Molecular sieve three-tower dehydration regeneration device for ethane recovery and control method

Abstract

The application discloses a kind of molecular sieve three-tower dehydration regeneration devices for natural gas ethane recovery, including three molecular sieve towers, raw material ethane manifold, cold blow inlet manifold, high-temperature hot gas outlet manifold, dehydrated ethane manifold, cold blow outlet manifold and high-temperature hot gas inlet manifold, also including temperature transmitter A, heater, temperature transmitter B and multiple control valves, the application can realize the dehydration regeneration of engineering raw material ethane.The application also discloses a kind of control method of molecular sieve three-tower dehydration regeneration program sequence for natural gas ethane recovery, including the selection of conditions, the confirmation of valve position state, timing determination step sequence, judging the switching of molecular sieve tower according to step sequence value, switching tower operation is carried out, the next switching cycle is repeatedly carried out, or alarm is executed and is interrupted and exits, the precision of the application meets the measurement demand, can complete ethane deep dehydration according to adsorption effect and does not need artificial intervention.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of natural gas processing and ethane recovery, and relates to a molecular sieve three-tower dehydration regeneration device for natural gas ethane recovery and a control method for a molecular sieve three-tower dehydration regeneration program sequence for natural gas ethane recovery. BACKGROUND

[0002] Ethane is a high-quality raw material for ethylene, and the production cost of ethylene produced by cracking ethane is two-thirds of that of naphtha. Internationally, the proportion of C2-C4 as ethylene raw material is about 48%, while in China, naphtha is mainly used as the raw material due to the restriction of raw materials. Recovering engineering raw material ethane from natural gas and processing and recovering the engineering raw material ethane can be used as a raw material for steam thermal cracking to produce ethylene, which has a positive effect on improving the yield of ethylene products, reducing the energy consumption of the ethylene plant, and improving quality and efficiency.

[0003] The Changqing oilfield produces a large amount of upper paleozoic natural gas, which contains a large amount of heavy hydrocarbon components such as ethane, and the recovered ethane can be used to build a large ethylene plant, which has important significance for the reform and innovation of the ethylene industry in China. Therefore, the engineering raw material ethane needs to be processed and recovered. SUMMARY

[0004] The purpose of the present application is to provide a molecular sieve three-tower dehydration regeneration device for natural gas ethane recovery, which can realize the dehydration regeneration of engineering raw material ethane.

[0005] Another purpose of the present application is to provide a control method for a molecular sieve three-tower dehydration regeneration program sequence for natural gas ethane recovery, which can complete deep dehydration of ethane according to the adsorption effect without human intervention.

[0006] The first technical solution adopted by the present application is a molecular sieve three-tower dehydration regeneration device for natural gas ethane recovery, which comprises three molecular sieve towers, each of which is connected with a raw material ethane manifold, a cold blow gas inlet manifold, a high-temperature hot gas outlet manifold, a dehydration ethane manifold, a cold blow gas outlet manifold, and a high-temperature hot gas inlet manifold through pipelines. A temperature transmitter A is arranged on the high-temperature hot gas outlet manifold. The cold blow gas outlet manifold and the high-temperature hot gas inlet manifold are communicated, and a heater and a temperature transmitter B are arranged at the connection between the cold blow gas outlet manifold and the high-temperature hot gas inlet manifold. Each of the molecular sieve towers is provided with a control valve on the pipeline connected with the raw material ethane manifold, the cold blow gas inlet manifold, the high-temperature hot gas outlet manifold, the dehydration ethane manifold, the cold blow gas outlet manifold, and the high-temperature hot gas inlet manifold.

[0007] The first technical solution of the present application is also characterized in that,

[0008] The control valves on the pipelines connected with the raw material ethane manifold, the cold blowing gas inlet manifold, the high temperature hot gas outlet manifold, the dehydrated ethane manifold, the cold blowing gas outlet manifold and the high temperature hot gas inlet manifold of each molecular sieve tower are respectively an adsorption inlet valve, a cold blowing inlet valve, a high temperature hot gas outlet valve, an adsorption outlet valve, a cold blowing outlet valve and a high temperature hot gas inlet valve.

[0009] The adsorption inlet valve, the cold blowing inlet valve and the high temperature hot gas outlet valve connected with each molecular sieve tower are arranged above the top of the tower, and the adsorption outlet valve, the cold blowing outlet valve and the high temperature hot gas inlet valve connected with each molecular sieve tower are arranged below the bottom of the tower.

