JPS6051372B2 - Gas treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating exhaust gas, and more particularly, to a method for treating exhaust gas that enables integration and miniaturization of equipment, and allows gas to be absorbed and oxidized and fixed with high efficiency.

When processing a large amount of gas in the conventional method, packed towers, plate towers, spray towers, ventilate scrubbers, etc. have been used as gas-liquid contact equipment, but continuous gas-liquid contact and solid precipitation have been used. The equipment that can be applied to perform this process efficiently is limited, and the systems described above only use spray towers and ventilate scrubbers.

However, in spray towers, erosion becomes an obstacle when solids are present, and restrictions are imposed on the materials and manufacturing aspects of the pumps and spray nozzles that apply pressure to form fine droplets. In addition, in the ventilate scrubber, since droplets are formed using the energy of high-speed gas, it cannot be effectively performed using low-pressure gas. Furthermore, the gas-liquid contact efficiency varies greatly due to changes in the amount of gas, making it difficult to increase the size. Furthermore, since the solids are continuously deposited, the solids are likely to deposit and adhere to the equipment. Therefore, in order to prevent this, it is necessary to lower the degree of supersaturation and suspend the crystals above a certain concentration so that they do not precipitate on the walls of the apparatus. For this purpose, a tank-type container equipped with a stirring means is used. However, the continuous contact between large volumes of gas and liquid and the precipitation of solids. If you do,
Since the functions and structures of each device are different, the common method has been to install the gas-liquid decontamination device and the solid precipitation device separately, and to connect them with piping using a pump. In particular, when processing a large volume of gas such as exhaust gas containing SOx and NOx, it is possible to simplify the catalytic reaction between gas and liquid and to precipitate the product as a solid in one tank. The emergence of miniaturized methods is highly desirable. As a result of repeated research in view of the current situation, the present inventors have discovered that gypsum is suspended in a flue gas desulfurization method that uses calcium compounds as a fixing agent, that is, a flue gas desulfurization method that fixes sulfur dioxide gas as gypsum. The exhaust gas is dispersed and introduced into the sulfuric acid acidic aqueous solution to form a first zone which is a gas-liquid contact layer with a continuous liquid phase consisting of fine bubbles of the exhaust gas and the sulfuric acidic aqueous solution, and the sulfuric acidic aqueous solution suspends the gypsum. Introducing an oxygen-containing gas to form a second zone consisting of microbubbles of the oxygen-containing gas and the sulfuric acid acidic aqueous solution, which is continuous with the first zone in the liquid phase and has a smaller amount of bubbles than the first zone. , a calcium compound is introduced in an amount sufficient to maintain the sulfuric acid concentration of the liquid-phase continuous sulfuric acid acidic aqueous solution at 1% by weight or less, and a suspension/liquid containing gypsum is added from the second zone to a slurry concentration of 3 to 4 volumes. We have developed a flue gas desulfurization method (see Japanese Patent Application Laid-Open No. 53-62783), which is characterized by extracting a sufficient amount to maintain a The present inventors have learned that the present invention can also be applied to harmful component-fixed lucium compounds and that it is effective even in cases other than the use of lucium compounds, and have completed a gas treatment method that is an extension of the above-mentioned method.

As is clear from the above description, an object of the present invention is to process not only sulfur dioxide gas but also nitrogen oxides in exhaust gas, a gas that is effective for desulfurization and denitration, by integrating processes and equipment, and using a miniaturized device. The goal is to provide the following. The present invention has the following configuration to achieve the above object.

