Cement kiln-based spodumene roasting and acidification system and method

Abstract

This invention provides a spodumene roasting and acidification system and method based on a cement kiln, relating to the field of spodumene roasting and acidification, including: Step 1: feeding spodumene concentrate powder into a five-stage preheater of a cement kiln system for preheating; Step 2: feeding the preheated spodumene concentrate powder into a decomposition furnace of the cement kiln system for secondary preheating and supplementary heating; Step 3: feeding the material processed in Step 2 into a rotary kiln of the cement kiln system for roasting; Step 4: feeding the material roasted in the rotary kiln into a cooling device for cooling; Step 5: feeding the cooled material into a grinding device for grinding; Step 6: feeding the ground powder and sulfuric acid together into an acidification roasting unit for acidification roasting reaction, ultimately obtaining acidified clinker. By implementing this method based on a cement kiln system (preheater, decomposition furnace, rotary kiln), the preheater is responsible for raising the temperature, the decomposition furnace is responsible for secondary preheating and supplementary heating, and the rotary kiln focuses on core roasting, avoiding the load bottleneck of a single device.

Description

Technical Field

[0001] This invention relates to the field of spodumene roasting and acidification, specifically to a spodumene roasting and acidification system and method based on a cement kiln. Background Technology

[0002] With social development, the demand for lithium resources continues to grow. Spodumene, as the core hard rock mineral for lithium extraction, has a dense and stable natural α-spodumene structure. Direct acid leaching results in an extremely low lithium extraction rate. It must undergo high-temperature roasting to achieve crystal transformation, and then acid roasting to convert lithium into soluble sulfates in order to meet the requirements of subsequent extraction.

[0003] Existing spodumene roasting systems, such as the method for lithium extraction from spodumene concentrate by suspension roasting disclosed in publication number CN111439762A, have the following problems: 1. The lack of a preheating process for mineral powder means that cold materials at room temperature will absorb a large amount of heat instantly after entering the furnace, causing a sudden drop in local temperature inside the furnace and disrupting the uniformity and continuity of the temperature field inside the furnace. 2. The heating device of the suspension roasting furnace needs to be responsible for heating the ore from room temperature to 1000-1100℃ across the entire temperature range. The heat load of the heating device is highly concentrated and the peak load is greatly increased, which directly limits the processing capacity and continuous stable operation efficiency of a single production line. Summary of the Invention

[0004] The present invention provides a lithium spodumene roasting and acidification system and method based on a cement kiln, which solves at least one of the technical problems mentioned in the background art.

[0005] To address the aforementioned technical problems, this invention discloses a method for roasting and acidifying spodumene in a cement kiln, comprising the following steps: Step 1: Feed the spodumene concentrate powder into the five-stage preheater of the cement kiln system for preheating treatment. Step 2: The preheated spodumene concentrate powder is fed into the decomposition furnace of the cement kiln system for secondary preheating and reheating. Step 3: The material processed in Step 2 is fed into the rotary kiln of the cement kiln system for calcination. Step 4: The material calcined in the rotary kiln is sent to a cooling device for cooling treatment. Step 5: The cooled material is fed into a grinding device for grinding. Step 6: The ground powder and sulfuric acid are fed into the acidification and roasting unit for acidification and roasting reaction, and finally acidified clinker is obtained.

[0006] Preferably, the flue gas discharged from the five-stage preheater is successively treated by the waste heat recovery unit and the carbon dioxide capture unit before being discharged.

[0007] Preferably, the sulfuric acid concentration in step 6 is 75%.

[0008] Preferably, the outlet temperature of the spodumene concentrate powder in the fifth-stage preheater is 550℃~650℃.

[0009] Preferably, the flue gas temperature in the rotary kiln tail flue is controlled at 1000℃~1200℃.

[0010] Preferably, the temperature of the material after step 2 is 850℃~950℃, and the flue gas temperature of the rotary kiln tail flue gas is reduced to 850℃~950℃ after heat exchange in the decomposition furnace, and enters the five-stage preheater at this temperature.

[0011] Preferably, in step 6, the mass ratio of sulfuric acid to spodumene powder is 0.26 to 0.35:1, the acidification roasting temperature is 150°C to 300°C, and the acidification roasting residence time of the mixture of sulfuric acid and spodumene powder in the acidification roasting unit is 60 min to 120 min.

