A modified phenolic resin, a graphitized cathode carbon block, and a method for preparing the same.

Abstract

This invention relates to the field of aluminum electrolysis technology, and provides a modified phenolic resin, a graphitized cathode carbon block, and their preparation methods. The modified phenolic resin preparation method involves: inhaling 1000 parts of phenol, heating, adding sodium hydroxide, and further heating; adding 950-1600 parts of formaldehyde solution, heating, and maintaining a constant temperature reaction; cooling, adding 20-75 parts of urea, heating, and maintaining a constant temperature reaction; cooling, and vacuum dehydration; adding 30-60 parts of methanol and 25-50 parts of ethylene glycol, and cooling. The graphitized cathode carbon block preparation method involves: mixing 100 parts of aggregate and 15-18 parts of modified phenolic resin; dry mixing the aggregate at room temperature, then wet mixing with the modified phenolic resin; vibrating the paste to form a mold at room temperature; drying at 60-100℃ to obtain a semi-cured carbon block; calcining; and graphitization. This invention can improve the molecular weight and adhesion of modified phenolic resin, increase the density and strength of graphitized cathode carbon blocks, reduce the heat energy consumption during kneading, molding and calcination, and avoid cracking during the curing process.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolysis technology, and in particular to a modified phenolic resin, a graphitized cathode carbon block, and a method for preparing the same. Background Technology

[0002] Carbon-graphite materials are widely used as lining materials for high-temperature furnaces such as aluminum electrolytic cells, blast furnaces, ferroalloy electric furnaces, and industrial silicon electric furnaces due to their low coefficient of thermal expansion, high-temperature strength, volume stability at high temperatures, resistance to corrosion from various media, and excellent electrical and thermal conductivity. Among these, graphitized cathode carbon blocks used as cathode linings in aluminum electrolytic cells are particularly crucial, as they are difficult to repair under thermal conditions, and their performance directly impacts the lifespan of the electrolytic cell. With the increasing size of electrolytic cells and advancements in electrolysis technology, increasingly higher performance requirements are being placed on graphitized cathode carbon blocks used as cathode linings.

[0003] The existing graphitized cathode carbon blocks for aluminum electrolysis mostly use coal tar pitch as a binder. The specific preparation method is as follows: coal tar pitch binder is added to carbonaceous aggregates such as calcined petroleum coke, pitch coke, and graphitized coke, and then kneaded, vibrated and shaped, and then roasted in coke powder at a temperature of about 1200℃. This preparation method has the following problems due to the use of coal tar pitch as a binder: (1) Kneading is required at a temperature 50-70℃ higher than the softening point of coal tar pitch (usually 140-160℃), and shaping is required at 130-150℃. Both the kneading pot and the molding mold need to be heated, which will consume a lot of heat energy; (2) The carbonization process of the binder during roasting is liquid phase carbonization. The carbon block softens first during the heating process, and then hardens and carbonizes, which makes the roasting time of the green blank very long, usually 400-700 hours, which will consume a lot of natural gas; (3) The graphitized cathode carbon blocks prepared have low strength and low apparent density, which affects the improvement of the electrolytic cell life.

[0004] To reduce energy consumption during the preparation of graphitized cathode carbon blocks, existing technologies use phenolic resin instead of coal tar pitch as a binder. However, existing phenolic resins have a small molecular weight and poor adhesion at room temperature, resulting in low strength of the graphitized cathode carbon blocks prepared using them as binders. Furthermore, the high drying temperature during the preparation process leads to complete curing of the phenolic resin, and large-sized graphitized cathode carbon blocks are prone to cracking during subsequent calcination, making industrial production difficult. For example, patent application CN103387221A uses a mixed resin of phenolic and furfural resins as a binder to prepare graphitized cathode carbon blocks. After the carbon blocks are formed, they need to be cured at 180-280℃ for 2-8 hours. Under these conditions, the resin is completely cured, making subsequent calcination prone to cracking. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a modified phenolic resin, a graphitized cathode carbon block, and a method for preparing the same. This method can improve the molecular weight and adhesiveness of the modified phenolic resin, increase the density and strength of the graphitized cathode carbon block, reduce the heat consumption during the mixing, molding, and calcination processes, avoid cracking during the curing process, simplify the process, and reduce production costs. It is especially suitable for the production of large-sized carbon blocks.

[0006] The technical solution of this invention is as follows:

[0007] This invention provides a method for preparing modified phenolic resin, comprising the following steps:

[0008] S1: By weight, 1000 parts of phenol are drawn into the reactor under vacuum, the temperature is raised to 45-50℃, sodium hydroxide catalyst is added into the reactor, and the temperature is raised to 70-80℃.

