JPH01307425A - Pressure-swinging adsorber - Google Patents

Abstract

PURPOSE:To enhance the purity of a recovered component gas by providing a gas holder between a regenerating gas inlet pipe provided in a pretreating device and a waste gas discharge pipe furnished to a pressure-swinging adsorption tower. CONSTITUTION:Raw air is compressed by a compressor 9, and sent to one between pretreating towers 2a and 2b. The H2O and CO2 in the air are adsorbed in the tower, and the remainder is sent to one among pressure-swinging adsorption towers 3a-3c through a temporary storage holder 11 to adsorb N2. The waste gas consisting essentially of O2 is transiently stored in a waste gas holder 12. Meanwhile, the adsorption towers 3a-3c are purged by the product N2 from a product gas holder 20, and then N2 is desorbed by a vacuum pump 6 and recovered in the product gas holder 20. The waste gas stored in the waste gas holder 12 is used as the purge gas for the pretreating towers 2a and 2b.

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 more specifically, to a pressure swing adsorption device (hereinafter simply referred to as a PSA device) used for producing high-purity gas. This article relates to a PSA device that can prevent as much as possible the contamination of impure components from the pretreatment device into the recovered gas and recover high-purity product gas when a pretreatment device is installed to remove impure components. be. In the following description, a PSA device for recovering N and gas from feed air with high purity will be described as a typical example thereof, but the scope of application of the device of the present invention should not be construed as limited by this.

[Prior Art] FIG. 2 is a schematic explanatory diagram of a pretreatment device R and a gas recovery device constructed on top of a PSA device that selectively adsorbs and recovers N2 gas. The raw air pressurized by the compressor 9 of the pretreatment device R is sent to either the pretreatment tower 2a or 2b, and the adsorbent in the tower adsorbs N20 and CO2 components, and the 02 /N2 mixed gas in 3-column type P
The pretreatment tower 2a shown in FIG. 4 is fed to the SA device P.

2b is an explanatory diagram showing the step 2b, in which an adsorption step and a desorption step are performed periodically. FIG.

The mixed gas that has been supplied to the PSA apparatus through the process gas outlet pipe 21, the storage holder 11 and the raw material gas inlet pipe 1a is transferred to the adsorption tower via automatic on-off valves (hereinafter simply referred to as valves) V+ to V. 3a, 3b.

3.C. An exhaust gas waste pipe 4a is connected to the bottom of each adsorption tower through valves v4 to v6, and the exhaust gas waste pipe 4a is connected to the pretreatment towers 2a and 2b through a regeneration gas introduction pipe 21 and valves 27 and 28. and adsorption tower 3a
, 3b, 3c, the exhaust gas whose main component is 0, is
It is used as a purge gas for desorption of H, O, and CO2 adsorbed in the pretreatment tower. In addition, adsorption towers 3a, 3b,
A desorption pipe 5 is connected to the bottom of 3c via a branch pipe, and the N2 gas desorbed by the vacuum pump 6 is stored in the product gas hole i20. The product gas holder 20 is provided with a cleaning pipe 8 for extracting a part of the product gas for cleaning, and the cleaning pipe 8 is connected to the adsorption tower 3a via branched vent valves V13 to VIS.

It is connected to the tops of 3b and 3c. In addition, each adsorption tower 3a, 3
b, 3c are continuous piping 10a, 1ob.

They are also connected in series by 10c.

FIG. 3 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.

[Problem N to be solved by the invention] Figure 5 shows the gas flow (
Fig. 6 is an explanatory diagram showing the gas flow (indicated by the broken line arrow) and the gas flow (indicated by the solid line arrow) during the adsorption process. From opening to leap, reverse valve Z4.
Za is switched from leap to open at almost the same time, and the raw air is compressed by compressor 9 to 4.0 kg/cm"G.
Even if the valves z6 and 26 are opened and closed at the same time, some of the pressurized gas will slip through the valve Za and enter the exhaust gas waste pipe 4a, causing a backflow as shown by arrows L+ and Lx. do. In particular, as PSA devices become smaller and vacuum solenoid valves are used as automatic open/close valves, most of the valves have directional properties for blocking gas flow, and for preventing backflow of gas. Since leaks are likely to occur due to the seal structure, there is a very high possibility that a portion of the pressurized gas during the adsorption process will leak to the exhaust gas waste pipe 4a side.