[0012] Preferably, the acidification roasting unit is an acidification rotary kiln, and S6 includes: S61: Obtain the rated feed flow range, initial feed flow, and rated control parameters of the rotary kiln for the current mixture of sulfuric acid and spodumene powder. S62: Based on the initial feed flow rate and the current rated control parameters of the rotary kiln, start the acid roasting reaction of the current mixture; S63: After the rotary kiln starts discharging acidified clinker, the discharge temperature and flow rate of the acidified clinker, as well as the pressure difference between the inlet and outlet areas of the rotary kiln, are detected within the first time period. Based on the detection results, a working condition correspondence table is constructed; and the first discharge time of the rotary kiln is determined. The working condition correspondence table reflects the correspondence between "detection period - discharge flow rate - discharge temperature - pressure difference between the inlet and outlet areas of the rotary kiln". S64: Determine the discharge temperature-to-flow ratio coefficient and the differential pressure state coefficient based on the working condition correspondence table, adjust the current rated speed of the rotary kiln based on the discharge temperature-to-flow ratio coefficient, and adjust the initial feed flow rate based on the differential pressure state coefficient to obtain the first speed and the current first feed flow rate of the rotary kiln. S65: Using the first rotation speed of the rotary kiln and the current first feed flow rate, continue the acid roasting reaction on the current mixture, and after the first discharge time of the rotary kiln is preset, start to detect the pressure difference between the flue gas inlet area and the flue gas outlet area of ​​the rotary kiln, redetermine the pressure difference state coefficient, and adjust the current first feed flow rate based on the redetermined pressure difference state coefficient to obtain the current second feed flow rate; S66: Continue the acidification and roasting reaction of the current sulfuric acid and powder at the second rotation speed of the rotary kiln and the current second feed flow rate.

[0013] The present invention also discloses a spodumene roasting and acidification system based on a cement kiln, which is applied to the aforementioned spodumene roasting and acidification method based on a cement kiln. The system includes a cement kiln system and an acidification roasting unit.

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves the following through pretreatment using a five-stage preheater and a decomposition furnace: Precise preheating and temperature control: The spodumene concentrate powder is first heated in a five-stage preheater to avoid thermal shock caused by the direct entry of room temperature material into high temperature equipment, thus maintaining the stability and continuity of the system's thermal regime.

[0016] Cascaded preheating and load reduction: The material is preheated and supplemented in a secondary preheating furnace, and the material temperature is increased in stages and in advance, and the heat energy is accumulated. The heating load is distributed to the preheating and supplementing heating sections, which greatly reduces the heating load of the rotary kiln, avoids drastic fluctuations in the temperature field inside the furnace, and ensures that the spodumene crystal transformation and roasting process is uniform and controllable.

[0017] 2. The preheater is responsible for primary heating, the decomposition furnace is responsible for secondary medium-temperature heat replenishment and storage, and the rotary kiln focuses on the high-temperature phase change core roasting of α-spodumene to β-spodumene, avoiding the load bottleneck of a single piece of equipment. Due to the reduced heat load and more stable temperature field of the rotary kiln, the system can achieve higher continuous operation efficiency and greater single-line processing capacity.

[0018] 3. After preheating and secondary reheating, spodumene has a high base temperature and lattice pre-expansion activity when it enters the rotary kiln, which is conducive to the efficient conversion of α-spodumene to β-spodumene and lays a good foundation for the subsequent acid roasting reaction.

[0019] After cooling and grinding, the material has a more uniform particle size, and the reaction is more complete when it comes into contact with sulfuric acid, which improves the efficiency of acid roasting reaction and ultimately yields acid clinker of better quality.

[0020] 4. The flue gas discharged from the five-stage preheater recovers heat through the waste heat recovery unit, significantly reducing system energy consumption and achieving cascaded energy utilization. The flue gas is then treated by the carbon dioxide capture unit before being discharged, effectively reducing greenhouse gas emissions, meeting environmental protection requirements, and solving the pain point of traditional processes failing to meet environmental standards.

[0021] 5. This method can be implemented using a mature cement kiln system (preheater, decomposition furnace, rotary kiln), eliminating the need for new specialized equipment, thus reducing investment costs and demonstrating promising prospects for industrial application. The standardized cement kiln system, combined with a segmented, tiered preheating and supplemental heating process, significantly improves the continuous operation rate of the production line and reduces equipment failures and downtime losses. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation

[0023] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0025] The present invention provides the following embodiments: Example 1: This embodiment of the invention provides a method for roasting and acidifying spodumene in a cement kiln, such as... Figure 1 As shown, it includes the following steps: Includes the following steps: Step 1: Feed the spodumene concentrate powder into the five-stage preheater of the cement kiln system for preheating treatment. Step 2: The preheated spodumene concentrate powder is fed into the decomposition furnace of the cement kiln system for secondary preheating and reheating. Step 3: The material processed in Step 2 is fed into the rotary kiln of the cement kiln system for calcination. Step 4: The material calcined in the rotary kiln is sent to a cooling device for cooling treatment. Step 5: The cooled material is fed into a grinding device for grinding. Step 6: The ground powder and sulfuric acid are fed into the acidification and roasting unit for acidification and roasting reaction, and finally acidified clinker is obtained.

