WO1995033681A1

WO1995033681A1 - Oxygen generating method based on pressure variation adsorption separation

Info

Publication number: WO1995033681A1
Application number: PCT/JP1995/001083
Authority: WO
Inventors: Shin Hayashi; Masato Kawai
Original assignee: Nippon Sanso Corporation
Priority date: 1994-06-02
Filing date: 1995-06-02
Publication date: 1995-12-14
Also published as: CN1042215C; JPH07330306A; JP3654661B2; CN1128979A

Abstract

This invention provides a pressure variation adsorption type oxygen generating method, which increases the rates of oxygen generation and material recovery and reduces power unit. This method comprises the steps of connecting an outlet end of an adsorption cylinder in which an adsorption step has been finished with an outlet end of an adsorption cylinder in which a regeneration step has been finished, recovering a residual gas from the former adsorption cylinder to the latter adsorption cylinder, and introducing a mixed gas, the composition of which is substantially identical with that of a raw gas, into an inlet end of at least one of these cylinders.

Description

Description Oxygen generation method by pressure fluctuation adsorption separation method

The present invention relates to a method for generating oxygen by a pressure fluctuation adsorption separation method, and more specifically, a mixed gas containing oxygen and nitrogen as main components by a pressure fluctuation adsorption method using an adsorbent that selectively adsorbs nitrogen. For example, it relates to a method for generating oxygen with a purity of about 90% from air.

Background art

As a method of generating concentrated oxygen by treating a mixed gas containing oxygen and nitrogen as main components, for example, air, an oxygen generation method using a pressure fluctuation adsorption method (hereinafter referred to as an oxygen PSA method) is widely used. I have. This oxygen PSA method is generally performed using an apparatus equipped with a plurality of adsorption columns filled with zeolite, which selectively adsorbs nitrogen as an adsorbent (oxygen PSA apparatus). For each adsorption column, concentrated oxygen is continuously generated by alternately repeating the adsorption process of operating at a relatively high pressure and the regeneration process of operating at a relatively low pressure. It is configured to In such an oxygen PSA system, oxygen is concentrated and separated from air by using the high selective adsorption characteristics of zeolite for nitrogen, but oxygen and argon have almost the same adsorption characteristics for zeolite. Therefore, the maximum concentration of oxygen separated and concentrated was approximately 95% because it contained argon.

On the other hand, when oxygen is used for cutting metal as a condition on the side using oxygen, if there is no oxygen concentration of about 99.5%, there is a problem in terms of cutting speed and cut surface, and Medical oxygen used in hospitals, etc. is specified by the Pharmaceutical Affairs Law as requiring an oxygen concentration of 99.5% or more. However, an oxygen concentration of 95% or less is sufficient for steelmaking using an electric furnace, and for most other oxygen applications, an oxygen concentration of around 90% is sufficient. The application range can be said to be extremely wide. For this reason, various improvements have been made to the PSA method in order to obtain oxygen at a lower cost for users with an oxygen concentration of around 90% and for consuming a large amount of oxygen. Was.

The points of interest for improving the performance of the oxygen PSA method are to increase the amount of oxygen generated per adsorbent used to reduce the size of the device, and to reduce the unit power consumption. There are two points to raise the product oxygen recovery rate.

As described above, the oxygen PSA method basically includes the adsorption step and the regeneration step, but in order to increase the oxygen recovery rate, a pressure recovery step, a repressurization step, etc. are added to this basic step. Yeah. In addition, instead of the pressure recovery step, a co-current depressurization step is performed to utilize the concentrated oxygen remaining in the adsorption column as a product or a purge gas. In order to increase the amount of oxygen generated per adsorbent, purging is performed with a part of the product gas in the regeneration process to promote the desorption of nitrogen from the adsorbent. This purging operation reduces the partial pressure of the gaseous easily adsorbed components by supplying a part of the product gas from the product outlet end when the pressure in the adsorption cylinder decreases due to the pressure reduction. This method promotes desorption, and is adopted regardless of the normal pressure regeneration and vacuum regeneration processes.

