JPH03249907A - Spiral type deaerating element and method for using this element - Google Patents

Abstract

PURPOSE:To make improvement in the deaeration performance of the dissolved gas in water in the above element by providing a partition in a central pipe and providing a partition wall for specifying the flow direction of permeated fluid at the specific point of a transmissible side flow passage. CONSTITUTION:A single set or plural sets of the units, one set of which consists of an envelop-shaped hydrophobic gas transmissible membrane 5, a transmissible side flow passage material 6 and a supply liquid flow passage material 4, are wound around the hollow central pipe 1 having holes on the surface. The partition 8 is provided in the central pipe 1 and the partition wall 9 for specifying the flow direction of the permeated fluid is provided at the specific point of the transmissible side flow passage. Consequently, the improvement in the deaeration performance of the dissolved gas in the water of the spiral type deaeration membrane element is made. This element is particularly highly effective for removing the dissolved oxygen and carbon dioxide in water.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a spiral degassing element using a hydrophobic gas permeable membrane for removing dissolved gas in water and a method of using the same.

[Prior art] Generally, gases such as oxygen, nitrogen, and carbon dioxide are dissolved in water, and when an equilibrium state is reached, it is normal that they do not disappear over time, or water treatment In many cases, these dissolved gases have an adverse effect. For example, in water circulation lines, dissolved oxygen in the water may accelerate corrosion of the inner surface of the piping in contact with liquid.
Furthermore, in ultrapure water production lines, dissolved carbon dioxide causes deterioration of the quality of ultrapure water, and depending on the situation, degassing treatment is performed by adding chemicals or using a vacuum method. However, the conventional method of deaeration using chemical treatment has problems such as chemical costs and residual components, and even vacuum deaeration has limitations in terms of equipment and operating costs, making it difficult to put it into practical use in a broad sense. It was hard to say that it was a suitable method.

In addition to these methods, a deaeration method has recently been put into practical use in which dissolved gases in water are removed using a hydrophobic membrane having a gas permeation function. In this method, the liquid to be treated is poured onto the front or back side of a membrane made of silicone or the like that has gas permeability and water impermeability, and the opposite side is brought into a reduced pressure state. Only the dissolved gas in the treatment liquid is removed through the membrane and degassed. This method does not have the problems of chemical residue that were seen with previous chemical addition methods, and compared to vacuum degassing methods, it has been recognized as having the advantage of simpler equipment and lower operating costs. .

[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. As shown in FIG. 6, a conventionally used general spiral module includes a hollow central tube 1 having a plurality of holes on its surface, an envelope-shaped hydrophobic gas permeable membrane 5, and a channel material on the permeate side. 6. It has a structure in which a single set or multiple sets of units including the supply liquid channel material 4 are wrapped around each other, and the raw liquid to be treated 7 is wrapped around the envelope-shaped hydrophobic gas permeable membrane 5.
is supplied, and the open end 1- of the central tube with one end blind is connected to a pressure reduction source to reduce the pressure in the permeation side region inside the envelope-shaped hydrophobic gas permeable membrane, and to reduce the pressure between the front and back sides of the hydrophobic gas permeable membrane. By applying a pressure difference to the undiluted solution, the dissolved gas in the undiluted solution to be treated permeates from the surface to the back side of the membrane, moves from inside the permeation side channel toward the central tube, and removes the dissolved gas in the undiluted solution to be treated. .

However, the degassing ability of a membrane is largely controlled by the difference in gas partial pressure between the front and back surfaces of the membrane, as well as the membrane's inherent gas permeability. Therefore, in order to improve the degassing ability of a single element, It is necessary to reduce the gas partial pressure 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 to be supplied to the membrane surface, that is, the degassing membrane element. However, both the degree of vacuum and the supply pressure have limits in view of practicality, making it difficult to improve the degassing performance at present.

