JP2006002966A - Cooling water multistage spray-type exhaust gas temperature decreasing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the quantity of cooling water in a combustion exhaust gas cooling device of a refuse incinerator, and to miniaturize the device. <P>SOLUTION: In this method of decreasing a temperature of exhaust gas by spraying the cooling water to the high-temperature exhaust gas in the exhaust gas temperature decreasing device, a plurality of cooling water spraying nozzles are mounted inside of the exhaust gas temperature decreasing device, the predetermined quantity of cooling water is supplied to a part of the spraying nozzles, and the quantity of the cooling water supplied to the remaining spraying nozzles is adjusted to keep a set value of the exhaust gas temperature at an exhaust gas outlet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for reducing the temperature of combustion exhaust gas in a waste treatment facility, a boiler facility or the like using a waste incinerator, a waste melting furnace, a waste pyrolysis furnace, or the like.

  In general, the high-temperature combustion exhaust gas discharged from a waste incinerator, etc., recovers heat with an exhaust heat recovery boiler, etc., and then is cooled down to a predetermined temperature with spray water etc. in a temperature reduction device, After being purified, it is dissipated into the atmosphere.

Thus, the temperature of the combustion exhaust gas is usually reduced by providing a cooling water spray nozzle 21 at the upper center of a vertical cylindrical cooling tower 20 having an exhaust gas inlet 20a and an exhaust gas outlet 20b as shown in FIG. By spraying the low-temperature water W supplied through the water supply pipe 22 into the high-temperature exhaust gas G, the high-temperature exhaust gas G is brought to a predetermined temperature (for example, 200 ° C. to 250 ° C.) by sensible heat of water, latent heat of vaporization, and sensible heat of water vapor. I'm trying to cool it down.
In FIG. 2, reference numeral 23 denotes a hollow body having a gas injection port 23a, which is provided in a state of surrounding the cooling water supply pipe 22. Reference numeral 24 denotes a scraper made of a hollow body having a plurality of gas injection ports 24a, and is disposed so as to be rotatable along the inner peripheral surface of the cooling tower 20 (Japanese Patent Laid-Open No. 6-201293).

  In the exhaust gas cooling or the like 20 in FIG. 2 described above, by ejecting gas from the hollow body 23 covering the cooling water supply pipe 22, the temperature-reduced water W is further atomized and the cooling performance is improved. By rotating, it is possible to prevent dust and the like from adhering to the inner wall surface of the cooling tower 20, and an excellent practical utility can be achieved.

  However, in the exhaust gas temperature reducing device configured to spray the temperature-decreasing water W from one place above the inside of the cooling tower 20 as shown in FIG. 2, the supply pressure of the temperature-decreasing water W is increased, or the gas ejection amount is increased. Even if the particle size of spray water is increased and the particle size of spray water is reduced, there is a limit to the improvement of the overall cooling capacity. As a result, the amount of spray water (cooled water amount) is reduced and the cooling tower height (evaporation distance) is significantly increased. There is a difficulty that reduction cannot be achieved.

  On the other hand, as a measure for increasing the exhaust gas cooling capacity in the cooling tower 20 of FIG. 2, sodium bicarbonate is dissolved in advance in the dewarmed water W sprayed into the tower, and this sodium bicarbonate is thermally decomposed when the temperature rises. A method in which the particle size of the spray water is further atomized using the generated carbon dioxide gas (Japanese Patent Laid-Open No. 2002-13880), or pressurization at a temperature higher than the boiling point of water as shown in FIG. The hot water Wt is sprayed as hot water in the high temperature exhaust gas G, and the atomization of water particles is greatly reduced in particle size to increase the evaporation rate in the cooling tower, improving the exhaust gas cooling capacity and exhaust gas cooling. A method (Japanese Patent Laid-Open No. 2000-274654) or the like that enables downsizing of the apparatus has been developed. In FIG. 3, 25 is a hot water production apparatus, 26 is a pressurizing pump, 27 is a flow control valve, and 27 is a temperature controller.

However, in the former method of reducing the temperature of Japanese Patent Application Laid-Open No. 2002-13880, there is a problem that the cost of the drug increases and a step for dissolving the drug in the dewarmed water is required, which increases the running cost of the exhaust gas temperature reducing device. is there.
Further, even in the latter method of temperature reduction disclosed in JP 2000-274654, the hot water production apparatus 25 and the hot water supply pump 26 are required, and the equipment cost and running cost are increased.

