JP2009006256A - Oxygen enricher - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxygen enricher which can inhibit the diffusion of moisture to an adsorption cylinder during a shutdown. <P>SOLUTION: This oxygen enricher 1 comprises a compressor 2 for compressing air, a plurality of adsorption cylinders 3a and 3b filled with an adsorbent a3 for adsorbing nitrogen selectively, and a switching means 4 for making the adsorption cylinders 3a and 3b adsorb nitrogen by alternately supplying the compressed air from the compressor 2 to each adsorption cylinder 3a and 3b, and on the other hand, making the adsorption cylinders 3a and 3b desorb/exhaust the nitrogen. In addition, moisture absorption cylinders 7a and 7b filled with a moisture absorbent "m" which absorbs moisture from the compressed air, are arranged independently between the switching means 4 and each adsorption cylinder 3a and 3b. Further, shut-off valves 8a and 8b which open during operation to enrich oxygen and close to shut off the penetration of moisture into the adsorption cylinders 3a and 3b during operation stoppage, are arranged between the moisture absorption cylinders 7a and 7b and each adsorption cylinder 3a and 3b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oxygen concentrator that concentrates oxygen in air and supplies high-concentration oxygen.

  An oxygen concentrator includes a plurality of adsorption cylinders filled with an adsorbent that selectively adsorbs nitrogen and uses a pressure swing adsorption (PSA) system.

  A conventional oxygen concentrator 31 as shown in FIG. 3 has an adsorption step in which high-pressure air flows into the adsorption cylinder 33 by the compressor 32, and nitrogen in the air is adsorbed and separated by the adsorbent a in the adsorption cylinder 33; By switching the flow path with the switching valve 34 and lowering the pressure of the adsorption cylinder 33, the nitrogen adsorbed on the adsorbent a of the adsorption cylinder 33 is released through the silencer 35 and the regeneration process (desorption) of regenerating the adsorbent a is performed. Steps) are alternately repeated to continuously produce high-concentration oxygen.

  The produced high-concentration oxygen is stored in a production gas tank (buffer tank) 36 installed on the downstream side of the adsorption cylinder 33 to reduce fluctuations in pressure, flow rate, and concentration.

  Part of the high-concentration oxygen produced in the adsorption process or stored in the production gas tank 36 is introduced into the adsorption cylinder 33 that is opened to the exhaust side in the regeneration process and purged with the nitrogen adsorbed on the adsorbent a. Facilitate.

  Since the compressed air sent to the adsorption cylinder 33 contains moisture in the atmosphere, there is a case where a drain pot or the like is installed at the outlet of the compressor 32 and a mechanism for removing the condensed moisture is employed (a drain pot is installed). May not be). In addition, the moisture sent as vapor without being condensed is removed by the hygroscopic agent m installed on the upstream side of the adsorption cylinder 33.

  Nitrogen adsorbents such as zeolite are hydrophilic, and it is known that nitrogen adsorption performance will deteriorate if moisture in the atmosphere is adsorbed by long-term use. During the process, it is desorbed by opening to the atmosphere, and purging is promoted by introducing a part of the dry oxygen that is the product gas.

  When the operation is stopped, intrusion of moisture from the outside may be prevented by closing each valve (valve) of the compressor side line, the exhaust side line, and the production gas tank side line connected to the adsorption cylinder 33.

  Further, the adsorbent and the hygroscopic agent may be filled independently in the adsorption cylinder and the moisture absorption cylinder, respectively.

  The prior art document information related to the invention of this application includes the following.

JP 58-120504 A

  However, in the conventional oxygen concentrator 31, although there is an upper limit for thermal equilibrium during the oxygen concentration operation (normal operation), some moisture remains without being desorbed by the hygroscopic agent m. This residual moisture may be partly desorbed from the moisture absorbent m depending on environmental conditions such as temperature and pressure during operation stop.

  In the prior art, the adsorbent a and the hygroscopic agent m are filled in the same adsorbing cylinder 33 as in the oxygen concentrator 31 or are connected only by piping even when they are installed independently. Moisture desorbed from the hygroscopic agent m reaches and is adsorbed to the adsorbent a by diffusion, leading to a decrease in nitrogen adsorption performance.

