JPH0331487B2 - - 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 can perform

A PSA device for recovering N ₂ gas with high purity from raw material air will be described below as a representative example, but this should not be construed as limiting the scope of application of the device of the present invention.

[Prior art] Methods for concentrating and recovering N ₂ gas by introducing pressurized air into a PSA device can be roughly divided into methods in which O ₂ gas is removed by adsorption to an adsorbent, and methods in which N ₂ gas is removed by adsorption to an adsorbent. It is classified into two methods: adsorption and further desorption and recovery. The latter method uses a synthetic zeolite-based adsorbent for N ₂ gas adsorption, and depressurizes the adsorption tower after adsorbing N ₂ gas to desorb and recover high-purity N ₂ gas. be done
The PSA device will be explained.

Figure 2 shows H ₂ O and
After removing CO ₂ , the O ₂ /N ₂ mixed gas is transferred to a three-column system.
FIG. 2 is a schematic explanatory diagram of a device that selectively recovers N ₂ gas by supplying it to a PSA device.

The air pressurized by the compressor 9 is sent to the pretreatment tower 2
a or 2b, H ₂ O and CO ₂ components are adsorbed on the adsorbent housed in the tower, and the O ₂ /N ₂ mixed gas that has passed through is sent to the three-column PSA device. The raw material gas is fed into the raw material gas supply pipe 1a. The raw material gas supply pipe 1a is an automatic opening/closing valve (hereinafter simply referred to as a valve) V ₁ to _{V 3}
are connected to adsorption towers 3a, 3b, and 3c via valves _V4 to _V6 at the bottom of each tower.
a are connected. The exhaust gas waste pipe 4a is connected to pretreatment towers 2a, 2b, and adsorption towers 3a, 3b, 3c.
The exhaust gas mainly composed of O ₂ gas that has passed through is used as a purge gas for desorption of H ₂ O and CO ₂ adsorbed in the pretreatment tower. Further, desorption pipes _5a , 5b, 5c are provided at the bottoms of the adsorption towers 3a, 3b, 3c upstream from the intervening points of the valves V4 _{to V6 ,} respectively.
It is joined downstream via ~V ₉ . The combined desorption tube 5 is provided with a vacuum pump 6 and connected to the product gas holder 20 to store the desorbed and recovered high-purity N ₂ gas. Product gas holder 2
0, a cleaning pipe 8 is disposed, and the cleaning pipe 8 is branched and then connected to the adsorption towers 3a and 3a through valves _V13 to _V15 .
It is connected to each top of 3b and 3c. Also, adsorption tower 3
a, 3b, 3c are connecting pipes 10a, 10b, 10
c, each connected in series by a valve V ₁₀
~V ₁₂ is provided.

Figure 3 is an example of a time schedule (time progresses from left to right) showing the operating steps of the adsorption towers 3a, 3b, and 3c. It is a cycle. As shown in the figure, this one-step cycle consists of an adsorption step, a recovery step, a washing step, and a desorption step. First, in the adsorption step, the inside of the adsorption tower after desorption is pressurized, and O ₂ /N ₂ mixed gas is supplied under pressure from the supply pipe 1a, so that the N ₂ gas, which is the target component to be recovered, is adsorbed on the adsorbent, and the impurity component gas (main component gas) is and O ₂ gas) is released through the exhaust gas waste pipe 4a. In the desorption step, the adsorption tower is depressurized by the vacuum pump 6, and N ₂ adsorbed by the adsorbent in the adsorption tower is desorbed and collected and stored in the product gas holder 20 through the desorption pipe 5.
Next, the recovery step and the washing step will be explained using the adsorption tower 3a as an example, as shown in FIGS. 5a and 5b. That is, in the state shown in FIG. 5a, high-purity N ₂ gas supplied from the product gas holder 20 passes through the cleaning pipe 8 to expel residual O ₂ in the adsorption tower 3c, and the adsorption tower after the adsorption process is removed. 3a via the connecting pipe 10c. At this time, a recovery process is performed in the adsorption tower 3a, and a washing process is performed in the adsorption tower 3c. In addition, in the state shown in Figure 5b,
The adsorption tower 3a is shown performing a cleaning process, and the adsorption tower 3b is shown performing a recovery process.

[Problem to be solved by the invention] The above-mentioned PSA equipment is being miniaturized so that it can be used in home production even in small-scale industrial fields. However, small and inexpensive vacuum solenoid valves have come into use.

