System and method for low energy consumption lithium spodumene transformation roasting

Abstract

This invention relates to the field of lithium extraction technology from lithium ore, and discloses a low-energy-consumption system and method for the conversion roasting of spodumene. The system includes a preheater, a kiln tail flue, a rotary kiln, a cooler, a drying pipe, a flue gas treatment system, and a dust removal device. The cooler has a drying heat source air intake connected to the air inlet of the drying pipe, and the drying pipe has a wet raw material feeding port. The clean hot air from the cooler dries the wet raw material. The air outlet of the drying pipe is connected to the air inlet of the first-stage cyclone separator of the preheater, and the air outlet of the first-stage cyclone separator is connected to the dust removal device. The flue gas exiting the first-stage cyclone separator is discharged to the chimney after dust removal. The air outlet of the second-stage cyclone separator is connected to the flue gas treatment system, and the flue gas exiting the second-stage cyclone separator needs to be treated for flue gas pollutants before being discharged. This invention simplifies the tail gas treatment process, eliminates the need for additional desulfurization and denitrification devices, solves the problems of crusting and blockage of high-moisture materials and ring agglomeration in the kiln, and reduces system energy consumption and environmental costs.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from lithium ore, and in particular to a system and method for low-energy spodumene conversion roasting. Background Technology

[0002] Lithium is an indispensable key mineral raw material for the development of the new energy industry, and it is widely used in lithium batteries, glass and ceramics, lithium-based lubricating grease, metallurgical casting, pharmaceuticals, and the nuclear energy industry. my country is rich in lithium ore resources, and the production of lithium carbonate using spodumene (Li₂O·Al₂O₃·4SiO₂) as raw material is currently the mainstream technical route. Currently, lithium extraction from spodumene mainly uses the sulfuric acid process, which involves: firstly, transforming and roasting the spodumene concentrate to convert the stable α-type spodumene into the more reactive β-type spodumene; then, through acidification, leaching, and carbonation processes, lithium carbonate is obtained.

[0003] In existing industrial production, the spodumene concentrate after flotation has a high moisture content of 12% to 18%, and is usually fed into a rotary kiln directly or after preheating by one or two stages of cyclone preheaters. When using one or two stages of cyclone preheaters, the material can only be preheated to 120 to 150°C before entering the kiln, and then the moisture drying, preheating, and crystal transformation are completed in the rotary kiln. Because the material only tumbles at the bottom in the rotary kiln, the drying and preheating efficiency is low, resulting in a long residence time of the material in the kiln. The rotary kiln is relatively large, with a low rotation speed, usually less than 1 r / min, resulting in low output and high energy consumption per unit product. The rotary kiln roasting process is prone to ring formation or large ball formation. Large lumps in the kiln not only affect the cooling effect of subsequent cooling processes, but also increase the system power consumption and equipment wear in the grinding section.

[0004] High-moisture spodumene has poor fluidity. When directly fed into a cyclone preheater, the material is unevenly distributed in the duct and tends to accumulate at the cone of the cyclone, causing the system to collapse. If directly fed into a rotary kiln, the low heat exchange efficiency requires a long time for moisture drying, resulting in a decrease in processing speed, an increase in heat loss, and low waste heat utilization efficiency.

[0005] To address the problems caused by high-moisture materials entering the kiln, some processes have attempted to pre-dry the wet raw materials outside the kiln. However, existing external kiln drying methods have the following shortcomings: First, rotary drying equipment is used, which generates significant heat, and the drying and roasting processes are separated. The dried material needs to be cooled and stored before being fed into the roasting system via an elevator, resulting in high system energy consumption. Second, hot air furnaces are typically used to generate high-temperature flue gas as the drying heat source. This method has the following problems: First, the hot air furnace requires additional fuel, increasing system energy consumption; second, the flue gas used as the drying heat source contains harmful components such as SO2 and NOx, and the exhaust gas treatment after heat exchange with the wet material is complex and environmental protection costs are high.

[0006] In summary, the problems with existing technologies are: 1. After flotation, the spodumene raw material has a high moisture content and poor fluidity. If it is directly fed into the preheater, it is easy to accumulate at the cyclone cone, causing the system to collapse. If it is directly fed into the kiln, the temperature gradient inside the rotary kiln is large and the kiln speed is low. The liquid phase is easy to appear on the surface of the material, resulting in high heat consumption, low output, and easy agglomeration in the rotary kiln, which affects the cooling effect and increases the grinding energy consumption.

