High-performance prebaked anode and preparation method thereof

Abstract

The invention provides a high-performance prebaked anode and a preparation method thereof, and belongs to the technical field of prebaked anodes. The preparation method of the prebaked anode comprises the following steps: (1) pretreatment of petroleum coke: carrying out surface high-temperature pre-oxidation treatment on petroleum coke granules, and spraying a compounded solution of a titanate coupling agent and a silane coupling agent KH-550; (2) modification of asphalt: carrying out composite modification by using polyisobutene PIB and high-temperature petroleum asphalt; (3) mixing and kneading: mixing and kneading the pretreated petroleum coke, petroleum coke powder with the particle size of 0.5 mm or less, modified liquid asphalt, conductive carbon black and carbon nanofibers, and carrying out pre-pressing molding; and (4) high-temperature roasting. According to the invention, the problems occurring when the petroleum coke is used for producing the prebaked anode are solved, the porosity of the prebaked anode can be reduced, the volume density is increased, the compressive strength of the anode is improved, the quality requirement of the anode for aluminum is ensured, and the application range of the petroleum coke is widened.

Description

Technical Field

[0001] The present invention relates to the technical field of prebaked anodes, and in particular to a high-performance prebaked anode and a preparation method thereof. Background Art

[0002] With the rapid development of the aluminum industry, the development and application of prebaked aluminum electrolytic cells has become increasingly widespread, and the demand for prebaked anodes has also increased. The quality of prebaked anodes directly affects the production and economic and technical indicators of aluminum electrolysis. In the same electrolysis production environment, high-quality prebaked anodes can ensure a stable aluminum electrolysis process and improve key technical and economic indicators, especially high current efficiency, good environmental conditions, and low labor intensity. The main symptoms of inferior prebaked anodes include anode cracks, faults, looseness (low strength, high porosity), high resistivity, poor oxidation resistance, high ash content, anode shedding, and anode bulging.

[0003] As one of the main raw materials for the production of aluminum carbon materials, petroleum coke has an important impact on the development of aluminum carbon. Petroleum coke is a carbonized product of heavy residual oil produced by crude oil processing (atmospheric and vacuum distillation, catalytic cracking, etc.). According to the form, it can be divided into sponge coke, needle coke and pellet coke. Pellets are also called spherical coke and are a form of delayed petroleum coke. It exists in the form of relatively hard, dense and non-porous or spherical molten masses. Due to changes in crude oil and refining processes, the quality of petroleum coke used to manufacture anodes has continued to decline, and the supply of high-quality petroleum coke has become increasingly tight. The proportion of pelletized coke in petroleum coke is increasing. If it is used to prepare prebaked anodes, there are the following shortcomings:

[0004] (1) The wettability with asphalt binder is low, the binder-petroleum coke interface is weak, the porosity increases after calcination, and the bulk density decreases, resulting in a significant decrease in the compressive strength and flexural strength of the anode, and it is easy to break or slag in the high temperature environment of the electrolytic cell;

[0005] (2) Contains a relatively large amount of disordered carbon structure (e.g., graphite-like crystallite orientation disorder), and the resistivity is usually 10-20 μΩ·m higher than that of ordinary calcined coke, which results in the cell voltage needing to be increased by 5-50 mV during aluminum electrolysis, thus increasing energy consumption;

[0006] (3) The coefficient of thermal expansion (CTE) is higher than that of conventional petroleum coke. Under the periodic temperature changes of the electrolytic cell, the thermal stress difference causes microcracks to expand, the slagging rate of the anode body to increase, and the life span is shortened by about 10-20%.

[0007] Therefore, in the face of the reality that the proportion of shot coke in petroleum coke is gradually increasing, it is of great significance to carbon production enterprises to ensure its smooth application in prebaked anodes, overcome the above-mentioned shortcomings, and improve the quality of prebaked anodes. Summary of the Invention

[0008] The purpose of the present invention is to provide a high-performance prebaked anode and a preparation method thereof in response to the above-mentioned problems. The present invention solves the problems arising from the use of petroleum coke containing pelletized coke in the production of prebaked anodes, can reduce the porosity of the prebaked anode, increase the volume density, improve the compressive strength and flexural strength of the anode, and ensure the quality requirements of aluminum anodes.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a high-performance prebaked anode comprises the following steps:

[0011] (1) Pretreatment of petroleum coke: crushing the petroleum coke and screening it by grade to obtain petroleum coke crushed material with a particle size of less than 6 mm; after screening out petroleum coke powder with a particle size of less than 0.5 mm, the petroleum coke pellets are subjected to surface high-temperature pre-oxidation treatment to obtain pre-oxidized petroleum coke; spraying a composite solution of a titanate coupling agent and a silane coupling agent on the surface of the pre-oxidized petroleum coke, transferring the spray-coated petroleum coke to a drying equipment, pre-drying at 60-80°C to remove ethanol, heating to 120-125°C, keeping the temperature for 40-60 minutes to promote condensation reaction, and drying to obtain pre-treated petroleum coke;

[0012] (2) Modification of asphalt: Dissolve polyisobutylene (PIB) with a molecular weight of 80,000 to 120,000 in cyclohexane to form a uniform PIB mother liquor; heat the high-temperature petroleum asphalt to 140 to 160°C to ensure complete melting without agglomeration; start high-speed stirring, maintain the temperature at 140 to 160°C, slowly add the PIB mother liquor to the molten asphalt, and simultaneously add dicumyl peroxide solution as an initiator; after the addition of the PIB mother liquor is complete, remove the solvent and cool the temperature to 120 to 130°C to obtain the modified liquid asphalt, which is then kept warm for later use;

