JP2511047B2 - Mixed gas separation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method for separating a mixed gas, more specifically, a mixed gas supplied by a pressure swing adsorption method using an adsorption device filled with activated carbon, molecular sieve activated carbon, zeolite or the like. The present invention relates to a method of operating a pressure swing adsorption device for separating an impurity component therein to obtain a target component gas having high purity. As the mixed gas to be supplied, hydrogen was the main component and CO ₂ , CH ₄ ,
It has a wide range of uses such as purification of hydrogen from gas containing CO, etc., separation of oxygen or nitrogen from air.

[Conventional technology]

Separation and purification of the target component gas from the mixed gas by the pressure swing adsorption method is currently widely used industrially in various fields because it is possible to obtain a target component gas of high purity and is excellent in economic efficiency. There is. This method is usually equipped with a plurality of adsorption columns each having several automatic switching valves at the inlet end and the discharge end, and these automatic switching valves are opened and closed by a sequencer,
While each adsorption tower repeats each step of adsorption, decompression, washing, and pressurization, by appropriately performing a combination of these respective steps of each tower, the target component gas is continuously obtained from the raw material gas in which impurities are mixed. It is to be separated and purified. Since these automatic switching valves are required to be opened and closed once every several minutes and to be completely shut off, highly reliable valves are used, but it cannot be said that malfunctions occur.

When the automatic switching valve malfunctions, conventionally, the operation of all towers is temporarily stopped, the tower having the automatic switching valve that has malfunctioned is cut off, and then the remaining towers are prepared for operation. The method of starting operation in the remaining tower was adopted.

In this method, after a malfunction occurs in the automatic switching valve,
It took a long time to start operation in the remaining towers and obtain a desired high purity target component gas, and an extremely large storage tank was required to compensate the required amount of the target component gas during this period. In addition, after the automatic switching valve is repaired or replaced, the operation of the remaining towers is temporarily stopped, all towers including the adsorption tower are prepared for operation, and the operation is returned to all towers. Was.

Therefore, despite the fact that the high-purity gas purification equipment by the pressure swing adsorption method is originally automated and requires almost no manpower during operation, in the case of these failures, the adsorption tower is disconnected, It took a lot of manpower to start up.

[Problems to be solved by the invention]

An object of the present invention is to automatically separate the adsorption tower in the event of a failure such as a malfunction of the automatic switching valve, and to provide a high-purity target component gas without stopping the operation in the remaining tower. (EN) A method of purifying / separating, and a method of repairing or replacing an automatic switching valve that has malfunctioned and then returning to operation by all columns including the adsorption column without stopping operation.

[Means for Solving Problems] That is, according to the present invention, four or more adsorption columns for selectively adsorbing impurities under high pressure and desorbing impurities under low pressure are provided to continuously supply the target component gas. During operation of the device for separation and purification, during normal operation, each column repeats four steps of adsorption process, decompression process, washing process, and pressurization process in sequence, and when one column is in the adsorption process, at least the other column is decompressed. Process, washing step and pressurizing step, and the depressurizing step and the pressurizing step are performed stepwise, and at least one step of the depressurizing step of one tower and at least one step of the pressurizing step of the other tower are simultaneously performed. When any one of the above towers fails, the tower is stopped, and the other towers are insufficiently washed / desorbed according to each step / stage at the time of failure, and the tower is washed with the target component gas and adsorbed. Towers that have not reached pressure In the method for separating a mixed gas, which is characterized in that the steps in the above-mentioned steady operation are reduced, the process order of one tower and the process relationship with the other tower are changed to an operation that does not change from the steady operation. is there.

 This method will be described in detail for the case of the steady operation of four towers.

Table 1 shows an example of steady operation of the four towers (hereinafter referred to as example A) in the present invention.

That is, each of the adsorption towers X, Y, Z, U has three adsorption steps (A
₁ , A ₂ , A ₃ ), decompression 4 steps (D ₁ , D ₂ , D ₃ , D ₄ ), washing 2 steps (P ₁ , P ₂ ), boost 3 steps (R ₁ , R ₂ , R ₃ ). Of 4
The 12 steps are sequentially repeated as one cycle, and the combination of steps between the adsorption towers is (A ₁ , R ₁ , D ₄ , D
₁ ), (A ₂ , R ₂ , P ₁ , D ₂ ) and (A ₃ , R ₃ , P ₂ , D ₃ ). These steps are performed by opening and closing several automatic switching valves provided at the inlet end and the discharge end of the adsorption tower,
The automatic opening / closing valve is opened / closed by a timer, a pressure switch, or a combination of both.