That is, the gas treatment method of the present invention is a method for removing harmful components in exhaust gas by contacting gas-liquid with an absorbing liquid, in which the exhaust gas is dispersed and introduced into the absorbing liquid to form a liquid consisting of fine bubbles of the exhaust gas and the absorbing liquid. A first zone is formed as a phase-continuous gas-liquid contact layer, and an oxygen-containing gas is introduced into the absorption liquid to form a first zone that is continuous with the first zone in the liquid phase and consists of fine bubbles of oxygen-containing gas and the absorption liquid. A second zone having a smaller amount of bubbles than the first zone is formed, and a harmful component fixing agent (excluding cases where the fixing agent is a lucium compound) is introduced into the absorption liquid. be. The method of the present invention employs a continuous liquid-phase gas-liquid contact method, which is different from the conventional gas-liquid contact that uses continuous gas-phase. The two reaction zones can be brought into contact without space, ie in liquid phase continuity.

Moreover, in this case, the volume of gas-liquid contact in the liquid phase continuity is small;
By changing the height of the liquid level, the gas-liquid contact area can be freely adjusted. The fixing agent for fixing harmful components in the exhaust gas may be introduced in either the first zone or the second zone, but for example, it can be introduced automatically at the contact surface between the first zone and the second zone. Fixatives are effectively used for the gas in the first zone as well as for the neutralization of the product (e.g. acid), and the process is integrated into the absorption tower, oxidation tower, neutralization tank, crystallization tower, etc. It is possible to integrate and downsize the tank. In the gas-liquid contact layer (first zone) in which the liquid phase is continuous in the present invention, mass transfer within the layer is caused by intense disturbance contact when high-speed gas collides with the liquid and causes gas phase splitting, and fine particles split within the layer. This is efficiently carried out by disturbed contact between the bubbles, that is, by making the contact interfacial area extremely large.

A stirrer and baffles may also be provided in the second zone to create a circulating flow and further increase gas-liquid contact.
One of the advantages of the present invention is that since the first zone and the second zone, which have different apparent specific gravities, are brought into continuous gas-liquid contact with the liquid phase, the absorbing liquid is forced into the gas flow unlike in the conventional gas phase continuous system. Since there is no need for a pump to feed the absorbent into the absorbent, the power cost for circulating the absorbent can be greatly reduced.

That is, the gas-liquid contact in the first zone is not carried out on the surface of fine droplets, but on the surface of fine bubbles that are generated when previously dispersed gas enters the liquid. In other words, in the conventional method, gas-liquid contact is performed using liquid energy, whereas in the present invention, gas-liquid contact is performed using gas energy. The feature of the present invention that the gas-liquid contact is carried out continuously in the liquid phase is also a great advantage in preventing the adhesion of solids. That is, once a solid adheres to a pipe wall or the like, it is difficult to remove it with a gas flow, but in the method of the present invention, since the pipe is always washed with liquid, blockage of solid hardly occurs. Furthermore, in the present invention, since the second zone adjacent to the first zone containing exhaust gas bubbles is also continuous in liquid phase and contains air bubbles, each of the first zone and the second zone is separated by means such as pumps and piping. There is no need to connect them, and the first and second bands can be arranged vertically or in some cases horizontally without special boundaries, making the device compact and economically inexpensive. There is an advantage.

Furthermore, the first zone of the present invention contains exhaust gas bubbles, and the second zone is a liquid phase containing air bubbles, but the amount of air bubbles in the latter is 10% of the amount of exhaust gas bubbles contained in the former. Since there is a difference in the rising force of the liquid due to the bubbles, it is also possible to mix the liquid without using a stirrer.

