CN115110120A - Method for reducing emission of perfluorocarbons in aluminum electrolysis - Google Patents
Method for reducing emission of perfluorocarbons in aluminum electrolysis Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 66
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 51
- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 51
- 238000005868 electrolysis reaction Methods 0.000 title claims abstract description 37
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 118
- 239000003792 electrolyte Substances 0.000 claims abstract description 102
- TXEYQDLBPFQVAA-UHFFFAOYSA-N tetrafluoromethane Chemical compound FC(F)(F)F TXEYQDLBPFQVAA-UHFFFAOYSA-N 0.000 claims abstract description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 19
- 230000015556 catabolic process Effects 0.000 claims description 17
- 229910004261 CaF 2 Inorganic materials 0.000 claims description 14
- 229910052799 carbon Inorganic materials 0.000 claims description 9
- 239000002893 slag Substances 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 6
- 229910016569 AlF 3 Inorganic materials 0.000 claims description 3
- 150000003839 salts Chemical class 0.000 claims description 3
- 239000013078 crystal Substances 0.000 abstract description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 20
- 238000004519 manufacturing process Methods 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 14
- 239000002994 raw material Substances 0.000 description 12
- 229910002092 carbon dioxide Inorganic materials 0.000 description 10
- 238000013461 design Methods 0.000 description 10
- 230000000737 periodic effect Effects 0.000 description 8
- 239000001569 carbon dioxide Substances 0.000 description 7
- 229920006926 PFC Polymers 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 4
- 239000004411 aluminium Substances 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 229910001635 magnesium fluoride Inorganic materials 0.000 description 2
- 238000005065 mining Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- LBVWYGNGGJURHQ-UHFFFAOYSA-N dicarbon Chemical compound [C-]#[C+] LBVWYGNGGJURHQ-UHFFFAOYSA-N 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/18—Electrolytes
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Abstract
The invention particularly relates to a method for reducing the discharge amount of perfluorocarbons in aluminum electrolysis, and belongs to the field of aluminum electrolysis. A method for reducing the discharge amount of perfluorocarbons in aluminum electrolysis comprises controlling the electrolyte composition of dissolved alumina; controlling parameters of the electrolytic cell; controlling the blanking parameters of the alumina. The method comprises the steps of obtaining a proper electrolyte primary crystal temperature by controlling electrolyte components for dissolving alumina, controlling parameters of an electrolytic cell, and optimizing energy distribution of an electrolytic cell area, so as to improve the solubility of the alumina in the electrolytic cell; by controlling the blanking parameters of the alumina and assisting the control, the lower limit concentration of the alumina in the electrolyte is improved, and the discharge amount of the perfluorocarbon is effectively reduced.
Description
Technical Field
The invention belongs to the field of aluminum electrolysis, and particularly relates to a method for reducing the discharge amount of perfluorocarbons in aluminum electrolysis.
Background
The aluminum industry is an important prop industry of national economy in China, the yield of the original aluminum in China reaches 3708 ten thousand tons in 2020, accounts for 54 percent of the yield of the original aluminum in the world, and is continuously established in the first world for 20 years. According to DEFERA data, the amount of carbon dioxide discharged by producing a single ton of electrolytic aluminum is about 11.5 tons, and the total emission amount of carbon dioxide in the electrolytic aluminum industry all year around is about 4.26 hundred million tons, which accounts for about 4% of the total net emission amount of carbon dioxide in China.
The aluminum industry comprises industrial chains of raw aluminum production (aluminum mining and mining, aluminum oxide production, anode production, electrolytic aluminum production), secondary aluminum, aluminum processing, product manufacturing and the like, wherein the emission of CO2 in the raw aluminum production accounts for 94.85% of the aluminum industry.
During operation of the aluminum electrolysis cell, besides carbon dioxide, Perfluorocarbon (PFCs) gases such as carbon tetrafluoride and dicarbon hexafluoride are generated, which are main products of the anode effect of aluminum electrolysis. The greenhouse effect coefficient of PFCs is much higher than CO2, and the contributions of 1 kg CF4 and 1 kg C2F6 to global warming are equivalent to 6630 kg and 11100 kg CO2, respectively. According to statistics, the average carbon dioxide emission converted by the PFCs in the aluminum electrolysis in China is about 0.6t/t Al, and a certain difference is still kept between the carbon dioxide emission and the recommended value of 0.260t/t Al converted by the PFCs proposed by the international aluminum cooperation at present.
