Waste heat utilization device and method for ore lithium extraction process

Abstract

The invention relates to the technical field of ore clinker waste heat utilization, in particular to a waste heat utilization device and method for an ore lithium extraction process. The device comprises a preheating device, a rotary roasting kiln, a large-particle-size screen, a rotary cooling device, a fixed outer cover, a cooling device water partition plate, a cooling device material partition plate, an air inlet air blower, a circulating water pump, a desulfurization fan, a closed chute, a high-temperature hot water outlet and the like. The cooling device material partition plates partition the cooling device in a staggered mode in a combed joint mode, and 2 / 3 of the cross sectional area is closed by the partition plates. By optimizing the air flowing path, air can enter the rotary cooling device through the discharging port area, the conveying path of hot air is remarkably prolonged, the heat exchange efficiency is improved, the interaction effect of the hot air and materials is remarkably enhanced in the mixing process of the hot air and the materials, the characteristics of the materials are fully utilized, and the energy consumption is reduced. Therefore, a remarkable energy-saving effect is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of ore clinker waste heat utilization, and in particular to a waste heat utilization device and method for an ore lithium extraction process. Background Art

[0002] In the production of lithium carbonate, high-temperature roasting of lithium ore (such as spodumene and lepidolite) is a critical step. The clinker reaches temperatures of 800-900°C after roasting and must be cooled to below 100°C before proceeding to the next process. Currently, the industry primarily uses grate coolers and cooling kilns to process high-temperature clinker, but both have significant drawbacks.

[0003] While grate coolers can recover some waste heat, they are expensive to invest in and consume 4-8 kWh of electricity per ton of clinker, making them uneconomical. Cooling kilns, on the other hand, lack waste heat recovery capabilities and are typically used in conjunction with circulating water cooling towers. Heat is absorbed by the cooling water and then released directly into the atmosphere, resulting in significant energy waste. In Yichun, Jiangxi Province, for example, the lithium salt method for roasting lepidolite consumes 43 tons of clinker to produce one 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 during the roasting phase alone. This waste heat is not effectively utilized, leading to significant energy waste.

[0004] At present, some lithium salt plants have tried to carry out technical transformation by installing coils or adding heat exchange tubes in the cooling kiln, but all have not been successful. The main problem is that the water hammer effect generated when water boils in the pipe leads to pipe rupture and other phenomena. In response to the above problems, the industry and academia have begun to actively explore more efficient and economical waste heat recovery technologies, in order to maximize energy utilization while ensuring production efficiency. On the one hand, the research focuses on the development of new high-temperature resistant and corrosion-resistant heat exchange materials to improve the stability and durability of the pipeline system and reduce equipment damage caused by water hammer. On the other hand, the structural design of the cooling system is optimized, such as the use of multi-stage heat exchange, segmented cooling and other technologies, to more flexibly control the temperature gradient during the cooling process, reduce energy loss, and further improve the waste heat recovery efficiency.

[0005] Furthermore, intelligent control technologies have been incorporated into the lithium ore roasting and cooling processes. By real-time monitoring of key parameters such as clinker temperature and flow, cooling strategies are dynamically adjusted to ensure cooling effectiveness while maximizing waste heat recovery potential. These intelligent systems not only automatically adjust cooling rates and waste heat recovery modes based on changing operating conditions, but also predict and prevent potential equipment failures, improving overall operational efficiency.

[0006] At the theoretical level, researchers are working to develop more accurate heat transfer models to simulate and analyze the energy flow and conversion mechanisms under different cooling methods, providing a scientific basis for the optimized design of waste heat recovery technologies. At the same time, interdisciplinary collaboration is key to driving technological innovation. Expertise from multiple fields, such as materials science, thermodynamics, and automated control, is being integrated and applied to promote efficient energy utilization in lithium carbonate production.

[0007] To sum up, facing the current situation of insufficient waste heat recovery in lithium carbonate production, achieving breakthroughs in waste heat recovery technology through technological innovation and intelligent transformation, combined with multidisciplinary research forces, is the main problem facing the sustainable development of the lithium industry in my country and even the world. Summary of the Invention

[0008] In order to solve the above technical problems, the present invention is solved through the following technical solutions.

