JP2008229493A - Pressure swing adsorption type oxygen concentrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure swing adsorption type oxygen concentrator mounted with a solenoid valve minimizing pressure loss of an exhaust gas valve, while suppressing electric power consumption. <P>SOLUTION: The pressure swing adsorption type oxygen concentrator includes: one or more adsorption cylinders 8a, 8b containing an adsorbent preferentially adsorbing nitrogen to oxygen; an air compressing/supplying means supplying compressed raw air to the adsorption cylinders; and a gas flow path switching means for switching air supply and discharge to the adsorption cylinders. In the pressure swing adsorption type oxygen concentrator, by repeating an adsorption process of adsorbing nitrogen in the supply air by pressurizing inside the adsorption cylinders to the adsorbent, and taking out oxygen which has not been adsorbed as product gas, and a desorption process discharging the inside of the adsorption cylinders via the switching means, desorbing nitrogen adsorbed in the adsorbent to discharge, oxygen in the air is concentrated and taken out. The switching means is the pilot type solenoid valve, and includes a pilot air exhaust mechanism performing discharging at a discharge pressure of the pilot air lower than the atmospheric pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oxygen concentrator for adsorbing and removing nitrogen in the air and taking out highly concentrated oxygen.

  FIG. 2 shows a configuration example of a pressure swing adsorption type oxygen concentrator that has been conventionally used. A-type or X-type zeolite is used as the adsorbent, and it is stored in two adsorption cylinders. In order to pressurize the adsorption cylinder and adsorb nitrogen, a compressor is connected as air compression supply means, and a switching means for controlling the process is provided between the adsorption cylinder and the compressor and between the adsorption cylinder and the exhaust port. A certain solenoid valve is inserted. In this example, there are two suction cylinders, but the number of suction cylinders is generally not limited.

  The basic process includes an adsorption process in which the adsorption cylinder is pressurized to adsorb nitrogen and oxygen that has not been adsorbed is extracted as product gas, and a desorption process in which the adsorption cylinder is decompressed to desorb the adsorbed nitrogen. In the adsorption process, one end of the adsorption cylinder (hereinafter referred to as a raw material end) is connected to a compressor, and pressurized air (raw material air) is fed. Inside the adsorption cylinder, the adsorbent preferentially adsorbs nitrogen molecules in the raw material air, and oxygen that has not been adsorbed is taken out from the other end (product end) of the adsorption cylinder through a check valve into the product tank. After being stored once, it is taken out as product gas through a pressure regulating valve and a flow regulating valve. In the desorption process, the raw material end of the adsorption cylinder is released to the atmosphere, the pressure inside the adsorption cylinder is reduced, and part of the product gas is refluxed (purged) through a pressure equalizing valve, thereby adsorbing the adsorbent. Desorb nitrogen.

  In a system using two adsorption cylinders as in this example, while one adsorption cylinder is performing an adsorption process, the other adsorption cylinder performs a desorption process so that product gas can be continuously taken out. It has become. Depending on the configuration of the system, in order to improve the efficiency of the desorption process, the pressure is reduced to a pressure lower than the atmospheric pressure using a pressure reducing means such as a vacuum pump during the desorption process. In addition, in order to save compressor power, there is a pressure equalization process that connects the adsorption cylinder after the adsorption process and the adsorption cylinder after the desorption process between the adsorption process and the desorption process, and equalizes the pressure of both. There are also things.

Japanese Patent Laid-Open No. 9-20503 JP 2002-79030 A Japanese Patent Laid-Open No. 9-141038 JP 2005-329251 A JP 2006-62932 A

  In the oxygen concentrator as described above, reduction of power consumption is a major issue as one of the performances of the apparatus. Of the components of the oxygen concentrator, the compressor that is the air compression supply means consumes the most electric power, and then the electromagnetic valve that is the switching means consumes a lot. Therefore, first of all, reducing the power consumption of the compressor is an important issue.

  The power consumption of the compressor is determined by the efficiency of the compressor and the compression power for supplying the compressed air necessary for the adsorption process. Among these, the compression power is determined by the pressure and flow rate of air necessary for the adsorption process to concentrate oxygen, and it is necessary to reduce these values by improving the efficiency of the adsorption process. As described above, the pressure swing adsorption process uses the property that the adsorbent adsorbs nitrogen preferentially over oxygen and the property that the adsorption amount changes depending on the pressure. Oxygen is extracted by adsorbing nitrogen by raising it, desorbing the adsorbed nitrogen by lowering pressure by vacuum pump or opening to the atmosphere, and regenerating so that the adsorbent can adsorb nitrogen again to repeat oxygen Is a process of continuously taking out Therefore, the amount of pressure increase and decrease greatly affects the performance of the process. Generally, the higher the pressure in the adsorption process and the lower the pressure in the desorption process, the higher the oxygen recovery rate, and the greater the amount of air with a small amount of air. The amount of air supplied to the compressor is small because it can generate oxygen.

