JPH047013A - Method and device for producing highly pure gas by adsorption process - Google Patents

Abstract

PURPOSE:To improve gas recovery rate by a method wherein the gas desorbed from primary adsorbers at the initial stage of desorption process is conducted into a secondary adsorber in order for the intended components of the gas to be adsorbed thereby and a highly pure product gas is released from the primary adsorbers and then a product gas from the secondary adsorber. CONSTITUTION:At the initial stage of desorption process, the gas desorbed from adsorbents in primary adsorbers 11 and 12 is conducted into a secondary adsorber 40 having adsorbent therein in order for the intended components of the gas to be adsorbed thereby. During a period from the initial stage of desorption to the end of the desorption process, the gas desorbed from the primary adsorbers 11 and 12 is recovered as product gas. After this desorption process, the inner pressure of the secondary adsorber 40 is reduced to desorb the gas from the adsorbent therein and this desorbed gas is recovered as product gas. As a result, a cleaning process can be reduced or removed, while the purity of the recovered product gas is being maintained at a high level, whereby a reduction in the expense of electric power or improvement of the product recovery rate can be contrived.

Description

[Detailed description of the invention] [Industrial application field] The present invention is directed to a pressure swing adsorption method (hereinafter referred to as PSA).

The present invention relates to a method and apparatus for extracting a target component gas from a source gas and recovering it with high purity by using the following method.

[Conventional technology]

BACKGROUND ART Conventionally, PSA, which utilizes the adsorption function of a specific gas by an adsorbent, has been widely known as a means for extracting and recovering a target component gas from a source gas. This PSA is suitable for concentrating and recovering carbon monoxide from converter gas whose main components are carbon oxide and nitrogen, and concentrating and recovering carbon dioxide from combustion exhaust gas whose main components are carbon dioxide and nitrogen. It is used for.

FIG. 8 shows an example of a conventional device for performing this PSA. This device includes a raw material gas blower 80, adsorbers 81, 82, a vacuum pump 84, a product gas storage tank 86, etc., and automatic valves 87 to 97 are provided at appropriate locations in each passage.

In this apparatus, the product gas is purified by sequentially performing and repeating the four steps described below. Here, a process performed in one adsorption device 81 will be described as an example.

(2) Adsorption process By operating the raw material gas blower 80, raw material gas is supplied into the adsorber 81 through the automatic valve 87. The gas not adsorbed here is disposed of outside the apparatus through an automatic valve 95.

■Cleaning (purging) process A part of the product gas stored in the product gas storage tank 86 is
Adsorber 8 through cleaning gas supply pipe 98 and automatic valve 91
1, and this gas expels non-target components within the adsorber 81, specifically, non-target component gas staying in dead spaces such as the outer surface of the adsorbent. In this cleaning process,
The cleaning exhaust gas discharged from the main adsorber 81 is rich in target components compared to the raw material gas, so it is collected again, that is, returned to the upstream side of the raw material gas blower 80 through the automatic valve 93 and the cleaning exhaust gas recovery pipe 99. , used for adsorption in other adsorbers 82.

(2) Desorption process The vacuum pump 84 is operated to suck the gas inside the adsorber 81 through the automatic valve 89, thereby reducing the pressure inside the adsorber 81. As a result, the target component gas adsorbed by the adsorbent is desorbed and recovered as a product gas.

■ Pressurization step Open the automatic valves 95 and 96 and send the gas in the adsorber 82 into the adsorber 81 1. This increases the pressure inside the adsorber 81.

The steps generally performed in PSA have been shown above, but in JP-A No. 62-61616, as a method for separating high-purity gas, the desorption step is divided into an initial step, a middle step, and a final step, and the middle step is A method is disclosed in which only the desorbed gas is recovered as a product gas. According to this method, the recovered gas at the early and final stages of desorption, which has relatively low purity, is used for cleaning, and only the recovered gas at the middle stage of desorption, which has relatively high purity, is recovered as product gas. Purification can be achieved.

[Invention or problem to be solved]

The conventional method described above with reference to FIG. 8 has the following problems.

(1) In the above method, in order to increase the purity of the recovered gas, a cleaning process is performed to expel non-target gas from the outer surface of the adsorbent, etc., but in this cleaning process, a part of the product gas (actually Because more than half of the recovered amount must be circulated within the device, the power cost for the entire device is double that of a case where no cleaning step is performed.

