JP2014180656A - Flue gas desulfurizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flue gas desulfurizer capable of compactifying the oxidation tank for a sulfite ion-containing seawater and of reducing the power for feeding the air for oxidation in a seawater desulfurization system.SOLUTION: A flue gas desulfurizer is provided with an absorption tower 1 having the seawater spray nozzles 9 for spraying seawater to a flue gas from a boiler, and an oxidation tank 14 for oxidizing the seawater after desulfurizing in the absorption tower 1. In the desulfurizer, a seawater collection member 10 is provided below the seawater spray nozzles 9, and the dust removal spray nozzles 8 below the collection member 10. A water pipe L4 for feeding the seawater of the collection member 10 to the oxidation tank 14, and a suction pipe L5 for feeding the air for oxidation from the atmospheric air to the oxidation tank 14 are provided, respectively. Further, a microbubble generator 15 is provided in the oxidation tank 14 below the collection member 10. The microbubbles can be easily generated by providing to the generator 15, a mechanism which sucks air by pressure of the supplied seawater at a mixture part mixing the seawater from the water pipe L4 and air from the suction pipe L5 and generates microbubbles in the oxidation tank 14.

Description

  The present invention relates to a flue gas treatment apparatus for removing sulfur oxides of harmful components in exhaust gas generated from a combustion apparatus such as a boiler installed in a thermal power plant or factory, and in particular, seawater is used as a desulfurization absorption liquid. In the flue gas desulfurization equipment, the marine pollution can be suppressed, and the oxidation tank for oxidizing the sulfite ions generated by the absorption of sulfur oxide is made compact and the oxidation air is supplied to the oxidation tank. The present invention relates to a flue gas desulfurization apparatus capable of reducing power.

  As a flue gas desulfurization device in a thermal power plant, a wet desulfurization device using seawater is sometimes used in coastal areas overseas, particularly in Southeast Asia. The cost of equipment can be reduced by a seawater desulfurization method in which seawater is used as an absorbing solution for sulfur oxide in exhaust gas, the seawater after absorbing sulfur oxide is aerated, and then discharged into the ocean. The system of the conventional wet desulfurization apparatus using seawater is shown in FIG.

  This wet desulfurization apparatus is mainly composed of a desulfurization absorption tower 1 for treating sulfur oxide (SOx) in combustion exhaust gas discharged from a boiler, an inlet duct 2 for introducing exhaust gas into the desulfurization absorption tower 1, and a desulfurization absorption tower 1 for SOx. The exhaust duct 3 that discharges the exhaust gas treated with water, the seawater spray nozzle 9 that sprays the absorption liquid (seawater) that absorbs SOx in the exhaust gas onto the exhaust gas, and the mist that removes minute droplets (mist) that accompany the flow of the exhaust gas Eliminator 7, booster pump 18 for supplying seawater to seawater spray nozzle 9, oxidation tank 14 for oxidizing sulfite ions generated by SOx absorption, oxidation air blower 16 for sending air to be supplied to oxidation tank 14, for oxidation The air blower 16 is composed of an air diffuser nozzle 17 and the like for ejecting air sent from the air blower 16.

  Combustion exhaust gas discharged from a boiler (not shown) is introduced from the inlet duct 2 to the desulfurization absorption tower 1 in a substantially horizontal direction by a desulfurization fan (not shown), and is discharged from an outlet duct 3 provided at the top of the desulfurization absorption tower 1. .

In the desulfurization absorption tower 1, seawater is pumped up by the seawater pump 13, and the seawater is sprayed as fine droplets from the seawater spray nozzle 9 through the absorption seawater water supply pipe L <b> 2 by the booster pump 18. When contact is made, SOx in the exhaust gas, mainly SO ₂ is selected on the surface of the absorbing droplets of the seawater spray nozzle 9 together with soot, hydrogen chloride (HCl), hydrogen fluoride (HF) and other acidic gases in the exhaust gas. Absorbed and removed.

  In the seawater atomized by spraying from the seawater spray nozzle 9, mist accompanying the flow of the exhaust gas is collected by a mist eliminator 7 installed in the outlet duct 3 at the top of the desulfurization absorption tower 1. The exhaust gas that has passed through the mist eliminator 7 is reheated as necessary, and then discharged into the atmosphere from a chimney (not shown).

