An automatic control system for synthesizing large-particle-size cobalt carbonate

Abstract

This invention relates to the field of wet synthesis technology of lithium cobalt oxide precursors, specifically to an automatic control system for synthesizing large-particle-size cobalt carbonate. This system addresses the problems of high labor intensity for operators, delayed pH / ammonia concentration detection, and large particle size detection errors in the current synthesis of large-particle-size cobalt carbonate, ultimately reducing the overall efficiency of the synthesis. The system consists of a reaction vessel, a pH / ammonia concentration composite probe, a particle size analyzer, a mold temperature controller, a batch valve assembly, and a DCS control station. It achieves closed-loop particle size control, automatic batch separation, and batch management through a multi-parameter coupling model of particle size, expansion rate, and time, and a batch separation model. The DCS system monitors and automatically adjusts parameters such as temperature, pH / ammonia concentration, solid content, and particle size in real time, eliminating the need for manual intervention throughout the process. This significantly improves the batch consistency of large-particle-size cobalt carbonate, ensures controllable particle size, greatly reduces the labor intensity of operators, and guarantees the unmanned and digitalized production requirements for cobalt carbonate synthesis.

Description

Technical Field

[0001] This invention relates to the field of wet synthesis technology of lithium cobalt oxide precursors, specifically to an automatic control system for synthesizing large-particle-size cobalt carbonate. Background Technology

[0002] Currently, the existing wet synthesis process for large-particle-size cobalt carbonate (D50≥15µm) suffers from the following pain points: raw material metering relies on manual labor, which is labor-intensive and carries the risk of cobalt salt exposure; traditional offline pH or ammonia concentration detection is lagging, leading to large fluctuations in finished product indicators; the cobalt carbonate synthesis reaction cycle is long, requiring manual sampling and solid content measurement to determine reactor separation / shutdown, which is time-consuming and subject to human error, failing to provide timely and accurate data for reactor separation / shutdown; single-loop PID only fine-tunes pH using ammonium bicarbonate flow rate, which cannot overcome external disturbances and requires frequent manual intervention; particle size detection is done offline, requiring operators to take samples at regular intervals, which leads to inconsistent sampling times or non-compliance with equipment operation requirements, making measurement errors highly likely. Furthermore, frequent sampling increases the workload of personnel, ultimately significantly impacting the production efficiency of large-particle-size cobalt carbonate synthesis. Summary of the Invention

[0003] This invention provides an automatic control system for synthesizing large-particle-size cobalt carbonate to solve the problems mentioned above.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: An automatic control system for synthesizing large-particle-size cobalt carbonate includes a reactor, a feeding subsystem connected to the top of the reactor, a reaction parameter detection subsystem connected to the feeding subsystem, a temperature control system connected to the side wall of the reactor, and the feeding subsystem, the reaction parameter detection subsystem, and the feeding subsystem are all connected to a DCS control station, which is also connected to a data and alarm subsystem.

[0005] The feeding subsystem includes a first metering pump, a second metering pump, a first flow meter, and a second flow meter. The first metering pump and the second metering pump are both connected to the top of the reactor. The first flow meter and the second flow meter are both located on both sides of the first metering pump. The first metering pump and the second metering pump are connected to the DCS control station.

[0006] The reaction parameter detection subsystem includes a pH / ammonia concentration composite probe, an online particle size analyzer, a second level gauge, and an online specific gravity meter. The pH / ammonia concentration composite probe is connected to an automatic cleaning device, and the pH / ammonia concentration composite probe, the online particle size analyzer, the second level gauge, and the online specific gravity meter are all connected to the DCS control station.

[0007] The temperature control system includes a mold temperature controller, and the mold temperature controller is connected to the DCS control station.

[0008] The data and alarm subsystem includes a display screen, a data analysis module, and an audible and visual alarm module, all of which are connected to the DCS control station.

[0009] Furthermore, the top of the reactor is equipped with a first level gauge, and the bottom of the reactor is also connected to an automatic dispensing valve assembly.

[0010] Furthermore, the data is connected to the alarm subsystem via a timing module.

[0011] Furthermore, the data analysis module (14) includes a particle size-expansion rate-time-flow coupling model (21), a separate vessel control model (22), and a multi-input-single-output pH / ammonia concentration control model (23). The separate vessel control model (22) is as follows: , .

[0012] Where M is the solid content (g / L), m is the mass of cobalt carbonate (g), and V is the slurry volume. Let represent the cobalt conversion rate, n represent the percentage of cobalt carbonate slurry separated, t1 and t2 represent any reaction time, T1 represents the time of the first separation, M(t1) represents the solid content at any time t1, and M(t2) represents the solid content at any time t2.

