Method and system for controlling the concentration of sulfur dioxide in clean flue gas

Abstract

The application provides a method and system for controlling the concentration of sulfur dioxide in clean flue gas. The method includes obtaining the sulfur dioxide content value in raw flue gas, the sulfur dioxide concentration value in clean flue gas, the actual slurry feeding amount of limestone slurry, and the slurry PH value. Based on the sulfur dioxide content value in raw flue gas, the theoretical slurry feeding amount of limestone slurry is determined. The actual slurry feeding amount is compared with the theoretical slurry feeding amount to obtain a comparison result. Based on the comparison result and the slurry PH value, the operating frequency of the slurry delivery pump is controlled. Based on the sulfur dioxide content value in raw flue gas and the sulfur dioxide concentration value in clean flue gas, at least part of the slurry circulating pump is controlled to operate at a preset regulation level. The scheme provided by the application can ensure efficient treatment of sulfur dioxide in raw flue gas with reasonable regulation resources, accurately control the concentration of sulfur dioxide in clean flue gas, and improve the regulation accuracy and reliability of the concentration of sulfur dioxide in clean flue gas.

Description

Technical Field

[0001] This invention relates to the field of automatic control technology, and in particular to a method and system for controlling the concentration of sulfur dioxide in clean flue gas. Background Technology

[0002] For boilers using high-sulfur coal, fuel oil, or fuel gas, the raw flue gas produced during combustion contains a large amount of sulfur dioxide. This sulfur dioxide needs to be treated by an absorption tower. Even after treatment, a small amount of sulfur dioxide still exists in the clean flue gas output. However, if the concentration of sulfur dioxide in the clean flue gas is not properly controlled, it will have an impact on the surrounding environment.

[0003] In related technologies, due to the unreasonable control of sulfur dioxide concentration in flue gas, there are cases of excessive control and untimely control in the desulfurization process. Excessive control can easily lead to waste of resources, while untimely control poses the risk of environmental pollution.

[0004] Therefore, traditional methods for controlling sulfur dioxide concentration in flue gas are not precise or reliable enough. Summary of the Invention

[0005] This invention provides a method and system for controlling the concentration of sulfur dioxide in clean flue gas, which solves the shortcomings of traditional flue gas sulfur dioxide concentration control schemes that are not precise and reliable enough.

[0006] In a first aspect, the present invention provides a method for controlling the concentration of sulfur dioxide in clean flue gas, the method being executed by a controller connected to at least a portion of the slurry delivery pump and the slurry circulation pump of the absorption tower, the method comprising:

[0007] Obtain the sulfur dioxide content in the raw flue gas, the sulfur dioxide concentration in the clean flue gas, the measured feed rate of the limestone slurry, and the pH value of the slurry;

[0008] Based on the sulfur dioxide content in the original flue gas, the theoretical feed rate of limestone slurry is determined.

[0009] The measured feed rate is compared with the theoretical feed rate to obtain the comparison results;

[0010] Based on the comparison results and the pH value of the slurry, the operating frequency of the slurry delivery pump is controlled;

[0011] Based on the sulfur dioxide content in the raw flue gas and the sulfur dioxide concentration in the clean flue gas, at least some of the slurry circulation pumps are controlled to operate in stages according to preset control levels, so as to control the sulfur dioxide concentration in the clean flue gas within a preset range.

[0012] According to the method for controlling sulfur dioxide concentration in clean flue gas provided by the present invention, the step of controlling the operating frequency of the slurry delivery pump based on the comparison results and the slurry pH value includes:

[0013] If the comparison result is that the measured slurry feed rate is less than the theoretical slurry feed rate, the slurry pH value is lower than the pH set value, and / or the slurry pH value continues to decrease, then an amplification signal is output to the slurry delivery pump to control and increase the operating frequency of the slurry delivery pump.

[0014] If the comparison result indicates that the measured slurry feed rate is greater than the theoretical slurry feed rate, the slurry pH value is higher than the pH set value, and / or the slurry pH value continues to rise, then a frequency reduction signal is output to the slurry delivery pump to control and reduce the operating frequency of the slurry delivery pump.

[0015] According to the method for controlling sulfur dioxide concentration in clean flue gas provided by the present invention, the controller is also connected to the slurry inlet regulating valve;

[0016] After the frequency reduction signal is output to the slurry delivery pump, the method further includes:

[0017] If the operating frequency of the slurry delivery pump drops below the preset lower frequency limit and the pH value of the slurry is higher than the first pH threshold, the opening of the slurry inlet regulating valve will be reduced.

[0018] According to the method for controlling sulfur dioxide concentration in clean flue gas provided by the present invention, the controller is also connected to the slurry inlet pneumatic valve;

[0019] After the frequency reduction signal is output to the slurry delivery pump, the method further includes:

[0020] If the operating frequency of the slurry delivery pump drops below the preset lower frequency limit and the pH value of the slurry is higher than the second pH threshold, then the slurry inlet pneumatic gate is controlled to close.

[0021] According to the method for controlling sulfur dioxide concentration in clean flue gas provided by the present invention, after controlling the slurry inlet pneumatic valve to close, the method further includes:

[0022] If the pH value of the slurry is lower than the third pH threshold, the slurry inlet pneumatic gate is opened.

[0023] According to the method for controlling sulfur dioxide concentration in clean flue gas provided by the present invention, the step of controlling at least a portion of the slurry circulation pumps to operate in stages according to preset control levels based on the sulfur dioxide content value in the original flue gas and the sulfur dioxide concentration value in the clean flue gas includes:

[0024] At least some of the slurry circulation pumps are classified into basic safety pumps, fine-tuning pumps, and coarse-tuning pumps according to preset control levels;

[0025] Control the operation of the basic safety pump and at least a portion of the fine-tuning pump;

[0026] The maximum total output value of the basic safety pump and the fine-tuning pump is obtained, and the difference between the sulfur dioxide content value in the original flue gas and the maximum total output value is calculated to obtain the target excess amount.

[0027] The operation of the coarse adjustment pump is controlled based on the target excess amount, the theoretical control amount of various coarse adjustment pumps, and the sulfur dioxide concentration value in the clean flue gas.