[0013] (3) Kneading: Pretreated petroleum coke, petroleum coke powder with a size of less than 0.5 mm, modified liquid asphalt, conductive carbon black, and nano-carbon fibers are mixed. The amount of petroleum coke is calculated based on the initial uncrushed mass. The mass ratio of petroleum coke, modified liquid asphalt, conductive carbon black, and nano-carbon fibers is 100:14-16:3-4:0.5-1. The kneading temperature is 140-160°C to obtain a homogeneous paste, which is then compression molded to obtain an anode green body.

[0014] (4) Molding and calcining: The anode green body is preheated, calcined and calcined again to obtain a prebaked anode.

[0015] In the present invention, further, the graded screening controls the particle size content of petroleum coke by weight percentage as follows: 6-4 mm content is 10-15%, 4-2 mm content is 40-48%, 2-0.5 mm content is 25-30%, the content of powder below 0.5 mm is 15-17%, and the content of powder below 0.075 mm is 9-12%.

[0016] In the present invention, further, the method of high-temperature pre-oxidation treatment is to first raise the temperature to 580-600°C in a rotary kiln, introduce air at a flow rate of 2-5 L / min, and treat for 30-35 minutes, then cool to 380-400°C, introduce air containing 5 vol.% water vapor at a flow rate of 2-5 L / min, and treat for 40-60 minutes.

[0017] In the present invention, further, the composite solution of the titanate coupling agent and the silane coupling agent KH-550 is prepared according to the following method: weigh and mix the raw materials according to the mass ratio of titanate coupling agent: ethanol: glacial acetic acid = 10:85:0.5, adjust the pH to 4.0-5.0, and stir and dissolve at 35-45°C for 20-35 minutes to obtain a pre-hydrolyzed titanate solution; weigh and mix the raw materials according to the mass ratio of KH-550: ethanol: deionized water = 10:80:10, adjust the pH to 4.0 with glacial acetic acid, and hydrolyze and activate at room temperature for 5 minutes. 0 to 60 minutes to obtain a pre-hydrolyzed silane solution; pour the pre-hydrolyzed titanate solution into a high-speed stirring kettle; slowly add the pre-hydrolyzed silane solution dropwise, and control the mixing temperature to be ≤35°C; add the dispersant after the addition is completed within 30 minutes, continue stirring for 15 to 25 minutes, adjust the pH to 5.2 to 5.5, and form a uniform and transparent compound liquid, which is allowed to stand for defoaming before use; the mass ratio of titanate coupling agent to silane coupling agent KH-550 is 7:3, and the amount of titanate coupling agent and silane coupling agent used is 0.8 to 1.0 wt.% of the mass of the petroleum coke pellets.

[0018] In the present invention, further, the polyisobutylene PIB and cyclohexane are mixed and dissolved in a mass ratio of 1:4-5, the amount of polyisobutylene PIB is 4-5% of the mass of asphalt, the amount of dicumyl peroxide is 0.8-1.5% of the mass of polyisobutylene PIB, and before use, dicumyl peroxide is dissolved in toluene to form a 5-10wt% solution and then added dropwise.

[0019] In the present invention, further, the method for removing the solvent in step (2) is to raise the temperature to 180-200° C. and introduce nitrogen to purge to remove the solvent.

[0020] In the present invention, further, the specific method of kneading in step (3) is to premix the conductive carbon black, nano-carbon fibers and dispersant BYK-2155 in a high-speed mixer, dry them at 100-110°C and set them aside; preheat the pre-oxidized petroleum coke to 100-120°C, add 30% of the total amount of conductive carbon black and nano-carbon fibers, and stir at low speed for 3-5 minutes; then heat it to 140-160°C, add petroleum coke powder below 0.5 mm, modified liquid asphalt, the remaining conductive carbon black and nano-carbon fibers, and shear them at high speed for 5-15 minutes; finally, mold them under nitrogen protection.

[0021] In the present invention, further, the specific method of the forming and roasting is to preheat the roasting furnace to 350-400°C at 8-12°C / h and keep it warm for 3-6 hours; then heat it to 1100-1150°C at 20-30°C / h and keep it warm for 35-50 hours; the secondary calcination is to heat it to 1300-1350°C at 40-50°C / h and keep it warm for 25-30 hours.

[0022] In the present invention, further, the diameter of the carbon nanofiber is 50 to 200 nm.

[0023] In the present invention, further, the dispersant is BYK-2155, and the amount used is 0.3-0.5% of the total amount of the titanate coupling agent and the silane coupling agent.

