JP7388731B2 - Pressure swing adsorption device and gas generation method - Google Patents

Description

The present invention relates to a pressure swing adsorption (PSA) device and a gas generation method using the pressure swing adsorption device.

A pressure swing adsorption device (hereinafter referred to as a PSA device) adsorbs a specific gas from a raw material gas to generate a target gas, and supplies this target gas as a product gas.

Patent Document 1 discloses a PSA device in which two adsorption towers form one group. The PSA device of Patent Document 1 introduces a raw material gas into one adsorption tower, pressurizes this adsorption tower, and generates a target gas, and during this time, regenerates the adsorbent in the other adsorption tower. The generated target gas is supplied to a buffer tank. The PSA unit then pressure equalizes both adsorption columns with respect to each other.

Then, the PSA device introduces the raw material gas into the other adsorption tower, pressurizes this adsorption tower to generate a target gas, and regenerates the adsorbent in one adsorption tower. The generated target gas is sent to a buffer tank. The PSA unit then pressure equalizes both adsorption columns with respect to each other. The PSA device repeats these steps.

During the pressure equalization step and from the pressure equalization step until the pressure of the adsorption tower rises to the buffer tank pressure due to feed gas supply, target gas is not supplied from any adsorption tower to the buffer tank. During this time, the target gas already stored in the buffer tank is supplied to the outside as a product gas, thereby making it possible to continuously supply the product gas to the outside. However, this reduces the pressure in the buffer tank.

In other words, it can be said that the pressure of the product gas provided to users decreases because there is a time when the target gas is not taken out from any adsorption tower.

Japanese Patent Application Publication No. 2010-75778 Publication number 07-002025

An object of the present invention is to provide a PSA device having a configuration that can contribute to always taking out a target gas from one of the adsorption towers. Another object of the present invention is to provide a gas generation method using the PSA device.

The present invention is a pressure swing adsorption apparatus that adsorbs a specific gas from a source gas to generate a target gas by a pressure swing adsorption method,
a group including three adsorption towers filled with an adsorbent that preferentially adsorbs the specific gas over the target gas;
a first compression means for compressing the raw material gas;
a second compression means for compressing the raw material gas to a pressure higher than the compression pressure by the first compression means;
a supply line connected to each of the adsorption towers;
a first supply switching means for switching the state of the supply passage in order to selectively supply the raw material gas compressed by the first compression means to the adsorption tower through the supply passage;
A second supply different from the first supply switching means that switches the state of the supply path in order to selectively supply the raw material gas compressed by the second compression means to the adsorption tower through the supply path. a switching means;
a discharge path connected to each of the adsorption towers;
discharge switching means for switching the state of the discharge passage in order to selectively discharge the specific gas from each of the adsorption towers through the discharge passage;
a communication path connected to each of the adsorption towers;
communication switching means for switching the state of the communication passage in order to equalize the pressure of any two of the adsorption towers in the group through the communication passage;
A take-out passage connected to each of the adsorption towers is provided to take out the target gas from the adsorption towers.

The first compression means
including a compressor that compresses the raw material gas,
The supply path is
a main path connected to the compressor and the group;
A bypass road that detours around the main road,
The second compression means
The bypass path may include at least one pressure increase valve for increasing the pressure of the raw material gas compressed by the compressor.

The first compression means
including a first compressor that compresses the raw material gas,
The second compression means
It may include a second compressor that compresses the raw material gas to a pressure higher than the compression pressure by the first compressor.

The first compression means
including a first compressor that compresses the raw material gas,
The second compression means
a second compressor that compresses the raw material gas to a pressure higher than the compression pressure by the first compressor;
a pressure increasing valve for further increasing the pressure of the raw material gas compressed by the first compressor,
The supply path is
a main path connected to the first compressor and the group;
a bypass path in which the pressure increase valve is interposed and bypasses the main path;
an auxiliary path connected to the bypass path and the second compressor,
The pressure swing adsorption device includes:
The apparatus may further include supply selection means for selecting which of the raw material gas compressed by the second compressor or the raw material gas pressure increased by the pressure increase valve is to be supplied to the group.

