JP3801664B2 - Jet bubbling reactor - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a jet bubbling reaction tank, and more particularly to a jet bubbling reaction tank improved so as to quickly stabilize the pH of an absorbent in a froth layer and the vicinity thereof at a set value.
[0002]
[Prior art]
In order to remove environmental pollutants such as sulfurous acid gas and dust from exhaust gas, a wet flue gas desulfurization method is frequently used. The wet flue gas desulfurization method is a method in which exhaust gas and an absorbent slurry are subjected to gas-liquid contact reaction to fix and remove sulfurous acid gas as sulfate. The absorbent slurry to be used is an absorbent that fixes sulfite gas as a sulfate, for example, a slurry aqueous solution (hereinafter referred to as an absorbent) in which limestone is dissolved and / or suspended in water.
Among them, wet flue gas desulfurization equipment using a jet bubbling reaction tank as an exhaust gas treatment tank that removes environmental pollutants in the exhaust gas by bringing gas exhaust into contact with the absorbing liquid contained in the tank, It is widely adopted as an apparatus that has a high contaminant removal rate and is economically superior.
[0003]
The configuration of a conventional jet bubbling reaction tank used in a wet flue gas desulfurization apparatus will be described below by taking as an example the case of removing sulfurous acid gas from exhaust gas.
A jet bubbling reactor typically absorbs environmental pollutants such as sulfurous acid gas as shown in FIG. 1 of Japanese Patent Publication No. 55-37295 and FIG. 1 of Japanese Patent Publication No. 3-70532. Gas-liquid contact reaction in which the liquid is stored in the lower part of the tank, and exhaust gas containing sulfurous acid gas is dispersed and introduced into the absorbing liquid to form a jet bubbling layer and react with the absorbent to fix the sulfurous acid gas as sulfate. It is a tank.
[0004]
Further, a jet bubbling reaction tank (hereinafter simply referred to as a reaction tank) 10 that uses limestone as an absorbent and removes sulfurous acid gas in exhaust gas will be described with reference to FIG. As shown in FIG. 3, the reaction tank 10 is partitioned into an exhaust gas outlet chamber 12, an exhaust gas inlet chamber 14 provided so as to cross the tank body, and a lower space for storing the absorbing liquid in order from the top. . The exhaust gas outlet chamber 12 and the exhaust gas inlet chamber 14 are partitioned by a first partition 16 that extends horizontally across the tank body, and the exhaust gas inlet chamber 14 and the lower space extend in parallel to the first partition 16. It is partitioned by two partition plates 18. The second partition plate 18 is positioned above the liquid surface of the absorbing liquid 20 and forms an exhaust gas outflow space 22 therebetween.
The exhaust gas outlet chamber 12 is connected to an outlet duct 24, and the lower exhaust gas inlet chamber 14 is connected to an inlet duct 26. Further, as a gas riser for allowing the treated exhaust gas to flow into the exhaust gas outlet chamber 12 from the space 22, a plurality of pipe-like communication pipes 28 (only one is shown in FIG. 3) penetrates the exhaust gas inlet chamber 14. The space 22 and the exhaust gas outlet chamber 12 are communicated with each other.
[0005]
The exhaust gas dispersion pipe 30 communicates with the exhaust gas inlet chamber 14 at the upper end and descends downward from the second partition plate 18 of the exhaust gas inlet chamber 14 so as to be immersed in the absorbent 20 at the lower end. A number of small openings are provided at the lower end, and the exhaust gas is dispersed in the absorbent 20 from these openings to form a floss layer (jet bubbling layer) A. The floss layer A is a gas / liquid phase continuous gas / liquid contact layer made of exhaust gas bubbles and an absorbing liquid.
The lower part of the reaction tank 10 accommodates the absorbing liquid 20, and the lower part of the tank is supplied with a stirrer 32 for stirring the absorbing liquid and limestone slurry, and oxygen necessary for fixing gypsum of sulfurous acid gas. And an air supply pipe 34 provided with an ejection nozzle for ejecting oxygen-containing gas, for example, air.
The rotating shaft 36 of the stirrer 32 extends downward from a driving device 38 on the tank via one communication pipe 28.