  However, since the power consumption of the compressor increases as the discharge pressure increases with the same air supply amount, it is necessary to devise a technique that can concentrate oxygen with a high recovery rate at as low a pressure as possible. For example, Japanese Patent Application Laid-Open No. 9-20503 describes a method in which the inside of the adsorption bed has a two-layer structure for reducing the adsorption efficiency due to the deterioration of the adsorbent and improving the process power consumption associated therewith. Specifically, by placing a low-performance adsorbent at the inlet of compressed air, it adsorbs moisture, which is the main factor that degrades the adsorbent, and is used mainly for adsorption / desorption of nitrogen / oxygen. The inside of the adsorption bed is configured so as to be disposed downstream of the low performance adsorbent. As a result, an increase in the work amount of the compressor due to the deterioration of the adsorbent can be suppressed, and an increase in power consumption over time can be prevented.

  Japanese Patent Laid-Open No. 2002-79030 has a problem in that, even in a medical oxygen concentrator, although there are a plurality of flow rate setting points used, the power consumption is the same at any point. A method is described in which the operation / non-operation of the pressure equalizing valve is controlled according to the flow rate setting value, so that the work amount of the compressor is suppressed to the minimum value necessary for the flow rate setting value, and the power consumption is reduced.

  In Japanese Patent Application Laid-Open No. 9-141038, an air tank having a volume three times larger than that of the adsorption bed is installed at a position downstream of the compressor and upstream of the adsorption bed, thereby increasing the adsorption efficiency of the adsorbent. Describes how to reduce the amount of work required.

  At the same time, by reducing the pressure loss of the piping and solenoid valve, in the adsorption process, the pressure of compressed air supplied from the compressor is supplied to the adsorption cylinder without being reduced as much as possible, and in the desorption process, the adsorption is performed. It is necessary to reduce the pressure in the cylinder as much as possible. However, when a solenoid valve having a large diameter is used to reduce pressure loss in the solenoid valve, there is a problem that a large force is required for switching the valve, resulting in an increase in power consumption of the solenoid valve.

  As a countermeasure, a plurality of methods for reducing power consumption by using a pilot valve as an electromagnetic valve have been disclosed. For example, Japanese Patent Laid-Open No. 2005-329251 describes that power consumption can be reduced by using a pilot type electromagnetic valve, compared to the case of using a conventional mainstream direct acting type electromagnetic valve. Furthermore, in Japanese Patent Laid-Open No. 2006-62932, among a number of types of pilot-type solenoid valves, a flow rate loss can be reduced and an increase in power consumption can be prevented by making the valve type used a diaphragm valve with less sliding. It is said.

  The structure of the diaphragm type pilot valve is as shown in FIG. 3, and the main valve 2 is opened and closed by moving the diaphragm 14 up and down. Pilot gas can be introduced into and exhausted from the upper space of the diaphragm through the pilot gas inlet / outlet 19. The pilot valve 3 is a small direct acting three-way solenoid valve, and the connection direction of the pilot gas inlet / outlet port 19 is switched between the pilot gas supply port 20 side and the pilot gas exhaust port 21 side. The diaphragm is pressed by a spring 16 from above.

  In the valve having such a configuration, when the pilot valve 3 is off, the pilot gas supply port 20 and the pilot gas inlet / outlet port 19 are connected, and the space above the diaphragm 14 is pressurized to the pilot gas pressure Ph. (FIG. 4). In this state, if the force at which the gas inlet pressure Pin and the gas outlet pressure Pout push the diaphragm 14 is smaller than the sum of the force by which the pilot gas Ph pushes the diaphragm 14 and the spring force, the diaphragm moves downward, the gas inlet 17 and the gas The space between the outlets 18 is blocked. Usually, since Pin is equal to or larger than Pout, if the pilot gas supply port 20 and the gas inlet 17 are connected, Pin and Ph are equal, and the diaphragm moves downward by the spring force. Often use method. The configuration is the same in the embodiment.