[0009] S2: After adding 950-1600 parts of formaldehyde solution dropwise into the reactor, heat the mixture to 80-90℃ and then keep it at a constant temperature for 1-2 hours.

[0010] S3: Cool down to 55-65℃, add 20-75 parts of urea to the reactor, then heat up to 70-80℃ and react at a constant temperature for 1-2 hours;

[0011] S4: Cool down to 50-60℃ and vacuum dehydrate the material in the reactor until the moisture content of the material reaches 4-6%;

[0012] S5: Add 30-60 parts methanol and 25-50 parts ethylene glycol to the reactor, and cool down to below 30°C to obtain modified phenolic resin.

[0013] Furthermore, in step S1, the phenol drawn into the reaction vessel is preheated molten phenol.

[0014] Furthermore, in step S2, the formaldehyde solution has a mass fraction of 37%.

[0015] The present invention also provides a modified phenolic resin, which is prepared by the same method used to prepare the modified phenolic resin.

[0016] Furthermore, by weight percentage, the modified phenolic resin has a free phenol content of 8-10.5%, a free aldehyde content of 0.5-0.6%, a moisture content of 4-6%, and a solid content of 78-83%. The modified phenolic resin has a molecular weight of 650-750, a viscosity of 24000-29000 mPa·s at 25°C, and a char residue rate of 46-50%.

[0017] This invention modifies phenolic resin by adding phenol, sodium hydroxide catalyst, formaldehyde solution, urea, methanol, and ethylene glycol in stages during the preparation process, while controlling the proportions of each raw material, the temperature at each stage, and the reaction time. This significantly improves the molecular weight and adhesiveness of the modified phenolic resin, resulting in a modified phenolic resin with a free phenol content of 8-10.5%, a free aldehyde content of 0.5-0.6%, a moisture content of 4-6%, a solid content of 78-83%, a molecular weight of 650-750, a viscosity of 24000-29000 mPa·s at 25°C, and a char residue rate of 46-50%.

[0018] The modified phenolic resin of this invention is a urea-modified liquid thermosetting phenolic resin, which is a brownish-red liquid. Compared to ordinary liquid thermosetting phenolic resin, the modified phenolic resin binder of this invention incorporates urea during synthesis. Urea can completely bind with the phenolic resin, reducing formaldehyde content and appropriately adjusting the molecular weight. In the preparation of the modified phenolic resin, after vacuum dehydration, 30-60 parts of methanol and 25-50 parts of ethylene glycol are added, controlling the viscosity (at 25°C) to 24000-29000 mPa·s, then cooling to below 30°C before discharging, canning, and low-temperature storage.

[0019] The present invention provides a graphitized cathode carbon block, using the modified phenolic resin as a binder.

[0020] Furthermore, the apparent density of the graphitized cathode carbon block is ≥1.65 g / cm³. 3 Compressive strength ≥25MPa, flexural strength ≥10MPa.

[0021] Furthermore, the graphitized cathode carbon block is 3200-4800mm long, 500-800mm wide, and 450-700mm high.

[0022] The graphitized cathode carbon block of the present invention significantly improves its density and strength by using modified phenolic resin as a binder. As shown in Table 1, comparing the technical indicators of the graphitized cathode carbon block of the present invention with those of the industry standard YS / T699-2018 for graphitized cathode carbon blocks used in aluminum electrolysis, it can be seen that the key technical indicator of the graphitized cathode carbon block of the present invention using modified phenolic resin as a binder is an apparent density ≥ 1.65 g / cm³. 3 The compressive strength is ≥25MPa and the flexural strength is ≥10MPa, far exceeding the requirements of industry standards.

[0023] Table 1

[0024]

[0025] The present invention also provides a method for preparing a graphitized cathode carbon block, comprising the following steps:

[0026] Step 1: Ingredients

[0027] By weight, 100 parts of aggregate and 15-18 parts of the modified phenolic resin are mixed together.

[0028] Step 2: Mix and knead

[0029] At room temperature, the aggregate is added to a mixing pot and dry-mixed for 30-50 minutes, then the modified phenolic resin is added and wet-mixed for 30-50 minutes to obtain a paste.

[0030] Step 3: Vibration molding

[0031] At room temperature, the paste is evenly distributed and then vibrated to form a shaped charcoal block.

[0032] Step 4: Drying

[0033] The shaped carbon blocks are dried, with the drying temperature controlled at 60-100℃ and the drying time at 12-48h, to obtain semi-cured carbon blocks.

[0034] Step 5: Roasting

[0035] The semi-solidified carbon blocks are hoisted into the roasting furnace for roasting.

[0036] Step 6: Graphitization

[0037] The calcined carbon blocks are graphitized in a graphitization furnace to obtain graphitized cathode carbon blocks.

