JPH0677671B2 - Exhaust gas treatment method and apparatus - Google Patents

Description

The present invention relates to a method and an apparatus for treating exhaust gas containing dust and chemical pollutants.

[Conventional technology and its problems]

Conventionally, in the wet flue gas desulfurization method, it is indispensable to cool the exhaust gas before the absorption desulfurization step of sulfurous acid gas. A dust removal tower with a circulation pump is installed to cool the exhaust gas and remove dust. As a result, the size of the entire apparatus is increased, and the costs of equipment, utilities, etc. are also increased, which is a drawback.

Therefore, in order to omit the dust removal tower, the present invention hands first contact the cooling liquid fine particles and the absorbing liquid fine particles with the high temperature exhaust gas in the desulfurization apparatus main body for absorbing and reacting with sulfurous acid gas to remove contaminants in the exhaust gas. In addition to capturing them in the liquid fine particles, the exhaust gas is humidified and cooled, and then the cooled exhaust gas is introduced into the absorbent through a gas dispersion pipe, where the sulfurous acid gas in the exhaust gas is absorbed and removed, and cleaned. A method for obtaining the converted exhaust gas has been proposed (Japanese Patent Laid-Open No. 64-18427).

However, this method, the exhaust gas to be introduced into the absorption liquid, contains the cooling liquid particles and the absorption liquid particles, further, since these particles contain dust in the exhaust gas, HCl, HF, Al and other contaminants, The problem that the desulfurization by-product, such as gypsum, deteriorates in quality due to the contamination of the absorption liquid as well as the dilution of the absorption liquid, and the dilution or absorption of the absorption liquid due to the mixing of cooling liquid particles. It was not yet satisfactory, including the problem that the desulfurization performance of the device was adversely affected due to the inclusion of contaminants in the liquid.

[Problems of the Invention]

INDUSTRIAL APPLICABILITY The present invention solves the problems found in the prior art as described above, can achieve cooling of exhaust gas and removal of dust and chemical contaminants contained in the exhaust gas with one device, and An object of the present invention is to provide a method and an apparatus for treating exhaust gas, in which dust in the exhaust gas and the cooling liquid used for cooling the exhaust gas are significantly reduced.

[Means for Solving the Problems]

The present inventors, as a result of repeated studies to solve the above problems, while cooling the exhaust gas by spraying a cooling liquid into the exhaust gas in a particulate form, the dust in the exhaust gas is trapped in the cooling liquid particles, and this Exhaust gas containing cooling liquid particles that have captured dust is collided with a vertical partition wall to convert the flow from a horizontal flow to an upward flow, and at the same time, cooling liquid particles that have captured dust from rising exhaust gas are dropped by gravity and separated. , The exhaust gas from which the cooling liquid particles have been separated is converted into a downward flow over the upper end of the partition wall and is once stored in the space part, and then distributed from the space part by a plurality of gas dispersion pipes and blown into the absorption liquid. The inventors have found that the above-mentioned problems can be solved by absorbing the chemical contaminants in the exhaust gas into the absorbing liquid and separating them from the exhaust gas, and have completed the present invention.

That is, according to the present invention, the step of spraying the cooling liquid into the exhaust gas in the form of fine particles, colliding the exhaust gas with the vertical partition walls to convert the exhaust gas into an upward flow and capturing dust in the exhaust gas from the rising exhaust gas The cooling liquid fine particles are dropped by gravity and separated from the exhaust gas, the cooling liquid fine particles separated from the exhaust gas are collected and discharged to the outside of the system, and the exhaust gas from which the cooling liquid fine particles are separated is separated. The process of converting into a downward flow beyond the upper end of the vertical partition and once storing it in the space part, distributing from this space part with a plurality of gas dispersion pipes and blowing it into the absorption liquid, chemical contaminants in the exhaust gas are absorbed. Provided is a method for treating exhaust gas containing dust and chemical pollutants, which comprises a step of absorbing it and separating it from exhaust gas.

