CN113481542B - A method and device for processing carbon residue and recovering electrolyte - Google Patents

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

A method and device for processing carbon residue and recovering electrolyte

technical field

The invention belongs to the technical field of non-ferrous aluminum smelting and recycling, and in particular relates to a method and a device for processing carbon residue and recycling electrolyte.

Background technique

In the traditional aluminum electrolysis process, due to the selective oxidation of the carbon anode and the erosion and erosion of the electrolyte, some carbon particles always fall off from the anode and enter the electrolyte melt to form carbon slag. The carbon residue is in the electrolyte, which is harmful to the electrolysis production process, so it is usually removed by the operator. However, the removed carbon residue contains more than 60% of fluoride electrolyte, which belongs to hazardous waste (referred to as hazardous waste). If the electrolyte in the carbon residue cannot be effectively recovered, and the carbon residue is directly discarded, it will not only lead to a large amount of waste of electrolyte, but also seriously pollute the environment. Therefore, electrolytic aluminum enterprises must carry out harmless treatment in the factory or entrust it with danger. Qualified waste disposal units.

At present, the treatment of carbon residue usually has two types: wet method and traditional fire method:

The wet treatment mainly adopts the method of flotation to separate the carbon and the electrolyte in the carbon residue. The method has the advantages of low processing cost, low labor consumption, low labor intensity of workers, and environment-friendly production process. However, the recovery rate of electrolyte by flotation method is not high, and the recovered carbon residue still contains a large amount of electrolyte, which is still hazardous waste. For electrolytic aluminum enterprises, only a small amount of electrolyte can be recovered through flotation, but carbon residue cannot be eliminated, and they still face the problem of carbon residue storage or entrusted treatment.

The traditional fire treatment mainly uses a high-temperature roaster for high-temperature roasting, burns the carbon in the carbon residue, recovers the remaining electrolyte, and returns it to the electrolysis plant, or does not recover the electrolyte. During high temperature roasting, the electrolyte in the carbon residue will volatilize and be discharged with the flue gas, which will bring about secondary environmental protection problems. In addition, a strong corrosive substance HF will be generated, the roasting furnace will be severely corroded, and the service life is very short. Therefore, the traditional fire processing environment is harsh and the cost is high.

Therefore, for aluminum electrolysis enterprises, there is an urgent need for a recycling method with a high electrolyte recovery rate without increasing the environmental burden.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned technical problems, the present invention provides a method and device for processing carbon residue and recovering electrolyte, which can effectively process carbon residue, has high electrolyte recovery rate, and is environmentally friendly and harmless. waste.

The technical scheme of the present invention is:

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

Obtaining carbon residue containing electrolyte with particle size ≤12cm;

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

The first mixture is heated to a temperature of ≥560°C and <650°C by using high-temperature flue gas discharged from the flame of the electrolytic cell, and the combustion reaction time is ≥6h, so as to process the carbon residue and recover the electrolyte.

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

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

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

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

Further, when the additive includes hydrogen peroxide, the molar ratio of the carbonate to the hydrogen peroxide is 0.9-1.1:1-2; when the additive includes aluminum fluoride, the carbonic acid The molar ratio of salt to the aluminum fluoride is 0.0-1.1:1-4.

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

In the second aspect, the embodiment of the present invention also provides a device for processing carbon residue and recovering electrolyte, which is used in the above-mentioned method. It is characterized in that, the device includes a crusher, a mixer and a combustion box arranged in sequence according to the process, in,

The crusher is used for crushing the carbon residue containing electrolyte into a particle size of less than or equal to 12cm;

The mixer is used for mixing additives including carbonate with carbon residue;

A tray is fixed in the combustion box, and the tray is used to place the first mixture formed by mixing the additive including carbonate with the carbon residue; the box body of the combustion box is provided with a flame hole for passing into the electrolytic cell and discharging The air inlet of the high temperature flue gas, the air inlet is used to make the high temperature flue gas discharged from the fire hole of the electrolytic cell enter the combustion box to heat the first mixture on the tray to ≥ 560 ° C and < 650 ° C Burning time ≥ 6 hours at the temperature.