(2) If the cleaning process has not yet been carried out, it is difficult to obtain high-purity product gas immediately from the start of the equipment, as many non-target components are contained in each main adsorber 81, 82. In reality, the purity of the gas must be gradually increased by repeatedly performing adsorption/desorption cycles. Therefore, it takes a relatively long time to obtain high-purity gas, and it is also difficult to reduce power costs.

(3) In the above method, while a part of the product gas is circulated to the adsorber as cleaning gas, the exhaust gas from this cleaning process is recovered and supplied to the adsorber. Even if this is done, it is impossible to extract 100% of the target component contained in this re-recovered gas, and a decrease in product recovery rate is inevitable.

On the other hand, according to the method disclosed in JP-A-62-61616, the purity of the product can be increased by extracting only the recovered gas in the middle stage of desorption, when the purity of the desorbed gas is highest, as the product gas. However, the gas recovered at the initial and final stages of desorption is also rich in target component gases compared to the raw material gas, and it is difficult to dispose of such recovered gas without extracting it as a product or to circulate it as a cleaning gas. This will lead to a decrease in product recovery rate, which will impair economic efficiency.

In view of these circumstances, the present invention aims to maintain the purity of the recovered product gas at a high level while reducing or eliminating the cleaning process, thereby reducing power costs and improving the product recovery rate. The purpose of the present invention is to provide a method and apparatus for purifying high-purity gas.

[Means to solve the problem]

The present invention includes an adsorption step in which a raw material gas is passed through a main adsorbent having an adsorbent, and a target component in the raw material gas is selectively adsorbed; The desorption process of desorbing the gas is performed sequentially.
In this high-purity gas purification method for recovering the desorbed gas, in the early stage of the desorption step, the gas desorbed from the adsorbent in the main adsorber is guided to a sub-adsorber having an adsorbent to remove the target component in the gas. During the period from the end of the initial stage of the desorption process to the end of the desorption process, the gas desorbed from the main adsorber is recovered as product gas, and after the desorption process, the pressure inside the sub-adsorber is reduced to recover this sub-adsorber. The gas adsorbed by the adsorbent in the adsorber is desorbed and this gas is recovered as a product gas (Claim 1).

Here, during the period from the initial end of the desorption process to the end of the desorption process, the gas desorbed from the main adsorber may be directly recovered as product gas, or the gas may be passed through the sub-adsorber. It may be collected later.

The present invention also provides an apparatus for implementing the above method, which includes a main adsorber having an adsorbent that selectively adsorbs target components in the raw material gas, and a raw material for supplying the raw material gas to the main adsorber. In a high-purity gas purification apparatus comprising a gas supply means and a desorption means for depressurizing the inside of the main adsorption device to desorb the gas, the gas is connected to the outlet side of the main adsorption device and is desorbed from the main adsorption device. a sub-adsorber having an adsorbent that selectively adsorbs the target component in the gas, a sub-desorption means for depressurizing the inside of the sub-adsorber to desorb the gas, and a passage on the outlet side of the sub-adsorber. A passage switching means is provided for selectively switching the gas discharged from the sub-adsorber between a passage to the recovery side and a passage to the disposal side (Claim 2).

[For production]

According to the above configuration, in the initial stage of the desorption process, the gas desorbed from the main adsorption device is directly guided to the sub adsorption device, and the target component in the gas is adsorbed. Thereafter, as the desorption process progresses and the purity of the desorbed gas from the main adsorber becomes high, this gas is recovered as a product gas either directly or through a sub-adsorber or the like. After the desorption step is completed, the sub-adsorber is depressurized, whereby the gas adsorbed by the sub-adsorber is desorbed and recovered as a product gas.

〔Example〕

1 to 6 show the overall configuration of an embodiment of an apparatus for carrying out the method of the present invention.

This device includes a raw material gas blower (raw material gas supply means) 10
, main adsorbers 11 and 12, a vacuum pump (also used as a desorption means and a sub-desorption means) 14, and a product gas storage tank 16, and each main adsorption device 11 and 12 selectively adsorbs target components in the raw material gas. It has a built-in adsorbent.