[0013] The particle size-expansion rate-time-flow coupling model (21) is as follows: The cobalt carbonate particle size is set at [D50]. n D50 n+1 The rate of increase within the range is If the time required for this range is t, then .

[0014] With a constant rate of increase, the flow rate will gradually increase as the granularity increases. The granularity at time T1 is D50. T t represents any time period, and its granularity is D50. t The traffic increment is ,but: .

[0015] The present invention has the following beneficial effects: The automatic control system for synthesizing large-particle-size cobalt carbonate provided by this invention achieves full automation: zero manual intervention from solution preparation to batch separation, reducing labor intensity and occupational health risks; controllable particle size and synthesis time: compared with the existing level of automation, in terms of particle size control, it has timed detection and timely control of the expansion rate, achieving controllable synthesis time, with D50 fluctuation ≤ ±0.1µm, and the synthesis time is controlled within the required range; controllable specific gravity: target specific gravity deviation ≤ ±0.01g / cm³; controllable synthesis time: batch cycle deviation ≤ ±1h; standardized batch separation: due to the long solid content measurement time, the batch separation process is basically impossible to achieve automatically, but it can achieve automatic batch separation with a separation accuracy ≤ ±1%; high batch consistency: the batch consistency of large-particle-size cobalt carbonate can reach CV ≤ 2%; energy saving and consumption reduction: the metering pump operates in the high-efficiency zone, reducing energy consumption by ≥15%, and the data is traceable; high precision in pH / ammonia concentration control: the cobalt carbonate synthesis process is a weakly alkaline system, and pH / ammonia concentration control has a lag, and the relationship between ammonia concentration and flow rate is uncertain, making manual control very difficult. This system achieves precise control. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the system structure connection of the present invention.

[0017] Figure 2 This is a schematic diagram of the overall control logic flow of the present invention.

[0018] Figure 3 This is a schematic diagram of the multi-input single-output ammonia flow control model of the present invention.

[0019] Figure 4 This is a schematic diagram showing the relationship between the specific gravity and solid content of the slurry in this invention.

[0020] The meanings of the reference numerals in the attached figures are as follows: 1. Reactor; 2a. First metering pump; 2b. Second metering pump; 3a. First flow meter; 3b. Second flow meter; 4. First level gauge; 5. pH / ammonia concentration composite probe; 6. Online particle size analyzer; 7. Automatic cleaning device; 8. Second level gauge; 9. Online hydrometer; 10. Mold temperature controller; 11. Automatic dispensing valve group; 12. Display screen; 13. DCS control station; 14. Data analysis module; 15. Timing module; 16. Audible and visual alarm module; 17. Reaction parameter detection subsystem; 18. Temperature control system; 19. Feeding subsystem; 20. Data and alarm subsystem; 21. Particle size-expansion rate-time-flow coupling model; 22. Dispensing control model; 23. Multi-input-single output pH / ammonia concentration control model. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1-3 As shown, an automatic control system for synthesizing large-particle-size cobalt carbonate includes a reactor 1. A feeding subsystem 19 is connected to the top of the reactor 1, and a reaction parameter detection subsystem 17 is connected to the feeding subsystem 19. A temperature control system 18 is connected to the side wall of the reactor 1. The feeding subsystem 19, the reaction parameter detection subsystem 17, and the feeding subsystem 19 are all connected to a DCS control station 13. The DCS control station 13 is also connected to a data and alarm subsystem 20.

[0023] The feeding subsystem 19 includes a first metering pump 2a, a second metering pump 2b, a first flow meter 3a, and a second flow meter 3b. The first metering pump 2a and the second metering pump 2b are both connected to the top of the reactor 1. The first flow meter 3a and the second flow meter 3b are both located on both sides of the first metering pump 2a. The first metering pump 2a and the second metering pump 2b are connected to the DCS control station 13.

[0024] The reaction parameter detection subsystem 17 includes a pH / ammonia concentration composite probe 5, an online particle size analyzer 6, a second level gauge 8, and an online hydrometer 9. The pH / ammonia concentration composite probe 5 is connected to an automatic cleaning device 7, and the pH / ammonia concentration composite probe 5, the online particle size analyzer 6, the second level gauge 8, and the online hydrometer 9 are all connected to the DCS control station 13 via 4–20mA+HART.

[0025] The temperature control system 18 includes a mold temperature controller 10, which is connected to a DCS control station 13. The system uses reaction time and target temperature as feedforward quantities, and the temperature control accuracy is ±0.5℃.

