A lithium tailings roasting gas recycling device

Abstract

The utility model discloses a kind of lithium tailings roasting gas recycling device, including primary recovery unit, secondary recovery unit and tertiary recovery unit, the primary recovery unit, secondary recovery unit and tertiary recovery unit are linearly arranged from left to right, and primary recovery unit, secondary recovery unit are communicated with a primary gas guide pipe between the two. Advantageous effect: through the linear arrangement and pertinence design of primary recovery unit, secondary recovery unit and tertiary recovery unit, the sequential separation and resource utilization of three kinds of gas are realized, the problem of "harmful gas is only removed not recycled, resource waste is serious" in traditional processing technology is solved. Among them, primary recovery unit uses 10-15%NaOH solution atomization spraying, relies on the increased gas-liquid contact area of filler layer, realizes the overall absorption of HF, and the NaF solution produced;Secondary recovery unit uses 5-8% ammonia as absorbent, cooperates with the compressed air of aeration pipe, realizes the removal of SO2.

Description

Technical Field

[0001] This utility model relates to the field of lithium tailings roasting, specifically to a device for recovering and utilizing gas after lithium tailings roasting. Background Technology

[0002] In the process of lithium mining and lithium salt production, a large amount of lithium tailings are generated. Roasting is a common process for recovering residual lithium and removing harmful impurities from lithium tailings. However, the roasting process releases a mixture of gases containing hydrogen fluoride (HF), sulfur dioxide (SO2), and carbon dioxide (CO2). Among these gases, HF is highly corrosive, and SO2 easily causes acid rain. If directly emitted, it will seriously pollute the atmosphere, soil, and water bodies, threatening the ecological environment and human health. At the same time, HF, SO2, and CO2 in these gases all have recovery value, and direct emission also results in resource waste.

[0003] Currently, the industry mostly employs a "single-stage decontamination" process for treating lithium tail roasting gases: either simply neutralizing HF and SO2 with alkali without recycling the products, leading to serious resource waste; or lacking targeted separation design, failing to achieve effective separation and recovery of the three gases. Furthermore, traditional processes rely on manual periodic monitoring of tail gas concentrations, resulting in detection lag. If tail gas levels exceed standards, direct emissions are likely, making it difficult to meet environmental compliance requirements. Therefore, there is an urgent need for a device that can achieve sequential gas separation and recovery, and provides efficient and safe tail gas emission guarantees, addressing the pain points of existing technologies: "incomplete environmental protection, low resource utilization, and high emission risks." Utility Model Content

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a device for recovering and utilizing gas after lithium tailings roasting. This device has the advantages of sequentially separating and recovering HF, SO2, and CO2, and ensuring safe and compliant emissions of tail gas, thereby solving the problems mentioned in the background technology.

[0005] (II) Technical Solution To achieve the advantages of sequentially separating and recovering HF, SO2, and CO2 while ensuring safe and compliant emissions of exhaust gas, the specific technical solution adopted by this utility model is as follows: A gas recovery and utilization device after lithium tailings roasting includes a primary recovery unit, a secondary recovery unit, and a tertiary recovery unit. The primary, secondary, and tertiary recovery units are arranged linearly from left to right. A primary gas guide pipe connects the primary and secondary recovery units, and a secondary gas guide pipe connects the secondary and tertiary recovery units. An air inlet pipe is connected to the lower surface of the primary recovery unit, and an exhaust pipe is connected to the top of the tertiary recovery unit. A packing layer is installed inside both the primary and secondary recovery units, and a circulation pipe is sealed on the right side wall of both units. Two sets of spray pipes are symmetrically installed at the upper end of the circulation pipes, and an atomizing nozzle is installed on the side of the spray pipes facing the packing layer. An air filling pipe is inserted into the side wall of the secondary recovery unit. An electric heater is embedded in the bottom of the inner side of the tertiary recovery unit, and a circulation pump is installed on the surface of the circulation pipe.

[0006] Furthermore, an online gas analyzer is installed on the surface of the exhaust pipe, and one end of the exhaust pipe is connected to an exhaust pipe and a vent pipe via a tee. Both the exhaust pipe and the vent pipe are equipped with electrically controlled valves. An emergency treatment tank is connected to the bottom of the vent pipe via a flange. A controller is installed on the top of the three-stage recovery unit, and the output of the controller is electrically connected to the electrically controlled valve. The online gas analyzer is electrically connected to the controller.

