A preparation device and method for fiber felt with gradient pore size

Abstract

The present invention discloses a fiber mat preparation device with a gradient pore size and a preparation method thereof, comprising a conveyor belt, a first pipeline, a second pipeline, and a barrier device. The first discharge port of the first pipeline is located above the conveyor belt, and the first fiber filaments entering the first pipeline through the first feed port are discharged onto the conveyor belt through the first discharge port; the second discharge port of the second pipeline is located above the conveyor belt and arranged in parallel with the first discharge port, and the second fiber filaments entering the second pipeline through the second feed port are discharged onto the conveyor belt through the second discharge port; the barrier device is located between the first discharge area and the second discharge area to control the degree of separation or fusion of the first discharge area and the second discharge area to form a fiber mat with a uniform gradient pore size. The present invention has a reasonable structure, a gradient distribution of fiber mat pore size, good quality stability, good flexibility, and a simple preparation process.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber felt preparation, in particular to a fiber felt preparation device with gradient pore size and a preparation method thereof. Background Art

[0002] Fiber felt is widely used in industrial production, such as in the field of water electrolysis. Hydrogen energy is a green new energy source with high energy density (140MJ / kg) and environmentally friendly characteristics. Water electrolysis technology can convert renewable energy such as solar and wind energy into electrical energy, store it in the form of hydrogen, and then achieve efficient conversion between chemical energy and electrical energy through fuel cell technology. Its production process does not emit CO2, making it an ideal energy conversion process. Proton exchange membrane (PEM) water electrolysis technology has the advantages of good safety, high conversion efficiency, and a wide operating current density range. Among them, the gas diffusion layer, as one of the core components of the PEM electrolyzer, accounts for 17% of the cost of the stack. The gas diffusion layer plays an important role in the electrolyzer supporting the catalyst-coated electrodes, evenly distributing the reaction water, promptly discharging the generated gas, and realizing electron transfer. It directly affects the reaction transfer process in the PEM electrolyzer. Due to the oxygen-rich, high-potential operating environment of the anode region of a PEM electrolyzer, the gas diffusion layer (GDL) is often constructed from metal fiber felts, such as stainless steel, titanium, and titanium alloys. The pore size distribution of the fiber felt is a key parameter in characterizing the GDL's performance. Research has shown that achieving a uniform, gradient-like pore size distribution is an effective method for improving the electrochemical performance of PEM electrolyzers.

[0003] In the prior art, there are methods for preparing fiber felts with a specific pore size distribution using various principles. For example, patent document CN115646071A discloses a gradient porous metal felt for electrolytic cells and its preparation method. At least one layer of spherical metal particles, formed by ion spraying, is attached to the outer surface of the metal fiber felt. This invention relies on the gaps between the metal particles to form a small-gap composite layer to achieve the gradient pore size of the metal fiber felt. However, the spherical metal particles sprayed by this method may fall off the fiber felt surface in actual use. The size of the gaps is mainly adjusted by controlling the size of the plasma-sprayed metal particles, resulting in a complex production process. Patent document CN110787534B also discloses a method for preparing high-precision fiber felt for high-temperature gas dust removal. Coarse fiber felt and ultrafine fiber felt are stacked together using a plying method to produce a high-precision metal fiber felt. The metal fiber felt prepared by this invention has only two pore size distributions, and there is no transition layer between the larger and smaller pore layers. Furthermore, this method requires three sintering steps, which is complex and energy-intensive. In addition, patent document CN110506352B also adopts a stacking method to prepare a metal fiber felt with a gradient pore size distribution. Similarly, the stacking method has a complicated preparation process, and the non-woven layers with different pore size distributions are not continuous. There are cross sections inside the fiber felt, which is not conducive to the material transfer process.

