Multi-stage preheater control system for high-pressure acid leaching process
By adopting a multi-stage preheater control system in the high-pressure acid leaching process, and using a cascade control system and frequency converter to regulate the feed pump frequency, the problem of stable operation and automatic control of the multi-stage preheater was solved, thereby improving production efficiency and safety.
Patent Information
- Application Number
- CN202520070839.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-10
- Publication Date
- 2026-01-09
- Estimated Expiration
- 2035-01-10
AI Technical Summary
Existing slurry preheating control systems are difficult to simultaneously ensure the stable operation of multiple preheaters and are difficult to automate, which can easily lead to production inefficiencies and safety hazards. The systems are also complex and difficult to apply in practice.
A multi-stage preheater control system is adopted, including a feed flow controller, a level controller, a flow meter, and a level meter connected in series to form an independent cascade control system. The operating frequency of the feed pump is adjusted by a frequency converter to achieve stable and automated control of each stage of the preheater.
Stable and independent control of multi-stage preheaters has been achieved, reducing system complexity and cost, improving production efficiency and safety, reducing the impact of failures, and enhancing control accuracy and stability.
Smart Images
Figure CN223783059U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of high-pressure acid leaching technology, and particularly to a multi-stage preheater control system for high-pressure acid leaching process. Background Technology
[0002] High-pressure acid leaching is an important metal (especially non-ferrous metal) extraction technology. Due to its high efficiency, environmental friendliness, and energy saving, it is widely used in metallurgy, chemical industry, and other fields. The preheating process is a fundamental and crucial step in high-pressure acid leaching, involving the treatment of the ore slurry. The ability to stably control the ore slurry preheating process significantly impacts the process parameters, production efficiency, and product quality. During ore slurry preheating, relevant parameters fluctuate frequently, equipment loads are high, and the process mechanism is complex, especially the preheater liquid level, which fluctuates dramatically during production. Failure to effectively control the ore slurry preheating process will not only affect the production efficiency and quality of high-pressure acid leaching but may also pose serious safety hazards.
[0003] Existing slurry preheating control systems struggle to ensure the stable operation of each stage of a multi-stage preheater simultaneously. Furthermore, they often lack full automation, requiring manual intervention from operators. Additionally, some slurry preheating control systems are overly complex and impractical for high-pressure acid leaching processes. Utility Model Content
[0004] This application is made in view of the aforementioned state of the prior art. The purpose of this application is to provide a multi-stage preheater control system for a high-pressure acid leaching process, used to control the multi-stage preheater of the high-pressure acid leaching process so that each stage preheater can be stably and independently automated.
[0005] This application provides a multi-stage preheater control system for a high-pressure acid leaching process, which is used to control the multi-stage preheater used in the high-pressure acid leaching process. The multi-stage preheater includes at least two preheaters connected in series, and each stage of the preheater includes a cascade control system.
[0006] The cascade control system includes:
[0007] One or more feed pumps are used to introduce slurry into the preheater for slurry preheating;
[0008] A feed flow controller is used to regulate the feed flow rate of the feed pump;
[0009] A level controller is used to regulate the slurry level in the preheater;
[0010] A flow meter, which is communicatively connected to the feed flow controller, is used to monitor the feed flow and transmit the feed flow information to the feed flow controller;
[0011] A level gauge, which is communicatively connected to the level controller, is used to monitor the slurry level and transmit the slurry level information to the level controller.
[0012] The feed flow controller, the flow meter, and the feed pump form the secondary loop of the cascade control system; the level controller, the level meter, the feed flow controller, and the feed pump form the main loop of the cascade control system, with the feed flow controller and the level controller connected in series.
[0013] In at least one possible implementation, the cascade control system further includes one or more frequency converters, and the feed flow controller is connected to the feed pump via the frequency converters to regulate the operating frequency of the feed pump through the frequency converters, thereby affecting the feed flow rate and the slurry level.
[0014] In at least one possible implementation, at least one of the cascade control systems includes one of the frequency converters and a plurality of the feed pumps, the frequency converter being selectively connected to one of the feed pumps; and / or
[0015] At least one of the cascade control systems includes an equal number of the frequency converters and the feed pumps, with each frequency converter connected to one of the feed pumps.
