Two-stage lithium-aluminosilicate transformation roasting system and method

Abstract

The application discloses a two-stage lithium-aluminum silicate transformation roasting system and method, and overcomes the shortcomings of low heat resistance and high cost of a whole electromagnetic induction heating cylinder by adopting a lithium-aluminum silicate transformation roasting system of a first-stage electromagnetic induction heating plus a second-stage sulfur oxidation self-heating, and has the advantages of long service life and low investment cost. In addition, the lithium-aluminum silicate transformation roasting is carried out in a clean way of electricity plus sulfur reaction heat, and is environment-friendly and low-carbon. The application is suitable for regions rich in electricity but lacking in fuels such as coal and natural gas and weak in logistics foundation.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from spodumene, specifically to a two-stage spodumene conversion roasting system and method. Background Technology

[0002] Lithium is a crucial basic material supporting the development of technologies such as new energy vehicles, aerospace, and nuclear industry.

[0003] Lithium is mainly extracted from spodumene, lepidolite, and salt lakes. Among them, spodumene has advantages such as high lithium content, mature technology, and relatively low extraction cost, making it the main raw material for lithium extraction.

[0004] Currently, the sulfuric acid roasting process is mainly used for lithium extraction from spodumene. In this process, α-spodumene is roasted at a high temperature of 950-1150℃ to transform it into β-spodumene. The β-spodumene is then mixed with sulfuric acid and roasted at 250-300℃ to allow the β-spodumene to undergo a displacement reaction with the sulfuric acid, generating soluble lithium sulfate. The roasted ore is then leached with water to obtain a lithium sulfate solution. This solution is then subjected to a process of impurity removal, evaporation and concentration, and lithium precipitation to obtain lithium carbonate.

[0005] Due to the lack of fuels such as coal and natural gas in some countries or regions and the weak logistics infrastructure, the cost of using existing internally heated rotary kilns for spodumene conversion roasting is extremely high. On the other hand, using electrically heated rotary kilns presents problems such as high roasting temperature, strict requirements for cylinder material, and high equipment investment costs. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention aims to provide a two-stage spodumene transformation roasting system and method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A two-stage spodumene transformation roasting system includes an electromagnetic induction rotary kiln and an internally heated rotary kiln.

[0009] The electromagnetic induction rotary kiln includes an electromagnetic induction rotary kiln body, an electromagnetic induction coil, and an electromagnetic heating controller; the electromagnetic induction coil is wound around the outside of the electromagnetic induction rotary kiln body and electrically connected to the electromagnetic heating controller, and the electromagnetic induction coil is controlled to generate heat by the electromagnetic heating controller.

[0010] The internally heated rotary kiln includes an internally heated rotary kiln body, a sulfur powder spray gun, and a compressed air spray gun; the sulfur powder spray gun and the compressed air spray gun are respectively connected to the interior of the internally heated rotary kiln body; the sulfur powder silo is connected to the sulfur powder spray gun; the sulfur powder spray gun is used to spray sulfur powder, and the compressed air spray gun is used to spray compressed air, compressed oxygen-enriched air, or compressed pure oxygen; the kiln tail of the electromagnetic induction rotary kiln body and the kiln head of the internally heated rotary kiln body are connected.

[0011] Furthermore, the system also includes a raw material silo and a feeder, wherein the raw material silo is connected to the kiln head of the electromagnetic induction rotary kiln via the feeder.

[0012] Furthermore, the above system also includes heat exchanger one, heat exchanger two, and a compressed air fan. The kiln tail of the internally heated rotary kiln body is connected to the feed inlet of heat exchanger one, and the discharge outlet of heat exchanger one is connected to the feed inlet of heat exchanger two. The heat exchange air inlet of heat exchanger two is connected to the compressed air fan, the heat exchange air outlet of heat exchanger two is connected to the heat exchange air inlet of heat exchanger one, and the heat exchange air outlet of heat exchanger one is connected to the compressed air spray gun.

