CN116242125A - Ultrahigh-temperature reducing atmosphere intermediate-frequency roasting furnace, graphite material and preparation method thereof - Google Patents

Abstract

The application provides an ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace, a graphite material and a preparation method thereof, and relates to the technical field of graphite materials. The ultrahigh-temperature reducing atmosphere intermediate-frequency roasting furnace comprises a first stokehold bin, a second stokehold bin, a preheating section, a high-temperature section, a cooling section, a water cooling section and a discharger which are connected in sequence from top to bottom; the outer surface of the high temperature section is also provided with a furnace body coil which is connected with an intermediate frequency cabinet, and the intermediate frequency cabinet is used for providing an intermediate frequency power supply to perform intermediate frequency heating on the furnace body coil. The preparation method of the graphite material comprises the following steps: waste cathode materials are fed into the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace, and high temperature roasting is carried out in the reducing atmosphere to obtain a graphite crude product; and purifying and magnetically separating to obtain the graphite material. The waste cathode material is treated in an ultrahigh-temperature reducing atmosphere intermediate-frequency roasting furnace, and sodium salt and ferric salt are reduced in situ in the reducing atmosphere to be used as catalysts, so that the graphite material with the graphene crystal structure is obtained.

Description

Ultrahigh-temperature reducing atmosphere intermediate-frequency roasting furnace, graphite material and preparation method thereof

Technical Field

The application relates to the technical field of graphite materials, in particular to an ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace, a graphite material and a preparation method thereof.

Background

Graphene (Graphene) is a material consisting of carbon atoms in sp ² The hybridized orbit forms a hexagonal two-dimensional carbon nanomaterial with honeycomb lattice. The material has excellent optical, electrical and mechanical properties, has important application prospects in the aspects of material science, micro-nano processing, energy sources, biomedicine, drug delivery and the like, and is considered as a revolutionary material in the future. The preparation method of the graphene material has been reported as follows: mechanical exfoliation, chemical oxidation, crystal epitaxial growth, chemical vapor deposition, organic synthesis, carbon nanotube exfoliation, and the like. The graphene product comprises powder graphene and film graphene, butThe research of preparing the graphene particles macroscopically and the graphene crystals microscopically has been rarely reported.

The yield of electrolytic aluminum in China is about 3853 ten thousand tons in 2021, which is 21 years old in the world. The aluminum industry in China is rapidly developed and simultaneously generates a large amount of dangerous wastes including waste overhaul tanks (overhaul slag) of electrolytic aluminum, anode carbon slag, secondary aluminum ash for aluminum processing and the like. The waste cathode of electrolytic aluminum is an important component of overhaul slag. In the long-term aluminum electrolysis process, naF and AlF permeate into the electrolytic aluminum cathode due to molten salt reaction and chemical reaction caused by heat action, chemical action, mechanical erosion action, electric action, sodium and electrolyte permeation and the like ₃ 、Al ₂ O ₃ Sodium metal, na ₂ CO ₃ NaCN, etc.; when the cathode generates larger cracks, the conductivity of the cathode is changed greatly, and the cathode needs to be dismantled to become a waste cathode when the electrolytic cell is possibly damaged. 15-20 kg of aluminum electrolysis cell overhaul slag is produced according to each ton of original aluminum, and calculated by the fact that the overhaul slag contains about 55% of waste cathodes, the production amount of aluminum electrolysis waste cathodes in 2021 China is 31.8-42.4 ten thousand tons. The spent cathode carbon block consisted essentially of carbon and fluoride, with a minor amount of cyanide, wherein the carbon content was about 65%, the fluoride content was about 35%, and the cyanide content was about 100ppm. The carbon in the waste cathode of the electrolytic aluminum is highly graphitized due to long-term high-temperature environment, so that the recovery value is high. According to research, an intercalation compound CxNa is generated between graphite layers in the formation process of the aluminum electrolysis waste cathode, so that the interlayer spacing of the graphite layers is increased, and further the Van der Waals force between the graphite layers is weakened, which means that carbon blocks of the waste cathode can be used as precursors for producing graphene after certain treatment, and the method has higher production efficiency and benefit compared with the conventional natural graphite and expanded graphite for producing graphene materials at present. Therefore, the waste cathode is defined as dangerous waste and has stronger resource.

At present, the industrialized waste cathode is rarely treated by harmless and recycling treatment technology. Most enterprises adopt landfill or storage modes to treat, sodium fluoride, aluminum fluoride, cryolite and the like are subjected to rain, and part of the sodium fluoride, aluminum fluoride, cryolite and the like infiltrate into soil to seriously harm the environment, so that fluorine pollution is caused; some enterprises adopt a combustion method, but secondary pollution caused by fluoride is difficult to meet the requirement of environmental protection. Under the current environment-friendly situation, electrolytic aluminum enterprises urgently need a plurality of applicable waste cathode harmless treatment devices and resource utilization technologies, and recycling of the waste cathodes is realized.

