JP3572880B2 - Cooling tower - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cooling tower for cooling exhaust gas discharged from an incinerator of a municipal waste incineration facility, a combustible waste treatment facility, or the like without generating wastewater.
[0002]
[Prior art]
The high-temperature exhaust gas of 800 ° C. or higher discharged from an incinerator or the like is cooled to about 250 to 350 ° C. by a thermal energy recovery means such as a boiler or an economizer or a water injection type cooling tower utilizing latent heat of vaporization of water. , And was introduced to and processed by a dust collector such as an electric dust collector at a later stage. However, in recent years, it has been known that dioxins, which are highly toxic, are generated at temperatures around 300 ° C. in incineration of garbage, and dust collection at around 300 ° C. is avoided, and a bag filter is used at 200 ° C. or less. Low-temperature dust collection is becoming mainstream.
[0003]
In order to reduce the exhaust gas to 200 ° C. or lower, a method of further reducing the temperature of the exhaust gas of about 250 to 350 ° C. recovered by heat with a boiler or the like, for example, by water spraying using a spray nozzle is used. That is, there are increasing cases where a cooling tower is installed between a boiler and a dust collector, and the temperature is reduced to 200 ° C. or less where generation of dioxins is small.
[0004]
Conventionally, as shown in FIG. 9 or FIG. 10, a cooling tower is provided with an exhaust gas introduction duct at a lower part of a cylindrical body and an exhaust gas discharge duct at an upper part, and a water spray spray nozzle is provided to cool the exhaust gas. It was installed above the introduction duct.
[0005]
[Problems to be solved by the invention]
However, in the conventional temperature-reducing tower, the flow of the exhaust gas to be introduced is not uniformly diffused over the entire body section in the main body, which is a temperature-reducing region for cooling the exhaust gas by the latent heat of evaporation of the spray water. In addition, the active and efficient evaporation of the spray water droplets is not performed, the wet surface of the tower inner wall is formed by the non-evaporated water droplets, the non-evaporated water droplets flow out to the subsequent pug filter, the sticking of dust due to the generation of wet dust, and the discharge of dust Problems such as difficulties have arisen.
[0006]
Explaining with reference to FIGS. 7 and 8, the exhaust gas introduced from the exhaust gas introduction duct 12 does not sufficiently diffuse in the process of reaching the cooling tower body 11, and reaches the exhaust gas discharge duct 19 by being short-circuited. That is, since the predetermined exhaust gas residence time cannot be obtained, a sufficient evaporation time of the spray water droplet cannot be obtained, and since the exhaust gas flow is not uniform in the body section, the evaporation of the spray water droplet is uniformly and effectively performed. However, since the temperature distribution is biased, it is impossible to completely evaporate the sprayed water droplets, thereby causing the above problem.
[0007]
These problems are, as described above, problems that have become more prominent in recent years at low dust collection temperatures.
An object of the present invention is to provide a high-performance cooling tower which can cope with low dust collection temperatures and does not cause the above problems.
[0008]
[Means for Solving the Problems]
In order to achieve the effective complete evaporation of the spray water droplets and to solve the above problems, the following means were devised aiming at rectification and uniformization of the gas flow in the cooling tower section.
First, it is a cooling tower that cools the exhaust gas by water spray without generating wastewater, regarding the shape of the exhaust gas introduction part,
B) A plurality of openings are installed along the circumference of the cooling tower at the height where the exhaust gas introduction duct is installed,
B) installing an exhaust gas introduction duct so as to cover the opening in a donut shape ;
Introducing the exhaust gas into the exhaust gas introduction duct in the radial direction of the cooling tower, guiding the exhaust gas along the circumferential direction of the cooling tower body, and guiding the exhaust gas into the cooling tower while colliding with each other from adjacent openings;
It is a cooling tower characterized by the following.