[0007] 2. The existing external kiln drying method is separate from the roasting process. The dried material needs to be cooled and stored before being fed into the roasting system through lifting equipment, resulting in high system energy consumption. Using hot air furnace flue gas drying requires additional fuel consumption, and the exhaust gas treatment is complex and environmental protection costs are high. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a low-energy-consumption spodumene conversion roasting system and method. By setting up a drying pipeline, the spodumene is dehydrated outside the kiln before being roasted in the kiln, effectively solving the common industry problem of high-moisture materials easily causing skin formation and blockage in the preheater in traditional processes.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A low-energy-consumption spodumene conversion roasting system includes a preheater, a kiln tail smoke chamber, a rotary kiln, a cooler, a drying pipeline, a flue gas treatment system, and a dust removal device. The preheater, kiln tail smoke chamber, rotary kiln, and cooler are connected in sequence. The preheater includes at least a first-stage cyclone separator and a second-stage cyclone separator. The cooler is equipped with a drying heat source air intake, which is connected to the air inlet of the drying pipeline. The drying pipeline is equipped with a wet raw material feeding port. The hot air discharged from the cooler is clean air free of sulfur oxides and nitrogen oxides, and this hot air is used as a drying heat source and introduced into the drying pipeline to dry the wet raw material. The air outlet of the drying pipeline is connected to the air inlet of the first-stage cyclone separator of the preheater. The outlet of the first-stage cyclone is only connected to the dust removal equipment. The flue gas exiting the first-stage cyclone can be discharged into the chimney after dust removal. The outlet of the second-stage cyclone is connected to the flue gas treatment system. The flue gas exiting the second-stage cyclone is discharged after being treated for flue gas pollutants.

[0010] Furthermore, the drying pipe is a vertically upward-arranged pipe with a constriction in the middle and an elbow at the bottom. An emergency buffer chamber is located below the elbow, and the outlet of the emergency buffer chamber is connected to the inlet of the kiln tail flue.

[0011] Furthermore, the head of the cooler is provided with a secondary air intake, which is connected to the secondary air inlet of the rotary kiln; the middle and / or tail of the cooler are provided with a drying heat source air intake, which is connected to the settling chamber, and the air outlet of the settling chamber is connected to the air inlet of the drying pipe.

[0012] Furthermore, the preheater includes 3-6 stages of cyclones, wherein the feed pipe of the previous stage cyclone is connected to the air inlet pipe of the next stage cyclone, and the feed pipe of the last stage cyclone is connected to the kiln tail flue.

[0013] Furthermore, it also includes a pre-calcining furnace, which is equipped with a raw material feeding point and a second burner, the second burner being located below the raw material feeding point; The feed pipe of the penultimate stage cyclone of the preheater is connected to the raw material feeding point of the precalcining furnace, and the air outlet of the precalcining furnace is connected to the air inlet of the final stage cyclone of the preheater.

[0014] Furthermore, the pre-calcining furnace is provided with a tertiary air inlet, which is located below the second burner and is connected to the head of the cooler.

[0015] This invention also discloses a low-energy-consumption spodumene conversion roasting method, comprising the following steps: Drying: Wet spodumene raw material is fed into the drying pipe, and hot air is drawn from the cooler as a drying heat source and introduced into the drying pipe, so that the wet raw material exchanges heat with the hot air and dehydrates in the drying pipe. Multi-stage preheating: The dehydrated dry raw material enters the first-stage cyclone with the airflow, and the separated material enters the air inlet pipe of the second-stage cyclone. It then passes through the subsequent cyclones for heat exchange. The flue gas discharged from the first-stage cyclone is discharged directly after dust removal, while the flue gas from the second-stage cyclone needs to be treated for flue gas pollutants before being discharged. Calcination transformation: The material collected from the final stage cyclone is fed into the rotary kiln through the kiln tail smoke chamber, where the crystal transformation calcination is completed. Cooling and waste heat recovery: The calcined clinker enters a cooler for cooling. The cooling medium is air. The hot air drawn from the cooler is used as the drying heat source, and the hot air from the head of the cooler is sent into the rotary kiln as secondary air.

