Flue gas desulfurization system full working condition slurry supply control system and method

Abstract

The present application belongs to the technical field of industrial process control. A flue gas desulfurization system full working condition slurry supply control system and method is provided. Through designing flue gas SO2 total amount change range judgment logic, automatically selecting clean flue gas SO2 concentration value and absorption tower slurry pH value cascade regulation and clean flue gas SO2 concentration regulation two control modes, and timely correcting limestone slurry supply amount required for flue gas SO2 absorption, the problems of existing system control lag and flue gas pollutant emission exceeding the standard under the working condition of large amplitude change of flue gas SO2 total amount are solved. The slurry pH value set value is automatically corrected by using clean flue gas SO2 concentration close to emission limit value logic signal, unit load instruction change signal and flue gas dust content change signal, the disturbance of unit parameter change on slurry pH value is quickly responded, the dynamic compensation of slurry pH value control under the condition of desulfurization full working condition is realized, SO2 in flue gas is more effectively absorbed, and the requirement of meeting emission environmental protection standard is met while avoiding limestone slurry waste.

Description

Technical Field

[0001] This invention relates to the field of industrial process control technology, specifically to a full-condition slurry supply control system and method for a flue gas desulfurization system. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] In the limestone-gypsum wet flue gas desulfurization system of power plants, the existing control strategy calculates the amount of limestone (CaCO3) slurry required for the desulfurization absorption tower based on the SO2 content of the raw flue gas at the desulfurization inlet. At the same time, the target value of the slurry supply is corrected by cascading adjustment of the SO2 concentration of the clean flue gas at the desulfurization outlet and the pH value of the absorption tower slurry. The opening degree of the limestone slurry supply regulating valve is changed to control the slurry supply to the absorption tower, so as to keep the SO2 concentration of the clean flue gas and the pH value of the slurry within the normal range.

[0004] In conventional control schemes, the pH value of the absorber slurry is only used to determine whether the current limestone slurry supply in the absorber matches the sulfur content of the flue gas. Due to the large volume of the slurry pool in the desulfurization absorber, pH changes exhibit significant delays and inertia. When the SO2 content of the original flue gas changes drastically, the pH response of the slurry is relatively slow, making it difficult for the system to adjust the slurry supply in a timely manner according to pH changes, resulting in excessive SO2 concentration in the clean flue gas or excessive slurry supply. In addition, conventional desulfurization control systems only control the pH value based on the deviation between the SO2 concentration at the clean flue gas outlet and the emission limit of flue gas pollutants, without considering the impact of disturbances in other operating parameters of the desulfurization system on the pH value. When the SO2 concentration in the clean flue gas is close to the emission limit, the unit load changes significantly, or the dust content in the flue gas remains excessively high, the pH setpoint of the absorber slurry is not automatically adjusted accordingly, leading to inaccurate control of the absorber slurry supply and easily resulting in excessive SO2 emissions in the flue gas or prolonged excessive slurry supply. Conventional control schemes clearly do not meet the requirements for full-condition slurry supply control of flue gas desulfurization systems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a full-condition slurry supply control system and method for flue gas desulfurization systems. By designing logic to judge the variation range of SO2 mass flow rate in the raw flue gas, it automatically selects two control modes: cascade adjustment of the SO2 concentration in the clean flue gas and the pH value of the absorber slurry, and adjustment of the SO2 concentration in the clean flue gas. This promptly corrects the amount of limestone slurry required for SO2 absorption in the raw flue gas, solving the problems of control lag and excessive emissions of flue gas pollutants in existing systems under conditions of large variations in the SO2 mass flow rate in the raw flue gas. The invention also uses logic signals indicating that the SO2 concentration in the clean flue gas is close to the emission limit, unit load command changes, and dust content changes in the flue gas to automatically correct the slurry pH setpoint. This rapidly responds to disturbances in the slurry pH value caused by changes in unit parameters, achieving dynamic compensation for slurry pH control under all desulfurization conditions. While meeting environmental emission standards, it effectively saves on limestone slurry supply.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a slurry supply control system for a flue gas desulfurization system under all operating conditions.

