JPH057719A - Pressure swinging-type mixed gas separation system - Google Patents

Abstract

PURPOSE:To carry out purge of an adsorbing agent bed by a hardly absorbable gas which is concentrated and separated, and carry out desorption and regeneration of the adsorbing agent under decreased pressure for a long period. CONSTITUTION:In a pressure swinging-type mixed gas separation system wherein an adsorbing agent absorbed an absorbable gas under pressing conditions is treated to desorb the gas from the adsorbing agent under decreased pressure to regenerate the adsorbing agent while a hardly absorbable gas which is concentrated and separated is used as a purge gas, a desorbing gas discharging pipeline 14 having switching valves 5A, 5B, 5C and a tank 20 for desorbing gas storage and having switching valves 11A, 11B, 11C are installed in parallel between the desorbing gas discharging outlets of adsorbing towers 2A, 2B, 2C and a vacuum pump 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure swing type (hereinafter referred to as PSA) mixed gas separating apparatus such as a pressure swing type oxygen producing apparatus for separating and concentrating oxygen gas from air.

[0002]

2. Description of the Related Art FIG. 4 is a system flow diagram of a conventional PSA oxygen production apparatus, and FIG. 5 is a pressure operation pattern diagram thereof.

This device, as shown in FIG.
₂ ) Three adsorption towers 2 with a built-in adsorbent bed of gas adsorbent
A, 2B and 2C are provided, and in each adsorption tower, when the air pressurized and fed by the raw air blower 1 passes through the adsorbent bed,
N ₂ gas or the like is adsorbed by the adsorbent, and oxygen (O ₂ ) gas is concentrated and separated (adsorption step). The adsorbent gas such as N ₂ gas adsorbed by the adsorbent is desorbed from the adsorbent by depressurizing the inside of the adsorption tower with the vacuum pump 3, and the adsorbent is regenerated (desorption regeneration step).

Further, between the desorption regeneration step and the adsorption step in the adsorption tower, the concentrated and separated O ₂ gas is introduced into the adsorption tower to pressurize the inside of the adsorption tower so that a rapid air flow in the adsorption step occurs. It prevents the occurrence (O ₂ re-pressurization process).

The pressure operation pattern in the above adsorption tower is shown in FIG. In each adsorption tower, the above-mentioned steps are sequentially and repeatedly performed with the phases thereof being different from each other, so that the O ₂ gas concentrated and separated continuously can be obtained.

In FIG. 4, the adsorption tower 2A is shown in the adsorption step, the adsorption tower 2B is shown in the O ₂ recompression step, and the adsorption tower 2C is shown in the desorption regeneration step. Also, 4
A to 4C are switching valves for air supply, 5A to 5C are switching valves for wearing and removing, 6A to 6C are switching valves for discharging O ₂ gas, and 7A to
7C is a switching valve for purging, which will be described later, and shows that the white valves in FIG. 4 are in the open state and the black valves are in the closed state.

[0007]

In order to improve the separation efficiency of the PSA mixed gas separation device and increase the product gas yield, the purity of the product gas must be increased as much as possible. For example, the PSA oxygen production apparatus shown in FIG. 4 for concentrating and separating O ₂ gas from air as a mixed gas using an N ₂ adsorbent will be described as an example to increase the concentration of O ₂ gas and improve the separation efficiency. In order to do so, unless the N ₂ gas is desorbed and the adsorbent is regenerated so much as the adsorbent on the O ₂ gas outlet side of the adsorption tower, it is not possible to efficiently obtain a high-concentration O ₂ gas.

As one of the means for highly regenerating the adsorbent toward the O ₂ outlet side of the adsorption tower, a purge desorption method of introducing a part of the concentrated and separated O ₂ gas into the adsorption tower has been widely adopted. ing.

The N ₂ gas contained in the air is adsorbed to and desorbed from the adsorbent by increasing / decreasing the N ₂ gas partial pressure PN _2. The partial pressure is PN ₂ = P.
It is generally expressed as (total pressure) × XN ₂ (gas phase N ₂ mole fraction).

The means for lowering PN ₂ is (1)
Method to reduce total pressure P and (2) XN which is N ₂ concentration in gas phase
There are two methods of lowering ₂ , but the depressurizing operation by the vacuum pump corresponds to (1) and the O ₂ purging operation corresponds to (2).

