Process and control method for continuous separation of hydrogen isotopes

Abstract

The invention discloses a process and a control method for continuous separation of hydrogen isotopes, and belongs to the technical field of hydrogen isotope separation. According to the process, a countercurrent continuous operation mode is adopted, an adsorption tower is divided into an adsorption area, a replacement area and a regeneration area, and reverse movement of an adsorbent and a material is simulated by periodically switching the material inlet and outlet positions of the adsorption tower; the adsorption towers and connecting pipelines are soaked in a constant-temperature coolant, and separation is realized by virtue of acting force difference of an adsorbent on hydrogen isotopes; according to the control method, digital control logic is adopted, the valve state is edited through a spreadsheet, software is controlled to analyze data, a PLC executes valve switching, and accurate regulation and control of the multi-tower operation state under different working conditions are achieved. The method provided by the invention solves the problems of high equipment investment and large energy consumption of a traditional separation method, has the advantages of high separation factor, high recovery rate and stable continuous operation, and is suitable for hydrogen isotope separation requirements of different feed gas proportions and different treatment capacities.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrogen isotope separation, and particularly relates to a process and control method for continuous separation of hydrogen isotopes. BACKGROUND

[0002] Hydrogen isotopes mainly include protium (H2), deuterium (D2) and tritium (T2), and have irreplaceable important values in the fields of nuclear energy, scientific research, medical diagnosis and cutting-edge industry. However, due to the same electron arrangement outside the isotope nucleus, the physical and chemical properties are extremely similar, which leads to difficult separation. Traditional hydrogen isotope separation methods, such as low-temperature rectification, thermal diffusion and chemical exchange, usually have problems such as high equipment investment, huge energy consumption and limited separation factor, which restricts their large-scale application. In recent years, adsorption separation technology based on quantum screening effect has shown great potential. This technology uses the difference in de Broglie wavelength of light mass isotopes (such as H2) and heavy mass isotopes (such as D2) at very low temperatures, as well as the difference in their interaction force with nanoporous materials, to achieve efficient screening, with the advantages of high separation factor and relatively low energy consumption.

[0003] Gas phase simulated moving bed device can realize high-purity and high-recovery continuous separation of hydrogen isotopes. However, for different adsorbents, different raw gas ratios, different gas processing requirements and other working conditions, for example, a ten-tower simulated moving bed device needs to be adjusted to 9-tower, 8-tower, 7-tower, 6-tower and other operating states and configured with different operating parameters according to specific working conditions. Moreover, the simulated moving bed has a large number of valves, and the operation modes of various operating states are different, which puts high requirements on the control method. SUMMARY

[0004] In order to realize the continuous separation of hydrogen isotopes by simulated moving bed under different working conditions of hydrogen isotope separation, the application provides a process and control method for continuous separation of hydrogen isotopes. In the application, the countercurrent continuous operation mode is adopted, and the effect of the adsorbent moving downward and the material moving upward is simulated by periodically changing the material inlet and outlet positions of the adsorption tower.

[0005] The technical scheme adopted by the application to achieve the above purpose is: a process for continuous separation of hydrogen isotopes, which is operated in a countercurrent continuous operation mode by using a simulated moving bed device, and the process comprises the following steps: Step 1: divide the adsorption tower of the simulated moving bed device into three independent functional zones, namely the adsorption zone, the displacement zone and the regeneration zone, and immerse the adsorption tower and the connecting pipeline in a coolant with constant temperature, and control the constant temperature of the coolant at 77-160K; Step 2: H2 / D2 mixed feed gas is introduced into the adsorption zone, D2 is preferentially adsorbed due to stronger adsorption force, H2 preferentially penetrates and is discharged from the top of the adsorption column as H2-rich light component gas, and the adsorption zone is improved by multi-column series to improve the utilization rate of the adsorbent; Step 3: Introduce D2-rich heavy component product gas into the displacement zone, and perform multi-stage displacement on the adsorption-saturated adsorption column to discharge the co-adsorbed H2 to increase the concentration of the product gas, and the small amount of tail gas discharged from the displacement zone is discharged into the adsorption zone to recover the heavy component; Step 4: Regenerate the adsorption column after displacement to desorb a high-purity D2-rich heavy component product gas, and the regeneration methods include purging, vacuum or vacuum purging; Step 5: After running for a certain time, switch the valves to realize zone switching: one adsorption column is switched from the adsorption zone to the displacement zone, one adsorption column is switched from the displacement zone to the regeneration zone, and one adsorption column is switched from the regeneration zone to the adsorption zone, and the remaining columns are moved in the same direction, simulating the reverse movement of the adsorbent and the gas flow.

