CN113481542A

CN113481542A - Method and device for treating carbon slag and recycling electrolyte

Info

Publication number: CN113481542A
Application number: CN202110723011.2A
Authority: CN
Inventors: 包生重; 陈开斌; 张旭贵; 王珣; 曹韶峰; 刘彦辉; 李昌林; 汪艳芳
Original assignee: Aluminum Corp of China Ltd
Current assignee: Aluminum Corp of China Ltd
Priority date: 2021-06-28
Filing date: 2021-06-28
Publication date: 2021-10-08
Anticipated expiration: 2041-06-28
Also published as: CN113481542B

Abstract

The invention discloses a method and a device for treating carbon slag and recovering electrolyte, wherein the method comprises the steps of obtaining the carbon slag containing the electrolyte, the particle size of which is less than or equal to 12 cm; mixing an additive comprising carbonate with the carbon residue to obtain a first mixture; and (3) heating the first mixture to a temperature of more than or equal to 560 ℃ and less than 650 ℃ by adopting high-temperature flue gas discharged from a fire hole of the electrolytic cell, wherein the combustion reaction time is more than or equal to 6 hours, so as to treat the carbon residue and recover the electrolyte. By adopting the method, the recovery rate of the electrolyte in the carbon residue is 98.07-98.68%, the recovery rate is high, the carbon content is 0.18-0.2%, the impurity content is low, and the carbon residue hazardous waste can be prevented from being discharged outside in an electrolytic aluminum workshop; the method fully utilizes the waste heat of the electrolytic cell and does not produce secondary pollution, so the method is energy-saving, environment-friendly and pollution-free.

Description

Method and device for treating carbon slag and recycling electrolyte

Technical Field

The invention belongs to the technical field of non-ferrous aluminum smelting recovery, and particularly relates to a method and a device for treating carbon slag and recovering electrolyte.

Background

In the traditional aluminum electrolysis process, due to factors such as selective oxidation of the carbon anode, erosion and scouring of electrolyte and the like, part of carbon particles fall off from the anode and enter electrolyte melt to form carbon slag. Carbon residue in the electrolyte is harmful to the electrolytic production process, and therefore, the carbon residue is usually fished out by operators. However, the fished carbon residue contains more than 60 percent of fluoride electrolyte and belongs to dangerous waste (called dangerous waste for short). If the electrolyte in the carbon slag can not be effectively recovered and the carbon slag is directly discarded, not only a large amount of electrolyte is wasted, but also the environment is seriously polluted, therefore, an electrolytic aluminum enterprise must carry out innocent treatment in a factory or entrust unit treatment with hazardous waste treatment qualification.

Currently, the treatment of carbon slag generally comprises two methods, namely a wet method and a traditional fire method:

the wet treatment mainly adopts a flotation method to separate carbon in the carbon residue from electrolyte. The method has the advantages of low treatment cost, less labor amount, low labor intensity of workers and environment-friendly production process. However, the recovery rate of the electrolyte by the flotation method is not high, and the recovered carbon residue still contains a large amount of electrolyte and is still dangerous waste. For the electrolytic aluminum enterprises, only a small amount of electrolyte can be recovered through flotation, carbon slag cannot be eliminated, and the problem of carbon slag piling or consignment treatment is still faced.

The traditional pyrogenic process mainly adopts a high-temperature roasting furnace to carry out high-temperature roasting, so that carbon in carbon slag is burnt, and the remaining electrolyte is recovered and returned to an electrolysis plant, or the electrolyte is not recovered. And when the carbon slag is roasted at a high temperature, the electrolyte in the carbon slag can volatilize and is discharged along with the flue gas, so that the secondary environmental protection problem can be caused. In addition, a strong corrosive substance HF is generated, and the roasting furnace is severely corroded, so that the service life is short. Therefore, the traditional pyrogenic process has a severe treatment environment and high cost.

Therefore, a recovery method with high electrolyte recovery rate without increasing environmental burden is urgently required for aluminum electrolysis enterprises.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method and a device for treating carbon slag and recycling electrolyte, which can effectively treat carbon slag, have high electrolyte recycling rate, are environment-friendly and harmless, and can realize that no carbon slag dangerous waste is discharged outside an electrolysis workshop.

