An electric, gas, and suspension triple-composite lithium ore roasting kiln system and process

Abstract

The present invention discloses an electric, gas, and suspension three-composite lithium ore roasting kiln system and process. The conversion of spodumene from the α form to the β form is achieved through the uniform drying and preheating by a suspension preheating device, the primary roasting in an electric heating kiln, and the secondary roasting in a gas kiln. Compared with the traditional rotary kiln using natural gas as fuel for the conversion roasting of spodumene, in the present invention, the temperature of spodumene has been raised to 600-800 °C through the preheating by the suspension preheating device and the primary roasting in the electric heating kiln. Only the subsequent temperature-raising work needs to be completed in the gas kiln, which can save a large amount of natural gas resources and reduce the emission of carbon dioxide, meeting the national "carbon neutrality" policy. It is very suitable for use in areas lacking natural gas but with rich electricity reserves or cheap electricity prices and high environmental protection requirements.

Description

Technical Field

[0001] The present invention relates to the field of lithium ore roasting kilns, and specifically to an electric, gas, and suspension triple composite lithium ore roasting kiln system and process. Background Art

[0002] In industrial production, spodumene is mainly used as the raw material for lithium extraction by the sulfuric acid method. Before acidification roasting, spodumene needs to be transformed by a roasting kiln. The dense and chemically stable α-type spodumene is transformed into the β-type spodumene with low density and loose structure, which can react with acids and bases. The quality of the transformation roasting directly affects the lithium extraction rate.

[0003] Currently, natural gas or pulverized coal is mostly used as fuel for the transformation roasting of spodumene. The rotary kiln is heated by fuel combustion to raise the temperature of the air in the kiln to above 1100°C for roasting spodumene, realizing the transformation of spodumene from the α-crystalline form to the β-crystalline form. However, there are also many problems with the above production methods. First, the distribution of natural gas resources is uneven. For regions lacking natural gas but with sufficient power supply, if a rotary kiln using natural gas as fuel (hereinafter referred to as a "gas kiln") is used to roast spodumene, it will generate high procurement, transportation, and storage costs for natural gas. In addition, the gas kilns used for roasting spodumene often need to be dozens of meters long. The combustion of the burner at the kiln head cannot ensure uniform heat transfer throughout the kiln, resulting in unstable temperature in the firing zone and affecting the transformation effect of spodumene. Moreover, the overly long cylinder will also cause unnecessary heat loss during the process of recovering waste heat through the internal circulation system, thereby increasing the overall energy consumption of the system.

[0004] Existing electric heating rotary kilns mainly use the principle of current thermal effect or electromagnetic induction to heat the spodumene material in the kiln. Although it reduces carbon emissions to a certain extent and the temperature field in the kiln is relatively stable, whether it is through the current thermal effect or electromagnetic heating, the rotary kiln cylinder itself will be heated. During the transformation roasting process of spodumene, the rotating cylinder is continuously heated at a high temperature above 1100°C, and existing conventional cylinder materials cannot ensure the strength of the cylinder during industrial continuous production. Currently, in the spodumene pyrometallurgical process, electric heating kilns are only used in the acidification roasting stage with a temperature requirement of 250 - 280°C and cannot be used as transformation roasting kilns. Summary of the Invention

[0005] In order to overcome the above deficiencies in the prior art, the present invention provides an electric, gas, and suspension triple composite lithium ore roasting kiln system and process. The drying of the ore is carried out in the suspension preheating section, the electric heating kiln completes the heating process of the ore, and the high-temperature roasting is achieved through the gas kiln. The above process flow provides an efficient and stable temperature field for lithium ore roasting while ensuring as little use of natural gas as possible, and improves the roasting efficiency of lithium ore.

[0006] The specific technical solutions are as follows:

[0007] An electric, gas, and suspension three-composite lithium ore roasting kiln system, comprising a silo, a metering device, a suspension preheating device, a lithium ore conveyor, an electric heating kiln, a scraper conveyor, a lock valve, a gas kiln, a combustion device, a grate cooler, and a roasted material conveying device connected in sequence.

[0008] The suspension preheating device includes a primary cyclone preheater and a secondary cyclone preheater; the primary cyclone preheater includes a primary cyclone, a drying pipe, and a primary discharge pipe, and the secondary cyclone preheater includes a secondary cyclone, a heat exchange pipe, and a secondary discharge pipe; wherein a primary cyclone flue gas outlet is provided at the top of the primary cyclone, a primary cyclone flue gas inlet is provided on the side wall of the primary cyclone, and a primary discharge pipe is provided at the bottom of the primary cyclone. A secondary cyclone flue gas outlet is provided at the top of the secondary cyclone, a secondary cyclone flue gas inlet is provided on the side wall of the secondary cyclone, and a secondary discharge pipe is provided at the bottom of the secondary cyclone.

[0009] A drying pipe is provided between the primary cyclone flue gas inlet and the secondary cyclone flue gas outlet, one end of the drying pipe is communicated with the primary cyclone flue gas inlet, and the other end is communicated with the secondary cyclone flue gas outlet. A heat exchange pipe is provided between the secondary cyclone flue gas inlet and the tail of the gas kiln, one end of the heat exchange pipe is communicated with the secondary cyclone flue gas inlet, and the other end is communicated with the tail of the gas kiln; the discharge port of the primary discharge pipe is arranged above the lithium ore conveyor, and the discharge port of the secondary discharge pipe is connected to the tail of the gas kiln.

[0010] A silo discharger is provided at the bottom of the silo to ensure uniform feeding of sticky and wet lithium ore. The metering device is arranged below the silo discharger, and the feeding position of the metering device is arranged above the feeding port of the drying pipe. When the system works, the lithium ore is discharged from the silo discharger at the bottom of the silo, weighed and transported by the metering device, and enters the primary cyclone preheater through the drying pipe; the lithium ore is blown and suspended in the gas under the action of the hot flue gas from the secondary cyclone preheater in the drying pipe, and is dried and preheated, and is carried into the primary cyclone for gas-solid separation; the gas in the flue gas is discharged along the primary cyclone flue gas outlet, and the lithium ore enters the lithium ore conveyor through the primary discharge pipe; the temperature of the dried and preheated lithium ore is about 200°C, and the water content is not more than 1%.

