JP3757616B2 - Absorbent slurry flow rate control method and apparatus for flue gas desulfurization apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an absorbent slurry flow rate control method and apparatus for a flue gas desulfurization apparatus.
[0002]
[Prior art]
In general, in power plants, in order to absorb and remove SO ₂ (sulfur oxide) from exhaust gas discharged from coal fired boilers, a flue gas desulfurization device using calcium carbonate (CaCO ₃ ) as an absorbent is provided. However, as shown in FIG. 4, the flue gas desulfurization apparatus normally has an absorption tower 3 in which a liquid reservoir 1a of the absorption liquid 1 is formed in the lower part and a number of spray nozzles 2 are arranged in the upper part. A plurality of circulation pumps 4 that pump up the absorption liquid 1 in the liquid reservoir 1a of the absorption tower 3 and circulate by spraying it from the spray nozzle 2, and oxidation that supplies oxidized air to the liquid reservoir 1a of the absorption tower 3 The air blower 5 is provided.
[0003]
In the case of the flue gas desulfurization apparatus as described above, the absorbing liquid 1 is circulated while being sprayed from the spray nozzle 2 by the operation of the circulation pump 4, and the exhaust gas sent to the absorption tower 3 from a coal fired boiler or the like not shown is The SO ₂ (sulfur oxide) is absorbed and removed by contact with the absorbing liquid 1 sprayed from the spray nozzle 2 and then discharged to the outside.
[0004]
On the other hand, the absorbing liquid 1 that has absorbed SO ₂ from the exhaust gas is dropped into the liquid reservoir 1 a and is forcibly oxidized by the oxidized air supplied into the liquid reservoir 1 a by the operation of the oxidizing air blower 5. Calcium sulfate (CaSO ₄ )) is generated, and a part of the absorbent 1 in the liquid reservoir 1a containing the gypsum is extracted as a gypsum slurry from the bottom of the absorption tower 3 and is sent to a gypsum recovery system (not shown). In the gypsum recovery system, water is removed from the gypsum slurry, and gypsum is generated and recovered.
[0005]
The absorber 3 is supplied with a required amount of absorbent slurry by appropriately controlling the opening degree of the flow rate adjusting valve 8 as necessary. A pH meter 7 that detects the pH (pH) of the absorbent 1 in the absorption tower 3, a desulfurization gas flow meter 9 that detects the desulfurization gas flow rate A, and an absorption tower inlet SO ₂ that detects the absorption tower inlet SO ₂ concentration B. A densitometer 10, an absorbent slurry flow meter 12 that detects the absorbent slurry flow rate D, and an absorbent slurry concentration meter 13 that detects the absorbent slurry concentration E, and are detected by the desulfurization gas flow meter 9. The desulfurization gas flow rate A, the absorption tower inlet SO ₂ concentration B detected by the absorption tower inlet SO ₂ concentration meter 10, the pH of the absorbent 1 detected by the pH meter 7, and the absorbent slurry concentration meter 13 Absorbent slurry concentration detected in Based on the above, a set absorbent slurry flow rate 28 (see FIG. 5) required to maintain the pH of the absorbent 1 at the set pH value is obtained, and the absorbent slurry flow rate D is set to the set absorbent slurry flow rate 28. A controller 6 that outputs an opening degree command 32 to the flow rate adjusting valve 8 is provided so as to be equal.
