JP2014117687A - Gas separation recovery system and gas separation recovery method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas separation recovery system and the like in which even if a pressure required for a product gas (permeation gas) is relatively high, the production gas can be efficiently recovered.SOLUTION: This gas separation recovery system concentrates and recovers a predetermined gas which is relatively easy to permeate a gas separation membrane from a gas mixture containing plural gases. A gas separation recovery system 101A comprises a first gas separation membrane unit 111, and a second gas separation membrane unit 113 which is connected to the first gas separation membrane unit 111 in series. The system 101A is characterized in that (i) a pressure on the permeation side of the second gas separation membrane unit 113 is lower than a pressure on the permeation side of the first gas separation membrane unit 111, and (ii) a pressure rising device 121 is provided in a second permeation gas line, whereby the pressure-risen permeation gas is mixed with the permeation gas in the first gas separation membrane unit 111 and recovered.

Description

  The present invention relates to a system and method for separating and recovering a predetermined gas from a mixed gas using a gas separation membrane, and in particular, in a system for recovering a gas that has permeated through a gas separation membrane as a product gas, the pressure of the product gas is The present invention relates to a gas separation and recovery system and method for efficiently recovering a product gas even in a relatively high case.

  Conventionally, a method using a polymer separation membrane for separating and recovering predetermined components such as hydrogen and helium from a mixed gas has been proposed. The advantages of such a separation membrane are as follows: 1) The equipment is compact and inexpensive. 2) Easy operation and good maintainability 3) When the source gas has sufficient pressure, separation can be performed without particularly applying external energy 4) The pressure of the non-permeate gas is substantially reduced (For example, Patent Document 1).

  FIG. 5 is for separating and recovering predetermined components in the gas using only one gas separation membrane module 111. By bringing the mixed gas supplied via the gas supply line 103 into contact with the gas separation membrane, a predetermined component in the mixed gas preferentially permeates the gas separation membrane, and the permeated gas passes through the permeated gas line 104a as a product gas. On the other hand, the non-permeate gas that has not been permeated through the gas separation membrane is sent through the non-permeate gas line 104b.

JP-A-63-296820

  In the gas separation and recovery system as described above, when the pressure required for the product gas is relatively high (that is, when the pressure in the permeate gas line 104a is relatively high), the pressure on the permeate side of the gas separation membrane is also relatively high. Since the pressure is increased and the differential pressure of the gas separation membrane is reduced, the gas separation efficiency is lowered.

  On the other hand, it is also assumed that the pressure on the permeate side will be increased again to a predetermined pressure afterwards while maintaining a sufficient differential pressure in the gas separation membrane by keeping the pressure on the permeate side below the pressure required for the product gas. The However, this method leaves room for improvement from the viewpoint of energy efficiency.

  Accordingly, an object of the present invention is to provide a gas separation / recovery system capable of efficiently collecting a product gas even when the pressure of the product gas is relatively high, in a system for collecting a gas that has permeated through a gas separation membrane as a product gas. And providing a method thereof.

This application discloses the following invention.
1. A gas separation and recovery system for concentrating and recovering a predetermined gas that is relatively easy to permeate a gas separation membrane from a mixed gas containing a plurality of gases,
A first gas separation membrane unit having a gas separation membrane;
A first permeate gas line for delivering the permeate gas of the first gas separation membrane unit;
A second gas separation membrane unit having a gas separation membrane and connected in series to the first gas separation membrane unit so that the non-permeating gas of the first gas separation membrane unit is supplied;
A second permeate gas line for delivering the permeate gas of the second gas separation membrane unit;
In a gas separation and recovery system comprising:
(I) the permeation side pressure of the second gas separation membrane unit is lower than the permeation side pressure of the first gas separation membrane unit, and
(Ii) A pressure increasing device is installed in the second permeation gas line, and the permeation gas of the second gas separation membrane unit boosted thereby is mixed with the permeation gas of the first gas separation unit and recovered. This is a gas separation and recovery system.

2. The separation selectivity of the gas separation membrane used for the second gas separation membrane unit is
2. The gas separation and recovery system as described in 1 above, wherein the separation selectivity of the gas separation membrane used in the first gas separation membrane unit is higher.
Here, “separation selectivity” refers to the permeation rate ratio between the gas to be recovered (permeate gas) and the main gas in the non-permeate gas. “High separation selectivity” means that the permeation rate ratio is It means big.