[0026] The data and alarm subsystem 20 includes a display screen 12, a data analysis module 14, and an audible and visual alarm module 16, and the display screen 12, the data analysis module 14, and the audible and visual alarm module 16 are all connected to the DCS control station 13.

[0027] The top of the reactor 1 is equipped with a first level gauge 4, and the bottom of the reactor 1 is also connected to an automatic dispensing valve group 11.

[0028] The data and alarm subsystem 20 is connected to the timing module 15.

[0029] The data analysis module 14 includes a particle size-expansion rate-time-flow coupling model 21, a batching control model 22, and a multi-input-single-output pH / ammonia concentration control model 23. The batching control model 22 calculates the cobalt carbonate mass at any given time based on the cobalt solution concentration and flow rate, and calculates the solid content at any given time point based on the volume within the reactor, eliminating the need for manual sampling to measure solid content. The initial solid content of reactor 1 is 0, and the solid content at any time t1 is M(t1). Assuming the first batching time is T1, and the slurry within the reactor is relatively uniform, the solid content at any time t2 after the first batching is M(t2), and this process continues for each batching. , , Where M is the solid content (g / L), m is the mass of cobalt carbonate (g), and V is the slurry volume. Let represent the cobalt conversion rate, n represent the percentage of cobalt carbonate slurry separated, t1 and t2 represent any reaction time, T1 represents the time of the first separation, M(t1) represents the solid content at any time t1, and M(t2) represents the solid content at any time t2.

[0030] Assuming the number of cobalt carbonate nuclei is fixed in the synthesis system, the internal mass distribution of cobalt carbonate is uniform, the particle size is consistent, and the required expansion rate varies for different particle size ranges, then the particle size-expansion rate-time-flow coupling model 21 is: Setting the cobalt carbonate particle size within [D50...] n D50 n+1 The rate of increase within the range is If the time required for this range is t, then .

[0031] With a constant rate of increase, the flow rate will gradually increase as the granularity increases. The granularity at time T1 is D50. T t represents any time period, and its granularity is D50. t The traffic increment is ,but: .

[0032] The multi-input, single-output pH / ammonia concentration control model 23 is as follows: The cobalt carbonate synthesis process is a weakly alkaline system. Different pH / ammonia concentrations are required at different stages of the synthesis process. It is necessary to control the pH / ammonia concentrations within a specified range at fixed times. Due to the lag, manual control is very difficult. It is assumed that the metal liquid flow rate is constant during the synthesis process, and the flow difference between increasing and decreasing the flow rate is the same each time. The pH / ammonia concentration is controlled only by adjusting the flow rate of ammonium bicarbonate. The flow vector of ammonium bicarbonate is... and pH / ammonia concentration vector Cross-correlation analysis was performed to determine the correlation strength between A (ammonium bicarbonate flow rate) and B (pH / ammonia concentration) at different lag times, and the correlation coefficients were obtained, as shown in Table 1. The analysis in the table shows that the correlation coefficient is the largest after the ammonium bicarbonate flow rate is adjusted, indicating that the average lag time of the change in ammonium bicarbonate flow rate to the change in pH / ammonia concentration is about 90 minutes.

[0033] Table 1 The first metering pump 2a and the second metering pump 2b are used to deliver cobalt salt solution and ammonium bicarbonate solution to reactor 1 in parallel at set flow rates. The first flow meter 3a and the second flow meter 3b output flow signals. The pH / ammonia concentration composite probe 5 is used to detect the pH value and ammonia concentration of the slurry in the reactor in real time. The automatic cleaning device 7 cleans the surface of the timed gas-liquid pulse cleaning probe. The online particle size analyzer 6 is used to measure the cobalt carbonate particle size D50 in real time. The second level gauge 8 is used to measure the slurry level in the reactor in real time and calculate the volume. The automatic dispensing valve group 11 is used to meet the following conditions: Automatic batch separation is achieved when conditions are set. The DCS control station 13 is used to realize closed-loop control of particle size, constant pH / ammonia concentration control, automatic batch separation and batch management. The data analysis module 14 has an embedded SPC control chart for real-time statistical process control. The timing module 15 is used to record the cumulative time of a single reaction and the batch cycle. The audible and visual alarm module 16 is used to issue an alarm and push information to the central control room when any key parameter exceeds the ±3σ control limit. The DCS control station 13 communicates with the upper-level MES system through the OPCUA interface to realize batch data traceability.