In FIG. 3, 40 is an absorbent supply pipe, and 42 is a discharge pipe for gypsum slurry generated by the reaction.
[0006]
Below, operation | movement of the reaction tank 10 is demonstrated. In FIG. 3, a slurry in which limestone powder that reacts with sulfurous acid gas and is immobilized on gypsum is dissolved and / or suspended in water is stored as an absorbing liquid in a lower portion of the reaction tank 10.
Exhaust gas is introduced from the inlet duct 26 through the exhaust gas inlet chamber 14 through the opening of the exhaust gas dispersion pipe 30 below the surface of the absorbing liquid, and is jetted out and rises while bubbling. Thereby, what is called a floss layer A is produced | generated on an absorption liquid. Sulfurous acid gas reacts with water, oxygen, and limestone to form gypsum as follows. The generated gypsum precipitates in the absorption liquid as crystals, and the absorption liquid becomes a slurry that floats a large amount of gypsum particles.
SO ₂ (gas) + H ₂ O → H ₂ SO ₃ (absorption)
H ₂ SO ₃ + 1 / 2O ₂ → H ₂ SO ₄ (oxidation)
H ₂ SO ₄ + CaCO ₃ → CaSO ₄ + H ₂ O + CO ₂ ↑ (neutralization)
CaSO ₄ + 2H ₂ O → CaSO ₄ · 2H ₂ O ↓ (crystallization)
[0007]
The exhaust gas from which the sulfurous acid gas has been removed passes through the communication pipe 28 and the exhaust gas outlet chamber 12 and is discharged out of the system by the outlet duct 24.
On the other hand, the slurry containing the crystallized gypsum thickly is discharged from the discharge pipe 42. Further, an amount of limestone slurry commensurate with the slurry extracted from the discharge pipe 42 is continuously supplied to the reaction tank 10 from the absorbent supply pipe 40.
[0008]
[Problems to be solved by the invention]
By the way, the concentration of sulfurous acid gas in the exhaust gas to be introduced is not necessarily constant, and often varies according to the variation of the operating conditions of the thermal power plant or boiler that generates the exhaust gas. If the concentration of sulfurous acid gas in the exhaust gas becomes high and the desulfurization rate is not increased, the concentration of sulfurous acid gas in the treated exhaust gas becomes higher than a predetermined value, causing environmental problems.
Therefore, it is necessary to increase the desulfurization rate in accordance with the increase in the concentration of sulfurous acid gas in the exhaust gas. In order to increase the desulfurization rate, it is necessary to increase the supply of limestone slurry and increase the pH of the absorbent.
[0009]
Therefore, in order to maintain the sulfurous acid gas concentration in the treated exhaust gas at a predetermined value in spite of the fluctuation of the sulfurous acid gas concentration in the introduced exhaust gas, the pH of the absorbing liquid is set to a predetermined value in accordance with the fluctuation of the sulfurous acid gas concentration in the exhaust gas. it is necessary to quickly adjust to the set value, and the accuracy of the measurements of the PH of the absorbing liquid importantly ing.
Further, even when the amount of introduced sulfurous acid gas varies due to changes in the flow rate of the introduced exhaust gas and the concentration of sulfurous acid gas, excess or deficiency of the supply amount of limestone occurs, and the pH of the absorbent varies from the set value. Unless this is quickly converged to the original set value, the sulfurous acid gas concentration of the treated exhaust gas cannot be maintained at a predetermined value.
The pH of the absorption liquid is conventionally measured in the lower part of the absorption liquid layer, specifically in the discharge pipe of the product slurry. Since the absorbent concentration of the supplied absorbent, for example, limestone slurry, the Ca concentration is substantially constant, the pH of the absorbent is adjusted by changing the supply flow rate of the absorbent. Therefore, a program indicating the relationship between the set value of PH and the supply flow rate of the absorbing liquid is created. When adjusting the PH, the supply flow rate of the absorbing liquid is adjusted according to the program so that the PH becomes the set value.