  Further, in each of the conventional exhaust gas temperature reducing devices, since the temperature-reducing water is sprayed from one place in the temperature reducing device (for example, the upper central portion of the temperature reducing tower), the dust on the inner wall surface of the temperature reducing device is reduced. The amount of adhesion tends to increase, and particularly when the exhaust gas temperature at the outlet of the temperature reducing device is set to a low temperature of 170 ° C. or lower, there is a problem that it is difficult to suppress the increase in the amount of dust adhesion.

JP-A-6-201293 JP 2002-13880 A JP 2000-274654 A

  The present invention has a problem as described above in the conventional combustion exhaust gas temperature reduction system such as this kind of incinerator, that is, it is difficult to further downsize the temperature reduction device, and the exhaust gas temperature is as low as about 170 ° C. In order to solve this problem, the amount of dust adhering to the inner wall surface of the temperature reducing device increases rapidly and cannot be reduced. High-temperature combustion exhaust gas such as waste incinerators that can reduce the amount of sprayed water, reduce the size of the temperature-reducing device, and reduce the amount of dust adhering without causing a significant increase in equipment costs by dispersing appropriately. A method for reducing the temperature is provided.

  The inventors repeated a number of exhaust gas temperature reduction tests using various conventional temperature reduction devices in order to achieve a reduction in the amount of water to be reduced, a reduction in the size of the temperature reduction device, and a reduction in the amount of dust attached. . Then, from these test results and analysis thereof, the inventors of the present application have departed from the fixed idea of spraying the temperature-reduced water from one location inside the temperature-reduction device, and the temperature-reduced water from a plurality of locations in the temperature-reduction device. The spray provided in the temperature reducing device is designed to reduce the amount of dust adhering to the inner wall surface of the temperature reducing device while efficiently reducing the exhaust gas temperature with a smaller amount of temperature reducing water. Various exhaust gas temperature reduction tests were repeated using the position of the nozzle and the amount of spray as parameters.

  The invention of the present application was created through the above-described process, and the invention of claim 1 is a method for reducing the temperature of exhaust gas in which low-temperature water is sprayed on high-temperature exhaust gas in an exhaust gas temperature reducing device. A plurality of temperature-reduced water spray nozzles are provided inside the exhaust gas temperature reducing device, and a predetermined amount of temperature-reduced water is supplied to some of the spray nozzles, and the amount of temperature-reduced water supplied to the remaining spray nozzles By adjusting the above, the basic configuration of the invention is that the exhaust gas temperature at the exhaust gas outlet is held at a set value.

  The invention of claim 2 is the invention of claim 1, wherein the temperature-reducing water spray nozzles are arranged above and below the exhaust gas temperature reducing device, and the high temperature exhaust gas is circulated in the exhaust gas temperature reducing device in an upward flow. While supplying a certain amount of temperature-reduced water to the temperature-reduced water spray nozzle located in the upper part, the amount of temperature-reduced water supplied to the temperature-reduced water spray nozzle located in the lower part is adjusted.

  The invention of claim 3 is the invention of claim 1, wherein the temperature-reduced water spray nozzles are arranged above and below the exhaust gas temperature reducing device, and the high temperature exhaust gas is circulated in the exhaust gas temperature reducing device in a downward flow. A certain amount of temperature-reduced water is supplied to the temperature-reduced water spray nozzle located below, and the amount of temperature-reduced water supplied to the temperature-reduced water spray nozzle located above is adjusted.

  According to a fourth aspect of the present invention, there is provided an exhaust gas temperature reducing device and an exhaust gas temperature reducing method in which reduced temperature water is sprayed on high temperature exhaust gas in an exhaust gas duct connected to the exhaust gas temperature reducing device. A plurality of temperature-reduced water spray nozzles are provided in the exhaust gas by supplying a predetermined amount of temperature-reduced water to some of the spray nozzles and adjusting the amount of temperature-reduced water supplied to the remaining spray nozzles. The basic configuration of the invention is that the exhaust gas temperature at the exhaust gas outlet of the duct is maintained at a set value.