[0007] Furthermore, corrosion-resistant fans are installed on the upper surfaces of both the primary and secondary air guide pipes, and one-way valves are installed on the surfaces of the primary, secondary, and inlet pipes.

[0008] Furthermore, the lengths of each set of spray pipes in the circulation pipe are different, and the end profile of each set of spray pipes in the circulation pipe is semi-circular. The length of the longest spray pipe in the circulation pipe is less than the inner diameter of the primary or secondary recycling unit.

[0009] Furthermore, the primary recovery unit is filled with 10-15% NaOH solution, the secondary recovery unit is filled with 5-8% ammonia solution, and the tertiary recovery unit is filled with 30% ethanolamine solution.

[0010] Furthermore, the lower surfaces of the primary recycling unit, the secondary recycling unit, and the tertiary recycling unit are all equipped with discharge pipes, and manual valves are installed on the surfaces of the discharge pipes.

[0011] Furthermore, an agitator is installed on the lower surface of the three-stage recycling unit, and the agitator consists of a drive motor and a stirring shaft with its output end fixed, and several impellers are installed at equal intervals on the stirring shaft of the agitator.

[0012] (III) Beneficial Effects Compared with the prior art, this utility model provides a device for recovering and utilizing gas after lithium tailings roasting, which has the following beneficial effects: (1) This utility model, through the linear arrangement and targeted design of a primary, secondary, and tertiary recovery unit, achieves the sequential separation and resource utilization of three gases, solving the problem of "only removing harmful gases without recycling them, resulting in serious resource waste" in traditional treatment processes. Specifically, the primary recovery unit uses a 10-15% NaOH solution for atomized spraying, relying on the increased gas-liquid contact area of ​​the packing layer to achieve comprehensive absorption of HF and produce NaF solution; the secondary recovery unit uses 5-8% ammonia water as the absorbent, combined with compressed air introduced through the air filling pipe, to remove SO2 and convert the absorption product into a 15-20% (NH4)2SO4 solution; the tertiary recovery unit recovers CO2 from the gas through adsorption with a 30% ethanolamine solution and desorption by an electric heater. This sequential recovery mode not only completely eliminates the corrosive and polluting effects of HF and SO2 on the environment but also transforms the original "waste gas" into high-value industrial raw materials, achieving the dual benefits of "environmental compliance" and "resource recycling."

[0013] (2) This utility model establishes a closed-loop control system by using an online gas analyzer, controller, electric control valve, and emergency treatment tank to construct a complete exhaust gas emission safety assurance system, avoiding the risks of "lagging manual detection and direct discharge of exhaust gas exceeding standards" in traditional processes. The online gas analyzer on the exhaust pipe can monitor the concentration of HF and CO2 in the exhaust gas in real time, and the data can be transmitted to the controller synchronously. The controller automatically judges whether the exhaust gas meets the standards based on preset environmental protection standards. If it meets the standards, it controls the electric control valve on the exhaust pipe to open and the electric control valve on the vent pipe to close, and the exhaust gas is discharged in compliance with regulations through the exhaust pipe. If the concentration exceeds the standard, the controller can complete the valve switching (closing the electric control valve on the exhaust pipe and opening the electric control valve on the vent pipe) within 0.5s, and introduce the non-compliant exhaust gas into the emergency treatment tank (soda lime or 30% NaOH solution in the tank can absorb harmful components for a second time) until the exhaust gas concentration drops to the standard range before switching to discharge. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1This is a schematic diagram of the overall structure of a lithium tailings roasting gas recovery and utilization device according to an embodiment of the present utility model. Figure 2 This is a schematic diagram of the internal structure of the primary recycling unit and the secondary recycling unit according to an embodiment of the present utility model; Figure 3 This is a schematic diagram of the internal structure of a three-stage recycling unit according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the circulation tube according to an embodiment of the present utility model.

