CN111689491A - Flexible graphite manufacturing process for hydrogen fuel cell bipolar plate - Google Patents
Flexible graphite manufacturing process for hydrogen fuel cell bipolar plate Download PDFInfo
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Abstract
The invention discloses a flexible graphite manufacturing process for a hydrogen fuel cell bipolar plate, which adopts a combined process of mechanical screening, airflow classification, mechanical crushing and airflow classification, and solves the problems of graphite raw material agglomeration after intercalation reaction and low raw material utilization rate caused by too wide graphite raw material particle size distribution. Concentrated sulfuric acid is used as an intercalation agent, and hydrogen peroxide is used as an oxidant, so that the harm to the environment and the use of products can be reduced. The high-temperature grading gas-material separation device is adopted to separate gas from material after puffing, so that harmful elements such as sulfur and the like are reduced to be attached to the material, and influence on the subsequent process is reduced. The special surface structure is pressed by adopting a rubber casting mold, so that the fine gas flow channel can be conveniently pressed and formed by a subsequent process. The combination of numerical control high-precision saw blades and negative pressure chip removal is adopted, the size control is accurate in the cutting process, negative pressure chip removal is carried out on the cut graphite chips, and the problems that the size precision requirement is high and graphite worms are adhered are solved.
Description
Technical Field
The invention relates to the technical field of preparation of fuel cell bipolar plates, in particular to a process for manufacturing a flexible graphite bipolar plate for a hydrogen fuel cell.
Background
Under the large background of energy conservation and environmental protection, clean and sustainable energy development becomes an energy technology which is mainly developed by people. The fuel cell has the advantages of high power generation efficiency, less environmental pollution and the like, is gradually applied to the fields of aerospace, electric automobiles and the like, and has wide application prospect. A hydrogen fuel cell is a kind of fuel cell, and since a raw material thereof is hydrogen gas and a product thereof is water and carbon dioxide, there is no problem of environmental pollution and thus it is receiving attention. One of the core components of a hydrogen fuel cell is a bipolar plate. The bipolar plate is composed of two electrode plates, a proton exchange membrane is clamped between the two electrode plates, wherein the electrode plates play a role in supporting an oxidant and a reducer and guiding the oxidant and the reducer to flow on the surfaces of the electrodes in the battery. The redox reaction of hydrogen and oxygen is completed in the whole bipolar plate, and the heat generated by the reaction must be timely conducted out to ensure the normal operation of the battery, so that the bipolar plate not only requires good electrical conductivity, but also requires good heat-conducting property, and meanwhile, in order to improve the utilization rate of the hydrogen and the oxygen, one of the important functions of the bipolar plate is to be used as a gas flow field, a flow channel and a power output line need to be pressed, and the flow channel needs to be ensured to be clear and smooth in the pressing process and has no defects of blockage and the like. The flexible graphite bipolar plate manufacturing process in the prior art has the disadvantages of low raw material utilization rate caused by agglomeration of expandable graphite after intercalation reaction and excessively wide particle size distribution; and an intercalation time period exists, and an interlayer compound is formed as a mixed stage, so that the expansion rate of the graphite raw material is influenced.
On the other hand, because the volume of the graphite-based material expands with acid and alkali during the expansion process at a high temperature of more than 1000 ℃, a large amount of gas is released during the expansion process, the gas contains a large amount of harmful elements such as sulfur and halogen elements introduced in the chemical intercalation treatment, and if the harmful elements cannot be separated from graphite worms in time, the large specific surface of the graphite worms can adsorb a large amount of harmful elements, so that various properties of the graphite material are seriously affected during processing, and more seriously, the harmful elements can affect subsequent processing, such as catalyst failure of subsequent reaction and the like. Some of the existing flexible graphite puffing processes directly do not have a gas-material separation step, so that the technical problems that the flexible graphite sheet has a large amount of harmful elements, the sulfur content exceeds the standard and the like are caused.
Regarding the preparation of the flexible graphite plate, since the bipolar plate has high requirements for uniformity, dimensional accuracy, surface morphology and surface cleanliness, the uniformity and surface morphology of the whole graphite plate need to be considered when the graphite plate is pressed, and the degree of cleaning and dimensional accuracy of the graphite plate surface need to be considered when the graphite plate is cut.