Seawater that has absorbed SO ₂ in the exhaust gas becomes sulfite ion-containing seawater, is extracted from the desulfurization absorption tower 1 by the sulfite ion-containing seawater water supply pipe L4, and is sent to the oxidation tank 14. Here, sulfite ion-containing seawater is diluted from the seawater for dilution sent from the seawater feed pipe L3 for dilution by the seawater pump 13, while being sent from the air blower 16 for oxidation and ejected from the air nozzle 17 (bubbles). It is oxidized by the dissolved oxygen and returned to the ocean 12 as treated seawater.

This conventional wet desulfurization apparatus does not require the provision of limestone supply equipment and gypsum recovery equipment as in the limestone-gypsum method, and the wastewater treatment after SO ₂ absorption is simple, and the cost of the desulfurization system is kept low. There is an advantage that can be.

However, in addition to sulfur oxides such as SO ₂ , the exhaust gas contains gaseous components of heavy metals such as soot and mercury that could not be removed by a dust collector (not shown) and absorbed in the same way as SO _2. Since it is absorbed and removed by the tower 1, it will be discharged into the ocean 12 together with the treated seawater treated in the oxidation tank 14, which may cause ocean pollution.

  In FIG. 2 of Patent Document 1, a secondary desulfurization spray nozzle for spraying seawater to exhaust gas is provided above the primary desulfurization spray nozzle for circulating the absorption liquid (including limestone) in the tank of the desulfurization absorption tower and spraying it to the exhaust gas. A configuration is disclosed in which seawater sprayed from a secondary desulfurization spray nozzle is received by a seawater recovery member and discharged to the ocean.

Moreover, there exist the following patent documents 2-3 etc. about the processing method of the used seawater in the wet desulfurization apparatus using seawater.
Patent Document 2 discloses a configuration of an aeration apparatus that generates fine bubbles in used seawater after desulfurization and ventilates. A header communicating with the air supply pipe is installed in a water channel through which used seawater flows, and fine bubbles are generated from an aeration nozzle extending vertically upward from the header.

  In Patent Document 3, the used seawater after desulfurization is sent to a drainage channel having a partition wall that gradually decreases in height from the upstream side to the downstream side. In order to generate simple air bubbles, a configuration in which the power of the downstream aeration apparatus is reduced is disclosed.

JP 2001-170444 A JP 2009-28570 A JP 2012-115764 A

  The invention described in Patent Document 1 is not originally related to a desulfurization system and is intended to improve the performance of the limestone-gypsum method, but dust and heavy metals in the exhaust gas are removed by a primary desulfurization spray nozzle below the seawater recovery member. As a result, it is possible to prevent the inflow to the upper secondary desulfurization spray nozzle side, and as a result, it can be a means for preventing contamination of the ocean by seawater after desulfurization.

  However, there is no description about the processing method and utilization method of the seawater recovered by the seawater recovery member, and it merely describes that the recovered seawater is discharged into the ocean. Since seawater containing sulfite ions cannot be discharged into the ocean as it is, oxidation treatment with air is usually performed before discharge.

  In order to oxidize sulfite ions in seawater, a large space oxidation tank is required to ensure a long residence time. Further, since it is necessary to supply a large amount of oxidizing air to the oxidation tank, the power for supplying the oxidizing air also increases.

  In the configuration described in Patent Document 2, the number of aeration nozzles installed can be increased by arranging the aeration nozzles vertically instead of horizontally. However, the increase in the number of installations increases the installation cost and operation. There is also a problem that it takes power.

  With the configuration described in Patent Document 3, the power of the aeration apparatus can be reduced, but the height of the partition walls is required to some extent, and if the height of adjacent partition walls is not changed to some extent, the waterfall effect is also halved. In addition, since multiple installations are required (four or more in the illustrated example), the installation cost of the partition wall is increased, the configuration of the drainage channel is complicated, and installation space is required. There's a problem.

  An object of the present invention is to provide a flue gas desulfurization apparatus that uses seawater as a desulfurization absorption liquid, and can reduce the power required for reducing the power required to supply the oxidizing air and reducing the size of an oxidation tank that oxidizes seawater containing sulfite ions. It is to provide a desulfurization apparatus.