Further, according to the present invention, the cooling liquid sprayer for ejecting the cooling liquid in the exhaust gas into fine particles, the vertical partition wall for converting the flow of the exhaust gas into the upward flow inside, and the dust in the exhaust gas separated from the exhaust gas are captured. An exhaust gas dust removal chamber having a collection plate for collecting cooling liquid fine particles, and a cooling liquid fine particles that have captured the dust are separated, and a space portion for temporarily storing the exhaust gas that has become a downflow over the upper end of the vertical partition wall, A plurality of gas dispersion pipes for distributing the exhaust gas accommodated in the space and blowing it into the absorption liquid, an exhaust gas chemical treatment chamber for absorbing chemical contaminants in the exhaust gas into the absorption liquid and separating the exhaust gas from the exhaust gas, Treatment of exhaust gas containing dust and chemical pollutants, characterized in that it is provided with an exhaust pipe for discharging the cooling liquid that has captured the dust collected on the cooling liquid collection plate in the exhaust gas dust removal chamber to the outside of the exhaust gas dust removal chamber Equipment provided

Next, the present invention will be described with reference to the drawings. FIG. 1 is a schematic vertical sectional view of one embodiment of the apparatus of the present invention, and FIG. 2 is a partially cutaway perspective view of the apparatus body. FIG. 3 is a schematic vertical sectional view of another embodiment of the apparatus of the present invention, and FIG. 4 is a partially cutaway perspective view of the apparatus body. 2 and 4
In the figure, the cooling liquid atomizer is not shown.

The apparatus main body of the present invention shown in FIG. 1 and FIG. 2 is formed into a closed container structure as a whole, and comprises an exhaust gas dust removal chamber A located above and an exhaust gas chemical treatment chamber B located below. There is. The exhaust gas dust removal chamber A has a cylindrical vertical partition 9 whose upper end is located below and spaced from the top plate 3, and is horizontally arranged between the lower end of the cylindrical vertical partition 9 and the side wall. It also has a cooling liquid collecting plate 5. The horizontal cross-sectional shape of the tubular body forming the tubular partition can be various shapes such as a circle, a semicircle, a square, and a rectangle. In addition, this cylindrical vertical partition 9 is also simply referred to as a vertical partition or a cylindrical body below. A gas inlet is provided on the side wall of the exhaust gas dust removal chamber A.
An exhaust gas introducing pipe 12 is connected to the gas introducing port 11. The uppermost end of the gas inlet 11 is a vertical partition 9
The uppermost end of the opening is located above the cooling liquid collecting plate 5. A cooling liquid discharge pipe 10 is opened on the cooling liquid collecting plate 5. The exhaust gas introduction pipe 12 is
It can also be arranged so as to be tangential to the side wall of the container. In the exhaust gas introducing pipe thus arranged, the exhaust gas rises in the dust removing chamber while rotating, so that the contact time between the cooling liquid particles and the exhaust gas becomes longer, and the enhanced exhaust gas dust removing effect and cooling effect can be obtained.

The exhaust gas dust removal chamber A and the exhaust gas chemical treatment chamber B have a large number of through holes 7 on the plate surface, and a horizontal partition plate 4 having a central portion opened through which a gas dispersion pipe 8 is hung is interposed. I am contacting you. Further, a space between the horizontal partition plate 4 and the upper end of the cylindrical vertical partition 9 is formed in a space for temporarily storing the exhaust gas which has passed the upper end of the partition 9 and has a downward flow. The lower end of the gas dispersion pipe 8 is located above and spaced from the bottom plate 2. The lower end of the gas dispersion pipe 8 is preferably located above the bottom plate 2 by about 1 to 10 m. Further, at the lower end of the gas dispersion pipe 8, a large number of through holes for blowing out exhaust gas are formed on the peripheral surface at a constant distance (about 5 to 50 cm) from the lower end, so that the exhaust gas is leveled from the peripheral surface of the lower end. It is preferable that the structure is such that it is ejected in the direction. An exhaust gas discharge pipe 6 is erected at the center opening of the horizontal partition plate 4, and the tip of the exhaust gas discharge pipe 6 passes through the inside of the cylindrical body forming the cylindrical vertical partition wall 9, penetrates the top plate 3, and is led out of the container 1. Has been done.

A cooling liquid sprayer 13 is arranged inside the exhaust gas introducing pipe 12 or above the cooling liquid collecting plate 5 in the exhaust gas dust removing chamber. The cooling liquid sprayer 13 may be of any type as long as it can spray the cooling liquid as fine particles, and examples thereof include a swirl type spray, a jet type spray, and a two-fluid nozzle.