The pressure swing adsorption device further includes:
a backflow prevention means interposed in the take-out passage for preventing the target gas from flowing back into the adsorption tower through the take-out passage; and a take-out switching means for switching the state of the take-out path in order to take out the container.

further comprising a control unit that controls the first supply switching means, the second supply switching means, the discharge switching means, and the communication switching means,
The control unit includes:
Among the group, one adsorption tower is used as a first adsorption tower, another adsorption tower is used as a second adsorption tower, and the remaining one adsorption tower is used as a third adsorption tower,
The raw material gas is supplied by the first compression means to the first adsorption tower through the supply path, the target gas is taken out from the first adsorption tower through the take-out path, and the specific gas is removed from the third adsorption tower. a first step of regenerating the adsorbent in the third adsorption tower by discharging it from the tower through the discharge passage;
The source gas is supplied to the first adsorption tower by the second compression means through the supply path, and the target gas is continued to be taken out from the first adsorption tower through the take-out path; The compression means supplies the second adsorption tower through the supply path to begin taking out the target gas from the second adsorption tower through the take-out path, and the specific gas is supplied from the third adsorption tower through the discharge path. a second step of discharging and continuing the regeneration treatment of the adsorbent in the third adsorption tower;
The raw material gas is continuously supplied by the first compression means to the second adsorption tower through the supply path and taken out from the second adsorption tower through the take-out path, and the first adsorption tower and the third adsorption tower and a third step of making the pressure equalize by communicating with each other through the communication path, and may be performed in order.

The control unit includes:
After carrying out the first to third steps,
The adsorption tower that was the first adsorption tower during the implementation of the first to third steps was used as the third adsorption tower, the adsorption tower that was the second adsorption tower was used as the first adsorption tower, and the adsorption tower that was the third adsorption tower You may carry out the said 1st to 3rd process again by using it as a 2nd adsorption tower.

Further, the present invention provides a gas generation method for generating the target gas using the pressure swing adsorption device described above.

According to the present invention, a PSA device is provided which has a configuration that can contribute to always taking out a target gas from one of the adsorption towers. Further, according to the present invention, a gas generation method using the above-mentioned PSA device is provided.

1 is a schematic diagram of an exemplary PSA device of the present invention; FIG. The first to third steps will be explained. The 1st to 3rd steps will be explained. The first to third steps will be explained. The cycle conditions of Examples are shown.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an exemplary PSA device. A PSA device adsorbs a specific gas from a source gas to generate a target gas using the PSA method. For example, a PSA device uses air as a raw material gas. In this case, the PSA device includes an oxygen PSA device that adsorbs nitrogen to generate oxygen, a nitrogen PSA device that adsorbs oxygen to generate nitrogen, and a PSA dryer that adsorbs moisture to generate dry air.

The PSA apparatus includes three adsorption towers Ta, Tb, and Tc that are arranged in parallel with each other, and one group G is formed by the three adsorption towers Ta, Tb, and Tc. An adsorbent (not shown) is filled in the adsorption towers Ta, Tb, and Tc. The adsorbent has the property of preferentially adsorbing a specific gas over a target gas. In the case of an oxygen PSA device, for example, a zeolite adsorbent that adsorbs nitrogen gas preferentially over oxygen gas is used. In the case of a nitrogen PSA device, for example, a molecular sieve activated carbon adsorbent that adsorbs oxygen gas preferentially over nitrogen gas is used. In the case of PSA dryers, a desiccant is used as an adsorbent.

When the adsorption tower is pressurized by supplying the raw material gas, the adsorbent adsorbs a specific gas in the raw material gas, and as a result, the target gas remains in the adsorption tower. In this way, the target gas is produced within the adsorption tower.

The PSA apparatus includes a first compression means 1A and second compression means 1B and 1C for compressing and supplying raw material gas. The PSA apparatus further includes a supply path 2 connected to the adsorption towers Ta, Tb, and Tc to supply compressed raw material gas. These configurations will be detailed later.

The PSA device further includes a discharge path 3 connected to the adsorption towers Ta, Tb, and Tc. The discharge passage 3 has two branch passages 3a, 3b, and 3c, and these branch passages 3a, 3b, and 3c are connected to three adsorption towers Ta, Tb, and Tc, respectively. Furthermore, the discharge path 3 has a discharge port 30 .

The PSA device further includes a discharge switching means that switches the state of the discharge passage 3 in order to selectively discharge the specific gas from each of the adsorption towers Ta, Tb, and Tc through the discharge passage 3 and the discharge port 30 to the external environment. Equipped with. The discharge switching means of the embodiment is on-off valves V4, V5, and V6 provided for each of the adsorption towers Ta, Tb, and Tc, and interposed in the branch paths 3a, 3b, and 3c of the discharge path 3. By controlling the opening and closing of valves 4V, 5V, and 6V, it is possible to select adsorption towers Ta, Tb, and Tc from which specific gases are discharged.