[0016] In at least one possible implementation, the secondary loop and the primary loop respectively form closed-loop control loops, and the feed flow controller and the liquid level controller are both reaction controllers, so that the secondary loop and the primary loop respectively form negative feedback regulation.
[0017] In at least one possible implementation, the feed flow controller and / or the level controller is a proportional-integral-derivative controller.
[0018] In at least one possible implementation, the proportional-integral-derivative controller is configured to include a proportional control algorithm and an integral control algorithm to improve the control accuracy and control stability of the cascade control system.
[0019] In at least one possible implementation, the feed flow controller and / or the level controller are configured to include an automatic control mode and a manual control mode.
[0020] In at least one possible implementation, the level gauge is a radioactive level gauge.
[0021] In at least one possible implementation, the multi-stage preheater includes a first preheater, a second preheater, and a third preheater connected in series; the first preheater includes a single-stage cascade control system, the second preheater includes a two-stage cascade control system, and the third preheater includes a three-stage cascade control system.
[0022] The primary cascade control system includes a primary frequency converter, a first-stage feed pump, and a second-stage feed pump. The primary frequency converter can be selectively connected to either the first-stage feed pump or the second-stage feed pump.
[0023] The two-stage cascade control system includes two two-stage frequency converters, a first two-stage feed pump, and a second two-stage feed pump. The first two-stage feed pump and the second two-stage feed pump are respectively connected to one of the two-stage frequency converters.
[0024] The three-stage cascade control system includes three three-stage frequency converters and a first three-stage feed pump, a second three-stage feed pump, and a third three-stage feed pump. The first three-stage feed pump, the second three-stage feed pump, and the third three-stage feed pump are each connected to one of the three-stage frequency converters.
[0025] In at least one possible implementation, the cascade control system of the multi-stage preheaters is connected in series to form overall control over the multi-stage preheaters.
[0026] The multi-stage preheater control system for the high-pressure acid leaching process provided in this application can achieve relatively stable and independent automated control of each preheater in the multi-stage preheater, thereby effectively improving the control level of the preheating process in the high-pressure acid leaching process. Cascade control of each preheater in the multi-stage preheater can reduce the complexity of the control system while ensuring the stability of the liquid level and feed flow rate of each preheater, saving control system costs and facilitating debugging and maintenance. It also avoids a significant impact on other preheaters when a failure occurs in one stage of the multi-stage preheater. Setting the preheater feed flow rate as a secondary variable in the secondary loop of the cascade control system for regulation can effectively and quickly overcome feed flow rate disturbances in the preheaters, improving the operational stability of the multi-stage preheater. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of a cascade control system according to one embodiment of this application.
[0028] Figure 2 This is a schematic diagram of a single-stage cascade control system according to one embodiment of this application.
[0029] Figure 3 This is a simplified circuit diagram of a cascade control system according to one embodiment of this application.
[0030] Explanation of reference numerals in the attached figures
[0031] 10. Single-stage cascade control system
[0032] 11. Primary feed flow controller
[0033] 12. Primary liquid level controller
[0034] 13. Primary flow meter
[0035] 14. Level gauge
[0036] 15. Primary feed pump
[0037] 16 motors
[0038] 20 Two-stage cascade control system
[0039] 21 Secondary feed flow controller
[0040] 22 Secondary liquid level controller
[0041] 23 Secondary flow meter
[0042] 24 Secondary level gauge
[0043] 25 First and Second Stage Feed Pumps
[0044] 26 Second and Secondary Feed Pumps
[0045] 30 Three-stage cascade control system
[0046] 31 Three-stage feed flow controller
[0047] 32 Three-level liquid level controller
[0048] 33 Three-stage flow meter
[0049] 34. Three-stage liquid level gauge
[0050] 35 First and third stage feed pumps
[0051] 36 Second and third stage feed pumps
[0052] 37 Third-stage feed pump
[0053] 100 First Preheater
[0054] 200 Second preheater
[0055] 300 Third Preheater Detailed Implementation
[0056] Exemplary embodiments of this application are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are for teaching those skilled in the art how to implement this application only, and are not intended to exhaustively describe all possible methods of this application, nor to limit the scope of this application.
