Processes and control methods for continuous separation of hydrogen isotopes

Abstract

This invention discloses a process and control method for continuous hydrogen isotope separation, belonging to the field of hydrogen isotope separation technology. The process employs a counter-current continuous operation mode, dividing the adsorption tower into three zones: adsorption, displacement, and regeneration. The inlet and outlet positions of the adsorption tower are periodically switched to simulate the counter-current movement of the adsorbent and material. Each adsorption tower and connecting pipeline are immersed in a coolant at a constant temperature, achieving separation by utilizing the difference in the adsorbent's force on hydrogen isotopes. The control method employs digital control logic, using spreadsheets to edit valve status, control software to parse data, and a PLC controller to execute valve switching, achieving precise control of the multi-tower operating status under different conditions. This invention solves the problems of high equipment investment and high energy consumption in traditional separation methods, possessing advantages such as high separation factor, high recovery rate, and stable continuous operation, and is suitable for hydrogen isotope separation needs with different feed gas ratios and different throughputs.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen isotope separation technology, specifically relating to a process and control method for continuous separation of hydrogen isotopes. Background Technology

[0002] Hydrogen isotopes, mainly including protium (H2), deuterium (D2), and tritium (T2), have irreplaceable value in nuclear energy, scientific research, medical diagnostics, and advanced industries. However, due to the identical electron configurations of isotopic atoms, their physicochemical properties are extremely similar, leading to difficulties in separation. Traditional methods for separating hydrogen isotopes, such as cryogenic distillation, thermal diffusion, and chemical exchange, typically suffer from high equipment investment, enormous energy consumption, and limited separation factors, hindering their large-scale application. In recent years, adsorption separation technology based on the quantum sieving effect has shown great potential. This technology utilizes the difference in de Broglie wavelengths between light and heavy isotopes (such as H2) and heavy isotopes (such as D2) at extremely low temperatures, as well as the difference in their interaction forces with the pores of nanoporous materials, to achieve efficient sieving with advantages such as high separation factors and relatively low energy consumption.

[0003] Using a gas-phase simulated moving bed device for adsorption separation can achieve continuous separation of hydrogen isotopes with high purity and high recovery rate. However, for different operating conditions such as different adsorbents, different feed gas ratios, and different gas processing requirements, taking a ten-tower simulated moving bed device as an example, the device needs to be adjusted to operate in 9-tower, 8-tower, 7-tower, or 6-tower configurations with different operating parameters according to specific operating conditions. Furthermore, the simulated moving bed has numerous valves, and the operating modes differ across various operating states, which places high demands on the control methods. Summary of the Invention

[0004] To simulate the continuous separation of hydrogen isotopes in a moving bed under different operating conditions, this invention provides a process and control method for continuous hydrogen isotope separation. In this invention, a countercurrent continuous operation is employed, and the inlet and outlet positions of the adsorption tower are periodically changed to simulate the effect of the adsorbent moving downwards while the material moves upwards.

[0005] The technical solution adopted by the present invention to achieve the above objectives is: a process for continuous separation of hydrogen isotopes, which employs a simulated moving bed device in a countercurrent continuous operation mode, and the process includes the following steps: Step 1: Divide the adsorption tower of the simulated moving bed device into three independent functional zones: adsorption zone, displacement zone, and regeneration zone. The adsorption tower and connecting pipelines are immersed in a coolant at a constant temperature, which is controlled at 77-160K. Step 2: Introduce H2 / D2 mixed feed gas into the adsorption zone. D2 is preferentially adsorbed due to its stronger interaction with the adsorbent, while H2 preferentially penetrates and is discharged from the top of the adsorption tower as a light component gas rich in H2. The adsorption zone improves the utilization rate of the adsorbent by connecting multiple towers in series. Step 3: Introduce D2-rich heavy component product gas into the replacement zone to perform multi-stage replacement on the adsorption tower that is saturated with adsorption, and discharge the co-adsorbed H2 to increase the concentration of product gas. A small amount of tail gas discharged from the replacement zone is discharged into the adsorption zone to recover heavy components. Step 4: Regenerate the adsorption tower after complete displacement to obtain a high-purity D2-rich heavy component product gas by desorption. Regeneration methods include purging, vacuum, or vacuum purging. Step 5: After running for a predetermined time, switch valves to achieve zone switching: one adsorption tower switches from the adsorption zone to the displacement zone, one adsorption tower switches from the displacement zone to the regeneration zone, one adsorption tower switches from the regeneration zone to the adsorption zone, and the remaining towers move in the same direction to simulate the counter-current movement of the adsorbent and the airflow.