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

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

The beneficial effects of the present invention at least include:

The present invention provides a method and device for treating carbon residue and recovering electrolyte. The method includes: obtaining carbon residue containing electrolyte with a particle size of less than or equal to 12 cm; mixing an additive including carbonate with the carbon residue to obtain a first The mixture; the first mixture is heated to a temperature of ≥560°C and <650°C by using the high-temperature flue gas discharged from the flame eye of the electrolytic cell, and the combustion reaction time is ≥6h, so as to process the carbon residue and recover the electrolyte. The invention increases the reaction area of the carbon combustion reaction by controlling the particle size of the carbon slag and mixing additives, and overcomes the obstacle of difficult combustion reaction caused by the carbon slag being wrapped by the reflowed electrolyte at high temperature. Due to the heating temperature control, the electrolyte in the carbon slag is difficult to volatilization, so that the carbon is reacted into gas and separated from the reflowed electrolyte, so as to achieve the purpose of recovering the electrolyte. By adopting the method of the invention, the recovery rate of the electrolyte is 98.07-98.68%, the recovery rate is high, the carbon content is 0.18-0.2%, and the impurity content is low, so that the electrolytic aluminum workshop can no longer discharge carbon slag hazardous waste. Since the method makes full use of the residual heat of the electrolytic cell, no corrosive hydrogen fluoride gas is generated, and no secondary pollution is generated, so the method is energy-saving, environmentally friendly, and pollution-free.

Description of drawings

Fig. 1 is the process diagram of a kind of processing carbon residue recovery electrolyte method of embodiment;

Fig. 2 is the structural representation of a kind of processing carbon residue recovery electrolyte device according to the embodiment;

3 is a schematic structural diagram of another device for processing carbon residues and recovering electrolyte according to the embodiment;

FIG. 4 is a schematic structural diagram of the combustion box in FIG. 3 .

Description of reference numbers:

101- Combustion box, 102- Electrolyzer, 103- Exhaust pipe, 104- Flue gas pipe, 105- Valve, 106- Intake pipe, 107- Gas collecting hood, 108- Electrolyzer flue end fire eye, 109- Insulation 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 - Pallet rack, 120-Gas collection duct.

Detailed ways

In order to make the application more clearly understood by those skilled in the technical field to which the application belongs, the technical solutions of the application are described in detail below with reference to the accompanying drawings and through specific embodiments.

The technical solutions provided by the embodiments of the present invention are to solve the above-mentioned technical problems, and the general idea is as follows:

In one aspect, an embodiment of the present invention provides a method for processing carbon residue to recover electrolyte, the method comprising:

S1, obtaining a carbon residue containing electrolyte with a particle size of ≤12 cm;

Carbon slag is formed by the selective oxidation of carbon anode or the erosion and scouring of electrolyte in the process of electrolytic production of aluminum, and some carbon particles fall off into the electrolyte melt. The carbon residue with small particle size is beneficial to increase the reaction area, which is beneficial to the recovery of the electrolyte. Generally speaking, the mass fraction of electrolyte in the carbon residue is 60-90%, the mass fraction of impurity lithium fluoride is 0.5-5.5%, and the mass fraction of impurity potassium fluoride is 0.5-5%.

S2, mixing an additive including carbonate with the carbon residue to obtain a first mixture;

As an implementation of the embodiment of the present invention, the 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 lithium and potassium, in which the molar ratio of aluminum fluoride and sodium fluoride in the fluoroaluminate is dynamically adjustable. At high temperature, the electrolyte in the carbon residue will become a soft mixture, and the carbon is still solid at this temperature, so that in a very small range, the soft electrolyte will wrap the solid carbon residue and prevent the reaction from proceeding. Carbonate is added, which can chemically react with fluoroaluminate in the electrolyte to form metal fluoride and carbon dioxide gas. The formation of metal fluoride can reduce the proportion of lithium and potassium impurity elements with very good wettability in the electrolyte. , thereby reducing the overall wettability of the electrolyte, so that the electrolyte in the reflow state is not conducive to wrapping the carbon, so that the carbon has a larger reaction contact area to facilitate the removal of carbon; The electrolyte produced by the slag can generate pores, which further improves the kinetic conditions of the carbon combustion reaction; in addition, the produced carbon dioxide can also react with the carbon in the carbon residue to generate carbon monoxide, and the carbon monoxide is burned to form carbon dioxide and discharged, which promotes the reaction. Too much carbonate added may cause excess carbonate, especially calcium carbonate, which will introduce impurity element calcium, which will affect the quality of the recovered electrolyte; too little carbonate may increase the reaction rate. obvious.

