JPH08131764A - Wet type exhaust gas treatment method and apparatus - Google Patents

Abstract

PURPOSE: To provide an exhaust gas treatment method which can reduce boron fluoride ion which is produced in a desulfurizer and discharged outside, the utilities of a treatment facility, and the volume of the facility. CONSTITUTION: In a treatment method in which combustion exhaust gas containing SOx, dust, boron components, and fluorine components is absorbed and dedusted by circulating absorption liquid in a dedusting tower 3, the exhaust gas after absorption and dedusting is introduced into an absorption tower 5, and SOx in the gas is absorbed by calcium type absorption liquid, the quantity 28 of at least one kind of Al, Fe, Sn, Be, and their compounds (F fixing agent) to be added into the dedusting tower 3 is determined on the basis of the quantity 26 of fuel to be supplied to a combustion furnace and the analytical results of the fuel. The determined quantity of the F fixing agent is added into the absorption liquid in the dedusting tower 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating a wet exhaust gas, and more particularly to an exhaust gas treatment apparatus for a wet exhaust gas desulfurization apparatus for reducing boron caused by SOx, soot and dust contained in exhaust gas. The present invention relates to a wet exhaust gas treatment method and apparatus suitable for reducing the capacity of a treatment apparatus for wastewater discharged from the apparatus.

[0002]

2. Description of the Related Art A conventional exhaust gas desulfurization system is shown in FIG. Exhaust gas 1 from a boiler or the like is introduced into a dust removing tower 3 by an inlet flue 2 soot and hydrogen chloride (HCl) in the exhaust gas 1,
Acidic gases such as hydrogen fluoride (HF) are removed. Thereafter, when the exhaust gas passes through the dust removing tower demister 4, the dust removing tower circulating absorbent mist in the exhaust gas 1 is removed. Then, the exhaust gas is introduced into the absorption tower 5, and SOx in the exhaust gas 1 passes through a spray stage 13 installed in the absorption tower 5 and droplets of an adsorbent sprayed from a large number of spray nozzles 14 in each spray stage. Upon contact, SOx is absorbed at the surface of the droplet.
The mist entrained in the gas is removed by the mist eliminator 6 provided in the upper part of the absorption tower, and the clean exhaust gas is discharged again from the chimney (not shown) after being reheated if necessary through the outlet flue 7.

Limestone which is an SOx adsorbent is used as a limestone slurry 8 by a limestone slurry pump 9 in an absorption tower circulation tank 11 in accordance with the SOx absorption amount.
Supplied by 0. The absorption liquid is pressurized by the absorption tower circulation pump 12 and supplied to the spray stage 13 in the absorption tower 5.
The SOx removed in the absorption tower 5 reacts with calcium in the absorption liquid to become calcium sulfite (including calcium bisulfite) as an intermediate product, which is oxidized to gypsum by the air 15 supplied to the absorption tower circulation tank 11. The final product (gypsum) is obtained. After that, the slurry is sent from the extraction pump 16 to the gypsum dewatering equipment 18 by the extraction flow rate control valve 17 according to the amount of generated gypsum, is recovered as powdery gypsum, and the separated water is reused in the system.

On the other hand, the soot and dust removed in the dust removing tower 3 falls into the dust removing tower circulation tank 19 together with the dust removing tower circulating absorbent that has absorbed and removed the acidic gas. The dust removal tower circulation absorption liquid is pressurized by the dust removal tower circulation pump 20 and supplied into the dust removal tower 3, and a part of it is discharged as desulfurization wastewater to the wastewater treatment facility 22 by the desulfurization wastewater flow control valve 21 in order to prevent the concentration of impurities. In the wastewater treatment facility 22, chemicals are added from the wastewater treatment chemical tank 23 by the wastewater treatment chemical pump 24 to treat the wastewater so as to be below the emission standard value for each component.