[0038] This invention involves mixing 100 parts aggregate and 15-18 parts modified phenolic resin at room temperature. First, the aggregate is dry-mixed for 30-50 minutes at room temperature, then the modified phenolic resin is added and wet-mixed for 30-50 minutes. The paste is then evenly distributed and vibrated to form the carbon block at room temperature. The formed carbon block is then dried at 60-100℃ for 12-48 hours to obtain a semi-cured carbon block. This block is then hoisted into a roasting furnace for roasting and finally graphitized. This process can improve the density and strength of the prepared graphitized cathode carbon block, reduce the heat consumption during mixing, forming, and roasting, and avoid cracking during the curing process.

[0039] The raw materials for the graphitized cathode carbon block of this invention consist of two parts: aggregate and modified phenolic resin binder.

[0040] Further, in step 1, the aggregate is calcined petroleum coke. The calcined petroleum coke is first crushed, ground, and sieved before being batched. The calcined petroleum coke is batched according to the following particle size distribution: the weight percentages of particle size ranges (0, 0.075), [0.075, 0.15), [0.15, 0.5), [0.5, 1), [1, 2), [2, 4), and [4, 8) are 20%, 10%, 14%, 14%, 14%, 14%, and 14%, respectively, with weight percentage deviations of ±1%, ±2%, ±3%, ±3%, ±3%, ±3%, ±3%, and ±3%, respectively; where the unit of particle size is mm. See Table 2 for details of the particle size distribution of the calcined petroleum coke.

[0041] Table 2

[0042] Percentage (by weight) 14 14 14 14 14 10 20 Percentage deviation % (by weight) ±3 ±3 ±3 ±3 ±3 ±2 ±1

[0043] The ratio of 100 parts aggregate and 15-18 parts modified phenolic resin in this invention is beneficial to improving the density and strength of graphitized cathode carbon blocks. Furthermore, by using calcined petroleum coke as aggregate and setting the particle size distribution of the calcined petroleum coke, the density and strength of graphitized cathode carbon blocks can be further improved.

[0044] After the aggregate and modified phenolic resin binder are batched, they are mixed and molded at room temperature. Compared with the method of preparing graphitized cathode carbon blocks using coal tar pitch as a binder, the process of mixing and molding at room temperature does not require any form of heating of the mixing pot and molding mold. This not only simplifies the process but also avoids heat consumption and reduces production costs.

[0045] Furthermore, in step 3, the paste is evenly distributed and then vibrated for molding. Specifically, this includes: discharging the paste from the mixing pot into a feeder, which then evenly discharges it into the lower molding die. The die is then vibrated on a vibration molding machine. The vibration molding machine is a pre-pressurized and shock-absorbing vibration molding machine with a vibration frequency of 17-25Hz, an amplitude of 1-3mm, and an eccentric torque of 40-50kg.m. The vibration molding machine is equipped with a vacuum device, and the vacuum tank of the vacuum device has a vacuum degree greater than -0.09MPa and a working vacuum degree greater than -0.08MPa.

[0046] After the molding process is completed, the molded charcoal blocks are placed in a drying kiln along with the trays for drying. The drying process of this invention differs from the curing process of refractory materials using phenolic resin as a binder in the prior art. The curing temperature of refractory materials usually needs to reach 120-240℃. Under these conditions, the phenolic resin is already fully cured. This curing process is only suitable for small-sized products. If large-sized charcoal blocks using phenolic resin as a binder are cured using this curing process, a large number of cracks are likely to occur, making production infeasible. This invention uses modified phenolic resin as a binder, allowing the charcoal blocks to be formed simply by drying at 60-100℃ in a drying kiln. This achieves low-temperature semi-curing drying of the modified phenolic resin. Specifically, at 60-100℃ in the drying kiln, the modified phenolic resin in the charcoal blocks gradually undergoes molecular condensation and releases moisture. After 12-48 hours of drying and dehydration, although the resin is not yet fully cured, the charcoal blocks themselves already have a certain strength and can be lifted into the furnace. This ensures that the dried charcoal blocks have sufficient strength for lifting while preventing the modified phenolic resin from fully curing, thus avoiding cracks during the subsequent roasting process. This method is particularly suitable for the production of large-sized charcoal blocks.

[0047] After drying, the semi-solidified charcoal blocks are hoisted and placed into a ring-type roasting furnace for roasting.

[0048] Furthermore, in step 5, the calcination process involves five stages of heating, specifically: first, heating from 150℃ to 350℃ at an average heating rate of 10℃ / h; then heating from 350℃ to 500℃ at an average heating rate of 5℃ / h; then heating from 500℃ to 800℃ at an average heating rate of 6℃ / h; then heating from 800℃ to 1200℃ at an average heating rate of 10℃ / h; and finally holding at 1200℃ for 28 hours. The temperature deviations for each stage are ±30℃, ±15℃, ±10℃, ±15℃, and ±20℃, respectively. The calcination heating mechanism of this invention is shown in Table 3 below.

