JPS6391105A - Degassing method - Google Patents

Abstract

PURPOSE:To enhance the degassing efficiency when the flow rate of the liq. in a tube is high by agitating the liq. in the tube in the title degassing method wherein the dissolved gas is removed by lowering the external pressure of the tube while the liq. passes through the inside of the tube of a porous polymeric membrane. CONSTITUTION:The gas dissolved in the liq. is removed through the wall of the porous polymeric membrane tube by making the external pressure of the pipe lower than the static pressure in the porous polymeric membrane tube 1 while the liq. dissolving the gas passes through the inside of the tube 1 made of a porous polymeric membrane. By this method, the liq. in the porous polymeric membrane tube 1 is agitated. A rotary agitator is provided in the tube to agitate the liq. in the porous polymeric membrane tube, or a stationary mixer is furnished in the tube. Although the gas dissolved in the liq. is removed through the inner wall of the tube, the concn. of the dissolved gas in the liq. in the vicinity of the inner wall of the tube decreases, and the dissolved gas diffuses from the liq. at the center part. The liq. is agitated, and diffusion is accelerated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for degassing dissolved gas contained in a liquid, and more specifically, the present invention relates to a method for degassing dissolved gas contained in a liquid, and more specifically, the present invention relates to a method for degassing dissolved gas contained in a liquid. It relates to a method for efficiently degassing dissolved gases in the liquid during its passage.

[Conventional technology]

When gas dissolved in a liquid is degassed, "degassed dust" is defined as a term that expresses the amount of gas removed, and when a large amount of dissolved gas is degassed, it is said that the amount of degassed dust is high. When the amount of dust is low, it is said that the deaerated dust is low.

In general, a deaerator A using a porous polymer membrane tube has a decompression chamber 2 containing a spiral-shaped porous polymer membrane tube 1, and a vacuum chamber 2, as shown in the flow sheet of Fig. 1. The vacuum pump 4 is detected by a pressure sensor 5 and activated or stopped by a control circuit 3.

When removing gas dissolved in the liquid 6 using the deaerator A, the liquid 6 is pumped into the porous polymer membrane tube 1 ( (hereinafter referred to as a tube) at a predetermined speed.

Deaerating dust depends on the material of the tube through which the liquid that should be deaerated passes,
Wall thickness, inner diameter, contact area with the liquid, straightness in the vacuum chamber, temperature +'a, and amount of the liquid to be degassed.

and viscosity.

Among the factors that affect the degassing dust, when it comes to tubes, the inner diameter is smaller and the wall thickness is thinner.

The larger the contact area of the liquid, the easier it is to degas, but there is a limit due to current tube forming technology. The thickness is limited to 0.2+am.

On the other hand, the higher the degree of vacuum in the decompression chamber, the easier it is to degas.
Liquid may permeate depending on the pore size and porosity of the tube. In this case, the higher the surface tension of the liquid, the smaller the pore diameter and the lower the porosity of the tube in terms of pore size and porosity, the less likely liquid permeation will occur. Therefore, once the material, pore diameter and porosity of the tube are determined, liquid permeation through the tube is closely related to the pressure difference inside and outside the tube and the surface tension of the liquid.

The material of the tube, as long as the liquid does not pass through the tube.
When the inner diameter and wall thickness are the same, the amount of degassed dust is determined by the length of the tube and the flow rate and viscosity of the liquid to be degassed. However, the longer the tube, the higher the amount of degassed dust, but conversely the pressure loss of the liquid to be degassed within the tube increases, making it impossible to obtain the desired flow rate. Therefore, in order to obtain the desired flow rate, the liquid to be degassed can be pumped through a tube using a pump, etc., but in this case, not only does the cost of pumps and other equipment increase, but also The pressure can cause liquid to permeate through the tube, or in severe cases, cause the tube to burst. Therefore, there is naturally a limit to the pressure that can be applied to a liquid.

After all, once the material, inner diameter, and wall thickness of the tube are determined, the maximum flow rate that can be obtained while ensuring a certain level of deaerated dust is determined by the length of the tube and the viscosity of the liquid to be deaerated.