[0011] Further, the metering device of this roasting kiln system is preferably a belt scale.

[0012] The discharging end of the lithium ore conveyor is connected to the kiln tail of the electric heating kiln through a pipeline; the heating temperature range of the electric heating kiln is controlled at 700 - 800 °C; the lithium ore between the electric heating kiln and the gas kiln is transported by a scraper conveyor; a lock air valve is arranged at the discharging opening of the scraper conveyor, and the gases in the electric heating kiln and the gas kiln are isolated from each other. The lithium ore that has completed drying and preheating is transported by the lithium ore conveyor to the electric heating kiln, heated to 650 - 750 °C in the electric heating kiln, and then transported to the gas kiln through the scraper conveyor. The setting of the lock air valve not only ensures that the material can be transported from the electric heating kiln to the gas kiln, but also effectively isolates the hot flue gas in the electric heating kiln and the gas kiln, preventing the high-temperature flue gas in the gas kiln from entering the electric heating kiln and affecting the stable temperature field of the electric heating kiln. The stable temperature field is helpful for the temperature control of the electric heating kiln.

[0013] The combustion device includes a burner and an external blower, and the burner is inserted from the kiln head end of the gas kiln; the gas kiln includes a feeding section, a firing section, and a cooling section arranged in sequence, and the temperature of the firing section is controlled at 1100 - 1200 °C. The combustion device continuously supplies heat to the gas kiln. The lithium ore enters the gas kiln, is pushed from the feeding section to the firing section, and generates calcined material at a heating temperature of 1100 - 1200 °C. The temperature of the calcined material leaving the kiln is controlled at about 1000 °C. The hot flue gas generated by the gas kiln then enters the suspension preheating device along the heat exchange pipes to carry out drying and preheating on the subsequent lithium ore.

[0014] The feeding opening of the grate cooler is arranged below the discharging opening at the kiln head of the gas kiln, and the calcined material conveying device is arranged below the discharging opening of the grate cooler. The high-temperature calcined material enters the grate cooler and is cooled to 100 °C, and then is sent to the next process through the calcined material conveying device.

[0015] Further, the roasting kiln system of the present invention further includes a tail gas treatment device, and the tail gas treatment device includes a high-temperature bag filter, an exhaust blower, and a chimney connected in sequence; the air inlet of the high-temperature bag filter is connected to the flue gas outlet of the primary cyclone through a pipeline, the air outlet is connected to the exhaust blower, and the ash discharging port is communicated with the feeding port of the lithium ore conveyor. The flue gas discharged from the flue gas outlet of the primary cyclone enters the high-temperature bag filter for dust removal treatment. The dust is discharged into the lithium ore conveyor from the ash discharging port, and the flue gas after dust removal is blown into the chimney by the exhaust blower and discharged to the outside of the system.

[0016] The surplus air of the traditional grate cooler is directly discharged into the dust collector, and the heat of the surplus air is not effectively utilized. Therefore, the grate cooler of the roasting kiln system of the present invention further includes a waste heat recovery device. A waste heat air pipe is arranged at the tail of the grate cooler. One end of the waste heat recovery device is connected to the waste heat air pipe, and the other end is connected to the secondary cyclone preheater. The high-temperature surplus air generated by the grate cooler enters the heat exchange pipes along the waste heat recovery device from the waste heat air pipe, providing heat source for the suspension preheating device, and realizing the recovery and utilization of the heat of the high-temperature surplus air generated by the grate cooler for cooling the high-temperature calcined material.

[0017] Furthermore, the waste heat recovery device is a cyclone dust collector; the cyclone dust collector is provided with a hot gas outlet, a hot gas inlet, and a dust outlet; the hot gas inlet is connected to the waste heat air duct, the hot gas outlet is connected to the heat exchange tube, and the dust outlet is arranged above the calcined material conveying device; a waste heat fan is also arranged between the cyclone dust collector and the heat exchange tube, and the waste heat fan can provide power for the waste air of the grate cooler. The high-temperature waste air generated by the grate cooler for cooling the high-temperature calcined material enters the cyclone dust collector through the waste heat air duct for dust removal treatment. After the dust is discharged, it is transported to the next process through the calcined material conveying device; the high-temperature waste air after dust removal is blown into the secondary cyclone preheater by the waste heat fan and mixed with the high-temperature flue gas generated by the gas kiln to provide heat source for the suspension preheating device.

[0018] Furthermore, an exhaust valve is arranged at the kiln head position of the electric heating kiln, and the exhaust valve is communicated with the air inlet of the high-temperature bag type dust collector through a pipeline. The heating of spodumene in the electric heating kiln itself does not generate a large amount of flue gas. The gas generated in the electric heating kiln is mainly a small amount of water vapor, so it will not cause a strong change in the air pressure of the electric heating kiln. The exhaust valve is regularly opened or closed according to the air pressure in the electric heating kiln to keep the air pressure in the kiln stable, thus ensuring the stable operation of the electric heating kiln.

[0019] Furthermore, the drying tube of the present invention adopts a "vertical tube + inverted U-shaped tube" structure. When the height of the flue gas inlet of the cyclone is the same, compared with the traditional "vertical tube + horizontal short tube" structure, adopting the "vertical tube + inverted U-shaped tube" structure, the residence time of the material is longer, and thus the preheating and drying effect of the material can be improved.

