JPH0714445B2 - Spiral type degassing element and method of using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a spiral type degassing element using a hydrophobic gas permeable membrane for removing dissolved gas in water, and a method for using the same.

[Prior Art] In general, gases such as oxygen, nitrogen, and carbon dioxide are dissolved in water, and when the equilibrium state is reached, it usually does not disappear over time. In many cases, these dissolved gases adversely affect. For example, in a water circulation line, dissolved oxygen in water may promote corrosion of the inner surface of the pipe in contact with liquid,
Further, in the ultrapure water production line, dissolved carbon dioxide causes deterioration of the water quality of ultrapure water, and depending on the case, degassing treatment by chemical addition or vacuum system is performed. However, degassing by chemical treatment, which is a conventional method, has problems such as chemical cost and residual components, and even vacuum degassing has restrictions in terms of equipment and operating cost, making it practical for use in a broad sense. It was hard to say that it was a suitable method.

In addition to these methods, a degassing method of removing a dissolved gas in water using a hydrophobic membrane having a gas permeable function has recently been put into practical use. In this method, the liquid to be treated is made to flow through the front or back surface of a film made of silicone or the like, which has a gas permeation function and has a property of impermeability of water, and the opposite surface is depressurized. Only the dissolved gas in the treatment liquid is removed by permeation through the membrane and then degassed. This method does not have the problem of chemical residue found in the conventional chemical addition method, and has the advantage that the apparatus is simpler and the operating cost is smaller than the vacuum degassing method. .

[Problems to be Solved by the Invention] In a deaerator using a hydrophobic gas permeable membrane, the membrane is usually unitized into a spiral module and used. As shown in FIG. 6, a generally used general spiral module has an envelope-shaped hydrophobic gas permeable membrane 5 and a permeation side flow path material around a hollow central tube 1 having a plurality of holes on the surface. 6. The structure is formed by winding a single set or multiple sets of units including the supply liquid flow path member 4 as one set, and the untreated liquid 7 is provided outside the envelope-shaped hydrophobic gas permeable membrane 5.
Is supplied, the open end 1'of the central tube with one end blinded is connected to a decompression source to decompress the permeation side region inside the envelope-shaped hydrophobic gas permeable membrane, and the front and back sides of the hydrophobic gas permeable membrane are By applying a pressure difference to the solution, the dissolved gas in the stock solution to be processed permeates from the front surface to the back surface of the membrane, moves from the inside of the permeate side flow path toward the central tube, and the dissolved gas in the stock solution to be processed is removed. .

However, the degassing ability of the membrane is largely governed by the difference in gas partial pressure between the front and back of the membrane, as well as the inherent gas permeation ability of the membrane. Therefore, in order to improve the degassing ability of one element, It is necessary to reduce the partial pressure of gas on the permeate side by increasing the degree of vacuum on the permeate side of the membrane, or to increase the supply pressure of the stock solution to be treated supplied to the membrane surface, that is, the degassing membrane element. However, both the degree of vacuum and the supply pressure are limited in consideration of practicality, and it is difficult to improve degassing performance one step further.

[Means for Solving the Problem] An object of the present invention is to provide an envelope-shaped hydrophobic gas permeable membrane, a permeation-side channel material, and a supply liquid channel material around a hollow central tube having a hole on the surface. A spiral type degassing element for removing dissolved gas in water, which is formed by winding a single set or multiple sets of units, and has a partition inside the central tube and permeates to a specific part of the permeate side flow path. A partition wall is provided for specifying the flow direction of the fluid, and further, a part of the leaf end portion of the partition wall that is opened without partitioning has a groove in the lateral direction with respect to the partition wall. It is basically achieved by using the characteristic spiral type degassing element.

A basic example of the structure of the spiral degassing element of the present invention is, as shown in FIGS. 1 and 2, unlike the conventional spiral element, a partition 8 is provided inside the central tube,
In addition, a partition wall 9 for specifying the flow direction of the permeate fluid is provided on the back surface of the envelope-shaped hydrophobic gas permeable membrane 5, that is, at a specific position of the permeate flow path on the permeate flow path member 6 side. The conventional spiral element does not have the partition 8 and the partition wall 9 shown in FIG. 2, and the permeated gas in the permeate-side channel gradually moves toward the central tube 1, but the permeate-side channel does not pass through the membrane surface. There is no inflow of fluid, the pressure is uniformly reduced to a constant degree of vacuum, and the partial pressure of the gas to be degassed is also kept constant. In order to improve the degassing performance, it is desirable to make the partial pressure of the gas to be degassed on the permeation side as small as possible. However, in the present invention, as shown in FIG. It is possible to flow gas, and this carrier gas can drive out the gas to be degassed on the back surface of the film, and the partial pressure of the gas can be made as close as possible to zero, resulting in a significant improvement in degassing performance. Becomes That is, for example, when it is desired to degas oxygen and carbon dioxide contained in water, the partial pressure of oxygen and carbon dioxide on the permeation side of the membrane is almost zero by flowing nitrogen as a carrier gas using the element of the present invention. Therefore, the deaeration capacity is greatly improved as compared with the case where the conventional deaeration element is used. Even if the carrier gas is flown through the conventional spiral element having no partition inside the permeation flow path partition and inside the central tube, most of the carrier gas does not flow toward the permeation side flow path and is discharged from the other end of the central tube. However, there is almost no improvement in degassing performance.