The PSA device further includes a communication path 4 connected to the adsorption towers Ta, Tb, and Tc. The communication passage 4 has three branch passages 4a, 4b, and 4c, and these branch passages 4a, 4b, and 4c are connected to three adsorption towers Ta, Tb, and Tc, respectively.

Further, the PSA device includes communication switching means for switching the state of the communication path 4 in order to equalize the pressures of any two adsorption towers in group G. The communication switching means of the embodiment are on-off valves V7, V8, and V9 provided for each of the adsorption towers Ta, Tb, and Tc, and interposed in the branch paths 4a, 4b, and 4c of the communication path 4. By controlling the opening and closing of valves V7, V8, and V9, two adsorption towers to be communicated with each other can be selected from Group G in order to carry out the pressure equalization step described below.

The PSA device further includes an extraction path 5 connected to the adsorption towers Ta, Tb, and Tc. A buffer tank BT is interposed in the take-out passage 5. The take-out passage 5 has three branch passages 5a, 5b, and 5c, and these branch passages 5a, 5b, and 5c are connected to three adsorption towers Ta, Tb, and Tc, respectively. The outlet passage 5 further has an outlet 50 . This take-out path 5 is a flow path for taking out the target gases generated in the adsorption towers Ta, Tb, and Tc as product gases, supplying them to the buffer tank BT, and supplying them to the outside of the PSA apparatus from the take-out port 50. It is.

In the embodiment, the PSA device prevents the target gas taken out from the adsorption towers Ta, Tb, and Tc through the take-out path 5 from flowing back from the buffer tank BT to the adsorption towers Ta, Tb, and Tc through the take-out path 5. As a backflow prevention means, check valves CVa, CVb, and CVc are provided in the branch passages 5a, 5b, and 5c, respectively.

Note that instead of the check valves CVa, CVb, and CVc, PSA devices (not shown) are provided for each of the adsorption towers Ta, Tb, and Tc, and are interposed in the branch passages 50a, 50b, and 50c of the take-out passage 50. In order to switch the state of the take-out passage 5, an on-off valve controlled by a control section 6, which will be described later, may be provided as the take-out switching means. Then, by controlling the opening and closing of these opening/closing valves, the state of the extraction passage 5 may be switched to select the adsorption tower from which the generated target gas is extracted.

The first compression means 1A is a compressor, compresses the raw material gas, and supplies the compressed raw material gas to the group G through the supply path 2. For example, the compressor 1A is a compressor located in an existing factory. For this purpose, the supply channel 2 comprises a main channel 20 . The main passage 20 has three branch passages 20a, 20b, and 20c, and these branch passages 20a, 20b, and 20c are connected to three adsorption towers Ta, Tb, and Tc, respectively. Furthermore, the main path 20 has a supply port 200, and the supply path 2 and the compressor 1A are connected to each other at the supply port 200. Therefore, the compressor 1A supplies the adsorption towers Ta, Tb, and Tc through the main path 20, respectively.

Furthermore, the PSA device has a first supply that switches the state of the supply path 2 (therefore, the main path 20) in order to selectively supply the raw material gas compressed by the compressor 1A to the adsorption towers Ta, Tb, and Tc. A switching means is provided. The first supply switching means are on-off valves V1, V2, and V3 provided for each of the adsorption towers Ta, Tb, and Tc, and interposed in the branch passages 20a, 20b, and 20c of the main passage 20. By controlling the opening and closing of the valves V1, V2, and V3, the adsorption towers Ta, Tb, and Tc that supply the raw material gas compressed by the compressor 1A can be selected.

There are two types of second compression means 1B and 1C. The first second compression means 1B is a pressure increase valve. For this purpose, the supply path 2 includes a bypass path 21 that detours around the main path 20. The pressure increase valve 1B is interposed in a bypass passage 21. The bypass path 21 includes three branch paths 21a, 21b, and 21c downstream thereof. These three branch passages 21a, 21b, 21c are connected to the branch passages 20a, 20b, 20c of the main passage 20, respectively, at positions between the valves V1, V2, V3 and the adsorption towers Ta, Tb, Tc. ing. When a part of the raw material gas compressed by the compressor 1A flows into the bypass path 21 at the detour start point 210, the pressure is increased by the pressure increase valve 1B, and then the gas is supplied to the group G. Two or more pressure increase valves may be provided as the second compression means 1B. In this way, raw material gas compressed to a pressure higher than the compression pressure by the compressor 1A is obtained.

