Automatic adaptive control system and control method for wet desulphurization slurry

Abstract

The invention discloses an automatic adaptive control system and method for wet desulphurization slurry, and the system comprises a calculation unit for the content of SO2 in original flue gas, which is used for calculating the content of SO2 in the original flue gas; the limestone slurry demanded quantity calculation unit is used for calculating the demanded quantity of the limestone slurry before correction; the in-slurry limestone purity iterative calculation unit is used for comparing the theoretical limestone demand slurry amount with the actual slurry supply amount and correcting the slurry demand amount for the first time; the slurry PH value correction loop is used for carrying out secondary correction on the slurry demand quantity; the clean flue gas SO2 concentration high override increase slurry supply loop is used for forcibly increasing the slurry supply amount under the condition that the instantaneous concentration of the clean flue gas exceeds the standard; and the slurry supply adjusting valve control loop outputs a slurry supply scheduling instruction under the action of the PID controller according to the deviation between the corrected slurry demand quantity and the input actual slurry supply quantity. The control system provided by the invention can realize automatic controllable adjustment of slurry supply under all working conditions of wet desulphurization, fuzzy control of SO2 concentration and self-adaption of slurry supply quality change.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal power generation, and in particular relates to an automatic adaptive control system and a control method for wet desulfurization slurry. Background Art

[0002] Limestone wet desulfurization is a very mature flue gas desulfurization process and has been widely used in industrial boilers. As environmental protection policy requirements become increasingly stringent, environmental risks are listed as major risks in the production and operation of enterprises. Therefore, the requirements for the stability and economic operation of the desulfurization system are becoming higher and higher.

[0003] The desulfurization reaction process in the desulfurization tower is affected by many factors such as flue gas volume, SO2 concentration in flue gas, slurry quality, pH value, liquid-gas ratio, etc., and it is difficult to perform accurate and automatic control. When personnel make manual adjustments, the labor intensity is high, the economy is poor, and environmental risks are prone to occur. With the increase in thermal power generation capacity, the pressure of environmental protection control and the demand for economic operation have increased. At present, many institutions inside and outside the industry have conducted research on the automatic desulfurization slurry supply.

[0004] The patent "Desulfurization slurry automatic adjustment system, method and desulfurization system" with announcement number CN116550128A discloses a SO2 concentration emission adjustment module and an absorber slurry pH value adjustment module connected in series. The SO2 concentration emission adjustment module calculates and adjusts the SO2 concentration emission set value and the SO2 concentration emission initial input value, and outputs a first-level adjustment value; the absorber slurry pH value adjustment module is connected to the output end of the SO2 concentration emission adjustment module, obtains the absorber slurry pH value input value and the slurry supply flow input value, calculates and adjusts the absorber slurry pH value and the slurry supply flow input value according to the first-level adjustment value, and outputs a third-level adjustment value; the opening of the slurry supply valve is controlled according to the third-level adjustment value. However, the patent performs cascade adjustment through the deviation between the outlet SO2 concentration set value and the actual value and the pH value deviation, without considering the influence of the unit load, the change of the sulfur content of the coal entering the furnace, the slurry quality, etc.

[0005] The patent "Desulfurization Island Slurry Supply Control Method, Device, Storage Medium and Electronic Equipment" with announcement number CN118403489A obtains the unit flue gas volume, unit inlet sulfur oxide concentration and unit outlet sulfur oxide concentration of the desulfurization island; determines the benchmark slurry supply according to the unit flue gas volume, unit inlet sulfur oxide concentration and unit outlet sulfur oxide concentration; performs PID control according to the unit outlet sulfur oxide concentration to determine the PID slurry supply compensation; according to the benchmark slurry supply and PID slurry supply compensation, adjusts the actual total slurry supply flow by controlling the slurry supply regulating valve, so as to realize automatic slurry supply and precise control of the desulfurization island slurry volume. However, in this scheme, the benchmark slurry supply is determined by the unit flue gas volume, unit inlet sulfur oxide concentration and unit outlet sulfur oxide concentration, and the benchmark slurry supply is compensated according to the unit outlet sulfur oxide concentration, without considering the impact of pH changes on the desulfurization reaction, nor the impact of slurry supply quality.