The technical scheme of the invention is as follows:

in one aspect, the present invention provides a method for treating carbon residue to recover electrolyte, the method comprising:

obtaining carbon slag containing electrolyte and with the grain diameter less than or equal to 12 cm;

mixing an additive comprising carbonate with the carbon residue to obtain a first mixture;

and heating the first mixture to a temperature of more than or equal to 560 ℃ and less than 650 ℃ by using high-temperature flue gas discharged from a fire hole of an electrolytic cell, and burning for reaction time of more than or equal to 6 hours to treat the carbon residue and recover the electrolyte.

Further, the combustion reaction time is 6-8 h.

Further, the carbonate is at least one of: sodium carbonate and calcium carbonate.

Further, the additive also comprises at least one of the following: hydrogen peroxide and aluminum fluoride.

Further, the mass ratio of the carbonate to the carbon slag is 1-5: 98-102.

Further, when the additive comprises hydrogen peroxide, the molar ratio of the carbonate to the hydrogen peroxide is 0.9-1.1: 1-2; when the additive comprises aluminum fluoride, the molar ratio of the carbonate to the aluminum fluoride is from 0.0 to 1.1: 1-4.

Further, the thickness of the first mixture is less than or equal to 5cm, and the mass fraction of oxygen in the gas used for combustion is more than or equal to 5%.

In a second aspect, the embodiment of the invention also provides a device for processing carbon residue and recovering electrolyte, which is used for the method, and is characterized in that the device comprises a crusher, a blending machine and a combustion box which are arranged in sequence according to the process, wherein,

the crusher is used for crushing the carbon slag containing the electrolyte into particles with the particle size less than or equal to 12 cm;

the mixing machine is used for mixing the additive containing carbonate with the carbon residue;

a tray is fixedly arranged in the combustion box and used for placing a first mixture formed by mixing an additive containing carbonate and carbon slag; and the box body of the combustion box is provided with an air inlet for introducing high-temperature flue gas discharged by the fire hole of the electrolytic cell, and the air inlet is used for enabling the high-temperature flue gas discharged by the fire hole of the electrolytic cell to enter the combustion box so as to heat the first mixture on the tray to a temperature of not less than 560 ℃ and less than 650 ℃ and burn for a time of not less than 6 hours.

Further, a heater is arranged at the bottom in the combustion box and is arranged below the tray.

Further, a temperature detector is arranged in the combustion box.

The beneficial effects of the invention at least comprise:

the invention provides a method and a device for treating carbon slag and recycling electrolyte, wherein the method comprises the steps of obtaining the carbon slag containing the electrolyte, the particle size of which is less than or equal to 12 cm; mixing an additive comprising carbonate with the carbon residue to obtain a first mixture; and (3) heating the first mixture to a temperature of more than or equal to 560 ℃ and less than 650 ℃ by adopting high-temperature flue gas discharged from a fire hole of the electrolytic cell, wherein the combustion reaction time is more than or equal to 6 hours so as to treat the carbon residue and recover the electrolyte. The invention increases the reaction area of carbon combustion reaction by controlling the particle size of the carbon slag and mixing the additive, overcomes the difficulty of combustion reaction caused by the wrapping of the carbon slag by the reflow electrolyte at high temperature, and ensures that the electrolyte in the carbon slag is not easy to volatilize due to the control of the heating temperature, thereby leading the carbon to be reacted into gas to be separated from the reflow electrolyte and achieving the purpose of recycling the electrolyte. By adopting the method, the recovery rate of the electrolyte is 98.07-98.68%, the recovery rate is high, the carbon content is 0.18-0.2%, the impurity content is low, and the carbon residue hazardous waste can be prevented from being discharged outside in an electrolytic aluminum workshop. The method fully utilizes the waste heat of the electrolytic cell, does not generate corrosive hydrogen fluoride gas, and does not generate secondary pollution, so the method is energy-saving, environment-friendly and pollution-free.

Drawings

FIG. 1 is a process diagram of a method for treating carbon residue and recovering electrolyte according to an embodiment;

FIG. 2 is a schematic structural diagram of an apparatus for processing carbon residue and recovering electrolyte according to an embodiment;

FIG. 3 is a schematic structural diagram of another apparatus for processing carbon residue and recovering electrolyte according to the embodiment;

fig. 4 is a schematic view of the structure of the combustion case in fig. 3.