[0028] According to the method for controlling sulfur dioxide concentration in clean flue gas provided by the present invention, the step of controlling the operation of the coarse adjustment pump based on the target excess amount, the theoretical adjustment amount of various coarse adjustment pumps, and the sulfur dioxide concentration value in the clean flue gas includes:

[0029] When the fine-tuning pump is operating at full output, if the target excess is greater than 0 and the sulfur dioxide concentration in the clean flue gas is higher than the first concentration threshold for a first preset duration, then at least one target coarse-tuning pump is determined based on the target excess, the operation of the at least one target coarse-tuning pump is controlled, and the operating frequency of the fine-tuning pump is reduced.

[0030] When the operating frequency of the fine-tuning pump drops to the preset lower frequency limit, if the sulfur dioxide concentration in the clean flue gas remains below the second concentration threshold for a second preset duration, the fine-tuning pump is controlled to reach the maximum operating frequency, and at least one target coarse-tuning pump in operation is controlled to stop operating.

[0031] According to the method for controlling sulfur dioxide concentration in clean flue gas provided by the present invention, the controller is also connected to an induced draft fan;

[0032] Controlling the operation of the basic safety pump includes:

[0033] When a start-up signal is detected after any of the induced draft fans are turned on, the basic safety pump is controlled to start operation.

[0034] According to the method for controlling sulfur dioxide concentration in clean flue gas provided by the present invention, determining the theoretical feed rate of limestone slurry based on the sulfur dioxide content in the original flue gas includes:

[0035] Based on the sulfur dioxide content in the original flue gas, the theoretical amount of calcium required to remove sulfur from the original flue gas is determined.

[0036] Determine the theoretical calcium content corresponding to a unit volume of limestone slurry;

[0037] The theoretical amount of calcium to be used is divided by the theoretical calcium content to obtain the theoretical feed rate of limestone slurry.

[0038] Secondly, the present invention also provides a control system for sulfur dioxide concentration in clean flue gas, the system comprising:

[0039] Pumping equipment, including at least a portion of the slurry delivery pump and slurry circulation pump for the absorption tower;

[0040] A controller, connected to at least some of the slurry delivery pumps and slurry circulation pumps, is used to acquire the sulfur dioxide content in the raw flue gas, the sulfur dioxide concentration in the clean flue gas, the measured slurry feed rate of the limestone slurry, and the slurry pH value; based on the sulfur dioxide content in the raw flue gas, the theoretical slurry feed rate is determined; the measured feed rate is compared with the theoretical feed rate to obtain a comparison result; based on the comparison result and the slurry pH value, the operating frequency of the slurry delivery pumps is controlled; based on the sulfur dioxide content in the raw flue gas and the sulfur dioxide concentration in the clean flue gas, at least some of the slurry circulation pumps are controlled to operate in stages according to preset control levels to control the sulfur dioxide concentration in the clean flue gas within a preset range.

[0041] The method and system for controlling sulfur dioxide concentration in clean flue gas provided by this invention, by comparing the measured feed rate with the theoretical feed rate and combining the slurry pH value, can accurately control the operating frequency of the slurry delivery pump, stabilizing the slurry pH value near the standard value, thereby stably removing some sulfur dioxide from the raw flue gas and reducing the sulfur dioxide concentration in the clean flue gas. Simultaneously, based on the sulfur dioxide content in the raw flue gas and the sulfur dioxide concentration in the clean flue gas, controlling at least some of the slurry circulation pumps to operate at preset control levels can keep the sulfur dioxide concentration in the clean flue gas within a preset range. Through the above control strategy, while ensuring efficient treatment of sulfur dioxide in the raw flue gas using reasonable control resources, the concentration of sulfur dioxide in the clean flue gas can be precisely controlled, thus improving the accuracy and reliability of sulfur dioxide concentration control in the clean flue gas. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0043] Figure 1 This is a schematic flowchart of the method for controlling the concentration of sulfur dioxide in clean flue gas provided in an embodiment of the present invention;

[0044] Figure 2 It is a schematic diagram of the process for controlling at least a portion of the slurry circulation pumps to operate in stages according to preset control levels;

[0045] Figure 3 This is one of the structural schematic diagrams of the control system for sulfur dioxide concentration in clean flue gas provided in the embodiments of the present invention;

[0046] Figure 4 This is the second schematic diagram of the control system for sulfur dioxide concentration in clean flue gas provided in the embodiments of the present invention;

[0047] Figure 5 This is the third schematic diagram of the control system for sulfur dioxide concentration in clean flue gas provided in this embodiment of the invention;

[0048] Figure 6 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention. Detailed Implementation

[0049] Embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be more thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0050] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0051] It should be understood that although the terms "first," "second," "third," etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0052] This embodiment relates to the field of automatic control, and can be specifically applied to the desulfurization of raw flue gas generated by industrial boiler combustion. In related technologies, due to improper control strategy settings in the desulfurization process, sulfur dioxide in the raw flue gas cannot be stably removed, and the concentration of sulfur dioxide in the clean flue gas cannot be effectively controlled, resulting in problems such as unreasonable resource utilization and inaccurate and unreliable monitoring of sulfur dioxide concentration in the clean flue gas.

[0053] The following is combined with Figures 1 to 6 This invention describes the detailed scheme of the method and system for controlling the concentration of sulfur dioxide in clean flue gas provided in embodiments of the present invention.

[0054] See Figure 1 This invention provides a method for controlling the concentration of sulfur dioxide in clean flue gas. This method can be executed by a controller, which is connected to at least a portion of the slurry delivery pump and the slurry circulation pump of the absorption tower. The method specifically includes:

[0055] Step 110: Obtain the sulfur dioxide content in the raw flue gas, the sulfur dioxide concentration in the clean flue gas, the measured feed rate of the limestone slurry, and the pH value of the slurry.

[0056] Understandably, the sulfur dioxide content in the raw flue gas can be determined by the calculated concentration of sulfur dioxide in the raw flue gas and the flue gas flow rate. Specifically, the calculated concentration of sulfur dioxide in the raw flue gas can be multiplied by the flue gas flow rate to obtain the sulfur dioxide content in the raw flue gas.

[0057] In some embodiments, the sulfur dioxide concentration in the clean flue gas can be obtained through online monitoring, for example, by installing a gas sensor for detecting sulfur dioxide concentration at the clean flue gas outlet.

