WO2006085731A1

WO2006085731A1 - Method for transporting a fluid containing unstable gas through bundles of tubes

Info

Publication number: WO2006085731A1
Application number: PCT/KR2006/000499
Authority: WO
Inventors: Hag-Joo Lee
Original assignee: Sem Technology Co., Ltd
Priority date: 2005-02-14
Filing date: 2006-02-13
Publication date: 2006-08-17
Also published as: KR100592982B1

Abstract

There is provided a method for transporting a fluid containing unstable gas. The method comprises a step of separately transporting the fluid containing unstable gas through bundles of small tubes. The method minimizes concentration loss caused by the degradation of the unstable gas contained in the fluid, during long distance transportation. In addition, the diameter of the transporting system can be reduced smaller than that of the conventional system adopting a single tube, even in a case that each of the fluid flow is maintained to the same Reynolds Number.

Description

METHOD FOR TRANSPORTING A FLUID CONTAINING UNSTABLE GAS THROUGH BUNDLES OF TUBES

Technical Field

[1] The present invention relates to a method for transporting a fluid containing unstable gas. Background Art

[2] Ozonated water has been used, in semiconductor manufacturing process, for example, to remove photoresist and to clean it after striping. Later, the ozonated water seems to be used on striping process itself. Ozone gas dissolved into suitable medium undergoes degradation by collision with neighboring ozone gas or a transporting tube. The degradation due to collisions decreases the concentration of ozone dissolved into the ozonated water. Especially, ozone is known to be an unstable gas sensitive to such degradation. Due to the disadvantage, ozonated water generators are installed close to semiconductor equipments. That is, the distance required for transporting the ozonated water is minimized as small as possible. Maximum concentration of the ozonated water, produced from the ozonated water generator, is about 120 ppm. Minimum concentration of the ozonated water required for removing remaining photoresist, which is typically located 20 m apart from the ozonated water generator, is about 60 ppm. Effective concentration for removing remaining photoresist is about 80 ppm. In order to obtain highly concentrated ozonated water, the transporting distance should be reduced as possible. However, the distance between the ozonated water generator and the semiconductor equipment requiring the ozonated water is preferable as far as possible. Further, it is ideal that the ozonated water, produced from the ozonated water generator, is supplied to multiple semiconductor equipments. Nevertheless, the demand for long distance transportation of the ozonated water and the concentration loss during the transportation of the ozonated water are conflicted matters. An efficient method for transporting the fluid containing unstable gas (for example, ozone) should be adopted to overcome this contradiction. Disclosure of Invention Technical Problem

[3] An object of the present invention is to provide a method for transporting a fluid containing unstable gas, in which degradation of the unstable gas by collision with neighboring gas and a transporting tube is reduced to minimize concentration loss of the fluid containing unstable gas.

[4] Another object of the present invention is to provide a method for transporting a fluid containing unstable gas, in which the diameter of the transporting system could be reduced smaller than that of the conventional system adopting a single tube, even in a case that each of the flow of the fluid is maintained at the same Reynolds Number.

[5] Further another object of the present invention is to provide a method for transporting a fluid containing unstable gas, in which concentration loss of the fluid containing the unstable gas is additionally reduced by prevention of heat loss of the fluid.

Technical Solution

[6] According to a preferred embodiment of the present invention, there is provided a method for transporting a fluid containing unstable gas which comprises transporting the fluid containing unstable gas through a transporting system, characterized in that the transporting system comprises bundles of small tubes, and the fluid containing unstable gas is separately transported through the bundles of small tubes.

[7] According to another preferred embodiment of the present invention, there is provided a method for transporting a fluid containing unstable gas, wherein the transporting system comprises an inner tube formed of bundles of small tubes, a fixation member having holes into which the small tubes are inserted and fixed, and an outer tube inside which an assembled body formed by the fixation of the small tubes into the fixation member is installed, and the fluid containing unstable gas is separately transported through the bundles of small tubes.

[8] According to further another preferred embodiment of the present invention, there is provided a method for transporting a fluid containing unstable gas, wherein the transporting system further comprises at least one groove formed at an edge of the fixation member, and a refrigerant is driven to flow through the groove.

[9] According to further another preferred embodiment of the present invention, there is provided a method for transporting a fluid containing unstable gas, wherein the unstable gas is a gas susceptible to degradation by collision with neighboring gas or an inner wall of the tube. Particularly suitable is ozonated water.