[0016] In the picture: 1. Primary recovery unit; 2. Secondary recovery unit; 3. Tertiary recovery unit; 4. Inlet pipe; 5. Primary air guide pipe; 6. Secondary air guide pipe; 7. Exhaust pipe; 8. Online gas analyzer; 9. Controller; 10. Waste gas pipe; 11. Electrically controlled valve; 12. Air intake pipe; 13. Emergency treatment tank; 14. Circulation pipe; 15. Circulation pump; 16. Packing layer; 17. Spray pipe; 18. Air filling pipe; 19. Electric heater; 20. Agitator; 21. Atomizing nozzle. Detailed Implementation

[0017] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0018] According to an embodiment of the present invention, a device for recovering and utilizing gas after roasting lithium tailings is provided.

[0019] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figure 1-4As shown, a lithium tailings roasting gas recovery and utilization device according to an embodiment of the present invention includes a primary recovery unit 1, a secondary recovery unit 2, and a tertiary recovery unit 3. The primary recovery unit 1, the secondary recovery unit 2, and the tertiary recovery unit 3 are arranged linearly from left to right. A primary gas guide pipe 5 connects the primary recovery unit 1 and the secondary recovery unit 2, and a secondary gas guide pipe 6 connects the secondary recovery unit 2 and the tertiary recovery unit 3. An air inlet pipe 4 is connected to the lower surface of the primary recovery unit 1, and the top of the tertiary recovery unit 3... The unit is connected to an exhaust pipe 7. The interior of the primary recovery unit 1 and the secondary recovery unit 2 is equipped with a packing layer 16. The right side wall of the primary recovery unit 1 and the secondary recovery unit 2 is sealed with a circulation pipe 14. Two sets of spray pipes 17 are symmetrically installed at the upper end of the circulation pipe 14. The side of the spray pipe 17 facing the packing layer 16 is equipped with an atomizing nozzle 21. An air filling pipe 18 is inserted through the side wall of the secondary recovery unit 2. An electric heater 19 is embedded in the bottom of the inner side of the tertiary recovery unit 3. A circulation pump 15 is installed on the surface of the circulation pipe 14.

