Process and system for recovering electrolyte and carbon powder from electrolytic aluminum anode carbon residues

Abstract

A process and system for recovering electrolyte and carbon powder from electrolytic aluminum anode carbon residues are characterized in that the electrolytic aluminum anode carbon residues are crushed, dried, ground and sieved, fine powder is sent to a cyclone combustion furnace for combustion, the electrolyte in the carbon residues is molten and then enters an electrolyte melting pool, and the surface of the electrolyte melting pool can be subjected to residue stirring; the bottom of the molten pool is poured with a high-temperature-resistant material and is provided with multiple holes, the molten electrolyte flows out of the holes and enters a rotary jet granulation device, the molten electrolyte is cut into frits with small particle sizes under the gas cutting action of rotary jet, meanwhile, the molten electrolyte is cooled by airflow, and the molten electrolyte is separated from the molten pool; the small frits are further cooled, so that the surfaces of the small frits are completely solidified, the small frits are discharged through a discharge port, and flue gas generated by combustion enters a tail flue, exchanges heat with a heat exchanger, enters a dust remover system for dust removal, then enters an alkali liquor spray tower and a denitration device, and is finally emptied; according to the method, the electrolytic aluminum carbon residues are subjected to resource recycling, and the electrolyte utilization rate is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of hazardous waste treatment of electrolytic aluminum carbon slag, and specifically relates to a process and system for recovering electrolyte and carbon powder from electrolytic aluminum anode carbon slag. Background Art

[0002] The anode carbon slag produced by electrolytic aluminum is a toxic and hazardous waste. At present, the main treatment methods for these wastes include roasting, bubbling fluidized bed, alkali fusion, vacuum smelting, flotation, leaching, high temperature and safe landfill, etc. These methods have their own advantages and disadvantages. From the perspective of environmental protection and reducing secondary pollution, roasting is more effective. The current heat treatment method, such as the patent application named "Method for harmless treatment of electrolytic aluminum anode carbon slag and harmless electrolytic aluminum anode carbon slag" (publication number: CN 116174444A), has high energy consumption, serious waste of waste heat, high temperature and high pollution in the heat treatment workshop environment, intermittent production, low efficiency, molten electrolyte cooling and crushing air accident, energy cannot be recovered, and secondary pollution is serious. At present, electrolytic aluminum plants cannot effectively treat carbon slag, the electrolyte recovery rate is low, the purity is low, resulting in large electrolyte consumption, high electrolytic aluminum cost, and hazardous waste cannot be treated in time, causing serious environmental problems, resulting in outstanding shutdown problems. Summary of the invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a process and system for recovering electrolyte and carbon powder from electrolytic aluminum anode carbon slag, thereby realizing the continuous and efficient disposal of electrolytic aluminum anode carbon slag, and at the same time realizing the resource recycling of electrolyte and carbon powder from electrolytic aluminum anode carbon slag, as well as efficient heat recovery.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A system for recovering electrolyte and carbon powder from electrolytic aluminum anode carbon slag, comprising a crusher 1, wherein the feed port of the crusher 1 is fed with electrolytic aluminum anode carbon slag, the discharge port of the crusher 1 is connected to the first inlet of a preheating and drying system 2, the second inlet of the preheating and drying system 2 is connected to the shell side outlet of a heat exchanger 9, the first outlet of the preheating and drying system 2 is connected to the first inlet of a grinder 3, the discharge port of the grinder 3 is connected to the inlet of a sieving machine 4, the coarse particle discharge port of the sieving machine 4 is connected to the second inlet of the grinder 3; the fine particle discharge port of the sieving machine 4 is connected to the first inlet of a cyclone combustion furnace 5, the first outlet of the cyclone combustion furnace 5 is connected to the tube side inlet of the heat exchanger 9, the second outlet of the cyclone combustion furnace 5 is connected to the electrolyte molten pool 6 The inlet of the heat exchanger 9 is connected; the first outlet of the electrolyte molten pool 6 recovers carbon powder, the second outlet of the electrolyte molten pool 6 is connected to the first inlet of the rotary jet granulator 7, the second inlet of the rotary jet granulator 7 is a cold air inlet, the first outlet of the rotary jet granulator 7 is connected to the second inlet of the cyclone combustion furnace 5, the second outlet of the rotary jet granulator 7 is connected to the inlet of the cooling device 8, and the outlet of the cooling device 8 is electrolyte powder particles; the shell side inlet of the heat exchanger 9 is the cold air inlet, the tube side outlet of the heat exchanger 9 is connected to the inlet of the cyclone separation device 10, the outlet of the cyclone separation device 10 is connected to the inlet of the alkali solution spray tower 11, and the outlet of the alkali solution spray tower 11 is connected to the inlet of the denitrification device 12.