[10] According to other preferred embodiment of the present invention, there is also provided a transporting system for transporting a fluid containing unstable gas, comprising an inner tube formed of bundles of small tubes through which the fluid containing unstable gas is separately transported, a fixation member having holes into which the small tubes are inserted and fixed, and an outer tube inside which an assembled body formed by the fixation of the small tubes into the fixation member is installed. Preferably, one or more grooves are formed at an edge of the fixation member for the passage of a refrigerant. Advantageous Effects [11] The method for transporting a fluid containing unstable gas according to the present invention provides following advantages:

[12] a) The method according to the present invention transports the fluid containing unstable gas through bundles of small tubes, thereby reducing concentration loss more than that of the single tube system. Especially, the transportation of the fluid through bundles of small tubes reduces the diameter of transporting system as low as about 1/10 of the single tube system. This provides the economical advantage by reducing the installation and management cost of the transporting system.

[13] b) The method according to the present invention adopts a shell and tube structure in which bundles of small tubes through which the fluid containing unstable gas (especially, the ozonated water) is transported are inserted into an outer tube. Cooling can be readily accomplished in order to minimize the concentration loss caused by collisions between the unstable gas molecules or between the unstable gas and the inner wall of the transporting tube. The transporting system can protect energy loss of the fluid, which additionally reduces the concentration loss.

[14] c) Generally, most of the chemically unstable gases are harmful to human, as thus leakage of the gases should be carefully protected as much as possible. The method according to the present invention adopts the shell and tube structure which relieves the danger caused from the leakage of the gases.

[15] d) The method according to the present makes it possible to transport the fluid containing unstable gas in a reduced concentration loss. This further enables to transport the fluid to a long distance. Therefore, the ozonated water generator can be installed to a distance such that one generator can be commonly shared by two or more semiconductor equipments. In order words, highly concentrated ozonated water produced from one generator can be supplied, through the shell and tube transporting system, to two or more semiconductor equipments.

Brief Description of the Drawings

[16] Fig. 1 is a graph showing flow rate-dependent concentration change of ozone transported through two tubes, each of which having 4 mm diameter and varied length. [17] Fig. 2 is a resolved perspective view showing a preferred embodiment of the transporting system having a shell and tube structure, in accordance with the present invention. [18] Fig. 3 is a combined cross sectional view showing a preferred embodiment of the transporting system having a shell and tube structure, in accordance with the present invention. [19] Fig. 4 is a cross sectional view showing a fixation member of small tubes used for transporting the fluid, which is shown in Fig. 2 and Fig 3. Mode for the Invention

[20] The present invention relates to a method for transporting a fluid containing unstable gas. More specifically, the present invention relates to a method for transporting ozonated water, wherein a fluid containing unstable gas is separately transported through bundles of small tubes.

[21] Generally, the flow of a fluid in a tube is classified into a laminar flow and a turbulent flow. In the laminar flow, fluid collision is minimized at an interface between the fluid and an inner wall of the transporting tube. To the contrary, in the turbulent flow, collision between the fluid and the inner wall of the transporting tube is actively progressed. Such a physical amount to describe the flow of the fluid is called Reynolds Number and is defined as following formula 1 :

[22] Re = pυD/μ (1)

[23] wherein, Re is a Reynolds Number, p is a fluid density, μ is a modulous friction factor, υ is a fluid velocity and D is a diameter of a transporting tube.

[24] The fluid flow having a Reynolds number of less than 2,300 is defined as the laminar flow, while the fluid flow of larger than 4,000 is defined as the turbulent flow. Transition region exists between the laminar flow and the turbulent flow. When a fluid containing unstable gas, for example, the ozonated water is transported, the flow rate of the fluid and the diameter of the transporting tube should be carefully determined such that the Reynolds number should be maintained to less than 2,300 in order to keep the flow of the fluid to the laminar flow.

[25] When the fluid containing unstable gas is transported, a friction factor should be also concerned. Since the friction factor of the fluid is represented as an amount of collision between particles in the flow of the fluid, it implicates the degradation of the dissolved gas by collision during the transportation of the fluid. The friction factor of the fluid having the laminar flow is represented by following formula 2:

[26] f = 16/Re = 16μ/pυD (2)

[27] wherein, f is a friction factor, and Re, p, μ, υ and D are the same those as defined in the formula 1.

[28]

[29] As shown in the formula 2, regarding that the friction factor and the density of the fluid are temperature-sensitive constants, the friction factor of the fluid can be suitably adjusted with the control of the temperature. However, since the friction factor of the fluid is reversely proportional to the Reynolds number, simple lowering of the friction factor results in the turbulent flow, which limits the lowering of the friction factor. Therefore, it is essential for the fluid to be transported in the laminar flow and with low friction factor, by suitably controlling the total flow rate, the diameter of a transporting pipe, and so on.