The second second compression means 1C is an additional compressor. Hereinafter, this will be referred to as an auxiliary compressor. The auxiliary compressor 1C compresses the raw material gas to a higher pressure than the compression pressure of the compressor 1A. For this purpose, the supply channel 2 is provided with an auxiliary channel 22 . The auxiliary passage 22 has a supply port 220 at one end thereof, and is connected to the auxiliary compressor 1C at the supply port 220. The auxiliary path 22 is connected to the bypass path 21 at the other end. Therefore, the raw material gas is compressed by the auxiliary compressor 1C to a pressure higher than the compression pressure by the compressor 1A, and is supplied to the group G via the auxiliary path 22 and then the bypass path 21.

Furthermore, the PSA device controls the state of the supply path 2 (therefore, the bypass path 21) in order to selectively supply the raw material gas compressed by the second compression means 1B, 1C to the adsorption towers Ta, Tb, Tc. A second supply switching means for switching is provided. The second supply switching means are on-off valves V10, V11, and V12 provided for each of the adsorption towers Ta, Tb, and Tc, and interposed in the branch paths 21a, 21b, and 21c of the bypass path 21. By controlling the opening and closing of the valves V10, V11, and V12, the adsorption towers Ta, Tb, and Tc that supply the raw material gas compressed by the second compression means 1B and 1C can be selected.

Further, the PSA device includes a supply selection means for selecting which of the raw material gas whose pressure has been increased by the pressure increasing valve 1B or the raw material gas which has been compressed by the auxiliary compressor 1C is to be supplied to the group G. In the embodiment, the supply selection means is a switching valve SV that is provided at a connection point between the bypass path 21 and the auxiliary path 22 and switches the communication state of these 21 and 22. By switching the valve SV, the user can select which of the raw material gas whose pressure has been increased by the pressure increase valve 1B or the raw material gas which has been compressed by the auxiliary compressor 1C is to be supplied to the group G.

One of the second compression means 1B/1C may be omitted. For example, when the pressure increase valve 1B and the bypass passage 21 are omitted, the auxiliary passage 22 is provided with three branch passages in which on-off valves V10, V11, and V12 are interposed, similar to the branch passages 21a, 21b, and 21c. The branch paths are connected to the branch paths 20a, 20b, 20c or each adsorption tower Ta, Tb, Tc.

The PSA device further includes a control section 6 that controls the on-off valves V1 to V12 as the switching means described above to carry out the steps described below. The control unit 6 may be configured with, for example, a programmable logic controller (PLC).

Referring to FIGS. 2-4, a cycle of gas production by the PSA device described above is illustrated. Among the valves V1 to V12 in FIGS. 2-4, those in the open state are painted white, and those in the closed state are painted black. In addition, in the following steps, the raw material gas compressed and supplied by the compressor 1A is referred to as "raw material gas", and the raw material gas compressed and supplied by the second compression means 1B, 1C is referred to as "auxiliary raw material gas". ”. Note that the "auxiliary raw material gas" is obtained by the pressure increase valve 1B or the auxiliary compressor 1C, but which "auxiliary raw material gas" is to be supplied can be selected using the aforementioned switching valve SV. The PSA device has already undergone a warm-up operation, which will be described later. FIG. 5 shows the opening and closing states of the valves in each of the following steps.

[First step]
The first step is a step of supplying the "raw material gas" to the first adsorption tower of Group G. In the first step, the adsorption tower Ta corresponds to the first adsorption tower. This is a step in which the "raw material gas" is supplied through the main passage 20 to the first adsorption tower, which has already generated and contains the target gas in the process of the previous cycle, and the target gas is taken out from the first adsorption tower through the extraction passage 5. .

In the first to third steps in FIG. 2, the adsorption tower Ta corresponds to the first adsorption tower. The adsorption tower Ta is pressurized to the pressure of the buffer tank BT through the steps before the first step (specifically, the 2'' and 3'' steps in FIG. 4 in the previous cycle). , a target gas is generated in the adsorption tower Ta and supplied to the buffer tank BT. Therefore, at the start of the first step, the target gas is already contained in the adsorption column Ta and continues to be produced in the adsorption column Ta during the first step. Valve V1 remains open following steps 2'' and 3'' of FIG. 4 in the previous cycle. Therefore, in the first step, the "raw material gas" is supplied to the adsorption tower Ta, and the target gas is supplied as a product gas from the adsorption tower Ta to the buffer tank BT (FIG. 1). Note that V4 and V7 are closed.