FIG. 6 is an explanatory cross-sectional view showing an example of a vacuum electromagnetic valve, in which a valve body 24 is provided at the tip of a plunger 23 that slides when the electromagnetic coil 21 is excited, and a valve seat 2 is provided.
It is configured so that it can come into contact with and separate from 7. FIG. 4 is an explanatory diagram showing the state during the desorption process of the adsorption tower 3b using the PSA apparatus in which the vacuum electromagnetic valves Z ₁ and Z ₂ having the above configuration are provided in the connecting pipes 10a and 10b. At this time, the pressure inside the adsorption tower 3b is reduced to about 100 Torr by the vacuum pump 6, and this reduced pressure region is shut off by the vacuum electromagnetic valves Z ₁ and Z ₂ . However, although the vacuum solenoid valves Z ₁ and Z ₂ described above exhibit effective blocking performance against gas flow in the direction of the white arrow F ₁ →F ₂ shown in FIG. With respect to gas flow in the opposite direction, the valve body 24 is only held down by the repulsive force of the spring 22, so it is likely to be pushed back from the valve seat 27 and cause gas leakage. That is, in the example shown in FIG. 4, leakage tends to occur in the direction of arrow P, and the O ₂ /
_N2 gas gets mixed into the desorption gas, causing a decrease in the purity of the recovered product gas.

Therefore, the present inventors conducted various studies and completed the present invention with the aim of making it possible to recover high-purity product gas even with a PSA device that uses a small and inexpensive vacuum electromagnetic valve.

[Means for Solving the Problems] The PSA device of the present invention that achieves the above objects has the following features:
The gist is that a pair of vacuum electromagnetic valves are arranged in series near both ends of the connecting pipe so that their inlet sides are back to back.

[Operations and Examples] FIG. 1 is a schematic explanatory diagram showing a typical example of the present invention, in which each connecting pipe 10a, 10b, 10c
have two vacuum solenoid valves X ₁ to X ₃ and Y ₁ to _{Y 3} respectively.
will be placed. The vacuum electromagnetic valves Y ₁ to Y ₃ are provided as close as possible to the bottom side of the adsorption towers 3a, 3b, and _3c , and _the outlet portions 26 (sixth
(Fig.) is disposed toward the bottom of the adsorption towers 3a, 3b, and 3c. The one-way valves X ₁ to X ₃ are arranged in opposite directions to the above-mentioned valves Y ₁ to _{Y 3} . That is, in the connecting pipe 10a, the vacuum electromagnetic valves X ₁ and Y ₁ are provided with their inlets 25 facing each other, and their opening and closing operations are controlled in the same manner at the same timing. Therefore, even if gas leaks in the direction of arrow L (see Fig. 6) from the solenoid valve _X1 during the desorption process of the adsorption tower 3a, this gas flow is completely blocked by the solenoid valve _Y1 on the adsorption tower 3a side, and the adsorption tower During the desorption step 3a, the O ₂ gas in the adsorption towers 3b and 3c does not get mixed in at all.

(Example) In a small PSA device with the configuration shown in Figures 1 and 2, the raw air supply amount was 3200N/h.
An experiment in which N ₂ gas was supplied at 5.5 Kg/cm ² G and recovered at 800 N/h was conducted using the following PSA device.

Adsorption tower inner diameter: 80 mm Adsorption tower height: 1000 mm Adsorbent: Synthetic zeolite 13X type (improved type) Desorption pressure: 100 Torr As a result, in the conventional PSA device (shown in Figure 2), the purity of recovered N ₂ gas is 99.9 %, but in the PSA device of the present invention, the limit was 99.997%.
% high purity was achieved.

The locations where the two vacuum solenoid valves are arranged in series as described above are not limited to the above embodiments, and the locations where the automatic on-off valves V ₄ to V ₆ provided in the exhaust gas disposal pipe 4a and other automatic on-off valves are provided. May be applied to Further, the present invention is not limited to the PSA device for separating recovered gas, but may be applied to a pretreatment device provided upstream of the PSA device. Furthermore, in addition to the above example of N ₂ gas recovery, O ₂
It can also be applied to PSA equipment for gas recovery, _H2 gas purification, etc.

[Effect of the invention] According to the present invention, a small vacuum solenoid valve is applied.
PSA equipment has also become able to recover product gas with high purity.

[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 example, Fig. 3 is a process explanatory diagram, and Fig. 4 shows the desorption process state of the adsorption tower 3b. FIGS. 5a and 5b are explanatory views showing the cleaning process and the recovery process, and FIG. 6 is a cross-sectional view showing an example of a vacuum electromagnetic valve. 1a... Raw material gas supply pipe, 2a, 2b... Pretreatment tower, 3a, 3b, 3c... Adsorption tower, 4a... Exhaust gas disposal pipe, 5... Desorption pipe, 6... Vacuum pump, 8... Cleaning pipe, 9... Compression machine, 10a, 10b, 10c...connection piping, 20...casing, 21...coil, 22
...Spring, 23...Plunger, 24...Valve body,
25... Inlet part, 26... Outlet part, 27... Valve seat.

Claims (1)

[Claims] 1. In a pressure swing adsorption device configured such that a raw material gas supply pipe, a desorption pipe, and a cleaning pipe are connected to each of a plurality of adsorption towers, and two adsorption towers are connected in series with each other by a connecting pipe, A pressure swing adsorption device characterized in that a pair of vacuum electromagnetic valves are arranged in series near both ends of the connecting pipe so that the inlet sides are back to back.