In order to improve the performance of the oxygen PSA method, conventional methods include, for example, the method described in Japanese Patent Application Laid-Open No. 63-144004, The pressure equalization process (simultaneous upper and lower pressure equalization) in which two adsorption cylinders are connected to collect gas from both the upper part (product gas outlet) and the lower part (source gas inlet) of each adsorption cylinder at the same time. Has adopted. In this case, a large amount of gas can be recovered, but in the adsorption column on the gas receiving side, a relatively oxygen-enriched gas is recovered at the top of the column, and air or some nitrogen rather than air is collected at the bottom of the column. Minute higher gas is recovered. Therefore, in this method, the product recovery rate is high, but the amount of oxygen generated per adsorbent is low.

Further, the one described in Japanese Patent Application Laid-Open No. 63-144401 discloses that, in the pressure equalization step, two cylinders are connected in the same manner as described above, and simultaneously from both the upper and lower parts of the cylinder. At this time, gas is collected. At this time, the lower line uses a vacuum exhaust line to exhaust part of the gas collected from the lower part, and adjusts the amount of gas collected from the lower part of the cylinder. This method has a problem that the product recovery rate is not so high because the amount of gas recovered is smaller than the above method, and the receiving cylinder has a low pressure rise due to recovery. The amount of oxygen required for oxygen charging is increased, and the cylinder in the adsorption process during oxygen generation There was a problem that the adsorption pressure was lowered.

In other words, in the oxygen PSA method, maintaining a high product recovery rate and increasing the amount of oxygen generated per adsorbent is a conflicting requirement. , Had not yet been developed.

Disclosure of the invention

Accordingly, an object of the present invention is to provide a pressure fluctuation adsorption type oxygen generation method that can increase the amount of generated oxygen while maintaining a high product recovery rate and can reduce the power consumption unit. . -In order to achieve the above object, the pressure fluctuation adsorption type oxygen generation method of the present invention comprises: an adsorption step in which a plurality of adsorption columns filled with zeolite as an adsorbent are each performed at a relatively high pressure; The pressure fluctuation adsorption separation method, which separates oxygen and nitrogen from a mixed gas containing oxygen and nitrogen as the main component, to generate oxygen In the oxygen generation method, an outlet end of the adsorption cylinder after the adsorption step is communicated with an outlet end of the adsorption cylinder after the regeneration step, and a gas remaining in the adsorption cylinder after the adsorption step is regenerated. At the same time as performing the pressure recovery step of recovering the mixed gas into the adsorption cylinder that has completed the adsorption process, and at the same time, adsorbing the mixed gas from at least one of the inlet ends of the adsorption cylinder that has completed the adsorption process and the adsorption cylinder that has completed the regeneration process. Introduced into It is characterized in Rukoto.

Further, according to the present invention, the adsorption cylinder for introducing the mixed gas is an adsorption cylinder after the regeneration step, and the primary pressurization step is performed by introducing the mixed gas at substantially atmospheric pressure. Performing a secondary pressurizing step of supplying a part of the product oxygen from the outlet end to the adsorption column after the step and continuing to introduce the mixed gas at substantially atmospheric pressure from the inlet end; The adsorbing cylinder into which the adsorbing step has been completed is an adsorbing cylinder that has completed the adsorbing step, and the mixed gas is introduced at substantially the same pressure as in the adsorbing step. It is characterized by simultaneous evacuation. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a system diagram showing an example of the oxygen PSA device.

FIG. 2 is a process chart showing a first embodiment of the present invention.

FIG. 3 is a process chart showing a second embodiment of the present invention. FIG. 4 is a process chart showing a third embodiment of the present invention.

FIG. 5 is a process chart showing a fourth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail based on embodiments shown in the drawings.