  On the other hand, when the pilot valve 3 is turned on, the pilot gas discharge port 21 and the pilot gas inlet / outlet port 19 are connected, and the pressure in the space above the diaphragm drops to Pl (FIG. 5). Normally, the pilot gas discharge port 21 is connected to the gas outlet 18 or opened to the atmosphere. If Pin is sufficiently larger than Pout, or if Pin and Pout are sufficiently larger than atmospheric pressure, the diaphragm moves upward to connect to the gas inlet 17. A gas outlet 18 communicates.

  In order to open and close the valve according to the principle described above, the pilot valve for switching the pilot air only needs to have a flow resistance as low as necessary to quickly pressurize and exhaust the space above the diaphragm of the main valve. The pilot valve can be made very small and the power consumption can be greatly reduced. Moreover, since the main valve is driven by pilot air, it does not consume power by itself. Therefore, the power consumption of the solenoid valve can be greatly reduced while keeping the pressure loss low.

  However, when the above configuration is applied to the exhaust valve of the oxygen concentrator, if the pressure reduction / desorption progresses and the pressure in the adsorption cylinder decreases, the above-mentioned Pin decreases, so Pl decreases to atmospheric pressure. Even if this is done, the pressure difference between Pl and Pin cannot be obtained sufficiently, the diaphragm descends and the valve closes. Therefore, a state occurs in which the adsorption cylinder cannot be depressurized below a certain pressure. As a result, the difference between the maximum pressure and the minimum pressure in the adsorption cylinder is reduced and the process efficiency is lowered, resulting in an increase in power consumption of the compressor.

  As a countermeasure, a vacuum source such as a vacuum pump is separately prepared and the pilot air discharge port is connected to the vacuum source. However, with this method, it is necessary to prepare a new vacuum source, and this leads to an increase in power consumption. As described above, a method for minimizing the pressure loss of the exhaust valve while reducing the power consumption of the solenoid valve has been demanded.

  As a result of intensive studies by the inventors to solve the above-mentioned problems, as a pilot type solenoid valve, a diaphragm type valve that can be driven with a small pressure difference is used. It has been found that the pressure difference required for the pilot solenoid valve can be reduced by selecting the inside of the suction side pipe of the means.

  That is, the present invention includes at least one adsorption cylinder containing an adsorbent that preferentially adsorbs nitrogen over oxygen, and takes in air from an air inlet and supplies compressed raw air to the adsorption cylinder. Air compression supply means, and supply of air to the adsorption cylinder, gas flow path switching means for switching the exhaust, supplying raw air to the adsorption cylinder from the air compression supply means through the switching means, An adsorption step of pressurizing the inside of the adsorption cylinder to adsorb nitrogen in the supply air to the adsorbent and taking out unadsorbed oxygen as product gas, exhausting the inside of the adsorption cylinder through the switching means, and the adsorbent In a pressure swing adsorption type oxygen concentrator that concentrates and extracts oxygen in the air by repeatedly desorbing and desorbing nitrogen adsorbed on the gas, the switching means is a pilot solenoid valve, There is provided a pressure swing adsorption-type oxygen concentrator characterized in that it comprises a pilot air exhaust mechanism for exhausting the exhaust pressure of the lot air at a pressure lower than atmospheric pressure.

  In addition to the above, the present invention further comprises flow path resistance means for restricting the air inflow amount at the raw air intake port of the air compression supply means, and the pilot air exhaust mechanism is connected to the pilot air discharge flow of the pilot solenoid valve. The present invention provides a pressure swing adsorption type oxygen concentrator, characterized in that it is a flow path connecting a flow path, the flow path resistance means, and the inside of an air suction flow path between the air compression supply means.

  In addition to the above, the present invention provides a pressure swing adsorption type oxygen concentrator, wherein the flow path resistance means is a noise reduction means for reducing noise released from the air inlet. Is.

  Further, in addition to the above, the present invention provides a pressure swing adsorption type oxygen, characterized in that the main valve of the pilot type solenoid valve is a diaphragm type, and the discharge pressure is less than 0 Kpa to 10 kPa or more in terms of gauge pressure. A concentrator is provided.

  The pressure swing adsorption type oxygen concentrator of the present invention can reduce the pressure loss of the exhaust valve, which greatly affects the performance of the oxygen concentration process, and can simultaneously reduce the power consumption of the solenoid valve and the power consumption of the compressor. Thus, a pressure swing adsorption type oxygen concentrator with lower power consumption than that of the above apparatus can be realized.