In this first step, gas is not supplied to or discharged from the second adsorption tower in group G. In the first to third steps in FIG. 2, the adsorption tower Tb corresponds to the second adsorption tower. In the first step, valves V2, V5, V8, and V11 are closed, and no gas is supplied to or discharged from the adsorption tower Tb.

In this first step, the adsorbent in the remaining third adsorption tower in group G is also regenerated. In the first to third steps in FIG. 2, the adsorption tower Tc corresponds to the third adsorption tower. In the adsorption tower Tc, the adsorbent has already adsorbed the specific gas in a cycle step before the first step. In the first step, the valve V6 is open and the valves V3, V9, and V12 are closed, so that the specific gas is desorbed from the adsorbent of the adsorption tower Tc and discharged from the adsorption tower Tc through the discharge path 3. and is released into the external environment from the outlet 30. As a result, the adsorbent in the adsorption tower Tc begins to be regenerated.

[Second step]
A second step is performed following the first step. In the second step in FIG. 2, the "auxiliary raw material gas" is supplied to the first adsorption tower through the bypass passage 21, the target gas is continued to be taken out from the first adsorption tower through the take-out passage 5, and the "raw material gas" is supplied to the first adsorption tower through the bypass passage 21. The second adsorption tower is supplied through the main passage 20, the target gas is started to be taken out from the second adsorption tower through the take-out passage 5, and the specific gas is discharged from the third adsorption tower through the discharge passage 3. Continue to regenerate the adsorbent.

As shown in the second step of FIG. 2, valve V1 is closed and valve V10 is opened. Therefore, the supply of "raw material gas" to the adsorption tower Ta is stopped, but the supply of "auxiliary material gas" is started. The pressure in the adsorption tower Ta is further increased by the supply of the "auxiliary raw material gas", and the target gas continues to be taken out from the adsorption tower Ta through the takeout passage 5 to the buffer tank BT.

In the second step, the valve V2 is further opened to start supplying the "raw material gas" to the adsorption tower Tb, and the adsorption tower Tb is pressurized by the supply of the "raw material gas". As a result, the specific gas is adsorbed by the adsorbent of the adsorption tower Tb, and the target gas is generated. The target gas is not taken out from the adsorption tower Tb to the buffer tank BT until the pressure in the adsorption tower Tb rises above the secondary side pressure (pressure in the buffer tank BT provided on the secondary side). Then, when the pressure in the adsorption tower Tb exceeds the secondary side pressure, the target gas passes through the check valve CVb and begins to be taken out from the adsorption tower Tb through the extraction passage 5.

In the second step, V6 remains open, and therefore the specific gas continues to be discharged from the adsorption tower Tc through the discharge passage 3 and discharged from the discharge port 30 to the external environment. Therefore, the regeneration process of the adsorbent in the adsorption tower Tc continues.

[Third step]
A third step is performed following the second step. In the third step in FIG. 2, the "raw material gas" is supplied to the second adsorption tower, continues to be taken out from the second adsorption tower through the take-out passage 5, and the first adsorption tower and the third adsorption tower are connected through a communication passage. 4 to communicate with each other to equalize the pressure.

As shown in the third step in FIG. 2, the valve V2 remains open and the "raw material gas" continues to be supplied to the adsorption tower Tb, so that the target gas continues to flow from the adsorption tower Tb through the extraction passage 5 to the buffer tank BT. continues to be taken out.

In the third step, the valve V10 is closed, and the supply of the "auxiliary raw material gas" to the adsorption tower Ta ends. Valve V6 is closed and the regeneration process of adsorption tower Tb is completed. Furthermore, the valves V7 and V9 are opened, and the adsorption tower Ta and the adsorption tower Tb communicate with each other through the communication path 4. As a result, gas is sent from the adsorption tower Ta to the adsorption tower Tc through the communication path 4, and the pressures of the adsorption tower Ta and the adsorption tower Tc are equalized with each other.

In this way, through the first to third steps, the target gas is always taken out from at least one of the two adsorption towers in group G, and the adsorbent in the remaining adsorption tower in group G is regenerated. be exposed. That is, in the first to third steps in FIG. 2, the target gas is always taken out from at least one of the adsorption towers Ta and Tb, and the adsorbent in the adsorption tower Tc is regenerated.

