Method for controlling pH value of wet desulphurization system

Abstract

The invention discloses a wet desulphurization system pH value control method, and relates to the technical field of thermal generator set control, and the method comprises the following steps: obtaining an absorption tower inlet flue gas flow, a sulfur dioxide concentration, a slurry pH operation value and an actual slurry supply amount in real time, and calculating a theoretical slurry supply amount based on the absorption tower inlet flue gas flow and the sulfur dioxide concentration; based on the slurry pH operating value, calculating the inlet deviation of the PID main controller at the current sampling moment; correcting a slurry supply coefficient according to the inlet deviation, and calculating a slurry supply amount set value at the current sampling moment according to the theoretical slurry supply amount and the corrected slurry supply coefficient; based on the slurry supply amount set value and the actual slurry supply amount, an opening instruction of the slurry supply valve at the current sampling moment is calculated, and the pH value is rapidly and stably controlled according to the opening instruction. The pH value of the slurry of the absorption tower can be rapidly and stably adjusted.

Description

Technical Field

[0001] The present invention relates to the technical field of control of thermal power generating units, and particularly to a method for controlling the pH value of a wet flue gas desulfurization system. Background Art

[0002] Due to China's resource endowment dominated by coal and the requirements for power grid peak shaving for accommodating new energy power generation, coal-fired thermal power generation will still be the main power generation method in China for some time to come. Sulfur dioxide emitted during the coal-fired power generation process is an important cause of regional acid rain and other atmospheric compound pollution problems. How to reduce the sulfur dioxide emissions of coal-fired power plants is of extremely important significance for realizing clean utilization of coal and ensuring energy security, and has become a national strategic requirement.

[0003] At present, there are many technical methods for desulfurization of coal-fired thermal power units. Generally speaking, there are mainly three types of coal desulfurization technologies, namely pre-combustion, in-combustion and post-combustion desulfurization. Pre-combustion desulfurization. It is estimated that there are more than 200 specific desulfurization technologies studied and used globally at present. Among the numerous desulfurization technologies, limestone-gypsum flue gas desulfurization in wet flue gas desulfurization is the most widely used desulfurization process worldwide. And in the control of wet flue gas desulfurization, the pH value of the slurry is the core index.

[0004] The current desulfurization control of coal-fired power plants is difficult from multiple aspects. First, in order to absorb a high proportion of renewable energy power generation, coal-fired units currently generally adopt a wide-load flexible operation mode, and the coal types are variable, resulting in a complex operation of the flue gas desulfurization system. And under this wide-load operation condition, since the mainstream control methods are all based on the dynamic characteristics modeling at typical loads, this will lead to uncertainty at the model level. Second, the pH value control system of the slurry in the absorption tower is a time-varying, large time-delay and large inertia process. Since the feedback of the pH value is much slower than the change rate of the flue gas volume, the current control strategy will lead to overshoot. Therefore, the current technical problem to be solved is how to ensure rapid and stable adjustment of the pH value of the slurry in the absorption tower and then control the sulfur dioxide concentration at the outlet of the absorption tower. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for controlling the pH value of a wet flue gas desulfurization system, which ensures that the pH value of the slurry in the absorption tower can be rapidly and stably adjusted.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] In a first aspect, a method for controlling the pH value of a wet flue gas desulfurization system according to the present invention includes:

[0008] Real-time acquisition of the flue gas flow rate V at the inlet of the absorption tower RG(n), sulfur dioxide concentration S IN (n), the operating value of the slurry pH, pH(n), and the actual slurry supply amount Q(n), where n is the current sampling time;

[0009] According to V RG (n) and S IN (n), calculate the theoretical slurry supply amount M(n);

[0010] Based on pH(n), calculate the inlet deviation e(n) of the PID main controller at the current sampling time;

[0011] According to e(n), correct the slurry supply coefficient. According to the theoretical slurry supply amount M(n) and the corrected slurry supply coefficient, calculate the corrected theoretical slurry supply amount, and the corrected theoretical slurry supply amount is the slurry supply amount set value Q sp (n);

[0012] Based on Q sp (n) and Q(n), calculate the opening command U(n) of the slurry supply valve at the current sampling time.