[0057] In this application, the “connection” between two objects can include a direct connection, an indirect connection through a structure such as a pipe, an electrical connection, and a communication connection (including wired communication connections and wireless communication connections).
[0058] The embodiments of this application provide a multi-stage preheater control system (hereinafter, sometimes simply referred to as the "control system") for a high-pressure acid leaching process, which can be used to control the operation of the multi-stage preheater in the high-pressure acid leaching process equipment, and in particular, can be used to control the operation of each feed pump of the multi-stage preheater.
[0059] In high-pressure acid leaching processes, the slurry needs to be preheated before being added to the pressurized reactor for the high-pressure acid leaching reaction. Using multi-stage (two or more stages) preheaters for slurry preheating can achieve a stable supply of preheated slurry, ensure a smooth heating process, and improve thermal efficiency. However, in multi-stage preheaters, the liquid level inside the preheater is subject to frequent dynamic parameter fluctuations due to various factors. Simple single-loop control systems are insufficient to meet the process requirements of maintaining stable slurry level and temperature during preheating.
[0060] The multi-stage preheater control system for the high-pressure acid leaching process provided in this application can include a relatively independent cascade control system for each preheater (not directly affected by other preheaters). It is understood that having a relatively independent cascade control system for each preheater can prevent a failure in one preheater from directly affecting the normal operation of the remaining preheaters. Having a relatively independent cascade control system for each preheater also helps to maintain a stable slurry level and feed flow rate within each preheater. Furthermore, compared to setting an overall control system for the multi-stage preheaters, setting a separate cascade control system for each preheater can save on control system costs, reduce the complexity of the control system, and decrease the difficulty of debugging and maintenance.
[0061] Specifically, such as Figure 1As shown, the cascade control system for each preheater may include a feed flow controller (QC), a level controller (LC), a flow meter (flow transmitter, QIT / QT), a level gauge (level transmitter, LIT / LT), one or more feed pumps, and one or more frequency converters. The feed flow controller can be a secondary controller (secondary regulator) of the cascade control system, used to adjust the feed flow rate of the feed pump based on the feed flow information. The level controller can be the primary controller (primary regulator) of the cascade control system, used to adjust the liquid level in the preheater based on the liquid level information. The feed pump and frequency converter can be actuators of the cascade control system, used to introduce material (slurry) into the preheater, and their operating state (especially the operating frequency) can affect (including directly and indirectly) the liquid level and feed flow rate of the preheater. The feed flow rate of the preheater can be a secondary variable (secondary controlled parameter) of the cascade control system, and the slurry level of the preheater can be a primary variable (primary controlled parameter) of the cascade control system.
[0062] Flow meters can be used to monitor the feed flow rate of the preheater's feed pump and transmit the feed flow rate information to the feed flow controller. Level gauges can be used to monitor the slurry level in the preheater and transmit the level information to the level controller. The feed pump can be connected to a frequency converter (VDC). Upon receiving a control signal (especially from the feed flow controller), the VDC can change its output frequency, thereby altering the feed pump's speed to regulate the feed flow rate and adjust its feeding capacity. When the cascade control system includes multiple VDCs, the feed flow controller can simultaneously send control signals to multiple VDCs. Multiple feed pumps can also be connected to the same VDC.
[0063] Preferably, the level gauge can be a radioactive level gauge, which measures the liquid level in the container based on the "ray absorption principle". This type of level gauge can adapt to various harsh working environments such as high temperature, high pressure, viscous materials and solid particulate materials, and is suitable for use in the preheating process of high-pressure acid leaching.
[0064] It is understandable that the slurry level in the preheater has high sensitivity to changes, which can significantly impact the preheating process and subsequent product quality. Due to its stringent process requirements, it is suitable as the primary variable in a cascade control system. Fluctuations in the feed flow rate of the preheater are the main disturbance in the slurry preheating process, exhibiting significant nonlinear characteristics. Cascade control systems have good adaptability to the nonlinear characteristics of secondary variables and can effectively overcome and suppress disturbances in these secondary variables. Therefore, the feed flow rate of the preheater is suitable as a secondary variable in a cascade control system. Setting a secondary variable can improve the control quality of the primary variable; that is, by promptly overcoming disturbances in the feed flow rate, the control quality of the slurry level can be improved, maintaining a relatively stable slurry level.