[0009] A waste heat utilization device for lithium extraction from ore, comprising a preheating device, a rotary roasting kiln, a large-size screen, a rotary cooling device, a fixed outer cover, a water partitioning plate for the cooling device, a material partition for the cooling device, an air inlet blower, a circulating water pump, a desulfurization fan, a closed chute, a high-temperature hot water outlet, etc. The water partitioning plate for the cooling device cleverly divides the cooling device and the fixed outer cover into 2 to 5 independent areas to achieve more precise temperature control and material processing. The material partitions for the cooling device separate the cooling devices in a staggered manner in a tooth-shaped manner. The partitions enclose 2 / 3 of the cross-sectional area, and the spacing between each two material partitions for the cooling device is 0.5 to 1 meter. This design significantly improves the material cooling efficiency and prevents material blockage.

[0010] A series structure of preheating device, rotary roasting kiln, rotary cooling device and fixed outer cover is adopted. The heat exchange space is divided into 2 to 5 independent areas by the water partition of the cooling device to achieve graded heat exchange. The material partitions of the cooling device are staggered in a tooth joint manner, with an angle of 0-3° to the axis. Combined with the central air inlet design of the air inlet blower, a cyclone 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, and the rotary cooling device maintains a slight positive pressure. Combined with a closed chute and a multi-layer sealing structure, heat leakage and the leakage of pollutants are reduced. Specifically, the feed opening of the kiln needs to be appropriately enlarged to ensure that the hot air in the cooling device can enter the kiln in the opposite direction of the material flow, thereby improving the heat exchange efficiency; the various sealing rings of the rotary kiln should also be equipped with a variable frequency fan to ensure that the kiln maintains a slight negative pressure state and prevents the leakage of harmful gases; the various sealing rings of the rotary cooling device should also be equipped with a variable frequency fan to ensure that the cooling device maintains a slight positive pressure state and prevents the outside air from polluting the material; the openings of each equipment (including the feed section using a closed chute for feeding) and gaps should be blocked and sealed as much as possible to reduce heat loss and improve the overall sealing performance of the system.

[0012] Water circulation optimization: A "low-in, high-out" zoned water circulation mode is adopted to avoid boiling caused by direct contact with high-temperature walls. The inlet water temperature is 25-40°C and the outlet water temperature is 95-98°C, which can be directly used for heating or production heat exchange. In the water circulation process of the rotary cooling device and the fixed outer cover, water is circulated and pumped into each area in sequence from low to high. Water is sprayed into the upper part of the fixed outer cover of each area and then pumped out from the lower part of the fixed outer cover. The inlet water temperature is set between 25°C and 40°C. After step-by-step heating, the pumped water temperature can reach about 95°C to 98°C. These high-temperature hot water can be used for heating or as a heat source for heat exchange in the wet section of the lithium carbonate workshop, thereby realizing the secondary utilization of energy and further improving the economic benefits 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 ore lithium extraction process, which comprises the following steps:

[0014] Step 1: Lithium ore enters the preheating device through a closed chute for preheating, and then enters the rotary roasting kiln for roasting under the action of the burner; the roasted clinker is screened by a large-particle screen and falls into the rotary cooling device; in the rotary cooling device, the material partition of the cooling device rotates with the device. During the 2 / 3 rotation cycle (the partition is not in the upper position), the material is blocked from moving forward, allowing the material to fully contact the hot air. During the 1 / 3 rotation cycle (the partition is rotated to the upper position of 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 of the rotary cooling device through the air inlet blower, mixed with the clinker and heated after heat exchange; hot air goes against the direction of material flow, enters the roasting kiln through the enlarged discharge port of the rotary roasting kiln, and then enters the preheating device, and finally is introduced into the desulfurization system through the desulfurization fan from the flue gas outlet of the preheating device for treatment;

[0016] Step 3: The circulating water pump pumps water at 25-40°C into the lower part of the fixed outer cover, and sends it into the independent areas divided by the water partition of the cooling device in sequence through the spray water pipe; in each independent area, the water is sprayed from the top to the outer wall of the rotary cooling device, and after heat exchange with the outer wall of the device in different temperature ranges, the hot water is finally discharged from the high-temperature hot water outlet at the lower part of the fixed outer cover.

