Novel graphitized cathode and preparation method thereof

Abstract

The invention provides a novel graphitized cathode and a preparation method thereof, and relates to the technical field of electrolysis. The modified asphalt comprises the following raw materials in percentage by mass: 18% of graphite scraps with the particle size of 4-8mm, 15% of graphite scraps with the particle size of 2-4mm, 32% of graphite scraps with the particle size of 0.075-2mm, 35% of graphite scraps with the particle size of less than or equal to 0.075 mm and 18-19% of modified asphalt. According to the graphitized cathode provided by the invention, the graphite scraps and the modified pitch are used as raw materials, the modified pitch is used as a binder, the graphite scraps are bonded together, the resistance of the graphite scraps is small, and the resistance of the cathode prepared from the graphite scraps is also small; and secondly, due to the addition of the modified asphalt, the compression strength and breaking strength of the cathode can be improved, and the service life of the cathode is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolysis, and more specifically, to a novel graphitized cathode and a preparation method thereof. Background Art

[0002] Graphite cathodes are key components in the electrolysis industry. Graphite cathodes mainly consist of aggregate and asphalt binder, and have good electrical conductivity, sodium erosion resistance, mechanical strength, and high temperature resistance. Graphite cathodes include graphitized cathodes and graphite cathodes. Graphitized cathodes are made by mixing calcined coke and asphalt, followed by kneading, roasting, graphitization, and shaping machine processing. They have the advantages of low resistance and power saving, but have disadvantages such as low pressure resistance and low flexural strength. Graphite cathodes are made using graphite chips generated during the shaping machine processing in the production process of graphitized cathodes as raw materials, mixed with anthracite and asphalt, and then processed through kneading, roasting, and shaping machine processing. They have the advantages of high pressure resistance and high flexural strength, but their high resistance leads to high energy consumption in the electrolytic cell. Summary of the Invention

[0003] An object of the present invention is to provide a novel graphitized cathode with low resistance, high pressure resistance, and high flexural strength.

[0004] Another object of the present invention is to provide a preparation method for a novel graphitized cathode, which reduces the resistance of the cathode through roasting and graphitization.

[0005] The present invention solves its technical problems by adopting the following technical solutions.

[0006] On the one hand, an embodiment of the present invention provides a novel graphitized cathode, which includes the following raw materials by mass fraction: Modified pitch 18 - 19% and the balance graphite chips; The graphite chips, by mass fraction, include 15 - 21% of graphite chips with a particle size of 4 - 8 mm, 12 - 18% of graphite chips with a particle size of 2 - 4 mm, 29 - 35% of graphite chips with a particle size of 0.075 - 2 mm, and 32 - 38% of graphite chips with a particle size ≤ 0.075 mm.

[0007] In some embodiments of the present invention, 18% of graphite chips with a particle size of 4 - 8 mm, 15% of graphite chips with a particle size of 2 - 4 mm, 32% of graphite chips with a particle size of 0.075 - 2 mm, and 35% of graphite chips with a particle size ≤ 0.075 mm.

[0008] In some embodiments of the present invention, the purity of the graphite chips ≥ 90%.

[0009] In some embodiments of the present invention, the resistivity of the graphite chips ≤ 120 μΩ·m, the ash content ≤ 0.5%, and the true density ≥ 2.18 g / cm 3, sulfur content ≤ 0.2%, moisture content ≤ 0.5%.

[0010] In some embodiments of the present invention, the softening point of the modified pitch is 105 - 115 °C, the coking value ≥ 56, the ash content ≤ 0.3%, and the moisture content ≤ 5%.

[0011] On the other hand, an embodiment of the present invention provides a method for preparing a novel graphitized cathode, comprising the following steps: S1, crushing and screening graphite fragments, classifying them according to particle size, and reserving them for later use. S2, dry-mixing graphite fragments of each particle size according to the ratio, and then adding modified pitch for kneading. S3, subsequently adding them into a mold for vibration molding to obtain a green body, and the green body is cooled and left standing. S4, subsequently performing roasting to obtain a roasted product, and cooling it to room temperature after taking it out of the furnace. S5, subsequently performing graphitization to obtain a cathode blank, and shaping it to obtain a graphitized cathode.

