JP2002263442A - So3 removing equipment for flue gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent releasing of a sulfuric acid mist to the atmospheric air in spite of a fluctuation in the concentration of SO3 in flue gas. SOLUTION: A flue 3 for introducing the flue gas of a boiler, etc., to a chimney 11 is provided with wet process desulfurizing equipment 7 for removing SO2 in the flue gas and the flue on the upstream side of the desulfurizing equipment is provided with a sodium carbonate supplying system 10 for injecting sodium hydrogencarbonate powder to the flue gas and forming sodium carbonate particles in the flue gas. The amount of the SO3 in the flue gas flowing in the flue on the upstream side of the sodium carbonate supplying system is detected by a controller 20 and the amount of the sodium carbonate to be supplied from the sodium carbonate supplying system to the flue gas is adjusted according to the detected amount of the SO3 . The sodium carbonate supplied to the flue forms Na2 SO4 by reacting with the sulfuric acid mist in the flue gas and is captured by the desulfurizing equipment and therefore the amount of the sulfuric acid mist released to the atmospheric air from the chimney is decreased regardless of the fluctuation in the amount of the SO3 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for removing SO _{3 from} flue gas, and more particularly, to an apparatus for removing SO ₃ (SO ₃ gas, H ₂ SO _4).
The present invention relates to an SO _{3 component} removing device that removes SO ₃ component in exhaust gas containing gas and mist, and prevents generation of purple smoke due to sulfuric acid mist when exhaust gas is released to the atmosphere.

[0002]

2. Description of the Related Art In a furnace such as a boiler using a fuel containing sulfur such as heavy oil, sulfur dioxide (SO ₂ ) is generated in flue gas by combustion of sulfur in the fuel. For this reason, in a furnace using heavy oil or the like, the flue gas is discharged by a desulfurization device before the flue gas is released to the atmosphere to remove SO ₂ .

[0003] However, a part of the SO _{2 in} the flue gas is further oxidized in a boiler or a denitration device to be converted into sulfur trioxide (SO ₃ ). SO ₃ passes through an air preheater, etc., and the flue gas temperature is lowered. For example, when the temperature falls to about 300 ° C. or less, the SO ₃ reacts with the moisture in the flue gas and SO ₃ + H ₂ O → H ₂ S
H ₂ SO ₄ gas is generated by the reaction of O ₄ . This H ₂ SO
_{The four} gases produce fine sulfuric acid mist when the flue gas temperature falls below the dew point of sulfuric acid. When a desulfurization device, especially a wet type desulfurization device, is used, the H ₂ SO ₄ gas in the flue gas becomes sulfuric acid mist because the flue gas temperature drops below the sulfuric acid dew point temperature when passing through the desulfurization device. Since the sulfuric acid mist removal rate is low, in a heavy oil fired boiler or the like, the exhaust gas at the outlet of the desulfurization device contains a relatively large amount of sulfuric acid mist. Sulfuric acid mist generates purple smoke when discharged into the atmosphere, and causes air pollution as acid deposition.

As a device for removing sulfuric acid mist in exhaust gas, a wet electric precipitator (hereinafter referred to as "wet EP") is generally used. In the wet EP, a water film is formed on an electrode of an electrostatic precipitator by spraying water or an alkaline solution on the electrode, and the collected sulfuric acid mist is washed and removed from the electrode.

[0005]

However, in a boiler or the like, the amount of SO _{3 in} flue gas fluctuates greatly due to fluctuations in load, sulfur concentration in the fuel used, boiler contamination, and the like.
For this reason, it is necessary to set the maximum processing capacity (collection capacity) of the wet EP to a large value with a margin for the maximum SO ₃ generation amount in consideration of various conditions. In addition, wet EP
Since a large installation area is usually required, increasing the processing capacity of the wet EP greatly increases equipment costs and construction costs, and raises the cost of the entire boiler plant.

[0006] In the wet EP, when the amount of mist in the exhaust gas increases, a charge disturbance occurs due to the space charge effect, and the dust collection rate is extremely reduced. For this reason, for example, when the sulfuric acid mist concentration in the flue gas increases at one time due to boiler load fluctuation or the like, even if the maximum processing capacity is set large, the sulfuric acid mist concentration at the wet EP outlet increases, There is a problem of generating purple smoke.

