JP5785601B2 - Gas filtration system - Google Patents

Description

  The present application relates to gas filtration systems, and more particularly to harmful gases emitted from fossil / fuel burning facilities such as incinerators, oil refineries, rubber factories, plastic factories, large container ships, energy plants and the like. The invention relates to a gas filtration system comprising a combination of tanks containing different amounts of water for cleaning.

  The rapid development of economies and industries around the world has increased greenhouse / hazardous gas / particulate emissions into the environment. Common greenhouse / hazardous gases in the Earth's atmosphere include carbon dioxide, sulfur dioxide, methane, nitrous oxide, ozone, and chlorofluorocarbons. The emission of these harmful gases leads to many problems such as acid rain and / or greenhouse effect. The greenhouse effect is one of several factors that, for example, affect the temperature of the earth and cause global warming. As a result of air pollution, many efforts have been made to reduce gas pollution in these gas emissions.

  Over the years, several devices have been developed to filter gases, such as cleaning exhaust gases. However, since most devices have a complicated structure, the cost of the device increases. In addition, methods for cleaning gases in the art sometimes require complex processes to obtain the desired efficiency. Some examples of conventional devices for cleaning gases are illustrated below.

  One apparatus for cleaning acidic or alkaline impurities from a gas stream is disclosed in Thomas (US Pat. No. 6,893,484). Specifically, as shown in Thomas's drawing, gas is introduced into the container and passes through a plurality of tubes located at the bottom of the container. The gas is then released from the hole in the tube and enters a sealed space containing the liquid absorbent material. Finally, the cleaned gas passes through the metal mesh and is released out of the container.

  Another method for cleaning the gas is disclosed in Trivett (US Pat. No. 7,056,367). Trivet discloses a method for cleaning the gas, i.e. the gas is pushed into the liquid tank and flows through the cleaning liquid. The gas then flows in the opposite direction through the mixing vanes, creating small bubbles, thereby enhancing the interaction between the gas contaminants and the cleaning liquid.

  Further, the smoke cleaning system disclosed in Lube (US Pat. No. 4,212,656) includes spraying water to facilitate smoke cleaning. In this configuration, the smoke passes through several chambers to fully contact the water spray. The cleaned smoke is then released out of the container. In order to obtain maximum efficiency, the Roube provides several nozzles, such as a fan spray type, to allow the water to effectively contact the smoke. In addition to inevitably increasing the manufacturing cost of such a smoke cleaning system, this arrangement is considered difficult to repair / maintain the nozzles located inside each container.

  Many other examples of development in the art are directed to similar objects.

  In one or more embodiments, the gas filtration system includes a liquid filtration system and a gas transfer system. The liquid filtration system has a plurality of tanks connected to each other for containing a liquid. The gas transfer system includes a pipe coupled to the tank for transferring gas. The tank of the liquid filtration system includes at least one tank that does not contain liquid. This tank, or drying tank, may be used for dry filtration, and in some cases may be used to put a pump to force the gas to flow through the gas filtration system.

  Another embodiment features a combination of tanks containing different amounts of water to filter / purify the gas. This is an important feature of the present invention.

1 is a perspective view showing an outer frame of one or more embodiments of a gas filtration system. FIG. 1 is a perspective view showing a gas transfer system of one or more embodiments of a gas filtration system. FIG. 1 is an exploded schematic perspective view showing an inner frame of one or more embodiments of a gas filtration system. FIG. FIG. 2 is a perspective view showing a gas capture process of a gas filtration system, schematically showing an example of two tanks connected to each other by pipes. 1 is a schematic perspective view showing a layer filter system according to one or more embodiments of a gas filtration system. FIG.

  FIG. 1 is a perspective view of an outer frame of one or more embodiments of a gas filtration system. The gas filtration system 10 includes a plurality of tanks 30. In at least one embodiment, one tank is not used for liquid filtration but includes a plurality of layer filters used for dry gas filtration. In an embodiment, the liquid that is desirably contained in the tank 30 is water. However, it should be noted that the liquid used in the gas filtration system 10 is not limited to water. Any other component that can accomplish the same function may be used in the gas filtration system 10.

  In some embodiments, the final stage of the filtration process is to pass a wash / wet (WET) filtration gas through a layer of dry filter comprising a particulate filter containing activated carbon / charcoal. As shown in FIG. 1, a filter is provided in the tank to provide several layers of gas filtration.

