas buffer tank 190 can stabilize the pressure of the desorption 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 desorption gas. Here, the desorption gas generated by reverse release and the desorption gas generated after vacuum pressurization to 20 kPaG can be discharged into the desorption gas buffer tank 190 through the desorption gas discharge pipe 130 and the vacuum pipe 140, respectively. Since the desorption process (i.e., the reverse release stage and the vacuum stage) may be accompanied by pressure fluctuations, the desorption gas buffer tank 190 can provide a stable pressure environment to ensure that the desorption gas flows out smoothly, thereby avoiding impact on the desorption gas blower 1010.

[0078] Optionally, the dehydrocarbonization unit 100 may also include a desorbed gas cooler 1020, which can cool the desorbed gas so that the desorbed gas meets emission requirements.

[0079] In other embodiments, the dehydrocarbon removal device 100 may include only the desorption gas blower 1010, excluding the desorption gas buffer tank 190. Specifically, the inlet of the desorption gas blower 1010 may be connected to the outlet of the desorption gas discharge pipe 130 and the outlet of the vacuum pipe 140, respectively. Alternatively, the dehydrocarbon removal device 100 may also exclude both the desorption gas buffer tank 190 and the desorption gas blower 1010.

[0080] In some embodiments, a product gas buffer tank 1030 may be provided between the gas outlet of the dehydrogenation unit 100 and the gas inlet of the dehydration unit 200. In this way, the product gas buffer tank 1030 can effectively balance the fluctuations in product gas pressure and flow rate at the outlet of the adsorption tower 110, ensuring a stable output of product gas and making the product gas flow rate more stable to meet the requirements of subsequent processes or equipment for gas flow stability. Simultaneously, due to the buffering effect of the product gas buffer tank 1030, the impact of product gas on subsequent pipelines and equipment can be reduced, lowering the wear and failure rate of the dehydration unit 200 and helping to extend the service life of the dehydration unit 200.

[0081] Of course, the product gas buffer tank 1030 may not be installed between the gas outlet of the dehydrogenation unit 100 and the gas inlet of the dehydration unit 200.

[0082] In an optional embodiment of this application, the dehydration device 200 may include a first drying tower 211, a second drying tower 212, and a third drying tower 213. Each of 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.

[0083] The first drying tower 211, the second drying tower 212, and the third drying tower 213 can each have a second operating cycle. This second operating cycle can include multiple second operating stages, including a drying stage, a cooling stage, and a regeneration stage. Furthermore, the second operating 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 operate alternately between different second operating stages, and at any given time, 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, ensuring the continuity of the dehydration process. Specifically, when one drying tower 210 is performing drying operations, one of the remaining drying towers 210 can undergo regeneration, and another can undergo cooling to meet the conditions for re-drying, thereby achieving uninterrupted dehydration of the product gas. Moreover, through reasonable inter-tower switching, the adsorption capacity of the desiccant can be maximized, and the downtime caused by waiting for regeneration can be shortened, thereby improving dehydration efficiency. Meanwhile, 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, avoiding equipment damage caused by local overheating.

[0084] In other embodiments, the dehydration device 200 may include only one drying tower 210, or the dehydration device 200 may include multiple drying towers 210, and the second operating stage of each drying tower 210 may be the same.

[0085] 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 the drying stage, cooling stage and regeneration stage respectively.

[0086] In an optional embodiment, the dehydration device 200 may further include a regeneration heater 220, a regeneration air inlet pipe 230, a regeneration air outlet pipe 240, and a product air inlet pipe 250.

[0087] Each drying outlet can be connected to the inlet of the regeneration heater 220 via a regeneration inlet pipe 230, and a fifth control valve 231 can be installed between each drying outlet and the regeneration inlet pipe 230 to control the on / off connection between the drying outlet and the regeneration inlet pipe 230. The outlet of the regeneration heater 220 can be connected to each drying outlet via a regeneration outlet pipe 240, and a sixth control valve 241 can be installed between the regeneration outlet pipe 240 and each drying outlet to control the on / off connection between the regeneration outlet pipe 240 and the drying outlet. Thus, the regeneration status of each drying tower 210 can be controlled by the fifth control valve 231 and the sixth control valve 241, allowing for alternating regeneration processes in each drying tower 210. Here, the regeneration heater 220 can heat the regeneration gas to 260°C.