[0065] A cascade control system can form a secondary loop (inner loop) and a primary loop (outer loop), and the secondary loop and the primary loop can each form a closed-loop control loop.
[0066] Specifically, the secondary loop may include a feed flow controller, a flow meter, a feed pump, and a frequency converter. The secondary loop can control the feed flow rate of the feed pump based on the feed flow rate information. The primary loop may include a level controller, a level gauge, a feed flow controller, a feed pump, and a frequency converter (the feed flow controller, feed pump, and frequency converter in the secondary loop can theoretically be considered as actuators in the primary loop). The primary loop can control the feed flow rate of the feed pump based on the slurry level information.
[0067] like Figure 1 and Figure 3 As shown, in the secondary loop, the flow meter can be connected (communication connection) to the feed flow controller, enabling the flow meter to transmit the monitored feed flow information to the feed flow controller. The feed flow controller can be connected to a frequency converter to control the output frequency of the frequency converter. In the primary loop, the level gauge can be connected (communication connection) to the level controller, enabling the level gauge to transmit the monitored slurry level information to the level controller. The feed flow controller can be connected in series with the level controller, so that the output information of the level controller can be used as an input information of the feed flow controller, thereby indirectly controlling the output frequency of the frequency converter. In the overall system, the feed flow controller and the level controller working in series can form a closed-loop control system. It can be understood that the level controller can calculate and output control information to the feed flow controller by combining the set value and the slurry level information monitored by the level gauge, and the feed flow controller can calculate and output control information to the feed pump based on the control information output by the level controller and / or the flow information delivered by the flow meter.
[0068] In a cascade control system, both the secondary and primary loops should form negative feedback regulation. In the secondary loop, the feed pump, acting as the actuator, should be configured to stop working when the system is powered off; that is, the actuator is "air-to-air" and acts positively. As the feed pump frequency increases, the feed flow rate to the preheater also increases, meaning the secondary variable, the feed flow rate, also increases, thus the secondary variable acts positively. When both the actuator and the secondary variable in the secondary loop act positively, the secondary controller (feed flow rate controller) needs to be set as a reverse-acting controller to enable negative feedback regulation in the secondary loop. When the primary variable (slurry level) and the secondary variable (feed flow rate) increase, the negative feedback regulation requires the feed pump, acting as the actuator, to reduce its operating frequency to decrease the slurry level and feed flow rate; that is, the actuator's action direction must be consistent when the primary and secondary variables change. Therefore, the primary controller (level controller) also needs to be set as a reverse-acting controller.
[0069] It is understandable that each stage of a multi-stage preheater can be connected in series, and the cascade control systems of each stage of a multi-stage preheater can also be connected in series to control the overall multi-stage preheater system.
[0070] Preferably, the feed flow controller and / or level controller can be a PID controller (proportional-integral-derivative controller). In a cascade control system, the main loop (main controller) plays a setpoint control role, and the secondary loop (secondary controller) plays a follow-up control role. Based on the actual production requirements of the multi-stage preheater, it is necessary to control and reduce the steady-state error of the feed flow (secondary variable) (the deviation between the system state and the command state when external disturbances exist). According to the PID control law, proportional regulation (P) can improve the response speed of the control system and reduce steady-state error, while integral regulation (I) can reduce the steady-state error of the control system. More preferably, both the feed flow controller and the level controller can be PID controllers. Both the feed flow controller and the level controller can be equipped with proportional regulation algorithms and integral regulation algorithms.
[0071] Furthermore, if the proportional coefficient (Kp) in the proportional control algorithm is too large, it may cause excessive overshoot (the ratio of the instantaneous maximum deviation to the steady-state value) in the control system, leading to system oscillations or an increase in the number of oscillations, thus reducing system stability. In this case, the Kp value can be appropriately reduced to decrease the effect of proportional control, gradually reducing the oscillations, lengthening the oscillation period, and increasing the damping ratio, thereby enhancing system stability. During the adjustment process of the main controller and the slave controller, if the oscillation period is too long, the integral coefficient (Ki) in the integral control algorithm can be appropriately reduced to increase the effect of integral control, thus intensifying the oscillations, shortening the oscillation period, and reducing the steady-state error. Conversely, if the oscillations are too severe during the controller's adjustment process, the integral coefficient (Ki) can be increased to reduce the effect of integral control.
