JPH1183346A - Water spray method for cooling tower and cooling tower having water spray device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To meet a lowering of dust collection temperature by performing a water spray while one of a plurality of spray nozzles for effecting the water spray, which are installed along a circumferential direction of a section of a tower, is being reciprocatively driven toward a center direction of the section of the tower. SOLUTION: A waste gas exhausted from an incinerator or the like and having a temperature of not less than 200C after recovery of heat by a boiler or the like is introduced into a cooling tower 1 via a waste gas introduction duct 2 installed above the cooling tower 1. Four spray nozzles 6 are installed in a same section A at uniform intervals in a circumferential direction and spray nozzle drivers 7 are provided on opposing two of them. The spray nozzles 6 are reciprocatively driven in a direction toward a center of the section by the driver 7 while spraying water, so that the waste gas is cooled by latent of evaporation of water droplets and the waste gas is discharged from a waste gas discharge duct 3 installed at a lower part of the cooling tower 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a municipal solid waste incineration plant,
The present invention relates to a water spraying method and a water spraying method in a cooling tower that spray-cools exhaust gas discharged from an incinerator or the like in a combustible waste treatment facility by a spray nozzle without generating wastewater.

[0002]

2. Description of the Related Art High-temperature exhaust gas of 800 ° C. or higher discharged from an incinerator or the like is heated to 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. The temperature was reduced to a certain extent, and it was introduced into a dust collector such as an electric dust collector at a later stage and was processed. However, it has become known in recent years that dioxins, which are highly toxic, are generated at temperatures around 300 ° C. in waste incineration, and dust collection at around 300 ° C. has been avoided.
Low-temperature dust collection using a bag filter at 200 ° C. or lower is becoming mainstream.

In order to reduce the temperature of exhaust gas to 200 ° C. or lower, a method of further reducing the temperature of exhaust gas of about 250 to 350 ° C. recovered by heat from a boiler or the like, for example, by spraying water using a spray nozzle is used. . That is, there is an increasing number of cases in which 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. Conventionally, water spraying by a spray nozzle in a cooling tower has been performed continuously with the spray nozzle fixed.

[0004]

However, in the above-mentioned conventional water spraying method in the cooling tower, since the spraying is performed continuously while the spray nozzle is fixed, the evaporation is actively activated in the vicinity of the spraying. Thus, the evaporation area of the spray water droplets in the tower was limited and fixed. That is, the high-temperature region and the low-temperature region are divided and fixed in the tower, and as a result, the contact between the spray water droplets and the exhaust gas has not been effectively performed in the entire space in the tower.

[0005] For this reason, in the low temperature region near the water spray, since the temperature is low, the water droplets in the spray and the water in the exhaust gas are condensed, and the dust contained in the exhaust gas becomes wet. There is a problem in that the gas adheres to and accumulates on the dust discharge portion, causes corrosion of the device due to the acid gas induced by moisture, generates scale due to dust accumulation in the tower, and makes it difficult to discharge dust.

[0006] These problems have become more prominent with the recent reduction in dust collection temperature described above. The present invention provides a water spray method and apparatus in a cooling tower that can cope with a low dust collection temperature and can overcome the above problems.

[0007]

The following means have been devised in order to prevent the formation of a biased low-temperature region in the cooling tower and to achieve effective complete evaporation of the spray water droplets. First, in a cooling tower where the exhaust gas is cooled by water spray without generating wastewater. A) One or more spray nozzles for water spray are installed along the circumferential direction of the tower cross section. A water spraying method for a cooling tower, characterized in that water spraying is performed while reciprocatingly driving at least one of the spray nozzles toward the center of the tower cross section.

[0008] Since the water spray is performed while the spray nozzle is reciprocated toward the center of the tower cross section, the spray flow of the water droplet by the spray nozzle is forcibly moved, and a low-temperature region is formed in the tower for a long time. Can be prevented. In other words, since the formation of the low-temperature region for a long time can be prevented, effective evaporation of the spray water can be performed, and the formation of wet dust, dust accumulation, equipment corrosion, etc. induced by condensation of moisture in the low-temperature region can be prevented. Eliminate problems.

