JP2000015043A - Dust concentration control method at outlet of flue gas desulfurization unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the number of circulating pumps to be operated in accordance with the concentration of dust flowing into an absorption tower, to reliably suppress the dust concentration at an outlet to a set value or less, and to realize an economical operation of the circulating pump. Provided is a method for controlling the concentration of dust and soot at an outlet of a flue gas desulfurization device which can also improve the performance. In a controller, an outlet dust concentration is determined based on an inlet dust concentration determined based on a load, an inlet dust particle size distribution, and a partial collection efficiency for each particle size, and the outlet dust concentration is determined. The liquid-gas ratio required to be equal to or less than the set value is obtained, and the absorption liquid 1 with respect to the detected exhaust gas flow rate 29 is determined.
The number of operating pumps is controlled by starting and stopping the circulation pump 4 so that the ratio of the circulation amount 31 becomes equal to the liquid-gas ratio, and the outlet dust concentration is set to a set value or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling dust concentration at an outlet of a flue gas desulfurization apparatus.

[0002]

2. Description of the Related Art Generally, in a power plant or the like, SO ₂ (sulfur oxide) is produced from exhaust gas discharged from a coal-fired boiler or the like.
A flue gas desulfurization device using calcium carbonate (CaCO ₃ ) as an absorbent is provided to absorb and remove
As shown in FIG. 7, the flue gas desulfurization apparatus generally includes an absorption tower 3 having a lower part formed with a liquid reservoir 1a for absorbing liquid 1 and a plurality of spray nozzles 2 disposed at an upper part. The absorption liquid 1 in the liquid reservoir 1a of the tower 3 is pumped up and the spray nozzle 2
A plurality of circulation pumps 4 for spraying and circulating the oxidized air, an oxidizing air blower 5 for supplying oxidized air to the liquid reservoir 1a of the absorption tower 3, and an absorbent extracted from the liquid reservoir 1a of the absorption tower 3. 1 and a gypsum collecting device 7 for collecting the gypsum 6.

[0003] The gypsum recovery device 7 is provided with an absorbent 1 that is withdrawn from a liquid reservoir 1 a of the absorption tower 3 through a withdrawal line 8.
A neutralization tank 10 for adding a neutralizing agent such as caustic soda (NaOH) supplied through a neutralizing agent supply line 9;
The absorbing solution 11 neutralized in the neutralizing tank 10 is introduced through a neutralizing absorbing solution line 12 to settle solids in the absorbing solution 11 and to remove a supernatant overflow water 13 through a drain line 14. Gypsum thickener 1 leading to wastewater treatment equipment 15
6 and a slurry 17 containing the solids settled by the gypsum thickener 16 were introduced through a slurry line 18, and the slurry 17 was dewatered to be separated into the gypsum 6 and the filtrate 19 and separated from the gypsum 6. A gypsum dewatering machine 21 for guiding the filtrate 19 to the gypsum thickener 16 via a filtrate line 20 is provided. In the middle of the slurry line 18, the gypsum dewatering machine supply tank 2 in which the slurry 17 introduced from the gypsum thickener 16 to the gypsum dewatering machine 21 is temporarily stored is provided.
2, a gypsum dewatering machine drain pit 23 for temporarily storing the filtrate 19 returned from the gypsum dewatering machine 21 to the gypsum thickener 16 is provided in the middle of the filtrate line 20. Is provided with an overflow water tank 24 in which overflow water 13 discharged from the gypsum thickener 16 to the wastewater treatment device 15 is temporarily stored. In the middle of the neutralizing agent supply line 9, there is provided a flow rate adjusting valve 25 for adjusting the flow rate of the neutralizing agent supplied to the neutralizing tank 10. A pH indicating controller 27 that detects the pH of the absorbing liquid 11 in 10 and outputs an opening command 26 to the flow regulating valve 25 so that the pH becomes a preset pH set value (usually 7.0). Is provided.

[0004] 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 absorbent 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. , Gypsum (calcium sulfate (CaS
O ₄ )) is produced, and a part of the absorbent 1 in the reservoir 1 a containing the gypsum is withdrawn through a withdrawal line 8 to a neutralization tank 10 of the gypsum recovery device 7. In the sum tank 10, the absorbent 11 neutralized by the neutralizing agent such as caustic soda (NaOH) supplied through the neutralizing agent supply line 9 and neutralized in the neutralizing tank 10 is used as the neutralized absorbing liquid. Introduced into the gypsum thickener 16 through the line 12, in which the solid content in the absorbent 11 settles,
The slurry 17 containing the solid content is introduced into the gypsum dewatering machine 21 via the slurry line 18 and the gypsum dewatering machine supply tank 22, and the slurry 17 is dewatered in the gypsum dewatering machine 21 and separated into the gypsum 6 and the filtrate 19. The gypsum 6 and the separated filtrate 19 are returned to the gypsum thickener 16 through the filtrate line 20 and the gypsum dewatering machine drain pit 23, and the supernatant overflow water 13 in the gypsum thickener 16 is removed.
Is led to a wastewater treatment device 15 through a wastewater line 14 and an overflow water tank 24, and in the wastewater treatment device 15, harmful nitrogen compounds are decomposed by the action of nitrifying bacteria,
And after the reducing substance represented by COD (Chemical Oxygen Demand) is adsorbed by the adsorption resin composed of a polymer material,
It is discharged outside.