  According to a fifth aspect of the present invention, in the invention of the fourth aspect, the dehumidified water spray nozzles are disposed in the upper and lower portions of the exhaust gas temperature reducing device and in the longitudinal passage portion of the exhaust gas duct, and the high temperature exhaust gas is introduced into the exhaust gas temperature reducing device. Is supplied to the upper part of the exhaust gas temperature reducing device and the reduced temperature water spray nozzle located in the exhaust gas duct, and the temperature reducing water located in the lower part of the exhaust gas temperature reducing device. The amount of temperature-reduced water supplied to the spray nozzle is adjusted.

  According to a sixth aspect of the present invention, in the fourth aspect of the present invention, the dehumidified water spray nozzle is disposed in the upper and lower portions of the exhaust gas temperature reducing device and in the longitudinal passage of the exhaust gas duct, and the high temperature exhaust gas is introduced into the exhaust gas temperature reducing device. Is supplied in a downward flow to supply a certain amount of temperature-reduced water to the temperature-reduced water spray nozzle located below and in the exhaust-gas duct, and to the temperature-reduced water spray nozzle located above the temperature-reduction device. The amount of dewarmed water supplied is adjusted.

  The invention of claim 7 is the invention of claim 1 or claim 4, wherein the temperature-decreasing water is composed of pressurized hot water having a temperature higher than the boiling point of water under atmospheric pressure, or a mixture of water and gas. It is designed to be a fluid.

In the present invention, the sprayed portions of the dehumidified water into the high-temperature exhaust gas are dispersed in a plurality of locations, so the amount of spray water from one location is reduced, and as a result, the contact efficiency between the spray water and the exhaust gas is improved and the cooling capacity is increased. And the sprayed water droplets can be easily evaporated.
This makes it possible to reduce the total amount of water required for temperature reduction compared to the case where sprayed temperature reduction water is sprayed from one location in the past, while reducing the size of the temperature reduction device and reducing the amount of dust adhering to the inner wall surface of the temperature reduction device. Etc. can be achieved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall system diagram of a multistage spray-type exhaust gas temperature reducing device A for temperature-reducing water that is an object of the present invention.

In FIG. 1, A is a multistage spray type exhaust gas temperature reducing device, 1 is an apparatus body, 1a is a high temperature exhaust gas inlet, 1b is an exhaust gas outlet, 2 is an exhaust gas duct, 2a is a low temperature exhaust gas outlet, and 3 is a first stage spray. Nozzle, 4 is a second stage spray nozzle, 5 is a third stage spray nozzle, T ₁ is a temperature detector for high temperature exhaust gas, T ₂ is an exhaust gas temperature detector inside the apparatus body, and T ₃ is an exhaust gas at the exhaust gas outlet of the apparatus body Temperature detector, T ₄ is an exhaust gas temperature detector at the duct outlet, 6 is a temperature controller, 7 is a temperature-reducing water amount controller, 8 is a pressurizing pump, 9a, 9b and 9c are flow control valves, and 10 is a temperature-reducing water tank. It is.

  The main body 1 of the exhaust gas temperature reducing device A is substantially the same as the conventional temperature reducing device main body, and is formed in a vertical cylindrical shape, with an exhaust gas outlet 1b at the upper side and an exhaust gas inlet at the lower side. 1a is formed. An exhaust gas duct 2 is connected to the exhaust gas outlet 1b, and its downstream side is connected to an exhaust gas treatment device (not shown).

A first-stage spray nozzle 3 and a second-stage spray nozzle 4 are provided at a lower position and an upper position inside the apparatus main body 1, and the high-temperature exhaust gas G becomes a so-called upward flow and flows upward from below. Flowing, the dewarmed water W is sprayed in the same direction.
The first stage spray nozzle 3 is disposed at substantially the same height as the high temperature exhaust gas inlet 1a. In addition, the third spray nozzle is disposed in a vertical channel portion in the exhaust gas duct 2 in a posture to spray spray water in the same direction as the exhaust gas flow.

  1, a total of three spray nozzles 3, 4, and 5 are provided. However, the nozzle 5 in the duct 2 may be removed, and three spray nozzles may be provided only in the apparatus main body 1. Of course, the number of nozzles in the apparatus main body 1 and the duct 2 may be appropriately increased or decreased.

  The structure of the spray nozzle used for the spray nozzles 3, 4 and 5 may be any structure including a two-fluid system, and it is desirable that the spray water particle size be as small as possible.