[0007] The present invention solves the above-mentioned problems and provides a simple and low-cost SO that can remove sulfuric acid mist with high efficiency even when the SO ₃ amount in flue gas fluctuates without using wet EP. It aims to provide a _three- minute removal device.

[0008]

According to the first aspect of the present invention, sodium carbonate is provided in a flue in which flue gas from a furnace for burning fuel containing sulfur flows, and in a flue upstream of the desulfurization apparatus. A sodium carbonate supply device for supplying (Na ₂ CO ₃ ), a desulfurization device arranged in the flue to remove sulfur dioxide (SO ₂ ) in the flue gas, and a flue gas at a predetermined location in the flue. sulfur trioxide content and SO ₃ minutes detecting means for detecting (SO ₃ minutes) amount, in accordance with the detected SO ₃ content of the SO ₃ minutes detector, sodium carbonate supply amount from the sodium carbonate supply device included in and control means for controlling, with a flue gas SO ₃ minutes removing device is provided.

That is, according to the first aspect of the present invention,_TwoC
O_ThreePowder is supplied to the flue gas upstream of the desulfurization unit. Flue gas
Na supplied in_TwoCO_ThreePowder is SO in flue gas_ThreeIs
Na_TwoCO_Three+ SO_Three→ Na_TwoSO_Four+ CO_TwoIn the form of
H in smoke_TwoSO_FourMeans Na_TwoCO _Three+ H_TwoSO_Four→ Na_TwoS
O_Four+ CO_Two+ H_TwoReact in the form of O_TwoSO_FourGenerate
You. In addition, the generated Na_TwoSO_FourIs water soluble and desulfurized
(Especially wet desulfurization equipment)_TwoWhen removing
Easily removed from the exhaust. That is, the SO in the exhaust
_Three, And SO_ThreeSulfuric acid gas and mist (H_Two
SO_Four) Is sodium carbonate (Na) upstream of the desulfurization unit._TwoCO
_Three) Can be removed from flue gas
It is. In this case, Na_TwoCO_ThreeOf sulfuric acid in flue gas
Mist amount can be reduced to the target level
Need to be adjusted exactly.

Therefore, in the present invention, the amount of sulfuric acid gas and mist in flue gas and the amount of SO ₃ are detected, and the amount of sulfuric acid mist in the flue gas is reduced to a predetermined value based on the detected value. have a Na ₂ CO ₃ is supplied to the flue gas upstream of the desulfurization apparatus. In order to calculate the Na ₂ CO ₃ amount required, it is necessary to detect the sulfuric acid mist content in the flue gas, SO ₃ generated in the furnace and the like has its almost entire amount in flue gas H _Since it is changed to ₂ SO ₄ mist, by detecting the amount of SO ₃ generated by combustion in a furnace etc.,
The required amount of Na ₂ CO ₃ can be calculated.

Therefore, in this specification, SO_ThreeAnd sulfuric acid gas
And the total amount with mist_ThreeAmount ”(or“ trioxide
Sulfur trioxide (SO)_Three) With itself
SO_ThreeSulfuric acid gas and mist generated from_ThreeMinutes "
Will be referred to collectively. In the present invention, in the predetermined position of the flue
Detected SO in flue gas_ThreeReleased to the atmosphere based on the quantity
The amount of sulfuric acid mist below the target value such as regulation value
Na required for _TwoCO_ThreeOf sodium carbonate
Na supplied from the feeder to the flue upstream of the desulfurizer_TwoC
O_ThreeTo control the amount of As a result, SO_ThreeQuantity
Even in the case of fluctuations, sulfuric acid mist in the exhaust
a_TwoSO_FourWill be collected in the form of, and will always be released to the atmosphere
Sulfuric acid mist volume can be maintained below the target value
Becomes

The amount of SO ₃ in the flue gas may be detected, for example, upstream of the desulfurization unit or downstream of the desulfurization unit. According to the invention described in claim 2, the S
2. The SO _{3 component} removing device according to claim 1, wherein the O _{3 component} detecting means detects an SO _{3 component} amount in the flue gas upstream of a location of the flue where sodium carbonate is supplied. ₃ .