3. 3. The gas separation and recovery system according to 1 or 2 above, wherein the permeation side pressure (that is, the second stage permeation side pressure) of the second gas separation membrane unit is reduced to an atmospheric pressure or lower.

4). On the non-permeating gas line of the first gas separation membrane unit, a cooling device for cooling the gas in the line is installed,
The gas separation and recovery system according to any one of the above items 1 to 3, wherein the operating temperature of the second gas separation membrane unit is lower than the operating temperature of the first gas separation membrane unit.

5. On the non-permeating gas line of the first gas separation membrane unit, a boosting device for boosting the gas in the line is installed,
The gas according to any one of 1 to 4 above, wherein the pressure of the gas supplied to the second gas separation membrane unit is higher than the pressure of the gas supplied to the first gas separation membrane unit. Separation and recovery system.

6). Any of 1 to 5 above, wherein a bypass line is provided for connecting a supply gas line to the first gas separation membrane unit and the non-permeating gas line of the first gas separation membrane unit. The gas separation and recovery system described in 1.

7). A gas separation method for concentrating and recovering a predetermined gas that is relatively easy to permeate a gas separation membrane from a mixed gas containing a plurality of gases,
Supplying a mixed gas to the first gas separation membrane unit and allowing the gas separation membrane to permeate to obtain a first permeable gas containing the predetermined gas;
Supplying the non-permeating gas of the first gas separation membrane unit to the second gas separation membrane unit and allowing the gas separation membrane to permeate to obtain a second permeable gas containing the predetermined gas;
Have
(I) the permeation pressure of the second gas separation membrane unit is lower than the permeation pressure of the first gas separation membrane unit, and
(Ii) A gas separation and recovery method, wherein the second permeated gas is pressurized and mixed with the first permeated gas for recovery.

  According to the present invention, in a system for recovering a gas that has permeated a gas separation membrane as a product gas, a gas separation and recovery system capable of efficiently recovering a product gas even when the pressure of the product gas is relatively high, and That method can be provided.

It is the figure which showed typically the gas separation collection system of 1st Embodiment. It is the figure which showed typically the gas separation collection system of 2nd Embodiment. It is the figure which showed typically the gas separation collection system of 3rd Embodiment. It is the figure which showed typically the gas separation collection system of 4th Embodiment. It is the figure shown to the gas separation collection system of the comparative example. It is the figure shown in the gas separation and recovery system of another comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
The gas separation / recovery system 101A in FIG. 1 separates and collects a predetermined component (for example, hydrogen, helium, carbon dioxide, etc.) contained in a mixed gas as a permeated gas that has permeated the gas separation membrane. The gas separation and recovery system 101A includes a first gas separation membrane unit 111 and a second gas separation membrane unit 113. The two gas separation membrane units 111 and 113 are connected in series so that the second gas separation membrane unit 113 is supplied with the non-permeating gas (details below) of the first gas separation membrane unit 111.

  As each of the gas separation membrane units 111 and 113, a gas separation membrane module that performs gas separation with a large number of hollow fiber membranes can be used. As an example, a bundle of hundreds to hundreds of thousands of hollow fiber membranes Examples include a hollow fiber bundle, a container that accommodates it, and a module that includes a tube sheet formed at one or both ends of the hollow fiber bundle. Each of the gas separation membrane units 111 and 113 may be either a so-called bore feed type or a shell feed type.

  Examples of the form of the hollow fiber bundle include a parallel arrangement, a cross arrangement, a woven form, and a spiral form. The hollow fiber bundle may be provided with a core tube at a substantially central portion, or a film may be wound around the outer peripheral portion of the hollow fiber bundle. Further, the hollow fiber bundle may have a cylindrical shape, a flat plate shape, a prismatic shape, or the like. The hollow fiber bundle is not limited to a straight form, but may be a form bent in a U shape, a form wound in a spiral form, or the like. As the gas separation membrane (hollow fiber membrane), any gas separation membrane (hollow fiber membrane) may be used as long as it allows a predetermined gas component (for example, hydrogen, helium, carbon dioxide, etc.) in the mixed gas to permeate preferentially. A well-known thing can be utilized.

