JPH10194708A - Oxygen concentrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both the durability and the oxygen concentration in a product gas without causing a remarkable mechanical change in a pressure swing adsorption type oxygen enricher by making an oxygen-enriched gas flow from a surge tank to an adsorption bed when a specific pressure swing width attains in a desorbing step for the adsorption bed filled with an adsorbent. SOLUTION: An adsorption bed 8 filled with an adsorbent for preferentially adsorbing nitrogen to oxygen is arranged in the interior of an adsorption column 1. Air is then fed from a changeover valve 4 through a compressor 5 into the adsorption column 1 to adsorb the nitrogen. The resultant oxygen-enriched gas is then discharged through conduits 3 and 23 equipped with automatic closing and opening means 2 and 22 and a surge tank 9. When the pressure variation width of the adsorption bed 8 attains <=10%, the oxygen-enriched gas is made to flow from the surge tank 9 through the conduits 3 and 23 to the adsorption bed 8. The nitrogen adsorbed on the adsorption bed 8 is then desorbed and discharged through the compressor 5 and the changeover valve 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen concentrator for separating and using an oxygen-enriched gas from the atmosphere.
More particularly, the present invention relates to a pressure fluctuation adsorption type oxygen concentrator, and more particularly, to an oxygen concentrator having an improved operation sequence which enables a small amount of supplied gas to supply an oxygen-enriched gas to a user.

[0002]

2. Description of the Related Art In recent years, the number of patients suffering from respiratory tract diseases such as asthma, emphysema and chronic bronchitis has been increasing, and one of the most effective treatments is oxygen inhalation. . In the oxygen inhalation method, a patient inhales oxygen gas or oxygen-enriched air. Oxygen gas cylinders have been used as a source of oxygen gas and oxygen-enriched air.However, in recent years, oxygen concentrators have been developed to separate oxygen-enriched gas from air, making it easier to use and easier to maintain and manage. It is becoming increasingly popular.

At present, there are a membrane type oxygen concentrator using an oxygen selective permeable membrane and an adsorption type oxygen concentrator using an adsorbent capable of preferentially adsorbing nitrogen. It is intended to improve the concentrator.

[0004] As a major one of the conventional adsorption type oxygen concentrators, there is a pressure fluctuation adsorption type oxygen concentrator using a compressor. Such an apparatus usually introduces compressed air pressurized by a compressor into an adsorption bed filled with an adsorbent capable of preferentially adsorbing nitrogen, and adsorbs nitrogen in a pressurized state to obtain an oxygen-enriched gas. And the desorption step of reducing the pressure in the adsorption bed to regenerate the adsorption bed is performed alternately to obtain an oxygen-enriched gas. In this case, a surge tank is used to temporarily store oxygen-enriched gas from the adsorbent bed. The surge tank is supplied with oxygen-enriched gas stored in the surge tank and a part of the gas is supplied to the adsorbent bed. Is often used for re-pressurizing the adsorption bed or purging for regeneration of the adsorption bed.

The adsorption bed of a generally used adsorption type oxygen concentrator includes a molecular sieve zeolite 5A or 13X having a separation coefficient based on a binary adsorption equilibrium in adsorption of about 2.0 to 3.0. Are filled in a single layer, stacked or mixed. In recent years, in the United States, a lithium zeolite exhibiting a high separation performance with a separation coefficient of 6.0 or more as compared with a conventional adsorbent as disclosed in Japanese Patent Publication No. 5-25527 has been developed.