The object of the present invention can be achieved by adopting the following constitution.
The invention according to claim 1 is a desulfurization absorption system including an absorption section that introduces exhaust gas discharged from a combustion apparatus including a boiler, sprays seawater on the exhaust gas, and absorbs and removes sulfur oxides contained in the exhaust gas. In a flue gas desulfurization apparatus comprising a tower and an oxidation tank for air-oxidizing sulfite ions in seawater that has absorbed and removed sulfur oxides in the desulfurization absorption tower, the absorption is provided below the absorption section of the desulfurization absorption tower. A seawater recovery member that recovers seawater that has absorbed and removed sulfur oxides at the section is provided, and the seawater is discharged into the exhaust gas introduced into the desulfurization absorption tower below the seawater recovery member and upstream of the absorption section in the exhaust gas flow direction. A dust removal unit that absorbs and removes dust in the exhaust gas by spraying is provided, a seawater supply unit that supplies sulfite ion-containing seawater recovered by the seawater recovery member into the oxidation tank is provided, and oxidation air is oxidized from the atmosphere. For oxidation supplied to the tank An air supply unit, a microbubble generator for generating microbubbles is provided in the oxidation tank below the seawater recovery member, and the seawater supplied from the seawater supply unit to the microbubble generator And the oxidizing air supplied from the oxidizing air supply unit are provided, and the oxidizing air is generated by the pressure of the supplied seawater having potential energy resulting from the difference in height between the seawater recovery member and the microbubble generator in the mixing unit. Is a flue gas desulfurization apparatus provided with a microbubble generating mechanism for sucking the gas and generating microbubbles in the oxidation tank.

  In the invention according to claim 2, the height of the seawater recovery member and the microbubble generator is set so that the pressure of the supplied seawater having the potential energy resulting from the height difference between the seawater recovery member and the microbubble generator is microbubbles. It is a flue gas desulfurization apparatus of Claim 1 provided in the height position used as the pressure which produces | generates the microbubble of an average bubble diameter of 10-100 micrometers with a generator.

  According to a third aspect of the present invention, there is provided an air diffuser nozzle for ejecting the air for oxidation in the oxidation tank, and an air blower for oxidation for supplying the air for oxidation to the air diffuser nozzle. Is a flue gas desulfurization apparatus.

A fourth aspect of the present invention is the flue gas desulfurization apparatus according to the third aspect, wherein the average diameter of the bubbles ejected from the aeration nozzle is 500 to 2000 μm.
In the present specification, the microbubble means a microbubble having a bubble diameter of a micrometer (μm) unit or less (including nanometers), specifically, a bubble having a bubble diameter of less than 500 μm. It is.
(Function)
According to the present invention, the microbubble generator that generates microbubbles in the oxidation tank is provided in the oxidation tank below the seawater recovery member that recovers sulfite ion-containing seawater. The seawater containing sulfite ions having potential energy resulting from the difference in height between the seawater recovery member and the microbubble generator is supplied into the microbubble generator at a pressure (water head pressure) corresponding to the potential energy.

  And when supply seawater flows at high pressure, a negative pressure generate | occur | produces in the mixing part of air | atmosphere, oxidization air is suck | inhaled, and the fine bubble of oxidization air is generated in an oxidation tank. These fine bubbles greatly improve the oxidation rate of sulfite ions, and accordingly the required liquid residence time is shortened and the air utilization rate is increased, so the oxidation tank is made compact and the amount of air for oxidation is reduced. Can be planned.

  Further, normally, the liquid pressurized by the pump is supplied to the microbubble generator. According to the invention of claim 1, the oxidation energy tank is constructed with a simple structure by effectively utilizing the potential energy of the sulfite ion-containing seawater. Microbubbles can be easily generated inside, and additional power for generating fine bubbles is not required.

Further, the oxidation rate of sulfite ions in seawater after absorbing SO ₂ in the exhaust gas is basically an oxygen dissolution rate-determining rate, and the oxidation rate is improved by reducing the bubble diameter of air.
The microbubble generator sucks the atmosphere by the ejector effect that generates a negative pressure just by supplying a liquid such as water at a pressure of 0.1 MPa (megapascal) or more, and can generate fine bubbles having an average diameter of 100 μm or less. There is something.

  For example, when the seawater recovery member is provided at a height of about 10 m from the bottom surface of the desulfurization absorption tower and the microbubble generator is provided at substantially the same height as the bottom surface of the desulfurization absorption tower, it contains sulfite ions collected by the seawater recovery member. Seawater has a potential energy of about 10 m (effective head minus pipe loss). Since the water head pressure at a height of 10 m is about 0.1 MPa, sulfite ion-containing seawater can be supplied to the microbubble generator at a pressure of about 0.1 MPa, and fine bubbles of about 10 to 100 μm are obtained. Will be.