[0024] The aggregate used in the present invention is petroleum coke. Since the pelletized coke particles it contains are usually spherical and have a dense and smooth surface, they have low wettability with asphalt binders, and the binder-petroleum coke interface is weak. After calcination, the porosity increases and the bulk density decreases, resulting in a significant decrease in the compressive strength and flexural strength of the anode, and it is easy to break or slag in the high-temperature environment of the electrolytic cell. In order to solve this problem, the present invention proposes to use a coupling agent to improve the bonding force of the binder-petroleum coke interface. However, due to the lack of its surface active groups (such as hydroxyl and carboxyl groups), the hydrolysis and condensation reaction (Si-OH and C-OH bonding) with the silane coupling agent is less efficient and the grafting rate is very low. In response to this problem, the present invention performs a high-temperature oxidation pretreatment on it, and the treatment process changes the single-stage pre-oxidation to about 600°C to promote the generation of carboxyl groups, and then drops to about 400°C for a staged oxidation process to stabilize the hydroxyl distribution. By introducing an atmosphere containing 5% water vapor, the surface hydroxyl density of the petroleum coke can be directionally increased, the subsequent coupling agent grafting efficiency is improved, and the excessive burning of the petroleum coke matrix is suppressed. The coupling agent is a compound of silane coupling agent and titanate coupling agent to improve compatibility with asphalt and form a strong organic-inorganic interface layer, thereby reducing the porosity after calcination, increasing the volume density, and improving the compressive strength and flexural strength of the anode, solving the problem of petroleum coke anode easily breaking or falling off in the high temperature environment of the electrolytic cell.

[0025] Since the addition of KH-550 silane coupling agent and titanate coupling agent will lead to a certain degree of increase in conductivity, the present invention compensates for this by adding conductive carbon black to increase conductivity; at the same time, KH-550 silane coupling agent and titanate coupling agent are compounded in a certain proportion to form an interpenetrating network, enhance the anchoring effect on the conductive carbon black, improve the interfacial peel strength, and avoid the interfacial embrittlement problem caused by a single coupling agent.

[0026] The present invention also uses low- to medium-molecular-weight PIB to modify high-temperature petroleum asphalt, significantly reducing system viscosity (from 4500 mPa·s to 2500 mPa·s at 130°C), improving fluidity support for dense packing. During the PIB-asphalt melt mixing stage, dicumyl peroxide (DCP) is introduced to induce mild crosslinking between the PIB and the light components of the asphalt, forming an interpenetrating network. These improvements increase the coking value of the modified asphalt and significantly enhance the anode's resistance to thermal cracking.

[0027] During the kneading process, 30% conductive carbon black and nano-carbon fibers are added in the initial low-speed stage. The residual active sites (-OR groups) of the titanate coupling agent react with the oxygen-containing groups on the carbon black surface (Ti-OC bonding), establishing a "point-to-point" conductive bridge between the cokes and reducing the contact resistance. In the subsequent high-speed stage, 70% conductive carbon black is added. The shear-thinning effect of PIB (viscosity ≤ 2500mPa·s at 130°C) disperses the conductive carbon black, filling the gaps between the cokes and forming a "surface-to-surface" conductive layer, reducing the resistivity. The graded addition of nano-carbon fibers can construct a multi-level conductive bridge of "petroleum coke-carbon fiber-carbon black", further reducing the anode resistivity.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] 1. The present invention reduces the porosity of the prebaked anode, increases the volume density, and improves the compressive and flexural strengths of the anode through multi-dimensional optimization of petroleum coke surface pre-oxidation modification, coupling agent double bonding, carbon black network embedding, and asphalt rheological modification. This solves the problem of petroleum coke anodes being easily broken or slagging in the high-temperature environment of the electrolytic cell, and increases the service life of the prebaked anode. At the same time, it can also reduce the anode resistivity, thereby reducing the voltage of the electrolytic cell, improving the electrolysis current efficiency, and comprehensively improving the performance of the anode.

[0030] 2. The present invention utilizes petroleum coke containing less than 15 wt% of pelletized coke, broadens the selection range of anode resources for aluminum, and is conducive to maintaining the sustainability of anode production. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing a high-performance prebaked anode comprises the following steps:

[0034] (1) Pretreatment of petroleum coke: The petroleum coke is crushed and graded to obtain petroleum coke crushed material with a particle size of less than 6 mm. The petroleum coke particle size content is controlled by weight percentage as follows: 10% for particles of 6 to 4 mm, 48% for particles of 4 to 2 mm, 25% for particles of 2 to 0.5 mm, 17% for particles below 0.5 mm, and 9% for particles below 0.075 mm. After removing particles below 0.5 mm, the petroleum coke pellets are subjected to a surface high-temperature preoxidation treatment in a rotary kiln. The temperature is first raised to 580° C., air is introduced at a flow rate of 2 L / min, and the treatment is carried out for 35 min. The petroleum coke is then cooled to 380° C., and air containing 5 vol.% water vapor is introduced at a flow rate of 2 L / min for 60 min to obtain preoxidized petroleum coke.

[0035] At the same time, a composite solution of titanate coupling agent and silane coupling agent KH-550 was prepared: the raw materials were weighed and mixed according to the mass ratio of titanate coupling agent TCA-201: ethanol = 10:85, glacial acetic acid was used to adjust the pH to 4.0, and the mixture was stirred and dissolved at 45 ° C for 20 minutes to obtain a pre-hydrolyzed titanate solution; the raw materials were weighed and mixed according to the mass ratio of KH-550: ethanol: deionized water = 10:80:10, the pH was adjusted to 4.0 with glacial acetic acid, and the mixture was hydrolyzed and activated at room temperature for 50 minutes. n, to obtain a pre-hydrolyzed silane solution; pour the pre-hydrolyzed titanate solution into a stirring kettle, slowly add the pre-hydrolyzed silane solution dropwise, control the mixing temperature to ≤35°C, and add the dispersant BYK-2155 after the addition is completed within 30 minutes, and then add the dispersant BYK-2155 in an amount of 0.3% of the total amount of the titanate coupling agent and the silane coupling agent. Continue stirring for 15 minutes, adjust the pH to 5.2, and form a uniform and transparent composite solution. Let it stand for defoaming before use; the mass ratio of the titanate coupling agent to the silane coupling agent KH-550 is 7:3.