[0006] These zeolites exhibit a high nitrogen adsorption amount, but have a very high affinity for water molecules, and have the property of adsorbing water molecules preferentially over nitrogen in the coexistence of water molecules. The zeolite that has adsorbed water molecules has a problem in that the amount of adsorbed nitrogen is greatly reduced, and it is difficult to completely desorb and regenerate zeolite by simply changing the pressure of the water molecules. Although it depends on the type and temperature of the zeolite, the zeolite, which is in a moisture absorption state of about 20 wt% with respect to the saturated water adsorption of water of zeolite, has a nitrogen equilibrium adsorption of about 30% lower than that of a new zeolite. If the zeolite of the pressure fluctuation adsorption type oxygen concentrator absorbs moisture as described above, the amount of nitrogen molecules remaining in the system will increase, causing problems such as a decrease in oxygen concentration and an increase in adsorption pressure. In an industrial-scale pressure fluctuation adsorption type oxygen concentrator, in order to avoid the above-mentioned problems, a dehumidifier for raw air is mounted in the system of the oxygen concentrator. However, in small oxygen concentrators for medical use, etc., due to various factors such as securing the product gas flow rate, the size and weight of the device, and the reduction in power consumption during operation of the device, the dehumidifier as in the above-mentioned industrial scale device Is not installed. Therefore, in such an oxygen concentrator, the influence of the amount of water molecules adsorbed on the adsorbent becomes large, and how to keep the amount of water adsorbed by the adsorbent low is a major factor in maintaining the performance of the oxygen concentrator.

[0007] Due to the above-mentioned problems, if the moisture absorption durability of the oxygen concentrator does not reach a desired time period, the adsorbent may be changed to improve the durability of the adsorption bed. By taking measures such as reducing the amount of supply air by improving the oxygen concentration efficiency, the amount of water supplied to the adsorption bed is reduced, and the mechanical improvement of the oxygen concentration device is performed by making mechanical improvements. Durability was secured. However, such a method cannot avoid problems such as an increase in the size of the device, an increase in power consumption, and an increase in production cost.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to improve durability against continuous use of an adsorbent without a large mechanical change of a pressure fluctuation adsorption type oxygen concentrator, and to improve oxygen in a product gas. It is an object of the present invention to improve the concentration, thereby reducing the amount of supplied air, to realize a smaller air supply means, and to reduce the power consumption of the apparatus.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies with the aim of solving such problems, and as a result, in a pressure fluctuation adsorption type oxygen concentrator, the pressure of the adsorbent bed during the desorption step of the adsorbent bed has been reduced. By purging oxygen-enriched gas from the surge tank means to the adsorbent bed with a fluctuation width of 10% or less, the adsorbed water accumulated in the adsorbent bed can be more efficiently removed, and the adsorbent bed can be used over time. It has been found that the oxygen concentration efficiency is improved by the action of displacement adsorption, and the present invention has been achieved.

That is, the present invention provides at least one adsorption bed filled with an adsorbent capable of preferentially adsorbing nitrogen over oxygen, and air supply means for supplying air to the adsorption bed.
In a pressure fluctuation adsorption type oxygen concentrator having a surge tank means for storing oxygen-enriched gas concentrated in the adsorption bed, the pressure fluctuation width of the adsorption bed is set to 10 in the adsorption bed desorption step. The oxygen concentrating device is characterized in that it has means for flowing the oxygen-enriched gas from the surge tank means to the adsorption bed at a concentration of not more than 10%.

Further, an oxygen concentrator in which the surge tank means starts to flow the oxygen-enriched gas to the adsorption bed at 80% or more of the maximum degree of vacuum of the adsorption bed is an example of the specific means. The means for flowing the oxygen-enriched gas from the surge tank means to the adsorbent bed comprises two conduit means for connecting the adsorbent bed and the surge tank,
The present invention provides an oxygen concentrator in which conduit means a is provided with automatic opening and closing valve means, and conduit means b is provided with automatic opening and closing valve means and flow control means.

According to the present invention, in the pressure fluctuation adsorption type oxygen concentrator, the automatic opening and closing valve means of the conduit means a and b are closed together with the start of the desorption step, and the automatic opening and closing valve means of the conduit means b is connected to the adsorption means. An oxygen concentrator characterized by opening when the internal pressure of the bed reaches 80% or more of the maximum vacuum and closing at the start of the adsorption step is included.