  Each tank 30 is formed in a substantially rectangular or cubic rigid shape. Several tanks are assembled together to define a front surface 24 and a top surface 22. In the particular embodiment shown in FIG. 1, eight tanks are arranged in two rows adjacent to each other. In addition, according to the particular embodiment shown in FIG. 1, each of the tanks 30 for containing a liquid is used to observe the liquid level in each tank 30 and indicate the appropriate timing to add the liquid. There is a transparent strip 26 on the front face 24 of 30. The filter / liquid capture observation device 28 is positioned outside the tank 30 and is generally positioned on the front surface 24 of the tank 30. The body of the device 28 may be made of transparent plastic so that the user can observe the color change of the liquid and determine when the liquid used in the tank needs to be replaced. It is not limited.

  In order to transfer gas to the respective tanks, in this embodiment, several tanks such as gas pumps 14a, 14b and liquid pump 16 are used in one or more tanks that are not themselves used for gas filtration. A pump is provided and positioned. With respect to the embodiment shown in FIG. 1, the gas pumps 14a, 14b and the water pump 16 are preferably placed in the same tank to save space. A control box 36 for controlling the pumps 14a, 14b and 16 is provided on the front wall of one of the tanks.

  A plurality of liquid transfer pipes 12 are connected to each tank adapted to contain liquid. The liquid transfer pipe 12 has a plurality of segments that define a liquid inlet 34 and a liquid outlet 32 for each tank 30. For example, the liquid used in the gas filtration system 10 is introduced from the liquid supply inlet 38 and transferred to each tank 30 via the liquid inlet 34 by the liquid transfer pipe 12. In the particular embodiment of FIG. 1, the liquid inlets 34 are arranged to connect to respective tanks 30 at the top of the front surface 24. When the gas filtration process is complete, the liquid used in the gas filtration system 10 is discharged from the liquid outlet 32. The liquid outlet 32 is adapted for discharging spent liquid from the tank. The liquid source inlet 38 is coupled to the liquid transfer pipe 12. A liquid outlet 32 is provided in each of the tanks 30 used to contain the liquid, so that the used liquid can be discharged from each tank 30 separately. The liquid pump 16 is placed in the tank 30 to force liquid to flow from the liquid source inlet 38 to the tank, for example.

  After using the gas filtration system for a while, contaminants remain in the tank 30. In order to clean these contaminants, a hose may be connected to a hose plug 80 formed on the front surface 24 of each tank 30 using a hose.

  During operation of the liquid transfer system, a liquid such as water used in the gas filtration system for filtration is transferred by the water pump 16 from the water source inlet 38 along the liquid transfer pipe 12 to the tank 30. The gas is fed by gas pumps 14a and 14b.

  FIG. 2 is a perspective view showing an embodiment of the gas transfer system 50 of the gas filtration system 10. Some tanks 30 are also connected by a gas transfer system 50 that includes a plurality of gas transfer pipes 52. In accordance with the embodiment of FIG. 2, gas transfer system 50 includes gas transfer pipes 52a, 52b,... For transferring gas from one tank to another. . . 52i (FIG. 3). In the preferred embodiment, the material of the gas transfer pipe is stainless steel. In some embodiments, each gas transfer pipe 52 is installed within the tank 30 and protrudes from the top surface 22 of the tank 30. The location where the gas transfer pipe protrudes does not necessarily have to be from the top surface 22, but is generally near the top surface of the tank for efficient delivery of as much gas as possible in a short time. Should do. The entire gas filtration process lasts about 10 seconds.

  A detailed structure of the gas transfer pipe 52 is shown below according to FIG. 3 showing the gas capture process in the tank 30. At the top surface 22 of the tank 30, a gas inlet 54 is connected to one of the tanks 30 for introducing gas into the tank 30 for filtration. In addition, a gas outlet 56 is installed on the top surface 22 of the tank 30 to release the gas after being cleaned by the gas filtration system 10. In some embodiments, the gas outlet 56 is desirably located on the top surface 22 of the tank 30 containing the layer filter for the final step of the gas filtration process. (The gas filtration process is shown below with reference to FIG. 3.)

