Patent Publication Number: US-2023158434-A1

Title: Coalescing filter element with double drainage layers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/CN2021/098053, filed on Jun. 3, 2021, which claims priority to Chinese Patent Application NO. 202110289457.9, filed on Mar. 18, 2021, entitled ‘coalescing filter element with drain function’, all of which are hereby incorporated by reference in their entireties. 
    
    
     FIELD 
     The present disclosure relates to a technical field of natural gas transportation, and particularly to a coalescing filter element with double drainage layers. 
     BACKGROUND 
     Pipeline transportation in natural gas transportation technology is the optimum way to realize a long-distance transmission of a large amount of oil and gas resources. To realize long-distance transportation, it is necessary to provide compressor stations along the pipeline to pressurize natural gas. The core power equipment of the compressor station is a compressor. Natural gas extracted from the ground usually contains some minerals, clay, water, condensate, or other impurities. If solid particles or droplets enter the compressor, the blade or dry gas seal system of the compressor will be worn, corroded, or thermally strained, which may cause the compressor to shut down in severe cases. 
     Generally, the natural gas entering the compressor station passes through devices such as a cyclone separator, a filter separator, and a coalescer in sequence to remove the solid and liquid impurities entrained in the gas, so as to ensure continuous and normal operation of the compressor for an extended period. The coalescer is mainly used to remove droplets with a diameter of less than 1 μm. The core component of the coalescer is coalescing filter elements. 
     The structure of the coalescer in the prior art is illustrated in  FIG.  1   . The coalescer is internally provided with a tube sheet  100 , which divides an interior of the coalescer into an upper portion and a lower portion. The lower portion is a liquid-containing gas chamber and the upper portion is a filtered gas chamber. The gas with droplets enters the liquid-containing gas chamber through an inlet  200  of the coalescer, then passes to the inner side of each coalescing filter element  300  through an opening at the bottom of the coalescing filter element  300  by the gas driving force, and then flows into the coalescing filter element  300  through pores of the filter material in the inner surface of the coalescing filter element  300 . After being coalesced, where tiny droplets in the gas collide, coalesce, and merge into larger droplets inside the filter material of the coalescing filter element  300 , the coalesced liquid drains through the outer surface of the coalescing filter element  300 . The drained liquid falls on the tube sheet  100  by gravity, and then drains from the coalescer through a first liquid vent  400  at the lower portion of the filtered gas chamber. The filtered gas flows through the outer surface of the coalescing filter element  300 , and then exits to the downstream process through an outlet  500  at the upper portion of the clean gas chamber. If the liquid content in the gas is extremely high, part of the liquid will be directly captured on the inner surface of the coalescing filter element  300 , then fall to the bottom of the liquid-containing gas chamber by gravity, and then drained from the coalescer through a second liquid vent  600  at the bottom of the liquid-containing gas chamber. 
     The structure of the coalescing filter element  300  in the prior art is illustrated in  FIGS.  2  and  3   . An inner support  3001  serves as a support for the coalescing filter element  300 . A coalescing layer  3002 , which is composed of multi-layer fibrous filter media for coalescing droplets and usually made up of glass fibers, is wrapped outside the inner support  3001 . An outer support  3003  is provided outside the coalescing layer  3002  to fix it. A drainage layer  3004  is wrapped outside the outer support  3003 . The drainage layer  3004 , which is composed of a single-layer fibrous filter medium for draining coalesced liquid, is capable of capturing large droplets caused by droplet re-entrainment from the coalescing layer  3002 . The drainage layer  3004  is usually made up of polymer fibers such as aramid fibers and is assembled outside the filter element. A bottom end cap  3005  and a top end cap  3006  of the filter element are connected with the drainage layer  3004  to seal both ends of the inner support  3001 , the coalescing layer  3002 , the outer support  3003 , and the drainage layer  3004 , so that the gas with liquid and solid contaminants can only pass through the coalescing filter element  300  in the radial direction, where the coalescence and filtration are completed efficiently during this process. 