Next, regarding the liquid that should be degassed, the higher the temperature of the liquid, the easier it is to be degassed. This can be understood from the fact that the higher the temperature of the liquid, the lower the solubility of a gas in a liquid. Also, the lower the flow rate of the liquid, the easier it is to be degassed. This can be understood from the fact that the longer the liquid stays in the tube, the more easily it is degassed. Also, the lower the viscosity of the liquid, the easier it is to degas. This is because when dissolved gas is degassed from the liquid at the tube wall, the dissolved gas also diffuses from the liquid in the center of the tube toward the tube wall, but at this time, depending on the viscosity of the liquid in the tube, the dissolved gas This is thought to be because the diffusion rates of the liquids are different, and the lower the viscosity of the liquid, the easier it is to diffuse.

From the above, for example, the inner diameter 1.8 mm and the wall thickness 0. When degassing gas dissolved in a liquid using a 211 tube of a certain length, the flow rate must be lower to increase the amount of degassed dust, and the higher the flow rate, the lower the amount of degassed dust. Become.

In order to reduce the pressure loss of the liquid to be degassed in the tube and to obtain the desired flow rate, the method of simply increasing the inner diameter of the tube is to reduce the contact area between the tube wall and the liquid volume, and to Since the diffusion time of the dissolved gas in the bulk liquid to the tube wall is longer than the residence time in the tube, the desired degassed dust cannot be obtained.

In other words, in conventional degassing methods, once the material, inner diameter, wall thickness, and length of the tube and the liquid to be degassed are determined, these are used to increase the amount of degassed dust in the liquid and to increase the flow rate. This is contradictory, and there has been a desire for a degassing method that does not reduce the amount of deaerated dust even if the flow rate is increased.

JP-A-59-216606 discloses a method of increasing the flow rate while ensuring the desired amount of deaerated dust.

Japanese Unexamined Patent Publication No. 1-25514 discloses that in order to obtain a large amount of liquid with desired deaerated dust, the material, inner diameter and wall thickness of the tube are determined, and a tube 1 that satisfies the desired deaerated dust and flow rate is disclosed. A method is described for finding the true length and determining the number of tubes required to fabricate a multi-tube module in which tubes are arranged in parallel.

[Problems to be Solved by the Invention] However, these methods do not essentially improve the degassing efficiency of the tube.

An object of the present invention is to reduce the pressure outside the tube to be lower than the static pressure inside the tube while a liquid containing gas dissolved therein passes through the tube made of a porous polymer membrane. A method for increasing the degassing efficiency of a liquid even when the flow rate is increased, when the material, inner diameter, and wall thickness of the tube are determined, and the length of the tube is constant, in a deaeration method for removing dissolved gas in the liquid. Our goal is to provide the following.

[Means for solving problems]

An object of the present invention is to reduce the pressure outside the tube by lowering the static pressure inside the porous polymer membrane tube while a liquid containing dissolved gas passes through the tube made of a porous polymer membrane. This is accomplished by a deaeration method in which dissolved gas in the liquid is removed through the wall of a porous polymer membrane tube, which is characterized by stirring the liquid within the porous polymer membrane tube.

As a method of stirring the liquid in the porous polymer membrane tube in the present invention, it is possible to install a rotary stirrer inside the tube, but a simple and effective method is to use a static mixer inside the tube. The method of providing a container is preferred.

[For production]

Dissolved gas in the liquid is degassed from the inner wall of the tube,
At this time, the concentration of dissolved gas in the liquid decreases near the inner wall of the tube, and the dissolved gas moves from the liquid in the center of the tube to the inner wall of the tube by diffusion. Therefore, the degassing rate of the dissolved gas is determined by the diffusion rate of the dissolved gas.

In the present invention, by installing a static mixer or the like in the tube and stirring the liquid, it is possible to forcibly promote the diffusion of the dissolved gas in the center of the liquid toward the inner wall of the tube. .

〔Example〕

Example 1 A tubular polytetrafluoroethylene membrane with an inner diameter of 12 mm, a wall thickness of 0.6 mm, and a length of 6 m was provided in the vacuum chamber 2, and the pressure inside the vacuum chamber 2 was set to 60 Torr, and the membrane was sufficiently stirred at 20°C to remove dissolved air. Ethylene glycol monomethyl ether saturated with ethylene glycol monomethyl ether was passed through the tube at varying flow rates, and the degree of deaeration of the passed ethylene glycol monomethyl ether was measured using a dissolved oxygen concentration meter. Next, five static mixers (consisting of four elements) as shown in FIG. 2 were installed at equal intervals in the duplex polytetrafluoroethylene membrane, and the degree of deaeration was similarly measured.