[0013] As a further optimization scheme of the pH value control method for a wet flue gas desulfurization system according to the present invention, e(n) = pH sp -pH(n),

[0014] where pH sp is the set value of the slurry pH.

[0015] As a further optimization scheme of the pH value control method for a wet flue gas desulfurization system according to the present invention, Q sp (n) is obtained by multiplying the corrected slurry supply coefficient by the theoretical slurry supply amount, and the corrected slurry supply coefficient is obtained by adding the default value of the slurry supply coefficient and the corrected value of the slurry supply coefficient;

[0016] Q sp (n) = (ΔC(n) + 1)M(n)

[0017] where ΔC(n) is the corrected value of the slurry supply coefficient.

[0018] As a further optimization scheme of the pH value control method for a wet flue gas desulfurization system according to the present invention, the default value of the slurry supply coefficient is 1, and the corrected value of the slurry supply coefficient ΔC(n) is calculated by the PID main controller according to the input deviations e(n), e(n - 1), e(n - 2), that is:

[0019]

[0020] where k p is the proportional coefficient, T iv is the integral time, T DTd is the differential time, T is the sampling period; e(n), e(n - 1), and e(n - 2) are the inlet deviations of the PID main controller at the nth sampling moment, the (n - 1)th sampling moment, and the (n - 2)th sampling moment, respectively.

[0021] As a further optimization scheme of the pH value control method for the wet flue gas desulfurization system described in the present invention, U(n) = PI[Q sp (n) - Q(n)],

[0022] where PI[*] is the secondary controller of the cascade slurry pH value control system, and Q sp (n) - Q(n) is the input signal of the PI secondary controller, and the output of the PI secondary controller is U(n).

[0023] As a further optimization scheme of the pH value control method for the wet flue gas desulfurization system described in the present invention, PI[*] is a proportional-integral controller.

[0024] As a further optimization scheme of the pH value control method for the wet flue gas desulfurization system described in the present invention,

[0025]

[0026] where ΔSS(n) is the SO 2 concentration removal value, is the molar mass of calcium carbonate, is the molar mass of SO 2 , S t is the calcium-sulfur molar ratio, F R is the calcium carbonate content in the limestone aggregate, W is the specific gravity of the limestone slurry, is the SO 2 removal efficiency at the current moment.

[0027] As a further optimization scheme of the pH value control method for the wet flue gas desulfurization system described in the present invention, the proportional gain k p and the integral time constant T iv are tuned according to the pH value response; the differential time T D is selected according to the jitter of the slurry supply valve command.

[0028] In a second aspect, an embodiment of the present invention further provides a computer device, including a memory, a processor, and a computer program stored in the memory and capable of running on the processor. When the processor executes the computer program, the steps of the pH value control method for the wet flue gas desulfurization system as described in the first aspect or any corresponding implementation manner thereof are implemented.

[0029] In a third aspect, an embodiment of the present invention further provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the steps of the pH value control method for the wet desulfurization system as described in the first aspect or any corresponding embodiment thereof are implemented.

[0030] Compared with the prior art, the present invention adopts the above technical solutions and has the following technical effects:

[0031] In view of the problem of large inertia and large time delay characteristics existing in the desulfurization process, which makes control relatively difficult, the present invention provides a control method based on the correction of the theoretical slurry supply amount. By calculating the theoretical slurry supply amount in real time, this method can make the pH value of the slurry reach the set value faster compared with the traditional feedback control. Compared with the traditional feedforward control, the innovation of the present invention lies in that the correction coefficient of the slurry amount is calculated by the outer-loop main controller, and the product of the theoretical slurry amount and the correction coefficient is used as the set value of the inner loop. The superiority of the present invention will be further elaborated in the specific implementation part. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a control logic diagram of the present invention;

[0033] Figure 2 It is a diagram showing the change of the control quality with different proportional gains of the outer loop in the embodiment of the present invention;

