Waste heat utilization device and method for ore lithium extraction process

Abstract

The present application relates to ore clinker waste heat utilization technical field, specifically, it relates to a kind of ore lithium extraction process waste heat utilization device and method, it includes preheating device, rotary calcination kiln, large-particle screen, rotary cooling device, fixed cover, cooling device moisture partition, cooling device material partition, air inlet blower, circulating water pump, desulfurization fan, closed chute, high-temperature hot water outlet etc..Cooling device material partition is staggered with the mode of herringbone to separate cooling device, and partition closes 2 / 3 cross-sectional area.The present application optimizes air flow path, so that air can enter rotary cooling device by discharge port area, significantly prolongs the transmission path of hot air, not only improves heat exchange efficiency, but also significantly enhances the interaction of hot air and material in the mixing process, fully utilizes the characteristics of material, so that significant energy-saving effect is realized.

Description

Technical Field

[0001] This invention relates to the field of waste heat utilization technology for ore clinker, and more specifically, to a waste heat utilization device and method for lithium extraction processes from ore. Background Technology

[0002] In the lithium carbonate production industry, high-temperature roasting of lithium ore (such as spodumene and lepidolite) is a crucial step. After roasting, the clinker temperature reaches as high as 800-900℃, and it needs to be cooled to below 100℃ before it can proceed to the next process. Currently, the industry mainly uses two cooling methods to process high-temperature clinker: grate coolers and cooling kilns, but both have significant drawbacks.

[0003] While grate coolers can recover some waste heat, their investment costs are high, and each ton of clinker requires 4-8 kWh of electricity, making them uneconomical. Cooling kilns, on the other hand, have no waste heat recovery function at all. They are usually used in conjunction with circulating water cooling towers, absorbing heat through cooling water and then directly releasing it into the atmosphere, resulting in significant energy waste. Taking Yichun, Jiangxi Province as an example, when using the lithium salt method to process lepidolite roasting, 43 tons of clinker are required to produce 1 ton of lithium carbonate. A plant with an annual production capacity of 10,000 tons of lithium carbonate consumes 34.4 million cubic meters of natural gas in the roasting stage alone, with waste heat not being effectively utilized, resulting in a prominent energy waste problem.

[0004] Currently, some lithium salt plants have attempted technical upgrades by installing coils or adding heat exchange tubes in the cooling kiln, but none have been successful. The main problem lies in the water hammer effect caused by water boiling in the pipes, leading to pipe ruptures. To address these issues, industry and academia have begun actively exploring more efficient and economical waste heat recovery technologies to maximize energy utilization while ensuring production efficiency. On one hand, research focuses on developing new high-temperature and corrosion-resistant heat exchange materials to improve the stability and durability of piping systems and reduce equipment damage caused by water hammer. On the other hand, optimizing the structural design of cooling systems, such as using multi-stage heat exchange and segmented cooling technologies, allows for more flexible control of the temperature gradient during the cooling process, reducing energy loss and further improving waste heat recovery efficiency.

[0005] Furthermore, intelligent control technology has been introduced into the lithium ore roasting and cooling process. By monitoring key parameters such as clinker temperature and flow rate in real time, the cooling strategy is dynamically adjusted to ensure cooling effectiveness while maximizing waste heat recovery potential. These intelligent systems can not only automatically adjust the cooling rate and waste heat recovery mode according to changes in operating conditions, but also predict and prevent potential equipment failures, thereby improving overall operational efficiency.

[0006] At the theoretical research level, researchers are working to build more accurate heat transfer models to simulate and analyze energy flow and conversion mechanisms under different cooling methods, providing a scientific basis for the optimized design of waste heat recovery technologies. Meanwhile, interdisciplinary collaboration has become key to driving technological innovation, with expertise from multiple fields such as materials science, thermodynamics, and automation control being integrated and applied to jointly promote the efficient use of energy in the lithium carbonate production process.

[0007] In conclusion, given the current inadequacy of waste heat recovery in lithium carbonate production, breakthroughs in waste heat recovery technology can be achieved through technological innovation and intelligent transformation, combined with multidisciplinary research efforts. This is a key issue facing the sustainable development of the lithium industry in my country and globally. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution.