  FIG. 1 shows a preferred embodiment of the present invention. The air pressurized by the compressor 1 through the silencer 12 from the atmosphere passes through the pressurizing valve main valve 2a or 2b and is guided to the adsorption cylinder 8a or 8b. An adsorbent with the ability to preferentially adsorb nitrogen over oxygen is built in the adsorption cylinder (not shown in the figure), and the nitrogen in the air introduced there is adsorbed and removed and remains. Oxygen is temporarily stored in the product tank (11) through the check valve 9a or 9b and taken out as product gas. The nitrogen gas adsorbed by the adsorbent passes through the exhaust valve main valve 4b or 4a, and is released into the atmosphere through the exhaust silencer 13.

  The operation of the apparatus shown in this embodiment is as follows. First, since the pressurizing valve main valve 2a of the adsorption cylinder 8a is opened and the pressure reducing valve main valve 4a is closed, the air compressed by the compressor is introduced into the raw material end of the adsorption cylinder 8a. Then, the pressure in the adsorption cylinder 8a increases. The adsorbent inside adsorbs more nitrogen as the nitrogen partial pressure of the gas in contact with it is higher, but because the amount of oxygen adsorbed is smaller, nitrogen molecules in the introduced air are preferentially adsorbed, and oxygen molecules Almost no adsorption. Therefore, nitrogen molecules are removed from the product end of the adsorption cylinder, and the gas having an increased oxygen concentration flows out. Since the pressure equalizing valve 9 is closed at this time, the outflow gas passes through the check valve 10a and is temporarily stored in the product tank 11 and then taken out as product gas. The above process is called a pressurization / adsorption process.

  At this time, since the pressure reducing valve main valve 4b is opened and the pressurizing valve main valve 2b is closed, the adsorption cylinder 8b is exhausted and the pressure is reduced. Since the adsorbent has a property of releasing adsorbed nitrogen when the gas pressure decreases, nitrogen is released from the adsorbent, and the nitrogen gas is exhausted through the pressure reducing valve main valve 4b. This is called a pressure reduction / desorption process.

  Next, the pressure equalizing valve 9 is opened while maintaining the states of the pressurizing valve main valves 2a and 2b and the pressure reducing valve main valves 4a and 4b. Then, the adsorption cylinder a maintains the supply of compressed air from the compressor, the adsorption of nitrogen from the adsorbent, the outflow of oxygen-enriched gas, and the supply of the oxygen-enriched gas to the product tank 11 via the check valve 10a. The oxygen-enriched gas is refluxed from the product end of the adsorption cylinder 8a to the product end of the adsorption cylinder 8b. This process is called an adsorption / purge gas supply process.

  In addition, when the oxygen-enriched gas is refluxed to the adsorption cylinder 8b, the nitrogen gas partial pressure in the adsorption cylinder b is further reduced, and the release of nitrogen gas from the adsorbent is promoted. This process is called a desorption / purge process.

  Next, the pressurized valve main valve 2b is opened and the reduced pressure valve main valve 4b is closed while maintaining the state of the pressurizing valve main valve 2a and the pressure reducing valve main valve 4a, so that compressed air is supplied from the adsorption cylinder 8a and the compressor to the adsorption cylinder 8b. Is supplied. In the adsorption cylinder 8a, the oxygen-enriched gas is extracted from the product end and the compressed air is extracted from the raw material end, so that the pressure is reduced, the check valve is closed, and the supply of the oxygen-enriched gas to the product tank is stopped. This is called a step-down pressure equalization step.

On the other hand, in the adsorption cylinder 8b, compressed air flows in from the adsorption cylinder raw material end, and oxygen-enriched gas flows in from the product end, and the pressure rises. This is called a pressure equalizing step.
Thereafter, the suction cylinders 8a and 8b are replaced and the above-described steps are repeated. As described above, the oxygen-enriched gas can be continuously taken out as a product gas.

  The configuration of the pressurizing valve and the pressure reducing valve is as follows. A pilot diaphragm valve is used as the pressurizing valve. As described above, in the pressurizing valve, the pilot air supply port is connected to the discharge port of the compressor similarly to the valve inlet, and the pilot air exhaust port is open to the atmosphere. When the valve is closed, the pressure in the space above the diaphragm is equal to the pressure at the valve inlet, that is, the compressor outlet, and the sum of the force due to the spring force and the pressure above the diaphragm is greater than the sum of the forces due to the pressure at the valve inlet and outlet. The valve becomes closed. When the valve is opened, the space above the diaphragm is reduced to atmospheric pressure, while the compressor discharge pressure and the pressure of the adsorption cylinder are sufficiently higher than atmospheric pressure, so the valve opens.