[0088] Of course, the fifth control valve 231 may not be installed between each drying outlet and the regeneration air inlet pipe 230, and the sixth control valve 241 may not be installed between each regeneration air outlet pipe 240 and each drying outlet.

[0089] Each drying inlet can be connected to the outlet of the dehydrocarbonization unit 100 via a product gas inlet pipe 250. A seventh control valve 253 can be installed between each drying inlet and the product gas inlet pipe 250 to control the opening and closing of the connection. This allows the seventh control valve 253 to control the feeding of each drying tower 210, facilitating the alternating drying process of each drying tower 210.

[0090] Of course, the seventh control valve 253 may not be installed between each drying inlet and the product gas inlet pipe 250.

[0091] Optionally, the product gas inlet pipe 250 may include a first inlet pipe 251 and a second inlet pipe 252. Each drying inlet can be connected to the outlet of the dehydrogenation device 100 through the first inlet pipe 251, and each drying inlet can also be connected to the outlet of the dehydrogenation device 100 through the second inlet pipe 252. A first inlet control valve 2531 may be provided between each drying inlet and the first inlet pipe 251. The first inlet control valve 2531 can be used to control the opening and closing of the drying inlet and the first inlet pipe 251. A second inlet control valve 2532 may be provided between each drying inlet and the second product gas inlet pipe. The second inlet control valve 2532 can be used to control the opening and closing of the drying inlet and the second inlet pipe 252. Here, the seventh control valve 253 may include the first inlet control valve 2531 and the second inlet control valve 2532.

[0092] The first component of product gas can enter the first drying tower 211 through the first inlet pipe 251. The first drying tower 211 dries the first component of product gas to form dry gas. The second component of product gas can be used as regeneration gas and enters the second drying tower 212 through the second inlet pipe 252. The second component of product gas can perform cold blowing on the second drying tower 212. Here, the second component of product gas can cool the second drying tower 212 to 40°C. After cold blowing, the second component of product gas can enter the regeneration heater 220 through the regeneration inlet pipe 230. After being heated by the regeneration heater 220, it enters the third drying tower 213 through the regeneration 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 material 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, reduce the demand for additional energy or gas, and directly using the product gas as regeneration gas can avoid additional heating or compression processes, thus helping to reduce energy consumption. At the same time, there is no need to set up an additional generation, storage and transportation system for the regeneration gas, simplifying the overall process flow and equipment configuration.

[0093] It should be noted that after the regeneration of the third drying tower 213 is completed, the regeneration gas can enter the third drying tower 213 through the drying inlet of the third drying tower 213 and cold blow the third drying tower 213 to cool it down to 40°C. Then the gas is heated to 260°C by the regeneration heater 220 and enters the first drying tower 211 to heat and regenerate the desiccant in the first drying tower 211.

[0094] In this embodiment, the first component can be 85%-90%, and the second component can be 10%-15%.

[0095] Optionally, the dehydration device 200 may further include a drying gas exhaust pipe 260. Each drying outlet can be connected to the air inlet of the liquefaction device 300 through the drying gas exhaust pipe 260. An eleventh control valve 261 can be installed between each drying outlet and the drying gas exhaust pipe 260. The eleventh control valve 261 can be used to control the on / off connection between the drying outlet and the drying gas exhaust pipe 260. In this way, the drying gas output of each drying tower 210 can be controlled by the eleventh control valve 261, so as to control the alternating drying processes of each drying tower 210.

[0096] 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.

[0097] The regeneration cooler 270 is used to cool the regeneration waste gas discharged from the drying inlet. Each drying inlet is connected to the inlet of the regeneration cooler 270 via a regeneration exhaust pipe 280. An eighth control valve 281 can be installed between each drying inlet and the regeneration exhaust pipe 280 to control the on / off connection between them. Thus, the emission of regeneration waste gas from each drying tower 210 can be controlled individually via the eighth control valve 281, facilitating further control of the alternating regeneration processes of each drying tower 210. Here, the regeneration cooler 270 can reduce the temperature of the regeneration waste gas to 40°C.

[0098] Of course, the eighth control valve 281 may not be installed between each drying inlet and the regeneration exhaust pipe 280.

[0099] The regeneration separator 290 can be used to separate moisture from 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 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 beneficial to improving resource utilization and sustainability.

[0100] Of course, the dehydration device 200 may not be included in the regeneration separator 290 and the regeneration and recycling pipeline 2010.