The switching time of each process is determined by the yield, purity and production amount of the target component gas, and each automatic switching valve is opened / closed based on this process time. And the operation of all these automatic switching valves (opening and closing order, switching time if necessary, etc.) is set by the program sequencer, but it is necessary to disconnect one of the adsorption towers due to failure of the switching valve or other reasons. A program that can handle the occurrence of such a problem is incorporated in advance.

The open / close status of the automatic switching valve is constantly monitored by the program sequencer for answerback from the limit switch, so that the valve operates for a certain period of time after the signal is output, despite the signal being opened or closed from the program sequencer. If not performed, or if the program sequencer does not output the open / close signal, but has operated, it is possible to detect these as malfunctions. It is also possible to use detection of abnormal pressure behavior in the adsorption tower as well.

However, even if a malfunction of the automatic switching valve can be detected by such monitoring with a limit switch, it takes a lot of manpower and a long time to prepare for the operation of the three towers after the stop and to start the operation of the three towers. I needed it.

According to the present invention, in the unlikely event that the automatic switching valve malfunctions, it automatically switches to the operation of the three towers, and if the malfunctioning switching valve is repaired and normal operation can be confirmed, the operation of the four towers will start immediately It is possible to return to.

In the following, even if a failure occurs in any step, the transition from 4 towers to 3 towers operation and 4 towers from 3 towers operation to 4
A method of returning to the tower operation will be specifically described. First, the operation of the three towers to be transferred is shown in Table 2.

That is, each of the adsorption towers T ₁ , T ₂ , T ₃ has 3 steps of adsorption (A ₁ , A ₂ , A ₃ ), 2 steps of decompression (D ′ ₁ , D ′ ₂ ), 1 step of washing (P), 3 steps of pressure increase. (R ₁ , R ₂ , R ₃ ) 4 steps 9 steps are sequentially repeated as one cycle,
The combination of steps between adsorption towers is (A ₁ , R ₁ ,
_{D '1), (A 2} , R 2, D' consists of _{2), (A 3, R} 3, P).

The present invention discloses a method for smoothly transitioning from any one of the four combinations of the four-column operation to any of the three combinations of the three-column operation, and a method for returning to the four-column operation. However, it is too complicated to explain all the steps of all the towers, and all combinations of these can be represented by one cycle of one tower. The operation transition of the three towers at the time of the failure of the U tower will be described by replacing the towers T ₁ , T ₂ and T ₃ in Table ₂ with the towers X, Y and Z, respectively.

1) Step 1 Step 1 is (A ₁ , R ₁ , D ₄ , D ₁ ) from Table ₁ , and this is transferred to (A ₂ , D' ₂ , R ₂ ). That is, after the transition, the process goes to Step II in Table 2 and the process (adsorption, decompression,
Since the pressure increase) is the same, it is possible to immediately shift to three-column operation. This corresponds to the above, and if it is written, it becomes Table 3.

2) Step 2 (corresponding to the above) immediately goes to III (4th
Table), 3) Step 3 (corresponding to the above) was washed with Z and then moved to IV (Table 5), 4) Step 4 (corresponding to the above) was immediately transferred to V (6th).
5) Step 5 (corresponding to the above) immediately goes to VI (7th table)
Table), 6) Step 6 (corresponding to the above) after washing X to VII (Table 8), 7) Step 7 (corresponding to above) after washing X to VIII (Table 9), 8) Step 8 (corresponding to the above) washes X and after pressurization IV
(Table 10), 9) Step 9 (corresponding to the above) is stepped up X, Y is washed and then to I (Table 11), 10) Steps 10, 11, 12 (corresponding to 4) are X Boost,
After cleaning Y, transfer to II (Tables 12 to 14), respectively.

As described above, by reliably performing washing and pressurization, which are important steps for the regeneration of the adsorbent and the adsorption of impurities, by the same operations as in the normal operation, the target gas of high purity is obtained immediately after the operation of the three columns. Can be obtained. Moreover, these operations can be automatically performed by the program sequencer.