[0006]
As shown in FIG. 5, the controller 6 desulfurizes by multiplying the absorption tower inlet SO ₂ concentration B detected by the absorption tower inlet SO ₂ concentration meter 10 by a set desulfurization rate (for example, 90%). A multiplier 15 for obtaining and outputting the SO ₂ concentration 14;
By multiplying the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9 by the desulfurization SO ₂ concentration 14 output from the multiplier 15, the SO flowing into the absorption tower 3 to be removed from the exhaust gas. A multiplier 17 for obtaining and outputting _two quantities 16;
A multiplier 19 that obtains and outputs an absorbent amount 18 by multiplying the SO ₂ amount 16 output from the multiplier 17 by a value of (absorbent amount / SO ₂ amount);
A multiplier 21 that obtains and outputs the necessary amount 20 of the absorbent that is actually required by multiplying the amount of absorbent 18 that is output from the multiplier 19 by a set absorbent excess rate (for example, 1.02); ,
A subtractor 23 for obtaining a difference between a preset pH value (for example, 5.0) set in advance and the pH of the absorbent 1 detected by the pH meter 7 and outputting a pH deviation 22;
A proportional-plus-integral controller 25 that outputs an absorbent conversion amount 24 for eliminating the pH deviation 22 by proportionally integrating the pH deviation 22 output from the subtractor 23;
An adder that obtains and outputs a pH-considered necessary absorbent amount 26 by adding an absorbent conversion amount 24 output from the proportional-plus-integral regulator 25 to the required absorbent amount 20 output from the multiplier 21. 27,
A divider that obtains and outputs a set absorbent slurry flow rate 28 by dividing the absorbent-considered absorbent amount 26 output from the adder 27 by the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13. 29,
A subtractor 31 for calculating a difference between the set slurry flow rate 28 outputted from the divider 29 and the absorbent slurry flow rate D detected by the absorbent slurry flow meter 12 and outputting an absorbent slurry deviation 30;
And a proportional integral controller 33 for outputting an opening degree command 32 of the flow rate adjusting valve 8 for eliminating the absorbent slurry deviation 30 by proportionally integrating the absorbent slurry deviation 30 output from the subtractor 31. It has the composition which becomes.
[0007]
During the operation of the flue gas desulfurization apparatus, the pH of the absorption liquid 1 detected by the pH meter 7, the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9, and the absorption tower inlet SO ₂ concentration meter 10 were detected. The absorption tower inlet SO ₂ concentration B, the absorbent slurry flow rate D detected by the absorbent slurry flow meter 12, and the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13 are input to the controller 6, By multiplying the absorption tower inlet SO ₂ concentration B detected by the absorption tower inlet SO ₂ concentration meter 10 in the multiplier 15 of the controller 6 by the set desulfurization rate, the desulfurization SO ₂ concentration 14 is obtained and multiplied. The desulfurization gas flow rate A detected by the desulfurization gas flow meter 9 in the multiplier 17 is multiplied by the desulfurization SO ₂ concentration 14 output from the multiplier 15 to be removed from the exhaust gas. Should be an absorption tower Is coming SO ₂ amount 16 flows outputted to the multiplier 19 is determined to respect SO ₂ amount 16 outputted from the multiplier 17 in the multiplier 19 (absorbent weight / SO ₂ volume) By multiplying the value, the absorbent amount 18 is obtained and output to the multiplier 21, and the multiplier 21 multiplies the absorbent amount 18 output from the multiplier 19 by the set absorbent excess rate. The required absorbent amount 20 actually required is obtained and output to the adder 27, while the preset pH value preset in the subtracter 23 and the pH of the absorbent 1 detected by the pH meter 7 The pH deviation 22 is output to the proportional integral controller 25, and the pH deviation 22 output from the subtractor 23 in the proportional integral controller (controller performing feedback control calculation) 25 is proportional. Integration Then, an absorbent conversion amount 24 for eliminating the pH deviation 22 is output to the adder 27, and the adder 27 outputs the necessary absorbent amount 20 output from the multiplier 21 from the proportional-integral controller 25. By adding the output amount 24 of the absorbent conversion, a pH-considered necessary absorbent amount 26 is obtained and output to the divider 29, and the pH-considered absorbent amount output from the adder 27 in the divider 29. 26 is divided by the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13, the set absorbent slurry flow rate 28 is obtained and output to the subtractor 31. The difference between the output set absorbent slurry flow rate 28 and the absorbent slurry flow rate D detected by the absorbent slurry flow meter 12 is obtained, and the absorbent slurry deviation 30 is the ratio. An example of the opening degree command 32 for eliminating the absorbent slurry deviation 30 is obtained by proportionally integrating the absorbent slurry deviation 30 outputted from the subtractor 31 in the proportional integral regulator 33. Output to the regulating valve 8, the opening degree of the flow regulating valve 8 is adjusted, and control is performed so that the absorbent slurry flow rate D becomes equal to the set absorbent slurry flow rate 28, thereby adjusting the pH of the absorbent 1. The set pH value is maintained.
