A method and apparatus for the harmless disposal of aluminum overhaul waste.

Abstract

This invention relates to a method and apparatus for the harmless disposal of aluminum overhaul waste slag, belonging to the technical field of hazardous waste disposal and utilization generated during aluminum electrolysis. The aluminum overhaul waste slag is divided into two main parts: waste cathode carbon blocks and refractory brick-insulating material. The waste cathode carbon blocks containing fluoride salts are crushed into fine blocks and granules and added to a side-blown burner. Air is introduced for side-blown combustion, producing fluoride-containing volatile flue gas. The obtained fluoride-containing volatile flue gas is passed through a fluoride salt recovery unit to separate fluoride salts from the hot gas. The hot gas, having removed most of the fluoride salts, is sent to a rotary kiln to heat and contact the refractory brick-insulating material, producing rotary kiln fluoride-containing volatile flue gas. The produced rotary kiln fluoride-containing volatile flue gas is then sent to a two-stage countercurrent alumina adsorption defluorination system to obtain purified gas. This invention proposes a method that uses the heat from the combustion of waste cathode carbon to heat the refractory bricks and insulation material, volatilizing and removing the fluoride salts, and a two-stage countercurrent adsorption method to remove fluoride from the fluoride-carrying gas stream, thus achieving the harmless disposal of overhaul slag.

Description

Technical Field

[0001] This invention relates to a method and apparatus for the harmless disposal of aluminum overhaul waste residue, belonging to the technical field of hazardous waste disposal and utilization generated during aluminum electrolysis. Background Technology

[0002] The initial main materials for the lining of aluminum electrolytic cells were carbonaceous materials, alumina, and mullite. During the aluminum electrolysis production process, at high temperatures, the electrolyte's penetration and corrosion of the lining material causes deformation or cracking of the lining structure. This leads to leakage of molten aluminum and electrolyte from the cracks, necessitating a shutdown and major overhaul in severe cases. Generally, electrolytic cells require major overhaul after 3-6 years of use. The overhaul involves removing all lining material, replacing it with a new lining, and producing overhaul slag. Overhaul slag mainly consists of refractory bricks, insulation materials, and cathode carbon blocks. Overhaul slag is an unavoidable solid waste in the aluminum electrolysis production process. When an aluminum electrolysis plant has an annual capacity of 200kt, the corresponding annual waste slag production can reach as high as 6000t. Carbonaceous materials account for approximately 30% to 40% of the overhaul slag from dismantled electrolytic cells, and fluoride salts account for approximately 20%. While both are valuable, they are hazardous substances whose discharge is restricted.

[0003] Although electrolytic cell overhaul slag is classified as hazardous waste, it is discharged dry. Without the influence of external water, it will not leach toxic components. However, once leached by rainwater or soaked in standing water, toxic components will inevitably leach out. Leachate seeping into the ground will pollute groundwater and surface water. Therefore, to prevent and reduce the environmental pollution caused by electrolytic cell overhaul slag, it is essential to first reduce rainwater leaching and soaking of the slag; secondly, it is crucial to prevent high-concentration fluoride-containing leachate from seeping into the ground and polluting groundwater. Thus, the selection of electrolytic cell overhaul slag disposal sites and the implementation of seepage prevention measures are particularly important. Currently, electrolytic aluminum plants in my country attach great importance to seepage prevention and prevention of leachate pollution in electrolytic cell overhaul slag disposal sites. For example, the Xiaochong slag disposal site at the Guizhou Aluminum Plant uses seepage prevention measures at the bottom of the slag disposal site, supplemented by mixing lime with the electrolytic slag; the Pingguo Aluminum Plant in Guangxi uses a layering method of slag and clay to cover the electrolytic cell waste slag disposal site; and Yunnan Aluminum uses clay at the bottom for seepage prevention. The purpose of these seepage prevention measures is to prevent groundwater from being contaminated by the leachate from electrolytic slag.

[0004] The environmental pollution caused by aluminum electrolysis overhaul slag mainly occurs through seepage into groundwater from the bottom strata of the slag dump, resulting in water pollution. Due to the large quantity stored, it is prone to leakage and dust accumulation, posing a potential threat to the surrounding environment, especially groundwater. To prevent adverse environmental impacts during storage, it is necessary to treat it to render it harmless.

[0005] Cathode carbon blocks contain fluoride salts, therefore they cannot be used as reducing agents in direct silicon smelting, nor can they be directly returned to the carbon processing stage to be processed into carbon block products. Refractory bricks and insulation materials in overhauled slag contain high levels of soluble fluoride. There are reports of attempts by enterprises to use co-processing methods to treat overhauled slag cement kilns, and to utilize and harmlessly dispose of overhauled slag, but no specific implementation plans have been found. Therefore, removing and recovering fluoride salts from overhauled slag, making it meet the requirements for ordinary solid waste, has significant economic and environmental benefits.

