JP5024693B2 - Vacuum deaerator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum deaerator for removing gas such as dissolved oxygen in a raw solution to be treated such as water in a pure water or ultrapure water production plant.
[0002]
[Prior art]
In a pure water or ultrapure water production plant, removing dissolved oxygen from water from which impurities have been removed through a prescribed treatment to reduce its content is to prevent corrosion of piping materials, heat exchangers, boilers, ions This is very important from the viewpoint of preventing oxidative degradation of the exchange resin.
In recent years, in the field of electronics industry that produces LSIs and VLSIs, it is required that the dissolved oxygen in water be 10 ppb or less, preferably 5 ppb or less, in order to prevent the formation of oxide films on semiconductor wafers.
[0003]
For this reason, many methods such as a vacuum degassing method, a nitrogen gas aeration method, a membrane degassing method, and a catalyst degassing method have been proposed as methods for reducing dissolved oxygen.
Among these methods, the vacuum deaeration method is performed from above the packing material packed in the vacuum deaeration tower while keeping the pressure in the vacuum deaeration tower at a vacuum level equal to or lower than the saturated vapor pressure at a predetermined water temperature. This is a method of removing dissolved gas by spraying and dropping water to be treated, and has an advantage that it is economical and has little risk of contamination.
[0004]
On the other hand, this vacuum degassing method has a problem that the reach limit of the dissolved oxygen concentration is somewhat high, such as several tens of ppb, in terms of degassing ability.
Therefore, when the degree of decompression in the apparatus is increased in order to improve the deaeration capability, there has been a problem that the amount of extraction increases and the exhaust capacity of the vacuum deaeration apparatus becomes remarkably large. In particular, when the concentration of dissolved oxygen is reduced to a low concentration of 50 ppb or less as well as the low concentration of 5 ppb or less required in the manufacturing process of ultrapure water required in the state-of-the-art semiconductor industry, Increased significantly, and the vacuum deaerator was virtually unable to accommodate this.
[0005]
In order to solve this problem, for example, in Japanese Patent Laid-Open No. 5-228305, the dissolved oxygen concentration is lowered to a low concentration of 50 ppb to 10 ppb or less by using a relatively small capacity vacuum pump according to a conceptual diagram as shown in FIG. A vacuum degassing method has been proposed.
That is, the vacuum deaeration device 200 includes a treated water supply device 105 for supplying the treated water 120 above the sandwiched bed 103 provided inside the vacuum degassing tower 101, and a treated water ( (Deoxygenated water) 121 is condensed in the middle of the extraction pipes 115a and 115 for connecting the vacuum pump 116 with the treated water storage part 102 for storing the 121 and the space part 102a between the packed bed 103 and the treated water storage part 102. A container 110 is included.
The temperature of the water to be treated 120 is a normal temperature of about 25 ° C., which is normally saturated with air, but the cooling water for cooling the condenser 110 is cooled by a refrigerator and is 10 ° C. or less at the inlet of the cooling water supply pipe 113.
70% or more of the steam of the treated water 120 extracted from the space 102a of the vacuum deaeration tower 101 and mixed in the deaeration that has entered the condenser 110 communicates with the cooling water supply pipe 113 and the cooling water discharge pipe 114. The condensed water 122 is cooled and condensed by the cooling device 110a, and the condensed water 122 is stored in the condensed water storage 118 through the condensed water discharge pipe 117 communicating with the lower portion of the condenser 110. For this reason, the vacuum pump 116 provided after the condenser 110 discharges a gas component such as degassed oxygen containing 30% or less of uncondensed residual steam of the water 120 to be treated, so that the exhaust capacity is reduced. Can be
The treated water (deoxygenated water) 121 in the treated water storage unit 102 obtained in this way is sent to a subsequent stage (not shown) through the treated water transfer pipe 107 provided at the lower part of the treated water storage unit 102.
