A control method of a two-compartment alternating agitation dosing system

Abstract

The application provides a control method of a two-compartment alternating stirring and dosing system, which comprises the following steps: continuously monitoring the liquid level of a current dosing tank, and determining whether the liquid level drops to a pre-warning liquid level, wherein the pre-warning liquid level is higher than a switching liquid level; when the liquid level of the current dosing tank drops to the pre-warning liquid level, starting a stirrer in a standby tank to perform re-stirring; after the re-stirring is completed, performing static setting and exhaust on the standby tank; wherein the re-stirring and the static setting and exhaust are both completed before the liquid level of the current dosing tank drops to the switching liquid level; when the liquid level of the current dosing tank drops to the switching liquid level, stopping the dosing of the current dosing tank, and starting the standby tank to perform dosing. The application can reduce the risk of uneven liquid concentration and blockage caused by long-time static setting and waiting of the standby tank under the premise of uninterrupted continuous dosing, and ensure that the liquid concentration is uniform and stable when switching the dosing.

Description

Technical Field

[0001] This application relates to the field of drug dosing system technology, and in particular to a control method for a two-compartment alternating stirring dosing system. Background Technology

[0002] In a two-compartment alternating stirring dosing system, two independent tanks are typically used. These two tanks alternately perform the dosing, stirring, maturation, and supply processes to achieve continuous and uninterrupted dosing. Taking the preparation of a commonly used flocculant in water treatment (such as polyacrylamide PAM) as an example, a typical process is as follows: while one tank (called the current supply tank) is in the supplying state, the other tank has completed the "water inlet-dosing-stirring-maturation" process and is in standby mode. The "water inlet-dosing-stirring-maturation" process involves first injecting a measured amount of clean water into the tank, simultaneously adding the powdered or soluble chemical agent in proportion; then starting the stirrer to ensure thorough mixing and dissolution; finally, stopping the stirring and allowing the solution to stand for a period of time to allow the polymer chains to fully extend and hydrate, achieving optimal flocculation activity.

[0003] After curing, the standby tank cannot be immediately put into operation for drug supply; instead, it must wait for the drug solution in the current supply tank to be depleted to the switching level. Since the drug supply rate is affected by downstream process requirements, if the waiting time is too long, the PAM molecular chains in the drug solution may become entangled or exhibit localized concentration gradients. Furthermore, if initial stirring is insufficient, undissolved gel clumps will gradually settle to the bottom or remain suspended, resulting in uneven drug concentration distribution within the tank. The extraction port is usually located at the bottom of the tank; during drug supply switching, the initial extracted drug concentration is often higher than the later concentration, causing drastic concentration fluctuations that affect flocculation efficiency. Additionally, gel clumps can easily clog pipelines and pump valves. Therefore, there is an urgent need for a control method that can automatically eliminate the risk of uneven drug concentration and clogging caused by prolonged waiting times without interrupting drug supply. Summary of the Invention

[0004] This application proposes a control method for a two-compartment alternating stirring dosing system, which aims to reduce the risk of uneven drug concentration and blockage caused by long-term static waiting of the standby tank without interrupting continuous drug supply, and to ensure uniform and stable drug concentration when switching drug supply.

[0005] The technical solution provided in this application includes:

[0006] A control method for a two-compartment alternating stirring dosing system, the method comprising:

[0007] Continuously monitor the liquid level of the current medicine supply tank to determine whether it has dropped to the warning level, wherein the warning level is higher than the switching level;

[0008] When the liquid level in the current supply tank drops to the warning level, the stirrer in the standby tank is activated to stir again;

[0009] After the re-stirring is completed, the standby tank is allowed to stand still and ventilate; wherein, both the re-stirring and the standing venting are completed before the liquid level in the current supply tank drops to the switching liquid level;

[0010] When the liquid level in the current drug supply tank drops to the switching liquid level, the drug supply from the current drug supply tank is disconnected, and the standby tank is started to supply drugs.

[0011] Furthermore, the re-stirring includes the following steps:

[0012] The stirrer in the standby tank stirs at a first speed for a first preset time;

[0013] Reduce to the second rotation speed and stir for the second preset time;

[0014] Stir in the opposite direction at the second rotation speed for the third preset time.

[0015] Stop stirring.

[0016] Furthermore, the first rotational speed is 30-50 rpm, and the first preset duration is 20-40 seconds;

[0017] The second rotational speed is 10-20 rpm, and the second preset duration is 8-15 seconds;

[0018] The third preset duration is 5-10 seconds.