Further, a required amount of absorbent slurry is supplied to the absorption tower 3 from an absorbent slurry supply line 28 as needed.

[0007]

In the flue gas desulfurization apparatus as described above, recently, not only the SO ₂ concentration but also the performance requirements regarding the dust concentration have become strict.

However, regarding the dust concentration,
The number of operating circulation pumps 4 is set large in consideration of a margin, and the amount of the absorbent 1 sprayed from the spray nozzle 2 into the absorption tower 3 is increased, so that the amount of dust collected in the absorption tower 3 is reduced. Only to an extent that the dust concentration at the outlet of the absorption tower 3 is reduced to fall below the regulation value, and furthermore, these operations rely on the intuition of the operator and the manual analysis of the dust concentration at the outlet. At present, specific control has not been established, and the circulation pump 4
There was also a problem in terms of economics in operation of the vehicle.

In view of such circumstances, the present invention can optimize the number of operating circulation pumps according to the dust concentration flowing into the absorption tower, and can reliably suppress the dust concentration at the outlet to a set value or less. It is an object of the present invention to provide a method for controlling the concentration of dust and soot at the outlet of a flue gas desulfurization apparatus, which can also improve the economical efficiency of the operation of the apparatus.

[0010]

SUMMARY OF THE INVENTION According to the present invention, while absorbing and circulating an absorbing solution into an absorption tower by operating a plurality of circulating pumps, the absorbing solution is brought into contact with exhaust gas discharged from a coal-fired boiler to reduce the amount of the exhaust gas. a outlet dust concentration control method of the exhaust gas desulfurizer for absorbing and removing SO _2, an inlet dust concentration is determined based on the load, the inlet dust particle size distribution, based on the partial efficiency of collecting particles each diameter The outlet dust concentration is determined, and the liquid-gas ratio required to make the outlet dust concentration equal to or less than the set value is determined, and the ratio of the circulation amount of the absorbing liquid to the detected exhaust gas flow rate is set to be equal to the liquid-gas ratio. Starting the pump
The present invention relates to an outlet dust concentration control method for a flue gas desulfurization device, characterized in that the number of operating units is controlled by stopping the operation and the outlet dust concentration is set to a set value or less.

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

During operation of the flue gas desulfurization apparatus, the outlet dust concentration is determined based on the inlet dust concentration determined based on the load, the inlet dust particle size distribution, and the partial collection efficiency for each particle size. The liquid / gas ratio required to reduce the dust concentration to the set value or less is determined, and the circulation pump is started / stopped so that the ratio of the circulating amount of the absorbent to the detected exhaust gas flow rate becomes equal to the liquid / gas ratio. The number of operating units is controlled, and the outlet dust concentration is maintained at or below a set value.

As a result, the desired dust removal performance can be obtained without relying on the operator's intuition and the manual analysis of the dust concentration at the outlet, and the circulation pump can be operated economically.

[0014]

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

FIGS. 1 to 6 show an embodiment of the present invention. In the drawings, the portions denoted by the same reference numerals as those in FIG. 7 represent the same components, and the basic configuration is shown in FIG. The present embodiment is the same as the conventional one shown in FIGS. 1 to 6, but is characterized by an exhaust gas flow rate detector 30 for detecting an exhaust gas flow rate 29 and a circulating amount 31 of the absorbent 1 as shown in FIGS. An absorbent circulating flow detector 32 for detecting the exhaust gas flow detector 30;
And a controller 34 which receives the exhaust gas flow rate 29 detected by the above and the circulating amount 31 of the absorbing liquid 1 detected by the absorbing liquid circulating flow rate detector 32 and outputs a start / stop control signal 33 to the circulating pump 4. Is additionally equipped, and in the controller 34,
It is necessary to determine the inlet dust concentration based on the load, the inlet dust concentration, the inlet dust particle size distribution, and the outlet dust concentration based on the partial collection efficiency for each particle size, and to reduce the outlet dust concentration to a set value or less. The circulating pump 4 is started and stopped so that the ratio of the circulating amount 31 of the absorbing liquid 1 to the detected exhaust gas flow rate 29 becomes equal to the liquefied gas ratio. The point is that the outlet dust concentration is set to be lower than the set value.

Since the amount of circulation of the absorbing liquid 1 can be recognized from the number of operating circulation pumps 4, the amount of circulation of the absorbing liquid 1 is recognized from the number of operating circulation pumps 4. In such a case, it is not always necessary to provide the absorbent circulation flow rate detector 32.

The inlet dust concentration obtained based on the load is stored as a function in the controller 34 as shown in FIG. 2 based on data collected during the test operation, and is constantly rewritten with the latest load data. Is to be done.

The above-mentioned inlet dust particle size distribution indicates how much of the inlet dust flowing into the absorption tower 3 is contained in each concentration and how much, for example, As shown in FIG. 3, the data is stored in the controller 34 as data collected in advance during the test operation.