[0020] Furthermore, after the hot flue gas generated from the gas kiln enters the suspension preheating device along the heat exchange tube, the secondary cyclone separates the gas from the solid. The solid in the flue gas will enter the gas kiln again along the secondary discharge pipe after gas-solid separation. Since the solid is already the calcined lithium ore, the above operation avoids its re-circulation and energy consumption in the suspension preheating device and the electric heating kiln, reducing the heat loss in the system.

[0021] Furthermore, the heating component of the electric heating kiln includes an electromagnetic coil, a power supply, and a control system. The electromagnetic coil is spirally wound outside the kiln body, and both ends form a closed loop with the power supply. The current size is controlled through the control system, and then the heating temperature change of the electric heating kiln is controlled.

[0022] Further, the drying tube of the system can be replaced by a flash dryer. The flue gas outlet of the flash dryer is connected to the flue gas inlet of the first-stage cyclone, and the flue gas inlet of the flash dryer is connected to the flue gas outlet of the second-stage cyclone; the feeding position of the metering device is set above the feed inlet of the flash dryer. When the system works, lithium ore is discharged from the silo discharger at the bottom of the silo, weighed and transported by the metering device, and enters the first-stage cyclone preheater through the flash dryer; the lithium ore is dried under the action of the hot flue gas from the second-stage cyclone preheater in the flash dryer and is carried into the first-stage cyclone for gas-solid separation; the gas in the flue gas is discharged along the flue gas outlet of the first-stage cyclone, and the lithium ore enters the lithium ore conveyor through the first-stage downcomer; the temperature of the lithium ore after drying and preheating is about 200°C, and the water content is not more than 1%.

[0023] An electro-thermal-suspension triple composite lithium ore roasting process includes the following steps:

[0024] Step S1. Uniform drying and preheating by the suspension preheating device:

[0025] Lithium ore is put into the suspension preheating device from the silo, and is dried and preheated by the hot flue gas from the gas kiln and the grate cooler in the suspension preheating device, so that the temperature of spodumene is raised to 200°C, and the water content is not more than 1%; this section of the process is mainly carried out in the inverted U-shaped pipe part of the drying tube. The operation of the lithium ore and the hot flue gas is relatively stable in flow velocity compared with the vertical pipe and the horizontal straight pipe, forming uniform drying and preheating.

[0026] Step S2. Primary roasting in the electric heating kiln:

[0027] The spodumene after drying and preheating is sent to the electric heating kiln for roasting through the lithium ore conveyor, and the heating temperature is controlled at 700-800°C, so that the temperature of the spodumene out of the kiln reaches 650-750°C.

[0028] Step S3. Secondary roasting in the gas kiln:

[0029] The spodumene heated by the electric heating kiln is sent to the gas kiln through the scraper conveyor for further transformation roasting. The heating temperature is controlled at 1100-1200°C, and the spodumene is transformed from α-type to β-type to generate roasted material. The temperature of the roasted material out of the kiln is 1000°C; the hot flue gas generated by the gas kiln enters the suspension preheating device along the heat exchange pipe to dry and preheat the subsequent lithium ore.

[0030] Step S4. Cooling of the roasted material:

[0031] After the high-temperature roasted material leaves the kiln, it enters the grate cooler for cooling treatment. The temperature of the roasted material is reduced to 100°C and is sent to the next process through the roasted material conveying device.

[0032] Further, the specific preheating process of the suspension preheating device in step S1 is as follows:

[0033] The lithium ore is discharged from the silo discharger at the bottom of the bin, weighed and transported via the metering device, and enters the primary cyclone preheater through the drying pipe; the lithium ore is dispersed by the hot flue gas from the secondary cyclone preheater in the drying pipe, suspended in the gas, dried and preheated, and then carried into the primary cyclone barrel for gas-solid separation; the gas in the flue gas is discharged along the flue gas outlet of the primary cyclone barrel, and the lithium ore enters the lithium ore conveyor through the primary discharge pipe; the temperature of the dried and preheated lithium ore is about 200°C, and the water content is not more than 1%.

[0034] Further, the roasting process of the present invention further includes: Step S5. Tail gas treatment:

[0035] The flue gas discharged from the flue gas outlet of the primary cyclone barrel in Step S1 enters the high-temperature bag filter for dust removal treatment. The dust is discharged into the lithium ore conveyor through the ash discharge port, and the flue gas after dust removal is blown into the chimney by the external exhaust fan and discharged out of the system.

[0036] Further, the roasting process of the present invention further includes: Step S6. Waste heat recovery:

[0037] The high-temperature residual air generated by the grate cooler cooling the high-temperature roasted material enters the cyclone dust collector through the waste heat air pipe for dust removal treatment. After the dust and solid are discharged, they are sent to the next process via the roasted material conveying device; the high-temperature residual air after dust removal is blown into the secondary

[0038] cyclone preheater by the waste heat fan, mixed with the high-temperature flue gas generated by the gas kiln, and provides heat source for the suspension preheating device, and the waste heat generated by the grate cooler is effectively utilized.

[0039] The waste heat is effectively utilized.

[0040] Further, the primary roasting in Step S2 of the electric heating kiln further includes the following operations:

[0041] The exhaust valve at the kiln head position of the electric heating kiln is regularly opened or closed according to the air pressure in the electric heating kiln to keep the air pressure in the kiln stable; the discharged flue gas is subjected to dust removal treatment through the tail gas treatment device.

[0042] The discharged flue gas is subjected to dust removal treatment through the tail gas treatment device.

[0043] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0044] (1) The roasting kiln system and process disclosed in the present invention realize the transformation of spodumene from the α-type to the β-type through the uniform drying and preheating of the suspension preheating device, the primary roasting in the electric heating kiln, and the secondary roasting in the gas kiln. Compared with the traditional rotary kiln for transformation roasting of spodumene using natural gas as fuel, the present invention has already increased the temperature of spodumene to 650 - 750 °C through the preheating of the suspension preheating device and the primary roasting in the electric heating kiln. In the gas kiln, only the subsequent temperature increase work needs to be completed, which can save a large amount of natural gas resources and reduce carbon dioxide emissions, meeting the national "carbon neutrality" policy. It is very suitable for use in areas lacking natural gas but with rich power reserves, cheap electricity prices, and high environmental protection requirements. Moreover, the electric heating kiln can use green electricity generated from solar energy and wind power, further reducing carbon emissions during the power generation process.

