JPH11244646A - Control of flow rate of absorbent slurry of stack gas desulfurizer and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the desulfurization efficiency constant and to decrease the SO2 concn. at the outlet of an absorption tower below a control value even if the flow rate of the waste gas introduced into the absorption tower exceeds a planned value transiently when the circulation of a liq. absorbent is maximized in the absorption tower. SOLUTION: While all the plural circulating pumps 4 of an absorption tower 1 are operated and further the activity of the absorbent is not lowered, a set pH value is temporarily raised and a set flow rate of the absorbent slurry is increased, when the SO2 concn. C at the outlet of the absorption tower is abnormally increased above the set value or the desulfurization efficiency is decreased below the set value. Further, the command 32 on the opening degree of a flow control valve 8 is outputted from a controller 6 so that the absorbent slurry flow rate D is equalized with the increased set absorbent slurry flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling a flow rate of an absorbent slurry in a flue gas desulfurization apparatus.

[0002]

2. Description of the Related Art Calcium carbonate (CaCO) is used as an absorbent.
_As shown in FIG. 5, a flue gas desulfurization apparatus using ₃ ) generally has an absorption tower 3 in which a liquid reservoir 1a for absorbing liquid 1 is formed at a lower part and a number of spray nozzles 2 are arranged at an upper part. A plurality of circulating pumps 4 for pumping up the absorption liquid 1 in the liquid reservoir 1a of the absorption tower 3 and spraying and circulating the same from the spray nozzle 2, and supplying oxidizing air to the liquid reservoir 1a of the absorption tower 3; And an oxidizing air blower 5.

[0003] In the case of the above-mentioned flue gas desulfurization apparatus, the absorption 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 mixed with the absorbent 1 sprayed from the spray nozzle 2. By contacting
After SO ₂ (sulfur oxide) is absorbed and removed, it is discharged to the outside.

On the other hand, a part of the absorbing liquid 1 which has absorbed SO ₂ from the exhaust gas is recovered as a gypsum slurry from the bottom of the liquid reservoir 1a of the absorption tower 3, and water is removed from the gypsum slurry to form gypsum. It has become so.

A required amount of the absorbent slurry is supplied to the absorption tower 3 by appropriately controlling the opening of the flow control valve 8 as necessary. The system includes a pH meter 7 for detecting the pH (pH) of the absorbing solution 1 in the absorption tower 3, a desulfurization gas flowmeter 9 for detecting the desulfurization gas flow rate A, and an absorption tower for detecting the SO ₂ concentration B at the inlet of the absorption tower. An inlet SO ₂ concentration meter 10, an absorbent slurry flow meter 12 for detecting an absorbent slurry flow rate D, and an absorbent slurry concentration meter 13 for detecting an absorbent slurry concentration E are provided. The detected 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 Densitometer 1
Based on the absorbent slurry concentration E detected in step 3, the set absorbent slurry flow rate 28 (see FIG. 6) required to maintain the pH of the absorbent 1 at the set pH value is determined. The controller 6 outputs the opening command 32 to the flow regulating valve 8 so that the flow rate D becomes equal to the set absorbent slurry flow rate 28.

As shown in FIG. 6, the controller 6 multiplies the SO ₂ concentration B detected by the SO ₂ concentration meter 10 by a set desulfurization rate (for example, 90%). Accordingly, a multiplier 15 which obtains and outputs the desulfurization SO ₂ concentration of 14, applying a desulfurizing SO ₂ concentration of 14 outputted from the multiplier 15 to the desulfurizing gas flowmeter 9 in the detected desulfurized gas flow a Accordingly, multiplying a multiplier 17 which obtains and outputs the SO ₂ volume 16 to be removed from the flue gas, relative to SO ₂ amount 16 outputted from the multiplier 17 the value of (absorbent weight / SO ₂ volume) As a result, the amount of the absorbent is 18
Is obtained by multiplying the amount of absorbent 18 output from the multiplier 19 by the set excess amount of the absorbent (for example, 1.02), thereby obtaining the required amount of absorbent actually required. A multiplier 21 for calculating and outputting 20; calculating a difference between a preset set pH value (for example, 5.0) and the pH of the absorbing solution 1 detected by the pH meter 7 to output a pH deviation 22; A subtractor 23 and p output from the subtractor 23
A proportional-integral controller 25 for outputting an absorbent conversion amount 24 obtained by converting the H deviation 22 into a proportional amount for eliminating the pH deviation 22 by eliminating the pH deviation 22, and a required absorbent amount output from the multiplier 21 An adder 27 for obtaining and outputting a pH-consideration-required absorbent amount 26 by adding an absorbent conversion amount 24 converted to an absorbent amount output from the proportional-integral controller 25 to the 20; A divider 29 for obtaining and outputting a set absorbent slurry flow rate 28 by dividing the pH-considered necessary absorbent quantity 26 outputted from 27 by the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13.
And a difference between the set absorbent slurry flow rate 28 output from the divider 29 and the absorbent slurry flow rate D detected by the absorbent slurry flow meter 12, and outputs a difference 30 of the absorbent slurry deviation. And a proportional-integral controller 33 for outputting a command 32 for opening the flow control valve 8 to eliminate the absorbent slurry deviation 30 by performing a proportional integral process on the absorbent slurry deviation 30 output from the subtractor 31. It has a configuration provided.