Electrolytic cell enterprises and electrolytic cell types in China are numerous, technical routes are different from one another, local differences exist between aluminum oxide raw materials and an electrolyte system, and perfluorocarbon emission in the aluminum electrolysis process is also greatly different. The electrolyte composition of individual enterprises is suitably controlled, the aluminum electrolysis process parameters are reasonably configured, the alumina concentration parameters are reasonably set, the emission of carbon dioxide converted by PFCs of the enterprises is lower than the recommended value proposed by the International aluminum agency, and on the contrary, in some enterprises, the electrolyte composition is not matched with the performance of alumina, the process parameter setting is not reasonable enough, the concentration of alumina in the electrolyte is low, the emission of perfluorocarbon is high, and the emission reaches multiple times of the recommended value proposed by the International aluminum agency.
Disclosure of Invention
The application aims to provide a method for reducing the emission of perfluorocarbons in aluminum electrolysis so as to solve the technical problem of high emission of perfluorocarbons in aluminum electrolysis in the prior art.
The embodiment of the invention provides a method for reducing the emission of perfluorocarbons in aluminum electrolysis, which comprises the following steps:
putting alumina in an electrolytic cell for aluminum electrolysis to obtain electrolyte;
adding auxiliary materials into the electrolyte to regulate and control the components of the electrolyte;
controlling parameters of the electrolytic cell;
and controlling the blanking parameters of the alumina.
Optionally, the electrolyte is added with an auxiliary material, and the regulation and control of the components of the electrolyte include:
control of LiF, KF, MgF 2 And CaF 2 The content of (A);
control of NaF and AlF 3 In a molar ratio of (a).
Optionally, the composition of the electrolyte satisfies the following relation:
CR＝3.334-0.0446×w(KF) electrolyte +0.0942×w(LiF) Electrolyte +0.0098×w(MgF 2 ) Electrolyte -0.0070×Δ T-0.0895×AO-0.0452×t+r；
Wherein:
CR represents NaF and AlF 2 The molar ratio of (A) to (B);
w(KF) electrolyte 、w(LiF) Electrolyte 、w(MgF 2 ) Electrolyte Respectively represent KF, LiF and MgF in the electrolyte 2 Mass ofA score;
Δ T represents the degree of superheat of the electrolyte in units of;
AO represents the type of alumina, when the alumina is planar: AO ═ 1, when the alumina is mesogenic: AO ═ 2, when the alumina is sandy: AO ═ 3;
t represents the time for completely dissolving 1 percent of alumina in the electrolyte molten salt, t is less than or equal to 20, and the unit is min;
r represents an adjustment constant, and r is 0 to 0.1.
Optionally, the controlling parameters of the electrolytic cell include:
controlling the average superheat degree of the electrolytic cell to be 8-15 ℃;
the electrolyte level of the cell is controlled.
Optionally, the electrolyte level of the electrolytic cell is more than or equal to 19 cm.
Optionally, the controlling the blanking parameters of the alumina includes:
controlling the crust breaking breakdown rate of the feed opening;
controlling the carbon slag coverage rate of the feed opening;
controlling the deviation between the blanking amount of the alumina and the theoretical value to be less than or equal to 10 percent;
the concentration of alumina is controlled.
Optionally, the crust breaking breakdown rate of the feed opening is more than or equal to 90%.
Optionally, the coverage rate of the carbon slag at the feed opening is less than or equal to 80%.
Optionally, the concentration of the alumina is more than or equal to 1.2%.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
according to the method for reducing the emission of the perfluorocarbons in the aluminum electrolysis, provided by the embodiment of the invention, the proper electrolyte primary crystal temperature is obtained by controlling the electrolyte components for dissolving the aluminum oxide, the parameters of the electrolytic cell are controlled, and the energy distribution of the area of the electrolytic cell is optimized, so that the solubility of the aluminum oxide in the electrolytic cell is improved; by controlling the blanking parameters of the alumina and assisting the control, the lower limit concentration of the alumina in the electrolyte is improved, and the discharge amount of the perfluorocarbon is effectively reduced.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a flow chart of a method provided by an embodiment of the invention.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention. For example, the room temperature may be a temperature within a range of 10 to 35 ℃.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
In order to solve the technical problems, the general idea of the embodiment of the application is as follows:
according to an exemplary embodiment of the present invention, a method for reducing the amount of perfluorocarbons discharged from aluminum electrolysis is provided, which comprises the following steps:
s1, placing the alumina in an electrolytic cell for aluminum electrolysis to obtain an electrolyte;
s2, adding auxiliary materials into the electrolyte to regulate and control the components of the electrolyte;
s3, controlling the parameters of the electrolytic cell;
and S4, controlling the blanking parameters of the alumina.