As shown in FIG. 3, the results show that the present invention reduces the relative amount of dissolved air by about 5% compared to the conventional method.

100% relative dissolved air content means a certain temperature (in this case, 20%).
When the liquid to be degassed is sufficiently stirred at ℃) to saturate the dissolved air, and the dissolved oxygen concentration is measured with a dissolved oxygen concentration needle,
Regarding the amount of dissolved air in the degassed liquid, the degassed liquid is brought to the same temperature as the liquid containing saturated dissolved air before being degassed (20°C in this case), and the same temperature is measured. The dissolved oxygen concentration is measured with a dissolved oxygen concentration needle, and this value is called the relative dissolved air amount and is expressed as a percentage. Therefore, it can be said that the smaller the relative amount of dissolved air, the higher the degree of deaeration.

Example 2 The degree of deaeration was measured under the same conditions as in Example 1 except that methyl ethyl ketone was used instead of ethylene glycol monomethyl ether in Example 1.

As shown in the results in FIG. 4, it can be seen that the present invention reduces the relative amount of dissolved air by 5% compared to the conventional method.

Example 3 The degree of deaeration was measured under the same conditions as in Example 1 except that a photosensitive coating liquid having the composition shown in Table 1 was used in place of ethylene glycol monomethyl ether in Example 1.

As shown in the results in FIG. 5, it can be seen that the present invention reduces the relative amount of dissolved air by about 5% compared to the conventional method.

Table 1 Naphthoquinone-(L2)-diazide-(2)-5 ~ Ester compound of sulfonic acid chloride and polyP-human'roxyethylene 0.7 parts by weight Novolak type phenol resin 2.0 〃Methyl ethyl ketone 15.0 〃Methyl Cellosolve acetate 25. O [Effects of the Invention] As described above, the degassing method according to the present invention includes installing a stirrer such as a static mixer in a degassing tube made of a porous polymer membrane, By stirring the liquid in the tube, the deaeration efficiency of the liquid can be greatly increased, so if you want to obtain at least the desired degree of deaeration, the length of the tube may be shortened or the flow rate may be adjusted to a certain level. In the case of long tubes, the flow rate can be increased while ensuring the desired degree of deaeration. In addition, stirring can forcefully promote the diffusion of dissolved gas in the center of the liquid to the inner wall of the tube, so the inner diameter of the tube can be reduced without being constrained by the conventional concept of having a smaller inner diameter and thinner wall thickness. It became possible to make it larger and thicker for efficient deaeration, and it was possible to change the type and processing capacity of the deaerator to a large IJ. Therefore, when manufacturing a deaerator consisting of a multi-tube module in which tubes are arranged in parallel, the device can be made compact.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the general flow of the degassing device according to the present invention, FIG. 2 is a diagram showing an example of a static mixer used in the present invention, FIGS. 3, 4, and FIG. 5 is a graph showing the relationship between the amount of liquid passing through and the relative amount of dissolved air in an example of the present degassing method when the liquids are ethylene glycol monomethyl ether, methyl ethyl ketone, and a photosensitive coating liquid. 1... Porous polymer membrane tube (tube) 2... Decompression chamber 3... Control circuit 4... Vacuum pump 5...
・Pressure sensor 6...Liquid 7...Pump Fig. 1 Fig. 2 Fig. 3 □Tsukant ('gin) Fig. 4 Mete Rue Konrusu Toso (zO”C) Isshiki @Quantity (007 Figure 5 Procedural amendment 1, J1 Cattle 1986 Patent Application No. 236180 2, Name of the invention Degassing method 3, Person making the amendment Relationship to the case: Name of patent applicant (520) Fuji Photo Film Co., Ltd. (1) Insert K "," after "The smaller the pore size" on page 3, line 12 of the specification. (2) Insert "," on page 4, line 16 of the same specification. (3) Delete ``This is a gas...'' from lines 16 to 18 in the 4th negative line of the same sentence.

Claims (2)

[Claims] (1) While a gas-dissolved liquid passes through a tube made of a porous polymer membrane, the pressure outside the tube is lower than the static pressure inside the porous polymer membrane tube, and the porous polymer membrane A degassing method for removing dissolved gas in the liquid through a membrane tube wall, the degassing method comprising stirring the liquid in the porous polymer membrane tube. (2) The deaeration method according to claim 1, characterized in that a static mixer is provided in the tube for stirring.