[0007] During operation of the flue gas desulfurization unit, the pH meter 7
, The desulfurization gas flow rate A detected by the desulfurization gas flow meter 9, and the SO ₂ concentration meter 1 at the inlet of the absorption tower.
0, the SO ₂ concentration B detected at the inlet of the absorption tower, the flow rate D of the absorbent slurry detected by the absorbent slurry flowmeter 12,
The absorbent slurry concentration E detected by the absorbent slurry concentration meter 13 is input to the controller 6, and the multiplier 1 of the controller 6
In 5, the desulfurization SO ₂ concentration 14 is obtained by multiplying the absorption tower inlet SO ₂ concentration B detected by the absorption tower inlet SO ₂ concentration meter 10 by the set desulfurization rate.
7 and the multiplier 17 compares the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9 with the multiplier 1.
The amount 16 of SO ₂ to be removed from the exhaust gas is obtained by multiplying by the concentration 14 of the desulfurized SO ₂ output from 5 and output to the multiplier 19, where the SO ₂ output from the multiplier 17 is output. For amount 16 (absorbent amount /
By multiplying by the value of (SO ₂ amount), the amount of absorbent 18 is obtained and output to the multiplier 21. By multiplying by the rate, the required amount of absorbent 20 actually required is obtained and output to the adder 27, while the set pH value preset in the subtractor 23 and the absorption detected by the pH meter 7 are determined. The difference from the pH of the liquid 1 is determined, and the pH deviation 22 is output to the proportional-integral controller 25,
In the proportional integration controller (controller performing feedback control calculation) 25, the pH deviation 22 output from the subtracter 23 is subjected to proportional integration processing, and the absorbent is converted into an absorbent amount for eliminating the pH deviation 22. The conversion amount 24 is output to the adder 27, where the multiplier 21
Is added to the required amount of absorbent 20 output from the above, and the converted amount of absorbent 24 converted to the amount of absorbent output from the proportional-plus-integral controller 25 is added.
6 is output to the divider 29. In the divider 29, the pH-considered absorbent amount 26 output from the adder 27 is determined by the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13. By dividing, the set absorbent slurry flow rate 28 is obtained and output to the subtracter 31, and the set absorbent slurry flow rate 28 output from the divider 29 and the absorbent slurry flow meter 1 in the subtracter 31.
2, the difference from the absorbent slurry flow rate D detected is obtained, and the absorbent slurry deviation 30 is output to the proportional-integral controller 33, where the subtractor 31
Is output from the flow rate control valve 8 to adjust the opening degree of the flow rate control valve 8, and the opening degree command of the flow rate control 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, whereby the pH of the absorbent 1 is maintained at the set pH value.

[0008]

Incidentally, in the case of the conventional flue gas desulfurization apparatus, the flow rate of the absorbent slurry supplied to the absorption tower 3 is controlled as described above. By controlling the circulation amount of the absorbent 1 in the absorption tower 3 by appropriately increasing or decreasing the number of operating circulating pumps 4, the desulfurization rate is maintained and S at the outlet of the absorption tower 3 is maintained.
The O ₂ concentration is kept below the regulation value.

However, if all the circulation pumps 4 are operated and the circulating amount of the absorbent 1 in the absorption tower 3 is at a maximum, the flow rate of the exhaust gas introduced into the absorption tower 3 is temporarily changed to the planned value. In the case where the SO ₂ concentration exceeds the limit, the SO ₂ concentration at the outlet of the absorption tower 3 may not be able to be suppressed to a regulated value or less while maintaining the desulfurization rate.