[0010] The second technical solution adopted by the present application is a kind of molecular sieve three-tower dehydration regeneration procedure sequence control method for natural gas ethane recovery, which controls the molecular sieve three-tower dehydration regeneration device for natural gas ethane recovery of the present application through PLC controller, realizes the deep dehydration of ethane, the raw material ethane is introduced from the inlet of the raw material ethane manifold, the cold blowing gas is introduced from the inlet of the cold blowing gas inlet manifold, the high temperature hot gas is discharged from the outlet of the high temperature hot gas outlet manifold, the dehydrated ethane is discharged from the outlet of the dehydrated ethane manifold, one tower of the three molecular sieve towers is adsorbed, one tower is cold blown, and one tower is heated, adsorption, heating and cold blowing start, end and switch at the same time, each control valve receives remote switch instruction, and detects switch state and feedback of each control valve, the timer set in the PLC controller includes device continuous operation timer Ta, step sequence timer Tb and delay timer Tc, the control of one switching cycle of the three molecular sieve towers is realized through the timer, the switching cycle is 8 hours, and the following steps are implemented in detail:

[0011] Step 1, according to the state of the three molecular sieve towers, one tower is adsorbed, one tower is cold blown, and one tower is heated to start running, or any step sequence of the step sequence timer Tb is selected to start running, so that the tower adsorbed at the start is tower A, the tower cold blown is tower B, and the tower heated is tower C;

[0012] Step 2, judge and switch the control valve according to the demand of each control valve;

[0013] Step 3, each timer starts timing, the step sequence timer Tb is set to 60 minutes, and is divided into 24 step sequences, each step sequence corresponds to the state of the three molecular sieve towers, and after the end of the 24 step sequences, the first step sequence is started again, and the cycle is repeated, when the Tb timer is full for 60 minutes, the Tb timer starts timing again, the step sequence Tx number is increased by 1, and when the Tx number is greater than 24, the counting is started again from 0, and the cycle is repeated.

[0014] Step 4, judging the Tx value, when Tx is not equal to 8, 16 or 24, repeating the timing; when the Tx value is equal to 8, it is determined that this time tower A adsorbs, tower B cold blows, and tower C heats; when the Tx value is equal to 16, it is determined that this time tower B adsorbs, tower C cold blows, and tower A heats; when the Tx value is equal to 24, it is determined that this time tower C adsorbs, tower A cold blows, and tower B heats.

[0015] Step 5, when the Tx value is equal to 8 or 16 or 24, and at the same time, the measured temperature TI of temperature transmitter A and temperature transmitter B satisfies TI≥220℃, switching tower operation is carried out; if TI does not satisfy TI≥220℃, switching tower operation is carried out after 20 minutes of delay.

[0016] Step 6, if the switching tower time is within the set time of the switching delay timer Tc, steps 2-6 are repeated to carry out the next switching period; if the switching tower time exceeds the set time of the switching delay timer Tc, an alarm and interruption exit are executed.

[0017] The second technical solution of the present application is also characterized in that,

[0018] The switching tower operation is specifically:

[0019] The cold blowing inlet valve and the cold blowing outlet valve corresponding to the heating tower are opened;

[0020] The cold blowing inlet valve and the cold blowing outlet valve corresponding to the cold blowing tower are closed;

[0021] The adsorption inlet valve and the cold blowing outlet valve corresponding to the cold blowing tower are opened;

[0022] The adsorption inlet valve and the cold blowing outlet valve corresponding to the adsorption tower are closed;

[0023] The high-temperature hot gas outlet valve and the high-temperature hot gas inlet valve corresponding to the adsorption tower are opened;

[0024] The high-temperature hot gas outlet valve and the high-temperature hot gas inlet valve corresponding to the heating tower are closed, and the switching tower process is ended.

[0025] The set time of the switching delay timer Tc is 100s.

[0026] The PLC controller controls the control valve by using DCS.