[0058] In practical applications, limestone slurry can remove some sulfur dioxide from the original flue gas. Therefore, whether the amount of limestone slurry fed into the flue gas matches the sulfur dioxide content in the original flue gas will affect the desulfurization effect, and thus affect the concentration of sulfur dioxide in the clean flue gas.

[0059] This embodiment mainly analyzes whether the limestone slurry feed rate matches the sulfur dioxide content in the raw flue gas by using the slurry pH value. The slurry pH value is used as the main signal, and the limestone slurry feed rate is adjusted according to the real-time monitored sulfur dioxide content in the raw flue gas, thereby taking into account both the resource utilization rate and the desulfurization effect in the desulfurization process.

[0060] Step 120: Determine the theoretical feed rate of limestone slurry based on the sulfur dioxide content in the original flue gas.

[0061] In one specific implementation, the theoretical feed rate of limestone slurry is determined based on the sulfur dioxide content in the original flue gas. This can specifically include:

[0062] The first step is to determine the theoretical amount of calcium required to remove sulfur from the original flue gas based on the sulfur dioxide content. In this embodiment, the calculation process for the theoretical amount of calcium is as follows:

[0063] C=P×Q÷64×1.05 (1)

[0064] Where C represents the theoretical amount of calcium used, P represents the converted concentration of sulfur dioxide in the raw flue gas, and Q represents the flue gas flow rate.

[0065] The second step is to determine the theoretical calcium content corresponding to a unit volume of limestone slurry.

[0066] In this embodiment, the theoretical calcium content can be calculated based on data such as slurry density, water density, limestone density, and purity.

[0067] For example, the density of the slurry in the limestone slurry tank is 1250 kg / m³. 3 The density of water is 1000 kg / m³. 3 The density of limestone is 2650 kg / m³. 3 In a scenario where the purity is 98%, the amount of Ca contained in the limestone slurry can be calculated as follows:

[0068] First, we can establish the following equation containing an intermediate unknown:

[0069] 2650 kg / m 3 ×0.98×a+1000㎏ / m 3 ×(1-a)=1250 kg / m 3 (2)

[0070] Based on the above equation, the intermediate unknown quantity a≈0.16 can be obtained. Then, the theoretical calcium content can be obtained by solving the following formula:

[0071] 2650 kg / m 3 ×0.98×0.16÷40=10.4 (3)

[0072] The solution shows that 1m 3 The amount of Ca contained in the limestone slurry is 10.4, which means the theoretical calcium content is 10.4.

[0073] The third step is to divide the theoretical amount of calcium used by the theoretical calcium content to obtain the theoretical feed rate of limestone slurry.

[0074] In this embodiment, the theoretical feed rate can be understood as the amount of limestone slurry required to remove all sulfur elements from sulfur dioxide in the original flue gas.

[0075] Step 130: Compare the measured feed rate with the theoretical feed rate to obtain the comparison results.

[0076] It is understandable that the measured slurry feed rate is the actual amount of limestone slurry fed into the system. This value may deviate from the theoretical feed rate. By comparing the two, it is possible to determine whether there is a deviation between them.

[0077] Step 140: Based on the comparison results and the pH value of the slurry, control the operating frequency of the slurry delivery pump.

[0078] In this embodiment, the process of controlling the operating frequency of the slurry delivery pump can be understood as a closed-loop control process. In this control process, the theoretical slurry feed rate is the feedforward signal, the measured slurry feed rate is the feedback signal, and the slurry pH value is the main signal. Through closed-loop control, the measured slurry feed rate can be made close to the theoretical slurry feed rate, while the slurry pH value is stabilized within a certain range, ensuring the stable and smooth operation of the desulfurization process and improving the resource utilization rate and desulfurization efficiency of the desulfurization stage.

[0079] Step 150: Based on the sulfur dioxide content in the raw flue gas and the sulfur dioxide concentration in the clean flue gas, control at least some of the slurry circulation pumps to operate in stages according to the preset control levels, so as to control the sulfur dioxide concentration in the clean flue gas within the preset range.

[0080] It should be noted that, based on the automatic control of the limestone slurry feeding process, the auxiliary control by using the staged operation of the slurry circulation pump can keep the sulfur dioxide concentration in the clean flue gas within the preset range, avoiding the problem of environmental pollution caused by unstable sulfur dioxide concentration in the clean flue gas, and improving the control accuracy of sulfur dioxide concentration in the clean flue gas.

[0081] In one embodiment, the operating frequency of the slurry delivery pump is controlled based on the comparison results and the slurry pH value, specifically including:

[0082] If the comparison results show that the measured slurry feed rate is less than the theoretical slurry feed rate, the slurry pH value is lower than the pH set value, and / or the slurry pH value continues to decrease, then an increased frequency signal will be output to the slurry delivery pump to control and increase the operating frequency of the slurry delivery pump.

[0083] If the comparison results show that the measured slurry feed rate is greater than the theoretical slurry feed rate, the slurry pH value is higher than the pH set value, and / or the slurry pH value continues to rise, then a frequency reduction signal will be output to the slurry delivery pump to control and reduce the operating frequency of the slurry delivery pump.

[0084] This embodiment uses frequency conversion regulation of the slurry delivery pump as the main control method. Based on the comparison between the theoretical slurry feed rate output by the feedforward signal and the measured slurry feed rate output by the feedback signal, or by comprehensively considering the slurry pH value, the operating frequency of the slurry delivery pump is controlled in advance to adjust the slurry pH value in the absorption tower in a timely manner. This can overcome the problem of slow pH adjustment caused by the large volume of the absorption tower.

[0085] In practical applications, when the unit load increases, the SO2 (sulfur dioxide) content in the raw flue gas rises, requiring more limestone slurry to meet desulfurization demands. Therefore, the controller can output a control signal to the slurry delivery pump to increase its operating frequency. If the measured slurry feed rate is less than the theoretical feed rate, a frequency-increasing signal can be output to the slurry delivery pump. When the slurry pH value is less than or even significantly less than the set pH value, a frequency-increasing signal can be output to the slurry delivery pump to accelerate its operating frequency increase. If the slurry pH value is greater than or even significantly greater than the set pH value, the controller can output a frequency-decrease signal to the slurry delivery pump to reduce its operating frequency. Once the slurry pH value begins to decrease, a frequency-increasing signal is immediately output to the slurry delivery pump again.