Secondly, the method according to claim 1, wherein a plurality of spray nozzles to be driven are provided, and the spray nozzles are arranged at positions where two or more axes of linear symmetry exist in the same cross section. It is.

As described above, when a plurality of spray nozzles are arranged at positions where two or more line symmetry axes exist in the same cross section, the symmetry of the water spray flow is obtained, and the water spray flow is applied to the opposed inner wall of the tower. It is possible to prevent the inner wall from forming a wet surface due to collision. Furthermore, in such an arrangement, if the spray nozzle is driven to reciprocate, the effect of preventing the formation of a low-temperature region can be obtained while maintaining the symmetry of the water spray flow, so that the first invention can be more reliably achieved. Action is obtained.

The arrangement in which two or more line symmetry axes exist is, for example, to arrange two spray nozzles at opposing positions or to arrange three spray nozzles at equal intervals in the circumferential direction. Details will be described in the embodiments of the invention.

Thirdly, in driving the spray nozzle according to claim 1 or 2, the time when the projection length of the spray nozzle becomes minimum to the maximum or half the reciprocating drive period is reduced. Of the average residence time of the exhaust gas in the
This is a water spraying method for a cooling tower, wherein the water spraying method is 10 times.

As described above, the time when the projection length of the spray nozzle is from the minimum to the maximum, or the half of the reciprocating driving cycle is set to 1 to 10 times the residence time of the exhaust gas, so that the inside of the cooling tower can be effectively reduced. Can be changed, and the formation time of the temporary low-temperature region can be suppressed within a range in which water does not condense and the accumulation of wet dust accompanying the water does not occur.

If the residence time of the exhaust gas is within one time, the residence time in the tower is usually about 2 to 10 seconds. Therefore, the spray nozzle must be frequently driven, and mechanical energy is wastefully consumed. That is, the convection time of the exhaust gas, that is, the time from the time when the exhaust gas is introduced into the cooling tower to the time when it is discharged from the outlet, is changed even if the projection length of the spray nozzle is changed. This is not preferable because the effect of offsetting the low-temperature region due to the exchange of the high-temperature region and the high-temperature region does not particularly increase.

If the ratio is more than 10 times, the operation of changing the protruding length of the spray nozzle is performed at a sufficiently long interval, so that a low-temperature region in the tower is formed for a long time, and water condensation and This is not preferable because a sufficient amount of time elapses to induce a problem of wet dust accumulation. However, even if it is out of this range, although the effect is relatively small, it is clear that the operation of the first invention for driving the spray nozzle can be obtained.

Fourthly, in a cooling tower for cooling exhaust gas by spraying water without generating wastewater, the spray nozzle according to any one of claims 1 to 3 and the spray nozzle are arranged in the direction of the center of the cross section of the tower. And a driving device for driving the water spraying device.

As described above, by equipping the cooling tower with the spray nozzle and the spray nozzle driving device satisfying one of the first to third requirements, it is possible to cope with a low dust collection temperature, and to solve the problem. An excellent temperature-reducing tower free of generation of water is easily obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 6 show an embodiment relating to a water spray method and apparatus of the present invention. Here, 1 is a cooling tower ｛body body), 2 is an exhaust gas introduction duct,
3 is an exhaust gas discharge duct, 4 is a dust collecting hopper, 5 is a dust discharge unit, 6 is a spray nozzle, 7 is a driving device, 8
Is a water spray flow, 9 is a water supply pipe, and 10 is an air supply pipe.

An embodiment of the present invention will be described below 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 an upper part of the cooling tower, and spray nozzles 6 are provided. As a result of the water spray, the exhaust gas is cooled by the latent heat of evaporation of the water droplets,
It is discharged from an exhaust gas discharge duct 3 installed at the lower part of the cooling tower. The discharged exhaust gas is introduced into a subsequent dust collector. However, the incinerator, boiler, and dust collector described here are not shown.