[0101] In an optional embodiment, the processing system may further include a dust filter 500, the inlet of which may be connected to the outlet of the dehydration unit 200, and the outlet of which may be connected to the inlet of the liquefaction unit 300. In this way, the dust filter 500 can filter out fine dust particles in the dry gas, preventing these particles from entering subsequent equipment or pipelines and causing wear or even clogging, thus affecting the normal operation and lifespan of the equipment. Simultaneously, the dust filter 500 further purifies the dry gas, removing impurities and thereby improving the purity and quality of the subsequently produced liquefied natural gas and hydrogen-rich gas.

[0102] Of course, the processing system may also exclude the dust filter 500. Specifically, the air outlet of the dehydration device 200 can be directly connected to the air inlet of the liquefaction device 300.

[0103] Optionally, the processing system may further include a pressurizing device 400, the inlet of which can be connected to the outlet of the dehydrogenation unit 100, and the outlet of which can be connected to the inlet of the dehydration unit 200. In this way, the pressurization by the pressurizing device 400 increases both the flow rate and pressure of the product gas, thereby improving its flow velocity and diffusion capacity within the drying tower 210, thus enhancing drying efficiency. Furthermore, the pressurized product gas can more fully contact the desiccant within the drying tower 210, resulting in more uniform and thorough drying, helping to reduce residual moisture and impurities in the dried gas, thereby improving its purity and quality. Here, the pressurizing device 400 can pressurize the product gas to 5 MPaG.

[0104] Of course, the processing system may also exclude the booster unit 400.

[0105] In some embodiments, the dehydration device 200 may further include a filter separator 2020, which may be located downstream of the pressurization device 400. Specifically, the inlet of the filter separator 2020 may be connected to the outlet of the pressurization device 400, and the outlet of the filter separator 2020 may be connected to each drying inlet. In this way, the filter separator 2020 can filter the product gas to remove some impurities or moisture from the product gas, thereby improving the subsequent dehydration efficiency and the purity and quality of the dried gas.

[0106] In an optional embodiment of this application, the liquefaction device 300 may include a liquefaction cold box 310, which 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 the 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 cooled gaseous natural gas.

[0107] The liquefaction unit 300 may also include a refrigeration mechanism 330, which can be used to provide a mixed refrigerant to the first heat exchange channel 312 so that the mixed refrigerant can exchange heat with the dry gas in the natural gas channel 311 in the first heat exchange channel 312, thereby causing the dry gas to form cooled gaseous natural gas.

[0108] The liquefaction unit 300 may also include a flash evaporation unit 340, which may be connected to the outlet of the natural gas flow channel 311. The flash evaporation unit 340 may be used to liquefy gaseous natural gas to form liquefied natural gas and hydrogen-rich gas.

[0109] With this setup, the dry gas is cooled to near the liquefaction temperature in the liquefaction cold box 310 before entering the flash evaporation unit 340. The flash evaporation unit 340 can separate the residual unliquefied gas from the liquefied natural gas (LNG), effectively extracting the natural gas and hydrogen components from the cracking tail gas, thereby improving the utilization rate of the cracking tail gas and the purity of the LNG. It can also reduce the energy consumption and initial investment of the processing system, maximizing the economic benefits of the cracking tail gas.

[0110] In other embodiments, the liquefaction device 300 may also include only a liquefaction cold box 310 and a refrigeration mechanism 330, and the natural gas flow channel 311 of the liquefaction cold box 310 can directly convert dry gas into liquefied natural gas. Furthermore, the liquefaction device 300 may also include a cryogenic distillation unit connected to the outlet of the natural gas flow channel 311. The cryogenic distillation unit is used to liquefy gaseous natural gas, converting it into liquefied natural gas and hydrogen-rich gas.

[0111] In an optional embodiment, the liquefaction device 300 may further include a second separator 320, which can be used to separate heavy components from the dry gas to generate gaseous natural gas. In this way, the second separator 320 can effectively remove heavy components from the dry gas to prevent these components from condensing or clogging the equipment during the liquefaction process, thereby ensuring the efficient operation of the liquefaction process and significantly improving the purity and quality of the natural gas.

[0112] Here, the second separator 320 can be a cryogenic separator.