[0009]
By configuring the exhaust gas introduction section of the cooling tower as described above, the exhaust gas flows at a relatively low flow rate into the tower from a plurality of openings installed in the circumferential direction of the cooling tower body by a gas suction action of an induction fan or the like. It is introduced and passes through the body while being cooled by evaporation of the water droplets sprayed from the spray nozzle, and is discharged from the exhaust gas discharge unit. Since the exhaust gas is guided from a plurality of openings into the tower, the exhaust gas flows from the adjacent openings collide with each other and are mixed.At the same time, since the plurality of openings, the exhaust gas introduction speed is low and the body cross section is uniform. It becomes upward flow.
[0010]
That is, since the flow of the exhaust gas is uniform in the body of the cooling tower related to the evaporation of the spray water droplets, the effect that the spray water droplets are effectively evaporated when water spray is performed by the spray nozzle is obtained.
[0011]
Second, a cooling tower that cools the exhaust gas by water spray without generating wastewater, regarding the shape of the exhaust gas introduction part,
C) A plurality of openings are installed along the circumferential direction of the cooling tower at the position where the exhaust gas introduction duct is installed,
D) A cooling tower characterized by connecting a plurality of branched exhaust gas introduction ducts to the opening.
[0012]
Also in this case, since the exhaust gas is introduced from the plurality of openings, the same effect as in the first invention can be obtained. .
Thirdly, in the cooling tower according to claim 1 or 2, the plurality of openings are installed so that the opening ratio is smaller on the side near the exhaust gas introduction duct.
[0013]
When the opening ratio is set in this manner, the amount of exhaust gas discharged from the opening closer to the exhaust gas introduction portion is relatively reduced, and at the same time, the amount of exhaust gas discharged from the opening farther from the exhaust gas introduction portion is relatively increased. I do. This is because the opening closer to the exhaust gas introduction duct has a smaller pressure loss, so that a more uniform amount of exhaust gas is introduced in consideration of the fact that more exhaust gas is likely to flow out. Therefore, the function of the first or second invention can be more effectively obtained in the exhaust gas introduction section.
[0014]
Fourth, a cooling tower according to any one of claims 1 to 3, wherein the entire area of the opening is set so that the average gas flow velocity of the opening is 5 m / s or less.
[0015]
When the entire area of the opening is set in this manner and the average gas flow velocity in the opening is reduced, the introduced exhaust gas does not extremely increase in the center in the body section, and the flow rate of the exhaust gas in the body section becomes more uniform. Exhaust gas upward flow is obtained. When the speed is 5 m / s or more, the exhaust gas introduced into the body from the opening concentrates at the center of the tower section, and the upward flow of the exhaust gas is biased near the axial center, making it difficult to achieve a uniform exhaust gas flow. It is not preferred.
[0016]
Fifth, with regard to the shape of the exhaust gas discharge section, the exhaust gas introduction duct according to any one of claims 1 to 4 is an exhaust gas discharge duct.
Even if the shape of the exhaust gas introduction section described in the first to fourth inventions is used as it is as the shape of the exhaust gas discharge section, an effect of making the exhaust gas uniform can be obtained.
[0017]
The uniformity of gas in the body of the cooling tower is greatly affected by the shape of the exhaust gas introduction section. However, if the shape of the exhaust gas exhaust section greatly biases the gas flow, the gas flow also in the cooling tower body May be impaired. Therefore, by setting the shape of the exhaust gas discharge section in this way, the exhaust gas is exhausted from multiple outlets instead of the uneven exhaust gas discharge by the conventional two ducts installed on the side, so that the exhaust gas is uniformly discharged. Can be discharged.
[0018]
In addition, since the exhaust gas discharge duct is installed on the side of the exhaust gas discharge unit, when installing the cooling tower, the length in the vertical direction is unnecessarily increased as the conventional exhaust gas discharge duct is installed at the top of the tower No need for a compact vertical length cooling tower.
[0019]
Sixth, a cooling tower for cooling exhaust gas by water spray without generating wastewater, wherein the exhaust gas introduction section has the shape of the exhaust gas introduction section according to claims 1 to 4, and the exhaust gas discharge section has the shape according to claim 5. It is a cooling tower characterized by the following.