In general, the average bubble diameter is 10 to 100 μm at a pressure of about 0.1 MPa.
Therefore, according to invention of Claim 2, in addition to the effect | action of the invention of said Claim 1, the position of a seawater collection | recovery member and a microbubble generator is made into the height difference of a seawater collection | recovery member and a microbubble generator. The pressure of the seawater supplied to the microbubble generator is set at a position where the pressure of the supplied seawater having the potential energy generated from the microbubble generator is such that the microbubble generator generates fine bubbles having an average diameter of 10 to 100 μm. The oxidation rate of sulfite ions can be greatly improved without requiring power to increase the sulfite ion.

  In addition, a sufficient effect can be obtained only by miniaturizing the bubbles as described above. According to the invention described in claim 3, in addition to the action of the invention described in claim 1 or 2, the oxidizing air By forcibly ejecting bubbles from the diffuser nozzle by the power of the blower, it is possible to obtain a higher oxidation effect of sulfite ions by combining the microbubble generator and the diffuser nozzle.

  When the oxygen supply rate becomes excessive due to miniaturization of the oxidization air, the oxidation reaction of sulfite ions shifts from the oxygen dissolution rate control to the sulfite ion diffusion rate control on the liquid side in the oxidation tank. The fine bubbles of less than 500 μm generated from the microbubble generator have a low ascending speed and a weak stirring effect on the liquid side. On the other hand, by using an air diffuser nozzle having an average bubble diameter of 500 μm or more, the bubble rising speed is increased and the liquid-side stirring effect is enhanced. However, if the bubble diameter is too large, the rising speed of the bubbles is also slowed down, so the average diameter of the bubbles from the diffuser nozzle is preferably 500 to 2000 μm.

  Therefore, according to the invention of claim 4, in addition to the action of the invention of claim 3, the diffusion rate of sulfite ions in the liquid is increased, and the oxidation rate of sulfite ions can be further improved. .

According to the first aspect of the invention, by effectively utilizing the potential energy of the sulfite ion-containing seawater recovered by the seawater recovery member, which arises from the difference in height between the seawater recovery member and the microbubble generator, with a simple configuration Microbubbles can be easily generated in the oxidation tank. Therefore, the oxidation rate of sulfite ions after SO ₂ absorption is greatly improved, and accordingly the required liquid residence time is shortened and the air utilization rate is increased, so the oxidation tank is made compact and the oxidizing air is supplied. To reduce the power required to do this. Further, additional power for generating fine bubbles is not required.

  According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, fine bubbles with an average diameter of 10 to 100 μm can be generated by the microbubble generator, so that the oxidation rate of sulfite ions Can be greatly improved.

  According to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, a higher sulfite ion oxidizing effect can be obtained by combining the aeration nozzle with the microbubble generator. be able to.

  According to the invention of claim 4, in addition to the effect of the invention of claim 3, the diffusion rate of sulfite ions in the liquid in the oxidation tank is increased, and the oxidation rate of sulfite ions can be further improved. Become.

It is a figure which shows the system | strain of the flue gas desulfurization apparatus which is one Example of this invention. It is the figure which showed the production | generation mechanism of the microbubble. It is an A-A 'line arrow directional view of the desulfurization absorption tower of FIG. It is a B-B 'line arrow directional view of the desulfurization absorption tower of FIG. It is the side view of the oxidation tank which showed arrangement | positioning of the microbubble generator of FIG. 1, and an aeration nozzle. It is the side view of the oxidation tank which showed the example of arrangement | positioning different from FIG. It is the figure which showed the relationship between the bubble diameter of oxidation air, and a sulfite ion oxidation rate. It is the figure which showed the relationship between the bubble diameter from a diffuser nozzle, bubble rising speed, and a sulfite ion oxidation rate. It is a figure which shows the system | strain of the flue gas desulfurization apparatus which is another Example of this invention. It is a figure which shows the system | strain of a flue gas desulfurization apparatus of a prior art.

  Embodiments of the present invention are shown below.

Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1, the system | strain of the flue gas desulfurization apparatus which is one Example of this invention is shown. In the wet desulfurization apparatus in FIG. 1, the description of members having the same reference numerals as in the wet desulfurization apparatus in FIG. 10 is partially omitted.

  The wet desulfurization apparatus of this embodiment is mainly composed of a desulfurization absorption tower 1 for treating SOx in combustion exhaust gas from a boiler, an inlet duct 2 for introducing exhaust gas into the desulfurization absorption tower 1, and an outlet for discharging exhaust gas from the desulfurization absorption tower 1. Duct 3, seawater spray nozzle 9 that sprays seawater that absorbs SOx in exhaust gas onto exhaust gas, mist eliminator 7 that removes mist accompanying the exhaust gas flow, booster pump 18 for supplying seawater to seawater spray nozzle 9, absorption of SOx The oxidation tank 14 oxidizes the sulfite ions generated by the oxidation, the oxidation air blower 16 that sends the air supplied to the oxidation tank 14, the air diffuser nozzle 17 that blows out the air sent by the oxidation air blower 16, and the like. Thus, it is the same as the wet desulfurization apparatus of FIG.