[0113] Optionally, the natural gas flow channel 311 may include a first natural gas flow channel 3111. Here, the inlet of the first natural gas flow channel 3111 can be the gas inlet of the liquefaction device 300, that is, the inlet of the first natural gas flow channel 3111 is connected to the gas 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. The first natural gas flow channel 3111 can exchange heat with the first heat exchange 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, thus preparing for the subsequent subcooling process. Furthermore, by pre-cooling the dry gas, the heat load of the dry gas in the subsequent subcooling process can be reduced, thereby improving the subcooling efficiency. At the same time, during the pre-cooling process, some impurities in the dry gas will liquefy or solidify as the temperature decreases, thus facilitating their removal by the second separator 320, thereby improving the purity of the gas phase natural gas.

[0114] The natural gas flow channel 311 may further include a second natural gas flow channel 3112. The inlet of the second natural gas flow channel 3112 can be connected to the outlet of the second separator 320, and the outlet of the second natural gas flow channel 3112 can be connected to the inlet of the flash evaporation mechanism 340. Furthermore, the second natural gas flow channel 3112 can exchange heat with the first heat exchange channel 312 to achieve subcooling of the gaseous natural gas. In this way, by subcooling the gaseous natural gas, its temperature can be further reduced to at or below its liquefaction point, thereby achieving the transformation from a gaseous to a liquid state.

[0115] In other embodiments, the liquefaction device 300 may not include the second separator 320, and the natural gas flow channel 311 may be a single flow channel. The natural gas flow channel 311 exchanges heat with the first heat exchange flow channel 312, which can directly subcool the dry gas, so that the dry gas forms subcooled gaseous natural gas.

[0116] In an optional embodiment, the flash evaporation 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 can be used to flash subcooled gaseous natural gas to produce 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 can be used to flash primary liquefied natural gas to produce mixed gas and liquefied natural gas. The high-pressure flash tank 341 can perform flash evaporation on gaseous natural gas under high pressure, utilizing the higher pressure difference to separate more high-boiling-point components from the gas phase, thereby improving separation efficiency and increasing the purity and quality of the hydrogen-rich gas. Furthermore, because the gaseous natural gas enters the high-pressure flash tank 341 at a higher pressure, the high-pressure flash tank 341 can more effectively utilize this pressure energy, thereby reducing energy consumption in subsequent processes. The low-pressure flash tank 342 operates at a lower pressure, which can significantly reduce the boiling point of compounds in primary liquefied natural gas, allowing high-boiling-point components to be converted into vapor at a lower temperature, thereby achieving more efficient separation to further remove impurities and non-condensable gases from primary liquefied natural gas and improve the purity and quality of liquefied natural gas.

[0117] Of course, the flash evaporation mechanism 340 may also include only the high-pressure flash tank 341, or the flash evaporation 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.

[0118] Optionally, a second throttle valve 343 can be installed 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 can throttle the flow to reduce the pressure of the subcooled gas phase natural gas, which in turn helps to reduce the temperature of the gas phase natural gas and thus facilitates the liquefaction of the gas phase natural gas.

[0119] Alternatively, a third throttle valve 344 can be installed 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 throttle the flow to reduce the pressure of the primary liquefied natural gas and can precisely control the amount of primary liquefied natural gas entering the low-pressure flash tank 342, avoiding system instability caused by excessive or insufficient flow.

[0120] 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 can 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 can be connected to the inlet of the refrigeration mechanism 330, so that the mixed refrigerant can flow back to the refrigeration mechanism 330.

[0121] The liquefied gas 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, and the outlet of the first reheating channel 314 may be connected to an external hydrogen transmission pipeline. The first reheating channel 314 may also exchange heat with a second heat exchange channel 313. In this way, 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 enabling the hydrogen-rich gas to meet the transmission requirements and be transported out through an external hydrogen transmission pipeline, such as to a hydrogenation unit in a petrochemical plant, so that the hydrogen-rich gas can be used as a raw material for the hydrogenation unit.

[0122] The liquefied cold box 310 may also include a second reheating channel 315. The inlet of the second reheating channel 315 may be connected to the outlet of the low-pressure flash tank 342, and the outlet of the second reheating channel 315 may be connected to the inlet of the dehydration device 200. The second reheating channel 315 may exchange heat with the second heat exchange channel 313. In this way, 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. The reheated mixed gas may then enter the dehydration device 200 to continue to recover hydrogen from the mixed gas.

[0123] In other embodiments, the liquefied cold box 310 may also exclude the first reheating channel 314 and the second reheating channel 315.