  FIG. 3 is an exploded schematic perspective view showing the internal configuration of one or more embodiments of the gas filtration system 10. Tanks 30a, 30b,. . . The tank 30 including 30 g includes a plurality of gas transfer pipes 52a, 52b,. . . They are connected together by a gas transfer system 50 such as 52i. The gas filtration system 10 includes several tanks for liquid filtration and at least one tank for layer filtration. In particular, as shown in FIG. 3, tanks 30a, 30b, 30d, 30e, 30f contain a predetermined amount of liquid for filtering / purifying gas. The tank 30g is connected to the tank 30f and contains a plurality of layer filters 72 (also shown in FIG. 5).

  More specifically, the tanks 30a, 30b,. . . 30h are positioned adjacent to each other and assembled together. In the particular embodiment shown in FIG. 3, each tank 30a, 30b,. . . 30h has dimensions of 24 "(inch) x 24" (inch) x 60 "(inch). The size of the tank 30 is not limited to that shown in FIG.

  Each tank 30a, 30b,. . . The amount of liquid contained in 30f is determined in advance based on the capabilities of the gas pumps 14a and 14b. Each tank 30a, 30b,. . . 30f has a liquid level that is related to the amount of that liquid. It should be noted that the height of the liquid level is not limited to the example shown, and the liquid level can be adjusted according to the amount of liquid. As a specific example shown in FIGS. 1-3, the capacity of each air pump motor is 230v, 4hp, 3451rpm, 18amps.

  Tanks 30a, 30b,... To achieve the desired efficiency. . . The liquid level in 30f, that is, the amount of liquid, is as follows as a practical example.

The first tank 30a contains a liquid volume of 36 "(inch) in height (89.9 gallons).
The second tank 30b contains 16 ″ (inch) high liquid (39.9 gallons).
The third tank 30c does not contain a liquid for gas filtration.
The fourth tank 30d contains 39 ″ (inch) high liquid (97.2 gallons).
The fifth tank 30e contains 24 ″ (inch) high liquid (59.8 gallons).
The sixth tank 30f contains 39 ″ (inch) high liquid (97.2 gallons).

  This liquid level defines a liquid level that divides the entire liquid tank into two spaces: an upper space without liquid and a lower space with liquid. In the particular embodiment shown in FIG. 3, for example, in the tank 30a, the tank 30a is divided into an upper space 66 where the liquid level 64 does not contain liquid and a lower space 68 which contains liquid.

  FIG. 3 also shows that the tanks 30 are connected to each other via a gas transfer pipe 52 or gas pumps 14a, 14b. Depending on the connection mode of the tank 30, the gas transfer pipe is divided into two types. More specifically, the gas transfer pipes 52a, 52b, 52d, 52e, 52g, and 52h are the first type gas transfer pipes I, which are installed on the top surface 22 of the tank 30 and have gas in each tank. For example, tanks 30a, 30b, 30c, 30d, 30e, 30f, and 30g are connected to the respective tanks. The gas transfer pipes 52c and 52f are second type gas transfer pipes II, which are installed on the top surface 22 of each tank such as the tanks 30b and 30d, for example, and the second type gas transfer pipes II are respectively Instead of connecting directly to the tank, it is connected to an air pump.

  Each of the first type gas transfer pipes I has three parts: an upper part 74, an intermediate part 72 and a lower part 70. The upper part 74 of the first type of gas transfer pipe I is positioned outside the tank and has two ends 76 and 78 that are located on each of the two tanks and connect to each other. In this particular embodiment, the first end 76 installed in the tank 30a and the second end 78 installed in the tank 30b connect the two tanks 30a, 30b together so that the gas is It is transferred to the intermediate part 72 through 74. Both the middle part 72 and the lower part 70 are placed in each tank 30. The intermediate portion 72 is formed substantially in a straight line and extends in the vertical direction along the front surface 24 of the tank 30. The lower part 70 connected to the middle part is curved and substantially occupies the lower space 68 of the tank 30. In some embodiments, the lower portion 70 of the first type of gas transfer pipe I is curved in a horizontal direction, for example, in a closed M-shaped shape, so that the desired efficiency of releasing gas bubbles into the liquid. To achieve.

  The gas transfer pipe 52 i is one of the first type gas transfer pipes and has an upper portion 74 and an intermediate portion 72. The gas transfer pipe 52i is installed on the top surface 22 of the tank 30f and is connected via an upper part 74 to a tank 30g containing a layer filter 18 for purifying gas. The difference between the gas transfer pipe 52i and other transfer pipes, for example 52a, 52b, 52d, 52e, 52g, 52h, etc. is that the lower part 70i is T-shaped and has at least one outlet 78 for releasing gas. It is to have. In some embodiments, the lower portion 70i may have two outlets 78a, 78b as shown in FIG.