[0036] A fluidized bed is used to spray a composite solution of a titanate coupling agent and a silane coupling agent KH-550 on the surface of pre-oxidized petroleum coke, wherein the amount of the titanate coupling agent and the silane coupling agent is 0.8 wt% of the mass of the petroleum coke particles. The spray-coated petroleum coke is transferred to a drying device, pre-dried at 60° C. to remove ethanol, heated to 120° C., kept warm for 60 minutes to promote a condensation reaction, and naturally cooled to obtain pretreated petroleum coke.

[0037] (2) Modification of asphalt: Polyisobutylene (PIB) with a molecular weight of 80,000 to 1,20,000 was heated and dissolved with cyclohexane at a mass ratio of 1:4 to form a uniform PIB mother liquor; the high-temperature petroleum asphalt was heated to 140°C to ensure complete melting without agglomeration; high-speed stirring was started at 500 rpm, the temperature was maintained at 140°C, and the PIB mother liquor was slowly added to the molten asphalt within 80 minutes. At the same time, 50% diisopropylbenzene peroxide initiator solution was added dropwise 10 minutes before the addition of the PIB mother liquor, and the remaining initiator solution was injected in the first 20 minutes; after the addition of the PIB mother liquor, the temperature was raised to 180°C, nitrogen was introduced to purge to remove the solvent, and the temperature was lowered to 120°C to obtain the modified liquid asphalt, which was kept warm for use; the amount of polyisobutylene PIB was 4% of the asphalt mass, and the amount of diisopropylbenzene peroxide was 0.8% of the polyisobutylene PIB mass. Before use, diisopropylbenzene peroxide was dissolved in a small amount of toluene to form a 10 wt% solution and then added dropwise;

[0038] (3) Kneading: The amount of petroleum coke is calculated according to the initial unbroken mass (including petroleum coke pellets and powder), and the raw materials are prepared according to the mass ratio of petroleum coke, modified liquid asphalt, conductive carbon black, and nanocarbon fiber of 100:14:3:0.5. The conductive carbon black, nanocarbon fiber and dispersant BYK-2155 are premixed in a high-speed mixer. The amount of dispersant is 0.8% of the total weight of the conductive carbon black and nanocarbon fiber. After drying at 100°C, the pre-oxidized petroleum coke is preheated to 100°C, and 30% of the total amount of conductive carbon black and nanocarbon fiber is added. The mixture is stirred at a low speed for 3 minutes. The mixture is heated to 140°C, and petroleum coke powder below 0.5 mm, modified liquid asphalt, the remaining conductive carbon black and nanocarbon fiber are added. The mixture is sheared at 500 rpm for 15 minutes to obtain a homogeneous paste. Finally, the mixture is molded under nitrogen protection with a kneading pressure of 10 MPa and cooled to room temperature at a rate of less than 5°C / min to obtain an anode green body.

[0039] (4) Calcination: Preheat the calciner to 350°C at 8°C / h and keep it warm for 6 hours; then heat it from room temperature to 1100°C at 20°C / h and keep it warm for 50 hours; the secondary calcination is to heat it from room temperature to 1300°C at 40°C / h and keep it warm for 30 hours.

[0040] Example 2

[0041] A method for preparing a high-performance prebaked anode comprises the following steps:

[0042] (1) Pretreatment of petroleum coke: petroleum coke containing less than 15 wt% of pelletized coke is crushed and graded to obtain petroleum coke crushed material with a particle size of less than 6 mm, and the petroleum coke particle size content is controlled by weight percentage as follows: 6-4 mm content is 12%, 4-2 mm content is 45%, 2-0.5 mm content is 27%, and the content of powder below 0.5 mm is 16%, of which the content of powder below 0.075 mm is 10%; after screening out powder below 0.5 mm, the petroleum coke pellets are subjected to surface high-temperature pre-oxidation treatment, firstly heating to 590° C. in a rotary kiln, introducing air at a flow rate of 4 L / min, and treating for 32 min, then cooling to 390° C., introducing air containing 5 vol% water vapor at a flow rate of 3 L / min, and treating for 50 min to obtain pre-oxidized petroleum coke;

[0043] At the same time, a composite solution of titanate coupling agent and silane coupling agent KH-550 was prepared: the raw materials were weighed and mixed according to the mass ratio of titanate coupling agent TCA-201: ethanol = 12:85, glacial acetic acid was used to adjust the pH to 4.5, and the mixture was stirred and dissolved at 40 ° C for 30 minutes to obtain a pre-hydrolyzed titanate solution; the raw materials were weighed and mixed according to the mass ratio of KH-550: ethanol: deionized water = 12:80:10, the pH was adjusted to 4.0 with glacial acetic acid, and the mixture was hydrolyzed and activated at room temperature for 55 minutes. n, to obtain a pre-hydrolyzed silane solution; pour the pre-hydrolyzed titanate solution into a stirring kettle, slowly add the pre-hydrolyzed silane solution dropwise, control the mixing temperature to ≤35°C, and add the dispersant BYK-2155 after the addition is completed within 30 minutes, and then add the dispersant BYK-2155 in an amount of 0.4% of the total amount of the titanate coupling agent and the silane coupling agent. Continue stirring for 20 minutes, adjust the pH to 5.3, and form a uniform and transparent composite solution. Let it stand for defoaming before use; the mass ratio of the titanate coupling agent to the silane coupling agent KH-550 is 7:3.