[Means for Solving the Problems] An object of the present invention is to provide an envelope-shaped hydrophobic gas permeable membrane, a permeation side channel material, and a feed liquid channel material around a hollow central tube having holes on the surface. In a spiral type deaeration element for removing dissolved gas in water, which is made by winding a single or multiple sets of units, a partition is provided inside the central pipe, and This is basically achieved by using a spiral type degassing element characterized by providing a partition wall for specifying the flow direction of the permeate fluid.

A basic example of the structure of the spiral degassing element of the present invention is shown in FIGS. 1 and 2, and unlike conventional spiral elements, a partition 8 is provided inside the center tube,
In addition, a partition wall 9 for specifying the flow direction of the permeated fluid is provided at a specific location of the permeate side flow path on the back surface of the envelope-shaped hydrophobic gas permeable membrane 5, that is, on the side of the permeate side flow path material 6. The spiral element does not have the partition 8 and the partition wall 9 shown in FIG. 2, and the permeate gas in the permeate side flow path gradually moves toward the center tube 1, but the permeate gas in the permeate side flow path does not contain any fluid other than through the membrane surface. There is no inflow of gas, the pressure is uniformly reduced to a constant degree of vacuum, and the partial pressure of the gas to be degassed is also maintained constant. In order to improve the degassing performance, it is desirable to reduce the partial pressure of the gas to be degassed on the permeate side as much as possible, but in the present invention, as shown in Fig. 2, carriers are introduced from one end of the central tube into the flow path on the permeate side. It is possible to flow gas, and this carrier gas can drive out the gas to be degassed from the back side of the membrane, making it possible to bring the partial pressure of the gas as close to zero as possible, making it possible to significantly improve degassing performance. becomes. In other words, if you want to degas oxygen and carbon dioxide contained in water, for example, by using the element of the present invention and flowing nitrogen as a carrier gas, the partial pressure of oxygen and carbon dioxide on the permeate side of the membrane can be reduced to almost zero. The degassing capacity is greatly improved compared to the case of using a conventional degassing element. In addition, even if carrier gas is passed through a conventional spiral element without a partition wall of the permeation channel or a partition inside the center tube, most of the carrier gas will not flow toward the permeation side channel but will be discharged from the other end of the center tube. However, almost no improvement in degassing performance was observed.

The hydrophobic gas-permeable membrane used in the spiral degassing element of the present invention is not particularly limited, but may be any flat membrane-shaped polymer membrane having a gas separation function, preferably silicone-based, fluorine thread, or boreolefin-based membranes. etc. are good. The feed liquid channel material located outside the envelope-shaped membrane is not particularly limited, but is preferably a plastic net-like spacer with a small pressure loss, and the thickness is 0. 3～
Approximately 2゜0■, materials include polyethylene, nylon,
Polypropylene is suitable. Although the type and shape of the permeation-side channel material located inside the envelope-like membrane is not particularly limited, polyester fabrics having longitudinal grooves, polypropylene nets, and the like are preferable.

Regarding the partition wall of the permeation side flow path that constitutes the present invention, it is basically possible to manufacture an element, and any material that can block the gas flow on the permeation side to some extent is sufficient, and there are no particular limitations on the material or shape. Preferably, a partition wall formed by applying an adhesive to the relevant area and curing it, or a partition wall having a structure in which a sheet-like material made of silicone rubber, foamed plastic sheet, nitrile rubber, or other elastic polymer material is arranged or adhered. is good. In addition, the length, width, location, number, etc. of partition walls are not specified, and Figure 3
- As shown in (a) and (b), it can be selected depending on the intended use. In addition, the partition provided inside the center tube may be made of any material that can block the passage of carrier gas to some extent, and the material may be hard PVC, AB
S, nylon, rubber, etc. can be selected as appropriate, and it does not matter whether they are bonded or not.

Regarding the partition wall of the permeate side channel, a part of the leaf end is often left open without partitioning so that the carrier gas flows uniformly over the entire back surface of the membrane. As shown in FIG. 4, it is also possible to partially attach a channel material 11 having grooves in the lateral direction.

