JP2014024025A - Dehumidification system and method of producing dry air - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dehumidification system capable of performing more efficient dehumidification, and a method of producing dry air.SOLUTION: A dehumidification system 1 includes: a gas separation membrane module 20 which separates vapor in a raw material gas through a hollow fiber membrane, and extracts dry air from a primary side and wet air from a secondary side; raw material gas supply means 15 for pressurizing the raw material gas and supplying it to the gas separation membrane module; depressurizing means 25 for depressurizing the secondary side; and purge gas supply means 22 for supplying a purge gas to the secondary side. The raw material gas supply means pressurizes the raw material gas to 200-1,000 kPaG, and supplies the raw material gas. The depressurizing means 25 depressurizes the secondary side so that the pressure ratio P2/P1 of the absolute pressure P1 of the gas on the primary side and the absolute value P2 of the gas on the secondary side is 0.05 or less.

Description

  TECHNICAL FIELD The present invention relates to a dehumidification system that removes water vapor contained in a raw material gas from a hollow fiber membrane and a method for producing dry air, and in particular, a dehumidification system and dry air that can perform dehumidification more efficiently. It relates to the manufacturing method.

  It has been conventionally proposed to dehumidify the raw material gas using a hollow fiber membrane type gas separation membrane module. Such a gas separation membrane module has a structure in which a plurality of hollow fiber membranes having selective permeability are contained in a container, and a pressurized raw material gas is introduced into the hollow fiber membrane. . Water vapor in the raw material gas passes through the hollow fiber membrane and moves to the outside of the hollow fiber membrane, while dehumidified dry air (dehumidified air) moves through the hollow fiber membrane as it is and is taken out from the outlet of the membrane. . A part of the extracted dry air is usually returned as a purge gas to the outside of the hollow fiber membrane of the gas separation membrane module, and this purge gas reduces the water vapor partial pressure on the permeate side and improves the dehumidification efficiency. The permeated water vapor is discharged together with the purge gas as humid air.

  For example, Patent Document 1 discloses a dehumidification system using a hollow fiber membrane and supplying a raw material gas into the hollow fiber membrane at a pressure of less than 200 kPaG.

Japanese Patent No. 4810748

  As described above, in the dehumidification using the hollow fiber membrane type gas separation membrane module, a part of the dry air is returned to the gas separation membrane module as a purge gas, which is appropriate when the pressure of the raw material gas is relatively low. A method for producing dry air that requires a large amount of purge gas and does not require high pressure requires a relatively large amount of dehumidifying energy or the number of modules.

  Therefore, an object of the present invention is to provide a dehumidification system and a method for producing dry air that can perform dehumidification more efficiently in a dehumidification technique that uses a hollow fiber membrane to remove water vapor contained in a raw material gas. There is.

According to one form of this invention, the following dehumidification system and the manufacturing method of dry air are provided.
1. A gas separation membrane module that separates water vapor in the raw material gas with a hollow fiber membrane and takes out dry air from the primary side and takes out as wet air from the secondary side;
A source gas supply means for boosting the source gas and supplying the gas to the gas separation membrane module;
Decompression means for decompressing the secondary side;
Purge gas supply means for supplying purge gas to the secondary side;
A dehumidification system comprising:
The source gas supply means pressurizes and supplies the source gas to 200 to 1000 kPaG,
The depressurizing means depressurizes the secondary side so that the pressure ratio P2 / P1 is 0.05 or less when the absolute pressure of the primary side gas is P1 and the absolute pressure of the secondary side gas is P2. To
Dehumidification system.

  In this specification, the terms “dry air” and “dehumidified air” are used, but these terms all mean air obtained by removing a certain amount of water vapor from the raw material gas. doing. It should be noted that the distinction of these terms does not limit the present invention in any way. On the other hand, “humid air” refers to air containing a large amount of water vapor extracted to the secondary side of the separation membrane.

  According to such a configuration, not only the pressure on the primary side of the membrane but also the secondary side of the membrane is decompressed by the decompression means, and specifically, the pressure ratio between the primary side and the secondary side is 0. By reducing the pressure so as to be 0.05 or less, it is possible to perform more efficient dehumidification (production of dry air) as compared with a configuration in which only the primary side is pressurized and the secondary side is not depressurized.

2. The purge gas supply means supplies a part of the gas on the primary side of the gas separation membrane module to the secondary side, and supplies the purge gas so that the purge rate is 20% or less.
2. The dehumidification system according to 1 above.

  In a configuration in which a part of the dry air is supplied as a purge gas to the secondary side, a high purge rate means that the recovery rate of the dry air is correspondingly reduced. Therefore, it is preferable to set the purge rate to 20% or less from the viewpoint of not reducing the recovery rate of dry air.