Of course, if there are solid particles generated in the liquid, a mechanical stirrer may be used to ensure that they float. In the present invention, by positioning the second zone directly below the first zone, the oxidation rate can be increased compared to conventional methods. That is, it is known that the rate of absorption of oxygen in the air is approximately proportional to the partial pressure of 02,
The air blown into the second zone under conditions of continuous liquid phase exists as independent bubbles not only in the second zone but also in the first zone, and always has the same partial pressure as air, about 0.2 atm. It is absorbed into the liquid at a rate that depends on the pressure and performs an oxidizing action.
However, with the conventional method of blowing 02 directly into the exhaust gas, the air is not in the form of bubbles and is mixed with the exhaust gas, so the partial pressure is less than 1 of the above, at most 0.02at.
m increases, and therefore the oxidation rate also slows down. Next, the method of the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a schematic diagram of an apparatus showing an embodiment of the present invention,
This device consists of a tank 2 for containing an absorption liquid 1 in which solids are suspended, a stirring blade 8 which is a means for forcibly circulating the absorption liquid 1, a baffle 9, and an oxygen-containing gas introduction pipe. an exhaust gas introduction pipe 5 that is below the surface of the liquid 1 and has an opening 10 in the circulation path; an introduction pipe 3 for introducing the fixative into the tank 2;
It is comprised of an exhaust pipe 6 for discharging the gas after the reaction from the tank 2, and a drain pipe 7 for taking out the solid suspension. Next, we selected a typical case in which exhaust gas containing SO2 and NO2 as harmful components (NO was gas-phase oxidized by adding ozone in a molar amount equal to the amount of NO) was fixed using NH3 as a fixing agent. Embodiments of the present invention will be described below.

SO2 and NO2 in which NO is oxidized in the gas phase by adding ozone
The exhaust gas containing the sulfuric acid is introduced from the exhaust gas introduction pipe 5 below the surface of the ammonium sulfate suspended sulfuric acid acidic aqueous solution in the tank 2.

At this time, a notch 11 as shown in FIG. 2 is provided in the opening 10 of the exhaust gas introduction pipe 5, and the exhaust gas is bubbled and dispersed through the notch 11. A stirring blade 8 is provided at the bottom of the opening 10, and as shown by the arrow in FIG. The liquid becomes bubbles and comes into contact with the absorption liquid 1. A cylindrical baffle 9 is provided around the stirring blade 8 to improve the efficiency of the formation of a circulating flow and to promote gas-liquid contact. That is, as shown in FIG. 1, by arranging the stirring blades 8 in the baffle 9 in the area where the absorption liquid in the tank 2 circulates, the chimney effect can be used to absorb water from inside the baffle 9. It is preferable to use a method in which the absorbing liquid is raised and the absorbing liquid is lowered to the outside.
Furthermore, the opening 10 of the exhaust gas introduction pipe 5 is connected to the second zone B.
It is desirable to have the blowing gas close enough to the second zone to contact the circulating flow of absorption liquid therein. Absorption liquid (
(including a fixative) is introduced from the fixative inlet pipe 3 in an amount sufficient to maintain a constant sulfuric acid concentration and mixed into the circulating flow.
Sulfur dioxide gas is absorbed in the first zone and converted to sulfite, and at the same time, air is introduced from the second zone into which air is introduced from the oxygen-containing gas introduction pipe 4 provided at a position lower than the opening 10 of the exhaust gas introduction pipe 5. oxidized to sulfate by oxygen. Furthermore, since the oxidizing air reduces the apparent specific gravity of the absorption liquid in the baffle 9, it has the effect of increasing the amount of circulating flow in conjunction with the rotation of the stirring blades 3. The amount of air has a large effect on the desulfurization rate and the denitrification rate; without this air, sulfite will accumulate in the absorption liquid and the absorption rate of sulfur dioxide gas will decrease significantly. Further, the NO2 absorption rate can be maintained by adjusting the amount of air in the second zone to make the apparent specific gravity 0.95 to 1.0. The relationship between the apparent specific gravity of the absorption liquid in the first zone and the second zone (the apparent specific gravity decreases when the amount of bubbles is large), the desulfurization rate, and the denitrification rate is shown in A and B of Figure 3, and The relationship between the liquid depth and the apparent specific gravity of the absorption liquid in the first zone and the second zone is as shown in C in FIG. 3. As shown in Figure 3B, the desulfurization rate decreases significantly when there are no bubbles in the oxidizing air, that is, when the apparent specific gravity is 1.0, and when the oxidizing air If the amount of bubbles is too large, that is, the apparent specific gravity is too small, the NO2 absorption rate will decrease. Therefore, if the amount of bubbles in the oxidizing air is adjusted to make the apparent specific gravity of the second zone about 0.95 to 1.0, SO2 or NO2
The removal rate of both can be maintained high. Furthermore, the apparent specific gravity of the absorbing liquid in both zones was low in the upper part of the first zone, but rose sharply near the boundary between the first and second zones, and remained approximately constant below the boundary. This can be seen from C in Figure 3. A suitable apparent specific gravity is 0.
2 to 0.7, 0.9 to 0.7 for desulfurization only in the second zone
1.0, and in the case of both desulfurization and denitrification, it is about 0.95 to 1 rainbow. Note that when ozone is added at a molar ratio of about 1 times the amount of NO to oxidize it to N2O5, the denitrification rate decreases even if the amount of oxidizing air is increased and the apparent specific gravity of the second zone is about 0J. do not. On the other hand, the gas from which SO2 and NO2 have been removed by vigorous contact with the absorption liquid is separated into gas and liquid in the space above the liquid level of the tank 2, and is discharged through the exhaust pipe 6. The absorption liquid containing gypsum is discharged out of the system from the drain pipe 7 in an amount sufficient to maintain the slurry concentration at 3 to 4 percent by volume. The discharged liquid containing ammonium sulfate is sent to a centrifugal separator 13 by a pump 12, where it is dehydrated and ammonium sulfate is separated. The mother liquor after ammonium sulfate separation is recycled and used. Regarding the means for blowing and dispersing exhaust gas in the present invention, the shape of the inlet pipe may be tubular or rectangular, and the opening may have a structure that can divide the gas and blow it out, such as a rectangular slit, a triangular slit, or a porous type. If necessary, it is desirable to provide a mesh plate, a grid, or a perforated plate above the opening, or to provide a rectifying plate such as a vertical cylinder, vertical plate, or vertical mesh plate to ensure smooth circulation of the absorbent liquid. .