As an implementation of the 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 present invention, the carbonate that has both effect and cost is sodium carbonate, and calcium carbonate can also be selected. Since calcium carbonate will introduce impurity element calcium, calcium carbonate should not be added too much.

As an implementation of the embodiments of the present invention, the additives further include, but are not limited to, at least one of the following: hydrogen peroxide and aluminum fluoride. Spray some hydrogen peroxide liquid, which can provide oxygen during the reaction to accelerate the combustion of carbon in the carbon residue; the addition of aluminum fluoride can reduce the molecular ratio of the electrolyte (the molecular ratio here refers to the sodium fluoride and aluminum fluoride in the electrolyte. molar ratio), thereby reducing the wettability of the electrolyte and carbon, so that the electrolyte in the reflow state is not conducive to wrapping the carbon, so that the carbon has a larger reaction contact area to facilitate the removal of carbon.

As an implementation of the embodiment of the present invention, when the additive includes 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 to provide accelerated combustion in the present invention, but adding too much may cause explosion and poor safety. Therefore, the added amount of hydrogen peroxide needs to be controlled.

As an implementation of the embodiment of the present invention, when the additive includes aluminum fluoride, the molar ratio of the carbonate to the aluminum fluoride is 0.9-1.1:1-4. Due to the high cost of aluminum fluoride, if the added mass of aluminum fluoride is too high, the treatment cost will be greatly increased; if the added mass of aluminum fluoride is too small, the effect of promoting the reaction is not obvious.

As an implementation manner of the embodiment of the present invention, the thickness of the first mixture is ≤5 cm.

The thickness of the first mixture is small, which can increase the reaction area and promote the carbon combustion reaction.

S3, the first mixture is heated to a temperature of ≥560°C and <650°C by using the high-temperature flue gas discharged from the flame of the electrolytic cell, and the combustion reaction time is ≥6h, so as to process the carbon residue and recover the electrolyte.

In the temperature range of ≥560 °C and <650 °C, the carbon in the carbon residue can be fully burned, and the electrolyte in the carbon residue will not be significantly melted and volatilized, leaving the electrolyte in a solid state. If the heating temperature is too low, it is not conducive to the occurrence of the carbon combustion reaction; if the heating temperature is too high, a large amount of electrolyte will be volatilized and the recovery rate of the electrolyte will be reduced; if the combustion reaction time is too short, the purity of the recovered electrolyte will be reduced. The traditional roaster roasting uses coal, natural gas, etc. as the heating heat source. Coal and natural gas contain carbon and hydrogen. During the combustion process, the hydrogen will be converted into water and mixed in the combustion flue gas. Under the heating condition, the electrolyte will be mixed with the flue gas. A large amount of highly corrosive HF is chemically reacted with the water in the electrolytic cell, and the present invention uses the high-temperature flue gas discharged from the fire hole of the electrolytic cell as the heat source, so neither the reactant nor the flue gas contains water, which can avoid the generation of highly corrosive HF. , friendly to the environment and equipment. And by adopting the method of the present invention, the waste carbon residue generated in the electrolysis process can be disposed of in the electrolysis workshop, so that the electrolysis workshop no longer discharges the carbon residue hazardous waste.

As an implementation of the embodiment of the present invention, the combustion reaction time may be 6-8h. If the combustion reaction time is too long, energy will be wasted.

As an implementation of the embodiment of the present invention, the gas such as carbon dioxide generated in the above reaction process can be discharged into the purification system of the electrolysis workshop, and the remaining electrolyte is returned to the electrolysis tank or stored for future use.

On the other hand, the embodiment of the present invention provides a device for processing carbon residue and recovering electrolyte, for realizing the above method, the device includes a crusher, a mixer and a combustion box 101 arranged in sequence according to the process, wherein,

The crusher is used to crush the carbon residue containing electrolyte into particle size ≤12cm;

The mixer is used to mix the additives including carbonate with the carbon residue;

A tray 113 is fixed in the combustion box 101, and the tray 113 is used for placing the first mixture formed by mixing the additive including carbonate and the carbon residue; the box body of the combustion box 101 is provided with a high temperature for discharging into the fire hole of the electrolytic cell an air inlet for flue gas, the air inlet is used to make the high-temperature flue gas discharged from the burner of the electrolytic cell enter the combustion box to heat the first mixture on the tray to a temperature of ≥560°C and <650°C, Combustion reaction ≥ 6h time.