     However, the above-mentioned coalescing filter element usually has the following disadvantages during the operation. 
     1. The coalescing layer of the coalescing filter element in the prior art is formed by tightly wrapping or pleating multiple layers of high-efficiency fiber media. In the coalescence and filtration process, a large amount of liquid is captured by the fiber materials and clogs the pores thereof, resulting in a gradual reduction in the filtration efficiency. 
     2. In the filtration process, the captured liquid moves to the outside of the filter element and forms a liquid film on the outer surface of the coalescing layer of the filter element. The liquid film will lead to a sudden increase in the pressure drop of the filter element and a significant increase in the energy consumption of the system. Meanwhile, the gas passing through the liquid film will cause the liquid film to break and become many tiny droplets, resulting in a significant decrease in the gas-liquid separation performance. 
     3. The coalescing filter element is usually cylindrical, with a length of about 0.9 m to 1.8 m. The coalescing filter element is mounted vertically, which will lead to an uneven distribution of the liquid captured by the coalescing filter element in the vertical direction. As a result, the closer to the bottom of the filter element, the more serious a liquid blockage and droplet re-entrainment in the filter material is, which will seriously affect the filtration performance of the filter element. The droplet re-entrainment is a process in which the droplets that have been separated from the gas phase are entrained again by the gas due to the gas flow. In addition, when there is a large amount of liquid in the filter media at the bottom of the filter element, the liquid content in other filter media adjacent to the bottom will increase due to the capillary action, which further weakens the capture of droplets by fibers, resulting in a decrease in filtration efficiency. 
     The above situations particularly exist in the fields such as a compressor station of a long-distance natural gas transportation pipeline and an offshore oil and gas exploitation platform. When the operating condition fluctuates or the content of submicron droplets in the gas suddenly increases, the efficiency of the filter element will decrease and the energy consumption of the system will increase. 
     However, there is still no effective solution in the prior art to solve the problem that the filtration performance of the coalescing filter element does not meet the requirements and in which the pores can be easily clogged by the droplets. 
     SUMMARY 
     An objective of the present disclosure is to provide a coalescing filter element with double drainage layers, which includes an inner and an outer coalescence structures, and a drainage space therebetween. Liquid coalesced by the inner coalescing component enters the drainage space, which greatly reduces the amount of liquid to be coalesced by the outer coalescing component, thus effectively avoiding the weakening influence of excessive amount of liquid on the filtration performance of the outer coalescing component, and effectively prolonging service life of the filter element and reducing energy consumption. 
     Another objective of the present disclosure is to provide a coalescing filter element with double drainage layers, in which the inner support and the outer coalescing component are segmented structures, and filter media of the inner coalescing component are arranged with gradient pore diameters, which can effectively restrain a sudden rise of pressure drop in the inner coalescing component and realize a timely drainage of liquid captured by the inner coalescing component, and re-entrained droplets from the inner coalescing component will be fully captured by the outer coalescing component, thus significantly improving filtration efficiency of the filter element. 
     The above objectives of the present disclosure can be achieved by the following technical solutions. 
     The above objectives of the present disclosure can be achieved by the following technical solutions. It is one aspect of the present disclosure to provide a coalescing filter element with double drainage layers, including an inner coalescing component configured to capture a large amount of liquid in gas, and an outer coalescing component configured to coalesce and filter a small amount of liquid remaining in the gas, wherein the inner coalescing component and the outer coalescing component are cylindrical structures disposed in a vertical direction and opened at two ends; the outer coalescing component is sleeved on an outer side of the inner coalescing component, and an annular drainage space is formed between the inner coalescing component and the outer coalescing component; a top end cap is provided on top ends of the inner coalescing component and the outer coalescing component; a bottom end cap is provided on bottom ends of the inner coalescing component and the outer coalescing component, and the bottom end cap is provided with a gas inlet communicated with an interior of the inner coalescing component. 