The present invention has been made in view of the above-mentioned circumstances, and in a state where the circulating amount of the absorbing liquid in the absorption tower is maximum,
When the flow rate of exhaust gas introduced into the absorption tower, such as increased beyond transiently planned well, the flue gas desulfurization apparatus holding the desulfurization rate can suppress the absorption tower outlet SO ₂ concentration below regulatory limits It is an object of the present invention to provide an absorbent slurry flow rate control method and apparatus.

[0011]

Means for Solving the Problems The present invention provides a desulfurizing gas flow rate is detected, and the absorption tower inlet SO ₂ concentration, pH of the absorbing liquid
And the pH of the absorbing solution based on the concentration of the absorbent slurry
Calculate the set absorbent slurry flow rate required to maintain the set pH value, and control so that the detected absorbent slurry flow rate is equal to the set absorbent slurry flow rate. In the control method, when all of the plurality of circulating pumps of the absorption tower are operated and the activity of the absorbent is not reduced, the outlet SO of the absorption tower is controlled.
_{(2) When} an abnormality occurs in which the concentration is equal to or higher than the high set concentration or the desulfurization rate is equal to or lower than the low set desulfurization rate, the set pH value is temporarily increased and the set absorbent slurry flow rate is increased. The present invention relates to a method for controlling the flow rate of an absorbent slurry in a smoke desulfurization apparatus.

[0012] 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, the absorption tower inlet SO ₂ for detecting the concentration absorption tower inlet SO ₂ and densitometer, and the absorption tower outlet SO ₂ concentration meter for detecting the absorption tower outlet SO ₂ concentration, and the absorbent slurry flow meter for detecting the absorbent slurry flow rate, and the absorbent slurry concentration meter for detecting an absorbent slurry concentration, a flow rate adjusting valve for adjusting the absorbent slurry flow supplied to the absorption tower, in normal operation, and the desulfurized gas flow rate, and the absorption tower inlet SO ₂ concentration, and pH of the absorbing liquid, said absorbent slurry concentration Based on the above, determine the set absorbent slurry flow rate required to maintain the pH of the absorbent at a set pH value, the flow rate adjusting valve so that the absorbent slurry flow rate is equal to the set absorbent slurry flow rate When the plurality of circulating pumps of the absorption tower are operated and no decrease in the activity of the absorbent occurs, the outlet SO
_{(2) When} an abnormality occurs in which the concentration is equal to or higher than the high set concentration or the desulfurization rate is equal to or lower than the low set desulfurization rate, the set pH value is temporarily increased, and the set absorbent slurry flow rate is increased,
A controller for outputting an opening command to the flow rate regulating valve so that the absorbent slurry flow rate is equal to the increased set absorbent slurry flow rate, wherein the absorbent slurry flow rate of the flue gas desulfurization device is provided. It depends on the control device.

According to the above means, the following effects can be obtained.

In the method for controlling the flow rate of an absorbent slurry in a flue gas desulfurization apparatus according to the present invention, the flow rate of the detected desulfurization gas, the concentration of SO _{2 at the} inlet of the absorption tower, the pH of the absorbent, and the concentration of the slurry of the absorbent slurry are determined. The set absorbent slurry flow rate required to maintain the pH of the absorbent at the set pH value is determined, and control is performed so that the detected absorbent slurry flow rate is equal to the set absorbent slurry flow rate. In a state in which all the circulation pumps of the absorption tower are operated and the activity of the absorbent is not reduced, the SO ₂ concentration at the outlet of the absorption tower is higher than the high set concentration or the desulfurization rate is lower than the low set desulfurization rate. , The set pH value is temporarily increased, and the set absorbent slurry flow rate is increased.

Further, in the absorbent slurry flow rate control apparatus of the flue gas desulfurization apparatus of the present invention, during normal operation, the detected desulfurization gas flow rate, the concentration of SO _{2 at the} inlet of the absorption tower, the pH of the absorbent, On the basis of the slurry concentration, the controller determines a set absorbent slurry flow rate necessary to maintain the pH of the absorbent at a set pH value, and the absorbent slurry flow rate is equal to the set absorbent slurry flow rate. As described above, the opening command is output to the flow control valve, and the plurality of circulating pumps of the absorption tower are all operated and the activity of the absorbent is not reduced.
When an abnormality occurs in which the O ₂ concentration is equal to or higher than the high set concentration or the desulfurization rate is equal to or lower than the low set desulfurization rate, the set pH value is temporarily increased, the set absorbent slurry flow rate is increased, and the absorbent slurry is increased. An opening command is output to the flow control valve so that the flow rate becomes equal to the set absorbent slurry flow rate that has been increased, and the opening degree of the flow control valve is adjusted.