Disclosure of Invention

The purpose of the application is to provide an ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace, a graphite material and a preparation method thereof. The graphite material with the graphene crystal structure is prepared by using the roasting furnace, adopting a high-temperature reduction roasting process, cooperatively utilizing sodium salt and ferric salt in the waste cathode, adopting a reducing atmosphere to reduce the sodium salt and the ferric salt into metal in situ and taking the metal as a catalyst.

In order to achieve the above object, the technical scheme of the present application is as follows:

in a first aspect, the application provides an ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace, which comprises a first stokehold bin, a second stokehold bin, a preheating section, a high temperature section, a cooling section, a water cooling section and a discharger which are sequentially connected from top to bottom;

the first stokehold bin is connected with the second stokehold bin through a discharge valve, and the second stokehold bin is connected with the preheating section through a feed valve;

the outer surface of high temperature section still is equipped with the furnace body coil, the furnace body coil links to each other with the intermediate frequency cabinet, the intermediate frequency cabinet is used for providing the intermediate frequency power supply to carry out the intermediate frequency heating to the furnace body coil.

With reference to the first aspect, in some optional embodiments, the intermediate frequency roasting furnace satisfies at least one of the following conditions:

a. the second stokehold bin is also provided with an air inlet and an air outlet, the air inlet is used for introducing inert gas, and the air outlet is used for discharging air in the second stokehold bin;

b. the inert gas comprises at least one of nitrogen, argon and helium;

c. the preheating section is of a structure with a thick middle part and a thin upper part and a thin lower part;

d. at least one chimney is arranged in the middle of the preheating section and used for discharging the volatilized flue gas of the high-temperature section;

e. the outer surface of the water cooling section is also provided with a cooling water pipe for cooling the material at the water cooling section;

f. lining materials in the preheating section, the high-temperature section, the cooling section and the water cooling section comprise carbon blocks and/or graphite crucibles;

g. the carbon content in the carbon block and/or the graphite crucible is more than or equal to 97 percent, and the ash content is less than or equal to 1 percent.

In a second aspect, the present application provides a method of preparing a graphite material, comprising:

waste cathode materials are fed into the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace in the first aspect, and high temperature roasting is carried out in reducing atmosphere to obtain a graphite crude product;

and purifying and magnetically separating the graphite crude product to obtain the graphite material.

With reference to the second aspect, in some alternative embodiments, the spent cathode material meets at least one of the following conditions:

A. the spent cathode material comprises a graphite cathode;

B. the waste cathode material comprises a waste cathode removed from an aluminum electrolysis cell built by using a graphitized cathode;

C. the service life of the aluminum electrolysis cell is 3 years to 10 years.

In some alternative embodiments, before the high temperature reduction roasting, the method further comprises: crushing the waste cathode material to 1mm-100mm.

In some alternative embodiments, the feeding the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace performs a high temperature roasting process under a reducing atmosphere, including:

the waste cathode material is firstly fed into the first stokehold bin, and then is fed into the second stokehold bin through the discharging valve;

after the air in the second stokehold bin is exhausted, the waste cathode material is fed into the preheating section through the feeding valve, enters the high-temperature section and is subjected to high-temperature roasting to obtain graphite fragments;

sequentially passing the graphite fragments through the cooling section and the water cooling section, and discharging the graphite fragments out of the intermediate frequency roasting furnace through the discharger to obtain the crude graphite;

the preheating section, the high temperature section, the cooling section and the water cooling section are all in reducing atmosphere, and the gas in the reducing atmosphere comprises at least one of hydrogen and carbon monoxide.

In some preferred embodiments, at least one of the following conditions is met:

D. when the second stokehold bin is provided with an air inlet and an air outlet, the air in the second stokehold bin is discharged, and the air discharging comprises:

closing the feeding valve and the discharging valve, introducing inert gas from the gas inlet, and discharging the air in the second stokehold bin from the gas outlet;

E. the inlet amount of the inert gas is 0.5L/kg-1.0L/kg;

F. the temperature at the high temperature section is 2400-2800 ℃;

G. the total time from the feeding of the first forehearth to the discharge from the discharger is 4 to 6 hours;

H. when at least one chimney is arranged in the middle of the preheating section, the pressure of the gas exhausted from the chimney is 20Pa-100Pa.