[0010]
However, the conventional reaction tank has a problem that when the set value of PH is changed, it takes a long time for the actual PH measurement value to converge to the set PH value, and the desulfurization rate fluctuates during that time. For example, the dotted line graph of FIG. 2 is a graph showing the measured PH value and elapsed time when the set value of PH is changed from 4 to 4.5 in a conventional reaction tank, and the measured PH value varies. It shows that it takes 60 minutes or more to converge on the set value.
In the meantime, since the pH has fluctuated, there has been a problem that the desulfurization rate of the exhaust gas treated in the jet bubbling reaction tank fluctuates more or less than necessary.
[0011]
Therefore, an object of the present invention is to provide a jet bubbling reaction tank having a structure in which the pH of an absorbing solution is easily converged to a set value.
[0012]
As a result of collecting and analyzing data from a commercial-scale jet bubbling reaction tank in operation, the present inventor showed that the pH of the absorption liquid is PH at the upper and lower parts of the absorption liquid layer in the reaction tank as shown in FIG. Found that they were very different. Furthermore, in the floss layer, the PH is small to absorb the sulfurous acid gas, while in the absorbing liquid layer below the floss layer, the PH increases as it moves away from the floss layer because it does not absorb the sulfurous acid gas. . In FIG. 4, graph 1 shows a case where PH is relatively small, and graph 2 shows a case where PH is relatively large.
Therefore, PH of the floss layer is the most important in the reaction mechanism of the jet bubbling reactor described above, and therefore PH measurement of the floss layer was attempted. However, due to jet bubbling of a large amount of exhaust gas, the measured values are not stable even when using a commercial industrial PH meter or a PH meter equipped with a protector that mitigates the effects of jet bubbling. Accurate measurement values could not be obtained. As a result, it has been found that it is technically difficult to apply the method of directly and continuously measuring the PH of the froth layer using a PH meter to a reaction vessel intended for commercial operation.
[0013]
On the other hand, in order to quickly stabilize the PH of the floss layer, the supply position of the absorbent was also studied. Therefore, first, an attempt was made to homogenize PH by injecting an absorbent (limestone slurry) into the froth layer. However, in the floss layer, vigorous stirring is performed in the vertical direction due to the jet bubbling action of a large amount of exhaust gas, so the moving speed of the absorbent is fast in the vertical direction but relatively slow in the horizontal direction. For this reason, there is a problem that PH increases locally and scale adheres to the exhaust gas dispersion pipe.
Furthermore, as a result of further research, the method of supplying limestone slurry to the lower part of the absorbing liquid layer and supplying the limestone slurry to the floss layer by the stirring action of the stirrer and the air nozzle can uniformly supply the absorbent to the floss layer. understood.
[0014]
[Means for Solving the Problems]
Based on the above knowledge, the jet bubbling reaction tank according to the present invention is arranged so as to cross the tank above the absorbing liquid layer accommodated in the lower part of the vertical tank, and has an exhaust gas inlet chamber for receiving exhaust gas, and an upper end thereof. An exhaust gas distribution pipe that communicates with the exhaust gas inlet chamber, extends in the vertical direction so that the lower end is immersed in the absorption liquid, and has an exhaust gas outflow hole at the lower end for discharging the exhaust gas into the absorption liquid, and supplies the absorbent The exhaust gas inlet chamber is provided with a supply port, a stirrer for stirring the absorption liquid, an air nozzle for supplying oxygen for oxidizing harmful acidic components in the exhaust gas, and a PH meter for measuring the pH of the absorption liquid. In a jet bubbling reaction tank in which exhaust gas is introduced into the absorbing liquid through the exhaust gas dispersion pipe and brought into gas-liquid contact, and harmful acidic components in the exhaust gas are contacted and removed by the absorbing liquid,
The detection end of the PH meter is installed 3 to 100 cm below the height level of the exhaust gas outlet hole of the exhaust gas dispersion pipe,
The stirring blade of the stirrer, the air nozzle, and the supply port for supplying the absorbent are installed at the bottom of the absorbent layer,
The supply port for supplying the absorbent is arranged at a position 10 to 300 cm higher from the higher of both the stirrer and the air nozzle ,
The supply port for supplying the absorbent is characterized by being located above the stirring blades of the stirrer .