As a result, in the method and the apparatus for controlling the flow rate of the absorbent slurry in the flue gas desulfurization apparatus according to the present invention, when all the circulation pumps are operated and the circulation amount of the absorbent in the absorption tower is maximum, Even when the flow rate of exhaust gas introduced into the absorption tower transiently rises above the planned value,
Desulfurization rate absorption tower outlet SO ₂ concentration is maintained also be suppressed to below the regulated value.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 4 show an example of an embodiment of the present invention. In the drawings, the portions denoted by the same reference numerals as those in FIGS. 5 and 6 represent the same components. This is similar to the conventional one shown in FIGS. 5 and 6, but the feature of this illustrated example is that as shown in FIGS.
_2. A switching relay 35 for switching and outputting a desired pH addition value in the controller 6 while additionally providing an absorption tower outlet SO ₂ concentration meter 34 for detecting the concentration C.
When the pH addition value 36 output from the controller changes, a process of restricting the rate of change to a range equal to or less than a set value is performed, and p
A rate-of-change limiter 37 that outputs an H-added value 36 ′, and a pH-added value 36 ′ output from the rate-of-change limiter 37.
An adder 38 for outputting to the subtractor 23 in addition to the H value, and an absorption tower outlet S detected by the absorption tower outlet SO ₂ concentration meter 34.
A switching relay control circuit 39 for switching the switching relay 35 based on the O ₂ concentration C and the absorption tower inlet SO ₂ concentration B detected by the absorption tower inlet SO ₂ concentration meter 10 is additionally provided. In the state where all the circulation pumps 4 are operated and the activity of the absorbent does not decrease, the SO ₂ concentration C at the outlet of the absorption tower is higher than the high set concentration or the desulfurization rate is lower than the low set desulfurization rate. When an abnormality occurs, the set pH value is temporarily increased, the set absorbent slurry flow rate 28 is increased, and the controller 6 controls the flow rate so that the absorbent slurry flow rate D becomes equal to the increased set absorbent slurry flow rate 28. The point is that the opening degree command 32 is output to the regulating valve 8.

The switching relay control circuit 39 for switching the switching relay 35 has a configuration as shown in FIG.

That is, the signal monitor switch 40 determines whether the SO ₂ concentration C at the outlet of the absorption tower is higher than the set high concentration or lower than the low set concentration.
_{2 If the} density C is equal to or higher than the high density, the set signal 42 is output to the single flip-flop 41, and
When the SO ₂ concentration C at the outlet of the absorption tower is lower than the low set concentration, the reset signal 4 is sent to the single flip-flop 41.
While output 3, the desulfurization rate in the arithmetic unit 44 based on the absorption tower inlet SO ₂ concentration B and absorption tower outlet SO ₂ concentration C (absorption tower inlet SO ₂ concentration B- absorption tower outlet SO ₂ concentration C) /
The SO ₂ concentration B × 100 [%] at the inlet of the absorption tower is calculated, and the signal monitor switch 45 determines whether the desulfurization rate is equal to or lower than the low set desulfurization rate or higher than the high set desulfurization rate. When the desulfurization rate is lower than the low set desulfurization rate, the set signal 47 is output to the single flip-flop 46. When the desulfurization rate is higher than the high set density, the reset signal 48 is output to the single flip-flop 46. , The single flip-flops 41, 4
6 are input to an OR circuit 51, and an OR signal 52 output from the OR circuit 51 is input.
When the plurality of circulating pumps 4 of the absorption tower 3 are all operated, the whole-unit operation signal 53 becomes “1”, and when the activity of the absorbent is not reduced, the whole-unit operation signal 53 is output via the NOT circuit 54. The signal 55 which becomes "1" is input to the AND circuit 56.