[0008]
[Problems to be solved by the invention]
However, in the conventional control system as described above, the proportionality constant and integral constant of the proportional-plus-integral regulator 25 for maintaining the pH of the absorbent 1 at the set pH value are the load (the SO that flows into the absorption tower 3). since is constant regardless of _the variations of _the amount of 16), for example, proportional constant and integral constant of the proportional integral controller 25, if that is the proper when the load is high, the load becomes lower absorption When the amount of SO ₂ 16 flowing into the tower 3 decreases, the pH deviation 22 of the absorbent 1 is the same as when the load is high, and the amount of absorbent slurry supplied to the absorber 3 is the same. Actually, an excessive amount of the absorbent slurry is supplied to the absorption tower 3, and the pH of the absorbent 1 becomes unstable. On the contrary, the proportional constant and integral constant of the proportional integral controller 25 are different. Appropriate when the load is low When the load increases and the SO ₂ amount 16 flowing into the absorption tower 3 increases, the pH deviation 22 of the absorption liquid 1 is the same as when the load is low, and the absorbent supplied to the absorption tower 3 Even if the amount of the slurry is the same, the absorbent slurry actually supplied to the absorption tower 3 is insufficient, and the convergence of the pH deviation 22 of the absorbent 1 is delayed. It was.
[0009]
In view of such circumstances, the present invention can quickly converge the pH deviation of the absorbent from a low load to a high load, and can stabilize the pH of the absorbent. The device is to be provided.
[0010]
[Means for Solving the Problems]
The present invention obtains the amount of SO ₂ flowing into the absorption tower based on the detected desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration, and the necessary amount of absorbent actually required based on the SO ₂ amount. On the other hand, a pH deviation between a preset pH value set in advance and the detected pH of the absorbing solution is obtained, and an absorbent conversion amount for eliminating the pH deviation is obtained by proportionally integrating the pH deviation, By adding the equivalent amount of the absorbent to the amount of the necessary absorbent, the pH-required necessary amount of absorbent is obtained, and the pH of the absorbent is obtained by dividing the pH-required necessary amount of absorbent by the detected concentration of the absorbent slurry. Obtain the set absorbent slurry flow rate required to maintain the set pH value, and adjust the detected exhaust slurry flow rate so that the detected absorbent slurry flow rate becomes equal to the set absorbent slurry flow rate. In the control method the absorbent slurry flow control method for flue gas desulfurization apparatus and sets, based on the SO ₂ amount proportional constant and integral constant and, respectively, come to flow into the absorption column at the time of proportional integral processing the pH deviation It is such a thing.
[0011]
Further, the present invention includes a pH meter for detecting the pH of the absorption liquid in the absorption tower, the desulfurization gas flow meter for detecting the desulfurized gas flow rate, and the absorption tower inlet SO ₂ concentration meter for detecting the absorption tower inlet SO ₂ concentration An absorbent slurry flow meter for detecting the absorbent slurry flow rate, an absorbent slurry concentration meter for detecting the absorbent slurry concentration, and a flow rate adjusting valve for adjusting the flow rate of the absorbent slurry supplied into the absorption tower,
The amount of SO ₂ flowing into the absorption tower is determined based on the desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration, and the necessary amount of absorbent actually required is calculated based on the amount of SO _2. A pH deviation between the set pH value and the pH of the absorbing solution is obtained, and the pH deviation is proportionally integrated using a proportional constant and an integral constant set based on the SO ₂ amount. To determine the amount of the absorbent required for pH consideration by adding the amount of the equivalent of the absorbent to the amount of the required absorbent, and determine the amount of the absorbent necessary for pH consideration as the concentration of the absorbent slurry. The flow rate adjustment valve is determined so that the set absorbent slurry flow rate required to maintain the pH of the absorbent at the set pH value is obtained by dividing the absorbent slurry flow rate by the set absorbent slurry flow rate. Open the opening command to In which according to the absorbent slurry flow controller flue gas desulfurization apparatus characterized by comprising a controller for.
[0012]
According to the above means, the following operation can be obtained.
[0013]
In the method of controlling the flow rate of the absorbent slurry of the flue gas desulfurization apparatus of the present invention, during operation, the amount of SO ₂ flowing into the absorption tower is determined based on the detected desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration. On the other hand, the necessary amount of absorbent actually required is obtained based on the amount of SO _2, while the pH deviation between the preset set pH value and the detected pH of the absorbent is obtained, and the pH deviation is proportional Absorbent equivalent amount for eliminating the pH deviation after integration processing is obtained, and by adding the absorbent equivalent amount to the required absorbent amount, the pH-required absorbent amount is obtained, and the pH consideration is necessary. By dividing the absorbent amount by the detected absorbent slurry concentration, the set absorbent slurry flow rate required to maintain the pH of the absorbent at the set pH value is obtained, and the detected absorbent slurry flow rate is Set absorbent To be equal to Larry flow, the control is carried out, the pH deviation is respectively the proportional constant and integral constant in the proportional integration processing is set based on the SO ₂ content coming flows into the absorption tower.