The cooling liquid discharge pipe 10 is connected to a liquid storage tank 15, and this liquid storage tank 15 is provided with a cooling liquid sprayer 13 via a circulation pump 16 and a pipe 17.
Connect to. A pipe 18 is connected to the pipe 17, which is connected to a dust separator 19. The pipe 20 is a drainage pipe.

On the side wall of the exhaust gas chemical treatment chamber B, a pipe for supplying the absorbent 26
Also, a pipe 27 for discharging the absorbing liquid is provided.

The exhaust gas chemical treatment chamber B is filled with the absorbing liquid L. The absorbing liquid is appropriately selected according to the type of exhaust gas, and various conventionally known absorbing liquids are used. Examples of such substances include pollutants in exhaust gas such as SO ₂ , SO ₃ , NO, and N _2.
In the case of an acidic substance such as O ₃ , NO ₂ , N ₂ O ₄ , N ₂ O ₅ , HCl and HF, a solution or slurry containing an alkaline substance such as an alkali metal compound or an alkaline earth metal compound is used. Calcium hydroxide slurry or calcium carbonate slurry is used. When calcium carbonate slurry or calcium hydroxide slurry is used as the absorbing liquid, these calcium compounds react with sulfurous acid gas to form calcium sulfite. In this case, by introducing air or oxygen into the absorbing liquid. , Calcium sulfite can be converted to calcium sulfate (gypsum). When the pollutant in the exhaust gas is an alkaline substance such as ammonia, an acidic aqueous solution may be used as the absorbing liquid. As the cooling liquid, ordinary water or an alkaline or acidic aqueous solution is appropriately used depending on the type of exhaust gas.

In order to process the exhaust gas containing dust and chemical pollutants using the apparatus shown in FIGS. 1 and 2, for example, high temperature exhaust gas such as flue gas is exhausted through the exhaust gas introducing pipe 12 into the exhaust gas dust removing chamber A.
To introduce. The cooling liquid is sprayed from the cooling liquid sprayer 13 into the exhaust gas introducing pipe 12 and / or the dust removing chamber A, and the high temperature exhaust gas is
The cooling liquid in the form of fine particles comes into contact with the cooling liquid, whereby it is cooled and humidified. At the same time, most of the dust in the exhaust gas is captured by the cooling liquid particles. The flow of the exhaust gas containing the cooling liquid particles can be changed to an upward flow by the vertical partition wall 9. On the other hand, the cooling liquid fine particles sprayed from the sprayer 13 drop downward in the space of the dust removing chamber A, drop on the cooling liquid collecting plate 5 and stay there, contrary to the upward flow direction of the exhaust gas. A retention liquid 25 is formed. A part of the dust contained in the high-temperature exhaust gas falls along with the cooling liquid particles due to gravity because the rising velocity of the gas in the dust removing chamber A is usually small at 1 to 5 m / sec, and is trapped in the retained liquid 25. The particulate dust in the high-temperature exhaust gas is generally entrained in the exhaust gas and is usually difficult to separate from the exhaust gas, but in the case of the present invention, contact with the cooling liquid particles formed by cooling liquid spraying The droplets are captured and coarsened to increase the sedimentation velocity, and easily fall by gravity and are taken into the retained liquid 25. In the dust removal chamber A, the horizontal gas flow velocity is usually 1 to
Since it is as small as 5 m / sec, there is almost no re-dispersion of cooling liquid fine particles, and the cooling liquid fine particles are efficiently separated from the exhaust gas.
The average particle size of the cooling liquid fine particles formed by spraying from the cooling liquid sprayer is preferably specified in the range of 400 to 4000 μm in consideration of the contact efficiency with exhaust gas and the separation efficiency from exhaust gas.