[0049] Table 3

[0050] 1 150-350 20 10 ±30 2 350-500 30 5 ±15 3 500-800 50 6 ±10 4 800-1200 40 10 ±15 5 1200 28 Insulation ±20 total 168

[0051] The semi-solidified charcoal blocks continue to solidify in the roasting furnace. Because the temperature rises slowly in the early stage of the roasting process, the charcoal blocks do not crack even though they are not completely solidified.

[0052] The five-stage heating mechanism of this invention allows the semi-cured carbon blocks to further solidify slowly in the roasting furnace. Combined with the preceding low-temperature semi-curing drying process, it avoids cracking during the curing process of large-sized graphitized cathode carbon blocks produced using phenolic resin as a binder. Furthermore, existing technologies using coal tar pitch as a binder for preparing graphitized cathode carbon blocks involve liquid-phase carbonization of the binder during roasting. The carbon blocks soften first, then harden and carbonize during heating, resulting in a long roasting time for the green blanks, typically 400-700 hours. In contrast, this invention uses urea-modified liquid thermosetting phenolic resin as a binder, making the heating process of the binder a solid-phase carbonization process. The carbon blocks carbonize directly during heating without softening, significantly shortening the roasting time to only 168 hours. This reduces natural gas consumption, lowers production costs, and further improves the density and strength of the graphitized cathode carbon blocks, which is beneficial for extending the service life of aluminum electrolytic cells.

[0053] The beneficial effects of this invention are as follows:

[0054] (1) The modified phenolic resin preparation method of the present invention achieves the modification of phenolic resin by adding phenol, sodium hydroxide catalyst, formaldehyde solution, urea, methanol and ethylene glycol in stages during the preparation process and controlling the ratio of each raw material, the temperature of each stage and the reaction time. This greatly improves the molecular weight and adhesion of the prepared modified phenolic resin, so that the free phenol content of the obtained modified phenolic resin reaches 8-10.5%, the free aldehyde content reaches 0.5-0.6%, the moisture content reaches 4-6%, the solid content reaches 78-83%, the molecular weight reaches 650-750, the viscosity at 25℃ reaches 24000-29000 mPa.s, and the char rate reaches 46-50%.

[0055] (2) The graphitized cathode carbon block of the present invention, by using modified phenolic resin as a binder, greatly improves the density and strength of the graphitized cathode carbon block, making the apparent density of the graphitized cathode carbon block ≥1.65 g / cm³. 3 Compressive strength ≥25MPa, flexural strength ≥10MPa.

[0056] (3) The method for preparing graphitized cathode carbon blocks of the present invention involves first dry mixing the aggregate for 30-50 minutes at room temperature with a ratio of 100 parts aggregate and 15-18 parts modified phenolic resin, then adding the modified phenolic resin and wet mixing for 30-50 minutes, uniformly distributing the paste, vibrating and molding at room temperature, drying the molded carbon blocks at 60-100℃ for 12-48 hours to obtain semi-cured carbon blocks, then hoisting them into a calcination furnace for calcination, and finally graphitizing them. This method can improve the density and strength of the prepared graphitized cathode carbon blocks, reduce the heat consumption during the mixing, molding, and calcination processes, and avoid cracks during the curing process. Specifically, 1) the ratio of 100 parts aggregate to 15-18 parts modified phenolic resin is beneficial to improving the density and strength of graphitized cathode carbon blocks. Furthermore, using calcined petroleum coke as aggregate and specifying its particle size distribution further enhances the density and strength of the graphitized cathode carbon blocks; 2) the use of room-temperature kneading and molding processes, compared to methods using coal tar pitch as a binder, eliminates the need for heating the kneading pot and molding mold, simplifying the process, avoiding heat consumption, and reducing production costs; 3) using the modified phenolic resin of this invention as a binder allows the carbon blocks to be dried in a drying kiln at 60-100℃, achieving low-temperature semi-curing drying of the modified phenolic resin. This ensures the raw carbon blocks have sufficient strength for lifting and also allows for... The modified phenolic resin is not completely cured, thus avoiding cracks in the subsequent roasting process, which is especially suitable for the production of large-sized carbon blocks; 4) A five-stage heating mechanism is further designed so that the semi-cured carbon blocks can be further slowly cured in the roasting furnace. Combined with the previous low-temperature semi-curing drying process, cracks can be avoided in the curing process of large-sized graphitized cathode carbon blocks produced with phenolic resin as a binder. Moreover, compared with the graphitized cathode carbon block preparation method using coal tar pitch as a binder, the use of the urea-modified liquid thermosetting phenolic resin of this invention as a binder makes the heating process of the binder a solid-phase carbonization process. The carbon blocks are directly carbonized during the heating process and will not soften, which greatly shortens the roasting time, reduces the amount of natural gas used, reduces the production cost, and further improves the density and strength of the graphitized cathode carbon blocks, which is beneficial to extending the service life of the aluminum electrolytic cell. Attached Figure Description