[0086] When the unit load decreases, the SO2 content in the raw flue gas decreases, reducing the required amount of limestone slurry. Therefore, the controller can output a control signal to the slurry delivery pump to reduce its operating frequency. If the actual slurry feed rate is greater than the theoretical feed rate, a frequency reduction signal can be output to the slurry delivery pump. If the slurry pH value is greater than or even significantly greater than the set pH value, a frequency reduction signal can be output to the slurry delivery pump to accelerate the reduction of its operating frequency. When the slurry pH value is less than or even significantly less than the set pH value, the main signal outputs a frequency increase signal to increase the operating frequency of the slurry delivery pump. Once the slurry pH value begins to rise, a frequency reduction signal is immediately output to the slurry delivery pump again.

[0087] Through the above closed-loop control process, the pH value of the slurry can be kept stable near the set pH value, which improves the rationality of resource consumption and the stability of regulation in the desulfurization process.

[0088] In one embodiment, the controller may also be connected to the slurry inlet regulating gate;

[0089] After outputting the frequency reduction signal to the slurry delivery pump, the above method may further include:

[0090] If the operating frequency of the slurry delivery pump drops below the preset lower limit and the slurry pH value is higher than the first pH threshold, the opening of the slurry inlet regulating valve will be reduced.

[0091] In this embodiment, based on the above closed-loop control, the slurry inlet regulating valve of the absorption tower can be used as an auxiliary control means to further improve the reliability of the control process.

[0092] In practical applications, under normal conditions, the slurry inlet control valve remains fully open. When the operating frequency of the slurry delivery pump drops below the preset lower limit, it becomes impossible to further reduce the limestone slurry feed rate by adjusting the operating frequency of the slurry delivery pump. If the slurry pH value is higher than the first pH threshold, for example, more than 0.2 times the pH setting value, the controller can control the slurry inlet control valve to reduce its opening or even close it to maintain the minimum slurry feed rate, thereby compensating for the limestone consumption during the normal desulfurization process. At the same time, it can play a certain buffering role in overcoming the slow change in slurry pH value caused by the large volume of the absorption tower and the slow regulation phenomenon of the closed-loop control process of controlling the operating frequency of the slurry delivery pump.

[0093] In one embodiment, the controller may also be connected to the pneumatic inlet gate;

[0094] After outputting the frequency reduction signal to the slurry delivery pump, the above method may further include:

[0095] If the operating frequency of the slurry delivery pump drops below the preset lower limit and the slurry pH value is higher than the second pH threshold, then the slurry inlet pneumatic gate will be closed.

[0096] In this embodiment, based on the above closed-loop control, the pneumatic gate for the slurry inlet of the absorption tower can be used as the main protection and control means to further improve the reliability of the control process.

[0097] In practical applications, the slurry inlet pneumatic valve is normally kept open. When the operating frequency of the slurry delivery pump drops below the preset lower limit and the slurry pH value is higher than the second pH threshold, such as more than 0.4 times the pH setting value, the slurry inlet pneumatic valve can be closed to prevent scaling caused by excessively high pH in the absorption tower, thereby improving the safety of the control process.

[0098] In one embodiment, after controlling the slurry inlet pneumatic door to close, the above method may further include:

[0099] If the pH value of the slurry is lower than the third pH threshold, the pneumatic gate for slurry inlet will be opened.

[0100] In some embodiments, after the slurry inlet pneumatic gate is closed, if the slurry pH value is detected to drop below the third pH threshold, such as below 0.2 times the pH set value, the slurry inlet pneumatic gate can be controlled to reopen.

[0101] For example, when the operating frequency of the slurry delivery pump is reduced to 30Hz, if the slurry pH value is still more than 0.2 times higher than the pH setting value, the slurry inlet regulating valve is controlled to reduce its opening or even close until the slurry inlet rate is maintained at 0.5t / h; if the slurry pH value begins to drop and falls to less than 0.1 times the pH setting value, the slurry inlet regulating valve is controlled to open until it is fully open.

[0102] In another example, when the pH value of the slurry is still more than 0.4 times higher than the pH setting value, the slurry inlet pneumatic gate is closed; when the pH value of the slurry drops to less than 0.2 times the pH setting value, the slurry inlet pneumatic gate is reopened.

[0103] In one embodiment, see Figure 2 Based on the sulfur dioxide content in the raw flue gas and the sulfur dioxide concentration in the clean flue gas, at least some of the slurry circulation pumps are controlled to operate in stages according to preset control levels, specifically including:

[0104] Step 210: Divide at least some of the slurry circulation pumps into basic safety pumps, fine-tuning pumps, and coarse-tuning pumps according to preset control levels.

[0105] To achieve the goal of graded control, this embodiment pre-classifies the slurry circulation pumps according to preset control levels, specifically into three categories: basic safety pumps, fine-tuning pumps, and coarse-tuning pumps.

[0106] In some embodiments, the slurry circulation pump of the first-stage tower A and the slurry circulation pump of the second-stage tower B can be used as the foundation safety pumps. Except for special circumstances such as maintenance, the foundation safety pumps should be kept running as much as possible, and the foundation safety pumps should be started first after startup.

[0107] In some embodiments, the primary tower D slurry circulation pump can be used as a fine-tuning pump. The fine-tuning pump can accurately control the SO2 concentration in the clean flue gas. In practical applications, a variable frequency pump can be selected as the fine-tuning pump.

[0108] In some embodiments, the slurry circulation pumps of the first-stage towers B and C, and the slurry circulation pumps of the second-stage towers A and C can be used as coarse adjustment pumps. The coarse adjustment pumps can meet the adjustment requirements when the SO2 concentration in the original flue gas changes abruptly. In practical applications, the coarse adjustment pumps can be selected from the power frequency pumps.

[0109] Step 220: Control the operation of the basic safety pump and at least part of the fine-tuning pump.