The combustion exhaust gas is introduced from the inlet duct 2 into the desulfurization absorption tower 1 in a substantially horizontal direction, and is discharged from the outlet duct 3 provided at the top of the desulfurization absorption tower 1. In the desulfurization absorption tower 1, seawater is pumped up by the seawater pump 13, and the seawater is sprayed as fine droplets from the seawater spray nozzle 9 through the absorption seawater water supply pipe L <b> 2 by the booster pump 18. By the contact, SOx (mainly SO ₂ ) in the exhaust gas is selectively absorbed and removed on the surface of the absorbing droplets of the seawater spray nozzle 9 together with soot dust and acidic gas such as HCl and HF in the exhaust gas.

  In the seawater atomized by spraying from the seawater spray nozzle 9, mist accompanying the flow of the exhaust gas is collected by a mist eliminator 7 installed in the outlet duct 3 at the top of the desulfurization absorption tower 1. The exhaust gas that has passed through the mist eliminator 7 is reheated as necessary, and then discharged into the atmosphere from a chimney (not shown).

  In the wet desulfurization apparatus of this embodiment, a collector 10 for collecting sprayed seawater and a collecting tank 11 (seawater recovery member) are provided below a seawater spray nozzle 9 for spraying seawater for absorbing SOx, and under these seawater recovery members A dust removal spray nozzle 8 different from the seawater spray nozzle 9 is provided between the inlet duct 2 located on the side and the collector 10. Absorbing liquid stored in the circulation tank 5 below the desulfurization absorption tower 1 is circulated and supplied to the dust removing spray nozzle 8 by the absorbing liquid circulation pump 4. The absorbent in the circulation tank 5 is stirred and oxidized by the stirrer 6. By spraying from the dust removing spray nozzle 8 while circulating the absorbing liquid for dust removal, soot and heavy metals in the exhaust gas are absorbed and removed.

  A part of the absorbing liquid in the circulation tank 5 is extracted from the absorbing liquid extraction pipe L1, and the dust and heavy metals in the absorbing liquid are coagulated and settled and removed. In addition, since absorption liquid evaporates with the heat | fever from waste gas, seawater is continuously replenished in the circulation tank 5 from the supplementary water supply pipe which is not shown in figure.

  Then, in the oxidation tank 14, the atmosphere is ejected by an ejector system (a system having a constricted portion inside a straight pipe and having an air supply pipe in a portion where the flow velocity of the liquid is highest and the static pressure is reduced to a negative pressure). A plurality of microbubble generators 15 that generate microbubbles by suction through the intake pipe L5 are provided. By supplying the sulfite ion-containing seawater recovered by the collector 10 and the collection tank 11 from the sulfite ion-containing seawater water supply pipe L4 to the microbubble generator 15, the oxidant tank 14 sucks the oxidation air from the atmosphere through the intake pipe L5. It is set as the structure which generate | occur | produces the fine bubble 20 of oxidizing air in the inside.

FIG. 2 shows the principle of an ejector system that is a microbubble generating mechanism of the microbubble generator 15.
This method is based on a mechanism in which pressurized water or steam is jetted by a nozzle to suck in ambient air (vacuum or negative pressure). Seawater flowing down from the sulfite ion-containing seawater water supply pipe L4 and supplied to the microbubble generator 15 passes through the nozzle portion 30 with a high pressure corresponding to the potential energy generated by the height difference between the collector 10 and the like and the microbubble generator 15. To do. At this time, the mixing unit 31 sucks the oxidizing air by the pressure difference from the low-pressure air from the intake pipe L5. The mixed fluid of seawater and oxidizing air is decelerated by the diffuser unit 32 to become a high-speed bubble flow, and the microbubbles 20 (FIG. 1) are discharged from the microbubble generator 15.

  In the oxidation tank 14, the seawater that has passed through the microbubble generator 15 is sent from the oxidation air blower 16 while being diluted with the seawater for dilution sent from the seawater feed pipe L3 for dilution by the seawater pump 13, and the diffuser nozzle 17. Is oxidized by oxygen dissolved from the bubbles ejected from the water and returned to the ocean 12 as seawater.