  Furthermore, each valve cannot block the outside air 100%, and the outside air may enter due to valve seat leakage or the like.

  Thus, in the prior art, it is not considered to completely prevent moisture from entering the adsorption cylinder while the operation is stopped.

  Therefore, an object of the present invention is to provide an oxygen concentrator that prevents moisture from diffusing into the adsorption cylinder during operation stop.

The present invention has been devised to achieve the above object, and the invention of claim 1 includes a compressor that compresses air, a plurality of adsorption cylinders filled with an adsorbent that selectively adsorbs nitrogen, In an oxygen concentrator provided with switching means for alternately supplying compressed air from the compressor to each adsorption cylinder to adsorb nitrogen, and desorbing and exhausting nitrogen from each adsorption cylinder,
A hygroscopic cylinder filled with a hygroscopic agent that absorbs moisture in the compressed air is provided independently between the switching means and each adsorption cylinder, and the oxygen absorption operation is opened between these moisture absorption cylinders and each adsorption cylinder. The oxygen concentrator is provided with a shutoff valve that is closed to shut off the intrusion of moisture into the adsorption cylinder during the stop.

  In the invention of claim 2, a common oxygen supply line is connected to each adsorption cylinder, and high concentration oxygen from each adsorption cylinder is temporarily stored in the oxygen supply line, and part of the high concentration oxygen is nitrogenated when the operation is stopped. The oxygen concentrator according to claim 1, further comprising a buffer tank that supplies each adsorption cylinder as a purge gas for moisture.

  The invention according to claim 3 is the oxygen concentration according to claim 1 or 2, wherein the upstream side of each of the moisture absorbing cylinders is filled with a moisture absorbent for roughing and dehumidifying, and the downstream side is filled with a moisture removing agent for precise dehumidification. It is a vessel.

  According to a fourth aspect of the present invention, an upstream side closing valve is provided between the compressor and the switching means, a downstream side closing valve is provided on the oxygen supply side, and a moisture absorbing cylinder corresponding to each adsorption cylinder is held at a positive pressure during operation stop. The oxygen concentrator according to any one of claims 1 to 3.

  The invention according to claim 5 is the oxygen concentrator according to claim 4, wherein each moisture absorption cylinder is held at a positive pressure while the operation is stopped, and the corresponding adsorption cylinder is held at a pressure higher than the positive pressure.

  According to a sixth aspect of the present invention, the switching means comprises a three-way valve, and the three-way valve is normally open on the compressor side, normally closed on the nitrogen exhaust side, and common on the moisture absorption cylinder side. It is an oxygen concentrator as described in above.

  According to a seventh aspect of the present invention, when the operation is stopped, the downstream stop valve and the upstream stop valve are closed, high concentration oxygen is supplied from the buffer tank to each adsorption cylinder, nitrogen and moisture are purged, and the switching is performed. The oxygen concentrator according to any one of claims 4 to 6, wherein each shutoff valve is closed after the means is closed.

  The invention of claim 8 is the oxygen concentrator according to any one of claims 1 to 7, wherein a drain trap for receiving moisture in the compressed air is provided between the compressor and the switching means.

  According to the present invention, it is possible to prevent moisture from diffusing into the adsorption cylinder while the operation is stopped, and to prevent a decrease in the nitrogen adsorption performance of the adsorbent.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram of an oxygen concentrator showing a preferred embodiment of the present invention.

  As shown in FIG. 1, the oxygen concentrator 1 according to the present embodiment is a PSA type oxygen concentrator, which is mainly used for an endoscope washer equipped with an ozonizer, a medical device used for home oxygen therapy, and the like. It is a relatively small oxygen concentrator used in medical equipment for medical use. In the following description, an example in which high-concentration oxygen (product gas) produced by the oxygen concentrator 1 is supplied to the ozonizer will be described.

This oxygen concentrator 1 includes a compressor 2 that compresses air and two adsorption cylinders (N ₂ adsorption cylinders) filled with an adsorption cylinder adsorbent (N ₂ adsorbent) a3 that selectively adsorbs nitrogen in the air. 3a, 3b and compressed air from the compressor 2 are alternately supplied to the adsorption cylinders 3a, 3b to adsorb nitrogen in the adsorption cylinder adsorbent a3, and on the other hand, desorb nitrogen from the adsorption cylinders 3a, 3b. It mainly comprises a switching valve 4 as switching means for exhausting.