In some alternative embodiments, the method of preparation further satisfies at least one of the following conditions:

I. the purification includes: grinding and crushing the graphite crude product, and then immersing the graphite crude product into mixed acid liquid for purification;

J. the particle size of the ground and crushed graphite crude product is less than or equal to 0.15mm;

K. the mixed acid liquid comprises hydrofluoric acid and hydrochloric acid;

and L, the liquid-solid mass ratio of the mixed acid liquid to the graphite crude product is 1: (1-4);

m. the immersion time is 0.5h-1.5h;

the mass concentration of the hydrofluoric acid is 40% -47%, the mass concentration of the hydrochloric acid is 30% -38%, and the volume ratio of the hydrofluoric acid to the hydrochloric acid is 1: (1-3).

In some alternative embodiments, the magnetic separation comprises: carrying out dry magnetic separation by using a magnetic separator;

the surface magnetic field intensity of the magnetic separator is 600KA/m-1600KA/m.

In a third aspect, the present application provides a graphite material prepared by the preparation method of the second aspect.

The beneficial effects of this application:

the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace has a simple structure, and can be used continuously and uninterruptedly by arranging the preheating section, the high temperature section, the cooling section and the water cooling section, so that the production recovery efficiency is greatly improved.

According to the preparation method, microcrystalline graphite with high graphitization degree in the waste cathode material is fully utilized, an ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace is used, an ultrahigh temperature roasting process is adopted, sodium salt and ferric salt in the waste cathode material are cooperatively utilized, after the reducing atmosphere is adopted to reduce into metal in situ, the metal material is used as a catalyst, the graphitization process of carbon is accelerated, a perfect graphene structure is formed, a graphite material with a graphene crystal structure is obtained, and harmless treatment and recycling of waste cathode carbon blocks are realized.

The carbon content of the graphite material is more than 99.99%, the purity is high, the graphite material has a graphene crystal structure, is a high-quality precursor for producing graphene, and can be directly processed into the graphene material.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope of the present invention.

FIG. 1 is a schematic structural diagram of an intermediate frequency roasting furnace in an ultra-high temperature reducing atmosphere.

Description of the drawings elements:

1-spent cathode material; 2-a first stokehold bin; 3-an air outlet; 4-a second stokehold bin; 5-a feed valve; 6-a discharge valve; 7-an air inlet; 8-a chimney; 9-a high temperature section; 10-furnace body coil; 11-a cooling section; 12-cooling water pipes; 13-a preheating section; 14-an intermediate frequency cabinet; 15-a water cooling section; 16-discharger; 17-crude graphite.

Detailed Description

The term as used herein:

"prepared from … …" is synonymous with "comprising". The terms "comprising," "including," "having," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

The conjunction "consisting of … …" excludes any unspecified element, step or component. If used in a claim, such phrase will cause the claim to be closed, such that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of … …" appears in a clause of the claim body, rather than immediately following the subject, it is limited to only the elements described in that clause; other elements are not excluded from the stated claims as a whole.

When an equivalent, concentration, or other value or parameter is expressed as a range, preferred range, or a range bounded by a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when ranges of "1 to 5" are disclosed, the described ranges should be construed to include ranges of "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a numerical range is described herein, unless otherwise indicated, the range is intended to include its endpoints and all integers and fractions within the range.

In these examples, the parts and percentages are by mass unless otherwise indicated.

"parts by mass" means a basic unit of measurement showing the mass ratio of a plurality of components, and 1 part may be any unit mass, for example, 1g may be expressed, 2.689g may be expressed, and the like. If we say that the mass part of the a component is a part and the mass part of the B component is B part, the ratio a of the mass of the a component to the mass of the B component is represented as: b. alternatively, the mass of the A component is aK, and the mass of the B component is bK (K is an arbitrary number and represents a multiple factor). It is not misunderstood that the sum of the parts by mass of all the components is not limited to 100 parts, unlike the parts by mass.

"and/or" is used to indicate that one or both of the illustrated cases may occur, e.g., a and/or B include (a and B) and (a or B).

As shown in fig. 1, the application provides an ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace, which comprises a first stokehold bin 2, a second stokehold bin 4, a preheating section 13, a high temperature section 9, a cooling section 11, a water cooling section 15 and a discharger 16 which are sequentially connected from top to bottom.

Wherein the first forehearth 2 is connected with the second forehearth 4 through a discharge valve 6, and the second forehearth 4 is connected with a preheating section 13 through a feed valve 5. The outer surface of the high temperature section 9 is also provided with a furnace body coil 10, the furnace body coil 10 is connected with an intermediate frequency cabinet 14, the intermediate frequency cabinet 14 is used for providing an intermediate frequency power supply to perform intermediate frequency heating on the furnace body coil 10, and further, the intermediate frequency heating is adopted at the high temperature section, so that a high temperature effect is realized.