[0045] (2) Compared with the prior art where the electric heating kiln can only be applied in the acid roasting stage of the spodumene pyrometallurgical process, the present invention innovatively uses the electric heating kiln as an intermediate heating process in the transformation roasting process, indirectly solving the problem that the existing electric heating kiln cylinder material cannot continuously withstand high-temperature roasting at 1100 °C, and making full use of the advantages of the electric heating kiln such as uniform heat transfer, stable temperature field, and easy temperature control, improving the working efficiency of the system.

[0046] (3) The conventional single rotary kiln scheme requires a longer kiln body. If the waste heat generated by the grate cooler is to be transferred to the preheating device, it needs to pass through the lengths of the grate cooler and the rotary kiln, resulting in a large amount of heat loss. Generally, an external boiler is used to recover the waste heat, but this method is not conducive to the internal circulation of the system heat. The present invention uses a combined kiln scheme of "electric heating kiln + gas kiln", effectively reducing the length of a single kiln body. Since the gas kiln is shorter, the hot gas generated at the tail of the grate cooler passes through a shorter distance through the grate cooler and the gas kiln, resulting in less heat loss. Therefore, the present invention connects the waste heat air duct of the grate cooler to the preheating device, enabling the heat to fully circulate inside the system and improving the system thermal efficiency.

[0047] (4) The present invention is provided with a air lock valve between the electric heating kiln and the gas kiln, so that the flue gas generated in the gas kiln cannot enter the electric heating kiln. The gas in the electric heating kiln and the gas in the gas kiln are isolated from each other, and the heating of the lithium ore in the electric heating kiln itself does not generate a large amount of flowing flue gas. A relatively uniform heating is formed in the electric heating kiln, ensuring the stability of the temperature field in the electric heating kiln and facilitating the control of the temperature inside the kiln.

[0048] (5) The suspension preheating device of the present invention is provided with a secondary cyclone. When the hot flue gas generated from the gas kiln and the high-temperature residual air from the grate cooler enter the suspension preheating device along the heat exchange tubes, the secondary cyclone performs gas-solid separation on the mixed flue gas. The solids in the flue gas will enter the gas kiln again along the secondary discharge pipe after gas-solid separation. Since the solids are already spodumene that has undergone transformation roasting, the above operation avoids the consumption of energy due to its recycling in the preheating device and the electric heating kiln, reducing the heat loss in the system.

[0049] (6) The drying pipe of the present invention adopts a "vertical pipe + inverted U-shaped pipe" structure. Under the condition that the flue gas inlet height of the cyclone is the same, compared with the traditional "vertical pipe + horizontal short pipe" structure, the drying pipe structure of the present invention has a longer residence time of the material and a more stable flue gas flow rate, thereby improving the preheating and drying effect of the material. Brief Description of the Drawings

[0050] Figure 1 is a schematic structural diagram of the roasting kiln system of the present invention;

[0051] Figure 2 is a schematic structural diagram of the suspension preheating device of the present invention;

[0052] Figure 3 is a schematic structural diagram of the gas kiln of the present invention;

[0053] Figure 4 is a comparison diagram of the drying pipe structure of the present invention and the conventional structure;

[0054] Figure 5 is a flow diagram of the high-temperature flue gas generated by the gas kiln.

[0055] Among them: 1. Silo; 1-1. Silo discharger; 2. Metering device; 3. Suspension preheating device; 31-1. Primary cyclone; 31-11. Primary cyclone flue gas outlet; 31-12. Primary cyclone flue gas inlet; 31-13. Primary discharge pipe; 31-2. Drying pipe; 32-1. Secondary cyclone; 32-11. Secondary cyclone flue gas outlet; 32-12. Secondary cyclone flue gas inlet; 32-13. Secondary discharge pipe; 32-2. Heat exchange tube; 4-1. Waste heat fan; 4-2. Cyclone dust collector; 4-21. Hot gas outlet; 4-22. Hot gas inlet; 4-23. Dust outlet; 5. Combustion device; 6. Grate cooler; 6-1. Waste heat air duct; 7. Roasted material conveying device; 8. Gas kiln; 8-1. Feeding section; 8-2. Firing section; 8-3. Cooling section; 91. Air lock valve; 10. Electric heating kiln; 10-1. Exhaust valve; 11. Lithium ore conveyor; 12-1. High-temperature bag filter; 12-11. Air inlet; 12-12. Air outlet; 12-13. Ash discharge port; 12-2. Exhaust fan; 12-3. Chimney. Detailed Embodiments

[0056] To make the objectives, technical solutions and advantages of the present invention clearer, the following will further describe the embodiments of the present invention in conjunction with the accompanying drawings. The following introduces a relatively optimal one among multiple possible embodiments of the present invention, aiming to provide a basic understanding of the present invention, but not aiming to identify the key or decisive elements of the present invention or limit the scope to be protected.

[0057] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0058] The following will further elaborate on the present invention in detail in conjunction with the accompanying drawings and specific embodiments, but the embodiments of the present invention are not limited thereto.

[0059] Embodiment 1:

[0060] Refer to the attached Figure 1-3 , a three-composite lithium ore roasting kiln system of electricity, gas and suspension disclosed in this embodiment includes a silo 1, a metering device 2, a suspension preheating device 3, a lithium ore conveyor 11, an electric heating kiln 10, a scraper conveyor, a lock air valve 91, a gas kiln 8, a combustion device 5, a grate cooler 6, and a roasted material conveying device 7, which are connected in sequence.