The hydrophobic gas permeable membrane used in the spiral degassing element of the present invention is not particularly limited, but any polymer membrane having a gas separation function in a flat membrane shape may be used, and preferably silicone-based, fluorine-based, or polyolefin-based. And so on. The feed liquid flow path material located outside the envelope-shaped membrane is not particularly limited, but preferably a plastic net-like spacer having a small pressure loss, and a thickness of 0.3 to 2.0 mm.
Polyethylene, nylon, polypropylene, etc. are suitable as materials and grades. The permeation-side channel material positioned inside the envelope-like membrane is not particularly limited in kind, but polyester fabric having vertical grooves, polypropylene net, etc. are preferable.

Regarding the partition wall of the permeate side flow path that constitutes the present invention, basically it is possible to manufacture an element, as long as it can block the gas flow on the permeate side to some extent, the material and the shape are not particularly limited, Preferably, a partition wall formed by applying an adhesive to the corresponding portion and curing it, or a partition wall having a structure in which a sheet material made of an elastic polymer material such as silicone rubber, foamed plastic sheet, nitrile rubber or the like is arranged or adhered Is good. Further, the length, width, arrangement location, number, etc. of the partition walls are not specified and can be selected according to the intended use as shown in FIGS. 3 (a) and 3 (b). Also, the partition provided inside the central tube may be any one that can block the passage of carrier gas to some extent, and the material can be appropriately selected from hard PVC, ABS, nylon, rubber, etc. It doesn't matter.

Regarding the partition wall of the permeate side channel, it is necessary to open a part of the leaf end part without partitioning so that the carrier gas flows uniformly over the entire back surface of the membrane, and also to facilitate the carrier gas flow. As shown in FIG. 4, partially adhering the flow path member 11 having a groove in the lateral direction or the like is one example of means for providing the groove.

In the operation of the degassing element of the present invention, even when comparing one element, a larger degassing capacity than that of the conventional spiral type degassing element can be obtained, but the degassing capacity is further improved by connecting a plurality of elements. Normally, every one to six elements are stored in the same element container, and in case of increasing the number of elements due to space relations, etc., a plurality of element-embedded containers accommodating one or more elements are stored. It can be connected in series or in parallel. When the element of the present invention is used,
Although it is possible to connect the elements-containing vessels and supply nitrogen to each vessel in parallel or in series, it is preferable to supply nitrogen in series. It is ideal to supply nitrogen gas in parallel from a plurality of supply sources to each container, and the exhaust gas of nitrogen gas supplied to the first container is supplied to the second container to the second container. When the discharged nitrogen is supplied in series as in the case of the third nitrogen, it is conceivable that the purity of nitrogen gradually decreases and the degassing efficiency decreases. However, as a result of diligent studies, the present inventors have found that even if the degassing efficiency decreases with a slight decrease in nitrogen purity, it can be almost solved by adjusting the nitrogen amount, and compared to the case of parallel supply of nitrogen. It has been found that the degassing operation cost can be greatly reduced, and the nitrogen supply system of the series system is preferable. As shown in FIG. 5, the order of supplying nitrogen may be based on the order of supplying the untreated water, or in consideration of the shape of the apparatus, the order of supplying the untreated water to each container is unrelated. You may. The flow rate of nitrogen can be appropriately determined depending on the target dissolved gas concentration, but a nitrogen flow rate (volume flow rate) of about 5% to 10% of the volumetric flow rate of water to be treated is preferable.

In addition, when accommodating a plurality of elements in the element container, in each element internal container, nitrogen can be supplied to each element in parallel or in series,
It is preferable to supply in series as in the above.

[Example 1] A hydrophobic gas permeable membrane in which a silicone thin film was formed on a support material made of polyester taffeta / polysulfone was used as a feed liquid flow made of a permeation side channel material made of polyester fabric having vertical grooves and a polypropylene net. Wrapped around a rigid PVC porous central tube together with the channel material, and a membrane area of 8 m ² with a partition wall made of an adhesive shown in FIG. A spiral type degassing element was manufactured. A blind stopper made of hard vinyl chloride was adhered and fixed to the central portion inside the central tube of this element, and this was put in a dedicated container, and the deaeration performance of tap water was measured while flowing nitrogen as a carrier gas. Tap water flow rate 1000L / h, vacuum degree 85Torr,
Under the operating conditions of nitrogen flow rate 1000cc / min and temperature 25 ° C,
The dissolved oxygen concentration of the stock solution to be treated (tap water), which was initially 8.0 ppm, decreased to 1.9 ppm.

Next, when degassed treated water (dissolved oxygen concentration 1.9 ppm) that had been degassed once was passed through this degassing element, and the degassing performance was measured under the same operating conditions as above, the dissolved oxygen concentration was
It dropped to 0.5ppm.