[0020]
By having the shapes of the exhaust gas introduction part shown in the first to fourth and the shape of the exhaust gas discharge part shown in the sixth at the same time, the first to sixth actions are synergistically obtained.
[0021]
Seventh, the installation position of the spray nozzle for cooling the exhaust gas by water spray is installed on the downstream side of the gas flow in the tower with respect to the opening in claim 1, and the symmetry of the water spray flow in the tower cross section is obtained. The cooling tower according to any one of claims 1 to 6, wherein a plurality of spray nozzles are provided in the circumferential direction of the tower body.
[0022]
By installing the spray nozzle for water spray in this way, the water droplet spray flow of the spray nozzle does not collide with the facing inner wall, i.e., the inner wall does not form a wet surface due to water spray, the trunk section , A symmetrical water spray stream is obtained, and uniformity of the water spray stream and complete evaporation in the column are effectively obtained.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 6 are diagrams showing one embodiment of a cooling tower according to the present invention.
7 and 8 are diagrams showing a conventional cooling tower for comparison with the present invention.
Here, 1 is a cooling tower outer tower or main body, 2 is an exhaust gas introduction duct, 5 is a dust collection hopper, 6 is a dust discharge section, 7 is an opening in the exhaust gas introduction section, and 8 is an exhaust gas discharge section. An opening, 9 is an exhaust gas discharge duct, 10 is a spray nozzle, 11 is a body of a cooling tower main body, 12 is an exhaust gas introduction duct, 15 is a dust collection hopper, 16 is a dust discharge section, and 19 is an exhaust gas discharge duct. .
[0024]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
Exhaust gas of 200 ° C. or higher after being discharged from an incinerator or the like and recovered by a boiler or the like is introduced into the cooling tower 1 through an exhaust gas introduction duct 2 installed at a lower part of the cooling tower, and spray nozzles 10 ( However, for the sake of simplicity, the spray nozzle is not shown in FIGS. 1 to 4. As shown in FIG. 5, the exhaust gas is cooled by the latent heat of vaporization of the water droplets and installed at the upper part of the cooling tower. From the exhaust gas discharge duct 9. The discharged exhaust gas is introduced into a dust collector installed at a later stage. However, the incinerator, boiler, and dust collector described here are not shown.
[0025]
The temperature of the exhaust gas cooled by the cooling tower varies depending on the conditions of the subsequent dust collector and other conditions related to operation. For example, in the case of a cooling tower installed in a refuse incineration facility, dioxin of 150 to 200 ° C is used. In recent years, it has been greatly desired to cool to a low temperature at which generation of a class is minimal. The temperature drop in the cooling tower, that is, the difference between the inlet temperature and the outlet temperature, depends on the size of the cooling tower and the spray performance of the spray nozzle, but is usually about 30 to 200 ° C.
[0026]
FIG. 1 shows that a plurality of openings 7 are provided along the circumferential direction of the temperature-reducing tower body 1 at the position where the exhaust gas introduction duct 2 is installed, and the exhaust gas introduction duct is covered so as to cover the openings in a donut shape. 2 is the shape of the exhaust gas introduction section when the apparatus is installed.
[0027]
Exhaust gas introduced from the exhaust gas introduction duct 2 is introduced into the tower at a relatively low flow rate from a plurality of openings 7 provided in the circumferential direction of the body 1 by a gas suction effect of an inducing fan or the like, and is sprayed by a spray nozzle. While being cooled by evaporation of water droplets, the water droplets pass through the body 1 and are discharged from an exhaust gas discharge unit (not shown).
[0028]
Since the exhaust gas is guided from a plurality of openings into the tower, the exhaust gas flows from the adjacent openings collide with each other and are mixed.At the same time, since the plurality of openings, the exhaust gas introduction speed is low and the body cross section is uniform. It becomes upward flow. That is, since the flow of exhaust gas is uniform in the body of the cooling tower related to the evaporation of the spray water droplets, the spray water droplets are effectively evaporated when water spray is performed by the spray nozzle.