[0110] In this embodiment, under normal operating conditions, it is necessary to ensure the operation of the basic safety pump and at least some fine adjustment pumps. Then, according to actual needs, the coarse adjustment pump is reasonably controlled to operate under appropriate conditions in order to achieve a precise graded control effect.

[0111] Step 230: Obtain the maximum total output value of the basic safety pump and the fine-tuning pump, and calculate the difference between the sulfur dioxide content value in the original flue gas and the maximum total output value to obtain the target excess amount.

[0112] In practical applications, the maximum total output of the basic safety pump and the fine-tuning pump can be measured experimentally. For example, the maximum total output of the basic safety pump and the fine-tuning pump can be 850 kg.

[0113] The excess sulfur dioxide content in the raw flue gas can be obtained by subtracting the maximum total output value from the original sulfur dioxide content, i.e., the target excess amount. In this embodiment, the target excess amount can be eliminated by controlling the operation of the coarse adjustment pump.

[0114] Step 240: Control the operation of the coarse adjustment pumps based on the target excess amount, the theoretical control amount of various coarse adjustment pumps, and the sulfur dioxide concentration value in the clean flue gas.

[0115] In a specific implementation, the theoretical control values ​​for various coarse adjustment pumps can be determined through the following process:

[0116] First, after starting the machine, maintain the pH of the absorption tower stable and start the basic safety pump. When the SO2 concentration in the clean flue gas is close to the limit, record the SO2 content in the original flue gas and the flue gas flow rate of the clean flue gas. The maximum desulfurization efficiency at this time can be calculated.

[0117] Afterwards, start the fine-tuning pump, set the SO2 concentration value in the clean flue gas, and gradually increase the output value of the fine-tuning pump to the maximum as the unit load increases. Record the SO2 content value in the original flue gas and the flue gas flow rate of the clean flue gas to obtain the output of the fine-tuning pump based on the operation of the basic safe pump.

[0118] Next, the coarse adjustment pump is started from the secondary tower. Taking the secondary tower C slurry circulation pump as an example, the SO2 concentration value in the clean flue gas is set. As the unit load increases, the output value of the coarse adjustment pump is gradually increased to the maximum. The SO2 content value in the original flue gas and the flue gas flow rate of the clean flue gas are recorded. The maximum output of the secondary tower C slurry circulation pump can be obtained when the basic safety pump and the fine adjustment pump are at their minimum and maximum output.

[0119] Then, by switching the secondary tower A slurry circulation pump, manually reducing the operating frequency of the fine-tuning pump to the lowest level, recording the SO2 content value in the original flue gas and the flue gas flow rate of the clean flue gas, and then setting the SO2 concentration value in the clean flue gas, the output value of the fine-tuning pump is gradually increased to the maximum. This allows us to obtain the maximum output of the secondary tower A slurry circulation pump when the basic safety pump and the fine-tuning pump are at their minimum and maximum outputs.

[0120] Finally, using the same method described above, the maximum output of the slurry circulation pumps in the first-stage towers B and C was tested to obtain the theoretical control values ​​for various coarse adjustment pumps.

[0121] In practical applications, the target coarse adjustment pump that can be used for this control can be determined from various coarse adjustment pumps according to the control range in which the target excess amount is located. For example, if the target excess amount falls within the control range of the first-stage tower, the target coarse adjustment pump is selected from the first-stage tower pumps. If the target excess amount falls within the control range of the second-stage tower, the target coarse adjustment pump is selected from the second-stage tower pumps.

[0122] In some embodiments, if multiple coarse adjustment pumps are available, selection can be made based on the downtime or running time of each pump. For example, when selecting between pumps B and C in the first-stage tower, the pump with the longer downtime can be prioritized for startup, and when shutting down, the pump with the longer running time can be prioritized for shutdown.

[0123] In one embodiment, the operation of the coarse adjustment pump is controlled based on the target excess amount, the theoretical control amount of various coarse adjustment pumps, and the sulfur dioxide concentration value in the clean flue gas. Specifically, this includes:

[0124] When the fine-tuning pump is operating at full output, if the target excess is greater than 0 and the sulfur dioxide concentration in the clean flue gas is higher than the first concentration threshold for a first preset duration, then at least one target coarse-tuning pump is determined based on the target excess, the operation of at least one target coarse-tuning pump is controlled, and the operating frequency of the fine-tuning pump is reduced.

[0125] When the operating frequency of the fine-tuning pump drops to the preset lower limit, if the sulfur dioxide concentration in the clean flue gas remains below the second concentration threshold for a second preset duration, the fine-tuning pump will be controlled to reach the maximum operating frequency, and at least one target coarse-tuning pump that is in operation will be controlled to stop operating.

[0126] In some embodiments, when the SO2 content in the raw flue gas increases, if the fine-tuning pump is operating at full capacity, the target excess is greater than 0, and the SO2 concentration in the clean flue gas is higher than a first concentration threshold, then the coarse-tuning logic can be activated. Specifically, the coarse-tuning pump with the longest standby time is selected to be activated based on the target excess; if all coarse-tuning pumps in the increment range are already running, the coarse-tuning pump with the longest standby time in another range can be automatically selected to run; at the same time, the operating frequency of the fine-tuning pump can be reduced based on the relationship between the SO2 concentration in the clean flue gas and the concentration setpoint.

[0127] In the above scenario, a certain delay can be set in the judgment stage before initiating the coarse adjustment logic to improve the reliability of the control process. For example, the judgment stage can determine if the SO2 concentration in the clean flue gas exceeds a first concentration threshold for a first duration, such as more than 5 seconds. A delay of 3 minutes can also be set before initiating the coarse adjustment logic. Setting a delay can avoid the impact of error points on control accuracy and improve the reliability of the control process.

[0128] In some embodiments, when the SO2 content in the raw flue gas decreases, the fine-tuning pump has been reduced to its minimum operating frequency. If the SO2 concentration in the clean flue gas is lower than the second concentration threshold and there are coarse-tuning pumps in operation, such as the A and C slurry circulation pumps of the secondary tower having any or simultaneous operating signals, the fine-tuning pump can be immediately increased to its maximum operating frequency, and then the coarse-tuning pump can be shut down. If both of the above coarse-tuning pumps are in operation at this time, the coarse-tuning pump with the longest operating time will be shut down first.