In summary, when a failure occurs in one of the four towers during operation, the tower is automatically stopped and, if necessary, the tower with insufficient cleaning / desorption is cleaned with the product gas from the target component gas storage tank. However, by raising the pressure of the column that has not reached the adsorption pressure and shifting to the three-column operation, it is possible to perform the operation without stopping the production of the target component gas or with the stop being minimized.

Next, after the failed tower is repaired, wait for the combination of the three towers to become the step of (A ₁ , D ′ ₁ , R ₁ ), and the repaired tower will be depressurized and then washed as necessary. Like (A ₂ , D ₂ ,
By returning to the combination step of P ₁ and R ₂ ), the target component gas can be smoothly separated and purified. If this is applied to each tower and displayed, it looks like Tables 15-18.

Another example of the steady operation of the four towers in the present invention is adsorption 3 steps (A ″ ₁ , A ″ ₂ , A ″ ₃ ), decompression 3 steps (D ″ ₁ , D ″ ₂ , D ″ ₃ ), washing 3 steps (P " ₀ , P"
₁ , P " ₂ ) and 3 steps of boosting pressure (R" ₁ , R " ₂ , R" ₃ ), and 12 steps of 4 steps are sequentially repeated and (A " ₁ , D" ₁ , P " ₀ , R " ₁ ), (A" ₂ , D " ₂ ,
P ″ ₁ , R ″ ₂ ) and (A ″ ₃ , D ″ ₃ , P ″ ₂ , R ″ ₃ ) are operated in combination, and if a failure occurs in any one of the above steps, the failure is detected. At the step that occurred, one of the towers in operation was stopped, and each of the remaining three towers was adsorbed in 3 steps (A ″ ₁ , A ″ ₂ , A ″ ₃ ) and depressurized in 2 steps (D).
₁ , D ₂ ), washing 1 step (P ′), pressurization 3 steps (R ″ ₁ , R ″ ₂ , R ″ ₃ ) 4 steps 9 steps are sequentially repeated and (A ″ ₁ , D between 3 towers). ₁ , R ″ ₁ ),
It operates so that it may become a combination of (A " ₂ , D ₂ , R" ₂ ) and (A " ₃ , P ', R" ₃ ).

More specifically, the final decompression step of the example A
Since D ₄ is replaced with the first cleaning step P ″ ₀ , the failure is D ″ ₁ during the combined operation of 1. (A ″ ₁ , D ″ ₁ , P ″ ₀ , R ″ ₁ ). Or immediately when it occurs in P ″ ₀ , and when it occurs in R ″ ₁ , after washing the P ″ ₀ operating tower (A ″ ₂ , D ″ ₂ , R ″ ₂ ) (however, in case of D ″ ₁ , R ″ _Two
"Moves to the combination of ₀ remains), 2. _(A" P is _2, D _{"2, P" 1,} R _"2 when a combination operation), failure _D" if they occur _two or P _"1 Immediately, if it occurs in R ″ ₂ , the P ″ ₁ operating tower moves to a combination of washing and pressurization (A ″ ₃ , P ′, R ″ ₃ ) and 3. (A ″ ₃ , D ″ ₃ , P " ₂ , R" ₃ ) In combination operation, if failure occurs at D " ₃ , after washing P" ₂ operating tower, if it occurs at P " ₂ , after washing D" ₃ operating tower R " _In case of occurrence in ₃ , P ″ ₂ operation tower pressure rise, D ″
_{3) After} operating the tower after washing (A ″ ₁ , D ″ ₁ , R ″ ₁ ) combination, 4. If it fails during A ″ ₁ , A ″ ₂ or A ″ ₃ operation,
After the R ″ ₁ , R ″ ₂ and R ″ ₃ operation towers are respectively pressurized or maintained and the P ″ ₀ , P ″ ₁ , P ″ ₂ operation towers are respectively washed or continuously washed (A ″ ₂ , D ₂ , R ″ ₂ )
To move to the combination of.

Next, after the failed tower has been repaired, wait for the combination of the three towers to reach step (A ″ ₁ , D ₁ , R ″ ₁ ),
By returning to the combination step of (A ″ ₂ , D ″ ₂ , P ″ ₁ , R ″ ₂ ) that requires a repaired tower and becomes a washing process after depressurization, it is possible to smoothly separate the target component gas. Purification takes place.