[0016] Furthermore, in the drying step, hot air at 300°C to 500°C is drawn from the middle and / or tail of the cooler as a drying heat source, and the raw material temperature exiting the drying pipe is 100°C to 150°C; the cross-sectional wind speed inside the drying pipe is 5m / s to 10m / s.

[0017] Furthermore, the flue gas temperature exiting the second-stage cyclone is below 250°C; the raw material temperature entering the rotary kiln is 400°C to 600°C; the rotation speed of the rotary kiln is 2 rpm to 4 rpm; and the calcination temperature inside the rotary kiln is 1100°C to 1200°C.

[0018] Furthermore, a pre-calcination step is included between the multi-stage preheating step and the roasting transformation step: the material collected by the penultimate stage cyclone of the preheater is fed into the pre-calcination furnace, so that the material is heated in a suspended state, and then separated by the final stage cyclone before entering the rotary kiln; tertiary air is drawn from the head of the cooler and sent into the pre-calcination furnace for combustion assistance; the outlet flue gas temperature of the pre-calcination furnace is 850°C to 900°C, and the temperature of the material entering the rotary kiln after pre-calcination is 750°C to 850°C; the cross-sectional wind speed in the pre-calcination furnace is not less than 5 m / s.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention features a drying pipeline connected in series with a multi-stage preheater. Wet spodumene is first rapidly dried with hot air outside the kiln, then preheated to 400-600°C in the preheater before entering the kiln. The drying pipeline has a simple structure with no moving parts, resulting in low operating and maintenance costs. The dried material enters the preheater directly without intermediate storage, eliminating the need for intermediate storage equipment, reducing heat loss, and lowering system heat consumption. The dried spodumene has good fluidity and disperses evenly within the cyclone separator, resulting in high heat exchange efficiency for suspended materials and preventing crusting and blockage of high-moisture materials within the preheater.

[0020] 2) Preheated spodumene enters the rotary kiln closer to its transformation temperature, significantly reducing the drying and preheating load on the kiln. The rotary kiln speed can be increased to 2-4 rpm, increasing the number of material tumbling cycles, improving heat exchange efficiency, increasing output for the same kiln diameter, reducing surface heat loss, and lowering overall system energy consumption. The kiln temperature is stable with fewer localized high temperatures, making it suitable for roasting lithium ore with narrow transformation temperature windows, and preventing ring formation and large agglomeration. The product is in powder or sand form, with high subsequent cooling efficiency and minimal wear on grinding equipment.

[0021] 3) This invention uses 300-500℃ hot air from the middle and tail sections of the cooler as the drying heat source. This hot air is clean air; the exhaust gas after heat exchange with the wet material contains only dust, which can be discharged in compliance with standards after dust removal, eliminating the need for desulfurization and denitrification devices. Compared with traditional processes that use flue gas from rotary kilns or hot air furnaces as the drying heat source, there are no exhaust gas treatment problems caused by SO2 and NOx, and the investment and operating costs of environmental protection equipment are lower.

[0022] 4) This invention can also include a pre-calcining furnace. The material collected by the penultimate stage cyclone separator of the preheater is fed into the pre-calcining furnace and pre-activated under flue gas at 850~900℃, raising the temperature of the material entering the kiln to 750~850℃. The material enters the rotary kiln at a temperature closer to the conversion temperature, resulting in a smaller temperature gradient within the kiln, more uniform heating of the material, shorter calcination time, reduced liquid phase, a powdery and granular product, higher subsequent cooling efficiency, less wear on the grinding equipment, more stable system operation, and higher production capacity. Attached Figure Description

[0023] Appendix Figure 1 This is a schematic diagram of the system in Embodiment 1 of the present invention.

[0024] Appendix Figure 2 This is a system schematic diagram of Embodiment 2 of the present invention.

[0025] In the diagram: 1-Preheater, 101-First-stage cyclone separator, 102-Second-stage cyclone separator, 103-Final-stage cyclone separator, 104-Penulous-stage cyclone separator; 2-Kiln tail flue chamber, 3-Rotary kiln, 301-First burner; 4-Cooler; 5-Drying pipe, 501-Wet raw material feed port, 502-Connecting elbow, 6-Emergency buffer bin, 7-Settling chamber, 8-Dust removal device, 9-Flue gas treatment system, 10-Pre-calcining furnace, 1001-Raw material feeding point, 1002-Second burner.