[0012] In some embodiments of the present invention, in the step S2, the temperature of dry-mixing ≥ 145 °C.

[0013] In some embodiments of the present invention, in the step S2, the kneading process is as follows: first kneading at 165 - 175 °C for 40 - 45 min, and then cooling to 155 - 160 °C.

[0014] In some embodiments of the present invention, in the step S4, the roasting temperature is 1000 - 1200 °C.

[0015] In some embodiments of the present invention, in the step S5, the graphitization temperature is 3100 - 3300 °C.

[0016] In some embodiments of the present invention, in the step S3, the temperature of vibration molding is 155 - 165 °C, and the temperature of the modified pitch added in the step S2 is 180 - 185 °C.

[0017] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: The graphitized cathode provided by the present invention uses graphite fragments and modified pitch as raw materials. The modified pitch serves as a binder to bond the graphite fragments together. The resistance of the graphite fragments is small, and thus the resistance of the cathode made of graphite fragments is also small. Secondly, the addition of the modified pitch can also improve the compressive strength and flexural strength of the cathode and extend the service life of the cathode.

[0018] The preparation method of the graphitized cathode provided by the present invention first uniformly mixes graphite chips of various particle sizes through dry mixing, so that the graphite chips of various particle sizes are evenly distributed; then modified pitch is added for kneading, and through vibration molding, under the action of vibration, the connection between raw materials is tighter, which can improve the compressive strength and flexural strength of the cathode. Subsequently, through roasting and graphitization, the resistance of the cathode is reduced. Detailed implementation manners

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.

[0020] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0021] On the one hand, an embodiment of the present invention provides a novel graphitized cathode, which includes the following raw materials by mass fraction: 18 - 19% of modified pitch and the balance of graphite chips; The graphite chips, by mass fraction, include 15 - 21% of graphite chips with a particle size of 4 - 8 mm, 12 - 18% of graphite chips with a particle size of 2 - 4 mm, 29 - 35% of graphite chips with a particle size of 0.075 - 2 mm, and 32 - 38% of graphite chips with a particle size of ≤0.075 mm.

[0022] Part of the modified pitch can be used as an adhesive to bond graphite chips of various particle sizes together, and the other part can be used as an infiltrant to enter the interior of the graphite chips, reduce pores, and improve the density. In the present invention, graphite chips of different particle sizes are selected for compounding. Among them, the larger particle size graphite chips can be used as a support framework, while the smaller graphite chips are used as fillers to fill the gaps, improve the real density of the graphitized cathode, and reduce the porosity. Especially when the proportion of graphite chips with a particle size of 0.075 - 2 mm and graphite chips with a particle size of ≤0.075 mm is 60 - 70%, they can be fully filled in the gaps formed by the larger particle size graphite chips to improve the real density.

[0023] It should be noted that in the present invention, the particle size of the graphite chips refers to the average particle size.

[0024] More preferably, the mass percentage of graphite chips is 82%, and the mass fraction of modified pitch is 18%. Among them, the graphite chips, by mass percentage, include: 18% of graphite chips with a particle size of 4-8 mm, 15% of graphite chips with a particle size of 2-4 mm, 32% of graphite chips with a particle size of 0.075-2 mm, and 35% of graphite chips with a particle size of ≤0.075 mm. The cathode prepared from this ratio has a small resistance and excellent mechanical properties.

[0025] More preferably, the purity of the graphite chips used in the embodiments of the present invention is ≥90%. The resistivity of the graphite chips is ≤120 μΩ·m, the ash content is ≤0.5%, the true density is ≥2.18 g / cm 3 , the sulfur content is ≤0.2%, and the moisture content is ≤0.5%. By controlling the purity, resistance, etc. of the graphite chips, a cathode with the optimal performance can be obtained.