[0006] Preferably, the adsorption zone comprises a feed gas feeding adsorption column and a light component discharging adsorption column; the displacement zone comprises a displacement gas feeding adsorption column and at least one series adsorption column; and the regeneration zone comprises at least one regeneration adsorption column.

[0007] Preferably, the simulated moving bed device is a 5-10 tower structure, or is adjusted to a 5-9 tower operating state according to the working condition requirements.

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

[0009] Preferably, at least one series adsorption column is arranged between the feed gas feeding adsorption column and the light component discharging adsorption column in the adsorption zone, and the regeneration zone comprises at least two regeneration adsorption columns to improve the regeneration efficiency.

[0010] Preferably, the coolant comprises a mixture of liquid nitrogen and an organic solvent; and 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 hydrogen isotope continuous separation process, which adopts a digital control mode and comprises the following steps: S1: According to the target process requirements, the valve state of each adsorption column in each time period is edited in an electronic table, with 0 indicating that the valve is closed and 1 indicating that the valve is opened; S2: The computer control software reads the valve state data in the electronic table and writes into the operation database after analysis; S3: The control software sends the valve state data in the running database to the PLC controller in real time, and the PLC controller controls the corresponding electromagnetic valve on the simulated moving bed device to switch to the target state; S4: After running for a certain time, the control software sends new valve state data, and the PLC controller performs valve switching operation to complete the partition switching cycle.

[0012] Preferably, when the Xth adsorption tower performs a certain operation, the control logic of its corresponding 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 raw material gas feeding adsorption tower, the control state of the 7 valves is [0, 0, 0, 1, 1, 0, 0]; when it is used as a series adsorption tower, the control state is [0, 0, 0, 1, 0, 0, 0] in turn; when it is used as a light component discharge adsorption tower, the control state is [0, 0, 1, 0, 0, 0, 0] in turn; when it is used as a displacement gas feeding adsorption tower, the control state is [0, 0, 0, 1, 0, 1, 0] in turn.

[0014] Preferably, when 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 turn; when performing vacuum regeneration, the valve control state is [0, 0, 0, 0, 0, 0, 1] in turn; 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 turn.

[0015] Preferably, the predetermined time of the partition switching is 10-20 min, which is dynamically adjusted according to the components of the raw material gas and the processing capacity.

[0016] The beneficial effects of the present application are: 1. High separation efficiency: based on quantum sieve effect, the difference in adsorption force of the adsorbent for H2 / D2 is used to realize high-efficiency separation, and the separation factor is significantly higher than that of traditional methods; the multi-tower series design improves the utilization rate of the adsorbent, and the introduction of heavy component displacement improves the product purity. The purity of the H2-rich light component can reach 90%, and the purity of the D2-rich heavy component can reach 95%.

[0017] 2. Low energy consumption: using a 77K liquid nitrogen cold trap constant temperature, no need for ultra-low temperature refrigeration system, compared with low-temperature rectification method, energy consumption is reduced by 30%-50%.

[0018] 3. Strong adaptability: the simulated moving bed device can be flexibly adjusted to operate in 5-9 tower states, suitable for different adsorbent types, raw material gas ratios (H2 / D2=10:90 to 90:10) and processing capacity requirements, and has strong versatility.

[0019] 4. Control precision stability: Digital control logic realizes precise regulation of valve state, PLC controller has fast response speed, stable switching cycle, avoids manual operation error; unified valve control logic simplifies parameter setting and reduces operation difficulty.