[0029]
FIG. 2 shows that a plurality of openings 7 are provided along the circumferential direction of the temperature-reducing tower body 1 at a position where the exhaust gas introduction duct 2 is installed, and the exhaust gas introduction duct 2 branched into a plurality of openings is connected to the opening 7. This is the shape of the exhaust gas introduction section connected to.
[0030]
Also in this case, the exhaust gas is introduced from a plurality of openings as in FIG. 1, so that the same operation as the first invention can be obtained.
Further, it is desirable to set the entire area of the opening so that the average gas flow velocity in the opening 7 is 5 m / s or less. When the average gas flow velocity in the opening is reduced in this way, the exhaust gas introduced can have a more uniform upward flow of exhaust gas in the body section without the flow velocity in the center part becoming extremely high in the body section. When the speed is 5 m / s or more, the exhaust gas introduced into the body from the opening concentrates at the center of the tower section, and the upward flow of the exhaust gas is biased near the axial center, making it difficult to achieve a uniform exhaust gas flow. It is not preferred.
[0031]
Further, as shown in FIG. 3, the opening 7 of the exhaust gas introduction section may be installed such that the opening ratio on the side close to the exhaust gas introduction port becomes small. With this arrangement, the amount of exhaust gas introduced from the opening closer to the exhaust gas introduction portion relatively decreases, and at the same time, the amount of exhaust gas introduced from the opening farther from the exhaust gas introduction portion relatively increases.
[0032]
This is because a more uniform amount of exhaust gas is discharged in consideration of the fact that the opening near the exhaust gas introduction duct has a smaller pressure loss, so that more exhaust gas is likely to flow out. Therefore, the effect shown in FIG. 1 or 2 can be more reliably obtained in the exhaust gas introduction section.
[0033]
FIG. 4 is a diagram showing a case where the shape of the exhaust gas introduction section of the present invention is used for an exhaust gas discharge section. Even when the shape of the exhaust gas introduction section is used for the exhaust gas discharge section, the effect of uniformly equalizing the gas flow can be obtained. Further, the opening ratio may be reduced on the side close to the exhaust gas discharge port.
[0034]
Further, as shown in FIG. 5, the shape of the exhaust gas introduction portion and the shape of the exhaust gas discharge portion may be used in combination at the same time, and it goes without saying that the effects described above are more remarkably obtained.
[0035]
Next, the spray nozzles 10 for water spraying are installed above the double tower portion of the exhaust gas introduction section, and a plurality of spray nozzles are arranged in the circumferential direction of the tower body so as to obtain the symmetry of the water spray flow in the tower cross section. It is desirable to install.
[0036]
FIG. 6 is a cross-sectional view of FIG. 5B, showing an embodiment in which the spray nozzles are arranged so as to obtain the symmetry of the water spray flow. FIG. 6A shows a case where four nozzles are installed at equal intervals in the same cross section, FIG. 6B shows a case where three nozzles are installed at equal intervals, and FIG. It is a figure each showing the case where two sets and a total of four are installed. It is clear that in each case the symmetry of the water spray flow is obtained.
[0037]
By installing the spray nozzle for water spray in this way, the water droplet spray flow of the spray nozzle does not collide with the facing inner wall, i.e., the inner wall does not form a wet surface due to water spray, the trunk section In this case, a symmetrical water spray stream is obtained, and uniformity of the water spray stream and complete evaporation in the column are effectively obtained.
[0038]
In FIG. 6, a plurality of spray nozzles are installed on the same cross section, but, of course, the installation cross section may be two or more.
The spray nozzle 10 varies depending on the operating conditions. For example, in the case of a cooling tower for low temperature such as cooling to 200 ° C. or less, a two-fluid nozzle using water and air that can obtain finer spray water droplets is employed. However, it is not particularly limited. Further, an acidic component in the exhaust gas may be removed by using an alkaline absorbing liquid such as slaked lime slurry as the spray water, and any method may be used as long as the exhaust gas can be cooled using the latent heat of water.