[0027] The present application has the following beneficial effects:

[0028] The natural gas ethane recovery molecular sieve three-tower dehydration regeneration device is a matching auxiliary system of the ethane and other light hydrocarbon recovery technology of the old natural gas, and realizes "three simultaneities", i.e., simultaneous start, simultaneous end and simultaneous switching, through three molecular sieve towers for adsorption, cold blowing and heating, so as to deeply dehydrate the ethane of the engineering raw material; the three molecular sieve towers reduce the adsorption rate of the ethane gas and also reduce the adsorption of the CO2 gas, thereby avoiding the circulation and accumulation of the CO2 gas; the qualified ethane gas after dehydration and regeneration can be all used as the product and exported or can be sent to the liquefaction device for liquefaction and storage.

[0029] The natural gas ethane recovery molecular sieve three-tower dehydration regeneration program sequence control method adopts the dehydration and regeneration method of three molecular sieve towers, which can realize the deep dehydration of the engineering raw material ethane, meet the requirement that the water dew point of the ethane gaseous product reaches 0.1 ppm mass index, automatically complete the adsorption, heating and cold blowing sequence control and circulation of the molecular sieve dehydration, and can adjust the set period or adjust the sequence control steps according to the adsorption effect at any time, so as to achieve the purpose of deep dehydration of ethane without human intervention. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a structure schematic view of the natural gas ethane recovery molecular sieve three-tower dehydration regeneration device according to Embodiment 2 of the present application;

[0031] Figure 2 is a control logic diagram of the natural gas ethane recovery molecular sieve three-tower dehydration regeneration program sequence control method according to Embodiment 4 of the present application;

[0032] Figure 3 is a corresponding relationship diagram of the opening and closing of each control valve and the state of the three molecular sieve towers in the natural gas ethane recovery molecular sieve three-tower dehydration regeneration program sequence control method according to Embodiment 4 of the present application.

[0033] In the figure, 1. raw material ethane, 2. raw material ethane manifold, 3. cold blow inlet manifold, 4. high temperature hot gas outlet manifold, 5. adsorption inlet valve A, 6. cold blow inlet valve A, 7. high temperature hot gas outlet valve A, 8. adsorption inlet valve B, 9. cold blow inlet valve B, 10. high temperature hot gas outlet valve B, 11. adsorption inlet valve C, 12. cold blow inlet valve C, 13. high temperature hot gas outlet valve C, 14. column A, 15. column B, 16. column C, 17. adsorption outlet valve A, 18. cold blow outlet valve A, 19. high temperature hot gas inlet valve A, 20. adsorption outlet valve B, 21. cold blow outlet valve B, 22. high temperature hot gas inlet valve B, 23. adsorption outlet valve C, 24. cold blow outlet valve C, 25. high temperature hot gas inlet valve C, 26. dehydrated ethane manifold, 27. cold blow outlet manifold, 28. high temperature hot gas inlet manifold, 29. dehydrated ethane, 30. cold blow inlet gas, 31. high temperature hot gas, 32. heater, 33. temperature transmitter A, 34. temperature transmitter B. DETAILED DESCRIPTION

[0034] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] The present embodiment provides a molecular sieve three-column dehydration regeneration device for natural gas ethane recovery, which comprises three molecular sieve columns, each of which is connected with a raw material ethane manifold 2, a cold blow inlet manifold 3, a high temperature hot gas outlet manifold 4, a dehydrated ethane manifold 26, a cold blow outlet manifold 27, and a high temperature hot gas inlet manifold 28 through pipelines. The high temperature hot gas outlet manifold 4 is provided with a temperature transmitter A 33. The cold blow outlet manifold 27 and the high temperature hot gas inlet manifold 28 are communicated, and a heater 32 and a temperature transmitter B 34 are arranged at the connection of the cold blow outlet manifold 27 and the high temperature hot gas inlet manifold 28. Each of the molecular sieve columns is provided with a control valve on the pipeline connected with the raw material ethane manifold 2, the cold blow inlet manifold 3, the high temperature hot gas outlet manifold 4, the dehydrated ethane manifold 26, the cold blow outlet manifold 27, and the high temperature hot gas inlet manifold 28.

[0037] Example 2

[0038] The present embodiment provides a molecular sieve three-column dehydration regeneration device for natural gas ethane recovery. On the basis of example 1, the control valves on the pipelines connected with the raw material ethane manifold 2, the cold blow inlet manifold 3, the high temperature hot gas outlet manifold 4, the dehydrated ethane manifold 26, the cold blow outlet manifold 27, and the high temperature hot gas inlet manifold 28 of each molecular sieve column are respectively adsorption inlet valves, cold blow inlet valves, high temperature hot gas outlet valves, adsorption outlet valves, cold blow outlet valves, and high temperature hot gas inlet valves.