The exhaust gas, which has been cooled and dust-removed as described above, and further has the cooling liquid fine particles removed, flows downward in the tubular body 9 beyond the upper end of the tubular body 9 forming the vertical partition wall. 9
Once housed in a space portion including the internal space of the tubular body 9 between the upper end of the and the horizontal partition plate 4, from this space portion,
The gas is distributed by the gas dispersion pipe 8 vertically provided on the horizontal partition plate 4 and blown into the absorbing liquid L in the chemical treatment chamber B to contact the absorbing liquid. The chemical contaminants are removed by the reaction between the absorbing liquid and the chemical contaminants in the exhaust gas, and the exhaust gas from which the chemical contaminants have been removed diffuses from the surface of the absorbing liquid and is discharged to the outside of the system through the exhaust gas discharge pipe 6. It The exhaust gas introduced into the absorption liquid L has been sufficiently cooled and dust-removed before that time, and since the cooling liquid particles contacted during the cooling have been removed, the exhaust gas is not treated with the cooling liquid. No adverse effect.

The accumulated liquid 25 on the cooling liquid collecting plate 5 is introduced into the liquid storage tank 15 through the cooling liquid discharge pipe 10, and then circulated to the cooling liquid sprayer 13 through the circulation pump 16 and the pipe 17. In addition, a part of the cooling liquid is extracted through the pipe 18, and the dust separator
It is sent to 19, where the dust in the cooling liquid is removed. From the dust separator 19, the waste liquid from which the dust has been removed is discharged through the pipe 20, and the dust 21 is also removed. The liquid storage tank 15 is replenished with new cooling liquid in accordance with the amount of drained liquid extracted through the pipe 20 and the amount of cooling liquid reduced by evaporation.

In the present invention, various changes can be made when the high temperature exhaust gas is brought into contact with the cooling liquid particles. For example, the cooling liquid does not necessarily have to be sprayed into both the exhaust gas introducing pipe 12 and the dust removing chamber A, but can be sprayed into only one of them. Further, by performing most of the cooling of the exhaust gas in the exhaust gas introducing pipe 12, it is possible to reduce the number of installed cooling liquid atomizers used in the dust removing chamber A.

The spraying of the cooling liquid in the dust removing chamber A is not only for cooling the exhaust gas but also for cleaning the solid content generated by the viscous liquid containing dust separated from the exhaust gas adhering to the vertical partition walls 9. Used. The cooling liquid particles are evenly applied to the surfaces of the vertical partition walls 9, whereby the partition walls 9 are kept clean.

The cooling liquid spray amount for cooling the exhaust gas can be appropriately selected in relation to the supplied high temperature exhaust gas amount, exhaust gas temperature, cooling liquid temperature, etc., but the ratio of spray liquid amount / high temperature exhaust gas amount is A range of about 0.5 to 5 is suitable as a standard.
Further, in order to bring the dust in the high-temperature exhaust gas into close contact with the cooling liquid fine particles to capture the dust sufficiently and to cool the gas sufficiently, the upper end of the opening of the tubular body 9 should have the exhaust gas introduction port 11
It is preferable to be located above the uppermost end of 250 mm or more and 1500 mm or less. Further, the cylindrical body 9 can be not only an upper opening but also a side opening having an opening on the peripheral surface thereof, and the shape of the side opening can be any shape such as a circle, a triangle, or a quadrangle. be able to. Furthermore, the position of the upper end of the opening of the tubular body 9 is 300 mm below the top plate 3 of the container.
As described above, it is preferable to place them at intervals of 3000 mm or less.

Further, in the exhaust gas treatment device shown in FIG. 1 and FIG. 2, in order to maintain the cooling efficiency of the exhaust gas and the separation efficiency of the cooling liquid particles from the exhaust gas at a high level and to make the entire device compact, From the total area of the partition plate 4 (container cross-sectional area) excluding the area of the central opening (cross-sectional area of the tubular body 9) and the area of the central opening (cross-sectional area of the tubular body 9) The ratio P / Q to the area Q excluding the cross-sectional area of the exhaust gas discharge pipe 6 penetrating the inside of the opening is preferably specified in the range of 1 to 5. If the area ratio P / Q becomes smaller than the above range, the temperature rise of the exhaust gas in the dust removing chamber A becomes excessive,
The efficiency of separating the cooling liquid particles from the exhaust gas deteriorates, and a considerable amount of the cooling liquid particles accompany the exhaust gas and become mixed in the absorbing liquid L. On the other hand, when the area ratio P / Q is larger than the above range, the gas flow velocity flowing down the gas dispersion pipe 8 becomes excessively large, and the loss of gas pressure increases. The diameter of the gas dispersion pipe 8 is usually about 5 to 50 cm.