     It is another aspect of the present disclosure to provide a coalescing filter element with double drainage layers, including an inner coalescing component and an outer coalescing component, wherein the inner coalescing component and the outer coalescing component are cylindrical structures disposed in a vertical direction; the outer coalescing component is sleeved on an outer side of the inner coalescing component, and an annular drainage space is formed between the inner coalescing component and the outer coalescing component; a top end of the inner coalescing component and a top end of the outer coalescing component are closed, a bottom end of the annular drainage space is closed, and a bottom end of an interior of the inner coalescing component is provided with a gas inlet. 
     The advantageous effects of the present disclosure are as follows. 
     1. The coalescing filter element with double drainage layers includes an inner coalescing component and an outer coalescing component. The inner coalescing component serves to capture a large amount of liquid in gas, and 80% to 90% of the liquid in the gas may be captured by the inner coalescing component, thus greatly reducing the amount of liquid to be coalesced and filtered by the outer coalescing component. In this case, the first outer coalescing layer of the outer coalescing component can be composed of high-efficiency filter media, resulting in high filtration efficiency and reduction in liquid clogging, by which more clean areas in the first outer coalescing layer are obtained for effectively capturing droplets for a long period of time. As a result, the service life of the filter element for highly efficient filtration can be prolonged at least 2 to 3 times compared to the coalescing filter element in the prior art, and the use cost can be greatly reduced. In addition, as the gas passes through the liquid film formed on the inner coalescing component, the droplets formed by the rupture of the liquid film will be captured by the outer first coalescing layer and be prevented from directly entering the downstream of the filter element. 
     2. In the coalescing filter element with double drainage layers, the first inner coalescing layer and the second inner coalescing layer are composed of different filter media with the same wettability, and pore diameters of the two kinds of filter media gradually increase from the inside to outside, so that the liquid can smoothly transport from the first inner coalescing layer towards the second inner coalescing layer. As there is no difference in wettability and no reduction in flow area, the liquid film will not form between the first inner coalescing layer and the second inner coalescing layer. The liquid film can only form on the outer surface of the filter medium with larger pore diameter (i.e., the second inner coalescing layer), thus effectively reducing the pressure drop in the coalescing filter element and ensuring normal use of the coalescing filter element. 
     3. In the coalescing filter element with double drainage layers, a lower portion of the first inner support is a blocking element without ventilation holes. Therefore, the liquid drained from the inner coalescing component can drop into the drainage space, or remain at a position in the lower portion of the inner coalescing layer with a same height as the blocking element. Therefore, the gas can smoothly pass through the upper portion of the inner coalescing component above the blocking element without directly impacting the liquid in the drainage space and the coalesced and filtered liquid in the lower portion of the inner coalescing layer, thus effectively reducing the droplet re-entrainment. 
     4. In the coalescing filter element with double drainage layers, the second outer drainage layer is composed of amphiphobic filter media. The second outer coalescing layer includes a super-amphiphilic layer and a super-amphiphobic layer covering the outside of the super-amphiphilic layer. When the liquid drained from the inner coalescing component drops into the drainage space, the liquid can be absorbed by the second outer coalescing layer and drained from the filter element through the second outer drainage layer in a short time, thus avoiding in liquid accumulation in the liquid drainage space and wetting the inner coalescing component, thereby further preventing droplet re-entrainment and ensuring highly efficient filtration of the coalescing filter element for a long period of time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawings are only intended to schematically illustrate and explain the present disclosure, rather than limiting the scope of the present disclosure. In the drawings, 
         FIG.  1    is a structural diagram of a coalescer in the prior art. 
         FIG.  2    is a structural diagram of a coalescing filter element in the prior art. 
         FIG.  3    is a cross-sectional view of the coalescing filter element in the prior art along lines C-C of  FIG.  2   . 
         FIG.  4    is a structural diagram of a coalescing filter element with double drainage layers of the present disclosure. 
         FIG.  5    is a cross-sectional view of the coalescing filter element of the present disclosure along lines A-A of  FIG.  4   . 