[0020] The system consists of a primary recovery unit 1 (HF recovery tower), a secondary recovery unit 2 (SO2 recovery tower), and a tertiary recovery unit 3 (CO2 recovery tower). These three units are arranged linearly from left to right according to the logic of decreasing toxicity and increasing separation difficulty. This arrangement ensures that the gas flows sequentially through each unit, avoiding short-circuiting or backflow of untreated gas, and also facilitates centralized installation and maintenance. The primary recovery unit 1 and the secondary recovery unit 2 are connected by a primary gas guide pipe 5, and the secondary recovery unit 2 and the tertiary recovery unit 3 are connected by a secondary gas guide pipe 6. All gas guide pipes are made of 316L stainless steel (resistant to acid and alkali corrosion, suitable for acidic gas environments such as HF and SO2), and the inner diameter of the pipes is designed according to the roasting gas processing capacity (e.g., 5000 m³). 3When the flow rate is 1.2 m / s, the inner diameter of the gas guide pipe is set to 200 mm to ensure that the gas flow rate is controlled at 1.2-1.5 m / s. This avoids insufficient absorption due to excessive flow rate and system blockage due to excessive flow rate. The lower surface of the primary recovery unit 1 is connected to the gas inlet pipe 4. The gas inlet pipe adopts the "bottom in, top out" gas inlet method - allowing the roasted gas to enter from the bottom of the absorption tower and form a countercurrent contact with the absorbent sprayed at the top, maximizing the gas-liquid contact time and improving absorption efficiency. The end of the gas inlet pipe is also equipped with a gas distributor (such as a porous sieve plate structure) to evenly disperse the gas into the tower and avoid the absorption dead zone caused by excessively high local gas concentration. The top of the tertiary recovery unit 3 is connected to an exhaust pipe 7, serving as the final exhaust gas emission channel. Its height must comply with environmental regulations (e.g., exceeding the height of the plant building to prevent localized exhaust gas accumulation). The lower surface of the primary recovery unit 1 is connected to an inlet pipe 4, which uses a "bottom-in, top-out" intake method—allowing the roasted gas to enter from the bottom of the absorption tower and form a counter-current contact with the absorbent sprayed at the top, maximizing the gas-liquid contact time and improving absorption efficiency. The end of the inlet pipe 4 is also equipped with a gas distributor (such as a porous sieve plate structure, not shown in the figure), which can evenly disperse the gas within the tower, preventing excessively high local gas concentrations that could lead to absorption dead zones. The top of the tertiary recovery unit 3 is connected to an exhaust pipe 7, serving as the final exhaust gas emission channel. Its height must comply with environmental regulations (e.g., exceeding the height of the plant building to prevent localized exhaust gas accumulation). Both the primary recovery unit 1 and the secondary recovery unit 2 are internally equipped with a packing layer 16. The packing material is polypropylene stepped rings (Φ50mm×50mm)—this packing material has a large specific surface area (approximately 200m²). 2 / m 3 With its high porosity (approximately 90%), polypropylene can significantly increase the gas-liquid contact area while reducing gas flow resistance; moreover, polypropylene is resistant to acid and alkali corrosion and is suitable for environments with absorbents such as NaOH solution and ammonia. Both units have a sealed circulation pipe 14 installed on the right side wall. One end of the circulation pipe 14 is connected to the absorbent storage area at the bottom of the tower, and the other end extends to the top of the tower to form an absorbent circulation loop. Two sets of spray pipes 17 are symmetrically installed at the upper end of the circulation pipe 14. The spray pipe 17 is equipped with an atomizing nozzle 21 (atomizing particle size 50-100μm) on the side facing the packing layer 16. The atomization design can disperse the absorbent into fine droplets, further improving the mixing uniformity with the gas, so that components such as HF and SO2 can react quickly with the absorbent. An air supply pipe 18 is installed on the side wall of the secondary recovery unit 2 to introduce compressed air (purity ≥99%) into the tower. Because the secondary unit adopts the ammonia desulfurization process, the (NH4)2SO3 generated by absorbing SO2 needs to be converted into stable (NH4)2SO4 by air oxidation. An aeration disc (not shown in the figure) is also provided at the end of the air supply pipe 18, which can evenly disperse the air into the absorbent liquid, and the oxidation efficiency reaches more than 98%. An electric heater 19 is embedded in the bottom inner side of the three-stage recycling unit 3 (the power is designed according to the tower volume, such as 10m³).3 The tower is equipped with a 15kW heater to heat the ethanolamine solution. After adsorbing CO2, ethanolamine needs to decompose and release high-concentration CO2 at 120-140℃. The electric heater uses a stainless steel heating tube (corrosion resistant) and is controlled by a temperature sensor to ensure that the heating temperature is stable within the optimal decomposition range. A circulation pump 15 (a corrosion-resistant centrifugal pump with a head of 15-20m and a flow rate matched to the tower's processing capacity) is installed on the surface of the circulation pipe 14 to provide power for the absorbent circulation and ensure stable spray volume (e.g., the spray volume of the first-stage unit is controlled at 8-10m). 3 / h, to ensure the packing layer is fully wetted).

[0021] Please refer to Figure 1 and Figure 3 An online gas analyzer 8 is installed on the surface of the exhaust pipe 7, and one end of the exhaust pipe 7 is connected to the exhaust pipe 10 and the intake pipe 12 via a tee. Both the exhaust pipe 10 and the intake pipe 12 are equipped with an electric control valve 11. The bottom of the intake pipe 12 is connected to an emergency treatment tank 13 via a flange. A controller 9 is installed on the top of the three-stage recovery unit 3, and the output of the controller 9 is electrically connected to the electric control valve 11. The online gas analyzer 8 is electrically connected to the controller 9.