However, when the total pressure P is large, a large amount of O ₂ gas is required for the O ₂ purging operation, which has a bad result of reducing the product O ₂ gas amount. Therefore, conventionally, the O ₂ purge is performed after the pressure inside the adsorption tower is sufficiently reduced.

In FIG. 5, which shows the operation pattern of the conventional PSA oxygen production apparatus, the O ₂ purge operation is performed in the desorption regeneration step. Of the 60 seconds of the desorption / regeneration process, the O ₂ purging effect is exhibited in the latter half of 30 to 40 seconds.

On the other hand, in the operation pattern shown in FIG.
Since the adsorption step, the desorption regeneration step and the O ₂ repressurization step are at the same time, the time for performing the O ₂ purge becomes insufficient, and the desorption regeneration level of the adsorbent, which governs the overall O ₂ yield, is insufficient.

The present invention aims to solve the above problems and provide a PSA mixed gas separation device capable of improving the desorption and regeneration levels of an adsorbent.

[0015]

[Means for Solving the Problems] 1. The present invention comprises an adsorption tower containing an adsorbent bed for selectively adsorbing a specific component gas, and adsorbing the adsorbent gas in the mixed gas to the adsorbent under a pressurized condition reduces the difficulty of adsorbing the adsorbent gas. The adsorbent is desorbed from the adsorbent by desorbing the adsorbent gas from the adsorbent by concentrating and separating, and then decompressing the inside of the adsorption tower with a vacuum pump and decompressing the adsorbent bed with a part of the hardly adsorbed gas concentrated and separated. In the pressure swing type mixed gas separation device for regeneration, between the desorption gas outlet of the adsorption tower and the vacuum pump for decompression, the desorption gas discharge pipe having a switching valve and the desorption gas outlet of the adsorption tower via the switching valve. It is characterized in that the connected desorption gas storage tank is arranged in parallel.

2. Further, the present invention is characterized in that, in the pressure swing type mixed gas separation apparatus of the above 1, the capacity of the desorption gas storage tank is not more than the capacity of the adsorption tower.

[0017]

In the present invention 1, the adsorbent gas is removed from the adsorbent by depressurizing the inside of the adsorption tower with the vacuum pump through the desorption gas discharge pipe and purging the adsorbent bed with the hardly adsorbed gas concentrated and separated. Are effectively desorbed and the adsorbent is regenerated. Moreover, even after this step was completed, the inside of the adsorption tower was connected to the desorption gas storage tank by operating the switching valve, and the adsorbent gas desorbed from the adsorbent was subsequently depressurized by the vacuum pump. N ₂
The gas is sucked into the gas storage tank and discharged from the adsorption tower, so that the purging of the adsorbent bed with the hardly adsorbable gas and the desorption / regeneration of the adsorbent are continued.

Therefore, purging of the adsorbent bed with the hardly adsorbed gas, desorption of the adsorbent gas from the adsorbent and regeneration of the adsorbent are carried out for a long time, and it is possible to sufficiently perform desorption regeneration of the adsorbent. Become.

Further, it is advantageous for sucking the adsorptive gas that the tank capacity has a certain size with respect to the adsorption tower capacity, but it will be described later in relation to the actual discharge amount of the vacuum pump. As described above, setting the tank capacity to be equal to or less than the adsorption tower capacity is effective for sufficiently performing desorption and regeneration of the adsorbent and thus increasing the purity of the hardly adsorbed gas obtained. In the second aspect of the present invention, by setting the capacity for desorption gas storage in the first aspect of the invention to be equal to or less than the capacity of the adsorption tower,
The adsorbent is sufficiently desorbed and regenerated, and the purity of the hardly adsorbed gas obtained can be increased.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. The present example relates to a PSA oxygen production apparatus equipped with three adsorption towers 2A, 2B, and 2C.