In the operation of the deaeration element of the present invention, a greater deaeration capacity can be obtained compared to a conventional spiral type deaeration element even when a single element is used, but the deaeration capacity is further improved by connecting a plurality of elements. Normally, every 1 to 6 elements are stored in the same element container, but if space is a constraint or you want to increase the number of elements, multiple element containers containing one or more elements may be stored. Can be connected in series or in parallel. When using the element of the present invention, the containers incorporating the elements can be connected and nitrogen can be supplied to each container in parallel or in series, but it is preferable to supply nitrogen in series. Ideally, nitrogen should be supplied in parallel from multiple sources to each container. When exhaust nitrogen is supplied in series, such as to a third pipe, the purity of the nitrogen gradually decreases, and the degassing efficiency may decrease. However, as a result of intensive study, the present inventors found that even if the degassing efficiency decreases due to a slight decrease in nitrogen purity, it can be almost solved by adjusting the amount of nitrogen, and compared to the case of parallel supply of nitrogen. It has been found that the serial nitrogen supply system is preferable because it can greatly reduce the cost of deaeration operation. As shown in Figure 5, nitrogen may be supplied based on the order in which the water to be treated is supplied, or it may be supplied to each container in an order unrelated to the order in which the water to be treated is supplied, taking into consideration the shape of the equipment, etc. You may do so. The flow rate of nitrogen can be appropriately determined depending on the target dissolved gas concentration, but preferably a nitrogen flow rate (volume flow rate) of about 5% to 10% of the volumetric flow rate of the water to be treated is appropriate.

In addition, when storing multiple elements in an element container, nitrogen can be supplied to each element in parallel or in series in each element-containing container.
It is preferable to supply them in series as 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 connected to a feed liquid stream made of a permeate channel material made of a polyester fabric having longitudinal grooves and a polypropylene net. A spiral spiral with a membrane area of 8 tubes and 4 sets of membrane envelopes is wound together with the channel material around a porous center tube made of hard PVC, and has a partition wall made of adhesive as shown in Figure 3-(a) in the center of the flow path on the permeate side. A type degassing element was manufactured. After a blind stopper made of hard PVC was adhesively fixed to the center of the central tube of this element, it was placed in a special container, and the degassing performance of tap water was measured while flowing nitrogen as a carrier gas. Tap water flow rate 1000 L/h, vacuum degree 85 Torr, nitrogen flow rate 1000 cc/min, temperature 25
Under operating conditions of .degree. C., the dissolved oxygen concentration of the raw solution to be treated (tap water), which was initially 8.0 ppm, decreased to 1.9 ppm.

Next, the degassed water that has been degassed (
When water was passed through the tank with a dissolved oxygen concentration of 1.9 ppm and the degassing performance was measured under the same operating conditions as above, the dissolved oxygen concentration decreased to 0.5 ppm.

[Comparative Example 1] A spiral degassing element was manufactured using the same members and gas permeable membrane as in Example 1, except that a partition wall made of adhesive was not provided at the center of the flow path on the permeate side. This was placed in a special container without a partition in the center of the center tube, and the degassing performance of tap water was measured without flowing carrier gas. Tap water flow rate 1000 L/h, vacuum degree 35 Torr,
Under operating conditions at a temperature of 25° C., the dissolved oxygen concentration of the stock solution to be treated, which was initially 8.0 pprn, decreased to 2.7 ppm. Further, when nitrogen was flowed as a carrier gas at 1000 cc/min under these operating conditions, the dissolved oxygen concentration of the water to be treated decreased to 2.6 pprn.

Next, the degassed water (dissolved oxygen concentration: 1.

When the degassing performance was measured under the same operating conditions as above (however, without nitrogen flow), the dissolved oxygen concentration decreased to 1.5 ppm.