[0129] In the above scenario, a certain delay can be set in the judgment stage before the coarse adjustment pump is shut down to improve the reliability of the control process. For example, if the SO2 concentration in the clean flue gas is lower than the second concentration threshold for more than a second time, such as more than 10 seconds, a certain delay can also be set after the judgment stage and before making a control decision. For example, after a 5-minute delay, the fine adjustment pump can be increased to the maximum operating frequency, and then the coarse adjustment pump can be shut down.

[0130] In other embodiments, when the SO2 content in the original flue gas decreases, the fine-tuning pump has been reduced to its minimum operating frequency, and the SO2 concentration in the clean flue gas is lower than the second concentration threshold. Furthermore, there is a coarse-tuning pump in operation, such as either or both primary towers B and C having an operating signal. In such cases, the fine-tuning pump can be increased to its maximum operating frequency, and then the coarse-tuning pump can be shut down. If both coarse-tuning pumps are in operation at this time, the coarse-tuning pump with the longest operating time will be shut down first.

[0131] In the above scenario, a certain delay can be set in the judgment stage before the coarse adjustment pump is shut down to improve the reliability of the control process. For example, if the SO2 concentration in the clean flue gas is lower than the second concentration threshold for more than a third time, such as more than 15 seconds, a certain delay can also be set after the judgment stage and before making a control decision. For example, after a 5-minute delay, the fine adjustment pump can be increased to the maximum operating frequency, and then the coarse adjustment pump can be shut down.

[0132] In one embodiment, the controller may also be connected to the induced draft fan;

[0133] Controlling the operation of the basic safety pump can specifically include:

[0134] When a start-up signal is detected after any induced draft fan is turned on, the basic safety pump is controlled to start running.

[0135] In this embodiment, the start-up process adds control logic on the furnace side to simultaneously start the induced draft fan and the basic safety pump. Specifically, when the boiler starts up, the induced draft fan is activated, and when any induced draft fan receives a start-up signal, the controller will simultaneously activate the basic safety pump, which can specifically be the first-stage tower A slurry circulation pump.

[0136] Optionally, since there is a certain delay between opening the door and starting the basic safety pump, during the process of controlling the start-up and operation of the basic safety pump, the bottom flushing component of the demister in the absorption tower can be started after the induced draft fan starts, and after a preset delay after the basic safety pump starts running, the bottom flushing component of the demister in the absorption tower can be deactivated.

[0137] For example, there is a 3 to 4 minute delay between opening the valve and starting the A slurry circulation pump in the first-stage tower. Therefore, after starting the induced draft fan, the bottom flushing of the first-stage tower demister can be automatically activated. After the A slurry circulation pump in the first-stage tower starts running, there is a 1 minute delay, after which the bottom flushing of the first-stage tower demister automatically stops.

[0138] The above-mentioned basic safety pump start-up control logic can further ensure the reliability and safety of the control process.

[0139] This embodiment, in addition to achieving automatic control of slurry feed to maintain stable slurry pH, also adds an automatic control strategy for the absorption tower spray layer. By classifying and regulating the slurry circulation pump, the precise control of sulfur dioxide concentration in the clean flue gas is further improved.

[0140] Based on the same general inventive concept, this invention also protects a control system for sulfur dioxide concentration in clean flue gas. The control system for sulfur dioxide concentration in clean flue gas provided by this invention will be described below. The control system for sulfur dioxide concentration in clean flue gas described below can be referred to in correspondence with the control method for sulfur dioxide concentration in clean flue gas described above.

[0141] See Figure 3 The control system for sulfur dioxide concentration in clean flue gas provided in this embodiment of the invention specifically includes:

[0142] Pumping equipment 310 includes at least a portion of the slurry transfer pump 3101 and the slurry circulation pump 3102 for the absorption tower.

[0143] The controller 320 is connected to at least a portion of the slurry delivery pumps 3101 and slurry circulation pumps 3102, respectively, and is used to acquire the sulfur dioxide content in the raw flue gas, the sulfur dioxide concentration in the clean flue gas, the measured slurry feed rate of the limestone slurry, and the slurry pH value; based on the sulfur dioxide content in the raw flue gas, it determines the theoretical slurry feed rate of the limestone slurry; it compares the measured slurry feed rate with the theoretical slurry feed rate to obtain a comparison result; based on the comparison result and the slurry pH value, it controls the operating frequency of the slurry delivery pumps 3101; based on the sulfur dioxide content in the raw flue gas and the sulfur dioxide concentration in the clean flue gas, it controls at least a portion of the slurry circulation pumps 3102 to operate in stages according to preset control levels, so as to control the sulfur dioxide concentration in the clean flue gas within a preset range.

[0144] In one embodiment, the controller 320 controls the operating frequency of the slurry delivery pump based on the comparison results and the slurry pH value, specifically including:

[0145] If the comparison results show that the measured slurry feed rate is less than the theoretical slurry feed rate, the slurry pH value is lower than the pH set value, and / or the slurry pH value continues to decrease, then an increased frequency signal will be output to the slurry delivery pump to control and increase the operating frequency of the slurry delivery pump.

[0146] If the comparison results show that the measured slurry feed rate is greater than the theoretical slurry feed rate, the slurry pH value is higher than the pH set value, and / or the slurry pH value continues to rise, then a frequency reduction signal will be output to the slurry delivery pump to control and reduce the operating frequency of the slurry delivery pump.

[0147] In one embodiment, see Figure 4 The controller 320 is also connected to the slurry inlet regulating gate 410;

[0148] After outputting the frequency reduction signal to the slurry delivery pump, the controller 320 is also used for:

[0149] If the operating frequency of the slurry delivery pump drops below the preset lower limit and the slurry pH value is higher than the first pH threshold, the opening of the slurry inlet regulating valve 410 will be reduced.

[0150] In one embodiment, see Figure 4 The controller 320 is also connected to the pneumatic inlet gate 420;

[0151] After outputting the frequency reduction signal to the slurry delivery pump, the controller 320 is also used for:

[0152] If the operating frequency of the slurry delivery pump drops below the preset lower limit and the slurry pH value is higher than the second pH threshold, then the slurry inlet pneumatic gate 420 will be closed.