[0007] A flue gas desulfurization system full-condition slurry supply control system includes at least: an analog quantity switching switch, a first adder, a timer, and a high-value over-limit module; The original flue gas SO2 mass flow rate is input to the first adder and the delay unit respectively. The first adder compares the original flue gas SO2 mass flow rate with the output result of the delay unit to generate the change in the original flue gas SO2 mass flow rate. The high value over-limit module receives the change in the original flue gas SO2 mass flow rate and compares it with the built-in limit value. When the change in the mass flow rate of SO2 in the raw flue gas exceeds the limit, or when the pH meter of the slurry is in the flushing state, the analog switch activates the control signal for the SO2 concentration of the clean flue gas to correct the slurry supply setpoint; otherwise, the analog switch selects to activate the cascade adjustment signal between the SO2 concentration control of the clean flue gas and the pH value of the absorber slurry to correct the slurry supply setpoint.

[0008] In one implementation of the first aspect of the present invention, the generation of the clean flue gas SO2 concentration value control signal includes: The first lead-lag module receives the measured value of SO2 concentration in the clean flue gas. The clean flue gas SO2 controller receives the output of the first lead-lag module and the set value of SO2 concentration in the clean flue gas, generates a control signal for SO2 concentration in the clean flue gas, and connects the output of the clean flue gas SO2 controller to one of the selector contacts of the analog quantity switching switch.

[0009] In one implementation of the first aspect of the present invention, the generation of the signal for controlling the SO2 concentration in the clean flue gas and cascading adjustment of the pH value of the absorber slurry includes: The first lead-lag module receives the measured value of SO2 concentration in the clean flue gas, and the clean flue gas SO2 controller receives the output of the first lead-lag module and the set value of SO2 concentration in the clean flue gas, and generates a control signal for SO2 concentration in the clean flue gas. The first function generator receives the SO2 concentration control signal of the clean flue gas, the second function generator receives the output of the first lead-lag module, the third function generator receives the unit load command signal, the fourth function generator receives the dust concentration of the original flue gas, and the second adder superimposes the outputs of the first function generator, the second function generator, the third function generator and the fourth function generator to generate the slurry pH set value. The second lead-lag module receives the measured pH value of the slurry, and the slurry pH controller receives the output of the second lead-lag module and the set pH value of the slurry. The output of the slurry pH controller is connected to the other selector switch contact of the analog quantity switching switch after passing through the limiter.

[0010] As a further limitation of the first aspect of the present invention, the third function generator and the fourth function generator have the same structure, both including a differential controller, a filtering module and a piecewise linear function generator connected in series.

[0011] In one implementation of the first aspect of the present invention, obtaining the mass flow rate of SO2 in the raw flue gas includes: The first filter module is used to receive the flue gas volume flow rate, the second filter module is used to receive the original flue gas SO2 mass volume concentration, and the first multiplier is used to multiply the output of the first filter module and the output of the second filter module to output the original flue gas SO2 mass flow rate.

[0012] In one implementation of the first aspect of the present invention, the second multiplier multiplies the original flue gas SO2 mass flow rate by the molar ratio constant and outputs the result to the third multiplier. The third multiplier multiplies the output of the second multiplier with the output of the analog quantity switch, and then inputs the result to the grout supply controller. The grout supply controller also receives the limestone content, and its output acts on the grout supply regulating valve.

[0013] As a further limitation of the first aspect of the present invention, the fourth multiplier multiplies the output of the third filter module with the output of the fourth filter module to obtain the limestone content, wherein the third filter module is used to filter the input slurry mass flow rate, and the fourth filter module is used to filter the input slurry mass concentration.

[0014] Secondly, the present invention provides a method for controlling the slurry supply of a flue gas desulfurization system under all operating conditions.