[0006] In summary, due to the complex working conditions in the desulfurization tower and the numerous factors that need to be considered, it is necessary to study a method and system that can comprehensively consider the various influencing factors of the desulfurization reaction, accurately determine and effectively correct the benchmark slurry supply, and achieve precise control of the desulfurization slurry supply and automatic adaptation to various working conditions. Summary of the invention

[0007] In order to solve the problems existing in the prior art, the present invention provides an automatic adaptive control system and control method for wet desulfurization slurry, which can realize automatic and controllable adjustment of slurry supply under all working conditions of wet desulfurization, fuzzy control of SO2 concentration and adaptive changes in slurry supply quality to prevent environmental protection indicators from exceeding standards.

[0008] The technical solution of the present invention is as follows:

[0009] The present invention provides an automatic adaptive control system for wet flue gas desulfurization slurry, comprising a calculation unit for SO2 content in raw flue gas, a calculation unit for theoretical CaCO3 demand, a unit for CaCO3 content in actual limestone slurry, a calculation unit for limestone slurry demand, an iterative calculation unit for limestone purity, a slurry pH value correction loop and a slurry supply valve control loop;

[0010] The SO2 content calculation unit in the original flue gas is used to receive the actual measured flue gas flow rate of the original flue gas CMES device, the SO2 concentration of the original flue gas after conversion and the total fuel quantity instruction signal of the boiler, and obtains the SO2 content signal in the original flue gas by calculation and selection; the CaCO3 theoretical demand calculation unit is used to receive the SO2 content signal in the original flue gas and calculate the theoretical demand for CaCO3; the actual CaCO3 content unit in the limestone slurry is used to receive the fresh limestone slurry density signal and calculate the CaCO3 content in the unit fresh limestone slurry; the limestone slurry demand meter The calculation unit is used to calculate the ratio of the theoretical demand for CaCO3 and the content of CaCO3 per unit of fresh limestone slurry, and output the demand for limestone slurry before correction; the limestone purity iterative calculation unit is used to calculate the purity of CaCO3 in the slurry, and complete a primary correction of the slurry demand; the slurry pH value correction loop performs a secondary correction on the slurry demand after the primary correction, and outputs the final corrected slurry demand; the slurry supply regulating valve control loop outputs a slurry supply scheduling instruction under the action of the PID controller through the deviation between the final slurry demand and the actual slurry supply input.

[0011] Preferably, the calculation method of the SO2 content signal y in the original flue gas in the SO2 content calculation unit is as follows:

[0012] y=max{x1,ax2}×the converted SO2 concentration of the original flue gas;

[0013] Among them, x1 is the measured flue gas flow rate of the original flue gas CMES device, x2 is the total fuel quantity instruction of the boiler, and a is the air-coal ratio coefficient.

[0014] Preferably, the CaCO3 theoretical demand calculation unit receives the SO2 content signal y in the original flue gas, and calculates and outputs the CaCO3 theoretical demand y1 under the conditions of determining the calcium-sulfur ratio and the purity of the limestone powder. The calculation method is as follows:

[0015]

[0016] Preferably, the actual content of CaCO in limestone slurry unit receives the density of fresh limestone slurry x3 and calculates the content of CaCO in unit fresh limestone slurry y2 by fitting function, and the calculation method is as follows:

[0017] y2=a1(x3-base density)+b1;

[0018] Among them, x3 is the density of fresh limestone slurry, the reference density is the reference value selected when fitting the linear function of limestone slurries with different densities, and a1 and b1 are the parameters of the linear function fitting of limestone slurries with different densities.

[0019] Preferably, the limestone slurry demand calculation unit calculates the pre-corrected limestone slurry demand y3 based on the ratio of the theoretical CaCO3 demand y1 to the CaCO3 content y2 in the unit fresh limestone slurry.

[0020] Preferably, the limestone purity iterative calculation unit calculates the ratio of the limestone slurry demand y3 before correction in the past time period to the actual slurry supply x6, as the CaCO3 purity a2 in the slurry in the current time period, and iterates the calculation continuously with 1 hour as the node to complete a correction of the slurry demand.