However, in the above-mentioned prior art, depending on the boiler fuel and the operating conditions of the desulfurization device, a plurality of boiler fuel components absorbed in the dust removal tower circulation absorption liquid or a plurality of substances derived from the fuel components react to cause desulfurization drainage. No consideration has been given to the fact that it may be difficult to collect substances with emission restrictions due to the formation of soluble substances in water.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Fluorine (F) and fluorine
When burning a boiler fuel containing boron (B),
Is the substance in the acid gas in the exhaust gas or in the collected dust?
It is absorbed in the absorption liquid circulated in the dust removal tower as the eluate. acid
Smell in circulating absorption liquid with low pH, which absorbs volatile gas and has low pH
Some of the absorbed F and B react to form borofluoride.
Ion (BF_Four ^-) Is easily generated. This dust removal
When a part of the tower circulation absorption liquid is discharged as desulfurization wastewater, F
Since there is a discharge regulation in the
Umm (Al ₂(SO_Four)₃) Etc. aluminum compounds
BF by adding (F fixative)_Four ^-Disassemble,
By adding calcium compounds and adjusting the pH, F is solid
It is necessary to convert it into a form such as
Generated BF_Four ^-The decomposition rate of
When decomposing, even if a large amount of F-fixing agent is added, BF_Four ^-
Takes time to disassemble. In the prior art, the above problem
BF in the absorption liquid circulating in the dust removal tower
_Four ^-There is no consideration for suppressing generation
Therefore, many utilities for wastewater treatment facilities are required and installed.
There was a problem that the storage capacity became large.

An object of the present invention is aluminum and its
Remove compounds or substances containing them in advance.
By supplying it to the dust tower circulation tank, part of it is removed.
BF in the circulation liquid of the dust removal tower that becomes sulfur wastewater_Four ^-Raw
Control the growth, and place aluminum in a more efficient position.
Nium and its compounds, or substances containing them
Desulfurization equipment by supplying the optimum amount of
BF generated in_Four ^-Desulfurization equipment while reducing the amount
Emitted from BF_Four ^-Reduce the amount of wastewater
To reduce the utility and equipment capacity of the physical equipment
is there. In addition, the aluminum and its compounds listed here
Substances, or substances that show the same effect as substances containing them
As a quality, iron (Fe), tin (Sn), beryllium (B
e) and their compounds, or those containing them
Examples include substances containing one or more kinds of quality.

[0008]

In order to achieve the above object, the invention claimed in the present application is as follows. (1) The combustion furnace exhaust gas containing sulfur oxide (SOx), soot dust, boron component, and fluorine component is absorbed and removed by the circulating absorption liquid in the dust removal tower, and the exhaust gas after absorption and dust removal is introduced into the absorption tower, In a wet exhaust gas treatment method of absorbing SOx in a SOx absorption liquid, aluminum (Al), iron (Fe), tin (Sn), based on a fuel supply amount to a combustion furnace and a property analysis result of the supplied fuel, Beryllium (B
e) and one or more compounds thereof (hereinafter referred to as F-fixing agent), and the addition amount of the determined F-fixing agent is added to the circulating absorbent in the dedusting tower. Wet exhaust gas treatment method characterized by suppressing the formation of borofluoride ions (BF ₄ ⁻ ) therein.

(2) In (1), Al and / or Al compound is added to the dust-removal tower circulation absorption liquid with respect to the amount of fluorine (F) calculated from the fuel supply amount and the fuel property analysis result.
The molar ratio (Al / F) of 0.3 is 0.3 or more, preferably 0.1.
A method for treating wet exhaust gas, which is added so as to be 3 or more and less than 0.5. (3) Wet exhaust gas treatment having a dust removal tower that removes SOx, soot, dust, fluorine components, and boron components in exhaust gas with a circulating absorption liquid, and an absorption tower that is provided on the downstream side and that absorbs SOx using the SOx absorption liquid In the apparatus, a means for adding one or more kinds of the F-fixing agent to the absorption liquid of the dust removing tower is provided, the wet exhaust gas treatment apparatus.

(4) A wet exhaust gas treatment apparatus according to (3), characterized in that the absorption liquid of the dust removing tower is water. (5) In a wet exhaust gas treatment method of removing soot, fluorine components, and boron components in exhaust gas as water as a circulating absorbent, and treating a part of the circulating absorbent as waste water, the pH of the circulating absorbent is less than 2 and the temperature is At 40 to 60 ° C., or at a position adjusted to the above conditions, by adding at least one of the F fixatives, and then adding an alkaline earth metal compound such as calcium. A wet exhaust gas treatment method, which comprises performing a fluorine (F) treatment.