[0039]
As an installation method when the spray nozzle 10 is installed in the cooling tower, for example, it may or may not protrude several 10 cm from the inner wall. In order to ensure the durability of the nozzle, a protection tube may be attached to the outer periphery of the nozzle, or purge air or the like may be used between the nozzle and the protection tube. Further, the nozzle may be installed with an elevation angle with respect to the cross section, or the nozzle tip may be bent in the gas flow direction. It is clear that the effect of the present invention can be similarly obtained in any case.
[0040]
In the present invention, for convenience of explanation, the case where the exhaust gas is introduced from the lower part of the cooling tower and discharged from the upper part has been described. Of course, the case where the exhaust gas is introduced from the upper part of the cooling tower and discharged from the lower part (see FIG. 5). It is clear that the present invention can be applied to a thick black arrow), and has the same effect.
[0041]
"Example"
Test results obtained by implementing the present invention in a cooling tower attached to a refuse incineration plant are shown in FIGS. 9 and 10 together with a conventional comparative example.
[0042]
FIG. 9 is a diagram showing test results when the present invention is implemented.
FIG. 10 is a diagram showing a conventional comparative example of test results when the present invention is not performed. Here, reference numeral 20 denotes accumulated dust.
[0043]
The embodiment is a temperature-reducing tower shown in FIG. 5 in which the shape of the exhaust gas introduction section shown in FIG. 1 is adopted also for the exhaust gas discharge section. The total area of the opening was set such that the average exhaust gas flow rate at the opening was 4 m / s.
[0044]
The comparative example was a cooling tower having the shape shown in FIG.
As common conditions, the external shape of the cooling tower is the same size, the exhaust gas throughput is 40000 Nm ³ / h, the residence time of the cooling tower exhaust gas is 4 seconds (calculated by the volume and the exhaust gas amount), and the exhaust gas temperature at the inlet of the cooling tower is about 200 ° C, and the temperature of the exhaust gas at the outlet (the water spray amount was adjusted to be constant) to 150 ° C. Four spray nozzles were installed at equal intervals on the same section, and a two-fluid nozzle was used.
[0045]
First, the gas flow rate distribution in the cross section of the tower was measured before water spraying, and then the water fog operation was performed for one month continuously, and the dust accumulation state in the tower one month later was confirmed.
[0046]
As a result, in the gas velocity distribution before water spraying, in the conventional comparative example, the gas flow from the exhaust gas introduction duct to the discharge duct was short-circuited and did not disperse. In the embodiment of the invention, a substantially uniform flow velocity distribution was obtained.
[0047]
Next, observing the dust accumulation in the tower one month later, in the comparative example, wet dust due to incomplete evaporation of the spray water droplets was deposited with a thickness of 10 cm or more over a wide range of the inner wall of the tower, and a part of the exhaust gas was detected by thermal analysis. On the other hand, in the example of the present invention, no accumulation of dust in the tower was observed, and the dust was slightly attached to the inner wall.
[0048]
Dust accumulation occurs because unevaporated water droplets adhere to the tower wall or promote the dust aggregation effect, so that the water droplets completely evaporate, and thus serve as a determination index of whether stable operation has been achieved.
[0049]
In other words, the cooling tower according to the present invention provides a uniform exhaust gas flow in the tower, effectively evaporates the sprayed water droplets even at a low temperature of 150 ° C., thereby causing problems such as dust accumulation due to incomplete evaporation. It was confirmed that it was not an excellent cooling tower.
[0050]
【The invention's effect】
By using the cooling tower of the present invention, the exhaust gas is effectively rectified in the exhaust gas introduction section, and a uniform gas flow is obtained in the body, so that the generation of dioxins is as low as about 150 ° C. In addition, it is possible to effectively evaporate the water droplets sprayed by the spray nozzle and thereby to achieve excellent exhaust gas cooling without causing problems such as dust accumulation in the tower due to incomplete evaporation.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an embodiment of an exhaust gas introduction section shape of a cooling tower according to the present invention.