  The compressor 2 and the switching valve 4 are connected, and the switching valve 4 and each of the adsorption cylinders 3a and 3b are connected by an air supply line 5 such as a pipe serving as a flow path. The air supply line 5 between the compressor 2 and the switching valve 4 is provided with a compressor stop valve 6 composed of an electromagnetic valve as an upstream side stop valve.

  In the oxygen concentrator 1, moisture absorbing cylinders 7a and 7b filled with a moisture absorbent m that absorbs moisture in compressed air between the switching valve 4 and the adsorption cylinders 3a and 3b correspond to the adsorption cylinders 3a and 3b. Thus, the suction cylinders 3a and 3b are provided independently.

  Further, the moisture absorption cylinders 7a and 7b and the adsorption cylinders 3a and 3b are opened during the oxygen concentration operation (normal operation), and the moisture intrusion into the adsorption cylinders 3a and 3b is blocked during the operation stop. Shut-off valves (adsorption cylinder-moisture-cylinder shut-off valves) 8a and 8b each including an electromagnetic valve that is closed as much as possible are provided.

  Each hygroscopic cylinder may be filled with only a single hygroscopic agent m. In the present embodiment, in order to further improve the moisture absorption performance, the upstream (switching valve 4) side in each of the moisture absorbing cylinders 7a and 7b is filled with the moisture absorbent m for roughing and dehumidifying, and the downstream (each of the adsorption cylinders 3a and 3b). The moisture absorbent in-cylinder adsorbent a7 was filled on the 3b) side as a moisture absorbent for precise dehumidification. In the present embodiment, zeolite having a hygroscopic function is used as the in-cylinder adsorbent a3 and the hygroscopic in-cylinder adsorbent a7, and activated alumina is used as the hygroscopic agent m.

  Each adsorption | suction cylinder 3a, 3b and each moisture absorption tower 7a, 7b are each equipped with the pressure sensor which does not show in figure which detects an internal pressure. However, the pressure sensor may be provided only at one place representing the entire system of the oxygen concentrator 1. In this case, the pressure in the system can be detected by a preliminary test.

  The switching valve 4 has a flow path for supplying compressed air from the compressor 2 to one adsorption cylinder 3a via one moisture absorption cylinder 7a during normal operation, and an adsorption cylinder adsorbent a3 on the other adsorption cylinder 3a. Is switched to a flow path for desorbing nitrogen adsorbed on the gas and exhausting the nitrogen through one of the moisture absorbing cylinders 7a. The same applies to the other adsorption cylinder 3b and the other moisture absorption cylinder 7b.

  The switching valve 4 is composed of two three-way valves 4a and 4b. The three-way valve 4a is provided so that the compressor 2 side is normally open (NO), the nitrogen exhaust side is normally closed (NC), and the adsorption cylinder 3a (humidity absorption cylinder 7a) side is common (C). The same applies to the three-way valve 4b.

  NO of each three-way valve 4a, 4b is connected to the air supply line 5 branched on the downstream side of the compressor shut-off valve 6, respectively. The NCs of the three-way valves 4a and 4b are connected to an exhaust line 9 shared by the adsorption cylinders 3a and 3b, respectively. A silencer 10 is connected to the exhaust port of the exhaust line 9 to mute the exhaust sound.

  A common oxygen supply line 11 is connected to the adsorption cylinders 3a and 3b on the downstream side of the adsorption cylinders 3a and 3b, and the adsorption cylinders 3a and 3b are connected between the oxygen supply line 11 and the adsorption cylinders 3a and 3b. Orifices 12 are provided as pressure adjusting means for adjusting the internal pressure.

In the middle of the oxygen supply line 11, high-concentration oxygen from the adsorption cylinders 3a and 3b is temporarily stored, and part of the high-concentration oxygen is supplied to the adsorption cylinders 3a and 3b as nitrogen and moisture purge gases when the operation is stopped. A buffer tank (O ₂ buffer tank) 13 is provided.