For example, chinese patent publication No. CN1225049C, entitled "method for manufacturing flexible graphite bipolar plate" with publication date of 2005, 10 and 26, discloses a method for manufacturing flexible graphite bipolar plate, and belongs to the technical field of manufacturing fuel cell bipolar plates. The method is characterized in that: the whole bipolar plate is composed of graphite worms, and a small amount of additives are mixed in the worms by using a method of impregnation and direct addition, or a film is formed on the surface of the bipolar plate by using a method of direct smearing. The preparation method specifically comprises the steps of filling graphite worms into a mold, and directly forming or step-by-step forming the bipolar plate by adopting a mold pressing or rolling method, wherein the forming pressure is 30-100 MPa. The density of the bipolar plate of the fuel cell prepared by the invention is 1.2-1.7 g/cm3, and the thickness is 1.0-3.0 mm. During preparation, the fact that the graphite worms are light and easy to adhere is not considered, graphite scraps in the cutting process are easy to adhere to the surface of a graphite plate and difficult to clean, failure of subsequent processes can be caused, metal machining needs to be carried out on the surface of a metal roller by adopting a rolling method, and the metal roller is difficult to machine on the surface of the metal roller in the actual use process, so that the cost is high.
For example, chinese patent publication No. CN100468838C, published as 2009, 03, 11, entitled "method for manufacturing flexible graphite bipolar plate", discloses a method for manufacturing a flexible graphite material two-sided grooved plate for a fuel cell, which uses natural flake graphite as a raw material, uses concentrated sulfuric acid as an intercalation agent, uses concentrated nitric acid, hydrogen peroxide, potassium permanganate or potassium chlorate as an oxidant, and is washed with water to generate a residual compound of graphite, i.e., expandable graphite; wherein the weight ratio of the natural crystalline flake graphite to the concentrated sulfuric acid is 1: 3, and the weight ratio of the oxidant to the concentrated sulfuric acid is 5: 95-10: 90. The intercalation reaction carried out by adopting the method is only one-time intercalation reaction, and because the reaction time is short, the formed interlaminar compound is a mixed stage, and the expansion rate of the graphite raw material is influenced. Meanwhile, the chemical raw materials containing heavy metal ions are adopted, so that the environment-friendly requirement is not met.
Disclosure of Invention
The invention aims to overcome the defects of low expansion rate and insufficient reaction of fine-particle scale raw materials in the prior art.
The second invention aims to overcome the problems of agglomeration and low raw material utilization rate of the expandable graphite raw material in the prior art.
The third invention aims to overcome the problem that the quality of the subsequent process and the graphite plate is influenced by a large amount of harmful elements such as sulfur elements, halogen elements, heavy metal ions and the like after the graphite raw material is expanded in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a process for manufacturing a flexible graphite bipolar plate for a hydrogen fuel cell, comprising the steps of:
the method comprises the following steps: selecting fine particle scales with the particle size larger than 150 meshes as a raw material, adding concentrated sulfuric acid and hydrogen peroxide with different weight ratios into the raw material for multiple times, and fully stirring and mixing the raw material and the concentrated sulfuric acid and the hydrogen peroxide in sequence to perform gradient intercalation reaction;
step two: mechanically screening the material obtained in the step one into coarse particles and fine particles, then carrying out airflow classification on the screened material through an airflow classifier, sending the material with the granularity of more than 80 meshes after airflow classification into a crusher for mechanical crushing, and then carrying out airflow classification again;
step three: starting a feeding fan to send the classified materials with the granularity of less than 80 into a bulking furnace for bulking at the temperature of 800-1200 ℃, and performing steam-discharging desulfurization in the bulking process of the graphite;
step four: performing high-temperature multi-stage gas-solid separation on the materials obtained in the third step by using a secondary gas-material separation device, performing static pre-separation on graphite particles and harmful gas in the secondary gas-material separation device under a high-temperature environment, performing cyclone separation, discharging at a discharge port of the separation device by using double cyclone, and enabling graphite to be mixed at outlets of two cyclones and flow rate to be complementary so as to enable the graphite to be densely stacked on a compression roller table;
step five; performing initial pressing on a rolling table, pressing into a flexible graphite plate, pressing the surface shape of the flexible graphite plate through a roller, and then shaping;
step six: and D, cutting the flexible graphite plate obtained in the step five by adopting a numerical control high-precision saw blade cutting machine tool, and removing scraps by adopting a negative-pressure scrap removing device to finally obtain the flexible graphite plate for the hydrogen fuel cell.