[0026] More preferably, the softening point of the modified pitch used in the embodiments of the present invention is 105-115°C, the coking value is ≥56, the ash content is ≤0.3%, and the moisture content is ≤5%.

[0027] The novel graphitized cathode of the embodiments of the present invention is prepared by the following method: S1, Crush and screen the graphite chips, classify them according to the particle size, and set aside for later use. S2, Dry-mix the graphite chips of each particle size at ≥145°C according to the ratio, then add modified pitch at a temperature of 180-185°C, knead at 165-175°C for 40-45 minutes, and then cool to 155-160°C. S3, Then add it into the mold and vibrate and form it at 155-165°C to obtain a green body. The green body is cooled and left standing for 5-10 days. S4, Then bake it at 1000-1200°C to obtain a baked product, and cool it to room temperature after taking it out of the furnace. S5, Then graphitize it at 3100-3300°C to obtain a cathode blank, and shape it to obtain a graphitized cathode.

[0028] The cathode preparation method provided by the present invention dry-mixes graphite fragments at 145°C. At this temperature, the temperature of the graphite fragments rises, which is beneficial for subsequent infiltration into the graphite fragments after adding modified pitch. Kneading is carried out at 165 - 175°C for 40 - 45 minutes. At this temperature, sufficient kneading is carried out to ensure sufficient mixing between the graphite fragments and between the graphite fragments and the modified pitch. Sufficient kneading time and relatively high temperature ensure uniform mixing of all materials. The kneaded material is calcined at 1000 - 1200°C. High-temperature calcination can fix the geometric shape of the product, discharge volatile components, reduce the resistivity, and improve the mechanical strength of the product. Subsequently, graphitization is carried out at 3100 - 3300°C. This process can remove ash, reduce resistance, improve thermal and electrical conductivity, and improve product stability. The cathode prepared by this method has a small resistance, high compressive strength, and high flexural strength.

[0029] The features and properties of the present invention will be further described in detail below in conjunction with embodiments.

[0030] Example 1 Prepare each raw material according to the following ratio: Graphite fragments 82%, modified pitch 18%; Among them, the compounding ratio of graphite fragments with different particle sizes is: graphite fragments with a particle size of 4 - 8mm 18%, graphite fragments with a particle size of 2 - 4mm 15%, graphite fragments with a particle size of 0.075 - 2mm 32%, and graphite fragments with a particle size ≤ 0.075mm 35%.

[0031] Among them, the purity of each graphite fragment is greater than 90%, the resistivity of the graphite fragment ≤ 120 μΩ·m, the ash content ≤ 0.5%, the true density ≥ 2.18 g / cm 3 , the sulfur content ≤ 0.2%, and the moisture content ≤ 0.5%. The softening point of the modified pitch is 105 - 115°C, the coking value ≥ 56, the ash content ≤ 0.3%, and the moisture content ≤ 5%.

[0032] Prepare the graphitized cathode of this example according to the following steps: S1, Crush and screen the graphite fragments, classify them according to particle size, and set aside for later use. S2, Dry-mix the graphite fragments of each particle size at a temperature not lower than 145°C according to the ratio, then add the modified pitch at 180°C, knead at 170°C for 45 minutes, and then cool to 155°C. S3, Then add it into the mold and vibrate and form at 160°C to obtain a green body. After the green body is cooled to room temperature, it is left standing for 7 days. S4, Then calcine at 1100°C for 28 days to obtain a calcined product, and cool it to room temperature after taking it out of the furnace. S5, Then carry out graphitization at 3100°C to obtain a cathode blank, shape it, and machine it to the corresponding size to obtain a graphitized cathode.

[0033] Example 2 Prepare each raw material according to the following ratio: Graphite scraps: 81%, modified pitch: 19%; Among them, the compounding ratio of graphite scraps with different particle sizes is: graphite scraps with a particle size of 4 - 8 mm: 18%, graphite scraps with a particle size of 2 - 4 mm: 15%, graphite scraps with a particle size of 0.075 - 2 mm: 32%, graphite scraps with a particle size ≤ 0.075 mm: 35%.