FIG. 3 shows an AA ′ arrow view of the desulfurization absorption tower of the flue gas desulfurization apparatus of FIG. 1, and FIG. 4 shows a BB ′ arrow view of FIG. These figures are schematic views.
In these drawings, the collector 10 is shown as an example in which a straight member having a U-shaped cross section (or a U-shaped cross section may be used) is arranged in a staggered manner in two upper and lower stages in plan view. May be more. Further, the collector 10 does not have to be U-shaped in cross section, and may have a shape capable of receiving sprayed seawater, and may be disposed with a gap through which exhaust gas passes.

  Depending on the seawater flow rate recovered by the collector 10, a plurality of sulfite ion-containing seawater water pipes L4 may be provided as shown in FIG. Seawater sprayed from the seawater spray nozzle 9 can be received by a plurality of collectors 10 provided below the seawater spray nozzle 9 and above the dust removal spray nozzle 8. A collection tank 11 is connected to the lower end of each collector 10, and seawater is collected in the collection tank 11. The collected and collected sulfite ion-containing seawater is supplied to the microbubble generator 15 from the sulfite ion-containing seawater pipe L4.

FIG. 5 shows an arrangement of the microbubble generators and the aeration nozzles of FIG. 1 (side view), and FIG. 6 shows an arrangement example different from FIG. 5 (side view).
As shown in FIG. 5, the arrangement of the microbubble generator 15 and the air diffuser nozzle 17 is arranged on the upstream side of the oxidation tank 14 (pointing to the connection side of the sulfite ion-containing seawater water pipe L4, left side of the drawing). It is preferable to provide a diffuser nozzle 17 on the downstream side (right side of the drawing). In this case, the seawater flowing down from the sulfite ion-containing seawater transmission pipe L4 can be supplied to the microbubble generator 15 as it is, and the length of the pipe can be shortened, so that the pipe loss is reduced and the potential energy of the sulfite ion-containing seawater is reduced. Can be used effectively.

  Further, as shown in FIG. 6, the microbubble generator 15 and the air diffusion nozzle 17 may be arranged in parallel. In FIG. 5, the zone of the microbubble generator 15 and the zone of the aeration nozzle 17 are separated on the upstream side and the downstream side of the oxidation tank 14, but the microbubble generator 15 and the aeration nozzle are vertically arranged as shown in FIG. 17 are arranged alternately on the upstream side and the downstream side of the oxidation tank 14, so that the high-speed bubble flow from the microbubble generator 15 and the bubbles from the diffuser nozzle 17 are likely to be mixed. The effect of the present invention can be maximized as compared with the arrangement.

  FIG. 7 shows the relationship between the bubble diameter of the oxidizing air and the sulfite ion oxidation rate, and FIG. 8 shows the bubble diameter from the aeration nozzle, the bubble rising speed (shown by a broken line), and the sulfite ion oxidation rate (solid line). The relationship is shown.

The oxidation rate of sulfite ions in seawater after absorbing SO ₂ in the exhaust gas is basically an oxygen dissolution rate limiting rate, and the oxidation rate is improved by reducing the bubble diameter of the air. In these figures, the oxidation rate of sulfite ions when the bubble diameter (average diameter) generated from the diffuser nozzle is 500 μm is set to 1.

  When seawater recovery members such as the collector 10 and the collection tank 11 are provided at a height of about 10 m from the bottom surface of the desulfurization absorption tower 1, and the microbubble generator 15 is provided at substantially the same height as the bottom surface of the desulfurization absorption tower 1, The seawater containing sulfite ions collected by the seawater recovery member has a potential energy (lift) of about 10 m. Since the water head pressure at a height of 10 m is about 0.1 MPa, sulfite ion-containing seawater can be supplied to the microbubble generator 15 at a pressure of about 0.1 MPa, and the average diameter is about 10 to 100 μm. Fine bubbles are obtained. A microbubble generator that can obtain fine bubbles of about 10 to 100 μm even at a pressure of about 0.1 MPa is generally used.

  Accordingly, as shown in FIG. 7, the oxidation rate of sulfite ions is improved by 1.5 to 2.9 times, and accordingly, the necessary liquid residence time is shortened and the air utilization rate is also increased. 14 can be made compact and the amount of air for oxidation can be reduced.

  Note that when the bubble diameter is close to a nanometer unit of less than 10 μm, a high head (pressure) of 0.3 MPa or more is required, and this level of potential energy alone is insufficient. Therefore, in that case, a larger potential energy is required, but the effect of improving the oxidation rate of sulfite ions is sufficiently obtained with fine bubbles having an average diameter of about 10 to 100 μm.