[0034] Figure 3 It is an operation flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Currently, although the prior art can control the pH value of the slurry by relying on the slurry supply amount in the wet desulfurization process, due to the large inertia and large time delay characteristics of this process, simply relying on feedback control cannot well solve the problem. To solve the above problem, the embodiment of the present application proposes a method for controlling the pH value of wet desulfurization based on the correction of the theoretical slurry supply amount. The method includes: obtaining the original flue gas flow rate and sulfur dioxide concentration of the unit in real time, and calculating the theoretical slurry supply flow rate based on this data; the inner loop uses a proportional-integral controller to correct non-linear characteristics such as valve jamming and hollowness, so that the actual slurry supply flow rate quickly tracks the set value of the slurry supply amount; the outer loop calculates the adjustment value of the slurry supply amount correction coefficient through a proportional-integral-derivative controller according to the deviation between the pH operating value and the pH set value, and adds the adjustment value to the default value of the correction coefficient to obtain the adjusted correction coefficient. The default value of the correction coefficient is one. Multiplying the theoretical slurry supply amount by the correction coefficient can obtain the corrected theoretical slurry supply amount, that is, the set value of the slurry supply amount; finally, the valve opening is adjusted according to the set value of the slurry supply amount to achieve rapid and stable control of the pH value.

[0037] A pH value control method for a wet desulfurization system based on the correction of theoretical slurry supply amount, comprising the following steps:

[0038] (1) Obtain the flue gas flow rate V RG (n) at the inlet of the absorption tower, the sulfur dioxide concentration S IN (n), the operating value pH(n) of the slurry pH, and the actual slurry supply amount Q(n) in real time.

[0039] (2) Calculate the theoretical slurry supply amount M(n).

[0040] (3) Calculate the inlet deviation e(n) of the PID main controller at the current sampling moment, e(n) = pH sp -pH(n), where pH sp is the set value of the slurry pH.

[0041] (4) Calculate the set value Q sp (n) of the slurry supply amount at the current sampling moment, which is obtained by multiplying the corrected slurry supply coefficient by the theoretical slurry supply amount, and the corrected slurry supply coefficient is obtained by adding the default value of the slurry supply coefficient and the corrected value of the slurry supply coefficient.

[0042] Among them, the default value of the slurry supply coefficient is 1, and the corrected value of the slurry supply coefficient ΔC(n) is calculated by the PID main controller according to the input deviations e(n), e(n - 1), e(n - 2), that is:

[0043]

[0044] In the formula, k p is the proportional coefficient; T iv is the integral time; T D is the differential time; T is the sampling period; e(n), e(n - 1), e(n - 2) are the inlet deviations of the PID main controller at the nth sampling moment, the (n - 1)th sampling moment, and the (n - 2)th sampling moment respectively.

[0045] The expression of the set value of the slurry supply amount is Q sp (n) = (ΔC(n) + 1)M(n)

[0046] (5) Calculate the opening command U(n) of the slurry supply valve at the current sampling moment. U(n) is the output of the PI secondary controller with Q sp (n) - Q(n) as the input signal, that is, U(n) = PI[Q sp (n) - Q(n)];

[0047] In the formula, Q sp (n) is the set value of the slurry supply amount at the current sampling moment; PI is the secondary controller of the cascade slurry pH value control system, which is a proportional integral controller.

[0048] Determine the set value of the internal loop slurry supply flow based on the set value of the slurry supply volume. The calculation formula for the theoretical slurry supply volume is as follows:

[0049]

[0050] Where, M(n): theoretical slurry supply volume, kg / h, V RG (n): flue gas flow at the inlet of the absorption tower, Nm 3 / h, ΔS(n): SO 2 concentration removal value, mg / Nm 3 ,

[0051] It is obtained by subtracting the inlet sulfur dioxide concentration value S IN (n), mg / Nm 3 , from the set value of the outlet sulfur dioxide concentration S sp (n), mg / Nm 3 . : molar mass of calcium carbonate, kg / kmol, : SO 2 molar mass of, kg / kmol, F R : calcium carbonate content (purity) in limestone aggregate, %, S t : C a / S molar ratio, slightly greater than 1, generally controlled in the range of 1.01 - 1.08, W: specific gravity of limestone slurry, %, : current moment SO 2 removal efficiency, %.

[0052] PID main controller parameter selection strategy, where the proportional gain k p and the integral time constant T iv can be tuned according to the pH value response. If the pH value changes too fluctuantly or oscillates, the coefficient k p can be appropriately reduced, and T iv increased; conversely, the coefficient k p is increased, and T iv decreased. The derivative time T D can be selected according to the jitter of the slurry supply valve command. As long as the opening command of the valve does not exhibit high-frequency jitter, it can be appropriately increased to improve the stability of the control system.