  According to FIG. 3, a detailed process for filtration including water / wet (WET) filtration and dry fiber filtration is shown and illustrated below.

  The first gas pump 14a forces gas to flow into the first tank 30a from the gas inlet 54 installed on the top surface 22 of the first tank 30a. The gas inlet 54 is connected to the first gas transfer pipe 52a.

  The gas is introduced from the gas inlet 54 and then forced to flow to the first gas transfer pipe 52a in the first tank 30a. Specifically, the gas is forced to flow downward through the intermediate portion 72 of the first gas transfer pipe 52a to the lower portion 70 of the first gas transfer pipe 52a, and further below the first tank 30a. Released into space 68.

  In an embodiment of the present invention, the lower portion 70 of the gas transfer pipe 52 includes a plurality of small holes 40 for releasing gas out of the pipe 52. Each hole 40 has a predetermined diameter, e.g., 3/16 "(inch), etc., for creating the desired gas / liquid interaction without providing flow resistance that impedes intended wet (WET) filtration. Have

  When the gas is released through the hole 40, a bubble effect (ie, a bubble) occurs naturally. This helps to maximize the surface area of the gas trapped in each bubble, thereby allowing water to interact properly with the gas. After the first round of filtration, the foam (gas) rises to the top of the liquid, which is defined by the liquid level 64 and further releases gas into the upper space 66 of the first tank 30a, after which The gas is forced to flow into the second tank 30b.

  The gas after the first round of filtration in the first tank 30a is forced to flow into the second gas transfer pipe 52b installed on the top surface 24 of the second tank 30b. The gas is forced to flow downward into the lower space 68 of the second water tank 30b through the intermediate portion 72 of the second gas transfer pipe 52b. The gas is then sent to the lower part 70 of the second gas transfer pipe 52b and released through the small hole 40. Similar to the first round of filtration, the gas is forced out of the small hole 40, so that the bubble effect naturally occurs again, maximizing the surface area of the gas trapped in each bubble. Allowing the liquid to fully interact with the gas to achieve the desired filtration. After two rounds of filtration, the bubbles (gas) rise to the top surface 64 of the liquid so that the gas collects in the upper space 66 of the second tank 30b and is then forced to flow into the third tank 30c.

  The filtered gas from the second tank 30b is then forced to flow into a third gas transfer pipe 52c connected to the gas pump 14a. The gas is forced to flow into the third tank 30c by the gas pump 14a through the fourth gas transfer pipe 52d.

  The gas is forced to flow by the gas pump 14a, and is also forced to flow by the gas pump 14b, and enters the fourth gas transfer pipe 52d installed on the top surface 22 of the third tank 30c. The gas is forced to flow downward to the lower space 68 of the third tank 30c through the intermediate portion 72 of the fourth gas transfer pipe 52d. The gas is then directed to the lower portion 70 of the fourth gas transfer pipe 52d and released through the small hole 40. The third tank 30c does not contain a liquid for gas filtration. The third tank 30c is used as a gas buffer that helps the first gas pump 14a and the second gas pump 14b smoothly move the gas to the next filtration tank. The filtered gas in the third water tank 30c is then forced to flow into the fourth tank 30d.

  The gas after passing through the third tank 30c is forced to flow into the fifth gas transfer pipe 52e installed on the top surface 22 of the fourth tank 30d. The gas is forced to flow downward to the lower space 68 of the fourth tank 30d through the intermediate portion 72 of the fifth gas transfer pipe 52e. The gas is then sent to the lower portion 70 of the fifth gas transfer pipe 52e and is released through the small hole 40 to produce the natural bubble effect described above. After three rounds of filtration, the bubbles (gas) rise to the liquid top surface 64 and the gas is released into the upper space 66 of the fourth tank 30d, after which the gas is collected and forced into the fifth tank 30e. Washed away.

  The gas from the fourth tank 30d is then forced to flow into the sixth gas transfer pipe 52f connected to the gas pump 14b. The gas is then forced to flow by the gas pumps 14a, 14b and enters the fifth tank 30e through the seventh gas transfer pipe 52g.