         FIG.  6    is a cross-sectional view of the coalescing filter element of the present disclosure along lines B-B of  FIG.  4   . 
         FIG.  7    is a structural diagram of a top end cap in the coalescing filter element with double drainage layers of the present disclosure. 
         FIG.  8    is a front view of the top end cap in the coalescing filter element with double drainage layers of the present disclosure. 
         FIG.  9    is a structural diagram of a bottom end cap in the coalescing filter element with double drainage layers of the present disclosure. 
         FIG.  10    is a front view of the bottom end cap in the coalescing filter element with double drainage layers of the present disclosure. 
         FIG.  11    is a structural diagram of a connecting member in the coalescing filter element with double drainage layers of the present disclosure. 
         FIG.  12    is a front view of the connecting member in the coalescing filter element with double drainage layers of the present disclosure. 
         FIG.  13    is a structural diagram of a first inner support in the coalescing filter element with double drainage layers of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     For a clearer understanding of the technical features, objectives and effects of the present disclosure, specific embodiments of the present disclosure will now be described with reference to the drawings. 
     As illustrated in  FIG.  4   , the present disclosure provides a coalescing filter element with double drainage layers, which includes an inner coalescing component  1  configured to capture a large amount of liquid in gas (i.e., natural gas), and an outer coalescing component  2  configured to coalesce and filter a small amount of liquid remaining in the gas. The inner coalescing component  1  and the outer coalescing component  2  are both cylindrical structures disposed in a vertical direction and opened at two ends. The outer coalescing component  2  is fixedly sleeved on the outer side of the inner coalescing component  1 , and an annular drainage space  3  is formed between the inner coalescing component  1  and the outer coalescing component  2 . Therefore, the inner coalescing component  1  and the outer coalescing component  2  constitute a double-layer drainage structure. A top end cap  4  is provided on top ends of the inner coalescing component  1  and the outer coalescing component  2  to clog a top opening of the inner coalescing component  1  and the top of the drainage space  3 . A bottom end cap  5  is provided on bottom ends of the inner coalescing component  1  and the outer coalescing component  2  to clog the bottom of the drainage space  3 . The bottom end cap  5  is provided with a gas inlet  503  communicated with an interior of the inner coalescing component  1 , through which the gas can enter the interior of the inner coalescing component  1 . 
     In the present disclosure, positions of the inner coalescing component  1  and the outer coalescing component  2  are fixed by the top end cap  4  and the bottom end cap  5 . The gas enters the interior of the inner coalescing component  1  through the gas inlet  503 , and then passes through the inner coalescing component  1  and the outer coalescing component  2  in sequence. The inner coalescing component  1  captures a large amount of liquid (about 80% to 90% of the total liquid) in the gas, which greatly reduces the amount of liquid to be coalesced and filtered by the outer coalescing component  2 . The outer coalescing component  2  only needs to coalesce and filter a small amount of liquid remaining in the gas, thus effectively avoiding the weakening influence of excessive amount of liquid on filtration performance of the outer coalescing component  2 , and effectively prolonging service life of the coalescing filter element and reducing energy consumption. 
     In addition, since the drainage space  3  is formed between the inner coalescing component  1  and the outer coalescing component  2 , the re-entrained droplets from the inner coalescing component  1  will enter the drainage space  3 , so as to be fully captured by the drainage space  3  and the outer coalescing component  2 , thus further avoiding the weakening influence of excessive amount of liquid on filtration performance of the outer coalescing component  2 , thereby significantly improving the filtration efficiency of the coalescing filter element. 
     Exemplarily, the drainage space  3  has a radial width of 2 mm to 5 mm. 