The apparatus main body of the present invention shown in FIGS. 3 and 4 has an overall structure similar to that of the apparatus shown in FIGS. 1 and 2, but in this case, The vertical partition 9 is formed of a plate-shaped body, and the exhaust gas discharge pipe 6 is arranged on the upper side wall of the chemical treatment chamber B. Further, in FIGS. 3 and 4, the same reference numerals as those shown in FIGS. 1 and 2 have the same meanings.

〔The invention's effect〕

According to the method of the present invention, it is possible to simultaneously and efficiently perform the three functions of exhaust gas cooling, dust removal and absorption reaction (for example, desulfurization reaction) in one device. Further, the apparatus of the present invention has a function capable of simultaneously performing exhaust gas cooling, dust removal and absorption reaction, so that compared with a conventional general desulfurization apparatus having a dust removal tower independent from the desulfurization apparatus main body,
It is remarkably miniaturized.

Further, since the exhaust gas descending beyond the vertical partition is once stored in the space and is distributed from this space by the gas dispersion pipe, the exhaust gas is evenly distributed to the gas dispersion pipe and blown into the absorbing liquid. In rare cases, efficient contact between the exhaust gas and the absorbing liquid is achieved.

In the apparatus of the present invention, since the vertical partition wall whose upper end is located above the uppermost end of the exhaust gas introduction port 11,
The cooling liquid fine particles that have captured the dust in the exhaust gas fall by gravity until the exhaust gas reaches the upper end of the partition wall 9 and are separated from the exhaust gas. As a result, the removal of cooling liquid particles and dust from the exhaust gas is achieved at the same time. Further, in the device of the present invention, since the exhaust gas introduced through the exhaust gas introduction pipe 12 is configured to collide with the wall surface of the vertical partition wall 9, the separation of the cooling liquid fine particles and the dust contained in the exhaust gas is Promoted by a collision. In the present invention, the proportion of the cooling liquid fine particles contained in the exhaust gas entering the chemical treatment chamber B from the dust removal chamber A is as low as 2% by weight or less.

Further, since the device of the present invention is configured such that the retained liquid 25 is formed on the cooling liquid collecting plate 5 in the dust removing chamber A, the dust in the exhaust gas that collides with the retained liquid is generated in this retained liquid. Incorporated to promote dust removal from exhaust gas.

Furthermore, in the device of the present invention, the exhaust gas introduced and dispersed in the absorbing liquid does not substantially contain the cooling liquid fine particles and the dust, so that the absorbing liquid is not diluted with the cooling liquid fine particles, and the absorbing liquid is It is not polluted by dust. In addition, HCl and H contained in the exhaust gas together with dust
Impurities such as F and Al are also removed by contact between the exhaust gas and the cooling liquid particles. Therefore, in the present invention, there is an advantage that the purity of the reaction product obtained by the reaction between the absorbing liquid and the chemical contaminant, for example, Gypsum, is increased and the product value thereof is enhanced.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of one embodiment of the apparatus of the present invention, and FIG. 2 is a partially cutaway perspective view of the apparatus body. FIG. 3 is a schematic vertical sectional view of another embodiment of the apparatus of the present invention, and FIG. 4 is a partially cutaway perspective view of the apparatus body. 1 ... Container, 4 ... Horizontal diaphragm, 5 ... Coolant collecting plate, 6
...... Exhaust gas exhaust pipe, 8 …… Gas dispersion pipe, 9 …… Vertical partition wall, 10 …… Coolant exhaust pipe, 12 …… Exhaust gas introduction pipe, 13 ……
Cooling liquid sprayer, 25 ... Retaining liquid, G ... Exhaust gas, L ... Absorption liquid.