  Usually, the liquid pressurized by the pump is supplied to the microbubble generator 15, but in the case of this embodiment, the potential energy of the sulfite ion-containing seawater is effectively utilized, so that the inside of the oxidation tank 14 can be formed with a simple configuration. Thus, the microbubbles 20 can be easily generated, and no additional power is required to generate the fine bubbles.

  In addition, a sufficient effect can be obtained only by reducing the size of the bubbles by the microbubble generator 15 as described above, but the bubbles are forcibly ejected from the aeration nozzle 17 by the power of the oxidizing air blower 16, thereby generating the microbubbles. By combining the generator 15 and the aeration nozzle 17, a higher oxidation effect of sulfite ions can be obtained.

  When the oxygen supply rate becomes excessive due to the miniaturization of the oxidizing air, the oxidation reaction of sulfite ions shifts from the oxygen dissolution rate control to the sulfite ion diffusion rate control on the liquid side in the oxidation tank 14. As can be seen from FIG. 8, the fine bubbles of 100 μm or less generated from the microbubble generator 15 have a slow rising speed of 0.02 m / s or less, and the liquid side stirring effect is weak. On the other hand, when the air diffusion nozzle 17 having an average bubble diameter of 500 μm or more is used, the bubble rising speed is 0.1 m / s or more, and the liquid side stirring effect is enhanced.

  Therefore, by combining the microbubble generator 15 and the diffuser nozzle 17 having an average bubble of 500 μm or more, the diffusion rate of sulfite ions in the liquid is increased, and the oxidation rate of sulfite ions can be further improved. Become. Further, if the bubble diameter exceeds 2000 μm, the oxidation rate of sulfite ions reaches a peak, and the bubble rising speed also decreases. Therefore, it is more effective if the average diameter of the bubbles from the air diffuser nozzle 17 is 500 to 2000 μm. .

The bubble diameter ejected from the air diffuser nozzle 17 can be easily changed and adjusted by changing the hole diameter of the nozzle.
Table 1 shows the calculation conditions and results of FIGS.

The boiler output is set to 800 MW, and the apparatus of FIG. 1 is used to introduce 2,465,000 (m ³ N / h) exhaust gas, and the flow rate of the sulfite ion-containing seawater flowing down from the sulfite ion-containing seawater pipe L4. Set to 20,000 (m ³ / h), 267 ejector-type microbubble generators 15 (YJ nozzle type YJ-40 manufactured by Enviro Vision Co., Ltd.) were installed in the oxidation tank 14.

A total of about 4,500 (m ³ N / h) of air can be sucked in through the intake pipe L 5 by all the microbubble generators 15, and oxidizing air can be blown into the oxidation tank 14 as the microbubbles 20.

  When the average bubble diameter of the microbubbles 20 is 30 μm, the sulfite ion oxidation rate is 2 times or more from FIG. 7, and when the average bubble diameter from the air diffuser nozzle 17 is 1000 μm, the sulfite ion oxidation rate is further 1.5 times from FIG. Thus, the oxidation rate is improved by about 3 times in total.

That is, according to the present embodiment, 4,500 (m ³ N / h) × 3 (times) = 13,500 (m ³ N / h), the bubble diameter can be obtained without using the microbubble generator 15. This corresponds to an oxidation air amount of 13,500 (m ³ N / h) when only an aeration nozzle of 500 μm is used.

Since the amount of oxidizing air necessary to oxidize sulfite ions is 40,000 (m ³ N / h) when the bubble diameter is 500 μm, the amount of oxidizing air that should actually be blown from the aeration nozzle 17 is 40 ^{, 000-13,500 = 26,500 (m 3 N} / h), also, for the case of 1000μm relative bubble diameter 500μm from 7 to decrease the oxidation rate 0.8, 26,500 (m ³ N / h) × (1.0 / 0.8) = 33,125 (m ³ N / h), which is about 17% with respect to the prior art oxidation air amount of 40,000 (m ³ N / h). The effect of reducing is obtained.

In FIG. 9, the system | strain of the flue gas desulfurization apparatus which is another Example of this invention is shown.
The flue gas desulfurization apparatus in FIG. 9 is different from the flue gas desulfurization apparatus in FIG. 1 in that the booster pump 19 is installed in the middle of the sulfite ion-containing seawater water supply pipe L4, but the other configurations are the same, and therefore the same The description of the part is omitted.