[0039] The adsorption inlet valve, the cold blowing inlet valve and the high temperature hot gas outlet valve connected with each molecular sieve tower are arranged above the top of the tower, and the adsorption outlet valve, the cold blowing outlet valve and the high temperature hot gas inlet valve connected with each molecular sieve tower are arranged below the bottom of the tower.

[0040] Embodiment 3

[0041] The embodiment provides a control method of a molecular sieve three-tower dehydration regeneration procedure sequence for natural gas ethane recovery. The molecular sieve three-tower dehydration regeneration device for natural gas ethane recovery is controlled by a PLC controller, deep dehydration of ethane is realized, raw material ethane 1 is introduced from the inlet of a raw material ethane manifold 2, cold blowing gas 30 is introduced from the inlet of a cold blowing gas manifold 3, high temperature hot gas 31 is discharged from the outlet of a high temperature hot gas outlet manifold 4, and dehydrated ethane 29 is discharged from the outlet of a dehydrated ethane manifold 26. One of the three molecular sieve towers is adsorbed, one is cold blown, and one is heated. The adsorption, heating and cold blowing start, end and switch at the same time. Each control valve receives a remote switch instruction and detects the switch state and feedback of each control valve. The timer arranged in the PLC controller includes a device continuous operation timer Ta, a step sequence timer Tb and a delay timer Tc. The control of one switching cycle of the three molecular sieve towers is realized through the timer. The switching cycle is 8 hours. The following steps are implemented:

[0042] Step 1. According to the state of the three molecular sieve towers, one tower is selected to be adsorbed, one tower is selected to be cold blown, and one tower is selected to be heated to start running. Alternatively, any step sequence of the step sequence timer Tb is selected to start running. The tower being adsorbed is tower A 14, the tower being cold blown is tower B 15, and the tower being heated is tower C 16.

[0043] Step 2. The control valve is opened and closed according to the requirements of each control valve.

[0044] Step 3. Each timer starts timing. The step sequence timer Tb is set to 60 minutes. There are 24 step sequences in total. Each step sequence corresponds to the state of the three molecular sieve towers. After the 24 step sequences end, the first step sequence is restarted to cycle. When the Tb timer is full for 60 minutes, the Tb timer is restarted, the step sequence Tx number is increased by 1, and when the Tx number is greater than 24, the counting is restarted from 0. This cycle is repeated.

[0045] Step 4. The Tx value is judged. When Tx is not equal to 8, 16 or 24, the timing is repeated. When the Tx value is equal to 8, it is determined that tower A 14 is adsorbed, tower B 15 is cold blown, and tower C 16 is heated at this time. When the Tx value is equal to 16, it is determined that tower B 15 is adsorbed, tower C 16 is cold blown, and tower A 14 is heated at this time. When the Tx value is equal to 24, it is determined that tower C 16 is adsorbed, tower A 14 is cold blown, and tower B 15 is heated at this time.

[0046] Step 5, when the Tx value is equal to 8 or 16 or 24, and at the same time the measured temperature TI of temperature transmitter A33 and temperature transmitter B34 satisfies TI≥220℃, switching tower operation is performed, if TI does not satisfy TI≥220℃, switching tower operation is performed after 20 minutes of delay;

[0047] Step 6, if the switching tower time is within the set time 100s of the switching delay timer Tc, steps 2-6 are repeated to perform the next switching cycle, if the switching tower time exceeds 100s, an alarm and interruption exit are performed.

[0048] Example 4

[0049] The natural gas produced by Changqing Oilfield contains a certain amount of ethane light hydrocarbon components, and the average content of ethane light hydrocarbon components is 5.4%, and the natural gas production reaches 300×10 8 m 3 / a, wherein 200×10 8 m 3 / a can be concentrated for ethane light hydrocarbon component recovery, and the raw material natural gas treatment capacity of Changqing Oilfield Upper Paleozoic Natural Gas Treatment Plant is 6000×10 4 m 3 / d (200 billion / year), and four sets of liquid hydrocarbon recovery treatment devices of the same size are set up, and the treatment capacity of a single device reaches 1500×10 4 m 3 / d. 105.27 million tons of raw material ethane, 35.63 million tons of liquefied petroleum gas, and 9.3 million tons of stable light hydrocarbon can be recovered annually, which has high economic recovery value.