[0124] The liquefaction process of the dry gas is as follows:

[0125] The dried gas after adsorption and dehydration enters the liquefaction cold box 310. After being pre-cooled by the mixed refrigerant, it enters the second separator 320. The gaseous natural gas after separation of heavy components is further subcooled to -162℃. It is then throttled and depressurized to -3.3MPa by the second throttle valve 343 and enters the high-pressure flash tank 341 to flash out hydrogen-rich gas. The hydrogen-rich gas is reheated and metered by the liquefaction cold box 310 and then transported out. The primary liquefied natural gas is then depressurized to -0.32MPa by the third throttle valve 344 and enters the low-pressure flash tank 342. The mixed gas flashed out is reheated by the liquefaction cold box 310 and sent to the inlet of the booster unit 400 to continue recovering hydrogen. The generated liquefied natural gas is throttled and depressurized to 0.2MPa by the fourth throttle valve 345 and then sent to the outside.

[0126] Specifically, the dry gas enters the first natural gas flow channel 3111 for pre-cooling and then enters the second separator 320. In the second separator 320, heavy components are separated to form gaseous natural gas. The gaseous natural gas enters the second natural gas flow channel 3112 for subcooling to -162°C, and then enters the high-pressure flash tank 341 after being throttled by the second throttling valve 343. The high-pressure flash tank 341 flashes out hydrogen-rich gas and primary liquefied natural gas. The hydrogen-rich gas enters the first reheat flow channel of the liquefied gas cold box 310. After reheating, the gas is transported out through an external hydrogen pipeline. The primary liquefied natural gas is then depressurized to -0.32 MPa 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. The mixed gas enters the second reheat channel 315 of the liquefied cold box 310 for reheating and then enters the dehydration device 200. The liquefied natural gas is depressurized to 0.2 MPa by the fourth throttle valve 345 and then sent to the outside for transportation.

[0127] Optionally, the refrigeration unit 330 can be a mixed refrigerant compressor unit, which adopts a closed-loop 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 3.3 MPaG in two stages by the mixed refrigerant compressor unit, it is cooled and separated before entering the cold box. The first stage precools it to -15°C, and after throttling and depressurization, it returns to the cold box; the second stage precools the refrigerant to -65°C, and after throttling and depressurization, it returns to the cold box; the cryogenic refrigerant is cryogenically cooled to -162°C, and after throttling and depressurization, it returns to the cold box for reheating. In the cold box, condensation, evaporation, and throttling expansion occur in stages to obtain different temperature levels of refrigeration capacity. Here, propylene is used instead of propane in the mixed refrigerant, which can reduce the purchase of external refrigerants, fully utilize resources, and generate greater economic value while meeting existing process requirements.

[0128] 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 liquefaction cold box 310. The outlet of the first compressor 331 may be connected to both the inlet of the second compressor 334 and the third separator 333. Here, the outlet of the first compressor 331 may be connected to the third separator 333 via the first cooler 332; the outlet of the second compressor 334 may be connected to the fourth separator 336 via the second cooler 335. The gas phase outlet of 336 can be connected to the inlet of the first heat exchange channel 312. Furthermore, the liquefaction cold box 310 may 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 connected to the inlet of the second compressor 334, and the liquid phase outlet of the first separator 180 can be connected to the inlet of the third heat exchange channel 316. The outlet of the third heat exchange channel 316 can be connected to the second heat exchange channel 313 via a first pipe 318. The liquid phase outlet of the second separator 320 can be connected to the inlet of the fourth heat exchange channel 317, and the outlet of the fourth heat exchange channel 317 can be connected to the second heat exchange channel 313 via a second pipe 319. Here, a fifth throttle valve 3181 can be installed on the first pipe 318, and a sixth throttle valve 3191 can be installed on the second pipe 319.

[0129] The gaseous mixed refrigerant flowing out of the gaseous outlet of the fourth separator 336 enters the first heat exchange channel 312 of the liquefaction cold box 310. In the liquefaction cold box 310, it undergoes staged condensation, evaporation, and throttling expansion to obtain cooling capacity at different temperature levels. Specifically, the gaseous mixed refrigerant is cooled to -162°C in the first heat exchange channel 312 of the liquefaction cold box 310. After being throttled by the first throttling valve 3121, it becomes a low-temperature, low-pressure mixed refrigerant and enters the second heat exchange channel 313. After providing liquefaction and subcooling capacity for the gaseous natural gas and the gas passing through the liquefaction cold box 310, a high-temperature, low-pressure mixed refrigerant is obtained. The high-temperature, low-pressure mixed refrigerant flows into the first compressor 331 for pressurization to carry out the next cycle. The liquid-phase 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. After being depressurized and cooled by the sixth throttle valve 3191 on the second pipe 319, it enters the second heat exchange channel 313. The liquid-phase mixed refrigerant from 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. After being depressurized and cooled by the fifth throttle valve 3181 on the first pipe 318, it enters the second heat exchange channel 313.