[0072] Preferably, both the main circuit and the auxiliary circuit (i.e., the level controller and the feed flow controller) can include both manual and automatic control modes. The following is a brief description of how the feed flow controller and the level controller operate in automatic and manual control modes, respectively.
[0073] If both the feed flow controller and the level controller are in automatic control mode, the cascade control system only needs to input the set value of the feed flow and the relevant parameters of the calibrated PID controller (including the feed flow controller and the level controller) to achieve automatic control of the primary preheater.
[0074] When the level controller is in automatic control mode, its output can be the setpoint of the feed flow controller. The level controller can then output a corresponding control signal based on the setpoint, the measured actual level information, and the PID algorithm configured in the level controller. Similarly, when the feed flow controller is in automatic control mode, it can output a corresponding control signal based on the input feed flow setpoint (from the level controller or manually input) and the measured actual feed flow value, combined with the PID algorithm configured in the feed flow controller.
[0075] When the level controller is in manual operation mode, the operating frequency of the feed pump (or the feed flow rate of the feed pump) can be a manually set value within the set range. When the feed flow controller is in manual control mode, the operating frequency of the feed pump (or the feed flow rate of the feed pump) can be a manually set value within the set range, and at this time, the slurry level in the preheater, as the main variable, will also be input into the level controller as its set value.
[0076] Preferably, the multi-stage preheater can be a three-stage preheater. For example... Figure 3 As shown, the three-stage preheater may include a first preheater 100, a second preheater 200, and a third preheater 300 connected in series with gradually increasing preheating temperatures. The first preheater 100, the second preheater 200, and the third preheater 300 are connected in series to progressively increase the temperature of the slurry material.
[0077] The first preheater 100 can be equipped with a single-stage cascade control system 10, the second preheater 200 can be equipped with a two-stage cascade control system 20, and the third preheater 300 can be equipped with a three-stage cascade control system 30. Correspondingly, the single-stage cascade control system 10 may include a single-stage feed flow controller 11, a single-stage level controller 12, a single-stage flow meter 13, and a single-stage level meter 14. The two-stage cascade control system 20 may include a single-stage feed flow controller 21, a single-stage level controller 22, a single-stage flow meter 23, and a single-stage level meter 24. The three-stage cascade control system 30 may include a single-stage feed flow controller 31, a single-stage level controller 32, a single-stage flow meter 33, and a single-stage level meter 34. The cascade control system within each preheater can employ the aforementioned component connection relationships and operating methods.
[0078] More preferably, such as Figure 2 and Figure 3As shown, the first-stage cascade control system 10 may include two first-stage feed pumps 15, namely a first-stage feed pump and a second-stage feed pump. Each first-stage feed pump 15 may be connected to a motor 16 (or the feed pump itself may include a motor). The first-stage cascade control system 10 may also include a (first-stage) frequency converter connected to either the first-stage or second-stage feed pump. In actual production, the operator of the control system can choose to connect the frequency converter to either the first-stage or second-stage feed pump. The performance parameters of the first-stage and second-stage feed pumps may be the same or different. It is understood that setting up two selectable first-stage feed pumps 15 enables alternating operation of the first-stage feed pumps, thereby extending their service life and facilitating their maintenance. When the performance parameters of the two first-stage feed pumps are different, the first-stage feed pump with the most suitable performance parameters can be selected for feeding operations according to actual production needs.