In the scheme, the combined process of mechanical screening, airflow classification, mechanical crushing and airflow classification is creatively adopted in the first step of the invention, so that the problem of graphite raw material agglomeration after intercalation reaction and the problem of low raw material utilization rate caused by too wide graphite raw material particle size distribution are solved. Concentrated sulfuric acid is used as an intercalating agent, hydrogen peroxide is used as an oxidant, and the conventional intercalating agent and oxidant of heavy metal ions and corrosive ions are not used, so that the harm to the environment and the use of products can be reduced. The expanded material is subjected to gas-material separation, so that the influence of harmful elements such as sulfur and the like attached to the material on the subsequent process is reduced. The combination of numerical control high-precision saw blades and negative pressure chip removal is adopted, the size control is accurate in the cutting process, negative pressure chip removal is carried out on the cut graphite chips, and the problems that the size precision requirement is high and graphite worms are easy to adhere are solved.
Preferably, the concentration range of the hydrogen peroxide adopted in the second step is 25-45%, the weight ratio is 5-20%, the concentration range of the adopted sulfuric acid is 95-98%, and the weight ratio range is 150-500%.
Preferably, the gas-material separation device in the fourth step is a second-stage gas-material separation device, the second-stage gas-material separation device comprises a feeding pipeline, a main separator, an exhaust pipe and a discharging pipeline, one end of the feeding pipeline is communicated with a discharge port of the expansion furnace, the other end of the feeding pipeline is communicated with the main separator, the exhaust pipe is communicated with the main separator, the discharging pipeline is communicated with the main separator and the pre-separator, the air inlet pipeline is provided with the pre-separator, a pipeline heat insulation assembly is arranged on an upstream pipeline of the separator, a return pipe is arranged on the feeding pipeline in a bypass mode, a return fan is arranged on the return pipe, and the return pipe is communicated with the exhaust pipe.
In the scheme, because the preseparator is arranged on the air inlet pipeline, and the pipeline heat preservation device is arranged on the upstream pipeline of the preseparator, the pipeline heat preservation device can be a protective layer made of heat insulation materials with heat insulation performance or a combination of a heat exchange coil pipe filled with refrigerant and a heat insulation shell, the refrigerant in the heat exchange coil pipe can form heat exchange or other heat preservation measures with the expansion furnace, a person skilled in the art can select the heat preservation device according to the actual requirement, the pipeline heat preservation device is adopted to ensure that the expanded raw material can be continuously kept in a high-temperature state after being conveyed out of the expansion furnace, so that the released harmful gas can maintain the gaseous state as far as possible, then the released harmful gas enters the preseparator, the mixture of the raw material and the harmful gas is subjected to standing physical sedimentation, and because the expanded graphite material is solid particles, the larger solid graphite raw material can, meanwhile, as the harmful gas is in a gaseous state, the harmful gas gradually rises to form primary layering with the raw materials, the graphite raw materials settled in the gaseous state are separated, and meanwhile, the gas-material mixture entering the main separator is subjected to pre-separation, so that the separation load of the main separator is reduced, and the separation efficiency and the separation effect are improved. The feeding pipeline is bypassed with a material returning pipe, and the material returning pipe is provided with a material returning fan. The returned materials are separated by the material returning fan, so that the separation is more thorough.
As preferred, the main separator includes two separation barrels, be equipped with the feeding distribution mouth on the inlet pipeline, feed line and two the separation barrel all communicate through the feeding distribution mouth, the outer wall of separation barrel is the round platform shape, be equipped with the unloading passageway in the separation barrel, the unloading passageway spiral is arranged downwards on the outer wall of separation barrel, two the unloading passageway of separation barrel all with the unloading pipeline intercommunication. By adopting the structure, the double-cyclone blanking of the separating device can be realized, and the flow complementation can be well formed by the double-cyclone blanking.