[0130] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A treatment system for cracking tail gas, characterized in that, include: A dehydrocarbon removal unit (100) is used to remove hydrocarbon components from the cracking tail gas and generate product gas; A dehydration device (200) is provided, wherein the inlet of the dehydration device (200) is connected to the outlet of the dehydrocarbonization device (100), and the dehydration device (200) is used to adsorb the moisture in the product gas, thereby forming dry gas. A liquefaction device (300) is provided, wherein the inlet of the liquefaction device (300) is connected to the outlet of the dehydration device (200), and the liquefaction device (300) is used to convert the dried gas into liquefied natural gas and hydrogen-rich gas.

2. The cracking tail gas treatment system according to claim 1, characterized in that, The dehydrogenation device (100) includes at least five adsorption towers (110), which are used to adsorb hydrocarbon components in the cracking tail gas. Each adsorption tower (110) is provided with a top opening and a bottom opening. The bottom opening of each adsorption tower (110) is used to allow the cracking tail gas to enter. The top opening of each adsorption tower (110) is used to communicate with the dehydration device (200). The outlet of the dehydrogenation device (100) includes the top opening. Each of the adsorption towers (110) has a first operating cycle, which includes multiple first operating stages, including an adsorption stage, a reverse release stage, a vacuum stage, a depressurization stage, and a pressurization stage. The first operating stages of at least five of the adsorption towers (110) are different from each other.

3. The cracking tail gas treatment system according to claim 2, characterized in that, The dehydrocarbon removal device (100) also includes: A conveying pipeline (120) is used to convey the cracking tail gas. The bottom opening of each adsorption tower (110) is connected to the conveying pipeline (120), and a first control valve (121) is provided between the bottom opening of each adsorption tower (110) and the conveying pipeline (120). The first control valve (121) is used to control the opening and closing between the bottom opening and the conveying pipeline (120). The desorption gas discharge pipe (130) is provided with the bottom opening of each of the adsorption towers (110) connected to the inlet of the desorption gas discharge pipe (130), and the outlet of the desorption gas discharge pipe (130) is used to connect to the external desorption gas delivery pipeline. A second control valve (131) is provided between the bottom opening of each adsorption tower (110) and the desorption gas discharge pipe (130). The second control valve (131) is used to control the opening and closing of the bottom opening and the desorption gas discharge pipe (130). A vacuum pipe (140) is provided, and the bottom opening of each of the adsorption towers (110) is connected to the inlet of the vacuum pipe (140). The outlet of the vacuum pipe (140) is used to connect to 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 of the adsorption towers (110) and the vacuum pipe (140). The third control valve (142) is used to control the opening and closing between the bottom opening and the vacuum pipe (140). The pressure regulating pipe (150) connects the top openings of each of the adsorption towers (110) and a fourth control valve (153) is provided between the top opening of each of the adsorption towers (110) and the pressure regulating pipe (150). The fourth control valve (153) is used to control the opening and closing of the top opening and the pressure regulating pipe (150).

4. The cracking tail gas treatment system according to claim 3, characterized in that, The dehydrocarbon removal device (100) further includes a first separator (180) disposed upstream of the adsorption tower (110), the first separator (180) being used to separate the liquid and gas in the cracking tail gas, and the conveying pipeline (120) being connected to the outlet of the first separator (180).

