JPH0523523A - Pressure swing adsorbing method separating and recovering carbon monoxide from gaseous mixture containing carbon monoxide - Google Patents

Abstract

PURPOSE:To efficiently desorb and recover a larger amount of high purity CO by using an adsorbent prepared by supporting a copper compound on an alumina carrier. CONSTITUTION:A pressure raising process, an adsorbing process, a pessure reducing process, a washing process and a desorbing process are successively executed in respective adsorbing towers A-D and a heater 14 or a hot water pipe 40 is used in the washing process to hold the temps. in the adsorbing towers A-D to 30-50 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure swing adsorption method (PSA method) for separating and recovering CO from a mixed gas containing carbon monoxide (CO).

[0002]

2. Description of the Related Art Conventionally, as a PSA method for separating and recovering CO from a mixed gas containing CO, there is, for example, Japanese Patent Publication No.
A method as disclosed in Japanese Patent Publication No. 37970 is known.
This method uses two or more adsorption towers equipped with a zeolite-based adsorbent, etc., and a pressure raising step of raising the pressure inside the adsorption tower with the raw material gas and adsorbing easily adsorbed components by flowing the raw material gas into the adsorption tower. The first adsorption step of adsorbing to the agent, the decompression step of decompressing the adsorption tower after completion of the first adsorption step to near atmospheric pressure, and the purging step of introducing the product gas into the adsorption tower after decompression to purge the hard-to-adsorb components And the desorption step of desorbing the easily adsorbed components by depressurizing the adsorption tower after purging to atmospheric pressure or less and collecting the product gas.

In such a PSA method, temperature control is generally not performed in each step, and for example, in the washing step, the operation is performed at almost room temperature.

[0004]

In recent years, CuC has been used as an active alumina carrier instead of the above zeolite-based adsorbents and the like.
The development of a method using an adsorbent supporting a copper compound such as 1 or CuCl ₂ is under way. In the latter adsorbent, C
Due to chemisorption between O and copper ions, CO
The amount of CO adsorbed far exceeds the amount of CO ₂ or N ₂ adsorbed, and therefore there is an advantage that only CO can be selectively adsorbed.

However, in such an adsorbent in which a copper compound is supported on an activated alumina carrier, CO is strongly adsorbed by the adsorbent, so that it is difficult for CO to be desorbed and a sufficient amount of CO recovery cannot be obtained. New points are emerging.

As a means for solving such a problem, it is conceivable to expand the capacity of the vacuum pump for desorption and recovery so as to lower the pressure at the time of desorption. However, when the adsorption force of the adsorbent is strong, it is not immediately desorbed even if the desorption pressure is lowered, and is gradually desorbed, so it is difficult to dramatically increase the CO desorption amount obtained in the entire desorption process. Is. In addition, if the desorption pressure is too low, the amount of impurities desorbed also increases because the difficultly adsorbed components easily reach the adsorption equilibrium, which causes a new problem of lowering the CO purity. It is also conceivable to extend the one cycle time and take the desorption step longer by that amount, but the CO desorption amount does not increase proportionally with the desorption time due to the characteristics of the desorption reaction described above. The CO desorption amount per unit time will be reduced.

Conventionally, in addition to the PSA method as described above, a temperature swing adsorption method (TSA method) aiming at a high recovery rate by operating the temperature in the adsorption tower has been known, but in each step Varying both pressure and temperature requires complex operations and large capital investment,
High costs are inevitable.

In view of such circumstances, the present invention provides a PSA method capable of easily and surely desorbing and recovering a large amount of high-purity CO by using an adsorbent in which a copper compound is supported on an activated alumina carrier. The purpose is to provide.

[0009]

In order to solve the above problems, the inventors of the present invention paid attention to the temperature inside the adsorption tower in the washing process before performing the desorption process, and as a result of repeated research, It was found that by keeping the temperature at 30 ° C. to 50 ° C., the adsorption capacity did not decrease so much and the desorption property was effectively improved, and the total CO desorption amount was improved.