  The separation selectivity of the gas separation membrane of the first gas separation membrane unit 111 and the separation selectivity of the gas separation membrane of the second gas separation membrane unit 113 may be the same or different, but as in this embodiment When a two-stage gas separation membrane unit is used, it is preferable that the separation selectivity of the gas separation membrane of the second gas separation membrane unit is higher than that of the first unit. The reason is as follows. That is, normally, in the second stage gas separation membrane unit, the concentration of the gas to be recovered is lower than that in the first stage. It is difficult to secure a partial pressure difference and it is difficult to perform efficient gas separation. Therefore, by adopting the above configuration, the gas can be recovered with high efficiency even in the second-stage gas separation membrane unit.

  As shown in FIG. 1, a gas supply line 103 is connected to the first gas separation membrane unit 111, and a mixed gas is supplied to the unit 111 via the gas supply line 103. By bringing the mixed gas into contact with the gas separation membrane, a predetermined component (for example, hydrogen, helium, carbon dioxide, etc.) in the mixed gas permeates the gas separation membrane, and the permeated gas is sent to the outside via the permeated gas line 104a. It is. On the other hand, the gas that has not permeated (non-permeate gas) is supplied to the second gas separation membrane unit 113 via the non-permeate gas line 104b.

  Similarly, in the second gas separation membrane unit 113, when the supplied gas is brought into contact with the gas separation membrane, a predetermined component in the gas permeates the gas separation membrane, and the permeated gas passes through the permeation gas line 105a. On the other hand, the gas that has not permeated (non-permeate gas) is sent through the non-permeate gas line 105b.

  The permeate gas line 105a from the second gas separation membrane unit 113 is connected to a part of the permeate gas line 104a from the first gas separation membrane unit 111, as shown in FIG. The permeated gas from the second gas separation membrane unit 113 can be mixed with the permeated gas from the first gas separation membrane unit 111. In the system of the present embodiment, the mixed gas is finally recovered as a product gas.

  In the present embodiment, a booster 121 is provided on the permeate gas line 105a. The booster 121 boosts the gas in the permeate gas line 105a to the same level (one example) as the gas pressure in the permeate gas line 104a, so that the permeate gas from the second gas separation membrane unit 113 is separated into the first gas. The permeated gas from the membrane unit 111 is well mixed.

The gas separation and recovery system 101A configured as described above is operated under the following conditions:
(I) The permeation side pressure of the second gas separation membrane unit 113 is lower than the permeation side pressure of the first gas separation membrane unit 111.
(Ii) The pressure of the permeated gas from the second gas separation membrane unit 113 is increased by the pressure increasing device 121, and the gas is mixed with the permeated gas from the first gas separation membrane unit 111.

  According to the gas separation and recovery system 101A of the present embodiment, the following operational effects can be obtained: That is, in order to produce a product gas having a relatively high pressure, only one stage of the gas separation membrane unit is used, and the supply side A method is also conceivable in which the pressure is set to a high pressure and the pressure on the permeate side is set to be relatively low (a pressure lower than the pressure required for the product gas), and the pressure of the gas is increased after the gas is recovered. However, in order to produce gas with more energy saving, it is preferable to adopt the configuration as in this embodiment (see also the examples). In particular, in the configuration of the present embodiment, the second gas separation membrane unit is operated so that the permeation side pressure of the second gas separation membrane unit is lower than the permeation side pressure of the first gas separation membrane unit. Gas can also be separated and recovered efficiently in the unit. Further, the permeating gas from the second gas separation membrane unit can be boosted by the booster.

  In addition, this invention is not limited to the said embodiment, A various change is possible.

  Another embodiment of the present invention will be described below. In addition, in the following description and FIGS. 2-4, the same code | symbol as FIG. 1 is attached | subjected to the structure part similar to FIG. 1, and the overlapping description is abbreviate | omitted. For structural parts that are not particularly described, the same or substantially the same as those in the first embodiment can be used.

(Second Embodiment)
A gas separation and recovery system 101B in FIG. 2 is obtained by further providing a gas cooling device 129 in the system in FIG. The gas cooling device 129 is disposed on the non-permeating gas line 104b connecting the two gas separation membrane units 111 and 113, and cools the non-permeating gas from the first gas separation membrane unit 111. By cooling the non-permeate gas in this way and lowering the operating temperature of the second gas separation membrane unit 113 (lower than that of the first gas separation membrane unit 111), the second gas separation membrane unit 113 Gas separation and recovery efficiency can be improved.