By controlling the electrolyte components for dissolving the alumina, proper electrolyte primary crystal temperature is obtained, the parameters of the electrolytic cell are controlled, and the energy distribution of the electrolytic cell area is optimized, so that the solubility of the alumina in the electrolytic cell is improved; by controlling the blanking parameters of the alumina and assisting the control, the lower limit concentration of the alumina in the electrolyte is improved, and the discharge amount of the perfluorocarbon is effectively reduced.
As an alternative embodiment, the adding of the auxiliary material to the electrolyte, and the adjusting of the components of the electrolyte include:
control of LiF, KF, MgF 2 And CaF 2 The content of (A);
control of NaF and AlF 3 In a molar ratio of (a).
As an alternative embodiment, the composition of the electrolyte satisfies the following relation:
CR＝3.334-0.0446×w(KF) electrolyte +0.0942×w(LiF) Electrolyte +0.0098×w(MgF2) Electrolyte -0.0070×Δ T-0.0895×AO-0.0452×t+r；
Wherein:
CR represents NaF and AlF 2 The molar ratio of (A) to (B);
w(KF) electrolyte 、w(LiF) Electrolyte 、w(MgF2) Electrolyte Respectively represent KF, LiF and MgF in the electrolyte 2 Mass fraction of (a);
Δ T represents the degree of superheat of the electrolyte in units of;
AO represents the type of alumina, when the alumina is planar: AO ═ 1, when the alumina is mesogenic: AO ═ 2, when the alumina is sandy: AO ═ 3;
t represents the time for completely dissolving 1 percent of alumina in the electrolyte molten salt, t is less than or equal to 20, and the unit is min;
r represents an adjustment constant, and r is 0 to 0.1.
The reason for limiting the above relation is that: in order to allow the limited range electrolyte to have a sufficient dissolution rate and dissolution capacity for the above-mentioned alumina.
As an alternative embodiment, the controlling of the parameters of the electrolytic cell comprises:
controlling the average superheat degree of the electrolytic cell to be 8-15 ℃;
the electrolyte level of the cell is controlled.
The reason why the average degree of superheat is controlled is that: in order to keep higher current efficiency, the current efficiency is adversely affected by too low or too high superheat degree, and the overall economic and technical indexes of the electrolysis process are affected.
As an alternative embodiment, the electrolyte level of the cell is 19cm or more.
The reason for controlling the electrolyte level is: the alumina dissolves while settling in the electrolyte, and is dissolved completely in order to maintain sufficient time for the alumina to dissolve in the electrolyte.
As an optional embodiment, the controlling the blanking parameters of the alumina comprises:
controlling the crust breaking breakdown rate of the feed opening;
controlling the carbon slag coverage rate of the feed opening;
controlling the deviation between the blanking amount of the alumina and the theoretical value to be less than or equal to 10 percent;
the concentration of alumina is controlled.
As an optional implementation mode, the crust breaking breakdown rate of the feed opening is more than or equal to 90%.
The reason for controlling the crust breaking breakdown rate of the feed opening is as follows: crust breaking breakdown of less than 90% can result in partial alumina not entering the electrolyte, ultimately affecting the alumina concentration in the electrolyte.
As an optional implementation mode, the coverage rate of the carbon slag at the feed opening is less than or equal to 80 percent.
The reason for controlling the carbon slag coverage rate of the feed opening is as follows: part of alumina with the carbon slag coverage rate of more than 80 percent can be mixed with the carbon slag to influence the dissolution of the alumina, and finally influence the concentration of the alumina in the electrolyte.
As an alternative embodiment, the concentration of the alumina is 1.2% or more.
The reason for controlling the concentration of alumina is that: the concentration of the alumina is lower than 1.2%, the effect coefficient of the electrolytic process is improved, and the discharge amount of the perfluorocarbon is increased.