[0004] Therefore, there is an urgent need for a method and a device for preparing a fiber felt with good stability, simple production process and uniform gradient pore size. Summary of the Invention

[0005] The present invention discloses a device and method for preparing a fiber mat with a gradient pore size, which solves the technical problems of uneven pore size distribution, poor stability, and complex and costly production processes in existing fiber mats. The device has the advantages of a reasonable structure, gradient pore size distribution, good quality stability, good flexibility, and a simple production process. The technical solution adopted is as follows:

[0006] A device for preparing a fiber felt with a gradient pore size, comprising:

[0007] a conveyor belt, capable of transporting the fiber mat forward under the action of the first driving unit;

[0008] The first pipeline includes a first feed port and a first discharge port, wherein the first discharge port is located above the conveyor belt, and the first fiber filaments entering the first pipeline through the first feed port are discharged onto the conveyor belt through the first discharge port, and a first discharge area formed between the first discharge port and the conveyor belt is tapered with a small upper portion and a large lower portion;

[0009] The second pipeline includes a second feed port and a second discharge port, wherein the second discharge port is arranged above the conveyor belt and parallel to the first discharge port, and the second fiber filaments entering the second pipeline through the second feed port are discharged onto the conveyor belt through the second discharge port, and a second discharge area formed between the second discharge port and the conveyor belt is tapered with a small upper portion and a large lower portion;

[0010] The barrier device is arranged between the first blanking area and the second blanking area to control the degree of separation or fusion of the first blanking area and the second blanking area to form a fiber felt with uniform gradient pore size.

[0011] On the basis of the above technical solution, the fiber felt is one of stainless steel fiber felt, titanium alloy fiber felt or nickel alloy fiber felt.

[0012] Based on the above technical solution, the wire diameter of the first fiber filament is 5 to 80 μm, the wire diameter of the second fiber filament is 80 to 200 μm, the wire diameter of the first fiber filament is smaller than the wire diameter of the second fiber filament, and the conveyor belt transports the fiber felt forward from the second discharge port to the first discharge port at a speed of 0.1 to 10 m / min.

[0013] Based on the above technical solution, a first fan is provided on the first pipeline, and the first fan can drive the first fiber filaments to pass through the first feed port and the first discharge port; a second fan is provided on the second pipeline, and the second fan can drive the second fiber filaments to pass through the second feed port and the second discharge port; and the mass ratio of the first fiber filaments and the second fiber filaments forming the fiber felt is 1:50 to 1:2.

[0014] On the basis of the above technical solution, it also includes a wind hood, a third fan and a filtering device. The conveyor belt is evenly distributed with a number of ventilation holes and includes a top section, a bottom section and two side sections connecting the top section and the bottom section. The wind hood is open at the top and is arranged upward close to the top section of the conveyor belt. The air outlet of the wind hood is connected to the third fan and the air inlet, and the air outlet of the third fan is connected to the air inlet of the filtering device.

[0015] Based on the above technical solution, the barrier device includes a partition with adjustable upper and lower positions. The partition is arranged between the first drop area and the second drop area. When the partition is set close to the conveyor belt, the partition separates the first drop area and the second drop area. When the partition is set away from the conveyor belt, the first drop area and the second drop area intersect and begin to merge.

[0016] A method for preparing a fiber mat with a gradient pore size, using the preparation device according to claim 1 to 4 or 6, comprising the following steps:

[0017] a. Preparing a first fiber having a wire diameter of 5 to 80 μm and a second fiber having a wire diameter of 80 to 200 μm, respectively, pre-opening and weighing the first fiber and the second fiber, and the mass ratio of the first fiber to the second fiber is 1:50 to 1:2;

[0018] b. adjusting the barrier device to control the degree of separation or fusion between the first and second drop areas; c. controlling the conveyor belt with a first drive unit to transport the material forward from the second discharge port to the first discharge port at a speed of 0.1 to 10 m / min, then opening the second feed port to allow the second fiber filaments to drop onto the conveyor belt, and then opening the first feed port to allow the first fiber filaments to drop onto the conveyor belt, so that a fiber mat with a thickness of 0.5 to 20 cm is formed on the conveyor belt, and the dropping speed of the first fiber filaments at the first discharge port is positively correlated with the ratio of the dropping speed of the second fiber filaments at the second discharge port and the mass ratio of the first fiber filaments to the second fiber filaments;

[0019] d. A fiber felt with a gradient pore size is formed on the conveyor belt;

[0020] e. Close the second feed port to stop the second fiber filament from falling, then close the first feed port to stop the first fiber filament from falling, and then shut down the first driving unit.