  The gas is forced to flow by the gas pumps 14a and 14b and enters a seventh gas transfer pipe 52g installed on the top surface 22 of the fifth tank 30e. The gas is forced to flow downward along the seventh gas transfer pipe 52g to the lower space 68 of the fifth water tank 30e through the intermediate portion 72 of the seventh gas transfer pipe 52g. The gas is then sent to the lower portion 70 of the seventh gas transfer pipe 52g and released through the small hole 40. After four rounds of filtration, the bubbles (gas) rise to the liquid top surface 64 and the gas is released into the upper space 66 of the fifth tank 30e and then forced to flow into the sixth tank 30f.

  The gas is forced to flow into an eighth gas transfer pipe 52h installed on the top surface 22 of the sixth tank 30f. The gas is drawn downward along the eighth gas transfer pipe 52h to the lower space 68 of the sixth tank 30f through the intermediate portion 72 of the eighth gas transfer pipe 52h. The gas is then sent to the lower portion 70 of the eighth gas transfer pipe 52h and discharged through the small hole 40. After five rounds of filtration, the foam (gas) rises to the top surface 64 of the water and is discharged into the upper space 66 of the sixth tank 30f and then forced to flow into the seventh tank 30g.

  In the fifth round of filtration in the sixth tank 30f, in certain embodiments, the gas is fully wet (WET) filtered via water filtration.

  The cleaned gas is forced to flow into the ninth gas transfer pipe 52i installed on the top surface 22 of the seventh tank 30g. In the embodiment shown in FIG. 3, the seventh tank 30g serves as the final filter tank. The final filter tank 30g includes other water tanks 30a, 30b,. . . You may have the same size as 30h. The cleaned gas is forced to flow downward through the ninth gas transfer pipe 52i to the lower space 68i of the tank 30g through the intermediate portion 72 of the ninth gas transfer pipe 52i. The ninth gas transfer pipe 52i includes a T-shaped lower portion 70i having two outlets 78a and 78b for discharging gas into the lower space 68i of the gas tank 30g. The lower space 68 i is defined by the layer filter 18. In the embodiment shown in FIG. 3, the layer filter 18 divides the tank 30g into several spaces, and gas is discharged from the outlets 78a, 78b into the lower space 68i. The cleaned gas is forced through several layers of filtration, such as the five-layer filter 18, in the lower-upper direction.

  Each layer filter 18 of filtration contains a particulate filter with activated carbon / charcoal in between. Activated charcoal enables odor neutralization / removal and particulate filters are used as an additional measure of filtration. After layer filtration, the cleaned gas is finally released into the atmosphere through a gas outlet 56 installed on the top surface 22 of the tank 30g.

  Because wet (WET) filtration removes most of the pollutants of the gas through five rounds of filtration, the layer filter can be used for a long period of time and only changed (for example) every few months.

  FIG. 4 schematically illustrates the gas capture process of the gas filtration system 10, showing an example of two common tanks according to the above-described embodiment.

  For simplicity of the gas capture process, only the middle and lower portions of the two gas transfer pipes 52 are shown in FIG. Basically, as described above with reference to FIG. 3, gas is forced through the gas transfer pipe 52 into the tank and released out through the small holes 40. The foam formed is discharged through an adjacent gas transfer pipe or pipe outlet (shown in FIG. 4). The small holes 40 are uniformly distributed in the lower portion 70 of the first type and second type gas transfer pipes 52. More specifically, the holes in this particular embodiment are spaced from each other by a predetermined distance 1 ″ (inches).

  FIG. 5 shows the internal configuration of the gas tank according to the present invention. The gas tank 30g has the same three dimensions as the other water tanks. In order to transfer the gas to the lower part of the gas tank 30g, a gas transfer pipe 52i is placed inside the gas tank 30g. The gas transfer pipe 52i is positioned to pass through all the layer filters, and the lower part of the pipe 52i is placed under the bottom layer filter. For this reason, the gas is filtered from the lowermost layer filter to the uppermost layer filter, and released to the outside of the gas tank 30g.

  Each layer filter 18 is positioned within the gas tank 30g and is spaced apart from one another by a predetermined distance, such as 9 ″ (inches). For example, the first layer is 48 ″ ( The second layer is spaced 39 ″ (inches) from the bottom of the gas tank 30g; the third layer is spaced 30 ″ (inches) from the bottom of the gas tank 30g. The fourth layer is spaced 21 ″ (inches) from the bottom of the gas tank 30g; the fifth layer is spaced 11 ″ (inches) from the bottom of the gas tank 30g.