1, the air inlet of the combustion box can be communicated with the upper end of the gas collecting hood 107 that collects the high temperature flue gas of the fire eye 108 at the flue end of the electrolysis tank through the air inlet pipe 106, and the air inlet of the combustion box can be provided with an oxygen content sensor 111 and a temperature sensor. 112. Both the oxygen content sensor 111 and the temperature sensor 112 are connected to a monitoring instrument box 115 disposed outside the combustion box 101 to monitor the temperature of the air inlet of the combustion box and the oxygen content of the incoming gas.

Specifically, with reference to FIG. 1 , in this embodiment, a plurality of trays 113 can be arranged in layers, and the thickness of the first mixture placed on each tray 113 is ≤5 cm, wherein the material of the tray can be 310s stainless steel, of course, it can also be Other materials that do not affect the separation of the electrolyte are selected, which are not specifically limited here.

Further, with reference to FIG. 1 , in this embodiment, a heater 110 may be provided at the bottom of the combustion box 101 , and the heater 110 may be arranged below the tray 113 . When the temperature of the combustion box 101 is lower than 560° C., it can be The heater 110 is activated to perform auxiliary heating, and when the temperature of the combustion box 101 is higher than 650° C., the heater 110 is turned off. Specifically, the heater 110 may be heated by direct current or by alternating current.

Further, with reference to FIG. 1, the top of the combustion box 101 is provided with an air outlet for exhausting gas, and the air outlet of the combustion box 101 is communicated with the flue gas pipe 104 of the electrolytic cell through the exhaust pipe 103, so that the inside of the flue gas pipe of the electrolytic cell can be used. The high-temperature flue gas discharged from the fire eye is sucked into the combustion box 101 by the negative pressure, and the carbon dioxide and other gases produced by the combustion can also be discharged into the flue gas pipeline 104 to enter the purification system of the electrolysis workshop. In addition, a valve 105 can also be set on the exhaust pipe 103 to control the opening degree and the suction negative pressure.

Further, with reference to FIG. 2 , a temperature detector 116 may be provided in the combustion box 101 for detecting the temperature in the combustion box 101 . More specifically, the temperature detector 116 may be arranged above the uppermost tray 113 . The temperature detector 116 A thermocouple with data transmission function can be selected, and the thermocouple is connected to the above-mentioned monitoring instrument box 115 so as to monitor the temperature above the tray 113 .

In order to improve the thermal insulation effect in the combustion box, in this embodiment, a thermal insulation brick 109 can be fixedly arranged on the top of the combustion box. Since the thermal insulation brick 109 is arranged at the lower part of the air outlet, the thermal insulation brick 109 is provided with through holes, In order to facilitate the movement of the gas to the outlet for discharge. The thermal insulation brick 109 can be made of high-alumina thermal insulation brick, which plays the role of thermal insulation and heat storage.

Of course, in order to improve the recovery efficiency of the electrolyte in the carbon residue, there may be a plurality of the above-mentioned combustion boxes, the air inlet of each combustion box is communicated with the pipe body of the air intake pipe 106, and the air outlet of each combustion box is connected to the The pipes of the exhaust pipe 103 are connected, so that multiple combustion boxes work simultaneously; the intake pipe 106 can be communicated with the high-temperature flue gas collecting hoods 107 corresponding to the fire holes 108 at the flue ends of the multiple electrolyzers, so that multiple combustion boxes can be formed into one The centralized combustion box realizes the collection and utilization of high-temperature flue gas from the flue end fire holes of multiple electrolyzers.

Further, referring to FIG. 3 , a plurality of combustion boxes can be arranged in a straight line, and the combustion box arranged in the middle is provided with first openings on both sides along the linear direction, and is connected in sequence through the first openings, and the combustion boxes arranged on the sides are provided with first openings. The side of the combustion box close to the middle combustion box is provided with a second opening, and the first opening of the combustion box arranged on the side is communicated with the second opening of the adjacent combustion box, so that the interior of the plurality of combustion boxes is formed into a large one. The heating combustion reaction chamber.

