JP2504448B2 - Pressure swing adsorption device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a pressure swing adsorption device (PSA device) for purifying a target gas for recovery such as CO and N ₂ to high purity,
Specifically, when the operation of the PSA device is restarted, it is possible to improve the purity of the target gas for recovery to a high level in a short time.
It concerns PSA devices.

Hereinafter, an example of recovering CO with high purity will be described in detail, but the present invention is not limited to this example and can be applied to the case of purifying other gas such as O ₂ and N ₂ .

[Prior Art] As a method for concentrating and recovering CO, a cryogenic separation method or a chemical absorption method is industrially widely used. These methods are suitable for mass purification or production of high-purity gas and can operate effectively, but have a drawback that the entire equipment becomes bulky and expensive.

On the other hand, the pressure swing adsorption method is easy to install and operate and is economically advantageous. Therefore, it is widely used as a gas separation method or a gas purification method for adsorbing and removing a specific component or desorbing and recovering the adsorbed specific component. It's being used.

For example, mixed gas composed of CO, N ₂ and H ₂ (eg converter gas)
Taking as a representative example a method of concentrating and recovering CO using as a raw material and using zeolite or the like as an adsorbent, the method will be described as follows. When a 4-tower PSA apparatus as shown in FIG. 3 (illustration) is used as the pressure swing adsorption apparatus, the steps will be described by focusing on the adsorption tower 2a.

A pressurized mixed gas (hereinafter also referred to as raw material gas) is introduced from the supply pipe 1, and an automatic opening / closing valve (hereinafter simply referred to as valve) V ₁
The CO in the raw material gas is adsorbed by the adsorbent in the adsorption tower 2a (pressurizing step), and the unadsorbed gas is discharged from the exhaust pipe 8 to the outside of the system. The supply of the raw material gas is stopped by operating the valve V ₁ immediately before the adsorbent in the adsorption tower 2a reaches a breakthrough, and then the adsorption towers 2a and 2b are connected by the bypass pipe 10a so that the pressure in the adsorption tower 3a is close to atmospheric pressure. Depressurize to. Then, in order to replace and remove the impure components remaining in the post-adsorption tower 2a, the high purity CO in the product gas tank 4 is pressurized by the cleaning gas blower 5, and the cleaning pipe 12 and the valves V ₆ , V ₃
It is introduced into the adsorption tower 2a via (cleaning step). That is, part of the product gas is consumed as cleaning gas, but the adsorption tower
The exhaust gas after cleaning 2a is fed to the adjacent adsorption tower 2b through the valve V ₅ and the bypass pipe 10a and is adsorbed and recovered again as a recovery target component. The adsorption tower 2a, which has completed the cleaning in the tower in this way, is connected to the vacuum pump 3 via the valve V ₂ and the recovery pipe 9.
The CO is desorbed by decompressing the inside of the tower (desorption process), and the desorbed high-purity CO is stored in the product gas tank 4 and is appropriately sent to the user side from the extraction pipe 7 by the product gas recovery blower 6.

On the other hand, in the adsorption tower 2a which has completed the desorption step, a series of steps starting from the above-mentioned raw material gas introduction (adsorption step) are repeated. And in each adsorption tower 2a ~ 2d
High-purity CO can be continuously produced by continuously shifting the cycle by 1/4 cycle.

[Problems to be Solved by the Invention] Although the converter gas has been described as an example of the raw material gas,
The converter, which is the source of converter gas, is regularly repaired once a month, and its operation is stopped. Therefore CO
The PSA device for recovery will have to be stopped accordingly.

Next, when the converter operation is restarted, the operation of the PSA device will be restarted, but at the start of the operation, the purity of CO is low and it takes a considerable time to obtain high-purity CO. ing. The conventional example of FIG. 2 shows an example thereof.
It takes at least 1 hour for the rise time to reach a high purity close to 100%, so the gas recovered during that time must be discarded unless a special application is developed.
The main cause of such low startup purity is the adsorption tower 2a-
It seems that there is no choice but to use the low-purity product gas generated after restarting the operation as the 2d cleaning gas. That is, it is a normal method that the product gas obtained by the previous operation is almost completely extracted from the product gas tank 4, and the adsorption operation is restarted in a state where the inside of the product gas tank 4 is substantially emptied. Therefore, it was considered to leave a part of high-purity CO in the product gas tank for PSA restart, but it is difficult to store an appropriate amount in the tank, and it is generated for other reasons when restarting operation. It has been found that the above countermeasure is not a preferable means, because the substance mixed with the low-purity gas cannot be used as a product and wastes the high-purity product gas.

From such a point, the present inventor has conducted various studies to provide a PSA device capable of extracting a high-purity recovery target component gas in a short time after the operation of the PSA device is restarted. It came to completion.