[0021] Based on the above technical solution, the diameter of the first fiber filament is 10-60 μm, the diameter of the second fiber filament is 100-150 μm, and the mass ratio of the first fiber filament to the second fiber filament is 1:20-1:5.

[0022] On the basis of the above technical solution, the conveyor belt transports the material forward from the second discharge port to the first discharge port at a speed of 0.5 to 5 m / min, and a fiber felt with a thickness of 1 to 10 cm is formed on the conveyor belt.

[0023] On the basis of the above technical solution, the preparation device also includes a wind hood, a third fan and a filtering device. The conveyor belt is evenly distributed with a number of ventilation holes and includes a top section, a bottom section and two side sections connecting the top section and the bottom section. The wind hood is open at the top and is arranged upward close to the top section of the conveyor belt. The air outlet of the wind hood is connected to the third fan and the air inlet, and the air outlet of the third fan is connected to the air inlet of the filtering device; the third fan is turned on before the first drive unit drives the conveyor belt to convey materials, and the third fan is turned off when the first drive unit shuts down the conveyor belt.

[0024] Beneficial effects

[0025] The present invention has a reasonable structure and adopts the method of feeding fibers of different wire diameters at the same time to lay fiber felt with gradient pore size at one time. By setting a barrier device, the thickness of the large-pore layer, the intermediate transition layer and the small-pore layer of the fiber felt can be flexibly adjusted, so that the pore size of the fiber felt in the thickness direction has a uniform gradient transition, and the transition is smoother; the porosity of the large-pore layer, the intermediate transition layer and the small-pore layer is adjusted by controlling the wire diameter of the first fiber filament and the second fiber filament, so that not only the pore size of the fiber felt in the thickness direction is smoothly transitioned, which is beneficial to the transmission of gas-liquid two-phase substances, but also the porosity transition is smooth, which is beneficial to further improve the transmission of gas-liquid two-phase substances.

[0026] In the present invention, the thickness of the large-pore layer, the middle transition layer and the small-pore layer is controlled by fusing or separating the first blanking area and the second blanking area through a barrier device. The fiber filaments in the fusion area of ​​the two blanking areas are randomly cross-stacked, which is beneficial to improving the overall flexibility and tear strength of the fiber felt. In addition, the transition layer between the middle layer and the layer of the present invention is formed by overlapping the fiber filaments that form the corresponding layer, which makes the pore size change smoother and is beneficial to improving the performance of the fiber felt.

[0027] This application uses an airflow method to form a fiber mat in a single pass. The first and second fiber filaments are prevented from adhering to each other under wind pressure, which helps maintain a loose state. This allows the fiber filaments to be evenly laid, thereby ensuring that the finished fiber mat has a good interstitial state and pore gradient performance. Furthermore, the first and second fiber filaments are fed through independent wire feed lines, which allows for precise control of the stacking thickness and cross-fusion area of ​​the first and second fiber filaments. This allows for precise control of the quality of the finished fiber mat, which helps improve the consistency of the finished product.

[0028] In the present invention, a wind hood is further provided below the top section of the conveyor belt, which is connected to the third fan. On the one hand, it is beneficial to guide the fiber filaments to fall to the conveyor belt, and on the other hand, it can prevent the fiber filaments from being suspended in the air, which is beneficial to creating a good air environment.

[0029] In the preparation method of the present invention, the third fan, the first drive unit, the second fan and the first fan are turned on and off in sequence, and the first fan is turned on in advance when the conveying speed of the conveyor belt is high, shortening the interval between the opening of the second fan and the first fan. In this way, while ensuring sufficient material supply, fiber raw materials can be saved and waste can be avoided, which is conducive to reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only one embodiment of the present invention. Those skilled in the art can also derive other implementation drawings based on the provided drawings without inventive effort.