That is, according to the second aspect of the present invention, the SOx in the flue gas upstream of the desulfurization apparatus before the supply of sodium carbonate is supplied.
_Three fractions are detected. Thus, the amount of sodium carbonate required to react with SO ₃ and reduce the amount of sulfuric acid mist released to the atmosphere to a target value or less is accurately calculated irrespective of the variation in the SO ₃ amount in the flue gas. . According to the third aspect of the present invention, the SO ₃ minute detecting means includes a sulfur content in a fuel used in the furnace, a load on the furnace, a degree of contamination of a heat transfer portion of the furnace, and a desulfurization device. entrance sO ₂ concentration, based on operating conditions of the furnace including any one or more, by calculating the sO ₃ content in the said flue gas, indirectly to detect the sO ₃ content in the flue gas, wherein S of smoke exhaustion described in Item 2
An O ₃ minute removal device is provided.

That is, according to the third aspect of the present invention, the SO _{3 in} the flue gas before the supply of sodium carbonate is supplied based on the operating state of the furnace.
The amount is detected indirectly. For example, the amount of SO ₃ generated from the furnace is calculated by comparing the amount of SO ₂ generated in the furnace with SO ₂ → SO ₃
To the conversion rate. On the other hand, the amount of SO ₂ generated is determined by the sulfur content in the fuel burned in the furnace and the amount of fuel burned. Further, the conversion ratio from SO _{2 to} SO ₃ varies depending on the degree of contamination of the furnace heat transfer section (for example, a boiler heat transfer tube), as described later. Therefore, if grasp the factors that have these SO ₃ generation amount, it is possible to calculate the SO ₃ content in the flue gas without detecting the SO ₃ content directly in the flue gas. This makes it possible to maintain the amount of sulfuric acid mist released to the atmosphere at or below the target value regardless of the variation in the SO ₃ amount in the exhaust gas.

According to the fourth aspect of the present invention, the SO
₃ min detecting means detects the SO ₃ content in the flue gas of the desulfurization apparatus downstream of the flue, the SO ₃ minutes removing apparatus according to claim 1 is provided. That is, in the invention of claim 4, the amount of SO ₃ (in this case, the amount of sulfuric acid mist) in the flue gas downstream of the desulfurization device is detected, and Na supplied to the upstream side of the desulfurization device in accordance with the detected SO ₃ amount. The amount of ₂ CO ₃ is controlled. Therefore, the amount of SO ₃ (the amount of sulfuric acid mist) downstream of the desulfurization unit
There it is possible to feedback control the sodium carbonate supply amount to meet the target value, SO ₃ present in the flue gas
Even when the amount fluctuates, it is possible to more accurately control the amount of sulfuric acid mist released into the atmosphere to a target value or less.

According to a fifth aspect of the present invention, the sodium carbonate supply device supplies sodium bicarbonate powder to a flue of a flue upstream of the desulfurization device, and converts sodium bicarbonate into a porous gas in a flue gas. The SO _{3 component} removing device according to any one of claims 1 to 4, wherein the device is converted to sodium carbonate fine particles. That is, in the fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the sodium carbonate supply device supplies sodium bicarbonate powder into flue gas to form sodium carbonate fine particles in the flue gas. I do. The sodium bicarbonate powder supplied during the flue gas causes a decomposition reaction of 2NaHCO ₃ → Na ₂ CO ₃ + CO ₂ + H ₂ O due to the heat of the flue gas, and sodium carbonate (Na ₂ CO ₃ ) is generated during the flue gas Is done. The Na ₂ CO ₃ particles become porous fine particles having a high porosity and a large specific surface area because the portion from which CO ₂ and H ₂ O are removed becomes voids. Therefore, the generated Na
₂ CO ₃ particles with SO ₃ minutes and efficiently react in the flue gas SO ₃
The minutes will be converted to Na ₂ SO ₄ .