[0057] Figure 1 This is a flowchart illustrating the method for preparing the graphitized cathode carbon block according to a specific embodiment of the present invention. Detailed Implementation

[0058] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0059] Example 1

[0060] In this Example 1, the preparation method of the modified phenolic resin of the present invention includes the following steps:

[0061] S1: By weight, 1000 parts of preheated molten phenol are drawn into the reactor under vacuum, then the temperature is raised to 45°C, sodium hydroxide catalyst is added to the reactor, and the temperature is raised to 70°C.

[0062] S2: After adding 950 parts of formaldehyde solution with a mass fraction of 37% into the reactor, the temperature is raised to 80℃ and then kept at a constant temperature for 1 hour.

[0063] S3: Cool down to 55℃, add 20 parts of urea into the reactor, then heat up to 70℃ and react at a constant temperature for 1 hour;

[0064] S4: Cool down to 50℃ and vacuum dehydrate the material in the reactor until the moisture content of the material reaches 4%;

[0065] S5: Add 30 parts methanol and 25 parts ethylene glycol to the reactor, and cool down to below 30°C to obtain modified phenolic resin.

[0066] The modified phenolic resin of the present invention is prepared by the method described above.

[0067] The graphitized cathode carbon block of the present invention uses the modified phenolic resin as a binder.

[0068] In this embodiment 1, the graphitized cathode carbon block is 3200mm long, 500mm wide, and 450mm high, which is a large-sized carbon block.

[0069] In this embodiment 1, the method for preparing the graphitized cathode carbon block of the present invention includes the following steps:

[0070] Step 1: Ingredients

[0071] By weight, 100 parts of aggregate and 15 parts of the modified phenolic resin are mixed together.

[0072] The aggregate is calcined petroleum coke. The calcined petroleum coke is first crushed, ground, and sieved before being batched. The calcined petroleum coke is batched according to the following particle size composition: the weight percentages of particle size ranges (0, 0.075), [0.075, 0.15), [0.15, 0.5), [0.5, 1), [1, 2), [2, 4), and [4, 8) are 20%, 10%, 14%, 14%, 14%, 14%, and 14%, respectively, and the deviations of the weight percentages are ±1%, ±2%, ±3%, ±3%, ±3%, ±3%, ±3%, and ±3%, respectively; wherein, the unit of particle size is mm.

[0073] Step 2: Mix and knead

[0074] Add the aggregate to a mixing pot and dry mix for 30 minutes, then add the modified phenolic resin and wet mix for 30 minutes to obtain a paste.

[0075] Step 3: Vibration molding

[0076] After the paste is evenly distributed, it is vibrated to form shaped charcoal blocks. The paste is discharged from the mixing pot and fed into the feeder, which evenly discharges it into the forming mold below. The mold is then vibrated on a vibration molding machine. The vibration molding machine is a pre-pressurized and shock-absorbing vibration molding machine with a vibration frequency of 17-25Hz, an amplitude of 1-3mm, and an eccentric torque of 40-50kg.m. The vibration molding machine is equipped with a vacuum device, and the vacuum tank of the vacuum device has a vacuum degree greater than -0.09MPa and a working vacuum degree greater than -0.08MPa.

[0077] Step 4: Drying

[0078] The shaped carbon blocks are dried, with the drying temperature controlled at 60℃ and the drying time at 12h, to obtain semi-cured carbon blocks.

[0079] Step 5: Roasting

[0080] The semi-solidified carbon blocks are hoisted into the roasting furnace for roasting.

[0081] The roasting process is divided into five stages of heating, specifically including: first, heating from 150℃ to 350℃ at an average heating rate of 10℃ / h; then heating from 350℃ to 500℃ at an average heating rate of 5℃ / h; then heating from 500℃ to 800℃ at an average heating rate of 6℃ / h; then heating from 800℃ to 1200℃ at an average heating rate of 10℃ / h; and finally holding at 1200℃ for 28 hours; the temperature deviations of each stage are ±30℃, ±15℃, ±10℃, ±15℃, and ±20℃, respectively.

[0082] Step 6: Graphitization

[0083] The calcined carbon blocks are graphitized in a graphitization furnace to obtain graphitized cathode carbon blocks.