[0009] A waste heat recovery device for lithium extraction from ore includes a preheating unit, a rotary roasting kiln, a large-diameter screen, a rotary cooling unit, a fixed outer casing, a water partition for the cooling unit, a material partition for the cooling unit, an air inlet blower, a circulating water pump, a desulfurization fan, a closed sluice, and a high-temperature hot water outlet. The water partition cleverly divides the cooling unit and the fixed outer casing into 2 to 5 independent zones for more precise temperature control and material handling. The material partitions use a toothed, staggered design to separate the cooling unit, with each partition enclosing 2 / 3 of its cross-sectional area. The distance between every two material partitions is 0.5 to 1 meter. This design significantly improves material cooling efficiency and prevents material blockage.

[0010] The system adopts a series structure consisting of a preheating device, a rotary kiln, a rotary cooling device, and a fixed outer cover. The heat exchange space is divided into 2 to 5 independent zones by the water partition of the cooling device, achieving staged heat exchange. The material partition of the cooling device is distributed in a toothed pattern, forming an angle of 0-3° with the axis. Combined with the central air intake design of the air inlet blower, a vortex is formed to enhance heat exchange.

[0011] Leakage Prevention and Pressure Control: The rotary kiln maintains a slight negative pressure through a sealing fan, while the rotary cooling device maintains a slight positive pressure. Combined with a closed chute and multi-layer sealing structure, this reduces heat leakage and contaminant outflow. Specifically, the feed inlet of the kiln needs to be appropriately enlarged to ensure that hot air from the cooling device can enter the kiln against the material flow direction, thereby improving heat exchange efficiency. Each sealing ring of the rotary kiln should also be equipped with a variable frequency fan to maintain a slight negative pressure within the kiln and prevent the leakage of harmful gases. Similarly, each sealing ring of the rotary cooling device should be equipped with a variable frequency fan to maintain a slight positive pressure within the cooling device and prevent external air from contaminating the material. All openings (including the feed section using a closed chute) and gaps in the equipment should be sealed as much as possible to reduce heat loss and improve the overall sealing performance of the system.

[0012] Water circulation optimization: A zoned water circulation mode of "low inlet, high outlet" is adopted to avoid boiling caused by direct contact with high-temperature walls. The inlet water temperature is 25-40℃, and the outlet water temperature is 95-98℃, which can be directly used for heating or heat exchange in production. In the water circulation process of the rotary cooling device and fixed outer casing, water is pumped into each zone sequentially from low to high temperature. Water is sprayed in from the top of the fixed outer casing in each zone and then pumped out from the bottom of the fixed outer casing. The inlet water temperature is set between 25℃ and 40℃, and after staged heating, the pumped water temperature can reach about 95℃ to 98℃. This high-temperature hot water can be used for heating or as a heat source for heat exchange in the wet process section of the lithium carbonate workshop, thereby realizing the secondary utilization of energy and further improving the economic efficiency and environmental friendliness of the entire process.

[0013] The present invention also provides a waste heat utilization method based on the waste heat utilization device for the above-mentioned lithium extraction process, which includes the following steps:

[0014] Step 1: Lithium ore is preheated in a preheating device via a closed chute, and then enters a rotary roasting kiln for roasting under the action of burners. The roasted clinker is screened through a large-diameter screen and falls into a rotary cooling device. Inside the rotary cooling device, the material baffle rotates with the device. During 2 / 3 of the rotation cycle (when the baffle is not directly above the kiln), the material is blocked from moving forward, allowing the material to fully contact the hot air. During 1 / 3 of the rotation cycle (when the baffle rotates to directly above the kiln body), the material is allowed to fall through the gap and finally discharged from the outlet.

[0015] Step 2: Outdoor cold air is sent into the center of the material outlet end of the rotary cooling device through the air inlet blower. After mixing and exchanging heat with the clinker, the temperature rises. The hot air flows against the material flow direction and enters the interior of the rotary kiln through the enlarged feed port. Then it enters the preheating device and finally enters the desulfurization system through the flue gas outlet of the preheating device via the desulfurization fan.