[0006] Numerous reports, both domestically and internationally, have addressed the harmless treatment of overhaul slag. In general, the main methods for treating overhaul slag fall into two categories: wet methods, which involve defluorination in aqueous solutions and recovery of fluoride salts; and pyrometallurgical methods, which utilize high-temperature processes such as oxidative roasting, reduction roasting, and vacuum roasting to treat the slag, causing the fluoride salts to volatilize and then be reabsorbed for recovery. Pyrometallurgical treatment can reduce the soluble fluoride content in overhaul slag to below 0.01% without producing hydrogen cyanide gas. Comparatively, pyrometallurgical harmless treatment of overhaul slag is more easily integrated with aluminum electrolysis plants.

[0007] Reports on the harmless treatment of overhaul slag by pyrometallurgical methods include: A patent published on August 20, 2021, describes a method and system for preparing alternative fuels from overhaul slag of aluminum electrolysis cells (application publication number: CN 113278459A). Specifically, it includes the following steps: Step S1: Crushing the overhaul slag into small particles with a particle size of less than 15mm; Step S2: Proportioning carbon-based additives and small particles, and feeding them into a tube mill for modified grinding to obtain modified grinding media. The invention also includes a system for this method. By mixing the crushed small particles with carbon-based additives according to a specific ratio and then modifying and grinding them, the carbon-based additives act as grinding and combustion aids, effectively reducing unit energy consumption by more than 20%. Compared to the original overhaul slag, the comprehensive calorific value of the modified grinding mixture increases to over 4000kcal / kg, and the volatile matter content increases from 0 to 5-10%. Simultaneously, the addition of carbon-based additives lowers the ignition point by approximately 100℃, improving combustion performance. September 28, 2021: A high-temperature harmless treatment device for aluminum electrolytic cell overhaul slag (Authorization Announcement No.: CN 214289961 U). The device includes a lifting rail mounted above the resistance furnace, with a lifting trolley slidably connected to the rail surface. A grab bucket is installed below the lifting trolley. Resistance wires are fixedly installed on the inner wall of the resistance furnace. Beneficial effects: This invention utilizes a resistance furnace, inlet and outlet, a holding plate, hydraulic rods, and a blocking plate. During the high-temperature treatment of the overhaul slag, the slag is transported to one end of the holding plate via the grab bucket below the lifting trolley. The holding plate is then moved to move the slag into the resistance furnace. The hydraulic rod shortens, and a spring pulls the blocking plate to seal the inlet and outlet at both ends of the resistance furnace. The resistance wire inside the furnace heats up, converting the overhaul slag into silicon carbide and graphitized carbon products through high temperature. This significantly reduces waste generation, improves the recycling efficiency of the overhaul slag, and thus significantly improves the efficiency of harmless treatment of the overhaul slag (dry treatment). July 9, 2021: A technology for co-processing aluminum electrolytic cell overhaul slag with thermal power generation (Application Publication No.: CN 113480204 A). The technology involves cooling waste cathode carbon blocks and hazardous solid waste from overhaul slag, then crushing them to meet the fineness requirements for use in power plant pulverized coal. The pulverized coal and overhaul slag are mixed in a ratio of 1:(0.002~0.004) and then burned. A small amount of cyanide decomposes directly at high temperature, while a large amount of fluoride enters the limestone-gypsum desulfurization system of the power plant through the flue gas and reacts with the limestone slurry. - With a large amount of excess Ca in the slurry 2+ The reaction produces CaF2 precipitate, and other unburned solid waste is discharged with the coal slag after sintering. Its main components are alumina, silicon dioxide, etc., which can be used as raw materials for cement production.

[0008] The presence of fluorides lowers the eutectic point of the electrolyte during combustion, causing the waste cathode carbon to agglomerate at relatively low temperatures. The amorphous carbon in the waste cathode carbon has already graphitized, affecting its combustion rate. Studies show that waste cathode carbon (bottom) combustion at different experimental temperatures: ash at 600℃ and 650℃ shows no agglomeration and is yellowish-brown; at 680℃–750℃, slight agglomeration occurs, but the ash is brittle; at 800℃, the ash becomes hard; and at 850℃, molten agglomeration occurs. Combustion treatment that avoids agglomeration of waste cathode carbon is a significant engineering challenge. Summary of the Invention

[0009] To address the issue of harmless treatment of overhaul mine slag using pyrometallurgical methods, this invention provides a pyrometallurgical method and apparatus for treating overhaul mine slag. This invention proposes a method that uses the heat from burning waste cathode carbon to heat refractory bricks and insulation materials, volatilizing and removing fluoride salts from them, and then employs a two-stage countercurrent adsorption process to remove fluoride from the fluoride-carrying gas stream, thereby achieving the harmless treatment of overhaul mine slag. This invention is achieved through the following technical solutions.

[0010] A method for the harmless disposal of aluminum overhaul waste includes the following specific steps:

[0011] The aluminum overhaul waste is divided into two main parts: waste cathode carbon blocks and refractory brick-insulation material.