The raw gas blower 10 is connected to the inlet of the main adsorber 11, 12 through automatic valves 19' and 20, respectively, and the vacuum pump 1
4 are also respectively connected to the inlets of the main adsorber 11.12 via automatic valves 23.24. The outlet of each main adsorber 11.12 is connected to the waste gas discharge pipe 30 through automatic valves 27.28, respectively, and is connected to the raw gas blower 10 through automatic valves 31.32 and cleaning exhaust gas recovery pipe 34. connected to the upstream side of the The product gas storage tank 16 is located downstream of the vacuum pump 14, and is connected to each main adsorber 11.
It is connected to the entrance side of 12.

Furthermore, as a feature of this apparatus, a sub-adsorption device 40 is provided between the vacuum pump 14 and the product gas storage tank 16. Similar to the main adsorbers 11 and 12, this sub-adsorber 40 also contains an adsorbent that selectively adsorbs only the target component in the raw material gas.

Automatic valves 42 to 44 are disposed between the sub-adsorber 40 and the vacuum pump 14. The outlet side passage pipe of the sub-adsorber 40 is the product gas recovery pipe 4 connected to the product gas storage tank 16.
6 and a waste pipe 47 that leads to the waste side.
Automatic valves (passage switching means) 50 and 51 for switching passages are provided in the container pipes 46 and 47. Further, the vacuum pump 14 and the product gas storage tank 16 are directly connected by a bypass pipe 54, and an automatic valve 56 is also provided in the middle of the bypass pipe 54.

Next, the product gas (high purity gas) produced by this equipment
The purification process will be explained. In this device, as shown in FIG. 7, four steps are performed sequentially in each main adsorber 11, 12 with a phase shift from each other, and adsorption/desorption steps are performed alternately in the sub-adsorber 40. According to
Here, the main adsorber 11
The explanation will mainly focus on the processes performed in .

■ Adsorption step (FIG. 1) The automatic valve 19 is opened, the raw material gas blower 10 is operated, and the raw material gas is supplied into the main adsorber 11. As a result, the target component in the raw material gas is adsorbed by the adsorbent in the main adsorber 11, and the unadsorbed gas is disposed of outside the apparatus from the waste gas discharge pipe 30 through the automatic valve 27.

■Cleaning process (FIG. 2) The automatic valve 37 is opened and the product gas stored in the product gas storage tank 16 is sent into the main adsorber 11 as a cleaning gas under approximately atmospheric pressure. With this cleaning gas, non-target component gases remaining in dead spaces such as the outer surface of the adsorbent are expelled.

At this time, the cleaning exhaust gas discharged from the main adsorber 11 is returned to the upstream side of the raw material gas blower 10 through the automatic valve 31 and the cleaning exhaust gas recovery pipe 34 to be recovered again.
It is again subjected to adsorption in the main adsorber 12.

■Desorption process (Figures 3 and 4)) Initial stage (Figure 3) Open the automatic valve 23, operate the vacuum pump 14 to reduce the pressure inside the main adsorber 11, and perform desorption.
44 is opened, and the gas desorbed from the main adsorption device 11 is sent into the sub adsorption device 40. This sub-adsorber 40 adsorbs the target component gas contained in the desorption gas.

At the initial stage of this desorption process, the desorption gas discharged from the main adsorber 11 still contains a large amount of non-target gas, so the remaining gas that was not adsorbed in the sub adsorber 40 is also used as the product gas. It does not have sufficient purity. Therefore, at this initial stage, the automatic valve 50 is closed and the automatic valve 51 is closed.
By opening only the sub-adsorber 40, the gas discharged from the sub-adsorber 40 is disposed of to the outside of the apparatus through the waste pipe 47.

ii) After the initial completion (FIG. 4) When the desorption progresses at the beginning or end of the desorption process, the amount of non-target components contained in the desorption gas becomes small, and the desorption gas has sufficient purity. Therefore, the gas that was not adsorbed by the sub-adsorber 40, that is, the sub-adsorber 4
The gas discharged from 0 also has a purity sufficient to be used as a product gas. Therefore, during this period, the automatic valve 51 is closed,
By opening only the automatic valve 50, the gas discharged from the sub-adsorber 40 is recovered as product gas.

In this way, after the initial stage of the desorption process is completed, the sub-adsorber 4
Since the product gas can be recovered even if the target component is not adsorbed at zero, there is no problem even if the adsorbent in the sub-adsorber 40 is in a breakthrough state.

Therefore, the adsorbent in the sub-adsorber 40 only needs to have an adsorption amount sufficient to perform good adsorption at least in the initial stage of the desorption process.