Further, according to the present invention, in the pressure fluctuation adsorption type oxygen concentrator, the automatic opening and closing valve means of the conduit means a and b are closed together with the start of the desorption step, and the automatic opening and closing means of the conduit means a is terminated. Opened immediately before, the automatic opening and closing valve means of the conduit means b is opened when the internal pressure of the adsorption bed reaches 80% or more of the maximum vacuum, and the automatic opening and closing valve means of the conduit means b is opened together with the start of the adsorption step. An oxygen concentrator characterized by closing is included.

Further, according to the present invention, the oxygen-enriched gas flowing through the conduit means b flows through the adsorption bed of the oxygen concentrator,
An oxygen concentrator characterized by being discharged out of the system is included.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The adsorbent used in the adsorbent bed of the oxygen concentrator of the present invention is not particularly limited, but 5A zeolite, 13X zeolite, and SiO ₂ / Al ₂ O ₃ of 2.0 are used.
It is 3.0, and at least 88% of its AlO ₄ tetrahedral units are X-type zeolite are associated with lithium ion. In particular, the ratio of SiO ₂ / Al ₂ O ₃ is 2.0
It is 3.0, and at least 88% of its AlO ₄ tetrahedral units are X-type zeolite are associated with lithium ion. In addition, two of these three types of zeolites
Adsorption beds can be used depending on the species or the combination of all zeolites.

Further, the air supply means used in the oxygen concentrator of the present invention functions as a compressor means for supplying raw material air to the adsorption bed in the adsorption step, and the air supply means in the adsorption bed in the desorption step. An oxygen concentrator functioning as a vacuum pump means for discharging gas is included.

Further, the present invention includes an oxygen concentrating apparatus which performs an adsorption step when the internal pressure of the adsorption bed is higher than the atmospheric pressure, and performs desorption when the internal pressure of the adsorption bed is lower than the atmospheric pressure.

Further, in the oxygen concentrator utilizing the present invention, the number of the adsorbing beds may be one or more, but in the case of a small medical oxygen concentrator, the number is preferably two or less. In particular, the case of one is excellent in that the whole apparatus is easily made compact.

Further, the oxygen concentrating apparatus utilizing the present invention has a surge tank for temporarily storing the concentrated oxygen-enriched air, and when the oxygen-enriched air is continuously supplied to the user via the tank. At the same time, there is a pressure fluctuation type oxygen concentrator in which the step of backflowing the oxygen-enriched gas stored in the surge tank means to the adsorption bed is included in the pressure fluctuation adsorption / desorption step. The effect of the present invention is that the configuration is such that the oxygen-enriched gas in the surge tank means flows back to the adsorption bed for purging in the re-pressurizing step or desorption step of the adsorption bed due to such a step. Is preferred. Specifically, during the adsorption bed desorption step, the pressure fluctuation width of the adsorption bed is set to 1
By purging oxygen-enriched gas from the surge tank means to the adsorbent bed at 0% or less, the adsorbed water accumulated in the adsorbent bed is more efficiently removed, and the durability of the adsorbent bed in use over time is improved. And the efficiency of oxygen concentration is improved by the action of displacement adsorption. When the flow purge is started at 80% or more of the maximum vacuum of the adsorbent bed, the adsorbed water is efficiently removed and the oxygen concentration efficiency is increased.

In the case where there is a step of flowing the oxygen-enriched gas from the surge tank to the adsorption tower, the pressure fluctuation width indicates the pressure fluctuation caused by the above-mentioned step relative to the pressure difference between the maximum pressure during the adsorption step and the minimum pressure during the desorption step. The ratio of

Furthermore, the maximum vacuum degree of the adsorption bed means the maximum vacuum degree reached when there is no step of flowing the oxygen-enriched gas from the surge tank to the adsorption tower.

In the oxygen concentrator utilizing the present invention, as a control method of the automatic opening / closing valve means, a pressure detecting means is provided on the adsorbent bed and the surge tank, and the automatic opening / closing valve is measured while measuring a change in pressure with time. Although a method of controlling the means is possible, a method of controlling the automatic opening / closing valve means by a timer or the like based on experimentally obtained data is also preferable.