[0012] (1) The waste cathode carbon blocks containing fluoride salts are crushed to 1.0-10.0 mm to obtain fine blocks, and the powder smaller than 1.0 mm is pressed into 1.0-10.0 mm granules;

[0013] (2) Add the fine blocks and granules obtained in step (1) into the side-blown burner, introduce air for side-blown combustion, control the combustion bed temperature of the side-blown burner to 900℃~1100℃, and the top temperature of the side-blown burner to 850℃~980℃, and produce fluorine-containing volatile flue gas during the side-blown combustion process.

[0014] (3) The fluorine-containing volatile flue gas obtained in step (2) is separated from the fluorine salt and hot gas by a fluorine salt recovery device. The hot gas that has removed most of the fluorine salt is sent into a rotary kiln and heated in contact with the refractory brick-insulating material in the rotary kiln to remove the fluorine from the refractory brick-insulating material and produce fluorine-containing volatile flue gas from the rotary kiln.

[0015] (4) The fluorine-containing volatile flue gas produced in step (3) is sent to the second stage countercurrent alumina adsorption defluorination to obtain purified gas.

[0016] The waste cathode carbon block containing fluoride salt in step (1) includes the following components by mass percentage: C 47.20~88.60wt%, F 4.00~14.60wt%.

[0017] In step (2), the excess air coefficient is controlled to be 1.05-1.16, and the linear velocity of the combustion bed airflow in the side-blown fluidized burner is 0.27m / s to 0.46m / s.

[0018] In step (3), the linear velocity of the fluorine-containing volatile flue gas in the fluoride salt recovery unit is 18m / s to 20m / s, and the fluorine recovery rate (accounting for a total fluorine content) is >42.20%; in step (4), the residence time of the refractory brick-insulating material in the rotary kiln is 20min, and the temperature of the rotary kiln is controlled at 700 to 950℃.

[0019] In step (4), the first-stage fluorine absorption rate (as a percentage of total fluorine) in the two-stage countercurrent alumina adsorption defluorination is >52.08%, and the second-stage fluorine absorption rate is >4.02%. The purified gas meets the emission requirements of GB25465-2010.

[0020] An apparatus for the harmless disposal of aluminum overhaul waste includes a side-blown burner 1, a fluoride recovery unit 6, a discharger 7, a rotary kiln 8, a feeder 9, a first-stage adsorber 10, a cyclone separator 11, a second-stage adsorber 14, and a bag filter 15. The side-blown burner 1 is equipped with a residual material discharge outlet 2, a spray nozzle 3, an air supply pipe 4, and a feeder 5. The fluorine-containing volatile flue gas outlet at the top of the side-blown burner 1 is connected to the fluoride recovery unit 6. The hot gas from the hot gas outlet of the fluoride recovery unit 6 enters one end of the rotary kiln 8 through the discharger 7. The other end of the rotary kiln 8 is equipped with a feeder 9. The fluorine-containing volatile flue gas from the other end of the rotary kiln 8 passes through the feeder 9, and then sequentially passes through the first-stage adsorber 10, the cyclone separator 11, the second-stage adsorber 14, and the bag filter 15 before being discharged from the clean gas outlet 16 on the bag filter 15.

[0021] The first-stage adsorber 10 is provided with a first-stage mixing port 12, and the second-stage adsorber 14 is provided with a second-stage mixing port 13.

[0022] A method for applying a device for the harmless disposal of aluminum overhaul waste residue includes the following specific steps:

[0023] The aluminum overhaul waste is divided into two main parts: waste cathode carbon blocks and refractory brick-insulation material.

[0024] Step 1: Crush the waste cathode carbon blocks containing fluoride salts to 1.0-10.0mm to obtain fine blocks, and press the powder smaller than 1.0mm into 1.0-10.0mm granules;

[0025] Step 2: The fine blocks and granules obtained in Step 1 are added to the side-blown burner 1 through the feeder 5, and air is introduced through the air supply pipe 4. The combustion occurs near the injection port 3. The combustion bed temperature of the side-blown burner 1 is controlled at 900℃~1100℃, and the top temperature of the side-blown burner is controlled at 850℃~980℃. Fluorine-containing volatile flue gas is produced during the side-blown combustion process.

[0026] Step 3: The fluorine-containing volatile flue gas produced in Step 2 is separated from the fluoride and hot gas by the fluoride recovery unit 6. The fluoride is discharged from the unloading port of the recovery unit and sent to the aluminum electrolysis workshop.

[0027] Step 4: The hot gas produced in Step 3 is added to the rotary kiln 8 through the unloader 7, and comes into countercurrent contact with the refractory brick-insulating material added to the rotary kiln 8 through the feeder 9 on the other side. During this process, fluorine-containing volatile flue gas is produced in the rotary kiln.

[0028] Step 5: The fluorine-containing volatile flue gas produced in Step 4 is sequentially passed through the first-stage adsorber 10, cyclone separator 11, second-stage adsorber 14, and bag filter 15 and discharged from the clean gas outlet 16 on the bag filter 15.

[0029] In step 5, the fluorinated alumina separated by the bag filter 15 is returned to the first-stage adsorber 10, and fresh alumina is added to the second-stage adsorber 14.

[0030] The fluorinated alumina produced by the cyclone separator 11 is sent to the aluminum electrolysis workshop.