[0050] The raw material ethane is an intermediate product in the natural gas ethane recovery project, which has been separated from propane in the ethane-depropanizer, and almost all CO2 in the ethane has been removed in the ethane-decarbonizer, and the remaining wet ethane gas is dehydrated by molecular sieve to meet the quality index requirements of commercial ethane and the quality requirements of ethane cracking or ethane liquefaction.

[0051] The embodiment provides a kind of molecular sieve three-tower dehydration regeneration program sequence control method for natural gas ethane recovery, by PLC controller to the like Figure 1The natural gas ethane recovery molecular sieve three-tower dehydration regeneration device of the shown embodiment 2 is controlled to realize deep dehydration of ethane, raw material ethane 1 is introduced from the inlet of raw material ethane manifold 2, cold blow inlet gas 30 is introduced from the inlet of cold blow inlet gas manifold 3, high temperature hot gas 31 is discharged from the outlet of high temperature hot gas outlet manifold 4, dehydrated ethane 29 is discharged from the outlet of dehydrated ethane manifold 26, one of the three molecular sieve towers is adsorbed, one is cold blown, and one is heated, adsorption, heating and cold blowing start, end and switch at the same time, the PLC controller controls the control valve by DCS, each control valve receives remote switch instructions and detects the switch state and feedback of each control valve, the timer set in the PLC controller includes device continuous running timer Ta, step sequence timer Tb and delay timer Tc, the control of one switching cycle of the three molecular sieve towers is realized through the timer, and the switching cycle is 8 hours, such as Figure 2 As shown, the following steps are implemented:

[0052] Step 1: According to the state of the three molecular sieve towers, select one tower to adsorb, one tower to cold blow, and one tower to heat to start running, or select any step sequence of step sequence timer Tb to start running, and let the tower that starts running to adsorb be tower A 14, the tower that cold blows be tower B 15, and the tower that heats be tower C 16.

[0053] Adsorption tower A 14 is connected with raw material ethane manifold 2, cold blow inlet gas manifold 3, high temperature hot gas outlet manifold 4, dehydrated ethane manifold 26, cold blow outlet gas manifold 27 and high temperature hot gas inlet manifold 28, and adsorption inlet valve A5, cold blow inlet valve A6, high temperature hot gas outlet valve A7, adsorption outlet valve A17, cold blow outlet valve A18 and high temperature hot gas inlet valve A19 are arranged on the pipelines connected with the above-mentioned manifolds, respectively; adsorption tower B 15 is connected with raw material ethane manifold 2, cold blow inlet gas manifold 3, high temperature hot gas outlet manifold 4, dehydrated ethane manifold 26, cold blow outlet gas manifold 27 and high temperature hot gas inlet manifold 28, and adsorption inlet valve B8, cold blow inlet valve B9, high temperature hot gas outlet valve B10, adsorption outlet valve B20, cold blow outlet valve B21 and high temperature hot gas inlet valve B22 are arranged on the pipelines connected with the above-mentioned manifolds, respectively; adsorption tower C 16 is connected with raw material ethane manifold 2, cold blow inlet gas manifold 3, high temperature hot gas outlet manifold 4, dehydrated ethane manifold 26, cold blow outlet gas manifold 27 and high temperature hot gas inlet manifold 28, and adsorption inlet valve C11, cold blow inlet valve C12, high temperature hot gas outlet valve C13, adsorption outlet valve C23, cold blow outlet valve C24 and high temperature hot gas inlet valve C25 are arranged on the pipelines connected with the above-mentioned manifolds, respectively.

[0054] Step 2: According to the requirements of each control valve, the control valve is judged and switched, and the corresponding relationship between the switch of each control valve and the state of the three molecular sieve towers is as shown in Figure 3 Figure 3 ON is the open state, and the rest is the closed state.

[0055] ​Step 3, each timer starts timing, step sequence timer Tb is set to 60 minutes, a total of 24 step sequences, each step sequence corresponds to the state of 3 molecular sieve towers, after 24 step sequences, the cycle starts from the first step sequence, and the cycle is repeated, when Tb timer is full 60 minutes, Tb starts timing again, and step sequence Tx number is added 1, when Tx number is greater than 24, the counting starts from 0, and the cycle is repeated.