[0031] Figure 1 : A schematic diagram of the three-dimensional structure of the fiber mat preparation device of the present invention;

[0032] Figure 2 : Figure 1 Schematic diagram of the cross-sectional structure along the AA direction;

[0033] Figure 3 : Figure 1 A schematic diagram of the structure in which the middle partition device does not isolate the first blanking area and the second blanking area, and a schematic diagram of the cross-sectional structure of the laid fiber mat;

[0034] Figure 4 : Figure 1 A schematic diagram of the structure of the intermediate baffle device partially isolating the first blanking area and the second blanking area, and a schematic diagram of the cross-sectional structure of the laid fiber mat;

[0035] Figure 5 : Figure 1 Schematic diagram of the structure of the middle partition device completely isolating the first blanking area and the second blanking area, and a schematic diagram of the cross-sectional structure of the laid fiber mat; DETAILED DESCRIPTION

[0036] The following description and accompanying drawings sufficiently illustrate the specific embodiments herein to enable those skilled in the art to practice them. Portions and features of some embodiments may be included in or substituted for portions and features of other embodiments. The scope of the embodiments herein includes the entire scope of the claims, including all available equivalents thereof. Herein, the terms "first," "second," and the like are used solely to distinguish one element from another and do not require or imply any actual relationship or order between these elements. In practice, the first element can also be referred to as the second element, and vice versa. Furthermore, the terms "comprise," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a structure, device, or apparatus comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such structure, device, or apparatus. Without further limitation, an element defined by the phrase "comprising a..." does not preclude the presence of other identical elements in the structure, device, or apparatus comprising the element. The various embodiments herein are described in a progressive manner, with each embodiment focusing on its differences from the other embodiments. Similar or identical parts between the various embodiments can be referenced to each other.

[0037] The terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like used herein to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are intended only to facilitate the description of this document and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention. In the description herein, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, they can be mechanical or electrical connections, or they can be internal connections between two elements, they can be directly connected, or they can be indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0038] As used herein, unless otherwise specified, the term "plurality" means two or more.

[0039] In this document, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B means: A or B.

[0040] In this article, the term "and / or" is used to describe the association relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or, A and B.

[0041] Example 1

[0042] like Figure 1 The fiber mat preparation device with a gradient aperture shown includes a conveyor belt 1, a first pipeline 2, a second pipeline 3, a baffle device 4, an air hood 8, a third fan 7, and a filter device 9. The conveyor belt 1 can transport the fiber mat forward under the action of a first drive unit. Specifically, the conveyor belt 1 is sleeved outside the first roller, the second roller, the third roller, and the fourth roller, and includes a top section, a bottom section, and two side sections connecting the top section and the bottom section. The first drive unit includes a first servo motor, and the rotor end of the first servo motor can transmit rotational motion to the first roller. In addition, a number of ventilation holes are evenly distributed on the conveyor belt 1. The air hood 8 is open at the top and is arranged upwardly close to the top section of the conveyor belt 1. The air outlet of the air hood 8 is connected to the air inlet of the third fan 7, and the air outlet of the third fan 7 is connected to the air inlet of the filter device. The filter device is conventional, and may include a filter bag, which is conventional and will not be described in detail here.

[0043] The first pipeline 2 includes a first feed port and a first discharge port. The first feed port is arranged near the feeding device of the first fiber yarn. The first discharge port is arranged above the conveyor belt 1. The first pipeline 2 is provided with a first fan 5. The first fan 5 can drive the first fiber yarn to pass through the first feed port and the first discharge port. The first fiber yarn entering the first pipeline 2 through the first feed port is dropped to the conveyor belt 1 after passing through the first discharge port, and the first drop area formed between the first drop port and the conveyor belt 1 is small at the top and large at the bottom and is conical. In this embodiment, as Figure 2 As shown, the second discharge port is roughly square, and correspondingly, the first drop area is roughly quadrangular pyramid-shaped, and the two side surfaces of the quadrangular pyramid parallel to the axis of the conveyor belt 1 are vertically arranged;

[0044] The second pipeline 3 includes a second feed port and a second discharge port. The second discharge port is arranged above the conveyor belt 1 and is arranged in parallel with the first discharge port along the axis of the conveyor belt 1. The second pipeline 3 is provided with a second fan 6. The second fan 6 can drive the second fiber filaments to pass through the second feed port and the second discharge port; the second fiber filaments entering the second pipeline through the second feed port are dropped onto the conveyor belt 1 after passing through the second discharge port, and the second drop area formed between the second drop port and the conveyor belt 1 is small at the top and large at the bottom and is conical. In this embodiment, as Figure 2 As shown, the second discharge port is square, and accordingly, the second drop area is roughly in the shape of a quadrangular pyramid, and the two side surfaces of the quadrangular pyramid are parallel to the axis of the conveyor belt 1 and are vertically arranged;

