JPH0517133Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a pressure swing adsorption device (hereinafter simply referred to as a PSA device) used in the production of high-purity gas. This relates to a PSA device that removes as many components as possible and recovers high-purity product gas. Below is a representative example of how to convert N ₂ from a mixed gas of O ₂ and N _2.
A description will be given of a PSA device that recovers high-purity water, but this should not be construed as limiting the scope of application of the device of the present invention.

[Prior Art] Methods of introducing compressed air into a PSA unit to concentrate and recover _N2 gas can be roughly divided into two categories: a method of adsorbing _O2 gas onto an adsorbent and a method of adsorbing _N2 gas onto an adsorbent. The latter method uses a zeolite adsorbent, adsorbs _N2 gas, and then depressurizes the adsorption tower with a vacuum pump or the like to desorb and recover high-purity _N2 gas. The PSA unit used in this method is described below.

FIG. 2 is a schematic explanatory diagram showing a three-column type PSA device, and the raw material gas (pressurized air) supply pipe 1 connected from the pretreatment device is equipped with an automatic on-off valve (hereinafter simply referred to as valve) V ₁ 〜V ₃ to adsorption towers 3a, 3b,
3c is connected to the bottom of each column, and an exhaust gas waste pipe 4 is connected to the bottom of each column via valves _V4 to _V6 . In addition, desorption pipes 5a, 5b, and 5c are branched from the middle of the exhaust gas waste pipe 4 (upstream of the valves _V4 to _V6 intervening points), and are branched from the exhaust gas disposal pipes 5a, 5b, and 5c on the downstream side via the valves _V7 to _V9, respectively. be merged.
A vacuum pump 6 is provided in the merged desorption tube 5 and connected to a product gas holder 9. The product gas holder 9 is provided with a product gas recovery pipe 2 as well as a cleaning pipe 8 for extracting a part of the product gas for cleaning, and the cleaning pipe 8 is branched and then connected to valves V ₁₃ to V ₁₅ . Adsorption towers 3a, 3b, 3
connected to each top of c. In addition, each adsorption tower 3a, 3
Pressure equalizing pipes 10a and 10 connecting b and 3c in series
b and 10c are provided via valves V ₁₀ to _{V 12} , respectively.

[Problems to be solved by the invention] FIG.
It is a time schedule showing the operation process of the tower,
When the operation steps performed from the start of the adsorption step to the start of the next adsorption step are defined as one step cycle, one step cycle is composed of an adsorption step, a recovery step, a washing step, and a desorption step. First, in the adsorption process, the interior of the desorbed adsorption tower is pressurized, and the raw material gas is supplied under pressure from the supply pipe 1 to remove the target components.
_N2 gas is adsorbed on an adsorbent and impure component gas (mainly
O ₂ gas) is released from the exhaust gas waste pipe 4. In the desorption process, the adsorption tower and the product gas holder 9 are communicated via the vacuum pump 6 and the desorption pipe 5, and the pressure inside the adsorption tower is reduced to desorb the N ₂ adsorbed by the desorbent and store it in the product holder 9. .

Further, the recovery step and the washing step will be explained using the adsorption tower 3a as an example, as shown in FIGS. 4a and 4b. That is, in the state shown in FIG. 4a, the high-purity N ₂ gas supplied from the product gas holder 9 passes through the cleaning pipe 8 to expel the residual O ₂ in the adsorption tower 3c, and the adsorption tower 3a after the adsorption process is completed. It is sent to via the pressure equalization piping 10c. As a result, adsorption tower 3
In a, a recovery process is performed, and in the adsorption tower 3c, a cleaning process is performed. Next, in the state shown in FIG. 4b, the adsorption tower 3a performs a cleaning process, and the adsorption tower 3b performs a recovery process.

The adsorption tower 3a that has undergone the cleaning process shown in FIG. Not only that, but the gas remaining in the pipe connected to the adsorption tower 3a (up to the point where it is shut off by the valve) is also drawn in (as shown by arrow _X1 in FIG. 2). Therefore, if low-purity _N2 gas remains in the pipe,
This causes a problem in that the purity of the product N ₂ gas collected in the product gas holder 9 is reduced. Pressure equalizing pipes 10a to 10 used especially during the recovery process
The low-purity N ₂ gas remaining in c is a large amount and is not purified and eliminated in the cleaning process, so it is a major factor in reducing the purity of the product N ₂ gas.

Therefore, the inventor of the present invention attempted to remove low-purity substances during the adsorption tower desorption process.
As a result of various research efforts to develop a device that does not contain and recover N ₂ gas, we have completed the PSA device of this invention.

[Means for Solving the Problems] The PSA device of the present invention, which has achieved the above object, has one end of the pressure equalizing pipe connected to the cleaning pipe immediately below the automatic opening/closing valve downstream of the pressure equalizing pipe. The main feature is that a purifying pipe for replacing the inside with cleaning gas is connected, and an automatic opening/closing valve is provided near the connection part of the purifying pipe with the pressure equalizing pipe.