[0013] Furthermore, the above system also includes a dust settling chamber, a bag filter, and an exhaust fan; the flue gas outlet of the electromagnetic induction rotary kiln is connected to the air inlet of the dust settling chamber, the air outlet of the dust settling chamber is connected to the air inlet of the bag filter, and the air outlet of the bag filter is connected to the exhaust fan.

[0014] Furthermore, the dust outlets of the dust settling chamber and the bag filter are respectively connected to the dust hopper 11 of the dust settling chamber and the dust hopper of the bag filter.

[0015] Furthermore, the material of the electromagnetic induction rotary kiln body is stainless steel; the power of a single electromagnetic induction heating controller is 100-2000kw, and each electromagnetic induction heating controller controls an electromagnetic induction coil with a kiln length of 1-3 meters; the internally heated rotary kiln body is made of carbon steel lined with refractory material.

[0016] Furthermore, the connection between the kiln tail of the electromagnetic induction rotary kiln body and the kiln head of the internally heated rotary kiln body is sealed with a sealing ring.

[0017] The present invention also provides a method for spodumene transformation roasting using the above system, the specific process of which is as follows:

[0018] The electromagnetic induction rotary kiln is turned on, and the kiln body begins to rotate. The electromagnetic heating controller then controls the electromagnetic induction coil to heat the kiln body. Alpha-type spodumene is fed into the kiln body. Through the rotation of the kiln body and the action of the dust-raising plates inside the kiln, the alpha-type spodumene is continuously tumbled and mixed. At the same time, the heated kiln body rapidly dries and preheats the alpha-type spodumene to 500-950℃.

[0019] Alpha-type spodumene moves into the internally heated rotary kiln via a spiral motion. Sulfur powder is injected into the kiln head through a sulfur powder spray gun, while compressed air, compressed oxygen-enriched air, or compressed oxygen is simultaneously sprayed through a compressed air spray gun. This causes the sulfur to react with the oxygen, releasing a large amount of heat and raising the temperature inside the internally heated rotary kiln to 950-1200℃. The amount of sulfur powder sprayed is 5-50% of the mass of the alpha-type spodumene. After being calcined in the internally heated rotary kiln, the alpha-type spodumene can be transformed into beta-type spodumene.

[0020] Furthermore, in the above method, the high-temperature β-type spodumene obtained by transformation enters heat exchanger one and heat exchanger two in sequence to exchange heat with compressed air, compressed oxygen-enriched air or compressed oxygen. The cooled β-type spodumene enters the sulfuric acid roasting and lithium extraction process, while the compressed air, compressed oxygen-enriched air or compressed oxygen that has been heated by heat exchange enters the internally heated rotary kiln.

[0021] Furthermore, in the above method, the flue gas generated by roasting inside the internally heated rotary kiln is first passed through the electromagnetic induction rotary kiln body by the exhaust fan to dry and preheat the α-type spodumene inside the electromagnetic induction rotary kiln body. Then, it enters the dust settling chamber from the kiln tail of the electromagnetic induction rotary kiln body to settle some of the flue gas dust. Then, it passes through a bag filter to further remove the flue gas dust. The SO2 flue gas after passing through the bag filter is transported to the acid production system to produce sulfuric acid. The sulfuric acid produced is used in the sulfuric acid roasting lithium extraction process and / or sold externally.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) The present invention proposes a lithium spodumene transformation roasting system with a first stage of electromagnetic induction heating and a second stage of sulfur oxidation self-heating, which overcomes the disadvantages of low heat resistance and high cost of the entire electromagnetic induction heating cylinder, and has the advantages of long service life and low investment cost.

[0024] (2) The present invention uses a clean method of electric + sulfur reaction heat to transform and roast spodumene, which is environmentally friendly and low-carbon.