  The buffer tank 13 has a first purpose of reducing fluctuations in the flow rate, pressure and concentration of the high concentration oxygen when the adsorption cylinders 3a and 3b are switched in order to stably supply the high concentration oxygen downstream. However, when the operation is stopped, the adsorption cylinder adsorbent a3 in each adsorption cylinder 3a, 3b, the moisture absorption cylinder adsorbent a7 in each of the moisture absorption cylinders 7a, 7b, and the capacity capable of sufficiently purging the adsorbed moisture of the moisture absorbent m are also provided. Shall.

  The oxygen supply line 11 on the downstream side of the buffer tank 13 is provided with a regulator 14 for adjusting the flow rate of the high concentration oxygen supplied to the ozonizer.

  The oxygen supply line 11 on the downstream side of the regulator 14 is provided with an ozonizer closing valve 15 made up of an electromagnetic valve as a downstream closing valve.

  Further, a drain trap (also referred to as a drain pot or drain pan) 17 that receives moisture in the compressed air is provided between the compressor 2 and the compressor shut-off valve 6 via a drain line 16, and the downstream side of the drain trap 17. A drain closing valve 18 is provided on the drain line 16.

  Furthermore, the oxygen concentrator 1 is provided with control means (not shown), and the control means controls the opening / closing of the compressor shut-off valve 6, the switching valve 4, the shut-off valves 8a and 8b, the ozonizer shut-off valve 15, and the drain shut-off valve 18. To do. Each pressure sensor (not shown) is also connected to the control means.

  The effect | action of this embodiment is demonstrated with operation | movement of the oxygen concentrator 1. FIG.

(Normal operation)
Prior to the normal operation of the oxygen concentrator 1, the compressor closing valve 6, the shutoff valves 8 a and 8 b and the ozonizer closing valve 15 are opened, and the drain closing valve 18 is closed.

  First, the three-way valve 4a is opened in the direction from the compressor 2 to the adsorption cylinder 3a, and is closed on the exhaust side, and the three-way valve 4b is closed in the direction from the compressor 2 to the adsorption cylinder 3b. At the same time, it is opened on the exhaust side.

  In this state, the compressor 2 is operated, and the compressed air is caused to flow into the adsorption cylinder 3a through the moisture absorption cylinder 7a. The moisture in the compressed air is removed by the hygroscopic agent m of the moisture absorbing cylinder 7a and the absorbent in the moisture absorbing cylinder a7, and the almost completely dry compressed air flows into the adsorption cylinder 3a. Part of the nitrogen in the compressed air is also adsorbed by the moisture absorbent in-cylinder adsorbent a7 of the moisture absorbent cylinder 7a.

  The nitrogen in the compressed air that has flowed into the adsorption cylinder 3a is mainly adsorbed by the adsorption cylinder adsorbent a3 of the adsorption cylinder 3a, and high-concentration oxygen (for example, the oxygen concentration is about 80 to 97%) passes through the oxygen supply line 11. And temporarily stored in the buffer tank 13.

  The high concentration oxygen stored in the buffer tank 13 is supplied to an ozonizer for producing ozone via the oxygen supply line 11.

  The oxygen concentration and supply amount (production amount or flow rate) of high-concentration oxygen are set by appropriately setting the discharge pressure of the compressor 2, the set value of the orifice 12, the capacity of the buffer tank 13, and the adjustment amount of the regulator 14. The flow rate and the pressure in the adsorption cylinder 3a are changed and determined. In the present embodiment, the discharge pressure of the compressor 2 is 0.2 MPa, the volume of the buffer tank 13 is 300 mL, and the supply amount of high concentration oxygen is 0.8 L / min.

  On the other hand, simultaneously with the oxygen concentration by the adsorption cylinder 3a, the desorption of nitrogen in the adsorption cylinder 3b and the desorption of moisture in the moisture absorption cylinder 7b are also performed (regeneration of the adsorption cylinder 3b and the moisture absorption cylinder 7b).