[0015] A method for controlling slurry supply under all operating conditions in a flue gas desulfurization system includes the following processes: The mass flow rate of SO2 in the raw flue gas is compared with the mass flow rate of SO2 in the raw flue gas after the delay device to generate data on the change in mass flow rate of SO2 in the raw flue gas per unit time. When the change in the mass flow rate of SO2 in the raw flue gas exceeds the set limit, or when the pH meter of the slurry is in the flushing state signal, the SO2 concentration of the clean flue gas is controlled to correct the slurry supply set value. When the change in the mass flow rate of SO2 in the raw flue gas is less than or equal to the set limit, and the pH meter of the slurry is not in the flushing state signal, the cascade regulation of the SO2 concentration control in the clean flue gas and the pH control of the absorber slurry is executed to correct the slurry supply set value.

[0016] In one implementation of the second aspect of the present invention, the limestone slurry pH value feedforward signal, which is composed of the logic signal of the SO2 concentration of the clean flue gas approaching the emission limit, the logic signal of the change in the unit load command, and the logic signal of the change in the dust content in the flue gas, is superimposed and calculated with the output signal of the SO2 concentration controller of the clean flue gas, and then output as the pH value set value of the limestone slurry. The measured pH value of limestone slurry was compared with the set pH value of limestone slurry after being processed by lead-lag. The comparison result was then processed by amplitude limiting and used as the cascade adjustment signal for flue gas SO2 concentration and absorption tower slurry pH value.

[0017] In one implementation of the second aspect of the present invention, the flue gas volume flow rate data is filtered and multiplied with the filtered original flue gas SO2 mass volume concentration data to generate the original flue gas SO2 mass flow rate. The original flue gas SO2 mass flow rate is multiplied with the fixed molar ratio of CaCO3 to SO2 to obtain the theoretical limestone mass setting value. The theoretical limestone mass setting value is multiplied with the correction coefficient of the slurry supply setting value output by the analog quantity switching switch to obtain the actual required limestone mass setting value. The filtered data of slurry mass flow rate and the filtered data of slurry concentration are multiplied together to generate limestone mass flow rate data in the slurry, which is used as the real-time measurement value of limestone content. The set value of limestone quality and the real-time measured value of limestone content are controlled by the slurry supply controller, which outputs a command signal as the opening degree of the limestone slurry supply regulating valve.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention innovatively proposes a full-condition slurry supply control system for a flue gas desulfurization system. By designing a logic to judge the variation range of SO2 mass flow rate in the raw flue gas, when the variation range of SO2 mass flow rate in the raw flue gas is large, or when the pH meter of the absorber slurry is in the flushing state, the net flue gas SO2 concentration is selected as feedback control to correct the slurry supply setpoint, and the limestone slurry supply is adjusted in a timely manner to ensure that the SO2 emission of the flue gas does not exceed the standard. When the unit is running stably and the variation of SO2 mass flow rate in the raw flue gas is small, the net flue gas SO2 concentration and the pH value of the absorber slurry are cascaded to correct the slurry supply setpoint, accurately adjusting the limestone slurry flow rate, achieving the predetermined desulfurization efficiency while maintaining a suitable slurry pH value, and ensuring that the limestone slurry supply is matched with the sulfur content of the flue gas.

[0019] 2. This invention innovatively proposes a full-condition slurry supply control method for a flue gas desulfurization system. It uses the logic signal of the SO2 concentration in the clean flue gas approaching the emission limit, the unit load command change signal, and the dust content change signal in the flue gas as feedforward signals for the pH controller of the absorber slurry. The pH setpoint is automatically adjusted according to the changes in operating conditions, which can timely and accurately regulate the amount of limestone slurry, so that SO2 in the flue gas can be absorbed more effectively. While ensuring that the SO2 concentration in the flue gas meets the environmental emission standards, it avoids the waste of limestone slurry.

[0020] 3. This invention innovatively proposes a full-condition slurry supply control method for flue gas desulfurization systems, which is applicable to various boiler control systems DCS (Distributed Control System) or PLC (Programmable Logic Controller), is easy to configure, and has good application prospects.