[0025] (3) The lithium spodumene transformation roasting system and method proposed in this invention, which consists of a first stage of electromagnetic induction heating and a second stage of sulfur self-heating, is suitable for regions with abundant electricity but lacking fuels such as coal and natural gas, and with weak logistics infrastructure. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the system structure in Embodiment 1 of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0028] Example 1

[0029] This embodiment provides a two-stage spodumene transformation roasting system, such as Figure 1 As shown, it includes a raw material silo 1, a feeder 2, an electromagnetic induction rotary kiln 3, a sealing ring 4, an internally heated rotary kiln 5, a sulfur powder silo 6, a heat exchanger 1 7, a heat exchanger 2 8, a compressed blower 9, a dust settling chamber 10, a dust settling chamber dust hopper 11, a bag filter dust collector 12, a bag filter dust hopper 13, and an exhaust fan 14.

[0030] The electromagnetic induction rotary kiln 3 includes an electromagnetic induction rotary kiln body 3-1, an electromagnetic induction coil 3-2, and an electromagnetic heating controller 3-3; the electromagnetic induction coil 3-2 is wound around the outside of the electromagnetic induction rotary kiln body 3-1 and electrically connected to the electromagnetic heating controller 3-3, and the electromagnetic induction coil 3-2 is controlled to generate heat by the electromagnetic heating controller 3-3.

[0031] The internally heated rotary kiln includes an internally heated rotary kiln body 5-1, a sulfur powder spray gun 5-2, and a compressed air spray gun 5-3; the sulfur powder spray gun 5-2 and the compressed air spray gun 5-3 are respectively connected to the interior of the internally heated rotary kiln body 5-1; the sulfur powder silo 6 is connected to the sulfur powder spray gun 5-2; the sulfur powder spray gun 5-2 is used to spray sulfur powder, and the compressed air spray gun 5-3 is used to spray compressed air, compressed oxygen-enriched air, or compressed pure oxygen.

[0032] The tail of the electromagnetic induction rotary kiln body 3-1 is connected to the head of the internally heated rotary kiln body 5-1, and the connection edge is sealed with a sealing ring 4.

[0033] In this embodiment, the raw material bin 1 is connected to the feeding port of the electromagnetic induction rotary kiln 3-1 via the feeder 2.

[0034] In this embodiment, the discharge port of the internally heated rotary kiln body 5-1 is connected to the inlet of heat exchanger 7, and the discharge port of heat exchanger 7 is connected to the inlet of heat exchanger 8; the heat exchange air inlet of heat exchanger 8 is connected to the compressed air fan 9, the heat exchange air outlet of heat exchanger 8 is connected to the heat exchange air inlet of heat exchanger 7, and the heat exchange air outlet of heat exchanger 7 is connected to the compressed air spray gun 5-3.

[0035] In this embodiment, the flue gas outlet of the electromagnetic induction rotary kiln 3-1 is connected to the air inlet of the dust settling chamber 10, the air outlet of the dust settling chamber 10 is connected to the air inlet of the bag dust collector 12, and the air outlet of the bag dust collector 12 is connected to the exhaust fan 14.

[0036] Furthermore, the dust outlets of the dust settling chamber 10 and the bag dust collector 12 are respectively connected to the dust settling chamber hopper 11 and the bag dust hopper 13.

[0037] More specifically, the electromagnetic induction rotary kiln body 3-1 is made of stainless steel such as 304, 316L, 310S, 904L, GH2747, Inconel 600, and Inconel 625. Each electromagnetic induction heating controller has a power of 100-2000 kW and controls an electromagnetic induction coil 1-3 meters long.

[0038] More specifically, the internally heated rotary kiln body 5-1 is made of carbon steel lined with refractory material.

[0039] Example 2

[0040] This embodiment provides a method for spodumene transformation roasting using the system described in Embodiment 1, such as... Figure 1 As shown, the specific steps include the following:

[0041] (1) Start the electromagnetic induction rotary kiln to make the kiln body rotate. At the same time, the electromagnetic induction heating controller starts to control the electromagnetic induction coil to quickly heat the stainless steel electromagnetic induction rotary kiln body, specifically 304 stainless steel. α-type spodumene is fed into the electromagnetic induction rotary kiln body from the raw material silo through a feeder. Through the rotation of the electromagnetic induction rotary kiln body and the action of the dust-raising plates inside the kiln, the α-type spodumene is continuously tumbled and mixed. Simultaneously, the high-temperature stainless steel electromagnetic induction rotary kiln body rapidly dries and preheats the α-type spodumene to 500℃.