[0045] The barrier device 4 is provided between the first blanking area and the second blanking area to control the degree of separation or fusion of the first blanking area and the second blanking area to form a fiber mat with a uniform gradient pore size. In this embodiment, the barrier device 4 includes a partition with adjustable upper and lower positions. The partition is provided between the first blanking area and the second blanking area. When the partition is set close to the conveyor belt 1, the partition separates the first blanking area and the second blanking area. When the partition is set away from the conveyor belt 1, the first blanking area and the second blanking area intersect and begin to merge. When the partition is at three different height positions, the size of the cross-fusion area of ​​the first blanking area and the second blanking area is as follows: Figures 3-5 As shown, the pore size gradient changes in the thickness direction of the fiber felt corresponding to the partition at three different height positions are as follows: Figures 3-5 The partition has smooth sides and anti-static function, such as the partition is made of organic glass, and the two sides of the organic glass are provided with anti-static devices, wherein the anti-static devices are prior art and will not be described in detail here.

[0046] In this embodiment, the first fiber filament is a titanium alloy fiber filament, and the first fiber filament has a diameter of 20 μm. The second fiber filament is made of the same material as the first fiber filament, and the second fiber filament has a diameter of 100 μm. The diameter of the first fiber filament is smaller than the diameter of the second fiber filament. The mass ratio of the first fiber filament to the second fiber filament forming the fiber mat is 1:10, and the conveyor belt conveys the fiber mat forward from the second discharge port to the first discharge port at a speed of 1 m / min, so that a fiber mat with a thickness of 6 cm is formed on the conveyor belt 1. In other embodiments of the present invention, the diameters of the first fiber filament and the second fiber filament can be adaptively selected according to the production requirements of the fiber mat.

[0047] A method for preparing a fiber felt with a gradient pore size, using the above preparation device, includes the following steps:

[0048] a. Preparing a first fiber having a wire diameter of 20 μm and a second fiber having a wire diameter of 100 μm, respectively, pre-opening and weighing the first fiber and the second fiber, and the mass ratio of the first fiber to the second fiber was 1:10;

[0049] b. Adjust the height position of the partition 4 in the spacer device to control the degree of separation or fusion between the first blanking area and the second blanking area; in this embodiment, the distance between the bottom surface of the partition and the conveyor belt 1 is controlled to 8 cm;

[0050] c. Turn on the third fan, and then the first drive unit controls the conveyor belt 1 to transport the material forward from the second discharge port to the first discharge port at a speed of 1 m / min, and then open the second feed port to allow the second fiber filament to fall onto the conveyor belt 1, and then open the first feed port to allow the first fiber filament to fall onto the conveyor belt 1, so that a fiber felt with a thickness of 6 cm is formed on the conveyor belt 1, and the falling speed of the first fiber filament at the first discharge port is positively correlated with the falling speed ratio of the second fiber filament at the second discharge port and the mass ratio of the first fiber filament to the second fiber filament. At the same time, the difference in the opening time of the second fan and the first fan is negatively correlated with the transmission speed of the conveyor belt 1, so as to ensure that the first fiber filament with a smaller wire diameter has sufficient falling thickness.

[0051] d. A fiber felt having a gradient pore size is formed on the conveyor belt 1;

[0052] e. Close the second feed port to stop the second fiber filament from falling, then close the first feed port to stop the first fiber filament from falling, then shut down the first drive unit, and then shut down the third fan.