First, FIG. 1 shows an example of an oxygen PSA apparatus for carrying out the method of the present invention, which has three adsorption cylinders A, B, and C each filled with zeolite as an adsorbent, and The figure shows a three-cylinder oxygen PSA device that separates and generates oxygen from air, which is a mixed gas containing nitrogen and nitrogen as a main component.

This oxygen PSA apparatus includes the three adsorption cylinders A, B, and C, a blower 1 that raises air as a raw material to a predetermined pressure and supplies the air to the adsorption cylinder, and evacuates the interior of the adsorption cylinder. A vacuum pump 2, a product storage tank 3 for temporarily storing product oxygen derived from the adsorption column, flow control valves 4 and 5 for controlling a gas flow rate in a regeneration process and a pressurization process, and a product oxygen gas supply amount. The flow control valve 6 to be controlled and a number of automatic valves 11, 12, 13, 14, 15, 16, 17 (for each adsorption) The valves attached to the cylinders are labeled a, b, and c corresponding to the respective adsorption cylinders A, B, and C.) and an air inlet pipe for introducing air at atmospheric pressure into the adsorption cylinder. 8 and.

The oxygen PSA device is configured to open and close the plurality of automatic valves in a predetermined order to continuously generate oxygen gas. For example, by repeating the nine steps shown in FIG. A mixed gas containing oxygen and nitrogen as main components, for example, oxygen and nitrogen in the air is separated to generate product oxygen.

Hereinafter, a first embodiment of the oxygen generating method of the present invention will be described with reference to the process chart shown in FIG. 2 using the above oxygen PSA device.

First, step 1 is a state in which the adsorption cylinder A is switched to the adsorption step, the adsorption cylinder B is switched to the pressure recovery step after the regeneration step is completed, and the adsorption cylinder C is switched to the pressure recovery step after the adsorption step is completed. In the adsorption column A, oxygen and nitrogen are separated.

That is, the raw material air, which has been pressurized to a predetermined pressure, for example, 500 mmAq (about 800 Torr) by the blower 1, is introduced into the adsorption column A, and the nitrogen in the air is transferred to the zeolite filled in the column. Adsorbs and separates from oxygen, and oxygen, a non-adsorbed component, becomes product oxygen Derived.

In addition, for the adsorption cylinder B in which the in-cylinder pressure is lower than the atmospheric pressure and the adsorption cylinder C in which the in-cylinder pressure is relatively high, pressure recovery is performed so that the outlet ends of the adsorption cylinders communicate with each other. The gas inside is introduced into the adsorption column B from the outlet side while the flow rate is adjusted by the flow control valve 5 (see Fig. 1). Air is inhaled. As a result, in the adsorption cylinder B, the relatively oxygen-rich gas in the adsorption cylinder C is collected at the outlet of the adsorption cylinder B, and the air as the raw material is discharged from the entrance of the adsorption cylinder B. The primary pressurization process, which accepts without pressurization by blower 1, is performed.

In step 2, adsorber A continuously receives pressurized raw material air from the lower part of the cylinder and generates product oxygen from the top of the cylinder, and adsorber B generates from adsorber A This is a secondary pressurization step of receiving a part of the product oxygen from the top of the cylinder. The adsorption cylinder C is a vacuum regeneration step in which the gas in the cylinder is exhausted by the vacuum pump 2 and the pressure in the cylinder is reduced to desorb the nitrogen adsorbed by the adsorbent.

In step 3, the adsorption cylinder A is in the adsorption step continuously, and the adsorption cylinder B is successively pressurized to the pressure during the adsorption step, that is, the pressure substantially equal to the adsorption pressure, in the secondary pressurization step . The adsorption cylinder C receives a part of the product oxygen generated from the adsorption cylinder A from the top of the cylinder while evacuation is performed when the degree of vacuum becomes relatively high due to the evacuation of the vacuum pump 2. A purge state (purge regeneration step) is established.