Hereinafter, the separation and purification of hydrogen from the coke oven gas will be described as an example, but the present invention can also be applied to other mixed gas systems and is not limited to this example.

〔Example〕

The method of the present invention was carried out using a four-bed type (Example A above) hydrogen purification apparatus using a coke oven gas as a raw material and a carbon molecular sieve and a zeolite molecular sieve as adsorbents.

 The driving specifications are as follows.

Adsorption pressure 9.9Kgf / cm ² G Desorption pressure 0.2Kgf / cm ² G 4 Pressure of each process during tower operation and time per cycle, etc. 1. Adsorption process (A ₁ + A ₂ + A ₃ ) 9.9Kgf / cm ² G 3 minutes 45 seconds 2. Decompression process (D ₁ ) 30 seconds to 4.9 Kgf / cm ² G 3. Decompression process (D ₂ ) 3.0 Kgf / cm ² G 2 minutes 15 seconds 4. Decompression process (D ₃ + D ₄ ) 90 seconds to 0.2 Kgf / cm ² G 5. Washing process (P ₁ + P ₂ ) 3 min 15 sec at 0.2 Kgf / cm ² G 6. Pressurizing process (R ₁ ) 4.9 Kgf / cm ² G 30 sec 7 .Pressure process (R ₂ + R ₃ ) 9.9Kgf / cm ² G up to 3 minutes 15 seconds Total 15 minutes. Product hydrogen composition H ₂ ＝ 99.9997% O ₂ ＋ Ar ＝ 1.0ppm N ₂ ＝ 2.0ppm Production 700Nm ³ / h Pressure of each process during 3 tower operation, time in 1 cycle, etc. 1. Adsorption process (A ₁ + A ₂ + A ₃ ) 9.9Kgf / cm ² G for 5 minutes 2. Decompression process (D ′ ₁ ) 4.9Kgf / cm ² G for 30 seconds 3. Decompression process (D ′ ₂ ) 0.2Kgf / cm ² G for 2 minutes 15 Second 4. Washing process (P) 0.2Kgf / cm ² G for 2 minutes 15 seconds 5. Pressurizing process (R ₁ ) 0.49Kgf / cm ² G up to 30 seconds 6. Pressurizing process (R ₂ + R ₃ ) 9.9Kgf / cm ² G 4 minutes 30 seconds Total 15 minutes. Example 1 During the operation of four towers, the U tower was stopped according to this method when the automatic switching valve of the U tower failed in step 4 of the above-mentioned Table 1 and automatically moved to the operation of three towers starting from step V (the above-mentioned Table 6). reference). Three
The product flow rate after the tower operation was changed to 520 Nm ³ / h and the product hydrogen composition after 5 minutes was H ₂ = 99.9997% O ₂ + Ar = 1.0ppm N ₂ = 2.0ppm, which was no difference from the 4 tower steady operation, No abnormalities were observed.

On the other hand, in the conventional method in which all equipment is stopped, the adsorption tower U is shut off, and the operation of three towers is selected and then operation is started, it takes 10 to 15 minutes until the start of hydrogen generation, during which hydrogen production is started. Stopped completely.

Example 2 During the operation of four towers, the automatic switching valve of the adsorption tower U failed in step 3 and the apparatus was temporarily stopped according to this method, hydrogen was automatically received from the hydrogen holder, and the adsorption tower Z was washed for 3 minutes, and then step Operation of three towers was started from IV (see Table 5 above).
The stop time during this period was about 3 minutes. Start operation of 3 towers 5
There was no change in the hydrogen composition of the product after the minute. The subsequent driving was also good.

Example 3 During the operation of four towers, the automatic switching valve of the adsorption tower U failed in step 8 and the apparatus was temporarily stopped according to this method, hydrogen was automatically received from the hydrogen holder, and the adsorption tower X was washed for 3 minutes and for 2 minutes. After raising the pressure, operation of the three towers was started from Step IX (the above-mentioned No. 1).
(See table 10). The stop time during this period was about 5 minutes. Three
No change was observed in the product hydrogen composition 5 minutes after the start of the tower operation. The subsequent driving was also good.