[0053] In the above preparation method, the conveyor belt 1 first passes through the second blanking area, so that the second fiber filaments first form a fiber felt bottom layer with a larger pore size on the conveyor belt 1, and the conveyor belt 1 transports the fiber felt bottom layer forward and passes through the fusion area formed by the first blanking area and the second blanking area, wherein the first fiber filaments and the second fiber filaments are subjected to wind pressure in at least two directions in the fusion area, which is not only conducive to breaking up the fiber filaments and preventing them from sticking together, but also makes the fiber felts of two wire diameters fully and evenly mixed and then dropped onto the conveyor belt 1 to form an intermediate transition layer, the pore size of the intermediate transition layer is slightly smaller than the bottom layer, and then the conveyor belt 1 continues to transport the fiber felt forward and passes through the first blanking area, so that the first fiber filaments drop onto the conveyor belt 1 and form a fiber felt top layer with a smaller pore size, the pore size of which is smaller than the pore size value of the intermediate transition layer, so that the pore size of the fiber felt in the thickness direction presents a gradient and smooth transition, and the porosity of the large-pore bottom layer, the intermediate transition layer and the small-pore top layer in the thickness direction also presents a gradient and smooth transition.

[0054] In addition, when the conveyor belt 1 transports the semi-finished fiber felt forward and passes through the junction of the second blanking area and the fusion area, and the junction of the fusion area and the first blanking area, overlapping transition areas of the large-pore bottom layer and the middle transition layer, and overlapping transition areas of the middle transition layer and the small-pore top layer are formed correspondingly, further improving the gradient smooth transition of the pore size and porosity of the fiber felt in the thickness direction.

[0055] Example 2

[0056] The difference between Example 2 and Example 1 is that the distance between the bottom surface of the partition and the conveyor belt 1 is controlled to be 16 cm, the ratio of the thickness of the intermediate transition layer to the total thickness of the fiber felt is increased, the pore size of the finished fiber felt in the thickness direction has a more obvious gradient uniformity trend, and the pore size gradient change is smoother.

[0057] Example 3

[0058] The difference between Example 3 and Example 2 is that the distance between the bottom surface of the partition and the conveyor belt 1 is controlled to be 16 cm, the ratio of the thickness of the intermediate transition layer to the total thickness of the fiber felt is further increased, the gradient uniformity of the pore size in the thickness direction of the finished fiber felt is more obvious, and the pore size gradient change is further smoothed.

[0059] Example 4

[0060] The difference between Example 4 and Example 1 is that the diameter of the first fiber filament is 10 μm, the diameter of the second fiber filament is 120 μm, and the total mass ratio of the first fiber filament to the second fiber filament is 1:5. The distance between the bottom surface of the partition and the conveyor belt 1 is controlled to be 10 cm, and the thickness of the formed fiber felt is 5 cm. Compared with Example 1, the ratio of the thickness of the middle transition layer to the total thickness of the fiber felt is slightly larger, and the ratio of the thickness of the top small-pore layer to the total thickness of the fiber felt is increased.

[0061] Example 5

[0062] The difference between Example 5 and Example 4 is that the conveying speed of the conveyor belt is 0.8 m / min, so after the second fan is turned on, the turning-on time of the first fan can be appropriately delayed.

[0063] The present invention has been described above by way of examples, but the present invention is not limited to the above specific embodiments. Any changes or modifications based on the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A device for preparing fiber mats with gradient pore size, characterized in that: include: A conveyor belt (1) capable of conveying the fiber mat forward under the action of a first driving unit; The first pipeline (2) comprises a first feed port and a first discharge port, wherein the first discharge port is arranged above the conveyor belt (1), and the first fiber filaments entering the first pipeline (2) through the first feed port are discharged to the conveyor belt (1) through the first discharge port, and a first discharge area formed between the first discharge port and the conveyor belt (1) is tapered with a small top and a large bottom; The second pipeline (3) comprises a second feed port and a second discharge port, wherein the second discharge port is arranged above the conveyor belt (1) and is arranged in parallel with the first discharge port, and the second fiber filaments entering the second pipeline through the second feed port are discharged to the conveyor belt (1) after passing through the second discharge port, and a second discharge area formed between the second discharge port and the conveyor belt (1) is tapered with a small upper portion and a large lower portion; The barrier device (4) is provided between the first blanking area and the second blanking area to control the degree of separation or fusion of the first blanking area and the second blanking area, so as to form a fiber felt with a uniform gradient pore size.