3. A gas separation membrane module that separates water vapor in the raw material gas with a hollow fiber membrane and takes out dry air from the primary side and takes out as wet air from the secondary side;
A source gas supply means for boosting the source gas and supplying the source gas to the separation membrane module;
Decompression means for decompressing the secondary side;
Purge gas supply means for supplying purge gas to the secondary side;
A method for producing dry air using a dehumidification system comprising:
A step of boosting and supplying a source gas to 200 to 1000 kPaG by the source gas boosting means;
When the absolute pressure of the primary side gas is P1 and the absolute pressure of the secondary side gas is P2, the secondary side is adjusted so that the pressure ratio P2 / P1 is 0.05 or less. Depressurizing; and
A method for producing dry air.

4). The purge gas supply means supplies a part of the gas on the primary side of the gas separation membrane module to the secondary side,
The purge gas supply means further comprises a step of supplying a purge gas so that a purge rate is 20% or less,
4. A method for producing dry air as described in 3 above.

5. 5. The method for producing dry air as described in 3 or 4 above, wherein in the step of supplying the raw material gas, the pressure of the raw material gas is increased to 300 kPaG or more.

  ADVANTAGE OF THE INVENTION According to this invention, the dehumidification system which can perform dehumidification more efficiently as mentioned above, and the manufacturing method of dry air can be provided.

It is a schematic diagram which shows the structure of the dehumidification system of one form of this invention.

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

  The dehumidifying system 1 in FIG. 1 supplies a raw material gas to the hollow fiber membrane of the gas separation membrane module 20, allows water vapor to pass through the permeation side (secondary side) of the hollow fiber membrane, and dehumidifies from the supply side (primary side). It is a system to take out the generated gas. The source gas may be any gas that can be dehumidified by a separation membrane, such as nitrogen, oxygen, and carbon dioxide. In the following description, an example in which air is supplied as a source gas will be described.

  The dehumidifying system 1 includes a supply line 11 connected to the primary side of the gas separation membrane module 20 and a compressor 15 disposed on the supply line 11. A drain separator 12 is disposed on the downstream side of the compressor 15, and instruments 31 a, 31 b, and 31 c for measuring the flow rate, temperature, and pressure of the gas in the supply line 11 are disposed.

  As the meter 31a for measuring the flow rate, for example, a flow meter type or capacity type flow rate measuring device can be used, and as the meter 31b for measuring the temperature, for example, a thermocouple type or resistance type temperature measuring device can be used. Yes, as the pressure measuring instrument 31c, for example, a bellows type or a Bourdon tube type pressure measuring instrument can be used. Note that only a part of these instruments 31a to 31b may be used in accordance with the process status or the like.

  As an example, the compressor 15 preferably has a performance of increasing the pressure of gas in a range of 200 kPaG to 1000 kPaG in terms of gauge pressure. The lower limit of the supply pressure of the source gas is preferably 200 kPaG or more, and may be 250 kPaG or more or 300 kPaG or more. The upper limit of the supply pressure of the raw material gas is preferably 1000 kPaG or less, and may be 900 kPaG or less, 800 kPaG or less, or 700 kPaG or less.

  The gas separation membrane module 20 may be either a so-called bore feed type or a shell feed type. As the gas separation membrane module 20 itself, a conventionally known one can be used. For example, hundreds to hundreds of thousands of hollow fiber membrane bundles (hollow fiber bundles), a container for housing the hollow fiber membranes, hollow fibers You may provide the tube sheet etc. which were formed in the one end or both ends of a bundle. In the case of the bore feed type, the raw material gas is fed into the hollow of the hollow fiber membrane from one opening of each hollow fiber membrane, and water vapor selectively permeates the membrane and is sent to the permeation side (secondary side). .

  The hollow fiber membrane may have a thickness of 10 to 500 μm and an outer diameter of about 50 to 2000 μm. The gas separation membrane may be homogeneous, may be non-uniform such as a composite membrane or an asymmetric membrane, and may be microporous or nonporous. Examples of the hollow fiber membrane include those formed of a polymer material such as polyimide, polyetherimide, polyamide, polyamideimide, polysulfone, polycarbonate, silicone resin, cellulose polymer, and ceramic material such as zeolite.

  Examples of the form of the hollow fiber bundle include a parallel arrangement, a crossing arrangement, and a woven form. Moreover, 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. Further, the hollow fiber bundle is not limited to a straight form, but may be a form bent in a U-shape.

  The number of gas separation membrane modules 20 used in the dehumidification system 1 is not particularly limited, and may be one or more.

  As shown in FIG. 1, a primary side line 21 and a secondary side line 23 are connected to the gas separation membrane module 20. The primary side line 21 is a line for taking out dehumidified dry air, and the secondary side line 23 is a line for sending wet air that has permeated through the hollow fiber membrane.