[0006] The cyclone combustion furnace 5 is provided with a gas burner and a slag feed port. The gas flow, together with the electrolytic aluminum slag ground into powder and hot air, enters the furnace through a rotating jet, burns and moves downward in the furnace, and an electrolyte molten pool is provided at the bottom of the furnace.

[0007] The electrolyte molten pool 6 has a high temperature resistant slag removal device on its upper part and a silicon carbide material casting bottom with circular holes of 1-2 mm in diameter on its bottom.

[0008] The jet granulation device 7 is provided with a plurality of air jet nozzles inside, and the jet pressure is 5 MPa, and the molten electrolyte is cut and cooled by the cold air jet.

[0009] The cooling device 8 utilizes cold air for cooling, and the cold air and the electrolyte frit are in direct countercurrent contact for heat exchange.

[0010] The heat exchanger 9 is a tubular partition-wall heat exchanger, with air passing through the shell side and flue gas passing through the shell side.

[0011] The alkali solution spray tower 11 is a wet flue gas desulfurization and dehydrogen fluoride device, and the alkali solution is lime water, which ensures that the desulfurization efficiency reaches more than 90% and the dehydrogen fluoride efficiency reaches more than 92%.

[0012] A process for recovering electrolyte and carbon powder from electrolytic aluminum anode carbon slag comprises the following steps:

[0013] In the first step, the electrolytic aluminum anode carbon slag is sent to the crusher 1 for crushing, the crushed electrolytic aluminum anode carbon slag is sent to the preheating dryer 2 for preheating, then sent to the grinder 3 for grinding, and then sent to the screening machine 3 for screening, the coarse particles after screening are recycled and sent to the grinder 3 for further grinding treatment, and the fine particles after screening are sent to the cyclone combustion furnace 5 for high-temperature combustion;

[0014] In the second step, the flue gas after high-temperature combustion in the cyclone combustion furnace 5 is sent to the tube side of the heat exchanger 9, and the cold air is sent to the shell side of the heat exchanger 9 for countercurrent heat exchange with the flue gas. After heat exchange by the heat exchanger 9, the cold air becomes hot air and is sent to the preheating and drying system 2 to preheat the electrolytic aluminum anode carbon slag, and then sent to the cyclone combustion furnace 5 for combustion assistance; the flue gas after heat exchange by the heat exchanger 9 is sent to the cyclone separation device 10 to remove particulate matter, and then sent to the alkali solution spray tower 11 to remove SO 2 and hydrogen fluoride, and then sent to the denitrification device 12 to remove nitrogen oxides, and finally the flue gas that meets the emission requirements is discharged from the system;

[0015] In the third step, the solid materials after combustion in the cyclone combustion furnace 5 are sent into the electrolyte melting pool 6, and the carbon powder is removed from the slag removal port of the electrolyte melting pool 6 to be recovered, and the molten electrolyte flows out from the bottom of the electrolyte melting pool 6 and is sent to the rotary jet granulation device 7. At the same time, cold air is sprayed from the air jet nozzle of the rotary jet granulation device 7 to cut the molten electrolyte and cool the molten electrolyte. Hot air is sent to the cyclone combustion furnace 5 to assist combustion, and the cut electrolyte powder particles are sent to the cooling device 8 to be cooled to room temperature to obtain electrolyte powder particles.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The cyclone combustion furnace 5 of the present invention can realize continuous combustion, closed operation, and no significant heat leakage. In addition, the cyclone combustion furnace 5 has no combustion bed, and the fluid in the furnace is in a swirling state, which is convenient for forming centrifugal force and is beneficial to the separation of molten electrolyte from flue gas and carbon powder.