(6) The wet exhaust gas treatment device as described in (3) to (4), wherein the F fixing agent is dust collected by an electrostatic precipitator containing aluminum and / or a compound thereof. (7) The wet exhaust gas treatment method according to (5), characterized in that an electrostatic precipitator-collected dust containing aluminum and / or a compound thereof is used as the F fixing agent.

[0012]

[Function] Aluminum (Al), iron (Fe), tin (Sn), in the absorption liquid (pH less than 2) in the dust removal tower circulation tank,
By adding beryllium (Be) and a substance containing at least one of these compounds, it becomes possible to suppress the BF ₄ ⁻ production reaction in the dust removal tower circulation tank. Further, since the absorbing solution in the tank is circulated at 40 to 60 ° C., it becomes possible to cause the decomposition reaction of BF ₄ ⁻ shown below in a highly efficient state. Aluminum (A
l), iron (Fe), tin (Sn), beryllium (Be)
And because one or more of the addition amount is controlled to the optimum amount determined by the arithmetic unit from the boiler fuel property analysis results and the fuel supply amount of those compounds, BF ₄ of dust tower circulating absorbent in ^- the density appropriate Since the amount of BF ₄ ⁻ extracted from the main body of the desulfurization device can be reduced, an excessive amount of F-fixing agent and a large capacity of wastewater treatment equipment are not required on the wastewater treatment side of the extracted liquid.

[0013]

EXAMPLE A system of a wet exhaust gas treatment apparatus according to the present invention is shown in FIG. In this figure, in the conventional desulfurization system shown in FIG. 6, the input signal 25 of the boiler fuel property analysis result and the signal 26 of the boiler fuel supply amount are input to the arithmetic unit 27, and the wastewater treatment chemical (F-fixing agent) is input. By setting the opening degree of the dust removal tower circulation tank chemical flow rate control valve 29 by the output signal 28 indicating the supply amount, chemicals (F-fixing agent) to the dust removal tower circulation tank 19
A system for controlling the supply amount is added. The pipe 33 is a supply pipe for the absorption liquid (mainly water is used) to the dust removal tower circulation tank 19, and the amount of extraction of the absorption liquid to the waste water treatment device 22 and the evaporation amount of the absorption liquid in the dust removal tower. Replenish the absorption liquid in an amount commensurate with.

FIG. 2 shows aluminum in the absorption liquid circulating in the dust removing tower.
Mu ion concentration and BF_Four ^-The results of examining the concentration relationship are shown.
You. The test conditions here are: total B concentration: 150 ppm, total
F concentration: 330 ppm, 0.15 M hydrochloric acid acidity, reaction temperature
Degree: 50 ° C., reaction time: 1 hour. As shown in Figure 2
On the other hand, when Al is not added (Al ion concentration is zero), B
F _Four ^-While the concentration is 110 ppm, BF_Four ^-Dark
The degree decreases as the aluminum ion concentration increases
BF in the absorption liquid circulating in the dust removal tower_Four ^-Suppression of production reaction
I understand that it will be done. For example, under this condition, BF_Four ^-concentration
Aluminum ion
The concentration must be 135ppm or higher.
When the relationship is expressed by the molar ratio of total Al to total F, it is 0.3
Become.

In FIG. 3, the molar ratio of total Al to total F is 0.1.
5 in case A, case B in which the molar ratio of total Al to total F is 0.3, case C in which the molar ratio is 0.5, and molar ratio 0.7.
The case D, pH and BF ₄ ^- shows the results of examining the relationship between the concentration. Thus pH2.5 or less, preferably BF ₄ below pH 2.0 ^- It can be seen that progresses decomposition reaction. Further, it can be seen that the molar ratio of total Al / total F is 0.3 or more, preferably 0.3 or more and less than 0.5.

The reaction time 1 hour 4, the molar ratio of 0.3 to total F of the entire Al, BF before and after the reaction and the decomposition reaction temperature in the conditions of pH 1.0 ₄ ^- shows the relationship between the concentration ratio. BF ₄ Thus, as the temperature increases ^- see that the decomposition reaction proceeds, BF ₄ wastewater treatment facility the temperature of the waste water to be treated is lower ^- than the disassembly of the temperature 4
It can be seen that it is effective to add aluminum and its compound, or a substance containing them to the circulating fluid in the dust removal tower of the exhaust gas desulfurization device at 0 to 60 ° C. In the embodiment of FIG. 1, the dust removal tower circulation tank 1
The wastewater extracted from the wastewater treatment equipment 22 and discharged to the wastewater treatment equipment 22 is treated with aluminum sulfate (Al ₂ (SO _2
4 ) It is possible to decompose BF ₄ ⁻ by adding an aluminum compound such as ₃ ), and to convert fluorine (F) into a solid form and separate it from the treated wastewater by adding a calcium compound and adjusting the pH. it can. FIG. 7 shows a schematic flow sheet in the wastewater treatment facility 22.