Description of reference numerals:

101-combustion box, 102-electrolytic cell, 103-exhaust pipe, 104-flue gas pipeline, 105-valve, 106-air inlet pipe, 107-gas collecting hood, 108-fire hole at flue end of electrolytic cell, 109-insulating brick, 110-heater, 111-oxygen content sensor, 112-temperature sensor, 113-tray, 114-first mixture, 115-instrument control box, 116-temperature detector, 117-carbon residue box, 118-crusher, 119-tray rack and 120-gas collecting pipeline.

Detailed Description

In order to make the present application more clearly understood by those skilled in the art to which the present application pertains, the following detailed description of the present application is made with reference to the accompanying drawings by way of specific embodiments.

In order to solve the technical problems, the embodiment of the invention provides the following general ideas:

in one aspect, an embodiment of the present invention provides a method for treating carbon residue to recover electrolyte, where the method includes:

s1, obtaining the carbon residue containing electrolyte and with the grain size less than or equal to 12 cm;

the carbon slag is formed by that in the process of producing aluminum by electrolysis, carbon anode selective oxidation or electrolyte erosion scouring and other factors, part of carbon particles fall off and enter an electrolyte melt, and the carbon slag is fished out and becomes a block together with solidified electrolyte, and is crushed into the carbon slag with small particle size, so that the reaction area is increased, and the electrolyte is recovered. Generally, the mass fraction of the electrolyte in the carbon residue is 60-90%, the mass fraction of the impurity lithium fluoride is 0.5-5.5%, and the mass fraction of the impurity potassium fluoride is 0.5-5%.

S2, mixing an additive containing carbonate with the carbon slag to obtain a first mixture;

as an implementation manner of the embodiment of the present invention, a mass ratio of the carbonate to the carbon residue is 1-5: 98-102.

The electrolyte in the carbon residue is a mixture containing fluoroaluminate compounds and impurity elements of lithium and potassium, wherein the molar ratio of aluminum fluoride to sodium fluoride in the fluoroaluminate is dynamically adjustable. At high temperatures, the electrolyte in the carbon residue becomes a soft mixture, and the carbon is solid at the temperature, so that in a very small range, the solid carbon residue is wrapped by the soft electrolyte to prevent the reaction from proceeding. The carbonate is added, which can chemically react with fluoroaluminate in the electrolyte to form metal fluoride and carbon dioxide gas, and the generation of the metal fluoride can reduce the proportion of impurity elements lithium and potassium with very good wettability in the electrolyte, so that the overall wettability of the electrolyte is reduced, the electrolyte in a soft melting state is not beneficial to wrapping carbon, and carbon has a larger reaction contact area so as to be beneficial to removing carbon; in addition, the generated carbon dioxide gas can also enable the electrolyte at the periphery of the carbon to generate pores, so that the dynamic condition of the carbon combustion reaction is further improved; moreover, the produced carbon dioxide can also react with carbon in the carbon residue to generate carbon monoxide, and the carbon monoxide is combusted to form carbon dioxide to be discharged, so that the reaction is promoted. Excessive addition of carbonate can cause excessive carbonate, particularly calcium carbonate can introduce impurity element calcium, which has influence on the quality of the recovered electrolyte; the addition of too little carbonate may not promote a significant reaction rate.

As an embodiment of the present invention, the carbonate includes, but is not limited to, at least one of the following: sodium carbonate and calcium carbonate.

In the invention, the carbonate with both effect and cost is sodium carbonate, and calcium carbonate can be selected, and calcium carbonate is not suitable to be added because calcium carbonate can introduce an impurity element of calcium.

As an embodiment of the present embodiment, the additive further includes, but is not limited to, at least one of the following: hydrogen peroxide and aluminum fluoride. Spraying hydrogen peroxide liquid which can provide oxygen to accelerate the combustion of carbon in the carbon residue in the reaction process; the addition of aluminum fluoride can reduce the molecular ratio of the electrolyte (the molecular ratio refers to the molar ratio of sodium fluoride to aluminum fluoride in the electrolyte), thereby reducing the wettability of the electrolyte and carbon, so that the electrolyte in a soft melting state is not beneficial to wrapping carbon, and the carbon has a larger reaction contact area, so that the carbon is beneficial to removing the carbon.

As an embodiment of the embodiments of the present invention, when the additive comprises hydrogen peroxide, the molar ratio of the carbonate to the hydrogen peroxide is 0.9-1.1: 1-2.

Hydrogen peroxide can be used as oxygen for accelerating combustion in the present invention, but it is added too much, which may cause explosion and is poor in safety, and therefore, it is necessary to control the amount of hydrogen peroxide added.