[0153] In one embodiment, see Figure 4 After the pneumatic gate for controlling the slurry inlet is closed, controller 320 is also used for:

[0154] If the pH value of the slurry is lower than the third pH threshold, the pneumatic gate 420 for slurry inlet will be opened.

[0155] In one embodiment, the controller 320 controls at least a portion of the slurry circulation pumps to operate in stages according to preset control levels based on the sulfur dioxide content in the raw flue gas and the sulfur dioxide concentration in the clean flue gas, specifically including:

[0156] At least some of the slurry circulation pumps are classified into basic safety pumps, fine-tuning pumps, and coarse-tuning pumps according to preset control levels;

[0157] Control the operation of the basic safety pump and at least some of the fine-tuning pumps;

[0158] Obtain the maximum total output value of the basic safety pump and the fine-tuning pump, and subtract the sulfur dioxide content value in the original flue gas from the maximum total output value to obtain the target excess amount;

[0159] The operation of the coarse adjustment pumps is controlled based on the target excess amount, the theoretical control amount of various coarse adjustment pumps, and the sulfur dioxide concentration in the clean flue gas.

[0160] In one embodiment, the controller 320 controls the operation of the coarse adjustment pump based on the target excess amount, the theoretical control amount of various coarse adjustment pumps, and the sulfur dioxide concentration value in the clean flue gas, specifically including:

[0161] When the fine-tuning pump is operating at full output, if the target excess is greater than 0 and the sulfur dioxide concentration in the clean flue gas is higher than the first concentration threshold for a first preset duration, then at least one target coarse-tuning pump is determined based on the target excess, the operation of at least one target coarse-tuning pump is controlled, and the operating frequency of the fine-tuning pump is reduced.

[0162] When the operating frequency of the fine-tuning pump drops to the preset lower limit, if the sulfur dioxide concentration in the clean flue gas remains below the second concentration threshold for a second preset duration, the fine-tuning pump will be controlled to reach the maximum operating frequency, and at least one target coarse-tuning pump that is in operation will be controlled to stop operating.

[0163] In one embodiment, see Figure 5 The controller 320 is also connected to the induced draft fan 510;

[0164] Controller 320 controls the operation of the basic safety pump, specifically including:

[0165] When a start-up signal is detected after any induced draft fan 510 is turned on, the foundation safety pump is controlled to start operation.

[0166] Optionally, since there is a certain delay between opening the door and starting the basic safety pump, during the process of controlling the start-up and operation of the basic safety pump, the bottom flushing component 520 of the demister in the absorption tower can be started after the induced draft fan 510 starts, and after a preset delay after the basic safety pump starts running, the bottom flushing component 520 of the demister in the absorption tower can be deactivated.

[0167] In one embodiment, the controller 320 determines the theoretical feed rate of limestone slurry based on the sulfur dioxide content in the original flue gas, specifically including:

[0168] Based on the sulfur dioxide content in the original flue gas, determine the theoretical amount of calcium required to remove sulfur from the original flue gas;

[0169] Determine the theoretical calcium content corresponding to a unit volume of limestone slurry;

[0170] The theoretical feed rate of limestone slurry is obtained by dividing the theoretical calcium usage by the theoretical calcium content.

[0171] In summary, the control system for sulfur dioxide concentration in clean flue gas provided by this invention, through the cooperation of the controller with the slurry delivery pump and the slurry circulation pump, can accurately control the operating frequency of the slurry delivery pump by comparing the measured slurry feed rate with the theoretical slurry feed rate and combining the slurry pH value. This stabilizes the removal of some sulfur dioxide from the raw flue gas, thereby reducing the sulfur dioxide concentration in the clean flue gas. Simultaneously, based on the sulfur dioxide content in the raw flue gas and the sulfur dioxide concentration in the clean flue gas, controlling at least some of the slurry circulation pumps to operate at preset control levels allows the sulfur dioxide concentration in the clean flue gas to be controlled within a preset range. This ensures efficient treatment of sulfur dioxide in the raw flue gas using reasonable control resources while precisely controlling the sulfur dioxide concentration in the clean flue gas, improving the accuracy and reliability of sulfur dioxide concentration control in the clean flue gas.

[0172] Figure 6 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention.

[0173] like Figure 6 As shown, the electronic device may include a processor 610, a communications interface 620, a memory 630, and a communication bus 640. The processor 610, communications interface 620, and memory 630 communicate with each other via the communication bus 640. The processor 610 can call logic instructions stored in the memory 630 to execute the sulfur dioxide concentration control method in the purified flue gas provided in the above embodiments.

[0174] Furthermore, the logical instructions in the aforementioned memory 630 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, essentially, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0175] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer is able to execute the method for controlling the concentration of sulfur dioxide in the clean flue gas provided in the above embodiments.

[0176] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to perform the method for controlling the concentration of sulfur dioxide in the clean flue gas provided in the above embodiments.