When an oxygen concentrator utilizing the present invention is used, if a desired oxygen concentration is obtained,
By lowering the overall adsorption pressure or shortening the closing time of the automatic opening / closing valve means, it is also possible to reduce the power consumption of the oxygen concentrator by partially lowering the adsorption pressure. .

The purging of the product gas into the adsorbent bed in the latter half of the desorption step in the present invention is different from the reverse flow of the product gas performed in the conventional single-tube pressure-fluctuation adsorption type oxygen concentrator. In the present invention, the back-flowed oxygen-enriched gas is completely discharged out of the system. In the conventional method, the backflow of the product gas is started about 1 to 2 seconds before the end of the desorption step, but pressurization is started immediately thereafter, and the backflowed gas is not released out of the system. According to this, the composition of the gas changes due to the flow of the dried oxygen-enriched gas into the column, and even if the adsorbed water molecules are desorbed from the adsorbent, they remain in the system. However, in the present invention, since the water is completely discharged, it is possible to increase the desorption efficiency of water molecules and extend the expiration date of the adsorbent.

In the present invention, the timing for opening the electromagnetic valve means having the flow rate control means in the desorption step is set to a pressure lower than the atmospheric pressure. This is because the effect of introducing a dry gas is weakened because there are many molecules remaining from the adsorption step.

The application of the oxygen concentrator using the present invention is not particularly limited, and is suitable for, for example, medical use used at home or the like.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the oxygen concentrator according to the present invention will be described below with reference to the drawings as necessary. However, the present invention is not limited to these examples.

Example 1 The ratio of SiO ₂ / Al ₂ O ₃ was 2.0
-3.0, and at least 88% of its AlO ₄ tetrahedral units are packed with X-type zeolite associated with lithium ions, and in the adsorption step, feed air is supplied to the adsorption bed; In the desorption step, a compressor that functions as a vacuum pump by switching valves, a surge tank for storing oxygen-enriched gas concentrated in the adsorption bed, and an automatic opening / closing valve for the adsorption bed and the surge tank The pressure fluctuation adsorption type oxygen concentrator was manufactured by connecting two kinds of conduits, a conduit provided with a means, and a conduit provided with an automatic opening / closing valve having a flow control means.

In this apparatus, one cycle of the adsorption and desorption was set to 17 seconds for the adsorption step and 17 seconds for the desorption step, and FIGS.
As shown in the figure, the automatic on-off valve having the flow control means is opened slightly before the end of the desorption step, and the automatic on-off valve means is closed simultaneously with the end of the desorption step. An oxygen concentrator with sequence control was manufactured.

[Comparative Example 1] The oxygen concentrator described in Example 1 was manufactured by removing the conduit means provided with the automatic on-off valve having the flow rate control means as shown in FIGS. did.

The internal pressure of the adsorption bed in Example 1 is reduced by the vacuum pump function of the compressor means at the start of the desorption step, and the automatic opening / closing valve means having the flow rate control means is opened 4 seconds before the end of the desorption step. . Thereby, oxygen-concentrated air is introduced into the adsorption bed at a constant flow rate, and the pressure in the adsorption bed rises. During this time, the vacuum pump function of the compressor means is continued, and the oxygen-enriched air introduced into the adsorption bed is discharged out of the system. One second before the end of the desorption step, the conduit means having an automatic opening / closing valve means is opened due to the pressure increase in the adsorbent bed, and the oxygen-enriched air stored in the surge tank means flows back to the adsorbent bed and the internal pressure is increased. , A series of changes over time was repeated.

The maximum vacuum of the adsorption bed of Example 1 was-
0.7 kgf / cm ² · G, -0.6 kgf / cm
Initiates auto-off valve controlled by ² · G. Further, the pressure fluctuation width accompanying the automatic opening / closing of the conduit means b of such a device is 7%.

When the oxygen concentrators of Example 1 and Comparative Example 1 were continuously operated under severe conditions of 35 ° C. and a relative humidity of 90%, the oxygen concentration in the purified oxygen-enriched air of the oxygen concentrator and the adsorbent Table 1 shows the pure oxygen gas productivity and the performance change over time.