  According to the present embodiment, the pressure of the seawater flowing down from the sulfite ion-containing seawater water supply pipe L4 is increased by the booster pump 19, whereby the pressure of the sulfite ion-containing seawater supplied to the microbubble generator 15 can be further increased. And when this high pressure seawater passes the nozzle part 30, the attraction | suction force of oxidizing air also increases with the pressure difference with the low pressure oxidizing air supplied by the intake pipe L5 in the mixing part 31. FIG. Then, the mixed fluid of seawater and oxidizing air becomes a higher-speed bubble flow than when the booster pump 19 is not installed, and finer microbubbles 20 are discharged from the microbubble generator 15.

Therefore, according to the present embodiment, the capacity of the microbubble generator 15 can be increased, and the number of installed units in the oxidation tank 14 can be reduced.
Also in this embodiment, the microbubble generator 15 and the air diffusion nozzle 17 may be combined, and in that case, a high oxidation effect of sulfite ions can be obtained. Further, a nozzle having an average bubble diameter of 500 to 2000 μm may be used as the diffuser nozzle 17, in which case the diffusion rate of sulfite ions in the liquid is increased, and the oxidation rate of sulfite ions is further improved. Is possible.

  In flue gas desulfurization equipment using seawater, etc., it may be used as a technology capable of downsizing an oxidation tank that oxidizes seawater containing sulfite ions and reducing the power of an oxidized air blower.

DESCRIPTION OF SYMBOLS 1 Desulfurization absorption tower 2 Inlet duct 3 Outlet duct 4 Absorption liquid circulation pump 5 Circulation tank 6 Stirrer 7 Mist eliminator 8 Dust removal spray nozzle 9 Seawater spray nozzle 10 Collector 11 Collection tank 12 Ocean 13 Seawater pump 14 Oxidation tank 15 Microbubble generator 16 Oxidizing air blower 17 Aeration nozzle 18, 19 Booster pump 20 Micro bubble (fine bubble)
30 Nozzle part 31 Mixing part 32 Diffuser part L1 Absorption liquid extraction pipe L2 Seawater water supply pipe for absorption L3 Seawater water supply pipe for dilution L4 Seawater water supply pipe containing sulfite ions L5 Intake pipe

Claims (4)

A desulfurization absorption tower having an absorption section for introducing exhaust gas discharged from a combustion apparatus including a boiler, spraying seawater on the exhaust gas to absorb and removing sulfur oxides contained in the exhaust gas, and the desulfurization absorption tower In a flue gas desulfurization apparatus equipped with an oxidation tank that air-oxidizes sulfite ions in seawater that has absorbed and removed sulfur oxides,
Provided below the absorption part of the desulfurization absorption tower is a seawater recovery member that recovers seawater that has absorbed and removed sulfur oxides in the absorption part,
Below the seawater recovery member and on the upstream side in the exhaust gas flow direction of the absorber, a dust removal unit is provided that sprays seawater on the exhaust gas introduced into the desulfurization absorption tower to absorb and remove the dust in the exhaust gas,
A seawater supply unit for supplying sulfite ion-containing seawater recovered by the seawater recovery member into the oxidation tank is provided,
An oxidizing air supply unit that supplies oxidizing air from the atmosphere into the oxidation tank is provided,
In the oxidation tank, provided below the seawater recovery member, a microbubble generator for generating microbubbles,
The microbubble generator is provided with a mixing section of seawater supplied from the seawater supply section and oxidizing air supplied from the oxidizing air supply section, and the mixing section is used to adjust the height of the seawater recovery member and the microbubble generator. A flue gas desulfurization apparatus provided with a microbubble generation mechanism for generating microbubbles in an oxidation tank by sucking oxidation air by the pressure of supplied seawater having potential energy resulting from a difference.   The height of the seawater recovery member and the microbubble generator is an average of 10 to 100 μm in the pressure of the supplied seawater having potential energy resulting from the difference in height between the seawater recovery member and the microbubble generator. The flue gas desulfurization apparatus according to claim 1, wherein the flue gas desulfurization apparatus is provided at a height position where pressure is generated to generate microbubbles having a bubble diameter.   The air nozzle for ejecting the air for oxidation in the said oxidation tank was provided, and the air blower for oxidation which supplies oxidation air to this air diffuser nozzle was provided, The air blower of Claim 1 or 2 characterized by the above-mentioned. Flue gas desulfurization equipment.   The flue gas desulfurization apparatus according to claim 3, wherein an average diameter of the bubbles ejected from the aeration nozzle is set to 500 to 2000 µm.

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