[0061] The suspension preheating device 3 includes a primary cyclone preheater and a secondary cyclone preheater. The primary cyclone preheater includes a primary cyclone cylinder 31-1, a drying pipe 31-2, and a primary blanking pipe 31-13. The secondary cyclone preheater includes a secondary cyclone cylinder 32-1, a heat exchange pipe 32-2, and a secondary blanking pipe 32-13. Among them, a primary cyclone cylinder flue gas outlet 31-11 is provided at the top of the primary cyclone cylinder 31-1, a primary cyclone cylinder flue gas inlet 31-12 is provided on the side wall of the primary cyclone cylinder 31-1, and the primary blanking pipe 31-13 is provided at the bottom of the primary cyclone cylinder 31-1. A secondary cyclone cylinder flue gas outlet 32-11 is provided at the top of the secondary cyclone cylinder 32-1, a secondary cyclone cylinder flue gas inlet 32-12 is provided on the side wall of the secondary cyclone cylinder 32-1, and the secondary blanking pipe 32-13 is provided at the bottom of the secondary cyclone cylinder 32-1.

[0062] One end of the drying pipe 31-2 is connected to the flue gas inlet 31-12 of the primary cyclone preheater, and the other end is connected to the flue gas outlet 32-11 of the secondary cyclone preheater. One end of the heat exchange pipe 32-2 is connected to the flue gas inlet 32-12 of the secondary cyclone preheater, and the other end is connected to the tail of the gas kiln 8. The discharge port of the primary blanking pipe 31-13 is arranged above the lithium ore conveyor 11, and the discharge port of the secondary blanking pipe 32-13 is connected to the tail of the gas kiln 8.

[0063] A silo discharger 1-1 is arranged at the bottom of the storage bin 1 to ensure uniform feeding of sticky and wet lithium ore. The metering device 2 is arranged below the silo discharger 1-1, and the feeding position of the metering device 2 is arranged above the feeding port of the drying pipe 31-2. When the system works, spodumene is discharged from the silo discharger 1-1 at the bottom of the storage bin 1, weighed and transported by the metering device 2, and enters the primary cyclone preheater through the drying pipe 31-2. The spodumene is dispersed by the hot flue gas from the secondary cyclone preheater in the drying pipe 31-2, suspended in the gas, dried and preheated, and then carried into the primary cyclone 31-1 for gas-solid separation. The gas in the flue gas is discharged along the flue gas outlet 31-11 of the primary cyclone, and the spodumene enters the lithium ore conveyor 11 through the primary blanking pipe 31-13. The temperature of the dried and preheated spodumene is about 200°C, and the water content is not more than 1%.

[0064] Furthermore, the metering device 2 of the roasting kiln system is preferably an electronic belt scale.

[0065] The discharge end of the lithium ore conveyor 11 is connected to the tail of the electric heating kiln 10 through a pipeline. The heating temperature range of the electric heating kiln 10 is controlled at 700-800°C. The spodumene between the electric heating kiln 10 and the gas kiln 8 is transported by a scraper conveyor. A lock valve 91 is arranged at the blanking port of the scraper conveyor to isolate the gas in the electric heating kiln 10 from the gas in the gas kiln 8. The spodumene that has completed drying and preheating is transported by the lithium ore conveyor 11 to the electric heating kiln 10, heated to 650-750°C in the electric heating kiln 10, and then transported to the gas kiln 8 by the scraper conveyor. The setting of the lock valve 91 not only ensures that the material can be transported from the electric heating kiln 10 to the gas kiln 8, but also effectively isolates the hot flue gas in the electric heating kiln 10 from the gas kiln 8, preventing the high-temperature flue gas in the gas kiln 8 from entering the electric heating kiln 10 and affecting the stable temperature field of the electric heating kiln 10. The stable temperature field helps to control the temperature of the electric heating kiln 10.

[0066] The combustion device 5 includes a burner and an external blower. The burner is inserted into the cylinder body of the gas kiln 8 from the head of the gas kiln. The gas kiln 8 includes a feeding section 8-1, a firing section 8-2, and a cooling section 8-3 arranged in sequence. The temperature of the firing section 8-2 is controlled at 1100 - 1200 °C. The combustion device 5 continuously supplies heat to the gas kiln 8. The spodumene enters the gas kiln 8 and is pushed from the feeding section 8-1 to the firing section 8-2. At a heating temperature of 1100 - 1200 °C, the spodumene is transformed from the α-type to the β-type to form a roasted material. The temperature of the roasted material leaving the kiln is controlled at about 1000 °C. The hot flue gas generated by the gas kiln 8 enters the suspension preheating device 3 along the heat exchange tube 32-2 to preheat the subsequent spodumene by drying.

[0067] The feeding port of the grate cooler 6 is arranged below the discharging port at the head of the gas kiln 8, and the roasted material conveying device 7 is arranged below the discharging port of the grate cooler 6. The high-temperature roasted material enters the grate cooler 6 and is cooled to 100 °C, and is then sent to the next process via the roasted material conveying device 7.

[0068] More specifically, the roasting kiln system of this embodiment further includes a tail gas treatment device. The tail gas treatment device includes a high-temperature bag filter 12-1, an exhaust blower 12-2, and a chimney 12-3 connected in sequence. The air inlet 12-11 of the high-temperature bag filter 12-1 is connected to the flue gas outlet 31-11 of the primary cyclone by a pipeline. The air outlet 12-12 is connected to the exhaust blower 12-2, and the ash discharge port 12-13 is communicated with the feeding port of the lithium ore conveyor 11. The flue gas discharged from the flue gas outlet 31-11 of the primary cyclone enters the high-temperature bag filter 12-1 for dust removal treatment. The dust is discharged into the lithium ore conveyor 11 from the ash discharge port 12-13. The flue gas after dust removal is blown into the chimney 12-3 by the exhaust blower 12-2 and discharged to the outside of the system.