That is, the present invention is a pressure swing adsorption method for separating and recovering carbon monoxide from a raw material gas by using an adsorption tower equipped with an adsorbent in which a copper compound is supported on an activated alumina carrier. An adsorption step of adsorbing a readily adsorbable component on the adsorbent by flowing a raw material gas containing from the inlet to the outlet of the adsorption tower, and reducing the pressure in the adsorption tower to a pressure near atmospheric pressure after the adsorption step, and exhaust gas from this adsorption tower The decompression process for discharging the product gas, the cleaning process for sending a part of the product gas into the adsorption tower to remove the difficultly adsorbed components, and the exhaust gas discharged from the adsorption tower, and the decompression inside the adsorption tower to below atmospheric pressure for easy adsorption. The desorption step of desorbing the components to recover the product gas and the step of increasing the pressure in the adsorption tower after the desorption step to a predetermined adsorption pressure are sequentially repeated, and the temperature in the adsorption tower during the washing step in the above washing step. To keep it at a 30 ° C. or higher 50 ° C. or less (claim 1).

As a specific embodiment, four adsorption towers are used, and the above steps are repeated for each adsorption tower with the phases shifted from each other. As the adsorption step, the concentration of the easily adsorbed component at the outlet of the adsorption tower is increased. The first adsorption step of discharging the exhaust gas derived from the adsorption tower outlet to the outside of the system until a predetermined time before reaching the concentration of the easily adsorbable component at the inlet, and the concentration of the easily adsorbed component at the adsorption tower outlet at the adsorption tower inlet After reaching a predetermined time point before reaching the concentration of the adsorbed component, a second adsorption step of introducing the exhaust gas into another adsorption tower and using it in the pressurization step is performed, and after the adsorption step is completed in the depressurization step. By connecting the outlet of the adsorption tower to the inlet of the adsorption tower after the desorption process, the pressure of both towers is brought to a pressure near atmospheric pressure, and the exhaust gas discharged from the outlet of the adsorption tower in the washing process is Gas is introduced into another adsorption tower and used in the pressure raising step, and as the pressure raising step, the former adsorption tower is connected by connecting the inlet of the adsorption tower after the desorption step and the outlet of the adsorption tower after the adsorption step. Is connected to the inlet of the adsorption tower after the completion of the first raising step and the outlet of another adsorption tower in the washing step to pressurize the inside of the former adsorption tower with gas from the latter adsorption tower. It is preferable to perform the second pressurizing step and the third pressurizing step for pressurizing the inside of the former adsorbing tower by connecting the inlet of the adsorbing tower after the second pressurizing step and the outlet of the adsorbing tower after the first adsorbing step. (Claim 2).

Further, in the above method, a preliminary desorption step of adjusting the pressure in the adsorption tower to a predetermined washing pressure by connecting a blowing means to the outlet of the depressurized adsorption tower between the depressurization step and the washing step. By performing the above, a more excellent effect as described below can be obtained (claim 3).

[0013]

According to the above method, as will be described later with reference to FIG. 3, the temperature of the cleaning gas introduced into the adsorption tower in the cleaning step before the desorption step and the temperature in the adsorption tower during the cleaning step are higher than room temperature. By setting the temperature to 30 ° C or higher, the CO desorption property from the adsorbent is enhanced, while by suppressing the temperature to 50 ° C or lower, the CO adsorption capacity is sufficiently maintained,
As a result, the total amount of CO desorbed and recovered will surely increase as compared with the conventional case. Moreover, as explained in FIG. 4 below,
The higher the temperature in the adsorption tower, the higher the CO purity of the product gas, and therefore the higher the product purity as compared with the case of operating at room temperature.

Further, by performing the preliminary desorption process as claimed in claim 3 before the cleaning process, the pressure in the adsorption tower can be surely set to a predetermined cleaning pressure, and in this state, the cleaning gas can be smoothly supplied. Can be introduced to.

[0015]

FIG. 1 shows an example of an apparatus for carrying out the method of the present invention.

