JP3059935B2 - Dioxin removal equipment in refuse incinerators - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates is, Daioki in refuse incineration furnace for incineration of refuse such as municipal waste and industrial waste
The present invention relates to an apparatus for removing synths .

[0002]

2. Description of the Related Art FIG.
It is sectional drawing which shows an example of the structure of the waste heat boiler cooling type refuse incinerator which took the conventional dioxin countermeasure.

In FIG. 5, refuse introduced into a combustion chamber b from a hopper a includes a dry grate C ₁ , a combustion grate C ₂ ,
Of the exhaust gas d generated by burning while being sequentially transferred on the post-combustion grate C ₃ , the gas mainly generated from the dry grate C ₁ contains a large amount of unburned gas and has a temperature of about 500 to 600 ° C. a combustible gas d _1, gas generated from the main combustion grate C ₂ and post-combustion grate C ₃ is free of unburned almost 70
0-950 is a combustion gas d ₂ of ° C..

The exhaust gas d collides with the ceiling of the combustion chamber b and the surface of the intermediate ceiling e ₁ provided at the exit of the combustion chamber, and radiates the retained heat into the combustion chamber b.
The secondary combustion in the combustion chamber b is promoted.

Subsequently, the exhaust gas d is supplied to the intermediate ceiling e ₁
Around the rear surface, it is induced to baffle e _2, e ₃ provided on the back portion the inlet of the intermediate ceiling e ₁ at a certain angle, to merge each deflect in one direction, in the mixing chamber f is Ascend while turning. Meanwhile, the unburned gas d ₁ secondary-combusted in the combustion chamber b becomes the high-temperature combustion gas d in the mixing chamber f.
By being mixed _2, unburned is afterburning the remaining mixed gas d ₃ is sent to the waste heat boiler g of next step, it is cooled to a predetermined temperature range.

That is, in the mixing chamber f, the residence time is extended by swirling the exhaust gas d inside the mixing chamber f, high-efficiency two-stage combustion is performed, and complete incineration of the unburned dioxin precursor is achieved. Device.

However, in this method, since the secondary combustion air is not supplied to the mixing chamber f and a proper control device is not provided, it is difficult to expect complete two-stage combustion. Needed.

[0008] To solve this problem, Japanese Patent No. 202343 filed by the same applicant as "method of incineration of waste in a waste incinerator equipped with a gas mixing device" and Japanese Utility Model Publication No. 7-49229, "waste equipped with a gas mixing device" Incinerator "
The outline is shown in FIG. 6 and FIG.

FIG. 6 is an overall view schematically showing the structure of a water-injection-cooled refuse incineration system in which measures against dioxins have been taken, and FIG. 7 is a sectional view schematically showing a gas mixing device. Note that the same reference numerals are given to devices having the same functions as those in FIG. 5 described above, and detailed description will be omitted.

[0010] In FIGS. 6 and 7, the supply of radiant heat and secondary combustion air h of combustion gases d _2, the unburned gas d ₁ that secondary combustion in the combustion chamber b, the combustion gases d ended combustion _Two
And it is passed provided in the installed gas mixing device j to the combustion chamber outlet, the communicating portion j ₂ between the plurality of inclined gas passages j ₁ and the combustion chamber outlet and a gas mixing device j.

Here, a ventilation pipe k for supplying tertiary combustion air and an injection port m are buried in each gas passage j ₁ and the communication portion j ₂ , respectively. It is connected to a tertiary air blower p via a control valve n for adjusting the injection air amount based on a command.

Therefore, the exhaust gas d receives the supply of tertiary combustion air, performs tertiary combustion in the vicinity of the outlet of the gas passage j ₁ , completely burns the remaining unburned portion to become exhaust gas d ₃ , and the exhaust gas d in the gas cooling chamber q. Ascend while turning.

A gas flow measuring device s is provided in the middle of the gas cooling chamber q in which a plurality of water injection nozzles r are installed, so that the flow rate distribution of the exhaust gas d ₃ in the gas cooling chamber q is equal. Thus, the injection amount of the tertiary combustion air is adjusted.

Here, in addition to the above-described functions, the gas mixing device j is configured to drop water droplets from the water injection nozzle r and to operate the gas cooling chamber q.
It also has a function of preventing adverse effects on the combustion chamber b due to radiant cooling from above.

When adjusting the amount of tertiary combustion air,
The combustion chamber outlet temperature is controlled as the first priority, the chimney inlet CO concentration is controlled as the second priority, and the chimney inlet O ₂ concentration is controlled as the third priority.