[0018] 2. The electrolyte molten pool 6 of the present invention is placed below the furnace of the cyclone combustion furnace 5, which is conducive to maintaining a high temperature environment, ensuring the effective separation of carbon powder and electrolyte, and facilitating the spraying of electrolyte from the cyclone combustion furnace 5 into the electrolyte molten pool 6.

[0019] 3. The rotary jet granulation device 7 of the present invention uses high-speed jet gas to cut the molten electrolyte, avoiding the cooling and crushing process of large pieces of electrolyte, and also avoiding secondary pollution and energy waste.

[0020] 4. The present invention recovers the waste heat in the flue gas and uses the high-temperature air in the rotating jet granulation device 7 to assist combustion in the cyclone combustion furnace 5, thereby reducing the energy consumption of the cyclone combustion furnace 5 and achieving the purpose of energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a schematic diagram of the process flow of an embodiment of the present invention.

[0022] Figure 2 This is a graph showing the calcination weight loss rate of electrolytic aluminum anode carbon slag versus calcination time in an embodiment of the present invention.

[0023] Figure 3 This is a picture of the sample after calcination at 900°C in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the embodiments and drawings.

[0025] Example 1, reference Figure 1 Take the treatment of electrolytic aluminum anode carbon slag with a carbon content of 25% and an electrolyte content of 75% with a treatment capacity of 1 ton / h as an example.

[0026] A system for recovering electrolyte and carbon powder from electrolytic aluminum anode carbon slag, comprising a crusher 1, wherein the feed port of the crusher 1 is fed with electrolytic aluminum anode carbon slag, the discharge port of the crusher 1 is connected to the first inlet of a preheating and drying system 2, the second inlet of the preheating and drying system 2 is connected to the shell side outlet of a heat exchanger 9, the first outlet of the preheating and drying system 2 is connected to the first inlet of a grinder 3, the discharge port of the grinder 3 is connected to the inlet of a sieving machine 4, the coarse particle discharge port of the sieving machine 4 is connected to the second inlet of the grinder 3; the fine particle discharge port of the sieving machine 4 is connected to the first inlet of a cyclone combustion furnace 5, the first outlet of the cyclone combustion furnace 5 is connected to the tube side inlet of the heat exchanger 9, the second outlet of the cyclone combustion furnace 5 is connected to the electrolyte molten pool 6 The inlet of the heat exchanger 9 is connected; the first outlet of the electrolyte molten pool 6 recovers carbon powder, the second outlet of the electrolyte molten pool 6 is connected to the first inlet of the rotary jet granulator 7, the second inlet of the rotary jet granulator 7 is a cold air inlet, the first outlet of the rotary jet granulator 7 is connected to the second inlet of the cyclone combustion furnace 5, the second outlet of the rotary jet granulator 7 is connected to the inlet of the cooling device 8, and the outlet of the cooling device 8 is electrolyte powder particles; the shell side inlet of the heat exchanger 9 is the cold air inlet, the tube side outlet of the heat exchanger 9 is connected to the inlet of the cyclone separation device 10, the outlet of the cyclone separation device 10 is connected to the inlet of the alkali solution spray tower 11, and the outlet of the alkali solution spray tower 11 is connected to the inlet of the denitrification device 12.

[0027] The cyclone combustion furnace 5 is provided with a gas burner and a charcoal slag feed port. The gas flow, together with the electrolytic aluminum charcoal slag ground into powder and hot air, enters the furnace through a rotating jet, burns and moves downward in the furnace, and an electrolyte molten pool is provided at the bottom of the furnace;

[0028] The electrolyte molten pool 6 has a high temperature resistant slag removal device on the top and a silicon carbide material casting bottom with a circular hole of 1-2 mm in diameter on the bottom.