[0017] The present invention adopts the above technical solution to achieve the following beneficial effects:

[0018] By optimizing the air flow path, this invention allows air to enter the rotary cooling device through the discharge port area, significantly extending the hot air transmission path to nearly double its original length. This innovative design not only improves heat exchange efficiency but also significantly enhances the interaction between the hot air and the material during mixing, fully utilizing the material's characteristics and 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] The present invention adopts a zoned water circulation and pipe-free boiling design, which completely solves the problem of pipe rupture caused by water hammer effect caused by water boiling in the pipe in the traditional cooling kiln transformation, thereby improving the stability and service life of the equipment.

[0020] The staggered distribution of the material partitions of the cooling device in the invention and the angle design with the axis form a cyclone vortex, which increases the contact area and contact time between air and material, greatly improves the heat exchange efficiency, and is higher than the heat exchange efficiency of traditional cooling kilns. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic structural diagram of the waste heat utilization device for the ore lithium extraction process in Example 1;

[0022] Figure 2 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 reference numerals are as follows:

[0025] 1. Closed chute; 2. Flue gas outlet; 3. Preheating device; 4. Rotary roasting kiln; 5. Burner; 6. Large particle size screen; 7. Rotary cooling device; 8. Spray water pipe; 9. Fixed outer cover; 10. High-temperature hot water outlet; 11. Cooling device water partition; 13. Cooling device material partition; 14. Air inlet blower; M. Sealing fan. DETAILED DESCRIPTION

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

[0027] Preheating device 3: It adopts a horizontal rotary structure. The feeding end receives lithium ore through a closed chute 1, and the discharging end is sealed and connected to a rotary roasting kiln 4 and preheated to 200-300°C.

[0028] Rotary roasting kiln 4: tilt angle 3°, burner 5 is provided at the feeding end, roasting temperature 850°C; discharge port diameter, 1 sealing fan M is provided at each sealing ring at both ends to maintain a slight negative pressure.

[0029] Large particle size screen 6: used to intercept clinker and return it to the rotary roasting kiln 4.

[0030] The rotary cooling device 7 has cooling device material partitions 13 provided on its inner wall. In this embodiment, the spacing between the cooling device material partitions 13 is 0.5 to 1 meter, and the width is greater than twice the maximum particle size of the material.

[0031] Tooth joint structure: Q345R steel plate (larger than 2 times the maximum particle size of the material) is preferably used; it is installed by the engagement of convex tenon and concave mortise. The convex tenon is provided with a dovetail groove, and the concave mortise is equipped with a dovetail block connected by a spring to compensate for displacement and ensure tight engagement.

[0032] Angle conversion structure: The angle between the cooling device material partition 13 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 resistant Hall sensor, with a ceramic fiber heat insulation cover). It can be switched between 0° or 180° (working position) and 90° or 270° (maintenance position), with a positioning error of ≤±1.5°; it is locked by a hydraulic locking pin (50mm diameter).

[0033] The fixed outer cover 9 is welded with Q345R steel plates and is divided into 2 to 5 independent areas by the cooling device water partition baffles 11. In this embodiment, the cooling device water partition baffles 11 separate the fixed outer cover into three independent areas: a high temperature area, a medium temperature area, and a low temperature area.

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

[0035] The water inlet pipes in each area are equipped with electromagnetic flow meters and electric regulating valves, and temperature monitoring points are set up every 2 meters. When the deviation exceeds ±10℃, the backup spray branch will be activated.

[0036] Air inlet blower 14: It is located at the center of the material outlet end of the rotary cooling device 7 and is used to supply cold air.

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

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

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

[0040] Formation of air and cyclone vortex: cold air enters from the center, is axially pushed by the material partition 13 of the 1° angle cooling device, and circumferentially deflected by the tooth joint structure. Combined with the "lifting-falling" impact of the material, a spiral vortex (12-15m / s) is formed, which is mixed with the clinker and heated to 600-700℃. It then flows in the opposite direction and enters the roasting kiln 4 for supplementary heat. 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 through the low-temperature zone (heated to 50℃) → the medium-temperature zone (70℃) → the high-temperature zone (96℃), and discharged from the high-temperature hot water outlet 10; the temperature is dynamically matched through the flow control valve, and the backup branch is activated when the deviation exceeds the limit to ensure uniform heat exchange.