[0016] Step 3: The circulating water pump pumps water at 25-40℃ from the bottom of the fixed outer cover, and sends it through the spray pipes to the independent areas divided by the water partition of the cooling device. In each independent area, the water is sprayed from the top to the outer wall of the rotary cooling device. After exchanging heat with the outer wall of the device at different temperature ranges, the hot water is finally discharged from the high-temperature hot water outlet at the bottom of the fixed outer cover.

[0017] The present invention, by adopting the above technical solution, can achieve the following beneficial effects:

[0018] This invention optimizes the airflow path, allowing air to enter the rotary cooling device through the discharge port area, significantly extending the hot air transmission path by almost twice as much. This innovative design not only improves heat exchange efficiency but also significantly enhances the interaction between hot air and materials during mixing, fully utilizing the material's properties and thus achieving significant energy savings. By fully utilizing the waste heat of the high-temperature clinker, natural gas consumption in the roasting section is reduced.

[0019] This invention adopts a zoned water circulation and pipeless boiling design, which completely solves the problem of water hammer effect caused by water boiling in pipes during the transformation of traditional cooling kilns, thus improving the stability and service life of the equipment.

[0020] The toothed distribution of the material baffles in the cooling device of the invention and the angle design with the axis form a vortex, which increases the contact area and contact time between air and material, thus improving the heat exchange efficiency significantly, which is higher than that of traditional cooling kilns. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the waste heat recovery device used in the lithium extraction process from ore in Example 1;

[0022] Figure 2 This is a cross-sectional view of the cooling device in Example 1 at 90° or 270°.

[0023] Figure 3 This is a cross-sectional view of the cooling device in Example 1 at 0° or 180°.

[0024] The attached figures are labeled as follows:

[0025] 1. Enclosed chute; 2. Flue gas outlet; 3. Preheating device; 4. Rotary kiln; 5. Burner; 6. Large-diameter screen; 7. Rotary cooling device; 8. Spray water pipe; 9. Fixed outer cover; 10. High-temperature hot water outlet; 11. Water partition of cooling device; 13. Material partition of cooling device; 14. Air inlet blower; M. Sealing fan. Detailed Implementation

[0026] Example 1: This example provides a waste heat recovery device for lithium extraction from ore, which includes the following structure:

[0027] Preheating device 3: It adopts a horizontal rotary structure. The feed end receives lithium ore through a closed chute 1, and the discharge end is sealed to a rotary roasting kiln 4 to preheat to 200-300℃.

[0028] Rotary roasting kiln 4: Inclined at 3°, with a burner 5 at the feed end, roasting temperature 850°C; discharge port diameter, and a sealing fan M at each of the two sealing rings to maintain a slight negative pressure.

[0029] Large-diameter screen 6: It is used to intercept clinker and return it to the rotary kiln 4.

[0030] Rotary cooling device 7: Its inner wall is provided with cooling device material partition 13: In this embodiment, the spacing between the cooling device material partitions 13 is 0.5 to 1 meter, and the width value is greater than twice the maximum particle size value of the material.

[0031] Toothed joint structure: Q345R steel plate (more than twice the maximum particle size of the material) is preferred; it is installed by the interlocking of the convex tenon and the concave tenon. The convex tenon is equipped with a dovetail groove, and the concave tenon is equipped with a spring-connected dovetail block to compensate for displacement and ensure tight interlocking.

[0032] Angle transformation structure: The angle between the material partition 13 of the cooling device and the main axis of the rotary cooling device 7 is 0-3°. In this embodiment, the angle formed by the two is 1°. It is equipped with a servo motor and a magnetic induction positioning sensor (Samarium cobalt magnet + high temperature Hall sensor with ceramic fiber heat insulation cover). It can switch between 0° or 180° (working position) and 90° or 270° (maintenance position). The positioning error is ≤ ±1.5°. It is locked by a hydraulic locking pin (50mm diameter).