(2) Desorption step of the sub-adsorber 40 (Fig. 5) By opening the automatic valves 42 and 43 and operating the vacuum pump 14, the pressure inside the sub-adsorber 40 is reduced and the adsorbed gas is desorbed. At the same time, by opening the automatic valve 56, the gas desorbed from the sub-adsorber 4° is sent through the bypass pipe 54 to the product gas recovery pipe 46, and the desorbed gas is recovered as product gas.

Note that while the desorption process of the sub-adsorber 40 is being performed, the automatic valves 27 and 28 are opened and the gas in the main adsorber 12 is supplied into the main adsorber 11, thereby depleting the main adsorber 11. The pressure is increased, and then the process returns to the adsorption step.

As described above, in this apparatus, the sub-adsorber 40 is provided on the outlet side of the main adsorber 11, 12, and the target component is also adsorbed in this sub-adsorber 40, so that the cleaning process can be performed as usual. It is possible to purify high-purity gas without relying on the gas or reducing the product recovery rate. For this reason,
It is possible to reduce the cleaning process described above, and in some cases eliminate the cleaning process. When eliminating the cleaning process,
The elements indicated by broken lines in FIGS. 1 to 5, namely the cleaning gas supply pipe 36, the cleaning exhaust gas recovery pipe 34, and the automatic valves 31, 32, 37, 38, can be omitted.

Moreover, in this method, when the initial stage of the adsorption process is completed,
That is, from the time when the purity of the desorption gas sucked from the main adsorption device 11 becomes sufficiently high, the gas passing through the sub-adsorption device 40 is also recovered as a product gas, and the gas passing through the sub-adsorption device 40 is also recovered as a product gas. Since the product gas is recovered in both the desorption processes of the adsorber 40, the amount of gas that must be recovered in the desorption process of the sub-adsorber 40 is equal to the amount of product gas recovered in the desorption process of the main adsorber 11. less.

Therefore, by reducing the power required for desorption of the sub-adsorber 40 as much as possible, it is possible to significantly reduce power costs compared to the conventional method of achieving high purity of product gas by performing a cleaning process. I can do it.

Next, experimental data will be shown. The conventional apparatus shown in FIG. 8 was operated under the conditions shown in Table 1 on the next page, and carbon oxide was recovered. After about 2.75 hours from the start of operation, the purity was 98.7. % of product gas could be stably obtained with a product recovery rate of 67%.

Table 1: On the other hand, the apparatus of the present invention shown in FIGS. By adjusting the switching timing, it was possible to obtain product gas with the above purity at a recovery rate of 73% within one hour after the start of operation. (Hereafter, blank space) Here, the amount of gas during cleaning is equivalent to 1/2 of the total amount of product gas recovered, but in reality, a larger amount of cleaning gas is required in order to achieve high purity of the product. That will happen.

In Table 2, the fact that the gas flow rate during cleaning is 0 indicates that substantially no cleaning process was performed.

This result shows that the method and apparatus of the present invention are superior to the conventional method in both stabilization time and product recovery rate.

In addition, in the method of the present invention, as in the conventional method of performing a cleaning step, it is necessary to perform both the desorption of the main adsorbers 11 and 12 and the desorption of the sub-adsorption device 40, as described above.
After the initial stage of the desorption process in the main adsorbers 11 and 12 is completed, the product gas is recovered even during this desorption process, so the amount of product gas recovered in the desorption process in the sub-adsorber 40 can be reduced accordingly. Compared to conventional methods that rely heavily on the cleaning process, power costs can be reduced. Specifically, in the apparatus shown in FIGS. 1 to 5, an integrating flow meter is provided downstream of the automatic valve 56, and the total amount of product gas desorbed and recovered from the sub-adsorber 40 during operation under the above conditions is measured. It has been confirmed that this amount is about 27% of the total recovery amount of the cycle.

Furthermore, in this example device, the vacuum pump 14 is used both as a desorption means for the main adsorber 11 and 12 and as a desorption device for the sub-adsorption device 40, so the device can be simplified and reduced in cost. This has the effect of preventing the desorption of the main adsorbers 11, 12 and the sub adsorption device 40 from being mistakenly performed at the same time.

In the above embodiment, the desorption gas from the main adsorbers 11 and 12 is led to the sub-adsorber 40 even after the end of the initial stage of the desorption process, but in the latter stage of the desorption process, the adsorption by the sub-adsorber 40 is particularly Since this is not necessary, as shown in FIG.
4 may be directly sent to the collection side.