[0044] A fluidized bed is used to spray a composite solution of a titanate coupling agent and a silane coupling agent KH-550 on the surface of pre-oxidized petroleum coke, wherein the amount of the titanate coupling agent and the silane coupling agent is 0.9 wt% of the mass of the petroleum coke particles. The spray-coated petroleum coke is transferred to a drying device, pre-dried at 70° C. to remove ethanol, heated to 123° C., kept at this temperature for 50 minutes to promote a condensation reaction, and naturally cooled to obtain pretreated petroleum coke.

[0045] (2) Modification of asphalt: Polyisobutylene (PIB) with a molecular weight of 80,000 to 1,20,000 was heated and dissolved with cyclohexane at a mass ratio of 1:5 to form a uniform PIB mother liquor; the high-temperature petroleum asphalt was heated to 150°C to ensure complete melting without agglomeration; high-speed stirring was started at 500 rpm, the temperature was maintained at 150°C, and the PIB mother liquor was slowly added to the molten asphalt within 70 minutes. At the same time, 50% diisopropylbenzene peroxide initiator solution was added dropwise 10 minutes before the addition of the PIB mother liquor, and the remaining initiator solution was injected in the first 25 minutes; after the addition of the PIB mother liquor, the temperature was raised to 190°C, nitrogen was introduced to purge to remove the solvent, and the temperature was lowered to 125°C to obtain the modified liquid asphalt, which was kept warm for use; the amount of polyisobutylene PIB was 4.5% of the asphalt mass, and the amount of diisopropylbenzene peroxide was 1.2% of the polyisobutylene PIB mass. Before use, diisopropylbenzene peroxide was dissolved in a small amount of toluene to form an 8wt% solution and then added dropwise;

[0046] (3) Kneading: The amount of petroleum coke is calculated according to the initial unbroken mass (including petroleum coke pellets and powder), and the raw materials are prepared according to the mass ratio of petroleum coke, modified liquid asphalt, conductive carbon black, and nanocarbon fiber of 100:35:4:0.8. The conductive carbon black, nanocarbon fiber and dispersant BYK-2155 are premixed in a high-speed mixer. The amount of dispersant is 1% of the total weight of the conductive carbon black and nanocarbon fiber. They are dried at 100-105°C and set aside. The pre-oxidized petroleum coke is preheated to 110°C, and 30% of the total amount of conductive carbon black and nanocarbon fiber is added. The mixture is stirred at a low speed for 4 minutes. The mixture is heated to 156°C, and petroleum coke powder below 0.5 mm, modified liquid asphalt, the remaining conductive carbon black and nanocarbon fiber are added. The mixture is sheared at 500 rpm for 10 minutes to obtain a homogeneous paste. Finally, the mixture is molded under nitrogen protection with a kneading pressure of 12 MPa and cooled to room temperature at a rate of less than 5°C / min to obtain an anode green body.

[0047] (4) Calcination: Preheat the calciner to 380°C at a rate of 10°C / h and keep it warm for 5 hours; then heat it from room temperature to 1120°C at a rate of 25°C / h and keep it warm for 42 hours; the secondary calcination is to heat it from room temperature to 1330°C at a rate of 45°C / h and keep it warm for 28 hours.

[0048] Example 3

[0049] A method for preparing a high-performance prebaked anode comprises the following steps:

[0050] (1) Pretreatment of petroleum coke: The petroleum coke is crushed and graded to obtain petroleum coke crushed material with a particle size of less than 6 mm, and the petroleum coke particle size content is controlled by weight percentage as follows: 6-4 mm content is 15%, 4-2 mm content is 40%, 2-0.5 mm content is 30%, and the content of powder below 0.5 mm is 15%, of which the content of powder below 0.075 mm is 12%; after screening out the powder below 0.5 mm, the petroleum coke pellets are subjected to surface high-temperature pre-oxidation treatment, firstly heating to 600°C in a rotary kiln, introducing air at a flow rate of 5 L / min, treating for 30 min, then cooling to 400°C, introducing air containing 5 vol% water vapor at a flow rate of 5 L / min, treating for 40 min, to obtain pre-oxidized petroleum coke;

[0051] At the same time, a composite solution of titanate coupling agent and silane coupling agent KH-550 was prepared: the raw materials were weighed and mixed according to the mass ratio of titanate coupling agent TCA-201: ethanol = 15:85, glacial acetic acid was used to adjust the pH to 5.0, and the mixture was stirred and dissolved at 45 ° C for 35 minutes to obtain a pre-hydrolyzed titanate solution; the raw materials were weighed and mixed according to the mass ratio of KH-550: ethanol: deionized water = 15:80:10, the pH was adjusted to 4.0 with glacial acetic acid, and the mixture was hydrolyzed and activated at room temperature for 60 minutes. n, to obtain a pre-hydrolyzed silane solution; pour the pre-hydrolyzed titanate solution into a stirring kettle, slowly add the pre-hydrolyzed silane solution dropwise, control the mixing temperature to ≤35°C, and add the dispersant BYK-2155 after the addition is completed within 30 minutes, and then add the dispersant BYK-2155 in an amount of 0.5% of the total amount of the titanate coupling agent and the silane coupling agent. Continue stirring for 25 minutes, adjust the pH to 5.5, and form a uniform and transparent composite solution. Let it stand for defoaming before use; the mass ratio of the titanate coupling agent to the silane coupling agent KH-550 is 7:3.