[0034] Among them, the purity of each graphite scrap is greater than 90%, the resistivity of graphite scrap is ≤ 120 μΩ·m, ash content is ≤ 0.5%, true density is ≥ 2.18 g / cm 3 , sulfur content is ≤ 0.2%, moisture content is ≤ 0.5%. The softening point of the modified pitch is 105 - 115 °C, coking value is ≥ 56, ash content is ≤ 0.3%, moisture content is ≤ 5%.

[0035] Prepare the graphitized cathode of this example according to the following steps: S1, Crush and screen the graphite scraps, divide them according to the particle size, and set aside for later use. S2, Mix the graphite scraps of each particle size dry at a temperature not lower than 145 °C according to the ratio, then add the modified pitch at 185 °C, knead at 175 °C for 45 minutes, and then cool to 155 °C. S3, Then add it into the mold, vibrate and form at 160 °C to obtain a green body. After the green body is cooled to room temperature, let it stand for 7 days. S4, Then roast at 1200 °C for 28 days to obtain a roasted product, and cool it to room temperature after taking it out of the furnace. S5, Then carry out graphitization at 3300 °C to obtain a cathode blank, shape it, and machine it to the corresponding size to obtain the graphitized cathode.

[0036] Example 3 Prepare each raw material according to the following ratio: Graphite scraps: 82%, modified pitch: 18%; Among them, the compounding ratio of graphite scraps with different particle sizes is: graphite scraps with a particle size of 4 - 8 mm: 15%, graphite scraps with a particle size of 2 - 4 mm: 18%, graphite scraps with a particle size of 0.075 - 2 mm: 29%, graphite scraps with a particle size ≤ 0.075 mm: 38%.

[0037] Among them, the purity of each graphite scrap is greater than 90%, the resistivity of graphite scrap is ≤ 120 μΩ·m, ash content is ≤ 0.5%, true density is ≥ 2.18 g / cm 3 , sulfur content is ≤ 0.2%, moisture content is ≤ 0.5%. The softening point of the modified pitch is 105 - 115 °C, coking value is ≥ 56, ash content is ≤ 0.3%, moisture content is ≤ 5%.

[0038] Prepare the graphitized cathode of this example according to the following steps: S1. Crush and screen the graphite fragments, classify them according to particle size, and reserve for later use. S2. Dry-mix the graphite fragments of each particle size at a temperature not lower than 145°C according to the ratio, then add the modified pitch at 180°C, knead at 170°C for 45 minutes, and then cool to 155°C. S3. Then add it into the mold and vibrate to form a green body at 155°C. After the green body is cooled to room temperature, let it stand for 10 days. S4. Then bake at 1200°C for 28 days to obtain a baked product, and cool it to room temperature after taking it out of the furnace. S5. Then graphitize at 3300°C to obtain a cathode blank, shape it, and machine it to the corresponding size to obtain a graphitized cathode.

[0039] Example 4 Prepare each raw material according to the following ratio: Graphite fragments 82%, modified pitch 18%. Among them, the compounding ratio of graphite fragments of different particle sizes is: graphite fragments with a particle size of 4 - 8mm 21%, graphite fragments with a particle size of 2 - 4mm 12%, graphite fragments with a particle size of 0.075 - 2mm 35%, and graphite fragments with a particle size ≤ 0.075mm 32%.

[0040] Among them, the purity of each graphite fragment is greater than 90%, the resistivity of the graphite fragment ≤ 120 μΩ·m, the ash content ≤ 0.5%, the true density ≥ 2.18 g / cm 3 , the sulfur content ≤ 0.2%, and the moisture content ≤ 0.5%. The softening point of the modified pitch is 105 - 115°C, the coking value ≥ 56, the ash content ≤ 0.3%, and the moisture content ≤ 5%.