[0053] PI secondary controller parameter selection strategy. The main task of the internal loop is to correct the unknown characteristics of the valve so that the actual slurry supply volume can track the set value of the slurry supply volume as soon as possible. Therefore, the proportional gain should be increased and the integral gain should be decreased.

[0054] The control logic of the present invention is as Figure 1 shown, Figure 3 which is the operation flowchart of the present invention.

[0055] S1. Obtain the flue gas flow rate V at the inlet of the absorption tower in real time RG (n), sulfur dioxide concentration S IN (n), the operating value pH(n) of the slurry pH, and the actual slurry supply amount Q(n).

[0056] S2. Calculate the theoretical slurry supply amount M(n).

[0057] The formula for calculating the theoretical slurry supply amount is as follows:

[0058]

[0059] Taking a certain 1000MW unit at a load of 650MW at a certain operating moment as an example, at this time, the flue gas flow rate V at the inlet of the absorption tower RG (n) is 2245639.303 Nm 3 / h, the sulfur dioxide concentration removal value ΔS(n) is 2022.5 mg / Nm 3 From the sulfur dioxide concentration value S at the inlet of the original flue gas at this time IN (n), 2052.5 mg / Nm 3 Subtracted from the set value S of the sulfur dioxide concentration at the outlet sp (n) 30 mg / Nm 3 The molar mass of calcium carbonate is 100.09 kg / kmol, and the molar mass of sulfur dioxide is 64.06 kg / kmol. The calcium carbonate content F in the limestone slurry R is 90%, the calcium-sulfur molar ratio S t is 1.01, the specific gravity W of limestone in the limestone slurry tank is 30%, and the desulfurization efficiency needs to be obtained according to the slurry pH from the empirical formula of this unit. In this example, it is taken as 96%, and the calculated theoretical slurry flow rate is 25483.62 kg / h.

[0060] S3. Calculate the inlet deviation e(n) of the PID main controller at the current sampling moment.

[0061] In the process of wet flue gas desulfurization, the pH value pH(n) of the slurry at the current sampling moment is collected in real time, and the set value pH of the slurry pH is set sp ; pH sp Generally set by the operator on the operation screen, usually taking values between 5.4 - 5.7. In this example, the value is taken as 5.6.

[0062] Calculate the inlet deviation e(n) of the PID main controller at the current sampling moment, e(n) = pH sp -pH(n)

[0063] S4. Calculate the set value Q of the slurry supply volume at the current sampling moment sp (n).

[0064] First, it is necessary to calculate the correction value ΔC(n) of the theoretical slurry supply coefficient at the current moment. The correction value ΔC(n) of the slurry supply coefficient is the output of the PID main controller with e(n), e(n - 1), and e(n - 2) as the input deviations, that is:

[0065]

[0066] In the formula, k p is the proportional coefficient; T iv is the integral time; T D is the differential time; T is the sampling period; e(n), e(n - 1), and e(n - 2) are the input deviations of the PID main controller at the nth sampling moment, (n - 1)th sampling moment, and (n - 2)th sampling moment, respectively.

[0067] Add the correction value ΔC(n) of the slurry supply coefficient to the default value of the slurry supply coefficient to obtain the actual slurry supply coefficient value, and multiply the slurry supply coefficient value by the theoretical slurry supply volume M(n) to obtain the set value of the slurry supply volume.

[0068] Q sp (n) = (ΔC(n) + 1)M(n)

[0069] The tuning of the outer loop controller parameters needs to be analyzed according to the characteristics of the controlled object. In actual applications, the controller parameters can be tuned as needed, and the outer loop controller can be selected as a P controller, a PI controller, an I controller, or a PID controller.