In step 4, adsorption column A is in the same pressure recovery step as adsorption column C in step 1, adsorption column B is in the same adsorption step as adsorption column A in step 1, and adsorption column C is the same as adsorption column B in step 1. It becomes primary pressurization. Hereinafter, in step 5, the adsorption cylinder A becomes a vacuum regeneration step, and the adsorption cylinder C becomes a secondary pressurization step. In step 6, the adsorption cylinder A becomes a purge regeneration step. Further, in Steps 7, 8, and 9, the state of the adsorption cylinder A in Steps 1 to 3 is indicated by the adsorption cylinder C, the state of the adsorption cylinder B is indicated by the adsorption cylinder A, and the state of the adsorption cylinder C is indicated by the adsorption cylinder B. After completing step 9, return to step 1.

As described above, the steps 1 to 9 are performed in each adsorption column, and the process returns to the step 1 from the step 9 and is repeated to continuously generate oxygen. The time of each process is set to 60 seconds of cycle time. Normally, processes 1, 4, and 7 are 5 to 10 seconds, and processes 2, 5, and 8 t 10-1 5 seconds, Steps 3, 6, and 9 are 40 to 45 seconds. In addition, the pressure in each step is usually 500 mmAq (approximately 800 Torr), the vacuum regeneration pressure is 200 Torr, and the final pressure in the primary pressurization step is 500 T orr, The final pressure in the secondary pressurization step is about 760 T orr.

As shown in the present embodiment, in the pressure recovery step, an adsorption cylinder having a relatively high in-cylinder pressure after the adsorption step and an adsorption cylinder having a in-cylinder pressure lower than the atmospheric pressure after the regeneration step are both used. The gas at the upper part of the adsorption cylinder after the adsorption step is collected from the top of the adsorption cylinder after the regeneration step, and the air at atmospheric pressure is discharged from the lower part of the adsorption cylinder after the adsorption step. By inhaling the gas, the gas rich in oxygen in the adsorption cylinder after the adsorption step can be recovered in the adsorption cylinder after the regeneration step, and the pressure of the adsorption cylinder can be efficiently increased. It can be carried out.

In other words, it is necessary for the adsorption cylinder that has completed the regeneration step to pressurize the inside of the cylinder to a pressure as close as possible to the adsorption pressure in the primary pressurization step and the secondary pressurization step before starting the next adsorption step. However, as described above, in the primary pressurization step, the gas rich in oxygen is recovered at the upper part of the adsorption cylinder after the regeneration step, and the air is sucked in from the lower part of the adsorption cylinder to recover the gas. The pressure in the adsorption column can be sufficiently increased while the gas amount is required and sufficient. Therefore, the pressure in the adsorption column at the time of entering the secondary pressurization step using a part of the product oxygen can be made higher than before, and the amount of product oxygen used can be reduced.

By reducing the amount of product oxygen used for pressurization, the adsorption operation of the adsorption column in the adsorption step can be performed in a stable state, and the amount of product oxygen generated can be increased. In addition, the air sucked into the adsorption cylinder in the primary pressurization step is air having the same composition as the raw material mixed gas, and this air is separated from the negative pressure in the cylinder and the atmospheric pressure without passing through the blower 1. Since the air is sucked into the adsorption cylinder due to the pressure difference, compression power is required by using the blower 1, and the actual amount of treated air is larger than that of the conventional blower. However, power costs can be reduced and the amount of product oxygen generated can be increased. FIG. 3 is a process diagram showing a second embodiment of the present invention. In the first embodiment, during the operation of the secondary pressurizing step, air is sucked until the in-cylinder pressure becomes close to the atmospheric pressure. Is to be continued. In the following embodiment, the same as the first embodiment is used. A detailed description of such parts will be omitted.