[0019] Furthermore, the static exhaust includes the following steps:

[0020] After stirring stops, let the standby tank stand for 5-15 seconds;

[0021] At the same time as the settling begins, open the vent valve on top of the standby tank;

[0022] After the venting process is complete, close the exhaust valve.

[0023] Furthermore, activating the standby tank to supply medication includes the following steps:

[0024] The metering pump is controlled to perform a soft start in a stepped, incremental frequency manner;

[0025] During the soft start process, the initial frequency of the metering pump is set to 3%-8% of the rated frequency and lasts for 1.5-3 seconds;

[0026] Then increase the rated frequency by 2%-4% every second until the target operating frequency is reached.

[0027] Furthermore, the warning liquid level is dynamically determined by the estimated duration and the rate of liquid level decline. The estimated duration is the time required for the liquid level to drop from the warning liquid level to the switching liquid level, and the estimated duration is longer than the total time required for re-stirring and venting.

[0028] Furthermore, the estimated duration is 20-60 seconds longer than the total time required for re-stirring and venting.

[0029] Furthermore, if a shutdown is detected, and the liquid level of the current medicine supply tank is located between the warning liquid level and the switching liquid level at the time of shutdown;

[0030] After restarting, calculate the remaining time required for the liquid level of the current medicine supply tank to drop to the switching liquid level, and subtract the remaining time from the estimated time to obtain the time already consumed;

[0031] The current drug supply tank temporarily stops supplying drugs until the standby tank has performed the re-stirring and static venting for the duration of the time already consumed, at which point the current drug supply tank resumes drug supply.

[0032] The technical solution provided in this application has at least the following advantages over the prior art:

[0033] 1. Improve the uniformity of drug concentration during switching: By re-stirring the standby tank when the current supply tank level drops to the warning level, and completing re-stirring and venting before the switching level is reached, the drug solution inside the standby tank is already in a uniform suspension state when supplying drugs. This avoids drug concentration stratification or sediment accumulation caused by prolonged settling, thereby reducing drug concentration fluctuations in the initial and later stages of switching. It also reduces the possibility of high-concentration sediments directly entering the intake port and metering pump during the initial supply phase, thus lowering the probability of blockage.

[0034] 2. Ensure continuous drug supply: Re-stirring and venting are completed in parallel during the current drug supply tank's supply process, without taking up time after switching. Therefore, when the liquid level in the current drug supply tank drops to the switching level, it can seamlessly switch to the standby tank for drug supply, avoiding drug supply interruption. Attached Figure Description

[0035] Figure 1 This is a flowchart of a control method for a two-compartment alternating stirring and dosing system provided in an embodiment of this application. Detailed Implementation

[0036] This specific embodiment is merely an explanation of this application and is not intended to limit it. Those skilled in the art, after reading this specification, can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application. To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0037] The term "comprising" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product or device.

[0038] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0039] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.

[0040] Figure 1 This application provides an exemplary embodiment of a control method for a two-compartment alternating stirring and dosing system, the method comprising:

[0041] S1: Continuously monitor the liquid level of the current medicine supply tank and determine whether it has dropped to the warning level, wherein the warning level is higher than the switching level.

[0042] Specifically, the switching tank's drug supply is triggered only when the liquid level in the current drug supply tank reaches the switching level. In this step, the control system acquires the liquid level value of the current drug supply tank in real time through a liquid level sensor and compares it with the internally stored warning liquid level and switching liquid level. If the warning liquid level is higher than the switching liquid level, the difference between the two needs to ensure sufficient time for subsequent preprocessing. By setting a warning liquid level, the preprocessing of the standby tank is triggered in advance, and the preprocessing action is executed in parallel with the normal drug supply of the current drug supply tank, so that the standby tank is ready when the switch is initiated.

[0043] S2: When the liquid level in the current supply tank drops to the warning level, the stirrer in the standby tank is activated to stir again.

[0044] Specifically, once the control system detects that the liquid level in the current supply tank has reached the warning level, it immediately sends a start command to the agitator in the standby tank to begin re-stirring the liquid that may have undergone concentration stratification or sedimentation due to prolonged standing. The purpose of re-stirring is to restore the liquid in the tank to a uniform suspension state and eliminate the aggregation of gel clumps or concentration stratification at the bottom.

[0045] In some embodiments, the re-stirring includes the following steps:

[0046] The stirrer in the standby tank stirs at a first speed for a first preset time;

[0047] Reduce to the second rotation speed and stir for the second preset time;

[0048] Stir in the opposite direction at the second rotation speed for the third preset time.