N ₂ is contained in the three adsorption towers 2A, 2B and 2C.
An adsorbent bed made of a gas adsorbent is built in, and an air supply line 13 equipped with an original air blower 1 and switching valves 4A, 4B, 4C is connected to the lower part of the adsorption towers 2A, 2B, 2C,
The raw material air pressure-fed by the raw air blower 1 is the adsorption tower 2
The N ₂ gas sent to A, 2B, and 2C is adsorbed by the adsorbent. Waste N ₂ gas line 1 equipped with switching valves 5A, 5B, 5C connected to the bottom of adsorption towers 2A, 2B, 2C
A vacuum pump 3 is provided at 4, and the N ₂ gas adsorbed by the adsorbent is sucked and discharged by the vacuum pump 3.

[0022] A N ₂ gas storage line 15 connected to the upstream side of the vacuum pump 3 with a N ₂ gas storage tank 20 and the switching valve 12 is provided in parallel with the waste N ₂ gas line 14, the N ₂ gas The switching valve 1 is provided on the upstream side of the storage line 15.
Adsorption towers 2A, 2B, 2C through 1A, 11B, 11C
Connected to the bottom of.

Further, an O ₂ gas line 1 equipped with switching valves 6A, 6B and 6C is provided above the adsorption towers 2A, 2B and 2C.
6 are connected to each, such as an O ₂ gas tank (not shown)
Configured to be sent to.

Furthermore, a purge O ₂ gas line 17 having switching valves 7A, 7B, 7C and a switching valve 8 provided on the upstream side, and switching valves 9A, 9B, 9C and a switching valve provided on the upstream side. Second purge O ₂ gas line 18 with 10
But the O ₂ adsorption towers 2A to be placed in parallel with the gas line, 2B, and is connected to 2C of the upper and O ₂ gas line.

Each of the adsorption towers 2A, 2B, 2 in this embodiment
In C, the adsorption step, the O ₂ recompression step, and the desorption regeneration step are sequentially and repeatedly performed with different phases, and in FIG. 1, the adsorption tower 2A is in the adsorption step and the adsorption tower 2B is in the adsorption step. Is in the O ₂ recompression step and the adsorption tower 2C is in the desorption regeneration step. Also, FIG.
In FIG. 1, the open valves of the switching valves in FIG. 1 are open, and the black valves are in the closed state.

FIG. 2 shows an operation pattern in this embodiment. The number of each switching valve in FIG.
2 corresponds to the reference numeral, and the state in which the switching valve is opened in each step shown in FIG. 2 is indicated by hatching.

Further, the operation pattern of the N ₂ gas storage tank 20 and the adsorption tower A (2A) as an example of the adsorption tower is also described in FIG. 2 corresponding to the step numbers. Further, the pressure pattern of the adsorption tower A (2A) is also shown in FIG.

The operation of the adsorption tower A (2A) in this embodiment will be described below with reference to FIG. (1) Step-1: Steps (1-1) and (1-2)
The raw air is pressurized and supplied by the raw air blower 1 from the full-time switching valve 4A, while the air flows through the adsorbent bed of the N ₂ adsorbent, the N ₂ gas is gradually adsorbed and the O ₂ gas is concentrated. , And is discharged outside the tower through the switching valve 6A. (2) Step-2: In the first half step (2-2), the switching valve 5A is opened and the pressure inside the adsorption tower A (2A) is reduced by the vacuum pump 3, so that the pressure drops from point A to point B.

In the next step (2-2), the switching valve 7A is also opened, a part of the separated O ₂ gas is supplied from the top of the column,
A part of the O ₂ gas is N ₂ while purging the adsorbent bed with O _{2.
The 2} gas is desorbed from the adsorbent and is discharged from the adsorption tower A (2A) by the vacuum pump 3 together with the desorbed N ₂ gas. The steps so far are the same as those in the conventional apparatus shown in FIG. (3) Step-3: In the conventional apparatus shown in FIG. 4, O ₂ gas is supplied from the switching valve 9A to raise the pressure in the tower as shown by the broken line in FIG. 7A is kept open during step (3-1) to continue supplying the O ₂ purge gas. During this time, the switching valve 11A of the N ₂ gas storage line 15 is also opened, and the desorbed gas of the adsorption tower A (2A) is sucked and stored in the N ₂ gas storage tank 20. That is, during this time, the adsorbent is desorbed and regenerated by the O ₂ purge, and the pressure moves from point C to point D.