[0042] (2) The preheated α-type spodumene is moved to the internally heated rotary kiln by a spiral motion. The internally heated rotary kiln is injected with sulfur powder of 25% of the mass of α-type spodumene through a sulfur powder spray gun, and at the same time, a compressed air spray gun is turned on to blow compressed oxygen-rich air, so that the sulfur reacts with oxygen and releases a large amount of heat, heating the temperature inside the rotary kiln to 950°C for spodumene transformation roasting.

[0043] (3) After the transformation, the high-temperature β-type spodumene enters heat exchanger one and heat exchanger two in sequence to exchange heat with compressed oxygen-enriched air, so that the temperature of the β-type spodumene decreases from 960℃ to 120℃, while the temperature of the oxygen-enriched air increases from 24℃ to 190℃. The cooled β-type spodumene enters the sulfuric acid roasting and lithium extraction process, while the preheated oxygen-enriched air enters the internally heated rotary kiln.

[0044] (4) Preheated compressed oxygen-enriched air is injected into the internally heated rotary kiln through an air gun to react with sulfur powder and generate high-temperature flue gas at a temperature of 1006℃. A blower creates negative pressure, putting the bag filter, dust settling chamber, electromagnetic induction rotary kiln, and internally heated rotary kiln into a negative pressure state. The high-temperature flue gas enters the electromagnetic induction rotary kiln to dry and preheat α-type spodumene, and finally enters the dust settling chamber from the kiln tail. At this point, the flue gas temperature is 255℃.

[0045] (5) The flue gas from the tail of the electromagnetic induction rotary kiln enters the dust settling chamber to settle some of the dust, and then enters the bag filter to further remove the entrained dust in the flue gas. The dust in the dust settling chamber is returned to the rotary kiln for roasting, while the dust from the bag filter enters the sulfuric acid roasting lithium extraction system. The SO2 flue gas after dust collection is transported to the acid production system to produce sulfuric acid, which is used in the sulfuric acid roasting lithium extraction process. Excess sulfuric acid can be sold externally.

[0046] Example 3

[0047] This embodiment provides a method for spodumene transformation roasting using the system described in Embodiment 1, such as... Figure 1 As shown, the specific steps include the following:

[0048] (1) Start the electromagnetic induction rotary kiln to make the kiln body rotate. At the same time, the electromagnetic induction heating controller starts to control the electromagnetic induction coil to quickly heat the stainless steel electromagnetic induction rotary kiln body, specifically 310S stainless steel. α-type spodumene is fed into the electromagnetic induction rotary kiln body from the raw material silo through a feeder. Through the rotation of the electromagnetic induction rotary kiln body and the action of the dust-raising plates inside the kiln, the α-type spodumene is continuously tumbled and mixed. At the same time, the high-temperature stainless steel electromagnetic induction rotary kiln body rapidly dries and preheats the α-type spodumene to 850℃.

[0049] (2) The preheated α-type spodumene is moved to the internally heated rotary kiln by a spiral motion. The internally heated rotary kiln is injected with sulfur powder of 32% of the mass of α-type spodumene through a sulfur powder spray gun, and at the same time, a compressed air spray gun is turned on to blow compressed oxygen-rich air, so that the sulfur reacts with oxygen and releases a large amount of heat, heating the temperature inside the rotary kiln to 1100℃ for spodumene transformation roasting.

[0050] (3) After the transformation, the high-temperature β-type spodumene enters heat exchanger one and heat exchanger two in sequence to exchange heat with compressed oxygen-enriched air, which reduces the temperature of the β-type spodumene from 1060℃ to 150℃, while the temperature of the oxygen-enriched air increases from 30℃ to 280℃. The cooled β-type spodumene enters the sulfuric acid roasting and lithium extraction process, while the preheated oxygen-enriched air enters the internally heated rotary kiln.