[0084] Example 2

[0085] In this Example 2, the preparation method of the modified phenolic resin of the present invention includes the following steps:

[0086] S1: By weight, 1000 parts of preheated molten phenol are drawn into the reactor under vacuum, the temperature is raised to 47°C, sodium hydroxide catalyst is added to the reactor, and the temperature is raised to 75°C.

[0087] S2: After adding 1200 parts of formaldehyde solution with a mass fraction of 37% into the reactor, the temperature is raised to 85℃ and then kept at a constant temperature for 1.5 hours.

[0088] S3: Cool down to 60℃, add 50 parts of urea to the reactor, then heat up to 75℃ and keep the temperature constant for 1.5 hours.

[0089] S4: Cool down to 55℃ and vacuum dehydrate the material in the reactor until the moisture content of the material reaches 5%;

[0090] S5: Add 50 parts methanol and 40 parts ethylene glycol to the reactor, and cool down to below 30°C to obtain modified phenolic resin.

[0091] The modified phenolic resin of the present invention is prepared by the method described above.

[0092] The graphitized cathode carbon block of the present invention uses the modified phenolic resin as a binder.

[0093] In this embodiment 2, the graphitized cathode carbon block is 4000mm long, 650mm wide, and 600mm high, which is a large-sized carbon block.

[0094] In this embodiment 2, the method for preparing the graphitized cathode carbon block of the present invention includes the following steps:

[0095] Step 1: Ingredients

[0096] By weight, 100 parts of aggregate and 17 parts of the modified phenolic resin are mixed together.

[0097] The aggregate is calcined petroleum coke. The calcined petroleum coke is first crushed, ground, and sieved before being batched. The calcined petroleum coke is batched according to the following particle size composition: the weight percentages of particle size ranges (0, 0.075), [0.075, 0.15), [0.15, 0.5), [0.5, 1), [1, 2), [2, 4), and [4, 8) are 20%, 10%, 14%, 14%, 14%, 14%, and 14%, respectively, and the deviations of the weight percentages are ±1%, ±2%, ±3%, ±3%, ±3%, ±3%, ±3%, and ±3%, respectively; wherein, the unit of particle size is mm.

[0098] Step 2: Mix and knead

[0099] Add the aggregate to a mixing pot and dry mix for 40 minutes, then add the modified phenolic resin and wet mix for 40 minutes to obtain a paste.

[0100] Step 3: Vibration molding

[0101] After the paste is evenly distributed, it is vibrated to form shaped charcoal blocks. The paste is discharged from the mixing pot and fed into the feeder, which evenly discharges it into the forming mold below. The mold is then vibrated on a vibration molding machine. The vibration molding machine is a pre-pressurized and shock-absorbing vibration molding machine with a vibration frequency of 17-25Hz, an amplitude of 1-3mm, and an eccentric torque of 40-50kg.m. The vibration molding machine is equipped with a vacuum device, and the vacuum tank of the vacuum device has a vacuum degree greater than -0.09MPa and a working vacuum degree greater than -0.08MPa.

[0102] Step 4: Drying

[0103] The shaped carbon blocks are dried, with the drying temperature controlled at 65℃ and the drying time at 30h, to obtain semi-cured carbon blocks.

[0104] Step 5: Roasting

[0105] The semi-solidified carbon blocks are hoisted into the roasting furnace for roasting.

[0106] The roasting process is divided into five stages of heating, specifically including: first, heating from 150℃ to 350℃ at an average heating rate of 10℃ / h; then heating from 350℃ to 500℃ at an average heating rate of 5℃ / h; then heating from 500℃ to 800℃ at an average heating rate of 6℃ / h; then heating from 800℃ to 1200℃ at an average heating rate of 10℃ / h; and finally holding at 1200℃ for 28 hours; the temperature deviations of each stage are ±30℃, ±15℃, ±10℃, ±15℃, and ±20℃, respectively.

[0107] Step 6: Graphitization

[0108] The calcined carbon blocks are graphitized in a graphitization furnace to obtain graphitized cathode carbon blocks.

[0109] Example 3

[0110] In this embodiment 3, the preparation method of the modified phenolic resin of the present invention includes the following steps:

[0111] S1: By weight, 1000 parts of preheated molten phenol are drawn into the reactor under vacuum, then the temperature is raised to 50°C, sodium hydroxide catalyst is added to the reactor, and the temperature is raised to 80°C.

[0112] S2: After adding 1600 parts of formaldehyde solution with a mass fraction of 37% into the reactor, the temperature is raised to 90℃ and then kept at a constant temperature for 2 hours.

[0113] S3: Cool down to 65℃, add 75 parts of urea into the reactor, then heat up to 80℃ and react at a constant temperature for 2 hours;

[0114] S4: Cool down to 60℃ and vacuum dehydrate the material in the reactor until the moisture content of the material reaches 6%;

[0115] S5: Add 60 parts methanol and 50 parts ethylene glycol to the reactor, and cool down to below 30°C to obtain modified phenolic resin.