     In an alternative embodiment of the present disclosure, as illustrated in  FIGS.  4 ,  7  to  10   , the top end cap  4  and the bottom end cap  5  are disc-shaped structures disposed in a horizontal direction. A bottom end surface of the top end cap  4  is provided with an annular first positioning groove  401  and an annular second positioning groove  402  disposed around the first positioning groove  401 . A top end surface of the bottom end cap  5  is provided with an annular third positioning groove  501  and an annular fourth positioning groove  502  disposed around the third positioning groove  501 . The gas inlet  503  is located at a middle position of the bottom end cap  5 . A top portion of the inner coalescing component  1  is fixedly embedded into the first positioning groove  401 , and a bottom portion of the inner coalescing component  1  is fixedly embedded into the third positioning groove  501 . A top portion of the outer coalescing component  2  is fixedly embedded into the second positioning groove  402 , and a bottom portion of the outer coalescing component  2  is fixedly embedded into the fourth positioning groove  502 . Therefore, the positions of the inner coalescing component  1  and the outer coalescing component  2  are fixed by the top end cap  4  and the bottom end cap  5 , so as to ensure the stability of the overall structure of the coalescing filter element. 
     In an alternative embodiment of the present disclosure, as illustrated in  FIGS.  4  to  6  and  13   , the inner coalescing component  1  includes a first inner support  101 , an inner coalescing layer, and a second inner support  104 . The first inner support  101  and the second inner support  104  are both cylindrical structures disposed in a vertical direction and opened at two ends. The second inner support  104  is fixedly sleeved on the outer side of the first inner support  101 , and the inner coalescing layer is interposed between an outer surface of the first inner support  101  and an inner surface of the second inner support  104 . The entire second inner support  104  and an upper portion of the first inner support  101  are respectively provided with a plurality of uniformly distributed ventilation holes, through which the gas can pass through the first inner support  101  and the second inner support  104 . The inner coalescing layer of the inner coalescing component  1  captures a large amount of liquid in the gas to prevent it from clogging the outer coalescing component  2 , so as to improve the coalescence and filtration performance. 
     Further, as illustrated in  FIGS.  4  and  13   , a lower portion of the first inner support  101  is a blocking element  105  with a cylindrical structure and made of a blind plate without ventilation holes. The coalescing filter element in the prior art is mounted in a vertical direction (i.e., an upright mode), so the closer to the bottom of the filter element, the more serious a liquid blockage and droplet re-entrainment in the filter material is. In the embodiment of the present disclosure, by configuring the blocking element  105 , the liquid drained from the inner coalescing component  1  all drops into the drainage space  3 , or remains at a position in the lower portion of the inner coalescing layer with a same height as the blocking element  105 . Therefore, the gas can smoothly pass through the upper portion of the inner coalescing component  1  above the blocking element  105  without directly impacting the liquid in the drainage space  3  and the coalesced and filtered liquid in the lower portion of the inner coalescing layer, thus effectively reducing the droplet re-entrainment. 
     Further, the blocking element  105  and the first inner support  101  may be, but not limited to, an integral structure. 
     Exemplarily, a ratio of a height of the blocking element  105  to a height of the inner coalescing component  1  is 1/4 to 1/5. 
     In an alternative embodiment of the present disclosure, as illustrated in  FIGS.  4  to  6   , the inner coalescing layer includes a first inner coalescing layer  102 , and an second inner coalescing layer  103  covering an outer surface of the first inner coalescing layer  102 . The diameter of filter pores of the first inner coalescing layer  102  is smaller than that of the filter pores of the second inner coalescing layer  103 . The first coalescing layer  102  and the second inner coalescing layer  103  have a same wettability to a same liquid. The wettability refers to a degree of wetting of a liquid to filter media, and is usually indicated by a contact angle between the liquid and the filter media. The contact angle less than 90 degrees indicates that the liquid is wettable for the filter media, and the contact angle greater than 90 degrees indicates that the liquid is non-wettable for the filter media. 
     In the prior art, the coalescing layer of the coalescing filter element is composed of multi-layer high-efficiency fibrous filter media, the average pore diameter of which is about 1 μm to 3 μm. The captured liquid moved to the outer surface of the coalescing layer will form a liquid film and clog the pores of the filter medium, resulting in a sudden increase in the pressure drop of the filter element. 