[0051] (4) Preheated compressed oxygen-enriched air is injected into the internally heated rotary kiln through an air gun to react with sulfur powder and generate high-temperature flue gas at a temperature of 1050℃. A blower creates negative pressure, putting the bag filter, dust settling chamber, electromagnetic induction rotary kiln, and internally heated rotary kiln into a negative pressure state. The high-temperature flue gas enters the electromagnetic induction rotary kiln to dry and preheat α-type spodumene, and finally enters the dust settling chamber from the kiln tail. At this point, the flue gas temperature is 272℃.

[0052] (5) The flue gas from the tail of the electromagnetic induction rotary kiln enters the dust settling chamber to settle some of the dust, and then enters the bag filter to further remove the entrained dust in the flue gas. The dust in the dust settling chamber is returned to the rotary kiln for roasting, while the dust from the bag filter enters the sulfuric acid roasting lithium extraction system. The SO2 flue gas after dust collection is transported to the acid production system to produce sulfuric acid, which is used in the sulfuric acid roasting lithium extraction process. Excess sulfuric acid can be sold externally.

[0053] Example 4

[0054] This embodiment provides a method for spodumene transformation roasting using the system described in Embodiment 1, such as... Figure 1 As shown, the specific steps include the following:

[0055] (1) Start the electromagnetic induction rotary kiln to make the kiln body rotate. At the same time, the electromagnetic induction heating controller starts to control the electromagnetic induction coil to quickly heat the stainless steel electromagnetic induction rotary kiln body, specifically 904L stainless steel. α-type spodumene is fed into the electromagnetic induction rotary kiln body from the raw material silo through a feeder. Through the rotation of the electromagnetic induction rotary kiln body and the action of the dust-raising plates inside the kiln, the α-type spodumene is continuously tumbled and mixed. At the same time, the high-temperature stainless steel electromagnetic induction rotary kiln body rapidly dries and preheats the α-type spodumene to 900℃.

[0056] (2) The preheated α-type spodumene is moved to the internally heated rotary kiln by a spiral motion. The internally heated rotary kiln is injected with sulfur powder of 50% of the mass of α-type spodumene through a sulfur powder spray gun, and at the same time, a compressed air spray gun is turned on to blow compressed oxygen-rich air, so that the sulfur reacts with oxygen and releases a large amount of heat, heating the temperature inside the rotary kiln to 1200℃ for spodumene transformation roasting.

[0057] (3) After the transformation, the high-temperature β-type spodumene enters heat exchanger one and heat exchanger two in sequence to exchange heat with compressed oxygen-enriched air, which reduces the temperature of the β-type spodumene from 1160℃ to 180℃, while the temperature of the oxygen-enriched air increases from 30℃ to 300℃. The cooled β-type spodumene enters the sulfuric acid roasting and lithium extraction process, while the preheated oxygen-enriched air enters the internally heated rotary kiln.

[0058] (4) Preheated compressed oxygen-enriched air is injected into the internally heated rotary kiln through an air gun to react with sulfur powder and generate high-temperature flue gas at a temperature of 1150℃. A blower creates negative pressure, putting the bag filter, dust settling chamber, electromagnetic induction rotary kiln, and internally heated rotary kiln into a negative pressure state. The high-temperature flue gas enters the electromagnetic induction rotary kiln to dry and preheat α-type spodumene, and finally enters the dust settling chamber from the kiln tail. At this point, the flue gas temperature is 320℃.

[0059] (5) The flue gas from the tail of the electromagnetic induction rotary kiln enters the dust settling chamber to settle some of the dust, and then enters the bag filter to further remove the entrained dust in the flue gas. The dust in the dust settling chamber is returned to the rotary kiln for roasting, while the dust from the bag filter enters the sulfuric acid roasting lithium extraction system. The SO2 flue gas after dust collection is transported to the acid production system to produce sulfuric acid, which is used in the sulfuric acid roasting lithium extraction process. Excess sulfuric acid can be sold externally.