The exhaust gas temperature detectors T ₁ , T ₂ , T ₃ , and T ₄ are the high temperature exhaust gas temperature at the exhaust gas inlet 1 a, the exhaust gas temperature between the spray nozzles 3 and 4 inside the apparatus body 1, and the exhaust gas from the apparatus body 1. The temperature of the exhaust gas at the outlet 1b and the temperature of the exhaust gas at the duct outlet 2a are detected, respectively, and the amount of temperature-reduced water supplied to the spray nozzles 3, 4 and 5 via the temperature controller 6 and the temperature-reduced water amount controller 7, respectively. Adjust automatically.

The temperature-reduced water W is stored in the temperature-reduced water tank 10, and in this embodiment, the room-temperature temperature-reduced water W pressurized to an appropriate pressure by the pressure pump 8 is supplied to the spray nozzles 3, 4, 5. .
Note that the dewarmed water W includes not only room temperature water but also pressurized hot water having a temperature higher than the boiling point of water under atmospheric pressure, such as all the spray nozzles 3, 4, 5, or some spray nozzles (for example, second nozzles). You may make it supply to the stage spray nozzle 4 and the 3rd stage spray nozzle 5).

  In addition, so-called blow water from boiler equipment may be used as pressurized hot water, and in the case of hot water spraying, the evaporation time is shorter than in the case of normal temperature water spraying due to micronization phenomenon due to boiling, The spray space (that is, the height dimension of the apparatus main body 1) can be further reduced.

  Furthermore, the temperature-reduced water W can be so-called two-fluid temperature-reduced water, and a mixed fluid such as water and air can be used as the temperature-reduced water W.

  In addition, in the embodiment shown in FIG. 1, the high temperature exhaust gas G is used as an upward flow, but it is needless to say that the high temperature exhaust gas G may be used as a downward flow. In this case, the exhaust gas duct is connected to an exhaust gas outlet provided below the apparatus main body.

Next, a method for reducing the temperature of the high temperature exhaust gas G according to the present invention will be described.
With reference to FIG. 1, first, the case where the third stage spray nozzle 5 is not installed in the exhaust gas duct 2 or the case where the third stage spray nozzle 5 is installed but not operated will be described.
First, the exhaust gas temperature T ₃ s at the exhaust gas outlet 1b of the main body 1 is set. Then, from the total flow rate and the setting of the exhaust gas of the exhaust gas outlet 1b temperature T ₃ s like high-temperature exhaust gas G flowing from the exhaust gas inlet 1a of the body 1, the reduced hot water W ₂ of constant flow rate was constant in advance by heat calculation above A fixed amount is supplied to the second stage spray water nozzle 4 located in the position and sprayed into the high temperature exhaust gas G.

In parallel with the spraying of the decreased hot water W _2, the flow rate of the reduced hot water W ₁ to spray from the first-stage spray nozzle 3 positioned below the apparatus main body 1, based on the detection value of the exhaust gas temperature detector T ₃ Control is performed by adjusting the opening degree of the flow rate control valve 9a via the temperature controller 6, and the exhaust gas temperature at the exhaust gas outlet 1b is maintained at the set temperature T ₃ s.

As an example, the temperature of the high-temperature exhaust gas G flowing into the exhaust gas temperature reducing device main body 1 is 240 ° C., the flow rate is 50,000 Nm ³ / min, the exhaust gas temperature set value 160 ° C. at the main body outlet 1b, the temperature of the dewar water W is 20 ° C. When the pressure is 5.0 kg / cm ² , the supply amount of dewarmed water to the second stage spray nozzle 4 is set to a flow rate of 490 L / min, and the amount of spray water from the first stage spray nozzle 3 at that time is about 1450 L / min. Based on the above, flow control is performed.

In addition, when the flow of the exhaust gas G is downward, a certain amount of temperature-reduced water is supplied to the spray nozzle located below the apparatus main body 1 and the temperature-reduced water to the spray nozzle located above the apparatus main body 1 is used. The supply amount is adjusted via the temperature controller 6 or the like.
In addition, when two or more spray nozzles are provided in the apparatus main body 1, they are appropriately grouped so that a certain amount of dewarmed water is supplied to one and the other is reduced while controlling the flow rate. Supply hot water.
Furthermore, in this embodiment, while supplying a certain amount of dewarmed water W ₂ to the upper second stage spray nozzle 4, the dewar water W ₁ flow rate control to be fed to the lower first stage spray nozzle 3 is controlled. Although are so performed, on the contrary, the reduced amount of hot water W ₂ flow rate of the second-stage spray nozzle 4 side so as to adjust the control while reducing the hot water W ₁ supplied a constant flow rate to the first stage spray nozzle 3 May be.