[0006]
[Problems to be solved by the invention]
However, such conventional techniques have the following problems.
When the water surface level of the condensed water 122 in the condensed water reservoir 118 falls and the lower end of the condensed water discharge pipe 117 is exposed to the atmosphere, the outside air flows backward and enters the vacuum deaeration tower via the condenser to be treated water (deoxygenated oxygen). Water) 121 is contaminated, so-called back-flow contamination occurs.
Further, the condensed water 122 is normally discarded due to contamination and is wasted.
Further, the condensate reservoir 118 is usually installed at a lower position having a height of 10.33 m or more in order to maintain a vacuum with respect to atmospheric pressure. For this reason, it is disadvantageous in terms of cost, for example, an installation space for the condensate reservoir 118 including the condensate discharge pipe 117 and the amount of the condensate reservoir 118 are required.
[0007]
In order to solve these problems, the object of the present invention is to provide a high-performance and high-performance (for example, reduced to a dissolved oxygen concentration of ultrapure water of 5 ppb or less), space-saving, and cost-effective without backflow contamination. It is another object of the present invention to provide a vacuum degassing device that is also advantageous.
[0008]
[Means for Solving the Problems]
In order to solve such a problem, the vacuum degassing apparatus of the present invention has a packed bed inside, a vacuum degassing tower for removing dissolved gas in the raw solution to be treated by vacuum degassing, and vacuum degassing It consists degassing pipe and a vacuum pump for the extraction communicating with the tower, and evacuating means for the vacuum degassing tower to a vacuum, treated stock solution supplying spraying the treated stock solution from the top of the fill layer A vacuum degassing apparatus having a supply means and a processing liquid storage section that is provided at a lower portion of the vacuum degassing tower and stores a processing liquid that has been degassed ,
Further, it is provided between the vacuum degassing tower and the degassing pipe and communicated with the inside of the upper part of the vacuum degassing tower or the upper part of the vacuum degassing tower to It was configured to have a condenser that condensed and allowed the condensate to flow directly down into the vacuum degassing tower.
[0009]
In addition, an inert gas supply pipe for continuously flowing an inert gas in an appropriate ratio with respect to the supply volume flow rate of the stock solution into the space between the packed bed and the treatment liquid storage unit is provided.
[0010]
In addition, the inflow ratio of the inert gas is 0.001 to 0.5 volume flow ratio with respect to the supply volume flow of the stock solution.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram of a vacuum degassing apparatus according to an embodiment of the present invention.
The vacuum degassing apparatus 100 according to an embodiment of the present invention has already been applied to the applicant of the present invention except for the vacuum evacuation means 10 provided in the upper part of the vacuum degassing tower 1 in order to evacuate the vacuum degassing tower 1. This is the same as the configuration disclosed in Japanese Patent Publication No. 6-73603 of Japanese Patent Application No. 2-321854 entitled “Method for Removing Dissolved Oxygen in Pure Water or Ultrapure Water”.
Therefore, although detailed description including the effect | action in the vacuum deaeration tower 1 is abbreviate | omitted, the main structures of the vacuum deaeration apparatus 100 of this invention are as follows.
Vacuum degassing for removing gas such as dissolved oxygen in the raw solution 20 to be treated, such as water, which has a packed layer 3 on the inner partition plate 4 and has been subjected to a predetermined treatment by vacuum degassing. A degassing unit that is provided in close communication with the upper part of the air tower 1 and the vacuum deaeration tower 1 through a nozzle 12 and that condenses the vapor of the raw solution 20 to be treated and bleeds in connection with the condenser 10a. Raw material supply means 5 to be processed comprising a vacuum exhaust means 10 comprising a piping 15 and a vacuum pump 16 and a spraying device 6 for supplying and dispersing the raw material 20 to be treated from the upper part of the packed bed 3 via a liquid supply pipe 5a. And a treatment liquid storage section 2 for storing a treatment liquid 21 such as deoxygenated water provided at the lower part of the vacuum deaeration tower 1.