[0060] Example 5

[0061] This embodiment provides a method for spodumene transformation roasting using the system described in Embodiment 1, such as... Figure 1 As shown, the specific steps include the following:

[0062] (1) Start the electromagnetic induction rotary kiln to make the kiln body rotate. At the same time, the electromagnetic induction heating controller starts to control the electromagnetic induction coil to quickly heat the stainless steel electromagnetic induction rotary kiln body, specifically 904L stainless steel. α-type spodumene is fed into the electromagnetic induction rotary kiln body from the raw material silo through a feeder. Through the rotation of the electromagnetic induction rotary kiln body and the action of the dust-raising plates inside the kiln, the α-type spodumene is continuously tumbled and mixed. At the same time, the high-temperature stainless steel electromagnetic induction rotary kiln body rapidly dries and preheats the α-type spodumene to 950℃.

[0063] (2) The preheated α-type spodumene is moved to the internally heated rotary kiln by a spiral motion. The internally heated rotary kiln injects 5% sulfur powder by weight of α-type spodumene through a sulfur powder spray gun, and at the same time, a compressed air spray gun is turned on to blow compressed oxygen-rich air, so that the sulfur reacts with oxygen to release a large amount of heat, heating the temperature inside the rotary kiln to 970°C for spodumene transformation roasting.

[0064] (3) After the transformation, the high-temperature β-type spodumene enters heat exchanger one and heat exchanger two in sequence to exchange heat with compressed oxygen-enriched air, so that the temperature of the β-type spodumene decreases from 960℃ to 120℃, while the temperature of the oxygen-enriched air increases from 30℃ to 280℃. The cooled β-type spodumene enters the sulfuric acid roasting and lithium extraction process, while the preheated oxygen-enriched air enters the internally heated rotary kiln.

[0065] (4) Preheated compressed oxygen-enriched air is injected into the internally heated rotary kiln through an air gun to react with sulfur powder and generate high-temperature flue gas at a temperature of 965℃. A blower creates negative pressure, putting the bag filter, dust settling chamber, electromagnetic induction rotary kiln, and internally heated rotary kiln into a negative pressure state. The high-temperature flue gas enters the electromagnetic induction rotary kiln to dry and preheat α-type spodumene, and finally enters the dust settling chamber from the kiln tail. At this point, the flue gas temperature is 290℃.

[0066] (5) The flue gas from the tail of the electromagnetic induction rotary kiln enters the dust settling chamber to settle some of the dust, and then enters the bag filter to further remove the entrained dust in the flue gas. The dust in the dust settling chamber is returned to the rotary kiln for roasting, while the dust from the bag filter enters the sulfuric acid roasting lithium extraction system. The SO2 flue gas after dust collection is transported to the sulfuric acid production system to produce sulfuric acid, which is used in the sulfuric acid roasting lithium extraction process.

[0067] For those skilled in the art, various corresponding changes and modifications can be made based on the above technical solutions and concepts, and all such changes and modifications should be included within the protection scope of the claims of this invention.

Claims

1. A two-stage spodumene conversion roasting system, characterized in that, This includes electromagnetic induction rotary kilns and internally heated rotary kilns; The electromagnetic induction rotary kiln includes an electromagnetic induction rotary kiln body, an electromagnetic induction coil, and an electromagnetic heating controller; the electromagnetic induction coil is wound around the outside of the electromagnetic induction rotary kiln body and electrically connected to the electromagnetic heating controller, and the electromagnetic induction coil is controlled to generate heat by the electromagnetic heating controller. The internally heated rotary kiln includes an internally heated rotary kiln body, a sulfur powder spray gun, and a compressed air spray gun; the sulfur powder spray gun and the compressed air spray gun are respectively connected to the interior of the internally heated rotary kiln body; the sulfur powder silo is connected to the sulfur powder spray gun; the sulfur powder spray gun is used to spray sulfur powder, and the compressed air spray gun is used to spray compressed air, compressed oxygen-enriched air, or compressed pure oxygen; the kiln tail of the electromagnetic induction rotary kiln body and the kiln head of the internally heated rotary kiln body are connected.