That is, in the step 1, as in the first embodiment, the adsorption column A receives the raw air from the blower 1 to generate product oxygen and the adsorption column A receives the raw air from the blower 1, and the pressure after the adsorption column B completes the regeneration step. The recovery step is a pressure recovery step after the adsorption cylinder C has completed the adsorption step.The adsorption cylinder B collects the oxygen-rich gas at the outlet side of the adsorption cylinder C at the outlet side, and at the inlet side. In the primary pressurization process in which air is sucked in from the side via the air introduction pipe 18, the process 2 is in the adsorption process, where the adsorption tube A is the adsorption process, the adsorption tube B is the secondary pressurization process, and the adsorption tube C is vacuum. This is a vacuum regeneration step in which gas in the cylinder is exhausted by the pump 2.At this time, in the adsorption cylinder B, a part of the product oxygen is received from the top of the cylinder, and air is sucked in from the lower part of the cylinder. ing. Therefore, in the adsorption cylinder B, secondary pressurization is performed by the product oxygen in the upper part of the cylinder and the air in the lower part of the cylinder.

In step 3, the adsorption cylinder A is in the adsorption step continuously, and the adsorption cylinder B is in the secondary pressurization step, but in the adsorption cylinder B, air is sucked in from the lower part of the cylinder according to the in-cylinder pressure. Is stopped, and pressurization is performed only by receiving product oxygen from the top of the cylinder. In addition, adsorption cylinder C is in a purge regeneration process that evacuates while receiving a part of the product oxygen from the top of the cylinder.

Hereinafter, as in the first embodiment, in step 4, the adsorption column A is subjected to the same pressure recovery step as the adsorption column C in step 1, and the adsorption column B is subjected to the same adsorption step as the adsorption column A in step 1. C has the same primary pressurization as the adsorption cylinder B in step 1, in step 5, adsorption cylinder A performs the vacuum regeneration step, adsorption cylinder C performs the secondary pressurization step, and in step 6, adsorption cylinder A purges It is a regeneration process. Further, in step 7, 8, 9, adsorption column C the state of the adsorption column A in step 1-3, the adsorption column A the status of the adsorption column B is, adsorption column B force ⁵ the state of the adsorption column C, respectively After completing step 9, return to step 1.

As shown in the present embodiment, in the secondary pressurizing step, the air suction is continued until the in-cylinder pressure becomes close to the atmospheric pressure, so that the air suction amount is larger than in the first embodiment. Therefore, the amount of product oxygen required for pressurization can be further reduced, and the amount of product oxygen generated can be further increased. In addition, in the secondary pressurization step, the pressure at which the suction of air is stopped can be near atmospheric pressure, but it is usually 600 to 700 T Orr is appropriate.

FIG. 4 is a process diagram showing a third embodiment of the present invention. In the first embodiment, at the time of pressure recovery, after the adsorption step is completed, the recovered gas is discharged to the adsorption cylinder on the suction side. The introduction of raw air was continued (steps 1, 4, and 7).

In this way, by continuing the introduction of the raw material air into the adsorption cylinder after the adsorption step and entering the pressure recovery step, the pressure in the adsorption cylinder can be maintained at the adsorption pressure, and the nitrogen from the adsorbent can be maintained. Since the desorption of water can be suppressed, the pressure of the adsorption column on the receiving side can be sufficiently increased while preventing nitrogen from being mixed into the gas collected from the upper portion of the adsorption column into the adsorption column after the regeneration step. It can be carried out.

FIG. 5 is a process diagram showing a fourth embodiment of the present invention. In the first embodiment, at the time of pressure recovery, the cylinder in the adsorption cylinder on the recovered gas discharge side after the adsorption step is completed. With the release of the recovered gas from the upper part, the vacuum evacuation from the lower part of the cylinder is started simultaneously (steps 1, 4, and 7). As a result, the idle time of the vacuum pump can be eliminated and the efficiency can be improved.

In the present invention, it is possible to carry out the embodiments in combination, and the number of adsorption tubes used is not limited to three, but may be two or four or more. The present invention can also be applied to an apparatus using an adsorption cylinder.

