JPH0463104A - Diaphragm degassing apparatus and degassing method - Google Patents

Abstract

PURPOSE:To accelerate degassing by using a scroll vacuum pump as a pressure reducing means. CONSTITUTION:Low pressure gas is sucked from a suction port 1a by the rotation of scrolls 4, 5 and enters a compression chamber 7 between the scroll blades 4b, 5b of the driving scroll 4 driven by a motor 2, and the following scroll 5 set eccentrically to the scroll 4. The gas is compressed to the central part of the chamber 7 by the rotation of the scrolls 4, 5, passed through an exhaust hole 4e and an exhaust path 3a, and exhausted from an exhaust port 1b.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is capable of removing gases and volatile substances contained in the liquid by bringing the liquid to be treated into contact with a reduced pressure gas phase across a membrane. The present invention relates to a diaphragm vacuum degassing device and method for removal or recovery through a membrane.

The present invention can be used to remove gases dissolved in water, such as deoxidizing boiler supply water, deoxidizing water for food use, and removing oxygen and carbon dioxide from cleaning water. For use in removing volatile substances that exist dissolved or dispersed, such as chloroform, trichloroethylene, methanol, acetone, toluene, etc.
It can be used for wastewater treatment and water purification. It can also be used for purposes such as removing malodorous substances contained in soil water and recovering aromatic components contained in water. Furthermore, it can be used for degassing organic liquids, such as deoxidizing vinyl monomers, deoxidizing edible oils, and removing hydrogen sulfide from sulfurized oils.

[Prior art] In the diaphragm vacuum degassing method, the liquid to be treated is passed through one side of a membrane that allows gases and volatile substances to pass through, but not liquids.
This is a method in which gases and volatile substances contained in the liquid are removed or recovered to the reduced pressure side through the membrane by reducing the pressure on the other side using a vacuum pump or the like.

Water ring type vacuum pump,
Vacuum pumps such as piston vacuum pumps, oil rotary vacuum pumps, diaphragm vacuum pumps, and ejectors such as steam ejectors and water aspirators are used.

[Problems to be Solved by the Invention] However, each of these pressure reducing means has disadvantages, and as a result, there are limits to diaphragm degassing.

In other words, for example, when removing gases such as oxygen or volatile substances such as trichlorethylene from water, piston type or oil rotary vacuum pumps that use lubricating oil as the lubricant,
When condensed water is mixed into the lubricating oil, the vapor pressure of the water becomes the lower limit of the degree of vacuum, making it impossible to reduce the residual concentration below a certain limit and resulting in a reduction in throughput. Furthermore, rusting and an increase in the amount of lubricating oil occurred, making it impossible to use for a long period of time. diaphragm vacuum pump, water ring vacuum pump,
Dry-type vacuum pumps that use solid lubricants, as well as ejectors and aspirators, can withstand the inhalation of large amounts of water vapor, but diaphragm-type and dry-type vacuum pumps have a low degree of pressure reduction (the degree to which atmospheric pressure goes to vacuum) and are difficult to heat. Replacement of parts is required. Water ring pumps can only reduce pressure to around the vapor pressure of water regardless of the displacement size, and seal water needs to flow. Aspirators can only reduce pressure to around the vapor pressure of water. On the other hand, the steam ejector has disadvantages such as a small exhaust capacity, a large steam ejector, limited usage conditions, and poor energy efficiency.

Furthermore, a water ring type pump with an air ejector requires a pump with a very large displacement, resulting in an increase in equipment and operating costs.

In addition, in applications where volatile substances such as chloroform and trichloroethylene are removed from water, types that use lubricating oil are difficult to remove as these volatile substances dissolve in the lubricating oil and the degree of vacuum decreases during long-term operation. There was a problem in that it led to a decline in performance.

For example, in an application where water is deoxidized, in order to degas the residual oxygen concentration to below 20 ppb (ppb = 1 (1 - @)), the vacuum pump must be able to reduce the pressure to below the vapor pressure of water. Also, in applications where volatile substances are removed from water, vacuum pumps can reduce the pressure to a sufficiently low level in order to reduce the residual II4 degree and increase the throughput.
Although it is necessary to use the vacuum pump continuously for a long period of time, a vacuum pump suitable for these purposes has not been known.