[0042] The waste heat utilization device for lithium extraction from ore in this embodiment has the following advantages compared to the prior art:

[0043] The cyclone vortex effectively improves the heat exchange efficiency between air and clinker. The hot air flows back into the roasting kiln to supplement heat and reduce natural gas consumption.

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

[0045] The zoned water circulation design (dividing the fixed outer cover into three zones, with water temperature gradually increasing from the low-temperature zone to the high-temperature zone) avoids boiling caused by direct contact of water with the high-temperature wall surface, and completely eliminates the water hammer effect.

[0046] The tooth-shaped structure (partition width is twice the maximum particle size of the material, and the angle is 0-3°) is used to prevent material jamming, and the angle change structure (90° or 270° maintenance position) simplifies maintenance.

[0047] Example 2: This example provides a method for utilizing waste heat based on the waste heat utilization device for lithium extraction from ore in Example 1, 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 and is roasted under the action of the burner 5; the roasted clinker is screened by the large-particle size screen 6 and falls into the rotary cooling device 7; in the rotary cooling device 7, the cooling device material partition 13 rotates with the device. During the 2 / 3 rotation cycle, the cooling device material partition 13 is in a non-upper position to block the material from moving forward, so that the material is fully exposed to hot air. Within the 1 / 3 rotation cycle, the cooling device material partition 13 rotates to the 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 fed into the center of the material outlet end of the rotary cooling device 7 through the air inlet blower 14, mixed with the clinker for heat exchange and then heated up; the hot air goes against the material flow direction, enters the roasting kiln 4 through the enlarged discharge port of the rotary roasting kiln 4, then enters the preheating device 3, and finally is introduced into the desulfurization system for treatment from the flue gas outlet 2 of the preheating device 3 through the desulfurization blower;

[0050] Step 3: The circulating water pump pumps water at 25-40°C from the bottom of the fixed outer cover 9, and sends it into the independent areas divided by the water partition baffles 11 of the cooling device in sequence through the spray water pipe 8; water is sprayed from the top to the outer wall of the rotary cooling device 7 in each independent area, and after heat exchange with the outer wall of the device in different temperature sections, 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 above method can achieve the following beneficial effects:

[0052] 1. In the above method, cold air is fully mixed with 800-900℃ clinker through cyclonic vortex in a rotary cooling device (step 2). After the temperature is raised to 600-700℃, it flows back into the roasting kiln and preheating device, directly replenishing the roasting heat and preheating the ore, reducing the natural gas consumption of the burner. At the same time, the water circulation heats the 25-40℃ water to 95-98℃ through zoned heat exchange (step 3), replacing steam for heating or wet process, further reducing energy waste. Compared with the problems of "no waste heat recovery" in cooling kilns and "low recovery efficiency" in grate coolers in the background technology, this method reduces the natural gas consumption in the roasting section and significantly improves energy utilization.

[0053] 2. 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 (the heat exchange temperature difference in the low temperature zone is 10-20°C, the medium temperature zone is 20-30°C, and the high temperature zone is 35-48°C). This avoids the problem of "water directly contacting the high-temperature wall and causing boiling" in traditional coil transformation, fundamentally eliminates the water hammer effect, and solves the technical pain point of "frequent pipe rupture" in the background technology.

[0054] During material processing (Step 1), the cooling device's material baffles utilize a "2 / 3 cycle blocking, 1 / 3 cycle releasing" design, coupled with an axis angle of 0-3°, to ensure full contact between the material and the hot air, resulting in uniform and efficient cooling, ultimately cooling the clinker to below 100°C. Furthermore, the baffles' tooth-shaped structure is twice the maximum particle size of the material, avoiding the "material jamming" problem common in prior art and ensuring a continuous and stable production process.

[0055] Example 3: This example is based on a production line with an annual output of 10,000 tons of lithium carbonate.