[0022] An online gas analyzer 8 (model such as GXH-3010N, detection accuracy ±1%FS) is installed on the surface of the exhaust pipe 7, which can monitor HF in the exhaust gas in real time (detection range 0-10mg / m³). 3 SO2 (0-100mg / m³) 3 The concentrations of CO2 (0-5%) are synchronously transmitted to controller 9, allowing operators to monitor the exhaust gas compliance status in real time. One end of exhaust pipe 7 is connected to exhaust pipe 10 (compliant exhaust gas emission channel) and vent pipe 12 (non-compliant exhaust gas return channel) via a tee (material: 316L stainless steel, sealing grade PN1.0). Both exhaust pipe 10 and vent pipe 12 are equipped with electrically controlled valves 11 (model such as ZCS-16P, corrosion-resistant solenoid valve, response time ≤0.5s) for switching exhaust gas flow direction. The bottom of vent pipe 12 is connected to an emergency treatment tank 13 (volume 5-10m³) via a flange (sealing gasket is PTFE, resistant to acid and alkali aging). 3 (Designed based on maximum exhaust gas treatment capacity), the tank is filled with soda lime (mainly Ca(OH)2) or 30% NaOH solution, which can perform secondary absorption of substandard exhaust gas—if the online analyzer detects HF > 0.01 mg / m³. 3 Or SO2 > 50 mg / m³ 3The controller 9 will immediately close the electrically controlled valve 11 of the exhaust pipe 10 and open the electrically controlled valve 11 of the vent pipe 12, allowing the exhaust gas to enter the emergency tank for treatment until the concentration reaches the standard before switching to emission, ensuring 100% compliance. The top of the three-stage recovery unit 3 is equipped with a controller 9 (model such as PLCS7-200SMART), whose output is electrically connected to the electrically controlled valve 11, which can automatically control valve switching; at the same time, the online gas analyzer 8 is electrically connected to the controller 9, forming a closed-loop control of "detection-judgment-execution". The controller 9 can also store exhaust gas concentration data for one year, which is convenient for environmental traceability.

[0023] Please refer to Figure 1 and Figure 2 Corrosion-resistant fans are installed on the upper surfaces of the primary air duct 5 and the secondary air duct 6, and one-way valves are installed on the surfaces of the primary air duct 5, the secondary air duct 6 and the air inlet pipe 4.

[0024] The upper surfaces of the primary air guide pipe 5 and the secondary air guide pipe 6 are equipped with corrosion-resistant fans (model such as 4-72-4.5A, made of fiberglass, with a wind pressure of 1500-2000Pa and an air volume matching the processing capacity of the device). As the gas will generate pressure loss (about 500-800Pa / unit) when it flows through the packing layer and absorbent, the fan can provide stable power to ensure that the gas flows at a uniform speed in the system (flow velocity 1.2-1.5m / s) and avoid gas stagnation due to insufficient pressure. One-way valves (model H44F-16, sealing material is fluororubber, resistant to acid and alkali corrosion) are installed on the surfaces of the primary gas guide pipe 5, the secondary gas guide pipe 6, and the inlet pipe 4. The function of the one-way valve is to prevent gas backflow: for example, if the absorbent in the primary unit is insufficient and HF is not completely removed, the one-way valve can prevent HF-containing gas from flowing back into the inlet pipe and contaminating the roasting furnace or upstream equipment; at the same time, it can prevent ammonia vapor from the secondary unit and ethanolamine vapor from the tertiary unit from entering the upstream units, and avoid the mixing of different absorbents leading to failure (e.g., mixing ammonia and NaOH will reduce HF absorption efficiency). The opening pressure of the one-way valve is set to 50-100 Pa, which ensures normal gas passage while effectively blocking backflow.

[0025] Please refer to Figure 2 and Figure 3 The lengths of each set of spray pipes 17 in the circulation pipe 14 are different, and the end profile of each set of spray pipes 17 in the circulation pipe 14 is semi-circular. The length of the longest spray pipe 17 in the circulation pipe 14 is less than the inner diameter of the primary recycling unit 1 or the secondary recycling unit 2.

[0026] The lengths of each set of spray pipes 17 in the circulation pipe 14 vary (e.g., within the primary unit, the length of the long spray pipe is 80% of the tower's inner diameter, and the length of the short spray pipe is 50%), and the end profile of each set of spray pipes 17 is semi-circular. The core purpose of this design is to achieve full spray coverage: the semi-circular structure allows the spray pipes 17 to fit snugly against the inner wall of the recovery unit, avoiding spray dead zones near the tower wall; the varying lengths cover different radius areas within the tower (from the center to the edge), ensuring that every part of the packing layer is uniformly wetted by the absorbent. Simultaneously, the longest spray pipe 17 in the circulation pipe 14 is shorter than the inner diameter of the primary recovery unit 1 or the secondary recovery unit 2 (the difference is approximately 50mm). This design avoids direct contact between the spray pipes 17 and the tower wall: on the one hand, it prevents wear of the spray pipes 17 due to tower wall vibration, extending their service life; on the other hand, it provides a 50mm gap, facilitating upward flow of gas from both sides of the tower wall, balancing the airflow distribution within the tower, and preventing excessively fast local airflow. In addition, the atomizing nozzles 21 on each set of spray pipes 17 are evenly arranged at 100mm intervals to ensure that the atomized droplets form a uniform spray zone in the tower, and the gas-liquid contact efficiency is increased to more than 95%.