[0116] The modified phenolic resin of the present invention is prepared by the method described above.

[0117] The graphitized cathode carbon block of the present invention uses the modified phenolic resin as a binder.

[0118] In this embodiment 3, the graphitized cathode carbon block is 4800mm long, 800mm wide, and 700mm high, which is a large-sized carbon block.

[0119] In this embodiment 3, the method for preparing the graphitized cathode carbon block of the present invention includes the following steps:

[0120] Step 1: Ingredients

[0121] By weight, 100 parts of aggregate and 18 parts of the modified phenolic resin are mixed together.

[0122] The aggregate is calcined petroleum coke. The calcined petroleum coke is first crushed, ground, and sieved before being batched. The calcined petroleum coke is batched according to the following particle size composition: the weight percentages of particle size ranges (0, 0.075), [0.075, 0.15), [0.15, 0.5), [0.5, 1), [1, 2), [2, 4), and [4, 8) are 20%, 10%, 14%, 14%, 14%, 14%, and 14%, respectively, and the deviations of the weight percentages are ±1%, ±2%, ±3%, ±3%, ±3%, ±3%, ±3%, and ±3%, respectively; wherein, the unit of particle size is mm.

[0123] Step 2: Mix and knead

[0124] Add the aggregate to a mixing pot and dry mix for 50 minutes, then add the modified phenolic resin and wet mix for 50 minutes to obtain a paste.

[0125] Step 3: Vibration molding

[0126] After the paste is evenly distributed, it is vibrated to form shaped charcoal blocks. The paste is discharged from the mixing pot and fed into the feeder, which evenly discharges it into the forming mold below. The mold is then vibrated on a vibration molding machine. The vibration molding machine is a pre-pressurized and shock-absorbing vibration molding machine with a vibration frequency of 17-25Hz, an amplitude of 1-3mm, and an eccentric torque of 40-50kg.m. The vibration molding machine is equipped with a vacuum device, and the vacuum tank of the vacuum device has a vacuum degree greater than -0.09MPa and a working vacuum degree greater than -0.08MPa.

[0127] Step 4: Drying

[0128] The shaped carbon blocks are dried, with the drying temperature controlled at 100℃ and the drying time at 48h, to obtain semi-cured carbon blocks.

[0129] Step 5: Roasting

[0130] The semi-solidified carbon blocks are hoisted into the roasting furnace for roasting.

[0131] The roasting process is divided into five stages of heating, specifically including: first, heating from 150℃ to 350℃ at an average heating rate of 10℃ / h; then heating from 350℃ to 500℃ at an average heating rate of 5℃ / h; then heating from 500℃ to 800℃ at an average heating rate of 6℃ / h; then heating from 800℃ to 1200℃ at an average heating rate of 10℃ / h; and finally holding at 1200℃ for 28 hours; the temperature deviations of each stage are ±30℃, ±15℃, ±10℃, ±15℃, and ±20℃, respectively.

[0132] Step 6: Graphitization

[0133] The calcined carbon blocks are graphitized in a graphitization furnace to obtain graphitized cathode carbon blocks.

[0134] In the above embodiment of the present invention, the modified phenolic resin has a free phenol content of 8-10.5%, a free aldehyde content of 0.5-0.6%, a moisture content of 4-6%, and a solid content of 78-83% by weight percentage. The modified phenolic resin has a molecular weight of 650-750, a viscosity of 24000-29000 mPa·s at 25°C, and a carbon residue rate of 46-50%. It can be seen that the preparation method of the modified phenolic resin of the present invention achieves the modification of phenolic resin by urea, which greatly improves the molecular weight and adhesion of the prepared modified phenolic resin.

[0135] In the above embodiment of the present invention, the apparent density of the graphitized cathode carbon block is ≥1.65 g / cm³. 3The compressive strength is ≥25MPa and the flexural strength is ≥10MPa. It can be mixed and molded at room temperature without any heating of the mixing pot and molding mold. Low-temperature semi-curing drying and calcination only require 168 hours and no cracks are generated during the curing process. It can be seen that the preparation method of graphitized cathode carbon block of the present invention improves the density and strength of the prepared graphitized cathode carbon block, reduces the heat consumption of the mixing, molding and calcination process, and avoids cracks generated during the curing process.