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a schematic configuration of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a furnace such as a boiler, 3 denotes a flue through which flue gas from the boiler 1 flows, and 7 denotes a desulfurization device for removing SO ₂ in the flue gas.
In this embodiment, the wet desulfurization unit of known type is the desulfurizer 7 (e.g., calcium hydroxide, to absorb the SO ₂ in the flue gas to calcium carbonate, which is removed in the form of CaSO _4, or water Use magnesium oxide or sodium hydroxide to remove SO ₂ in flue gas from MgSO ₄ or Na ₂ S
O ₄ removal) is used. The flue gas from which SO ₂ has been removed by the desulfurization device 7 passes through a flue 9 on the downstream side, and is discharged from the chimney 11 to the atmosphere.

The combustion gas (smoke exhaust) generated by the combustion of heavy oil in the boiler 1 passes through an air preheater (not shown) provided in the flue 3 and the combustion air and heat supplied to the boiler. After the replacement, the air is sucked by the desulfurization fan 5, flows through the flue 3, and is supplied to the desulfurization device 7. Combustion of heavy oil containing relatively large amount of sulfur (for example, about 3%) as fuel,
SO ₂ is produced by oxidation of sulfur, some become SO ₃ is further oxidized. When the flue gas temperature is reduced, for example, by passing through an air preheater, the SO ₃ reacts with the moisture in the flue gas to generate gaseous or fine mist sulfuric acid (H ₂ SO ₄ ).

Therefore, the flue gas supplied to the desulfurization unit 7 by the desulfurization fan 5 contains not only SO ₂ but also sulfuric acid gas and mist, and the temperature of the flue gas drops below the sulfuric acid dew point temperature when passing through the desulfurization unit. Therefore, all the sulfuric acid gas in the flue gas becomes sulfuric acid mist. Although the desulfurization apparatus 7 SO ₂ is removed with high efficiency, because low removal rate of sulfuric acid mist, typically, sulfuric acid mist concentration in the flue gas in the desulfurization apparatus 7 outlet is a relatively high value from (for example, 30 45 PPM).

When the flue gas containing the sulfuric acid mist having a relatively high concentration is discharged directly from the chimney 11 into the atmosphere, the fine sulfuric acid mist forms purple smoke at the chimney, and the so-called "purple smoke flutters" phenomenon. appear. Further, when the sulfuric acid mist is released into the atmosphere, it becomes an acidic fallout, which causes a problem of falling to the surroundings. Therefore, when the wet desulfurization apparatus 7 is used, the sulfuric acid mist in the flue gas is collected by using the wet EP 8 before discharging the flue gas to the atmosphere.

The wet EP is an electric precipitator of the type in which the collected sulfuric acid mist is washed from the electrode by spraying an alkaline solution or water onto the precipitating electrode. Since the sulfuric acid mist in the flue gas is a submicron particle having a very small particle size, when the sulfuric acid mist is removed using a wet EP in order to increase the efficiency of collecting the sulfuric acid mist, the wet EP Two or more sections need to be arranged in series. Therefore, if wet EP is used for removing sulfuric acid mist, there is a problem that the construction cost of the entire plant increases due to an increase in the size of the apparatus and an increase in the installation area.

In the present embodiment, the flue upstream of the desulfurizer 7
Sodium carbonate (Na) _TwoCO_Three) Fine powder
By supplying, during the exhaust without using wet EP
It is possible to remove sulfuric acid mist. This implementation
In the form, sodium bicarbonate (sodium bicarbonate,
NaHCO_Three) By injecting the fine powder into the flue 3
During the smoke exhaust_TwoCO_Three(Sodium carbonate) particles are formed
I do.

In FIG. 1, reference numeral 10 designates a sodium carbonate supply device for injecting sodium hydrogen carbonate powder into the flue 3 on the inlet side of the desulfurization fan 5. Sodium carbonate supply device 10
The amount of sodium bicarbonate powder supplied to the flue 3 from is controlled by the control device 20 by a method described later.
For example, the particle size 20
Injecting sodium bicarbonate powder of about micron meters or less into the flue gas results in a relatively low flue gas temperature (eg 60
Decomposition reaction of sodium bicarbonate
HCO ₃ → Na ₂ CO ₃ + CO ₂ + H ₂ O are produced, gaseous CO ₂ and H ₂ O are released, and sodium carbonate (Na ₂ C
O ₃ ) is produced. The generated sodium carbonate is a porous particle having a large porosity, though the particle size hardly changes from the sodium hydrogencarbonate powder, since a portion from which the gas is released remains as a void.