[0027] Please refer to Figure 1-3 The primary recovery unit 1 is filled with 10-15% NaOH solution, the secondary recovery unit 2 is filled with 5-8% ammonia solution, and the tertiary recovery unit 3 is filled with 30% ethanolamine solution.

[0028] The primary recovery unit 1 is filled with a 10-15% NaOH solution—this concentration is the optimal choice considering both HF absorption rate and reagent cost: too low a concentration (<10%) will lead to insufficient HF absorption (absorption rate <99%), requiring more cycles and increasing energy consumption; too high a concentration (>15%) will increase the difficulty of dissolving NaOH and easily cause packing blockage due to excessively high local concentrations. A 10-15% NaOH solution can achieve an HF absorption rate of over 99.9%, and the resulting NaF solution concentration is stable at 8-12%, facilitating subsequent crystallization and purification. The secondary recovery unit 2 is filled with 5-8% ammonia water. The key to setting the ammonia water concentration is to balance SO2 absorption efficiency and volatilization loss: when the concentration is below 5%, the SO2 absorption capacity is insufficient, requiring frequent replenishment of ammonia water; when the concentration is above 8%, the ammonia water is easily volatilized (especially when air is introduced through the air filling pipe), resulting in an ammonia escape rate >5%, increasing reagent loss and ammonia pollution in the exhaust gas. A 5-8% ammonia solution can achieve a SO2 absorption rate of 99%, generating a (NH4)2SO4 solution with a concentration of 15-20%, which meets the concentration requirements for subsequent evaporation and crystallization. The tertiary recovery unit 3 is internally filled with a 30% ethanolamine (MEA) solution. 30% is the optimal concentration for ethanolamine to adsorb CO2: too low a concentration (<25%) will reduce the CO2 adsorption capacity, leading to an increase in the desorption frequency; too high a concentration (>35%) will increase the solution viscosity, reduce circulation flow, and easily cause degradation due to high-temperature desorption (generating heat-stable salts, affecting adsorption performance). A 30% ethanolamine solution can achieve a CO2 adsorption capacity of 0.5 mol CO2 / mol MEA, with a CO2 purity of over 99.5% after desorption.

[0029] Please refer to Figure 1 The lower surfaces of the primary recycling unit 1, the secondary recycling unit 2, and the tertiary recycling unit 3 are all equipped with discharge pipes, and manual valves are installed on the surfaces of the discharge pipes.

[0030] The lower surfaces of primary recycling unit 1, secondary recycling unit 2, and tertiary recycling unit 3 are all equipped with discharge pipes (inner diameter 50-80mm, material adapted to each unit: polytetrafluoroethylene for primary, and 316L stainless steel for secondary and tertiary). The discharge pipes are used to discharge the "crude products" generated by each unit: primary discharges NaF solution (discharged once every 24 hours, discharge volume adjusted according to solution concentration), secondary discharges (NH4)2SO4 solution (discharged once every 12 hours), and tertiary discharges degraded ethanolamine waste liquid (discharged once every 30 days, because the MEA recycling rate is ≥95%, the waste liquid volume is small). The discharge pipe is equipped with a manual valve (model such as Q41F-16, valve stem material is 2Cr13, sealing surface is PTFE). A manual valve was chosen instead of an automatic valve primarily because each unit has a long discharge cycle (non-continuous operation), and manual valves have lower maintenance costs (automatic valves require periodic replacement of seals, and automatic valves suitable for acid and alkaline environments are more expensive). Furthermore, the manual valve allows operators to observe the discharge status on-site (such as solution color and clarity) to determine whether to stop discharge (e.g., if a large amount of NaF solution precipitates, it must be cleaned before discharge to avoid clogging the pipe). The manual valve has an operating torque ≤50 N•m, facilitating single-person operation, and offers excellent sealing performance with no leakage.

[0031] Please refer to Figure 3 A stirrer 20 is installed on the lower surface of the three-stage recycling unit 3. The stirrer 20 consists of a drive motor and a stirring shaft with its output end fixed. Several impellers are installed at equal intervals on the stirring shaft of the stirrer 20.