[0021] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 This is a schematic diagram of a flue gas desulfurization system's slurry supply control system under all operating conditions, provided as an exemplary embodiment of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] This implementation proposes a full-condition slurry supply control system for a flue gas desulfurization system, such as... Figure 1 As shown, it includes: a first lead-lag module 1, a clean flue gas SO2 concentration controller 2, an analog quantity switching switch 3, a first function generator 4, a second adder 5, a second function generator 6, a third function generator 7, a fourth function generator 8, a slurry pH controller 9, a limiter 10, a second lead-lag module 11, a first filter module 12, a first multiplier 13, a second filter module 14, a second multiplier 15, a delay unit 16, a first adder 17, a high value over-limit module 18, an OR gate logic module 19, a third multiplier 20, a slurry supply controller 21, a third filter module 22, a fourth filter module 23, a fourth multiplier 24, a slurry supply regulating valve 25, a differential controller 26, a fifth filter module 27, and a piecewise linear function generator 28.

[0027] The flue gas SO2 concentration controller 2 is used to receive the set value of flue gas SO2 concentration and the measured value of flue gas SO2 concentration after passing through the first lead-lag module 1. The output terminal of the flue gas SO2 concentration controller 2 is connected to the first input port of the analog quantity switch 3. The slurry pH controller 9 is used to receive the set value of slurry pH value output from the second adder 5 and the measured value of slurry pH value after passing through the second lead-lag module 10. The output terminal of the slurry pH controller 9 is connected to the second input port of the analog quantity switch 3.

[0028] The output of the clean flue gas SO2 concentration controller 2 is connected to the first input port of the second adder 5 after being output from the first function generator 4. The measured value of the clean flue gas SO2 concentration is connected to the second input port of the second adder 5 after being output from the first lead-lag module 1 and the second function generator 6. The unit load command signal is connected to the third input port of the second adder 5 after being output from the third function generator 7. The original flue gas dust concentration value is connected to the fourth input port of the second adder 5 after being output from the fourth function generator 8. The second adder 5 simultaneously receives the signals from the above four input terminals. The output value of the second adder 5 is used as the set value of the slurry pH value, and its output terminal is connected to the negative input terminal of the slurry pH controller 9. Among them, the third function generator 7 is composed of... Figure 1 The differential controller 26, the fifth filter module 27, and the piecewise linear function generator 28 within the dashed frame are connected in series; the fourth function generator 8 is also composed of... Figure 1 The differential controller 26, the fifth filter module 27, and the piecewise linear function generator 28 within the dashed frame are connected in series.

[0029] The first multiplier 13 is used to receive the flue gas volume flow rate signal after passing through the first filter module 12 and the original flue gas SO2 mass volume concentration signal after passing through the second filter module 14, and generate the original flue gas SO2 mass flow rate data (i.e., the total amount of original flue gas SO2 data). The output of the first multiplier 13 and its output after passing through the delay unit 16 are respectively connected to the first adder 17, and the original flue gas SO2 mass flow rate change data per unit time is generated by comparison. The output of the first adder 17 is connected to the input of the high value over-limit module 18. The output of the high value over-limit module 18 and the flushing status signal of the slurry pH meter are respectively connected to the input of the OR gate logic module 19. The output of the OR gate logic module 19 is connected to the switching trigger signal input of the analog quantity switching switch 3.

[0030] The second multiplier 15 is used to receive the raw flue gas SO2 mass flow rate data and the fixed molar ratio of SO2 to desulfurizing agent limestone (CaCO3) from the output of the first multiplier 13. The output of the second multiplier 15 and the output of the analog quantity switching switch 3 (output slurry supply setpoint correction coefficient) are respectively connected to the two inputs of the third multiplier 20. The output of the third multiplier 20 is connected to the positive input of the slurry supply controller 21.

[0031] The fourth multiplier 24 is used to receive the slurry mass flow rate signal after the third filter module 22 and the slurry concentration signal after the fourth filter module 23, and generate limestone mass flow rate data in the slurry. The output of the fourth multiplier 24 is connected to the negative input of the slurry quantity controller 21, and the output of the slurry quantity controller 21 is connected to the input of the slurry regulating valve 25.