This apparatus comprises four adsorption towers A, B, C and D.
And a single raw material compressor 11 for compressing the raw material gas. In each of the adsorption towers A to D, an adsorbent that selectively adsorbs CO among the components in the raw material gas, specifically, an activity. C on the alumina carrier or its surface with carbon attached
An adsorbent carrying a copper compound such as uCl or CuCl ₂ is provided. The raw material compressor 11 has four adsorption towers A, B, C via a common raw material gas passage 21 and valves 31A, 31B, 31C, 31D provided for the adsorption towers A, B, C, D, respectively. , D are respectively connected to the upper part (inlet).

Lower part (exit) of each adsorption tower A, B, C, D
Is a valve 33 provided for each adsorption tower A, B, C, D
A common gas recirculation passage 23 is connected via A, 33B, 33C, and 33D, and this gas recirculation passage 23 is provided with valves 36A and 3 for the adsorption towers A, B, C, and D, respectively.
6B, 36C, 36D through the respective adsorption tower A,
It is connected to the upper part of B, C, and D. The lower portion of each adsorption tower A, B, C, D is connected to a common off-gas passage 26 via valves 37A, 37B, 37C, 37D provided for each adsorption tower A, B, C, D, respectively. And a valve 3 provided for each adsorption tower A, B, C, D
2A, 32B, 32C and 32D are respectively connected to a common gas discharge passage 22, and a blower (blowing means) 13 is provided in this gas discharge passage 22. Furthermore, the lower part of each adsorption tower A, B, C, D
Valves 35A, 35B, 35C, 35 provided for D
Vacuum pump 1 via D and common recovery gas passage 25
2 is connected to the inlet side of the vacuum pump 12, and the surge tank 4 is connected to the outlet side of the vacuum pump 12. The surge tank 4 is for storing the product gas collected by the vacuum pump 12, and the product gas is appropriately extracted into the surge tank 4. The surge tank 4 has a common cleaning gas passage 24 and valves 34A, 34B, provided for the adsorption towers A, B, C, D, respectively.
34C, 34D through the respective adsorption towers A, B, C,
It is connected to the upper part of D.

Further, a heater 14 into which steam is appropriately introduced via a valve 16 is arranged at a position immediately downstream of the raw material compressor 11 in the raw material gas passage 21, and the valve 16 is opened and closed. A temperature controller 15 for controlling is provided. The temperature regulator 15 detects the gas temperature on the downstream side of the heater 14, and the raw material gas temperature is 30 ° C. or higher when the cleaning gas temperature introduced into each of the adsorption towers A to D in the cleaning step is 50 ° C. or higher. The heating control of the heater 14 is performed by opening and closing the valve 16 so that the temperature is maintained at a temperature equal to or lower than ° C.

On the other hand, in each of the adsorption towers A to D, a hot water pipe 40 for heating the adsorption towers is spirally provided (in FIG. 1, only the adsorption tower A is shown for convenience). A hot water tank 44 is connected to an inlet end of the hot water pipe 40 via a hot water circulation pump 42, and an outlet end of the hot water pipe 40 is directly connected to the hot water tank 44 through a passage 43. The hot water in the hot water tank 44 is circulated through the hot water pipe 40 by the operation of. Steam is appropriately supplied to the hot water tank 44 through a valve 46, and the valve 46 is controlled to be opened and closed by a temperature regulator 48 that detects the temperature in the hot water tank 44. The temperature controller 48 has a temperature in the adsorption tower heated by the hot water pipe 40 of 30 ° C. or higher and 50 ° C. or higher in the washing step.
The opening / closing control of the valve 46 is performed as follows.

Next, the CO separation and recovery process performed in this apparatus will be described. Here, the main focus is on the adsorption tower A, and the description will be started from the state where the desorption process is completed. In addition,
The relationship between the steps in the adsorption tower A and the steps in the other adsorption towers B, C and D is shown in FIG.

1) Pressure raising step First, as the first pressure raising step, the valve 33B and the valve 36A are opened to connect the upper portion of the adsorption tower A after the desorption step and the lower portion of the adsorption tower B after the adsorption step. The exhaust gas from the adsorption tower B in the depressurization step is introduced into the adsorption tower A through the valve 33B, the gas circulation passage 23, and the valve 36A, and the inside of the adsorption tower A is brought to near atmospheric pressure (about 0 kg / cm ² G). Boost.