The temperature of the exhaust gas cooled in the cooling tower varies depending on the conditions of the subsequent dust collector and other conditions relating to operation. For example, in the case of a cooling tower installed in a refuse incineration facility, 150 to 200 ° C. In recent years, it has been greatly desired to reduce the temperature to a temperature at which generation of dioxins is extremely small.
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.

FIGS. 1 to 3 show a spray nozzle 6.
Is a cooling tower according to the present invention, which is installed above the cooling tower together with the spray nozzle driving device 7. Four spray nozzles are installed on the same section A at equal intervals in the circumferential direction, and two opposing spray nozzles are provided with the spray nozzle driving device 7.

As shown in FIG. 5, the spray nozzle 6 is reciprocated toward the center of the cross section by the driving device 7 while spraying water. Since the water spray is performed while being driven back and forth in this manner, the spray flow of the water droplets by the spray nozzle is forcibly moved, and the formation of a low-temperature region in the tower for a long time can be prevented. That is, since the low-temperature region can be prevented from being formed for a long time, the effective spray water is evaporated, and the formation of wet dust, the accumulation of dust, the corrosion of the device, etc. induced by the condensation of the moisture in the low-temperature region can be prevented. Eliminate problems.

The number of the spray nozzles 6 to be driven (including the drive device 7) and the number of the spray nozzles 6 not to be driven are not particularly limited, but it is preferable that the number of the spray nozzles 6 to be driven is plural. If the number of driven spray nozzles is one, the symmetry in the cross section of the water spray flow is slightly impaired, which is relatively undesirable.

The spray nozzle 6 to be driven is preferably installed at a position where two or more axes of line symmetry exist along the circumferential direction of the same cross section, as shown in FIG. However, in FIG. 4, the spray nozzle driving device 7 is omitted for simplicity.

For example, FIG. 4 (a) shows two spray nozzles installed in the opposite direction, and there are two linear symmetry axes (a, b). FIG. 4 (b) shows three of them installed at equal intervals, and there are three (a, b, c) axes of line symmetry. FIG. 4 (c) shows a case where four lines are installed so that the distance between the two lines facing each other is the same, and there are two (a, b) axis of symmetry. Fig. 4 (d) shows two of them installed at 90 degree intervals.
There is only one axis of symmetry (a). Among these, FIGS. 4A, 4B, and 4C are preferable because two or more axes of linear symmetry exist, and thus the symmetry of the water spray flow can be obtained.
In (d), since there is only one axis of symmetry, the symmetry of the water spray flow cannot be obtained, which is not preferable. Of course, it is needless to say that the arrangement is preferably such that there are two or more axisymmetric axes in the same cross section, including the spray nozzle that is not driven.

In the example shown in FIG. 2, the spray nozzles to be driven and the spray nozzles not to be driven are respectively arranged, or both are arranged such that two or more axes of line symmetry exist.

As described above, when a plurality of spray nozzles 6 are arranged at positions where two or more axes of linear symmetry exist in the same cross section, the symmetry of the water spray flow is obtained, and the water spray flow is opposed to the inner wall of the tower. Can be prevented from forming a wet surface on the inner wall due to collision with the inner wall. Furthermore, in such an arrangement,
When the spray nozzle is reciprocated, the effect of preventing the formation of the low-temperature region can be obtained while the symmetry of the water spray flow is secured, so that the operation of the first invention can be obtained more reliably.

FIG. 6 shows an example of the operation of the projection length of the tip of the spray nozzle from the inner wall when the spray nozzle 6 is driven to reciprocate. The operation is not limited to that shown in FIG. 6, and if a periodic reciprocating drive is achieved, an operation such as a sine curve may be used.

At this time, the time required for the spray nozzle 6 to be driven to protrude from the inner wall of the cooling tower 1 from the minimum to the maximum, or a half of the reciprocating driving cycle, is equal to the cooling tower 1.
Is preferably 1 to 10 times the average residence time of the exhaust gas.

With this setting, the gas flow in the cooling tower can be effectively changed, and the formation time of the temporary low-temperature region can be reduced by the condensation of water or the wet dust associated therewith. Can be suppressed within a range in which the accumulation of slag does not occur.