An AND signal 57 output from the AND circuit 56 is input to an on-delay timer 58 having a time delay T set in advance, and a delay signal 59 output from the on-delay timer 58 is used as a set signal to generate a single signal. The output signal 62 input to the flip-flop 60 and the OR circuit 61 is output from the single flip-flop 60 to the switching relay 35, the AND circuit 63 and the OR signal.
The data is input to the circuit 64.

The OR signal 52 output from the OR circuit 51 is input to an AND circuit 63 via a NOT circuit 65, and an AND signal 66 output from the AND circuit 63 is output.
Is input to the single flip-flop 67 as a set signal, and the output signal 68 output from the single flip-flop 67 is
The logical sum signal 70 input to the R circuit 69 and output from the OR circuit 64 is input to the switching relay 35 via the NOT circuit 71.

Also, a push button (P
When B) is pressed, the reset signal 73 output via the one shot 72 is input to the OR circuit 69 and the OR circuit 61, and the OR signal 74 output from the OR circuit 69 is used as a reset signal. The signal is input to the single flip-flop 60 and the OR signal 75 output from the OR circuit 61 is input to the single flip-flop 67 as a reset signal.

Next, the operation of the illustrated example will be described.

During normal 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 SO ₂ concentration meter 10 in the detected absorption tower inlet SO ₂ concentration B, absorbent slurry flow meter 12 at the detected absorbent slurry flow rate D
And the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13 are input to the controller 6, and the absorption tower detected by the absorber inlet SO ₂ concentration meter 10 in the multiplier 15 of the controller 6. By multiplying the inlet SO ₂ concentration B by the set desulfurization rate, the desulfurized SO ₂ concentration 14 is determined and output to the multiplier 17, where the desulfurized gas flow rate detected by the desulfurized gas flow meter 9 is measured. A is multiplied by the desulfurized SO ₂ concentration 14 output from the multiplier 15 to obtain the SO ₂ amount 16 to be removed from the exhaust gas and output to the multiplier 19. By multiplying the SO ₂ amount 16 output from 17 by the value of (absorbent amount / SO ₂ amount), the absorbent amount 18
Is calculated and output to the multiplier 21. The multiplier 21 multiplies the amount of the absorbent 18 output from the multiplier 19 by the set excess amount of the absorbent, thereby obtaining the required amount of the absorbent actually required. 20 is obtained and output to the adder 27, while the set pH set in the subtractor 23 is set in advance.
The difference between the measured value and the pH of the absorbing solution 1 detected by the pH meter 7 is obtained, and the pH deviation 22 is output to the proportional-integral controller 25, which outputs the value from the subtractor 23. The pH deviation 22 is proportionally integrated, and the converted amount of the absorbent 2 converted to the amount of the absorbent for eliminating the pH deviation 22
4 is output to the adder 27, and in the adder 27, the required amount of absorbent 20 output from the multiplier 21 is converted into the amount of absorbent output from the proportional-integral controller 25. 24, the amount of the pH-considering necessary absorbent 26 is obtained and output to the divider 29. In the divider 29, the amount of the pH-considering necessary absorbent 26 output from the adder 27 is converted into the absorbent slurry concentration. By dividing by the absorbent slurry concentration E detected by the total 13, a set absorbent slurry flow rate 28 is obtained and output to the subtracter 31, and the set absorbent slurry output from the divider 29 in the subtracter 31. The difference between the flow rate 28 and the absorbent slurry flow rate D detected by the absorbent slurry flowmeter 12 is obtained, and the absorbent slurry deviation 30 is output to the proportional-integral controller 33, In the proportional integral controller 33, the absorbent slurry deviation 30 output from the subtractor 31 is proportionally integrated, and an opening command 32 for eliminating the absorbent slurry deviation 30 is output to the flow regulating valve 8 to adjust the flow rate. The opening of the 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, whereby the pH of the absorbent 1 is maintained at the set pH value.

During the normal operation of the flue gas desulfurization apparatus, the all-unit operation signal 53 and the signal 55 shown in FIG.
Since at least one of them is "0", the switching relay 35 is switched to the c side, and the pH added value is 0, whereby the set pH value is input to the subtracter 23 without being increased. Have been.