[0032] Based on the above-mentioned flue gas desulfurization system full-condition slurry supply control system, a flue gas desulfurization system full-condition slurry supply control method is disclosed, including the following process: The raw flue gas SO2 mass flow rate data and the raw flue gas SO2 mass flow rate data after the delay timer 16 are compared to generate raw flue gas SO2 mass flow rate change data per unit time. When the change in the mass flow rate of the original flue gas SO2 exceeds the limit set by the high-value over-limit module 18 or when the slurry pH meter is in the flushing state, the analog quantity switching switch 3 will be automatically triggered to select and conduct the output signal of the clean flue gas SO2 concentration controller 2 to correct the slurry supply setting value and adjust the limestone slurry flow rate in a timely manner. When the change in the mass flow rate of the original flue gas SO2 does not exceed the limit set by the high-value over-limit module 18 and the slurry pH meter is not in the flushing state, the analog quantity switching switch 3 is automatically triggered to select the cascade adjustment of the clean flue gas SO2 concentration value and the pH value of the absorber slurry to correct the slurry supply setting value and accurately adjust the limestone slurry flow rate. The limestone slurry pH value feedforward signal, composed of the logic signal of the flue gas SO2 concentration approaching the emission limit, the logic signal of the unit load command change, and the logic signal of the change in dust content in the flue gas, is superimposed and calculated with the output signal of the flue gas SO2 concentration controller 2, and the output is used as the set value of the limestone slurry pH value. The measured value of the limestone slurry pH value is compared with the set value of the limestone slurry pH value after being processed by lead-lag. The comparison result is limited by the limiter 10 and used as the cascade adjustment signal of the flue gas SO2 concentration value and the pH value of the absorber slurry.

[0033] In this implementation, the measured SO2 concentration in the clean flue gas is sequentially output through the first lead-lag module 1 and the second function generator 2 as a feedforward signal for the slurry pH value. This method automatically and appropriately increases the pH setpoint of the desulfurization slurry when the measured SO2 concentration in the clean flue gas approaches the limit, accelerating the absorption of SO2 in the flue gas and preventing excessive flue gas emissions. The unit load command signal is output through the third function generator 7 as a feedforward signal for the slurry pH value. The third function generator 7 is specifically composed of a differential controller 26, a filter module 27, and a piecewise linear function generator 28 connected in series. This method... When the unit load command signal changes significantly, the pH setting of the desulfurization slurry is automatically adjusted appropriately to avoid the slurry pH not meeting the requirements when the load is increased rapidly, and to prevent the limestone slurry supply from mismatching with the sulfur content of the flue gas. The original flue gas dust concentration value is output by the fourth function generator 8 as a feedforward signal for the slurry pH value. The fourth function generator 8 is specifically composed of a differential controller 26, a filter module 27, and a piecewise linear function generator 28 connected in series. This method enables the automatic adjustment of the desulfurization slurry pH setting when the original flue gas dust concentration value changes significantly, to prevent excessive slurry supply when the dust concentration in the flue gas remains too high.

[0034] The flue gas volume flow rate data is filtered and multiplied with the filtered original flue gas SO2 mass volume concentration data to generate the original flue gas SO2 mass flow rate (mass flow rate). The original flue gas SO2 mass flow rate is multiplied with the fixed molar ratio of CaCO3 to SO2 to obtain the theoretical limestone mass set value. The theoretical limestone mass set value is multiplied with the correction coefficient of the slurry supply set value output by analog quantity switch 3 to obtain the actual required limestone mass set value. The mass flow rate of the slurry after passing through the filter module and the concentration of the slurry after passing through the filter module are multiplied together, and the resulting calculation generates the mass flow rate of limestone in the slurry as a real-time measurement value of limestone content. The set value of limestone quality and the real-time measured value of limestone content are controlled by the slurry supply controller 21, which outputs a command signal as the opening degree of the limestone slurry supply regulating valve 25, and finally realizes the control of limestone slurry flow rate.