As an embodiment of the embodiments of the present invention, when the additive comprises aluminum fluoride, the molar ratio of the carbonate to the aluminum fluoride is 0.9-1.1: 1-4. The cost of the aluminum fluoride is high, and the treatment cost is greatly increased due to the excessive addition quality of the aluminum fluoride; the addition of aluminum fluoride is too low in mass, and the effect of promoting the reaction is not obvious.

As an implementation of the embodiment of the invention, the thickness of the first mixture is less than or equal to 5 cm.

The first mixture has a small thickness, and can increase the reaction area and promote the carbon combustion reaction.

And S3, heating the first mixture to a temperature of more than or equal to 560 ℃ and less than 650 ℃ by using high-temperature flue gas discharged from a fire hole of the electrolytic cell, and carrying out combustion reaction for more than or equal to 6 hours to treat the carbon residue and recover the electrolyte.

In the temperature range of more than or equal to 560 ℃ and less than 650 ℃, the carbon in the carbon slag can be fully combusted, and the electrolyte in the carbon slag can not be obviously melted and volatilized, so that the electrolyte is left in a solid state. The heating temperature is too low, which is not beneficial to the generation of carbon combustion reaction; the heating temperature is too high, so that a large amount of electrolyte is volatilized, and the recovery rate of the electrolyte is reduced; too short a combustion reaction time may reduce the purity of the recovered electrolyte. In the traditional roasting furnace, coal, natural gas and the like are used as heating heat sources, the coal and the natural gas contain carbon and hydrogen, the hydrogen can be converted into water to be mixed in combustion flue gas in the combustion process, and electrolyte can chemically react with water in the flue gas to generate a large amount of HF with strong corrosivity under the heating condition. The method of the invention can treat the waste carbon residue generated in the electrolysis process in the electrolysis workshop, so that the electrolysis workshop does not discharge the carbon residue hazardous waste.

As an implementation of the inventive example, the combustion reaction time may be 6-8 h. The combustion reaction time is too long, which can cause energy waste.

As an embodiment of the present invention, the gas such as carbon dioxide generated in the above reaction process may be discharged into a purification system of an electrolysis plant, and the remaining electrolyte may be returned to the electrolysis bath or stored for later use.

In another aspect, an embodiment of the present invention provides an apparatus for processing carbon residue and recovering electrolyte, which is used for implementing the above method, and the apparatus includes a crusher, a mixer, and a combustion box 101, which are arranged in sequence according to a process, wherein,

a tray 113 is fixedly arranged in the combustion box 101, and the tray 113 is used for placing a first mixture formed by mixing an additive containing carbonate and carbon slag; an air inlet for introducing high-temperature flue gas discharged by the fire hole of the electrolytic cell is formed in the box body of the combustion box 101, the air inlet is used for enabling the high-temperature flue gas discharged by the fire hole of the electrolytic cell to enter the combustion box so as to heat the first mixture on the tray to a temperature which is more than or equal to 560 ℃ and less than 650 ℃, and the combustion reaction lasts for more than or equal to 6 hours.

Referring to fig. 1, the air inlet of the combustion box can be communicated with the upper end of the gas collecting hood 107 for collecting high-temperature flue gas from the flue end fire hole 108 of the electrolytic cell through the air inlet pipe 106, the air inlet of the combustion box can be provided with an oxygen content sensor 111 and a temperature sensor 112, and the oxygen content sensor 111 and the temperature sensor 112 are both connected with a monitoring instrument box 115 arranged outside the combustion box 101 so as to monitor the temperature of the air inlet of the combustion box and the oxygen content of the entering gas.

Specifically, referring to fig. 1, in this embodiment, a plurality of trays 113 may be arranged in layers, and the thickness of the first mixture placed on each tray 113 is less than or equal to 5cm, wherein the tray may be made of 310s stainless steel, or may be made of other materials that do not affect the separation of the electrolyte, and are not limited specifically herein.

Further, referring to fig. 1, in the present embodiment, the heater 110 may be disposed at the bottom of the combustion chamber 101, the heater 110 may be disposed below the tray 113, the heater 110 may be activated to perform auxiliary heating when the temperature of the combustion chamber 101 is lower than 560 ℃, and the heater 110 may be deactivated when the temperature of the combustion chamber 101 is higher than 650 ℃. Specifically, the heater 110 may be heated by direct current or alternating current.