  Since the adsorption cylinder 3b and the moisture absorption cylinder 7b are open to the atmosphere, and the internal pressure is lower than when oxygen is concentrated, the nitrogen and moisture adsorbed on the adsorption cylinder adsorbent a3 of the adsorption cylinder 3b and the adsorption in the moisture absorption cylinder 7b are absorbed. Nitrogen and moisture adsorbed on the agent a7 and moisture adsorbed on the hygroscopic agent m of the moisture absorbing cylinder 7b are desorbed and discharged from the silencer 10 to the outside via the exhaust line 9.

  At this time, the purge of nitrogen and moisture can be promoted by supplying a part of the absolutely dry high-concentration oxygen as the purge gas from the adsorption cylinder 3a during the adsorption process to the adsorption cylinder 3b and the moisture absorption cylinder 7b.

  After a predetermined time (a time earlier than the adsorption capacity of the adsorption cylinder 3a becomes insufficient), the three-way valve 4b is closed on the exhaust side in order to efficiently perform oxygen concentration in the adsorption cylinder 3b, and the adsorption cylinder 3a. The pressure in the adsorption cylinder 3b is equalized. This predetermined time is preset in the control means.

  Then, the three-way valve 4b is opened in the direction from the compressor 2 to the adsorption cylinder 3b, and is closed on the exhaust side, and the three-way valve 4a is closed in the direction from the compressor 2 to the adsorption cylinder 3a, and is opened on the exhaust side. Then, oxygen concentration by the adsorption cylinder 3b is performed in the same manner.

  Thereafter, the switching valve 4 is appropriately switched, and the above operation is alternately performed in the adsorption cylinders 3a and 3b. Further, the water in the compressed air dripped from the air supply line 5 through the drain line 16 and received by the drain trap 17 is drained at predetermined intervals according to the environmental (ambient) temperature, environmental humidity, and environmental atmospheric pressure. 18 is opened and drained to the outside.

Thus, an adsorption step of adsorbing moisture in the compressed air to the hygroscopic agent m and the hygroscopic in-cylinder adsorbent a7 and adsorbing nitrogen to the adsorbent in-cylinder a3 to separate high-concentration oxygen, and an adsorption in-cylinder adsorbent Regeneration that releases nitrogen adsorbed by a3 and releases moisture adsorbed by the moisture absorbent m and the moisture absorbent in-cylinder a7 to regenerate the moisture absorbent in-cylinder adsorber a7, the adsorbent in-cylinder adsorbent a3, and the moisture absorbent m Repeat the process (desorption process).
(When operation is stopped, operation is stopped)
When the operation is stopped, the oxygen concentrator 1 first closes the ozonizer closing valve 15 and the compressor closing valve 6, and closes the three-way valves 4a and 4b in the direction from the compressor 2 toward the adsorption cylinders 3a and 3b, respectively. Open on the exhaust side. Thereafter, the compressor 2 is stopped.

  Thereby, a part of the high-concentration oxygen in the completely dry state is supplied from the buffer tank 13 to the adsorption cylinders 3a and 3b and the moisture absorption cylinders 7a and 7b as a purge gas to purge nitrogen and moisture (one point in FIG. 1). Chain arrow A, B).

  The three-way valves 4a and 4b are closed on the exhaust side while the purge gas is maintained at a positive pressure (pressurized state higher than the atmospheric pressure: first pressure), and each adsorption cylinder is stopped while the operation is stopped. The pressure in the moisture absorbing cylinders 7a and 7b corresponding to the inside of 3a and 3b is maintained at a positive pressure.

  More specifically, the shutoff valves 8a and 8b are closed, and the inside of each of the hygroscopic cylinders 7a and 7b is held at a positive pressure during operation stop, and a higher pressure (second pressure) than the positive pressure is supported. The adsorption cylinders 3a and 3b are held.

  When the operation is stopped, the compressor closing valve 6, the ozonizer closing valve 15, the three-way valves 4a and 4b, and the shut-off valves 8a and 8b are closed in advance by setting the closing order of each valve and its time interval in the control means. deep.

  As described above, the oxygen concentrator 1 is provided with the moisture absorbing cylinders 7a and 7b independently between the switching valve 4 and each of the adsorption cylinders 3a and 3b, and between the moisture absorbing cylinders 7a and 7b and each of the adsorption cylinders 3a and 3b. 8a and 8b are provided.