[0006] Preferably, the adsorption zone includes a feed gas adsorption tower and a light component discharge adsorption tower; the displacement zone includes a displacement gas feed adsorption tower and at least one adsorption tower connected in series; and the regeneration zone includes at least one regeneration adsorption tower.

[0007] Preferably, the simulated moving bed device has a 5-10 tower structure, or can be adjusted to a 5-9 tower operating state according to the working conditions.

[0008] Preferably, the pressure in the adsorption tower in the adsorption zone is controlled at 110-130 kPa, the pressure in the adsorption tower in the displacement zone is controlled at 130-150 kPa, and the pressure in the adsorption tower in the regeneration zone is controlled at 10-20 kPa.

[0009] Preferably, the adsorption zone includes at least one adsorption tower connected in series between the feed gas adsorption tower and the light component discharge adsorption tower, and the regeneration zone includes at least two regeneration adsorption towers to improve regeneration efficiency.

[0010] Preferably, the coolant comprises a mixture of liquid nitrogen and an organic solvent; the organic solvent comprises one or more of isopentane, n-pentane, diethyl ether, ethanol, methanol, acetone, hexane, n-butanol, ethyl acetate, and propylamine.

[0011] A control method for a continuous hydrogen isotope separation process, employing digital control, includes the following steps: S1: According to the target process requirements, edit the valve status of each adsorption tower for each time period in the spreadsheet, with 0 indicating valve closed and 1 indicating valve open; S2: The computer control software reads the valve status data from the spreadsheet, analyzes it, and writes it into the operating database; S3: The control software sends the valve status data from the running database to the PLC controller in real time. The PLC controller controls the corresponding solenoid valve on the simulated moving bed device to switch to the target state. S4: After a predetermined running time, the control software sends out new valve status data, and the PLC controller executes the valve switching operation to complete the zone switching cycle.

[0012] Preferably, when the Xth adsorption tower performs a certain operation, the control logic of its valves V(7X-6) to V(7X) is consistent with the valve control logic when the 1st adsorption tower performs the same operation.

[0013] Preferably, when the adsorption tower is used as a feed gas adsorption tower, the control state of the 7 valves is [0,0,0,1,1,0,0]; when used as a series adsorption tower, the control state is [0,0,0,1,0,0,0]; when used as a light component discharge adsorption tower, the control state is [0,0,1,0,0,0,0]; and when used as a displacement gas feed adsorption tower, the control state is [0,0,0,1,0,1,0].

[0014] Preferably, the adsorption tower is used as a regeneration adsorption tower. When performing purge regeneration, the valve control state is [1,0,0,0,0,0,1] or [0,1,0,0,0,0,1] in sequence; when performing vacuum regeneration, the valve control state is [0,0,0,0,0,0,1] in sequence; when performing vacuum purge regeneration, the valve control state is [1,0,0,0,0,0,1] or [0,1,0,0,0,0,1] in sequence.

[0015] Preferably, the predetermined time for the zone switching is 10-20 minutes, which is dynamically adjusted according to the composition of the raw gas and the processing volume.

[0016] The beneficial effects of this invention are: 1. High separation efficiency: Based on the quantum sieving effect, it utilizes the difference in adsorption forces of the adsorbent for H2 / D2 to achieve highly efficient separation, with a separation factor significantly higher than traditional methods; the multi-tower series design improves adsorbent utilization, and the introduction of heavy component replacement improves product purity. The purity of H2-rich light components can reach 90%, and the purity of D2-rich heavy components can reach 95%.

[0017] 2. Low energy consumption: It adopts a 77K liquid nitrogen cold trap for constant temperature, eliminating the need for an ultra-low temperature refrigeration system, and reducing energy consumption by 30%-50% compared to the cryogenic distillation method.

[0018] 3. High adaptability: The simulated moving bed device can be flexibly adjusted to a 5-9 tower operation mode, adapting to different adsorbent types, feed gas ratios (H2 / D2=10:90 to 90:10) and processing capacity requirements, making it highly versatile.