Furthermore, referring to fig. 1, the top of the combustion box 101 is provided with a gas outlet for discharging gas, and the gas outlet of the combustion box 101 is communicated with the flue gas duct 104 of the electrolytic cell through the exhaust pipe 103, so that high-temperature flue gas discharged from the fire hole can be sucked into the combustion box 101 by using the negative pressure in the flue gas duct of the electrolytic cell, and gas such as carbon dioxide generated by combustion can be discharged into the flue gas duct 104 to enter the purification system of the electrolytic plant. In addition, a valve 105 may be provided in the exhaust pipe 103 to control the opening degree and control the suction negative pressure.

Further, referring to fig. 2, a temperature detector 116 may be disposed in the combustion chamber 101 for detecting the temperature in the combustion chamber 101, and more specifically, the temperature detector 116 may be disposed above the uppermost tray 113, and the temperature detector 116 may be a thermocouple having a data transmission function, and the thermocouple may be connected to the monitoring instrument box 115 to monitor the temperature above the tray 113.

In order to improve the heat preservation effect in the combustion box, in this embodiment, the heat preservation brick 109 can be fixedly arranged at the top in the combustion box, and the heat preservation brick 109 is arranged at the lower part of the gas outlet, so that the heat preservation brick 109 is provided with a through hole so that the gas can be conveniently moved to the gas outlet and discharged. The insulating brick 109 can be made of high-alumina insulating bricks, and plays a role in heat preservation and heat storage.

Of course, in order to improve the recovery efficiency of the electrolyte in the carbon slag, a plurality of combustion boxes can be arranged, the air inlet of each combustion box is communicated with the pipe body of the air inlet pipe 106, the air outlet of each combustion box is communicated with the pipe body of the exhaust pipe 103, and thus the plurality of combustion boxes work simultaneously; the air inlet pipe 106 can be communicated with the high-temperature flue gas collecting hood 107 corresponding to the flue end fire holes 108 of the plurality of electrolytic cells, so that a plurality of combustion boxes can form a centralized combustion box, and the collection and utilization of the high-temperature flue gas of the flue end fire holes of the plurality of electrolytic cells are realized.

Further, referring to fig. 3, the plurality of combustion boxes may be arranged in a straight line, first openings are disposed on both sides of the middle combustion box along a straight line direction and sequentially communicated with each other through the first openings, a second opening is disposed on one side of the side portion of the combustion box close to the middle combustion box, and the first opening of the side portion of the combustion box is communicated with the second opening of the adjacent combustion box, so that a large heating and combustion reaction chamber is formed inside the plurality of combustion boxes.

In addition, when the arrangement of the plurality of combustion boxes is adopted, with reference to fig. 3, according to the space, the charcoal slag box 117, the crusher 118 and the tray rack 119 may be further reasonably arranged, wherein the charcoal slag box 17 may be used for collecting and storing charcoal slag, the crusher 118 may be further provided with a gas collection pipeline, and smoke generated in the charcoal slag crushing process is discharged into the flue gas pipeline through the gas collection pipeline 120 and is processed; the pallet rack 119 may be used to place pallets.

The method for treating carbon residue to recover electrolyte provided by the invention will be described with reference to specific examples and comparative examples.

Example 1

A burning box is arranged at the flue end of a 400kA electrolytic cell of an electrolytic aluminum enterprise, as shown in figure 1. The 400kA cell produced a total of about 30kg of char residue per day (about 10kg per 8 hours).

1) The carbon residue to be treated generated after the electrolysis of the electrolytic cell is smashed to ensure that the granularity of the carbon residue is less than 12 cm. Mixing carbon slag particles and sodium carbonate according to a mass ratio of 3: 100, mixing by using a mixer to form a first mixture, subpackaging the first mixture in three trays 113, wherein each tray 113 contains 4kg, and the charcoal slag is spread to be less than 5cm in thickness;

2) the tray 113 is placed in the combustion chamber of the combustion box 101, and the box door is closed;

3) opening a valve 105 on the exhaust pipe 103 to enable high-temperature flue gas discharged from a fire hole at the flue end of the electrolytic cell to enter the combustion box 101; in the process, according to the temperature display of the instrument, when the temperature in the combustion box is lower than 560 ℃, auxiliary heating is started. The auxiliary heating adopts direct current which is taken from a bus of an upright post of the electrolytic cell and a wiring terminal at a short-circuit port. The voltage difference of the two wiring terminals is 3.82V, the direct current on the copper cable is measured to be 1.6kA, and the heating power of the auxiliary heating device is about 6.1 kW. And when the temperature in the combustion box is higher than 650 ℃, the auxiliary heating is cut off. According to the oxygen content of the instrument, when the oxygen content in the combustion box is lower than 5%, the position of the gas collecting hood of the air inlet pipe is slightly moved, and the air inlet amount is increased, so that the oxygen content is larger than 10%. In example 1, the temperature in the combustion chamber was controlled to 565 ℃.