[0014]
Further, in the absorbent slurry flow control device of the flue gas desulfurization apparatus of the present invention, during operation, the pH of the absorption liquid detected by the pH meter, the desulfurization gas flow rate detected by the desulfurization gas flow meter, and the absorption tower inlet The absorption tower inlet SO ₂ concentration detected by the SO ₂ concentration meter, the absorbent slurry flow rate detected by the absorbent slurry flow meter, and the absorbent slurry concentration detected by the absorbent slurry concentration meter are input to the controller. In the controller, the amount of SO ₂ flowing into the absorption tower is determined based on the desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration, and it is actually necessary based on the SO ₂ amount. While the amount of the absorbent is obtained, a pH deviation between a preset pH value set in advance and the pH of the absorbent is obtained, and a proportional constant and an integral constant are set based on the SO ₂ amount. Proportional integral processing using Absorbent equivalent amount for eliminating pH deviation is determined, and by adding the absorbent equivalent amount to the necessary absorbent amount, the pH-required absorbent amount is obtained, and the pH-required absorbent amount By dividing by the absorbent slurry concentration, the set absorbent slurry flow rate required to maintain the pH of the absorbent at the set pH value is determined, so that the absorbent slurry flow rate becomes equal to the set absorbent slurry flow rate. An opening degree command is output to the flow rate adjustment valve, and the opening degree of the flow rate adjustment valve is adjusted.
[0015]
As a result, in the absorbent slurry flow rate control method and apparatus of the flue gas desulfurization apparatus of the present invention, the proportionality constant and the integral constant at the time of the proportional-integration processing performed to maintain the pH of the absorbent at the set pH value are: Since it is always set to an appropriate value according to the change in the amount of SO ₂ flowing into the absorption tower, for example, when the load is low and the amount of SO ₂ flowing into the absorption tower is small, the pH deviation of the absorption liquid Even if the load is the same as when the load is high, the amount of the absorbent slurry supplied to the absorption tower is reduced by a required amount compared to the case of a high load, and an excessive amount of the absorbent slurry is not supplied to the absorption tower. On the other hand, when the pH of the absorption liquid is stabilized, on the contrary, when the load is high and the amount of SO ₂ flowing into the absorption tower is large, the absorption liquid is supplied to the absorption tower even if the pH deviation of the absorption liquid is the same as at low load. The amount of absorbent slurry is required from low load Only increases, prevents the absorbent slurry supplied to the absorption tower is insufficient convergence of pH deviation of the absorption liquid is be carried out promptly.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 shows an example of an embodiment of the present invention. In the figure, the same reference numerals as those in FIGS. 4 and 5 denote the same components, and the basic configuration is shown in FIGS. Although the same as the conventional one shown in FIG. 1, the characteristic feature of this example is that the proportionality constant 34 of the proportional-plus-integral regulator 25 is obtained based on the SO ₂ amount 16 as shown in FIG. And a function generator 37 for obtaining an integral constant 36 of the proportional-plus-integral regulator 25 based on the SO ₂ amount 16 and outputting it to the proportional-plus-integral regulator 25.
[0018]
The function generator 35 is input with a function as shown in FIG. 2, which indicates that the proportional constant 34 is increased or decreased in proportion to the increase or decrease in the SO ₂ amount 16. Yes. Further, the function generator 37 is input with a function as shown in FIG. 3, which indicates that the integration constant 36 is increased or decreased in proportion to the increase or decrease of the SO ₂ amount 16. Yes.
[0019]
Next, the operation of the illustrated example will be described.