[0033] Fixed outer cover 9: Welded from Q345R steel plate, it is divided into 2 to 5 independent areas by the cooling device water partition 11. In this embodiment, the cooling device water partition 11 divides the fixed outer cover into 3 independent areas: specifically including high temperature area, medium temperature area and low temperature area.

[0034] A spray pipe 8 is installed at the top, and a 5° inclined water collection tank is installed at the bottom, connected to a high-temperature hot water outlet 10.

[0035] Each area's inlet pipe is equipped with an electromagnetic flow meter and an electric regulating valve. Temperature monitoring points are set every 2 meters. When the deviation exceeds ±10℃, the backup spray branch is activated.

[0036] Air inlet blower 14: Located at the center of the material outlet end of the rotary cooling device 7, used to deliver cold air.

[0037] Circulating water pump and sealing system: water circulation in series, with two variable frequency fans M installed at the sealing ring of the cooling device to maintain a slight positive pressure.

[0038] The working principle of the waste heat recovery device for lithium extraction from ore in this embodiment is as follows:

[0039] Material handling process: Lithium ore enters the preheating device 3 through the closed chute 1, and after being preheated to 200-300℃, it enters the rotary roasting kiln 4, where it is roasted at 850℃ for 2 hours to produce clinker (temperature 800-900℃). After being screened by the large-diameter screen 6, the clinker falls into the rotary cooling device 7. Under the action of the material baffle 13 in the cooling device: within 2 / 3 of the rotation cycle, the material baffle 13 blocks the material from moving forward (the toothed structure prevents the material from getting stuck); within 1 / 3 of the rotation cycle, the material baffle 13 rotates to the top of the kiln body, and the material falls through the gap of the material baffle 13 (because the material baffle 13 is at a 1° angle to the axis, the material is pushed along the spiral path), and is finally cooled to 80-100℃ and discharged to the next stage.

[0040] Air and vortex formation: Cold air enters from the center, is axially propelled by the material baffle 13 of the 1° angled cooling device, and circumferentially deflected by the toothed structure. Combined with the material's "lifting-falling" impact, a spiral vortex (12-15 m / s) is formed, which mixes with the clinker and heats up to 600-700℃. It then enters the roasting kiln 4 in the opposite direction for reheating, and after passing through the preheating device 3, it enters the desulfurization system (temperature 150-200℃) from the flue gas outlet 2.

[0041] Water circulation: 30℃ soft water is sprayed in the low temperature zone (heated to 50℃) → medium temperature zone (70℃) → high temperature zone (96℃) and discharged from the high temperature hot water outlet 10; the temperature is dynamically matched by the flow regulating valve, and the backup branch is activated when the deviation exceeds the limit to ensure uniform heat exchange.

[0042] Compared with the prior art, the waste heat recovery device for lithium extraction from ore in this embodiment has the following advantages:

[0043] Cyclone vortex effectively improves the heat exchange efficiency between air and clinker, and hot air enters the kiln in the opposite direction to supplement heat and reduce natural gas consumption;

[0044] The heat in clinker can be recovered and utilized, which effectively solves the core problem of "waste heat not being effectively utilized" in the background technology.

[0045] By using a zoned water circulation design (dividing the fixed outer casing into 3 zones, with water gradually heated from the low-temperature zone to the high-temperature zone), boiling caused by direct contact between the water and the high-temperature wall surface is avoided, thus completely eliminating the water hammer effect.

[0046] The toothed joint structure (the width of the partition is more than twice the maximum particle size of the material, with an included angle of 0-3°) prevents material jamming, and the angle-changing structure (90° or 270° inspection position) simplifies maintenance.

[0047] Example 2: This example provides a waste heat utilization method based on the waste heat utilization device for lithium extraction from ore in Example 1 described above, which includes the following steps:

[0048] Step 1: Lithium ore enters the preheating device 3 through the closed chute 1 for preheating, and then enters the rotary roasting kiln 4 for roasting under the action of the burner 5; the roasted clinker is screened through the large particle size screen 6 and falls into the rotary cooling device 7; inside the rotary cooling device 7, the cooling device material baffle 13 rotates with the device. During 2 / 3 of the rotation cycle, the cooling device material baffle 13 is in a non-directly upward position to block the material from moving forward, so that the material can fully contact the hot air. During 1 / 3 of the rotation cycle, the cooling device material baffle 13 rotates to the direct top of the kiln body to allow the material to fall through the gap and finally be discharged from the outlet.