[0026] Preferably, the flue gas discharged from the five-stage preheater is successively treated by the waste heat recovery unit and the carbon dioxide capture unit before being discharged.

[0027] Preferably, the sulfuric acid concentration in step 6 is 75%.

[0028] Preferably, the outlet temperature of the spodumene concentrate powder in the fifth-stage preheater is 550℃~650℃.

[0029] Preferably, the flue gas temperature in the rotary kiln tail flue is controlled at 1000℃~1200℃.

[0030] Preferably, the temperature of the material after step 2 is 850℃~950℃, and the flue gas temperature of the rotary kiln tail flue gas is reduced to 850℃~950℃ after heat exchange in the decomposition furnace, and enters the five-stage preheater at this temperature.

[0031] Preferably, in step 6, the mass ratio of sulfuric acid to spodumene powder is 0.26 to 0.35:1, the acidification roasting temperature is 150°C to 300°C, and the acidification roasting residence time of the mixture of sulfuric acid and spodumene powder in the acidification roasting unit is 60 min to 120 min.

[0032] To investigate the effects of acid concentration and acid amount on the transformation and leaching processes, conditional experiments were conducted with acid concentrations of 98%, 75%, and 70% and acid amounts of 0.3 times and 0.32 times the amount of raw ore, respectively. The results are shown in the table below.

[0033]

[0034] It can be observed that as the acid concentration increases from 70% to 98%, the leaching rate increases from 92.07% to 94.76% (an increase of 2.69%). High-concentration acid can reduce the acid quantity requirement by increasing the hydrogen ion activity, while low-concentration acid can compensate for insufficient concentration by increasing the total amount of hydrogen ions. There is room for cost substitution between the two. If the preparation cost of 98% high-concentration acid is high, 75% medium-concentration acid can be used and the acid quantity can be slightly increased to reduce the raw material cost while ensuring the leaching rate.

[0035] The beneficial effects of this invention are as follows: 1. This invention achieves the following through pretreatment using a five-stage preheater and a decomposition furnace: Precise preheating and temperature control: The spodumene concentrate powder is first heated in a five-stage preheater to avoid thermal shock caused by the direct entry of room temperature material into high temperature equipment, thus maintaining the stability and continuity of the system's thermal regime.

[0036] Cascaded preheating and load reduction: The material is preheated and supplemented in a secondary preheating furnace, and the material temperature is increased in stages and in advance, and the heat energy is accumulated. The heating load is distributed to the preheating and supplementing heating sections, which greatly reduces the heating load of the rotary kiln, avoids drastic fluctuations in the temperature field inside the furnace, and ensures that the spodumene crystal transformation and roasting process is uniform and controllable.

[0037] 2. The preheater is responsible for primary heating, the decomposition furnace is responsible for secondary medium-temperature heat replenishment and storage, and the rotary kiln focuses on the high-temperature phase change core roasting of α-spodumene to β-spodumene, avoiding the load bottleneck of a single piece of equipment. Due to the reduced heat load and more stable temperature field of the rotary kiln, the system can achieve higher continuous operation efficiency and greater single-line processing capacity.

[0038] 3. After preheating and secondary reheating, spodumene has a high base temperature and lattice pre-expansion activity when it enters the rotary kiln, which is conducive to the efficient conversion of α-spodumene to β-spodumene and lays a good foundation for the subsequent acid roasting reaction.

[0039] After cooling and grinding, the material has a more uniform particle size, and the reaction is more complete when it comes into contact with sulfuric acid, which improves the efficiency of acid roasting reaction and ultimately yields acid clinker of better quality.

[0040] 4. The flue gas discharged from the five-stage preheater recovers heat through the waste heat recovery unit, significantly reducing system energy consumption and achieving cascaded energy utilization. The flue gas is then treated by the carbon dioxide capture unit before being discharged, effectively reducing greenhouse gas emissions, meeting environmental protection requirements, and solving the pain point of traditional processes failing to meet environmental standards.