  The pressure reducing valve has the same configuration, but the pilot gas exhaust port 21 is connected to a compressor air intake passage that connects the compressor 1 and the intake silencer 12. In a normal pilot type solenoid valve, the pilot gas discharge port 21 is connected to the gas outlet 18 or released to the atmosphere as described above. In such a normal configuration, the pressure reducing valve main valve 4 is opened and the adsorption cylinder is opened. When 8 is reduced to near atmospheric pressure, the gas inlet pressure Pin and the gas outlet pressure Pout become substantially equal to the pilot gas discharge pressure Pl, and the force for pushing up the diaphragm is lost and the main valve 4 is closed. Therefore, when the pressure in the adsorption cylinder is lowered to a certain pressure, the adsorption cylinder cannot be further depressurized. Therefore, nitrogen adsorbed by the adsorbent cannot be exhausted sufficiently, and the oxygen concentration of the product gas is lowered.

  In order to recover this, it is necessary to increase the discharge pressure of the compressor and increase the maximum adsorption amount of the adsorbent or increase the supply flow rate of the compressor and increase the number of oxygen molecules sent to the adsorption cylinder. Leads to an increase in power consumption.

On the other hand, in this embodiment, the pilot gas exhaust port 21 is connected to a compressor air intake passage connecting the compressor 1 and the intake silencer 12. Usually, the purpose of the intake silencer is to reduce the intake noise of the compressor, and its principle is to smooth the intake flow rate of the compressor by providing an appropriate flow path resistance between the compressor air intake port. Therefore, the air suction flow path between the compressor and the intake silencer has a slight negative pressure. The pressure is usually between about the same pressure as the atmospheric pressure and about -10 kPa. However, if the main valve is a diaphragm type, the diaphragm can be sufficiently driven with such a pressure.
As the flow path resistance, it is possible to use a dust-proof intake filter, a flow path throttle means, etc. in addition to the intake silencer.

  By the invention as described above, in the pressure swing adsorption type oxygen concentrator, the pressure loss of the exhaust valve that greatly affects the performance of the oxygen concentration process is reduced, and the power consumption of the solenoid valve and the power consumption of the compressor are simultaneously reduced. This makes it possible to realize a pressure swing adsorption oxygen concentrator with lower power consumption than conventional devices.

The flow block diagram which shows the embodiment of the pressure swing adsorption type oxygen concentrator of this invention. The flow block diagram which shows the embodiment of the conventional pressure swing adsorption type oxygen concentrator. The block diagram of a diaphragm type pilot valve. The block diagram of a diaphragm valve in case a pilot valve is an OFF state. The block diagram of the diaphragm valve in case a pilot valve is an ON state.

Claims (5)

  At least one adsorption cylinder containing an adsorbent that preferentially adsorbs nitrogen over oxygen; air compression supply means for taking in air from an air inlet and supplying compressed air into the adsorption cylinder; A gas flow path switching means for switching supply and exhaust of air to the adsorption cylinder, supplying raw air to the adsorption cylinder from the air compression supply means through the switching means, and adding the inside of the adsorption cylinder The adsorption step of adsorbing nitrogen in the supply air to the adsorbent and taking out unadsorbed oxygen as product gas, exhausting the inside of the adsorption cylinder through the switching means, and desorbing nitrogen adsorbed on the adsorbent In the pressure swing adsorption type oxygen concentrator that concentrates and extracts oxygen in the air by repeatedly performing the desorption step of discharging, the switching means is a pilot type solenoid valve, and the discharge pressure of the pilot air A pressure swing adsorption type oxygen concentrator comprising a pilot air exhaust mechanism that exhausts air at a pressure lower than atmospheric pressure.   The raw air intake port of the air compression supply means is provided with flow path resistance means for limiting the amount of air inflow, and the pilot air exhaust mechanism includes a pilot air discharge flow path of the pilot solenoid valve, the flow path resistance means, 2. The pressure swing adsorption type oxygen concentrator according to claim 1, wherein the pressure swing adsorption oxygen concentrator is a flow path connecting the inside of the air suction flow path between the compressed air supply means.   3. The pressure swing adsorption type oxygen concentrator according to claim 2, wherein the flow path resistance means is noise reduction means for reducing noise emitted from the air inlet.   The pressure swing adsorption type oxygen concentrator according to any one of claims 1 to 3, wherein a main valve of the pilot type solenoid valve is a diaphragm type.   The pressure swing adsorption type oxygen concentrator according to any one of claims 1 to 4, wherein the discharge pressure is a gauge pressure of less than 0 KPa and -10 kPa or more.