The ultrahigh temperature in the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace mainly refers to high temperature of 2400-2800 ℃, and the reducing atmosphere is to provide reducing gas like hydrogen, carbon monoxide and the like at least in a preheating section and a high temperature section so as to realize the protection of substances in the furnace.

The preheating section 13 has a structure with thick middle, thick upper and thin lower parts, receives the materials supplied by the second stokehold bin 4 from the upper part, and then discharges from the lower part into the high temperature section 9.

The middle part of the preheating section 13 is also provided with at least one chimney 8, more preferably 2, for rapidly discharging the volatilized flue gases in the high temperature section.

The second stokehold bin 4 is also provided with an air inlet 7 and an air outlet 3, wherein the air inlet 7 is used for introducing inert gas, and the air outlet 3 is used for discharging air in the second stokehold bin 4.

Further, the inert gas comprises at least one of nitrogen, argon and helium;

the outer surface of the water cooling section 15 is also provided with a cooling water pipe 12 for cooling the material at the water cooling section 15 so as to ensure that the material can be discharged from the discharger at normal temperature.

In a preferred embodiment of the present application, in order to use the intermediate frequency roasting furnace for preparing graphite material, carbon blocks and/or graphite crucibles are used as lining materials in the preheating section 13, the high temperature section 9, the cooling section 11 and the water cooling section 15, thereby preventing unnecessary pollution to graphite. Wherein, the carbon content in the carbon block and/or the graphite crucible is more than or equal to 97 percent, and the ash content is less than or equal to 1 percent.

The application also provides a preparation method of the graphite material, which uses the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace, and specifically comprises the following steps:

(1) Providing spent cathode material. The waste cathode material is preferably a graphite cathode material, more preferably a waste cathode material after the aluminum electrolysis cell built by using a graphitized cathode is dismantled, and the service life of the aluminum electrolysis cell is generally 3-10 years.

(2) The spent cathode material is crushed to 1mm to 100mm, more preferably 20mm to 70mm.

(3) The crushed waste cathode material 1 is fed into a first stokehold bin 2 of an ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace, then is fed into a second stokehold bin 4, a feeding valve 5 and a discharging valve 6 are closed, then inert gas nitrogen or argon is introduced from an air inlet 7, air in the second stokehold bin 4 is expelled, and then the air inlet 7 and the air outlet 3 are closed. More preferably, nitrogen is introduced from the inlet 7, and the amount of nitrogen used is 0.5L/kg to 1.0L/kg.

(4) The feed valve 5 is opened and the spent cathode material is fed into the preheating section 13 of the ultra-high temperature reducing atmosphere intermediate frequency roasting furnace.

(5) Intermittent feeding is carried out from the upper part of the preheating section 13, and continuous discharging is carried out from the lower part; the preheating section 13 has a structure with a thick middle part and a thin upper part and a thin lower part, so that the compact accumulation of the waste cathode materials in the high-temperature section 9 is ensured, and then the chimney 8 is arranged in the middle part of the preheating section 13, so that the smoke volatilized at high temperature is ensured to be discharged as soon as possible.

(6) After the waste cathode material passes through the preheating section 13 and enters the high temperature section 9, the waste cathode material is heated to 2400-2800 ℃ at the high temperature section 9, for example, 2400 ℃ 2500 ℃, 2600 ℃, 2700 ℃, 2800 ℃ or any value between 2400-2800 ℃ and the reducing atmosphere in the furnace is maintained. Then some substances such as fluoride in the material are discharged out of the furnace body along with the reducing gas from the chimney 8, and the pressure of the flue gas at the outlet of the chimney is positive pressure and is between 20Pa and 100Pa. Further, the high temperature section 9 adopts intermediate frequency heating, and the furnace body coil 10 is heated through the intermediate frequency cabinet 14.

(7) After roasting at the high temperature section 9, the materials are sent to a cooling section 11, then enter a water cooling section 15 and are discharged out of the furnace body through a discharger 16 to obtain a crude graphite product 17, wherein the total time required from feeding to discharging from the discharger 16 is 4-6 h. The material obtained after roasting at the high temperature section 9 also contains some impurities, so that the material discharged from the discharger 16 is a crude graphite product.