[0029] The jet granulation device 7 is provided with a plurality of air jet nozzles, the jet pressure is 5 MPa, and the molten electrolyte is cut and cooled by the cold air jet;

[0030] The cooling device 8 utilizes cold air for cooling, and the cold air and the electrolyte frit are in direct contact and heat exchange in countercurrent;

[0031] The heat exchanger 9 is a tubular partition-type heat exchanger, with air passing through the shell side and flue gas passing through the shell side;

[0032] The alkali solution spray tower 11 is a wet flue gas desulfurization and dehydrogen fluoride device, and the alkali solution is lime water, which ensures that the desulfurization efficiency reaches more than 90% and the dehydrogen fluoride efficiency reaches more than 85%;

[0033] A process for recovering electrolyte and carbon powder from electrolytic aluminum anode carbon slag comprises the following steps:

[0034] In the first step, the electrolytic aluminum anode carbon slag is fed into a crusher 1 at a rate of 1 ton / h for crushing, and the electrolytic aluminum anode carbon slag that is crushed to less than 5 cm is fed into a preheating dryer 2 for preheating to 50-60° C., and then fed into a grinder 3 for further grinding, and then fed into a screening machine 3 for screening, and the coarse particles larger than 5 mm after screening are recycled and fed into the grinder 3 for further grinding treatment, and the fine particles less than 5 mm after screening are fed into a cyclone combustion furnace 5 for high temperature combustion at 900-1000° C.;

[0035] In the second step, the high-temperature flue gas after high-temperature combustion in the cyclone combustion furnace 5 is sent to the tube side of the heat exchanger 9, and the cold air is sent to the shell side of the heat exchanger 9 for countercurrent heat exchange with the flue gas. After the cold air is heated to 300-400°C by the heat exchanger 9, it becomes hot air and is sent to the preheating and drying system 2 to preheat the electrolytic aluminum anode carbon slag, and then sent to the cyclone combustion furnace 5 for combustion assistance; the flue gas after heat exchange in the heat exchanger 9 is sent to the cyclone separation device 10 to remove particulate matter, and the removal rate is controlled to be greater than 85%, and then sent to the alkali solution spray tower 11 to remove SO 2 and hydrogen fluoride, of which SO 2 The removal rate is controlled at more than 90%, and the removal rate of hydrogen fluoride is controlled at more than 92%. Then, the flue gas is sent to the denitration device 12 to remove nitrogen oxides, and the removal rate is greater than 80%. Finally, the flue gas that meets the emission requirements is discharged from the system;

[0036] In the third step, the solid material after combustion in the cyclone combustion furnace 5 is sent into the electrolyte melting pool 6, and the carbon powder is removed from the slag removal port of the electrolyte melting pool 6 at a flow rate of 0.2 tons / h to recover the carbon powder, and the molten electrolyte flows out from the bottom of the electrolyte melting pool 6 at a flow rate of 0.73 tons / h and is sent to the rotary jet granulation device 7. At the same time, cold air is sprayed from the air jet nozzle of the rotary jet granulation device 7 at a pressure of 5MPa to cut the molten electrolyte, and the molten electrolyte is cooled to 100-150°C, and hot air is sent to the cyclone combustion furnace 5 to assist combustion. The cut electrolyte powder particles are sent to the cooling device 8 to be cooled to room temperature to obtain electrolyte powder particles.

[0037] Reference Figure 2 When the calcination temperature is 900℃, the calcination weight loss rate of electrolytic aluminum anode carbon slag can reach more than 35% within 20min, which can realize the continuous and efficient disposal of electrolytic aluminum anode carbon slag; after calcination, the carbon powder in the electrolytic aluminum anode carbon slag floats on the electrolyte, such as Figure 3 As shown, the electrolyte and carbon powder can be separated and recycled as resources. The high-temperature flue gas after calcination is used to preheat the sample and assist combustion in the cyclone combustion furnace, thereby achieving efficient energy recovery.

[0038] The embodiments described above are merely descriptions of preferred implementation modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by those skilled in the art shall all fall within the scope of protection determined by the claims of the present invention.