[Function] In the present invention, a purification pipe is installed to connect the downstream side of the automatic on-off valve of the pressure equalization pipe to the cleaning pipe, and an automatic on-off valve is installed on the pressure equalization pipe side, which is the downstream position of the purification pipe. establish. Then, at the start of the adsorption tower cleaning process (after the recovery process is completed), the automatic on-off valve installed in the purification pipe is opened, and the low-purity gas remaining in the pressure equalization pipe is removed.
By expelling the gas into the adsorption tower that is about to proceed to the cleaning step, the pressure equalizing pipe is replaced with high-purity cleaning gas. Therefore, when the adsorption tower and the piping connected to it are depressurized during the desorption process, low-purity gas will not mix with the product gas and be recovered to the product holder, and as a result, the recovered product gas will have high purity. It becomes possible to achieve this. Note that impurity components are removed from the inside of each adsorption tower by high-purity gas sent through a cleaning pipe.

[Example] FIG. 1 is a schematic explanatory diagram showing a typical example of a PSA device of the present invention, and the differences from the conventional PSA device shown in FIG. 2 are as follows. That is, the valves V 10 to _{V 12 of} the pressure equalizing pipes 10a, 10b, 10c connect two adsorption towers 3a, 3b, 3c in series.
The purifying pipes 11a to 11c are connected to the downstream side of the pipes 11a to 11c (the gas flow direction when using the pressure equalizing pipes 10a to 10c is as shown by arrows _Y1 to _Y3 ), and the purifying pipes 11a to 11c and other The end side is connected to the cleaning pipe 8,
Valves _V13 to _V15 are arranged in the purification pipes 11a to 11c.

FIG. 5 shows a time schedule for using such a PSA device. That is, a purification step is provided after the recovery step and before the start of the cleaning step. The cleaning step may be performed independently as a single step, or may be performed concurrently during the initial stage of the cleaning step.

FIG. 6 is a schematic explanatory diagram when the purification process in the adsorption tower 3a is performed simultaneously with the washing process. The cleaning N ₂ gas for the cleaning process is directly introduced into the adsorption tower 3a from the cleaning pipe 8, while a part of the cleaning N ₂ gas passes from the cleaning pipe 8 to the purification pipe 11c and reaches the pressure equalization pipe 10c. From the pressure equalization pipe 10c to the adsorption tower 3a
be led to. At this time, the low-purity _N2 gas remaining in the pressure equalization pipe 10c is transferred to the adsorption tower 3a and the pressure equalization pipe 1
The gas that passes through the adsorption tower 3b and is not adsorbed in the adsorption tower 3b is discharged from the exhaust gas waste pipe 4.

Example A PSA device with the structure shown in Fig. 1 was prototyped, and
An experiment was conducted to selectively recover N ₂ gas from a mixed gas consisting of N ₂ gas (79%) and O ₂ gas (21%) according to the process shown in the figure. The size of the adsorption tower is 450 mm in inner diameter.
mm, height 2000 mm, and synthetic zeolite type 5A adsorbent was used.

The raw material gas has an adsorption pressure of 4.0Kg/cm ² G and 70Nm ³ /
h, and the desorption pressure is 0.1Kg/cm ² G.
The one-step cycle time of the adsorption tower (the time from the start of adsorption to the start of the next adsorption) was set to 3 minutes.

As a result, the conventional PSA device shown in Figure 2
_N2 gas purity of 99.997% can now be achieved at 99.999%, using cryogenic air separation equipment.
The same purity as that used for N ₂ gas recovery was obtained. Also, when using the PSA device of this invention, N ₂
The gas recovery rate was over 40%, which was almost the same as the recovery rate when using a conventional PSA device.

The above example has been explained by showing an example of N ₂ gas concentration recovery, but the present invention is also applicable to H ₂ gas recovery in addition to N ₂ gas recovery.
It is also applied to gas recovery, CO gas recovery, etc.

[Effects of the invention] By using the PSA device of the present invention, it has become possible to obtain a highly purified target component gas without reducing the recovery rate of the target component.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram showing a typical embodiment of the present invention, Fig. 2 is a schematic explanatory diagram showing a conventional PSA device, and Fig. 3 is a schematic explanatory diagram showing the process when using the conventional PSA device. Figure 4a and b are the adsorption tower 3a.
Fig. 5 is a schematic illustration showing the process when using the PSA device of the present invention, and Fig. 6 is an explanation showing the state of the purification process using the PSA device shown in Fig. 1. It is a diagram. 1... Raw material gas supply pipe, 2... Product gas extraction pipe, 4... Exhaust gas disposal pipe, 5... Desorption pipe, 6...
...Vacuum pump, 8...Cleaning pipe, 9...Product gas holder, 10a, 10b, 10c...Pressure equalization piping,
11a, 11b, 11c...Purification pipe, _V1 to _V19 ...
...Automatic on-off valve.

Claims (1)

[Scope of utility model registration request] In addition to installing multiple adsorption towers in parallel, each adsorption tower is connected to a cleaning pipe to feed high-purity gas.
A pressure swing adsorption device in which two adsorption towers selected from the group of adsorption towers are connected to each other by a pressure equalization pipe through which washed exhaust gas flows, and the pressure equalization pipe is provided with an automatic opening/closing valve. , a purification pipe is connected to the cleaning pipe at one end thereof to replace the inside of the pressure equalization pipe with cleaning gas, directly below the automatic opening/closing valve downstream of the pressure equalization pipe, and the pressure equalization pipe in the purification pipe is A pressure swing adsorption device characterized in that an automatic opening/closing valve is provided near the connection part with the pressure swing adsorption device.