[0016]

In the above-mentioned improvement measures, although the exhaust gas is agitated and burned by the gas mixing device, the unburned gas generated in the combustion chamber has already been subjected to the secondary combustion. Because the gas is introduced into the gas mixing device, the combustible content in the gas is very small, and reliable re-combustion near the gas mixing device cannot be guaranteed, preventing the generation of dioxins or thermal decomposition in the incinerator. There is a possibility that the operation is not completely performed.

[0017]

According to a first aspect of the present invention , there is provided an apparatus for removing dioxins in a refuse incinerator, comprising: a combustion chamber of a refuse incinerator for incinerating refuse such as general waste and industrial waste; In the middle of the gas cooling equipment installed in
In a refuse incinerator provided with a reburning chamber for reburning unburned gas at a high temperature and provided with gas mixing means at the bottom of the reburning chamber, a reflection wall provided on an upper part of the reburning chamber; And a first control means for controlling the oxygen concentration of the tertiary combustion air supplied to the recombustion chamber or the gas mixing means and the supply amount thereof so as to maintain the temperature within a preset specified range. .

The apparatus for removing dioxins in the incinerator of the invention according to claim 2, as held in a preset specified range the reducing atmosphere temperature of the combustion chamber,
A second controlling a supply amount of the drying air supplied to the combustion chamber;
Control means is provided.

[0019]

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view and a schematic flow chart showing an example of the overall configuration of a dioxin removing apparatus in a refuse incinerator according to the present invention, and FIG. 2 is a sectional view showing a schematic configuration of a reburning chamber portion. is there. In this embodiment, a water injection cooling type waste incinerator will be described as an example.

1 and 2, reference numeral 1 denotes an incinerator comprising a charging hopper 11, a combustion chamber 12, a dry grate 13, a combustion grate 14, a post-combustion device 15, and the like.

Above the outlet on the downstream side of the combustion chamber 12, a gas mixing device (gas mixing means) 2 made of refractory, a cylindrical reburning chamber 3 made of refractory and steel, and a gas cooling device A room GC is provided.

The gas mixing device 2 is made of a refractory material having a plurality of inclined or curved gas passages 21 and has a protruding portion 22 from the combustion chamber 12 at the bottom of the reburning chamber 3 located at the combustion chamber outlet. Is held by a support mechanism (not shown) with a gap 23 between the two.

A tertiary combustion air outlet 24 is provided in each of the gas passage 21 and the protrusion 22.

A reflection wall 32 made of a refractory and having a built-in air cooling pipe 31 is provided on a ceiling portion of the reburning chamber 3 which is a connection portion with the gas cooling chamber GC.

The central portion of the recombustion chamber is provided with an air cooling chamber 33 on the outer periphery.
Is a reburning space 35 constructed of a body 34 made of a refractory having a high thermal conductivity such as silicon carbide, and the outer surface of the air cooling chamber 33 is kept warm by a heat insulating material 36. Is provided with a heating burner 37.

On the other hand, the tertiary air 42 sucked by the tertiary blower 41 reaches the mixer 44 via the damper 43, and the oxygen 46 sent from the oxygen generating means 45 is supplied to the mixer 44 via the control valve 47. 44 and are mixed to form tertiary combustion air 48 having a high oxygen content.

The tertiary combustion air 48 delivered from the mixer 44 is heated in the air cooling chamber 33 on the outer periphery of the body 34 through the air cooling pipe 31 in the reflecting wall 32, and then is tertiary combustion through a plurality of control valves 49. The pipe is arranged so as to reach the air ejection port 24.

A gas-heated air preheater 51 is provided at the outlet of the gas cooling chamber GC. The combustion air 61 sucked by a not-shown push-in blower is heated by the air preheater 51 and then discharged by a damper. The air volume is adjusted by 52 to 55 and supplied to the combustion chamber 12 from the lower part of each grate.

Next, the situation of the exhaust gas treatment in the refuse incinerator configured as described above will be described.

The refuse sent from the charging hopper 11 into the combustion chamber 12 burns while being sequentially transferred on the dry grate 13, the combustion grate 14, and the post-combustion device 15, and the incinerated ash is supplied from the post-combustion device 15 and the like. It is discharged to an ash processing device (not shown).