If the residence time of the exhaust gas is within one time, the residence time in the tower is usually about 2 to 10 seconds. Therefore, the spray nozzle must be frequently driven, and mechanical energy is wastefully consumed. That is, the convection time of the exhaust gas, that is, the time from the time when the exhaust gas is introduced into the cooling tower to the time when it is discharged from the outlet, is changed even if the projection length of the spray nozzle is changed. This is not preferable because the effect of offsetting the low-temperature region due to the exchange of the high-temperature region and the high-temperature region does not particularly increase.

On the other hand, if it is 10 times or more, the operation for changing the projection length of the spray nozzle is performed at a sufficiently long interval, so that a low-temperature region in the tower is formed for a long time, and the water content is reduced. It is not preferable because a sufficient amount of time elapses to cause a problem of condensation and the accompanying accumulation of wet dust. However, even if it is out of this range, although the effect is relatively small, it is clear that the operation of the first invention for driving the spray nozzle can be obtained.

The minimum projection length, the maximum projection length, and the drive width when driving the spray nozzle 6 are not particularly limited. However, the drive width or the maximum protrusion length is set to 0.
It is not preferred that the ratio be 5 times or more, because the operation becomes mechanically inconvenient and the function of eliminating the low temperature region in the tower does not particularly increase. According to the investigation by the present inventors, even with a short drive width of about several tens of cm (about 0.1 times the inner diameter of the tower),
It has been found that the effect of eliminating the low temperature region of the gas flow in the column was sufficiently obtained.

Next, the spray nozzle driving device 7 drives the spray nozzle 6 to reciprocate in the center of the cross section.
It is a mechanical drive device composed of members such as a motor, a gear, a bearing, a bearing, and a rotation speed control device. However, these members are not shown. In addition, a known drive device using hydraulic pressure, air pressure, or the like may be used, and a drive device capable of easily adjusting the drive width and the reciprocating drive cycle is desirable.

The spray nozzle 6 varies depending on the operating condition of the cooling tower. For example, in the case of a cooling tower for cooling at a low temperature of 200 ° C. or less, water and air which can obtain finer spray water droplets are used. It is preferable to use a two-fluid nozzle, but 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.

In order to ensure the durability of the spray nozzle 6, a protective 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 protective tube. When driving the spray nozzle, the spray nozzle may be driven together with the protective tube, or only the spray nozzle may be driven.

The water spray by the spray nozzle is preferably a substantially constant amount spray. However, the water spray amount may be controlled by feedback control or the like so as to obtain a predetermined exhaust gas temperature. May be changed.

The present invention has been described with reference to the case where the exhaust gas is introduced from the upper part of the cooling tower and discharged from the lower part in the cylindrical cooling tower. It is clear that the present invention can be applied even in the case where it is not the same, and an equivalent effect can be obtained.

[Examples] The results obtained by carrying out the water spraying method of the cooling tower according to the present invention are shown in FIGS. 7 and 8 in comparison with the conventional method.

FIG. 7 is a diagram showing an example of test results when the water spraying method of the present invention is performed. FIG. 8 is a diagram illustrating test results when the present invention is not performed. Here, reference numeral 11 denotes accumulated dust.

In the embodiment, the spray nozzle shown in FIG. 1 was used, and two spray nozzles for reciprocating drive and two spray nozzles for non-drive were arranged in the same cross section as shown in FIG. The drive width in the center direction of the cross section is 50 cm,
The minimum value of the projection length from the inner wall of the spray nozzle is 30c
m, and the maximum value was 80 cm. A half time of the reciprocating drive cycle was set to 10 seconds, which is 2.5 times the average residence time of the exhaust gas of 4 seconds.

The comparative example is a cooling tower of the same type as the example.
All four spray nozzles were fixed. As a common test condition, a two-fluid spray nozzle having a maximum water droplet diameter of about 150 μm is adopted, the processing gas amount is 40000 Nm ³ / h, the inlet exhaust gas temperature is about 220 ° C., and the outlet exhaust gas temperature is 150 ° C. (it is fixed by controlling the amount of water spray). And the test period was one month.