[0024] Thus, when the Na ₂ CO ₃ consisting of large porous particles of porosity in the flue gas is generated, sulfuric acid gas and mist in the flue gas is adsorbed into the pores of the particles Na ₂ C
O ₃ and Na ₂ CO ₃ + H ₂ SO ₄ → Na ₂ SO ₄ + CO ₂ + H
It reacts in the form of ₂ O to produce Na ₂ SO ₄ (sodium sulfate). Further, SO ₃ present in the flue gas is similarly reacted in the form of Na ₂ CO ₃ and _{Na 2 CO 3 + SO 3 →} Na 2 SO 4 + CO 2,
It becomes Na ₂ SO ₄ . This Na ₂ SO ₄ is a particle that maintains a diameter almost the same as Na ₂ CO ₃ . Na ₂ SO ₄ particles,
Since both unreacted Na ₂ CO ₃ particles are water-soluble, they can be easily removed from flue gas by the wet desulfurization device 7.

The amount of Na ₂ CO ₃ supplied to the flue gas is
It must be changed according to the amount of SO ₃ in the flue gas. For example, Na ₂ CO having a reaction equivalent or less with respect to the SO ₃ amount in flue gas
₃ than was supplied can not be naturally removed the entire amount of SO ₃ minutes from the flue gas, it will be released to the atmosphere through a stack 11 portion of the SO ₃ minutes through the desulfurization apparatus 7 . Furthermore, the experimental and supplying sodium bicarbonate powder only generate SO ₃ Na ₂ CO ₃ above 1.2-5 equivalents relative quantities, almost completely SO ₃ minutes in the flue gas It has been found that it can be removed.

Therefore, when the amount of SO ₃ generated in the boiler 1 fluctuates, it is necessary to supply an appropriate amount of Na ₂ CO ₃ according to the amount of SO ₃ . It is difficult to directly detect the amount of SO ₃ (the amount of SO ₃ , sulfuric acid gas, and sulfuric acid mist) in flue gas in real time because there is no appropriate sensor at present. For this reason, in the present embodiment,
Sulfur content of the fuel, the boiler operating load, operating time from performing the heat transfer tube cleaning, by calculating the SO ₃ content in the flue gas based such as SO ₂ concentration in the desulfurization apparatus inlet indirectly The amount of SO _{3 in} flue gas is detected.

For example, if the sulfur content of the fuel is different, the amount of SO ₃ generated from the boiler changes even if the boiler load (heat amount) is the same. Further, since the amount of fuel to be burned in a boiler or the like varies according to the load, the SO ₃ amount in the smoke exhaust varies according to the fuel amount. Furthermore, even if the load and the sulfur content in the fuel are the same, the amount of SO ₃ generated varies depending on the contamination of the boiler heat transfer tube. For example, heavy fuel oil contains a small amount of vanadium, and vanadium forms vanadium pentoxide (V ₂ O ₅ ) by combustion and adheres to the outer wall of the boiler heat transfer tube. Vanadium pentoxide is converted from SO ₂ →
Since it functions as a catalyst for promoting the conversion of SO ₃ , as fouling of the boiler heat transfer tube progresses and the amount of attached vanadium pentoxide increases, S ₂ of the SO ₂ generated by combustion increases.
The rate of conversion to O ₃ increases, and the amount of SO ₃ generated increases.

In this embodiment, an electronic control unit 20 including a microcomputer of a known type is provided, and the sulfur content of the input fuel, the load of the boiler, the operation time after maintenance of the boiler (previous heat transfer tube) The operation time after the cleaning is performed), the SO ₃ generation amount of the boiler 1 is calculated based on data such as the SO ₂ concentration at the entrance of the desulfurization device.

More specifically, when the boiler load is input manually or directly from the boiler control device, the control device 20 calculates the fuel consumption per unit time based on the boiler load. Then, the amount of SO ₂ generated by combustion per unit time is calculated from the fuel consumption based on the data on the sulfur content of the fuel input in advance. Also, based on the operating time since the last time the heat transfer tube was cleaned (that is, the degree of contamination of the heat transfer section), based on the SO ₃ conversion rate data previously measured during the actual operation of the boiler, the generated SO _{3 The} amount converted into SO ₃ out of ₂ is calculated, and the amount of SO ₃ generated in the boiler per unit time is calculated. Also,
The amount of SO ₃ generated from the difference between the SO ₂ amount flowing to the desulfurization unit per above and SO ₂ generated amount calculated based on the fuel sulfur content data, the unit calculated from SO ₂ concentration in the desulfurization apparatus entrance time May be calculated.