In addition, in the present invention, the specific time at the initial stage of the desorption process may be set as appropriate depending on the specific specifications of the apparatus (specifically, the desorption process starts when the desorption gas stabilizes in a high purity state). It is desirable to end the process at the beginning of the process.

Further, in the present invention, the main adsorption device and the sub adsorption device may be appropriately set regardless of their specific structure and number. However, by equipping a plurality of main adsorbers as shown in the above embodiment, the product gas can be continuously purified.

〔Effect of the invention〕

As described above, in the present invention, in the early stage of the desorption process of the main adsorber, the desorbed gas is further guided to the sub-adsorber, where the target component is adsorbed, and after the desorption process is completed, the desorbed gas is This system recovers the desorbed gas as product gas, and then desorbs the sub-adsorber after the desorption process and recovers the desorbed gas as product gas. The purity of the product can be maintained at a high level, which has the effect of reducing power costs and improving the product recovery rate.

[Brief explanation of drawings]

1st □□□ is an overall configuration diagram showing the gas flow during the adsorption process of the main adsorber in a high purity gas purification device according to an embodiment of the present invention, and Fig. 2 is a diagram showing the flow of gas during the main adsorber cleaning process in the same device. Figure 3 is an overall configuration diagram showing the gas flow at the beginning of the desorption process in the main adsorber in the same equipment, and Figure 4 is an overall diagram showing the gas flow in the same equipment at the beginning of the desorption process in the main adsorption unit. Figure 5 is an overall configuration diagram showing the gas flow during the pressure increase process in the main adsorber and the desorption process in the sub-adsorber in the same equipment, and Figure 6 is an overall configuration diagram showing the gas flow in the equipment during the pressure increase process in the main adsorber and the desorption process in the sub-adsorber. An overall configuration diagram showing a modified example of the gas flow during the desorption process of the adsorber, Fig. 7 is a process diagram showing the steps executed in each main adsorber and sub-adsorber of the same device, and Fig. 8 is a conventional FIG. 1 is an overall configuration diagram showing an example of a high purity purification apparatus. 10... Raw material gas blower (raw material gas supply means), 11
．． 12... Main adsorption device, 14... Vacuum pump (desorption means and sub-desorption means), 40... Sub-adsorption device, 46...
・Product gas recovery pipe, 47...Disposal pipe, 50.51...
・Automatic valve (passage switching means). Patent Applicant Kobe Steel Oriyo Co., Ltd. Patent Attorney Etsushi Kotani

Claims (1)

[Claims] 1. An adsorption step in which a raw material gas is passed into a main adsorbent having an adsorbent to selectively adsorb target components in the raw material gas, and the adsorbent is removed by reducing the pressure inside the main adsorbent. In a high-purity gas purification method that sequentially performs a desorption step of desorbing the gas adsorbed to the gas and recovering the desorbed gas,
At the beginning of the desorption process, the gas desorbed from the adsorbent in the main adsorbent is guided to the sub-adsorption unit having an adsorbent to adsorb the target component in the gas, and from the end of the initial desorption process to the end of the desorption process. During the period up to, the gas desorbed from the main adsorber is recovered as product gas, and after the desorption step, the pressure inside the sub-adsorber is reduced to desorb the gas adsorbed by the adsorbent in this sub-adsorber. A method for purifying high-purity gas using an adsorption method, which is characterized by recovering this gas as a product gas. 2. A main adsorber having an adsorbent that selectively adsorbs target components in the raw material gas, a raw material gas supply means for supplying the raw material gas to the main adsorber, and a gas supply unit that reduces the pressure inside the main adsorber to In a high-purity gas purification apparatus equipped with a desorption means for desorption, an adsorbent is connected to the outlet side of the main adsorption device and selectively adsorbs the target component in the gas desorbed from the main adsorption device. a sub-adsorber having a sub-adsorber, a sub-desorption means for depressurizing the inside of the sub-adsorber to desorb the gas, and a passage on the outlet side of the sub-adsorber for sending gas discharged from the sub-adsorber to a recovery side. 1. An apparatus for purifying high-purity gas using an adsorption method, characterized by comprising a passage switching means for selectively switching between a passage to a waste side and a passage to be sent to a waste side.