2. The fiber mat preparation device with gradient pore size according to claim 1, characterized in that: The fiber felt is one of stainless steel fiber felt, titanium alloy fiber felt or nickel alloy fiber felt.

3. The fiber mat preparation device with gradient pore size according to claim 2, characterized in that: The diameter of the first fiber filament is 5~80 μm, the diameter of the second fiber filament is 80~200 μm, the diameter of the first fiber filament is smaller than the diameter of the second fiber filament, and the conveyor belt transports the fiber felt forward from the second discharge port to the first discharge port at a speed of 0.1~10 m / min.

4. The device for preparing a fiber mat with gradient pore size according to claim 3, characterized in that: The first pipeline (2) is provided with a first fan (5), and the first fan (5) can drive the first fiber filaments to pass through the first feed port and the first discharge port; the second pipeline (3) is provided with a second fan (6), and the second fan (6) can drive the second fiber filaments to pass through the second feed port and the second discharge port; and the mass ratio of the first fiber filaments to the second fiber filaments forming the fiber mat is 1:50~1:

2.

5. The device for preparing a fiber mat with gradient pore size according to any one of claims 1 to 4, characterized in that: The barrier device (4) comprises a partition whose upper and lower positions are adjustable, and the partition is arranged between the first drop area and the second drop area. When the partition is arranged close to the conveyor belt (1), the partition separates the first drop area and the second drop area. When the partition is arranged away from the conveyor belt (1), the first drop area and the second drop area intersect and begin to merge.

6. A method for preparing a fiber mat with gradient pore size, characterized in that: The preparation device according to any one of claims 1 to 4 comprises the following steps: a. preparing a first fiber having a wire diameter of 5 to 80 µm and a second fiber having a wire diameter of 80 to 200 µm, respectively, pre-opening and weighing the first fiber and the second fiber, and the mass ratio of the first fiber to the second fiber is 1:50 to 1:2; b. adjusting the spacer device (4) to control the degree of separation or fusion between the first blanking area and the second blanking area; c. The first driving unit controls the conveyor belt (1) to transport the material forward from the second discharge port to the first discharge port at a speed of 0.1 to 10 m / min, then opens the second feed port to allow the second fiber filament to fall onto the conveyor belt (1), then opens the first feed port to allow the first fiber filament to fall onto the conveyor belt (1), so that a fiber mat with a thickness of 0.5 to 20 cm is formed on the conveyor belt (1), and the falling speed of the first fiber filament at the first discharge port is positively correlated with the ratio of the falling speed of the second fiber filament at the second discharge port and the mass ratio of the first fiber filament to the second fiber filament; d. forming a fiber felt having a gradient pore size on the conveyor belt (1); e. Close the second feed port to stop the second fiber filament from falling, then close the first feed port to stop the first fiber filament from falling, and then shut down the first driving unit.

7. The method for preparing a fiber mat with gradient pore size according to claim 6, characterized in that: The diameter of the first fiber filament is 10-60 μm, the diameter of the second fiber filament is 100-150 μm, and the mass ratio of the first fiber filament to the second fiber filament is 1:20-1:

5.

8. The method for preparing a fiber mat with gradient pore size according to claim 6, characterized in that: The conveyor belt (1) transports the material forward from the second discharge port to the first discharge port at a speed of 0.5 to 5 m / min, and forms a fiber felt with a thickness of 1 to 10 cm on the conveyor belt (1).

9. The method for preparing a fiber mat with gradient pore size according to claim 7 or 8, characterized in that: The preparation device further comprises an air hood (8), a third fan (7) and a filter device (9); the conveyor belt (1) is evenly distributed with a plurality of ventilation holes and comprises a top section, a bottom section and two side sections connecting the top section and the bottom section; the air hood (8) is open at the top and is arranged upwardly close to the top section of the conveyor belt (1); the air outlet of the air hood (8) is connected to the third fan (7) and the air inlet; the air outlet of the third fan (7) is connected to the air inlet of the filter device (9); the third fan (7) is turned on before the first drive unit drives the conveyor belt (1) to transport materials, and the third fan (7) is turned off after the first drive unit stops the conveyor belt.

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