  After the liquid and bed filtration processes, the liquid used for filtration is returned to the tank 30 for subsequent filtration by the liquid transfer pipe 12. The liquid used as the filtrate, such as water, can be easily replaced with clean water, allowing the gas filtration system to be used continuously with an infinite lifetime.

  Furthermore, it is noted that when (for example) spent water needs to be replaced, it may be recovered from the gas filtration system. According to an experiment in which the collected used water was tested on a grass patch, there was no significant deterioration of the grass. The collected waste water can be easily sprayed, for example, on grassland or a septic tank disposal system.

  As indicated previously, layer filters, such as particulate filters, may simply be replaced every few months. This is the fact that the particulate filter is used in the final step of the overall filtration process and the liquid lasts longer because it filters out most harmful contaminants before reaching the dry filtration stage. For.

  It should be noted that a predetermined amount of water combination in each tank is required to obtain the desired result. Further, as indicated above, the size of each hole 40 in such a desired combination is 3/16 ″ (inch).

  Those skilled in the art will readily appreciate that the present invention serves all of the purposes set forth above. After reading the foregoing specification, one skilled in the art can make various modifications, equivalent replacements, and various aspects of the invention as broadly disclosed herein. Accordingly, the protection afforded this invention is intended to be limited only by the definitions contained in the appended claims and their equivalents.

Claims (7)

A method used in a gas filtration system for filtering gas comprising:
Transferring each of the gases through a pipe to a plurality of tanks,
The tank contains a liquid for cleaning the gas,
The pipe for transferring the gas is:
A first gas transfer pipe installed on the top surface of each tank and extending into each adjacent tank;
A second gas transfer pipe installed on the top surface of the respective tank for transferring the gas and connected to a pump for forcing the gas to flow into or out of the tank;
A third gas transfer pipe installed on the top surface of each of the tanks for transferring the gas through a layer filter;
Including
The first gas transfer pipe includes a closed substantially M-shaped portion,
The third gas transfer pipe includes a T-shaped portion positioned in a lower space of the tank and having two outlets for discharging the gas;
The method further includes
Sending the gas into the liquid in the form of bubbles through a plurality of holes distributed along the closed generally M-shaped portion ;
Sending the gas up from the tank and then sending the gas down into the adjacent tank through the respective pipes;
Releasing the gas from the tank;
A gas filtration method comprising: A method used in a gas filtration system for filtering gas comprising:
Transferring each of the gases through a pipe to a plurality of tanks,
The tank contains a liquid for cleaning the gas,
The pipe for transferring the gas is:
A first gas transfer pipe installed on the top surface of each tank and extending into each adjacent tank;
A second gas transfer pipe installed on the top surface of each of the tanks for transferring the gas and connected to a pump for forcing the gas into or out of the tank; Including
The lower part of each of the first gas transfer pipes defines a closed substantially M-shape, and a hole is provided substantially along the entire length of the pipe;
The method further comprises passing the gas through the hole in the form of bubbles into the liquid;
Sending the gas up from the tank and then sending the gas down into the adjacent tank through the respective pipes;
Releasing the gas from the tank;
A gas filtration method comprising: A gas filtration method according to claim 1 or 2,
A gas filtration method in which the gas is sent to a plurality of tanks through the pipe, and the tank includes a drying tank that does not contain liquid, thereby reducing pressure and allowing the gas to move smoothly between adjacent tanks. A gas filtration method according to claim 1 or 2,
Before the step of releasing the gas, the method further includes the step of sending the gas to a drying tank not containing liquid and forcing the gas through the layer filter provided in the drying tank. A gas filtration method according to claim 1 or 2,
A gas filtration method in which the liquid contains water. The gas filtration method according to claim 1,
Each of the first gas transfer pipes is
A lower portion extending into the lower space of the tank and having a hole for releasing the gas;
An upper portion extending continuously to the lower portion;
A gas filtration method comprising: A gas filtration method according to claim 2,
Each of the first gas transfer pipes is
A lower portion extending into the lower space of the tank and having a hole for releasing the gas;
An upper portion extending continuously to the lower portion;
A gas filtration method comprising:

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