Next, the case where the dewarmed water W _{3 is} sprayed into the exhaust gas duct 2 will be described.
In this case, first, the exhaust gas temperature T ₄ s at the exhaust gas outlet 2a of the duct 2 is set (for example, 160 ° C. to 200 ° C.).
Next, the temperature-decreasing water W ₂ and the temperature-decreasing water W ₃ having flow rates calculated in advance from the exhaust gas temperature T ₄ s and the temperature and inflow amount of the high-temperature exhaust gas G are supplied to the second-stage spray nozzle 4 and the third-stage spray nozzle 5. A fixed amount is supplied and sprayed.

Further, the flow rate of the warm water W ₁ sprayed from the first stage spray nozzle 3 in parallel with the supply of the warm water W ₂ and the warm water W ₃ is controlled by adjusting the opening of the flow control valve 9a in the same manner as described above. The exhaust gas temperature at the duct exhaust gas outlet 2a is maintained at the set temperature T ₄ s.

As an example, the temperature of the high-temperature exhaust gas G is 240 ° C., the inflow rate is 50,000 Nm ³ / min, the exhaust gas temperature setting value 170 ° C. at the main body outlet 1b, the exhaust gas temperature setting value 160 ° C. at the duct outlet 2b, the temperature of the dewar water W 20 ° C. When the applied pressure is 5.0 kg / cm ² , the dewarmed water supply amount to the second stage spray nozzle 4 is set to 730 L / min, and the dewarmed water supply amount to the third stage spray nozzle 5 is set to 230 L / min. The amount of water sprayed from the first stage spray nozzle 3 is controlled based on about 900 L / min.

Even in the case where the temperature-reduced water is sprayed into the exhaust gas duct 2 at the same time, the amount of the temperature-reduced water W ₂ supplied to the second-stage spray nozzle 4 located in the upper part of the apparatus main body 1 is controlled to be located below. A fixed amount of dewarmed water W ₁ may be supplied to the first stage spray nozzle 3.
Further, a plurality of spray nozzles are arranged in the exhaust duct 2 to reduce the temperature of the high-temperature exhaust gas to a predetermined temperature only in the exhaust duct 2, that is, the exhaust duct 2 itself is used as the main body 1 of the temperature reducing device A. Of course, it is possible to reduce the temperature of the high-temperature exhaust gas.

Using the temperature reducing device A having the same outer dimensions, the amount of inflow and temperature of the high temperature exhaust gas G, the temperature and pressure of the reduced temperature water W are the same, and the reduced temperature water W is sprayed only from the first stage spray nozzle 3 The comparison was made with the case where the dewarmed waters W ₁ and W ₂ were sprayed by the two-stage method of the present invention.

  As a result, when the amount of spray dewarming water was the same, in the present invention, the exhaust gas temperature at the exhaust gas outlet 1b could be lowered by about 10 ° C. compared to the former case.

  Further, when the exhaust gas temperature at the exhaust gas outlet 1b was made the same, the amount of vertical spray water was reduced by about 20% compared to the case of one-stage spray.

  Furthermore, the amount of dust adhering to the inner wall surface of the temperature reducing device main body was also compared. It was found that the amount was reduced by about 70%.

  The present invention is mainly applied to cooling combustion exhaust gas discharged from a waste treatment facility, a boiler facility, etc. using a waste incinerator, a waste melting furnace, a waste gasification treatment furnace, etc. The present invention can be applied not only to a cooling device but also to exhaust gas cooling in an exhaust gas duct or the like.

1 is an overall system diagram of a multistage spray exhaust gas temperature reducing device to which the present invention is applied. It is a longitudinal section schematic diagram showing an example of a conventional exhaust gas temperature reducing device. It is a systematic diagram showing an example of other conventional exhaust gas temperature reducing devices.