In addition, when the above-mentioned arrangement of multiple combustion boxes is adopted, with reference to FIG. 3 , the charcoal slag box 117 , the crusher 118 and the pallet rack 119 can also be reasonably arranged according to the space, wherein the charcoal slag box 17 can be used to collect and store charcoal slag, the crusher 118 may also be provided with a gas collection pipe, and the smoke and dust generated during the crushing process of the carbon residue is discharged into the flue gas pipe through the gas collection pipe 120 and processed; the tray rack 119 can be used for placing trays.

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

Example 1

A combustion box is installed at the flue end of a 400kA electrolytic cell in an electrolytic aluminum enterprise, as shown in Figure 1. The 400kA electrolytic cell produces a total of about 30kg of carbon residue per day (about 10kg every 8 hours).

1) Pulverize the to-be-treated carbon residue generated after the electrolysis of the electrolytic cell so that the particle size is less than 12 cm. The carbon residue particles and sodium carbonate are mixed with a mixer according to a mass ratio of 3:100 to form a first mixture, which is divided into three trays 113, each tray 113 is loaded with 4kg, the carbon residue is flattened, and the flattened thickness is less than 5cm ;

2) Put the tray 113 into the combustion chamber of the combustion box 101, and close the box door;

3) Open the valve 105 on the exhaust pipe 103, so that the high-temperature flue gas discharged from the fire hole at the flue end of the electrolytic cell enters the combustion box 101; during this process, according to the temperature display of the instrument, when the temperature in the combustion box is lower than 560 ℃ , start auxiliary heating. Auxiliary heating adopts direct current, which is taken from the column busbar of the electrolytic cell and the terminals at the short-circuit port. The voltage difference between the two terminals is 3.82V, the DC current on the measured copper cable is 1.6kA, and the heating power of the auxiliary heating device is about 6.1kW. And when the temperature in the combustion box is higher than 650 ℃, the auxiliary heating is turned off. According to the oxygen content display of the instrument, when the oxygen content in the combustion box is lower than 5%, slightly move the position of the air intake pipe hood to increase the air intake, so that the oxygen content is greater than 10%. In Example 1, the temperature in the combustion chamber was controlled to be 565°C.

4) The carbon slag is burned in the combustion box 101 for 7 hours, and the color becomes off-white, and the original granular carbon slag is formed into a block and becomes a solid electrolyte.

5) Take out the solid electrolyte left after burning the carbon residue and put it directly into the electrolytic cell, or store it for later use.

Using the method provided in Example 1, three furnaces were processed every day, and all the carbon residues in the electrolytic cell were processed, totaling about 30 kg, and 22.5 kg of electrolyte was recovered accumulatively. The total working time of the auxiliary heating system is 4.5h per day, and the cumulative DC power consumption is 27.5kwh. The average power consumption per kilogram of carbon residue is 0.917kwh/kg. The recovered electrolyte is sampled, and the carbon content is analyzed. The carbon content is about 0.18%, which is basically the same as the analysis result of the carbon content of the electrolyte in the electrolytic cell. The carbon residue treatment speed, treatment effect, and economy have all achieved the expected results.

Example 2

In a reserved area of a certain work area of a 400kA electrolysis workshop of an electrolytic aluminum enterprise, a centralized combustion box is set up, as shown in Figure 3-4.

There are 36 400kA electrolytic cells in this work area, which produce about 360kg of carbon residue every 8 hours, and a total of about 1080kg of carbon residue is produced every day.

1) The carbon slag in the entire work area of the electrolysis workshop is placed in the carbon slag box 117, and the carbon slag is crushed in the crusher 118 to become carbon slag particles with a particle size of less than 12 mm; during the crushing process, open the gas collection pipe 120 to discharge the soot to in the flue gas duct 104 .