[0079] like Figure 3 As shown, the two-stage cascade control system 20 may include two two-stage feed pumps, namely a first two-stage feed pump 25 and a second two-stage feed pump 26. The first two-stage feed pump 25 and the second two-stage feed pump 26 can each be connected to a (two-stage) frequency converter. The first two-stage feed pump 25 and the second two-stage feed pump 26 can be connected in series. The three-stage cascade control system 30 may include three three-stage feed pumps, namely a first three-stage feed pump 35, a second three-stage feed pump 36, and a third three-stage feed pump 37. The first three-stage feed pump 35, the second three-stage feed pump 36, and the third three-stage feed pump 37 can each be connected to a (three-stage) frequency converter. The first three-stage feed pump 35, the second three-stage feed pump 36, and the third three-stage feed pump 37 can be connected in series. It can be understood that connecting multiple feed pumps in series can effectively increase the pump head without significantly changing the flow rate.
[0080] After preheating by a multi-stage preheater, the slurry can be pumped into a pressurized reactor for high-pressure acid leaching. Preferably, the preheated slurry can be pumped into the pressurized reactor by a diaphragm pump. The diaphragm pump can be a fixed-frequency diaphragm pump.
[0081] The embodiments of this application also provide a method for operating a multi-stage preheater control system for a high-pressure acid leaching process (hereinafter sometimes simply referred to as the "operating method"). Here, the cascade control system of the three-stage preheater described above will be used as an example for explanation.
[0082] Working methods may include:
[0083] In the secondary loop adjustment process, the feed flow meter can monitor the feed flow and transmit the feed flow information to the feed flow controller. The feed flow controller can adjust the working status of the feed pump to affect the feed flow.
[0084] In the main circuit regulation process, the level gauge monitors the slurry level and transmits the information to the level controller. The level controller then transmits the regulation information to the feed flow controller, which adjusts the operating status of the feed pump to influence the slurry level.
[0085] The working method may also include the commissioning method, which puts the multi-stage preheater and its control system into actual production.
[0086] When the control system is actually put into use, its highest-level preheater (the third preheater 300 in the aforementioned three-stage preheater) is connected to the pressure vessel to introduce slurry into it, thus the discharge flow rate of the highest-level preheater is relatively stable. During the actual operation of the multi-stage preheater, the automatic control mode of the highest-level level controller (main controller) can be activated first, followed by the automatic control mode of the corresponding highest-level feed flow controller (secondary controller). After the highest-level preheater and its control system stabilize, the lower-level level controllers and feed flow controllers can be sequentially put into automatic control mode. If the higher-level preheater fails to meet the relevant parameter requirements for stable operation, the relevant parameter settings of the controllers (especially the secondary controllers) can be corrected and adjusted until the preheater can operate stably and meet the relevant requirements before activating the controllers of the lower-level preheaters. That is, in a three-stage preheater system, the third preheater 300, the second preheater 200, and the first preheater 100 are put into operation sequentially. Within a single preheater, the actual commissioning operation is carried out in the order of first activating the liquid level flow controller and then the feed flow controller. This commissioning method can quickly find the system equilibrium point of the multi-stage preheater, reducing the preparation time for commissioning the multi-stage preheater and its control system. Here, "commissioning" specifically means connecting the controller (in its automatic control mode) to the multi-stage preheater to regulate the slurry preheating process.
[0087] The following is a brief description of some of the beneficial effects of the above-described embodiments of this application.
[0088] The multi-stage preheater control system and its operating method for a high-pressure acid leaching process provided in this application form a relatively stable and independent automated control for each stage of the multi-stage preheater, effectively improving the control level of the preheating process in the high-pressure acid leaching process. Cascade control of each stage of the multi-stage preheater ensures stable liquid level and feed flow rate in each stage while reducing the complexity of the control system, saving control system costs, and facilitating debugging and maintenance. It also prevents a significant impact on other preheaters from a single stage failure. Adjusting the preheater feed flow rate as a secondary variable in the secondary loop of the cascade control system effectively and quickly overcomes feed flow rate disturbances, improving the operational stability of the multi-stage preheater. Furthermore, both the feed flow controller and the liquid level controller in the control system can be PID controllers; by setting proportional and integral adjustment algorithms within the controllers, the control accuracy and stability of the control system can be improved.
[0089] It is understood that, in this application, when the number of parts or components is not specifically limited, the number can be one or more, where multiple refers to two or more. For cases where the number of parts or components shown in the drawings and / or described in the specification is, for example, two, three, four, etc., this specific number is generally exemplary and not restrictive, and can be understood as multiple, i.e., two or more; however, this does not mean that this application excludes the case of one.