[0034] The automatic cleaning device 7 adopts a timed gas-liquid pulse structure, and the cleaning cycle can be set within the range of 3–5 hours. The online particle size analyzer 6 is based on the principle of laser diffraction, with a measurement range of 0.1–3000µm and a data update frequency of ≤1min. The automatic dispensing valve group 11 is interlocked with a pneumatic ball valve and a mass flow meter, with a dispensing accuracy of ±1%. The DCS control station 13 calculates the theoretical solid content through the dispensing control model 22 and makes a dual judgment with the particle size D50 target value to trigger automatic dispensing without manual sampling. The DCS control station 13 links the second liquid level gauge 8 and the online hydrometer 9 through the linear model Y=aX+b to achieve precise liquid dispensing at the target specific gravity. The working range of the first metering pump 2a and the second metering pump 2b is controlled within 30%–100% of the rated flow rate to reduce energy consumption and maintain efficient operation.

[0035] The display screen 12 displays the flow rate, pH / ammonia concentration, D50, solid content, and cumulative reaction time in real time. The data analysis module 14 uses the SPC control chart. When any parameter exceeds ±3σ, the audible and visual alarm module 16 is activated and pushes the abnormal information to the central control room.

[0036] Proportioning and water replenishment control: The online hydrometer 9 and the second level gauge 8 are linked. The DCS control station 13 automatically calculates the water replenishment amount according to Y=aX+b, where Y is the water replenishment mass and X is the current specific gravity, so as to achieve accurate liquid preparation at the target specific gravity.

[0037] Timing and Batch Management: The timing module 15 records the cumulative reaction time for a single operation and automatically generates a batch report. The DCS control station 13 uploads the report to the upper-level MES via OPCUA, enabling full-process traceability.

[0038] Control Logic: Particle Size Closed-Loop Control: The online particle size analyzer 6 sends the D50 value to the DCS control station 13. The DCS control station 13 calculates the cobalt salt flow correction value through the particle size-expansion rate-time coupling model 21 and sends it to the variable metering pump to achieve D50 fluctuation of ±0.1µm.

[0039] pH / ammonia concentration control: A multi-input-single-output pH / ammonia concentration control model 23 is established. Under constant temperature and stirring conditions, the flow ratio of cobalt salt to ammonium bicarbonate is a fixed value. The DCS control station 13 adjusts the flow rate of ammonium bicarbonate in real time to keep the pH and ammonia concentration constant.

[0040] Dispensing / Stop-of-Dispenser Control: A dispensing control model 22 is established. The automatic dispensing valve group 11 is triggered by the DCS control station 13 based on the dual logic of "theoretical solid content (confirmed by slurry specific gravity) ≥ set threshold and particle size D50 reaches the target value." This eliminates the need for manual sampling to measure solid content (or slurry specific gravity). Since the slurry specific gravity measurement takes less time and can be performed in real-time using a specific gravity meter, automated measurement is achieved. To prevent errors in the theoretically calculated solid content due to abnormal flow data during synthesis, the relationship between slurry specific gravity and solid content needs to be considered. Figure 4 As shown, the accuracy of the solid content data obtained through theoretical calculations is confirmed.

[0041] Process flow: The synthesis process of cobalt carbonate is "solution preparation - synthesis - aging - washing", with the synthesis stage being the core step. Solution preparation: Prepare cobalt-containing solutions (cobalt sulfate, cobalt chloride, or cobalt nitrate) and ammonium bicarbonate separately, and filter to remove impurities. Synthesis: In reactor 1 equipped with stirring, temperature control, and online pH monitoring (or ammonia concentration), a certain volume of deionized water or dilute mother liquor is first added as a base liquid, and the temperature is raised to the process temperature; Continuous feeding: Cobalt salt solution and precipitant are simultaneously pumped into the reactor at the set flow rate, maintaining a constant molar ratio and pH range; Dynamic concentration: As the liquid level rises to the "full reactor" mark or the required liquid level, the concentration program is started—the clear liquid is continuously extracted through microfiltration, causing the solid content in the reactor to gradually increase; Reactor separation and circulation: When the solid content reaches the process set value, the reactor is immediately separated, and about 1 / 2, 1 / 3, or 1 / 4 of the slurry is transferred to the next stage aging reactor, causing the liquid level in the reactor to drop sharply; Then, feeding continues, and the liquid level slowly rises again to the full reactor or the required liquid level, and concentration and separation are repeated; Repeat: The "feeding-concentration-separation" cycle shown is repeated 3–5 times until the cobalt carbonate particle size D50 reaches the target value, usually 16-25µm. Throughout the process, temperature, pH or ammonia concentration, stirring speed, and separation timing are all controlled in a closed loop by DCS control station 13 to ensure narrow particle size distribution and regular crystal morphology. Aging: After the final separation, the slurry is transferred to an aging tank and stirred at low speed at the same temperature to allow for further crystal growth, defect repair, and crystal stabilization. Subsequent processing: Separation and countercurrent washing are performed sequentially to remove impurities such as Cl⁻, yielding the finished cobalt carbonate product.