4) The carbon slag is burned in the combustion box 101 for 7 hours, the color is changed into grey white, and the original granular carbon slag plates are agglomerated into blocks to form solid electrolyte.

5) Taking out the solid electrolyte left after burning the carbon slag, and directly putting the solid electrolyte into an electrolytic cell or storing the solid electrolyte for later use.

The treatment was carried out 3 times a day by the method provided in example 1, and the total amount of carbon slag in the electrolytic cell was about 30kg, and 22.5kg of the electrolyte was recovered in total. The total working time of the auxiliary heating system is accumulated to be 4.5h every day, and the accumulated consumed direct current is 27.5 kwh. The average power consumption per kilogram of carbon slag is 0.917 kwh/kg. The recovered electrolyte was sampled and subjected to carbon content analysis, and the carbon content was about 0.18%, which was substantially equivalent to the analysis result of the carbon content of the electrolyte in the electrolytic cell. The carbon slag treatment speed, the treatment effect and the economy all achieve the expected effect.

Example 2

In a reserved area of a work area of a 400kA electrolytic plant of an electrolytic aluminum enterprise, a centralized combustion box is arranged, as shown in figures 3-4.

The work area is provided with 36 400kA electrolytic cells, about 360kg of carbon slag is generated every 8 hours, and about 1080kg of carbon slag is generated in total every day.

1) Carbon slag in the whole work area of the electrolysis workshop is intensively placed in a carbon slag box 117, and the carbon slag is crushed in a crusher 118 to become carbon slag particles with the particle size of less than 12 mm; the crushing process opens the gas collection duct 120 to discharge the fumes into the flue gas duct 104.

2) Mixing the crushed carbon slag into industrial AlF accounting for 5 percent of the mass of the carbon slag₃And calcium carbonate accounting for 1% of the mass of the carbon slag, mixing to form a first mixture, loading the first mixture into trays, wherein each tray contains 8kg of carbon slag, and the carbon slag is flattened to a thickness of less than 5 cm; putting the tray filled with the carbon slag particles into a combustion chamber of a combustion box, and closing a box door;

3) and (3) opening a valve on the exhaust pipe 103, enabling high-temperature flue gas discharged from a fire hole at the flue end of the electrolytic cell to enter a combustion box for heating and combustion, and starting auxiliary heating when the temperature in the combustion box is lower than 560 ℃ according to the temperature display of the instrument control box 115 in the process. The auxiliary heating adopts direct current which is taken from a wiring terminal at a short circuit port of an upright post bus of the electrolytic cell. When the circuit is on, the DC voltage of the auxiliary heating device is about 4V. The total direct current on the copper cable was measured to be 17.1kA and the heating power of the auxiliary heating was about 68.4 kW. And when the temperature in the combustion box is higher than 650 ℃, the auxiliary heating is cut off. According to the oxygen content display of the instrument, when the oxygen content in the combustion box is lower than 5%, the position of the gas collecting hood of the air inlet pipe is slightly moved, the air inlet amount is increased, or an opening control valve on the exhaust pipe is opened to enable the oxygen content to be higher than 10%. In example 2, the temperature in the combustion chamber was controlled to 595 ℃ and the volume fraction of oxygen was 11%.

4) The carbon slag is burnt in the burning box for 6.5 hours, the color of the burnt carbon slag is changed into grey white, and the original granular carbon slag plates are agglomerated into blocks to form solid electrolyte.

7) Taking out the solid electrolyte left after burning the carbon slag, and directly putting the solid electrolyte into an electrolytic cell or storing the solid electrolyte for later use.

The treatment effect is as follows:

1) the treatment is carried out for 3 times every day, the total carbon residue of thirty-six electrolytic tanks in the work area is treated, the total amount is about 1080kg, and the accumulated recovered electrolyte is about 752 kg. The total working time of the auxiliary heating system is accumulated to be about 12 hours each day, and the accumulated consumed direct current is about 820.8 kwh. The average power consumption per kilogram of carbon residue is 0.76 kwh/kg.