The adsorbent used is a zeolite that preferentially adsorbs a larger amount of nitrogen than oxygen, for example, so-called MS-5A, MS-10X, MS-13X, mordenite. In addition, zeolite obtained by ion-exchanging metals in zeolite can be used so as to have pores capable of adsorbing nitrogen at a sufficiently high adsorption rate. Further, the mixed gas containing oxygen and nitrogen as main components is not limited to air, and a mixed gas having an arbitrary composition can be used. In this case, the above-described air introduction pipe may be connected to a mixed gas generating section or a storage tank serving as a raw material. Next, using the apparatus having the configuration shown in FIG. 1, the operation methods described in the first to fourth embodiments and the simultaneous upper and lower pressure equalization method as a conventional example were performed. The experimental results of the measurements will be described.

The adsorber cylinder has an inner diameter of 15.5 mm x 1.6 m in height. A 1.6 mm diameter pellet with a sieve 5A was used. The operating conditions were an adsorption pressure of 500 mm Aq and a vacuum regeneration pressure of 200 Torr. The cycle time is 60 seconds, the step corresponding to step 1 is 5 to 10 seconds, the step corresponding to step 2 is 10 15 seconds, and the step corresponding to step 3 is 40 to 45 seconds. Seconds. Table 1 shows the experimental results.

As described above, according to the pressure fluctuation adsorption type oxygen generation method of the present invention, during the primary pressurizing step, the raw material gas or a mixed gas having substantially the same composition as the raw material gas is introduced into the adsorption column, so that the regeneration step The adsorption column can be sufficiently pressurized while preventing nitrogen from flowing into the completed adsorption column, and the amount of product oxygen used for pressurization can be reduced to increase the amount of product oxygen generated. Can be.

In particular, by sucking the raw material gas or a mixed gas having substantially the same composition as the raw material gas into the adsorption column after the regeneration process without using a pressurizing means such as a blower, the power is reduced compared to the processing amount. Costs can be reduced. In addition, when the raw material gas is air, the air taken into the adsorption column is sent at atmospheric pressure, which can be excluded from the raw material supply amount by the blower, and therefore, the oxygen recovery rate is substantially remarkable. Can be increased.

Claims

The scope of the claims

1. A plurality of adsorption columns filled with zeolite as an adsorbent are alternately and successively subjected to an adsorption step performed at a relatively high pressure and a regeneration step performed at a pressure lower than the atmospheric pressure. A method for separating oxygen and nitrogen from a mixed gas containing oxygen and nitrogen as main components to generate oxygen gas by a pressure fluctuation adsorption separation method, comprising: an outlet end of an adsorption cylinder having completed the adsorption step; The outlet end of the adsorption cylinder that has completed the regeneration process is communicated with the outlet end, and the pressure recovery process that recovers the gas remaining in the adsorption cylinder that has completed the adsorption process into the adsorption cylinder that has completed the regeneration process is performed. A method for generating oxygen by a pressure fluctuation adsorption separation method, wherein the mixed gas is introduced into the adsorption column from at least one of the inlet ends of the adsorption column that has been completed and the adsorption column that has completed the regeneration step.

2. The adsorption cylinder that introduces the mixed gas is an adsorption cylinder that has been subjected to the regeneration step, and performs a primary pressurization step by introducing the mixed gas at substantially atmospheric pressure. 2. A method for generating oxygen by the pressure fluctuation adsorption separation method according to claim 1.

3. After the primary pressurizing step, the adsorption cylinder supplies a part of the product oxygen gas from the outlet end, and performs the secondary pressurizing step of continuing the introduction of the substantially atmospheric pressure mixed gas from the inlet end. 3. The method for generating oxygen by the pressure fluctuation adsorption separation method according to claim 2, wherein the method is performed.

4. The adsorption cylinder for introducing the mixed gas is an adsorption cylinder that has been subjected to the adsorption step, and the mixed gas is introduced at substantially the same pressure as in the adsorption step. An oxygen generation method according to the pressure fluctuation adsorption separation method described above.

5. The oxygen generating apparatus according to claim 1, wherein the adsorption column that has completed the adsorption step simultaneously performs vacuum exhaust from the inlet end during the pressure recovery step. .