[0049] Stop stirring.

[0050] Specifically, to avoid the generation of eddies, air entrainment, and disruption of the uniformity of the drug solution caused by sudden starting and stopping of the stirrer, this embodiment breaks down the re-stirring process into multiple stages:

[0051] First, the mixture is stirred at a relatively high initial rotation speed for a predetermined duration. After prolonged settling, the sediment at the bottom of the tank or areas with high concentrations exhibits high yield stress, requiring sufficient shear force to redisperse it. Preferably, the initial rotation speed is selected as 30-50 rpm to ensure sufficient turbulence intensity to agitate the bottom sediment. If the rotation speed is too low, the sediment cannot be effectively suspended; if the rotation speed is too high (e.g., exceeding 80 rpm), a large number of microbubbles will be generated, potentially shearing and degrading the PAM molecular chains. Furthermore, the first predetermined duration is selected as 20-40 seconds to ensure the sediment layer is completely agitated.

[0052] Next, reduce the rotation speed to a second speed (preferably 10-20 rpm) and stir for a second preset time (preferably 8-15 seconds). After the main suspension is complete, continuing high-speed stirring is unnecessary and will introduce more air bubbles. Reducing the rotation speed to a second speed allows the liquid to transition from strong turbulence to weak turbulence, maintaining a uniform distribution of the already suspended particles with lower energy consumption, while allowing larger air bubbles to begin to rise. This stage creates stable flow conditions for subsequent reverse stirring and static degassing.

[0053] Next, the mixture is stirred in the opposite direction at a second rotation speed for a third preset time (preferably 5-10 seconds). When the stirrer suddenly stops, the liquid inertia creates a continuous rotating flow field. Solid particles, under centrifugal force, aggregate towards the periphery, resulting in a lower concentration in the center and a higher concentration at the edges, ultimately forming an uneven distribution with a higher concentration at the outside and a lower concentration at the inside when the mixture comes to rest. Furthermore, unidirectional rotation creates a vortex depression in the center of the tank; when the mixture suddenly stops, the collapse of this vortex depression can draw air from above the liquid surface into the deeper layers of the liquid. By rotating in the opposite direction at a low speed, the original unidirectional vortex structure can be actively disrupted: the tangential force generated by the reverse rotation is opposite to the original flow direction, causing the momentum in the flow field to dissipate rapidly, and the liquid surface depression to disappear quickly, thus avoiding secondary stratification and air entrainment after the mixture stops.

[0054] Finally, stop stirring. At this point, the medicine solution is in a relatively uniform suspension.

[0055] S3: After the re-stirring is completed, the standby tank is allowed to stand still and ventilate; wherein, both the re-stirring and the standing venting are completed before the liquid level of the current drug supply tank drops to the switching liquid level.

[0056] Specifically, after re-stirring, the control system puts the standby tank into a static state and simultaneously performs venting. The purpose of static setting is to allow the trace bubbles generated during stirring to rise naturally, while venting releases these bubbles outside the tank, preventing them from entering the metering pump with the liquid and causing airlock. Although re-stirring has reduced the number of bubbles through reverse vortex elimination, a small number of tiny bubbles still need time to rise. Of course, the static venting time should not be too long to avoid causing new settling.

[0057] In some embodiments, the static venting includes the following steps:

[0058] After stirring stops, let the standby tank stand for 5-15 seconds;

[0059] At the same time as the settling begins, open the vent valve on top of the standby tank;

[0060] After the venting process is complete, close the exhaust valve.

[0061] S4: When the liquid level of the current drug supply tank drops to the switching liquid level, disconnect the drug supply of the current drug supply tank and start the standby tank to supply drugs.

[0062] Specifically, the control system continues to monitor the liquid level of the current supply tank. When the liquid level reaches the switching level, it immediately closes the bottom inlet valve of the current supply tank to stop supplying medicine. At the same time, it opens the bottom inlet valve of the standby tank and starts the metering pump to draw the medicine from the standby tank. At this time, the medicine in the standby tank has been re-stirred and allowed to settle and degas, and is in a state of uniform suspension with very few bubbles.

[0063] However, even if the medication solution in the standby tank is basically uniform, the impact negative pressure of the metering pump at startup may still draw in a very small amount of residual air bubbles or deposits near the dispensing port. To further smooth the startup process, in some embodiments, starting the standby tank to dispense medication includes the following steps:

[0064] The metering pump is controlled to perform a soft start in a stepped, incremental frequency manner;

[0065] During the soft start process, the initial frequency of the metering pump is set to 3%-8% of the rated frequency and lasts for 1.5-3 seconds;

[0066] Then increase the rated frequency by 2%-4% every second until the target operating frequency is reached.