[0012]
The vacuum deaeration tower 1 is not described in detail so as to achieve gas-liquid equilibrium, but is designed on the basis of a general gas absorption theory, and the packed bed 3 is provided with a filler such as Raschig ring. Filled to height.
Further, inert gas such as nitrogen gas or argon gas in a ratio of 0.001 to 0.5 volume flow rate with respect to the supply volume flow rate of the processing stock solution 20 in the space 2a between the packed bed 3 and the processing solution storage unit 2 An inert gas supply pipe 9 through which gas continuously flows is provided.
The inert gas injection is described in detail in the above Japanese Patent Publication No. 6-73603, and detailed description thereof is omitted here. However, by such a method, a vacuum is formed from the upper portion of the vacuum deaeration tower 1. It is possible to degas the gas such as dissolved oxygen in the processing stock solution 20 to 5 ppb or less at a higher rate than in the conventional method in which the vacuum deaeration tower 1 is simply evacuated while being pulled.
[0013]
The temperature of the water to be treated 20 is a normal temperature of about 25 ° C., which is normally saturated with air, and the vacuum deaeration tower 1 is maintained at a degree of vacuum of about 25 Torr, for example.
The cooling water for cooling the condenser 10a is cooled by a refrigerator, and specifically selected according to the target condensation rate in the condenser 10a. For example, at the inlet of the cooling water supply pipe 13, the cooling water is 10 ° C. or lower. It is.
The vapor of the unprocessed stock solution 20 extracted from the upper part of the vacuum degassing tower 1 and mixed into the degass such as dissolved oxygen that has entered the condenser 10a through the demister 11 and the nozzle 12 that drop and remove the droplets is, for example, 80 to 90% or more is cooled and condensed by the cooler 10 b communicating with the cooling water supply pipe 13 and the cooling water discharge pipe 14.
For this reason, the vacuum pump 16 provided after the condenser 10a exhausts a gas component such as degassed oxygen containing 20 to 10% or less of uncondensed residual vapor of the raw solution 20 to be treated. The capacity can be reduced.
The vapor condensate in the condenser 10 a is configured to flow down directly into the vacuum deaeration tower 1. For this reason, as shown in FIG. 3, the condensate drain pipe 117 and the condensate reservoir 118, which have been installed so as to have a height of 10.33 m or more in order to maintain a vacuum in the lower part of the conventional condenser, This eliminates the need for these facilities and allows the condensate to be effectively used as a treatment liquid without being discarded.
The treatment liquid 21 such as deoxygenated water in the treated water storage unit 2 obtained in this way is sent to a later stage (not shown) by the pump 8 through the treatment liquid transfer pipe 7 provided at the lower part of the treatment liquid storage unit 2. It is.
[0014]
Next, another embodiment according to the present invention will be described with reference to the accompanying drawings.
FIG. 2 is a conceptual diagram of a vacuum degassing apparatus according to another embodiment of the present invention.
The vacuum degassing apparatus 100 according to another embodiment of the present invention is the same as the embodiment of the present invention except for the configuration of the vacuum exhaust means 10 provided at the top of the vacuum degassing tower 1 (FIG. 1). ).
That is, the vacuum evacuation means 10 includes a condenser 10a disposed integrally with the vacuum degassing tower 1 on the upper part of the spraying device 6 in the vacuum degassing tower 1, and a tip portion communicating with the upper part of the condenser 10a. Is composed of a deaeration pipe 15 and a vacuum pump 16 connected to the demister 11. Inside the condenser 10a, a cooler 10b communicating with the cooling water supply pipe 13 and the cooling water discharge pipe 14 is provided.
Although detailed description including the operation of the vacuum degassing apparatus 100 configured as described above is omitted, the condensed liquid obtained by cooling and condensing the vapor of the raw solution to be treated 20 by the cooler 10b is directly in the vacuum degassing tower 1. It is the structure which flows down to the lower part of.