[0031] The principle of this invention: In thermogravimetric analysis with uniform heating, when the temperature exceeds 680℃, the waste cathode carbon (bottom) becomes sticky, affecting its combustion process. Based on high-temperature combustion kinetics research of waste cathode carbon blocks, this invention overcomes the slagging that occurs during the combustion of waste tank lining carbon blocks containing fluoride salts. Waste tank lining carbon requires an airflow above its ignition temperature to achieve a high combustion rate. Fluorine in the waste tank lining carbon blocks mainly exists in electrolyte form. In a humid airflow or during combustion, fluoride salts and fluoride oxides react chemically with gaseous water, decomposing to generate highly volatile fluorine-containing gases, which are then volatilized and removed. Side-blown combustion of waste tank lining carbon achieves a fluorine volatilization rate 6-8 times higher than static bed combustion. Fluorine in refractory bricks and insulation materials from overhauled slag can also be volatilized and removed at high temperatures, achieving a fluorine volatilization rate 6 times higher than static bed combustion, reducing the residence time from 120 min to 20 min.

[0032] The beneficial effects of this invention are:

[0033] (1) Excellent removal of fluorine and cyanide: Cyanide in overhaul slag decomposes easily at high temperatures, and fluorine compounds volatilize in the air at high temperatures. This invention can remove 98.38% of the fluorine from overhaul slag. Relevant literature indicates that cyanide decomposes almost completely at high temperatures. During the reaction, fluorine is discharged with the gas flow. The fluorinated alumina produced by the fluoride salt recovery unit and the alumina two-stage countercurrent absorption unit for fluorine in the gas enters the aluminum electrolysis system, and the tail gas meets the GB 25465-2010 standard.

[0034] (2) Enhanced reaction: At the same temperature, the side-blown combustion rate of waste cathode carbon is 10 times faster than that in a muffle furnace, and the fluorine volatilization rate in the refractory brick-insulating material is 6 times higher in the rotary kiln than in the static bed. The combustion rate of waste carbon in the side-blown fluidized burner is >86.40%, and the slagging rate is about 3.60%, which is significantly higher than the combustion rate of 21.64% in the muffle furnace (static bed). This solves the problem of the difficulty in utilizing the slag accumulated during major repairs.

[0035] (3) Suitable for aluminum electrolysis process: The aluminum electrolysis plant has no wet process and equipment, and the waste produced is treated harmlessly by pyrolysis. The fluorine-containing substances produced by the side-blown combustion-rotary kiln harmless treatment of the overhauled slag meet the requirements for entering the aluminum electrolysis process, and the fluorine resource utilization rate is high.

[0036] (4) The utilization of the heat generated by the combustion of waste cathode carbon is even more difficult. This invention uses the heat generated by the combustion of waste cathode carbon to treat waste refractory bricks-insulation materials, thus comprehensively treating the overhaul slag produced by aluminum electrolysis. Attached Figure Description

[0037] Figure 1 This is a process flow diagram of the present invention;

[0038] Figure 2 This is a schematic diagram of the device structure of the present invention.

[0039] In the diagram: 1-Side-blown burner; 2-Residue discharge port; 3-Pulse nozzle; 4-Air supply pipe; 5-Feeder; 6-Fluoride salt recovery unit; 7-Unloader; 8-Rotary kiln; 9-Feeder; 10-First-stage adsorber; 11-Cyclone separator; 12-First-stage mixing port; 13-Second-stage mixing port; 14-Second-stage adsorber; 15-Bag collector; 16-Clean air outlet. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] like Figure 2As shown, the device for the harmless disposal of aluminum overhaul waste includes a side-blown burner 1, a fluoride recovery unit 6, a discharger 7, a rotary kiln 8, a feeder 9, a first-stage adsorber 10, a cyclone separator 11, a second-stage adsorber 14, and a bag filter 15. The side-blown burner 1 is equipped with a residual material discharge outlet 2, a spray nozzle 3, an air supply pipe 4, and a feeder 5. The fluorine-containing volatile flue gas outlet at the top of the side-blown burner 1 is connected to the fluoride recovery unit 6. The hot gas from the hot gas outlet of the fluoride recovery unit 6 enters one end of the rotary kiln 8 through the discharger 7. The other end of the rotary kiln 8 is equipped with a feeder 9. The fluorine-containing volatile flue gas from the other end of the rotary kiln 8 passes through the feeder 9, and then sequentially passes through the first-stage adsorber 10, the cyclone separator 11, the second-stage adsorber 14, and the bag filter 15 before being discharged from the clean gas outlet 16 on the bag filter 15.

[0043] The first-stage adsorber 10 is provided with a first-stage mixing port 12, and the second-stage adsorber 14 is provided with a second-stage mixing port 13.

[0044] like Figure 1 As shown, the application method of this device for the harmless disposal of aluminum overhaul waste residue includes the following specific steps:

[0045] The aluminum overhaul waste is divided into two main parts: waste cathode carbon blocks and refractory brick-insulation material.