  For this reason, in the oxygen concentrator 1, by closing the ozonizer closing valve 15 and the shutoff valves 8a and 8b when the operation is stopped, moisture remaining in the respective moisture absorption tubes 7a and 7b is retained in the respective adsorption tubes 3a and 3b during the operation stop. Can be prevented from diffusing.

In other words, the oxygen concentrator 1 has an adsorption cylinder corresponding to each of the hygroscopic cylinders 7a and 7b even if residual moisture is desorbed from the hygroscopic agent m in the respective hygroscopic cylinders 7a and 7b and the adsorbent a7 in the hygroscopic cylinder during operation stop. 3a, since the inter-3b is blocked, desorbed moisture adsorption column 3a, can not diffuse transition to the adsorption cylinder in the adsorption agent a3 in 3b, the N ₂ adsorption performance due to moisture adsorption of the adsorption cylinder in the adsorption agent a3 Decline can be prevented.

In particular, when the PSA type oxygen concentrator has a long operation stop period, it is difficult for moisture to escape from the adsorbent in the adsorption cylinder, and the N ₂ adsorption performance of the adsorbent in the adsorption cylinder decreases significantly. For example, the N ₂ adsorption performance of the adsorption agent a3 in the adsorption cylinder can be maintained even when the operation stop period is long.

  Further, the oxygen concentrator 1 holds each of the moisture absorption cylinders 7a and 7b at a positive pressure during operation stop, and also holds the corresponding adsorption cylinders 3a and 3b at a pressure higher than the positive pressure. There is a pressure difference in the order of internal holding pressure, moisture absorption cylinder holding pressure, and atmospheric pressure.

  For this reason, in the oxygen concentrator 1, even if there is a change in the environmental temperature or the atmospheric pressure, the outside air (moisture) is leaked due to the valve seat leakage of each valve (particularly, the compressor closing valve 6, the switching valve 4, and the ozonizer closing valve 15). It does not enter the apparatus, and it is possible to reliably prevent the desorption moisture of the moisture absorbing cylinders 7a and 7b from entering the adsorption cylinders 3a and 3b.

  Further, the oxygen concentrator 1 fills each of the moisture absorption cylinders 7a and 7b with the moisture absorbent m for roughing and dehumidifying on the upstream side and the adsorption cylinder adsorbent a7 for precise dehumidification on the downstream side. Therefore, it is possible to reliably prevent moisture from entering the adsorption cylinders 3a and 3b not only during normal operation but also during operation stop.

  The oxygen concentrator 1 is provided with a drain trap 17 between the compressor 2 and the switching valve 4, and after receiving a part of the moisture in the compressed air by the drain trap 17, the oxygen trap 1 drains this to each moisture absorption cylinder 7 a. , 7a, and the dehumidifying function is lightened, and compressed air in an almost completely dry state can easily flow into the adsorption cylinders 3a, 3b.

  Here, with respect to the oxygen concentrator 1 according to the present embodiment (an example in which pressurization is not held during operation stop) and the conventional oxygen concentrator 31 described with reference to FIG. The relationship between the moisture increase in the adsorption cylinder was investigated. The result is shown in FIG.

  In FIG. 2, the moisture absorption cylinder at the time of shutoff of the oxygen concentrator 1 having the shutoff valves 8a and 8b is represented by ◯, the adsorption cylinder at the shutoff is represented by *, and the non-blocking adsorption moisture absorption cylinder of the conventional example without the shutoff valve is represented by Δ. In the oxygen concentrator 1, the adsorption cylinder adsorbent a3 of each adsorption cylinder 3a, 3b was 400 g, the moisture absorption cylinder adsorbent a7 for moisture absorption of each moisture absorption cylinder 7a, 7b was 90 g, and the moisture absorbent m was 90 g. In the conventional example, the adsorption in-cylinder a3 of each adsorption cylinder 33 is 380 g, and the hygroscopic agent m is 20 g.

  As indicated by * in FIG. 2, when the oxygen concentrator 1 is closed between the adsorption cylinder and the moisture absorption cylinder by the shutoff valves 8a and 8b in FIG. The increase in weight is almost 0 g, which indicates that moisture can be prevented from entering the adsorbent. As can be seen from the circles in FIG. 2, the increase in the weight of the hygroscopic cylinder increased by 20 g after about 70 days of operation.