[0041] Prepare the graphitized cathode of this example according to the following steps: S1. Crush and screen the graphite fragments, classify them according to particle size, and reserve for later use. S2. Dry-mix the graphite fragments of each particle size at a temperature not lower than 145°C according to the ratio, then add the modified pitch at 185°C, knead at 165°C for 45 minutes, and then cool to 155°C. S3. Then add it into the mold and vibrate to form a green body at 165°C. After the green body is cooled to room temperature, let it stand for 7 days. S4. Then bake at 1200°C for 28 days to obtain a baked product, and cool it to room temperature after taking it out of the furnace. S5. Then graphitize at 3200°C to obtain a cathode blank, shape it, and machine it to the corresponding size to obtain a graphitized cathode.

[0042] Example 5 Prepare each raw material according to the following ratio: Graphite fragments 81%, modified pitch 19%. Among them, the compounding ratio of graphite fragments with different particle sizes is as follows: graphite fragments with a particle size of 4 - 8 mm account for 20%, graphite fragments with a particle size of 2 - 4 mm account for 15%, graphite fragments with a particle size of 0.075 - 2 mm account for 30%, and graphite fragments with a particle size of ≤0.075 mm account for 35%.

[0043] Among them, the purity of each graphite fragment is greater than 90%, the resistivity of the graphite fragment is ≤120 μΩ·m, the ash content is ≤0.5%, the true density is ≥2.18 g / cm 3 , the sulfur content is ≤0.2%, and the moisture content is ≤0.5%. The softening point of the modified pitch is 105 - 115°C, the coking value is ≥56, the ash content is ≤0.3%, and the moisture content is ≤5%.

[0044] Prepare the graphitized cathode of this example according to the following steps: S1, Crush and screen the graphite fragments, classify them according to particle size, and reserve them for use. S2, Dry - mix the graphite fragments of each particle size at a temperature not lower than 145°C according to the ratio, then add the modified pitch at 180°C, knead at 175°C for 40 minutes, and then cool to 155°C. S3, Then add it into the mold and vibrate - mold at 155°C to obtain a green body. After the green body is cooled to room temperature, let it stand for 7 days. S4, Then bake at 1200°C for 28 days to obtain a baked product, and cool it to room temperature after taking it out of the furnace. S5, Then carry out graphitization at 3300°C to obtain a cathode blank, shape it, and machine - process it to the corresponding size to obtain the graphitized cathode.

[0045] Comparative Example 1 The difference from Example 1 is that calcined coke is used to replace the graphite fragments in Example 1, and the rest of the raw materials and preparation methods are the same as those in Example 1.

[0046] Comparative Example 2 The difference from Example 1 is that 30% of graphite fragments and 70% of anthracite are used to replace the graphite fragments in Example 1 in the raw materials, and the total proportion of the two is 75%, and the modified pitch accounts for 25%. In its preparation method, graphitization treatment is not carried out, and the rest is the same as that in Example 1.

[0047] Experimental Example Detect the cathode electrodes of Example 1, Comparative Example 1 and 2, and the results are shown in Table 1: Table 1 Performance of each cathode

[0048] As can be seen from Table 1, the graphite cathode provided by the embodiments of the present invention has a lower resistivity, higher compressive strength, and higher flexural strength compared with traditional graphitized cathodes and graphite cathodes. Although the resistivity in Comparative Example 1 is lower than that in Example 1, the flexural strength in Comparative Example 1 is significantly lower than that in Example 1. That is, on the premise that the cathode in Example 1 has better mechanical properties, the resistivity only increases by a small part, and this resistivity still meets the use standard of the cathode.