Another embodiment of the present invention is shown in FIG. In this embodiment, a liquid aluminum and its compound or a substance containing them is used as an input signal 25 of a boiler fuel property analysis result and a boiler fuel supply amount input signal 26 in FIG.
In contrast to the output signal 28 indicating the supply amount calculated by inputting to the arithmetic unit 27, the dust removal tower circulation tank chemical flow rate control valve 29 was controlled to supply the dust removal tower circulation tank 19 to the output signal 28. By controlling the number of rotations of the powder supply feeder 32 by means of the powder 30 in the powder silo 31
A system for supplying (aluminum and its compound, or a substance containing them) to the dust removal tower circulation tank 19 is shown. Also in this case, by properly maintaining the molar ratio of Al and F in the dust removal tower circulation absorbent, B in the dust removal tower circulation absorbent can be improved.
Generation of F ₄ ⁻ can be suppressed. The effect of this example is that since the dust collected by the electrostatic precipitator or the like can be used as aluminum and its compound, or solid matter containing them, the utility of wastewater treatment is not required. .

As another embodiment, it is possible to extract the circulating liquid of the dust removing tower into a separate tank, and supply the aluminum and its compound or the substance containing them to the separated liquid. The peculiar effect of this example is produced by supplying aluminum and its compound, or a substance containing them to the absorption liquid circulating in the dust removing tower when the purity of the gypsum recovered in the absorbing tower is regulated. It is possible to prevent the solid matter from flowing into the absorption tower, and as a result, reducing the purity of the gypsum recovered in the absorption tower.

As another example, iron (Fe), tin (Sn), beryllium (B) having the same effect as aluminum and its compounds or substances containing them.
e) and their compounds, or a substance containing at least one substance containing them can be used as the F-fixing agent as in the above examples.

[0020]

According to the present invention, the acidic gas in the exhaust gas generated due to the boiler fuel component in the absorption liquid circulating in the dust removal tower is absorbed, or is eluted from the collected dust, etc., or these substances are absorbed. Soluble substances (BF ₄
^- ), Aluminum (Al),
Dust tower circulation absorption liquid in which iron (Fe), tin (Sn), beryllium (Be) and their compounds, or a substance containing at least one substance containing them, is partially desulfurized wastewater. BF at medium ₄ ^- that the product can be suppressed, and aluminum (Al) more efficient position, iron (Fe), tin (Sn), beryllium (be) and their compounds, or substances the one containing them the ability optimal amount supplied material containing more as F fixative, BF ₄ produced in the desulfurization apparatus ^-
The amount of BF that can be reduced and discharged from the desulfurization equipment
₄ ^{-Because the} amount can be reduced, there is an effect that it is possible to reduce the utility and facility capacity of the wastewater treatment facility side.

[Brief description of drawings]

FIG. 1 is a diagram showing a system of a wet exhaust gas treatment device according to the present invention.

FIG. 2 is a diagram showing the relationship between the aluminum ion concentration and the BF ₄ ⁻ concentration in the absorption liquid circulating in the dust removing tower.

FIG. 3 is a diagram showing the results of examining the relationship between pH and BF ₄ ⁻ concentration.

FIG. 4 is a diagram showing the results of examining the relationship between the decomposition reaction temperature and the BF ₄ ⁻ concentration ratio before and after decomposition.

FIG. 5 is a diagram showing a system of a wet exhaust gas treatment apparatus according to another embodiment of the present invention.

FIG. 6 is a diagram showing a system of a conventional wet exhaust gas desulfurization device.

7 is a diagram showing a treatment flow sheet of the drainage facility in the embodiment shown in FIG.