Regarding the introduction of the oxygen-containing gas, a fixed aeration means such as a perforated type, a wrapper type, a ring type, a nozzle type, or the like, or a rotary type aeration means that rotates to generate fine bubbles can be used as the blowout shape. Gases targeted by the present invention include SO2, SO3, NO, N2O3, NO2, N2O4
, N2O5, vaporized gases such as hydrogen chloride and organic acids can be mentioned.

Examples of gas fixing agents include alkali metal compounds, alkaline earth metal compounds other than calcium compounds, ammonia, dolomite, fly ash, red mud, slag, and salts of organic acids.

Dolomite, fly ash, red mud, and slag are mixtures of alkali metal compounds and alkaline earth metal compounds, so they can be used as fixatives in the same way as fixing with Mg(0H)2, Mg0, Na0H, K0H, etc. Sulfur oxides can be fixed as sulfates, nitrogen oxides can be fixed as nitrates or salts of sulfamic acid or imidodisulfonic acid compounds, hydrogen chloride can be fixed as hydrochloride, and organic acids can be fixed as organic acid salts. can do.

In the case of ammonia, sulfur oxides are fixed as ammonium sulfate, nitrogen oxides are fixed as ammonium salts of ammonium nitrate, sulfamic acid compounds, and imidodisulfonic acid compounds, and hydrogen chloride and organic salts are fixed as ammonium chloride and ammonium organic acids.

Since NO cannot be easily absorbed, ozone, peroxides, halides, halogen acids, and potassium permanganate can be used to remove N2O3.
, NO2, N2O4, N2C)-, and is absorbed and fixed.

Ozone and halogen acids produce peroxides, halides, and
Potassium permanganate is oxidized in the liquid phase. In addition, as catalysts for promoting the reaction, Fe, Cu, Mn, CO, Ni, N
Sulfates, chlorides or mixtures thereof of a, K, Ca, Al, Mg, Zn, NH3 are effective.