[0019] 4. Precise and stable control: Digital control logic enables precise regulation of valve status, PLC controller has fast response speed and stable switching cycle, avoiding human operation errors; unified valve control logic simplifies parameter setting and reduces operation difficulty.

[0020] 5. Continuous operation capability: Through periodic zone switching, continuous feeding, continuous discharge, and continuous separation of hydrogen isotopes are achieved, which solves the problem of low efficiency of traditional intermittent separation methods and meets the needs of large-scale industrial production. Attached Figure Description

[0021] Figure 1 A schematic diagram of the adsorption tower connections for a ten-tower simulated moving bed device; Figure 2 A schematic diagram of valve operation for adsorption tower 1 as the feed gas to the adsorption tower; Figure 3 A schematic diagram of valve operation for adsorption tower 1 as a series adsorption tower; Figure 4 A schematic diagram of the valve operation for discharging light components from adsorption tower 1; Figure 5 A schematic diagram of the valve operation for adsorption tower 1 as the feed gas to the adsorption tower; Figure 6 A schematic diagram of the valve operation for purging and regeneration of adsorption tower 1; Figure 7 A schematic diagram of the valve operation for vacuum regeneration of adsorption column 1; Figure 8 A schematic diagram of the valve operation for vacuum purging and regeneration of adsorption column 1; Figure 9 This is a schematic diagram of the operating status of each tower during the first switching in Example 1. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0023] This invention provides a process and control method for continuous separation of hydrogen isotopes. The invention employs a countercurrent continuous operation mode, periodically changing the material inlet and outlet positions of the adsorption tower to simulate the effect of the adsorbent moving downwards while the material moves upwards.

[0024] In this invention, a process for continuous separation of hydrogen isotopes is constructed by dividing the overall adsorption tower into three zones: an adsorption zone, a displacement zone, and a regeneration zone. The adsorption tower and connecting pipelines are immersed in a coolant and kept at a constant temperature of 77K. A scissor lift is used to immerse or remove the adsorption column and corresponding gas pipelines from a cold trap containing liquid nitrogen.

[0025] A mixed feed gas of H2 / D2 is introduced into the adsorption zone. Due to the stronger interaction between D2 and the adsorbent, D2 is preferentially adsorbed, while H2, with its weaker interaction with the adsorbent, preferentially permeates through, and the H2-rich light component gas is discharged from the top of the adsorption tower. The total adsorbent bed height is increased by connecting multiple towers in series, thereby improving adsorbent utilization.

[0026] In the replacement zone, a multi-stage adsorption tower saturated with D2-rich heavy component product gas is used to replace and remove co-adsorbed H2, further increasing the product gas concentration. A small amount of heavy component product gas tail gas discharged from the replacement zone is then returned to the adsorption zone for adsorption and recovery of the heavy components, improving the recovery rate.

[0027] The adsorption tower is completely regenerated in the regeneration zone, and desorption yields a high-purity D2-rich heavy component product gas. Regeneration methods include purging, vacuum, and vacuum purging.

[0028] After a predetermined running time, the valves are switched to simulate the reverse movement of the adsorption tower relative to the airflow direction. One adsorption tower switches from the adsorption zone to the displacement zone, another switches from the displacement zone to the regeneration zone, and yet another switches from the regeneration zone to the adsorption zone.

[0029] The adsorption zone includes a feed gas adsorption tower, several adsorption towers connected in series, and a light component discharge adsorption tower.

[0030] The displacement zone includes a displacement gas feed adsorption tower and several adsorption towers connected in series.

[0031] The regeneration zone contains several regeneration adsorption towers.

[0032] To operate the aforementioned process, a digital control device is used. The required operations are edited on a spreadsheet, and preset operations are read using control software on a computer. A PLC controller operates the solenoid valves on the simulated moving bed device. The specific operation is as follows: Step 1: Based on the specific process requirements, edit the status of the valves on each adsorption tower for each time period in the spreadsheet, using 0 to represent closed and 1 to represent open.

[0033] Step 2: The control software on the computer reads the edited spreadsheet, analyzes the valve status for each time period, and writes it into the operating database.

[0034] Step 3: Run the control software on the computer. The control software will send the valve status data from the database to the connected PLC in real time. The PLC will then control the corresponding solenoid valve to switch to the open or closed state.

[0035] Step 4: After the predetermined time has elapsed, the control software sends the new valve data status to the PLC, and the PLC executes the valve switching operation.