Preferably, the blanking pipeline is provided with a sieve separator with adjustable angle. The screening device enables materials falling from the separation cylinder to be uniformly and densely stacked on the compression roller table, and lays a foundation for the density uniformity of the flexible graphite plate formed by pressing.
Preferably, the blanking channel is provided with irregularly arranged combing blades.
Preferably, the gradient intercalation reaction in the first step specifically comprises the following steps:
s1: selecting 1 part of flake graphite with the granularity of +100 meshes, adding 2 parts of 98% concentrated sulfuric acid in parts by weight, mixing and stirring for 30 minutes, adding 0.1 part of 30% hydrogen peroxide in parts by weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, and drying to water content less than 1%;
s2: taking 1 part of the dried material obtained in the step S1, adding 98% concentrated sulfuric acid in 3 parts by weight, mixing and stirring for 30 minutes, adding 0.15 part of 35% hydrogen peroxide in weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, and drying to water content less than 1%; testing the expansion rate;
s3: taking 1 part of the dried material obtained in the step S2, adding 4 parts of 98% concentrated sulfuric acid in parts by weight, mixing and stirring for 30 minutes, adding 0.15 part of 35% hydrogen peroxide in parts by weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, and drying to water content less than 1%; the expansion rate was tested.
Preferably, in the step five, a roller press is adopted to press the patterns on the surface of the graphite plate, and a pressing template formed by rubber casting is sleeved on the surface of a press roller of the roller press.
The invention has the beneficial effects that: (1) the intercalation reaction is thorough, and the expansion rate of the graphite raw material is high; (2) after intercalation reaction, the agglomeration phenomenon of the expandable graphite is less, and the utilization rate of raw materials is high; (3) the expanded harmful gas has less adhesion and good gas-material separation effect.
Drawings
FIG. 1 is a schematic structural diagram of a secondary gas-material separation device of the present invention.
In the figure: the device comprises a feeding pipeline 1, a material returning pipe 11, a material returning fan 12, a main separator 2, an exhaust pipe 3, a pre-separator 4 and a pipeline heat preservation device 5.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention are clearly explained and illustrated below with reference to the accompanying drawings, but the following embodiments are only preferred embodiments of the present invention, and not all embodiments. Based on the embodiments in the implementation, other embodiments obtained by those skilled in the art without any creative effort belong to the protection scope of the present invention.
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present scheme, and are not construed as limiting the scheme of the present invention.
These and other aspects of embodiments of the invention will be apparent with reference to the following description and attached drawings. In the description and drawings, particular embodiments of the invention have been disclosed in detail as being indicative of some of the ways in which the principles of the embodiments of the invention may be practiced, but it is understood that the scope of the embodiments of the invention is not limited thereby. On the contrary, the embodiments of the invention include all changes, modifications and equivalents coming within the spirit and terms of the claims appended hereto.
In the description of the present invention, it is to be understood that the terms "thickness", "upper", "lower", "horizontal", "top", "bottom", "inner", "outer", "circumferential", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., and "several" means one or more unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "fixed," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral connections, either mechanical or electrical, or communicating with each other; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Example 1: the manufacturing process of the flexible graphite bipolar plate for the hydrogen fuel cell comprises the following specific steps:
step (1): selecting fine particle scales with the particle size larger than 150 meshes as raw materials, adding concentrated sulfuric acid and hydrogen peroxide with different weight ratios into the raw materials for multiple times, and fully stirring and mixing the raw materials in sequence to perform gradient intercalation reaction.
Step (2): and D, mechanically screening the material obtained in the step I into coarse particles and fine particles, then carrying out airflow classification on the screened material through an airflow classifier, sending the material with the granularity larger than 80 meshes after airflow classification into a crusher for mechanical crushing, and then carrying out airflow classification again.
And (3): and starting a feeding fan to send the classified material with the granularity of less than 80 meshes into a bulking furnace for bulking at the temperature of 1000 ℃, and performing steam-discharging desulfurization in the bulking process of the graphite.