[0035] In this invention, a full-condition slurry supply control system for a flue gas desulfurization system is proposed. By detecting the SO2 concentration in the clean flue gas, the pH value of the slurry, the unit load command, the dust concentration in the raw flue gas, the volumetric flow rate of the flue gas, the SO2 concentration in the raw flue gas, the mass flow rate of the slurry, and the slurry concentration, and importing the measured data into the DCS system, the full-condition slurry supply control logic for the flue gas desulfurization system can be designed. Specifically, it includes the following processes: Since the introduction of differential control can easily cause oscillations in the regulating system, the slurry supply regulating valve 25 will operate frequently and the valve's actuator structure will be easily damaged. The slurry supply controller 21 is designed as a PI controller; the flue gas SO2 concentration controller 2 and the slurry pH controller 9 are designed as PID controllers. The pH controller's setpoint range is 5.2 to 5.8; The limiter 10 output by the pH controller has a setting range of 0.85 to 1.15; The fixed molar ratio of CaCO3 (limestone) to SO2 is 100 / 64; The time for delay 16 is set to 10 seconds. The setting value of the high-value over-limit module 18 is set at 10% of the original flue gas SO2 mass flow rate; The filtering time of the first filtering module 12 and the second filtering module 14 is set to 5 seconds; the filtering time of the third filtering module 22 and the fourth filtering module 23 is set to 2 seconds; the filtering time of the filtering module in the third function generator 7 and the filtering module in the fourth function generator 8 is set to 3 seconds. Based on the above scheme, design the full-condition slurry supply control logic of the flue gas desulfurization system in the DCS configuration software. After the control logic is compiled and checked by the DCS configuration software, it is downloaded to the DCS controller. The DCS operator station screen is designed with a flue gas SO2 concentration controller 2, a slurry pH controller 9, and a slurry supply controller 21, so that the unit operators can manually correct the controller settings, set the offset, and switch between manual and automatic modes on the DCS screen.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A full-condition slurry supply control system for a flue gas desulfurization system, characterized in that, It includes at least: an analog quantity switching switch, a first adder, a timer, and a high-value over-limit module; The original flue gas SO2 mass flow rate is input to the first adder and the delay unit respectively. The first adder compares the original flue gas SO2 mass flow rate with the output result of the delay unit to generate the change in the original flue gas SO2 mass flow rate. The high value over-limit module receives the change in the original flue gas SO2 mass flow rate and compares it with the built-in limit value. When the change in the mass flow rate of SO2 in the raw flue gas exceeds the limit, or when the pH meter of the slurry is in the flushing state, the analog switch activates the control signal for the SO2 concentration of the clean flue gas to correct the slurry supply setpoint; otherwise, the analog switch selects to activate the cascade adjustment signal between the SO2 concentration control of the clean flue gas and the pH value of the absorber slurry to correct the slurry supply setpoint.

2. The flue gas desulfurization system full-condition slurry supply control system as described in claim 1, characterized in that, The generation of the control signal for the SO2 concentration value in the clean flue gas includes: The first lead-lag module receives the measured value of SO2 concentration in the clean flue gas. The clean flue gas SO2 controller receives the output of the first lead-lag module and the set value of SO2 concentration in the clean flue gas, generates a control signal for SO2 concentration in the clean flue gas, and connects the output of the clean flue gas SO2 controller to one of the selector contacts of the analog quantity switching switch.

3. The flue gas desulfurization system full-condition slurry supply control system as described in claim 1, characterized in that, The generation of signals for controlling SO2 concentration in clean flue gas and cascading pH adjustment in the absorber slurry includes: The first lead-lag module receives the measured value of SO2 concentration in the clean flue gas, and the clean flue gas SO2 controller receives the output of the first lead-lag module and the set value of SO2 concentration in the clean flue gas, and generates a control signal for SO2 concentration in the clean flue gas. The first function generator receives the SO2 concentration control signal of the clean flue gas, the second function generator receives the output of the first lead-lag module, the third function generator receives the unit load command signal, the fourth function generator receives the dust concentration of the original flue gas, and the second adder superimposes the outputs of the first function generator, the second function generator, the third function generator and the fourth function generator to generate the slurry pH set value. The second lead-lag module receives the measured pH value of the slurry, and the slurry pH controller receives the output of the second lead-lag module and the set pH value of the slurry. The output of the slurry pH controller is connected to the other selector switch contact of the analog quantity switching switch after passing through the limiter.