[0041] 5. This method can be implemented using a mature cement kiln system (preheater, decomposition furnace, rotary kiln), eliminating the need for new specialized equipment, thus reducing investment costs and demonstrating promising prospects for industrial application. The standardized cement kiln system, combined with a segmented, tiered preheating and supplemental heating process, significantly improves the continuous operation rate of the production line and reduces equipment failures and downtime losses.

[0042] Example 2, based on Example 1, S6 includes: S61: Obtain the rated feed flow range, initial feed flow, and rated control parameters of the rotary kiln for the current mixture of sulfuric acid and spodumene powder. S62: Based on the initial feed flow rate and the current rated control parameters of the rotary kiln, start the acid roasting reaction of the current mixture; first, carry out the acid roasting reaction with a relatively small optimal feed flow rate to judge the reaction effect of the current mixture under the current rotary kiln. S63: After the rotary kiln starts discharging acidified clinker, the discharge temperature and flow rate of the acidified clinker, as well as the pressure difference between the inlet and outlet areas of the rotary kiln, are detected within the first time period (the time for judging the initial discharge effect, with a value range of 5 min to 12 min). Based on the detection results, a working condition correspondence table is constructed; and the first discharge time of the rotary kiln is determined. The working condition correspondence table reflects the correspondence between "detection time period - discharge flow rate - discharge temperature - pressure difference between the inlet and outlet areas of the rotary kiln". S64: Determine the discharge temperature-to-flow ratio coefficient and pressure differential state coefficient based on the working condition correspondence table; adjust the current rated speed of the rotary kiln based on the discharge temperature-to-flow ratio coefficient; adjust the initial feed flow rate based on the pressure differential state coefficient to obtain the first speed and the current first feed flow rate of the rotary kiln; judge the reaction effect (heating state) of the current mixture under the current rotary kiln based on the acidification and roasting reaction effect in S63; and make a minor adjustment to the feed flow rate and speed based on the heating state (the minor adjustment is to ensure that the feed flow rate is not adjusted too much and that the acidified clinker quality is still relatively good in S65) to adapt to the current mixture; S65: Using the first rotational speed of the rotary kiln and the current first feed flow rate, continue the acid roasting reaction on the current mixture, and after the first discharge time of the rotary kiln (preset multiple), start detecting the pressure difference between the flue gas inlet and outlet zones of the rotary kiln (after adjusting the flow rate and starting discharge, when the kiln is relatively fully filled, obtain the pressure difference status at this time), redetermine the pressure difference state coefficient, and adjust the current first feed flow rate based on the redetermined pressure difference state coefficient to obtain the current second feed flow rate; the preset multiple is 1.5 times; When the differential pressure state coefficient is less than 0.93, the current second feed flow rate is 1.02 times the current first feed flow rate; when the differential pressure state coefficient is greater than 0.93, the current second feed flow rate is equal to the current first feed flow rate. S66: Using the second rotation speed and the current second feed flow rate of the rotary kiln, continue the acidification and roasting reaction of the current sulfuric acid and powder; and after the first discharge time of the preset double rotary kiln, detect and determine the pressure difference and temperature difference between the flue gas inlet area and the flue gas outlet area of ​​the rotary kiln (this reflects the initial theoretical heat exchange effect under the rotation speed and flow rate conditions), and use them as the initial pressure difference and initial temperature difference. It can also perform the following: During the continuous acid roasting reaction, periodically detect and determine the pressure difference and temperature difference between the flue gas inlet and outlet areas of the rotary kiln. When at least one of the following occurs, an early warning will be issued: the pressure difference deviates significantly from the initial pressure difference or the temperature difference deviates significantly from the initial temperature difference. It can also construct rotary kiln running time-pressure difference curves and rotary kiln running time-temperature difference curves to judge the trend of temperature difference and pressure difference changes, and issue an early warning when the trend is abnormal.

[0043] In S61: Same type of mixed material: Specifically refers to a mixed material whose main component is spodumene concentrate powder and industrial sulfuric acid, used in the same cement kiln for co-acidification roasting process; such materials are allowed to have normal industrial production fluctuations in spodumene grade, particle size, moisture content, sulfuric acid concentration, and acid-to-material ratio between different batches. The rated control parameters of the rotary kiln are the optimal control parameters of the rotary kiln. These optimal control parameters are determined through process testing and are the optimal benchmark parameters for adapting to a whole type of material. For example, the optimal control parameters for a certain mixture are: acid roasting temperature of 220-260℃, acid roasting residence time of the mixture in the rotary kiln of 80-100 min, and acid-to-material ratio of 0.26-0.35:1. These optimal parameters can accommodate normal minor fluctuations between batches of the same material.