[0021] Preferably, the slurry pH value correction loop includes a SO2 hourly average statistical unit, which receives the real-time SO2 concentration signal of the net flue gas and calculates the hourly average value of the current period. The function output pre-correction value x5 is used to pre-correct the slurry pH set value. Through the deviation between the corrected PH set value and the actual value, the PID control output correction coefficient a3 is used to perform a secondary correction on the slurry demand to form the final corrected slurry demand y4. The calculation method is as follows:

[0022]

[0023] x5 = f (the average value of SO2 in the current period of clean flue gas);

[0024] y4=y3×a2×a3;

[0025] Among them, x4 is the deviation between the pH set value and the actual value of the desulfurization tower slurry; x5 is the pre-correction value of the SO2 average value of the clean flue gas in the current period to the pH set value, which is linearly related to the SO2 average value in the current period; k1 is the proportional coefficient, t1 is the integration time, k2 is the differential coefficient, t2 is the differential time, and a2 is the CaCO3 purity in the slurry in the current period.

[0026] As a preferred embodiment, the system also includes an overriding slurry supply increase circuit for emergency correction of the real-time limestone slurry demand; when the instantaneous concentration of net flue gas SO2 exceeds the standard value, the emergency limestone slurry demand y5 of the determined proportion a4 is increased, and the calculation method is as follows:

[0027] y5=y4×a4;

[0028] a4 = (the current SO2 concentration in the clean flue gas - the reference value) × k3;

[0029] Among them, the benchmark value is the SO2 emission standard value implemented by the unit, and k3 is the proportional coefficient.

[0030] Preferably, the slurry supply valve control loop receives the final corrected slurry demand y4 and the emergency limestone slurry demand y5, calculates the final slurry demand y6, and outputs the slurry supply scheduling instruction y7 under the action of the PID controller according to the deviation between the final slurry demand y6 and the input actual slurry supply x6. The calculation method is as follows:

[0031] y6=y4+y5;

[0032]

[0033] Among them, k3 is the proportional coefficient, t3 is the integral time, k4 is the differential coefficient, and t4 is the differential time.

[0034] The present invention also provides a wet desulfurization slurry automatic adaptive control method, which is implemented based on the wet desulfurization slurry automatic adaptive system, and the method comprises the following steps:

[0035] Calculate the SO2 content signal y in the original flue gas through the SO2 content calculation unit in the original flue gas;

[0036] Calculate the theoretical demand of CaCO3 using y1 through the CaCO3 theoretical demand calculation unit;

[0037] Calculate the CaCO3 content y2 in the unit fresh limestone slurry through the CaCO3 content unit in the actual limestone slurry;

[0038] The limestone slurry demand y3 before correction is calculated by the limestone slurry demand calculation unit;

[0039] The purity a2 of CaCO3 in the slurry is calculated by the limestone purity iterative calculation unit, and the slurry demand is corrected once;

[0040] The slurry pH value correction loop calculates and outputs a pre-correction value x5 to pre-correct the slurry pH set value, and outputs a correction coefficient a3 based on the deviation between the corrected pH set value and the actual value, and performs secondary correction on the slurry to form a corrected slurry demand y4;

[0041] By overriding the increase in the slurry supply circuit, when the instantaneous concentration of SO2 in the clean flue gas exceeds the standard value, the emergency limestone slurry demand y5 of the determined proportion a4 is increased;

[0042] Through the slurry supply regulating valve control loop, according to the deviation between the calculated final slurry demand y6 and the input actual slurry supply x6, the slurry supply scheduling instruction y7 is output under the action of the PID controller.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. The automatic adaptive control system and control method of wet flue gas desulfurization slurry provided by the present invention can realize automatic controllable adjustment of slurry supply under all working conditions of wet flue gas desulfurization, fuzzy control of SO2 concentration and adaptive changes in slurry supply quality, so as to prevent environmental protection indicators from exceeding standards;