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

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

[0058] Stability: The tooth-shaped joint structure achieves zero sticking, partitioned water circulation without pipe rupture, and continuous operation for 300 days; the angle-changing structure shortens maintenance time to 2 hours per time.

[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 short, the above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the patent of the present invention.

Claims

1. A waste heat utilization device for lithium extraction process from ore, characterized in that: include: A rotary cooling device (7) for cooling roasted lithium ore clinker; a fixed outer cover (9) sleeved on the outside of the rotary cooling device (7) to form a closed heat exchange space with the rotary cooling device (7); a cooling device water partition plate (11) disposed 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 material partitions (13) of the cooling device are arranged at intervals along the inner wall of the rotary cooling device (7), the material partitions (13) of the cooling device enclose 2 / 3 of the cross-sectional area of ​​the rotary cooling device (7), and the angle between the material partitions (13) and the main axis of the rotary cooling device (7) is 0-3 degrees, and the material partitions (13) of the cooling device are staggered in a tooth-shaped manner; the air inlet blower (14) has an air outlet connected to the center of the material outlet end of the rotary cooling device (7); the circulating water pump has a water inlet end connected to the lower part of the fixed outer cover (9) and a water outlet end connected to the spray water pipe (8) on the upper part of the fixed outer cover (9), and is used to circulate water into the independent area from low to high in sequence.

2. The waste heat utilization device for lithium extraction process from ore according to claim 1, characterized in that: It also includes a rotary roasting kiln (4) and a burner (5), wherein the discharge end of the rotary roasting kiln (4) is connected to the feed end of the rotary cooling device (7), and the burner (5) is arranged at the feed end of the rotary roasting kiln (4).

3. The waste heat utilization device for lithium extraction from ore according to claim 2, characterized in that: It also includes a preheating device (3) and a large-particle size screen (6), wherein the discharge end of the preheating device (3) is connected to the feed end of the rotary roasting kiln (4), and the large-particle size screen (6) is arranged between the rotary roasting kiln (4) and the rotary cooling device (7).

4. The waste heat utilization device for lithium extraction process from ore according to claim 2, characterized in that: Each sealing ring of the rotary cooling device (7) is provided with a sealing fan (M) to maintain a slight positive pressure.

5. The waste heat utilization 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 is greater than twice the maximum particle size of the material.

6. The waste heat utilization device for lithium extraction process from ore according to claim 3, characterized in that: It also includes a closed chute (1) and a desulfurization fan, wherein the closed chute (1) is arranged 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).

7. A method for utilizing waste heat from a waste heat utilization device for lithium extraction from ore according to any one of claims 1 to 6, comprising the following steps: Step 1: lithium ore enters the preheating device (3) through the closed chute (1) for preheating, and then enters the rotary roasting kiln (4) and roasts under the action of the burner (5); the roasted clinker is screened by the large particle size screen (6) and falls into the rotary cooling device (7); in the rotary cooling device (7), the cooling device material partition (13) rotates with the device, and blocks the material from moving forward during 2 / 3 of the rotation cycle (the cooling device material partition (13) is not directly above the position), so that the material is fully exposed to hot air, and allows the material to fall through the gap during 1 / 3 of the rotation cycle (the cooling device material partition (13) is rotated to the directly above the kiln body) and is finally discharged from the outlet; Step 2: Outdoor cold air is fed into the center of the material outlet end of the rotary cooling device (7) through the air inlet blower (14), mixed with the clinker for heat exchange and then heated; hot air flows in the opposite direction of the material flow, enters the roasting kiln (4) through the enlarged discharge port of the rotary roasting kiln (4), and then enters the preheating device (3), and finally is introduced into the desulfurization system for treatment from the flue gas outlet (2) of the preheating device (3) through the desulfurization fan; Step 3: The circulating water pump pumps water at 25-40°C from the lower part of the fixed outer cover (9), and sends it to the independent areas divided by the water partition baffles (11) of the cooling device in sequence through the spray water pipe (8); the water is sprayed from the top to the outer wall of the rotary cooling device (7) in each independent area, and after heat exchange with the outer wall of the device in different temperature sections, the hot water is finally discharged from the high-temperature hot water outlet (10) at the lower part of the fixed outer cover (9).

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