[0036] Taking adsorption tower 1 as an example, its valve, which serves as the feed gas adsorption tower, operates as follows: Figure 2 The valve control table is shown below:

[0037] Taking adsorption tower 1 as an example, its operation as a valve in a series adsorption tower is as follows: Figure 3 The valve control table is shown below:

[0038] Taking adsorption tower 1 as an example, its valve, which discharges light components from the adsorption tower, operates as follows: Figure 4 The valve control table is shown below:

[0039] Taking adsorption tower 1 as an example, its valve, which serves as the feed valve for the displacement gas adsorption tower, operates as follows: Figure 5 The valve control table is shown below:

[0040] Taking adsorption tower 1 as an example, the valves that perform purging and regeneration operate as follows: Figure 6 As shown, the valve control table is as follows; the vacuum pump is not working at this time:

[0041] or

[0042] Taking adsorption tower 1 as an example, the valves that perform vacuum regeneration operate as follows: Figure 7 The valve control table is shown below:

[0043] Taking adsorption column 1 as an example, the valves that perform vacuum purging and regeneration operate as follows: Figure 8 The valve control table is shown below:

[0044] or

[0045] Similarly, when the Xth adsorption tower performs a certain operation, similar to the operation performed by the adsorption tower 1, the control states of its valves V(7X-6) to V(7X) are sequentially the valve control states corresponding to that operation.

[0046] Example 1: As Figure 1 As shown, a ten-tower simulated moving bed apparatus is used, with 13X zeolite as the adsorbent, to perform a 50% H2 and 50% D2 separation operation. The adsorption zone contains five adsorption towers, the displacement zone contains three adsorption towers, and the regeneration zone contains two adsorption towers. The towers in the adsorption zone are connected in series and fed with the adsorption feed gas; the towers in the displacement zone are connected in series and fed with the displacement gas, and are also connected in series with the adsorption zone; the two towers in the regeneration zone are connected in parallel to perform a vacuum purging regeneration operation. The switching time is 15 minutes. The process operation mode is as follows: Step 1: Edit the spreadsheet according to the required process. The valve control table for each time period is shown below:

[0047]

[0048]

[0049]

[0050]

[0051] The functions performed by the adsorption tower at each time period are shown below:

[0052] Step 2: The control software on the computer reads the edited spreadsheet, analyzes the valve status for each time period, and writes it into the operating database.

[0053] Step 3: Run the control software on the computer. The control software will send the valve status data from the database to the connected PLC in real time. The PLC will then control the corresponding solenoid valves to switch between open and closed states. The first switch of the operating status of each tower is as follows: Figure 9 As shown, the adsorption zone includes towers 6-10, the displacement zone includes towers 3-5, and the regeneration zone includes towers 1-2.

[0054] Step 4: Every 15 minutes, the control software sends the new valve data status to the PLC, and the PLC executes the valve switching operation. The valves are switched regularly to simulate the countercurrent flow of the adsorbent and gas.

[0055] Taking the first switch to the second as an example, tower 1 moves from the regeneration zone to the last tower in the adsorption zone, tower 3 moves from the displacement zone to the second tower in the regeneration zone, tower 6 moves from the adsorption zone to the last tower in the displacement zone, and the remaining towers move in the same direction.

[0056] The specific experimental parameters and operating results are as follows: The adsorption tower is made of stainless steel, with a single column length of 10cm and a diameter of 1cm. The adsorbent used is 13X zeolite, and the adsorption temperature is 77K. The switching time is 15 min. The ratio of H2 to D2 in the feed gas is 1:1. The pressure inside the adsorption tower in the adsorption zone is approximately 120 kPa, the pressure in the displacement zone is approximately 140 kPa, and the pressure in the regeneration zone is approximately 15 kPa. The purity of H2 in the obtained light component product gas reaches 90%, and the purity of D2 in the heavy component product gas reaches 95%.