Next, the controller 20 supplies sodium hydrogen carbonate per unit time necessary to reduce the sulfuric acid mist generated from the SO ₃ to a predetermined target value based on a predetermined equivalent ratio. The amount is calculated, and the amount of sodium hydrogen carbonate supplied from the sodium carbonate supply device 10 is controlled to the calculated amount. This allows
The sulfuric acid mist in the flue gas is discharged from the desulfurizer 5 upstream of Na ₂ CO ₃
And the sulfuric acid mist concentration is reduced to the target value. In addition, Na ₂ SO ₄ particles generated by the reaction and unreacted Na
_{Since 2} CO ₃ is collected by the desulfurization device 7, it is prevented from being released to the atmosphere as dust.

FIG. 2 is a diagram illustrating the configuration of the sodium carbonate supply device 10 of the present embodiment. In FIG. 2, 1
01 is a silo for storing sodium bicarbonate powder, 11
0 indicates sodium hydrogen carbonate powder stored in the silo 101. At the outlet of the silo 101, a known type, for example, a rotary feeder type variable capacity powder quantitative supply device 106 is provided, and the sodium bicarbonate powder in the silo 101 is transported at a constant flow rate by a transport pipe 108.
To supply. The supply amount of sodium hydrogen carbonate is adjusted by controlling the motor rotation speed of the rotary feeder by the control device 20.

The transport pipe 108 is connected to the flue 3, and supplies sodium bicarbonate powder into the flue 3 by the carrier air supplied from the air transport blower 107.
Reference numeral 115 in FIG. 2 denotes an injection nozzle that injects sodium bicarbonate powder into the flue 3 together with the carrier air.
The injection nozzle 115 will be described later. Fluid soybean air is supplied to the silo 101 such that the fluidity of the sodium hydrogen carbonate powder in the silo is increased so that the supply amount of the sodium hydrogen carbonate powder from the quantitative supply device becomes uniform. Fluid soy air is injected from the flue soy blower 104 through the air pipe 105 into the sodium hydrogen carbonate powder 110 from many pores of the diffuser plate 103 provided on the lower wall surface of the silo 101. Thus, the sodium hydrogen carbonate powder in the silo 101 flows smoothly without forming a lump and flows into the fixed amount supply device 106. After passing through the sodium bicarbonate powder 110, the fluid air is discharged outside through a bag filter 109 provided above the silo 101.

Next, the configuration of the sodium hydrogen carbonate powder injection nozzle 115 will be described. When injecting sodium bicarbonate powder into the flue, increase the reaction efficiency between the generated sodium carbonate and sulfuric acid gas or mist by dispersing the sodium bicarbonate powder as uniformly as possible in the flue gas in the flue. Is preferred. Therefore, in the present embodiment, as shown in FIG. 3, the nozzle 115 is provided near the center of the cross section of the flue, and the sodium bicarbonate powder is transferred together with the transport air toward the upstream side of the flow of the flue gas (FIG. 3, arrow A). I try to inject. The sodium bicarbonate powder injected toward the upstream collides with the flow of the flue gas and diffuses, so that the sodium bicarbonate powder can be uniformly dispersed in the flue gas.

As shown in FIGS. 4A and 4B,
If a throttle tip 115a made of a material having high abrasion resistance is arranged in the nozzle 115 or at the outlet portion, the flow velocity at the time of passing through the throttle tip increases, and the sodium hydrogencarbonate powder is separated from each other. Dispersion of the sodium bicarbonate powder in the flue gas is further improved. In addition, in the example of FIG. 3, an example in which a single nozzle injection hole is provided is illustrated. However, as illustrated in FIG. 5, a plurality of injection holes 115 b to 115 c are provided in By dispersing the sodium bicarbonate powder from a location, the dispersion of the sodium bicarbonate powder can be improved. Furthermore, as shown in FIG. 6, if nozzles 115A to 115C having a plurality of injection holes are arranged in parallel on the cross section of the flue, and sodium hydrogen carbonate powder is injected from each of the injection holes, it is extremely favorable. It becomes possible to disperse the sodium hydrogen carbonate powder.