[0070] Next, take a 1000MW unit as an example for analysis. After applying a step change to the slurry flow rate of limestone in this unit, it is very difficult for the pH of the slurry pool to spontaneously reach a steady state or it takes a relatively long dynamic time to gradually stabilize. Mechanistically, this is because when the amount of limestone slurry added is greater than the amount of slurry required for spraying and absorbing sulfur dioxide, the pH in the slurry pool will keep rising. However, since the entire absorption process in the slurry pool is very slow, this link shows an integral characteristic, that is, a non-self-stabilizing characteristic. The dynamic characteristics of the controlled process are as follows:

[0071]

[0072] Since this is a non-self-stabilizing process containing an integral process, the outer loop only needs a proportional controller to make the system stable. Therefore, the integral time constant T iv should be adjusted as large as possible. In this example, T iv = 500, and the differential time constant T D= 2. The action logic of the proportional controller is that when the running pH value is lower than the set pH value, a positive deviation is output. Based on this deviation, the proportional controller gives a positive adjustment value, thereby increasing the slurry supply flow rate to raise the pH value of the slurry in the desulfurization tower. When the running pH value is higher than the set pH value, a negative deviation is output. Based on this deviation, the proportional controller gives a negative adjustment value, thereby reducing the slurry supply flow rate to lower the pH value of the slurry in the desulfurization tower. During actual operation, the maximum range of pH value fluctuation is between 4.6 and 6.6. In this example, the set value of the pH value is set to 5.6. In the extreme case, the deviation between the output value and the set value is 1. The range of the amplitude limiting module connected in series after the proportional controller is between 0.8 and 1.2, which indicates that the absolute value of the output value of the proportional controller is 0.2. At this time, the maximum proportional gain of the proportional controller is 0.2. Next, analyze the influence of the magnitude of the proportional gain on the control quality, as Figure 2 shown. It can be found that for the wet desulfurization process, as the proportional gain decreases, the controlled output tends to be flat. When k p = 0.01, satisfactory control quality can be obtained.

[0073] S5. Calculate the opening command U(n) of the slurry supply valve at the current sampling moment.

[0074] U(n) is the output of the PI secondary controller with Q sp (n) - Q(n) as the input signal, that is, U(n) = PI[Q sp (n) - Q(n)];

[0075] In the formula, Q sp (n) is the set value of the slurry supply amount at the current sampling moment; PI is the secondary controller of the cascade slurry pH value control system, which is a proportional-integral controller.

[0076] Since the original mechanical characteristics of the actuator responsible for slurry supply will be affected to varying degrees after long-term operation, the linear relationship between the opening of the slurry valve and the slurry supply flow rate is damaged. When the influence is small, this uncertainty of the actuator can be handled by negative feedback control; however, when the influence is large, this uncertainty will greatly reduce the effect of the closed-loop control system. In response to this phenomenon, a PI controller is used in the inner loop for flow correction, thereby reducing the mismatch characteristic between the control amount of the actuator and the slurry supply flow rate. Since the main task of the inner loop is to make the actual slurry supply amount track the set value of the slurry amount as soon as possible, the proportional gain of the inner loop controller needs to be adjusted as large as possible, and the integral gain is relatively adjusted smaller.

[0077] Taking a 1000MW unit as the research object, the dynamic characteristics of the valve opening with respect to the slurry supply flow rate are identified through a step response experiment as shown below

[0078]

[0079] where M v is the slurry supply flow rate (t / h), and O v is the valve opening percentage (%). When the slurry valve actuator is in a linear operating condition, only the steady-state gain in the above link (i.e., the proportional relationship between the opening and the flow rate) needs to be known. At this time, the dynamics of this link can be ignored or approximated as a time delay compared to the dynamics of the subsequent flow rate and slurry pH. In this case, there is no need to use a cascade structure, nor to identify the dynamic parameters of this link. However, due to the non-linearity of the valve and the uncertainties brought about by long-term operation, the steady-state gain in the above model will change under different slurry supply loads. Therefore, it is necessary to identify the complete dynamic model including the inertial time constant, and construct a closed-loop control for the inner loop based on this model, so as to restore the corresponding relationship between the slurry supply flow rate and the slurry valve opening.

[0080] For the controlled object of the inner loop of the cascade control system described by the first-order inertia, since its inertial time is small, the PI control based on the direct synthesis method can be directly used to adjust it. In this example, the proportional and integral gains are set to k p = 1.5, k i = 0.15.

[0081] It can be found that under the action of establishing the closed-loop PI control in the inner loop, the gain from the slurry command input to the actual slurry output channel becomes 1, ensuring that the two are equal in the steady state, thus realizing the correction of problems such as valve non-linearity. In addition, due to the use of relatively conservative PI control parameters, the closed-loop dynamics of the inner loop are similar to the dynamics of the inner loop valve object, thereby also preventing problems such as valve mechanism execution failures caused by the over-fast action of the inner loop of the cascade system.