[0042] Specifically, taking cobalt carbonate with a target D50 of 20.2µm and a solid content of 158g / L as an example, the system operates according to the following steps: Step 1: Input the target parameters on display screen 12; The second step involves the DCS control station 13 automatically replenishing water to the ammonium bicarbonate solution tank and adjusting it to a specific gravity of 1.075 g / cm³, and automatically replenishing water to the cobalt salt solution tank and adjusting it to a specific gravity of 1.212 g / cm³. Step 3: Raise the temperature to 40℃ and stabilize it within ±0.5℃; Step 4: Start the first metering pump 2a and the second metering pump 2b to feed in parallel flow, with a cobalt salt flow rate of 3.5 L / min and an ammonium bicarbonate flow rate of 4.2 L / min; Step 5: When the particle size analyzer 6 measures D50H = 11.8µm and the expansion rate is greater than 0.15, the DCS control station 13 fine-tunes the cobalt salt flow rate to 3.3L / min. Step 6: When the cumulative reaction time reaches 6 hours and the theoretical solid content is ≥158g / L, and the particle size reaches 16µm, the reaction mixture is automatically separated into individual batches. Step 7: After the batch is completed, the system will automatically clean and generate a PDF report.

Claims

1. An automatic control system for synthesizing large-particle-size cobalt carbonate, characterized in that: The reactor includes a reactor (1), a feeding subsystem (19) connected to the top of the reactor (1), a reaction parameter detection subsystem (17) connected to the feeding subsystem (19), a temperature control system (18) connected to the side wall of the reactor (1), the feeding subsystem (19), the reaction parameter detection subsystem (17) and the feeding subsystem (19) are all connected to the DCS control station (13), and the DCS control station (13) is also connected to the data and alarm subsystem (20); The feeding subsystem (19) includes a first metering pump (2a), a second metering pump (2b), a first flow meter (3a), and a second flow meter (3b). The first metering pump (2a) and the second metering pump (2b) are both connected to the top of the reactor (1). The first flow meter (3a) and the second flow meter (3b) are both located on both sides of the first metering pump (2a). The first metering pump (2a) and the second metering pump (2b) are connected to the DCS control station (13). The reaction parameter detection subsystem (17) includes a pH / ammonia concentration composite probe (5), an online particle size analyzer (6), a second level gauge (8), and an online hydrometer (9). The pH / ammonia concentration composite probe (5) is connected to an automatic cleaning device (7), and the pH / ammonia concentration composite probe (5), the online particle size analyzer (6), the second level gauge (8), and the online hydrometer (9) are all connected to the DCS control station (13). The temperature control system (18) includes a mold temperature controller (10), and the mold temperature controller (10) is connected to the DCS control station (13); The data and alarm subsystem (20) includes a display screen (12), a data analysis module (14), and an audible and visual alarm module (16), and the display screen (12), the data analysis module (14), and the audible and visual alarm module (16) are all connected to the DCS control station (13).

2. The automatic control system for synthesizing large-particle-size cobalt carbonate according to claim 1, characterized in that: The reactor (1) is equipped with a first level gauge (4) at the top and an automatic dispensing valve group (11) at the bottom.

3. The automatic control system for synthesizing large-particle-size cobalt carbonate according to claim 1, characterized in that: The data and alarm subsystem (20) is connected to a timing module (15).

4. The automatic control system for synthesizing large-particle-size cobalt carbonate according to claim 1, characterized in that: The data analysis module (14) includes a particle size-expansion rate-time-flow coupling model (21), a separate vessel control model (22), and a multi-input-single-output pH / ammonia concentration control model (23). The separate vessel control model (22) is as follows: ， ； Where M is the solid content (g / L), m is the mass of cobalt carbonate (g), and V is the slurry volume. Let t1 be the cobalt conversion rate, n be the percentage of cobalt carbonate slurry separated out, t1 and t2 be any reaction time, T1 be the time of the first separation, M(t1) be the solid content at any time t1, and M(t2) be the solid content at any time t2. The particle size-expansion rate-time-flow coupling model (21) is as follows: The cobalt carbonate particle size is set at [D50]. n D50 n+1 The rate of increase within the range is If the time required for this range is t, then ； With a constant rate of increase, the flow rate will gradually increase as the granularity increases. The granularity at time T1 is D50. T t represents any time period, and its granularity is D50. t Traffic increment is ,but: 。

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