2) The recovered electrolyte is sampled and analyzed for carbon content, and the carbon content is 0.2 percent, which is basically equivalent to the average value of the analysis results of the carbon content of the electrolyte in a plurality of electrolytic cells in the work area.

3) The carbon slag treatment speed, the treatment effect and the economy all achieve the expected effect.

Example 3

Example 3 referring to example 1, example 3 differs from example 1 in that:

spraying hydrogen peroxide accounting for 30% of the mass fraction of the sodium carbonate on the surface of the first mixture, wherein the mass ratio of the carbon slag particles to the sodium carbonate is 5: 100, heating temperature 610 ℃, the rest is the same as example 1.

The treatment effect is as follows:

1) the treatment is carried out 3 times per day, the total carbon residue in the tank is treated, the total amount is about 30kg, and the accumulated recovered electrolyte is about 21.8 kg. The accumulated consumption of the alternating current of the auxiliary heating system is about 24kwh every day, and the average power consumption of each kilogram of carbon slag is 0.8 kwh/kg.

2) The recovered electrolyte was sampled and subjected to carbon content analysis, and the carbon content was about 0.191%, which was substantially equivalent to the analysis result of the carbon content of the electrolyte in the electrolytic cell.

Example 4

Example 4 referring to example 1, example 4 is different from example 1 in that the mass ratio of the carbon residue particles to the sodium carbonate is 4: 100, and the temperature in the combustion chamber is 630 ℃ during the combustion process.

Example 5

Example 5 referring to example 2, example 5 differs from example 2 in that: hydrogen peroxide accounting for 60 percent of the mass fraction of the calcium carbonate is sprayed in the first mixture.

The treatment effect is as follows:

1) the treatment is carried out for 3 times every day, the total carbon residue of thirty-six electrolytic tanks in the work area is treated, the total amount is about 1080kg, and the accumulated recovered electrolyte is about 752 kg. The auxiliary heating system consumes an alternating current of about 768kwh per day. The average power consumption per kilogram of carbon residue is 0.711 kwh/kg.

2) The recovered electrolyte was sampled and subjected to carbon content analysis, and the carbon content was about 0.196%, which was substantially equivalent to the average value of the results of carbon content analysis of the electrolyte in the plurality of electrolytic cells in the work area.

Comparative example 1

Comparative example 1 provides a method for recovering electrolyte from electrolytic carbon residue, comprising,

weighing 1000 g of aluminum electrolysis carbon slag with the granularity of less than 3mm, adding 10 g of clean coal with the granularity of less than 3mm and 100 g of industrial pure calcium fluoride, uniformly mixing the three materials, roasting the mixed material at 850 ℃ (TC for 1 hour to obtain an electrolyte with good dispersibility after roasting, and analyzing that the content of impurities in the electrolyte is 0.20 percent and the impurities are mainly oxides of iron and silicon.

Comparative example 2

Comparative example 2 provides a method for recovering electrolyte from carbon residue, and the difference between comparative example 2 and example 1 is that the particle size of carbon residue is less than or equal to 30mm, the heating temperature is 720 ℃, and the burning time is 10 hours.

Comparative example 3

Comparative example 3 provides a method for recovering electrolyte from carbon residue, and the difference between comparative example 3 and example 1 is that the particle size of carbon residue is less than or equal to 30mm, the heating temperature is 500 ℃, and the burning time is 4 hours.

TABLE 1

Table 1 shows data collected during the treatment of the methods of examples 1 to 5 of the present invention and comparative examples 1 to 3, and it can be seen from the data in Table 1 that:

in the embodiments 1 to 5 of the invention, the recovery rate of the electrolyte in the carbon residue is 98.07 to 98.68 percent, the recovery rate is high, the mass fraction of carbon in the recovered electrolyte is 0.18 to 0.22 percent, the impurities are few, the electricity consumption per kilogram of the carbon residue is 0.76 to 0.917kwh/kg, the electricity consumption is low, and corrosive HF gas is not generated. Only examples 3 and 5, only a small amount of HF gas was detected due to the use of hydrogen peroxide as an additive.

The method for recycling the carbon residue electrolyte provided by the comparative example 1 adopts coal as a heating source, the recycling rate of the electrolyte in the carbon residue is 88 percent, the recycling rate is not as high as that of the method provided by the invention in the examples 1-5, the mass fraction of the carbon in the recycled electrolyte is 0.16 percent, and a large amount of corrosive HF gas is generated.