[0044] The rated feed flow range of the current mixed material (e.g., 12t / h to 14t / h under the above-mentioned optimal rotary kiln control parameters) is the specific optimal feed flow range for this type of material, determined through process testing and steady-state commissioning of the production line under the corresponding optimal rotary kiln control parameter conditions. This flow rate is based on the corresponding optimal rotary kiln control parameters as an operating premise, satisfying the conditions of kiln flow stability, equipment load-bearing capacity, and system thermal balance. Furthermore, the acidification and roasting reaction is sufficient, and the sulfuric acid utilization rate is in the optimal range (e.g., 96% to 98%; where 98% is the optimal stable utilization rate for this type of material determined through process testing and steady-state commissioning of the production line). It is a universal optimal benchmark for all types of materials that takes into account reaction effect, production capacity, and equipment safety.

[0045] The initial feed flow rate of the current mixture in the rotary kiln: take the minimum value of the rated feed flow rate range of the current mixture (e.g., 12t / h). S63: The pressure difference between the flue gas inlet area and the flue gas outlet area of ​​the rotary kiln is: air pressure in the flue gas inlet area of ​​the rotary kiln - air pressure in the flue gas outlet area of ​​the rotary kiln; Within the first duration (which is divided into several detection periods according to the preset detection period length (which can be 1 to 2 minutes), discharge temperature and discharge flow rate data are continuously collected at fixed time intervals (e.g., 10 seconds / time).

[0046] The table is structured with "detection period" as the row and "discharge flow rate, discharge temperature, and pressure difference between the rotary kiln inlet and outlet areas" as the columns. Each row represents a detection period, and each column represents a type of process parameter, ultimately forming a well-structured four-dimensional data table that can be directly used for operating condition judgment.

[0047] For example:

[0048] S64: Pressure differential state coefficient = average pressure differential within the first time period ÷ actual pressure differential determined when determining the minimum value of the rated feed flow range of S61; The average pressure difference within the first time period is: the arithmetic mean of the pressure differences at all sampling times within the first time period; Discharge temperature to flow rate ratio coefficient = ; R represents the number of detection time periods divided by the first duration; , These are the average discharge temperature and average discharge flow rate during the i-th detection period, respectively. This is the optimal discharge temperature (greater than the qualified discharge temperature) for the current acidified clinker. The actual acidified clinker discharge flow rate is determined when the minimum value of the rated feed flow rate range of S61 is determined; Because acid roasting is started at a relatively low optimal flow rate, generally It is greater than 1; The rotary kiln speed in the rated control parameters is V; When 0.98 ≤ discharge temperature-to-flow ratio coefficient ≤ 1.02: the first rotational speed is V; When 0.90 ≤ discharge temperature-to-flow ratio coefficient < 0.98: the first rotational speed is 0.95V; When the discharge temperature-to-flow ratio is <0.90: the first rotation speed is 0.9V; When 1.02 < discharge temperature / flow ratio coefficient ≤ 1.15: the first rotation speed is 1.05V; When the discharge temperature-to-flow ratio is >1.15: the first rotation speed is 1.1V; Determination of the first feed flow rate: Let the initial feed flow rate be W. Adjust the differential pressure state coefficient (at which point the differential pressure state coefficient will not be abnormal); When 0.95 ≤ pressure differential state coefficient ≤ 1 (normal flow state inside the kiln): the initial first feed flow rate is W; When 0.9 < pressure difference state coefficient ≤ 0.95 (pressure difference is too high, kiln resistance is high): the initial first feed flow rate is 1.01~1.02W. When the differential pressure state coefficient is less than 0.90, the initial first feed flow rate is 1.03W.

[0049] In this embodiment, the rotary kiln specifically refers to an acidification rotary kiln; The beneficial effects of this embodiment are: This embodiment solves the problem of "mismatch between flow rate and kiln condition, and unqualified output requiring post-processing" in the rotary kiln acid roasting process by adopting a closed-loop, step-by-step online adjustment strategy throughout the entire process (S61~S66).

[0050] 1. Using the "smallest optimal flow rate" as the starting benchmark avoids problems such as kiln overload, pressure surge, and material blockage caused by excessive initial feed rate, and reserves sufficient safety margin for subsequent adjustments.