[0015]
【Effect of the invention】
The vacuum degassing apparatus according to the present invention described in detail above is configured so that the condensate of the raw liquid to be processed in the condenser flows down directly into the lower part of the vacuum degassing tower. The condensate discharge pipe 117 and the condensate reservoir 118 installed so as to have a height of water column of 10.33 m or more in order to maintain the vacuum in the lower part, and the relative distance between the vacuum deaeration tower and the condenser. The large-diameter deaeration pipe 115a is unnecessary, and the installation space and cost can be reduced by omitting these facilities.
Furthermore, the backflow contamination caused by the backflow of the outside air from the condensate reservoir, which has conventionally occurred, is eliminated.
Further, the vapor condensate of the raw solution to be treated in the condenser can be effectively used as the treatment liquid without being discarded.
Further, nitrogen gas or argon gas in a ratio of 0.001 to 0.5 volume flow rate with respect to the supply volume flow rate of the processing stock solution from an inert gas supply pipe provided in the space between the packed bed and the processing solution storage portion The process stock solution at a higher rate than the conventional method in which the inside of the vacuum degassing tower is simply evacuated while evacuating from the upper part of the vacuum degassing tower by continuously flowing an inert gas such as There is an excellent effect that has not been achieved so far, such as the ability to degas the gas such as dissolved oxygen therein to 5 ppb or less.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a vacuum degassing apparatus according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram of a vacuum degassing apparatus according to another embodiment of the present invention.
FIG. 3 is a conceptual diagram of a conventional vacuum degassing apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,101 Vacuum deaeration tower 2,102 Process liquid (water) storage part 2a, 102a Space part 3,103 Packing layer 4 Partition plate 5,105 Processed raw liquid (water) supply means 5a Supply liquid (water) pipe 6 Liquid (water) device 7, 107 Treatment liquid (water) transfer pipe 8, 108 Pump 9 Inert gas supply pipe 10 Vacuum exhaust means 10a, 110 condenser 10b, 110a Cooler 11 Demister 12, 112 Nozzle 13, 113 Cooling water Supply pipes 14, 114 Cooling water discharge pipes 15, 115, 115a Deaeration (bleeding) pipes 16, 116 Vacuum pumps 20, 120 (To be treated) Stock solution (water)
21, 121 Treatment liquid (deoxygenated water)
100, 200 Vacuum deaerator 117 Condensate (water) discharge pipe 118 Condensate (water) storage 122 Condensate (water)

Claims (3)

A vacuum degassing tower having a packed bed inside for removing dissolved gas in the raw solution to be treated by vacuum degassing;
Consists degassing pipe and a vacuum pump for the extraction and communicating with the vacuum degassing tower, a vacuum exhaust means for evacuating the vacuum degassing tower,
And the object to be processed solution feed means for feeding spraying the treated stock solution from the top of the packed bed,
A vacuum degassing apparatus having a processing liquid storage section that is provided at a lower portion of the vacuum degassing tower and stores a processing liquid that has been degassed,
Further, interposed between the vacuum degassing tower and the degassing pipe, and provided in communication with the inside of the upper part of the vacuum degassing tower or the outside of the upper part of the vacuum degassing tower, A vacuum degassing apparatus comprising a condenser for condensing the vapor of the processing raw solution and causing the condensate to flow directly into the vacuum degassing tower. An inert gas supply pipe for continuously flowing an inert gas in an appropriate ratio with respect to a supply volume flow rate of the stock solution into a space between the packed bed and a processing liquid storage unit. Item 2. A vacuum degassing apparatus according to Item 1. The vacuum degassing apparatus according to claim 2, wherein the inflow ratio of the inert gas is 0.001 to 0.5 volume flow rate ratio with respect to the supply volume flow rate of the stock solution.

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