[0026] a-Wet raw feed, b-Clinker, c-Fuel, A-Air.

[0027] The dashed line with arrows indicates the airflow direction, and the solid line with arrows indicates the material flow direction. Detailed Implementation

[0028] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0029] like Figure 1 As shown, the present invention provides a low-energy spodumene conversion roasting system, which includes: a preheater 1, a kiln tail smoke chamber 2, a rotary kiln 3, a cooler 4, a drying pipe 5, a dust removal device 8, and a flue gas treatment system 9.

[0030] The discharge pipe of the first-stage cyclone 101 of the preheater 1 is connected to the air inlet pipe of the second-stage cyclone 102, the discharge pipe of the second-stage cyclone 102 is connected to the air inlet pipe of the next stage cyclone, and so on, with the discharge pipe of the final stage cyclone 103 connected to the kiln tail smoke chamber 2. The discharge port of the kiln tail flue 2 is connected to the feed end of the rotary kiln 3, and the kiln head of the rotary kiln 3 is equipped with a first burner 301; the fuel can be pulverized coal or ash-free gaseous fuel, such as natural gas, coal gasification, alternative fuel gasification, etc. The discharge end of the rotary kiln 3 is connected to the feed inlet of the cooler 4; the head of the cooler 4 is provided with a secondary air intake, which is connected to the secondary air inlet of the rotary kiln 3 through a pipe, so that the high-temperature hot air from the head of the cooler is sent into the rotary kiln as combustion air; the middle and / or tail of the cooler 4 are each provided with a drying heat source air intake, which is connected to the air inlet at the bottom of the drying pipe 5 through a connecting pipe. The drying pipe 5 is a vertically upward-arranged pipe, with its upper air outlet connected to the air inlet of the first-stage cyclone 101. The lower part of the drying pipe 5 is provided with a wet raw material feeding port 501, which uses the clean hot air from the cooler to dry the wet raw material. Since the drying heat source is the hot air discharged from the cooler, which does not contain sulfur oxides and nitrogen oxides, the flue gas from the drying pipe contains only dust, which is directly discharged into the atmosphere after dust removal.

[0031] The air outlet of the drying pipe is connected to the air inlet of the first-stage cyclone of the preheater. The air outlet of the first-stage cyclone is not connected to any desulfurization or denitrification device, but is only connected to the air inlet of the dust removal equipment. The air outlet of the dust removal equipment 8 is connected to the chimney. The flue gas exiting the first-stage cyclone can be discharged after dust removal. The air outlet of the second-stage cyclone is connected to the flue gas treatment system. The flue gas exiting the second-stage cyclone needs to be treated for flue gas pollutants before being discharged.

[0032] Preferably, the flue gas treatment system includes a desulfurization device, a denitrification device, and a dust removal device. The flue gas exiting the second-stage cyclone is discharged after being treated by desulfurization, denitrification, and dust removal.

[0033] Preferably, the preheater 1 has 3 to 6 stages, and in this embodiment, it has 4 stages. The feed pipe of the upper-stage cyclone is connected to the air inlet pipe of the lower-stage cyclone, and the feed pipe of the final-stage cyclone is connected to the kiln tail flue, forming a countercurrent heat exchange channel between the material and the flue gas. The dry raw material exiting the drying pipe 5 enters the preheater 1 with the airflow, and undergoes gas-solid separation and heat exchange in sequence through the preheater. The material and flue gas exchange heat in a countercurrent manner stage by stage, resulting in high heat exchange efficiency and low system heat consumption.

[0034] Preferably, the drying pipe 5 has a constriction in the middle and an elbow at the bottom. An emergency buffer chamber is located below the elbow. If a system malfunction occurs during the drying process, the material can be temporarily stored in the emergency buffer chamber at the bottom of the drying pipe and directly sent into the kiln tail smoke chamber, avoiding system shutdown. The discharge port of the emergency buffer chamber is connected to the feed port of the kiln tail smoke chamber 2.