  A purge gas line 22 is connected in the middle of the primary side line 21, and a part of the dry air is returned to the secondary side of the gas separation membrane module 20 as a purge gas through the purge gas line 22. By operating the adjustment valve 32a provided in the purge gas line 22 and the adjustment valve 32b provided in the primary side line 21, the flow rate of the dry air and the flow rate of the purge gas can be adjusted. In FIG. 1, an instrument 31 d that measures the gas concentration and / or flow rate in the primary line 21 is arranged. Of course, other instruments for measuring the temperature and pressure of the gas may be arranged. The instrument 31d may be a dew point meter.

  The secondary line 23 is provided with a decompression device 25 for decompressing the secondary side. As the decompression device 25, a blower, an ejector, a vacuum pump, or the like can be used. In FIG. 1, instruments 31 e and 31 f for measuring the pressure and flow rate of the gas in the line are arranged on the secondary line 23. Of course, other instruments for measuring the temperature of the gas may be arranged.

  The dehumidification system 1 includes a control unit 30, and the operation of the compressor 15 and the decompression device 25 is controlled by the control unit 30. The controller 30 also controls the operation of at least one of the adjusting valves 32a and 32b for changing the flow rate of the purge gas. The control unit 30 may include a CPU, a storage unit, and the like, and execute a predetermined operation using a predetermined control program. The control unit 30 executes a predetermined determination step based on at least one of the information from each of the meters 31a to 31f, and executes a step for causing the compressor 15 and the like to perform a predetermined operation based on the determination result.

  In the dehumidifying system 1 of the present embodiment configured as described above, the gas separation membrane is operated in a state in which the compressor 15 and the pressure reducing device 25 are driven to cause a pressure difference between the primary side and the secondary side of the hollow fiber membrane. Pressurized air is supplied to the module 20. While the pressurized air passes through the hollow fiber membrane, water vapor therein selectively passes through the hollow fiber membrane and is sent to the secondary line 23, while dehumidified dry air (product air) Is taken out from the primary line 21.

  Although the atmospheric pressure dew point of dry air is suitably changed according to the level requested | required of a product, it may be -20 degrees C or less, -40 degrees C or less, or -60 degrees C or less, for example. Such low dew point dry air obtained by the dehumidifying system 1 is used in various fields including industrial equipment and medical equipment.

  Examples and comparative examples performed for examining the relationship between the supply pressure P1 of the source gas, the pressure (permeation pressure) P2 on the secondary side, and the dehumidification efficiency will be described below. In the following description, “dew point” refers to the atmospheric pressure dew point.

(Example)
Tables 1 and 2 are tables showing the implementation conditions and results of the examples. As the source gas, water vapor saturated air at 40 ° C. at the supply pressure was used by heating to 45 ° C. in order to prevent condensation. In all the examples, the primary side was increased in pressure and the secondary side was reduced in pressure. Examples 1-1 to 1-4 (also simply referred to as “Example 1”) have a supply pressure of 700 kPaG, a dew point of dehumidified air of −40 ° C., and a pressure ratio (details below) of 0.005 to 0.00. Within the range of 050. Example 2-1 basically has the same conditions as Example 1, but the dew point of the dehumidified air is set to -60 ° C. Examples 3-1 to 3-4 (also simply referred to as “Example 3”) are basically the same conditions as in Example 1, but the supply pressure is 300 kPaG. Example 4-1 (also simply referred to as “Example 4”) has a supply pressure of 300 kPaG and a dew point of dehumidified air of −60 ° C. Examples 5-1 to 5-2 (also simply referred to as “Example 5”) and 6-1 to 6-2 (also simply referred to as “Example 6”) shown in Table 2 have supply pressures of 900 and 200 kPaG, respectively. The dew point of the dehumidified air is -40 ° C.

(Comparative example)
In Comparative Examples 1-1 to 1-5 and Comparative Examples 2-1 to 2-5, the supply pressure of the source gas is set to 200 kPaG to 900 kPaG, but the secondary side is not depressurized. In Comparative Examples 1-a, 2-a, 3-a, and 4-a, the pressure on the primary side is increased and the pressure on the secondary side is decreased so that the pressure ratio (detailed below) is 0.075. Comparative Examples 1-1 to 1-5 have a dew point of −40 ° C., and Comparative Examples 2-1 to 2-5 (also simply referred to as “Comparative Example 2”) have a dew point of −60 ° C. Comparative Examples 3-a and 4-a (also simply referred to as “Comparative Example 3” and “Comparative Example 4”) have dew points of −40 ° C. and −60 ° C., respectively.