In the next step (3-2), the switching valve 7
A and 11A are closed, the switching valve 9A is opened, the adsorption tower A (2A) is restored to the pressure point A by O ₂ gas, and the next adsorption step is prepared. On the other hand, in the N ₂ gas storage tank 20, the switching valve 11A is closed and the valve 12 is opened, so that the vacuum pump 3 discharges the N ₂ desorption gas inside the tank 20 to the outside of the system.

Although the respective steps in the adsorption tower 2A have been described above, in the adsorption towers 2A, 2B and 2C, the above steps are sequentially repeated with the phases different from each other, and the O ₂ gas is continuously concentrated and separated. Is performed.

As described above, in the present embodiment, the adsorbent desorption / regeneration step is performed in steps (2-1), (2-2),
As compared with the conventional apparatus shown in (3-1) and FIG. 4, the time can be greatly extended, and the O ₂ purge time can be sufficiently taken. Therefore, the regeneration efficiency of the adsorbent can be greatly improved.

Hereinafter, an example of an experiment conducted for this embodiment will be explained.
Reveal Table 1 shows the essential PSA oxygen production equipment.
Then, an experiment was conducted under the operating conditions shown in Table 2. Main experiment
Then N₂Gas storage tank 20 capacity 0-1.25m
³Up to 6 steps, and adjust the volume ratio with the internal volume of the adsorption tower.
I changed it as a meter. The results are shown in Table 3 and FIG.
You

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

As is clear from the results of this experiment, N₂gas
O increases as the volume ratio of the storage tank to the adsorption tower increases.
₂Purity increases sharply, and the present invention is very effective
It is shown. Also, in this volume ratio, 50% is pure O₂
The peak was generated. N ₂Gas storage tank is an adsorption tower
It is considered to be industrially effective range up to the same capacity (100%)
To be N₂True if the gas storage tank gets too big
The actual discharge amount of the empty pump decreases and O₂Not much for improving yield
It is estimated to have no effect.

[0038]

According to the present invention, the desorption gas discharge pipe and the desorption gas storage tank are arranged in parallel between the desorption gas outlet of the adsorption tower and the vacuum pump for decompression, as shown in the claims. Due to the arrangement, as described above, the adsorbent bed can be purged and the adsorbent can be desorbed and regenerated by the concentrated and separated hardly adsorbed gas, which makes it possible to perform purification of the adsorbent having a higher purity than the mixed gas. The characteristic gas can be concentrated and separated.

[Brief description of drawings]

FIG. 1 is a system flow diagram of an embodiment of the present invention.

FIG. 2 is an operation pattern diagram of the embodiment.

FIG. 3 is a graph showing a relationship between a pure O ₂ generation amount and an N ₂ gas storage tank / adsorption tower capacity ratio in an experiment using the same example.

FIG. 4 is a system flow diagram of a conventional pressure swing type oxygen production apparatus.

FIG. 5 is a pressure operation pattern diagram of the conventional pressure swing type oxygen producing apparatus.

[Explanation of symbols]

1 Raw air blower 2A, 2B, 2C Adsorption tower 3 Vacuum pumps 4A-4C, 5A-5C, 6A-6C Switching valves 7A-7C, 9A-9C, 11A-11C, 12 Switching valve 14 Waste N ₂ gas line 15 N ₂ gas storage line 20 N ₂ gas storage tank

Claims (2)

[Claims] 1. A non-adsorbent gas comprising an adsorbent column containing an adsorbent bed for selectively adsorbing a specific component gas, wherein the adsorbent gas in a mixed gas is adsorbed by the adsorbent under a pressurized condition. The adsorbent is desorbed from the adsorbent by desorbing the adsorbent from the adsorbent bed by partially depressurizing the inside of the adsorption tower with a vacuum pump and decompressing the adsorbent bed with a part of the hardly adsorbed gas that has been concentrated and separated. In the pressure swing-type mixed gas separation device for regenerating, the desorption gas outlet of the adsorption tower via the desorption gas discharge pipe having a switching valve and the switching valve between the desorption gas outlet of the adsorption tower and the vacuum pump for decompression. A desorption gas storage tank connected in parallel with the desorption gas storage tank. 2. The pressure swing type mixed gas separation apparatus according to claim 1, wherein the capacity of the desorption gas storage tank is not more than the capacity of the adsorption tower.