JPH048086B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] 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, and in particular, 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 be recovered at a high rate.

A PSA device for recovering N ₂ gas with high purity from feed air will be exemplified below, but this should not be construed as limiting the scope of application of the device of the present invention.

[Prior Art] Fig. 3 shows an N ₂ gas system comprising a pretreatment device R and a PSA device P that selectively adsorbs and recovers N ₂ gas.
FIG. 2 is a schematic explanatory diagram of a gas recovery device. Pretreatment device R
The raw air pressurized by the compressor 9 is sent to either the pretreatment tower 2a or 2b and is applied to the adsorbent.
After adsorbing H ₂ O and CO ₂ components, the O ₂ /N ₂ mixed gas that has passed through this is sent to the three-column PSA device P. FIG. 6 is an explanatory diagram showing the steps of the pretreatment towers 2a and 2b, in which adsorption steps and desorption steps are carried out periodically and alternately.

Pretreated gas outlet pipe 21, temporary storage holder 11
The mixed gas supplied to the PSA device P via the raw material gas supply pipe 1a is passed through the adsorption towers 3a, 3b, ₃ via automatic on-off valves (hereinafter simply referred to as valves) _V1 to V3.
c. Valve at the bottom of each tower
The exhaust gas waste pipe 4a is connected via V ₄ to _{V 6} ,
The exhaust gas waste pipe 4a is connected to the regeneration gas introduction pipe 22 of the pretreatment towers 2a, 2b, and
The exhaust gas mainly composed of O ₂ that has passed through b and 3c is used as barge gas for desorption of H ₂ O and CO ₂ adsorbed in the pretreatment tower. Also, adsorption tower 3
A desorption tube 5 is connected to the lower part of a, 3b, and 3c via a branch pipe, and is desorbed by a vacuum pump 6.
N ₂ gas is stored in the product gas holder 20 . A cleaning pipe 8 is installed in the product gas holder 20,
After the cleaning pipe 8 is branched, it is connected to the tops of the adsorption towers 3a, 3b, and 3c via valves _V13 to _V15 . Each adsorption tower 3a, 3b, 3c is connected to a connecting pipe 10.
They are also connected in series by a, 10b, and 10c.

FIG. 4 is an explanatory diagram showing the operating steps of the adsorption towers 3a, 3b, and 3c, and the operating steps from the start of the adsorption step to the end of the desorption step are defined as one step 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. In the adsorption process, the interior of the adsorption tower after desorption is completed is pressurized, and O ₂ /N ₂ mixed gas is supplied under pressure from the supply pipe 1a, so that the target N ₂ gas 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 and the pretreatment device R. In the desorption step, the adsorption tower is depressurized by the vacuum pump 6, and the 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 case of adsorption etc. 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 is supplied to the adsorption tower 3c through the cleaning pipe 8, the residual O ₂ component in the tower is expelled, and the adsorption tower 3a is connected to the adsorption tower 3a where the adsorption process has been completed. The N ₂ component in the cleaned exhaust gas is recovered by sending it through the 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 the state shown in FIG. 5b, the adsorption tower 3a performs a cleaning process, and the adsorption tower 3b performs a recovery process.

[Problem to be solved by the invention] At the initial stage of the adsorption process, the adsorption towers 3a, 3
The concentration of the N ₂ component in the exhaust gas that has passed through b and 3c is relatively low, and even if the exhaust gas is released as a purge gas for regeneration of the pretreatment device R, the recovery rate of the product N ₂ gas will not be significantly reduced.

However, although the exhaust gas flowing into the exhaust gas waste pipe 4a in the recovery process passes through two adsorption towers in series [shown in Figure 5 a and b] after the adsorption process, the concentration of N ₂ gas is high ( (approximately 90%), and if this exhaust gas is released via the pretreatment device R, the recovery rate of N ₂ gas will be significantly reduced. In addition, _N2 in the exhaust gas at the end of the adsorption process
Gas concentration is also relatively high, and dissipating this leads to a decrease in recovery rate.

Therefore, the present inventors have completed various studies with the aim of improving the recovery rate while maintaining the concentration of the target component gas to be recovered at a high purity, and have completed the present invention.

[Means for Solving the Problems] The present invention, which has achieved the above object, has a structure in which the pipe connecting the exhaust gas waste pipe and the regeneration gas introduction pipe is branched into two systems, and further joined together, and the pressure swing is The gist is that a recovery adsorption tower containing an adsorbent for adsorbing the recovered component gas in the adsorption tower is provided in one of the two systems.

[Operations and Examples] Fig. 1 is a schematic explanatory diagram showing a typical embodiment of the present invention.Compared with the conventional example shown in Fig. 3, the characteristic configuration of the present invention is as follows. . That is, the exhaust gas waste pipe 4a and the regeneration gas introduction pipe 22 are connected in parallel by two systems: the bypass pipe 12 and the recovery adsorption tower pipe 13, and the recovery adsorption tower pipe 1
3 is provided with a recovery adsorption tower 14 and valves X ₂ and X ₃ , and the bypass pipe 12 is provided with a valve X ₁ . The recovery adsorption tower 14 is loaded with synthetic zeolite that selectively adsorbs _N2 , which is the target component to be recovered.

The bypass pipe 12 and recovery adsorption column pipe 13 are used as shown in FIGS. 2A to 2C. That is, when there is little _N2 component in the exhaust gas passing through the exhaust gas waste pipe _4a , valves X _{2 and} 22 to the pretreatment towers 2a and 2b.