At this time, of the exhaust gas generated, the gas generated from the first half of the drying grate 13 and the combustion grate 14 is carbonized in order to narrow down and operate the drying air 62 and 63 which are so-called drying air. An unburned gas 71 of 400 to 600 ° C. containing a large amount of unburned components such as hydrogen and odor components such as ammonia.
5 The gas generated from above is 750-95
It is a combustion gas 72 at 0 ° C.

Here, the unburned gas 71 creates a reducing atmosphere, and functions to self-denitrate nitrogen oxides in the combustion chamber 12. The high-temperature combustion gas 72 rises and rises to the combustion chamber ceiling and the gas mixing device 2. And promotes drying and burning of the refuse on the combustion grate 14 and thermally decomposes a part of the unburned gas 71 by the amount of heat retained.

Thereafter, the unburned gas 71 and the combustion gas 72
Into a high-temperature exhaust gas 73 of about 700 to 900 ° C., and the inclined or curved gas passage 2 of the gas mixing device 2.
The tertiary combustion air 48 is injected while passing through the gap 1 and the gap 23, and rises to the reburning space 35 while turning.

In the reburning space 35, unburned substances in the unburned gas 71 burn violently due to excess oxygen in the tertiary combustion air 48, and are radiated by the reflecting wall 32 and the gas mixing device 2 to 1300 to 1400. When the temperature reaches ° C., not only the unburned substances in the unburned gas but also the remaining odorous components are thermally decomposed. Therefore, hydrocarbons and suspended carbon particles which are dioxin precursors can be completely incinerated and decomposed.

When the temperature of the reburn space 35 does not reach the specified value at the time of startup or for some reason, the temperature of the heating burner 3 is increased.
7 to raise the temperature.

Then, the reburn gas 74 after the reburn has been completed.
Enters the gas cooling chamber GC through the space of the reflecting wall 32,
A plurality of water injection nozzles S arranged above the gas cooling chamber GC
It is cooled by N to form an exhaust gas 75 of about 450 ° C. and enters the air preheater 51, and thereafter, is discharged into the atmosphere from a chimney via an unillustrated residual heat utilization facility and an exhaust gas treatment facility.

The gas mixing device 2 does not affect the high temperature in the reburning space 35 to the lower combustion chamber 12. Therefore, the incinerator 1 needs to have a conventional structure and material. The wall 32 has an effect of reducing not only the radiation effect described above but also the effect of radiation cooling from the low-temperature portion above the gas cooling chamber GC to the reburning chamber 3.

FIG. 3 is a schematic diagram showing the interrelationship of each device with respect to the specific control for removing the above-mentioned dioxins, and FIG. 4 is a block diagram schematically showing a control system.

In FIGS. 3 and 4, the inside of the combustion chamber 12 above the dry grate 13 is supplied with the supply air amounts 62 and 63 by a dry grate damper 52 and a combustion grate first damper 53.
Is reduced, so that the atmosphere becomes a reducing atmosphere. As the temperature of this portion is lower, the unburned component contained in the exhaust gas (unburned gas) 71 tends to be larger.

Therefore, the temperature of the reducing atmosphere is detected by the detector 8.
1 and the average temperature per unit time obtained by the comparison / delay operation circuit 82 is compared with the reducing atmosphere temperature setting device 821. The dry grate under the damper drive 5
The dry air amount to be supplied is controlled preferentially by controlling the operation of the combustion grate 21, and if necessary, the first grate damper 53 below the combustion grate is driven by the first grate damper drive unit below the grate by the combustion grate air amount control unit 84. By controlling the operation of 531 and supplementarily adjusting the first air amount of the combustion grate, the reducing ambient temperature is kept within a specified range.

The above constitutes the second control system 8.

The unburned gas 71 passes through the gas mixing device 2, so that the latter half of the combustion grate 14 and the post-combustion device 1
5 is stirred and mixed with the high-temperature combustion gas 72 generated from
The tertiary combustion air 48 having a high oxygen content burns violently. That is, under the high temperature state brought by the combustion gas 72,
The high-concentration oxygen is supplied to perform high-temperature combustion using unburned components in unburned gas as fuel.

As a specific control method, a temperature detector 91 is provided at the outlet of the re-combustion chamber, and a large temperature fluctuation is obtained as an average value per unit time by a comparison / delay operation circuit 92. The comparison signal is sent to the tertiary combustion air calculation section 93.

Here, the detected value is much lower than the set value, such as at the time of starting or when the combustion state deteriorates (for example, 1100).
In this case, the comparison / delay operation circuit 92 instructs the temperature-increase burner control section 371 for the time being,
Is started to raise the temperature to a specified lower limit (for example, 1250 ° C.).