(Third embodiment)
The gas separation / recovery system 101C in FIG. 3 is obtained by further adding a booster 123 to the system in FIG. The booster 123 is disposed on the non-permeating gas line 104b and boosts the non-permeating gas from the first gas separation membrane unit 111. In this way, by increasing the pressure of the non-permeating gas and supplying it to the second gas separation membrane unit 113, the differential pressure of the gas separation membrane in the unit is ensured, and the gas separation and recovery in the second gas separation membrane unit 113 is ensured. Efficiency can be improved. In one embodiment, it is also preferable that the gas supply pressure to the second gas separation membrane unit 113 is higher than the gas supply pressure to the first gas separation membrane unit.

(Fourth embodiment)
A gas separation / recovery system 101D in FIG. 4 is obtained by further providing a bypass line 103a to the system in FIG. The bypass line 103a connects the gas supply line 103 and the non-permeate gas line 104b, and a valve 119 for opening and closing the flow path and / or adjusting the flow rate is disposed on the line as an example. Yes.

  The valve 119 may be manually operated, or may be automatically switched. In the case of manual operation, for example, the gas supply line 103 is provided with means for detecting the gas flow rate or pressure in the line, and the operator confirms the detected value and the detected value exceeds a predetermined value. When the determination is made, the operator manually operates the valve 119 to open it. On the other hand, in the case of automatic, the valve 119 may be configured as follows: the gas separation and recovery system 101D is provided in a control device (not shown) for controlling the operation of the valve 119 and the gas supply line 103. Means for detecting the gas flow rate or pressure in the line, and the control device determines whether or not the flow rate or pressure exceeds a predetermined value based on the detection result, and determines that it has exceeded. If this happens, the valve 119 is automatically opened.

  According to the above configuration, when the flow rate or pressure of the gas supplied to the first gas separation membrane unit 111 exceeds a predetermined value, the excess gas is separated from the second gas separation via the bypass line 103a. It can be sent to the membrane unit 113. Therefore, it becomes possible to use gas more efficiently as the whole system. Such a bypass line may be provided in the second gas separation membrane unit 113.

  As mentioned above, although several embodiment was described with reference to drawings, this invention is not limited to each embodiment, The component shown to each embodiment can also be combined suitably.

A gas separation and recovery system as shown in FIG. 1 is used, a purity of 93 mol% or more and a product pressure of 3 MPaG are set, and a mixed gas (H ₂ : CO: N ₂ : CH ₄ = 65: 10: 10 : 15) Hydrogen was separated and recovered. The mixed gas was supplied at 50000 Nm ³ / h.

  Table 1 shows the conditions and results of Example 1 and Comparative Examples 0 and 1-1 to 1-3, and Table 2 shows the conditions and results of Example 2 and Comparative Examples 0 and 2-1 to 2-3. Show. In Examples 1 and 2, the gas separation and recovery system as shown in FIG. 1 was used, and in both Examples 1 and 2, the number of modules in the first stage and the pressure were the same, but for the second stage, In Example 1, the number of modules was 3, and the permeation pressure was 1.9 MPaG. In Example 2, the number of modules was 4, and the permeation pressure was 1.5 MPaG.

  Comparative Example 0 has only one gas separation membrane module as shown in FIG. 5, and Comparative Examples 1 and 2 have only one gas separation membrane module as shown in FIG. A booster 125 is disposed. Comparative Example 1 has the same hydrogen recovery rate (about 66%) as Example 1, and Comparative Example 2 has the same hydrogen recovery rate as Example 2 (about 77%). is there.

  As shown in Table 1 and Table 2, the hydrogen recovery rate of the entire system is 66.6% in Example 1 and 76.9% in Example 2, while Comparative Example 0 (one step, no pressure increase) The hydrogen recovery rate of this system was 44.3%. From these comparisons, it was confirmed that the hydrogen recovery rate was improved by the system according to the present invention.

  Even in the one-stage system as in Comparative Example 1, the hydrogen recovery rate can be made similar to that in Examples 1 and 2 by reducing the pressure on the permeate side. However, in the case of Comparative Example 1, it is necessary to pressurize the recovered permeated gas again. As can be seen from the comparison between Example 1 and Comparative Examples 1-1 and 1-2 in Table 1, even when the same recovery rate is obtained, it is more energy saving to use two stages as in this embodiment instead of one stage. It was confirmed that there was. Specifically, in this example, the pressure required as the product gas is assumed to be 3 MPaG. However, in Comparative Examples 1-1 to 1-3, the “permeation pressure” is less than 3 MPaG. The total amount needs to be increased to 3 MPaG or more. On the other hand, in Example 1, the “permeation pressure” in the first stage reaches 3 MPaG, and it is only necessary to increase the pressure for the second stage permeate gas (product gas). The energy required for this pressure increase is indicated as “product gas compression power” in the table. In Example 1, this value is 157 kW, which is lower than any of the values 315 kW, 199 kW, and 160 kW of Comparative Examples 1-1 to 1-3, and the energy saving performance of the system of Example 1 was confirmed.