     Researches show that the pressure drop caused by the liquid film is mainly influenced by capillary action, and is closely related to the pore diameter of the fibrous filter medium, i.e., the smaller the pore diameter, the greater the pressure drop. In the present disclosure, the inner coalescing layer includes two kinds of filter media, i.e., the first and second inner coalescing layers  102 ,  103 . These two kinds of filter media have the same wettability, and pore diameters of the two kinds of filter media gradually increase from the inside to outside, so that the liquid can smoothly transport from the first inner coalescing layer  102  towards the second inner coalescing layer  103 . As there is no difference in wettability and no reduction in flow area, the liquid film will not be formed between the first inner coalescing layer  102  and the second inner coalescing layer  103 . The liquid film can only form on an outer surface of the second inner coalescing layer  103  with larger pore diameter. 
     Exemplarily, the pore diameter of the filter medium of the first inner coalescing layer  102  may be, but not limited to, 3 μm to 6 μm; the pore diameter of the filter medium of the second inner coalescing layer  103  may be, but not limited to, 6 μm to 10 μm. The pore diameter of the second inner coalescing layer  103  is more than two times of that of the high-efficiency fibrous filter medium of the coalescing filter element in the prior art. Compared with the prior art, the first and second inner coalescing layers  102 ,  103  with larger average pore diameters can reduce the influence of capillary action, thus effectively reducing the pressure drop in the filter element and the power consumption of the filter system. 
     In an alternative embodiment of the present disclosure, as illustrated in  FIGS.  4  and  5   , the outer coalescing component  2  includes a first outer support  201 , a first outer coalescing layer  202 , a second outer support  203 , and a first outer drainage layer  204 . The first outer support  201  and the second outer support  203  are both cylindrical structures disposed in a vertical direction and opened at two ends. The second outer support  203  is fixedly sleeved on the outside of the first outer support  201 , the first outer coalescing layer  202  is interposed between an outer surface of the first outer support  201  and an inner surface of the second outer support  203 . The first outer drainage layer  204  covers an outer surface of the second outer support  203 . The first outer support  201  and the second outer support  203  are respectively provided with a plurality of uniformly distributed ventilation holes, through which the gas can pass through the first outer support  201  and the second outer support  203 . The first outer coalescing layer  202  and the first outer drainage layer  204  cooperate to coalesce and filter the gas, so as to filter out the small amount of liquid remaining in the gas. 
     Further, the first outer coalescing layer  202  is composed of high-efficiency filter media, and the first outer drainage layer  204  is composed of amphiphobic filter media, which may be, for example, amphiphobic glass fibre filter media, amphiphobic polypropylene fibre filter media, amphiphobic polyester fibre filter media. The pore diameter of the filter media of the first outer coalescing layer  202  is smaller than that of the first outer drainage layer  204 . The first outer coalescing layer  202  can coalesce and filter the small amount of liquid in the gas, and the first outer drainage layer  204  can drain the liquid outside the coalescing filter element in a short time. 
     Optionally, the pore diameter of the filter media of the first outer coalescing layer  202  may be, but not limited to, 1 μm to 3 μm; the pore diameter of the filter media of the first outer drainage layer  204  may be, but not limited to, 20 μm to 40 μm. 