On the other hand, in a state where the plurality of circulating pumps 4 of the absorption tower 3 are all operated and the activity of the absorbent is not reduced, the concentration C _{2 of the} SO _{2 at the} outlet of the absorption tower is higher than a high concentration. Alternatively, when an abnormality occurs in which the desulfurization rate is lower than the low set desulfurization rate, the all-unit operation signal 53, the signal 55, and the logical sum signal 52 shown in FIG.
6 changes from “0” to “1”, and when a time delay T preset in the on-delay timer 58 elapses, the on-delay timer 58 outputs the delayed signal 59 that has changed to “1”. Is input to the single flip-flop 60 as a set signal and the OR circuit 6
1 and the output signal 62 of “1” output from the single flip-flop 60
The signal is input to the ND circuit 63 and the OR circuit 64, and the switching relay 3
5 is switched to the a side.

When the switching relay 35 is switched to the "a" side, the switching relay 35 outputs the added pH value (for example, 1.
0) is output to the change rate limiter 37 as the pH added value 36, and the change rate limiter 37 performs a process of limiting the change rate of the pH added value 36 to a range equal to or less than a set value.
The added value 36 'is output to the adder 38, and the pH added value 36' output from the change rate limiter 37 is added to the set pH value and output to the subtracter 23, and thereby, The set pH value is increased, the set absorbent slurry flow rate 28 is increased by that amount, and the controller 6 is opened to the flow regulating valve 8 so that the absorbent slurry flow rate D becomes equal to the increased set absorbent slurry flow rate 28. Degree command 32
Is output, the opening degree of the flow control 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.

When the set pH value is increased, and the set absorbent slurry flow rate 28 is increased accordingly, as shown in FIG. 4, the rising SO ₂ concentration C at the outlet of the absorption tower is increased as the pH is increased. The SO ₂ concentration C at the outlet of the absorption tower becomes lower than the low set concentration, the reset signal 43 becomes “1”, and the desulfurization rate becomes higher than the high set desulfurization rate, and the reset signal 48 becomes “1”. ", The OR signal 52 output from the OR circuit 51 becomes" 0 ", a signal" 1 "is output to the AND circuit 63 via the NOT circuit 65, and the output from the single flip-flop 60 Since the output signal 62 is input to the AND circuit 63 as “1”, the AND signal 66 output from the AND circuit 63 becomes “1”, and is output from the single flip-flop 67. The output signal 68 changes from “0” to “1”, the OR signal 74 output from the OR circuit 69 changes to “1”, and the single flip-flop 60
Output signal 62 changes from "1" to "0", and the output signal 68 switches the switching relay 35 from the a side to the b side.

When the switching relay 35 is switched from the side a to the side b, as shown in FIG. 2, the pH added value 36 'output from the rate-of-change limiter 37 is
5, the setting p inputted to the subtractor 23
The H value is held at the increased value at that time, and as shown in FIG. 4, the actual pH is kept at a high value and leveled off, and the SO ₂ concentration C at the outlet of the absorption tower is almost at that time. Stay at the value of.

After exiting from a transient state in which the desulfurization gas flow rate A exceeds the planned value and the SO ₂ concentration C at the outlet of the absorption tower further decreases, a push button (PB) is determined at an appropriate point in time by the operator. ) Is pressed, one shot 7
2 changes from “0” to “1”, and is input to the OR circuit 69 and the OR circuit 61, and the OR signal 75 output from the OR circuit 61 changes from “0” to “1”. ”Is input to the single flip-flop 67 as a reset signal, the output signal 68 output from the single flip-flop 67 changes from“ 1 ”to“ 0 ”, and the OR signal 70 output from the OR circuit 64 changes to“ 1 ”. To "0", the signal output from the NOT circuit 71 changes from "0" to "1", and the switching relay 35 is switched from the b side to the c side.

When the switching relay 35 is switched from the b-side to the c-side, the switching relay 35 outputs the pH added value (0).
Is output to the change rate limiter 37 as the pH addition value 36,
The change rate limiter 37 performs a process of limiting the change rate of the pH addition value 36 to a range equal to or less than a set value, and outputs the pH addition value 36 ′ to the adder 38. PH added value 3 output from limiter 37
6 ′ is added to the set pH value and output to the subtractor 23,
As a result, the set pH value is gradually returned to the original value, and the actual pH is gradually decreased as shown in FIG. 4 and is maintained at the original value.

Thus, in the state where all the circulation pumps 4 are operated and the circulating amount of the absorbing liquid 1 in the absorption tower 3 is the maximum, the flow rate of the exhaust gas introduced into the absorption tower 3 transiently exceeds the planned value. Even in the case where the concentration exceeds the limit, the SO ₂ concentration C at the outlet of the absorption tower can be suppressed to a regulated value or less while maintaining the desulfurization rate.