[Means for Solving the Problems] The present invention has been made to solve the above problems, and is a diaphragm degassing device that includes a membrane module incorporating a diaphragm that allows gas to pass therethrough but not liquids, a pressure reducing means, and accessories. The present invention is characterized in that a scroll-type vacuum pump is used as the pressure reducing means.

In addition, as a degassing method, by flowing the liquid to be treated on one side of the diaphragm and connecting a pressure reducing means to the other side to reduce the pressure,
It is characterized by removing gases and volatile substances contained in the liquid to the reduced pressure side through a membrane.

The present invention will be explained in further detail. The scroll type vacuum pump used in the present invention is a combination of two spiral blades, a driving scroll and a fixed or driven scroll.
By driving the drive scroll using the power of a motor, the contact area between the two spiral blades moves from the outer periphery to the center, or from the center to the outer periphery, and as a result, a contact area is formed between the two spiral blades. By moving the space (compressed part) from the outer periphery to the center, or from the center to the outer periphery,
A type of vacuum pump that compresses gas.

As the lubricant, a solid lubricant or vacuum pump oil can be used.

Figure 1 shows a rotary scroll pump P used in the example.
shows the structure of

This pump P includes a cylindrical casing 1, a motor 2 fixed to the top of the casing 1, and a motor 2 that rotates the casing 1 inside the casing 1.
A drive shaft 3 extending coaxially with the drive shaft 3 and having an exhaust passage 3a formed therein, a drive scroll 4 integrally provided at the lower end of the drive shaft 3, and a drive scroll 4 rotatably mounted on the bottom of the casing l. A driven scroll 6 is provided.

As shown in FIG. 4(a), the drive scroll 4 has a spiral blade 4b integrally formed on a substrate 4a integrated with the shaft 3, and a spiral blade 4b has a tip extending perpendicularly to the substrate 4a. The pin 4C is integrally formed, and the spiral blade 4 of the substrate 4a
1 for pin 4C at the outer periphery of the surface where b is formed.
A guide groove 4d extends in the radial direction of the substrate 4a at an 80° position.
Further, an exhaust hole 4e is formed in the center of the substrate 4a.

Further, as shown in FIG. 4(b), the driven scroll 5 has a spiral vane 5b fixed to a base plate 5a in a direction opposite to the spiral vane 4b of the driving scroll 4. A pin 5c is formed at the tip of the pin 5b, and a guide groove 5d is formed in the substrate 5a.

The driven scroll 5 is set in the casing 1 eccentrically with respect to the driving scroll 4 through the shaft 7 at the bottom of the casing 1, and in this state, as shown in FIGS. 4C15C are mutually guide grooves 5d, 4
d, the spiral blades 4b and 5b are combined with each other. The gap created between the spiral blades 4b and 5b serves as a compression chamber 7, and this compression chamber 7 communicates with the exhaust passage 3a of the drive shaft 3 through an exhaust hole 4e formed in the base plate 4a of the drive scroll 4. are doing.

Further, the casing 1 is formed with an intake port 1a and an exhaust port 1b that communicate with the inside of the casing 1, and is further provided with an upper oil filler plug 8a and a lower oil filler plug 8b, respectively.

According to the pump P, when the motor 2 is driven, the drive scroll 4 rotates via the drive shaft 3, and the pin 4C of the drive scroll 4 is inserted into the guide groove 5d of the driven scroll 5.
By moving along, the driven scroll 5 is rotated at the same rotation speed as the driving scroll 4. that time,
The pin 5C of the driven scroll 5 moves along the guide groove 4d of the drive scroll 4.

Due to the rotation of both scrolls 4.5, low-pressure gas is taken in from the intake port 1a, and this low-pressure gas is fed to the drive scroll 4 driven by the motor 2 and the driven scroll set eccentrically with respect to the drive scroll 4. It enters the compression chamber 7 between the spiral vanes 4b and 5b of the scroll 5, is compressed into the center of the compression chamber 7 as each scroll 4.5 rotates, and from there passes through the exhaust hole 4e and the exhaust passage 3a to the exhaust port 1b. is discharged to the outside. Note that the scroll type vacuum pump P used in the present invention preferably has an air bleeder mechanism.