[0035] The connecting pipe is equipped with a settling chamber 7, which is located between the drying heat source air intake of the cooler 4 and the air inlet of the drying pipe 5, and is used to remove clinker dust carried in the hot air.

[0036] Working principle: Wet spodumene raw meal a with a moisture content of 10%~15% is fed into drying pipe 5 through wet raw meal feed port 501. The particle size of the spodumene raw meal is less than 200 micrometers. Small-particle-size raw meal has good heat exchange effect and is heated evenly in the kiln, making it less prone to ring formation. At the same time, hot air at 300~500℃ is drawn from the middle and / or tail of cooler 4. This hot air first passes through settling chamber 7 to remove entrained clinker dust, and then is sent to the bottom of drying pipe 5. The hot air comes into direct contact with the wet raw meal in the vertically upward pipe and performs gas-solid heat exchange, and the moisture in the raw meal evaporates rapidly. The cross-sectional wind speed in drying pipe 5 is controlled at 5~10m / s to keep the raw meal in a suspended state, improve gas-solid heat exchange efficiency, and avoid material deposition. The moisture content of the raw meal exiting drying pipe 5 is reduced to below 1%, and the temperature rises to 100~150℃.

[0037] The dried raw material is carried by the airflow into the first-stage cyclone 101 for gas-solid separation. The separated flue gas enters the dust removal equipment 8 from the outlet of the first-stage cyclone 101 and is directly discharged after dust removal. Since the flue gas of the first-stage cyclone comes from the drying pipe and does not contain pollutants SO2 and NOx, it can meet the emission standards after dust removal, without the need for desulfurization and denitrification treatment, which simplifies the tail gas treatment process. The separated raw material enters the inlet pipe of the second-stage cyclone 102 through the feed pipe of the first-stage cyclone 101 and enters the second-stage cyclone 102 for secondary gas-solid separation. The material passes through each subsequent cyclone in this way, and exchanges heat with the rising flue gas in a countercurrent manner, and the temperature gradually increases.

[0038] The material separated by the final stage cyclone separator 103 reaches a temperature of 400~600℃ and is directly fed into the kiln tail smoke chamber 2 through the feed pipe, and then enters the rotary kiln 3. Compared with the traditional kiln feeding process of 120~150℃, the kiln feeding temperature is increased, which greatly reduces the preheating load of the rotary kiln and creates conditions for shortening the roasting time and increasing the output.

[0039] Rotary kiln 3 operates at a speed of 2-4 rpm, with the roasting temperature controlled between 1100℃ and 1200℃. Within rotary kiln 3, the material undergoes a crystal transformation from α-type spodumene to β-type spodumene. Traditional rotary kilns typically operate at speeds below 1 rpm. In contrast, the rotary kiln of this application increases the speed, leading to more material tumbling and significantly improved heat exchange efficiency. This further enhances the production capacity advantage, resulting in a substantial reduction in the rotary kiln's heat load. With the same kiln diameter, output can be significantly increased, surface heat loss is reduced, and overall system energy consumption decreases. When the production capacity is the same as with traditional processes, the rotary kiln specifications of this application can be significantly reduced, lowering roasting heat consumption. Simultaneously, the stable temperature regime within the rotary kiln avoids localized high temperatures, making it suitable for roasting lithium ore with narrow crystallization temperature windows. This fundamentally solves the problem of ring formation and large agglomeration caused by directly feeding high-moisture materials into the kiln.

[0040] The fuel required for rotary kiln 3 is injected through the first burner 301.

[0041] After roasting, the β-type spodumene clinker enters the cooler 4 from the discharge end of the rotary kiln 3, where it is cooled with ambient temperature air. The clinker temperature exiting the cooler 4 is ≤100℃, and it is in powder or sand form. The high-temperature hot air at the head of the cooler 4 is drawn back into the rotary kiln 3 as secondary air to aid combustion. The 300~500℃ hot air in the middle and tail of the cooler 4 is circulated as a drying heat source after being dusted in the settling chamber 7. The high-temperature hot air at the head is used to aid combustion, taking advantage of its high temperature. The medium-temperature hot air in the middle and tail is dusted in the settling chamber before entering the drying pipe for drying, which can effectively remove clinker dust entrained in the hot air and ensure the purity of the raw meal after drying.