Claims

1. A system for recovering electrolyte and carbon powder from electrolytic aluminum anode carbon slag, comprising a crusher (1), wherein the feed port of the crusher (1) is fed with electrolytic aluminum anode carbon slag, the discharge port of the crusher (1) is connected to the first inlet of a preheating and drying system (2), the second inlet of the preheating and drying system (2) is connected to the shell side outlet of a heat exchanger (9), the first outlet of the preheating and drying system (2) is connected to the first inlet of a grinder (3), the discharge port of the grinder (3) is connected to the inlet of a sieving machine (4), the coarse particle discharge port of the sieving machine (4) is connected to the second inlet of the grinder (3); the fine particle discharge port of the sieving machine (4) is connected to the first inlet of a cyclone burner (5), the first outlet of the cyclone burner (5) is connected to the tube side inlet of the heat exchanger (9), the second outlet of the cyclone burner (5) is connected to the electrolyte molten pool ( 6); the first outlet of the electrolyte molten pool (6) is used to recover carbon powder; the second outlet of the electrolyte molten pool (6) is connected to the first inlet of the rotary jet granulating device (7); the second inlet of the rotary jet granulating device (7) is a cold air inlet; the first outlet of the rotary jet granulating device (7) is connected to the second inlet of the cyclone combustion furnace (5); the second outlet of the rotary jet granulating device (7) is connected to the inlet of the cooling device (8); the outlet of the cooling device (8) is electrolyte powder particles; the shell side inlet of the heat exchanger (9) is the cold air inlet; the tube side outlet of the heat exchanger (9) is connected to the inlet of the cyclone separation device (10); the outlet of the cyclone separation device (10) is connected to the inlet of the alkali solution spray tower (11); the outlet of the alkali solution spray tower (11) is connected to the inlet of the denitration device (12).

2. The system for recovering electrolyte and carbon powder from aluminum electrolysis anode carbon slag according to claim 1, characterized in that: The cyclone combustion furnace (5) is provided with a gas burner and a charcoal slag feed port. The gas flow, together with the electrolytic aluminum charcoal slag ground into powder and hot air, enters the furnace through a rotating jet, burns and moves downward in the furnace, and an electrolyte molten pool is provided at the bottom of the furnace.

3. The system for recovering electrolyte and carbon powder from aluminum electrolysis anode carbon slag according to claim 1, characterized in that: The upper part of the electrolyte molten pool (6) is provided with a high temperature resistant slag removing device, and the bottom is a silicon carbide material casting bottom with circular holes having a diameter of 1-2 mm.

4. The system for recovering electrolyte and carbon powder from aluminum electrolysis anode carbon slag according to claim 1, characterized in that: The jet granulation device (7) is internally provided with a plurality of air jet nozzles, the jet pressure is 5 MPa, and the molten electrolyte is cut and cooled by the cold air jet.

5. The system for recovering electrolyte and carbon powder from aluminum electrolysis anode carbon slag according to claim 1, characterized in that: The cooling device (8) utilizes cold air for cooling, and the cold air and the electrolyte melt are in direct contact and heat exchange in countercurrent.

6. The system for recovering electrolyte and carbon powder from aluminum electrolysis anode carbon slag according to claim 1, characterized in that: The heat exchanger (9) is a tubular partition-type heat exchanger, with air passing through the shell side and flue gas passing through the shell side.

7. The system for recovering electrolyte and carbon powder from aluminum electrolysis anode carbon slag according to claim 1, characterized in that: The alkali solution spray tower (11) is a wet flue gas desulfurization and dehydrofluorination device, and the alkali solution is lime water, which ensures that the desulfurization efficiency reaches more than 90% and the dehydrofluorination efficiency reaches more than 92%.