[0051] Establish a unified process benchmark: Optimal control parameters, calibrated through process experiments, are adapted to normal fluctuations in the same batch of materials (spodumene grade, moisture content, sulfuric acid concentration, etc.). Under the premise of ensuring stable flow within the kiln, equipment load capacity, and thermal balance, the rated feed flow rate range locks the sulfuric acid utilization rate within the optimal range of 96%~98%, achieving an optimal balance between reaction sufficiency, production capacity, and equipment safety, laying a quality foundation for subsequent production increases.

[0052] 2. Low kiln filling rate and sufficient thermal redundancy at low flow rates allow for safe verification of material compatibility with the rotary kiln, avoiding irreversible problems such as under-burning, over-burning, and material blockage caused by direct full-load start-up, thus significantly reducing trial production risks. It provides accurate and stable operating data for parameter detection in S63 and speed / flow rate fine-tuning in S64, avoiding adjustment distortion caused by operating condition fluctuations.

[0053] The reaction is sufficient at low flow rates, and the initial output can reach a high quality level. This eliminates substandard output from the start-up stage, eliminating the need for subsequent rework and reducing production losses.

[0054] 3. By collecting multiple parameters simultaneously, the system comprehensively covers the three core indicators of "temperature (reaction sufficiency), flow rate (capacity matching), and pressure difference (flow state in the kiln)," thus constructing a complete operating condition diagnosis system. The structured operating condition correspondence table clearly presents the changes in process parameters at different times, providing accurate data for calculating the discharge temperature-to-flow ratio coefficient and pressure difference state coefficient of S64.

[0055] The initial duration setting precisely matches the stabilization cycle of the initial output, avoiding both unstable operating conditions and data distortion caused by detecting too early, and delayed adjustments caused by detecting too late.

[0056] 4. The initial feed flow rate is adjusted slightly based on the differential pressure state coefficient (the flow rate is further fine-tuned but not too much, so that the flow rate and speed are matched first), and the first speed and the first feed flow rate are obtained. This completes the "one-time fine-tuning" to ensure that the flow rate does not change significantly and the S65 output quality is better (it eliminates unqualified output and does not require subsequent rework).

[0057] The division of labor is clearly defined: "rotation speed is responsible for temperature control, and flow rate is responsible for differential pressure control." The rotation speed is precisely adjusted by the discharge temperature-flow rate ratio coefficient: when overburning occurs, the rotation speed is increased to shorten the residence time, and when underburning occurs, the rotation speed is decreased to extend the residence time. This completely solves the problem of "mutual interference and control oscillation between temperature and flow rate" in traditional processes, ensuring that the discharge temperature is always stable within the optimal range.

[0058] 5. Based on the initial fine-tuning of S64, after the kiln conditions have fully stabilized, a very small 2% increase in production is made only when the pressure differential safety margin is sufficient. This fully utilizes the kiln's excess capacity without causing excessive pressure differential or material blockage (eliminating substandard output and eliminating the need for subsequent rework). The second feed flow rate is the optimal flow rate verified through a triple process of "small flow start-up - one fine-tuning - two kiln stabilization," providing stable process parameters for the long-term continuous production of S66 and ensuring consistently qualified output.

[0059] The closed-loop process of "calibration-start-testing-adjustment-kiln stabilization-monitoring" enables the automation and intelligence of the rotary kiln acid roasting process, while ensuring qualified production.

[0060] Example 3, based on Example 1, For each type of spodumene concentrate powder, the air-material matching experiment determined a set of benchmark process parameters. The set of benchmark process parameters includes: benchmark fan speed range, benchmark powder flow rate, and sub-speed range matching relationship. The benchmark fan speed range is divided into several sub-speed ranges. The sub-speed range matching relationship is the matching relationship of "sub-speed range, average wind speed in the top cyclone in the five-stage preheater, and residence time of powder in the five-stage cyclone". The preheating of spodumene concentrate powder is initiated when the preheating pre-adaptation conditions are met. The preheating pre-adaptation process includes: Step 1a: Start the preheating of the five-stage preheater with the reference powder flow rate and the median value of the intermediate sub-speed range, and set the preheating test duration for the current spodumene concentrate powder (e.g., 5 min to 10 min), and detect the powder outlet temperature of the five-stage preheater during the preheating test. Step 1b: Based on step 1a, determine the actual residence time of the powder in the five-stage preheater; Step 1d: Based on the powder discharge temperature of the five-stage preheater, the actual residence time of the powder in the five-stage preheater, and the matching relationship of the sub-speed range, the fan speed corresponding to the preheating test is corrected once, and the current spodumene concentrate powder (same batch) is preheated again based on the corrected speed.