On the other hand, when the recovery process is performed in any of the adsorption towers 3a, 3b, and 3c (see Fig. 4),
Alternatively, in the latter stage of the adsorption process, that is, when high concentration N ₂ gas is mixed in the exhaust gas flowing in the exhaust gas disposal pipe 4a, valve X ₁ is closed and valves X ₂ and X ₃ are opened, as shown in FIG. 2B. As shown in the figure, the exhaust gas is introduced into the recovery adsorption tower 14, the N ₂ component in the exhaust gas is adsorbed by the adsorbent, and only the gas that has passed through the recovery adsorption tower 14 is led to the regeneration gas introduction pipe 22.

The above-mentioned opening _/ closing control of the valves X ₁ to _{X 3} may be controlled temporally in accordance with the process schedule shown in FIG. Valve depending on the detection value of the measuring device
It may be configured so that opening and closing of X ₁ to _{X 3} can be controlled.

Further, the N ₂ component adsorbed in the recovery adsorption tower 14 is desorbed by the method described below to regenerate the adsorbent and recover the N ₂ component again. That is, as shown in FIG. 2C, the adsorption tower (for example, 3a) and the recovery adsorption tower 14 are in a reduced pressure state after the desorption process is completed.
are communicated by opening valves X ₂ and V ₄ .
At this time, valves X ₁ and X ₃ are closed. Through this operation, the adsorbent in the recovery adsorption tower 14 is regenerated under reduced pressure, and the desorbed N ₂ component is adsorbed in the adsorption tower 3a and recovered again. After this operation, the adsorption process is started in the adsorption tower 3a, and the operation is repeated according to the process sequence shown in FIG.

Note that the method for regenerating the recovery adsorption tower 14 is not limited to the above example; a vacuum pump and a gas holder are separately connected in series to the recovery adsorption tower 14, and when the recovery adsorption tower 14 is not in use, the pressure is reduced to desorb the _N2 component. The gas holder and the adsorption towers 3a, 3b, 3c may be connected via separate piping, and the gas may be fed to the adsorption towers 3a, 3b, 3c at any point in the adsorption process. do not have.

Further, a gas holder for storing exhaust gas is provided downstream of the confluence of the bypass pipe 12 and the recovery adsorption tower piping 13 on the side of the regeneration gas introduction pipe 22, and the gas holder is provided for storing exhaust gas. At the same time, the pressure of the O ₂ /N ₂ mixed gas that may flow back through valves Z ₇ and Z ₈ is reduced to prevent it from flowing back to the adsorption towers 3a, 3b, and 3c. It is recommended that you do so.

(Experimental Example) Using the apparatus shown in FIGS. 1 and 3, an N ₂ gas recovery experiment was conducted under the following conditions, and the N ₂ gas recovery rates were compared.

Pretreatment tower inner diameter: 50mm Pretreatment tower height: 1000mm Pretreatment tower adhesive: Synthetic zeolite 13X type and silica gel Raw air supply amount: 3200N/h Raw material air supply pressure: 5.0Kg/cm ² G Adsorption tower inner diameter: 80mm Adsorption Column height: 1000 mm Adsorption tower adsorbent: Synthetic zeolite 5A type Desorption pressure: 100 Torr According to this experiment, the recovery rate was about 25% with the conventional device shown in Figure 3, but the recovery rate with the device of the present invention was We were able to increase the rate to 36%. In both devices, the purity of the recovered N ₂ gas was 99.99%.

[Effects of the Invention] According to the present invention, the concentration of the target component to be recovered remains high in purity, and the recovery rate of product gas can be improved compared to conventional devices.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram showing a typical embodiment of the present invention, Fig. 2 A, B, and C are explanatory diagrams showing the operating state of the device of the present invention, and Fig. 3 is a schematic explanatory diagram showing an example of a conventional device. Figure 4 is an explanatory diagram showing the process of the adsorption tower shown in Figure 3, Figures 5a and b are explanatory diagrams showing the cleaning process and recovery process, and Figure 6 is an explanatory diagram showing the process of the pretreatment tower. It is. 1a... Pressurized raw material gas introduction pipe, 2a, 2b...
Pretreatment tower, 3a, 3b, 3c... adsorption tower, 4a...
...Exhaust gas waste pipe, 6...Vacuum pump, 8...Cleaning pipe, 9...Compressor, 10...Product gas holder,
10a, 10b, 10c...connection piping, 12...
Bypass pipe, 13... Exhaust gas holder, 14... Recovery adsorption tower, 21... Pretreated gas outlet pipe, 22...
...Gas introduction pipe for regeneration.

Claims (1)

[Claims] 1 Connect the pretreated gas outlet pipe provided in the pretreatment tower and the pressurized raw material gas introduction pipe provided in the pressure swing adsorption tower, and connect the exhaust gas waste pipe provided in the pressure swing adsorption tower and the regeneration gas provided in the pretreatment tower. In a pressure swing adsorption device formed by connecting inlet pipes, the pipe connecting the waste gas waste pipe and the regeneration gas inlet pipe is branched into two systems, which are then recombined, and the collected component gas in the pressure swing adsorption tower is A pressure swing adsorption apparatus characterized in that a recovery adsorption tower containing an adsorbent for adsorbing is provided in one of the two systems.