The present application will be described in detail below with reference to examples, comparative examples, and experimental data.
Example 1
Provides a method for reducing the discharge amount of perfluorocarbons in aluminum electrolysis, which adopts intermediate alumina as a raw material and comprises electrolyte components of LiF 4.3-4.5%, KF 2.3-2.5% and CaF 2 3.8-4.0％、MgF 2 0.7-0.8%, molar ratio (NaF/AlF) 3 )2.50 plus or minus 0.05, the bath temperature is 935 plus or minus 5 ℃, and the average superheat degree is 12 ℃. The electrolyte level is 19cm in the production process, the crust breaking breakdown rate of the feed opening is 96% in the alumina crust breaking and blanking process, the carbon residue coverage rate of the feed opening is 80% in the blanking process, and the blanking amount deviates 10% from the design in the alumina blanking process. The control parameters of the alumina concentration are set as the periodic switching coefficient of the alumina concentration of 12 mu omega, the increment rate of 1.2, the decrement rate of 1.2, the maximum time of 30min for the excess period and the maximum time of 3min for the normal period. The lower concentration of alumina in the electrolyte is 1.3%.
Example 2
Provides a method for reducing the discharge amount of perfluorocarbons in aluminum electrolysis, which adopts intermediate alumina as a raw material and comprises electrolyte components of LiF 4.3-4.5%, KF 2.3-2.5% and CaF 2 3.8-4.0％、MgF 2 0.7-0.8%, molar ratio (NaF/AlF) 3 )2.40 plus or minus 0.05, the bath temperature is 935 plus or minus 5 ℃, and the superheat degree is averagely 15 ℃. The electrolyte level is 19cm in the production process, the crust breaking breakdown rate of the feed opening is 90% in the alumina crust breaking and blanking process, the carbon residue coverage rate of the feed opening is 50% in the blanking process, and the blanking amount deviates 10% from the design in the alumina blanking process. Alumina concentration control parameter setSetting the alumina concentration cycle switching coefficient to be 12 mu omega, the increment rate to be 1.2, the decrement rate to be 1.2, the maximum time of the excess period to be 30min and the maximum time of the normal period to be 3 min. The lower concentration of alumina in the electrolyte is 1.2%.
Example 3
A process for reducing the discharge of perfluorocarbon in aluminium electrolysis features that planar alumina is used as raw material, and the electrolyte components Li F5.6-6.0%, KF 2.8-3.0%, and CaF 2 3.2-3.7％、MgF 2 1.3-1.5%, molar ratio (NaF/AlF) 3 )2.80 plus or minus 0.05, the bath temperature of 925 plus or minus 5 ℃, and the average superheat degree of 10 ℃. The electrolyte level is 20cm in the production process, the crust breaking breakdown rate of the feed opening is 97% in the alumina crust breaking and blanking process, the carbon residue coverage rate of the feed opening is 36% in the blanking process, and the blanking amount deviates 10% from the design in the alumina blanking process. The control parameters of the alumina concentration are set as the periodic switching coefficient of the alumina concentration of 11 mu omega, the increment rate of 1.2, the decrement rate of 1.2, the maximum time of 25min for the excess period and the maximum time of 3min for the normal period. The lower concentration of alumina in the electrolyte is 1.4%.
Example 4
A process for reducing the discharge of perfluorocarbon in aluminium electrolysis features that planar alumina is used as raw material, and the electrolyte components Li F3.6-4.0%, KF 2.8-3.0%, and CaF 2 3.2-3.7％、MgF 2 1.3-1.5%, molar ratio (NaF/AlF) 3 )2.50 plus or minus 0.05, the bath temperature 930 plus or minus 5 ℃ and the average superheat degree of 8 ℃. The electrolyte level is 20cm in the production process, the crust breaking breakdown rate of the feed opening is 96% in the alumina crust breaking and blanking process, the carbon residue coverage rate of the feed opening is 30% in the blanking process, and the blanking amount deviates 10% from the design in the alumina blanking process. The control parameters of the alumina concentration are set as the periodic switching coefficient of the alumina concentration of 11 mu omega, the increment rate of 1.2, the decrement rate of 1.2, the maximum time of 25min for the excess period and the maximum time of 3min for the normal period. The lower concentration of alumina in the electrolyte is 1.4%.