If the temperature of the outlet of the reburning chamber is equal to or higher than the specified temperature, the tertiary combustion air controller 93 sets the chimney inlet CO concentration detector 94 and the CO concentration integration so as to reach the set temperature (for example, 1300 to 1400 ° C.). The oxygen control valve 47 by the oxygen supply controller 96 is preferentially controlled with reference to the CO concentration calculated by the device 941, the CO average concentration setting device 942, and the CO concentration comparing section 943, and the The opening of the damper 43 is adjusted by controlling the operation of the damper driving unit 431 according to a command from the air amount control unit 97, or the tertiary air amount is adjusted by controlling the rotation speed of the tertiary blower 41.

The above constitutes the first control system 9.

Here, the CO concentration detector 94 is a chimney SS
Although provided at the inlet, it may be provided before and after an exhaust gas treatment device (not shown) in the same measurable temperature range.

With the above control, the inside of the reburning space 35 is maintained at the set temperature, and the unburned substances in the unburned gas 71 can be completely incinerated and removed.

In this embodiment, the incinerator has been exemplified as a horizontal type using a three-stage grate of drying, burning and post-combustion. However, a vertical incinerator may be used. Although the injection cooling type is exemplified, a waste heat boiler cooling type may be adopted and an oxygen generator may be installed instead of the oxygen cylinder.

The shape of the gas mixing device may be any shape as long as the purpose is achieved.

Further, the control of the temperature of the reducing atmosphere may be performed in combination with the control of the amount of secondary combustion air or the control of water injection in the furnace, and an additional air heater may be provided for heating the tertiary combustion air.

The tertiary combustion air may be injected not only from the vicinity of the illustrated gas mixing device but also from the wall surface of the reburning chamber.

[0055]

As described above, according to the present invention, according to the removal equipment of dioxins in the incinerator of the present invention, by generating more unburnt gas with unburnt content in the incinerator, a gas mixing device After mixing and mixing with the high-temperature combustion gas, high-temperature combustion is performed in the reburning chamber with increased combustion efficiency by injecting tertiary combustion air with an increased oxygen concentration.
Reburning in the reburning chamber can be reliably achieved, and unburned carbonaceous particles as a dioxin precursor can be completely burned, thereby preventing the generation of dioxins.

Further, by providing the reflecting wall on the upper part of the reburning chamber, the radiation effect by the reflecting wall and the effect of reducing the influence of the radiation cooling from the low temperature part on the upper part of the gas cooling chamber to the reburning chamber can be obtained. Further, dioxins can be effectively removed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view and a schematic flow chart showing an example of an entire configuration of a dioxin removing apparatus in a refuse incinerator according to the present invention.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a reburn chamber.

FIG. 3 is a schematic diagram showing the interrelationship between devices related to control.

FIG. 4 is a block diagram schematically showing a control system.

FIG. 5 is a cross-sectional view showing an example of the structure of a waste heat boiler-cooled refuse incineration system in which conventional dioxin countermeasures are taken.

FIG. 6 is an overall view showing the outline of the structure of a conventional water-injection cooling type refuse incineration facility in which measures against dioxin are also taken.

FIG. 7 is a sectional view schematically showing a gas mixing device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 incinerator 12 combustion chamber 2 gas mixing device (gas mixing means) 3 reburn chamber 32 reflective wall 8 second control system (second control means) 9 first control system (first control means)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F23G 5/50 ZAB F23G 5/14 ZAB

Claims (2)

(57) [Claims] 1. Reburning of unburned gas at a high temperature between a combustion chamber of a refuse incinerator for incinerating refuse such as municipal waste and industrial waste, and a gas cooling facility installed downstream thereof. In a refuse incinerator provided with a reburning chamber and provided with gas mixing means at the bottom of the reburning chamber, a reflecting wall provided on an upper portion of the reburning chamber, and a temperature in the reburning chamber within a predetermined specified range. To control the oxygen concentration of the tertiary combustion air to be supplied to the reburning chamber or the gas mixing means and the amount of supply thereof.
A dioxin removal device in a refuse incinerator, comprising: a control unit. 2. A second control means for controlling a supply amount of drying air supplied to the combustion chamber so as to maintain a reducing atmosphere temperature in the combustion chamber within a predetermined range. Item 4. A dioxin removal device in a refuse incinerator according to Item 1.