2. The system according to claim 1, characterized in that, It also includes a raw material silo and a feeder, wherein the raw material silo is connected to the kiln head of the electromagnetic induction rotary kiln body via the feeder.

3. The system according to claim 1, characterized in that, It also includes heat exchanger one, heat exchanger two, and a compressed air fan. The kiln tail of the internally heated rotary kiln body is connected to the feed inlet of heat exchanger one, and the discharge outlet of heat exchanger one is connected to the feed inlet of heat exchanger two. The heat exchange air inlet of heat exchanger two is connected to the compressed air fan, the heat exchange air outlet of heat exchanger two is connected to the heat exchange air inlet of heat exchanger one, and the heat exchange air outlet of heat exchanger one is connected to the compressed air spray gun.

4. The system according to claim 1, characterized in that, It also includes a dust settling chamber, a bag filter, and an exhaust fan; the flue gas outlet of the electromagnetic induction rotary kiln is connected to the air inlet of the dust settling chamber, the air outlet of the dust settling chamber is connected to the air inlet of the bag filter, and the air outlet of the bag filter is connected to the exhaust fan.

5. The system according to claim 4, characterized in that, The dust collection chamber and the dust outlet of the bag filter are respectively connected to the dust hopper of the dust collection chamber and the dust hopper of the bag filter.

6. The system according to claim 1, characterized in that, The electromagnetic induction rotary kiln body is made of stainless steel; the electromagnetic induction heating controller has a power of 100-2000kw per unit, and each electromagnetic induction heating controller controls an electromagnetic induction coil with a kiln length of 1-3 meters; the internally heated rotary kiln cylinder is made of carbon steel lined with refractory material.

7. The system according to claim 1, characterized in that, The connection between the kiln tail of the electromagnetic induction rotary kiln body and the kiln head of the internally heated rotary kiln body is sealed with a sealing ring.

8. A method for spodumene transformation roasting using the system described in any one of claims 1-7, characterized in that, The specific process is as follows: The electromagnetic induction rotary kiln is turned on, and the kiln body begins to rotate. The electromagnetic heating controller then controls the electromagnetic induction coil to heat the kiln body. Alpha-type spodumene is fed into the kiln body. Through the rotation of the kiln body and the action of the dust-raising plates inside the kiln, the alpha-type spodumene is continuously tumbled and mixed. At the same time, the heated kiln body rapidly dries and preheats the alpha-type spodumene to 500-950℃. Alpha-type spodumene moves into the internally heated rotary kiln via a spiral motion. Sulfur powder is injected into the kiln head through a sulfur powder spray gun, while compressed air, compressed oxygen-enriched air, or compressed oxygen is simultaneously sprayed through a compressed air spray gun. This causes the sulfur to react with the oxygen, releasing a large amount of heat and heating the temperature inside the internally heated rotary kiln to 950-1200℃. The amount of sulfur powder sprayed is 5-50% of the mass of the alpha-type spodumene. After being roasted in the internally heated rotary kiln, the alpha-type spodumene can be transformed into β-type spodumene.

9. The method according to claim 8, characterized in that, The high-temperature β-type spodumene obtained from the transformation enters heat exchanger one and heat exchanger two in sequence to exchange heat with compressed air, compressed oxygen-enriched air or compressed oxygen. The cooled β-type spodumene enters the sulfuric acid roasting process for lithium extraction, while the compressed air, compressed oxygen-enriched air or compressed oxygen that has been heated by the heat exchange enters the internally heated rotary kiln.

10. The method according to claim 8, characterized in that, The flue gas generated during roasting inside the internally heated rotary kiln is first passed through the electromagnetic induction rotary kiln body by the exhaust fan to dry and preheat the α-type spodumene inside the electromagnetic induction rotary kiln body. Then, it enters the dust settling chamber from the kiln tail of the electromagnetic induction rotary kiln body to settle some of the flue gas dust. After passing through the bag dust collector, the SO2 flue gas is transported to the acid production system to produce sulfuric acid. The sulfuric acid produced is used in the sulfuric acid roasting lithium extraction process and / or sold externally.

Images