Example 5
A process for reducing the discharge of perfluorocarbon in aluminium electrolysis features that planar alumina is used as raw material, and the electrolyte components Li F1.9-2.1%, KF 1.9-2.1% and CaF 2 4.8-5.2％、MgF 2 0.9-1.1%, molar ratio (NaF/AlF) 3 )2.40 plus or minus 0.05, the bath temperature of 945 plus or minus 5 ℃, and the average superheat degree of 12 ℃. The electrolyte level is 19cm in the production process, the crust breaking breakdown rate of the feed opening is 98% in the alumina crust breaking and blanking process, the carbon residue coverage rate of the feed opening is 20% in the blanking process, and the blanking amount deviates 10% from the design in the alumina blanking process. The control parameters of the alumina concentration are set as the periodic switching coefficient of the alumina concentration 11 mu omega, the increment rate 1.2, the decrement rate 1.2, the maximum time of the excess period 25min and the maximum time of the normal period 3 min. The lower concentration of alumina in the electrolyte is 1.5%.
Comparative example 1
An enterprise adopts intermediate alumina as raw material, and electrolyte components of LiF 4.3-4.5%, KF 2.3-2.5%, and CaF 2 3.8-4.0％、MgF 2 0.7-0.8%, molar ratio (NaF/AlF) 3 )2.40 plus or minus 0.05, the bath temperature 930 plus or minus 5 ℃ and the average superheat degree of 10 ℃. The electrolyte level is 17cm in the production process, the crust breaking breakdown rate of the feed opening is 85 percent in the alumina crust breaking and blanking process, the carbon residue coverage rate of the feed opening is 90 percent in the blanking process, and the blanking amount is 20-30 percent of the design deviation in the alumina blanking process. The control parameters of the alumina concentration are set as the periodic switching coefficient of the alumina concentration of 11 mu omega, the increment rate of 1.2, the decrement rate of 1.2, the maximum time of 25min for the excess period and the maximum time of 3min for the normal period. The lower concentration of alumina in the electrolyte was 1.0%.
Comparative example 2
An enterprise adopts intermediate alumina as raw material, and electrolyte components of LiF 4.3-4.5%, KF 2.3-2.5%, and CaF 2 3.8-4.0％、MgF 2 0.7-0.8%, molar ratio (NaF/AlF) 3 )2.40 plus or minus 0.05, the bath temperature of 925 plus or minus 5 ℃, and the average superheat degree of 5 ℃. The electrolyte level is 18cm in the production process, the crust breaking breakdown rate of the feed opening is 80% in the alumina crust breaking and blanking process, the carbon residue coverage rate of the feed opening is 85% in the blanking process, and the blanking amount is 20-30% of the design deviation in the alumina blanking process. The control parameters of the alumina concentration are set as the periodic switching coefficient of the alumina concentration of 11 mu omega, the increment rate of 1.2, the decrement rate of 1.2, the maximum time of 25min for the excess period and the maximum time of 3min for the normal period. The lower concentration of alumina in the electrolyte was 1.0%.
Comparative example 3
Planar alumina is adopted as a raw material by a certain enterprise, and electrolyte components of LiF 5.6-6.0%, KF 2.8-3.0% and CaF 2 3.2-3.7％、MgF 2 1.3-1.5%, molar ratio (NaF/AlF) 3 )2.50 plus or minus 0.05, the bath temperature of 915 plus or minus 5 ℃ and the average superheat degree of 8 ℃. The electrolyte level is 18cm in the production process, the crust breaking breakdown rate of the feed opening is 85 percent in the alumina crust breaking and blanking process, the carbon residue coverage rate of the feed opening is 72 percent in the blanking process, and the blanking amount is 20-30 percent of the design deviation in the alumina blanking process. The control parameters of the alumina concentration are set as the periodic switching coefficient of the alumina concentration of 11 mu omega, the increment rate of 1.2, the decrement rate of 1.2, the maximum time of 25min for the excess period and the maximum time of 3min for the normal period. The lower concentration of alumina in the electrolyte is 1.1%.