[0067] The specific meaning of step-increment soft start is that the metering pump does not start directly at the target frequency, but starts from a very low initial frequency, maintains it for a short time, and then gradually increases the frequency until the target frequency is reached. For example, for a metering pump with a rated frequency of 50Hz, the initial frequency is set to 2.5Hz (5%) and held for 2 seconds; then it increases by 1.5Hz (3%) every second, reaching 50Hz after about 12 seconds. Under this starting method, the negative pressure at the pump inlet is gradually built up, rather than reaching its maximum value instantaneously. This achieves the following beneficial effects: First, it avoids the instantaneous strong negative pressure "pulling" any tiny air bubbles that may remain near the dispensing port into the pump chamber, because the air bubbles have a chance to be carried away by the flowing liquid or compressed under the slowly increasing pressure difference, thus preventing airlock; Second, it avoids the instantaneous strong negative pressure sucking in any loose deposits that may exist at the bottom of the tank (even after re-stirring, there may still be a small amount of incompletely suspended micro-dust in the dispensing port area), causing wear or blockage of the pump chamber.

[0068] In some embodiments, the warning liquid level is dynamically determined by the estimated duration and the rate of liquid level decline, wherein the estimated duration is the time required for the liquid level to drop from the warning liquid level to the switching liquid level, and the estimated duration is longer than the total time required for re-stirring and the settling and venting.

[0069] Specifically, the control system first obtains the current liquid level drop rate of the supply tank (the height the liquid level drops per unit time). This rate can be calculated by combining the operating frequency or stroke of the metering pump with the cross-sectional area of ​​the tank, or it can be calculated by continuous sampling from the liquid level sensor.

[0070] Because the rate of liquid level descent changes in real time with the drug supply rate, the warning liquid level is also dynamically adjusted accordingly, eliminating the need for manual setting of a fixed value. This dynamic determination method allows the system to automatically adapt to different operating conditions (such as fluctuations in drug supply rate caused by changes in downstream process requirements), avoiding insufficient pretreatment time due to excessively fast drug supply rate, or prolonged idleness and re-settling after the standby tank has been re-stirred due to excessively slow drug supply rate.

[0071] In some embodiments, the estimated duration is 20-60 seconds longer than the total duration required for re-stirring and venting.

[0072] Specifically, the extra time expected compared to the total time required for re-stirring and venting is a safety margin. This is because some uncertainties exist during actual operation, such as instantaneous fluctuations in the rate of liquid level drop (e.g., fine-tuning of the metering pump stroke), sensor sampling errors, and stirrer start-up delays. These disturbances may cause the current drug supply tank level to drop to the switching level before the re-stirring and venting are completed, forcing the system to switch in an incomplete state and affecting the quality of drug dosing. However, the expected time should not be too long. If the standby tank remains in a static state for an extended period after pretreatment, slight concentration stratification may occur again, weakening the pretreatment effect.

[0073] In some embodiments, if a shutdown is detected, and the liquid level of the current drug supply tank is located between the warning liquid level and the switching liquid level at the time of shutdown;

[0074] After restarting, calculate the remaining time required for the liquid level of the current medicine supply tank to drop to the switching liquid level, and subtract the remaining time from the estimated time to obtain the time already consumed;

[0075] The current drug supply tank temporarily stops supplying drugs until the standby tank has performed the re-stirring and static venting for the duration of the time already consumed, at which point the current drug supply tank resumes drug supply.

[0076] Specifically, the purpose of this embodiment is to enable the system to automatically recover and ensure the quality of subsequent switchovers even in the event of an unexpected shutdown, without the need for manual intervention or reset. This improves the robustness and reliability of the system. The workflow is as follows:

[0077] First, after an unexpected shutdown and system restart, the control system calculates the remaining time required for the liquid level to drop from the shutdown level to the switching level, based on the current liquid level at the time of shutdown, the switching level, and the current rate of liquid level decline. Then, this remaining time is subtracted from the previously determined estimated time (i.e., the total estimated time for the liquid level to drop from the warning level to the switching level) to obtain the elapsed time. This elapsed time represents the time that has passed between the warning triggering and the shutdown time, during which the standby tank should have been re-stirred and allowed to settle and vent, but this was interrupted due to the shutdown.