[0045] 2. The automatic adaptive control system and control method of wet desulfurization slurry in the present invention takes the calcium-sulfur ratio as the main line and introduces the medium balance theory to make the reference slurry supply more accurate; at the same time, all power stations are implementing near-zero or zero wastewater discharge, and limestone powder slurry is generally prepared using desulfurization filtrate water or industrial wastewater. The CaCO3 content in the new slurry supply is unstable. The present invention uses the CaCO3 purity representing the slurry quality to make a correction to the reference slurry supply, and combines it with the environmental monitoring standard, and iterates the calculation continuously with 1 hour as the node; introduces the current period SO2 mean value to pre-correct the PH set value, and performs a secondary correction on the reference slurry supply through the PH value deviation PID calculation, which not only considers the influence of PH value and slurry quality changes on the desulfurization reaction, but also takes into account the current environmental protection policies and economic adjustment needs;

[0046] 3. The control system of the present invention uses existing data for simple calculations, and does not require complex sensors or monitoring equipment. It can instantly calculate the SO2 average value and slurry supply demand for the current time period, and through calculation, iteration, coefficient correction, adaptive load, sulfur content of coal entering the furnace, slurry quality changes and other influencing factors.

[0047] 4. An override circuit for increasing the slurry supply is introduced into the control system of the present invention. When the instantaneous concentration of SO2 in the clean flue gas exceeds the standard value, the demand for limestone slurry is urgently increased by a certain proportion, which can avoid the average SO2 value in this period from exceeding the environmental protection standard and reduce the risk of exceeding the environmental protection standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of the automatic adaptive control system for wet desulfurization slurry of the present invention;

[0049] The symbols in the accompanying drawings are:

[0050] 1. Calculation unit for SO2 content in original flue gas; 2. Calculation unit for theoretical CaCO3 demand; 3. Unit for CaCO3 content in actual limestone slurry; 4. Calculation unit for limestone slurry demand; 5. Iterative calculation unit for limestone purity; 6. Slurry pH value correction loop; 7. SO2 hourly average statistical unit; 8. Override slurry supply loop; 9. Slurry supply regulating valve control loop. DETAILED DESCRIPTION

[0051] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments.

[0052] Example 1

[0053] This embodiment provides an automatic adaptive control system for wet desulfurization slurry, such as Figure 1 As shown, it includes a calculation unit 1 for SO2 content in the original flue gas, a calculation unit 2 for the theoretical demand for CaCO3, a unit 3 for the actual content of CaCO3 in the limestone slurry, a calculation unit 4 for the demand for limestone slurry, an iterative calculation unit 5 for limestone purity, a slurry pH value correction circuit 6, and a slurry supply valve control circuit 9;

[0054] The original flue gas SO2 content calculation unit is used to receive the original flue gas CMES device flue gas actual flow rate, the original flue gas converted SO2 concentration and the boiler total fuel command signal, and obtain the original flue gas SO2 content signal y by calculation and selection; the original flue gas SO2 content calculation unit 1 is connected to the CaCO3 theoretical demand calculation unit 2, and the original flue gas SO2 content signal y obtained by the original flue gas SO2 content calculation unit 1 is input into the CaCO3 theoretical demand calculation unit 2;

[0055] Among them, when the measured flue gas flow rate of the original flue gas CMES device, the SO2 concentration after conversion of the original flue gas, the total fuel quantity instruction of the boiler and other signals are of bad quality or fluctuate greatly, the SO2 content y in the original flue gas can be self-maintained and alarmed;

[0056] The CaCO3 theoretical demand calculation unit 2 receives the SO2 content signal y in the original flue gas, and calculates the CaCO3 theoretical demand y1 under the conditions of the determined calcium-sulfur ratio and the purity of the limestone powder; the CaCO3 theoretical demand calculation unit 2 is connected to the limestone slurry demand calculation unit 4, and the CaCO3 theoretical demand y1 obtained by the CaCO3 theoretical demand calculation unit 2 is input into the limestone slurry demand calculation unit 4;

[0057] The actual content of CaCO3 in limestone slurry unit 3 receives the fresh limestone slurry density signal x3, and calculates the content of CaCO3 in unit fresh limestone slurry y2; the actual content of CaCO3 in limestone slurry unit 3 is connected to the limestone slurry demand calculation unit 4, and the content of CaCO3 in unit fresh limestone slurry y2 obtained by the actual content of CaCO3 in limestone slurry unit 3 is input into the limestone slurry demand calculation unit 4;

