JPH11207144A - Method for controlling flow rate of oxidizing air of desulfurizer for stack gas and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method and device for controlling the flow rate of oxidizing air of a desulfurizer for stack gas by which an appropriate amt. of oxidizing air is supplied to a liq. reservoir of an absorption tower, neither too much nor too less, the formation of oxidizing matter is suppressed, the function of a waste water treating device is not lowered, and the lowering of the desulfurizing performance is prevented. SOLUTION: The amt. 14 of inflow SO2 is obtained from the detected flow rate A of a gas to be desulfurized and SO2 concn. B at the inlet of an absorption tower, the amt. 25 of SO2 to be naturally oxidized obtained from the flow rate A and the O2 concn. D of the waste gas introduced into the tower, the amt. 25 of SO2 to be naturally oxidized is subtracted from the amt. 14 of the inflow SO2 to obtain the amt. 14' of the SO2 to be forcedly oxidized, the set flow rate 16 of oxidizing air is obtained from the amt. 14' of the SO2 to be forcedly oxidized, and the actual amt. C of oxidizing air supplied to the liq. reservoir of the tower is equalized to the set flow rate 16 of oxidizing air.

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 an oxidizing air flow rate of a flue gas desulfurization apparatus.

[0002]

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

[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, the absorbing liquid 1 having absorbed SO ₂ from the exhaust gas drops into the liquid reservoir 1a and is forcibly oxidized by the oxidizing air supplied into the liquid reservoir 1a by the operation of the oxidizing air blower 5. , Plaster (calcium sulfate (CaC
O ₄ )) is generated, and the absorbent 1 in the liquid reservoir 1 a containing the gypsum is extracted as a gypsum slurry from the bottom of the absorption tower 3, and water is removed from the gypsum slurry to recover gypsum. The absorption tower 3 is supplied with a required amount of an absorbent slurry as needed.

The flow rate of the oxidizing air supplied into the liquid reservoir 1a by the operation of the oxidizing air blower 5 is controlled by adjusting the opening of the flow rate adjusting damper 7. system, desulfurization gas flowmeter 9 for detecting the desulfurized gas flow a, the absorption tower inlet SO ₂ concentration meter 10 for detecting the absorption tower inlet SO ₂ concentration B, the reservoir portion 1a by the operation of the oxidation air blower 5 Oxidation air flow rate C to be supplied
Oxidizing air flow meter 11 for detecting the flow rate of desulfurization gas detected by the desulfurization gas flow meter 9 and the inlet S of the absorption tower detected by the SO ₂ concentration meter 10 for the absorption tower.
A controller 6 is provided which outputs an opening command 20 to the flow rate adjusting damper 7 based on the O ₂ concentration B and the oxidizing air flow rate C detected by the oxidizing air flow meter 11.

[0006] As shown in FIG. 5, the controller 6 adjusts the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9 to the absorption tower entrance SO ₂ concentration meter 10 detected by the absorption tower entrance SO ₂ concentration meter 10. Multiplier 15 that calculates and outputs inflow SO ₂ amount 14 to be removed from exhaust gas by multiplying by ₂ concentration B
A function generator 17 for obtaining and outputting a set oxidized air flow rate 16 required for forced oxidation based on the inflow SO ₂ amount 14 output from the multiplier 15; and a set oxidized air output from the function generator 17. A subtracter 19 for calculating a difference between the flow rate 16 and the actual oxidizing air flow rate C detected by the oxidizing air flow meter 11 and outputting an oxidizing air flow rate deviation 18;
And a proportional-integral adjuster 21 for outputting an opening command 20 of the flow rate adjusting damper 7 for eliminating the oxidizing air flow rate deviation 18 by performing a proportional integration process on the oxidizing air flow rate deviation 18 output from the controller. doing.

The function generator 17 receives a function as shown in FIG.
₂ Set the oxidizing air flow rate 1 in proportion to the increase / decrease of the quantity 14.
6 is increased or decreased.