The present inventors have found that by using the scroll type vacuum pump as described above as a pressure reduction means for diaphragm vacuum degassing, it is possible to reduce the pressure to a sufficient degree of vacuum even when water vapor or volatile liquid vapor is sucked, and It was discovered that degassing is possible and that there is no problem with long-term operation. For example, as seen in the examples, by operating at a pressure of about IQtorr, oxygen can be efficiently removed from water and the residual oxygen concentration can be reduced to 20
It has been found that it is possible to reduce the amount to 1 ppb or less depending on the conditions, and that it is possible to increase the throughput at the same residual concentration.

The diaphragm of the present invention allows gases and vapors of volatile substances to pass through it, but does not allow liquids to pass therethrough while they are still liquids. As a membrane with such characteristics, non-porous homogeneous membrane (for example,
8-20261), heterogeneous membranes or composite membranes having non-porous layers (e.g. JP-A No. 63-258605), porous membranes composed of hydrophobic materials (e.g. JP-A No. 63-264127)
These membranes can be used in the present invention.

However, the present invention can exhibit its advantages more when a non-porous homogeneous membrane, a heterogeneous membrane having a non-porous layer, or a composite membrane is used. Porous membranes generally allow an excessive amount of liquid vapor to permeate, and even with a scroll-type vacuum pump, condensed water accumulates in the lubricating oil, making oil-water separation necessary.

Any membrane shape or module shape can be used. For example, a flat membrane, a tubular membrane, a hollow fiber membrane, etc. can be used as a diaphragm, and a laminated type, spiral type, etc. can be used as a membrane module.
External perfusion rate, internal perfusion rate, etc. can be used.

There are no particular restrictions on the liquid to be treated, which is the object of the present invention, such as water, aqueous solutions, suspensions using water as a dispersion medium, acids,
This applies to general liquids such as alkalis, mineral oils, vegetable oils, animal oils, organic solvents, etc., but especially liquids, liquids with a vapor pressure of Q, l torr or more at room temperature, and water or liquids containing water. Particularly useful in certain cases. In the case of a liquid with a vapor pressure of less than 0.1 torr at room temperature, an oil rotary vacuum pump commonly used can be used.

There are no particular restrictions on the gases or volatile substances that are the object of the present invention, such as oxygen, nitrogen, carbon dioxide, carbon oxide, hydrocarbons such as methane, halogens such as chlorine, inert gases such as helium, halogenated gases, etc. Hydrogen, hydrogen sulfide, ammonia, amines, halogenated hydrocarbons such as trichloroethylene, fluorine-containing compounds such as fluorocarbons, petroleum,
Organic solvents, odorous substances such as 2-methylinborneol,
Examples include.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

◆Example 1 A hollow fiber heterogeneous membrane manufactured by a melt molding method using poly-4 methylpentene 1 as a material had an outer diameter of 260 μm and an inner diameter of 20 μm.
6 μm, and the gas permeation characteristics measured according to ASTM D1434 are oxygen permeation rate 2, I
O-4cm3 (STP)/cm2. see, cmH
g, and the oxygen/nitrogen separation coefficient was 1.2.

A module with an effective area of 13 m2 was produced using this hollow fiber membrane. Then, as shown in Fig. 1, displacement 26
Using 01/win rotating scroll vacuum pump P,
A deaerator having the configuration shown in FIG. 5 was assembled.

This deaerator 9 has a liquid population 11a and a liquid outlet 11b on the upper and lower sides of a module case 10, and a decompression port 12.
- 12 are provided inside the module case 10 so that the hollow fiber membrane 13 is supported by a resin sealing part 14, and each pressure reducing port 12 is connected to the inlet port 1a of the pump P.

25℃ tap water was flowed through this device at several flow rates.
The dissolved oxygen concentration (Do) of the raw water and treated water and the pressure on the reduced pressure side at that time were measured. The results are shown in the first column along with Comparative Example 1.
Shown in the table.