(8) Grinding and crushing the graphite crude product to be less than or equal to 0.15mm, and adding mixed acid of hydrofluoric acid and hydrochloric acid for purification. Preferably, hydrofluoric acid with the mass concentration of 40-47% and hydrochloric acid with the mass concentration of 30-38% are used for mixing, and the volume ratio of the hydrofluoric acid to the hydrochloric acid is 1: 1. 1: 2. 1:3 is either 1: any value between (1-3), more preferably 1:2; then the liquid-solid mass ratio of the mixed acid to the graphite crude product is 1: (1-4), for example, may be 1: 1. 1: 2. 1: 3. 1:4 is either 1: any value between (1-4), more preferably 1:3, a step of; the pickling time is 0.5h to 1.5h, more preferably 1h.

(9) After the acid-washed matter is washed and dried by clean water, some magnetic metal impurities such as iron are contained, so that trace iron with magnetism is removed by magnetic separation, and the surface magnetic field strength of the magnetic separator is 600-1600KA/m, more preferably 1200-1600KA/m. The finally obtained non-magnetic product is the high-purity graphite material with the graphene crystal structure.

The gas in the reducing atmosphere in the intermediate frequency roasting furnace is mainly at least one of hydrogen and carbon monoxide. The carbon monoxide can be provided from outside or naturally generated in the roasting furnace due to low oxygen content. In the roasting process, the basic principle is that hydrogen or carbon monoxide gas at high temperature reacts with metal oxides in the waste cathode material to form metal simple substances which can be used as catalysts to accelerate the graphitization process of carbon in the cathode and form a perfect graphene structure.

More preferably, the roasting furnace is operated by positive pressure, which can avoid a large amount of air from entering the furnace, and a small amount of oxygen in the air reacts with carbon in the furnace to form carbon monoxide, so that the high-temperature roasting furnace can be kept in a strong reducing atmosphere. In addition, hydrogen can be introduced to maintain the positive pressure and the reducing atmosphere in the furnace, wherein the mass of the hydrogen is 1-3% of that of the waste cathode material.

The technical scheme has the advantages that:

1. the used waste cathode material contains a large amount of fine crystalline graphite which is formed in an aluminum electrolysis cell at a low temperature (about 960 ℃) for a long time (about 4-10 years) and has an imperfect graphene crystal structure, and the invention fully utilizes the characteristics of the waste cathode;

2. the ultra-high temperature roasting process and the acid leaching and magnetic separation purification process are adopted, so that the process is short and industrialization is easier;

3. the adopted reducing atmosphere can cooperatively utilize graphite and metal compound impurities in the waste cathode at ultrahigh temperature, and after the metal compound is reduced to metal at high temperature, the graphitization process of carbon is accelerated and a perfect graphene structure is formed, so that the high-quality utilization of the waste cathode is realized;

4. the purity of the graphite material is further improved by acid leaching, magnetic separation and the like, so that the high-purity graphite material with the carbon content of more than 99.99 percent can be obtained, the high-purity graphite material has a graphene crystal structure, is a high-quality precursor for producing graphene, and can be directly processed into the graphene material.

Embodiments of the present invention will be described in detail below with reference to specific examples, but it will be understood by those skilled in the art that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

The carbon blocks in the raw materials of the aluminum electrolysis waste cathode used in the following embodiment have the same components, and specifically are C:63.34%, O:2.52%, F:12.31%, na:14.21%, al:3.25%, si:2.12%, S:0.12%, ca:1.20%, fe:0.54%. And the ultra-high temperature reducing atmosphere intermediate frequency roasting furnace described in fig. 1 was used in the following examples.

Example 1

The embodiment provides a graphite material, and the specific preparation method comprises the following steps:

1) The raw materials are the waste cathode of aluminum electrolysis which is removed after being used for 4-6 years;

2) Crushing the above electrolytic aluminum waste cathode carbon blocks to 20-50 mm;

3) Feeding the crushed waste cathode material into a first stokehold bin 2 in an ultrahigh-temperature reducing atmosphere intermediate frequency roasting furnace, then feeding into a second stokehold bin 4, closing a feeding valve 5 and a discharging valve 6, then introducing nitrogen from an air inlet 7, wherein the nitrogen dosage is 1L/kg, expelling air in the stokehold bin, and then closing the air inlet 7 and an air outlet 3;

4) Opening a feed valve 5, and feeding the waste cathode material into a preheating section 13 in the intermediate frequency roasting furnace in the ultra-high temperature reducing atmosphere;

5) After passing through the preheating section 13 and the high temperature section 9, the waste cathode material, fluoride salt and other substances are discharged from the chimney 8 into the furnace body at high temperature;

6) Heating the waste cathode to 2400-2500 ℃ in an intermediate frequency roasting furnace in an ultra-high temperature reducing atmosphere, wherein the residence time of the waste cathode in the high temperature furnace (the time from the blanking of the first stokehold bin 2 to the discharging of the discharger 16) is 5 hours;