[0058] The limestone slurry demand calculation unit 4 receives the theoretical CaCO3 demand y1 and the CaCO3 content y2 in the unit fresh limestone slurry, and calculates the pre-correction limestone slurry demand y3; the limestone slurry demand calculation unit 4 is connected to the limestone purity iterative calculation unit 5, and the pre-correction limestone slurry demand y3 obtained by the limestone slurry demand calculation unit 4 is input into the limestone purity iterative calculation unit 5;

[0059] The limestone purity iterative calculation unit 5 is used to calculate the CaCO3 purity in the slurry, and the CaCO3 purity a2 in the slurry in the current period is calculated by calculating the ratio of the limestone slurry demand y3 before correction in the past period to the actual slurry supply, and completes a correction of the slurry demand; the limestone purity iterative calculation unit 5 is connected to the slurry pH value correction loop 6, and the CaCO3 purity a2 in the slurry obtained by the limestone purity iterative calculation unit 5 is input into the slurry pH value correction loop 6;

[0060] The slurry pH value correction loop 6 receives the real-time SO2 concentration signal of the clean flue gas, and calculates the hourly current period average value, and uses the function output pre-correction value x5 to pre-correct the slurry pH setting value, and through the deviation between the corrected pH setting value and the actual value, the PID control output correction coefficient a3 is used to perform a secondary correction on the slurry demand, and the final corrected slurry demand y4 is output to the slurry supply valve control loop 9;

[0061] The slurry supply valve control loop 9 receives the corrected slurry demand y4 and the emergency limestone slurry demand y5, calculates the final slurry demand y6, and outputs the slurry supply scheduling instruction y7 under the action of the PID controller based on the deviation between the final slurry demand y6 and the input actual slurry supply x6.

[0062] Example 2

[0063] In this embodiment, the wet desulfurization slurry automatic adaptive control system is as follows: Figure 1 As shown, it includes a calculation unit 1 for SO2 content in the original flue gas, a calculation unit 2 for the theoretical demand of CaCO3, a unit 3 for the actual content of CaCO3 in the limestone slurry, a calculation unit 4 for the demand of limestone slurry, an iterative calculation unit 5 for the purity of limestone, a slurry pH value correction loop 6, an overrunning slurry supply increase loop 8 and a slurry supply regulating valve control loop 9;

[0064] The difference from Example 1 is that it also includes an override slurry supply increase circuit 8 for emergency correction of the real-time limestone slurry demand, and the override slurry supply increase circuit 8 receives the final corrected slurry demand y4 obtained by the slurry pH value correction circuit 6;

[0065] When the instantaneous concentration of SO2 in the net flue gas exceeds the standard value, the emergency limestone slurry demand y5 of the determined proportion a4 is increased; the limestone slurry demand y5 is calculated based on the determined proportion a4 and the final corrected slurry demand y4;

[0066] The slurry supply valve control loop 9 receives the corrected slurry demand y4 and the emergency limestone slurry demand y5, calculates the final slurry demand y6, and outputs the slurry supply scheduling instruction y7 under the action of the PID controller based on the deviation between the final slurry demand y6 and the input actual slurry supply x6.

[0067] Example 3

[0068] This embodiment provides a wet desulfurization slurry automatic adaptive control method, which is implemented based on the wet desulfurization slurry automatic adaptive system of embodiment 1 or embodiment 2, and the method includes the following steps:

[0069] The SO2 content signal y in the original flue gas is calculated by the SO2 content calculation unit 1 in the original flue gas; the SO2 content in the original flue gas is the higher value of (the actual measured flue gas flow rate of the original flue gas CMES device × the SO2 concentration after the original flue gas is converted) and (the boiler total fuel quantity instruction × the wind-coal ratio coefficient × the SO2 concentration after the original flue gas is converted), and the calculation method is as follows:

[0070] y=max{x1,ax2}×the converted SO2 concentration of the original flue gas;

[0071] Among them, x1 is the measured flow rate of flue gas from the original flue gas CMES device, x2 is the total fuel quantity instruction of the boiler, and a is the air-coal ratio coefficient; in this embodiment, the air-coal ratio coefficient can be 8.1.