The method for recycling the carbon residue electrolyte provided by the comparative example 2 has the advantages that the recycling rate of the electrolyte in the carbon residue is 85.96 percent, the recycling rate is lower than that of the method in the examples 1 to 5, the mass fraction of carbon in the recycled electrolyte is 9.1 percent, the impurity content is high, the electricity consumption per kilogram of the carbon residue is 1.558kwh/kg, and the electricity consumption is high.

The invention provides a method and a device for treating carbon slag and recycling electrolyte, wherein the method comprises the steps of obtaining the carbon slag containing the electrolyte, the particle size of which is less than or equal to 12 cm; mixing an additive comprising carbonate with the carbon residue to obtain a first mixture; the first mixture is heated to a temperature of more than or equal to 560 ℃ and less than 650 ℃, the combustion reaction lasts for more than or equal to 6 hours, gases such as carbon dioxide and the like generated in the reaction process are discharged into an electrolytic workshop purification system, and the rest electrolyte is returned to an electrolytic tank or stored for later use, so that the purpose of treating the carbon slag and recovering the electrolyte is achieved. By adopting the method, the recovery rate of the electrolyte is 98.07-98.68%, the recovery rate is high, the carbon content is 0.18-0.2%, the impurity content is low, and the carbon residue hazardous waste can be prevented from being discharged outside in an electrolytic aluminum workshop. The method makes full use of the waste heat of the electrolytic bath, so that corrosive hydrogen fluoride gas is not generated, secondary pollution is not generated, and the method is energy-saving, environment-friendly and pollution-free.

While the preferred embodiments of the present application 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 alterations and modifications as fall within the scope of the application.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims

1. A method for treating carbon residue to recover electrolyte, the method comprising:

and (3) heating the first mixture to a temperature of more than or equal to 560 ℃ and less than 650 ℃ by adopting high-temperature flue gas discharged from a fire hole of the electrolytic cell, wherein the combustion reaction time is more than or equal to 6 hours, so as to treat the carbon residue and recover the electrolyte.

2. The method for processing carbon residue to recover electrolyte as claimed in claim 1, wherein the combustion reaction time is 6-8 h.

3. The method for processing carbon residue to recover electrolyte as claimed in claim 1, wherein the carbonate is at least one of the following: sodium carbonate and calcium carbonate.

4. A method for processing carbon residue to recover electrolyte as claimed in claim 1, wherein the additive further comprises at least one of: hydrogen peroxide and aluminum fluoride.

5. The method for treating carbon slag to recover electrolyte according to claim 1, wherein the mass ratio of the carbonate to the carbon slag is 1-5: 98-102.

6. The method for treating carbon residue to recover electrolyte as claimed in claim 4, wherein when the additive comprises hydrogen peroxide, the molar ratio of the carbonate to the hydrogen peroxide is 0.9-1.1: 1-2; when the additive comprises aluminum fluoride, the molar ratio of the carbonate to the aluminum fluoride is from 0.9 to 1.1: 1-4.

7. The method for processing carbon slag to recover electrolyte as claimed in claim 1, wherein the thickness of the first mixture is not more than 5cm, and the mass fraction of oxygen in the gas used for combustion is not less than 5%.

8. A device for processing carbon slag and recovering electrolyte is used for realizing the method of any one of claims 1 to 7, and is characterized by comprising a crusher, a blending machine and a combustion box which are sequentially arranged according to the process, wherein,

a tray is fixedly arranged in the combustion box and used for placing a first mixture formed by mixing an additive containing carbonate and carbon slag; and an air inlet for introducing high-temperature flue gas discharged by the fire hole of the electrolytic cell is formed in the box body of the combustion box, and the air inlet is used for enabling the high-temperature flue gas discharged by the fire hole of the electrolytic cell to enter the combustion box so as to heat the first mixture on the tray to a temperature of not less than 560 ℃ and less than 650 ℃ for combustion reaction for a time of not less than 6 hours.

9. An apparatus for processing carbon residue to recover electrolyte as claimed in claim 8, wherein a heater is disposed at the bottom of the combustion chamber, and the heater is disposed below the tray.

10. An apparatus for processing carbon residue and recovering electrolyte as claimed in claim 8, wherein a temperature detector is disposed in the combustion chamber.