JP3176864B2 - Method and apparatus for cooling incinerator exhaust gas using special nozzle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for cooling incinerator exhaust gas using a special nozzle. More specifically, the present invention particularly suppresses the regeneration of dioxins,
The present invention relates to a method and an apparatus for cooling incinerator exhaust gas so that harmful substances such as dioxins and mercury can be efficiently removed by a bag filter together with hydrogen chloride gas and sulfur oxide gas.

[0002]

2. Description of the Related Art Exhaust gas discharged from municipal solid waste incinerators contains trace components such as dust, hydrogen chloride (HCl), SOx, NOx, heavy metals including mercury, and dioxins. From a standpoint, it is necessary to remove these harmful substances. Among them, dioxins (PCDD: polychlorinated dibenzodioxin and PCDF: general term for polychlorinated dibenzofuran) are extremely toxic,
Moreover, it is reported that it has carcinogenicity, and the collection and removal of dioxins has been taken up as an urgent issue.

FIG. 3 shows a conventional example of a municipal solid waste incinerator plant equipped with an exhaust gas treatment device. In the apparatus shown in FIG. 3, the refuse collected in the refuse pit 1 is sent to the incinerator 2 by a crane (not shown) or the like. Garbage incinerator 2
After being incinerated in the secondary combustion chamber 3, it is completely burned by the secondary air in the secondary combustion chamber 3. Ash after burning in incinerator 2
1 is taken out. The exhaust gas generated by complete combustion in the secondary combustion chamber 3 is then heat-recovered by the waste heat boiler 4 and the waste heat recovery unit (preheater) 5 and reaches the quenching reaction tower 6.

In the quenching reaction tower 6, slaked lime slurry is sprayed from a slaked lime storage tank 7 to remove hydrogen chloride (HCl) and sulfur oxides (SOx) contained in exhaust gas. The exhaust gas is then guided to the bag filter 8 further downstream to remove dust, HCl, SOx, heavy metals and dioxins remaining in the exhaust gas. Reference numeral 9 denotes an induced exhaust fan, which sucks the exhaust gas after the treatment as described above and discharges the exhaust gas to the atmosphere via a chimney 10.

[0005] However, even when the exhaust gas from the incinerator is treated using the above-mentioned exhaust gas treatment apparatus, there are cases where dioxins cannot be reduced to a desired low concentration. That is, dioxins generated in the incineration process of refuse are almost decomposed in the secondary combustion chamber, but the heat recovery process, the cooling reaction process,
In each process of the dust collection process, the incinerator exhaust gas
It is necessary to lower the temperature from a high temperature of about 0 to 900 ° C. to a low temperature. However, particularly at around 300 ° C., the regeneration of highly toxic dioxins is likely to occur. Therefore, in the above-mentioned conventional exhaust gas treatment apparatus, dioxins are regenerated in each step, and as a result, dioxins are converted into desired dioxins. There is a problem that it cannot be collected and removed to a low concentration.

Among the above, the waste heat recovery device as an exhaust gas cooling technique has a problem that the cooling time is slightly long, the gas flow is partially uneven, and dust adheres and accumulates on the surface of the equipment. I do. Also, if there is a change in the temperature or the gas flow rate, the outlet temperature will change. As a result, the generation of dioxins increases, and a water jet cooling means is required to further control the temperature. When using a water injection cooling tower as exhaust gas cooling means, to cool with coarse water droplets,
The temperature of the gas cannot be controlled, and the dust becomes slurry. As a result, the bag filter cannot be used, and it is difficult to treat the dust. Further, as a water injection cooling means, there is a method of spraying water or slurry onto a duct or a tower-shaped portion, but there is a drawback that uniform cooling of gas cannot be performed. Regarding the control of dioxin emission as described above, the Ministry of Health and Welfare formulated the “Guidelines on Prevention of Dioxin Generation” in 1990, and the emission concentration of dioxins was 0.5 ng-TEQ (concentration equivalent to toxicity) / Nm ^3. Was expected to be less than
In October, the above guidelines were reviewed and the emission concentration of dioxins in the future waste incineration continuous furnace was set at 0.1.
NG-TEQ (concentration equivalent to toxicity) / Nm ³ or less is being studied.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and limits the recovery of waste heat from exhaust gas to a temperature range in which the generation of dioxins can be suppressed. Rapidly, especially around 300 ° C
By cooling at a short cooling rate of less than seconds,
The emission concentration of dioxins from the incinerator plant was set at 0.
It is an object of the present invention to provide an economical and easy-to-maintain incinerator exhaust gas cooling method and apparatus which can reduce the dust to 1 ng-TEQ / Nm ³ or less and can collect dust in a dry state.

[0008]

That is, according to the present invention, there is provided a method for cooling incinerator exhaust gas for purifying high-temperature exhaust gas discharged from a waste incinerator in a post-process, comprising: The incinerator exhaust gas is introduced into a spray cooling chamber having a gas distribution chamber on the upstream side to give a swirling flow to the incinerator exhaust gas.
And the incinerator exhaust gas velocity from the gas distribution chamber is 10 to 5
0 m / s, the swirling speed of the incinerator exhaust gas is 1 to 30 rad
/ S, from a spray nozzle having a double pipe structure installed at the upper center of the spray cooling chamber, and a flow rate of 0.1 to 100 k per nozzle.
g / min of cooling liquid spouts while swirling.
Pressurized air with a pressure of 5 to 40 kPa is ejected while turning
This allows the cooling liquid to be atomized at a spray angle of 5 to 90 degrees.
By allowed to contact touch mixed with spray cooling liquid that has, as well as rapid cooling to a predetermined temperature below with the incinerator flue gas as the temperature is decreased to between 250 to 350 ° C. for a short time within one second, the incinerator flue gas A method for cooling incinerator exhaust gas, comprising separating dust contained in a dry state,
Is provided. In the present invention, the inlet temperature is 350-9.
Preferably, the gas at 00C is rapidly cooled to an outlet temperature of 80-250C .

Further, according to the present invention, there is provided an incinerator exhaust gas cooling device for purifying high-temperature exhaust gas discharged from a waste incinerator in a post-process, wherein a downstream end portion has an inverted conical shape. A substantially cylindrical chamber, a gas distribution chamber disposed upstream of the chamber, and a cooling liquid passing through the inside of the chamber and a pressurized air passing therethrough at the upper center of the chamber. A cooling liquid spray nozzle having a double pipe structure ,
The cooling liquid spray nozzle is used to control the flow
While the amount of cooling liquid of 0.1 to 100 kg / min swirls
Pressurized air with a pressure of 5 to 40 kPa is swirled around it.
By spraying while turning, the cooling liquid is atomized.
Then, the incinerator exhaust gas is heated for 1 second between 250 and 350 ° C.
A cooling device for incinerator exhaust gas , wherein the temperature is decreased within a short time within the range . In the cooling device, it is preferable that the part of the wall portion constituting the gas distribution chamber and the jacket structure.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic operation of cooling incinerator exhaust gas according to the present invention will be described. As described above, incinerator exhaust gas has a high temperature of about 350 to 900 ° C., and when the exhaust gas temperature is about 300 ° C. in the process of falling from the high temperature to the low temperature, dioxins are regenerated. Therefore, in the present invention, as a cooling method, in rapidly cooling high-temperature exhaust gas, the temperature is reduced from 250 to 350 ° C., which is around 300 ° C., in a short time within 1 second, so that the exhaust gas 3
The residence time around 00 ° C. is extremely shortened to minimize the regeneration of dioxins.

According to the present invention, in order to achieve such rapid cooling of the exhaust gas, the incinerator exhaust gas is introduced into a spray cooling chamber whose downstream end is formed in a substantially cylindrical shape having an inverted conical shape. While mixing with the spray cooling liquid while giving a swirling flow. In the present invention, increasing the cooling rate (cooling rate) around 300 ° C. means that the cooling rate is uniformly high in each part of the exhaust gas, thereby suppressing the regeneration of dioxins from the exhaust gas. Important above. Therefore, for this purpose, in the present invention, a spray nozzle having a special double pipe structure is used as a spray means for the coolant,
A cooling liquid having a flow rate of 0.1 to 100 kg / min is ejected while swirling inside the double pipe structure, and a pressure of 5 to 40 is applied around the cooling liquid.
The atomization spray of the cooling liquid is performed so that the pressurized air of kPa is ejected while swirling, and the atomization spray liquid, the gas velocity is 10 to 50 m / s, and the gas swirl velocity is 1 to 30 ra
It is preferable to mix with d / s exhaust gas. As the cooling liquid to be sprayed, water is usually used.
Alkaline slurry such as lime milk, and wastewater containing treated salts discharged from a water treatment facility attached to an incinerator plant can be used.

[0012] As in the present invention, 300 ° C of incinerator exhaust gas
By making the residence time in the vicinity extremely short and minimizing the regeneration of dioxins as much as possible, passing through subsequent processing steps (for example, slaked lime powder, activated carbon addition processing, processing with bag filters, etc.) Thus, the emission concentration of dioxins into the atmosphere can be reduced to 0.1 ng-TEQ / Nm ³ or less according to the guidelines formulated by the Ministry of Health and Welfare. To explain this point in detail, the removal efficiency of dioxins in the subsequent treatment steps such as slaked lime powder and activated carbon addition treatment, treatment with a bag filter, etc. can be reduced to about 98% by adjusting the exhaust gas temperature and the amount of activated carbon. Can be achieved. Therefore, the concentration of dioxins after the rapid cooling treatment of the present invention, which is the preceding step, is 1.5 ng (TEQ) / Nm.
^In the case of ³ , 0.02 ng (T
EQ) / Nm ³ next to, below effortlessly guidelines,
On the other hand, in the conventional waste heat recovery device and quenching reaction tower shown in FIG. 4, the concentration of dioxins is 10 ng (TEQ).
/ Nm ³ , and the guideline value of 0.1 ng-TEQ / Nm ^3,
That is all.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing one embodiment of a spray cooling chamber used in the present invention. In FIG. 1, reference numeral 20 denotes a chamber, the lower end of which is formed in an inverted conical shape, the upper end of which is formed in a conical shape, and the body portion is formed in a substantially cylindrical shape. A gas distribution chamber 21 provided with a swirl vane 25 is arranged on the upper side of the chamber 20 and communicates with an inlet duct 22 to which exhaust gas (hot gas) from an incinerator (not shown) is sent. Gas distribution room 2
In the case of 1, when the exhaust gas temperature exceeds 600 ° C., it is preferable that a part of the wall portion is formed into a jacket structure to allow the cooling water to flow, so that cheap equipment materials can be used.
A cooling liquid spray nozzle 23 having a double pipe structure is provided at the upper center of the chamber 20. Water is supplied from a water supply device 24 to the outer periphery of the cooling liquid spray nozzle 23 inside the cooling liquid spray nozzle 23. Are formed so that pressurized air is sent from the blower 30. When the cooling liquid spray nozzle 23 is used, the cooling liquid spouts inside the double pipe structure while swirling, and the pressurized air spouts around the inside while swirling. The jetted pressurized air scatters and the cooling liquid is atomized. The degree of atomization can be adjusted by the flow rate of the cooling liquid, the pressure of the pressurized air, or the like. Preferably, the flow rate of the cooling liquid is in the range of 0.1 to 100 kg / min.
The pressure of the pressurized air is preferably in the range of 5 to 40 kPa. This provides a spray condition in which the average particle size of the droplets decreases as the flow rate of the cooling liquid decreases. here,
As the cooling liquid spray nozzle 23 having a double pipe structure suitably used in the present invention, Japanese Patent No.
As described in Japanese Patent No. 524379 and JP-A-4-281872, a pressure swirl nozzle for blowing out a liquid and a high-speed gas blowing tubular body provided around the nozzle are used. Things can be mentioned.
In this cooling liquid spray nozzle, there are two atomization stages. First, the atomization is performed by the pressure of the liquid itself of the pressure swirl nozzle. In this primary atomization, the liquid is ejected in a conical annular shape. Next, even when the liquid is sprayed at a low pressure, the primary atomized liquid droplets are intensively collided with the high-speed gas blown from the blow-off tubular body to cause secondary atomization. , Can achieve the atomization of the liquid,
Control of the droplet diameter can also be performed. A dust outlet 26 is provided at the lower end of the chamber 20, and an exhaust pipe 27 for exhausting exhaust gas is opened in the inverted conical portion 29 of the chamber 20. Reference numeral 28 denotes a slaked lime powder blowing port.

The spray cooling chamber 15 is configured as described above. Exhaust gas treatment will be described. Exhaust gas (high-temperature gas) sent from the inlet duct 22 is supplied to the gas distribution chamber 21.
Will be sent to The gas distribution chamber 21 is provided with a swirl vane 25. The swirl vane 25 imparts a swirling flow of a predetermined gas speed and swirling speed to the exhaust gas, and the exhaust gas gradually descends while swirling inside the chamber 20. I will do it.
On the other hand, the coolant atomized as described above is sprayed from the coolant spray nozzle 23, and is instantaneously contact-mixed with the exhaust gas. The TIC indicates a temperature control device, which detects the inlet exhaust gas temperature and the outlet gas temperature, feeds forward and feeds back the respective values, and controls the amount of water supplied from the water supply equipment 24 to the coolant spray nozzle 23. are doing.

When the exhaust gas (high-temperature gas) and the cooling liquid are contact-mixed in this way, the atomized and sprayed cooling liquid is contact-mixed with the high-temperature gas provided with the swirling flow.
The contact efficiency between the coolant and the gas is extremely good.
The 900 ° C. hot gas is cooled rapidly, and it takes about 8
The temperature is lowered to about 0 to 250 ° C. In addition, the temperature of the high-temperature gas can be uniformly reduced at a high rate, and the temperature can be cooled within 250 seconds within a range of 250 to 350 ° C., which is necessary for suppressing the generation of dioxins. In addition, fluctuation of the temperature of the hot gas,
As described above, rapid cooling can be achieved by adjusting and controlling the spray amount of the cooling liquid to be sprayed even when the gas amount fluctuates. Also, when the outlet gas temperature is set to a predetermined temperature, it can be achieved by controlling the spray amount of the cooling liquid. In the spray cooling chamber 15, the exhaust gas is contact-mixed with a coolant and cooled to a predetermined temperature, and then cooled to a low temperature, and the exhaust gas is cooled to a downstream side from an exhaust pipe 27 opened in the inverted conical portion 29 of the chamber 20. Exhausted. At this time, slaked lime powder is blown into the exhaust pipe 27 from the slaked lime powder blowing port 28 to react with SOx and HCl to remove these substances. A part of the dust contained in the exhaust gas is taken out from the dust outlet 26 at the lower end of the chamber 20 in a dry state.

FIG. 2 is an explanatory diagram showing one embodiment of an incinerator plant incorporating the exhaust gas treatment apparatus of the present invention. In the apparatus of FIG. 2, the configuration from the waste pit 1, the incinerator 2, the secondary combustion chamber 3, and the waste heat boiler 4 is the same as the configuration of FIG. Exhaust gas (high-temperature gas) that has been recovered in heat by the waste heat boiler 4 and slightly cooled is then discharged to the spray cooling chamber 12.
And rapidly cooled to a predetermined temperature. The cooled exhaust gas is exhausted from the spray cooling chamber 12 through the exhaust pipe 13, and slaked lime powder is blown from the slaked lime powder storage tank 14 in the middle of the exhaust pipe 13, so that SOx,
Reacts with HCl to remove these materials. here,
It is preferable that the blowing amount of the slaked lime powder is 2 to 4 times the equivalent of SOx and HCl in the exhaust gas.

Activated carbon is fed into the exhaust pipe 13 from the activated carbon storage tank 16 to further remove heavy metals such as mercury and dioxins contained in the exhaust gas. The amount of activated carbon to be fed depends on the dust concentration, slaked lime amount, and circulating dust amount, but is 0.05 to 0.30 g / Nm ^3. Is preferable. The exhaust gas thus reacted and adsorbed to the powder to which SOx, HCl, heavy metals and dioxins are added,
Next, it is guided to the bag filter 8 and separated into solid and gas, and dust, HCl, SOx, heavy metals and dioxins remaining in the exhaust gas are removed. In addition, bag filter 8
A part of the dust separated in the above can be circulated to the exhaust pipe 13. Further, depending on the layout plan of the incinerator plant, the spray cooling chamber can be freely arranged such as a horizontal type, an upside-down type or an inclined type. The exhaust gas that has passed through the bag filter 8 is drawn by the draft fan 9 and discharged from the chimney 10 into the atmosphere.

Hereinafter, the present invention will be described more specifically. (Design example) The following exhaust gas cooling is designed using the spray cooling chamber (invention) using the cooling liquid spray nozzle of the double pipe structure having the dimensions and performance shown in Table 1 with the structure of FIG. did. For comparison, exhaust gas cooling was similarly designed using a two-fluid nozzle having the dimensions and performance shown in Table 1, a high-pressure nozzle, and a spray cooling chamber using a rotating disk type water sprayer. did.

[0019]

[Table 1]

[Exhaust gas] Inlet gas flow rate: 120,000 kg / hr Inlet gas temperature: 500 ° C. Inlet gas speed: 25 m / s Inlet gas swirl speed: 3 rad / s Dioxin concentration: 1.0 ng / Nm ³ Dust concentration: 6 g / Nm ³ [spray liquid] Water amount: about 17 ton / hr

When the exhaust gas is cooled using the various spray cooling chambers described above, in the case of the present invention, the temperature of the outlet gas can be set to 130 ° C.
° C within 1 second, so that the concentration of dioxins in the exhaust gas is 1.0 ng (TEQ) / Nm
Increases only from ³ to 1.3 ng (TEQ) / Nm ³ ,
Regeneration of dioxins can be suppressed.
Further, after adding slaked lime powder, activated carbon and the like, the concentration of dioxins in the exhaust gas collected and cleaned by the bag filter can be 0.1 ng (TEQ) / Nm ³ or less.

On the other hand, even when a two-fluid nozzle, a high-pressure nozzle, and a rotating disk type water atomizer are used, the outlet gas temperature can be set to 150 ° C., and the concentration of dioxins in the exhaust gas is 1.0 ng (TEQ). / Nm ³ to 2.0 ng (T
EQ) / Nm ³ and can suppress the regeneration of dioxins. Therefore, after adding slaked lime powder, activated carbon, etc., the concentration of dioxins in exhaust gas that has been collected by a bag filter and cleaned is reduced to 0. 1 ng (TEQ) / Nm ³
It can be: However, in the case of a two-fluid nozzle, uniform cooling in the room is difficult, and an extremely large number of nozzles are required, so that the management becomes complicated, and compressed air (the pressure is 2 kg / cm ² or more) is required. The required power cost is 3 to 20 times that of the present invention, which is not economical. In the case of a high-pressure nozzle, in addition to maintaining the high-pressure pipe and corroding due to dew condensation, there is a problem that atomization is difficult during startup and operation at the time of stopping, and effective cooling cannot be performed. In addition, in the case of a rotating disk type, maintenance, that is, maintenance must be performed by a person with specialized skills, that high temperatures require many safety devices for the machine,
Further, there is a problem that it is difficult to take countermeasures at the time of emergency stop or trouble of the rotating machine, and there is no flexibility in piping. On the other hand, in the case of using the cooling liquid spray nozzle having the double pipe structure of the present invention, stable operation is possible regardless of start-up or stoppage, and uniform indoor cooling is excellent, and Operating costs are low and maintenance is easy.

(Conventional example) When the same treatment as described above is performed under the conditions of an inlet gas temperature of 280 ° C. and an outlet gas temperature of 150 ° C. using the waste heat recovery unit and the quenching reaction tower of the conventional example shown in FIG. Dioxins concentration at the inlet of the reaction tower is 10 ng
(TEQ) / Nm ³ , and the same applies to the outlet of the quenching reaction tower. Even after the cleaning treatment with a bag filter, the amount becomes only about 0.5 ng (TEQ) / Nm ³ , and 0.1 ng ( TEQ) / Nm ³ cannot be cleared.

[0024]

As described above, according to the present invention,
High-temperature exhaust gas can be cooled rapidly, especially around 300 ° C with a large cooling rate of less than 1 second, so that dioxins can be prevented from regenerating and dust can be recovered in a dry state. And a remarkable effect of being economical and easy to maintain.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a spray cooling chamber used in the present invention.

FIG. 2 is an explanatory diagram showing one embodiment of an incinerator plant incorporating the exhaust gas treatment device of the present invention.

FIG. 3 is an explanatory diagram showing an example of a municipal waste incinerator plant provided with a conventional exhaust gas treatment device.

[Explanation of symbols]

15: spray cooling chamber, 20: chamber, 21: gas distribution chamber, 22: inlet duct, 23: cooling liquid spray nozzle, 24
... water supply equipment, 25 ... swirl vane, 26 ... dust outlet,
27: exhaust pipe, 28: lime powder inlet, 29: inverted conical part, 30: blower.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shizuo Aijima 3847 Ikebe-cho, Tsuzuki-ku, Yokohama-shi, Kanagawa Prefecture Inside Okawara Kakoki Co., Ltd. (56) References JP-A-4-281872 (JP, A) JP-A-5 -231633 (JP, A) Japanese Utility Model 60-148839 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23J 15/04 B01D 51/10

Claims (4)

(57) [Claims] 1. A method for cooling an incinerator exhaust gas for purifying a high-temperature exhaust gas discharged from a waste incinerator in a post-process, wherein the incinerator exhaust gas is supplied to an upstream gas distribution chamber. giving a swirling flow in the incinerator flue gas is introduced into a spray cooling chamber having,該Ga
The incinerator exhaust gas speed from the gas distribution chamber is 10 to 50 m /
s, the swirling speed of the incinerator exhaust gas is 1 to 30 rad / s.
Then , from a spray nozzle having a double pipe structure installed in the upper center of the spray cooling chamber, a flow rate per one nozzle is 0.1 to 100 kg / m.
in coolant whirls and circulates, and the pressure around
To pressurized air of ~ 40 kPa while whirling
More, by the cooling liquid is allowed to mix come in contact with the atomized sprayed sprayed coolant in the spray angle 5 to 90 degrees, the temperature is lowered the incinerator exhaust gas between 250 to 350 ° C. for a short time within one second A method for cooling incinerator exhaust gas, which comprises rapidly cooling to a predetermined temperature or less and separating dust contained in the incinerator exhaust gas in a dry state. 2. The method according to claim 1, wherein the gas having an inlet temperature of 350 to 900 ° C. is rapidly cooled to an outlet temperature of 80 to 250 ° C. 3. An incinerator exhaust gas cooling device for purifying high-temperature exhaust gas discharged from a waste incinerator in a post-process, wherein the downstream end portion has a substantially cylindrical shape having an inverted conical shape. A formed chamber; a gas distribution chamber disposed upstream of the chamber; and a cooling liquid having a double pipe structure provided at an upper center portion of the chamber, through which the cooling liquid passes and through which the pressurized air passes. A spray nozzle, wherein the coolant spray nozzle circulates and jets a coolant having a flow rate of 0.1 to 100 kg / min per one inside the double pipe structure, and pressurizes around the periphery with a pressure of 5 to 40 kPa. The pressurized air is ejected while swirling, so that the cooling liquid is atomized.
A cooling device for incinerator exhaust gas, wherein the temperature is decreased in a short time within seconds. 4. The cooling device for incinerator exhaust gas according to claim 3, wherein a part of a wall constituting the gas distribution chamber has a jacket structure.