[1st to 3rd steps]
Next, after implementing the first to third steps, the control unit 6 changes the adsorption tower that was the first adsorption tower during the implementation of the first to third steps to the third adsorption tower, and uses the second adsorption tower as the third adsorption tower. The first to third steps are carried out again, using the adsorption tower that was the adsorption tower as the first adsorption tower, and the adsorption tower that was the third adsorption tower as the second adsorption tower. These steps will be referred to as 1' to 3' steps below. The 1st to 3rd steps are shown in FIG.

That is, as shown in FIG. 3, the adsorption tower Ta becomes the third adsorption tower, the adsorption tower Tb becomes the first adsorption tower, and the adsorption tower Tc becomes the second adsorption tower. During the 1' to 3' steps, the target gas is always taken out from at least one of the adsorption towers Tb and Tc. In the 1' to 2' steps, the adsorption tower Ta is regenerated, and in the 3' step, the pressures of the adsorption tower Ta and the adsorption tower Tb are made equal to each other. The 1' to 3' steps are the same as the 1st to 3rd steps, so FIGS. 3 and 5 show the open and closed states of the valves V1 to V12, and the explanation thereof will be omitted.

[1st'' to 3rd'' steps]
After carrying out the 1' to 3' steps, the adsorption tower that was the first adsorption tower when carrying out the 1' to 3' steps is now the third adsorption tower, and the adsorption tower that was the second adsorption tower is now the third adsorption tower. The first to third steps are carried out again using the first adsorption tower and the third adsorption tower as the second adsorption tower. These steps will be referred to as 1'' to 3'' steps below. The first'' to third'' steps are shown in FIG.

That is, as shown in FIG. 4, the adsorption tower Tb becomes the third adsorption tower, the adsorption tower Tc becomes the first adsorption tower, and the adsorption tower Ta becomes the second adsorption tower. During the 1'' to 3'' steps, the target gas is always taken out from at least one of the adsorption towers Tc and Ta. In the 1'' to 2'' steps, the adsorption tower Tb is regenerated, and in the 3'' step, the pressures of the adsorption tower Tc and the adsorption tower Tb are made equal to each other. Since the first to third steps are the same in principle as the first to third steps, FIGS. 4 and 5 show the open and closed states of the valves V1 to V12, and the explanation thereof will be omitted.

The control unit 6 considers a total of nine steps from the first to third'' steps as one cycle, and repeats this cycle. In the conventional two-column type PSA apparatus, there is a time when the target gas cannot be taken out from the adsorption column. On the other hand, according to the three-column PSA device of the present application, which uses "raw material gas" and "auxiliary material gas" separately, the first to third steps, the first' to third' steps, and the first'' to third' In the process, the target gas is always taken out from one of the adsorption towers Ta, Tb, and Tc. Therefore, it is possible to solve the problem of supplying the target gas as a product gas to the outside at low pressure, as described in the prior art.

The check valves CVa, CVb, and CVc of the take-out passage 5 in the embodiment are replaced with on-off valves, and the on-off valves are appropriately controlled by the control unit 6, so that the target gas is always directed to one of the adsorption towers Ta, It is possible to carry out a cycle of gas production that can be extracted from Tb, Tc.

Note that the warm-up operation may be performed, for example, as follows.
(1) Open valves V4 to V6 for about 20 seconds after the start of operation to relieve pressure from each adsorption tower Ta to Tc.
(2) For about 5 minutes from the start of operation, the gas outlet valve (not shown) downstream of the buffer tank BT is closed, and a total of 9 steps of the above-mentioned 1st to 3'' steps are performed, and each adsorption tower Ta to Tc Adsorption and desorption of the adsorbent is performed once or twice to prepare for extraction of the target gas from each adsorption tower Ta to Tc.
(3) Approximately 5 minutes after the start of operation, open the above gas outlet valve and discharge the gas.

<Example>
A three-column PSA device shown in FIG. 1 was prepared. Using the PSA apparatus, a cycle consisting of nine steps of steps 1 to 3'' in FIGS. 2 to 4 was performed under the cycle conditions shown in FIG. 5 to generate product gas. Using air as a raw material gas, oxygen, carbon dioxide, and water vapor as specific gases were adsorbed from the raw material gas by an adsorbent to generate nitrogen gas as a product gas (target gas).

The pressure of the raw air obtained by the compressor 1A was 0.6 MPa. Further, the pressure of the compressed air obtained by the compressor 1A was increased to 0.65 MPa by the pressure increasing valve 1B. The pressure of the raw material air obtained by the auxiliary compressor 1C was 0.65 MPa.