Then, in the second pressurizing step, the cleaning gas supplied from the surge tank 4 to the adsorption tower B is introduced into the adsorption tower A through the valve 33B, the gas circulation passage 23, and the valve 36A, and the valve 32A is opened. The exhaust gas that has passed through the adsorption tower A is discharged to the outside through the gas discharge passage 22.

After that, the valves 33B, 3 are operated as a third pressure increasing step.
2A is closed, valves 33D and 36A are opened, and the adsorption exhaust gas in the latter stage of the adsorption process of adsorption tower D is supplied to adsorption tower A through valve 33D, gas circulation passage 23, and valve 36A. As a result, the pressure in the adsorption tower A is increased from a pressure near atmospheric pressure to a predetermined adsorption pressure (usually about 1.0 to 5.0 kg / cm ² G).

2) Adsorption Step First, as the first adsorption step, the valves 33D and 36A are closed and the valves 31A and 32A are opened, and the raw material gas compressor 11 is opened.
The raw material gas pressurized in 1 is led to the adsorption tower A through the raw material gas passage 21 and the valve 31A, and the exhaust gas after passing through the inside of the adsorption tower A is discharged to the outside of the system through the valve 37A and the off gas passage 26. Here, the source gases are CO, CO ₂ , N ₂ , and H _2.
CO, which is an easily adsorbed component of these components, is adsorbed to the adsorbent in the adsorption tower A under pressure, and other hardly adsorbed components such as N ₂ and H ₂ are mixed in the off-gas passage. Two
6 and the valve 37A to be released to the outside of the system.

The first adsorption step as described above is carried out until a predetermined time point before the CO concentration in the exhaust gas from the adsorption tower A becomes equal to the carbon monoxide concentration in the raw material gas, and after this time point has elapsed, The second adsorption step is performed. That is, the valve 32A
While closing the valve, the valves 33A and 36C are opened to allow the exhaust gas from the adsorption tower A to flow through the valve 33A, the gas circulation passage 23, and the valve 36C.
Through the adsorption tower C and used to raise the pressure of the adsorption tower C.

3) Depressurizing Step After performing the adsorption step, the valve 36C is closed and the valves 33A and 36B are opened. As a result, the raw material gas in the adsorption tower A, which has been pressurized to the planned adsorption pressure, is supplied to the valve 33A,
It is introduced into the adsorption tower B through the gas circulation passage 23 and the valve 36B, and the adsorption tower A is depressurized to almost atmospheric pressure, while the adsorption tower B is pressurized from the vacuum state to almost atmospheric pressure.

4) Preliminary desorption step In the above depressurization step, since the pressure inside the adsorption tower A and the pressure inside the adsorption tower B are only equalized, the pressure inside the adsorption tower A is the washing pressure (here, 0 kg / cm ² It may not be completely lowered to G). Therefore, after the depressurization step is completed, in this preliminary desorption step, the valve 33A is closed, the valve 32A is opened, and the blower 13 is actuated to actively release the gas in the adsorption tower A to the outside of the system, thereby adsorbing the gas. Make sure that the pressure in the tower A is lowered to the washing pressure. By performing such a preliminary desorption process, the introduction of the cleaning gas in the next cleaning process proceeds extremely smoothly.

5) Washing process In this washing process, the valves 33A, 36B, 34A, 32B are used.
Open and open a part of the product gas stored in the surge tank 4 through the cleaning gas passage 24 and the valve 34A.
Introduce inside. As a result, the difficult-to-adsorb components remaining in the adsorption tower A are purged, and the exhaust gas discharged from the adsorption tower A at this time includes the valve 33A, the gas circulation passage 23, and the valve 3
It is introduced into the adsorption tower B through 6B, further passed through the adsorption tower B, and then discharged to the outside through the valve 32B and the discharge passage 22.

In this washing step, the temperature in the adsorption tower A is maintained at 30 ° C. or higher and 50 ° C. or lower in order to control the temperature by the heater 14 and the hot water pipe 40.