[0032] A stirrer 20 is installed on the lower surface of the tertiary recovery unit 3. The stirrer 20 consists of a drive motor (power 1.5-3kW, protection rating IP65, suitable for humid and corrosive environments) and a stirring shaft fixed at its output end. Several paddle-type impellers (4-6 blades, made of 316L stainless steel, 5mm thick) are evenly spaced on the stirring shaft. The core function of the stirrer 20 is to improve the contact efficiency between the ethanolamine solution and CO2: the tertiary unit uses "amine adsorption of CO2". When the solution is static, "local adsorption saturation" is prone to occur (high CO2 concentration and fast adsorption near the inlet of the gas pipe, slow adsorption in areas further away), resulting in a decrease in overall adsorption efficiency. The stirrer 20, through the rotation of the paddle-type impellers (speed 60-100rpm), can make the ethanolamine solution form a uniform vortex, which can quickly disperse CO2 into the entire solution, improving the adsorption efficiency by 15-20%. At the same time, during the heating and desorption stage of the electric heater 19, the stirrer 20 can ensure that the solution is heated evenly (temperature deviation ≤5℃), avoiding local overheating that could lead to MEA degradation. The sealing joint between the stirring shaft and the tower body adopts "double mechanical seal + polytetrafluoroethylene sealing ring" to ensure no solution leakage and a service life of more than 20,000 hours.

[0033] Working principle: The mixed gas (containing HF, SO2, CO2, and dust, after pretreatment) generated from the roasting of lithium tailings enters the primary recovery unit 1 (HF recovery tower) through the inlet pipe 4. The gas distributor at the end of the inlet pipe 4 evenly disperses the gas into the tower. At this time, the circulation pump 15 on the circulation pipe 14 starts, transporting the 10-15% NaOH solution from the bottom storage area of ​​the tower to the two sets of spray pipes 17 at the top of the tower. The solution is atomized by the atomizing nozzles 21 (atomizing particle size 50-100μm) into fine droplets, which come into countercurrent contact with the gas rising from the bottom of the tower. The NaOH in the solution reacts rapidly with HF to form NaF, while the packing layer 16 (polypropylene stepped rings, specific surface area approximately 200m²) reacts with the HF. 2 / m 3 This further extends the gas-liquid contact time, ensuring that HF ​​is fully removed (concentration reduced to below 1 ppm). The gas after HF removal enters the secondary recovery unit 2 (SO2 recovery tower) under the power of a corrosion-resistant fan (1500-2000 Pa) on the primary gas guide pipe 5. The one-way valve on the gas guide pipe can prevent the gas from flowing back to the primary unit. The circulating pump 15 inside the tower delivers 5-8% ammonia water to the spray pipe 17 for atomization. The ammonia water reacts with SO2 to generate (NH4)2SO3. At the same time, the air filling pipe 18 introduces compressed air with a purity of ≥99% into the tower. After the air is evenly dispersed by the aeration disc, it oxidizes (NH4)2SO3 into stable (NH4)2SO4, achieving deep removal of SO2 (concentration reduced to below 50ppm). The packing layer 16 also plays a role in enhancing gas-liquid contact and improving absorption efficiency. The gas after SO2 removal (mainly containing CO2 and N2) enters the tertiary recovery unit 3 (CO2 recovery tower) through the secondary air guide pipe 6 (powered by a corrosion-resistant fan and protected by a one-way valve to prevent backflow). Inside the tower, a 30% ethanolamine (MEA) solution forms a uniform vortex under the action of stirrer 20 (60-100 rpm), which fully contacts the gas and adsorbs CO2. When the ethanolamine adsorption reaches saturation, the electric heater 19 at the bottom of the tower is started (temperature controlled at 120-140℃) to heat the solution and release CO2, resulting in CO2 gas with a purity ≥99.5% (which can be collected for further purification). The tail gas after CO2 recovery (mainly N2) enters the exhaust pipe 7. The online gas analyzer 8 detects the concentration of HF and SO2 in the tail gas in real time and transmits the data to the controller 9 at the top of the three-stage recovery unit. If the test results meet environmental standards, the controller 9 controls the opening of the electrically controlled valve 11 on the exhaust pipe 10, and the exhaust gas is discharged at high altitude through the exhaust pipe 10 (the exhaust pipe is more than 5m above the factory building to avoid local accumulation); if the exhaust gas concentration is detected to exceed the standard, the controller 9 immediately switches the state of the electrically controlled valve 11 (closing the electrically controlled valve 11 of the exhaust pipe 10 and opening the electrically controlled valve of the priming pipe 12), so that the exhaust gas enters the emergency treatment tank 13 through the priming pipe 12. After secondary absorption by the soda lime or NaOH solution in the tank to meet the standard, the controller 9 switches the valve to achieve compliant discharge. The whole process forms an automated control closed loop of "detection-judgment-execution".