[0049] Step 2: Outdoor cold air is sent into the center of the material outlet end of the rotary cooling device 7 through the air inlet blower 14. After mixing and exchanging heat with the clinker, the temperature rises. The hot air flows against the material flow direction and enters the interior of the rotary kiln 4 through the enlarged discharge port. Then it enters the preheating device 3 and finally enters the desulfurization system through the flue gas outlet 2 of the preheating device 3 via the desulfurization fan.

[0050] Step 3: The circulating water pump pumps water at 25-40℃ from the bottom of the fixed outer cover 9, and sends it through the spray water pipe 8 to the independent areas divided by the water partition plate 11 of the cooling device. In each independent area, the water is sprayed from the top to the outer wall of the rotary cooling device 7. After exchanging heat with the outer wall of the device at different temperature ranges, the hot water is finally discharged from the high temperature hot water outlet 10 at the bottom of the fixed outer cover 9.

[0051] In this embodiment, the beneficial effects that can be achieved by the above method are as follows:

[0052] First, in the above method, cold air and clinker at 800-900℃ are thoroughly mixed in a rotary cooling device via a cyclone vortex (step two). After being heated to 600-700℃, the air enters the roasting kiln and preheating device in a reverse direction, directly supplementing the roasting heat and preheating the ore, thus reducing the natural gas consumption of the burner. Simultaneously, water circulation, through zoned heat exchange (step three), heats water at 25-40℃ to 95-98℃, replacing steam for heating or the wet process section, further reducing energy waste. Compared to the problems of "complete non-recovery of waste heat" in the cooling kiln and "low recovery efficiency" in the grate cooler in the background technology, this method reduces natural gas consumption in the roasting section and significantly improves energy utilization.

[0053] Second, the water circulation adopts a step-by-step heating mode of "low temperature zone → medium temperature zone → high temperature zone" (step three). The temperature difference between the water and the outer wall of the cooling device is controlled within a reasonable range (10-20℃ for heat exchange in the low temperature zone, 20-30℃ in the medium temperature zone, and 35-48℃ in the high temperature zone). This avoids the problem of "water directly contacting the high temperature wall surface and causing boiling" in traditional coil modification, fundamentally eliminates the water hammer effect, and solves the technical pain point of "frequent pipe rupture" in the background technology.

[0054] III. In the material handling process (step one), the material baffle of the cooling device, through a design of "2 / 3 cycle blocking and 1 / 3 cycle releasing," combined with an axial angle of 0-3°, ensures that the material is in full contact with the hot air, resulting in uniform and efficient cooling, ultimately stabilizing the clinker to below 100°C. Simultaneously, the baffle width of the toothed structure is more than twice the maximum particle size of the material, avoiding the "material jamming" problem common in the background technology and ensuring a continuous and stable production process.

[0055] Example 3: This example uses a lithium carbonate production line with an annual output of 10,000 tons as an illustration.

[0056] A lithium extraction plant in Yichun, Jiangxi Province, produces 10,000 tons of lithium carbonate annually. The raw material is lithium mica with a Li2O grade of 2.0%. Each ton of lithium carbonate requires 43 tons of clinker. The cooling device (7) has a processing capacity of 43 tons / hour.

[0057] Energy saving benefits: Natural gas consumption is reduced from 34.4 million m³ / year to 27.52 million m³ / year (saving 20%), 80 t / h of 96℃ hot water is recovered, meeting 60% of the heating demand of the wet process section, and replacing 1.2 t / h of steam.

[0058] Stability: The toothed joint structure achieves zero jamming, the zoned water circulation ensures no pipe rupture, and it can operate continuously for 300 days; the angle-changing structure reduces maintenance time to 2 hours per operation.