[0072] The CaCO3 theoretical demand calculation unit 2 receives the SO2 content signal y in the original flue gas, and calculates and outputs the CaCO3 theoretical demand y1 under the conditions of determining the calcium-sulfur ratio and the purity of the limestone powder. The calculation method is as follows:

[0073]

[0074] The calcium-sulfur ratio is an empirical weighted value of long-term operation under different loads of the desulfurization system. The purity of limestone powder is the test purity of the purchased limestone powder, which may be different from limestone powder of different origins. In this embodiment, the molecular weight of CaCO3 is 100, the molecular weight of SO2 is 64, the calcium-sulfur ratio is 1.03, and the purity of limestone powder is 90%. Therefore, the calculated y1 is as follows:

[0075]

[0076] After receiving the continuously monitored fresh limestone slurry density x3 through the actual limestone slurry CaCO3 content unit 3, the CaCO3 content y2 in the unit fresh limestone slurry is calculated through the fitting function. The calculation method is as follows:

[0077] y2=a1(x3-base density)+b1;

[0078] Among them, x3 is the density of fresh limestone slurry, the reference density is the reference value selected when fitting the linear function of limestone slurries with different densities, and a1 and b1 are the parameters of the linear function fitting of limestone slurries with different densities;

[0079] In order to improve the accuracy of the calculation of the CaCO3 content unit 3 in the actual limestone slurry, it is necessary to conduct as many density point limestone slurry preparation experiments as possible to make the fitting function representative; the reference density selected in this embodiment is 1100kg / m 3 , after experiments on different density slurry configurations and fitting a linear function, a1 is taken as 1.12 and b1 is taken as 211.

[0080] The limestone slurry demand y3 before correction is calculated by the limestone slurry demand calculation unit 4; the limestone slurry demand y3 before correction is the ratio of the theoretical CaCO3 demand y1 to the CaCO3 content y2 in the unit fresh limestone slurry;

[0081] y3=y1 / y2.

[0082] The purity a2 of CaCO3 in the slurry is calculated by the limestone purity iterative calculation unit 5. The purity a2 of CaCO3 in the slurry in the current period is obtained by calculating the ratio of the limestone slurry demand y3 before correction in the past period to the actual slurry supply. The calculation is iterated continuously with 1 hour as the node to complete one correction of the slurry demand.

[0083] The real-time SO2 concentration signal of the clean flue gas is received through the slurry pH correction loop 6, and the hourly current period average is calculated. The slurry pH set value is pre-corrected using the function output pre-correction value x5. The correction coefficient a3 is output based on the deviation between the corrected pH set value and the actual value, and the slurry is corrected twice to form the final corrected slurry demand y4. The calculation method is as follows:

[0084]

[0085] x5 = f (the average value of SO2 in the current period of clean flue gas);

[0086] y4=y3×a2×a3;

[0087] Among them, x4 is the deviation between the pH setting value and the actual value of the desulfurization tower slurry; x5 is the pre-corrected value of the average SO2 value of the clean flue gas in the current period to the pH setting value, which is linearly related to the average SO2 value in the current period; k1 is the proportional coefficient, t1 is the integration time, k2 is the differential coefficient, t2 is the differential time, and a2 is the CaCO3 purity in the slurry in the current period;

[0088] The pH set value is pre-corrected by the average SO2 value in the current period. When the average value in the current period is high, a positive correction is made to prevent the hourly average value from exceeding the standard; when the average value in the current period is low, a negative correction is made to improve the operating economy.

[0089] In this embodiment, the correction value of the average SO2 value of the clean flue gas in the current period to the PH setting value = (the average SO2 value of the clean flue gas in the current period - 25) × 0.01; the proportional coefficient k1 is 1.5, the integral time t1 is 360s, the differential coefficient k2 is 0, and the differential time t2 is 0.

[0090] By overriding the increase in the slurry supply circuit 8, the real-time limestone slurry demand is corrected in an emergency. When the instantaneous concentration of SO2 in the net flue gas exceeds the standard value, the ratio a4 is urgently increased to calculate the limestone slurry demand y5. The calculation method is as follows:

[0091] y5=y4×a4;

[0092] a4 = (the current SO2 concentration in the clean flue gas - the reference value) × k3;

[0093] The reference value is the SO2 emission standard value implemented by the unit, and k3 is the proportionality coefficient. In this embodiment, the reference value is 35 mg / Nm 3 , k3 takes 0.02.