As a result, in the example in which the present invention was carried out, even at the end of the test one month later, almost no accumulation of dust in the tower was observed, and the dust adhered slightly to the inner wall. However, in the comparative example, as shown in FIG. 8, accumulation of wet dust having a thickness of 10 cm or more was observed on the entire inner wall of the tower, and a part of the dust was fixed by sensible heat of the exhaust gas.

Since the accumulation of dust is caused by unevaporated water droplets adhering to the inner wall of the tower and promoting the agglomeration effect of the dust, it serves as an index for determining whether the water droplets have completely evaporated and stable operation has been performed. Become.

From the test results, it can be seen that the water spray method of the present invention prevents the formation of a low-temperature area in the tower and achieves complete evaporation of water droplets, thereby preventing troubles due to accumulation of wet dust in the tower. It was confirmed that this was an excellent water spray method for a cooling tower.

[0046]

According to the water spray method of the present invention, the spray nozzle is reciprocated along the center of the tower cross section, so that a long-term low-temperature region of gas in the cooling tower can be prevented. Even when the temperature is as low as about 150 ° C., where the generation of dioxins is extremely small, the spray water droplets are effectively evaporated by the spray nozzle, thereby preventing problems such as accumulation of wet dust in the tower due to incomplete evaporation. Exhaust gas cooling becomes possible.

Further, by providing a spray nozzle arranged so as to obtain the symmetry of the water spray flow by the spray nozzle and a simple driving device of the spray nozzle, an excellent temperature-reducing tower having the above effects can be easily obtained. can get.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of an embodiment of a cooling tower according to the present invention.

FIG. 2 is a sectional view taken along a point A in FIG. 1;

FIG. 3 is a perspective view around a spray nozzle driving device according to the present invention.

FIG. 4 is an explanatory view of an installation state when a plurality of spray nozzles according to the present invention are installed.

FIG. 5 is an explanatory diagram of a driving state of a spray nozzle according to the present invention.

FIG. 6 is an explanatory diagram of a reciprocating drive state of a spray nozzle according to the present invention.

FIG. 7 is an explanatory diagram showing an operation result of the water spray method according to the present invention.

FIG. 8 is an explanatory diagram showing operation results of a conventional water spray method.

[Explanation of symbols]

1 ... cooling tower (body part) 2 ... exhaust gas introduction duct 3 ...
Exhaust gas exhaust duct, 4 ... Dust collecting hopper, 5 ... Dust exhaust, 6 ... Spray nozzle, 7 ... Driver, 8 ... Water spray, 9 ... Water supply pipe, 10 ... Air supply pipe, 11 ... Deposited dust .

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masato Kato 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Within Nihon Kokan Co., Ltd. Inside Nippon Kokan Co., Ltd. (72) Inventor Takehiko Inada 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd.

Claims (4)

[Claims] 1. A cooling tower for cooling exhaust gas by water spraying without generating wastewater. A) One or more spray nozzles for water spraying are installed along the circumferential direction of the tower cross section; A water spray method for a cooling tower, characterized in that water spray is performed while reciprocatingly driving at least one of the spray nozzles toward the center of the tower cross section. 2. A water spraying method for a cooling tower according to claim 1, wherein a plurality of spray nozzles to be driven are provided, and the spray nozzles are arranged at positions where two or more axes of linear symmetry exist in the same cross section. 3. The cooling nozzle according to claim 1, wherein when the spray nozzle is driven, a time when the projection length of the spray nozzle is from a minimum to a maximum, or a half of a reciprocating driving cycle is set in the cooling tower. A water spray method for a cooling tower, wherein the average residence time of exhaust gas is 1 to 10 times. 4. A cooling tower for cooling exhaust gas by water spray without generating wastewater, wherein the spray nozzle according to any one of claims 1 to 3 and the spray nozzle are driven in the direction of the center of the cross section of the tower. A cooling tower provided with a water spray device having a driving device for causing the temperature to be reduced.