[0042] When the system malfunctions, the material in the drying pipe 5 can be temporarily stored in the emergency buffer bin at its bottom and then directly sent to the kiln tail smoke chamber 2 to avoid system shutdown.

[0043] The flue gas temperature at the outlet of the second-stage cyclone 102 is below 250℃. This flue gas enters the flue gas treatment system 9 and is discharged in compliance with standards after desulfurization, denitrification, and dust removal.

[0044] The spodumene roasting conversion system provided in this application significantly reduces roasting heat consumption. This is due to three main reasons: first, the rotary kiln size is greatly reduced, resulting in less surface heat dissipation; second, the system's waste heat is fully utilized, with the cooler efficiently recovering heat from the hot material in the rotary kiln, and the generated hot air being used entirely for fuel combustion and spodumene moisture drying; and third, the added 3-6 stage cyclone preheaters fully recover heat from the flue gas, ensuring the system's exhaust gas temperature is below 250℃. However, because the system's heat consumption is significantly reduced, the amount of flue gas exiting the preheater is also greatly reduced. Utilizing only the heat from this portion of the flue gas for drying high-moisture spodumene raw materials is insufficient; therefore, hot air needs to be drawn from the cooler for drying.

[0045] Example 2 Please see Figure 2 Unlike Example 1, this solution also includes a pre-calcining furnace 10.

[0046] The system also includes a pre-calcining furnace 10, which has a raw material feeding point 1001 and a second burner 1002 below it; the preheater 1, the pre-calcining furnace 10, and the kiln tail flue chamber 2 are connected in sequence. The preheater 1 has 5 stages, including the penultimate cyclone separator 104 and the final cyclone separator 103. The feed pipe of the penultimate cyclone separator 104 is connected to the raw material feeding point 1001 of the pre-calcining furnace 10, and the air outlet of the pre-calcining furnace 10 is connected to the air inlet of the final cyclone separator 103. The combustion air for the pre-calcining furnace 10 is provided by secondary air from the cooler 4. The outlet flue gas temperature of the pre-calcining furnace 10 is 850℃ to 900℃, and the material temperature entering the rotary kiln 3 after pre-calcination is 750℃ to 850℃; the cross-sectional wind velocity inside the pre-calcining furnace 10 is not less than 5m / s.

[0047] Furthermore, the pre-calcining furnace 10 is also provided with a tertiary air inlet, which is located below the second burner 1002 and is connected to the cooler 4.

[0048] The roasting system includes a pre-calcining furnace, forming a two-stage roasting process combining suspension preheating, pre-calcination, and a rotary kiln. The pre-calcining furnace further raises the temperature of the material entering the kiln to 750-850℃. The material enters the rotary kiln when it is close to the transformation temperature. The pre-calcining furnace handles most of the heating, and the material in the rotary kiln only needs to complete the crystallization reaction. This extends the effective crystallization zone length within the kiln, resulting in a smaller temperature gradient, rapid material tumbling, uniform heating, further shortening the roasting time, reducing liquid phase formation, producing a powdery, granular product, high subsequent cooling efficiency, and minimal wear on the grinding equipment. The overall system stability and production capacity are significantly improved.

[0049] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A low-energy-consumption spodumene conversion roasting system, comprising a preheater, a kiln tail smoke chamber, a rotary kiln, a cooler, a drying pipeline, a flue gas treatment system, and a dust removal device; the preheater, kiln tail smoke chamber, rotary kiln, and cooler are connected in sequence; the preheater includes at least a first-stage cyclone separator and a second-stage cyclone separator; characterized in that, The cooler is equipped with a drying heat source air intake, which is connected to the air inlet of the drying pipe. The drying pipe is equipped with a wet raw material feeding port. The hot air discharged from the cooler is clean air free of sulfur oxides and nitrogen oxides. This hot air is used as a drying heat source and is introduced into the drying pipe to dry the wet raw material. The air outlet of the drying pipe is connected to the air inlet of the first-stage cyclone separator of the preheater. The outlet of the first-stage cyclone is only connected to the dust removal equipment. The flue gas exiting the first-stage cyclone can be discharged into the chimney after dust removal. The outlet of the second-stage cyclone is connected to the flue gas treatment system. The flue gas exiting the second-stage cyclone is discharged after being treated for flue gas pollutants.