[0056] Step 4, Tx value is judged, when Tx is not equal to 8, 16 or 24, the timing is repeated, when Tx value is equal to 8, it is determined that tower A14 is adsorbed, tower B15 is cold blown, and tower C16 is heated, x=tower A14, y=tower B15, and z=tower C16 are given, x represents adsorption, y represents cold blowing, and z represents heating, when Tx value is equal to 16, it is determined that tower B15 is adsorbed, tower C16 is cold blown, and tower A14 is heated, x=tower B15, y=tower C16, and z=tower A14 are given, and when Tx value is equal to 24, it is determined that tower C16 is adsorbed, tower A14 is cold blown, and tower B15 is heated, x=tower B15, y=tower C16, and z=tower A14 are given.

[0057] Step 5, when Tx value is equal to 8 or 16 or 24, that is, the assignment condition is met, and the measured temperature TI of temperature transmitter A33 and temperature transmitter B34 is greater than or equal to 220 DEG C, the switching tower operation is performed, if TI is not greater than or equal to 220 DEG C, the switching tower operation is performed after 20 minutes of delay.

[0058] The switching tower operation is specifically as follows:

[0059] The cold blowing inlet valve and the cold blowing outlet valve corresponding to the heated tower are opened.

[0060] The cold blowing inlet valve and the cold blowing outlet valve corresponding to the cold blown tower are closed.

[0061] The adsorption inlet valve and the cold blowing outlet valve corresponding to the cold blown tower are opened.

[0062] The adsorption inlet valve and the cold blowing outlet valve corresponding to the adsorbed tower are closed.

[0063] The high-temperature hot gas outlet valve and the high-temperature hot gas inlet valve corresponding to the adsorbed tower are opened.

[0064] The high-temperature hot gas outlet valve and the high-temperature hot gas inlet valve corresponding to the heated tower are closed, and the switching tower process is ended.

[0065] Step 6, if the switching tower time is within the set time 100s of the switching delay timer Tc, steps 2-6 are repeated to perform the next switching cycle, if the switching tower time exceeds 100s, the alarm and interruption are executed.

[0066] In conclusion, the natural gas ethane recovery molecular sieve three-tower dehydration regeneration procedure sequence control method can be used as the key step and component of the intermediate product raw material ethane deep dehydration in the ancient natural gas ethane recovery project, can be used as the ethane quality index technical guarantee, provides high-quality raw materials for ethane cracking to produce ethylene, is beneficial to improve the relatively backward naphtha cracking to produce ethylene technology in China, fills the technical blank of the deep dehydration of the intermediate product raw material ethane after deep CO2 removal in the natural gas ethane recovery project in China, and is the main component of the natural gas ethane recovery project series key technology and device.

Claims

1. A three-tower molecular sieve dehydration and regeneration device for natural gas ethane recovery, characterized in that, The system includes three molecular sieve towers. Each molecular sieve tower is connected to a raw material ethane manifold (2), a cold-blown gas inlet manifold (3), a high-temperature hot gas outlet manifold (4), a dehydrated ethane manifold (26), a cold-blown gas outlet manifold (27), and a high-temperature hot gas inlet manifold (28) via pipelines. A temperature transmitter A (33) is installed on the high-temperature hot gas outlet manifold (4). The cold-blown gas outlet manifold (27) and the high-temperature hot gas inlet manifold (28) are connected. A heater (32) and a temperature transmitter B (34) are installed at the connection between the cold-blown gas outlet manifold (27) and the high-temperature hot gas inlet manifold (28). Each molecular sieve tower is connected to a control valve on the pipelines of the raw material ethane manifold (2), the cold-blown gas inlet manifold (3), the high-temperature hot gas outlet manifold (4), the dehydrated ethane manifold (26), the cold-blown gas outlet manifold (27), and the high-temperature hot gas inlet manifold (28). The control valves on the pipelines connecting each of the molecular sieve towers to the raw material ethane manifold (2), cold blowing gas inlet manifold (3), high temperature hot gas outlet manifold (4), dehydrated ethane manifold (26), cold blowing gas outlet manifold (27), and high temperature hot gas inlet manifold (28) are respectively the adsorption inlet valve, cold blowing inlet valve, high temperature hot gas outlet valve, adsorption outlet valve, cold blowing outlet valve, and high temperature hot gas inlet valve; The adsorption inlet valve, cold blowing inlet valve, and high-temperature hot gas outlet valve connected to each of the molecular sieve towers are located above the top of the tower, while the adsorption outlet valve, cold blowing outlet valve, and high-temperature hot gas inlet valve connected to each of the molecular sieve towers are located below the bottom of the tower.