[0034]

[Table 1]

[0035]

According to the oxygen concentrating apparatus of the present invention, the automatic opening / closing valve means is opened in the latter half of the desorption step, and the dried oxygen-enriched air stored in the surge tank is returned to the adsorption bed and discharged out of the system. Water molecules, which are present in the water and have been a major factor in lowering the oxygen concentration performance, can be eliminated to enhance the regeneration effect. As a result, the long-term stability of the apparatus performance is improved, the number of times of maintenance and the number of times of replacement of the adsorbent are reduced, and cost reduction can be realized.

In addition, by sufficiently flowing oxygen-enriched air to the adsorbent bed in the latter half of the desorption regeneration step, oxygen molecules are adsorbed in the adsorbent before the start of the adsorption step. At the same time, the effect that the displacement adsorption with the molecule occurs and the recovery rate of the oxygen-enriched gas is increased is obtained.

The long-term cost reduction resulting from this improvement and the improvement in the recovery rate obtained at the same time have made it possible to obtain high-concentration oxygen-enriched air stably over a long period of time and at low cost. Furthermore, since the recovery rate is also improved, it is possible to reduce the amount of supplied air without lowering the oxygen concentration in the product gas, which is also effective in reducing the size of the air supply means and reducing power costs. It is.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an opening / closing pattern of an automatic opening / closing valve described in Example 1 and Comparative Example 1.

FIG. 2 is a diagram showing an opening / closing pattern of an automatic opening / closing valve and a pressure fluctuation pattern of an adsorption bed according to a first embodiment.

FIG. 3 is a diagram showing an opening / closing pattern of an automatic opening / closing valve and a pressure fluctuation pattern of an adsorption bed described in Comparative Example 1.

FIG. 4 is a schematic diagram schematically showing a preferred embodiment of the oxygen concentrator according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adsorption tower 2 Automatic opening / closing valve means (electromagnetic valve 1) 3 Conduit means a 4 Switching valve 5 Compressor means 8 Adsorption bed 9 Surge tank 18 Pressure detecting means 19 Pressure detecting means 20 Control means 21 Flow control means 22 Automatic opening / closing valve means ( Solenoid valve 2) 23 conduit means b

Claims (6)

[Claims] 1. At least one adsorption bed filled with an adsorbent capable of preferentially adsorbing nitrogen over oxygen, air supply means for supplying air to the adsorption bed, A pressure fluctuation adsorption type oxygen concentrator having a surge tank means for storing the oxygen-enriched gas stored therein, wherein the pressure fluctuation range of the adsorption bed is 10% or less in the desorption process of the adsorption bed. An oxygen concentrator comprising means for flowing gas from said surge tank means to said adsorption bed. 2. The oxygen concentrator according to claim 1, wherein the timing of starting the flow of the oxygen-enriched gas from the surge tank means to the adsorption bed is at least 80% of the maximum vacuum of the adsorption bed. 3. The means for flowing oxygen-enriched gas from the surge tank means to the adsorption bed comprises two conduit means for connecting the adsorbent bed and the surge tank.
2. An automatic opening / closing valve means is provided on the pipe, and the automatic opening / closing valve means and the flow control means are provided on the conduit means b.
Or the oxygen concentrator according to 2. 4. The automatic opening and closing valve means of the conduit means a is closed at the start of the desorption step, and the automatic opening and closing valve means of the conduit means b is
The oxygen concentrator according to claim 3, wherein the adsorbent bed is opened when the internal pressure of the adsorbent reaches 80% or more of the maximum vacuum degree, and is closed when the adsorption step is started. 5. The oxygen concentrator according to claim 4, wherein the automatic opening / closing valve means of the conduit means a is opened immediately before the end of the desorption step. 6. The oxygen concentrator according to claim 4, wherein the oxygen-enriched gas flowing through the conduit means b flows through the adsorption bed of the oxygen concentrator and is discharged out of the system. apparatus.