The partial collection efficiency for each particle size indicates how much particle size dust is collected in the entrance dust flowing into the absorption tower 3 and This changes according to the liquid / gas ratio (L / G), and is stored in the controller 34 as data collected in advance during a test run, for example, as shown in FIG.

Here, as shown in FIG. 5, the collection limit particle diameter at a certain liquid / gas ratio (L / G) is Dc, the maximum particle diameter is Dmax, and the inlet dust particle diameter distribution is P (D) (FIG. 3), the partial collection efficiency ηt (D) [%] is ηt (D) = 100 when D ≧ Dc, ηt (D) = 100−100 × expｅｘ− when D <Dc.
K × (L / G)｝ (where K is a constant coefficient determined by the combustion characteristics of the boiler and the properties of the coal), so the overall dust removal efficiency η [%] is

(Equation 1) By multiplying the dust removal efficiency η by the inlet dust concentration obtained in FIG. 2, the outlet dust concentration of the absorption tower 3 is obtained.

The controller 34 stores, as shown in FIG. 6, a function of the concentration of the outlet dust with respect to the liquid-gas ratio based on the data collected during the test operation. The liquid-gas ratio required to reduce the outlet dust concentration of the absorption tower 3 obtained by multiplying the inlet dust concentration to a set value or less is obtained from the function of FIG. Circulation amount of 1 31
The controller 34 outputs a start / stop control signal 33 from the controller 34 to the circulation pump 4 so that the ratio becomes equal to the liquid-gas ratio.

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

During operation of the flue gas desulfurization apparatus, the exhaust gas flow rate detector 30 detects the exhaust gas flow rate 29, the absorbent circulating flow rate detector 32 detects the circulating amount 31 of the absorbent 1, and the exhaust gas flow rate detector 30. The detected exhaust gas flow rate 29 and the circulating amount 31 of the absorbent 1 detected by the absorbent circulating flow detector 32 are input to the controller 34.

In the controller 34, the inlet dust concentration (see FIG. 2) obtained based on the load, the inlet dust particle size distribution (see FIG. 3), and the partial collection efficiency for each particle size (see FIG. 4) ), And the liquid-gas ratio required to make the outlet dust concentration equal to or less than the set value is determined as shown in FIG.
From the controller 34 to the circulation pump 4 so that the ratio of the circulation amount 31 of the absorbent 1 to
The stop control signal 33 is output, the circulating pump 4 is started / stopped, the number of operating pumps is controlled, and the outlet dust concentration is kept below a set value.

As a result, the desired dust removal performance can be obtained without relying on the intuition of the operator or the manual analysis of the dust concentration at the outlet, and the operation of the circulation pump 4 can be performed economically.

In this way, the number of operating circulation pumps 4 can be optimized in accordance with the concentration of the dust flowing into the absorption tower 3, and the concentration of the dust and dust at the outlet can be reliably suppressed to a set value or less. Can also be improved.

It should be noted that the method for controlling the concentration of dust at the outlet of a flue gas desulfurization apparatus according to the present invention is not limited to the above-described example, and various changes can be made without departing from the gist of the present invention. Of course.

[0028]

As described above, according to the method for controlling the concentration of dust in the outlet of a flue gas desulfurization apparatus according to the present invention, the number of operating circulation pumps can be optimized according to the concentration of dust in the absorption tower. It is possible to achieve an excellent effect that the concentration can be surely suppressed to a set value or less, and the economy of the operation of the circulation pump can be improved.

[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 diagram showing a function of an inlet dust concentration with respect to a load.

FIG. 3 is a diagram showing an inlet dust particle size distribution.

FIG. 4 is a diagram showing a partial collection efficiency for each particle size.

FIG. 5 is a diagram showing a partial collection efficiency for each particle size at a certain liquid-gas ratio.

FIG. 6 is a diagram showing a function of an outlet dust concentration with respect to a liquid-gas ratio.

FIG. 7 is an overall schematic configuration diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Absorbent liquid 3 Absorption tower 4 Circulation pump 29 Exhaust gas flow rate 30 Exhaust gas flow rate detector 31 Circulation amount 32 Absorbent liquid circulating flow rate detector 33 Control signal 34 Controller

Claims (1)

[Claims] 1. A flue gas for absorbing and removing SO ₂ in exhaust gas by contacting exhaust gas discharged from a coal-fired boiler while spraying and circulating the absorbent into an absorption tower by operating a plurality of circulation pumps. A method of controlling the concentration of dust at an outlet of a desulfurization device, comprising: determining an outlet dust concentration based on an inlet dust concentration determined based on a load, an inlet dust particle size distribution, and a partial collection efficiency for each particle size. Determine the liquid-gas ratio required to reduce the dust concentration below the set value, start and stop the circulation pump so that the ratio of the circulating amount of the absorbent to the detected exhaust gas flow rate is equal to the liquid-gas ratio. An exhaust dust concentration control method for a flue gas desulfurization device, wherein the number of operating units is controlled and the outlet dust concentration is set to a set value or less.