During operation of the flue gas desulfurization apparatus, the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9 and the absorption tower inlet S
An absorption tower inlet SO ₂ concentration B detected by an O ₂ concentration meter 10;
The oxidizing air flow rate C detected by the oxidizing air flow meter 11 and the oxidizing air flow rate C are input to the controller 6, and the multiplier 15 of the controller 6 absorbs the desulfurizing gas flow rate A detected by the desulfurizing gas flow meter 9 into the absorption amount. By multiplying the SO ₂ concentration B detected by the SO ₂ concentration meter 10 at the inlet of the absorption tower, the inflow SO ₂ amount 14 to be removed from the exhaust gas is obtained, and the function generator 17
Is output to the multiplier 15 in the function generator 17.
A set oxidizing air flow rate 16 is obtained based on the inflow SO ₂ amount 14 output from the oxidizing air flow rate 16 and the oxidizing air flow rate detected by the oxidizing air flow meter 11. The difference from the flow rate C is determined,
The oxidizing air flow deviation 18 is output to a proportional-integral controller 21, and the oxidizing air flow deviation 18 output from the subtractor 19 is proportionally integrated in the proportional-integral controller 21 to eliminate the oxidizing air flow deviation 18. The opening degree command 20 is output to the flow rate adjusting damper 7, the opening degree of the flow rate adjusting damper 7 is adjusted, and the oxidizing air flow rate C is set to the set oxidizing air flow rate 1
Control is performed so as to be equal to 6.

[0009]

In the case of the above-mentioned conventional flue gas desulfurization apparatus, a multiplier is used without considering the concentration of oxygen (O ₂ ) contained in the exhaust gas introduced into the absorption tower 3 at all. Since the inflow SO ₂ amount 14 output from 15 is input as it is to the function generator 17 as the SO ₂ amount to be forcibly oxidized, and the set oxidized air flow rate 16 is obtained based on the inflow SO ₂ amount 14, The set oxidizing air flow rate 16 may be actually excessive or insufficient. If the set oxidizing air flow rate 16 is excessive, S ₂ O ₈ (persulfuric acid) is used as a side reaction. Oxidizing substances such as acetic acid and IO ₃ (iodic acid) are generated, and the concentration of the oxidizing substances increases, causing a decrease in the activity of nitrifying bacteria in a wastewater treatment device (not shown) of the absorption tower 3 or causing nitrifying bacteria. Died and the drainage While the function of the device is decreased, when the setting oxidation air flow 16 is insufficient, the desulfurization performance had deteriorated.

[0010] In view of such circumstances, the present invention can supply an appropriate amount of oxidizing air to the liquid storage section of the absorption tower without excess and deficiency, suppress the generation of oxidizing substances, and improve the function of the wastewater treatment apparatus. It is an object of the present invention to provide a method and an apparatus for controlling an oxidizing air flow rate of a flue gas desulfurization device capable of preventing a decrease and preventing a decrease in desulfurization performance.

[0011]

According to the present invention, an inflow SO ₂ based on a detected desulfurization gas flow rate and an absorption tower inlet SO ₂ concentration.
The amount of natural oxidized SO ₂ is determined based on the desulfurization gas flow rate and the exhaust gas O ₂ concentration introduced into the absorption tower,
Obtains the inlet SO forced oxidation SO ₂ amount by subtracting the natural oxidation SO ₂ amount from said ₂ weight determines the setting oxidation air flow rate based on the forcible oxidation SO ₂ amount, the actual supplied to the liquid reservoir of absorption tower The present invention relates to a method for controlling an oxidizing air flow rate of a flue gas desulfurization device, wherein control is performed such that the oxidizing air flow rate is equal to the set oxidizing air flow rate.