[0020] 5. Continuous operation ability: Through periodic partition switching, continuous feeding, continuous discharge and continuous separation of hydrogen isotopes are realized, solving the problem of low efficiency of traditional batch separation method and meeting the needs of industrial large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Figure 1 is a schematic diagram of the connection of the adsorption tower of the ten-tower simulated moving bed device; Figure 2 Figure 2 is a schematic diagram of the valve operation of adsorption tower 1 as a raw gas feeding adsorption tower; Figure 3 Figure 3 is a schematic diagram of the valve operation of adsorption tower 1 as a series adsorption tower; Figure 4 Figure 4 is a schematic diagram of the valve operation of adsorption tower 1 as a light component discharge adsorption tower; Figure 5 Figure 5 is a schematic diagram of the valve operation of adsorption tower 1 as a displacement gas feeding adsorption tower; Figure 6 Figure 6 is a schematic diagram of the valve operation of adsorption tower 1 for performing purge regeneration; Figure 7 Figure 7 is a schematic diagram of the valve operation of adsorption tower 1 for performing vacuum regeneration; Figure 8 Figure 8 is a schematic diagram of the valve operation of adsorption tower 1 for performing vacuum purge regeneration; Figure 9 Figure 9 is a schematic diagram of the operation state of each tower in the first switching in Example 1. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0023] The present application provides a process and control method for continuous separation of hydrogen isotopes. The present application uses countercurrent continuous operation mode, and changes the material inlet and outlet position of the adsorption tower periodically, thereby simulating the effect of downward movement of the adsorbent and upward movement of the material.

[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] Third step: run the control software on the computer, the control software will run the valve state data in the database real-time to the connected PLC. PLC control corresponding electromagnetic valve switch to open or closed state.

[0035] Fourth step: run the specified time, the control software will issue the new valve data state to the PLC, PLC execute valve switching operation.

[0036] Take adsorption tower 1 as an example, as raw material gas feeding adsorption tower valve operation as shown in Figure 2 , the valve control table as follows:

[0037] Take adsorption tower 1 as an example, as series adsorption tower valve operation as shown in Figure 3 , the valve control table as follows:

[0038] Take adsorption tower 1 as an example, as light component discharge adsorption tower valve operation as shown in Figure 4 , the valve control table as follows:

[0039] Take adsorption tower 1 as an example, as displacement gas feeding adsorption tower valve operation as shown in Figure 5 , the valve control table as follows:

[0040] Take adsorption tower 1 as an example, as purge regeneration valve operation as shown in Figure 6 , the valve control table as follows, the vacuum pump does not work:

[0041] Or

[0042] Take adsorption tower 1 as an example, as vacuum regeneration valve operation as shown in Figure 7 , the valve control table as follows:

[0043] Take adsorption tower 1 as an example, as vacuum purge regeneration valve operation as shown in Figure 8 , the valve control table as follows:

[0044] Or

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

[0046] Example 1: As shown in the following table, a ten-column simulated moving bed device was used to perform a 50% H2 and 50% D2 separation operation using 13X zeolite material as the adsorbent. The adsorption zone included five adsorption columns, the displacement zone included three adsorption columns, and the regeneration zone included two adsorption columns. The columns in the adsorption zone were connected in series and were fed with the adsorption feed gas; the columns in the displacement zone were connected in series and were fed with the displacement gas, and were connected in series with the adsorption zone; the two columns in the regeneration zone were connected in parallel and performed a vacuum purge regeneration operation. The switching time was 15 minutes. The process was run as follows: Figure 1 First step: An electronic table was edited according to the required process, and the valve control table for each time period is shown in the following table:

[0047]

[0048]

[0049]

[0050]

[0051] The functions performed by the adsorption columns in each time period are shown in the following table:

[0052] Second step: The control software on the computer read the edited electronic table and analyzed the valve state for each time period, and wrote the data into the running database.

[0053] Third step: The control software on the computer was run, and the control software transmitted the valve state data in the running database to the connected PLC in real time. The PLC controlled the corresponding electromagnetic valve to switch to the open or closed state. The first switching of the running state of each column is shown in the following table, in which the adsorption zone includes columns 6-10, the displacement zone includes columns 3-5, and the regeneration zone includes columns 1-2. Figure 9

[0054] Fourth step: Every 15 minutes, the control software transmitted the new valve data state to the PLC, and the PLC performed the valve switching operation. The valves were regularly switched to simulate the reverse flow of the adsorbent and the gas.

[0055] ​​Take the first switching as the second time for example, tower 1 moves from the regeneration zone to the adsorption zone last tower, tower 3 moves from the displacement zone to the regeneration zone second tower, tower 6 moves from the adsorption zone to the displacement zone last tower, the rest of the towers are moved in the same direction.

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