As a typical example in which the present invention can be effectively carried out, reaction conditions will be described below in which the harmful component is SO2 and the fixative is NH3. The concentration of the sulfuric acid acidic aqueous solution suitable for implementing the method of the present invention is suitably 1% by weight or less, and if it is 1% by weight or more, it becomes difficult to maintain a high desulfurization rate.

Furthermore, when the sulfuric acid concentration is high (for example, 1% by weight), it is effective to add a trivalent iron compound as a catalyst.
In addition, when carrying out the method of the present invention (when the harmful gas in the exhaust gas is SO2), the concentration of sulfate (ammonium sulfate) in the tank should be
It is preferably kept at 5 to 2 vol.%, but this is done in order to obtain coarse ammonium sulfate crystals, to lower the degree of supersaturation of the absorption liquid, and to prevent so-called scaling in which solids precipitate on the tank walls. is important.

When the ammonium sulfate concentration is less than 3% by weight, the particle size of ammonium sulfate crystals becomes small and scale tends to occur. Furthermore, if the ammonium sulfate concentration exceeds 4% by volume, clogging of tanks and piping is likely to occur, making operation difficult, and there is little effect on the particle size of ammonium sulfate crystals, so operation at concentrations above 4% by volume must be avoided. or,
The reaction temperature is usually 30 to 90°C, preferably 40 to 70°C. According to the present invention, it is possible to simplify the process and downsize the device, and to efficiently absorb, oxidize, and fix various harmful gases. Therefore, the present invention is useful and can be widely applied in the field of flue gas treatment. It is something. EXAMPLES Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these in any way. Example 1 The type of apparatus used is shown in Fig. 1, and the diameter of the tank 2 having a circular cross section is 800 mm.
The depth of the TI1m1 liquid level was 180h, four pipes with a diameter of 3 inches were used as the flue gas introduction pipes 5, and the depth of the opening 10 was 200wn below the liquid level.

Inside this tank 2, a stirring blade 8 and a cylindrical baffle 9 with a diameter of 500 gourds were provided. Flue gas containing 1250 to 1300 ppm of sulfur dioxide gas and 3 to 4% oxygen was blown into the flue gas introduction pipe 5 at 980 N/hour, and while stirring, it was 14007 m below the liquid level.
Air was blown in at a rate of 10 Nd/hour from the oxygen-containing gas introduction pipe 4 installed at
．． 9k9/hour) was supplied so that the pH of the absorption liquid was 5 to 6. Desulfurized gas (sulfur dioxide gas 0-10ppm)
was discharged from the exhaust pipe 6 through a gas-liquid separator.

The absorption liquid drain pipe 7 is operated by the pump 12 to adjust the liquid height.
The amount of absorbent extracted through the process is 100e/hour,
The solid ammonium sulfate concentration was 10-15% by weight. The ammonium sulfate produced was separated using a centrifuge, and the analysis results were as follows. As is clear from the above results, in the device used in the present invention, not only the absorption and oxidation of sulfur dioxide gas are performed simultaneously, but also the concentration of sulfate, which is a by-product, is carried out in a single device. Therefore, even if dust is contained in the exhaust smoke, it can be carried out without considering blockage of the equipment, and therefore the device has the advantage of having a wide tolerance range and being able to be miniaturized.

In addition, since the partial pressure of oxygen in air is approximately 10% compared to the partial pressure of oxygen in exhaust gas, oxidation is carried out effectively, and the COD is 100%.
ppm or less, and there was no sign of scaling at all.
Example 2 Using the apparatus shown in Figure 1, sulfur dioxide gas 1250-130
0 ppm 1 Nitrogen monoxide 200 ppm 1 Ozone in an amount equivalent to a molar ratio of 1j times the amount of nitrogen monoxide is added to flue gas (heavy oil combustion exhaust gas) containing 3 to 4% oxygen to 800N.
d/hour, oxidizing air was blown into the tank 2 at a rate of 10 Nd/hour through the oxygen-containing gas introduction tube 4, and NH3 was further supplied through the introduction tube 3 so that the pH of the absorption liquid was 4 to 5.