[Means for Solving the Problems] The PSA device of the present invention which has achieved the above object is provided with a heating type adsorption tower for adsorbing a part of the recovery target component gas in parallel with the product gas tank, and The gist of the type adsorption tower is that it is connected to the cleaning gas pipe of the pressure swing adsorption tower.

[Operation and Example] FIG. 1 is an explanatory view showing a typical example of the present invention. The structure of the adsorption towers 2a-2d and the product gas tank 4 is the third
Although it is similar to the PSA device shown in the figure, a characteristic part of the present invention is that a CO adsorption device R is additionally provided in addition to the product gas tank 4. That is, the product gas tank 4 is provided with an inlet pipe 13 via a valve V ₁₀ , a CO adsorption tower 11 is joined to the inlet pipe 13, and the outlet side of the adsorption tower 11 is led out via a valve V ₁₂ and a pressure regulating valve V _13. A pipe 15 is provided, and the outlet pipe 15 is connected to the cleaning pipe 12. The CO adsorption tower 11 is filled with a Co adsorbent 11a in which CuCl is supported on alumina, and the adsorption tower 11 is additionally provided with a heating device 16 capable of introducing a heating medium. The pipe number 14 indicates a relief pipe, and is a CO adsorption tower.
High purity when CO is supplied in excess of 11
It is for sending CO into the extraction pipe 7. The method of using the CO adsorption device R is as follows. That is, during steady operation of the PSA device, the valve V ₁₀ is opened to adsorb high-purity CO to the adsorbent 11a in the CO adsorption tower 11, and the PSA device is stopped so that the product gas tank 4 does not contain high-purity CO. Even in this case, CO is kept in the CO adsorption tower 11. And PSA
When the device is restarted, the heat medium is introduced into the heating device 16, and the adsorbent 11a
Adsorption towers 2a-2
It is used as a cleaning gas for d. At this time, the cleaning gas blower 5 is stopped and the valve V ₆ is closed. By doing so, the adsorption towers 2a to 2d will have high purity C even at the initial startup of the PSA device.
Since it is cleaned by O, the product gas in the desorption process can be quickly raised to a predetermined concentration. It is possible to install a pressure tank instead of the CO adsorption tower 1, but if a pressure tank is installed, a compressor or the like must be installed separately because the product gas pressure needs to be increased, so the equipment cost is low. It will be expensive. Moreover, since the pressure tank has a smaller CO storage amount than the CO adsorption tower, there is the inconvenience that a large pressure tank must be prepared.

The broken line graph shown in FIG. 2 shows the behavior of the product gas purity when the PSA apparatus is restarted using the conventional apparatus shown in FIG. 3, and the example of the present invention shown by the solid line is the first 7 shows the behavior of product gas purity when the apparatus of the present invention shown in the figure is used to restart the apparatus. In the case of the conventional apparatus, it took about 4 hours for the product gas to reach the predetermined purity, but when the apparatus of the present invention is used, it is possible to obtain the predetermined purity of about 1/8 of about 30 minutes. It has become possible to significantly reduce the gas consumption and the pre-operation time of the PSA device.

[Advantages of the Invention] By using the PSA apparatus of the present invention, a high-purity recovery target component gas can be obtained within a short time when the PSA apparatus is restarted, and the waste of raw material gas when the PSA apparatus is restarted P
It has become possible to suppress the unnecessary preliminary operation time of the SA device as much as possible. Moreover, these effects can be achieved by adding a minimum amount of equipment, which is extremely economical.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a typical embodiment of the present invention, FIG. 2 is a graph showing a change in product gas purity at the time of restart by the device of the present invention and a conventional device, and FIG. 3 is an explanation of the conventional device. It is a figure. 1 ... Raw material gas supply pipe, 2a to 2d ... PSA adsorption tower 3 ... Vacuum pump, 4 ... Product gas tank 5 ... Cleaning gas blower 6 ... Product gas recovery blower 7 ... Extraction pipe, 8 ... Discharge Pipe 9 …… Recovery pipe, 10a …… Bypass pipe 11 …… CO adsorption tower, 12 …… Cleaning pipe 13 …… Introduction pipe, 14 …… Escape pipe 15 …… Outlet pipe, 16 …… Heating device

Claims (1)

(57) [Claims] 1. A pressure swing adsorption device for adsorbing a recovery target component gas on an adsorbent in a pressure swing adsorption tower, and recovering the recovery target component gas at a high concentration into a product gas tank by desorption and desorption of the adsorption tower. And a heating type adsorption tower for adsorbing a part of the target gas for collection is provided in parallel with the product gas tank, and the outlet side of the heating type adsorption tower is connected to the cleaning gas pipe of the pressure swing adsorption tower. A pressure swing adsorption device characterized by the following.