[30] Therefore, when the fluid containing unstable gas, such as the ozonated water, is transported to a long distance, degradations of the unstable gas caused from absorption to and collision with the inner wall of a transporting tube are closely related to both the Reynolds number and the friction factor of the fluid. Firstly, the transporting system should be designed such that the fluid can have Reynolds number of less than 2,300 in order to be maintained in the laminar flow. Fig 1 is a graph showing flow rate- dependent concentration change of the ozonated water transported through two single tubes, each of which having 4 mm diameter and varied length. In a case that the ozone is transported through a transporting tube having 4 m length, at a flow rate of less than 5 LPM, no significant concentration loss was observed. However, about 90% of ozone was destroyed when the ozone is transported through a transporting tube having 48 m length at a flow rate of more than 5 LPM. When the fluid flows at a flow rate of 1 LPM, the Reynolds number of the fluid is about 350. As thus, the Reynolds number of the fluid having 5 LPM flow rate is about 1,750. This value indicates that, even the fluid has the laminar flow, the length of the transporting tube may cause serious concentration loss of unstable gas, because the Reynolds number is close to the turbulent flow region. Although the length of a transporting tube is not a main factor to be concerned on calculating Reynolds number, extended staying on a transporting tube may lead rapid concentration loss of the unstable gas. In the transportation of the fluid containing the unstable gas to a long distance, therefore, it is very important to keep the perfect laminar flow.

[31] Let us assume that a fluid is transported at a flow rate of 600 LPM using a single transporting tube under one atmospheric pressure. In this case, a transporting tube having a diameter of more than 1,200 mm should be used to keep the Reynolds number 700. In order to transport the fluid under the same Reynolds number and at the same flow rate, the fluid might be transported through three hundreds of small tubes having 4 mm diameter at a flow rate of 2 LPM. If three hundreds of small tubes are assembled in a cylindrical shape, the diameter of the assembled body will be about 120 mm, which is 1/10 of the diameter of the single transporting tube. Namely, transportation of the fluid through bundles of small tubes can decrease the diameter of the transporting system as much as 1/10, compared to that of the single tube.

[32] Chemically unstable gas such as ozone has the tendency to form a stable compound throughout the collision. Such a collision phenomena is proportional to the temperature of the fluid. Especially, when gases pass through the transportation tube, the friction factor of the fluid implicates collisions between the gas molecules in the fluid or between the gas molecule and the inner wall of the transporting tube. As shown in the formula 2, the friction factor is reciprocally proportional to the Reynolds number. The fluid density and the friction factor, which are used for the calculation of Reynolds number, are the function of temperature, and those are listed in Table 1 :

[33] Table 1

[34] Namely, in the transportation of the ozonated water using the 4 mm diameter tube, at a flow rate of 2 LPM, the friction factor of the fluid can be reduced by about 27.6% when the temperature of the transporting tube is 250 K compared to 300 K. Even though the Reynolds number at the temperature of 250 K is 930 which means about 35% increase, the fluid has the laminar flow. If the temperature of the transporting pipe is reduced on condition that the fluid is maintained to the laminar flow, the concentration loss of the unstable gas can be additionally reduced.

[35] Fig. 2 is a resolved perspective view showing a preferred embodiment of the transporting system used in the transportation of the fluid containing unstable gas, in accordance with the present invention, and Fig. 3 is a combined cross sectional view of transporting system shown in Fig. 2. As shown in Fig. 2 and Fig. 3, the transporting system, in accordance with the present invention, comprises an inner tube (or an inner transporting tube) 100 formed of bundles of small tubes 101, an fixation member 200 for accommodating the bundles of small tubes 101, and an outer tube (or an outer transporting tubes) 300 inside which the fixation member 200 is installed. More specifically, the bundles of small tubes 101 provides a passage of the fluid containing unstable gas (particularly, an ozonated water inside which ozone gas is dissolved into a water), in order to insure the laminar flow of the fluid due to small diameter. The number and the diameter of small tubes 101, and the flow rate can be suitably chosen regarding the concentration loss during the transportation of the fluid. Herein, the Reynolds number is maintained to below 2,300. The bundles of small tubes 101 are inserted and fixed into holes 201 formed inside the fixation member 200. The bundles of small tubes 101 fixed into the fixation member 200, thereafter, are inserted into the inner space 301 of the outer tube 300 to form a shell and tube structure. Even Fig. 2 and Fig. 3 show respectively only one assembly, multiple assemblies connected in parallel can be used in the long distance transportation. Herein, interconnection between two assemblies can be easily achieved through holes 302, which are formed on the outer tube 300, by using suitable connecting member (example: a bolt and nut). Meanwhile, according to the preferred embodiment of the present invention, it is preferable to cool down the transporting system to minimize concentration loss during the transportation of the fluid containing unstable gas. Cooling is accomplished by flowing refrigerant through grooves 202a, 202b, 202c and 202d formed at edges of the fixation member 200, which is shown in Fig. 4. Referring to Fig. 4 which shows a cross sectional view of the fixation member for bundles of small tubes, the grooves 202a, 202b, 202c and 202d act as a passage of the refrigerant, and the refrigerant freely flows between the assemblies through the grooves 202a, 202b, 202c and 202d. This structure makes it possible to accomplish the cooling without any increase of the diameter of the transporting system. Therefore, when the ozonated water is transported through the bundles of small tubes 101 housed into the holes 201 of the fixation member 200, concentration loss can be additionally decreased with aid of the cooling. Herein, the small tubes 101, the fixation member 200 having many holes 201, and the outer tube 300 can be made of various synthetic resins or metals, but are not limited thereto. Regarding external impacts, a metal tube is preferable as an outer tube 300. In an economic point of view, the small tubes 101 and the disk-type fixation member 200 are preferably made of synthetic resins.