5. The cracking tail gas treatment system according to claim 3, characterized in that, The dehydrocarbon removal device (100) further includes a desorption gas buffer tank (190) and a desorption gas blower (1010). The inlet of the desorption gas buffer tank (190) is connected to the outlet of the desorption gas discharge pipe (130) and the outlet of the vacuum pipe (140), respectively. The outlet of the desorption gas buffer tank (190) is connected to the inlet of the desorption gas blower (1010), and the outlet of the desorption gas blower (1010) is used to connect to the external desorption 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 treatment system according to claim 1, characterized in that, The dehydration device (200) includes 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. The air inlet of the dehydration device (200) includes the drying inlet, and each of the drying outlets is connected to the air inlet of the liquefaction device (300). The first drying tower (211), the second drying tower (212), and the third drying tower (213) each have a second operating cycle. The second operating cycle includes multiple second operating stages, including a drying stage, a cooling stage, and a regeneration stage. 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 treatment system according to claim 6, characterized in that, The dehydration device (200) further includes: Regenerative heater (220); The regeneration air intake pipe (230) is provided, and each of the drying outlets is connected to the inlet of the regeneration heater (220) through the regeneration air intake pipe (230). A fifth control valve (231) is provided between each of the drying outlets and the regeneration air intake pipe (230). The fifth control valve (231) is used to control the opening and closing of the drying outlet and the regeneration air intake pipe (230). The outlet of the regeneration heater (220) is connected to each of the drying outlets through the regeneration outlet pipe (240), and a sixth control valve (241) is provided between the regeneration outlet pipe (240) and each of the drying outlets. The sixth control valve (241) is used to control the opening and closing of the regeneration outlet pipe (240) and the drying outlet. Product gas inlet pipe (250), each of the drying inlets is connected to the outlet of the dehydrocarbonization device (100) through the product gas inlet pipe (250), and a seventh control valve (253) is provided between each of the drying inlets and the product gas inlet pipe (250), the seventh control valve (253) is used to control the opening and closing between the drying inlet and the product gas inlet pipe (250).

8. The cracking tail gas treatment system according to claim 6, characterized in that, The dehydration device (200) further includes: A regeneration cooler (270) is used to cool the regeneration exhaust gas discharged from the drying inlet; The regeneration exhaust pipe (280) is connected to the inlet of the regeneration cooler (270) through the regeneration exhaust pipe (280), and an eighth control valve (281) is provided between each of the drying inlets and the regeneration exhaust pipe (280). The eighth control valve (281) is used to control the opening and closing between the drying inlet and the regeneration exhaust pipe (280). A regeneration separator (290) is used to separate the moisture in the regeneration waste gas, and the inlet of the regeneration separator (290) is connected to the outlet of the regeneration exhaust pipe (280); The regeneration and recovery pipeline (2010) has its inlet connected to the outlet of the regeneration separator (290), and its outlet connected to the drying inlet.

9. The cracking tail gas treatment system according to claim 1, characterized in that, The processing system also includes a dust filter (500), the inlet of which is connected to the outlet of the dehydration device (200), and the outlet of which is connected to the inlet of the liquefaction device (300). And / or, The processing system also includes a booster device (400), the inlet of which is connected to the outlet of the dehydrogenation device (100), and the outlet of which is connected to the inlet of the dehydration device (200).

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

11. The cracking tail gas treatment system according to claim 10, characterized in that, The liquefaction unit (300) further includes a second separator (320) for separating heavy components from the dried gas to generate the gaseous natural gas. The natural gas flow channel (311) includes 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 evaporation mechanism (340). The first natural gas flow channel (3111) can exchange heat with the first heat exchange channel (312) to precool the dry gas. The second natural gas flow channel (3112) can exchange heat with the first heat exchange channel (312) to subcool the gas phase natural gas.

12. The cracking tail gas treatment system according to claim 10, characterized in that, The flash evaporation mechanism (340) includes: High-pressure flash tank (341), the inlet of which is connected to the outlet of the natural gas flow channel (311), the high-pressure flash tank (341) is used to flash the subcooled gas phase natural gas to produce hydrogen-rich gas and primary liquefied natural gas. A low-pressure flash tank (342) is provided, the inlet of which is connected to the liquid outlet of the high-pressure flash tank (341). The low-pressure flash tank (342) is used to flash the primary liquefied natural gas to produce a mixture of gas and liquefied natural gas.

13. The cracking tail gas treatment system according to claim 12, characterized in that, The liquefied gas cooler (310) also includes: The second heat exchange channel (313) has its inlet connected to the outlet of the first heat exchange channel (312) via a first throttle valve (3121), and its outlet is connected to the inlet of the refrigeration mechanism (330). The first reheating channel (314) has its inlet connected to the outlet of the high-pressure flash tank (341), and its outlet is connected to the external hydrogen delivery pipeline. The first reheating channel (314) can exchange heat with the second heat exchange channel (313). The second reheating channel (315) has its inlet connected to the outlet of the low-pressure flash tank (342) and its outlet connected to the inlet of the dehydration device (200). The second reheating channel (315) can exchange heat with the second heat exchange channel (313).

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