[0090] It should be understood that the above embodiments are merely exemplary and are not intended to limit this application. Those skilled in the art can make various modifications and changes to the above embodiments under the teachings of this application without departing from the scope of this application.
Claims
1. A multi-stage preheater control system for a high pressure acid leach process, characterized by, A multi-stage preheater for controlling a high-pressure acid leaching process, the multi-stage preheater comprising at least two stages of preheaters connected in series, each stage of the preheaters comprising a cascade control system, the cascade control system comprising: one or more feed pumps for feeding ore slurry into the preheaters for preheating the ore slurry; a feed flow controller for regulating a feed flow rate of the feed pumps; a liquid level controller for regulating a liquid level of the ore slurry in the preheaters; a flow meter in communication with the feed flow controller for monitoring the feed flow rate and transmitting feed flow rate information to the feed flow controller; a liquid level meter in communication with the liquid level controller for monitoring the liquid level of the ore slurry and transmitting liquid level information to the liquid level controller; the feed flow controller, the flow meter and the feed pumps form a secondary loop of the cascade control system; the liquid level controller, the liquid level meter, the feed flow controller and the feed pumps form a primary loop of the cascade control system, the feed flow controller and the liquid level controller being connected in series.
2. The multi-stage preheater control system for a high pressure acid leach process of claim 1, wherein, the cascade control system further comprises one or more frequency converters, the feed flow controller connecting the feed pumps via the frequency converters to regulate operating frequencies of the feed pumps via the frequency converters, thereby affecting the feed flow rate and the liquid level of the ore slurry.
3. The multi-stage preheater control system of the high-pressure acid leaching process according to claim 2, wherein: at least one of the cascade control systems comprises one of the frequency converters and a plurality of the feed pumps, the frequency converter being selectively connected to one of the feed pumps; and / or at least one of the cascade control systems comprises an equal number of the frequency converters and the feed pumps, each of the frequency converters being connected to one of the feed pumps.
4. The multi-stage preheater control system for a high pressure acid leach process of claim 1, wherein, the secondary loop and the primary loop form closed-loop control loops respectively, the feed flow controller and the liquid level controller being both reaction controllers, so that the secondary loop and the primary loop form negative feedback adjustments respectively.
5. The multi-stage preheater control system for a high pressure acid leach process of claim 1, wherein, the feed flow controller and / or the liquid level controller is a proportional-integral-derivative controller.
6. The multi-stage preheater control system for a high pressure acid leach process of claim 5, wherein, the proportional-integral-derivative controller is configured to include a proportional adjustment algorithm and an integral adjustment algorithm to improve control accuracy and control stability of the cascade control system.
7. The multi-stage preheater control system for a high pressure acid leach process of claim 1, wherein, the feed flow controller and / or the liquid level controller is configured to include an automatic control mode and a manual control mode.
8. The multi-stage preheater control system for a high pressure acid leach process of claim 1, wherein, the liquid level meter is a radioactive liquid level meter.
9. The multi-stage preheater control system for a high pressure acid leach process of claim 1, wherein, the multi-stage preheater comprises a first preheater, a second preheater and a third preheater connected in series, the first preheater comprising a first cascade control system, the second preheater comprising a second cascade control system, and the third preheater comprising a third cascade control system, the first cascade control system comprises a first frequency converter and a first feed pump and a second feed pump, the first frequency converter being selectively connected to the first feed pump or the second feed pump; The secondary cascade control system comprises two secondary frequency converters and a first secondary feed pump and a second secondary feed pump, and the first secondary feed pump and the second secondary feed pump are connected with one of the secondary frequency converters respectively; The tertiary cascade control system comprises three tertiary frequency converters and a first tertiary feed pump, a second tertiary feed pump and a third tertiary feed pump, and the first tertiary feed pump, the second tertiary feed pump and the third tertiary feed pump are connected with one of the tertiary frequency converters respectively.
10. The multi-stage preheater control system for a high pressure acid leach process of claim 1, wherein, The cascade control systems of the multi-stage preheaters are connected in series in turn to form a control of the whole multi-stage preheaters.