[0082] An embodiment of the present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and capable of running on the processor. When the processor executes the computer program, the steps of the pH value control method for the wet desulfurization system as described in the first aspect or any corresponding implementation manner above are implemented.

[0083] An embodiment of the present invention also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the steps of the pH value control method for the wet desulfurization system as described in the first aspect or any corresponding implementation manner above are implemented.

[0084] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The solutions in the embodiments of the present invention can be implemented in various computer languages. For example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript, etc.

[0085] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0086] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing devices to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0087] These computer program instructions can also be loaded onto a computer or other programmable data processing devices, so that a series of operation steps are executed on the computer or other programmable devices to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable devices provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0088] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0089] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A method for controlling pH value of a wet flue gas desulfurization system, characterized in that: include: Obtain the flue gas flow rate V at the absorption tower inlet in real time RG (n), sulfur dioxide concentration S IN (n), slurry pH operating value pH(n) and actual slurry supply Q(n), where n is the current sampling time; According to V RG (n) and S IN (n), calculate the theoretical slurry supply M(n); Based on pH(n), calculate the inlet deviation e(n) of the PID main controller at the current sampling time; According to e(n), the slurry supply coefficient is corrected. According to the theoretical slurry supply M(n) and the corrected slurry supply coefficient, the corrected theoretical slurry supply is calculated. The corrected theoretical slurry supply is the slurry supply setting value Q at the current sampling time. sp (n); Based on Q sp (n) and Q(n), calculate the opening instruction U(n) of the slurry supply valve at the current sampling moment.

2. A method for controlling pH value of a wet flue gas desulfurization system according to claim 1, characterized in that: e(n)=pH sp -pH(n), Among them, pH sp Set the pH value for the slurry.

3. The pH value control method of a wet flue gas desulfurization system according to claim 1, characterized in that: Q sp (n) is obtained by multiplying the corrected slurry supply coefficient by the theoretical slurry supply amount. The corrected slurry supply coefficient is obtained by adding the default value of the slurry supply coefficient and the corrected value of the slurry supply coefficient. Q sp (n)=(ΔC(n)+1)M(n) Among them, ΔC(n) is the correction value of the slurry supply coefficient.

4. A method for controlling pH value of a wet flue gas desulfurization system according to claim 3, characterized in that: The default value of the slurry supply coefficient is 1, and the slurry supply coefficient correction value ΔC(n) is calculated by the PID main controller according to the input deviations e(n), e(n-1), and e(n-2): Among them, k p is the proportionality coefficient, T iv is the integration time, T D is the differential time, T is the sampling period; e(n), e(n-1), and e(n-2) are the inlet deviations of the PID master controller at sampling time n, sampling time n-1, and sampling time n-2, respectively.

5. The method for controlling pH value of a wet flue gas desulfurization system according to claim 1, characterized in that: U(n)=PI[Q sp (n)-Q(n)], Among them, PI[*] is the sub-controller of the cascade slurry pH control system, Q sp (n)-Q(n) is the input signal of the PI sub-controller, and the output of the PI sub-controller is U(n).

6. A method for controlling pH value of a wet flue gas desulfurization system according to claim 5, characterized in that: PI[*] is a proportional-integral controller.

7. The method for controlling pH value of a wet flue gas desulfurization system according to claim 5, characterized in that: Among them, ΔS(n) is the SO2 concentration removal value, is the molar mass of calcium carbonate, is the molar mass of SO2, S t is the calcium-sulfur molar ratio, F R is the content of calcium carbonate in limestone, W is the specific gravity of limestone slurry, is the SO2 removal efficiency at the current moment.

8. The method for controlling pH value of a wet flue gas desulfurization system according to claim 4, characterized in that: Proportional gain k p With the integration time constant T iv Adjust according to pH value response; differential time T D Select according to the jitter of the slurry supply valve command.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that: When the processor executes the computer program, the steps of the pH value control method for a wet flue gas desulfurization system as described in any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the pH value control method for a wet flue gas desulfurization system as described in any one of claims 1 to 8 are implemented.

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