2) Mix the crushed carbon residue into industrial AlF ₃ that accounts for 5% of the carbon residue mass and calcium carbonate that accounts for 1% of the carbon residue mass, form a first mixture after mixing, load it into trays, each tray is loaded with 8kg, and the carbon residue is spread out. flat, and the thickness of the flattening is less than 5cm; put the tray containing the carbon residue particles into the combustion chamber of the combustion box, and close the door of the box;

3) Open the valve on the exhaust pipe 103, so that the high-temperature flue gas discharged from the fire hole at the flue end of the electrolytic cell enters the combustion box for heating and combustion. During this process, according to the temperature display of the instrument control box 115, when the temperature in the combustion box is low At 560°C, auxiliary heating was started. The auxiliary heating adopts direct current, which is taken from the terminal at the short-circuit port of the column bus of the electrolytic cell. When the circuit is turned on, the DC voltage of the auxiliary heating device is about 4V. The total DC current measured on the copper cable is 17.1kA, and the heating power of the auxiliary heating device is about 68.4kW. And when the temperature in the combustion box is higher than 650 ℃, the auxiliary heating is turned off. According to the oxygen content display of the instrument, when the oxygen content in the combustion box is lower than 5%, slightly move the position of the air collecting hood of the intake pipe to increase the air intake, or open the opening control valve on the exhaust pipe to make the oxygen content greater than 10%. In Example 2, the temperature in the combustion chamber was controlled to be 595°C, and the oxygen volume fraction was 11%.

4) The carbon slag is burned in the combustion box for 6.5 hours, the color of the carbon slag becomes off-white after burning, and the original granular carbon slag is formed into a block and becomes a solid electrolyte.

7) Take out the solid electrolyte left after burning the carbon residue and put it directly into the electrolytic cell, or store it for later use.

Processing effect:

1) 3 furnaces are processed every day, and all the carbon residues of the thirty-six electrolyzers in this work area are processed, a total of about 1080kg, and the cumulative recovery of electrolyte is about 752kg. The total working time of the auxiliary heating system is about 12h every day, and the cumulative DC power consumption is about 820.8kwh. The average power consumption per kilogram of carbon residue is 0.76kwh/kg.

2) Sampling the recovered electrolyte, and analyze the carbon content. The carbon content is 0.2%, which is basically the same as the average value of the carbon content analysis results of the electrolytes in the electrolytic cells in the work area.

3) The carbon residue treatment speed, treatment effect, and economy have all achieved the expected results.

Example 3

Embodiment 3 takes Embodiment 1 as a reference, and the difference between Embodiment 3 and Embodiment 1 is:

Hydrogen peroxide with a mass fraction of 30% of sodium carbonate was sprayed on the surface of the first mixture, the mass ratio of carbon residue particles to sodium carbonate was 5:100, the heating temperature was 610°C, and the rest were the same as in Example 1.

Processing effect:

1) 3 furnaces are processed every day, all the carbon residues in this tank are processed, a total of about 30kg, and the accumulated electrolyte is about 21.8kg. The auxiliary heating system consumes about 24kwh of AC power every day, and the average power consumption per kilogram of carbon residue is 0.8kwh/kg.

2) Sampling the recovered electrolyte to analyze the carbon content. The carbon content is about 0.191%, which is basically the same as the analysis result of the carbon content of the electrolyte in the electrolytic cell.

3) The carbon residue treatment speed, treatment effect, and economy have all achieved the expected results.

Example 4

Example 4 takes Example 1 as a reference. The difference between Example 4 and Example 1 is that the mass ratio of carbon residue particles to sodium carbonate is 4:100. During the combustion process, the temperature in the combustion box is 630°C.

Example 5

Example 5 takes Example 2 as a reference. The difference between Example 5 and Example 2 is that hydrogen peroxide with a mass fraction of 60% of calcium carbonate was sprayed into the first mixture.

Processing effect:

1) Three furnaces are processed every day, and all the carbon residues of the thirty-six electrolyzers in this work area are processed, totaling about 1080kg, and the accumulated electrolyte recovered is about 752kg. The auxiliary heating system consumes about 768kwh of AC power every day. The average power consumption per kilogram of carbon residue is 0.711kwh/kg.

2) Sampling the recovered electrolyte and analyze the carbon content. The carbon content is about 0.196%, which is basically the same as the average value of the carbon content analysis results of the electrolytes in the electrolytic cells in the work area.

3) The carbon residue treatment speed, treatment effect, and economy have all achieved the expected results.