[Comparative Example 1] A spiral degassing element was manufactured by using the same members and gas permeable membrane as in Example 1 except that a partition wall made of an adhesive was not provided in the central portion of the permeate side flow passage. This was placed in a dedicated container without partitioning the central part of the central tube, and the degassing performance of tap water was measured without flowing a carrier gas. Under the operating conditions of a tap water flow rate of 1000 L / h, a vacuum degree of 85 Torr, and a temperature of 25 ° C., the dissolved oxygen concentration of the stock solution to be treated, which was initially 8.0 ppm, decreased to 2.7 ppm. In addition, when nitrogen was flowed at 1000 cc / min as a carrier gas under these operating conditions, the dissolved oxygen concentration of the water to be treated was reduced to 2.6 ppm.

Next, degassed water (dissolved oxygen concentration 1.9 ppm) once degassed by the method of Example 1 was passed through this degassing element,
When the degassing performance was measured under the same operating conditions as above (without flowing nitrogen), the dissolved oxygen concentration decreased to 1.5 ppm.

[Example 2] Four spiral-type degassing elements (having a passage-side flow path partition wall and a central part inside the central tube) that are the same as those used in Example 1 were manufactured, and each of these contained one element. The container was housed in a total of four containers, and as shown in FIG. 5- (b), a degassing apparatus was produced in which a stock solution to be treated (tap water) and a nitrogen pipe were connected in series. The degassing performance was measured while flowing nitrogen as a carrier gas. Tap water flow rate 15
00L / h, vacuum degree 85Torr, nitrogen flow rate 1500cc / min, temperature 25 ° C
Under the above operating conditions, the dissolved oxygen concentration of the stock solution to be treated, which was initially 8.0 ppm, decreased to 0.2 ppm.

[Effect] According to the present invention, the improvement of the degassing performance of the dissolved gas in water of the spiral type degassing membrane element is achieved. It is particularly effective in removing dissolved oxygen and carbon dioxide in water.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view of the spiral degassing element of the present invention in an unwound state, and FIG. 2 similarly shows only the central tube and the permeation-side channel material portion of the spiral degassing element of the present invention. It is a partial cross-sectional perspective view. Figure 3
-(A) and FIG. 3- (b) are partial cross-sectional perspective views showing an arrangement example of a partition wall on the permeation side flow path of the spiral degassing element of the present invention and a partition inside the central tube.
FIG. 4 is a partial cross-sectional perspective view showing an example in which another channel material is attached to a part of the permeation-side channel material of the spiral degassing element of the present invention. Fig. 5- (a), Fig. 5-
(B) is a flow chart of a stock solution to be treated and a carrier gas in an example of a deaerator in which a plurality of element-embedded vessels each containing a spiral deaerator of the present invention are connected and a carrier gas is flown in series. FIG. 6 is a partially sectional perspective view of a state in which a conventional spiral type degassing element is unwound. In the figure, 1 is a hollow central tube 1'having a hole on the surface, 1 is an open end of the central tube, 2 is an adhesive sealing portion, 3 is a membrane-permeable dissolved gas, and 4 is a supply liquid channel material. , Hydrophobic gas permeable membrane 6, permeate side channel material 7, 7 ′, stock solution for supply (stock solution to be treated) 8, partition inside central tube 9, permeate side channel partition wall 10, carrier gas inlet 10 'is a carrier gas outlet 11, a second permeation side flow path member 12, a spiral degassing element built-in container 13, a treated stock solution line 14, a carrier gas aeration line 15 and a treated stock solution inlet 16 Is the untreated liquid outlet (degassed water outlet) 17, the carrier gas inlet 18 and the carrier gas outlet 19 are in the groove direction of the permeation side flow path member.

Claims (6)

[Claims] 1. A single set or a double set of units in which an envelope-shaped hydrophobic gas permeable membrane, a permeation side flow path member, and a supply liquid flow path material are provided as a set around a hollow central tube having holes on the surface. In the spiral type degassing element for removing dissolved gas in water, which is wound around, a partition is provided inside the center tube and a partition for specifying the flow direction of the permeate fluid at a specific location of the permeate side flow path. A wall is provided, and a flow path material having a groove in a lateral direction with respect to the partition wall is partially attached to a part of the partition wall which is opened without partitioning a part of a leaf end part of the partition wall. Spiral type degassing element. 2. The spiral type degassing element according to claim 1, wherein the partition wall of the permeate side flow path is made of an elastic polymer material. 3. The spiral degassing element according to claim 1, wherein the partition wall of the permeate side flow passage is formed by curing an adhesive. 4. The spiral degassing element according to claim 1, wherein water to be treated is supplied to the front surface of the membrane, and a carrier gas is flown from one end of the central tube to the other end of the central tube through the back surface of the membrane. How to use. 5. A degassing apparatus comprising a plurality of spiral-type degassing elements and a plurality of element-embedded containers which are housed in the same element container. The degassing device comprises one carrier gas supply source. The method of using the spiral degassing element according to claim 1, wherein a carrier gas is supplied in series to each element-containing container. 6. The spiral type degassing element according to claim 1, wherein a channel material having a groove is partially attached as a means for providing the groove.