4. The flue gas desulfurization system full-condition slurry supply control system as described in claim 3, characterized in that, The third function generator has the same structure as the fourth function generator, both including a differential controller, a filter module, and a piecewise linear function generator connected in series.

5. The flue gas desulfurization system full-condition slurry supply control system as described in any one of claims 1-4, characterized in that, Obtaining the SO2 mass flow rate of the raw flue gas includes: The first filter module is used to receive the flue gas volume flow rate, the second filter module is used to receive the original flue gas SO2 mass volume concentration, and the first multiplier is used to multiply the output of the first filter module and the output of the second filter module to output the original flue gas SO2 mass flow rate.

6. The flue gas desulfurization system full-condition slurry supply control system as described in any one of claims 1-4, characterized in that, The second multiplier multiplies the original flue gas SO2 mass flow rate by the molar ratio constant and outputs the result to the third multiplier. The third multiplier multiplies the output of the second multiplier with the output of the analog quantity switch, and then inputs the result to the grout supply controller. The grout supply controller also receives the limestone content, and its output acts on the grout supply regulating valve.

7. The flue gas desulfurization system full-condition slurry supply control system as described in claim 6, characterized in that, The fourth multiplier multiplies the output of the third filter module with the output of the fourth filter module to obtain the limestone content. The third filter module is used to filter the input slurry mass flow rate, and the fourth filter module is used to filter the input slurry mass concentration.

8. A method for controlling slurry supply under all operating conditions in a flue gas desulfurization system, characterized in that, Includes the following processes: The mass flow rate of SO2 in the raw flue gas is compared with the mass flow rate of SO2 in the raw flue gas after the delay device to generate data on the change in mass flow rate of SO2 in the raw flue gas per unit time. When the change in the mass flow rate of SO2 in the raw flue gas exceeds the set limit, or when the pH meter of the slurry is in the flushing state signal, the SO2 concentration of the clean flue gas is controlled to correct the slurry supply set value. When the change in the mass flow rate of SO2 in the raw flue gas is less than or equal to the set limit, and the pH meter of the slurry is not in the flushing state signal, the cascade regulation of the SO2 concentration control in the clean flue gas and the pH control of the absorber slurry is executed to correct the slurry supply set value.

9. The method for controlling the slurry supply under all operating conditions of a flue gas desulfurization system as described in claim 8, characterized in that, The limestone slurry pH value feedforward signal, which is composed of the logic signal of SO2 concentration in clean flue gas approaching the emission limit, the logic signal of unit load command change, and the logic signal of dust content change in flue gas, is superimposed with the output signal of SO2 concentration controller in clean flue gas and output as the set value of pH value of limestone slurry. The measured pH value of limestone slurry was compared with the set pH value of limestone slurry after being processed by lead-lag. The comparison result was then processed by amplitude limiting and used as the cascade adjustment signal for flue gas SO2 concentration and absorption tower slurry pH value.

10. The method for controlling the slurry supply under all operating conditions of a flue gas desulfurization system as described in claim 8, characterized in that, The original flue gas SO2 mass flow rate is generated by multiplying the filtered flue gas volume flow rate data with the original flue gas SO2 mass volume concentration data. The original flue gas SO2 mass flow rate is then multiplied with the fixed molar ratio of CaCO3 to SO2 to obtain the theoretical limestone mass setpoint. The theoretical limestone mass setpoint is then multiplied with the correction coefficient of the slurry supply setpoint output by the analog quantity switch to obtain the actual required limestone mass setpoint. The filtered data of slurry mass flow rate and the filtered data of slurry concentration are multiplied together to generate limestone mass flow rate data in the slurry, which is used as the real-time measurement value of limestone content. The set value of limestone quality and the real-time measured value of limestone content are controlled by the slurry supply controller, which outputs a command signal as the opening degree of the limestone slurry supply regulating valve.

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