[0094] The slurry supply regulating valve control loop 9 receives the corrected slurry demand y4 or the emergency limestone slurry demand y5 after emergency correction, calculates the final slurry demand y6, and outputs the slurry supply scheduling instruction y7 under the action of the PID controller according to the deviation between the final slurry demand y6 and the input actual slurry supply x6. The calculation method is as follows:

[0095] y6=y4+y5;

[0096]

[0097] Among them, k3 is the proportional coefficient, t3 is the integral time, k4 is the differential coefficient, and t4 is the differential time; in this embodiment, the proportional coefficient k4 is 7.0, the integral time t3 is 30s, the differential coefficient k5 is 0, and the differential time t4 is 0.

[0098] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0099] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An automatic adaptive control system for wet desulfurization slurry, characterized by: It includes a calculation unit for SO2 content in raw flue gas (1), a calculation unit for theoretical CaCO3 demand (2), a unit for CaCO3 content in actual limestone slurry (3), a calculation unit for limestone slurry demand (4), an iterative calculation unit for limestone purity (5), a slurry pH value correction circuit (6) and a slurry supply valve control circuit (9); The original flue gas SO2 content calculation unit (1) is used to receive the original flue gas CMES device flue gas actual flow rate, the original flue gas converted SO2 concentration and the boiler total fuel command signal, and obtain the original flue gas SO2 content signal through calculation and selection; the CaCO3 theoretical demand calculation unit (2) is used to receive the original flue gas SO2 content signal and calculate the CaCO3 theoretical demand; the actual limestone slurry CaCO3 content unit (3) is used to receive the fresh limestone slurry density signal and calculate the CaCO3 content per unit fresh limestone slurry; the limestone slurry demand meter The calculation unit (4) is used to calculate the ratio of the theoretical demand for CaCO3 and the content of CaCO3 in the unit of fresh limestone slurry, and output the demand for limestone slurry before correction; the limestone purity iterative calculation unit (5) is used to calculate the purity of CaCO3 in the slurry, and complete the primary correction of the slurry demand; the slurry pH value correction circuit (6) performs a secondary correction on the slurry demand after the primary correction, and outputs the corrected slurry demand; the slurry supply valve control circuit (9) outputs the slurry supply scheduling instruction under the action of the PID controller through the deviation between the final slurry demand and the input actual slurry supply.

2. The automatic adaptive control system for wet desulfurization slurry according to claim 1 is characterized in that: The calculation method of the SO2 content signal y in the original flue gas in the SO2 content calculation unit (1) is as follows: y=max{x1,ax2}×the converted SO2 concentration of the original flue gas; Among them, x1 is the measured flue gas flow rate of the original flue gas CMES device, x2 is the total fuel quantity instruction of the boiler, and a is the air-coal ratio coefficient.

3. The automatic adaptive control system for wet desulfurization slurry according to claim 2 is characterized in that: The CaCO3 theoretical demand calculation unit (2) receives the SO2 content signal y in the original flue gas, and calculates and outputs the CaCO3 theoretical demand y1 under the conditions of determining the calcium-sulfur ratio and the purity of the limestone powder. The calculation method is as follows:

4. The automatic adaptive control system for wet desulfurization slurry according to claim 3 is characterized by: The actual content of CaCO in limestone slurry (3) receives the density of fresh limestone slurry x3 and calculates the content of CaCO in unit fresh limestone slurry y2 by fitting function. The calculation method is as follows: y2=a1(x3-base density)+b1; Among them, x3 is the density of fresh limestone slurry, the reference density is the reference value selected when fitting the linear function of limestone slurries with different densities, and a1 and b1 are the parameters of the linear function fitting of limestone slurries with different densities.

5. The automatic adaptive control system for wet desulfurization slurry according to claim 4 is characterized in that: The limestone slurry demand calculation unit (4) calculates the pre-corrected limestone slurry demand y3 based on the ratio of the theoretical CaCO3 demand y1 to the CaCO3 content y2 in the unit fresh limestone slurry.