And (4): performing high-temperature multi-stage gas-solid separation on the material obtained in the step (3) by using a secondary gas-material separation device, performing static pre-separation on graphite particles and harmful gas in the secondary gas-material separation device under a high-temperature environment, performing cyclone separation, discharging at a discharge port of the separation device by using double-cyclone, and enabling graphite to be mixed at outlets of two cyclones and flow rates to be complementary to each other, so that the graphite is densely stacked on a compression roller table; as shown in fig. 1, the secondary gas-material separation device comprises a feeding pipeline 1, a main separator 2, an exhaust pipe 3 and a blanking pipeline, wherein one end of the feeding pipeline is communicated with a discharge port of the expansion furnace, the other end of the feeding pipeline is communicated with the main separator, the exhaust pipe is communicated with the main separator, a pre-separator 4 is arranged on the air inlet pipeline, a pipeline heat insulation assembly 5 is arranged on an upstream pipeline of the separator, a return pipe 11 is bypassed on the feeding pipeline, a return fan 12 is arranged on the return pipe, the return pipe is communicated with the exhaust pipe, and the blanking pipeline is communicated with the main separator and the pre-separator; furthermore, the main separator comprises two separation barrels, a feeding distribution port is formed in the feeding pipeline, the feeding pipeline is communicated with the two separation barrels through the feeding distribution port, the outer wall of each separation barrel is in a circular truncated cone shape, a discharging channel is arranged in each separation barrel, the discharging channel is spirally and downwards arranged on the outer wall of each separation barrel, and the discharging channels of the two separation barrels are communicated with the discharging pipeline; furthermore, the blanking pipeline is provided with a sieve separator with adjustable angle; furthermore, the blanking channel is provided with irregularly arranged combing blades.
Step (5); performing initial pressing on a rolling table, pressing into a flexible graphite plate, pressing the surface shape of the flexible graphite plate through a roller, and then shaping; the method comprises the following steps of (1) pressing surface patterns of a graphite plate by using a roller press, wherein a pressing template formed by rubber casting is sleeved on the surface of a compression roller of the roller press; and pressing the surface of the graphite plate into a surface structure with a specific structure by adopting a roller press matched with a pressing template.
And (6): and (3) cutting the flexible graphite plate obtained in the step (5) by adopting a numerical control high-precision saw blade cutting machine tool, and removing scraps by adopting a negative-pressure scrap removing device to finally obtain the flexible graphite plate for the hydrogen fuel cell.
The production of flexible graphite for hydrogen fuel cell bipolar plates using the above process has the following advantages: the combined process of mechanical screening, airflow classification, mechanical crushing and airflow classification is adopted, so that the problems of graphite raw material agglomeration after intercalation reaction and low raw material utilization rate caused by too wide particle size distribution of the graphite raw material are solved. Concentrated sulfuric acid is used as an intercalating agent, hydrogen peroxide is used as an oxidant, and the conventional intercalating agent and oxidant of heavy metal ions and corrosive ions are not used, so that the harm to the environment and the use of products can be reduced. The expanded material is subjected to gas-material separation, so that harmful elements such as sulfur and the like are prevented from being attached to the material, and the influence on the subsequent process is reduced. The combination of numerical control high-precision saw blades and negative pressure chip removal is adopted, the size control is accurate in the cutting process, negative pressure chip removal is carried out on the cut graphite chips, and the problems that the size precision requirement is high and graphite worms are easy to adhere are solved.