[0059] This embodiment verifies the feasibility of the device in efficiently recovering waste heat, reducing energy consumption and costs, and solves the key defects of traditional cooling technology.

[0060] In summary, the above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the present invention.

Claims

1. A waste heat recovery device for lithium extraction from ore, characterized in that, include: A rotary cooling device (7) is used to cool the roasted lithium ore clinker; a fixed outer cover (9) is fitted outside the rotary cooling device (7) to form a closed heat exchange space with the rotary cooling device (7); a water partition plate (11) of the cooling device is set between the rotary cooling device (7) and the fixed outer cover (9) to divide the heat exchange space into 2 to 5 independent areas from high to low along the material flow direction; The cooling device material partitions (13) are arranged circumferentially along the inner wall of the rotary cooling device (7). The cooling device material partitions (13) enclose 2 / 3 of the cross-sectional area of ​​the rotary cooling device (7) and the angle between them and the main axis of the rotary cooling device (7) is 0-3°. The cooling device material partitions (13) are arranged in a staggered manner. The air inlet blower (14) has its air outlet connected to the center of the material outlet end of the rotary cooling device (7). The circulating water pump has its water inlet connected to the lower part of the fixed outer cover (9) and its water outlet connected to the spray water pipe (8) on the upper part of the fixed outer cover (9). It is used to pump water into the independent area from low to high in sequence. It also includes a rotary kiln (4) and a burner (5), the discharge end of the rotary kiln (4) is connected to the feed end of the rotary cooling device (7), and the burner (5) is located at the feed end of the rotary kiln (4). It also includes a preheating device (3) and a large-diameter screen (6). The discharge end of the preheating device (3) is connected to the feed end of the rotary kiln (4). The large-diameter screen (6) is located between the rotary kiln (4) and the rotary cooling device (7). The rotary cooling device (7) is equipped with a sealing fan (M) at each sealing ring to maintain a slight positive pressure.

2. The waste heat recovery device for lithium extraction from ore according to claim 1, characterized in that, The spacing between the material partitions (13) of the cooling device is 0.5 to 1 meter, and the width value is greater than twice the maximum particle size value of the material.

3. The waste heat recovery device for lithium extraction from ore according to claim 1, characterized in that, It also includes a closed chute (1) and a desulfurization fan. The closed chute (1) is located at the feed end of the preheating device (3), and the desulfurization fan is connected to the flue gas outlet (2) of the preheating device (3).

4. A method for utilizing waste heat from a waste heat utilization device used in lithium extraction from ore according to any one of claims 1-3, comprising the following steps: Step 1: Lithium ore is preheated in a preheating device (3) via a closed chute (1), and then enters a rotary roasting kiln (4) for roasting under the action of a burner (5); the roasted clinker is screened by a large-diameter screen (6) and falls into a rotary cooling device (7); in the rotary cooling device (7), the material partition (13) of the cooling device rotates with the device, and during 2 / 3 of the rotation cycle (when the material partition (13) of the cooling device is not directly above the kiln), it blocks the material from moving forward, so that the material can fully contact the hot air, and during 1 / 3 of the rotation cycle (when the material partition (13) of the cooling device rotates to directly above the kiln body), the material is allowed to fall through the gap and finally discharged from the outlet; Step 2: Outdoor cold air is sent into the center of the material outlet end of the rotary cooling device (7) through the air inlet blower (14), and is heated after mixing and exchanging heat with the clinker; hot air flows against the material flow direction and enters the interior of the rotary roasting kiln (4) through the enlarged feeding port, and then enters the preheating device (3), and finally enters the desulfurization system through the flue gas outlet (2) of the preheating device (3) via the desulfurization blower. Step 3: The circulating water pump pumps water at 25-40℃ from the bottom of the fixed outer cover (9), and sends it through the spray water pipe (8) to the independent areas divided by the water partition plate (11) of the cooling device. The water is sprayed from the top of each independent area to the outer wall of the rotary cooling device (7). After exchanging heat with the outer wall of the device at different temperature ranges, the hot water is finally discharged from the high temperature hot water outlet (10) at the bottom of the fixed outer cover (9).

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