[0012] Further, the present invention provides a desulfurizing 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 exhaust gas O ₂ concentration is introduced into the absorption tower An exhaust gas O ₂ concentration meter to be detected, an oxidizing air blower for supplying oxidizing air to a liquid reservoir of the absorption tower, and an inflow SO ₂ amount based on the desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration. seeking a natural oxide SO ₂ amount based on the gas flow rate and the exhaust gas O ₂ concentration, the calculated inflow SO forced oxidation SO ₂ amount by subtracting the natural oxidation SO ₂ amount from said ₂ weight set based on the forcible oxidation SO ₂ amount A controller for determining an oxidizing air flow rate and controlling the actual oxidizing air flow rate supplied from the oxidizing air blower to the liquid reservoir of the absorption tower to be equal to the set oxidizing air flow rate. Oxidizing air in flue gas desulfurization equipment In which according to the quantity control device.

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

[0014] Oxidizing air flow rate control of the flue gas desulfurization apparatus of the present invention
In the method, during the operation of the flue gas desulfurization unit,
Desulfurization gas flow rate and SO at inlet of absorption tower_TwoInflow based on concentration
SO_TwoAmount and the desulfurization gas flow rate and absorption
Exhaust gas O introduced into the tower_TwoNatural oxidation SO based on concentration_Two
The quantity is determined and said inflow SO_TwoFrom the amount of the natural oxidation SO _Two
The amount is deducted and forced oxidation SO_TwoThe quantity is determined and said
Oxidized SO_TwoThe set oxidizing air flow rate is determined based on the
The actual flow rate of oxidizing air supplied to the liquid reservoir of the
Control is performed so as to be equal to the constant oxidation air flow rate.

Further, in the oxidizing air flow control device of the flue gas desulfurization apparatus of the present invention, when the flue gas desulfurization apparatus is operated, the desulfurization gas flow rate detected by the desulfurization gas flow meter and the absorption tower inlet S
And O ₂ concentration meter detected absorption tower inlet SO ₂ concentration, and the oxidation air flow rate detected by the oxidation air flow meter, and the exhaust gas O ₂ concentration detected by the exhaust gas O ₂ concentration meter are inputted to the controller,
In the controller, the desulfurization gas flow rate and absorption tower inlet SO
₂ concentration, the amount of inflow SO ₂ is determined, and based on the desulfurization gas flow rate and the exhaust gas O ₂ concentration, natural oxidized SO ₂
The amount is determined, the natural oxidation from the inflow SO ₂ amount SO ₂
The amount is determined has forced oxidation SO ₂ amount is subtracted, set oxidized air flow based on the forcible oxidation SO ₂ amount is determined, the actual oxidation air flow supplied from the oxidation air blower to the reservoir of the absorption column Is controlled to be equal to the set oxidizing air flow rate.

As a result, in the method and apparatus for controlling the oxidizing air flow rate of the flue gas desulfurization apparatus according to the present invention, the set oxidizing air flow rate is determined in consideration of the concentration of the exhaust gas O ₂ contained in the exhaust gas introduced into the absorption tower. In this case, the set oxidizing air flow rate is optimized, and the generation of oxidizing substances such as S ₂ O ₈ (persulfuric acid) and IO ₃ (iodic acid) as side reactions is suppressed,
The decrease in the activity of the nitrifying bacteria and the death of the nitrifying bacteria in the wastewater treatment device of the absorption tower are prevented, so that the function of the wastewater treatment device does not decrease and the desulfurization performance does not decrease.

[0017]

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

FIGS. 1 and 2 show an embodiment of the present invention.
This is an example, in which the same reference numerals as in FIGS. 4 and 5 are used.
The parts represent the same thing, and the basic configuration is shown in FIG.
It is the same as the conventional one shown in FIG.
1 and 2, as shown in FIG. 1 and FIG.
Exhaust gas O to be introduced_TwoExhaust gas O for detecting concentration D_TwoDensitometer
22, the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9
The exhaust gas O _TwoExhaust gas detected by the concentration meter 22
O_TwoBy multiplying by the concentration D, the flow contained in the exhaust gas
O_TwoA multiplier 24 for obtaining and outputting the quantity 23;
Inflow O output from 24_TwoInside the absorption tower 3 based on the quantity 23
Oxidized SO which is naturally oxidized in_TwoFor the quantity 25
Function generator 26 for output and output from multiplier 15
Inflow SO_TwoFrom the amount 14, the natural oxidized SO_TwoDeduct 25
Oxidized SO to be forcibly oxidized_TwoAmount 14 '
And a subtractor 27 for outputting to the function generator 17
It is in the point.