  As can be seen from the comparison between Example 1 and Comparative Example 1-3, or the comparison between Example 2 and Comparative Example 2-3, when the total number of modules becomes the same (for example, Example 1 [8+ 3 = 11] and 11 in Comparative Example 1-3), the power difference becomes smaller, so it seems that the effectiveness of the system according to the present invention is small. However, considering the case where a compressor trouble occurs, for example, the system according to the present invention is advantageous from the following viewpoints. That is, if the compressor cannot be used due to some trouble, the pressure of the first-stage product gas does not reach 3 MPaG in the configuration of the comparative example, and the compressor cannot be pressurized, so the specified product gas is not at all. It will not be obtained. On the other hand, in Example 1, since the product gas of 3 MPaG is obtained in the first stage and can be used, the operation can be continued although the amount of product gas is reduced.

101A to 101D Gas separation and recovery system 103 Gas supply line 103a Bypass lines 104a and 105a Permeation side lines 104b and 105b Non-permeation side lines 111 and 113 Gas separation membrane unit 119 Valve 121 and 123 Booster 125 Booster 129 Cooler

Claims (7)

A gas separation and recovery system for concentrating and recovering a predetermined gas that is relatively easy to permeate a gas separation membrane from a mixed gas containing a plurality of gases,
A first gas separation membrane unit having a gas separation membrane;
A first permeate gas line for delivering the permeate gas of the first gas separation membrane unit;
A second gas separation membrane unit having a gas separation membrane and connected in series to the first gas separation membrane unit so that the non-permeating gas of the first gas separation membrane unit is supplied;
A second permeate gas line for delivering the permeate gas of the second gas separation membrane unit;
In a gas separation and recovery system comprising:
(I) the permeation side pressure of the second gas separation membrane unit is lower than the permeation side pressure of the first gas separation membrane unit, and
(Ii) A booster is installed in the second permeate gas line, and the permeate gas of the second gas separation membrane unit boosted thereby is mixed with the permeate gas of the first gas separation unit and recovered. This is a gas separation and recovery system. The separation selectivity of the gas separation membrane used for the second gas separation membrane unit is
The gas separation recovery system according to claim 1, wherein the gas separation membrane used in the first gas separation membrane unit has a higher separation selectivity than the gas separation membrane unit. The gas separation and recovery system according to claim 1 or 2, wherein a permeation side pressure of the second gas separation membrane unit is reduced to an atmospheric pressure or lower. On the non-permeating gas line of the first gas separation membrane unit, a cooling device for cooling the gas in the line is installed,
The gas separation recovery system according to any one of claims 1 to 3, wherein an operation temperature of the second gas separation membrane unit is lower than an operation temperature of the first gas separation membrane unit. On the non-permeating gas line of the first gas separation membrane unit, a boosting device for boosting the gas in the line is installed,
The pressure of the gas supplied to the second gas separation membrane unit is higher than the pressure of the gas supplied to the first gas separation membrane unit. The gas separation and recovery system described. The bypass line which connects the gas supply line to the said 1st gas separation membrane unit and the said non-permeation | transmission gas line from a 1st gas separation membrane unit is installed. The gas separation and recovery system according to any one of the above. A gas separation method for concentrating and recovering a predetermined gas that is relatively easy to permeate a gas separation membrane from a mixed gas containing a plurality of gases,
Supplying a mixed gas to the first gas separation membrane unit and allowing the gas separation membrane to permeate to obtain a first permeation gas containing the predetermined gas;
Supplying a non-permeating gas of the first gas separation membrane unit to a second gas separation membrane unit, and obtaining a second permeable gas containing the predetermined gas by permeating the gas separation membrane;
Have
(I) the permeation pressure of the second gas separation membrane unit is lower than the permeation pressure of the first gas separation membrane unit, and
(Ii) A gas separation and recovery method, wherein the second permeated gas is pressurized and mixed with the first permeated gas for recovery.

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