[0052] A fluidized bed is used to spray a composite solution of a titanate coupling agent and a silane coupling agent KH-550 on the surface of pre-oxidized petroleum coke, wherein the amount of the titanate coupling agent and the silane coupling agent is 1.0 wt% of the mass of the petroleum coke particles. The spray-coated petroleum coke is transferred to a drying device, pre-dried at 80° C. to remove ethanol, heated to 125° C., kept warm for 40 minutes to promote a condensation reaction, and naturally cooled to obtain pretreated petroleum coke.

[0053] (2) Modification of asphalt: Polyisobutylene (PIB) with a molecular weight of 80,000 to 1,20,000 was heated and dissolved in cyclohexane at a mass ratio of 1:5 to form a uniform PIB mother liquor; the high-temperature petroleum asphalt was heated to 160°C to ensure complete melting without agglomeration; high-speed stirring was started at 500 rpm, the temperature was maintained at 160°C, and the PIB mother liquor was slowly added to the molten asphalt within 80 minutes. At the same time, 50% diisopropylbenzene peroxide initiator solution was added dropwise 10 minutes before the addition of the PIB mother liquor, and the remaining initiator solution was injected in the first 30 minutes; after the addition of the PIB mother liquor, the temperature was raised to 200°C, nitrogen was introduced to purge to remove the solvent, and the temperature was lowered to 130°C to obtain the modified liquid asphalt, which was kept warm for use; the amount of polyisobutylene PIB was 5% of the asphalt mass, and the amount of diisopropylbenzene peroxide was 1.5% of the polyisobutylene PIB mass. Before use, diisopropylbenzene peroxide was dissolved in a small amount of toluene to form a 5wt% solution and then added dropwise;

[0054] (3) Kneading: The amount of petroleum coke is calculated according to the initial unbroken mass (including petroleum coke pellets and powder), and the raw materials are prepared according to the mass ratio of petroleum coke, modified liquid asphalt, conductive carbon black, and nanocarbon fiber of 100:16:4:1. The conductive carbon black, nanocarbon fiber and dispersant BYK-2155 are premixed in a high-speed mixer. The amount of dispersant is 1.2% of the total weight of the conductive carbon black and nanocarbon fiber. The mixture is dried at 110°C and set aside. The pre-oxidized petroleum coke is preheated to 120°C, and 30% of the total amount of conductive carbon black and nanocarbon fiber is added. The mixture is stirred at a low speed for 5 minutes. The mixture is heated to 160°C, and petroleum coke powder below 0.5 mm, modified liquid asphalt, the remaining conductive carbon black and nanocarbon fiber are added. The mixture is sheared at 500 rpm for 5 minutes to obtain a homogeneous paste. Finally, the mixture is molded under nitrogen protection with a kneading pressure of 15 MPa and cooled to room temperature at a rate of less than 5°C / min to obtain an anode green body.

[0055] (4) Calcination: Preheat the calciner to 400°C at a rate of 12°C / h and keep it warm for 3 hours; then heat it from room temperature to 1150°C at a rate of 30°C / h and keep it warm for 35 hours; the secondary calcination is to heat it from room temperature to 1350°C at a rate of 50°C / h and keep it warm for 25 hours.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 2 is that there is no high-temperature pre-oxidation treatment step in step (1).

[0058] Step (1) is as follows:

[0059] Pretreatment of petroleum coke: The petroleum coke is crushed and graded to obtain petroleum coke crushed material with a particle size of less than 6 mm. The petroleum coke particle size content is controlled by weight percentage as follows: 6-4 mm content is 12%, 4-2 mm content is 45%, 2-0.5 mm content is 27%, the content of fines below 0.5 mm is 16%, of which the content of fines below 0.075 mm is 10%;

[0060] Prepare a composite solution of titanate coupling agent and silane coupling agent KH-550: weigh and mix the raw materials according to the mass ratio of titanate coupling agent TCA-201: ethanol = 12:85, adjust the pH to 4.5 with glacial acetic acid, and stir and dissolve at 40°C for 30 minutes to obtain a pre-hydrolyzed titanate solution; weigh and mix the raw materials according to the mass ratio of KH-550: ethanol: deionized water = 12:80:10, adjust the pH to 4.0 with glacial acetic acid, and hydrolyze and activate at room temperature for 55 minutes. , to obtain a pre-hydrolyzed silane solution; pour the pre-hydrolyzed titanate solution into a stirring kettle, slowly add the pre-hydrolyzed silane solution dropwise, control the mixing temperature to ≤35°C, and add the dispersant BYK-2155 after the addition is completed within 30 minutes, and then add the dispersant BYK-2155 in an amount of 0.4% of the total amount of the titanate coupling agent and the silane coupling agent. Continue stirring for 20 minutes, adjust the pH to 5.3, and form a uniform and transparent composite liquid. Let it stand for defoaming and set aside; the mass ratio of the titanate coupling agent to the silane coupling agent KH-550 is 7:3.