More importantly, a secondary gas-material separation device is adopted to carry out high-temperature grading gas-material separation, a preseparator is arranged on an air inlet pipeline, a pipeline heat preservation device is arranged on an upstream pipeline of the preseparator, the pipeline heat preservation device can be a protective layer made of heat insulation materials with heat insulation performance or a combination filled with a refrigerant heat exchange coil and a heat insulation shell, the refrigerant in the heat exchange coil can form heat exchange with an expansion furnace or other heat preservation measures, technicians in the field can select the pipeline heat preservation device according to actual requirements, the expanded raw material can be continuously kept in a high-temperature state after being conveyed out of the expansion furnace by adopting the pipeline heat preservation device, so that the released harmful gas can be kept in a gaseous state as much as possible, then the harmful gas enters the preseparator, the mixture of the raw material and the harmful gas is subjected to standing physical sedimentation, and the expanded graphite material is solid particles, can subside great solid graphite raw materials, simultaneously, because harmful gas is the gaseous state, can rise gradually and form preliminary layering with the raw materials, separate the graphite raw materials that wherein subside, also for the gas material mixture that gets into main separator carries out the preliminary separation simultaneously, has reduced the separation load of main separator, is favorable to improving separation efficiency and separation effect. Simultaneously, adopt the combination of two separating cylinders and feeding distribution mouth, there is the air current division board in the feeding distribution mouth to divide into multichannel air current with the feeding, carry out many air currents whirlwind separation, the striking between graphite granule in the multichannel air current can increase the feeding, this is the difference of graphite granule speed of throwing away that produces because centrifugal force's difference, the reinforcing separation effect, this temperature of material after the popped that has been maintained of pipeline heat preservation device, make and form the high temperature field in separator, the harmful element who produces after the popped is gaseous form in a large number, so can maintain harmful element gaseous form, and utilize the gas-solid separation principle to carry out harmful element's forced separation, the separation effect is good. And a material returning pipe is arranged on the feeding pipe in a bypass mode, and a material returning fan is arranged on the material returning pipe. The returned materials are separated by the material returning fan, so that the separation is more thorough. The double-cyclone blanking is adopted, so that flow complementation can be well formed, and the material falling from the separation cylinder can be uniformly and densely stacked on the compression roller table by the screening device, so that a foundation is laid for the density uniformity of the pressed flexible graphite plate.
Example 2, the remainder of this example refers to example 1, with the difference that the gradient intercalation reaction in step one specifically comprises the following steps:
step S1: selecting 1 part of flake graphite with the granularity of +100 meshes, adding 2 parts of 98% concentrated sulfuric acid in parts by weight, mixing and stirring for 30 minutes, adding 0.1 part of 30% hydrogen peroxide in parts by weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, and drying to water content less than 1%;
step S2: taking 1 part of the dried material obtained in the step S1, adding 98% concentrated sulfuric acid in 3 parts by weight, mixing and stirring for 30 minutes, adding 0.15 part of 35% hydrogen peroxide in weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, drying to water content less than 1%, and testing expansion rate at 150 ml/g;
example 3, the following: the remainder of this example refers to example 1, with the difference that the gradient intercalation reaction in step one specifically comprises the following steps:
step S1: selecting 1 part of flake graphite with the granularity of +100 meshes, adding 2 parts of 98% concentrated sulfuric acid in parts by weight, mixing and stirring for 30 minutes, adding 0.1 part of 30% hydrogen peroxide in parts by weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, and drying to water content less than 1%;
step S2: taking 1 part of the dried material obtained in the step S1, adding 98% concentrated sulfuric acid in 3 parts by weight, mixing and stirring for 30 minutes, adding 0.15 part of 35% hydrogen peroxide in weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, drying to water content less than 1%, and testing expansion rate at 150 ml/g;
step S3: taking 1 part of the dried material obtained in the step S2, adding 4 parts of 98% concentrated sulfuric acid by weight, mixing and stirring for 30 minutes, adding 0.15 part of 35% hydrogen peroxide by weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, drying to water content less than 1%, and testing swelling rate at 200 ml/g.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (8)
1. The flexible graphite manufacturing process for the hydrogen fuel cell bipolar plate is characterized by comprising the following steps of:
the method comprises the following steps: selecting fine particle scales with the particle size larger than 150 meshes as a raw material, adding concentrated sulfuric acid and hydrogen peroxide with different weight ratios into the raw material for multiple times, and fully stirring and mixing the raw material and the concentrated sulfuric acid and the hydrogen peroxide in sequence to perform gradient intercalation reaction;
step two: mechanically screening the material obtained in the step one into coarse particles and fine particles, then carrying out airflow classification on the screened material through an airflow classifier, sending the material with the granularity of more than 80 meshes after airflow classification into a crusher for mechanical crushing, and then carrying out airflow classification again;
step three: starting a feeding fan to send the classified material with the granularity of less than 80 meshes into a bulking furnace for bulking at the temperature of 800-1200 ℃, and performing steam-discharging desulfurization in the bulking process of the graphite;
step four: performing high-temperature multi-stage gas-solid separation on the materials obtained in the third step by using a secondary gas-material separation device, performing static pre-separation on graphite particles and harmful gas in the secondary gas-material separation device under a high-temperature environment, performing cyclone separation, discharging at a discharge port of the separation device by using double cyclone, and enabling graphite to be mixed at outlets of two cyclones and flow rate to be complementary so as to enable the graphite to be densely stacked on a compression roller table;
step five; performing initial pressing on a rolling table, pressing into a flexible graphite plate, pressing the surface shape of the flexible graphite plate through a roller, and then shaping;
step six: and D, cutting the flexible graphite plate obtained in the step five by adopting a numerical control high-precision saw blade cutting machine tool, and removing scraps by adopting a negative-pressure scrap removing device to finally obtain the flexible graphite plate for the hydrogen fuel cell.