Comparative example 4
Planar alumina is adopted as a raw material by a certain enterprise, and electrolyte components of LiF 5.6-6.0%, KF 2.8-3.0% and CaF 2 3.2-3.7％、MgF 2 1.3-1.5%, molar ratio (NaF/AlF) 3 )2.50 plus or minus 0.05, the bath temperature of 915 plus or minus 5 ℃ and the average superheat degree of 8 ℃. The electrolyte level is 17cm in the production process, the crust breaking breakdown rate of the feed opening is 72% in the alumina crust breaking and blanking process, the carbon residue coverage rate of the feed opening is 55% in the blanking process, and the blanking amount is 10% different from the design in the alumina blanking process. The control parameters of the alumina concentration are set as the periodic switching coefficient of the alumina concentration 11 mu omega, the increment rate 1.2, the decrement rate 1.2, the maximum time of the excess period 25min and the maximum time of the normal period 3 min. The lower concentration of alumina in the electrolyte is 1.1%.
Comparative example 5
Planar alumina is adopted as a raw material by a certain enterprise, and electrolyte components of LiF are 1.9-2.1%, KF is 1.9-2.1%, and CaF 2 4.8-5.2％、MgF 2 0.9-1.1%, molar ratio (NaF/AlF) 3 )2.30 plus or minus 0.05, the bath temperature of 940 plus or minus 5 ℃, and the average superheat degree of 12 ℃. The electrolyte level is 17cm in the production process, the crust breaking breakdown rate of the feed opening is 80% in the alumina crust breaking and blanking process, the carbon residue coverage rate of the feed opening is 80% in the blanking process, and the blanking amount is 10% different from the design in the alumina blanking process. The alumina concentration control parameters were set to an alumina concentration cycle switching coefficient of 11 μ Ω, an increment rate of 1.2, a decrement rate of 1.2, and an excessThe maximum time is 25min, and the maximum time in the normal period is 3 min. The lower concentration of alumina in the electrolyte is 1.1%.
Examples of the experiments
The perfluorocarbon emissions of examples 1-5 and comparative examples 1-5 were measured and are shown in the following table.
In combination with the above table, it can be seen from the comparison of example 1 and comparative example 1, the comparison of example 2 and comparative example 2, the comparison of example 3 and comparative example 3, the comparison of example 4 and comparative example 4, and the comparison of example 5 and comparative example 5 that the method for reducing the amount of perfluorocarbon emission for aluminum electrolysis provided by examples 1-5 of the present invention is effective in reducing the amount of perfluorocarbon emission, which is 800kg/t-Al or less, compared to comparative examples 1-5, and the amount of perfluorocarbon emission, which is 1760kg/t-Al or more, compared to comparative examples 1-5.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (9)
1. The method for reducing the discharge amount of perfluorocarbon in aluminum electrolysis is characterized by comprising the following steps:
placing alumina in an electrolytic bath for aluminum electrolysis to obtain electrolyte;
adding auxiliary materials into the electrolyte to regulate and control the components of the electrolyte;
controlling parameters of the electrolytic cell;
and controlling the blanking parameters of the alumina.
2. The method for reducing the emission of perfluorocarbons in aluminum electrolysis according to claim 1, wherein the step of adding an auxiliary material to the electrolyte to control the composition of the electrolyte comprises:
adding LiF, KF and MgF 2 And CaF 2 And controlling LiF, KF, MgF 2 And CaF 2 The content of (A);
control of NaF and AlF 3 In a molar ratio of (a).
3. The method for reducing the amount of perfluorocarbon emitted from aluminum electrolysis as recited in claim 2, wherein the composition of the electrolyte satisfies the following relationship:
CR＝3.334-0.0446×w(KF) electrolyte +0.0942×w(LiF) Electrolyte +0.0098×w(MgF 2 ) Electrolyte -0.0070×ΔT-0.0895×AO-0.0452×t+r；
Wherein:
CR represents NaF and AlF 2 The molar ratio of (A) to (B);
w(KF) electrolyte 、w(LiF) Electrolyte 、w(MgF 2 ) Electrolyte Respectively represent KF, LiF and MgF in the electrolyte 2 Mass fraction of (a);
Δ T represents the degree of superheat of the electrolyte in units of;
AO represents the type of alumina, when the alumina is in the form of a sheet: AO ═ 1, when the alumina is mesogenic: AO ═ 2, when the alumina is sandy: AO is 3;
t represents the time for completely dissolving 1 percent of alumina in the electrolyte molten salt, t is less than or equal to 20, and the unit is min;
r represents an adjustment constant, and r is 0 to 0.1.