7) The flue gas pressure at the outlet of a chimney in the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace is positive pressure and 50Pa, and the reducing atmosphere in the high temperature furnace is maintained;

8) Crushing and grinding the graphite crude product to be less than or equal to 0.15mm, and then purifying again by adopting mixed acid of hydrofluoric acid and hydrochloric acid, wherein the mass concentration of the hydrofluoric acid is 40%, the mass concentration of the hydrochloric acid is 37%, and the volume ratio of the hydrofluoric acid to the hydrochloric acid is 1:2, the liquid-solid mass ratio of the mixed acid to the graphite crude product is 3, and the acid leaching time is 1h;

9) And removing trace iron with magnetism from the re-purified graphite powder by adopting magnetic separation, wherein the magnetic field intensity of the surface of a magnetic separator is 1000KA/m, so that the high-purity graphite material with a graphene crystal structure is obtained, and the fixed carbon content is 99.992%.

Example 2

The embodiment provides a graphite material, and the specific preparation method comprises the following steps:

1) The raw materials are the waste cathode of aluminum electrolysis which is removed after being used for 4-6 years;

2) Crushing the above electrolytic aluminum waste cathode carbon blocks to 20-50 mm;

3) Feeding the crushed waste cathode material into a first stokehold bin 2 in an ultrahigh-temperature reducing atmosphere intermediate frequency roasting furnace, then feeding into a second stokehold bin 4, closing a feeding valve 5 and a discharging valve 6, then introducing nitrogen from an air inlet 7, wherein the nitrogen dosage is 1L/kg, expelling air in the stokehold bin, and then closing the air inlet 7 and an air outlet 3;

4) Opening a feed valve 5, and feeding the waste cathode material into a preheating section 13 in the intermediate frequency roasting furnace in the ultra-high temperature reducing atmosphere;

5) After passing through the preheating section 13 and the high temperature section 9, the waste cathode material, fluoride salt and other substances are discharged from the chimney 8 into the furnace body at high temperature;

6) Heating the waste cathode material to 2550-2600 ℃ in an ultrahigh-temperature reducing atmosphere intermediate-frequency roasting furnace, wherein the residence time of the waste cathode in the high-temperature furnace (the time from the blanking of the first stokehold bin 2 to the discharging of the discharger 16) is 6 hours;

7) The flue gas pressure at the outlet of a chimney in the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace is positive pressure and 50Pa, and the reducing atmosphere in the high temperature furnace is maintained;

8) Crushing and grinding the graphite crude product to be less than or equal to 0.15mm, and then purifying again by adopting mixed acid of hydrofluoric acid and hydrochloric acid, wherein the mass concentration of the hydrofluoric acid is 40%, the mass concentration of the hydrochloric acid is 37%, and the volume ratio of the hydrofluoric acid to the hydrochloric acid is 1:2, the liquid-solid mass ratio of the mixed acid to the graphite crude product is 3, and the acid leaching time is 1h;

9) And removing trace iron with magnetism from the re-purified graphite powder by adopting magnetic separation, wherein the magnetic field intensity of the surface of a magnetic separator is 1000KA/m, so that the high-purity graphite material with a graphene crystal structure is obtained, and the fixed carbon content is 99.994%.

Example 3

The embodiment provides a graphite material, and the specific preparation method comprises the following steps:

1) The raw materials are the waste cathode of aluminum electrolysis which is removed after being used for 4-6 years;

2) Crushing the above electrolytic aluminum waste cathode carbon blocks to 10-40 mm;

3) Feeding the crushed waste cathode material into a first stokehold bin 2 in an ultrahigh-temperature reducing atmosphere intermediate frequency roasting furnace, then feeding into a second stokehold bin 4, closing a feeding valve 5 and a discharging valve 6, then introducing nitrogen from an air inlet 7, wherein the nitrogen dosage is 1L/kg, expelling air in the stokehold bin, and then closing the air inlet 7 and an air outlet 3;

4) Opening a feed valve 5, and feeding the waste cathode material into a preheating section 13 in the intermediate frequency roasting furnace in the ultra-high temperature reducing atmosphere;

5) After passing through the preheating section 13 and the high temperature section 9, the waste cathode material, fluoride salt and other substances are discharged from the chimney 8 into the furnace body at high temperature;

6) Heating the waste cathode material to 2600-2650 ℃ in an ultrahigh-temperature reducing atmosphere intermediate-frequency roasting furnace, wherein the residence time of the waste cathode in the high-temperature furnace (the time from the blanking of the first stokehold bin 2 to the discharging of the discharger 16) is 8 hours;