8. A process for recovering electrolyte and carbon powder from the electrolytic aluminum anode carbon slag according to claims 1 to 7, characterized in that: The following steps are involved: In the first step, the electrolytic aluminum anode carbon slag is sent to a crusher (1) for crushing, the crushed electrolytic aluminum anode carbon slag is sent to a preheating dryer (2) for preheating, then sent to a grinder (3) for grinding, and then sent to a sieving machine (3) for sieving, the coarse particles after screening are recycled and sent to the grinder (3) for further grinding treatment, and the fine particles after screening are sent to a cyclone combustion furnace (5) for high-temperature combustion; In the second step, the flue gas after high-temperature combustion in the cyclone combustion furnace (5) is sent to the tube side of the heat exchanger (9), and at the same time, cold air is sent to the shell side of the heat exchanger (9) for countercurrent heat exchange with the flue gas. After heat exchange in the heat exchanger (9), the cold air becomes hot air and is sent to the preheating and drying system (2) to preheat the electrolytic aluminum anode carbon slag, and then sent to the cyclone combustion furnace (5) for combustion assistance; the flue gas after heat exchange in the heat exchanger (9) is sent to the cyclone separation device (10) to remove particulate matter, and then sent to the alkali liquid spray tower (11) to remove SO2 and hydrogen fluoride, and then sent to the denitrification device (12) to remove nitrogen oxides. Finally, the flue gas that meets the emission requirements is discharged from the system; In the third step, the solid material after combustion in the cyclone combustion furnace (5) is sent into the electrolyte melting pool (6), and the carbon powder is removed from the slag removal port of the electrolyte melting pool (6) to recover the carbon powder, while the molten electrolyte flows out from the bottom of the electrolyte melting pool (6) and is sent into the rotary jet granulation device (7). At the same time, cold air is sprayed from the air jet nozzle of the rotary jet granulation device (7) to cut the molten electrolyte and cool the molten electrolyte. Hot air is sent to the cyclone combustion furnace (5) to assist combustion. The cut electrolyte powder particles are sent to the cooling device (8) to be cooled to room temperature to obtain electrolyte powder particles.

9. The process according to claim 8, characterized in that The following steps are involved: The first step is to feed the electrolytic aluminum anode carbon slag into a crusher (1) at a rate of 1 ton / h for crushing, and the electrolytic aluminum anode carbon slag that is crushed to less than 5 mm is fed into a preheating dryer (2) for preheating to 50-60° C., and then fed into a grinder (3) to further grind particles larger than 5 mm, and then fed into a sieving machine (3) for sieving, and the coarse particles larger than 5 mm after sieving are recycled and fed into the grinder (3) for further grinding, and the fine particles smaller than 5 mm after sieving are fed into a cyclone combustion furnace (5) for high-temperature combustion at 900-1000° C.; In the second step, the high-temperature flue gas after high-temperature combustion in the cyclone combustion furnace (5) is sent to the tube side of the heat exchanger (9), and at the same time, cold air is sent to the shell side of the heat exchanger (9) for countercurrent heat exchange with the flue gas. After the cold air is heat-exchanged to 300-400°C in the heat exchanger (9), it becomes hot air and is sent to the preheating and drying system (2) to preheat the electrolytic aluminum anode carbon slag, and then sent to the cyclone combustion furnace (5) for combustion assistance; the flue gas after heat exchange in the heat exchanger (9) is sent to the cyclone separation device (10) to remove particulate matter, and the removal rate is controlled to be greater than 85%, and then sent to the alkali liquid spray tower (11) to remove SO2 and hydrogen fluoride, wherein the SO2 removal rate is controlled to be greater than 90%, and the hydrogen fluoride removal rate is controlled to be greater than 92%, and then sent to the denitration device (12) to remove nitrogen oxides, and the removal rate is greater than 80%. Finally, the flue gas that meets the emission requirements is discharged from the system; In the third step, the solid material after combustion in the cyclone combustion furnace (5) is sent to the electrolyte melting pool (6), and the carbon powder is removed from the slag removal port of the electrolyte melting pool (6) at a flow rate of 0.2 tons / h to recover the carbon powder, while the molten electrolyte flows out from the bottom of the electrolyte melting pool (6) at a flow rate of 0.73 tons / h and is sent to the rotary jet granulation device (7). At the same time, cold air is sprayed from the air jet nozzle of the rotary jet granulation device (7) at a pressure of 5MPa to cut the molten electrolyte, and the molten electrolyte is cooled to 100-150°C. Hot air is sent to the cyclone combustion furnace (5) to assist combustion. The cut electrolyte powder particles are sent to the cooling device (8) to be cooled to room temperature to obtain electrolyte powder particles.

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