[0020]
During operation of the flue gas desulfurization apparatus, the pH of the absorbent 1 detected by the pH meter 7, the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9, and the absorption detected by the absorption tower inlet SO ₂ concentration meter 10. The tower inlet SO ₂ concentration B, the absorbent slurry flow rate D detected by the absorbent slurry flow meter 12, and the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13 are input to the controller 6, The multiplier 15 of the controller 6 multiplies the absorption tower inlet SO ₂ concentration B detected by the absorption tower inlet SO ₂ concentration meter 10 by the set desulfurization rate to obtain the desulfurization SO ₂ concentration 14 and the multiplier. The desulfurization gas flow rate A detected by the desulfurization gas flow meter 9 in the multiplier 17 is multiplied by the desulfurization SO ₂ concentration 14 output from the multiplier 15 to be removed from the exhaust gas. To the power absorption tower 3 Input to come SO ₂ amount 16 is outputted to the multiplier 19 being sought, the value of the relative SO ₂ amount 16 outputted from the multiplier 17 in the multiplier 19 (absorber weight / SO ₂ volume) , The amount of the absorbent 18 is obtained and output to the multiplier 21, and the multiplier 21 multiplies the amount of absorbent 18 output from the multiplier 19 by the set absorbent excess rate. The necessary amount of absorbent 20 that is actually required is obtained and output to the adder 27.
[0021]
On the other hand, the difference between the preset pH value set in advance in the subtractor 23 and the pH of the absorbent 1 detected by the pH meter 7 is obtained, and the pH deviation 22 is output to the proportional integration controller 25, where the proportional integration is performed. In the regulator 25, the pH deviation 22 output from the subtractor 23 is subjected to proportional integration processing and an absorbent conversion amount 24 for eliminating the pH deviation 22 is output to the adder 27. Here, the multiplier 17 The function generator 35 obtains the proportionality constant 34 of the proportional-plus-integral regulator 25 based on the SO ₂ amount 16 outputted from the proportional-plus-integral regulator 25 and outputs it to the proportional-plus-integral regulator 25 and the SO ₂ outputted from the multiplier 17. output in function generator 37 based on the amount 16 is demanded integration constant 36 of the proportional integral controller 25 to the proportional integral controller 25, the proportional integral controller 25 in accordance with the SO ₂ volume 16 at that time Example constant 34 and the integral constant 36 and the proportional-plus-integral calculator since the form is re-set 25, operations are performed to quickly stabilize the absorption tower fluid pH.
[0022]
In the adder 27, an absorbent conversion amount 24 output from the proportional-plus-integration controller 25 is added to the required absorbent amount 20 output from the multiplier 21, thereby obtaining a pH-required required absorbent amount 26. Is obtained and output to the divider 29, and the divider-required absorbent amount 26 in consideration of pH output from the adder 27 is divided by the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13. As a result, the set absorbent slurry flow rate 28 is obtained and output to the subtractor 31, which is detected by the set absorbent slurry flow rate 28 output from the divider 29 and the absorbent slurry flow meter 12. The difference from the absorbent slurry flow rate D is obtained, and the absorbent slurry deviation 30 is output to the proportional-plus-integral adjuster 33. The absorbent slurry deviation 30 output from 1 is proportionally integrated, and an opening degree command 32 for eliminating the absorbent slurry deviation 30 is outputted to the flow rate adjustment valve 8, and the opening degree of the flow rate adjustment valve 8 is adjusted, Control is performed so that the absorbent slurry flow rate D becomes equal to the set absorbent slurry flow rate 28.
[0023]
As a result, as described above, the proportionality constant 34 and the integration constant 36 of the proportional-plus-integral controller 25 for maintaining the pH of the absorbent 1 at the set pH value are the load (the amount of SO ₂ flowing into the absorption tower 3). 16) is always reset to an appropriate value in accordance with the change in 16). For example, when the load 16 is low and the amount of SO ₂ flowing into the absorption tower 3 is small, the pH deviation 22 of the absorbent 1 is high. The amount of the absorbent slurry supplied to the absorption tower 3 is less than the required amount even when the load is high, so that an excessive amount of the absorbent slurry is not supplied to the absorption tower 3 and the absorption On the other hand, when the pH of the liquid 1 is stabilized, on the contrary, when the load is high and the SO ₂ amount 16 flowing into the absorption tower 3 is large, even if the pH deviation 22 of the absorption liquid 1 is the same as that at the low load, the absorption tower The amount of absorbent slurry supplied to 3 is the required amount from the time of low load Only increases, prevents a shortage of the absorbent slurry supplied to the absorption tower 3, the convergence of pH deviation 22 of the absorbing liquid 1 is be carried out promptly.