In this example,
“Supply pressure” is the pressure (gauge pressure) of the raw material gas supplied to the gas separation membrane module.
“Permeation pressure” is the gas pressure (gauge pressure) on the secondary side of the membrane.
The “pressure ratio (P2 / P1)” is a ratio obtained by dividing the absolute pressure (P2) of the permeation pressure by the absolute pressure (P1) of the supply pressure.

The “supply air atmospheric pressure dew point” is the atmospheric pressure dew point of the raw material gas.
“Dehumidified air atmospheric dew point” is the atmospheric dew point of dry air.
“Dehumidified air flow rate (Nm ³ / h)” is a flow rate of dry air taken out from the primary side line.
“Dehumidification energy (kW / Nm ³ )” is energy necessary for dehumidification per unit volume.
“Dehumidification air flow rate increase rate (%)” indicates the ratio (increase rate) between the dehumidification air flow rate of the example and the corresponding dehumidification air flow rate of the comparative example. 136 (%) ”, it is calculated by the calculation formula of (32.3-13.7) /13.7×100.
“Dehumidification energy reduction rate (%)” is the ratio (increase rate) between the dehumidification energy of the example and the dehumidification energy of the corresponding comparative example.

  As shown in Examples 1 and 3 of Table 1, when producing dry air having a dew point of −40 ° C., the secondary side is set so that the pressure ratio is 0.050 or less with respect to the supply pressure (700 kPaG, 300 kPaG). By reducing the pressure, the amount of dehumidified air was increased in any of the examples, and the reduction of dehumidification energy was also achieved.

  Focusing on the gauge pressure of the permeation pressure, for example, in the case of Examples 1 and 3, the permeation pressure is preferably in the range of −60 to −100 kPaG. In order to make the P2 / P1 pressure ratio less than 0.005 (for example, 0.001), it is necessary to remarkably reduce the permeation pressure, and a high-output pressure reducing means is required. Therefore, the lower limit of the P2 / P1 pressure ratio is preferably 0.005 or more.

  In addition, as shown in Examples 2 and 4, when producing dry air having a dew point of −60 ° C., the secondary side so that the pressure ratio is, for example, 0.050 with respect to the supply pressure (700 kPaG, 300 kPaG). By reducing the pressure, the amount of dehumidified air was increased in any of the examples, and the dehumidifying energy was reduced.

  As described above, according to the method and system of the present invention, it was possible to generate dry air more efficiently than the conventional method and system.

DESCRIPTION OF SYMBOLS 1 Dehumidification system 11 Supply line 12 Drain separator 15 Compressor 20 Gas separation membrane module 21 Primary side line 22 Purge gas line 23 Secondary side line 25 Decompression device 30 Control part 31a-31f Instrument 32a, 32b Control valve

Claims (5)

A gas separation membrane module that separates water vapor in the raw material gas with a hollow fiber membrane, takes dry air from the primary side and takes wet air from the secondary side;
A source gas supply means for boosting the source gas and supplying the gas to the gas separation membrane module;
Decompression means for decompressing the secondary side;
Purge gas supply means for supplying purge gas to the secondary side;
A dehumidification system comprising:
The source gas supply means pressurizes and supplies the source gas to 200 to 1000 kPaG,
The depressurizing means depressurizes the secondary side so that the pressure ratio P2 / P1 is 0.05 or less when the absolute pressure of the primary side gas is P1 and the absolute pressure of the secondary side gas is P2. To
Dehumidification system. The purge gas supply means supplies a part of the gas on the primary side of the gas separation membrane module to the secondary side, and supplies the purge gas so that the purge rate is 20% or less.
The dehumidification system according to claim 1. A gas separation membrane module that separates water vapor in the raw material gas with a hollow fiber membrane, takes dry air from the primary side and takes wet air from the secondary side;
A source gas supply means for boosting the source gas and supplying the source gas to the separation membrane module;
Decompression means for decompressing the secondary side;
Purge gas supply means for supplying purge gas to the secondary side;
A method for producing dry air using a dehumidification system comprising:
A step of boosting and supplying a source gas to 200 to 1000 kPaG by the source gas boosting means;
When the absolute pressure of the primary side gas is P1 and the absolute pressure of the secondary side gas is P2, the secondary side is adjusted so that the pressure ratio P2 / P1 is 0.05 or less. Depressurizing; and
A method for producing dry air. The purge gas supply means supplies a part of the gas on the primary side of the gas separation membrane module to the secondary side,
The purge gas supply means further comprises a step of supplying a purge gas so that a purge rate is 20% or less,
The method for producing dry air according to claim 3.   The method for producing dry air according to claim 3 or 4, wherein in the step of supplying the source gas, the source gas is pressurized to 300 kPaG or more.

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