It should be noted that, as shown in FIG.
Is arranged in the flue on the inlet side of the desulfurization fan 5, the stirring effect of the desulfurization fan 5 is further added, so that the dispersion of the sodium hydrogencarbonate powder can be further improved. As described above, in the present embodiment, the amount of SO ₃ generated from the boiler 1 is indirectly detected based on the operation state of the boiler 1, and the flue gas upstream of the desulfurization device 7 is detected based on the detected amount of SO _3. Since the amount of sodium carbonate supplied to the boiler 1 is adjusted, even when the operating state of the boiler 1 fluctuates, the amount of sulfuric acid mist released to the atmosphere can always be maintained at or below the target value.

In the present embodiment, sodium carbonate is supplied to the flue on the inlet side of the desulfurization fan 5. However, sodium carbonate may be supplied to the flue between the desulfurization fan 5 and the desulfurization device 7. good. Next, another embodiment of the present invention will be described with reference to FIG. 7, the same reference numerals as those in FIG. 1 represent the same elements.

In the present embodiment, the flow rate of the flue gas flowing through the flue 3 upstream of the desulfurization device 7 and the concentration of the sulfuric acid mist in the flue gas are directly detected and input to the control device 20 to directly input the flue gas to the flue gas. Calculate the SO ₃ volume. In FIG. 7, what is indicated by 21 is a known appropriate type of flow meter. The flow meter 21 detects the flow rate of the flue gas flowing through the flue on the upstream side of the sodium carbonate supply device 10 and inputs it to the control device 20 in the form of a flow signal.

In FIG. 7, reference numeral 23 denotes SO _{3 in the} flue gas flowing through the flue upstream of the sodium carbonate supply device 10.
This is an SO ₃ minute detecting means for detecting the concentration (in this embodiment, sulfuric acid gas or mist). The control device 20 includes the flow meter 2
And a flow rate signal input from 1, based on the SO ₃ minutes density signal inputted from SO ₃ minutes detector 23 calculates the SO ₃ content in the flue gas flowing through the flue 3 per unit time, sulfate The amount of sodium hydrogen carbonate required to reduce the mist emission concentration to the target value is calculated, and the amount of sodium hydrogen carbonate supplied from the fixed quantity supply device 106 of the sodium carbonate supply device 10 is adjusted. Thus, as in the embodiment of FIG. 1, even if SO ₃ minutes concentration in the flue gas varies, always so that SO ₃ minutes concentration flowing into the desulfurization apparatus 7 is reduced to the target value.

At present, there is no suitable sensor capable of accurately detecting the concentration of SO ₃ in flue gas in real time, but when such a sensor is developed, the present embodiment is not applicable. It can be used as the SO ₃ minute detecting means 23. Also, instead of an SO ₃ sensor capable of detecting SO ₃ minutes in real time, SO ₃ minute detecting means 23 is used.
As a result, the SO in the smoke exhausted at regular intervals by sampling
_The concentration is measured for ₃ minutes, and the measurement result is manually entered into the control device 20.
May be input.

Next, FIG. 8 shows a third embodiment of the present invention. In each of the above embodiments, the amount of SO _{3 in} the flue gas before the supply of sodium carbonate was detected,
In this embodiment, using the same SO ₃ minute detecting means 23 as in FIG. 7, the SO ₃ minute concentration in the flue gas from the flue 9 downstream of the desulfurization device 7 (SO ₃ , Since the H ₂ SO ₄ gas is all sulfuric acid mist, the SO ₂ gas in this case is
_{(The three-} minute concentration means the concentration of sulfuric acid mist).

The concentration of sulfuric acid mist in the flue gas downstream of the desulfurization unit 7 is substantially the same as the concentration of sulfuric acid mist in the flue gas discharged from the chimney 11 to the atmosphere. Therefore, in the present embodiment, for example, the control device 20 feeds back the sodium hydrogen carbonate supply amount from the sodium carbonate supply device 10 so that the sulfuric acid mist concentration detected by the SO ₃ minute detecting means 23 becomes a predetermined target concentration. By performing the control, the concentration of the sulfuric acid mist released into the atmosphere can be reliably maintained at or below the target concentration.