[0024]
Thus, the pH deviation 22 of the absorbent 1 can be quickly converged from a low load to a high load, and the pH of the absorbent 1 can be stabilized.
[0025]
In addition, the absorbent slurry flow rate control method and apparatus of the flue gas desulfurization apparatus of the present invention is not limited to the above illustrated examples, and various modifications can be made without departing from the scope of the present invention. Of course.
[0026]
【The invention's effect】
As described above, according to the absorbent slurry flow rate control method and apparatus of the flue gas desulfurization apparatus of the present invention, the pH deviation of the absorption liquid can be quickly converged from low load to high load, and the pH of the absorption liquid It is possible to achieve an excellent effect that can be stabilized.
[Brief description of the drawings]
FIG. 1 is a control block diagram illustrating an example of an embodiment of the present invention.
FIG. 2 is a diagram representing a function input to a function generator 35 shown in FIG.
FIG. 3 is a diagram representing a function input to the function generator 37 shown in FIG.
FIG. 4 is an overall schematic configuration diagram of a conventional example.
FIG. 5 is a control block diagram of the controller shown in FIG. 4;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Absorbent 3 Absorption tower 6 Controller 7 pH meter 8 Flow control valve 9 Desulfurization gas flow meter 10 Absorption tower inlet SO ₂ concentration meter 12 Absorbent slurry flow meter 13 Absorbent slurry concentration meter 16 SO ₂ amount 20 Necessary amount of absorbent 22 pH deviation 24 Absorbent conversion amount 25 Proportional integral controller 26 Absorbent amount required for pH 28 Setting absorbent slurry flow rate 32 Opening command 34 Proportional constant 35 Function generator 36 Integration constant 37 Function generator A Desulfurization gas flow rate B Absorption Tower inlet SO ₂ concentration D Absorbent slurry flow rate E Absorbent slurry concentration

Claims (2)

While obtaining the amount of SO ₂ flowing into the absorption tower based on the detected desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration, and obtaining the necessary amount of absorbent actually required based on the amount of SO ₂ , Obtain a pH deviation between a preset pH value set in advance and the pH of the detected absorbent, determine an absorbent conversion amount for eliminating the pH deviation by proportionally integrating the pH deviation, and the required amount of absorbent By adding the amount in terms of the absorbent to the pH, the pH-required absorbent amount is obtained, and the pH-required absorbent amount is divided by the detected absorbent slurry concentration to set the pH of the absorbent to the set pH value. In the absorbent slurry flow rate control method of the flue gas desulfurization apparatus that performs control so as to obtain a set absorbent slurry flow rate required to maintain the flow rate and to make the detected absorbent slurry flow rate equal to the set absorbent slurry flow rate, pH deviation Absorbent slurry flow control method for flue gas desulfurization apparatus characterized by setting proportionality constant in the proportional integration processing and integral constants and the respective, based on the SO ₂ content coming flows into the absorption tower. A pH meter for detecting the pH of the absorption liquid in the absorption tower, the desulfurization gas flow meter for detecting the desulfurized gas flow rate, and the absorption tower inlet SO ₂ concentration meter for detecting the absorption tower inlet SO ₂ concentration, the absorbent slurry flow rate An absorbent slurry flow meter for detecting, an absorbent slurry concentration meter for detecting the absorbent slurry concentration, a flow rate adjusting valve for adjusting the flow rate of the absorbent slurry supplied into the absorption tower,
The amount of SO ₂ flowing into the absorption tower is determined based on the desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration, and the necessary amount of absorbent actually required is calculated based on the amount of SO _2. A pH deviation between the set pH value and the pH of the absorbing solution is obtained, and the pH deviation is proportionally integrated using a proportional constant and an integral constant set based on the SO ₂ amount. To determine the amount of the absorbent required for pH consideration by adding the amount of the equivalent of the absorbent to the amount of the required absorbent, and determine the amount of the absorbent necessary for pH consideration as the concentration of the absorbent slurry. The flow rate adjustment valve is determined so that the set absorbent slurry flow rate required to maintain the pH of the absorbent at the set pH value is obtained by dividing the absorbent slurry flow rate by the set absorbent slurry flow rate. Open the opening command to Absorbent slurry flow controller flue gas desulfurization apparatus characterized by comprising a controller for.

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