The method and the apparatus for controlling the flow rate of the absorbent slurry of the flue gas desulfurization apparatus of the present invention are not limited to the above-described examples, and various modifications may be made without departing from the scope of the present invention. Obviously you can get it.

[0035]

As described above, according to the method and the apparatus for controlling the flow rate of the absorbent slurry in the flue gas desulfurization apparatus of the present invention,
In the state where the amount of circulation of the absorbent in the absorption tower is the maximum, even if the flow rate of the exhaust gas introduced into the absorption tower transiently rises above the planned value, the desulfurization rate is maintained. the absorption tower outlet SO ₂ concentration an excellent effect may kept below regulatory limits.

[Brief description of the drawings]

FIG. 1 is an overall schematic configuration diagram of an example of an embodiment of the present invention.

FIG. 2 is a control block diagram of a controller according to an example of an embodiment of the present invention.

FIG. 3 is a control block diagram of a switching relay control circuit shown in FIG. 2;

FIG. 4 is a diagram showing an example of changes in pH and SO ₂ concentration at the outlet of an absorption tower in an example of an embodiment of the present invention.

FIG. 5 is an overall schematic configuration diagram of a conventional example.

FIG. 6 is a control block diagram of a conventional example.

[Explanation of symbols]

1 absorbing fluid 3 sets absorption tower 4 circulating pump 6 controller 7 pH eight flow regulating valve 9 desulfurized gas flowmeter 10 absorption tower inlet SO ₂ concentration meter 12 absorbent slurry flow meter 13 absorbent slurry concentration meter 28 absorbent slurry flow rate 34 Absorption tower outlet SO ₂ concentration meter 35 Switching relay 36 ′ pH addition value 38 Adder 39 Switching relay control circuit 52 Logical sum signal 53 All-unit operation signal 55 Signal A Desulfurization gas flow rate B Absorption tower inlet SO ₂ concentration C Absorption tower outlet SO ₂ concentration D Absorbent slurry flow rate E Absorbent slurry concentration

Claims (2)

[Claims] 1. Based on the detected desulfurization gas flow rate, the concentration of SO _{2 at the} inlet of the absorption tower, the pH of the absorbent, and the concentration of the absorbent slurry, it is necessary to maintain the pH of the absorbent at a set pH value. In the absorbent slurry flow rate control method of the flue gas desulfurization apparatus for controlling so that the detected absorbent slurry flow rate is equal to the set absorbent slurry flow rate, In the state where all the circulation pumps are operated and the activity of the absorbent is not reduced, the concentration of SO _{2 at the} outlet of the absorption tower is higher than the high concentration,
Alternatively, when an abnormality occurs in which the desulfurization rate becomes lower than the low set desulfurization rate, the set pH value is temporarily increased, and the set absorbent slurry flow rate is increased, wherein the absorbent slurry flow rate of the flue gas desulfurization device is increased. Control method. A pH meter for detecting the pH of the absorption liquid in wherein 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, Absorption tower outlet S for detecting absorption tower outlet SO ₂ concentration
O ₂ concentration meter, absorbent slurry flow meter for detecting the absorbent slurry flow rate, absorbent slurry concentration meter for detecting the absorbent slurry concentration, and flow rate adjustment for adjusting the flow rate of the absorbent slurry supplied into the absorption tower and the valve, during normal operation, and the desulfurized gas flow rate, and the absorption tower inlet SO ₂ concentration, and pH of the absorption liquid, on the basis of said absorbent slurry concentration, to maintain the pH of the absorbing solution to set pH value Determine the set absorbent slurry flow rate required for
An opening command is output to the flow control valve so that the absorbent slurry flow rate is equal to the set absorbent slurry flow rate,
Moreover, setting while a plurality of the circulation pump of the absorption tower is not reduced activity of and absorbent are operated all platform occurs, the absorption tower outlet SO ₂ concentration is high set concentration or more, or desulfurization rate is low When an abnormality occurs below the desulfurization rate, the setting p
Control for temporarily increasing the H value, increasing the set absorbent slurry flow rate, and outputting an opening degree command to the flow rate regulating valve so that the absorbent slurry flow rate becomes equal to the increased set absorbent slurry flow rate And an absorber slurry flow rate control device for a flue gas desulfurization device.