It was confirmed that 0.6 MPa of nitrogen gas could be taken out as the product gas when either the pressure increase valve 1B or the auxiliary compressor 1C was used as the second compression means. Here, the pressure of the nitrogen gas is the minimum value of the pressure of the buffer tank BT, and this is the pressure of the nitrogen gas that can be provided to the user (customer) (the same applies hereinafter). In addition, it was confirmed that 0.5 MPa of nitrogen gas could be taken out when neither the pressure increase valve 1B nor the auxiliary compressor 1C was used. If there is no limit to the amount of raw material gas, 0.7 MPa of nitrogen gas can be obtained by increasing the number of pressure booster valves 1B or increasing the compression pressure by the auxiliary compressor 1C.

From the above, it can be seen that the three-column PSA device according to the example is useful in the following points. In recent years, medium-sized and large-scale factories have been encouraged to use more energy-efficient air compressors, and even smaller factories are also encouraged to make their air compressors more energy-efficient. Power consumption is being reduced by reducing the discharge pressure of the factory's raw air. Currently, many factories are changing the pressure of raw material air from 0.8 MPa to 0.6 MPa.

Theoretically, if the pressure of raw air is lowered from 0.8 MPa to 0.6 MPa, the shaft power of the air compressor will be reduced by about 14% with the same amount of air (the rationale for this will be explained later). . As a result, the electricity bill of 10 million yen/year will be reduced to 8.6 million yen/year, resulting in a significant cost reduction of 1.4 million yen/year.

However, for example, in the case of the two-column PSA device (comparative example) disclosed in Patent Document 1, when nitrogen gas is generated as a product gas from compressed air of 0.6 MPa, the pressure of the nitrogen gas is 0.4 MPa. Become. Nitrogen gas at 0.4 MPa greatly limits its uses and often does not meet the needs of users (customers). Therefore, PSA devices are not employed. As described above, existing PSA devices are currently unable to respond to the trend of energy saving.

As shown in the above results, the three-column PSA device according to the example has a 0.0 .65 MPa of nitrogen gas can be provided as a product gas.

In other words, by mainly using compressed air of 0.6 MPa from the factory compressor 1A and only making up for the shortage with the pressure booster valve 1B or auxiliary compressor 1C, the pressure of the resulting nitrogen gas can be increased to 0.5 MPa or more. It is possible to do so. Therefore, the PSA device according to the embodiment can respond to the above-mentioned energy saving trend and satisfy customer demands. Moreover, the pressure increase valve 1B can be prepared at low cost, and the auxiliary compressor 1C can also be prepared at low cost since it may be an auxiliary one to compensate for the shortage. Therefore, it contributes to reducing the cost of equipment included in the PSA device of the present application.

Note that the above does not limit the scope of the present invention. That is, a PSA apparatus may be provided in which three towers form one group, a plurality of such groups are provided, and each group performs the steps shown in FIGS. 2 to 4 as one cycle.

The basis for the fact that when the pressure of compressed air is lowered from 0.8 MPa to 0.6 MPa, the shaft power of the air compressor is reduced by about 14% with the same amount of air is as follows. The calculation formula for the theoretical shaft power is shown in Equation 1 below.

The part in [ ] on the right side of Equation 1 is a relational expression of the pressure ratio between suction pressure and discharge pressure. The reduction rate of the theoretical shaft power when the discharge pressure is lowered from 0.69 MPaG to 0.59 MPaG is estimated as follows, assuming two-stage compression, specific heat ratio 1.4, and suction pressure 0.1013 MPaABS.

From the above, it can be seen that if the discharge pressure is lowered by 0.1 MPaG, the power will be reduced by about 7%. Therefore, it can be seen that when the pressure of compressed air is lowered from 0.8 MPa to 0.6 MPa, the shaft power is reduced by about 14%.

Note that even when the auxiliary compressor 1C is used, it is used auxiliary to make up for the shortage, so high power is not required. Therefore, even if the auxiliary compressor 1C is used, the total shaft power can be reduced compared to the conventional one.