FIG. 2 is a view showing another example of the embodiment of the exhaust gas introduction section shape of the cooling tower according to the present invention.
FIG. 3 is a view showing another example of the embodiment of the shape of the exhaust gas introduction portion of the cooling tower according to the present invention.
FIG. 4 is a view showing an example of an embodiment of an exhaust gas discharge section shape of a cooling tower according to the present invention.
FIG. 5 is a diagram showing an example of an embodiment of a cooling tower according to the present invention.
FIG. 6 is a view showing an example of an embodiment of installation of a spray nozzle of a cooling tower according to the present invention.
FIG. 7 is a diagram showing an example of a conventional cooling tower.
FIG. 8 is a diagram showing another example of a conventional cooling tower.
FIG. 9 is a view showing an operation result of the cooling tower according to the present invention.
FIG. 10 is a view showing an operation result of a conventional cooling tower.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Outer tower or main body of cooling tower, 2 ... Exhaust gas introduction duct, 5 ... Dust collection hopper section, 6 ... Dust discharge section, 7 ... Opening in exhaust gas introduction section, 8 ... Opening in exhaust gas discharge section , 9: Donut exhaust gas discharge duct, 10: Spray nozzle, 11: Cooling tower body, 12: Exhaust gas introduction duct, 15: Dust collection hopper, 16: Dust discharge unit, 19: Exhaust gas discharge duct, 20 ... dust dust.

Claims (7)

It is a cooling tower that cools exhaust gas by water spray without generating wastewater, and regarding the shape of the exhaust gas introduction part,
B) A plurality of openings are installed along the circumference of the cooling tower at the height where the exhaust gas introduction duct is installed,
B) installing an exhaust gas introduction duct so as to cover the opening in a donut shape ;
Introducing the exhaust gas into the exhaust gas introduction duct in the radial direction of the cooling tower, guiding the exhaust gas along the circumferential direction of the cooling tower body, and guiding the exhaust gas into the cooling tower while colliding with each other from adjacent openings;
A cooling tower. It is a cooling tower that cools exhaust gas by water spray without generating wastewater, and regarding the shape of the exhaust gas introduction part,
C) A plurality of openings are installed along the circumference of the cooling tower body at the height where the exhaust gas introduction duct is installed,
D) connecting a plurality of branched exhaust gas introduction ducts to the opening;
A cooling tower. 3. The cooling tower according to claim 1, wherein the plurality of openings are installed such that an opening ratio is smaller on an upstream side of a flow of the exhaust gas . The cooling tower according to any one of claims 1 to 3, wherein the entire area of the opening is set such that the average gas flow velocity in the opening is 5 m / s or less. A cooling tower that cools exhaust gas by water spray without generating wastewater, and regarding the shape of the exhaust gas discharge part,
E) A plurality of openings are installed along the circumference of the cooling tower at the height where the exhaust gas discharge duct is installed,
F) Install an exhaust gas exhaust duct so as to cover the opening like a donut,
Discharging the exhaust gas from the inside of the cooling tower to the exhaust gas discharge duct through the opening, and discharging the exhaust gas in the radial direction of the cooling tower;
A cooling tower. A cooling tower for cooling exhaust gas by water spray without generating wastewater, wherein the exhaust gas introduction part has the shape of the exhaust gas introduction part according to claims 1 to 4, and the exhaust gas discharge part has the shape according to claim 5. A cooling tower. The installation position of the spray nozzle that cools the exhaust gas by water spray is installed on the downstream side of the gas flow in the tower with respect to the opening, and the periphery of the tower body is obtained so as to obtain the symmetry of the water spray flow in the tower cross section. The cooling tower according to any one of claims 1 to 6, wherein a plurality of spray nozzles are provided in the direction.

Images