[0046] Step 1: Crush the waste cathode carbon blocks containing fluoride salts to 1.0-10.0 mm to obtain fine blocks. Press the powder smaller than 1.0 mm into 1.0-10.0 mm granules. The carbon content of the waste cathode carbon blocks is as follows (mass percentage): C 47.20 wt%, F 14.60 wt%.

[0047] Step 2: The fine lumps and granules obtained in Step 1 are added to the side-blown burner 1 through the feeder 5. Air is introduced through the air supply pipe 4, and the excess air coefficient is controlled at 1.05. The combustion occurs near the injection port 3. The linear velocity of the combustion bed airflow in the side-blown fluidized burner 1 is 0.27 m / s. The combustion bed temperature of the side-blown burner 1 is controlled at 900℃, and the top temperature of the side-blown burner is controlled at 850℃. Fluorine-containing volatile flue gas is produced during the side-blown combustion process.

[0048] Step 3: The fluorine-containing volatile flue gas produced in Step 2 is separated from the fluoride and hot gas by the fluoride salt recovery unit 6. The linear velocity of the airflow at the inlet of the fluoride salt recovery unit 6 is 18 m / s. The fluoride is discharged from the discharge port of the recovery unit. The fluorine recovery rate (accounting for 42.81% of the total fluorine) is fluoride salt recovered and sent to the aluminum electrolysis workshop.

[0049] Step 4: The hot gas produced in Step 3 is added to the rotary kiln 8 via the unloader 7, and comes into countercurrent contact with the refractory brick-insulating material added to the rotary kiln 8 via the feeder 9 on the other side. During this process, fluorine-containing volatile flue gas is produced in the rotary kiln. The residence time of the refractory brick-insulating material in the rotary kiln 8 is 20 minutes, and the temperature at the feed end of the rotary kiln 8 is controlled at 700℃ and the temperature at the discharge end is 950℃.

[0050] Step 5: The fluorine-containing volatile flue gas produced in Step 4 is sequentially passed through the first-stage adsorber 10, cyclone separator 11, second-stage adsorber 14 and bag filter 15 and discharged from the clean gas outlet 16 on the bag filter 15. During this process, two-stage countercurrent alumina adsorption defluorination is carried out.

[0051] In step 5, the fluorinated alumina separated by the bag filter 15 is returned to the first-stage adsorber 10, while fresh alumina is added to the second-stage adsorber 14. The fluorinated alumina produced by the cyclone separator 11 is sent to the aluminum electrolysis workshop. The pressure inside the first-stage adsorber 10 is controlled at -200 Pa (relative pressure), and the pressure inside the second-stage adsorber 14 is controlled at -300 Pa (relative pressure). The fluorine absorption rate of the first stage (as a percentage of total fluorine) is 52.02%, and the fluorine absorption rate of the second stage is 4.02%. The purified gas contains 2.8 mg / m³ of fluorine. 3 It meets the emission requirements of GB25465-2010.

[0052] Example 2

[0053] like Figure 2 As shown, the device for the harmless disposal of aluminum overhaul waste includes a side-blown burner 1, a fluoride recovery unit 6, a discharger 7, a rotary kiln 8, a feeder 9, a first-stage adsorber 10, a cyclone separator 11, a second-stage adsorber 14, and a bag filter 15. The side-blown burner 1 is equipped with a residual material discharge outlet 2, a spray nozzle 3, an air supply pipe 4, and a feeder 5. The fluorine-containing volatile flue gas outlet at the top of the side-blown burner 1 is connected to the fluoride recovery unit 6. The hot gas from the hot gas outlet of the fluoride recovery unit 6 enters one end of the rotary kiln 8 through the discharger 7. The other end of the rotary kiln 8 is equipped with a feeder 9. The fluorine-containing volatile flue gas from the other end of the rotary kiln 8 passes through the feeder 9, and then sequentially passes through the first-stage adsorber 10, the cyclone separator 11, the second-stage adsorber 14, and the bag filter 15 before being discharged from the clean gas outlet 16 on the bag filter 15.

[0054] The first-stage adsorber 10 is provided with a first-stage mixing port 12, and the second-stage adsorber 14 is provided with a second-stage mixing port 13.

[0055] like Figure 1 As shown, the application method of this device for the harmless disposal of aluminum overhaul waste residue includes the following specific steps:

[0056] The aluminum overhaul waste is divided into two main parts: waste cathode carbon blocks and refractory brick-insulation material.

[0057] Step 1: Crush the waste cathode carbon blocks containing fluoride salts to 1.0-10.0 mm to obtain fine blocks. Press the powder smaller than 1.0 mm into 1.0-10.0 mm granules. The carbon content of the waste cathode carbon blocks is as follows (mass percentage): C 88.60 wt%, F 4.00 wt%.

[0058] Step 2: The fine lumps and granules obtained in Step 1 are added to the side-blown burner 1 through the feeder 5. Air is introduced through the air supply pipe 4, and the excess air coefficient is controlled at 1.16. Combustion occurs near the injection port 3. The linear velocity of the combustion bed airflow in the side-blown fluidized burner 1 is 0.46 m / s. The combustion bed temperature of the side-blown burner 1 is controlled at 1100℃, and the top temperature of the side-blown burner is 980℃. Fluorine-containing volatile flue gas is produced during the side-blown combustion process.