[0069] The surplus air of the traditional grate cooler is directly discharged into the dust collector, and the heat of the surplus air is not effectively utilized. Therefore, the grate cooler 6 of the roasting kiln system of this embodiment further includes a waste heat recovery device. A waste heat air pipe 6-1 is arranged at the tail of the grate cooler 6. One end of the waste heat recovery device is connected to the waste heat air pipe 6-1, and the other end is connected to the secondary cyclone preheater. The high-temperature surplus air generated by the grate cooler 6 enters the heat exchange tube 32-2 along the waste heat recovery device from the waste heat air pipe 6-1, providing a heat source for the suspension preheating device 3, and realizing the recovery and utilization of the heat of the high-temperature surplus air generated by the grate cooler 6 for cooling the high-temperature roasted material.

[0070] More specifically, the waste heat recovery device is a cyclone dust collector 4-2; the cyclone dust collector 4-2 is provided with a hot gas outlet 4-21, a hot gas inlet 4-22 and a dust outlet 4-23; the hot gas inlet 4-22 is connected to the waste heat air duct 6-1, the hot gas outlet 4-21 is connected to the heat exchange tube 32-2, and the dust outlet 4-23 is arranged above the burden conveying device 7; a waste heat fan 4-1 is also arranged between the cyclone dust collector 4-2 and the heat exchange tube 32-2, and the waste heat fan 4-1 can provide power for the surplus air of the grate cooler 6. The high-temperature surplus air generated by the grate cooler 6 when cooling the high-temperature burden enters the cyclone dust collector 4-2 from the waste heat air duct 6-1 for dust removal treatment. After the dust is discharged, it reaches the next process through the burden conveying device 7; the high-temperature surplus air after dust removal is blown into the secondary cyclone preheater by the waste heat fan 4-1 and mixed with the high-temperature flue gas generated by the gas kiln 8 to provide heat source for the suspension preheating device 3.

[0071] More specifically, an exhaust valve 10-1 is arranged at the kiln head position of the electric heating kiln 10, and the exhaust valve 10-1 is communicated with the air inlet 12-11 of the high-temperature bag type dust collector 12-1 through a pipeline. The heating of spodumene in the electric heating kiln 10 itself does not generate a large amount of flue gas. The gas generated is mainly a very small amount of water vapor. Therefore, the air pressure in the electric heating kiln 10 will not change strongly. The exhaust valve 10-1 is regularly opened or closed according to the air pressure in the electric heating kiln 10 to keep the air pressure in the kiln stable, so as to ensure the stable operation of the electric heating kiln 10.

[0072] More specifically, refer to the attached Figure 5 In this embodiment, the drying tube 31-2 adopts a "vertical tube + inverted U-shaped tube" structure. When the heights of the flue gas inlets of the cyclones are the same, compared with the traditional "vertical tube + horizontal short tube" structure, adopting the "vertical tube + inverted U-shaped tube" structure, the residence time of the material is longer, and thus the preheating and drying effect of the material can be improved.

[0073] More specifically, for the hot flue gas generated by the gas kiln 8, after entering the suspension preheating device 3 along the heat exchange tube 32-2, the secondary cyclone 32-1 performs gas-solid separation on the flue gas. The solid in the flue gas will enter the gas kiln 8 again along the secondary blanking pipe 32-13 after gas-solid separation. Since the solid is already spodumene that has undergone transformation roasting, the above operation avoids its re-circulation and energy consumption in the suspension preheating device 3 and the electric heating kiln 10, reducing the heat loss in the system.

[0074] More specifically, the electric heating kiln 10 includes an electromagnetic coil, a power supply and a control system. The electromagnetic coil is spirally wound outside the kiln body, and both ends form a closed loop with the power supply. The magnitude of the current is controlled through the control system, and thus the change of the heating temperature of the electric heating kiln is controlled.

[0075] More specifically, the drying pipe 31-2 in this embodiment can be replaced by a flash dryer. The flue gas outlet of the flash dryer is connected to the flue gas inlet 31-12 of the first-stage cyclone, and the flue gas inlet of the flash dryer is connected to the flue gas outlet 32-11 of the second-stage cyclone; the feeding position of the metering device 2 is set above the feed inlet of the flash dryer. When the system operates, spodumene is discharged from the discharging barrel feeder 1-1 at the bottom of the silo 1, weighed and transported by the metering device 2, and enters the first-stage cyclone preheater through the flash dryer; the spodumene is dried under the action of the hot flue gas from the second-stage cyclone preheater in the flash dryer and is carried into the first-stage cyclone 31-1 for gas-solid separation; the gas in the flue gas is discharged along the flue gas outlet 31-11 of the first-stage cyclone, and the spodumene enters the lithium ore conveyor 11 through the first-stage feeding pipe 31-13; the temperature of the lithium ore after drying and preheating is about 200°C, and the water content is not more than 1%.

[0076] Embodiment 2:

[0077] This embodiment provides an electric, gas, and suspension three-composite lithium ore roasting process. Refer to the appendix Figure 4 , including the following steps:

[0078] Step S1. Uniform drying and preheating by the suspension preheating device:

[0079] Spodumene is fed from the silo into the suspension preheating device 3 and is preheated and dried by the hot flue gas from the gas kiln 8 and the grate cooler 6 in the suspension preheating device 3, so that the temperature of the spodumene is preheated to 200°C and the water content is not more than 1%; this section of the process is mainly carried out in the inverted U-shaped pipe part of the drying pipe 31-2. The flow of the spodumene and the hot flue gas is relatively stable compared to the vertical pipe and the short horizontal pipe.