[0136] Obviously, the above embodiments are merely some, not all, of the embodiments of the present invention. The above embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without inventive effort, that is, all modifications, equivalent substitutions, and improvements made within the spirit and principle of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing modified phenolic resin for graphitized cathode carbon blocks, characterized in that, Includes the following steps: S1: By weight, 1000 parts of preheated molten phenol are drawn into the reactor under vacuum, then the temperature is raised to 45-50℃, sodium hydroxide catalyst is added to the reactor, and the temperature is raised to 70-80℃. S2: After adding 950-1600 parts of formaldehyde solution with a mass fraction of 37% into the reactor, heat the mixture to 80-90℃ and then keep it at a constant temperature for 1-2 hours. S3: Cool down to 55-65℃, add 20-75 parts of urea to the reactor, then heat up to 70-80℃ and react at a constant temperature for 1-2 hours; S4: Cool down to 50-60℃ and vacuum dehydrate the material in the reactor until the moisture content of the material reaches 4-6%; S5: Add 30-60 parts of methanol and 25-50 parts of ethylene glycol to the reactor, cool down to below 30°C, and obtain modified phenolic resin; By weight percentage, the modified phenolic resin has a free phenol content of 8-10.5%, a free aldehyde content of 0.5-0.6%, a moisture content of 4-6%, and a solid content of 78-83%. The modified phenolic resin has a molecular weight of 650-750, a viscosity of 24000-29000 mPa·s at 25°C, and a char residue rate of 46-50%.

2. A modified phenolic resin for graphitized cathode carbon blocks, characterized in that, The graphitized cathode carbon block was prepared using the method for preparing modified phenolic resin as described in claim 1.

3. A method for preparing a graphitized cathode carbon block, characterized in that, Includes the following steps: Step 1: Ingredients By weight, 100 parts of aggregate and 15-18 parts of modified phenolic resin for graphitized cathode carbon blocks as described in claim 2 are used for batching; the aggregate is calcined petroleum coke, which is first crushed, ground, and sieved before batching, and the calcined petroleum coke is batched according to the following particle size composition: the weight percentages of particle size ranges (0, 0.075), [0.075, 0.15), [0.15, 0.5), [0.5, 1), [1, 2), [2, 4), [4, 8) are 20%, 10%, 14%, 14%, 14%, 14%, 14%, and 14%, respectively, and the deviations of the weight percentages are ±1%, ±2%, ±3%, ±3%, ±3%, ±3%, ±3%, ±3%; wherein, the unit of particle size is mm; Step 2: Mixing and kneading At room temperature, the aggregate is added to a mixing pot and dry-mixed for 30-50 minutes, then the modified phenolic resin is added and wet-mixed for 30-50 minutes to obtain a paste. Step 3: Vibration molding At room temperature, the paste is evenly distributed and then vibrated to form a shaped charcoal block. Step 4: Drying The shaped carbon blocks are dried, with the drying temperature controlled at 60-100℃ and the drying time at 12-48h, to obtain semi-cured carbon blocks. Step 5: Roasting The semi-solidified carbon blocks are hoisted into a roasting furnace for roasting. The roasting process is divided into five stages of heating, specifically: first, heating from 150℃ to 350℃ at an average heating rate of 10℃ / h; then heating from 350℃ to 500℃ at an average heating rate of 5℃ / h; then heating from 500℃ to 800℃ at an average heating rate of 6℃ / h; then heating from 800℃ to 1200℃ at an average heating rate of 10℃ / h; and finally holding at 1200℃ for 28 hours. The temperature deviations for each stage are ±30℃, ±15℃, ±10℃, ±15℃, and ±20℃, respectively. Step 6: Graphitization The calcined carbon blocks are graphitized in a graphitization furnace to obtain graphitized cathode carbon blocks.

4. The method for preparing graphitized cathode carbon block according to claim 3, characterized in that, In step 3, the paste is evenly distributed and then vibrated to form the final product. Specifically, this includes: discharging the paste from the mixing pot into a feeder, which then evenly discharges it into the lower forming mold. The mold is then vibrated on a vibration molding machine. The vibration molding machine is a pre-pressurized and shock-absorbing vibration molding machine with a vibration frequency of 17-25Hz, an amplitude of 1-3mm, and an eccentric torque of 40-50kg.m. The vibration molding machine is equipped with a vacuum device, and the vacuum tank of the vacuum device has a vacuum degree greater than -0.09MPa and a working vacuum degree greater than -0.08MPa.

5. A graphitized cathode carbon block, characterized in that, The graphitized cathode carbon block was prepared using the method described in claim 3 or 4.

6. The graphitized cathode carbon block according to claim 5, characterized in that, The graphitized cathode carbon block has an apparent density ≥1.65 g / cm³, a compressive strength ≥25MPa, and a flexural strength ≥10MPa.

7. The graphitized cathode carbon block according to claim 5, characterized in that, The graphitized cathode carbon block is 3200-4800mm long, 500-800mm wide, and 450-700mm high.

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