6) Desorption process After the washing process is completed, the valves 33A, 34A and 36B are closed, and the adsorption tower A is stopped until the desorption process of the adsorption tower D is completed. Then, at the same time when the desorption process of the adsorption tower D is completed, the valve 35A is opened and the desorption process of the adsorption tower A is started. In this desorption process, the easily adsorbed component (C) adsorbed in the adsorption tower A is activated by the operation of the vacuum pump 12.
O) is desorbed and desorbed under reduced pressure, and is recovered in the surge tank 4 through the valve 35A and the recovery gas passage 25. The desorption process in the adsorption tower A is continuously performed while the adsorption process is performed in another adsorption tower B, the decompression process, the washing process, and the rest process in the adsorption tower C, and the pressurization process is performed in the adsorption tower D. To do so. By such a desorption process, the pressure in the adsorption tower A is finally reduced to about -1 kg / cm ² G.

By repeating the above steps 1) to 6) in sequence for the adsorption tower A, CO can be separated and recovered.

According to such a method, the desorption amount of CO can be improved more than before by maintaining the temperature in the adsorption tower during the washing step at 30 ° C. or higher and 50 ° C. or lower.

FIG. 3 shows the relationship between the temperature in the adsorption tower and the CO degassing amount per 1 cc of the adsorbent during the washing step when the same steps are performed in the same apparatus as described above. From this figure, it can be seen that C
It can be seen that the degassing amount of O reaches its peak. It is considered that this is because if the washing process temperature is too low, CO is difficult to be desorbed, and conversely, if the washing process temperature is too high, the CO adsorption capacity decreases, and the balanced temperature between the two is about 40 ° C. it can. Here, since the maximum amount of CO deaeration obtained in the conventional operation at normal temperature is about 9.5 cc / cc, from the results shown in FIG.
By keeping the temperature below ℃, more C than the conventional method
We come to the conclusion that an O 2 degassing rate can be reliably obtained.

FIG. 4 shows the relationship between the average temperature of the temperature inside the adsorption tower in each step and the CO purity in the product gas in the above apparatus. Since the average temperature in the adsorption tower is substantially equal to the cleaning temperature, it can be said that this FIG. 4 approximately shows the relationship between the cleaning temperature and the gas purity.

As can be seen from FIG. 4, the higher the average temperature, the higher the CO purity of the product gas. this is,
It can be considered that this is because the cleaning effect in the tower by the cleaning gas increases with the increase of the average temperature, and the hardly adsorbed components are removed more reliably. Therefore, as described above, by maintaining the cleaning process temperature at 30 ° C to 50 ° C higher than room temperature,
Product gas purity will also be improved.

In the above embodiment, the temperature of the raw material gas and the adsorption tower is controlled to keep the temperature during the cleaning step constant, but the present invention does not require any means for controlling the temperature. Further, in the present invention, the method is not limited to the method using the four adsorption towers A to D as described above, and PS that sequentially performs the pressurizing step, the adsorbing step, the depressurizing step, the washing step, and the desorbing step.
This is applicable to method A.

[0037]

As described above, according to the present invention, the pressurizing step, the adsorbing step, the depressurizing step, the washing step, and the desorbing step are carried out in order, and in the washing step, the temperature and the washing of the washing gas introduced into the adsorption tower The temperature in the adsorption tower during the process is 30 ℃
Since the temperature is kept at 50 ° C. or lower, there is an effect that the desorption recovery amount of CO can be easily and surely increased as compared with the conventional method without making a large capital investment. In addition, such temperature control increases the cleaning effect, and the effect that CO of higher purity can be constantly and stably recovered can be obtained.

Further, as in the method of claim 3, between the depressurizing step and the washing step, a blowing means is connected to the outlet of the depressurized adsorption tower so that the pressure in the adsorption tower becomes a predetermined washing pressure. By performing the preliminary desorption process to be adjusted, the pressure in the adsorption tower can be surely lowered to the cleaning pressure, which has the effect that the cleaning gas can be smoothly introduced in the cleaning process.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example of an apparatus for carrying out the method of the present invention.

FIG. 2 is a time chart showing steps in each adsorption tower in the above apparatus.

FIG. 3 is a graph showing a relationship between a cleaning process temperature and a CO degassing amount in the above method.