[0019] Thus, in the function generator 17 is a conventional inlet SO ₂ amount 14 rather than forced oxidation S as
The set oxidizing air flow rate 16 is obtained based on the O ₂ amount 14 ′ (see FIG. 6).

[0020] Incidentally, the function generator 26 is input function as shown in FIG. 3, the function number, the inflow amount of O ₂ 2
3 indicates that the natural oxidized SO ₂ amount 25 is increased or decreased substantially in proportion to the increase or decrease in the amount of natural oxide SO ₂ .

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

During operation of the flue gas desulfurization unit, the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9 and the absorption tower inlet SO ₂
The controller controls the SO ₂ concentration B at the inlet of the absorption tower detected by the concentration meter 10, the oxidizing air flow rate C detected by the oxidizing air flow meter 11, and the exhaust gas O ₂ concentration D detected by the exhaust gas O ₂ concentration meter 22. is input to 6, the absorption tower inlet SO ₂ concentration detected by the absorption tower inlet SO ₂ concentration meter 10 for the detected desulfurized gas flow a by the desulfurization gas flowmeter 9 in the multiplier 15 of the controller 6 B, the inflow SO ₂ amount 14 to be removed from the exhaust gas is determined and output to the subtractor 27, while the desulfurization gas flow meter 9
Is multiplied by the exhaust gas O ₂ concentration D detected by the exhaust gas O ₂ concentration meter 22 to the desulfurization gas flow rate A detected by the above, the inflow O ₂ amount 23 contained in the exhaust gas is obtained, and is sent to the function generator 26. The naturally oxidized SO ₂ amount 25 which is output and is naturally oxidized in the absorption tower 3 based on the inflow O ₂ amount 23 output from the multiplier 24 in the function generator 26.
Is output to the subtractor 27, and the subtractor 27
, The inflow SO ₂ amount 1 output from the multiplier 15
4 is subtracted from the natural oxidized SO ₂ amount 25 to obtain a forced oxidized SO ₂ amount 14 ′ to be forcibly oxidized and output to the function generator 17, where the output from the subtractor 27 is output. The set oxidizing air flow rate 16 is obtained based on the forced oxidized SO ₂ amount 14 ′ and output to the subtractor 19, where the set oxidizing air flow rate 16 and the oxidized air detected by the oxidizing air flow meter 11 are detected. The difference from the flow rate C is determined, and the oxidizing air flow rate deviation 18 is output to the proportional-integral controller 21. The oxidizing air flow rate deviation 18 output from the subtractor 19 is proportional-integrated in the proportional-integral controller 21. An opening degree command 20 for eliminating the oxidizing air flow rate deviation 18 is output to the flow rate adjusting damper 7, the opening degree of the flow rate adjusting damper 7 is adjusted, and the oxidizing air flow rate C becomes equal to the set oxidizing air flow rate 16 or the like. Kunar so control is performed.

As a result, the set oxidizing air flow rate 16 is determined in consideration of the exhaust gas O ₂ concentration D contained in the exhaust gas introduced into the absorption tower 3, so that the set oxidizing air flow rate 16 is optimized. The formation of oxidizing substances such as S ₂ O ₈ (persulfuric acid) and IO ₃ (iodic acid) as side reactions is suppressed,
A decrease in the activity of the nitrifying bacteria and the death of the nitrifying bacteria in the wastewater treatment device (not shown) of the absorption tower 3 are prevented, so that the function of the wastewater treatment device does not decrease and the desulfurization performance does not decrease.

In this manner, an appropriate amount of oxidizing air can be supplied to the liquid storage section 1a of the absorption tower 3 without excess or shortage, and generation of oxidizing substances can be suppressed to prevent deterioration of the function of the wastewater treatment apparatus. In addition, a decrease in desulfurization performance can be prevented.