[Explanation of symbols]

1 ... Exhaust gas, 2 ... Inlet flue, 3 ... Dust removal tower, 4 ... Dust removal tower demister, 5 ... Absorption tower, 6 ... Mist eliminator, 8 ... Limestone slurry, 9 ... Limestone slurry pump, 10 ... Limestone slurry flow control valve, 11 ... Absorption tower circulation tank, 12 ... Absorption tower circulation pump, 13 ... Spray stage, 14 ... Spray nozzle,
15 ... Air, 16 ... Extraction pump, 17 ... Extraction flow rate control valve, 18 ... Gypsum dewatering equipment, 19 ... Dust tower circulation tank, 2
0 ... dust removal tower circulation pump, 21 ... desulfurization drainage flow rate control valve, 2
2 ... Wastewater treatment facility, 23 ... Wastewater treatment chemical tank, 24 ...
Wastewater treatment chemical pump, 25 ... Boiler fuel property analysis input signal, 26 ... Boiler fuel supply amount input signal, 27 ... Computing device, 28 ... Dust removal tower circulation tank chemical flow rate output signal, 29 ...
Dust removal tower circulation tank chemical flow control valve, 30 ... powder, 31 ...
Powder silo, 32 ... Powder supply feeder.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location B01D 53/46 53/68 B01D 53/34 120 A 134 C (72) Inventor Ryoichi Miyataka Hiroshima Prefecture 6-9 Takaramachi, Kure-shi Babcock Hitachi Kure Factory (72) Inventor Tadaaki Mizoguchi 3-36 Takaracho Kure-shi, Hiroshima Babcock Hitachi Kure Research Institute

Claims (7)

[Claims] 1. A combustion furnace exhaust gas containing sulfur oxide (SOx), soot dust, a boron component, and a fluorine component is absorbed and removed by a circulating absorption liquid in the dust removal tower, and the exhaust gas after the absorption and dust removal is introduced into the absorption tower. In a wet exhaust gas treatment method in which SOx in an exhaust gas is absorbed by an SOx absorbent, aluminum (Al), iron (Fe), tin (Sn) based on a fuel supply amount to a combustion furnace and a property analysis result of the supplied fuel. ), Beryllium (Be) and one or more of its compounds are added, and the determined addition amount of the metal or its compound is added to the circulating absorbent in the dedusting tower to obtain the circulating absorbent. The method for treating a wet exhaust gas, which comprises suppressing the formation of borofluoride ions (BF ₄ ⁻ ) of the above. 2. The aluminum (Al) and / or aluminum compound as claimed in claim 1, wherein the amount of fluorine (F) calculated based on the fuel supply amount and the fuel property analysis result is such that aluminum (Al) and / or an aluminum compound is contained in the absorption liquid circulating in the dust removing tower. Ratio (Al /
A method for treating a wet exhaust gas, characterized in that F) is added so as to be 0.3 or more. 3. SOx, soot and dust, and fluorine components in exhaust gas,
In a wet exhaust gas treatment apparatus having a dust removal tower for removing a boron component by a circulating absorption liquid and an absorption tower provided on the downstream side for absorbing SOx by using the SOx absorption liquid, aluminum (Al ), Iron (Fe),
A wet exhaust gas treatment apparatus provided with means for adding at least one of tin (Sn), beryllium (Be), and a compound thereof. 4. The wet exhaust gas treatment device according to claim 3, wherein the dust removal tower absorption liquid is water. 5. A wet exhaust gas treatment method in which water, such as soot dust, fluorine components, and boron components in exhaust gas, is removed as a circulating absorbent, and a part of the circulating absorbent is treated as waste water, wherein the pH of the circulating absorbent is less than 2. , Aluminum (Al), iron (Fe), tin (Sn), beryllium (B) at a temperature of 40 to 60 ° C. or a temperature adjusted to the above condition.
e) and one or more of its compounds are added, and then a compound of an alkaline earth metal such as calcium is added to treat fluorine (F) in the waste water, thereby treating the wet exhaust gas. 6. The wet exhaust gas treatment device according to claim 3, wherein the aluminum and / or the compound thereof is dust collected by an electrostatic precipitator containing aluminum and / or the compound. 7. The wet exhaust gas treatment method according to claim 5, wherein the dust collected by the electrostatic precipitator containing aluminum and / or its compound is used as aluminum and / or its compound.