As a result, the residual sulfur dioxide gas in the gas coming out of the exhaust pipe 6 was 1
0 to 20 ppm, and nitrogen oxides (NOx) are 30 to 20 ppm.
It was 50 ppm. The COD of the absorption liquid was 50 ppm or less. Analysis of the absorption liquid revealed that nitrogen oxides were NH4.
It turned out that it was fixed as NO3. The ammonium sulfate produced is an aqueous solution of 15 to 1% by weight, and the ammonium sulfate concentration in tank 2 is 15%.
It was discharged out of the system at a constant concentration of ~18% by weight. Example 3 The same flue gas as in Example 2 was treated using the apparatus of FIG.

A molar amount of ozone equivalent to the amount of nitrogen monoxide was added to the flue gas at 800 Nd/hour and introduced into the tank 2. 100 ppm of copper sulfate (CuSO4) and 2 l% of CaCl were added to the absorption liquid, and oxidizing air was introduced into the oxygen-containing gas inlet pipe 4 at a rate of 5 Nd/hour.
Blow in more Mg so that the pH of the absorption liquid becomes 5 to 6.
CO3 was supplied from the fixative inlet tube 3. As a result, the residual sulfur dioxide gas in the gas discharged from the exhaust pipe 6 is 0 to 10p.
pm, and nitrogen oxides (NOx) are 10 to 20 ppm
It was hot. The concentration of solid magnesium sulfate produced was reduced to 10
It was extracted into a centrifuge while maintaining the concentration at ~15% by weight, and taken out of the system as solid magnesium sulfate. Example 4 Using the apparatus shown in Fig. 1, exhaust gas from a boiler fueled with heavy oil (SO2l25O~1300ppm1monoacid.
Nitrogen 200ppm1 Oxygen 4%, 200°C) 980N
A gas added with 1.9k9/hr of ammonia (NH3) at 7T1/hr was blown into an absorption liquid containing 500ppm of iron ions (Fe3), and 10Nd of oxidizing air was added.
The sulfuric acid concentration was maintained at 0.02 to 0.0% by heel weight.

The desulfurization rate at this time was 90 to 98%. No ammonia (NH3) was detected in the exhaust gas. Example 5 Using the apparatus shown in Figure 1, a molar amount of ozone equivalent to 200 ppm of nitrogen monoxide was added to the same heavy oil combustion exhaust gas as in Example 4 at 950 Nd/hour, and copper sulfate (CuSO4) 10
0 ppm and HClO. Oxidizing air 6N7T1/hour was introduced into the absorption liquid containing 7% by weight, and Mg(0H)2 was introduced so as to maintain the pH at 4 to 5.

The desulfurization rate at this time was 94-97%, and the denitrification rate was 91-96%.
It was %. Example 6 Using the apparatus shown in Fig. 1, sulfur dioxide gas was
980 NTr1/hour of incinerator flue gas containing 0 ppm and 500 ppm of hydrogen chloride (vinyl chloride waste was auxiliary incinerated with heavy oil) was introduced into tank 2.

The liquid in the tank 2 was initially water, but the absorbed sulfur dioxide gas was oxidized by the air blown in from the inlet pipe 4 to become sulfuric acid, and its concentration became 0. The weight has increased to %. on the other hand,
NaOH was introduced from the fixative introduction tube 3 to control the rise in sulfuric acid concentration. Hydrogen chloride in flue gas is also absorbed at the same time and becomes Na.
It was fixed as Cl7. Furthermore, sulfur dioxide gas in the flue gas was fixed as Na2sO4. The amount of sulfur dioxide gas coming from the exhaust pipe 6 was 10 to 30 ppm, and the amount of hydrogen chloride was a trace amount.
Example 7 The same flue gas as in Example 2 was treated using the apparatus of FIG.