6. The automatic adaptive control system for wet desulfurization slurry according to claim 5 is characterized by: The limestone purity iterative calculation unit (5) calculates the ratio of the limestone slurry demand y3 before correction in the past period to the actual slurry supply x6, which is used as the CaCO3 purity a2 in the slurry in the current period, and performs iterative calculations continuously with 1 hour as a node to complete a correction of the slurry demand.

7. The automatic adaptive control system for wet desulfurization slurry according to claim 6 is characterized by: The slurry pH value correction loop (6) includes a SO2 hourly average statistical unit (7), which receives the real-time SO2 concentration signal of the clean flue gas and calculates the hourly average value of the current period, and uses the function output pre-correction value x5 to pre-correct the slurry pH set value. According to the deviation between the corrected pH set value and the actual value, the PID control output correction coefficient a3 is used to perform a secondary correction on the slurry demand to form the final corrected slurry demand y4. The calculation method is as follows: x5 = f (the average value of SO2 in the current period of clean flue gas); y4=y3×a2×a3; Among them, x4 is the deviation between the pH set value and the actual value of the desulfurization tower slurry; x5 is the pre-correction value of the SO2 average value of the clean flue gas in the current period to the pH set value, which is linearly related to the SO2 average value in the current period; k1 is the proportional coefficient, t1 is the integration time, k2 is the differential coefficient, t2 is the differential time, and a2 is the CaCO3 purity in the slurry in the current period.

8. The automatic adaptive control system for wet desulfurization slurry according to claim 7 is characterized by: It also includes an overriding slurry supply increase circuit (8) for emergency correction of the real-time limestone slurry demand; when the instantaneous concentration of SO2 in the net flue gas exceeds the standard value, the emergency limestone slurry demand y5 is increased by a certain proportion a4, and the calculation method is as follows: y5=y4×a4; a4 = (the current SO2 concentration in the clean flue gas - the reference value) × k3; Among them, the benchmark value is the SO2 emission standard value implemented by the unit, and k3 is the proportional coefficient.

9. The automatic adaptive control system for wet desulfurization slurry according to claim 8, characterized in that: The slurry supply valve control loop (9) receives the corrected slurry demand y4 and the emergency limestone slurry demand y5, calculates the final slurry demand y6, and outputs the slurry supply scheduling instruction y7 under the action of the PID controller according to the deviation between the final slurry demand y6 and the input actual slurry supply x6. The calculation method is as follows: y6=y4+y5; Among them, k3 is the proportional coefficient, t3 is the integral time, k4 is the differential coefficient, and t4 is the differential time.

10. A wet desulfurization slurry automatic adaptive control method, characterized in that: The wet desulfurization slurry automatic adaptation system according to any one of claims 1 to 9 is implemented, and the method comprises the following steps: Calculating the SO2 content signal y in the original flue gas by the SO2 content calculation unit (1) in the original flue gas; Calculate the theoretical demand of CaCO3 using y1 through the theoretical demand calculation unit of CaCO3 (2); Calculate the CaCO3 content y2 in the unit fresh limestone slurry through the CaCO3 content unit (3) in the actual limestone slurry; Calculating the limestone slurry demand y3 before correction by the limestone slurry demand calculation unit (4); The purity a2 of CaCO3 in the slurry is calculated by the limestone purity iterative calculation unit (5), thereby completing a correction of the slurry demand. The slurry pH value correction circuit (6) calculates and outputs a pre-correction value x5 to pre-correct the slurry pH set value, and outputs a correction coefficient a3 based on the deviation between the corrected pH set value and the actual value, and performs secondary correction on the slurry to form a final corrected slurry demand y4; By overriding the slurry supply circuit (8), when the instantaneous concentration of SO2 in the clean flue gas exceeds the standard value, the emergency limestone slurry demand y5 of the determined proportion a4 is increased; Through the slurry supply valve control loop (9), according to the deviation between the calculated final slurry demand y6 and the input actual slurry supply x6, the slurry supply scheduling instruction y7 is output under the action of the PID controller.

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