[0049] In summary, the graphitized cathode provided by the embodiments of the present invention uses graphite fragments and modified pitch as raw materials. The modified pitch is used as a binder to bond the graphite fragments together. The graphite fragments have a small resistance, and thus the cathode made of graphite fragments also has a relatively small resistance. The modified pitch can also be used as an infiltrant to enter the interior of the graphite fragments, reduce pores, and improve the density. The addition of the modified pitch can also increase the compressive strength and flexural strength of the cathode and extend the service life of the cathode. In the present invention, graphite fragments of different particle sizes are selected for compounding. Among them, the larger particle size graphite fragments can be used as a support framework, while the smaller graphite fragments are used as fillers to fill the gaps, improve the real density of the graphitized cathode, and reduce the porosity. In particular, the proportion of graphite fragments with a particle size of 0.075 - 2 mm and graphite fragments with a particle size ≤ 0.075 mm is 60 - 70%, which can fully fill the gaps formed by the larger particle size graphite fragments and improve the real density.

[0050] The preparation method of the graphitized cathode provided by the present invention first mixes graphite fragments of various particle sizes evenly by dry mixing, so that the graphite fragments of various particle sizes are evenly distributed; then modified pitch is added for kneading, and through vibration molding, under the action of vibration, the connection between raw materials is closer, and the smaller particle size graphite fragments can fully fill the gaps formed by the larger particle size, so as to improve the real density of the cathode, reduce the porosity, and further improve the compressive strength and flexural strength of the cathode. Subsequently, through roasting and graphitization, the resistance of the cathode is reduced.

[0051] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. A novel graphitized cathode, characterized in that, It includes the following raw materials by mass fraction: modified pitch 18 - 19% and the balance of graphite fines; The graphite fines, by mass fraction, include graphite fines with a particle size of 4 - 8 mm accounting for 15 - 21%, graphite fines with a particle size of 2 - 4 mm accounting for 12 - 18%, graphite fines with a particle size of 0.075 - 2 mm accounting for 29 - 35%, and graphite fines with a particle size ≤ 0.075 mm accounting for 32 - 38%.

2. The novel graphitized cathode according to claim 1, characterized in that, The graphite fines, by mass fraction, include: graphite fines with a particle size of 4 - 8 mm accounting for 18%, graphite fines with a particle size of 2 - 4 mm accounting for 15%, graphite fines with a particle size of 0.075 - 2 mm accounting for 32%, and graphite fines with a particle size ≤ 0.075 mm accounting for 35%.

3. The novel graphitized cathode according to claim 1, characterized in that, The purity of the graphite fines ≥ 90%.

4. The novel graphitized cathode according to claim 1, characterized in that, The resistivity of the graphite fragments is ≤ 120 μΩ·m, the ash content is ≤ 0.5%, the true density is ≥ 2.18 g / cm 3 , the sulfur content is ≤ 0.2%, and the moisture content is ≤ 0.5%.

5. The novel graphitized cathode according to claim 1, wherein The softening point of the modified pitch is 105 - 115°C, the coking value ≥ 56, the ash content ≤ 0.3%, and the moisture content ≤ 5%.

6. A preparation method of a novel graphitized cathode as described in any one of claims 1-5, characterized in that, It includes the following steps: S1, crush and screen the graphite fines, classify them by particle size, and set aside for later use. S2, dry - mix the graphite fines of each particle size according to the ratio, and then add the modified pitch and carry out kneading. S3, then add them into a mold, vibrate and form to obtain a green body, and the green body is cooled and left standing. S4, then carry out roasting to obtain a roasted product, and the product is taken out of the furnace and cooled to room temperature. S5, then carry out graphitization to obtain a cathode blank, and shape it to obtain a graphitized cathode.

7. The preparation method of the novel graphitized cathode according to claim 6, characterized in that, In the step S2, the temperature of the dry - mixing ≥ 145°C.

8. The preparation method of the novel graphitized cathode according to claim 6, characterized in that, In the step S2, the kneading process is: first knead at 165 - 175°C for 40 - 45 min, and then cool to 155 - 160°C.

9. The preparation method of the novel graphitized cathode according to claim 6, characterized in that In the step S4, the roasting temperature is 1000 - 1200°C.

10. The preparation method of the novel graphitized cathode according to claim 6, characterized in that, In the step S5, the graphitization temperature is 3100 - 3300°C.

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