[Example 2] Four spiral-type degassing elements (having a permeate side flow path partition wall and a central partition inside the center tube) were manufactured, and each of these elements was used for one element. A deaerator was fabricated in which the raw solution to be treated (tap water) and the nitrogen pipes were connected in series, as shown in FIG. 5-(b). Degassing performance was measured while flowing nitrogen as a carrier gas. Tap water flow rate 1
000 L/h, vacuum degree 85 Torr, nitrogen flow rate 150
Under the operating conditions of 0 cc/min and a temperature of 25°C, initially 8.
The dissolved oxygen concentration of the raw solution to be treated, which was 0 ppm, was 0.
21) I) decreased to m.

[Effects] According to the present invention, it is possible to improve the degassing performance of the spiral type degassing membrane element for gas dissolved in water.

It is particularly effective in removing dissolved oxygen and carbon dioxide from water.

[Brief explanation of drawings]

FIG. 1 is a partially sectional perspective view of the spiral-type degassing element of the present invention in an unrolled state, and FIG. 2 is a partially sectional perspective view of the spiral-type degassing element of the present invention with only the center tube and permeation side channel material portion taken out. FIG. 3 is a partially sectional perspective view. Figure 3
- (a) and FIG. 3(b) are partially cross-sectional perspective views showing examples of the arrangement of the partition wall on the permeation side flow path and the partition inside the central tube of the spiral type degassing element of the present invention. Moreover, FIG. 4 is a partially sectional perspective view showing an example in which another channel material is laminated to a part of the permeation side channel material of the spiral type degassing element of the present invention. Figure 5-(a)2 Figure 5-(b)
) is a flowchart of an undiluted solution to be processed and a carrier gas in an example of a deaerator in which a plurality of element-containing containers each incorporating a spiral-type deaeration element of the present invention are connected and a carrier gas is flowed in series. FIG. 6 is a partially sectional perspective view of a conventional spiral degassing element in an unrolled state. In the figure, 1 is a hollow central tube 1' having holes on its surface, an open end portion 2 of the central tube, an adhesive sealing portion 3, a dissolved gas permeating through the membrane 4, and a feed liquid channel material 5. , the hydrophobic gas permeable membrane 6, the permeation side channel material 7, 7', the supplied stock solution (the stock solution to be treated), the partition 9 inside the central tube, the permeation side channel partition wall 10, the carrier gas inlet. 10' is the carrier gas outlet 11, the second permeation side channel material 12, the built-in spiral degassing element 1-3, 14, 15, 16, 17, 18, 19, It is. Container Processed stock solution line Carrier gas ventilation line Processed stock solution inlet Processed stock solution outlet (degassed water outlet) Carrier gas inlet Carrier gas outlet Groove direction of permeate side channel material

Claims (5)

[Claims] (1) A single or multiple unit consisting of an envelope-shaped hydrophobic gas permeable membrane, a channel material on the permeate side, and a channel material for the feed liquid is placed around a hollow central tube with holes on its surface. In a spiral deaeration element for removing dissolved gas in water, the element is wound around a central tube, and a partition is provided inside the central tube, and
A spiral type degassing element characterized by providing a partition wall at a specific point in a permeate side flow path for specifying the flow direction of the permeate fluid. (2) The spiral type degassing element according to claim 1, wherein the partition wall of the permeation side flow path is made of an elastic polymer material. (3) The spiral type degassing element according to claim 1, wherein the partition wall of the permeation side flow path is formed by curing an adhesive. (4) Use of the spiral type degassing element according to claim 1, characterized in that the water to be treated is supplied to the membrane surface, and the carrier gas is caused to flow from one end of the central tube to the other end of the central tube via the back surface of the membrane. Method. (5) One or more spiral-type deaerator elements In a deaerator composed of a plurality of element-containing containers housed in the same element container, 1
2. The method of using a spiral type degassing element according to claim 1, wherein the carrier gas is supplied in series from multiple carrier gas supply sources to the container containing each element.