7) The flue gas pressure at the outlet of a chimney in the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace is positive pressure and 50Pa, and the reducing atmosphere in the high temperature furnace is maintained;

8) Crushing and grinding the graphite crude product to be less than or equal to 0.15mm, and then purifying again by adopting mixed acid of hydrofluoric acid and hydrochloric acid, wherein the mass concentration of the hydrofluoric acid is 40%, the mass concentration of the hydrochloric acid is 37%, and the volume ratio of the hydrofluoric acid to the hydrochloric acid is 1:2, the liquid-solid mass ratio of the mixed acid to the graphite crude product is 3, and the acid leaching time is 1h;

9) And removing trace iron with magnetism from the re-purified graphite powder by adopting magnetic separation, wherein the magnetic field intensity of the surface of a magnetic separator is 1000KA/m, so that the high-purity graphite material with a graphene crystal structure is obtained, and the fixed carbon content is 99.995%.

Example 4

The embodiment provides a graphite material, and the specific preparation method comprises the following steps:

1) The raw materials are the waste cathode of aluminum electrolysis which is removed after being used for 4-6 years;

2) Crushing the above electrolytic aluminum waste cathode carbon blocks to 10-40 mm;

3) Feeding the crushed waste cathode material into a first stokehold bin 2 in an ultrahigh-temperature reducing atmosphere intermediate frequency roasting furnace, then feeding into a second stokehold bin 4, closing a feeding valve 5 and a discharging valve 6, then introducing nitrogen from an air inlet 7, wherein the nitrogen dosage is 1.5L/kg, expelling air in the stokehold bin, and then closing the air inlet 7 and an air outlet 3;

4) Opening a feed valve 5, and feeding the waste cathode material into a preheating section 13 in the intermediate frequency roasting furnace in the ultra-high temperature reducing atmosphere;

5) After passing through the preheating section 13 and the high temperature section 9, the waste cathode material, fluoride salt and other substances are discharged from the chimney 8 into the furnace body at high temperature;

6) Heating the waste cathode material to 2550-2600 ℃ in an ultrahigh-temperature reducing atmosphere intermediate-frequency roasting furnace, wherein the residence time of the waste cathode in the high-temperature furnace (the time from the blanking of the first stokehold bin 2 to the discharging of the discharger 16) is 8 hours;

7) The flue gas pressure at the outlet of a chimney in the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace is positive pressure and is 20Pa, and the reducing atmosphere in the high temperature furnace is maintained;

8) Crushing and grinding the graphite crude product to be less than or equal to 0.15mm, and then purifying again by adopting mixed acid of hydrofluoric acid and hydrochloric acid, wherein the mass concentration of the hydrofluoric acid is 40%, the mass concentration of the hydrochloric acid is 37%, and the volume ratio of the hydrofluoric acid to the hydrochloric acid is 1:3, the liquid-solid mass ratio of the mixed acid to the graphite crude product is 3, and the acid leaching time is 1.5h;

9) And removing trace iron with magnetism from the re-purified graphite powder by adopting magnetic separation, wherein the magnetic field intensity of the surface of a magnetic separator is 1000KA/m, so that the high-purity graphite material with a graphene crystal structure is obtained, and the fixed carbon content is 99.996%.

Comparative example 1

The comparative example provides a graphite material, the specific preparation method of which comprises:

1) The raw materials are the waste cathode of aluminum electrolysis which is removed after being used for 4-6 years;

2) Crushing the above electrolytic aluminum waste cathode carbon blocks to 10-40 mm;

3) Directly putting the crushed waste cathode material into an ultrahigh temperature heating furnace with the temperature of 2550-2600 ℃, heating for a period of time and taking out a sample, wherein a certain amount of air is arranged in the high temperature furnace;

4) The sample was also subjected to acid washing and magnetic separation in the same manner as in the acid washing and magnetic separation step of example 4, to obtain a graphite material. Compared with the example 4, the graphite material has the advantages that the mass is reduced by 10%, and the graphite lacks obvious graphene crystal structure, and the fixed carbon content is 99.9%.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Furthermore, those skilled in the art will appreciate that while some embodiments herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims below, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Claims (10)

1. The intermediate frequency roasting furnace is characterized by comprising a first stokehold bin, a second stokehold bin, a preheating section, a high-temperature section, a cooling section, a water cooling section and a discharger which are sequentially connected from top to bottom;

the first stokehold bin is connected with the second stokehold bin through a discharge valve, and the second stokehold bin is connected with the preheating section through a feed valve;

the outer surface of high temperature section still is equipped with the furnace body coil, the furnace body coil links to each other with the intermediate frequency cabinet, the intermediate frequency cabinet is used for providing the intermediate frequency power supply to carry out the intermediate frequency heating to the furnace body coil.