On the other hand, in the conventional method, after shutting down all equipment and cutting off the adsorption tower U, a line for cleaning the adsorption tower X is set.

After washing the adsorption tower X, a line for raising the pressure of the adsorption tower X is set, the pressure of the adsorption tower X is raised, and then the step of operating three towers is selected to start the operation of three towers. During this period, it takes 25 to 30 minutes, during which hydrogen generation stops.

Example 4 In Examples 1 to 3 above, after depressurizing the adsorption tower U which had been repaired after the failure during the operation of the three towers and shut off, the four tower operation return switch was turned on. To 4
Moving to step 5 of the tower operation, the four tower operation was started from the step of washing the adsorption tower U. In each example, no abnormality was found in the product hydrogen composition after the start of the operation of the four towers.

〔The invention's effect〕

As described in detail above, according to the method of the present invention, even in the case of one tower failure during multi-column operation in the pressure swing adsorption equipment, the operation smoothly shifts to the remaining towers, and almost continuously. The separation and purification of the target component gas can be continued, and it is easy to return to multi-column operation after repairing the failure. The operation of switching the operation can be automatically performed without human labor,
This is an extremely advantageous method for operation. It goes without saying that this method can be used not only for application at the time of failure but also for maintenance and inspection.

Claims (6)

(57) [Claims] 1. To selectively adsorb and separate one or more gas components from a feed mixed gas by providing four or more adsorption columns that selectively adsorb impurities under high pressure and desorb impurities under low pressure. In the operation of the pressure swing adsorption method, the four columns of adsorption process, decompression process, washing process, and pressurization process are sequentially repeated in each column during steady state, and when one column is in the adsorption process, the other columns are repeated. Is at least in the depressurizing step, the washing step and the pressurizing step, and the depressurizing step and the pressurizing step are performed stepwise, and at least one step of the depressurizing step of one tower and at least one step of the pressurizing step of the other tower are performed. At the same time, if any one of the above towers fails, stop that tower,
Depending on each process and step at the time of failure, the other column is not sufficiently washed and desorbed, and the column is washed with the target component gas, and the column that does not reach the adsorption pressure is boosted, and the steps within the above-mentioned steady operation process The method for separating a mixed gas is characterized in that the process sequence of one tower and the process relationship with the other column are changed to the same operation as in the steady operation. 2. In an apparatus provided with four adsorption towers, each tower is adsorbed in three steps (A ₁ , A ₂ , A ₃ ) and decompressed in 4 steps (D ₁ , D ₂ , D ₃ , D ₄ ), washing 2 steps (P ₁ ,
P ₂ ), boosting 3 steps (R ₁ , R ₂ , R ₃ ) 4 steps 12 steps are repeated in sequence, and (A ₁ , D ₁ , D ₄ ,
R _1), caused a failure in _{(A 2, D 2, P} 1, R 2), operated so that a combination of _{(A 3, D 3, P} 2, R 3), the one of step In case of failure, one of the towers in operation is stopped at the step where the failure occurs, and the remaining three towers each have adsorption 3 steps (A ₁ , A ₂ , A ₃ ), decompression 2 steps (D ′ ₁ , D ′) ₂ ), 1 step of washing (P), 4 steps of 3 steps of pressurization (R ₁ , R ₂ , R ₃ ) are sequentially repeated, and (A ₁ , D ′ ₁ , R ₁ ), ( A method of operating to obtain a combination of (A ₂ , D ′ ₂ , R ₂ ) and (A ₃ , P, R ₃ ), which is a combination of 1. (A ₁ , D ₁ , D ₄ , R ₁ ). During operation, if a failure occurs at D ₁ or D ₄ , immediately after it occurs at R ₁ , after washing the D ₄ operating tower (A ₂ , D ′ ₂ ,