Ozone in a molar amount equal to the amount of nitrogen monoxide was added to this flue gas at 800 NTr1/hour and introduced into tank 2. Copper sulfate (CUSO4) 300PPm1CaC1.1% was added to the absorption liquid, and oxidizing air was introduced into the oxygen-containing gas inlet pipe 4 at a rate of 3N7T1/hour.
The fixing agent was supplied from the fixing agent introduction pipe 3 so that the pH of the absorption liquid was 3 to 4. The following four types of fixatives were operated for 5 days each. After heating the absorption liquid to 150°C, Ca(0H)2 was added, and NH3 was generated in both cases, so it is thought that NO2 was fixed as a salt of a sulfamic acid compound.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a specific example of the apparatus used in carrying out the method of the present invention, FIG. 2 is a diagram showing the opening of the gas introduction pipe, and A and B in FIG. FIG. It is a graph showing the relationship between the apparent specific gravity of the liquid and the depth of the absorption liquid.

Claims (1)

[Scope of Claims] 1. A method for removing harmful components in exhaust gas by bringing them into gas-liquid contact with an absorbing liquid, in which exhaust gas is introduced dispersedly into the absorbing liquid to form a continuous liquid phase consisting of fine bubbles of the exhaust gas and the absorbing liquid. At the same time, a first zone, which is a liquid contact layer, is formed, and an oxygen-containing gas is introduced into the absorption liquid to form microbubbles of oxygen-containing gas and the absorption liquid, which are continuous with the first zone in the liquid phase and bubbles from the first zone. A second zone having a small amount is formed, and a harmful component fixing agent (
A method for treating gas, which comprises introducing a fixative into the absorption liquid (except when the fixative is a calcium compound). 2. The method according to claim 1, wherein the fixative is introduced at the interface between the first zone and the second zone. 3. The method according to claim 1, in which the first zone and the second zone are vertically connected in a liquid phase. 4. The apparent specific gravity of the absorption liquid is between 0.2 and 0.2 in the first zone.
7. The method according to claim 1, wherein the second band is 0.9 to 1.0. 5. The method according to any one of claims 1 to 4, wherein the harmful component in the exhaust gas is sulfur dioxide gas or nitrogen oxide. 6. Any one of claims 1 to 5, wherein the fixative is one or more selected from the group consisting of an alkali metal compound, an alkaline earth metal compound (excluding calcium compounds), or ammonia. Method described. 7. The method according to any one of claims 1 to 6, wherein the exhaust gas containing nitrogen oxides is treated with ozone in advance. 8. The method according to any one of claims 1 to 7, wherein the absorption liquid contains a catalyst. 9 When the harmful components are sulfur dioxide gas and nitrogen oxides, the apparent specific gravity of the absorption liquid is maintained at 0.95 to 1.0 by adjusting the amount of bubbles caused by the oxygen-containing gas in the second zone, and the sulfur dioxide gas and the method according to any one of claims 1 to 8, which adjusts the removal rate of nitrogen oxides. 10 When the harmful components are sulfur dioxide gas and nitrogen oxides, sulfur dioxide gas is fixed in the absorption liquid as sulfate, nitrogen oxides are fixed as salts of sulfamic acid compounds, and then concentrated and taken out of the system. A method according to any one of claims 1 to 9. 11 The harmful components are sulfur dioxide gas and nitrogen oxides, and when nitrogen oxides are fixed as sulfamic acid compounds in the absorption liquid, they are hydrolyzed at 100 to 200°C to acidic ammonium sulfate, and then neutralized with ammonia. The method according to any one of claims 1 to 10, in which ammonium sulfate is produced by 12 When the harmful components are sulfur dioxide gas and nitrogen oxides and the nitrogen oxides are fixed as sulfamic acid compounds in the absorption liquid, heating at 200 to 900°C will remove sulfates and nitrogen.
_2. The method according to any one of claims 1 to 10.