[0078] Next, the control system temporarily stops the current supply tank from supplying medication (i.e., closes its bottom inlet valve, preventing the liquid level from dropping further), while simultaneously controlling the standby tank to begin re-stirring and venting. When the cumulative pretreatment time actually performed by the standby tank reaches the aforementioned consumed time, the system resumes medication supply from the current supply tank. At this point, the liquid level in the current supply tank remains between the warning level and the switching level, while the standby tank has made up for the missing pretreatment time, and the subsequent sequence returns to normal.

[0079] In summary, this application provides a control method for a two-compartment alternating stirring dosing system. By re-stirring the standby tank when the current supply tank level drops to a warning level, and completing re-stirring and venting before the switching level is reached, the method ensures that the drug solution inside the standby tank is in a uniform suspension state when dosing begins. This avoids drug concentration stratification or sediment accumulation caused by prolonged settling, thereby reducing fluctuations in drug concentration during the initial and later stages of switching. It also reduces the possibility of high-concentration sediments directly entering the intake port and metering pump during the initial dosing phase, thus lowering the probability of blockage. Furthermore, re-stirring and venting are completed in parallel during the current supply tank's dosing process, without occupying time after switching. Therefore, when the current supply tank level drops to the switching level, the system can seamlessly switch to the standby tank for dosing, avoiding interruptions in dosing.

[0080] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application.

Claims

1. A control method for a two-compartment alternating stirring and dosing system, characterized in that, The method includes: Continuously monitor the liquid level of the current medicine supply tank to determine whether it has dropped to the warning level, wherein the warning level is higher than the switching level; When the liquid level in the current supply tank drops to the warning level, the stirrer in the standby tank is activated to stir again; After the re-stirring is completed, the standby tank is allowed to stand still and ventilate; wherein, both the re-stirring and the standing venting are completed before the liquid level in the current supply tank drops to the switching liquid level; When the liquid level in the current drug supply tank drops to the switching liquid level, the drug supply from the current drug supply tank is disconnected, and the standby tank is started to supply drugs.

2. The control method for the two-compartment alternating stirring and dosing system according to claim 1, characterized in that, The re-stirring includes the following steps: The stirrer in the standby tank stirs at a first speed for a first preset time; Reduce to the second rotation speed and stir for the second preset time; Stir in the opposite direction at the second rotation speed for the third preset time. Stop stirring.

3. The control method for the two-compartment alternating stirring and dosing system according to claim 2, characterized in that: The first rotational speed is 30-50 rpm, and the first preset duration is 20-40 seconds; The second rotational speed is 10-20 rpm, and the second preset duration is 8-15 seconds; The third preset duration is 5-10 seconds.

4. The control method for the two-compartment alternating stirring and dosing system according to claim 1, characterized in that, The static exhaust process includes the following steps: After stirring stops, let the standby tank stand for 5-15 seconds; At the same time as the settling begins, open the vent valve on top of the standby tank; After the venting process is complete, close the exhaust valve.

5. The control method for the two-compartment alternating stirring and dosing system according to claim 1, characterized in that, The step of activating the standby tank to supply medicine includes the following steps: The metering pump is controlled to perform a soft start in a stepped, incremental frequency manner; During the soft start process, the initial frequency of the metering pump is set to 3%-8% of the rated frequency and lasts for 1.5-3 seconds; Then increase the rated frequency by 2%-4% every second until the target operating frequency is reached.

6. The control method for the two-compartment alternating stirring and dosing system according to claim 1, characterized in that: The warning liquid level is dynamically determined by the estimated time and the rate of liquid level drop. The estimated time is the time required for the liquid level to drop from the warning liquid level to the switching liquid level. The estimated time is longer than the total time required for re-stirring and venting.

7. The control method for the two-compartment alternating stirring and dosing system according to claim 6, characterized in that: The estimated duration is 20-60 seconds longer than the total time required for re-stirring and venting.

8. The control method for the two-compartment alternating stirring and dosing system according to claim 7, characterized in that: If a shutdown is detected, and the liquid level of the current medicine supply tank is located between the warning liquid level and the switching liquid level at the time of shutdown; After restarting, calculate the remaining time required for the liquid level of the current medicine supply tank to drop to the switching liquid level, and subtract the remaining time from the estimated time to obtain the time already consumed; The current drug supply tank temporarily stops supplying drugs until the standby tank has performed the re-stirring and static venting for the duration of the time already consumed, at which point the current drug supply tank resumes drug supply.

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