  On the other hand, as shown by Δ in FIG. 2, in the conventional example, the weight of the adsorption hygroscopic cylinder increases as the operating days elapse, and the operating days increase as much as 20 g after about the 30th day. Has invaded.

  The switching valve 4 and the compressor shut-off valve 6 are parts for shutting off the outside air when the operation is stopped. However, if four two-way valves are used as switching means, the compressor shut-off valve 6 can be omitted.

  Supply of high-concentration oxygen for water or nitrogen purge when the operation is stopped may be performed by providing a capacity in a dedicated tank other than the buffer tank 13 or in the piping system (for example, making the piping thicker).

  In the above embodiment, the example in which the two adsorption cylinders 3a and 3b and the two moisture absorption cylinders 7a and 7b are provided has been described. However, the adsorption cylinder and the corresponding moisture absorption cylinders may be provided at least two.

It is the schematic of the oxygen concentrator which shows suitable embodiment of this invention. FIG. 2 is a diagram illustrating a relationship between an increase in water content in an adsorption cylinder and a moisture absorption cylinder and the number of operating days in the oxygen concentrator illustrated in FIG. 1 and a conventional oxygen concentrator. It is the schematic of the conventional oxygen concentrator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oxygen concentrator 2 Compressor 3a, 3b Adsorption cylinder 4 Switching valve (switching means)
7a, 7b Hygroscopic cylinders 8a, 8b Shut-off valve a3 Adsorbent in the adsorbing cylinder a7 Adsorbent in the hygroscopic cylinder m Hygroscopic agent

Claims (8)

A compressor for compressing air; a plurality of adsorption cylinders filled with an adsorbent for selectively adsorbing nitrogen; and supplying compressed air from the compressor to each adsorption cylinder alternately to adsorb nitrogen, In an oxygen concentrator comprising switching means for desorbing and exhausting nitrogen from the adsorption cylinder,
A hygroscopic cylinder filled with a hygroscopic agent that absorbs moisture in the compressed air is provided independently between the switching means and each adsorption cylinder, and the oxygen absorption operation is opened between these moisture absorption cylinders and each adsorption cylinder. An oxygen concentrator comprising a shut-off valve that is closed to shut off moisture intrusion into the adsorption cylinder during stoppage.   A common oxygen supply line is connected to each adsorption cylinder, and high-concentration oxygen from each adsorption cylinder is temporarily stored in the oxygen supply line, and a part of the high-concentration oxygen is used as a nitrogen and moisture purge gas when the operation is stopped. The oxygen concentrator according to claim 1, further comprising a buffer tank to be supplied to the cylinder.   The oxygen concentrator according to claim 1 or 2, wherein the upstream side of each of the moisture absorbing cylinders is filled with a hygroscopic agent for rough dehumidification and the downstream side is filled with a hygroscopic agent for precise dehumidification.   An upstream side closing valve is provided between the compressor and the switching means, a downstream side closing valve is provided on the oxygen supply side, and the moisture absorbing cylinder corresponding to each adsorption cylinder is held at a positive pressure during operation stop. An oxygen concentrator according to the above.   5. The oxygen concentrator according to claim 4, wherein each of the hygroscopic cylinders is held at a positive pressure while the operation is stopped, and the corresponding adsorption cylinder is held at a pressure higher than the positive pressure.   The oxygen concentrator according to any one of claims 1 to 5, wherein the switching means comprises a three-way valve, wherein the compressor side is normally open, the nitrogen exhaust side is normally closed, and the hygroscopic cylinder side is common.   When the operation is stopped, the downstream stop valve and the upstream stop valve are closed, high concentration oxygen is supplied from the buffer tank to each adsorption cylinder, nitrogen and moisture are purged, and the switching means is closed. The oxygen concentrator according to any one of claims 4 to 6, wherein each shut-off valve is closed.   The oxygen concentrator according to any one of claims 1 to 7, wherein a drain trap for receiving moisture in compressed air is provided between the compressor and the switching means.

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