Comparative Example 1

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

Weigh 1000 grams of aluminum electrolytic carbon residue with a particle size of less than 3mm, mix 10 grams of clean coal with a particle size of less than 3mm, and 100 grams of industrial pure calcium fluoride, mix the three materials evenly, and roast the mixture at a roasting temperature of 850 ° C (0°C, calcination time is 1 hour, and good dispersibility electrolyte is obtained after calcination. The content of impurities in the electrolyte is 0.20% by analysis, mainly oxides of iron and silicon.

Comparative Example 2

Comparative example 2 provides a method for recovering the electrolyte in carbon residue. Taking Example 1 as a reference, the difference between Comparative Example 2 and Example 1 is that the particle size of the carbon residue is ≤ 30 mm, the heating temperature is 720 ° C, and the burning time is 10 hours.

Comparative Example 3

Comparative Example 3 provides a method for recovering electrolytes in carbon residues. Taking Example 1 as a reference, Comparative Example 3 is different from Example 1 in that the particle size of the carbon residues is less than or equal to 30 mm, the heating temperature is 500 ° C, and the combustion time is 4 hours.

Table 1

Table 1 is the data collected by the method processing process of Examples 1-5 of the present invention and Comparative Examples 1-3, according to the data in Table 1:

In Examples 1-5 of the present invention, the recovery rate of the electrolyte in the carbon residue is 98.07-98.68%, the recovery rate is high, the carbon mass fraction in the recovered electrolyte is 0.18-0.22%, the impurities are few, and the electricity consumption per kilogram of carbon residue is 0.76-0.917 kwh/kg, low power consumption and no corrosive HF gas. Only in Example 3 and Example 5, only a small amount of HF gas was detected due to the use of hydrogen peroxide as an additive.

The method for recovering the carbon residue electrolyte provided by Comparative Example 1 uses coal as the heating source, the recovery rate of the electrolyte in the carbon residue is 88%, the recovery rate is lower than that of Examples 1-5 of the present invention, and the carbon mass fraction in the recovered electrolyte is 0.16%, A large amount of corrosive HF gas is produced.

In the method for recovering carbon residue electrolyte provided by Comparative Example 2, the recovery rate of the electrolyte in the carbon residue is 85.96%, which is lower than that of Examples 1-5 of the present invention. The carbon mass fraction in the recovered electrolyte is 9.1%, and the impurity content is high. The power consumption of carbon residue is 1.558kwh/kg, and the power consumption is high.

The present invention provides a method and device for treating carbon residue and recovering electrolyte. The method includes: obtaining carbon residue containing electrolyte with a particle size of less than or equal to 12 cm; mixing an additive including carbonate with the carbon residue to obtain a first mixture; heating the first mixture to a temperature of ≥560°C and <650°C, the combustion reaction time is ≥6h, the carbon dioxide and other gases generated in the reaction process are discharged into the purification system of the electrolysis workshop, and the remaining electrolyte is returned to the electrolysis tank or It is stored for use in order to realize the purpose of processing the carbon residue and recovering the electrolyte. The present invention increases the reaction area of the carbon combustion reaction by controlling the particle size of the carbon residue and mixing additives, so as to overcome the difficulty in burning caused by the carbon residue being wrapped by the reflowed electrolyte at high temperature. The obstacle to the reaction is that the electrolyte in the carbon residue is not easily volatilized due to the control of the heating temperature, so that the carbon is reacted into a gas and separated from the reflowed electrolyte to achieve the purpose of recovering the electrolyte. By adopting the method of the invention, the recovery rate of the electrolyte is 98.07-98.68%, the recovery rate is high, the carbon content is 0.18-0.2%, and the impurity content is low, so that the electrolytic aluminum workshop can no longer discharge carbon slag hazardous waste. Since the method makes full use of the residual heat of the electrolytic cell, no corrosive hydrogen fluoride gas is generated, and no secondary pollution is generated, so the method is energy-saving, environmentally friendly, and pollution-free.

While the preferred embodiments of the present application have been described, additional changes and modifications to these embodiments may occur to those of ordinary skill in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be construed to include the preferred embodiment and all changes and modifications that fall within the scope of this application.

Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these 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 also intended to include these modifications and variations.

Claims (7)

1. 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 (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 processing carbon residue to recover electrolyte as claimed in claim 1, wherein the mass ratio of the carbonate to the carbon residue 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 residue to recover electrolyte as claimed in claim 1, wherein 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 greater than or equal to 5%.

Images