[0034] In this utility model, unless otherwise explicitly specified and limited, the terms "installation", "setting", "connection", "fixing", "screw connection", etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0035] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A device for recovering and utilizing gas after roasting lithium tailings, comprising a primary recovery unit (1), a secondary recovery unit (2), and a tertiary recovery unit (3), characterized in that, The primary recovery unit (1), secondary recovery unit (2), and tertiary recovery unit (3) are arranged linearly from left to right. A primary air duct (5) connects the primary recovery unit (1) and the secondary recovery unit (2), and a secondary air duct (6) connects the secondary recovery unit (2) and the tertiary recovery unit (3). An air inlet pipe (4) connects to the lower surface of the primary recovery unit (1), and an exhaust pipe (7) connects to the top of the tertiary recovery unit (3). The interiors of the primary recovery unit (1) and the secondary recovery unit (2) are equipped with… The first-stage recovery unit (1) and the second-stage recovery unit (2) are equipped with a packing layer (16) and a circulation pipe (14) is sealed on the right side wall. Two sets of spray pipes (17) are symmetrically installed at the upper end of the circulation pipe (14), and an atomizing nozzle (21) is installed on the side of the spray pipe (17) facing the packing layer (16). An air-filling pipe (18) is inserted into the side wall of the second-stage recovery unit (2). An electric heater (19) is embedded in the bottom of the inner side of the third-stage recovery unit (3). A circulation pump (15) is installed on the surface of the circulation pipe (14).

2. The lithium tailings roasting gas recovery and utilization device according to claim 1, characterized in that, An online gas analyzer (8) is installed on the surface of the exhaust pipe (7), and one end of the exhaust pipe (7) is connected to the exhaust pipe (10) and the intake pipe (12) through a tee. An electric control valve (11) is installed on the surface of both the exhaust pipe (10) and the intake pipe (12). An emergency treatment tank (13) is connected to the bottom of the intake pipe (12) through a flange. A controller (9) is installed on the top of the three-stage recovery unit (3), and the output end of the controller (9) is electrically connected to the electric control valve (11). The online gas analyzer (8) is electrically connected to the controller (9).

3. The lithium tailings roasting gas recovery and utilization device according to claim 1, characterized in that, Corrosion-resistant fans are installed on the upper surfaces of the primary air duct (5) and the secondary air duct (6), and one-way valves are installed on the surfaces of the primary air duct (5), the secondary air duct (6) and the air inlet pipe (4).

4. The lithium tailings roasting gas recovery and utilization device according to claim 1, characterized in that, The lengths of each set of spray pipes (17) in the circulation pipe (14) are different, and the end profile of each set of spray pipes (17) in the circulation pipe (14) is semi-circular. The length of the longest spray pipe (17) in the circulation pipe (14) is less than the inner diameter of the primary recycling unit (1) or the secondary recycling unit (2).

5. The lithium tailings roasting gas recovery and utilization device according to claim 1, characterized in that, The primary recovery unit (1) is filled with 10-15% NaOH solution, the secondary recovery unit (2) is filled with 5-8% ammonia solution, and the tertiary recovery unit (3) is filled with 30% ethanolamine solution.

6. The lithium tailings roasting gas recovery and utilization device according to claim 1, characterized in that, The lower surfaces of the primary recycling unit (1), secondary recycling unit (2) and tertiary recycling unit (3) are all equipped with discharge pipes, and manual valves are installed on the surfaces of the discharge pipes.

7. The lithium tailings roasting gas recovery and utilization device according to claim 1, characterized in that, The lower surface of the three-stage recycling unit (3) is equipped with a stirrer (20), which consists of a drive motor and a stirring shaft with its output end fixed. Several impellers are installed at equal intervals on the stirring shaft of the stirrer (20).

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