Ta, Tb, Tc Adsorption tower G Adsorption tower group 1A Compressor (as first compression means/first compressor)
1B Pressure increase valve 1C Auxiliary compressor (as second compression means/second compressor)
2 Supply path 20 Main path 21 Bypass path 22 Auxiliary path 3 Discharge path 4 Communication path 5 Output path 6 Control section V1 to V12 Opening/closing valve (as each switching means)

Claims (7)

A pressure swing adsorption device that adsorbs a specific gas from a source gas to generate a target gas using a pressure swing adsorption method,
a group including three adsorption towers filled with an adsorbent that preferentially adsorbs the specific gas over the target gas;
a first compression means for compressing the raw material gas;
a second compression means for compressing the raw material gas to a pressure higher than the compression pressure by the first compression means;
a supply line connected to each of the adsorption towers;
a first supply switching means for switching the state of the supply passage in order to selectively supply the raw material gas compressed by the first compression means to the adsorption tower through the supply passage;
A second supply different from the first supply switching means that switches the state of the supply path in order to selectively supply the raw material gas compressed by the second compression means to the adsorption tower through the supply path. a switching means;
a discharge path connected to each of the adsorption towers;
discharge switching means for switching the state of the discharge passage in order to selectively discharge the specific gas from each of the adsorption towers through the discharge passage;
a communication path connected to each of the adsorption towers;
communication switching means for switching the state of the communication passage in order to equalize the pressure of any two of the adsorption towers in the group through the communication passage;
an extraction path connected to each of the adsorption towers to take out the target gas from the adsorption tower;
A control unit that controls the first supply switching means, the second supply switching means, the discharge switching means, and the communication switching means,
The control unit includes:
Among the group, one adsorption tower is used as a first adsorption tower, another adsorption tower is used as a second adsorption tower, and the remaining one adsorption tower is used as a third adsorption tower,
The raw material gas is supplied by the first compression means to the first adsorption tower through the supply path, the target gas is taken out from the first adsorption tower through the take-out path, and the specific gas is removed from the third adsorption tower. a first step of regenerating the adsorbent in the third adsorption tower by discharging it from the tower through the discharge passage;
The source gas is supplied to the first adsorption tower by the second compression means through the supply path, and the target gas is continued to be taken out from the first adsorption tower through the take-out path; The compression means supplies the second adsorption tower through the supply path to begin taking out the target gas from the second adsorption tower through the take-out path, and the specific gas is supplied from the third adsorption tower through the discharge path. a second step of discharging and continuing the regeneration treatment of the adsorbent in the third adsorption tower;
The raw material gas is continuously supplied by the first compression means to the second adsorption tower through the supply path and taken out from the second adsorption tower through the take-out path, and the first adsorption tower and the third adsorption tower and a third step of communicating with each other through the communication path to equalize the pressure, in order.
A pressure swing adsorption device characterized by: The first compression means
including a compressor that compresses the raw material gas,
The supply path is
a main path connected to the compressor and the group;
A bypass road that detours around the main road,
The second compression means
at least one pressure increasing valve interposed in the bypass passage for increasing the pressure of the raw material gas compressed by the compressor;
A pressure swing adsorption device according to claim 1. The first compression means
including a first compressor that compresses the raw material gas,
The second compression means
a second compressor that compresses the raw material gas to a pressure higher than the compression pressure by the first compressor;
A pressure swing adsorption device according to claim 1. The first compression means
including a first compressor that compresses the raw material gas,
The second compression means
a second compressor that compresses the raw material gas to a pressure higher than the compression pressure by the first compressor;
a pressure increasing valve for further increasing the pressure of the raw material gas compressed by the first compressor,
The supply path is
a main path connected to the first compressor and the group;
a bypass path in which the pressure increase valve is interposed and bypasses the main path;
an auxiliary path connected to the bypass path and the second compressor,
The pressure swing adsorption device includes:
further comprising supply selection means for selecting which of the raw material gas compressed by the second compressor or the raw material gas pressure increased by the pressure increasing valve is to be supplied to the group;
A pressure swing adsorption device according to claim 1. a backflow prevention means interposed in the take-out passage for preventing the target gas from flowing back into the adsorption tower through the take-out passage; further comprising a take-out switching means for switching the state of the take-out path in order to take out the
A pressure swing adsorption device according to any one of claims 1 to 4. The control unit includes:
After carrying out the first to third steps,
The adsorption tower that was the first adsorption tower during the implementation of the first to third steps was used as the third adsorption tower, the adsorption tower that was the second adsorption tower was used as the first adsorption tower, and the adsorption tower that was the third adsorption tower is used as a second adsorption tower, and the first to third steps are carried out again.
A pressure swing adsorption device according to claim 1 . A gas generation method for generating the target gas using the pressure swing adsorption device according to any one of claims 1 to 6 .

Images