[0080] Step S2. Primary roasting in the electric heating kiln:

[0081] The spodumene after drying and preheating is sent to the electric heating kiln 10 for roasting through the lithium ore conveyor 11, and the heating temperature is controlled at 700-800°C, so that the temperature of the spodumene out of the kiln is 650-750°C;

[0082] Step S3. Secondary roasting in the gas kiln

[0083] The spodumene heated by the electric heating kiln 10 is transported to the gas kiln 8 through the scraper conveyor 11 for further transformation roasting. The heating temperature is controlled at 1100-1200°C, and the spodumene is transformed from the α-type to the β-type to generate the roasted material. The temperature of the roasted material out of the kiln is 1000°C; the hot flue gas generated by the gas kiln 8 enters the suspension preheating device 3 along the heat exchange pipe 32-2 to preheat and dry the subsequent spodumene;

[0084] Step S4. Cooling of the roasted material:

[0085] After the high-temperature calcined material leaves the kiln, it enters the grate cooler 6 for cooling treatment. The calcined material is cooled to 100°C and sent to the next process through the calcined material conveying device 7.

[0086] More specifically, the specific process of preheating the suspension preheating device in step S1 is as follows:

[0087] The spodumene is discharged from the bottom silo discharger 1-1 of the silo 1 of the bin, weighed and transported via the metering device 2, and enters the primary cyclone preheater through the drying pipe 31-2; the spodumene is dispersed under the action of the hot flue gas from the secondary cyclone preheater in the drying pipe 31-2, suspended in the gas, preheated by drying, and carried into the primary cyclone cylinder 31-1 for gas-solid separation; the gas in the flue gas is discharged along the flue gas outlet 31-11 of the primary cyclone cylinder, and the spodumene enters the spodumene ore conveyor 11 through the primary discharge pipe 31-13; the temperature of the spodumene ore after preheating by drying is about 200°C, and the water content is not more than 1%.

[0088] More specifically, the roasting process of this embodiment further includes: step S5. Tail gas treatment:

[0089] The flue gas discharged from the flue gas outlet 31-11 of the primary cyclone cylinder in step S1 enters the high-temperature bag filter 12-1 for dust removal treatment. The dust is discharged into the spodumene ore conveyor 11 through the ash discharge port 12-13, and the flue gas after dust removal is blown into the chimney by the external exhaust fan 12-2 and discharged to the outside of the system.

[0090] More specifically, the roasting process of this embodiment further includes: step S6. Waste heat recovery:

[0091] The high-temperature waste air generated by the grate cooler 6 for cooling the high-temperature calcined material enters the cyclone dust collector 4-2 through the waste heat air pipe 6-1 for dust removal treatment. After the dust and solid are discharged, they are sent to the next process through the calcined material conveying device 7; the high-temperature waste air after dust removal is blown into the secondary cyclone preheater by the waste heat fan 4-1 and mixed with the high-temperature flue gas generated by the gas kiln 8 to provide heat source for the suspension preheating device 3, and the waste heat generated by the grate cooler 6 is effectively utilized.

[0092] More specifically, the primary roasting of the electric heating kiln in step S2 further includes the following operations:

[0093] The exhaust valve 10-1 at the kiln head position of the electric heating kiln 10 is regularly opened or closed according to the air pressure in the electric heating kiln 10 to keep the air pressure in the kiln stable; the discharged flue gas is subjected to dust removal treatment through the tail gas treatment device.

[0094] The roasting process of this embodiment can be implemented by using the roasting kiln system in Embodiment 1.

[0095] In this text, the directional terms such as front, rear, upper, and lower are defined based on the positions of the components in the drawings and their positions relative to each other, solely for the clarity and convenience of expressing the technical solution. It should be understood that they are relative concepts and can change accordingly depending on different usage and placement methods. The use of these directional terms should not limit

[0096] the scope of protection claimed in this application.

[0097] Without conflict, the above-mentioned embodiments and the features in the embodiments in this text can be combined with each other.

[0098] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An electric, gas, and suspension triple-composite lithium ore roasting kiln system, characterized in that: It includes a silo (1), a metering device (2), a suspension preheater (3), a lithium ore conveyor (11), an electric heating kiln (10), a scraper conveyor, a lock air valve (91), a gas kiln (8), a combustion device (5), a grate cooler (6), and a roasted material conveying device (7) that are connected in sequence; The suspension preheater (3) includes a primary cyclone preheater and a secondary cyclone preheater. The primary cyclone preheater includes a primary cyclone cylinder (31-1), a drying pipe (31-2), and a primary discharge pipe (31-13). The secondary cyclone preheater includes a secondary cyclone cylinder (32-1), a heat exchange pipe (32-2), and a secondary discharge pipe (32-13); a primary cyclone cylinder flue gas outlet (31-11) is provided at the top of the primary cyclone cylinder (31-1), a primary cyclone cylinder flue gas inlet (31-12) is provided on the side wall of the primary cyclone cylinder (31-1), and the primary discharge pipe (31-13) is provided at the bottom of the primary cyclone cylinder (31-1); a secondary cyclone cylinder flue gas outlet (32-11) is provided at the top of the secondary cyclone cylinder (32-1), a secondary cyclone cylinder flue gas inlet (32-12) is provided on the side wall of the secondary cyclone cylinder (32-1), and the secondary discharge pipe (32-13) is provided at the bottom of the secondary cyclone cylinder (32-1); one end of the drying pipe (31-2) is communicated with the primary cyclone cylinder flue gas inlet (31-12), and the other end is communicated with the secondary cyclone cylinder flue gas outlet (32-11); one end of the heat exchange pipe (32-2) is communicated with the secondary cyclone cylinder flue gas inlet (32-12), and the other end is communicated with the tail of the gas kiln (8); the discharge port of the primary discharge pipe (31-13) is arranged above the lithium ore conveyor (11), and the discharge port of the secondary discharge pipe (32-13) is connected to the tail of the gas kiln (8); A silo discharger (1-1) is provided at the bottom of the silo (1), the metering device (2) is arranged below the silo discharger (1-1), and the feeding position of the metering device (2) is arranged above the feeding port of the drying pipe (31-2); the discharging end of the lithium ore conveyor (11) is connected to the tail of the electric heating kiln (10) through a pipeline; the heating temperature range of the electric heating kiln (10) is controlled at 700-800 °C; the lithium ore between the electric heating kiln (10) and the gas kiln (8) is conveyed by a scraper conveyor; the lock air valve (91) is arranged at the discharging port of the scraper conveyor, and the gas in the electric heating kiln (10) and the gas in the gas kiln (8) are isolated from each other; The combustion device (5) includes a burner and an external blower, and the burner is inserted into the gas kiln cylinder body from the head of the gas kiln; the gas kiln (8) includes a feeding section (8-1), a firing section (8-2), and a cooling section (8-3) arranged in sequence, and the temperature of the firing section (8-2) is controlled at 1100-1200 °C; the feeding port of the grate cooler (6) is arranged below the discharging port at the head of the gas kiln (8), and the roasted material conveying device (7) is arranged below the discharging port of the grate cooler (6); The lithium ore roasting kiln system further includes a tail gas treatment device, which includes a high-temperature bag filter (12-1), an exhaust fan (12-2), and a chimney (12-3) connected in sequence; the air inlet (12-11) of the high-temperature bag filter (12-1) is connected to the flue gas outlet (31-11) of the primary cyclone through a pipeline, the air outlet (12-12) is connected to the exhaust fan (12-2), and the ash discharge port (12-13) is communicated with the feeding port of the lithium ore conveyor (11); The drying pipe (31-2) includes a vertical pipe and an inverted U-shaped pipe. The top of the vertical pipe is connected to one end of the inverted U-shaped pipe, and the other end of the inverted U-shaped pipe is connected to the primary cyclone (31-1).