[0059] Step 3: The fluorine-containing volatile flue gas produced in Step 2 is separated from the fluoride and hot gas by the fluoride salt recovery unit 6. The linear velocity of the airflow at the inlet of the fluoride salt recovery unit 6 is 20 m / s. The fluoride is discharged from the discharge port of the recovery unit. The fluoride recovery rate (accounting for 42.2% of the total fluoride) is fluoride salt recovered and sent to the aluminum electrolysis workshop.

[0060] Step 4: The hot gas produced in Step 3 is added to the rotary kiln 8 via the unloader 7, and comes into countercurrent contact with the refractory brick-insulating material added to the rotary kiln 8 via the feeder 9 on the other side. During this process, fluorine-containing volatile flue gas is produced in the rotary kiln. The residence time of the refractory brick-insulating material in the rotary kiln 8 is 20 minutes, and the temperature at the feed end of the rotary kiln 8 is controlled at 700℃ and the temperature at the discharge end is 950℃.

[0061] Step 5: The fluorine-containing volatile flue gas produced in Step 4 is sequentially passed through the first-stage adsorber 10, cyclone separator 11, second-stage adsorber 14 and bag filter 15 and discharged from the clean gas outlet 16 on the bag filter 15. During this process, two-stage countercurrent alumina adsorption defluorination is carried out.

[0062] In step 5, the fluorinated alumina separated by the bag filter 15 is returned to the first-stage adsorber 10, while fresh alumina is added to the second-stage adsorber 14. The fluorinated alumina produced by the cyclone separator 11 is sent to the aluminum electrolysis workshop. The pressure inside the first-stage adsorber 10 is controlled at -200 Pa (relative pressure), and the pressure inside the second-stage adsorber 14 is controlled at -300 Pa (relative pressure). The fluorine absorption rate of the first stage (as a percentage of total fluorine) is 52.84%, and the fluorine absorption rate of the second stage is 4.11%. The purified gas contains 2.6 mg / m³ of fluorine. 3 It meets the emission requirements of GB25465-2010.

[0063] Example 3

[0064] like Figure 2 As shown, the device for the harmless disposal of aluminum overhaul waste includes a side-blown burner 1, a fluoride recovery unit 6, a discharger 7, a rotary kiln 8, a feeder 9, a first-stage adsorber 10, a cyclone separator 11, a second-stage adsorber 14, and a bag filter 15. The side-blown burner 1 is equipped with a residual material discharge outlet 2, a spray nozzle 3, an air supply pipe 4, and a feeder 5. The fluorine-containing volatile flue gas outlet at the top of the side-blown burner 1 is connected to the fluoride recovery unit 6. The hot gas from the hot gas outlet of the fluoride recovery unit 6 enters one end of the rotary kiln 8 through the discharger 7. The other end of the rotary kiln 8 is equipped with a feeder 9. The fluorine-containing volatile flue gas from the other end of the rotary kiln 8 passes through the feeder 9, and then sequentially passes through the first-stage adsorber 10, the cyclone separator 11, the second-stage adsorber 14, and the bag filter 15 before being discharged from the clean gas outlet 16 on the bag filter 15.

[0065] The first-stage adsorber 10 is provided with a first-stage mixing port 12, and the second-stage adsorber 14 is provided with a second-stage mixing port 13.

[0066] like Figure 1 As shown, the application method of this device for the harmless disposal of aluminum overhaul waste residue includes the following specific steps:

[0067] The aluminum overhaul waste is divided into two main parts: waste cathode carbon blocks and refractory brick-insulation material.

[0068] Step 1: Crush the waste cathode carbon blocks containing fluoride salts to 1.0-10.0 mm to obtain fine blocks. Press the powder smaller than 1.0 mm into 1.0-10.0 mm granules. The carbon content of the waste cathode carbon blocks is as follows (mass percentage): C 54.54 wt%, F 14.06 wt%.

[0069] Step 2: The fine lumps and granules obtained in Step 1 are added to the side-blown burner 1 through the feeder 5. Air is introduced through the air supply pipe 4, and the excess air coefficient is controlled at 1.10. Combustion occurs near the injection port 3. The linear velocity of the combustion bed airflow in the side-blown fluidized burner 1 is 0.32 m / s. The combustion bed temperature of the side-blown burner 1 is controlled at 1000℃, and the top temperature of the side-blown burner is 950℃. Fluorine-containing volatile flue gas is produced during the side-blown combustion process.

[0070] Step 3: The fluorine-containing volatile flue gas produced in Step 2 is separated from the fluoride and hot gas by the fluoride salt recovery unit 6. The linear velocity of the airflow at the inlet of the fluoride salt recovery unit 6 is 18 m / s. The fluoride is discharged from the discharge port of the recovery unit. The fluoride recovery rate (accounting for 42.26% of the total fluoride) is fluoride salt recovered and sent to the aluminum electrolysis workshop.