[0061] When the powder discharge temperature of the fifth-stage preheater is qualified, the corrected rotation speed is equal to the rotation speed in step 1a. When the powder discharge temperature of the fifth-stage preheater does not meet the process temperature requirements; Determine the time difference = actual residence time of powder in the fifth-stage preheater - "the median residence time corresponding to the sub-speed range of the speed in step 1a in the sub-speed range matching relationship"; When the discharge temperature is higher than the upper limit of the process temperature requirement range (time difference greater than 0): target residence time median = residence time median of the sub-speed range corresponding to the speed in step 1a - time difference; In the sub-speed matching table, select the sub-speed range whose median dwell time is closest to the target value. When the discharge temperature is lower than the lower limit of the process (time difference is less than 0): the median of the target residence time = the median of the residence time in the sub-speed range corresponding to the speed in step 1a - the time difference; In the sub-speed matching table, select the sub-speed range whose median dwell time is closest to the target value. Furthermore, during the continued preheating process, an alarm will be triggered if the average wind speed inside the top cyclone of the actual five-stage preheater deviates significantly from the average wind speed range corresponding to the target sub-rotation speed range in the sub-rotation speed range matching relationship (10% deviation from the maximum or minimum value, relative deviation).

[0062] (1) For each type of spodumene concentrate powder, an initial working condition adaptation experiment is first carried out. Through gradual debugging, the core process parameters that are stable in operation and have qualified preheating quality and efficiency are found. The core process parameters that are finally determined are recorded as the corresponding benchmark process parameters of the powder.

[0063] The so-called same type of spodumene concentrate powder refers to powder from the same mining area, the same beneficiation and grinding process, and with highly consistent key physical properties: lithium oxide grade, particle size distribution, moisture content, bulk density and main impurity content all meet the corresponding range.

[0064] When conducting initial working condition adaptation experiments for each type of spodumene concentrate powder; The typical range of flue gas inlet temperature for a five-stage preheater is 850–950℃; The reference fan speed range is: values ​​taken from 77% to 85% of the fan's rated operating speed (this range can ensure the optimal balance between fan operating efficiency and system stability). For each type of spodumene concentrate powder, select an initial feeding speed (the median of the benchmark fan speed range) within the benchmark fan speed range for several batches or a specific batch. First, conduct a trial run with a lower feed rate to monitor the smoothness of material feeding, system pressure difference, and dust content at the top cyclone outlet. Under stable operating conditions, gradually increase the feed rate to match the air velocity inside the cyclone with the feed rate. Finally, determine the maximum stable feed rate (which matches the benchmark fan speed range) that ensures smooth material feeding without blockage, meets the dust content standard at the outlet, ensures stable fan operation, and sufficient heat exchange of the powder, and use this as the benchmark powder flow rate for that powder.

[0065] Taking a rated fan speed of 960 r / min as an example, the corresponding benchmark parameters are: benchmark powder flow rate of 18 t / h, and benchmark fan speed range of 739 r / min to 816 r / min (corresponding to an average wind speed of 18 m / s to 22 m / s in the top cyclone of the five-stage preheater; and in determining the benchmark fan speed range, when the fan is not running, the pressure of the flue gas used by the five-stage preheater is the benchmark flue gas pressure). Within the reference fan speed range, based on the average wind speed of the top cyclone corresponding to the speed, the difference between the maximum and minimum average wind speed of the top cyclone in each sub-speed range is less than or equal to 1 m / s. In one instance:

[0066] (2) Meeting the preheating pre-adaptation conditions includes: The parameters affecting the heat exchange effect of the powder (such as particle size, moisture, grade, etc.) change significantly (significant change is defined as: parameter fluctuations exceeding preset thresholds, such as moisture content change > 0.5%, particle size D50 change > 12%, lithium oxide grade change > 0.5%). The beneficial effects of this embodiment are: This solution establishes a precise matching relationship between "sub-speed range - average wind speed of top cyclone - powder residence time", dividing the benchmark fan speed into sub-ranges to achieve a precise correspondence between fan speed and powder heat exchange requirements; at the same time, based on the closed-loop correction logic of discharge temperature and actual residence time, the target residence time is calculated by time difference, automatically matching the optimal sub-speed range, and quickly adjusting the heat exchange time of powder in the preheater, which can quickly adapt to the preheating of the same but different spodumene powders; This scheme strictly limits the reference fan speed to 77% to 85% of the rated fan speed. This range is the optimal range for efficient fan operation: it avoids problems such as powder blockage, wall adhesion, and uneven heat exchange caused by insufficient air velocity at low speeds, and also prevents a significant increase in fan energy consumption at high speeds.