2. The lithium ore roasting kiln system according to claim 1, wherein: The grate cooler (6) further includes a waste heat recovery device. A waste heat air pipe (6-1) is arranged at the tail of the grate cooler (6). One end of the waste heat recovery device is connected to the waste heat air pipe (6-1), and the other end is connected to the secondary cyclone preheater.

3. The lithium ore roasting kiln system according to claim 2, wherein: The waste heat recovery device includes a cyclone dust collector (4-2); the cyclone dust collector (4-2) is provided with a hot gas outlet (4-21), a hot gas inlet (4-22), and a dust outlet (4-23); the hot gas inlet (4-22) is connected to the waste heat air pipe (6-1), the hot gas outlet (4-21) is connected to the heat exchange pipe (32-2), and the dust outlet (4-23) is arranged above the calcined material conveying device (7).

4. The lithium ore roasting kiln system according to claim 3, wherein: An exhaust valve (10-1) is arranged at the kiln head position of the electric heating kiln (10), and the exhaust valve (10-1) is communicated with the air inlet (12-11) of the high-temperature bag filter (12-1) through a pipeline.

5. A combined electro-, gas-, and suspension-type roasting process for lithium ore, which is implemented based on the lithium ore roasting kiln system described in claim 4, and is characterized in that: It includes the following steps: Step S1. Uniform preheating by the suspension preheating device: Spodumene is fed from the silo (1) into the suspension preheating device (3), and is preheated and dried in the suspension preheating device (3) by the hot flue gas from the gas kiln (8) and the grate cooler (6), so that the temperature of the spodumene is preheated to 200 °C and the water content is not more than 1%; Step S2. Primary roasting in the electric heating kiln: The preheated and dried spodumene is sent to the electric heating kiln (10) by the lithium ore conveyor (11) for roasting, and the heating temperature is controlled at 700-800 °C, so that the temperature of the spodumene out of the kiln is 650-750 °C; Step S3. Secondary roasting in the gas kiln: The spodumene heated by the electric heating kiln (10) is transported to the gas kiln (8) by the lithium ore conveyor (11) for secondary transformation roasting, and the heating temperature is controlled at 1100-1200 °C, so that the spodumene is transformed from α-type to β-type to generate calcined material, and the temperature of the calcined material out of the kiln is 1000 °C; the hot flue gas generated by the gas kiln (8) enters the suspension preheating device (3) along the heat exchange pipe (32-2) to preheat and dry the subsequent spodumene; Step S4. Cooling of the calcined material: The calcined material is transported to the grate cooler (6) after leaving the kiln for cooling treatment, so that the calcined material is reduced to 100 °C and is sent to the next process through the calcined material conveying device (7).

6. The electro-, gas-, and suspension-composite lithium ore roasting process according to claim 5, wherein: It further includes step S5. Tail gas treatment: In step S1, the flue gas discharged from the primary cyclone flue gas outlet (31-11) enters the high-temperature bag filter (12-1) for dust removal treatment. The dust is discharged into the lithium ore conveyor (11) through the ash discharge port (12-13). The flue gas after dust removal is blown into the chimney by the external exhaust fan (12-2) and discharged to the outside of the system.

7. The electro-, gas- and suspension-composite lithium ore roasting process according to claim 6, characterized in that: It also includes step S6. Waste heat recovery: The high-temperature waste air generated by the grate cooler (6) cooling the high-temperature calcined material enters the cyclone dust collector (4-2) through the waste heat air duct (6-1) for dust removal treatment. After the dust and solid are discharged, they are sent to the next process via the calcined material conveying device (7). The high-temperature waste air after dust removal is blown into the secondary cyclone preheater by the waste heat fan (4-1) and mixed with the high-temperature flue gas generated by the gas kiln to provide heat source for the suspension preheating device (3). The waste heat generated by the grate cooler (6) is effectively utilized.

8. The electro-, gas-, and suspension-composite lithium ore roasting process according to claim 7, wherein: The primary roasting of the electric heating kiln in step S2 further includes the following operations: The exhaust valve (10-1) at the kiln head of the electric heating kiln (10) is regularly opened or closed according to the air pressure in the electric heating kiln (10) to keep the air pressure in the kiln stable. The discharged flue gas is subjected to dust removal treatment through the tail gas treatment device.

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