In each of the above embodiments, the amount of Na ₂ CO ₃ supplied to the flue upstream of the desulfurizer is controlled in accordance with the amount of SO ₃ in the flue gas, so that the wet EP is not used. Although the concentration of sulfuric acid mist released to the atmosphere is maintained at or below the target value, it goes without saying that the concentration of sulfuric acid mist released to the atmosphere can be further reduced by providing a wet EP downstream of the desulfurization device. .

[0043]

According to the invention described in each claim, even when the SO ₃ amount in flue gas fluctuates, the target amount of sulfuric acid mist released to the atmosphere can be reliably achieved without using a wet EP. It has a common effect that it can be maintained below the concentration.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a sodium carbonate supply device in FIG. 1;

FIG. 3 is a diagram illustrating an example of a configuration of a sodium hydrogen carbonate powder injection nozzle.

FIG. 4 is a diagram showing an example of a configuration of a sodium hydrogen carbonate powder injection nozzle.

FIG. 5 is a diagram showing an example of a configuration of a sodium hydrogen carbonate powder injection nozzle.

FIG. 6 is a view showing an example of a configuration of a sodium hydrogen carbonate powder injection nozzle.

FIG. 7 is a diagram illustrating a schematic configuration of an embodiment different from FIG. 1 of the present invention.

FIG. 8 is a diagram illustrating a schematic configuration of another embodiment of the present invention which is different from FIGS. 1 and 7;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Boiler 3 ... Flue 5 ... Desulfurization fan 7 ... Wet desulfurization apparatus 9 ... Flue 10 ... Sodium carbonate supply apparatus 11 ... Chimney 20 ... Control device 23 ... SO ₃ minute detection means

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Katsura Yada 5-34-7 Shiba, Minato-ku, Tokyo Mitsubishi Heavy Industries Environmental Engineering Co., Ltd. F-term (reference) 4D002 AA02 AC01 BA02 BA03 CA01 DA02 DA16 EA02 FA04 GA02 GA03 GB02 GB06 HA07

Claims (5)

[Claims] 1. A flue through which flue gas from a furnace for burning fuel containing sulfur flows, and a sulfur dioxide (S) disposed in the flue gas and contained in the flue gas.
A desulfurizer for removing O ₂ ), and sodium carbonate (Na ₂ C) in a flue upstream of the desulfurizer.
O ₃₎ and sodium carbonate supply device for supplying a SO ₃ minutes detecting means for detecting the sulfur trioxide content (SO ₃ min) content in the flue gas of a predetermined portion of the flue, the SO ₃ minutes Detection in accordance with the detected SO ₃ content of means, and control means for controlling the sodium carbonate supply from the sodium carbonate supply device, comprising a flue gas SO ₃ minutes remover. 2. The SO ₃ minute detecting means, wherein the SO _{3 in} the flue gas upstream of a location of the flue where sodium carbonate is supplied.
The SO _{3 component} removing device according to claim 1, wherein the device detects a _{three component} amount. 3. The SO ₃ minute detecting means includes: a sulfur content in a fuel used in the furnace, a load on the furnace, a degree of contamination of a heat transfer portion of the furnace, and a SO ₂ concentration at a desulfurization device entrance. Based on the operating conditions of the furnace, including any one or more,
The apparatus for removing SO _{3 from} flue gas according to claim 2, wherein the amount of SO ₃ in flue gas is detected indirectly by calculating the amount of SO ₃ in flue gas. Wherein said SO ₃ minutes detector detects the SO ₃ content in the flue gas of the desulfurization apparatus downstream of the flue, SO ₃ minutes removing apparatus according to claim 1. 5. The sodium carbonate supply device supplies sodium hydrogen carbonate powder to a flue of a flue upstream of the desulfurization device, and converts sodium hydrogen carbonate into porous sodium carbonate fine particles in flue gas. 5. The apparatus for removing SO _{3 according} to any one of claims 1 to 4.