Explanation of symbols

A is a multi-stage spray type exhaust gas temperature reducing device G is a high temperature exhaust gas G _O is a low temperature exhaust gas 1 is a main body 1a of the exhaust gas temperature reducing device 1a is a high temperature exhaust gas inlet 1b is an exhaust gas outlet 2 is an exhaust gas duct 2a is a low temperature exhaust gas outlet 3 is a first stage spray nozzle 4 and the second stage the spray nozzle 5 the exhaust gas temperature detector T ₄ temperature detector T ₂ are the exhaust gas temperature detector T ₃ is the body waste gas outlet of the inner body of the third-stage spray nozzles T ₁ is a high temperature exhaust gas Exhaust gas temperature detectors T _3S and T _{4S at the} duct outlet are the exhaust gas temperature set value 6 is the temperature controller 7 is the temperature-reducing water amount controller 8 is the pressurizing pump 9a, 9b and 9c is the flow rate control valve 10 is the de-warming water tank

Claims (7)

  In the exhaust gas temperature reducing method in which the low temperature water is sprayed on the high temperature exhaust gas in the exhaust gas temperature reducing device, a plurality of temperature reducing water spray nozzles are provided inside the exhaust gas temperature reducing device, and some of them are provided. A configuration in which the exhaust gas temperature at the exhaust gas outlet is held at a set value by supplying a predetermined amount of dewar water to the spray nozzle and adjusting the amount of dewar water supplied to the remaining spray nozzle. Multi-stage spray-type exhaust gas temperature reduction method featuring reduced temperature water.   A temperature-reduced water spray nozzle is arranged above and below the exhaust gas temperature reducing device, and high-temperature exhaust gas is circulated in the exhaust gas temperature reducing device in an upward flow, and a certain amount of water is supplied to the temperature-reduced water spray nozzle located in the upper part. The multistage spray-type exhaust gas temperature reduction method of temperature-reduced water according to claim 1, wherein the amount of temperature-reduced water supplied to the temperature-reduced water spray nozzle located in the lower part is adjusted while supplying the temperature-reduced water.   The temperature-reducing water spray nozzles are arranged above and below the exhaust gas temperature reducing device, and the high-temperature exhaust gas is circulated in the exhaust gas temperature reducing device in a downward flow, and a certain amount of reduction is made to the temperature-reducing water spray nozzle located below. The multistage spray-type exhaust gas temperature reduction method of temperature-reduced water according to claim 1, wherein the amount of temperature-reduced water supplied to the temperature-reduced water spray nozzle located above is adjusted while supplying warm water.   In an exhaust gas temperature reducing device and an exhaust gas temperature reducing method in which reduced temperature water is sprayed on high temperature exhaust gas in an exhaust gas duct connected to the exhaust gas temperature reducing device, a plurality of reduced temperature water sprays are provided inside the exhaust gas temperature reducing device and the exhaust gas duct. At the exhaust gas outlet of the exhaust gas duct, nozzles are provided and a predetermined amount of dewarmed water is supplied to some of the spray nozzles, and the amount of dewarmed water supplied to the remaining spray nozzles is adjusted. A multistage spray-type exhaust gas temperature reduction method for reduced temperature water, characterized in that the exhaust gas temperature is maintained at a set value.   A temperature-reduced water spray nozzle is disposed in the upper and lower portions of the exhaust gas temperature reducing device and in the longitudinal passage portion of the exhaust gas duct, and high-temperature exhaust gas is circulated in the exhaust gas temperature reducing device in an upward flow. A certain amount of temperature-reduced water is supplied to the upper part and the temperature-reduced water spray nozzle located in the exhaust gas duct, and the amount of temperature-reduced water supplied to the temperature-reduced water spray nozzle located in the lower part of the exhaust gas temperature reduction device is adjusted. 5. The multistage spray-type exhaust gas temperature reduction method for temperature-reduced water according to claim 4.   The temperature-reduced water spray nozzles are arranged in the upper and lower portions of the exhaust gas temperature reducing device and in the vertical passage of the exhaust gas duct, and the high temperature exhaust gas is circulated in the exhaust gas temperature reducing device in a downward flow. 5. A predetermined amount of temperature-reduced water is supplied to the temperature-reduced water spray nozzle located below and in the exhaust gas duct, and the amount of temperature-reduced water supplied to the temperature-reduced water spray nozzle located above the temperature reducing device is adjusted. Multistage spray type exhaust gas temperature reduction method described in 1.   The temperature-reduced water according to claim 1 or 4, wherein the temperature-reduced water is pressurized hot water having a temperature higher than the boiling point of water under atmospheric pressure or a fluid comprising a mixture of water and gas. Multistage spray type exhaust gas temperature reduction method.

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