     In an alternative embodiment of the present disclosure, as illustrated in  FIGS.  4  and  6   , a third outer support  205  is disposed below the first outer support  201 , a second outer coalescing layer  206  is disposed below the first outer coalescing layer  202 , a fourth outer support  207  is disposed below the second outer support  203 , and a second outer drainage layer  208  is disposed below the first outer drainage layer  204 . The third and fourth outer supports  205 ,  207  are both cylindrical structures disposed in a vertical direction and opened at two ends. The fourth outer support  207  is fixedly sleeved on the outside of the third outer support  205 , and the second outer coalescing layer  206  is interposed between an outer surface of the third outer support  205  and an inner surface of the fourth outer support  207 . The second outer drainage layer  208  covers an outer surface of the fourth outer support  207 . The third and fourth outer supports  205 ,  207  are respectively provided with a plurality of uniformly distributed ventilation holes, through which the gas can pass through the third and fourth outer supports  205 ,  207 . The second outer drainage layer  208  is composed of amphiphobic filter media, which may be, for example, amphiphobic glass fibre filter media, amphiphobic polypropylene fibre filter media, or amphiphobic polyester fibre filter media. The second outer coalescing layer  206  is composed of media capable of quickly absorbing and draining liquid. The second outer coalescing layer  206  includes a super-amphiphilic layer composed of super-amphiphilic media and a super-amphiphobic layer made of super-amphiphobic media. For example, the super-amphiphilic media may be super-amphiphilic glass fibre filter media, super-amphiphilic polypropylene fibre filter media, or super-amphiphilic polyester fibre filter media, and the super-amphiphobic media may be amphiphobic glass fibre filter media, amphiphobic polypropylene fibre filter media, amphiphobic polyester fibre filter media. The super-amphiphobic layer covers the outside of the super-amphiphilic layer. When the liquid drained from the inner coalescing component  1  drops into the drainage space  3 , the liquid can be absorbed by the second outer coalescing layer  206  and transported to the second outer drainage layer  208  in a short time, and then drained from the filter element through the second outer drainage layer  208 , thus avoiding in liquid accumulation in the drainage space  3  and wetting the inner coalescing component  1 , thereby further preventing droplet re-entrainment and ensuring highly efficient filtration of the first outer coalescing layer  202  and the first outer drainage layer  204  for a long period of time. 
     Further, the first and second outer coalescing layers  202 ,  206  in a clean state have basically the same resistance to the passage of gas, so as to ensure that the gas passes through the first and second outer coalescing layers  202 ,  206  at a same rate, thus improving the filtration efficiency of the coalescing filter element. 
     Further, the media of the second outer coalescing layer  206  capable of quickly absorbing and draining liquid may be, but not limited to, fiber material. Different wettability (i.e., the super-amphiphilic and the super-amphiphobic layers) on both sides of the second outer coalescing layer  206  may be obtained by performing a solution modification or ion spraying on inner and outer sides of the second outer coalescing layer  206 , or by other methods that can make the second outer coalescing layer  206  quickly absorb and drain liquid. 
     Further, as illustrated in  FIG.  4   , top end surfaces of the third and fourth outer supports  205 ,  207 , a top end surface of the second outer coalescing layer  206 , and a top end surface of the second outer drainage layer  208  are all flush with the top end surface of the blocking element  105 . Bottom end surfaces of the third and fourth outer supports  205 ,  207 , a bottom end surface of the second outer coalescing layer  206 , and a bottom end surface of the second outer drainage layer  208  are all flush with the bottom end surface of the blocking element  105 . 
     In an alternative embodiment of the present disclosure, as illustrated in  FIGS.  4 ,  11  and  12   , the outer coalescing component  2  further includes a connecting member  209 , which has a circular structure disposed in a horizontal direction. A top end surface of the connecting member  209  is provided with a circular fifth positioning groove  2091 , and a bottom end surface of the connecting member  209  is provided with a circular sixth positioning groove  2092 . Bottom portions of the first and second outer supports  201 ,  203 , a bottom portion of the first outer coalescing layer  202 , and a bottom portion of the first outer drainage layer  204  are all fixedly embedded into the fifth positioning groove  2091 . Top portions of the third and fourth outer supports  205 ,  207 , a top portion of the second outer coalescing layer  206 , and a top portion of the second outer drainage layer  208  are all fixedly embedded into the sixth positioning groove  2092 . Therefore, the upper and lower portions of the outer coalescing component  2  are fixed by the connecting member  209 , so as to ensure that the outer coalescing component  2  has good stability as a whole. 
     Those described above are just illustrative embodiments of the present disclosure, and are not intended to limit the scope of the present disclosure. Any equivalent change or modification made by a person skilled in the art without departing from the concept and principle of the present disclosure should fall within the scope of the present disclosure.