2. A method for controlling the sequence of a three-tower dehydration and regeneration process for molecular sieves used in natural gas ethane recovery, comprising controlling the three-tower dehydration and regeneration device for natural gas ethane recovery as described in claim 1 using a PLC controller to achieve deep dehydration of ethane, characterized in that... Raw material ethane (1) is introduced through the inlet of raw material ethane manifold (2), and cold blowing gas (30) is introduced through the inlet of cold blowing gas manifold (3). One of the three molecular sieve towers is for adsorption, one for cold blowing, and one for heating. Adsorption, heating, and cold blowing start, end, and switch simultaneously. Each control valve receives remote switching commands and detects and provides feedback on the switching status of each control valve. The timers set in the PLC controller include the device continuous operation timer Ta, the step sequence timer Tb, and the delay timer Tc. The timers are used to control one switching cycle of the three molecular sieve towers. The switching cycle is 8 hours. The specific implementation is as follows: Step 1: Select one tower for adsorption, one tower for cold blowing, and one tower for heating according to the state of the three molecular sieve towers, or select any step sequence of the step sequence timer Tb to start operation. Let the tower for adsorption be tower A (14), the tower for cold blowing be tower B (15), and the tower for heating be tower C (16). Step 2: Determine and switch the control valves according to their requirements; Step 3: Each timer starts timing. The step sequence timer Tb is set to 60 minutes, with a total of 24 steps. Each step corresponds to the status of 3 molecular sieve towers. After every 24 steps, the cycle restarts from the first step. When the Tb timer reaches 60 minutes, it restarts timing, and the step sequence number Tx is incremented by 1. When the Tx number is greater than 24, it restarts counting from 0. This cycle continues. Step 4: Determine the Tx value. If Tx is not equal to 8, 16, or 24, repeat the timing. If Tx is equal to 8, determine that tower A (14) is adsorbing, tower B (15) is cold blowing, and tower C (16) is heating. If Tx is equal to 16, determine that tower B (15) is adsorbing, tower C (16) is cold blowing, and tower A (14) is heating. If Tx is equal to 24, determine that tower C (16) is adsorbing, tower A (14) is cold blowing, and tower B (15) is heating. Step 5: When the Tx value is equal to 8, 16 or 24, and the measured temperature TI of temperature transmitter A (33) and temperature transmitter B (34) is simultaneously satisfied to be ≥220℃, then the switching tower operation is performed. If TI does not satisfy TI≥220℃, then the switching tower operation is performed after a delay of 20 minutes. Step 6: If the tower switching time is within the set time of the switching delay timer Tc, repeat steps 2-6 for the next switching cycle. If the tower switching time exceeds the set time of the switching delay timer Tc, execute an alarm and exit the interruption. The switching tower operation specifically includes: Open the cold air inlet valve and cold air outlet valve of the corresponding heating tower; Close the corresponding cold blowing inlet valve and cold blowing outlet valve of the cold blowing tower; Open the adsorption inlet valve and the cold blowing outlet valve of the corresponding cold blowing tower; Close the adsorption inlet valve and cold blow outlet valve of the corresponding adsorption tower; Open the high-temperature hot gas outlet valve and high-temperature hot gas inlet valve of the corresponding adsorption tower; The high-temperature hot gas outlet valve and high-temperature hot gas inlet valve of the corresponding heating tower are closed, and the tower cutting process ends.

3. The method for controlling the sequence of the three-tower dehydration and regeneration process of molecular sieve for natural gas ethane recovery according to claim 2, characterized in that, The switching delay timer Tc is set to 100 seconds.

4. The method for controlling the sequence of the three-tower dehydration and regeneration process of molecular sieve for natural gas ethane recovery according to claim 2, characterized in that, The PLC controller uses a DCS to control the control valve.

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