◆Comparative Example 1 A water ring type vacuum pump with a displacement of 501/win was used as the vacuum pump, and the test was conducted in the same manner as in Example 1 except that it was operated at a water sealing rate of 1501/hr. The results are shown in Example 1.
Shown in the table.

Table 1 ◆ Example 2 The state of Do of the treated water when the experiment of Measurement Example 1 of Example 1 was continued for 72 hours is shown in FIG. 6 together with Comparative Example 2.

After reaching a stable state of 30 ppb approximately 1 hour after the start of operation, no change was observed even after 72 hours. Also, no change was observed in the lubricant level after 72 hours.

◆Comparative Example 2 The same deaerator as in Example 1 was manufactured except that an oil rotary vacuum pump with a displacement of 1501/min was used as the vacuum pump, and it was continuously operated for 72 hours at a raw water flow rate of 2801/hr. Figure 6 shows the changes in Do of the treated water when
Shown with The concentration reached 30 ppb approximately one hour after the start of operation. After that, the residual concentration gradually increases and deteriorates to about 90 ppb after 72 hours. There was also an increase in lubricant levels after 72 hours.

■.

◆Example 3 Using the same deaerator as in Example I, the raw water was 1°0 p.
10 pm of water at 25°C containing trichlorethylene
FIG. 7 shows the temporal change in the residual concentration of trichloroethylenine in the treated water when flowing at a rate of 0.01/ff1 in. Approximately 1 hour after the start of operation, a stable state of o, tsppm was reached.
No change was observed even after 72 hours had passed.

◆Comparative Example 3 The same degassing device as in Example 1 was prepared, except that an oil rotary vacuum pump with exhaust jl l 501/win was used as the vacuum pump, and the same measurements as in Example 3 were performed. The residual trichlorethylene concentration reached 0.15 ppm, the same as in Example 3, about 1 hour after the start of operation.

After that, the residual concentration gradually increased, and after 72 hours, it was about 0.
It worsens to 2 ppm, and there is a tendency for it to increase further.

[Effects of the Invention] The degassing device and the degassing method of the present invention provide the following advantages: The liquid to be treated is a liquid exhibiting a vapor pressure exceeding 0.1 torr at room temperature;
In particular, even if the substance to be removed from the liquid is water or a substance that is liquid at room temperature, the degree of pressure reduction on the pressure reduction side will be small, and therefore the residual concentration of the substance to be removed can be reduced. , and the throughput can be increased at the same residual concentration. For example, in the case of water deoxygenation, the residual concentration is 1 p
It can be lowered to below pb, and the same residual concentration,
For example, when setting the amount to 30 ppb, the throughput can be increased nearly three times as much as when using a water ring vacuum pump used for boat fishing.

Furthermore, even under the above conditions, operations such as frequent replacement of lubricating oil and separation of oil and water are not required, corrosion progresses slowly, and long-term operation is possible.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a scroll-type vacuum pump used in an embodiment of the present invention, FIGS. 2 and 3 are side views of main parts,
4(a) and 4(b) are plan views of the driving scroll and driven scroll of the vacuum pump, respectively, FIG. 5 is a conceptual diagram showing the configuration of the deaerator of the present invention, and FIG. 6 is a plan view of the driving scroll and the driven scroll of the vacuum pump, and FIG. Graph showing the measurement results of Comparative Example 2, Figure 7 is Example 3
and a graph showing the measurement results of Comparative Example 3. Fig. 6 4... Drive scroll, 5... Followed scroll, 9... Deaerator, P... Scroll type vacuum pump. Applicant: Dainippon Ink & Chemicals Co., Ltd. Time (h'') Figure 7 Time (h'') Figure 4 (a) (b) h Figure 2 (Figure 3) Figure 5

Claims (2)

[Claims] (1) A diaphragm deaeration system comprising a membrane module incorporating a diaphragm that allows gas to pass through but not liquids, a pressure reduction means, and attached piping, and is characterized in that a scroll-type vacuum pump is used as the pressure reduction means. Device. (2) By flowing the liquid to be treated on one side of the diaphragm and reducing the pressure by connecting a pressure reducing means to the other side, gases and volatile substances contained in the liquid are removed through the membrane to the reduced pressure side. A degassing method characterized by: