JP4437957B2 - High temperature exhaust gas treatment method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for reducing the temperature of high-temperature exhaust gas generated when melting incineration residue of municipal waste and / or industrial waste in a melting furnace.

  Conventionally, methods such as water injection and air injection using a spray nozzle have been used as a method for reducing the temperature of high-temperature exhaust gas of 1000 ° C or higher generated when melting incineration residue of municipal waste and / or industrial waste in a melting furnace. It has been. In this case, since the resynthesis of dioxins which are harmful substances in the exhaust gas is remarkable at 300 to 400 ° C., the exhaust gas needs to be cooled to a temperature of 200 ° C. or less in the temperature reducing device.

  However, high-temperature exhaust gas contains a lot of adherent salts, and when a large amount of water is sprayed from the spray nozzle, non-evaporated water is generated and there is a problem of salt fixation due to water adhesion to the inner wall of the temperature reducing device. It becomes. For this reason, when it is going to fully evaporate the injected water, the problem that a temperature reduction apparatus will enlarge will arise. Further, if there is not enough water to be injected, a new problem arises that the high-temperature exhaust gas enters the exhaust gas treatment facility in the subsequent stage without being sufficiently reduced in temperature by the temperature reducing device, and the exhaust gas treatment facility is damaged. Thus, for example, Patent Document 1 attempts to prevent the cooling water from adhering to the inner surface of the temperature reducing device by supplying the cooling water upward when the exhaust gas is in an upward flow.

On the other hand, Patent Document 2 discloses a method by air cooling, and Patent Document 3 discloses a method of cooling high-temperature exhaust gas by liquid injection while swirling with swirl vanes.
Japanese Patent No. 3257466 Japanese Patent No. 3202453 JP-A-10-267256

  However, in patent document 1, in the high temperature exhaust gas from a melting furnace, the amount of water injection with respect to the amount of exhaust gas becomes large, and it takes time to evaporate. In addition, the upward exhaust gas easily contacts the surface of the spray nozzle, causing dust around the nozzle, and when dust starts to adhere around the nozzle, cooling water spraying with an appropriate particle size is performed. It becomes difficult. That is, in the temperature range of 700 to 800 ° C. near the melting point of the salt, the semi-molten salt is very firmly fixed to the inner surface of the temperature reducing device and the periphery of the spray nozzle, and the fixed matter does not easily fall off. However, such a temperature region is unavoidable due to the limitation of the evaporation rate of water. In addition, when a dust discharge device for discharging dust attached to the inner wall of the temperature reducing device is provided, the damage rate of the dust discharge device is increased by the high-temperature exhaust gas if the water injection amount is small.

  On the other hand, Patent Document 2 has a problem that the exhaust gas after cooling becomes five times or more, and the downstream process of the exhaust gas treatment becomes large. Further, in Patent Document 3, sufficient swirling cannot be obtained with a small amount of exhaust gas at a high temperature such as molten exhaust gas, and salt sticking to the swirl vane becomes a problem.

  The present invention has been made in consideration of the above-described problems in high-temperature exhaust gas treatment, and can effectively reduce the temperature of high-temperature exhaust gas generated from a melting furnace, and can also be used around the spray nozzle and the inner wall surface. The present invention provides a high-temperature exhaust gas treatment method and apparatus capable of reducing the temperature of high-temperature exhaust gas without adhering to the dust.

  The invention according to claim 1 is a method for reducing the temperature of a high temperature exhaust gas generated when melting incineration residue of municipal waste and / or industrial waste in a melting furnace using a temperature reducing device. The cooling gas is supplied so as to form a swirling flow accompanying the upward high-temperature exhaust gas introduced in the above, and the cooling water is sprayed downward from the top of the temperature reducing device to reduce the temperature of the high-temperature exhaust gas. It is characterized by processing.

  The invention according to claim 2 is an apparatus for reducing the temperature of high-temperature exhaust gas generated when melting incineration residue of municipal waste and / or industrial waste in a melting furnace, and the high temperature of the upward flow introduced into the apparatus main body. A cooling gas nozzle for supplying a cooling gas so as to form a swirl flow accompanying the exhaust gas, and a cooling water spray nozzle for spraying the cooling water downward from the top in the apparatus main body are provided. is there.

  According to a third aspect of the present invention, the apparatus main body is formed in a cylindrical shape extending vertically, and an inlet nozzle for high temperature exhaust gas is provided at the lower part of the apparatus main body. It is preferable to provide the cooling gas nozzle in a state inclined with respect to the direction.

  As in the fourth aspect of the invention, it is preferable to provide a high temperature exhaust gas outlet nozzle at the periphery of the top of the apparatus main body and a cooling water spray nozzle at the center of the top of the apparatus main body.

  As in the fifth aspect of the invention, the cooling water spray nozzle is preferably formed so that the water droplet spray angle is an angle of 90 degrees or less.

  As in the invention described in claim 6, it is preferable that the tip of the cooling water spray nozzle protrudes from the inner wall surface of the apparatus main body by 30 cm or more.

  More preferably, the tip of the cooling water spray nozzle is protruded from the inner wall surface of the apparatus main body within a range of 50 to 150 cm.

  According to the first and second aspects of the present invention, the cooling gas is supplied to the upward high-temperature exhaust gas introduced into the temperature reducing device so as to form a swirling flow. The exhaust gas is swirled by the swirling flow of the cooling gas even with a small amount of the high-temperature exhaust gas such as the high-temperature exhaust gas. Further, the high-temperature exhaust gas is efficiently reduced in temperature by the strong stirring action of the upward-flowing high-temperature exhaust gas mixed with the cooling gas and the cooling water jetted in the opposite direction.

  In addition, since the cooling water is sprayed downward from the top of the temperature reducing device main body, the salt and dust in the exhaust gas do not come into direct contact with the tip of the cooling water spray nozzle, and the tip of the cooling water spray nozzle Salts are less likely to stick. Thereby, even if it drive | operates for a long time, a cooling water can always be sprayed in a suitable state.

  In addition, since cooling by both cooling gas and cooling water is adopted, the amount of sprayed water can be reduced compared to the temperature reduction method using only the cooling gas, and the sprayed water is completely evaporated by a strong stirring action. As a result, it becomes difficult for salt to adhere to the inner wall of the temperature reducing device due to the non-evaporated water.

  As a result, an increase in the size of the temperature reducing device is prevented, and even when a dust discharging device for discharging dust from the temperature reducing device is provided, the problem that the dust discharging device is damaged by the high temperature exhaust gas does not occur.

  According to the third aspect of the present invention, the apparatus main body is formed in a cylindrical shape extending vertically, the high temperature exhaust gas inlet nozzle is provided at the lower part of the apparatus main body, and the lower part of the apparatus main body is provided at a portion below the height of the inlet nozzle. Since the cooling gas nozzle is provided in a state inclined with respect to the circumferential direction, the cooling gas is supplied to the upward high-temperature exhaust gas introduced into the apparatus body so as to form a swirling flow. The

  According to the invention described in claim 4, since the outlet nozzle for the high temperature exhaust gas is provided in the peripheral part of the top part of the apparatus main body and the cooling water spray nozzle is provided in the center part of the top part of the apparatus main body, A strong stirring action of the flowing high temperature exhaust gas and the cooling water jetted in the opposite direction can be obtained.

  According to the invention described in claim 5, by setting the water droplet spray angle of the cooling water spray nozzle to 90 degrees or less, the end flow of the water spray flow does not reach the inner wall surface of the apparatus main body and is not evaporated on the inner wall surface. As a result of being able to evaporate completely without adhering moisture, dust is less adhered. Thereby, mixing with a high temperature exhaust gas and residence time become long, and salt fixation to the inner wall of the temperature reducing apparatus by non-evaporated water can be further prevented.

  According to the inventions of claims 6 and 7, by causing the tip of the cooling water spray nozzle to protrude from the inner wall surface by 30 cm or more, preferably 50 to 150 cm, the end flow of the water spray flow is caused by fluctuations or drift of the exhaust gas flow. There is no possibility of reaching the exhaust gas outlet nozzle provided at the periphery of the top of the apparatus main body. Thereby, it is possible to perform the temperature reduction treatment by completely evaporating the non-evaporated water together with the exhaust gas whose temperature has been reduced without being accompanied by the exhaust gas treatment facility at the subsequent stage.

  FIG. 1 shows an example of the overall configuration of a waste incineration residue melting treatment facility for carrying out the high-temperature exhaust gas treatment method of the present invention.

  In FIG. 1, 1 is an ash feeder, 2 is a plasma melting furnace as a melting furnace, 6 is a slag cooling device, 7 is a slag hopper, 9 is a molten exhaust gas temperature reducing tower as a temperature reducing device, 10 is a bag filter, 11 is A molten fly ash solidifying device, 12 is a solidified bunker, 14 is a molten exhaust gas cleaning treatment device, 15 is a reheater, and 16 is an induction blower.

  As shown in FIG. 1, the ash supply device 1 quantitatively supplies ash as an incineration residue of municipal waste and / or industrial waste to the plasma melting furnace 2 with a screw conveyor, for example.

  The plasma melting furnace 2 melts the ash by high temperature plasma generated by the plasma torch 3. The molten slag is extracted from the slag discharge port 4, and a water tank (not shown) of the slag cooling device 6 is submerged to lower the temperature, and then guided to the slag hopper 7. The low-temperature slag is transported out of the facility by the truck 8 from the slag hopper 7 and is effectively used as an asphalt mixture.

  On the other hand, the high-temperature molten exhaust gas (high-temperature exhaust gas) from the plasma melting furnace 2 is discharged from the furnace side portion 5 and led to the molten exhaust gas temperature reducing tower 9 on the downstream side. As will be described in detail later, the temperature of the molten exhaust gas is lowered by mixing with cooling water and cooling air.

  The low-temperature molten exhaust gas is dedusted by the bag filter 10 at the subsequent stage, subjected to desalting and desulfurization processing by the molten exhaust gas cleaning processing device 14, and then discharged to the outside by the induction blower 16 through the reheater 5. .

  On the other hand, the dust discharged from the molten exhaust gas temperature reducing tower 9 and the bag filter 10 is solidified by the molten fly ash solidifying device 11 and guided to the solidified bunker 12. From the solidified bunker 12, the solidified material is carried out by a truck 13 to a solidified material processing plant outside the facility.

  Hereinafter, the structural example of the molten exhaust gas temperature-reduction tower as an exhaust gas processing apparatus which concerns on one Embodiment of this invention is shown. 2 is a longitudinal sectional view of the molten exhaust gas temperature reducing tower, FIG. 3 is a partially enlarged view of FIG. 2, FIG. 4 is a sectional view taken along line AA in FIG. 2, and FIG. 6 is a sectional view taken along line CC.

  As shown in FIGS. 2 to 6, the tower main body (apparatus main body) 91 of the molten exhaust gas temperature reducing tower 9 is formed in a cylindrical shape extending vertically. An inlet nozzle 92 for molten exhaust gas is provided at the lower portion of the tower main body 91, and six nozzles are inclined at substantially the same direction with respect to the circumferential direction of the lower portion of the tower main body 91 at a portion below the height of the inlet nozzle 92. The cooling gas nozzle 96 is provided. Each cooling gas nozzle 96 penetrates the peripheral wall of the tower body 91 and is connected to a cooling air header 96a, and cooling air (cooling gas) is supplied from the cooling air header 96a.

  In addition, an outlet nozzle 93 for molten exhaust gas is provided at one peripheral portion of the top of the tower main body 91, and one cooling water spray nozzle 95 is provided at the center of the top of the tower main body 91. The cooling water spray nozzle 95 protrudes downward from the inner wall surface at the top of the tower body 91 by a nozzle insertion length L so that the cooling water can be sprayed at a spray angle α. The nozzle insertion length L and the spray angle α are set based on experimental results to be described later.

  Further, at the bottom of the tower main body 91, a dust scraper (dust discharge device) 97 is provided for collecting the dust adhering to the inner wall of the tower main body 91 by scraping the blade 97b rotated by the motor 97a. A discharge port 94 is provided for discharging the scraped dust.

  Hereinafter, the function of the molten exhaust gas temperature reducing tower 9 will be described.

  First, the high-temperature molten exhaust gas is introduced from the lower portion of the tower main body 91 along the circumferential tangent line by the inlet nozzle 92 as shown in FIG.

  The cooling air is supplied to a cooling air header 96a attached to the outer periphery of the lower portion of the tower main body 91 using a blower (not shown). As shown in FIG. 6, the cooling air appropriately dispersed from the cooling air header 96 a is projected along the circumferential tangent line of the tower main body 91 by the six cooling gas nozzles 96 protruding into the tower main body 91. It is blown so as to form a swirling flow accompanying the molten exhaust gas. In order to form this swirling flow, the superficial velocity of the molten exhaust gas mixed with the cooling air (the velocity of the mixture of the molten exhaust gas and the cooling air in the tower main body 91 of the molten exhaust gas temperature-decreasing tower 9) is set to 0. 5 m / sec or more is desirable.

  The cooling air also serves to cool the blades 97b and the like of the dust scraper 97. The supply amount of the cooling air is controlled based on, for example, a detection value of a thermometer 96b inserted slightly above the molten exhaust gas inlet nozzle 92. Specifically, by controlling so that the temperature after mixing the cooling air and the molten exhaust gas is 400 to 500 ° C., a temperature range (700 to 900 ° C.) in which salts are likely to adhere to the inner wall of the tower body 91. ) Can be avoided to prevent this salt sticking.

  The molten exhaust gas mixed with the cooling air rises while forming a swirling flow to become a so-called swirling upward flow, and the cooling water blown downward at the spray angle α by the cooling water spray nozzle 95 as shown in FIGS. The temperature is reduced to about 200 ° C. by the strong stirring action. The supply amount of the cooling water is controlled based on, for example, a detection value of a thermometer 93a provided in the melted exhaust gas outlet nozzle 93. At this time, the cooling water is sprayed in the opposite direction to the swirling upward flow of the mixture of the exhaust gas and the cooling air, so that it completely evaporates on the way and does not reach the inner wall of the apparatus main body 91. Further, since a sufficient residence time for evaporating the sprayed cooling water can be obtained, the height of the tower main body 91 required for this complete evaporation can be reduced and the size can be reduced.

  Dust generated in the tower body 1 is scraped off and collected by the blade 97b rotated by the motor 97a of the dust scraper 97, and is discharged from the dust discharge port 94.

  Below, the experimental result of this invention is demonstrated.

  Table 1 shows experimental conditions such as properties of the exhaust gas entering the molten exhaust gas temperature reducing tower 9 and spraying conditions.

  From the experimental results based on the experimental conditions and the like, the optimum performance of the cooling water spray nozzle 95 was obtained as follows. In addition, the superficial velocity in the tower main body 91 of the molten exhaust gas temperature reducing tower 9 is 0.5 m / sec or more as described above.

  7A and 7B are explanatory views showing the trajectory of the spray cooling water, wherein FIG. 7A is a longitudinal sectional view, and FIG. 7B is a transverse sectional view. Here, spraying was performed at a spray angle α = 30 ° (degrees) using a cooling water spray nozzle 95 having a nozzle insertion length L = 100 cm into the tower main body 91 of the molten exhaust gas temperature reducing tower 9.

  As shown in FIGS. 7A and 7B, the sprayed cooling water gradually decreases in water droplet diameter of 47 μm while swirling in association with the upward flow of the mixture of molten exhaust gas and cooling air. Evaporation is completed without adhering to the inner wall surface of the tower main body 91 and without the unevaporated water accompanying the molten exhaust gas to the subsequent stage.

  FIG. 8 is an explanatory view showing the temperature distribution in the molten exhaust gas temperature reducing tower at this time. As shown in the figure, the 1344 ° C. molten exhaust gas entering the tower main body 91 of the molten exhaust gas temperature-decreasing tower 9 is rapidly cooled to about 300 ° C., and the outlet nozzle of the tower main body 91 of the molten exhaust gas temperature-decreasing tower 9. In the vicinity of 93, the temperature is reduced to 200 ° C.

  And as a result of experimenting by changing only the spray angle α of the cooling water spray nozzle 95 in the experimental conditions, the spray angle α is an angle of 90 ° or less, preferably an angle in the range of 20-40 °, Regardless of the nozzle insertion length L, the end flow of the water spray does not reach the side wall of the tower main body 91 and can be completely evaporated without adhering non-evaporated moisture to the inner wall surface. Less adherence. As a result, it was confirmed that the mixing with the high temperature exhaust gas and the residence time became longer, and it was possible to prevent the salt from adhering to the inner wall of the temperature reducing device due to the non-evaporated water.

  Moreover, as a result of experimenting by changing only the nozzle insertion length L of the cooling water spray nozzle 95 in the experimental condition, the nozzle insertion length L is set to 30 cm or more, preferably 50 to 150 cm, whereby the spray angle α Regardless of the above, there is no possibility that the end flow of the water spray flow reaches the molten exhaust gas outlet nozzle 93 provided at the periphery of the top of the tower main body 91 due to the fluctuation or drift of the exhaust gas flow. Thus, it was confirmed that the temperature can be reduced by reliably evaporating the melted exhaust gas from which the unevaporated moisture has been reduced without being accompanied by the exhaust gas treatment facility (such as the bag filter 10) in the subsequent stage.

  As described above, according to the present embodiment, the cooling air is supplied from the cooling gas nozzle 96 so as to form a swirling flow accompanying the upward flowing molten exhaust gas introduced into the molten exhaust gas temperature reducing tower 9. Since it is supplied, the exhaust gas is swirled by the swirling flow of the cooling air even with a small amount of high-temperature exhaust gas such as the molten exhaust gas discharged from the melting furnace 2. Further, the molten exhaust gas is efficiently reduced in temperature by a strong stirring action of the upward flowing molten exhaust gas mixed with cooling air and the cooling water sprayed from the cooling water spray nozzle 95 in the opposite direction.

  Further, since the cooling water is sprayed downward from the top of the tower main body 91 of the molten exhaust gas temperature-decreasing tower 9, the salt and dust in the molten exhaust gas are not in direct contact with the tip of the cooling water spray nozzle 95. Salt or the like is difficult to adhere to the nozzle tip. Thereby, even if it drive | operates for a long time, a cooling water can always be sprayed in a suitable state.

  In addition, since cooling by both cooling air and cooling water is adopted, the amount of sprayed water can be reduced compared with the conventional temperature reduction treatment method using only cooling air, and the sprayed water is completely agitated. It is difficult for salt to adhere to the inner peripheral wall of the tower main body 91 of the molten exhaust gas temperature-decreasing tower 9 due to un-evaporated water.

  As a result, the molten exhaust gas temperature reducing tower 9 is prevented from being enlarged, and even when the dust scraper 97 is provided in the molten exhaust gas temperature reducing tower 9, the blades 97b of the dust scraper 97 are heated by the high temperature exhaust gas. Problems such as damage will not occur.

  In the above embodiment, air is used as the cooling gas, but other gases having a cooling effect can also be used.

  Moreover, in the said embodiment, although the six cooling gas nozzles 96 were provided in the state inclined in the substantially same direction with respect to the circumferential direction of the column main body 91 lower part of the molten exhaust gas temperature reduction tower 9, the nozzle shape and the number of nozzles are provided. The nozzle shape is not limited to this, and may have a nozzle shape that gives an upward blowing angle as long as an effect of forming a swirling upward flow is generated in association with the molten exhaust gas. Seven or more books may be provided.

  Moreover, in the said embodiment, although the one cooling water spray nozzle 95 is provided in the center part of the tower main body 91 top part of the melted exhaust gas temperature reduction tower 9, the nozzle shape and the number of nozzles are not limited to this, The above-mentioned As long as the effect of spraying the cooling water in the direction opposite to the swirling upward flow is obtained, for example, the nozzle shape may extend from the side wall of the tower body 91 to the vicinity of the central portion and bend downward, and the number of nozzles may be 2 You may make it provide more than this.

  In the above embodiment, the cooling air supply amount and the cooling water supply amount are controlled based on the detection values of the thermometers 93a and 96b, respectively. If the temperature and gas volume) hardly change, manual adjustment is sufficient.

1 is an overall configuration diagram of a waste incineration residue melting treatment facility to which a high-temperature exhaust gas treatment method according to the present invention is applied. It is a longitudinal cross-sectional view of a molten exhaust gas temperature-reduction tower. It is the elements on larger scale in FIG. It is the sectional view on the AA line in FIG. It is the BB sectional view taken on the line in FIG. It is CC sectional view taken on the line in FIG. It is a figure which shows the locus | trajectory of the spray water in the molten exhaust gas temperature reduction tower by experiment. It is a figure which shows the temperature distribution in the molten exhaust gas temperature-reduction tower by experiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ash supply apparatus 2 Plasma melting furnace (equivalent to a melting furnace)
7 Slag hopper 9 Molten exhaust gas temperature reduction tower (corresponds to a temperature reduction device and a high temperature exhaust gas treatment device)
91 Tower body (corresponds to the apparatus body)
92 Melting exhaust gas inlet nozzle 93 Melting exhaust gas outlet nozzle 94 Dust discharge port 95 Cooling water spray nozzle 96 Cooling gas nozzle 97 Dust scraper 10 Bag filter 11 Melting fly ash solidification device 12 Solidified bunker 14 Melting exhaust gas cleaning processing device 15 Re Heater 16 Induction fan

Claims (7)

In a method for reducing the temperature of a high-temperature exhaust gas generated when melting incineration residue of municipal waste and / or industrial waste in a melting furnace using a temperature reducing device,
Along with the upward high-temperature exhaust gas introduced into the temperature reducing device, the cooling gas is supplied so as to form a swirling flow, and the cooling water is sprayed downward from the top of the temperature reducing device to increase the temperature. A high-temperature exhaust gas treatment method characterized by subjecting exhaust gas to a temperature reduction treatment. In an apparatus for reducing the temperature of high-temperature exhaust gas generated when melting incineration residue of municipal waste and / or industrial waste in a melting furnace,
A cooling gas nozzle that supplies cooling gas to form a swirl flow accompanying the upward high-temperature exhaust gas introduced into the apparatus main body, and a cooling water spray nozzle that sprays cooling water downward from the top in the apparatus main body And a high-temperature exhaust gas treatment apparatus.   The device body is formed in a cylindrical shape extending vertically, and an inlet nozzle for high-temperature exhaust gas is provided at the lower part of the device body, and cooling is performed in a state inclined to the circumferential direction of the lower part of the device body at a portion below the height of the inlet nozzle. The high-temperature exhaust gas treatment device according to claim 2, wherein a gas nozzle is provided.   The high-temperature exhaust gas treatment apparatus according to claim 2 or 3, wherein an outlet nozzle for the high-temperature exhaust gas is provided in a peripheral part of the top part of the apparatus main body, and a cooling water spray nozzle is provided in the central part of the top part of the apparatus main body.   The high-temperature exhaust gas treatment apparatus according to any one of claims 2 to 4, wherein the cooling water spray nozzle is formed so that a water droplet spray angle is an angle of 90 degrees or less.   The high-temperature exhaust gas treatment apparatus according to any one of claims 2 to 5, wherein a tip of the cooling water spray nozzle is protruded by 30 cm or more from an inner wall surface of the apparatus main body.   The high-temperature exhaust gas treatment apparatus according to any one of claims 2 to 5, wherein a tip end portion of the cooling water spray nozzle is protruded within a range of 50 to 150 cm from an inner wall surface of the apparatus main body.

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