2. The system for low energy consumption transformation roasting of spodumene according to claim 1, characterized in that, The drying pipe is a vertically upward-arranged pipe with a constriction in the middle and an elbow at the bottom. An emergency buffer chamber is located below the elbow, and the outlet of the emergency buffer chamber is connected to the inlet of the kiln tail flue.

3. The system for low energy consumption transformation roasting of spodumene according to claim 1, characterized in that, The head of the cooler is provided with a secondary air intake, which is connected to the secondary air inlet of the rotary kiln; the middle and / or tail of the cooler is provided with a drying heat source air intake, which is connected to a settling chamber, and the air outlet of the settling chamber is connected to the air inlet of the drying pipe.

4. The system for low energy consumption transformation roasting of spodumene according to claim 1, characterized in that, The preheater includes 3-6 stages of cyclones, wherein the feed pipe of the previous stage cyclone is connected to the air inlet pipe of the next stage cyclone, and the feed pipe of the last stage cyclone is connected to the kiln tail flue.

5. The system for low energy spodumene transformation roasting of claim 1, wherein, It also includes a pre-calcining furnace, which is equipped with a raw material feeding point and a second burner, the second burner being located below the raw material feeding point; The feed pipe of the penultimate stage cyclone of the preheater is connected to the raw material feeding point of the precalcining furnace, and the air outlet of the precalcining furnace is connected to the air inlet of the final stage cyclone of the preheater.

6. The system for low energy consumption transformation roasting of spodumene according to claim 5, characterized in that, The pre-calcining furnace is provided with a tertiary air inlet, which is located below the second burner and is connected to the head of the cooler.

7. A method for low energy consumption transformation roasting of spodumene, characterized by, Includes the following steps: Drying: Wet spodumene raw material is fed into the drying pipe, and hot air is drawn from the cooler as a drying heat source and introduced into the drying pipe, so that the wet raw material exchanges heat with the hot air and dehydrates in the drying pipe. Multi-stage preheating: The dehydrated dry raw material enters the first-stage cyclone with the airflow, and the separated material enters the air inlet pipe of the second-stage cyclone. It then passes through the subsequent cyclones for heat exchange. The flue gas discharged from the first-stage cyclone is discharged directly after dust removal, while the flue gas from the second-stage cyclone needs to be treated for flue gas pollutants before being discharged. Calcination transformation: The material collected from the final stage cyclone is fed into the rotary kiln through the kiln tail smoke chamber, where the crystal transformation calcination is completed. Cooling and waste heat recovery: The calcined clinker enters a cooler for cooling. The cooling medium is air. The hot air drawn from the cooler is used as the drying heat source, and the hot air from the head of the cooler is sent into the rotary kiln as secondary air.

8. The method of low energy consumption transformation roasting of spodumene according to claim 7, characterized in that, In the drying step, hot air at 300°C to 500°C is drawn from the middle and / or tail of the cooler as the drying heat source, and the raw material temperature exiting the drying pipe is 100°C to 150°C; the cross-sectional wind speed inside the drying pipe is 5m / s to 10m / s.

9. The method of low energy consumption transformation roasting of spodumene according to claim 7, characterized in that, The flue gas temperature exiting the second-stage cyclone is below 250°C; the raw material temperature entering the rotary kiln is 400°C to 600°C; the rotation speed of the rotary kiln is 2 rpm to 4 rpm; and the calcination temperature inside the rotary kiln is 1100°C to 1200°C.

10. The method of low energy consumption transformation roasting of spodumene according to claim 7, characterized in that, Between the multi-stage preheating step and the roasting transformation step, a pre-calcination step is also included: the material collected by the penultimate stage cyclone of the preheater is fed into the pre-calcination furnace, so that the material is heated in a suspended state, and then separated by the final stage cyclone before entering the rotary kiln; tertiary air is drawn from the head of the cooler and sent into the pre-calcination furnace for combustion support; the outlet flue gas temperature of the pre-calcination furnace is 850℃ to 900℃, and the temperature of the material entering the rotary kiln after pre-calcination is 750℃ to 850℃; the cross-sectional wind speed in the pre-calcination furnace is not less than 5m / s.

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