[0015]
The PH meter used in the present invention may be a commercially available one, but it is disposed at a position below the exhaust gas outflow hole in order to reduce the influence of the jet bubbling action. The distance varies depending on the strength of the jet bubbling action, that is, the opening shape of the exhaust gas dispersion pipe, the exhaust gas outflow speed, etc., but is preferably 3 to 100 cm. The supply port for supplying the absorbent is disposed at a position higher than both the stirring blades and the air nozzle of the stirrer in order to use the stirring action of the stirrer and the air nozzle. The distance from the higher one of the stirring blade or the air nozzle to the supply port is preferably 10 to 300 cm. The type of the stirring blade of the stirrer is not particularly limited, and may be a blade (paddle) type or a propeller type.
[0016]
[Action]
In the present invention, the absorbing liquid is supplied to the lower part of the absorbing liquid, and the absorbing liquid can be moved upward by using the stirring action of the stirrer and the air nozzle, and supplied to the floss layer with a uniform distribution. On the other hand, by measuring PH at the upper part of the absorption liquid layer that is very close to the froth layer, it is possible to measure the pH of the supply absorption liquid to the floss layer, which is most important for the removal reaction of harmful acidic components in the exhaust gas. The detection end of PH meter, because it is placed slightly lower than the exhaust gas outlet hole of the gas dispersion pipe, without receiving the jet bubbling action of froth layer directly, accurately measure the PH of the absorbing liquid in the froth layer near can do.
With the above configuration, as shown in FIG. 2 described later, it is possible to significantly reduce the elapsed time until the PH reaches a steady state after changing the set value of the PH, as compared with the conventional jet bubbling reaction tank. it can.
[0017]
【Example】
Hereinafter, the present invention will be described in more detail based on examples with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view showing a main configuration of an embodiment of a jet bubbling reaction tank (hereinafter simply referred to as a reaction tank) according to the present invention. The parts and parts not specifically described here are the same as those provided in the conventional reaction tank 10 shown in FIG.
[0018]
In the reaction tank 50 of the present embodiment, as shown in FIG. 1, a blade-type stirrer 52, a baffle plate 54 for improving the stirring effect by the stirrer 52, and an air nozzle 56 of the air supply pipe 34 are installed in the lower part of the tank. Has been.
In consideration of clogging due to precipitation of gypsum, the air supply pipe 34 is provided so as to be inserted and lowered from the upper portion of the side wall of the tank, and a plurality of air nozzles 56 having an inner diameter of, for example, an inner diameter of 5 cm are spoke-shaped (see FIG. In FIG. 1, only two of them are shown). The air supply pipe 34 is arranged at the lower end so as to eject air downward. Although only one air supply pipe 34 is shown in FIG. 1, a plurality of air supply pipes 34 may be inserted at equal intervals from the tank side wall over the entire circumference.
Absorbent supply pipe 40 for supplying limestone slurry is inserted into skewed downwardly into the reaction vessel 5 in 0, the supply port 58 provided on the tip is above the blades 60 and the air nozzle 56 of the agitator 52 For example, it is located 50 cm above. Although only one absorbent supply pipe 40 is shown in FIG. 1, a plurality of absorbent supply pipes 40 may be inserted at equal intervals from the tank side wall over the entire circumference.
The detection end 62 of the PH meter, slightly above the exhaust gas outlet hole 5 1 of gas dispersion pipes 30, for example 30 cm (indicated by in FIG. 1 L) is installed downward. The PH meter is a commercially available meter, and its detection end is protected by a cylindrical protector.
[0019]
FIG. 2 is a graph showing the course of convergence to the set value when the set value of the absorption liquid PH in the vicinity of the froth layer in the reaction tank 50 shown in FIG. 1 is changed from 4 to 4.5. The time is plotted on the vertical axis and the PH measured value by the PH meter is shown. The solid line graph shows the time course of PH in the reaction tank 50, and the dotted line graph shows the time course of PH in the conventional reaction tank 10.