The method and apparatus for controlling the flow rate of oxidized air in the flue gas desulfurization apparatus according to the present invention are not limited to the above-described example, but the exhaust gas O ₂ for detecting the concentration of the exhaust gas O ₂ introduced into the absorption tower. _{2 The} concentration meter does not necessarily need to be provided near the inlet of the absorption tower 3 as shown in FIG. 1, and may be used if it is already provided on the upstream side of the absorption tower 3. etc. utilizing exhaust gas O ₂ set value of the boiler control unit for discharging the other, it is a matter of course that within the scope not departing from the gist of the present invention that various changes and modifications may be made.

[0026]

As described above, according to the method and apparatus for controlling the oxidizing air flow rate of a flue gas desulfurization apparatus of the present invention, an appropriate amount of oxidizing air can be supplied to the liquid reservoir of the absorption tower without excess or shortage. Thus, an excellent effect of suppressing the generation of the oxidizing substance to prevent a decrease in the function of the wastewater treatment apparatus and preventing a decrease in the desulfurization performance can be obtained.

[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 illustrating an example of an embodiment of the present invention.

FIG. 3 is a diagram showing a function set in a function generator (26) shown in FIG. 2;

FIG. 4 is an overall schematic configuration diagram of a conventional example.

FIG. 5 is a control block diagram of a conventional example.

FIG. 6 is a diagram showing functions set in the function generator (17) shown in FIGS. 2 and 5;

[Explanation of symbols]

1 absorption liquid 1a liquid reservoir 3 absorption tower 5 oxidation air blower 6 controller 7 flow control damper 9 desulfurized gas flowmeter 10 absorption tower inlet SO ₂ concentration meter 11 oxidation air meter 14 flows SO ₂ amount 14 'forced oxidation SO ₂ The amount 15 the multiplier 16 set oxide airflow 17 function generator 18 oxidizing air flow rate difference 19 subtractor 20 opening command 21 proportional integral adjuster 22 exhaust gas O ₂ concentration meter 23 flows O ₂ amount 24 the multiplier 25 natural oxidation SO ₂ amount 26 function generator 27 subtractor A desulfurizing gas flow B absorption tower inlet SO ₂ concentration C oxidation air flow D exhaust gas O ₂ concentration

Claims (2)

[Claims] 1. Detected desulfurization gas flow rate and absorption tower inlet S
O_TwoInflow SO based on concentration_TwoAnd the amount
Sulfur gas flow rate and exhaust gas O introduced into the absorption tower_TwoBased on concentration
Natural oxidation SO_TwoAnd determine the quantity_TwoFrom the quantity
Natural oxidation SO _TwoSubtract the amount to force oxidation SO_TwoFind the quantity,
The forced oxidation SO_TwoObtain the set oxidizing air flow rate based on the amount,
The actual oxidizing air flow rate supplied to the liquid reservoir of the absorption tower is
Perform control so that it is equal to the set oxidizing air flow rate.
A method for controlling an oxidizing air flow rate of a flue gas desulfurization apparatus. 2. A desulfurization gas flow meter for detecting a desulfurization gas flow rate.
And the absorption tower entrance SO _TwoAbsorption tower inlet SO for detecting concentration_TwoDark
Meter and exhaust gas O introduced into the absorption tower_TwoDetect concentration
Exhaust gas O_TwoSupply oxidizing air to the concentration meter and the liquid reservoir of the absorption tower
Oxidizing air blower, and the desulfurization gas flow rate and absorption tower inlet SO_TwoFlow based on concentration
Enter SO_TwoAmount and the desulfurization gas flow rate and exhaust gas
O_TwoNatural oxidation SO based on concentration_TwoThe flow rate
O_TwoFrom the amount of the natural oxidation SO_TwoForced oxidation S by subtracting the amount
O_TwoAnd the forced oxidation SO_TwoSet oxidizing air based on quantity
Obtain the flow rate from the oxidizing air blower to the liquid reservoir of the absorption tower
The actual oxidizing air flow supplied is equal to the set oxidizing air flow.
And a controller for controlling so as to be equal to
A oxidizing air flow control device for flue gas desulfurization equipment.