[0061] After screening out powder smaller than 0.5 mm, a mixed solution of a titanate coupling agent and a silane coupling agent KH-550 is sprayed on the surface of the petroleum coke particles using a fluidized bed, wherein the amount of the titanate coupling agent and the silane coupling agent is 0.9 wt% of the mass of the petroleum coke particles. The spray-coated petroleum coke is transferred to a drying device, pre-dried at 70° C. to remove ethanol, heated to 123° C., kept at this temperature for 50 minutes to promote a condensation reaction, and naturally cooled to obtain pretreated petroleum coke.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 2 is that the silane coupling agent KH-550 in step (1) is replaced by an equal amount of titanate coupling agent.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 2 is that the mass ratio of the titanate coupling agent to the silane coupling agent KH-550 in step (1) is 3:7.

[0066] Comparative Example 4

[0067] The difference between this comparative example and Example 2 is that there is no step (2) of modifying the high-temperature petroleum asphalt, and the high-temperature petroleum asphalt is directly used for kneading.

[0068] Comparative Example 5

[0069] The difference between this comparative example and Example 2 is that the molecular weight of the polyisobutylene PIB in step (2) is less than 60,000.

[0070] Comparative Example 6

[0071] This comparative example differs from Example 2 in that the molecular weight of the polyisobutylene (PIB) in step (2) is greater than 150,000. The performance parameters of the prebaked anodes obtained in each example and comparative example were tested in accordance with industry standard YS / T63. The performance parameters were measured using an anode air reaction detector and a carbon dioxide reaction detector, and the residual air and carbon dioxide reaction rates were calculated. The results are shown in Table 1 below.

[0072] Table 1 Performance test results

[0073]

[0074] From the above results, it can be seen that the comparative example 1 has no high-temperature pre-oxidation treatment, which directly affects the surface hydroxyl content of the petroleum coke. Insufficient surface hydroxyl groups lead to uneven coverage of the coupling agent, decreased interfacial bonding force, and insufficiently dense structure, which in turn affects the apparent density, compressive strength, and structural stability of the coke, resulting in a decrease in the residual rate of CO2 and air reaction, an increase in porosity, and an increase in resistivity.

[0075] Comparative Example 2 replaces silane with titanate. In Example 2, the original titanate coupling agent and silane coupling agent were compounded. The titanate coupling agent provided better interfacial bonding, while the silane coupling agent enhanced heat resistance and oxidation resistance. Replacing the entire titanate with titanate improved interfacial bonding, but the synergistic effect of the two coupling agents disappeared. The lack of the oxidation protection provided by the silane coupling agent resulted in a decrease in the residual air and CO2 content.

[0076] In Comparative Example 3, the coupling agent ratio was adjusted. A higher ratio of silane coupling agent improved oxidation resistance (increased residual rate), but the interfacial bonding was weakened because of the reduction of titanate, which also led to a decrease in compressive strength.

[0077] Comparative Example 4: Unmodified asphalt. Direct use of high-temperature petroleum asphalt reduces asphalt fluidity and filling efficiency, leading to increased porosity and decreased bulk density and strength. Furthermore, the residual structure of unmodified asphalt after coking is less than optimal, making it more susceptible to expansion under temperature fluctuations, resulting in an increased thermal expansion coefficient.

[0078] The molecular weight range of the PIB in Comparative Examples 5 and 6 varied. The use of a low molecular weight in Comparative Example 5 resulted in insufficient asphalt viscosity, poor filling performance, high porosity, and decreased density and strength. The use of a high molecular weight PIB in Comparative Example 6 resulted in excessively high asphalt viscosity, making it difficult to fully infiltrate the petroleum coke, similarly affecting porosity and density. It also increased energy consumption during the kneading process, resulting in overcrowding in some areas and an uneven structure, which in turn reduced overall performance. For example, compressive strength decreased due to internal stress.

[0079] The present invention can reduce the porosity of the prebaked anode, increase the volume density, and improve the compressive strength and flexural strength of the anode through multi-dimensional optimization of petroleum coke surface pre-oxidation modification, coupling agent double bonding, carbon black network embedding, and asphalt rheological modification. This solves the problem that the petroleum coke anode is prone to cracking or slagging in the high-temperature environment of the electrolytic cell, and increases the service life of the prebaked anode. At the same time, it can also reduce the anode resistivity, thereby reducing the voltage of the electrolytic cell, improving the electrolysis current efficiency, and comprehensively improving the performance of the anode.