4. The method of reducing aluminum electrolysis perfluorocarbon emissions as claimed in claim 1, wherein said controlling parameters of said electrolysis cell comprises:
controlling the average superheat degree of the electrolytic cell to be 8-15 ℃;
controlling the electrolyte level of the electrolytic cell.
5. The method for reducing the emission of perfluorocarbons in aluminum electrolysis according to claim 4, wherein the electrolyte level of the electrolytic cell is 19cm or more.
6. The method of reducing the amount of perfluorocarbon emitted from aluminum electrolysis as claimed in claim 1, wherein the controlling the alumina blanking parameters comprises:
controlling the crust breaking breakdown rate of the feed opening;
controlling the carbon slag coverage rate of the feed opening;
controlling the deviation between the blanking amount of the alumina and the theoretical value to be less than or equal to 10 percent;
controlling the concentration of the alumina.
7. The method for reducing the emission of perfluorocarbons in aluminum electrolysis according to claim 6, wherein the crust breaking rate of the feed opening is greater than or equal to 90%.
8. The method for reducing the emission of perfluorocarbons in aluminum electrolysis according to claim 6, wherein the coverage of the carbon slag at the feed opening is less than or equal to 80%.
9. The method for reducing the emission of perfluorocarbons in aluminum electrolysis according to claim 6, wherein the concentration of the alumina is 1.2% or more.
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| CN202210713148.4A CN115110120B (en) | 2022-06-22 | 2022-06-22 | Method for reducing emission of perfluorocarbon in aluminum electrolysis |
| PCT/CN2023/098543 WO2023246499A1 (en) | 2022-06-22 | 2023-06-06 | Method for reducing perfluorocarbon emissions from aluminum electrolysis |
| CA3237847A CA3237847A1 (en) | 2022-06-22 | 2023-06-06 | Method for reducing perfluorocarbon emissions from aluminum electrolysis |
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| WO2023246499A1 (en) * | 2022-06-22 | 2023-12-28 | 中国铝业股份有限公司 | Method for reducing perfluorocarbon emissions from aluminum electrolysis |
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| CN1873057A (en) * | 2006-04-28 | 2006-12-06 | 中国铝业股份有限公司 | Preparation method of lead electrobath for transitting to electrolysis in low termperature |
| CN205046205U (en) * | 2015-09-29 | 2016-02-24 | 贵州理工学院 | Full carbon fluoride suppression device of prebake aluminium cell |
| CN113373481A (en) * | 2021-05-27 | 2021-09-10 | 中国铝业股份有限公司 | Aluminum electrolysis method adopting potassium-rich aluminum oxide and having low carbon residue amount and high current efficiency |
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| CN101260543A (en) * | 2007-11-28 | 2008-09-10 | 河南中孚实业股份有限公司 | Method for adjusting aluminum electrolysis production technique |
| IN2015DN00211A (en) * | 2012-06-11 | 2015-06-12 | Inner Mongolia United Ind Co Ltd | |
| CN103352237B (en) * | 2013-06-25 | 2016-03-02 | 中国铝业股份有限公司 | The method of alumina density balance is set up under a kind of complicated electrolyte system |
| CN115110120B (en) * | 2022-06-22 | 2024-01-23 | 中国铝业股份有限公司 | Method for reducing emission of perfluorocarbon in aluminum electrolysis |
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| CN1873057A (en) * | 2006-04-28 | 2006-12-06 | 中国铝业股份有限公司 | Preparation method of lead electrobath for transitting to electrolysis in low termperature |
| CN205046205U (en) * | 2015-09-29 | 2016-02-24 | 贵州理工学院 | Full carbon fluoride suppression device of prebake aluminium cell |
| CN113373481A (en) * | 2021-05-27 | 2021-09-10 | 中国铝业股份有限公司 | Aluminum electrolysis method adopting potassium-rich aluminum oxide and having low carbon residue amount and high current efficiency |
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| WO2023246499A1 (en) * | 2022-06-22 | 2023-12-28 | 中国铝业股份有限公司 | Method for reducing perfluorocarbon emissions from aluminum electrolysis |
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| WO2023246499A1 (en) | 2023-12-28 |
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