R ₂ ) combination, and during the combined operation of 2. (A ₂ , D ₂ , P ₁ , R ₂ ), if a failure occurs at D ₂ or P ₁ , immediately, if a failure occurs at R ₂ , , P ₁ operating tower is switched to the combination of (A ₃ , P, R ₃ ) after washing and pressurization, and the failure becomes D ₃ during the combined operation of 3. (A ₃ , D ₃ , P ₂ , R ₃ ). If it occurs, after washing the P ₂ operating tower If it occurs at P ₂ , after washing the D ₃ operating tower If at R ₃ , raise the pressure of the P ₂ operating tower, after washing the D ₃ operating tower (A ₁ , D ′ ₁ , R ₁ ) combination, 4. If A ₁ , A ₂ or A ₃ fails during operation, R ₁ , R ₂ and
Claim 1 wherein the pressure is applied to each of the R ₃ operation towers and the combination of (A ₂ , D ′ ₂ , R ₂ ) is performed after washing each of the D ₄ , P ₁ , P ₂ operation towers. Method described in section. 3. The invention according to claim 2, wherein the steady state is shifted from the combination of (A ₁ , D ′ ₁ , R ₁ ) to the combination of (A ₂ , D ₂ , P ₁ , R ₂ ). Method described in section. 4. An apparatus provided with four adsorption towers, wherein each tower has three adsorption steps (A ″ ₁ , A ″ ₂ ,
A ″ ₃ ), decompression 3 steps (D ″ ₁ , D ″ ₂ , D ″ ₃ ), washing 3 steps (P ″ ₀ , P ″ ₁ , P ″ ₂ ), boosting 3 steps (R ″ ₁ , R ″ ₂₎ , R ″ ₃ ) 4 steps 12 steps are sequentially repeated, and (A ″ ₁ , D ″ ₁ , P ″ ₀ ,
R ″ ₁ ), (A ″ ₂ , D ″ ₂ , P ″ ₁ , R ″ ₂ ), (A ″ ₃ ,
D ″ ₃ , P ″ ₂ , R ″ ₃ ) are operated in combination, and when a failure occurs in any one of the above steps, the operating tower is stopped at the step where the failure occurs and the remaining Of 3
Each tower has 3 steps of adsorption (A ″ ₁ , A ″ ₂ ,
A ″ ₃ ), depressurization 2 steps (D ₁ , D ₂ ), washing 1 step (P ′), pressurization 3 steps (R ″ ₁ , R ″ ₂ ,
R ″ ₃ ) 4 steps 9 steps are repeated in sequence,
(A ″ ₁ , D ₁ , R ″ ₁ ), (A ″ ₂ , D ₂ ,
R ″ ₂ ), (A ″ ₃ , P ′, R ″ ₃ ), which is a method of operating so as to have a combination of 1. (A ″ ₁ , D ″ ₁ , P ″ ₀ , R ″ ₁ ). During operation, if a failure occurs in D ″ ₁ or P ″ ₀ , immediately, if it occurs in R ″ ₁ , after cleaning the P ″ ₀ operating tower (A ″ ₂ , D ₂ , R ″ ₂ ) When a fault occurs in D " ₂ or P" ₁ during the combined operation of 2. (A " ₂ , D" ₂ , P " ₁ , R" ₂ ), immediately after it occurs in R " _2. Shifts to the combination of P ″ ₁ operating tower after washing and pressurization (A ″ ₃ , P ′, R ″ ₃ ), and the setting of 3. (A ″ ₃ , D ″ ₃ , P ″ ₂ , R ″ ₃ ) In combination operation, if a failure occurs at D ″ ₃ , after cleaning the P ″ ₂ operation tower, if P ″ ₂ occurs at D ″ ₃ operation, after cleaning the tower, if R ″ ₃ occurs at P ″ ₂ operation Boost the tower, D ″
_{3 After} operating the washing tower after washing (A ″ ₁ , D ₁ , R ″ ₁ ) combination, 4.A ″ ₁ , A ″ ₂ , or A ″ ₃ If a failure occurs during operation,
After the R ″ ₁ , R ″ ₂ and R ″ ₃ operation towers are respectively pressurized or maintained and the P ″ ₀ , P ″ ₁ , P ″ ₂ operation towers are respectively washed or continuously washed (A ″ ₂ , D ₂ , R ″ ₂ )
The method according to claim 1, wherein the method moves to the combination of. 5. A patent in which the normal time is changed from the combination of (A ″ ₁ , D ₁ , R ″ ₁ ) to the combination of (A ″ ₂ , D ″ ₂ , P ″ ₁ , R ″ ₂ ). The method according to claim 4. 6. The method according to any one of claims 1 to 5, wherein the feed mixed gas contains hydrogen, and the hydrogen is separated and purified from the feed gas.