[0071] Step 4: The hot gas produced in Step 3 is added to the rotary kiln 8 via the unloader 7, and comes into countercurrent contact with the refractory brick-insulating material added to the rotary kiln 8 via the feeder 9 on the other side. During this process, fluorine-containing volatile flue gas is produced in the rotary kiln. The residence time of the refractory brick-insulating material in the rotary kiln 8 is 20 minutes, and the temperature at the feed end of the rotary kiln 8 is controlled at 700℃ and the temperature at the discharge end is 950℃.

[0072] Step 5: The fluorine-containing volatile flue gas produced in Step 4 is sequentially passed through the first-stage adsorber 10, cyclone separator 11, second-stage adsorber 14 and bag filter 15 and discharged from the clean gas outlet 16 on the bag filter 15. During this process, two-stage countercurrent alumina adsorption defluorination is carried out.

[0073] In step 5, the fluorinated alumina separated by the bag filter 15 is returned to the first-stage adsorber 10, while fresh alumina is added to the second-stage adsorber 14. The fluorinated alumina produced by the cyclone separator 11 is sent to the aluminum electrolysis workshop. The pressure inside the first-stage adsorber 10 is controlled at -200 Pa (relative pressure), and the pressure inside the second-stage adsorber 14 is controlled at -300 Pa (relative pressure). The fluorine absorption rate of the first stage (as a percentage of total fluorine) is 52.23%, and the fluorine absorption rate of the second stage is 4.09%. The purified gas contains 2.8 mg / m³ of fluorine. 3 It meets the emission requirements of GB25465-2010.

[0074] Example 4

[0075] like Figure 2 As shown, the device for the harmless disposal of aluminum overhaul waste includes a side-blown burner 1, a fluoride recovery unit 6, a discharger 7, a rotary kiln 8, a feeder 9, a first-stage adsorber 10, a cyclone separator 11, a second-stage adsorber 14, and a bag filter 15. The side-blown burner 1 is equipped with a residual material discharge outlet 2, a spray nozzle 3, an air supply pipe 4, and a feeder 5. The fluorine-containing volatile flue gas outlet at the top of the side-blown burner 1 is connected to the fluoride recovery unit 6. The hot gas from the hot gas outlet of the fluoride recovery unit 6 enters one end of the rotary kiln 8 through the discharger 7. The other end of the rotary kiln 8 is equipped with a feeder 9. The fluorine-containing volatile flue gas from the other end of the rotary kiln 8 passes through the feeder 9, and then sequentially passes through the first-stage adsorber 10, the cyclone separator 11, the second-stage adsorber 14, and the bag filter 15 before being discharged from the clean gas outlet 16 on the bag filter 15.

[0076] The first-stage adsorber 10 is provided with a first-stage mixing port 12, and the second-stage adsorber 14 is provided with a second-stage mixing port 13.

[0077] like Figure 1 As shown, the application method of this device for the harmless disposal of aluminum overhaul waste residue includes the following specific steps:

[0078] The aluminum overhaul waste is divided into two main parts: waste cathode carbon blocks and refractory brick-insulation material.

[0079] Step 1: Crush the waste cathode carbon blocks containing fluoride salts to 1.0-10.0 mm to obtain fine blocks. Press the powder smaller than 1.0 mm into 1.0-10.0 mm granules. The carbon content of the waste cathode carbon blocks is as follows (mass percentage): C 72.20 wt%, F 11.06 wt%.

[0080] Step 2: The fine lumps and granules obtained in Step 1 are added to the side-blown burner 1 through the feeder 5. Air is introduced through the air supply pipe 4, and the excess air coefficient is controlled at 1.16. Combustion occurs near the injection port 3. The linear velocity of the combustion bed airflow in the side-blown fluidized burner 1 is 0.46 m / s. The combustion bed temperature of the side-blown burner 1 is controlled at 1000℃, and the top temperature of the side-blown burner is 900℃. Fluorine-containing volatile flue gas is produced during the side-blown combustion process.

[0081] Step 3: The fluorine-containing volatile flue gas produced in Step 2 is separated from the fluoride and hot gas by the fluoride salt recovery unit 6. The linear velocity of the airflow at the inlet of the fluoride salt recovery unit 6 is 19 m / s. The fluoride is discharged from the discharge port of the recovery unit. The fluoride recovery rate (accounting for 42.27% of the total fluoride) is fluoride salt recovered and sent to the aluminum electrolysis workshop.

[0082] Step 4: The hot gas produced in Step 3 is added to the rotary kiln 8 via the unloader 7, and comes into countercurrent contact with the refractory brick-insulating material added to the rotary kiln 8 via the feeder 9 on the other side. During this process, fluorine-containing volatile flue gas is produced in the rotary kiln. The residence time of the refractory brick-insulating material in the rotary kiln 8 is 20 minutes, and the temperature at the feed end of the rotary kiln 8 is controlled at 700℃ and the temperature at the discharge end is 950℃.

[0083] Step 5: The fluorine-containing volatile flue gas produced in Step 4 is sequentially passed through the first-stage adsorber 10, cyclone separator 11, second-stage adsorber 14 and bag filter 15 and discharged from the clean gas outlet 16 on the bag filter 15. During this process, two-stage countercurrent alumina adsorption defluorination is carried out.