Claims

1. A process for continuous separation of hydrogen isotopes, characterized in that: The process, which employs a simulated moving bed device in a countercurrent continuous operation mode, includes the following steps: Step 1: Divide the adsorption tower of the simulated moving bed device into three independent functional zones: adsorption zone, displacement zone, and regeneration zone. The adsorption tower and connecting pipelines are immersed in a coolant at a constant temperature, which is controlled at 77-160K. Step 2: Introduce H2 / D2 mixed feed gas into the adsorption zone. D2 is preferentially adsorbed due to its stronger interaction with the adsorbent, while H2 preferentially penetrates and is discharged from the top of the adsorption tower as a light component gas rich in H2. The adsorption zone improves the utilization rate of the adsorbent by connecting multiple towers in series. Step 3: Introduce D2-rich heavy component product gas into the replacement zone to perform multi-stage replacement on the adsorption tower that is saturated with adsorption, and discharge the co-adsorbed H2 to increase the concentration of product gas. A small amount of tail gas discharged from the replacement zone is discharged into the adsorption zone to recover heavy components. Step 4: Regenerate the adsorption tower after complete displacement to obtain a high-purity D2-rich heavy component product gas by desorption. Regeneration methods include purging, vacuum, or vacuum purging. Step 5: After running for a predetermined time, switch valves to achieve zone switching: one adsorption tower switches from the adsorption zone to the displacement zone, one adsorption tower switches from the displacement zone to the regeneration zone, one adsorption tower switches from the regeneration zone to the adsorption zone, and the remaining towers move in the same direction to simulate the counter-current movement of the adsorbent and the airflow.

2. The process for continuous separation of hydrogen isotopes according to claim 1, characterized in that: The adsorption zone includes a feed gas adsorption tower and a light component discharge adsorption tower; the displacement zone includes a displacement gas feed adsorption tower and at least one adsorption tower in series; the regeneration zone includes at least one regeneration adsorption tower.

3. The process for continuous separation of hydrogen isotopes according to claim 1, characterized in that: The simulated moving bed device has a 5-10 tower structure, or can be adjusted to a 5-9 tower operating state according to the working conditions.

4. The process for continuous separation of hydrogen isotopes according to claim 1, characterized in that: The pressure in the adsorption tower in the adsorption zone is controlled at 110-130 kPa, the pressure in the adsorption tower in the displacement zone is controlled at 130-150 kPa, and the pressure in the adsorption tower in the regeneration zone is controlled at 10-20 kPa.

5. The process for continuous separation of hydrogen isotopes according to claim 2, characterized in that: The adsorption zone includes at least one adsorption tower connected in series between the feed gas adsorption tower and the light component discharge adsorption tower; the regeneration zone includes at least two regeneration adsorption towers.

6. A control method for implementing the process for continuous separation of hydrogen isotopes as described in any one of claims 1 to 5, characterized in that: The digital control method includes the following steps: S1: According to the target process requirements, edit the valve status of each adsorption tower for each time period in the spreadsheet, with 0 indicating valve closed and 1 indicating valve open; S2: The computer control software reads the valve status data from the spreadsheet, analyzes it, and writes it into the operating database; S3: The control software sends the valve status data from the running database to the PLC controller in real time. The PLC controller controls the corresponding solenoid valve on the simulated moving bed device to switch to the target state. S4: After a predetermined running time, the control software sends out new valve status data, and the PLC controller executes the valve switching operation to complete the zone switching cycle.

7. The control method according to claim 6, characterized in that: When the Xth adsorption tower performs a certain operation, the control states of its valves V(7X-6) to V(7X) are sequentially the valve control states corresponding to that operation.

8. The control method according to claim 6, characterized in that: When the adsorption tower is used as a feed gas adsorption tower, the control states of the 7 valves are [0,0,0,1,1,0,0] in sequence; when used as a series adsorption tower, the control states are [0,0,0,1,0,0,0] in sequence; when used as a light component discharge adsorption tower, the control states are [0,0,1,0,0,0,0] in sequence; and when used as a displacement gas feed adsorption tower, the control states are [0,0,0,1,0,1,0].

9. The control method according to claim 6, characterized in that: The adsorption tower serves as a regeneration adsorption tower. When performing purge regeneration, the valve control states are sequentially [1,0,0,0,0,0,1] or [0,1,0,0,0,0,1]; when performing vacuum regeneration, the valve control states are sequentially [0,0,0,0,0,0,1]; and when performing vacuum purge regeneration, the valve control states are sequentially [1,0,0,0,0,0,1] or [0,1,0,0,0,0,1].

10. The control method according to claim 6, characterized in that: The predetermined time for switching between zones is 10-20 minutes, which is dynamically adjusted according to the composition of the raw gas and the required processing volume.

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