In this embodiment, as shown in FIG. 2, the delay of the PH control of the absorbing solution, which has been a problem when measured at the lower portion of the conventional absorbing solution layer, is greatly improved, and the PH set value is changed from 4 to 4.5. In this case, the time required for 60 minutes or more in the conventional reaction tank 10 could be shortened to 20 minutes in the reaction tank 50 of this example.
[0020]
【The invention's effect】
According to the configuration of the present invention, in the jet bubbling reaction tank, the detection end of the PH meter is installed 3 to 100 cm below the height level of the exhaust gas outlet hole of the exhaust gas dispersion pipe, the stirring blade of the stirrer, the oxidation air nozzle, The supply port for supplying the absorbent is installed at the lower part of the absorption liquid layer, and the supply port for supplying the absorbent is arranged at a position 10 to 300 cm higher from the higher of both the stirrer and the air nozzle for oxidation , and absorbs it. the Rukoto is located above the stirring blade of the stirring machine supply port for supplying the agent, as compared with the conventional jet bubbling reactor, after changing the set value of PH, the elapsed time until the PH is in a steady state It can be greatly shortened.
Therefore, if the jet bubbling reaction tank according to the present invention is employed, the pH can be easily adjusted according to the variation of the sulfurous acid gas concentration of the introduced exhaust gas, that is, the desulfurization rate can be easily adjusted. It is easy to maintain at a predetermined value.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a main configuration of an embodiment of a jet bubbling reaction tank according to the present invention.
FIG. 2 shows a comparison between the time taken for a conventional jet bubbling reaction tank and the jet bubbling reaction tank according to the present invention to change to a steady state by changing the set value of the absorption liquid pH from 4 to 4.5. The solid line is a graph when the jet bubbling reaction tank according to the present invention is used, and the broken line is a graph when the conventional jet bubbling reaction tank is used.
FIG. 3 is a schematic cross-sectional view of a conventional jet bubbling reaction tank.
FIG. 4 is a graph showing a change in pH in an absorbing liquid layer of a jet bubbling reaction tank.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Conventional jet bubbling reaction tank 12 Exhaust gas outlet chamber 14 Exhaust gas inlet chamber 16 1st partition plate 18 2nd partition plate 20 Absorbent liquid 22 Space part 24 Outlet duct 26 Inlet duct 28 Communication pipe 30 Exhaust gas dispersion pipe 32 Stirrer 34 Air supply pipe 36 Rotating shaft 38 Drive device 40 Absorbent supply pipe 42 Discharge pipe 50 Example of jet bubbling reaction tank according to the present invention 52 Blade type stirrer 54 Baffle plate 56 Air nozzle 58 Supply port 60 Blade 62 Detection end of PH meter

Claims (1)

Arranged so as to cross the tank above the absorbing liquid layer accommodated in the lower part of the vertical tank so that the exhaust gas inlet chamber for receiving the exhaust gas, the upper end communicates with the exhaust gas inlet chamber, and the lower end is immersed in the absorbing liquid Exhaust gas dispersion pipe that extends in the vertical direction and has an exhaust gas outflow hole at the lower end that allows exhaust gas to flow into the absorption liquid, a supply port that supplies the absorbent, a stirrer that stirs the absorption liquid, and harmful substances in the exhaust gas The tank is equipped with an air nozzle that supplies oxygen to oxidize acidic components and a PH meter that measures the pH of the absorption liquid, and the exhaust gas is introduced into the absorption liquid through the exhaust gas inlet chamber and the exhaust gas dispersion pipe. In a jet bubbling reaction tank that is brought into contact with gas and liquid, and harmful acid components in the exhaust gas are contacted and removed by the absorbing liquid,
The detection end of the PH meter is installed 3 to 100 cm below the height level of the exhaust gas outlet hole of the exhaust gas dispersion pipe,
The stirring blade of the stirrer, the air nozzle, and the supply port for supplying the absorbent are installed at the bottom of the absorbent layer,
The supply port for supplying the absorbent is arranged at a position 10 to 300 cm higher from the higher of both the stirrer and the air nozzle ,
A jet bubbling reaction tank characterized in that a supply port for supplying an absorbent is located above a stirring blade of a stirrer .

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