Claims (7)

[Claims] 1. A step of spraying a cooling liquid in the form of fine particles in the exhaust gas, a cooling liquid in which dust in the exhaust gas is captured from the rising exhaust gas while colliding the exhaust gas with a vertical partition wall to convert the exhaust gas into an upward flow. The step of dropping the fine particles by its gravity to separate them from the exhaust gas, the step of collecting the cooling liquid particles separated from the exhaust gas and discharging them to the outside of the system, the exhaust gas from which the cooling liquid particles have been separated to the vertical partition wall Process of converting into a downward flow beyond the upper end and once accommodating it in the space part, distributing from this space part with multiple gas dispersion pipes and blowing it into the absorption liquid, absorbing chemical contaminants in the exhaust gas into the absorption liquid A method for treating exhaust gas containing dust and chemical contaminants, which comprises a step of separating the exhaust gas from the exhaust gas. 2. The method according to claim 1, wherein the exhaust gas contains sulfur oxides, and the absorption liquid is a desulfurization liquid. 3. A cooling liquid sprayer for ejecting the cooling liquid in the exhaust gas in the form of fine particles, a vertical partition wall for converting the flow of the exhaust gas into an upward flow, and a cooling liquid for trapping the dust in the exhaust gas separated from the exhaust gas. An exhaust gas dust removal chamber having a collection plate that collects fine particles, and a cooling liquid fine particles that have captured the dust are separated, and a space portion that temporarily stores the exhaust gas that has become a downflow over the upper end of the vertical partition wall in the space portion. , A plurality of gas dispersion pipes for distributing the exhaust gas contained in the space and blowing it into the absorption liquid, and an exhaust gas chemical treatment chamber for absorbing chemical contaminants in the exhaust gas into the absorption liquid and separating the exhaust gas from the exhaust gas, Of exhaust gas containing dust and chemical pollutants, characterized in that it is provided with a discharge pipe for discharging the cooling liquid, which has captured the dust collected on the cooling liquid collection plate in the exhaust gas dust removal chamber, to the outside of the exhaust gas dust removal chamber. Processing equipment. 4. The apparatus according to claim 3, wherein the cooling liquid atomizer is arranged in an exhaust gas introducing pipe connected to a gas introducing port of the exhaust gas dust removing chamber and / or in an exhaust gas dust removing chamber. 5. The exhaust gas dust removal chamber is installed above the exhaust gas chemical treatment chamber, and the exhaust gas dust removal chamber and the exhaust gas chemical treatment chamber form a horizontal partition plate having a large number of gas dispersion pipes suspended on the plate surface. The device according to claim 3 or 4, which is in communication with each other. 6. A cylindrical vertical partition having an upper end located below and spaced from a top plate, and a cooling liquid collecting plate horizontally disposed between a lower end of the cylindrical vertical partition and a side wall. An exhaust gas dust removal chamber having a gas inlet whose uppermost opening is located below the upper end of the cylindrical vertical partition in the side wall, and whose uppermost opening is located above the cooling liquid collecting plate; An exhaust gas introduction pipe connected to the introduction port, an exhaust gas chemical treatment chamber disposed below the exhaust gas dust removal chamber, and a large number of gas dispersion pipes on a plate surface connecting the exhaust gas dust removal chamber and the exhaust gas chemical treatment chamber. A horizontal partition plate having an open central portion and a flue gas exhaust pipe erected at the central opening of the horizontal partition plate and penetrating the top plate through the inside of the tubular vertical partition wall in the exhaust gas dust removal chamber. A cooling liquid sprayer disposed in the exhaust gas introducing pipe and / or above the cooling liquid collecting plate; Exhaust gas treatment device containing dust and chemical contaminants, characterized in that it comprises a cooling liquid discharge pipe opening into 却液 collection plate. 7. A plate-shaped vertical partition having an upper end located below and spaced from a top plate, and a cooling liquid collecting plate horizontally disposed between a lower end and a side wall of the plate-shaped vertical partition. An exhaust gas dust removal chamber having a gas inlet whose uppermost opening is located below the upper end of the plate-like vertical partition wall and whose lowermost opening is located above the cooling liquid collecting plate; An exhaust gas introduction pipe connected to the introduction port, an exhaust gas chemical treatment chamber arranged below the exhaust gas dust removal chamber, and a large number of gas dispersion pipes on a plate surface connecting the exhaust gas dust removal chamber and the exhaust gas chemical treatment chamber. A suspended horizontal partition plate, a gas exhaust port arranged in an upper side space of the exhaust gas chemical treatment chamber, an exhaust gas exhaust pipe connected to the gas exhaust port, and in the exhaust gas introduction pipe and / or the cooling liquid. Cooling liquid sprayer disposed above the collecting plate, and cooling liquid discharge pipe opening to the cooling liquid collecting plate Exhaust gas treatment device containing dust and chemical contaminants, characterized in that it comprises.