[0067] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for roasting and acidifying spodumene in a cement kiln, characterized in that: Includes the following steps: Step 1: Feed the spodumene concentrate powder into the five-stage preheater of the cement kiln system for preheating treatment. Step 2: The preheated spodumene concentrate powder is fed into the decomposition furnace of the cement kiln system for secondary preheating and reheating. Step 3: The material processed in Step 2 is fed into the rotary kiln of the cement kiln system for calcination. Step 4: The material calcined in the rotary kiln is sent to a cooling device for cooling treatment. Step 5: The cooled material is fed into a grinding device for grinding. Step 6: The ground powder and sulfuric acid are fed into the acidification and roasting unit for acidification and roasting reaction, and finally acidified clinker is obtained.

2. The method for calcining and acidifying spodumene based on a cement kiln according to claim 1, characterized in that: The flue gas discharged from the five-stage preheater is successively treated by the waste heat recovery unit and the carbon dioxide capture unit before being discharged.

3. The method for calcining and acidifying spodumene based on a cement kiln according to claim 1, characterized in that: In step 6, the sulfuric acid concentration is 75%.

4. The method for roasting and acidifying spodumene based on a cement kiln according to claim 1, characterized in that: The outlet temperature of the spodumene concentrate powder in the fifth-stage preheater is 550℃~650℃.

5. The method for calcining and acidifying spodumene based on a cement kiln according to claim 1, characterized in that: The flue gas temperature in the tail smoke chamber of the rotary kiln is controlled at 1000℃~1200℃.

6. The method for calcining and acidifying spodumene in a cement kiln according to claim 1, characterized in that: The temperature of the material after step 2 is 850℃~950℃. The flue gas temperature of the rotary kiln tail flue gas is reduced to 850℃~950℃ after heat exchange in the decomposition furnace, and enters the five-stage preheater at this temperature.

7. The method for roasting and acidifying spodumene based on a cement kiln according to claim 1, characterized in that: In step 6, the mass ratio of sulfuric acid to spodumene powder is 0.26 to 0.35:1, the acidification roasting temperature is 150°C to 300°C, and the acidification roasting residence time of the mixture of sulfuric acid and spodumene powder in the acidification roasting unit is 60 min to 120 min.

8. The method for roasting and acidifying spodumene based on a cement kiln according to claim 1, characterized in that: The acidification and roasting unit is an acidification rotary kiln, S6 includes: S61: Obtain the rated feed flow range, initial feed flow, and rated control parameters of the rotary kiln for the current mixture of sulfuric acid and spodumene powder. S62: Based on the initial feed flow rate and the current rated control parameters of the rotary kiln, start the acid roasting reaction of the current mixture; S63: After the rotary kiln starts discharging acidified clinker, the discharge temperature and flow rate of the acidified clinker, as well as the pressure difference between the flue gas inlet and outlet areas of the rotary kiln, are detected within the first time period. Based on the detection results, a working condition correspondence table is constructed; and the first discharge time of the rotary kiln is determined. The working condition correspondence table reflects the correspondence between "detection time period - discharge flow rate - discharge temperature - pressure difference between the flue gas inlet and outlet areas of the rotary kiln". S64: Determine the discharge temperature-to-flow ratio coefficient and the differential pressure state coefficient based on the working condition correspondence table, adjust the current rated speed of the rotary kiln based on the discharge temperature-to-flow ratio coefficient, and adjust the initial feed flow rate based on the differential pressure state coefficient to obtain the first speed and the current first feed flow rate of the rotary kiln. S65: Using the first rotation speed of the rotary kiln and the current first feed flow rate, continue the acid roasting reaction on the current mixture, and after the first discharge time of the rotary kiln is preset, start to detect the pressure difference between the flue gas inlet area and the flue gas outlet area of ​​the rotary kiln, redetermine the pressure difference state coefficient, and adjust the current first feed flow rate based on the redetermined pressure difference state coefficient to obtain the current second feed flow rate; S66: Continue the acidification and roasting reaction of the current sulfuric acid and powder at the second rotation speed of the rotary kiln and the current second feed flow rate.

9. A spodumene roasting and acidification system based on a cement kiln, applied to a spodumene roasting and acidification method based on a cement kiln as described in any one of claims 1-8, characterized in that: The system includes: Cement kiln system and acid roasting unit.

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