2. The ultra-high temperature intermediate frequency roasting furnace of claim 1, wherein at least one of the following conditions is satisfied:

a. the second stokehold bin is also provided with an air inlet and an air outlet, the air inlet is used for introducing inert gas, and the air outlet is used for discharging air in the second stokehold bin;

b. the inert gas comprises at least one of nitrogen, argon and helium;

c. the preheating section is of a structure with a thick middle part and a thin upper part and a thin lower part;

d. at least one chimney is arranged in the middle of the preheating section and used for discharging the volatilized flue gas of the high-temperature section;

e. the outer surface of the water cooling section is also provided with a cooling water pipe for cooling the material at the water cooling section;

f. lining materials in the preheating section, the high-temperature section, the cooling section and the water cooling section comprise carbon blocks and/or graphite crucibles;

g. the carbon content in the carbon block and/or the graphite crucible is more than or equal to 97 percent, and the ash content is less than or equal to 1 percent.

3. A method of preparing a graphite material, comprising:

feeding the waste cathode material into the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace of claim 1 or 2, and roasting at high temperature in reducing atmosphere to obtain a graphite crude product;

and purifying and magnetically separating the graphite crude product to obtain the graphite material.

4. The method of manufacturing according to claim 3, wherein the spent cathode material meets at least one of the following conditions:

A. the spent cathode material comprises a graphite cathode;

B. the waste cathode material comprises a waste cathode removed from an aluminum electrolysis cell built by using a graphitized cathode;

C. the service life of the aluminum electrolysis cell is 3 years to 10 years.

5. The method of claim 3, further comprising, prior to the high temperature reduction firing: crushing the waste cathode material to 1mm-100mm.

6. The method according to claim 3, wherein the step of feeding the powder into the ultrahigh temperature reducing atmosphere intermediate frequency roasting furnace and conducting high temperature roasting in a reducing atmosphere comprises the steps of:

the waste cathode material is firstly fed into the first stokehold bin, and then is fed into the second stokehold bin through the discharging valve;

after the air in the second stokehold bin is exhausted, the waste cathode material is fed into the preheating section through the feeding valve, enters the high-temperature section and is subjected to high-temperature roasting to obtain graphite fragments;

sequentially passing the graphite fragments through the cooling section and the water cooling section, and discharging the graphite fragments out of the intermediate frequency roasting furnace through the discharger to obtain the crude graphite;

the preheating section, the high temperature section, the cooling section and the water cooling section are all in reducing atmosphere, and the gas in the reducing atmosphere comprises at least one of hydrogen and carbon monoxide.

7. The method of manufacturing according to claim 6, wherein at least one of the following conditions is satisfied:

D. when the second stokehold bin is provided with an air inlet and an air outlet, the air in the second stokehold bin is discharged, and the air discharging comprises:

closing the feeding valve and the discharging valve, introducing inert gas from the gas inlet, and discharging the air in the second stokehold bin from the gas outlet;

E. the inlet amount of the inert gas is 0.5L/kg-1.0L/kg;

F. the temperature at the high temperature section is 2400-2800 ℃;

G. the total time from the feeding of the first forehearth to the discharge from the discharger is 4 to 8 hours;

H. when at least one chimney is arranged in the middle of the preheating section, the pressure of the gas exhausted from the chimney is 20Pa-100Pa.

8. A method of preparing as claimed in claim 3, wherein at least one of the following conditions is met:

I. the purification includes: grinding and crushing the graphite crude product, and then immersing the graphite crude product into mixed acid liquid for purification;

J. the particle size of the graphite crude product after grinding and crushing is less than or equal to 0.15mm;

K. the mixed acid liquid comprises hydrofluoric acid and hydrochloric acid;

and L, the liquid-solid mass ratio of the mixed acid liquid to the graphite crude product is 1: (1-4);

m. the immersion time is 0.5h-1.5h;

the mass concentration of the hydrofluoric acid is 40% -47%, the mass concentration of the hydrochloric acid is 30% -38%, and the volume ratio of the hydrofluoric acid to the hydrochloric acid is 1: (1-3).

9. The method of any one of claims 3-8, wherein the magnetic separation comprises: carrying out dry magnetic separation by using a magnetic separator;

the surface magnetic field intensity of the magnetic separator is 600KA/m-1600KA/m.

10. A graphite material prepared by the preparation method according to any one of claims 3 to 9.

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