FIG. 4 is a graph showing the relationship between the average temperature in the adsorption tower and the CO purity of the product gas in the above method.

[Explanation of symbols]

A, B, C, D adsorption tower 4 surge tank 12 Vacuum pump 13 Blower (Blower) 14 heater 15,48 Temperature controller 21 Raw material gas passage 22 Gas release passage 23 Gas circulation passage 24 Cleaning gas passage 25 gas suction passage 26 Off-gas passage 40 hot water pipe

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Fumihiko Kasuya             65-1, Teriya-cho, Kakogawa-cho, Kakogawa-shi, Hyogo             No. 701

Claims (3)

[Claims] 1. A pressure swing adsorption method for separating and recovering carbon monoxide from a raw material gas using an adsorption tower equipped with an adsorbent in which a copper compound is supported on an activated alumina carrier, the raw material containing carbon monoxide. An adsorption step of adsorbing an easily adsorbable component on the adsorbent by flowing gas from the inlet to the outlet of the adsorption tower, and reducing the pressure inside the adsorption tower to a pressure near atmospheric pressure after the adsorption step, and deriving exhaust gas from this adsorption tower. Decompression process, a cleaning process in which part of the product gas is sent into the adsorption tower to remove difficultly adsorbed components and exhaust gas is discharged from the adsorption tower, and the adsorption tower is depressurized to atmospheric pressure or less to desorb easily adsorbed components. Then, the desorption step of recovering the product gas and the step of increasing the pressure in the adsorption tower after the desorption step to a predetermined adsorption pressure are sequentially repeated, and the temperature in the adsorption tower during the washing step in the washing step is set to 30 ° C. 50 ° C or above A pressure swing adsorption method for separating and recovering carbon monoxide from a mixed gas containing carbon monoxide, which is characterized in that: 2. A pressure swing adsorption method for separating and recovering carbon monoxide from a mixed gas containing carbon monoxide according to claim 1, wherein four adsorption towers are used, and the steps for each adsorption tower are out of phase with each other. Repeatedly, as the adsorption step, the exhaust gas discharged from the adsorption tower outlet is discharged to the outside of the system until a predetermined time before the concentration of the easily adsorbed ingredient at the adsorption tower outlet reaches the concentration of the easily adsorbed ingredient at the adsorption tower inlet. 1 Adsorption step, and after the concentration of the easily adsorbed component at the outlet of the adsorption tower reaches a predetermined point before reaching the concentration of the easily adsorbed component at the inlet of the adsorption tower, the exhaust gas is introduced into another adsorption tower to increase the pressure. The second adsorption step used for the above, and by connecting the outlet of the adsorption tower after completion of the adsorption step and the inlet of the adsorption tower after completion of the desorption step in the depressurization step, the pressure of both towers To a pressure near the atmospheric pressure, and the exhaust gas derived from the adsorption tower outlet in the cleaning step is introduced into another adsorption tower and used in the pressurizing step, and as the pressurizing step, of the adsorption tower after the desorption step is completed. A first pressurizing step for connecting the inlet and an outlet of the adsorption tower after the adsorption step to pressurize the former adsorption tower, an inlet of the adsorption tower after the completion of the first pressurizing step, and an outlet of another adsorption tower in the washing step And a second pressure raising step for increasing the pressure in the former adsorption tower by gas from the latter adsorption tower, the adsorption tower inlet after the second pressure raising step and the first
A pressure swing adsorption for separating and recovering carbon monoxide from a mixed gas containing carbon monoxide, characterized in that a third pressurizing step for pressurizing the inside of the former adsorption tower by connecting with the outlet of the adsorption tower after the adsorption step is performed. Method. 3. A pressure swing adsorption method for separating and recovering carbon monoxide from a mixed gas containing carbon monoxide according to claim 1 or 2, wherein between the depressurizing step and the washing step,
Separation of carbon monoxide from a mixed gas containing carbon monoxide, characterized by performing a preliminary desorption step of connecting a blowing means to the outlet of the depressurized adsorption tower to adjust the pressure in the adsorption tower to a predetermined cleaning pressure. Pressure swing adsorption method to recover.