If a large amount of 02/N2 mixed gas enters the exhaust gas waste pipe 4a due to the above leak, the leak gas has a higher pressure than the exhaust gas in the waste gas waste pipe 4a, so any of the adsorption towers 3a, 3b, and 3c You can easily reach the inside of the tower. This is because, as shown in Fig. 3, the adsorption process is carried out in one of the adsorption towers throughout the entire time, and the recovery process is also carried out intermittently.
This is because any of V4 to V6 are alternately in the open state.

As a result, the amount of impurity components remaining in the adsorption towers 3a, 3b, and 3c would increase, and it was thought that it would be difficult to increase the purity of the final product gas.

Therefore, the present inventors removed the adsorption towers 3a and 3b from the pretreatment device R.
, 3c and to improve the purity of the recovered component gas, the present invention was completed after conducting various researches.

[Means for Solving the Problems] The present invention, which has achieved the above object, has a regeneration gas inlet pipe and a pressure swing installed in the pretreatment tower in order to prevent the backflow of impurity components from the pretreatment device to the pressure swing adsorption tower. The fact that a gas holder was installed between the flue gas waste pipes installed in the swing adsorption tower
This is a summary.

[Operations and Examples] FIG. 1 is a schematic explanatory diagram showing a typical example of the present invention. The characteristic configuration different from the conventional example shown in Fig. 2 is as follows:
The point is that an exhaust gas holder 12 is provided between the regeneration gas introduction pipe 22 and the exhaust gas waste pipe 4a. The exhaust gas containing 02 as a main component that has passed through the adsorption towers 3a, 3b, and 3c during the adsorption step in the PSA device and the exhaust gas during the recovery step are temporarily stored in the above-mentioned exhaust gas holder 12, and then transferred to the pretreatment tower 2.
Used as a purge gas for CO□ and H2O in a and 2b.

Furthermore, the pressurized 0□/N2 mixed gas leaking or flowing back through the valves Zy and Za of the pretreatment device R is
Introduced into the exhaust gas holder 12, the mixed gas is expansively depressurized and decelerated within the exhaust gas holder 12. Therefore, this mixed gas is absorbed into the adsorption towers 3a, 3b, 3c.
No more backflow to the inside, N2 gas recovery P
There is no longer any negative impact on the recovered N2 gas concentration of SA equipment P.

(Experiment example) Pretreatment tower inner diameter: 50 mm Pretreatment tower height: 1000+am Pretreatment tower adsorbent: Synthetic zeolite 13X type and silica gel Feedstock air supply amount: 320ONjl/h Feedstock air supply pressure: 5. Okg/cm2G adsorption tower inner diameter
=80fflII Adsorption tower height: 1000mm Adsorption tower adsorbent Bisynthetic zeolite type 5A desorption pressure
: 100 Torr Product N2 recovery amount: 80 ONj2/h The apparatus shown in FIGS. 1 and 2 was operated continuously under the above conditions, and the N2 gas purity in the product gas holder 20 was compared.

As a result, in the conventional apparatus shown in FIG. 2, the upper limit of N2 gas purity was 99.9%, but in the apparatus of the present invention shown in FIG. 1, it was possible to achieve 99.99% or more.

[Effects of the Invention] The present invention prevents impurity components from entering the PSA device from the pretreatment device, making it possible to achieve high purity of the components to be recovered.

[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 an explanatory diagram showing the adsorption tower process, and Fig. 4 is a pretreatment tower. An explanatory diagram showing the process of
FIG. 5 is an explanatory diagram showing the gas flow in the pretreatment device.

Claims (1)

[Claims] A process gas outlet pipe provided in the pretreatment tower is connected to a raw material gas introduction pipe provided in the pressure swing adsorption tower, and an exhaust gas waste pipe provided in the pressure swing adsorption tower is connected to a regeneration gas introduction pipe provided in the pretreatment tower. 1. A pressure swing adsorption device comprising: a gas holder for preventing backflow of regeneration gas; a gas holder is disposed between the exhaust gas disposal pipe and the regeneration gas introduction pipe;