[0084] In step 5, the fluorinated alumina separated by the bag filter 15 is returned to the first-stage adsorber 10, while fresh alumina is added to the second-stage adsorber 14. The fluorinated alumina produced by the cyclone separator 11 is sent to the aluminum electrolysis workshop. The pressure inside the first-stage adsorber 10 is controlled at -200 Pa (relative pressure), and the pressure inside the second-stage adsorber 14 is controlled at -300 Pa (relative pressure). The fluorine absorption rate of the first stage (as a percentage of total fluorine) is 52.12%, and the fluorine absorption rate of the second stage is 4.07%. The purified gas contains 2.6 mg / m³ of fluorine. 3 It meets the emission requirements of GB25465-2010.

[0085] This invention achieves a side-blown combustion rate of waste cathode carbon that is 10 times faster than that in a muffle furnace at the same temperature, and a fluorine volatilization rate in the refractory brick-insulating material that is 6 times higher in a rotary kiln than in a static bed. The combustion rate of waste carbon in the side-blown fluidized burner is >86.40%, with a slagging rate of approximately 3.60%, which is significantly higher than the 21.64% combustion rate in a muffle furnace (static bed).

[0086] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for the harmless disposal of aluminum overhaul waste residue, characterized in that: The aluminum overhaul waste is divided into two main parts: waste cathode carbon blocks and refractory brick-insulation material. (1) The waste cathode carbon blocks containing fluoride salts are crushed to 1.0-10.0 mm to obtain fine blocks, and the powder smaller than 1.0 mm is pressed into 1.0-10.0 mm granules; (2) Add the fine blocks and granules obtained in step (1) into the side-blown burner, introduce air for side-blown combustion, control the combustion bed temperature of the side-blown burner to 900℃~1100℃, the top temperature of the side-blown burner to 850℃~980℃, control the excess air coefficient to 1.05-1.16, and the combustion bed airflow linear velocity of the side-blown fluidized burner to 0.27m / s~0.46m / s, and produce fluorine-containing volatile flue gas during the side-blown combustion process; (3) The fluorine-containing volatile flue gas obtained in step (2) is separated from the fluoride salt and hot gas by passing it through a fluoride salt recovery device. The linear velocity of the fluorine-containing volatile flue gas in the fluoride salt recovery device is 18m / s to 20m / s. The hot gas that has removed most of the fluoride salt is sent into a rotary kiln and heated to contact the refractory brick-insulating material in the rotary kiln. The residence time of the refractory brick-insulating material in the rotary kiln is 20min. The temperature of the rotary kiln is controlled at 700 to 950℃. The fluorine in the refractory brick-insulating material is removed to produce fluorine-containing volatile flue gas in the rotary kiln. (4) The fluorine-containing volatile flue gas produced in step (3) is sent to the second stage countercurrent alumina adsorption defluorination to obtain purified gas.

2. The method for harmlessly disposing of aluminum overhaul waste slag according to claim 1, characterized in that: The waste cathode carbon block containing fluoride salt in step (1) includes the following components by mass percentage: C 47.20~88.60wt%, F 4.00~14.60wt%.

3. An apparatus for the harmless disposal of aluminum overhaul waste slag used in the method according to claim 1, characterized in that: The system includes a side-blown burner (1), a fluoride salt recovery unit (6), a discharger (7), a rotary kiln (8), a feeder (9), a first-stage adsorber (10), a cyclone separator (11), a second-stage adsorber (14), and a bag filter (15). The side-blown burner (1) is equipped with a residual material discharge outlet (2), a spray nozzle (3), an air supply pipe (4), and a feeder (5). The fluorine-containing volatile flue gas outlet at the top of the side-blown burner (1) is connected to the fluoride salt recovery unit (6). The hot gas from the hot gas outlet of the fluoride salt recovery unit (6) enters one end of the rotary kiln (8) through the unloader (7). The other end of the rotary kiln (8) is equipped with a feeder (9). The fluorine-containing volatile flue gas from the other end of the rotary kiln (8) passes through the feeder (9) and then passes through the first-stage adsorber (10), cyclone separator (11), second-stage adsorber (14), and bag dust collector (15) in sequence, and is discharged from the clean gas outlet (16) on the bag dust collector (15).

4. The apparatus for the harmless disposal of aluminum overhaul waste slag according to claim 3, characterized in that: The first-stage adsorber (10) is provided with a first-stage mixing port (12), and the second-stage adsorber (14) is provided with a second-stage mixing port (13).

5. The apparatus for the harmless disposal of aluminum overhaul waste slag according to claim 3, characterized in that: The fluorinated alumina separated by the bag filter (15) is returned to the first-stage adsorber (10), and fresh alumina is added to the second-stage adsorber (14).

6. The apparatus for the harmless disposal of aluminum overhaul waste slag according to claim 3, characterized in that: The fluorinated alumina produced by the cyclone separator (11) is sent to the aluminum electrolysis workshop.

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