2. The process for manufacturing flexible graphite for hydrogen fuel cell bipolar plates according to claim 1, wherein the concentration range of hydrogen peroxide used in the first step is 25-45%, the weight ratio is 5-20%, the concentration range of sulfuric acid used is 95-98%, and the weight ratio is 150-500%.
3. The manufacturing process of the flexible graphite bipolar plate for the hydrogen fuel cell as claimed in claim 1, wherein the secondary gas-material separation device in the fourth step comprises a feeding pipeline, a main separator, an exhaust pipe and a discharging pipeline, one end of the feeding pipeline is communicated with a discharge port of the expansion furnace, the other end of the feeding pipeline is communicated with the main separator, the exhaust pipe is communicated with the main separator, a pre-separator is arranged on the feeding pipeline, a pipeline heat insulation assembly is arranged on an upstream pipeline of the separator, a return pipe is bypassed on the feeding pipeline, a return fan is arranged on the return pipe, the return pipe is communicated with the exhaust pipe, and the discharging pipeline is communicated with the main separator and the pre-separator.
4. The process of claim 3, wherein the main separator comprises two separation cylinders, the feeding pipe is provided with a feeding distribution port, the feeding pipe is communicated with the two separation cylinders through the feeding distribution port, the outer wall of each separation cylinder is in a circular truncated cone shape, the separation cylinder is internally provided with a discharging channel, the discharging channel is spirally and downwardly arranged on the outer wall of the separation cylinder, and the discharging channels of the two separation cylinders are communicated with the discharging pipe.
5. The process for manufacturing flexible graphite for hydrogen fuel cell bipolar plates according to claim 4, wherein the blanking pipeline is provided with an angle-adjustable screen separator.
6. The process for manufacturing flexible graphite for hydrogen fuel cell bipolar plates according to claim 3, wherein the blanking channel is provided with irregularly arranged combing blades.
7. The process for manufacturing flexible graphite for hydrogen fuel cell bipolar plates according to any one of claims 1 to 6, wherein the gradient intercalation reaction in the first step comprises the following steps:
s1: selecting 1 part of flake graphite with the granularity of +100 meshes, adding 2 parts of 98% concentrated sulfuric acid in parts by weight, mixing and stirring for 30 minutes, adding 0.1 part of 30% hydrogen peroxide in parts by weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, and drying to water content less than 1%;
s2: taking 1 part of the dried material obtained in the step S1, adding 98% concentrated sulfuric acid in 3 parts by weight, mixing and stirring for 30 minutes, adding 0.15 part of 35% hydrogen peroxide in weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, and drying to water content less than 1%; testing the expansion rate;
s3: taking 1 part of the dried material obtained in the step S2, adding 4 parts of 98% concentrated sulfuric acid in parts by weight, mixing and stirring for 30 minutes, adding 0.15 part of 35% hydrogen peroxide in parts by weight, and continuously stirring for 60 minutes; washing with clear water to neutrality, dehydrating, and drying to water content less than 1%; the expansion rate was tested.
8. The process for manufacturing flexible graphite for hydrogen fuel cell bipolar plates, as claimed in claim, wherein in step five, a roller press is used for surface pattern pressing of the graphite plate, and a pressing template made of rubber through casting is sleeved on the surface of a pressing roller of the roller press.
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