[36] The present invention can be applied to the transportation of the fluid containing various unstable gases. As used herein, the unstable gas means a gas susceptible to degradation by collision with a neighboring gas or the inner wall of the transporting tube. Ozone, chlorine or fluorine can be mentioned as an unstable gas. These gases can be dissolved into a suitable medium and transported using the method of the present invention.

[37]

[38] Examples

[39] Example 1

[40] Pipes having diameter of 4 mm and length of 20 m, were used as small tubes 101.

Each of four small tubes 101 was arranged at a corner of a square to form a 2x2 matrix. Ozonated water was transported through each of the four small tubes 101 at a flow rate of 0.5 LPM (total flow rate: 2 LPM). After completion of the transportation of the ozonated water, 9% of concentration loss was observed.

[41]

[42] Comparative example 1

[43] For the purpose of comparison, ozonated water was transported through a single pipe having a diameter of 8 mm and a length of 20 m. Row rate of the ozonated water was adjusted to 2 LPM, which is the same condition that of Example 1. After transportation of the ozonated water to a distance of 20 m under the room temperature, 13% of concentration loss was measured.

[44] [45] Comparing the transporting systems of the example 1 and the comparative example

1, internal specific surface area of the example 1 has 2 times higher than that of the comparative example 1. Surprisingly enough, in spite of such an increased specific surface area, the example 1 showed reduced concentration loss compared to the comparative example 1. This implies that the transportation of the ozonated water through multiple small tubes secure more stable flow.

[46]

[47] Example 2

[48] Pipes having diameter of 4 mm and length of 20 m, were used as small tubes 101.

Sixty small tubes 101 were assembled into a fixation member 200 having a disk shape, as shown in Fig. 3. The assembled body was inserted into an outer tube 300 having a diameter of 80 mm. Ozonated water was transported through each of the small tubes 101 at a flow rate of 0.35 LPM. In order to cool down the ozonated water, cold water was used as a refrigerant (refrigerant temperature: about 5°C). The cold water was driven to flow through grooves 202a, 202b, 202c and 202d formed on the fixation member 200. The concentration of the ozonated water was measured after it was transported to a distance of 20 m. About 5% of concentration loss was observed, which was significantly very low value, compared to the conventional transportation of the ozonated water through the single tube.

Claims

[1] A method for transporting a fluid containing unstable gas which comprises transporting the fluid containing unstable gas through a transporting system, characterized in that the transporting system comprises bundles of small tubes, and the fluid containing unstable gas is separately transported through the bundles of small tubes.

[2] The method as set forth in claim 1, wherein the transporting system comprises an inner tube formed of bundles of small tubes, a fixation member having holes into which the small tubes are inserted and fixed, and an outer tube inside which an assembled body formed by the fixation of the small tubes into the fixation member is installed, and the fluid containing unstable gas is separately transported through the bundles of small tubes.

[3] The method as set forth in claim 2, wherein the transporting system further comprises at least one groove formed at an edge of the fixation member, and a refrigerant is driven to flow through the groove.

[4] The method as set forth in claim 1, wherein the fluid containing unstable gas has a laminar flow in each of the small tubes.

[5] The method as set forth in claim 1, wherein the unstable gas is a gas susceptible to degradation by collision with neighboring gas or an inner wall of the tube.

[6] The method as set forth in claim 1, wherein the fluid containing unstable gas is ozonated water.

[7] A transporting system for transporting a fluid containing unstable gas, comprising an inner tube formed of bundles of small tubes through which the fluid containing unstable gas is separately transported, a fixation member having holes into which the small tubes are inserted and fixed, and an outer tube inside which an assembled body formed by the fixation of the small tubes into the fixation member is installed.

[8] The transporting system as set forth in claim 7, further comprising at least one groove, formed at an edge of the fixation member, which acts as a passage of a refrigerant.