[0177] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0178] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0179] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the concentration of sulfur dioxide in clean flue gas, characterized in that, The method, executed by a controller connected to at least a portion of the slurry delivery pump and the slurry circulation pump of the absorption tower, comprises: Obtain the sulfur dioxide content in the raw flue gas, the sulfur dioxide concentration in the clean flue gas, the measured feed rate of the limestone slurry, and the pH value of the slurry; Based on the sulfur dioxide content in the original flue gas, the theoretical feed rate of limestone slurry is determined. The measured feed rate is compared with the theoretical feed rate to obtain the comparison results; Based on the comparison results and the slurry pH value, the operating frequency of the slurry delivery pump is controlled, including: if the comparison results indicate that the measured slurry feed rate is less than the theoretical slurry feed rate, the slurry pH value is lower than the pH set value, and / or the slurry pH value continues to decrease, then an increase frequency signal is output to the slurry delivery pump to control and increase the operating frequency of the slurry delivery pump; if the comparison results indicate that the measured slurry feed rate is greater than the theoretical slurry feed rate, the slurry pH value is higher than the pH set value, and / or the slurry pH value continues to increase, then a decrease frequency signal is output to the slurry delivery pump to control and decrease the operating frequency of the slurry delivery pump. Based on the sulfur dioxide content in the raw flue gas and the sulfur dioxide concentration in the clean flue gas, at least a portion of the slurry circulation pumps are controlled to operate in a tiered manner according to a preset control level, including: classifying at least a portion of the slurry circulation pumps into basic safety pumps, fine-tuning pumps, and coarse-tuning pumps according to a preset control level; controlling the operation of the basic safety pumps and at least a portion of the fine-tuning pumps; obtaining the maximum total output value of the basic safety pumps and fine-tuning pumps, and subtracting the sulfur dioxide content in the raw flue gas from the maximum total output value to obtain the target excess; based on the target excess, the theoretical control values ​​of various coarse-tuning pumps, and the sulfur dioxide concentration in the clean flue gas, controlling the operation of the coarse-tuning pumps, including: in the fine-tuning pumps... When the pump is operating at full capacity, if the target excess is greater than 0 and the sulfur dioxide concentration in the clean flue gas remains higher than the first concentration threshold for a first preset duration, then at least one target coarse adjustment pump is determined based on the target excess, and the operation of the at least one target coarse adjustment pump is controlled to operate, while the operating frequency of the fine adjustment pump is reduced. When the operating frequency of the fine adjustment pump drops to a preset lower frequency limit, if the sulfur dioxide concentration in the clean flue gas remains lower than the second concentration threshold for a second preset duration, then the fine adjustment pump is controlled to reach its maximum operating frequency, and at least one target coarse adjustment pump in operation is controlled to stop operating, so as to control the sulfur dioxide concentration in the clean flue gas within a preset range.

2. The method for controlling sulfur dioxide concentration in clean flue gas according to claim 1, characterized in that, The controller is also connected to the slurry inlet regulating gate; After the frequency reduction signal is output to the slurry delivery pump, the method further includes: If the operating frequency of the slurry delivery pump drops below the preset lower frequency limit and the pH value of the slurry is higher than the first pH threshold, the opening of the slurry inlet regulating valve will be reduced.

3. The method for controlling sulfur dioxide concentration in clean flue gas according to claim 1 or 2, characterized in that, The controller is also connected to the pneumatic inlet valve; After the frequency reduction signal is output to the slurry delivery pump, the method further includes: If the operating frequency of the slurry delivery pump drops below the preset lower frequency limit and the pH value of the slurry is higher than the second pH threshold, then the slurry inlet pneumatic gate is controlled to close.

4. The method for controlling sulfur dioxide concentration in clean flue gas according to claim 3, characterized in that, After the pneumatic gate for controlling the slurry inlet is closed, the method further includes: If the pH value of the slurry is lower than the third pH threshold, the pneumatic gate for slurry inlet is opened.

5. The method for controlling sulfur dioxide concentration in clean flue gas according to claim 1, characterized in that, The controller is also connected to the induced draft fan; Controlling the operation of the basic safety pump includes: When a start-up signal is detected after any of the induced draft fans are turned on, the basic safety pump is controlled to start operation.

6. The method for controlling sulfur dioxide concentration in clean flue gas according to claim 1, characterized in that, The determination of the theoretical feed rate of limestone slurry based on the sulfur dioxide content in the original flue gas includes: Based on the sulfur dioxide content in the original flue gas, the theoretical amount of calcium required to remove sulfur from the original flue gas is determined. Determine the theoretical calcium content corresponding to a unit volume of limestone slurry; The theoretical amount of calcium to be used is divided by the theoretical calcium content to obtain the theoretical feed rate of limestone slurry.

7. A control system for sulfur dioxide concentration in purified flue gas, characterized in that, include: Pumping equipment, including at least a portion of the slurry delivery pump and slurry circulation pump for the absorption tower; The controller is connected to at least a portion of the slurry delivery pump and the slurry circulation pump, respectively, and is used to acquire the sulfur dioxide content in the raw flue gas, the sulfur dioxide concentration in the clean flue gas, the measured slurry feed rate of the limestone slurry, and the pH value of the slurry; based on the sulfur dioxide content in the raw flue gas, the theoretical slurry feed rate is determined; and the measured slurry feed rate is compared with the theoretical slurry feed rate to obtain a comparison result. Based on the comparison results and the slurry pH value, the operating frequency of the slurry delivery pump is controlled, including: if the comparison results indicate that the measured slurry inflow is less than the theoretical slurry inflow, the slurry pH value is lower than the pH set value, and / or the slurry pH value continues to decrease, then an increase frequency signal is output to the slurry delivery pump to control an increase in the operating frequency of the slurry delivery pump; if the comparison results indicate that the measured slurry inflow is greater than the theoretical slurry inflow, the slurry pH value is higher than the pH set value, and / or the slurry pH value continues to increase, then a decrease frequency signal is output to the slurry delivery pump to control a decrease in the operating frequency of the slurry delivery pump; based on the sulfur dioxide content value in the raw flue gas and the sulfur dioxide concentration value in the clean flue gas, at least some of the slurry circulation pumps are controlled to operate in a graded manner according to a preset control level, including: classifying at least some of the slurry circulation pumps into basic safety pumps, fine-tuning pumps, and coarse-tuning pumps according to a preset control level; controlling the operation of the basic safety pumps and at least some of the fine-tuning pumps; obtaining... The maximum total output value of the basic safety pump and the fine-tuning pump is calculated, and the difference between the sulfur dioxide content value in the raw flue gas and the maximum total output value is used to obtain the target excess amount. Based on the target excess amount, the theoretical control amount of various coarse-tuning pumps, and the sulfur dioxide concentration value in the clean flue gas, the operation of the coarse-tuning pump is controlled, including: when the fine-tuning pump is in full-output operation, if the target excess amount is greater than 0 and the sulfur dioxide concentration value in the clean flue gas is higher than a first concentration threshold for a first preset duration, then at least one target coarse-tuning pump is determined based on the target excess amount, the operation of the at least one target coarse-tuning pump is controlled, and the operating frequency of the fine-tuning pump is reduced; when the operating frequency of the fine-tuning pump drops to a preset lower frequency limit, if the sulfur dioxide concentration value in the clean flue gas is lower than a second concentration threshold for a second preset duration, then the fine-tuning pump is controlled to reach its maximum operating frequency, and at least one target coarse-tuning pump in operation is controlled to stop operating, so as to control the sulfur dioxide concentration value in the clean flue gas within a preset range.

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