[0080] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing a high-performance prebaked anode, characterized in that: The following steps are involved: (1) Pretreatment of petroleum coke: crushing the petroleum coke and screening it by grade to obtain petroleum coke crushed material with a particle size of less than 6 mm; after screening out petroleum coke powder with a particle size of less than 0.5 mm, the petroleum coke pellets are subjected to surface high-temperature pre-oxidation treatment to obtain pre-oxidized petroleum coke; spraying a composite solution of a titanate coupling agent and a silane coupling agent on the surface of the pre-oxidized petroleum coke, transferring the spray-coated petroleum coke to a drying equipment, pre-drying at 60-80°C to remove ethanol, heating to 120-125°C, keeping the temperature for 40-60 minutes to promote condensation reaction, and naturally cooling to obtain pre-treated petroleum coke; (2) Modification of asphalt: Dissolve polyisobutylene (PIB) with a molecular weight of 80,000 to 120,000 in cyclohexane to form a uniform PIB mother liquor; heat the high-temperature petroleum asphalt to 140 to 160°C to ensure complete melting without agglomeration; start high-speed stirring, maintain the temperature at 140 to 160°C, slowly add the PIB mother liquor to the molten asphalt, and simultaneously add dicumyl peroxide solution as an initiator; after the addition of the PIB mother liquor is complete, remove the solvent and cool the temperature to 120 to 130°C to obtain the modified liquid asphalt, which is then kept warm for later use; (3) Kneading: Pretreated petroleum coke, petroleum coke powder with a size of less than 0.5 mm, modified liquid asphalt, conductive carbon black, and nano-carbon fibers are mixed. The amount of petroleum coke is calculated based on the initial uncrushed mass. The mass ratio of petroleum coke, modified liquid asphalt, conductive carbon black, and nano-carbon fibers is 100:14-16:3-4:0.5-1. The kneading temperature is 140-160°C to obtain a homogeneous paste, which is then compression molded to obtain an anode green body. (4) Molding and calcining: The anode green body is preheated, calcined and calcined again to obtain a prebaked anode.

2. The preparation method according to claim 1, wherein: The graded screening controls the petroleum coke particle size content by weight percentage as follows: 6-4 mm content is 10-15%, 4-2 mm content is 40-48%, 2-0.5 mm content is 25-30%, the content of powder below 0.5 mm is 15-17%, of which the content of powder below 0.075 mm is 9-12%.

3. The preparation method according to claim 1, wherein: The method of high-temperature pre-oxidation treatment is as follows: first, in a rotary kiln, the temperature is raised to 580-600° C., air is introduced at a flow rate of 2-5 L / min, and the treatment is carried out for 30-35 minutes; then, the temperature is cooled to 380-400° C., air containing 5 vol.% water vapor is introduced at a flow rate of 2-5 L / min, and the treatment is carried out for 40-60 minutes.

4. The preparation method according to claim 1, wherein: The composite solution of the titanate coupling agent and the silane coupling agent KH-550 is prepared as follows: weighing and mixing raw materials according to the mass ratio of titanate coupling agent, ethanol, and glacial acetic acid = 10:85:0.5, adjusting the pH to 4.0-5.0, stirring and dissolving at 35-45° C. for 20-35 minutes to obtain a pre-hydrolyzed titanate solution; weighing and mixing raw materials according to the mass ratio of KH-550, ethanol, and deionized water = 10:80:10, adjusting the pH to 4.0 with glacial acetic acid, and hydrolyzing and activating at room temperature for 50-60 minutes. in to obtain a pre-hydrolyzed silane solution; pour the pre-hydrolyzed titanate solution into a high-speed stirring kettle; slowly add the pre-hydrolyzed silane solution dropwise, controlling the mixing temperature to ≤35°C; add a dispersant after the addition is completed within 30 minutes, continue stirring for 15 to 25 minutes, adjust the pH to 5.2 to 5.5, and form a uniform and transparent compound solution. Let it stand for defoaming before use; the mass ratio of titanate coupling agent to silane coupling agent KH-550 is 7:3, and the amount of titanate coupling agent and silane coupling agent used is 0.8 to 1.0 wt.% of the mass of the petroleum coke pellets.

5. The preparation method according to claim 1, wherein: The polyisobutylene PIB and cyclohexane are mixed and dissolved in a mass ratio of 1:4-5. The amount of polyisobutylene PIB is 4-5% of the mass of asphalt, and the amount of dicumyl peroxide is 0.8-1.5% of the mass of polyisobutylene PIB. Before use, dicumyl peroxide is dissolved in toluene to form a 5-10wt% solution and then added dropwise.

6. The preparation method according to claim 1, wherein: The method for removing the solvent in step (2) is to raise the temperature to 180-200° C. and introduce nitrogen to purge to remove the solvent.

7. The preparation method according to claim 1, wherein: The specific method of kneading in step (3) is to premix the conductive carbon black, nano-carbon fibers and dispersant BYK-2155 in a high-speed mixer, dry them at 100-110° C. and set them aside; preheat the pre-oxidized petroleum coke to 100-120° C., add 30% of the total amount of conductive carbon black and nano-carbon fibers, and stir at low speed for 3-5 minutes; then heat it to 140-160° C., add petroleum coke powder below 0.5 mm, modified liquid asphalt, the remaining conductive carbon black and nano-carbon fibers, and shear them at high speed for 5-15 minutes; finally, perform compression molding under nitrogen protection.

8. The preparation method according to claim 1, wherein: The specific method of the forming and roasting is to preheat the roasting furnace to 350-400°C at 8-12°C / h and keep it warm for 3-6 hours; then heat it to 1100-1150°C at 20-30°C / h and keep it warm for 35-50 hours; the secondary calcination is to heat it to 1300-1350°C at 40-50°C / h and keep it warm for 25-30 hours.

9. The preparation method according to claim 1, wherein: The dispersant is BYK-2155, and its usage amount is 0.3-0.5% of the total amount of the titanate coupling agent and the silane coupling agent.

10. The high performance prebaked anode prepared according to any one of claims 1 to 9.

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